AU2007202672A1 - Combined cycle engine using a multiple input coupling - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT COMBINED CYCLE ENGINE USING A MULTIPLE INPUT COUPLING The following statement is a full description of this invention, including the best method of performing it known to me.

The terms "invention" and "present invention" refer to the whole of the Combined Cycle Engine. The term "engine" refers only to the internal combustion engine component of the Combined Cycle Engine. The term "water" also implies "liquid", "coolant" and "other working fluid". The term "steam" also implies "vapour of coolant" and "vapour of other working fluid" and "vapour of liquid" COMBINED CYCLE ENGINE USING A MULTIPLE INPUT COUPLING Purpose and Application Rurpose The purpose of the present invention is to provide significantly improved fuel efficiency for internal combustion engines. With rising fuel prices and concerns about global warming there is increasing need for engines to operate at the highest possible fuel efficiency. The invention provides a means to achieve substantial fuel efficiency gains, and offers a choice of enhanced performance or greater economy of operation. Opportunities to improve the fuel efficiency of vehicles and other machines, have become important to Regulatory authorities, commercial operators and the public.

Application The invention targets multi-cylinder, liquid cooled four-stroke engines, but is not restricted to these, or to any particular size of engine, or engine operating cycle (Otto, diesel or other), or to any particular fuel type and includes emerging fuels like ethanol, biodiesel and hydrogen.

The invention can be used in a wide range of applications where I.C. engines are the prime energy source, and where increased power output and/or lower cost of operation is important. This will include, but is not limited to, most forms of road transport, diesel and diesel-electric rail and marine applications, some aircraft, as well as stationary applications such as pumping and generating.

Used in suitable hybrid vehicles, the invention provides opportunities for further reductions in greenhouse gas emissions and greater economy of operation.

In motor sports and in military vehicles powered by I.C. engines, the invention offers significantly increased speed, acceleration or range, or a combination of these and therefore can provide a critical strategic advantage.

Background Multicylinder, liquid cooled internal combustion engines operate at efficiencies up to about 40% for diesel engines and 30% for petrol (gasoline) engines, representing the percentage of heat energy of the fuel that is converted to mechanical work. The remaining 60% to 70% of heat energy is lost through the exhaust and cooling systems, except for about 10% lost as friction and in other ways. Clearly it is of benefit to recover and reuse as much lost energy as is technically and economically feasible.

Throughout the history of internal combustion engines low fuel efficiency has been of concern. Many inventions have proposed the recovery and reuse of waste heat but most were not adopted because added manufacturing costs and technical complexity could not be justified while fuel costs were low and emissions were not a serious issue. However circumstances have changed.

While lost heat energy is the main cause of low fuel efficiency, the kinetic energy of the exhaust gasses represents a further source of recoverable energy that is currently underexploited. Exhaust gasses can generate powerful gas flows even at moderate throttle settings and a suitably designed turbine can recover some of this energy to do useful work.

At the present time, exhaust turbines are mostly used to drive turbochargers.

These are most beneficial when engines operate at high speed and high load, however in some engines these conditions may apply for only a small part of the normal operating cycle with the result that turbochargers contribute little or nothing to engine performance most of the time. Also turbochargers are further restricted in function by the need for a wastegate valve which bypasses exhaust gasses away from the turbine to protect the engine. Exhaust turbines have the capacity to do more work than they actually do.

Recovering 25% of heat energy that is otherwise wasted, can increase overall fuel efficiency by 15%. Also, a further 5% efficiency gain can be achieved using a suitably designed exhaust turbine. In a large diesel installation such as a motor ship or rail prime mover, fuel efficiency could therefore increase from to 60%, thus reducing operating costs. In the case of less efficient engines such as those using petrol (gasoline) or liquefied petroleum gas (LPG) the potential efficiency gain is greater.

The present invention therefore addresses these two deficiencies in I.C. engine design and operation. It uses waste heat to drive a steam turbine and it uses exhaust gasses to drive an exhaust turbine. Together they generate mechanical energy to boost engine output. This increases fuel efficiency, reduces operating costs and cuts emissions.

Overview In most engines generated heat is actively and passively dispersed. However in the present invention measures are taken to retain heat wherever feasible because retained heat is heat that can be recovered to do more work. It is basic to the combined cycle engine concept, that necessary cooling of the engine is achieved by maximising heat loss through the latent heat of evaporation and minimising losses through conduction, convection and radiation. To achieve this, engine block temperatures are raised and insulation is provided to selected components where feasible.

The combined cycle engine comprises an internal combustion engine, a heat recovery system, a steam turbine, an exhaust turbine and a coupling device.

Waste heat from the engine is recovered and used to drive a steam turbine, thereby converting some of the energy in the steam into mechanical energy.

Recovered energy is also available from an exhaust turbine and a means is provided to combine mechanical power from the two turbines (above) with that produced by the internal combustion engine. Application of the combined cycle engine to motor vehicles is described later.

3 Description SFigure 1 is a plan diagram showing the main components of the combined cycle engine in exploded form. It shows the relative positions of components and systems in the combined cycle engine. In the following description reference is made to Figure 1.

The combined cycle engine comprises a plurality of components including, Ni 1. a modified internal combustion engine operating at a temperature O elevated above normal, 2. a heat recovery system to recover waste heat generated by the above engine, to form a Rankine cycle whereby generated steam drives a turbine 3. a waste steam condensing system, a reservoir to hold condensate and means to recirculate condensate through the Rankine cycle, 4. an exhaust-driven turbine a means to combine the outputs of components and above, using a multiple input coupling and means to deliver the boosted output to a load.

Operating parameters for the internal combustion engine, steam production processes and turbine function are maintained within specified limits using pumps, valves, sensors and other components.

Eunction-Modifiedinternalcombustionengi ne In the combined cycle engine, the cylinder block and head of the I.C. engine is the primary "boiler" for the Rankine cycle, although vaporisation does not occur here.

The process of heat recovery and steam generation begins in the cylinder block and cylinder head. To facilitate heat recovery engine temperature is elevated above the usual 90-950C to 125C or more. Where the coolant is water, increased pressure is required to maintain coolant in liquid state. Elevated temperature contributes to overall efficiency of the engine in two ways. Firstly it ensures that water exiting the cylinder block and head en route to the steam turbine is provided with as much initial heat energy as possible, consistent with pressure and other operational requirements of the engine. Secondly, within the engine combustion chambers a small improvement in combustion efficiency results because less combustion heat is lost through hotter cylinder walls.

When the engine reaches the specified operating temperature, heated water is discharged into the exhaust heat recovery system comprising successive heat exchangers of various kinds. Water discharged from the engine is replaced.

If required, alternative working fluids and additional heat exchangers are used.

Function- Heat recoverysystem (Rankinecycle) Heat is recovered primarily, but not exclusively from the cylinder block and head and the exhaust system including the exhaust manifold the exhaust turbine and an exhaust gas heat exchanger by the circulation of water through suitable tubes and passages, forming a Rankine cycle. Steam produced during the Rankine cycle is used to drive steam turbine Energy generated by this turbine feeds into the power train via a multiple input coupling.

The water flow sequence constituting the Rankine cycle is shown in Fig.1. Water from coolant tank is delivered under pressure from pump to the cylinder block and cylinder head of the engine. Here flow rates are restricted until engine operating temperatures are reached at which time, heated water is discharged from the cylinder block and head into the water-jacketed exhaust manifold the water- jacketed exhaust turbine and an exhaust gas heat exchanger, collecting heat energy as it does, and cooling the components at the same time. Prior to water discharge from the cylinder block and head, a high pressure is imparted to the water in order to pressurise the exhaust heat recovery system and ultimately the steam turbine nozzles.

Water exits the final heat exchanger as dry steam, travelling then to by-pass valve which directs the steam onto steam turbine Low pressure steam exiting this turbine is conveyed to condenser where heat is lost and a phase change back to water occurs, and it returns to the coolant tank Sensors, valves and other devices regulate flow rates through the combined cycle engine to maintain specified operating temperatures to optimise performance and ensure safe and reliable operation. Heat exchanger(s) and alternative working fluids are used as required.

Function -Exhaust turbine A second turbine (or device of similar function) is driven by the passage of exhaust gasses from the internal combustion engine. This turbine may be similar in design to the turbine component of turbo-chargers. However, in the combined cycle engine, the energy generated by this turbine is fed directly or indirectly into the power train of the combined cycle engine via a multiple input coupling Suitably designed, this turbine can contribute useful supplementary energy over a wide range of engine operating conditions and particularly can make a substantial energy contribution at times of high engine load. The capacity for this turbine to generate additional energy is not restricted by a waste gate valve.

Exhaust turbine functions independently from the above Rankine cycle and steam turbine However it is provided with a water jacket cooled by the passage of steam through the water jacket provided, and therefore supplies heat into the Rankine cycle.

Both turbines, and are mounted on shafts capable of transmitting energy when the turbines rotate. High rotational speeds can be reduced, and torque increased if required, Turbocharging can be provided in other ways if necessary.

Multiple Input Coupling Situations occur where there is a need to combine the mechanical energy generated by several energy producing devices or systems into a common output. In the present invention, an internal combustion engine generates, in addition to mechanical energy, heat and other energies which can be recovered and converted into mechanical energy using turbines. Recovered energy can boost engine output provided there is a means to incorporate the additional energy in ways compatible with engine function, turbine function and the load.

Because there is a lag effect with turbine function, there are potential problems with synchronisation in some applications.

This multiple input coupling is an essential component of the present invention.

It was specifically designed to provide a suitable energy-combining function for the combined cycle engine to meet it's primary objective, namely a substantial gain in fuel efficiency for internal combustion engines over a wide range of applications. This energy-combining function was made possible by employing peripheral drive on the ring gear elements of the planetary gear sets, a device not previously used in this context.

The coupling can accept mechanical energy that is constant in speed and torque while at the same time accepting from several sources, additional mechanical energy that may vary in speed, torque and continuity and deliver boosted power smoothly to a load. As a result, this combined cycle engine can power private motor vehicles, heavy transport vehicles and a wide range of other internal combustion engines, and can deliver maximum boost to engine output at times of greatest load. This feature can reduce fuel consumption.

In the combined cycle engine, the coupling main input accepts mechanical energy from an internal combustion engine the supplementary inputs accept energy from two turbines and and the output is connected with a load The coupling main function is to combine the input energies and transfer the combined energies to the load Gear ratios within the coupling can be selected to suit particular applications and to deliver boosted output either as increased speed or torque.

Description Figure 3 is an elevation and a section illustrating a multiple input coupling, relevent components and their interactions. References in the text of this section refer to figure 3.

The multiple input coupling comprises interacting planetary gear sets and other components enclosed within a suitable housing and supplied with adequate lubrication.

The energy-combining feature of the multiple input coupling results from the interaction of sets of planetary gears and other components, specific elements of which are driven to rotate as a direct result of primary and secondary energy inputs. Of particular note is the employment of peripheral drive on ring gears (R1) and (R2) providing the energy-combining function of the coupling. The combined input energies are transferred to an output shaft to be Sfurther transferred to a load. A multiple input coupling having two planetary gear C sets is described.

Set 1 comprises sun gear (S1) fixed to and driven by the primary energy input, planetary gears planetary gear carrier (PC1), and ring gear In the present application in the combined cycle, sun gear (S1) is fixed to and driven IDby the crankshaft of an internal combustion engine. Set 2 comprises sun gear C (S2) which is integral with and drives an output shaft planetary gears (P2), O planetary gear carrier (PC2), and ring gear Both ring gears (Ri) and (R2) are capable of being independently driven to rotate by peripheral drive from external inputs (T1) and respectively. Planetary gear carriers (PC1) and (PC2) are effectively locked together, and therefore rotate as a single unit. A central shaft maintains alignment of co-axially located components.

To function as designed, ring gear (R1) is restricted to rotate only in the same direction as sun gear while ring gear (R2) can only rotate in the opposite direction. A means is provided to prevent ring gears (R1) and (R2) from rotating in directions other than that intended, which they will tend to do, when subject to torque caused by the combined effects of crankshaft rotation and resistance generated by a load. However, in normal operation in a combined cycle engine, this tendency to counter-rotation will be resisted and reversed by turbine inputs (T1) and (T2).

Function For the purpose of explanation, it is assumed that matching gears within the planetary gear sets have the same diameters. In practice this may not be the case and also the arrangement of gears and gear sets within the coupling housing may differ from that shown and described. However the principles of function remains the same and enable the coupling to deliver increased output shaft speed or torque, resulting from energy inputs from turbines (T1) and Eunctionwithprimary input alone Input at the primary shaft (CS) causes rotation of attached sun gear but with no secondary inputs at (T1) and ring gears (R1) and (R2) do not rotate. Under this condition rotation of sun gear (S1) causes planetary gears (P1) to "walk" around inward facing teeth of ring gear which causes the planetary gear carrier (PC1) to rotate, but at reduced speed, compared to sun gear (S1).

Planetary gear carrier (PC2) being locked to (PC1), rotates at the same speed as (PC1) and causes planetary gears (P2) to "walk" around the inner teeth of ring gear The rotation of planetary gears both around their own axes, and, as a result of being carried circumferentially around the central axis, causes sun gear (S2) and integral output shaft (OS) to rotate at an elevated speed compared to that of planetary gear carrier (PC2).

Under this condition, and provided the sizes of matching gears is the same, (see Function), the step-down ratio (S1) to (PC1) is the same as the later stepup ratio (PC2) to so the output shaft (OS) will rotate at the same speed as the primary input shaft.

In the context of a combined cycle or hybrid engine, this is likely to occur only at idle and low throttle settings, when the internal combustion engine is producing no recoverable waste heat or other energy so no energy input is available at (T1) and (T2).

Eunctionwithprimary andsecondary inputs At higher throttle settings, with input at the primary shaft (CS) and with sufficient energy input at ring gear will be driven peripherally to rotate. For the purposes of explanation, in a hypothetical situation unlikely to occur in practice, it is assumed that ring gear (R1) is driven to rotate at primary input shaft speed.

In this case, planetary gears (P1) will not rotate on their own axes, and as a result, planetary gear carrier (PC1) will rotate at the same speed as both the primary input shaft with attached sun gear and ring gear (RI).

Under this condition there is no first stage step-down in speed. Planetary gear carrier (PC2), because it is effectively fixed to (PC1) rotates much faster than previously, hence it's planetary gears (P2) which engage the stationary ring gear are also driven to rotate on their axes much faster than previously.

The combined effects of these elevated rotational speeds is to cause sun gear (S2) and integral output shaft (OS) to now rotate substantially faster than primary input shaft.

Assume now that input at (T2) causes ring gear (R2) to rotate. This motion, in the opposite direction to that of planetary gear carrier (PC2), causes planetary gears (P2) to rotate still faster on their axes, resulting in a further increase in rotational speed of sun gear (S2) and integral output shaft (OS).

In this way, inputs at (T1) and (T2) that peripherally drive ring gears (R1) and/or (R2) to rotate, are capable of increasing the rotational speed of output shaft relative to the primary input shaft while maintaining the torque of the input shaft except for frictional and associated losses. Alternatively, different gearing within the coupling, can boost torque instead of rotational speed.

Specificapplication-Motor Vehicles Figure 2 shows modifications likely to be necessary in motor vehicles.

Where the combined cycle engine is used in motor vehicles, the multiple input coupling component will usually be additional to the normal transmission.

Because the coupling is located between the driving end of the crankshaft, and the load, the coupling housing will attach to the driving end of the crankcase, replacing the clutch/torque-converter housing, which is relocated to the output side of the coupling. From this point, boosted power is supplied to the transmission in a conventional way.

The need for suitable gearing on the driving end of the crankshaft to feed power directly into the multiple input coupling (and other considerations) may require relocating the flywheel, attached starter ring gear and starter motor to the opposing end of the crankshaft (Fig. 2).

The above preferred embodiment does not, however, preclude the possibility of incorporating the essential functions of the multiple input coupling into the vehicle's transmission.

Combined cycleengine features Feature 1. The combined cycle engine (as a whole concept) The Combined Cycle Engine is a new combination of the following components, some of which also claim aspects of novelty of method, function or design; 1. a modified internal combustion engine, having operating temperatures significantly elevated above conventional engine operating temperatures, 2. a means to recover waste heat from the above engine, to generate steam to form a Rankine Cycle and to drive a steam turbine to produce useful mechanical or other energy, 3. an exhaust turbine driven by the passage of exhaust gasses produced by the above engine, to provide useful mechanical or other energy, 4. A means to combine the energy outputs of and using a Multiple Input Coupling (see Feature 2 below), having a primary input and two (or more) supplementary inputs, and a single output.

A review of related literature has failed to reveal any combination of separate elements, concepts and methods that closely match those of the Combined Cycle Engine as presently described.

Feature_2._Multiplel nput _Coupling The multiple input coupling was specifically designed as an integral part of the combined cycle engine. It's function is to enable the power output of a primary source (an internal combustion engine), to be boosted by combination with power from supplementary sources (in this case a steam turbine and an exhaust turbine), when power from these sources is available. This function is a necessary requirement to achieve the main objective of the Combined Cycle Engine, namely to provide a way to obtain substantial fuel efficiency gains for internal combustion engines.

The coupling provides a new capacity to combine a main or primary mechanical energy input with a plurality of secondary energy inputs and to transfer the combined energies to a load in a way compatible with many internal combustion engine applications.This function of the coupling was obtained by employing peripheral drive on the outer periphery of one or more ring gears within the planetary qear sets, a method not seen in reviewinq related literature.