GB2103288A - Rotary positive-displacement fluid-machines - Google Patents

Abstract

An I.C. engine comprises two identical stator casings 11, each having sidewalls 12 and a circumferential wall 13 defining a cylindrical chamber 15. Two identical rotors 10 are mounted one in each chamber 15 and coaxially upon a common drive-shaft 1, which is supported by four main roller-bearings 2. Each pair of bearings 2 is mounted on a supporting structure 3. The chamber 15 is sealed relative to the drive shaft 2 by gaskets 16a. <IMAGE>

Description

SPECIFICATION votary external combustion, opposed and uwatermittent firing couple-acting engine The present invention relates to an engine.

Reciprocating internal combustion engines are susceptible to a number of problems. In particular their reciprocation causes wear and vibration problems. Their internal combustion causes thermal problems. They operate best on high quality expensive fuels and are inherently ill adapted to using a variety of fuels.

.The engine of the invention is envisaged as an improvement on such conventional engines. For this purpose it has been designed with the aim of achieving the following basic features: Maximum saving in engine-room space, minimal vibrations by designing all substantial moving parts to rotate and have rotary symmetry, external combustion by designing the engine to have the combustion chambers placed remote from the rotor space and further by eliminating the use of valves in the combustion chambers to avoid thermal problems and benefit the capability of burning a variety of fuels, the engine provided with two combustion chambers per rotor placed opposite each other so that upon combustion in the two combustion chambers a couple is applied on the rotor instead of a single force, as will be explained later in detail in the engine description.In order to achieve fuel economy the engine is designed to have intermittent combustion in each combustion chamber pair of a rotor simultaneously, and further full advantage of the expansion of the combustion products is taken by including a sliding arm pair in the design of each rotor in order to achieve compression of the air used for combustion upon the expansion of the combustion products, each rotor being designed to rotate concentrically around its drive shaft hence eliminating the use of a crankshaft or eccentric gear.

Hence, to achieve the above mentioned aims the engine is designed as a rotary external combustion, opposed and intermittent firing couple-acting engine comprising in combination of two identical stator casings each having opposed spaced sidewalls and an intervening, enclosing tranverse cylindrical wall referred to as the peripheral or circumferential part of the stator casing, defining together therein a cylindrical housing chamber and two identical variable shape rotors each mounted in the cylindrical housing chamber of each stator casing said rotors coaxially mounted upon a drive shaft which is rotatably supported on four main roller bearings, each pair of such bearings placed externally and on either side of the opposed sidewalls of each corresponding stator casing and mounted on the engine supporting structure and said shaft also rotatably sealed by suitable gaskets which are situated coaxially and peripherally in the cylindrical shaft opening of each of the afore mentioned opposed sidewalls and extending from one stator casing through to the other one where it is established in an identical manner.

According to one aspect of the Invention there is provided an engine comprisng a housing having a rotor space and two external combustion chambers each communicating with the rotor space via a passage herein referred to as the gas expansion passage, said chambers positioned at 180 to each other, a rotor mounted for rotation in the rotor space and rotating in an anticlockwise direction around the centre of its drive shaft.

The rotor consists of three arm pairs, two trailing arms, two buffer arms and two sliding arms, each of the latter initially having its forward reaction face adjacent to the radial face of its consecutive trailing arm while its backward face is linked to a piston herein referred to as the buffer piston the latter mounted in a cylinder positioned circumferentially in each rotor buffer arm and at a right angle to the buffer arm radial face, said cylinder containing gas under a given pressure, the arrangement being such that when the combustion products impinge on the forward reaction face of each sliding arm after combustion has occured in the combustion chambers each sliding arm is free to slide forward along the rotor shroud sliding surface in the direction of rotation of the rotor until the buffer piston linked to the backward face of each sliding arm has moved from its bottom dead centre which corresponds with the buffer arm radial face, to its top dead centre at the end of the buffer cylinder.

Each of the two trailing arms of the rotor is provided with reaction blade stages having between them guiding vanes both mounted radially on each trailing arm tangential surface. Each trailing arm of the rotor is also equipped with a spring loaded strip seal mounted at a right angle to the radial surface of the said arm, the free end of the seal always being adjacent to the forward reaction face of the sliding arm under the action of its spring. Each buffer arm is equipped with the above mentioned buffer piston which prevents the backward face of each sliding arm against knocking on the buffer arm radial face once the sliding arm has moved from its original position and has travelled forward through its full slide.

Hence, with the above arrangement three pairs of rotor chambers are defined in the rotor space between the rotor arms. Two rotor gas chambers situated diametrically opposite, each such chamber at any moment comprising of a space with boundaries defined by the forward reaction face of the sliding arm, the tagential face of the trailing arm initially at a right angle to the sliding arm forward reaction face, and the arc formed by the cylindrical wall of the casing enclosed by the opposed sidewalls of the stator casing.Two rotor neutral chambers situated diametrically opposite, each such chamber at any moment comprising of a space with boundaries defined by the concave surface of the rotor between the rotor buffer arm and its preceding trailing arm and common to both arms, and the arc formed by the cylindrical wall of the casing and enclosed by the opposed side-walls of the stator casing, said rotor arms also defining two more pockets situated diametrically opposite therein referred to as rotor air chambers each such chamber at any moment comprising of a space with with boundaries defined by the backward face of the rotor sliding arm, the rotor shroud sliding surface, the radial face of the buffer arm facing the backward surface of the sliding arm, and the arc formed by the cylindrical wall of the casing enclosed by the opposed side-walls of the stator casing, as seen in the attached drawings.

The engine is provided with means for intermittently supplying air under pressure to the combination chambers, means for intermittently supplying fuel to the combustion chambers and means for initiating intermittent ignition of the fuel with the pressure air in the combustion chambers, the arrangement being such that on ignition of the fuel with the pressure air in the combustion chambers, combustion products leave the combustion chambers with high velocity, are directed substantially circumferentially of the rotor by guiding vanes placed before the mouth of each gas expansion passage and impinge vertically on the reaction blade stages, which are mounted radially on the tangential face of each trailing arm, thus creating a couple on the rotor and causing it to turn.

Once the combustion products strile on the first stage of reaction blades they are directed through guiding vanes to strike on the following reaction blade stage and thence through further guiding vanes are directed to impinge on the forward reaction face of each rotor sliding arm. The latter in turn slides forward in the direction of rotation of the rotor under the force created by the combustion products when they impinge on its forward reaction face until it reaches full slide at the position where the buffer piston connected to the backward face of the said arm reaches its top dead centre.Hence, as each of the rotor sliding arms slides forward along the rotor shroud sliding surface in the direction of rotation of the rotor, the air in each rotor air chamber is compressed as the volume of each rotor air chamber decreases with the motion of the sliding arms and leaves the two rotor air chambers through suitable piping each such pipe fitted with a one way non-return air outlet valve and enters the lower part of the engine air receiver herein referred to as the air receiver charging portion which feeds the combustion chambers with pressure air inter m ittently.

For exhausting the combination products, they are preferably carried around the rotor space in the two rotor gas chambers until each such chamber comes in communication with an exhaust passage in the peripheral part of the rotor housing. The exhaust passages may communicate with a turbo-charger which supplies air to the charging portion of the air receiver through a one way non-return air onlet valve, the air receiver charging portion acting as a reservoir from which the air under pressure is intermittently supplied to the combustion chambers. The turbo-charger may be supplemented or replaced by a compressor driven by the rotor and mounted coaxially on the engine drive shaft.

The pressure air could be introduced directly into the combustion chambers, for instance via a rotary valve provided in a short passage from the combustion chamber to the rotor space. However, it is preferred that the pressure air be introduced via the rotor gas chamber which provides communication between a charge air passage and the gas expansion passage leading to the combustion chamber during a certain period of rotor rotation prior to ignition. With this arrangement the mouth of the charge air passage leading to the rotor space is located to be passed first by a given part of the rotor, before that part passes the mouth of the gas expansion passage which communicates the combustion chamber with the rotor space.

In a preferred embodiment there are provided two similar rotors each having two rotor gas chambers, two rotor air chambers, two rotor neutral chambers and two combustion chambers the latter communicating with the rotor space by means of their respective gas expansion passage. However, for big horsepowers more than two rotors may be incorporated in the engine assembly.

Circumferentially between each rotor gas and air chambers a neutral chamber is provided in each rotor for scavenging of the combustion chambers. On initial communication of one of the rotor air chambers with both a gas expansion passage and one of the air inlet pipes, the latter fitted with a one way non-return air inlet valve and an air filter and situated between the gas expansion passage and the charge air pipe, one of the rotor neutral chambers is also still in communication with the said gas expansion passage and through it with the combustion chamber.

Thus, air can enter the rotor air chamber from the air inlet pipe and through it enter the gas expansion passage and its corresponding combustion chamber to scavenge it and displace any exhaust remaining in the latter to the rotor neutral chamber which at this position of the rotor is in communication with the gas expansion passage corresponding to the said combustion chamber. Hence, as the rotor rotates the rotor buffer arm tips seal off the gas expansion passages from the rotor neutral chambers, each combustion chamber and corresponding gas expansion passage still being in communication with a rotor air chamber and thus both combustion chambers and their corresponding gas expansion passages fill up with atmospheric air,the rotor neutral chambers having filled with the exhaust gas.

As the rotor continues to rotate, at a certain position of the rotor each rotor neutral chamber now full with exhaust gas comes in communication with both a scavenge air port and an exhaust port and hence, scavenge air flows rom the scavenging portion of the air receiver and through the scavenge passages, each of the latter equiped with a one way non-return air inlet valve and a set of guiding vanes, enters each rotor neutral chamber to scavenge it and displace the exhaust to the next exhaust port from which through suitable piping the exhaust enters the turbine side of the turbocharger to drive it.

Scavenging of the rotor gas chambers occured prior to the rotor neutral chamber scavenging when each rotor gas chamber was in communication with both a scavenge air port and an exhaust port.

The air receiver allocated to each rotor is divided in two parts, the "charging" and "scavenging" portion by a partition equipped with a pressure sensitive spring loaded valve which permits only such air as is in excess of the requirement for charging the combustion chambers to pass from the charging portion to the scavenging portion of the air receiver. To provide that the pressure air needed for scavenging the rotor gas and neutral chambers and for charging the combustion chambers is only supplied intermittently at given positions of each rotor as determined by its cycle, an air timing valve is provided between each portion of each air receiver and its corresponding air outlet passage leading to the air inlet ports in the circumferential member of each housing.

Two such air timing valves are provided to each air receiver, one for each portion of the receiver.

The scavenge air timing valve opens first to allow pressure air to flow from the air receiver scavenging portion to the scavenge ports and scavenge the two rotor gas chambers and then after closing and reopening to scavenge the two rotor neutral chambers. Once scavenging of both the rotor gas and neutral chambers has occured and when each rotor gas chamber in in communication with both a charge air port and a gas expansion passage, the charge air timing valve opens to allow pressure air to flow from the charging portion of the air receiver and through the charge air passages and rotor gas chambers and gas expansion passages charge the two combustion chambers.

The scavenge air timing valve is controlled by a twin lobe cam while the charge air timing valve is controlled by a single lobe cam, both cams mounted on the engine camshaft which is driven from the engine drive shaft by a gear at twice the engine shaft speed of rotation in a clockwise direction.

Preferably the fuel is injected directly into the combustion chambers by fuel injectors, The fuel supply to the injectors of each combustion chamber pair of each rotor is conveniently controlled by a fuel timing valve arranged similarly to the pressure air timing valves to be opened by a single lobe cam mounted on the engine cam shaft.

According to another aspect of the invention there is provided a lubrication system for an engine having a rotor with a plurality of chambers distributed therearound and peripheral regions peripherally separating adjacent chambers and rotatably mounted by a shaft in a rotor space in a housing, the systen split in three parts, one for lubricating the sliding surfaces of the rotor shroud and sliding arms, one for lubricating the lateral side faces of the rotor and the other for lubricating the peripheral regions of the rotor arm tips and the inner wall of the circumferential member of the rotor housing.

The sliding surface lubrication system comprises of a lubricant pump arranged to supply oil to the rotor shroud sliding surfaces via the drive shaft central oil feel bore, positioned around the centre of the drive shaft and extending axially along part of the drive shaft length, which joins with radial drillings in the drive shaft the latter extending up to the centre of the rotor shroud sliding surfaces from where the oil spreads along the whole of each sliding surface and extends centrifugally to enter the clearance between the rotor sliding arm lateral surfaces and the inner face of the housing sidewall members to return to the oil sump via the central oil return bore as will be described below.

Lubrication of the rotor lateral surfaces is achieved by means of a lubricant pump in conjunction with a timing device and an oil distributor supplying oil intermittently to oil injector quills located in the rotor housing sidewalls, laterally bounding the rotor space, and positioned around a circle concentric with the rotor and having equal to half the radius of the rotor. From the oil injector quills the oil spreads along the rotor lateral surfaces and lubricates them. To provide sealing of the oil against escape from the rotor lateral surfaces sideways to the rotor chambers through the clearance between the inner surface of the housing side walls and adjacent lateral faces of the rotor, spring loaded strip seals are provided in grooves on the lateral surfaces of the rotor following the profile of each rotor arm.

The circumferential lubrication system com prises of a lubricant pump in conjunction with a timing device and an oil distributor supply ing oil intermittently to oil injector quills placed around the circumferential wall mem ber of the rotor housing, said injector quills injecting oil onto the peripheral regions of the rotor arm tips, at least one cylindrical roller mounted in each rotor arm tip for rolling contact with the inner surface of the circumferential wall of the housing circumferentially bounding the rotor space.

In all three above mentioned systems the oil returns to the oil sump to be recirculated via the clearance between the rotor lateral surfaces and the inner surface of the rotor hous ing opposed sidewalls which join with radial drillings in the engine drive shaft which through further axial drillings along the drive shaft join with the central oil return bore, the latter extending axially along part of the length of the drive shaft and ending at the entrance of the oil sump.

Preferably the roller or rollers provided in each rotor arm tip have individual bearing supports locating the rollers circumferentially of the rotor. The rollers and their supports are free to move radially of the rotor to permit the rollers to make firm contact with the inner surface of the circumferential member of the rotor housing. The supports may be spring biased towards the circumferential wall. At each individual peripheral region where there is a plurality of rollers, the rollers may be provided with a single common bearing support. The timing device mentioned above enables oil to be injected through the injector quills at the exact instant when the position of the rotor is such that the injector quill falls between two consecutive rollers of a rotor arm.

To help understanding of the invention, a specific embodiment thereof will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic longitudinal section of an engine according to the the invention, Figure 2 incorporates a cross-section on the line ll-ll in Fig. 1 as well as a longitudinal section of a rotor along the centre of its sliding arms, Figure 3 is a cross-section of a rotor on the line Ill-Ill in Fig. 2, Figures 4 to 10 are views similar to Fig. 3 showing successive stages in the working cycle of the engine, Figure 11 is a cross-section on the line XII- XII of Fig. 1 showing a scavenge air timing valve arrangement, Figure 12 is a cross-section on the line XIII-XIII of Fig. 1 showing a charge air timing valve arrangement, Figure 13 is a cross-section on the line XIV-XIV of Fig.1 showing a fuel injection timing valve arrangement, Figure 14 is a view similar to Fig. 1 showing the camshaft for the timing valve arrangement together with the various cams, the upper corresponding to the first rotor timing valves and the lower to the second rotor timing valves.

Figure 15 is a view similar to Fig. 1 but on a larger scale showing the full lubrication of the engine, Figure 16 is an enlarged view of a portion of a rotor buffer arm showing in detail the roller assembly on a rotor arm tip, the spring loaded strip seals following the profile of the rotor arms and a circumferential oil injector quill, Figure 1 7 is an enlarged view of a portion of Fig. 3 showing the structure of a combination chamber and its associated gas expansion passage with its corresponding convergingdiverging nozzles and gas guiding vanes, and Figures 18 andl8a are a Table of the engine's workimg cycle.

Referring first to Fig. 1, the engine has a shaft 1 mounted in four bearings 2 which are supported in a composite engine fixed structure 3. The left hand end of the shaft 1 carries a flywheel, not shown, and associated drive and starting components. The right hand end of the shaft drives an air compressor 4 which feeds pressure air to an accumulator 5 herein referred to as the air receiver. Intermediate the ends of the shaft it carries a gear 6 which, via further gear 7, drives a camshaft 8 at a two to one drive ratio. The camshaft carries six cams 9 which control admission of pressure air to the rotors and fuel to the combination chambers twice per revolution of the engine as will be described below.

Between each pair of bearings towards each end of the shaft 1 is secured on the shaft a rotor 10. Both rotors and their associated housings 11 are indentical. The rotors and their housings may be arranged at any convenient angle, in the direction of shaft rotation; however, it is preferred that they be set with a 90 phase difference in their working cycles which are identical to each other. Each rotor housing consists of side wall members 12, a circumferential wall member 1 3 between the side wall membersl2, and end plates 14 outside the circumferential wall members.

These members and plates are securely bolted together and form part of the engine fixed structure 3. A rotor space 1 5 and cooling water passages 1 6 are defined by the members and plates.

The line diagram in Fig. 1 illustrates the flow of charge air and exhaust gas. The black tip arrows illustrate the flow of exhaust gas leaving the rotors from the exhaust ports 20 and entering the turbine side of the turbocharger 27 to drive it. The twin coloured tip arrows illustrate the flow of charge air being drawn from the atmosphere into the compres sor side of the turbo-charger 27 where it is compressed and through suitable piping is delivered to the inlet of the air compressor 4 which compresses the pressure air further to deliver it to the charging portion of the air receiver 5 which supplies air to the charge air ports 1 9 of each rotor housing, the charge air admission to each rotor being controlled by its corresponding charge air timing valve 29.

Fig. 2 right hand side is a cross section on the line ll-ll of Fig. 1 and illustrates a section of the rotor housing side walls showing the water passages 16, and the cooling water flow pattern. The side wall members are each split and retain, when bolted together, a seal 16a. The left hand side of Fig. 2 is a longitudinal section of a rotor along the centre of its sliding arms 1 7a which are rotably supported on the sliding surfaces 57 of the rotor shroud 56 which is secured to the engine drive shaft 1. The rotor sliding arms are free to slide along the sliding surfaces 57 in the direction of rotation of the drive shaft; and are supported circumferentially by the housing circumferential wall member 1 3 and laterally by the inner surtfaces of the housing side wall members 12.

Fig. 3 shows a cross-section of a rotor 10 on the line Ill-Ill of Fig. 2, the latter mounted within the rotor space 1 5 of the housing and secured on the shaft 1. The rotor is of general "cruciform" shape defining between its trailing arms 1 7b and buffer arms 1 7c two rotor "neutral chambers" 1 8', between its sliding arms 1 7a and ttrailing arms 1 7b two rotor "gas chambers" 18, and between its buffer arms 1 7c and sliding arms 1 7a two rotor "air chambers" 18".

The housing circumferential wall member 1 3 has two charge air passages 1 9 each fitted with a one way non-return air inlet valve 64 and charge air guiding vanes 46, two scavenge air passages 19' each fitted with a similar valve 64 and scavenge air guiding vanes 46, two air inlet passages 1 9" each fitted with a similar valve 64 and an air filter, two air outlet passages 1 9" each connected to the air inlet of the charging portion 49 of the air receiver 5 and fitted with a one way non-return air outlet valve 64, and two exhaust gas passages 20 each fitted with a rotary exhaust gas timing valve 58, all ten passages opening into the rotor space 15, and two combustion chambers 21 connected by their respective gas expansion passage 22 to the rotor space 1 5. Each gas expansion passage 22 is equipped with a set of convergentdivergent nozzles 26 and gas guiding vanes 46 and opens to the rotor space 1 5. The combustion chambers 21 are each fitted with a spark plug 23 and a fuel injector 24.

The rotor sliding arms 1 7a are free to slide along the rotor shroud sliding surfaces 57 in the direction of rotation of the rotor up to position 17a' when the buffer pistons 59, connected to the sliding arms backward surface by linkage 60 and mounted in cylinders 66 containing gas under a given pressure, have moved from their bottom dead centre corresponding to position 59a to their top dead centre at position 59b shown by the dotted lines in Fig.3. Each rotor trailing arm 1 7b is equipped with a spring loaded sliding seal 61 to seal the rotor shroud sliding surfaces 57 from the combustion products once the rotor sliding arms begin their slide.Each trailing arm is also provided on its tangential surface 65 with reaction blade stages 62 and bgas guiding vanes 63 fitted between the reaction blade stages, and both reaction blade stages and guiding vanes secured radially on each tangential surface 65.

The cycle of operation will now be described with reference to Figs. 4 to 10. At 0 engine angle, analogous to top dead centre in a reciprocating engine, shown in Fig. 4 by the trailing edge 65 of the tangential surface of the trailing arm 1 7b coinciding with 0" of the scale marked around the rotor space 1 5, the spark plugs 23 initiate combustion in the combustion chambers 21 and the combustion products through guiding vanes 46 are driven to impinge vertically on the reaction blade stages 62 of each rotor gas chamber, thus creating a couple on the rotor urging the latter to rotate.Once the combustion products strike on the final stage of reaction blades in each rotor gas chamber they are directed through guide vanes 63 to impinge on the reation face 25 of each sliding arm 17a, the latter beginning to slide forward along the rotor shroud sliding surface 57 in the direction of rotation of the rotor under the force applied by the combustion products on its reaction face 25.

To maintain the velocity of the combustion products as they leave each combustion chamber 21 through its respective gas expansion passage 22, one or more sets of convergent-divergent nozzles 26 are fitted thereto.

The combustion products are guided to impinge vertically on the first stage of reaction blades 62 of each rotor gas chamber by gas guiding vanes 46 placed near the mouth of each gas expansion passage. Similar vanes 46 are fitted near the mouth of each of the charge air and scavenge air passages 1 9 and 19'respectively.

After 30 of rotation of the rotor both combustion chambers are sealed off from their respective rotor gas chamber and most of the combustion products are trapped in the rotor gas chamber resulting in pressure being built up in each rotor gas chamber. Hence, each rotor sliding arm 1 7a slides all the way forward along the rotor shroud sliding surface 57 under the pressure of the combustion products until the buffer piston 59 has moved from its bottom dead centre 59a to its top dead centre 59b, see Fig. 5. Hence, by the sliding arm movement the volume of each rotor air chamber 1 8" decreases substantially, resulting in compression of the air in the said chambers.At this position of the rotor corresponding to 30 rotation, each rotor air chamber 1 8" is in communication with an air oulet passage 1 9',,, the latter leading to the entrance of the charging portion 49 of the air receiver 5, and the compressed air leaves each rotor air chamber to fill up the air receiver charging portion.

As the rotor rotates from 0" to 30 some of the combustion products pass back in the direction of rotation from the combustion chambers 21 to the rotor neutral chambers 18' each of which is in communication with both a combustion chamber 21 and air inlet passage 19" through which air may enter the rotor neutral chamber 18'.In Fig. 5 the air is symbolized by the heavy dots and the combustion products by the light dots, while the arrows illustrate the flow of air into and out of the rotor space 1 5. To prevent blow back of exhaust into the charge air passages 1 9 and scavenge air passages 19' and escape of pressure air from the air receiver, a one way non-return air inlet valve 64 is fitted to each passage, and air timing valves described in more detail below controlled by two of the three pairs of cams 9, close the charge and scavenge air passages at the time of ingnition.

In addition, in order to prevent the air in each rotor air chamber from leaving through the exhaust passages 20, a rotary exhaust timing valve 58 is fitted thereto which closes each exhaust passage 20 until each such passage is in communication with a rotor gas chamber 18 for exhausting the combustion products.

As the rotor continues to rotate the combustion products are carried around in each rotor gas chamber towards each exhaust passage 20 next in the direction of rotation, until at 60' rotation when each rotor gas chamber 18 is in communication with both one exhaust pasage 20 and a scavenge air passage 19', the rotary exhaust timing valves 58 open to allow the combustion products to leave each rotor gas chamber from the exhaust passages 20, and similtaneously one of the cams 9 opens the scavenge air timing valve and allows pressure air to flow from the scavenging portion 47 of the air receiver 5 and scavenge the rotor gas chambers, see Fig. 6.As the exhaust gasses leave the rotor gas chambers 1 8 through the exhaust passages 20, the gas pressure in each rotor gas chamber falls and each sliding arm 1 7a is pushed back to its original position by the gas acted buffer piston 59 which returns to its bottom dead centre position 59a. In Fig. 6 the light dots symbolize the air and the heavy dots symbolize the exhaust gas, while the arrows illustrate the flow of the scavenge air and exhaust gas.

Since each rotor sliding arm 1 7a has moved back to its original position, each rotor air chamber volume increases substantially and a partial vacum is crested in each air chamber 18".

As the rotor rotates, at 70 of rotation each rotor air chamber 1 8" is in communication with an air inlet passage 19" and air is sucked in each air chamber through the passages 1 9" to fill up the vacum in the said chambers.

At 80 rotation the rotor gas chamber scavenging process ends and at this position of the rotor each rotor air chamber 1 8" is in communication with both one of the air inlet passages 1 9" and one of the combustion chambers 21 via its corresponding gas expansion passage 22, which in turn communicates with the next rotor neutral chamber 18', see Fig. 7. Hence, air enters each rotor air chamber through the air inlet passages 1 9" and is directed to each combustion chamber via its correspoding gas expansion passage, to scavenge each combustion chamber and displace any exhaust remaining in each such chamber to the next rotor neutral chamber 18'.The convegent-divergent nozzles 26 increase the pressure of the scavenge air entering each combustion chamber via its corresponding gas expansion passage, while inversely dropping the scavenge air velocity . In Fig. 7 the air is symbolized by the light dots and the exhaust gas by the heavy dots, while the arrows illustrate the flow of scavenge air.

At 90 rotation the tips of the rotor buffer arms 1 7c seal off the combustion chambers 21 from the rotor neutral chambers 18', the latter at this point being full with exhaust gas, and the combustion chamber scavenging process ends. At this position of the rotor each combustion chamber is in communication with one of the rotor air chambers 1 8" and an air inlet passage 19", hence more air is sucked in the rotor air chambers through which it enters the gas expansion passages 22 and hence, the combustion chambers fill up with atmospheric air.The rotor gas chamber exhaust process ends at 110" rotation when the tips of the rotor trailing arms 1 7b cover the exhaust ports 20, and at 120 rotation when each rotor neutral chamber 18' is in communication with both one scavenge air passage 19' and an exhaust passage 20, see Fig. 8, the scavenge air timing valve is activated by one of the cams 9 and scavenge air flows from the scavenging portion 47 of the air receiver 5, and through the scavenge air passages 19' enters each rotor neutral chamber 18' to scavenge it and displace the exhaust gas to the exhaust passages 20 through which it leaves and enters the turbine side of turbo-charger 27 to drive it. In Fig. 8 the air is symbolized by the light dots and the exhaust by the heavy dots, while the arrows illustrate the flow of the scavenge air and exhaust gas.The neutral chamber scavenging process continues at 130 rotation and at this position of the rotor the rotor gas chambers 1 8 are in communication with the air inlet passages 19" and air may flow from the said passages in to the rotor gas chambers.

The rotor neutral chamber scavenging process ends at 140 rotation and at this position of the rotor, the charge air timing valve is activated by one of the cams 9 and pressure air is allowed to flow from the charging portion 49 of the air receiver and through the charge air passages 1 9 to enter each rotor gas chamber 1 8 through which it enters the gas expansion passages 22 and associated combustion chambers 21 to charge them, see Fig.

9.. Hence the air pressure in the combustion chambers builds up to the value required for ignition f the fuel. During the air charging process of the combustion chambers, the sliding arms 1 7a are held back to their original position by means of the gas-acted buffer pistons 59 since the gas pressure in the cylinders 66 is equal to the air pressure required for ignition of the fuel. In Fig. 9 the air is symbolized by the light dots and the exhaust gas by the heavy dots, while the arrows illustrate the flow of the charge air.

The combustion chamber air charging process .continues up to 170 rotation and at this position of the rotor the rotating exhaust timing valves 58 close.

Fuel injection takes place from 155 up to 175 rotation, see Fig. 10, and this process is controlled by a fuel timing valve activated by one of the cams 9. The dots in Fig. 10 symbolize the air while the dashes symbolize the injected fuel.

Fuel injection ceases at 175 and firing occurs at 180 rotation. From 180 to 360 the cycle is repeated, but with each combustion chamber co-operating with the other rotor gas, air and neutral chambers of the rotor. A tabulation of the engine's working cycle is set out, for both rotors, in the accompanying Table shown in Figs. 18, 18a.

Fig. 11 shows one of the cams 9, 9a which controls the scavenge air process. It has twin lobes 54 and 54' for opening the scavenge air timing valve 53 four times per revolution of the engine shaft, since the camshaft and the engine shaft are connected by two to one gearing 6, 7. Lobe 54 controls the duration of the rotor gas chamber scavenging while lobe 54' controls the duration of the rotor neutral chamber scavenging. The beginning and end of the rotor gas chamber scavenging correspond with points (i) and (ii) of the cam lobe respectively, while the beginning and end of the rotor neutral chamber scavenging process correspond with points (iii) and (iv) of the cam lobe respectively.When the scavenge air timing valve 53 is open, pressure air is allowed to flow from the scavenging portion 47 of the air receiver 5, through the valve and dividing into two at air way branch 55 enters the rotor space 1 5 from the scavenge air passages 19' as and when described above.

Fig. 1 2 shows one of the cams 9, 9b which controls the charge air and hence the duration of the air charging process of the combustion chambers. It has a single lobe 28 for opening the charge air timing valve 29 twice per revolution of the engine shaft, since the camshaft and the engine shaft are connected by two to one gearing 6, 7. Lobe 28 controls the duration of the combustion chamber air pressure charging process. The beginning and end of the combustion chamber air charging process correspond with points (v) and (vi) of the cam lobe respectively. When the charge air timing valve 29 is open, pressure air allowed to flow from the charging portion 49 of the air receiver 5, through the valve, divides into two at air way branch 30 and enters the combustion chambers 21 through the charge air passages 1 9 and rotor gas chambers 18, as and when described above.Pressure air enters the air receiver 5 via a one way nonreturn air inlet valve 48 into the charging portion 49 of the receiver. The charging portion has sufficient volume that pressure air admitted to the combustion chambers from the charging portion of the receiver via the air way branch 30, under control of the charge air timing valve 29, will fully charge the combustion chambers of one rotor to the desired pressure for the ignition of the fuel. If for instance air is delivered to the air receiver charging portion 49 at twice the pressure required for the combustion, the minimum volume of the charging portion is only half of the total volume of the two combustion chambers 21 and gas expansion passages 22 the two rotor gas chambers 1 8 and associated air spaces including the charging portion of the receiver itself.After charging, once the charging portion 49 is refilled with pressure air, excess air passes through a pressure sensitive valve 51 in the partition 52 between the two portions, to the scavenging portion 47 of the air receiver. Both Figs. 11 and 1 2 illustrate the position of the air timing cam at which the air timing valve is fully open, i.e, at the position when the tip of the cam lobe touches the valve spindle roller. At the end of the pressure air supply the spring 77 pushes the valve spindle 79 back to the valve closing position with the spindle roller touching the base circle of the cam.

Fig. 1 3 shows a similar view of another of the cams 9, 9c this one controlling a fuel injection timing valve 31. Fuel is fed to the valve 31 via line 32, under a pressure dependent upon engine speed. When the valve is "closed' 'the fuel is returned to a fuel tank via return line 32'. When the valve is "open" fuel is fed to the combustion chamber injectors 24 via fuel feed line 33. As with the air timing valve, the fuel timing valve 31 controls the duration of fuel injection to the combustion chambers 21 of one rotor; the feed line 33 dividing to the combustion chambers. The cam 9c has a single lobe 70 for pushing the fuel timing valve spindle 80 to the "open" position of the valve 31 twice per revolution of the engine shaft, since the cam shaft and the engine shaft are connected by two to one gearing 6,7.Lobe 70 controls the duration of fuel supply to the injectors 24. The beginning and end of fuel injection correspond with points (vii) and (viii) of the cam lobe respectively. Fig. 1 3 illustrates the position of the cam 9c at which the fuel injection timing valve 31 is at its "open" position, i.e. when the tip of the lobe 70 touches the valve spindle roller. At the end of the fuel supply to the injectors 24 the spring 78 pushes the valve spindle 80 back to the valve 31 "closed" position with the spindle roller touching the base circle of the cam 9c.

Since the two rotors are set at 90 with respect to their working cycles, both the charge air, scavenge air and fuel injection timing valve cams associated with the two rotors are set with a 90 phase difference, see Fig. 14.

Fig. 1 4 shows the profiles of the cams 9a, 9b, 9c, with the scavenge air control cam 9a having two profiles of 20 which are both effective in opening the scavenge air timing valve 53, the charge air control cam 9b having 30 of profile which is effective in opening the charge air timing valve 29, whilst the fuel injection control cam 9c is only effective over 20 . These angles correspond to the angular rotation of the rotor from the beginning to the end of scavenging, air charging and fuel injection respectively. The cams 9a, 9b, 9c shown in the upper half of Fig. 14 are for one of the rotors while the cams 9a', 9b', 9c' in the lower half are for the other rotor.

Figs. 15, 1 6 illustrate the rotor lubrication system. Referring first to Fig. 15, oil is fed under pressure from an oil pump, not shown, to the central oil feed tube 34 extending axially along part of the length of shaft 1 and drilled around the centre of the shaft 1. From tube 34 the oil is fed via radial drillings 36 in the shaft 1 to the rotor shroud sliding surfaces 57, to lubricate both the rotorshroud and sliding arm surfaces. From the sliding surfaces 57 the oil migrates along the clearance between the rotor side faces and the inner surfaces 90 of the housing sidewalls 12, to enter further radial drillings 87 in the shaft 1 which through further axial drillings in the shaft join with the oil return tube 88 which is drilled around the centre of the shaft 1 and extends axially along part of its length and ends at the inlet of the oil sump.

For lubrication of the rotor side faces, oil injector quils 72 are fitted in the rotor housing side walls 12, said quils 72 positioned around a circle concentric with the rotor and having diameter equal to half the rotor diameter The injector quils 72 are fed with oil intrmittently from a lubricant pump in conjunction with a timing device and an oil distributor.

Sealing rollers 38 are mounted in individual bearing supports 39 located in the peripheral region of each rotor arm tip, see Fig. 16, said rollers and supports spring biased outwardly of the rotor to maintain the rollers in firm contact with the inner surface 40 of the circumferential member 1 3 of the rotor housing. Oil is fed to the rollers 38 intermittently from a lubricating pump in conjunction with an oil feed timing device and an oil distributor, via oil injector quils 71 positioned around the circumferential member 1 3 of the rotor housing. The oil timing device enables oil to be fed a quil 71 at the position of the rotor when the quil 71 falls between two consecutive rollers 38 of a rotor arm. As the rotor rotates in the housing, an oil film forms around the rotating cylindrical rollers 38 and in contact with the wall 40.The rollers, their supports and oil films act to seal the rotor chambers on either side of the rotor arms from each other.

During rotation, as more oil is fed to the rollers 38 it migrates to the end of the rollers and through the clearance between the rotor side faces and the inner sufaces 90 of the housing sidewalls 1 2 enters radial drillings 87 in the shaft 1 which join with the central oil return tube 88 which leads the oil back to the oil sump. Suitable grooves may be provided in the rotor side faces and sliding surfaces 57 to direct the flow of oil.Strip seals 100 following the profile of each rotor arm are provided in grooves in the rotor side faces to provide gasketing and thus prevent the oil from escaping from the rotor side faces sideways into the rotor chambers, see Figs. 16, 1 7. Said seals are spring biased outwardly of the rotor side faces to maintain them in firm contact with the inner surfaces 90 of the housing sidewall members 1 2.

Fig. 1 7 is an enlarged view of a portion of the rotor showing the structure of a combustion chamber 21 and its corresponding gas expansion passage 22. The combustion chamber is of a spherical shape for better air/fuel mixing and consists of a thin suitably shaped plate 73 in order to maintain the temperature of combustion and remain glowing throughout the engine operation to keep the charge air at the required temperature for the ignition of the fuel. Outwardly, the combustion chamber is fitted with a suitably shaped insulation plate 74 which has provisions for fitting a fuel injector 24 and spark plug 23.The gas expansion passage 22 consists partly of member 73 and 74 and is equipped with a set of convergent-divergent nozzles 26 and gas guiding vanes 46 located near its mouth at the opening to the rotor space 1 5. The nozzles 26 decrease the velocity and increase the pressure of the charge air incoming the combustion chamber, while inversely decreasing the pressure and increasing the velocity of the combustion products leaving the combustion chamber after combustion has occured. Also shown in the figure is one of the air inlet passages 19" equipped with an air filter 75 and a one way non-return air inlet vlave 64, and one of the charge air passages 1 9 equipped with a similar valve 64 and with charge air guide vanes 46 located near its mouth at the opening to the rotor space 1 5.

The above described engine has the following advantages: (i) Eight firings are achieved per shaft rotation with two rotors, making the two rotor engine equivalent to an eight cylinder two stroke or a sixteen cylinder four stroke piston engine, hence resulting in substantial engineroom space saving (ii) The engine has no crankshaft as such and thus avoids problems associated with crankshafts.

(iii) All substantial working parts rotate and have rotary symmetry and thus give rise to little or no vibration (iv) Due to the combustion taking place externally of the rotor the rotor is not highly thermally stressed.

(v) The combustion chambers have no valves and further, the exhaust, charge air and scavenge air timing valves are provided remote from the combustion chambers relieving them of having to sustain combustion gas pressure.

(vi) By incorporation of the rotor sliding arms in the design of each rotor, the engine benefits both the full expansion of the combustion products as well as compression of the air to be used for the combustion.

(vii) The engine may be adapted, by interalia altering the pressure at which the charge air is delivered to the combustion chambers, to run on any hydrocarbon fuel, from LPG to heavy fuel oil and indeed on slurries, e.g. of coal.

(viii) The engine is of a simple design occupying minimum engine-room space and providing for the minimum of rotaing and sliding parts, thus ensuring easy maintenance and reliability.

Claims (11)

1. A rotary external combustion opposed and intermittent firing couple-acting engine comprising (a) in combination of two identical stator casings, each having opposed space sidewalls and an intervening, enclosing tranverse cylindrical wall referred to as the circumferential part of the stator casing, defining together therein a cylindrical housing chamber and (b) two identical variable shape rotors each mounted in the cylindrical housing chamber of each stator casing said rotors coaxially mounted upon (c) a drive shaft which is rotatably supported on (d) four main roller bearings, each pair of such bearings placed externally and on either side of the opposed sidewalls of each corresponding stator casing and mounted on the engine supporting structure and said shaft also rotatably sealed by gaskets which are situated coaxially around the cylindrical shaft opening of each of the aforementioned opposed sidewalls, said shaft extending from one stator casing through to the other where it is established in an identical manner.

2. The rotary external combustion opposed and intermittent firing couple-acting engine as defined in claim 1 whose rotors are mounted on the drive shaft in such a way as to rotate in one certain direction, anticlockwise, concentrically around the centre of the drive shaft, hence eliminating the need for an eccentric gear drive, each of these rotors comprising (a) of three arm pairs, two sliding arms, two buffer arms and two trailing arms, each arm being rotatably supported on the circumferential part of the stator casing by (b) suitable cylindrical type rollers which are fitted to the peripheral region of each rotor arm tip and spring loaded from inside to push them outwards towards the inner surface of the circumferential part of the stator casing and thus ensure good contact and gas sealing circumferentially, the side surfaces of each rotor arm being adjacent to the inner surface of the opposed sidewalls of its corresponding stator casing, thus defining two gas pockets therein referred to as (c) rotor gas chambers, situated diametrically opposite, each such chamber at any moment comprising of a space with boundaries defined by the forward reaction face of a sliding arm, the tangentical face of the trailing arm following the sliding arm and initially at a right angle to the sliding arm forward reaction face and the arc formed by the cylindrical wall of the casing enclosed by the opposed sidewalls of the stator casing, (d) said rotor arms also defining two pockets situated diametrically opposite therein referred to as rotor neutral chambers each such chamber at any moment comprising of a space with boundaries defined by the concave surface between the rotor buffer arm and its preceding trailing arm and common to both arms and the arc formed by the cylindrical wall of the casing and enclosed by the opposed sidewalls of the stator casing and (e) said rotor arms also defining two more pockets situated diametrically opposite therein referred to as rotor air chambers each such chamber at any moment comprising of a space with boundaries defined by the backward face of a sliding arm, the rotor shroud sliding surface, the radial face of its consecutive buffer arm and the arc formed by the cylindrical wall of the casing and enclosed by the opposed sidewalls of the stator casing, the arrangement of each rotor being such that the two sliding arms of one rotor are each initially positioned with their forward reaction face adjacent to the radial face of their consecutive trailing arm while their backward face is linked to (f) a buffer piston mounted in a cylinder in each buffer arm containing gas under a given pressure, each such cylinder positioned circumferentially and at a right angle to the buffer arm radial face, the arrangement being such that after combustion once the combustion products impinge on the forward reaction face of each sliding arm the latter is free to slide along the rotor shroud sliding surface in the direction of rotation of the rotor until the buffer piston moves from its bottom dead centre which coincides with the radial face of the rotor buffer arm, to its top dead centre and thus, the above arrangement benefits the full expansion of the combustion products while simultaneously achieving compression of the air in each rotor air chamber as the volume of each such chamber decreases with the forward sliding motion of each sliding arm, thus obtaining useful work from the expansion of the combustion products.

3. The rotary external combustion opposed and intermittent firing couple acting engine as defined in claim 1 whose combustion chambers are in communication with the rotor space by means of their respective gas expansion passage, the latter being equipped with (a) gas guiding vanes placed near its mouth at the opening to the rotor space which direct the combustion products as they leave the combustion chambers with high velocity substantially circumferentially of the rotor to impinge vertically on (b) the reaction blade stages placed radially along each rotor trailing arm tangential surface and through further guiding vanes arranged similarly to the reaction blade stges said combustion products after having passed through the reaction blade stages are directed to impinge on the forward reaction face of each rotor sliding arm and thus, during their expansion the combustion products create a couple on the rotor since the reaction blade stages and the forward reaction face of the sliding arms of the two rotor gas chambers are set at 180 to each other and the combustion products impinge vertically on the reaction blade stages and the forward reaction face of each rotor sliding arm, and for relieving the combustion chambers from exhaust after combustion has occurred (c) two rotor neutral chambers as they are defined diametrically opposite in each rotor by the rotor arms carry any exhaust gas left in the combustion chambers once the combustion chamber scavenging process begins and transport these exhaust gases to (d) the exhaust manifolds each equipped with (e) a rotary exhaust timing valve and located on the circumferential part of the stator casing, from where they leave the rotor neutral chambers through suitable exhaust piping connected to the exhaust manifolds and enter the turbine side of (f) the turbo-chargers to drive them, the turbo-chargers in turn supplying compressed air to the inlet of (g) an air compressor mounted coaxially on the free end of the engine drive shaft, the other end o the shaft carrying the engine flywheel, which in turn compresses the air further and delivers it to (h) the charging portion of each of the two air receiver accumulators, each one of the latter allocated to charge with compressed air the pair of combustion chambers correspoding to one rotor assembly, each air receiver being divided in two portions, the charging portion described above and scavenging portion which is allocated to supply pressure air to the scavenge ports located in the circumferential wall member of each stator casing for the scavenging of the rotor gas and neutral chambers, the supply of air to the scavenge ports and charge air ports being controlled by (i) spring loaded air timing valves placed at the outlet of each portion of the air receivers and activated directly by (j) the engine cam shaft, the latter being rotated in a clockwise direction at twice the rotational speed as that of the engine drive shaft, the two being connected by suitable gearing having two to one ratio, and thus with the above arrangement the air is supplied (k) intermittently at constant pressure, (I) the fuel being supplied by a suitable fuel injection system simultaneously to each combustion chamber pair allocated to each one of the rotors intermittently again by (m) spring loaded fuel timing valves activated by the cam shaft in an identical manner as for the pressure air supply.

4. The rotary external combustion opposed and intermittent firing couple-acting engine as defined in claim 3, having combustion chambers of (a) spherical design for optimum air/fuel mixing, (b) said combustion chambers carry no valves and (c) are constructed from a suitably shaped thin lamina in order to maintain a high temperature during engine operation, every combustion chamber being connected to the fuel supply line and carrying (d) one injector (e) one spark plug and means for feeding the latter with an electrical charge intermittently at the moment whenever each individual rotor is in the firing position whereby since the combustion chambers are positioned remote of the rotor and carry no vlaves the engine may be adapted, by interalia altering the pressure at which the charge air is delivered to said chambers, to run on any hydrocarbon fuel from L.P.G. to heavy fuel oil and indeed on slurries e.g. of coal.

5. The rotary external combustion opposed and intermittent firing couple-acting engine as defined in claim 3 where the products of combustion leave each combustion chamber through (a) an aperture connected to (b) its corresponding gas expansion passage which opens to the rotor space and is equipped with one or more sets of convergent-divergent nozzles placed near the entrance of each combustion chamber which increase the velocity and decrease the pressure of the combustion products leaving its corresponding combustion chamber, while also serving inversely to reduce the charge air velocity and increase its pressure during the combustion chamber air charging part of the cycle, the other end of each gas expansion passage which is near the entrance to the rotor space being fitted with (d) gas guide vanes which direct the combustion products substantially circumferentially of the rotor to impinge vertically on the first reaction blade stage of each rotor gas chamber.

6. The rotary external combustion opposed and intermittent firing couple-acting engine as defined in claim 1 comprising of two identical stator casings, each having opposed spaced sidewalls and an intervening, enclosing transverse cylindrical wall referred to as the circumferential part of the stator casing which is equipped at the position as determined by the engine fundamental cycle of operation with (a) two scavenge air inlet ports each fitted with suitable scavenge air guide vanes and a one way non-return air inlet valve, (b) two exhaust gas outlet ports, each equipped with a rotary exhaust timing valve, the latter relieving the rotor gas and neutral chambers from the exhaust gases, (c) two apertures referred herein as combustion gas outlet ports which serve to communicate each of the combustion chambers via its respective gas expansion passage with a rotor gas chamber at a given position of the rotor, (d) two charge air inlet ports each equipped with suitable charge air guide vanes and a one way non-return air inlet valve, (e) two pressure air outlet ports each fitted with a one way nonreturn air outlet valve and communicating with the air inlet of the charging portion of the air receivers and (f) two atmospheric air inlet ports each fitted with a one way non-return air inlet valve and an air filter at the end of its air inlet passage.

7. The rotary external combustion opposed and intermittent firing couple-acting engine as defined in claim 6 whose stator casing sidewalls are suitably designed to allow cooling by water circulation supplied by an externally situated pump, each sidewall being made up from suitably shaped parts bolted together and each complete pair of sidewalls bolted to the circumferential part of the casing to form one complete stator casing which turn is mounted on the engine supporting structure.

8. The rotary external combustion opposed and intermittent firing couple-acting engine as defined in claim 2 where sealing of the gases is ensured by (a) the spring loaded cylindrical type rollers carried at the peripheral region of each rotor arm tip and in firm contact with the inner surface of the circumferential wall of the casing, (b) by the strip seals loaded by sinusoidal springs from inside pushing the latter outwards towards the stator casing opposed sidewalls to ensure firm contact between said seals and the inner surfaces of the sidewalls of the casing, said strip seals embedded in (c) suitable grooves following the profile of each rotor arm thus together providing adequate gasketing for the gases to escape from the rotor gas chamber in any direction rendering the latter gastight.

9. The rotary external combustion opposed and intermittent firing couple-acting engine as defined in claim 1 whose lubrication system is split in three parts, the sliding surfaces lubrication, the rotor side faces lubrication and the rotor arm tip peripheral regions lubrication, whereby in the first system lubrication is provided by oil circulation supplied through an externally positioned circulating pump directing the flow to (a) the engine drive shaft central oil feed bore drilled around the centre of the shaft and extending axially along part of its length where it communicates with (b) radial drillings in the drive shaft extending up to (c) the centre of the rotor shroud sliding surfaces and supplying both the rotor shroud and rotor sliding arm sliding surfaces with oil, the oil hence returning to its sump through (d) the clearance between the rotor side faces and the inner surfaces of the housing sidewalls which communicates with (e) radial drillings in the drive shaft which in turn through further axial drillings in the shaft join with (f) the central oil return bore drilled around the centre of the shaft and extending axially along part of its length leading to the entrace of the oil sump, and in the rotor side face lubrication system oil is supplied intermittently to the rotor side faces by a lubricant pump in conjunction with a timing device and an oil distributor, via (g) oil injector quills, positioned around a circle concentric with the rotor and having half its diameter, placed in the sidewalls of each stator casing, the oil returning to its sump as described above, and in the peripheral region lubrication system (h) the cylindrical rollers placed at the peripheral region of each rotor arm tip are lubricated with oil supplied intermittently by a lubricant pump in conjunction with a timing device and an oil distributor, via (i) oil injector quills placed in the circumferential wall member of each stator casing, the oil spreading along each roller forming an oil film and thence entering the clearance between the rotor side faces and the inner surfaces of the housing opposed sidewalls to join the central oil return bore as described previously.

10. The rotary external combustion opposed and intermittent firing couple-acting engine as defined in claim 3 designed suitably so that the cycle of each rotor dictates two pairs of firings i.e. four single firings in all per rotor per revolution and thus, two couples are applied on each rotor during every one complete revolution of the rotor, each pair of firings occuring every 180 revolution for each rotor, hence the firing cycle of each rotor is repeated every 180 , the firing cycle between the two rotors having a 90 phase difference and thus a couple is acting on the engine drive shaft at intervals of 90 revolution, the gap between successive couples being 90 and during that time the rotational movement of the engine is maintained by the flywheel mounted coaxially on the free end of the engine drive shaft, however more than two rotors may be incorporated in the engine design if desired, in which case the firing cycle between any two consecutive rotors has a phase difference of(180") . (number of rotors), hence with the above arrangement each rotor is equivalent to a four cylinder twostroke or an eight cylinder four-stroke engine, thus resulting in substantial engine-room space saving.

11. The rotary external combustion opposed and intermittent firing couple-acting engine substantially as hereinbefore described with reference to the accompanying drawings.