GB1567946A - Pressure intensifying device for supplying liquid fuel under pressure to a combustion chamber - Google Patents

Description

(54) A PRESSURE INTENSIFYING DEVICE FOR SUPPLYING LIQUID FUEL UNDER PRESSURE TO A COMBUSTION CHAMBER (71) We, NOEL PENNY TURBINES LIMITED, a British Company, of Siskin Drive, Toll Bar End, Coventry, West Midlands, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a pressure intensifying device for supplying liquid fuel under pressure to a combustion chamber.

In a fuel injection, internal combustion engine or in any other engine, boiler or heater where liquid fuel is to be injected into a combustion chamber through a nozzle under high pressure, it has hitherto been necessary to provide a fuel pump or equivalent source of high pressure fuel capable of discharging fuel at the required pressure and time and piping between the fuel pump or equivalent source and the nozzle capable of wlthstanding the pressure involved. An object of the invention is to provide a pressure intensifying device which is capable of supplying fuel intermittently to a fuel nozzle at a high pressure but which only requires a fuel supply at a comparatively low pressure.

According to the invention, a pressure intensifying device for use with a combustion chamber and to supply liquid fuel under pressure to the combustion chamber comprises a first piston means movable in a first cylinder and arranged to be subjected, in use, at one end face thereof adjacent one end of the first cylinder to the internal pressure of the combustion chamber, the first cylinder having an inlet thereto controlled by a non-return valve for the admission into the first cylinder of a low pressure fluid to be applied to an end face of said first piston means remote from said one end face thereof and a valve-controllable outlet for the removal from the first cylinder of said low pressure fluid, and a second piston means of smaller effective area than said first piston means and movable in a second cylinder having an inlet thereto controlled by a non-return valve through which liquid fuel is introduced into said second cylinder, in use, at a low pressure and an outlet leading to a spray orifice controlled by a pressure-openable valve, said spray orifice communicating, in use, with the combustion chamber, the pressure-openable valve being movable relatively to said first and second piston means, and the two piston means being so arranged that movement of said first piston means will effect corresponding movement of said second piston means, whereby, in use, on opening of the valvecontrollable outlet from said first cylinder, the internal pressure in the combustion chamber will effect displacement of said piston means, which will thereby effect corresponding displacement of said second piston means and hence increase the pressure of fuel in said second cylinder, the increase in the pressure of fuel moving the pressure-openable valve to open said spray orifice to permit fuel within said second cylinder to be discharged therefrom through said spray orifice into the combustion chamber, and, on closing of the valvecontrollable outlet from said first cylinder, the discharge of fuel from said second cylinder will cease, whereby the internal pressure in the combustion chamber will fall sufficiently to permit said first and second piston means to return to their initial positions and the pressure-openable valve to move relatively to said first and second piston means to close said spray orifice, low pressure fluid and low pressure fuel being admitted to said first and second cylinders respectively during the return movement of said first and second piston means.

The arrangement of the device allows the increase in the pressure of fuel in said second cylinder to be a multiple, approximating to the ratio of the area of said one end face of said first piston means to the area of an end face of said second piston means adjacent said fuel inlet in said second cylinder, of the pressure in the combustion chamber.

Conveniently, but not necessarily, the low pressure fluid applied to said first piston means is liquid fuel from the same supply as that introduced to said second cylinder.

Conveniently, said first and second piston means are portions of different effective areas of a single differential piston, each portion being movable in a respective cylinder portion, constituting respectively said first and second cylinders, of a housing containing the differential piston.

Preferably the fuel discharged from said second cylinder passes through the differential piston to a chamber therewithin containing the pressure-openable valve which is moved relatively to said first and second piston means by the increase in the pressure of fuel discharged through the differential piston to the chamber therein to open said spray orifice, said spray orifice being provided in the portion of the differential piston constituting the said first piston means and communicating through a duct in said first piston means with the chamber in the piston.

The pressure-openable valve is conveniently a needle valve mounted in the chamber in the piston and urged by spring means into engagement with a seat formed in the chamber in the piston to close the duct leading to said spray orifice. The needle valve may have a hollow stem which is slidable in the differential piston and forms a throughway leading from said second cylinder to the chamber in the piston.

By way of example an embodiment of a pressure intensifying device in accordance with the invention and incorporating a fuel nozzle is now described with reference to the accompanying drawings, in which: Figure I is a section through the device at the beginning of a liquid fuel injection period; Figure 2 is a similar section at the end of a liquid fuel injection period; Figure 3 is a typical liquid fuel system including the device shown in Figures 1 and 2, and Figure 4 is an alternative liquid fuel system including the device shown in Figures 1 and 2.

Referring first to Figures 1 and 2 the device comprises a tubular housing 1 defining a cylinder in which the larger diameter portion 2A of a differential piston is slidable. The housing 1 is closed at one end by a block 3 having a spigot portion which is screwed into the end of the housing 1 at 4.

The spigot portion of the block 3 defines a cylinder 5 in which the smaller diameter portion 2B of the differential piston is slidable. The other end of the housing 1 contains a tubular insert 7 screwed into the end of the housing 1 and is open to the interior of a combustion chamber at 6. The differential piston carries an end cap 8 constituting a fuel nozzle containing fuel spray orifices 9 and is urged to the position shown in Figure 1 in which the end cap 8 is held in engagement with an end flange on the insert 7 by a helical spring 10 acting between the block 3 and the piston portion 2A. The end cap 8 of the piston portion 2A has an internal chamber 11 therein in which a needle valve 12 is slidable and is engageable with a seat 13 formed in the chamber 11 communicating through a duct 13A with the spray orifices 9.The needle valve 12 has a stem 14 which is slidable within an axial throughway in the differential piston. The stem 14 is urged into the position in which the needle valve 12 engages the seat 13 by a collar 15 engaging a shoulder on the stem 14 and a spring 16 acting between a flange on the collar 15 and the differential piston. The chamber 11 communicates through a throughway 17 in the stem 14 with the cylinder 5. Thus when the needle valve 12 is moved away from the seat 13 as will be hereinafter explained, liquid fuel will flow from the cylinder 5 to the spray orifices 9 but when the needle valve 12 engages the seat 13, flow of liquid fuel to the spray orifices 9 is prevented, similarly to a fuel injector of the kind normally used in compression-ignition engines.

The block 3 contains a fuel inlet 18 which admits liquid fuel at a low pressure to a duct 19 leading to a portion 23 of the cylinder defined by the housing 1 at the side of the piston portion 2A remote from the combustion chamber and to a duct 20 leading to the cylinder 5. Return flow through the ducts 19 and 20 is prevented by non-return ball valves 21 and 22 respectively. The cylinder portion 23 is supplied with low pressure liquid fuel flowing past the ball valve 21 from the duct 19 and also communicates with a fuel return or bleed outlet 24 provided in the housing 1.

As the piston portion 2A is subjected to the pressure within the combustion chamber at 6, there should be no leakage between the piston portion and the surrounding cylinder wall formed by the housing 1. The working clearance should therefore be as small as possible or sealing devices such as a rollsock or piston rings should be provided. In the example illustrated in Figures 1 and 2 a roll-sock 40 is provided. The roll-sock 40 is accommodated in an annular space provided partly by an annular recess 41 in the peripheral wall of the piston portion 2A and partly by an annular recess 42 in the adjacent peripheral wall of the housing 1.

The axial lengths of the two annular recesses are equal and so are their radial depths. This results in there being a constant volume in the annular space which is unoccupied by the roll-sock 40 whatever the relative positions of the piston and the housing 1.

Assuming that the piston moves through a distance 2L between its extreme positions shown respectively in Figures 1 and 2, the curved end of the roll-sock will move through a distance L and so the two recesses 41, 42 of the annular space unoccupied by the roll-sock 40 will always have a combined total length L and therefore have a substantially constant volume as the radial depth of each annular recess 41 and 42 is small compared with the radius of the piston portion 2A. This means therefore that the annular recesses 41 and 42 do not have to be vented to permit movement of the piston and rolling of the roll-sock 40.

Referring now to Figure 3, the device shown in Figures 1 and 2 is indicated by the references 1 and 3. A low pressure fuel inlet pipe 25 communicates with the fuel inlet 18 and is supplied by a low pressure fuel pump 26 (e.g., a gear pump) which receives liquid fuel through a supply pipe 27 from a fuel tank 28. The bleed outlet 24 communicates with a bleed valve 29 which, when open, allows liquid fuel to return through a pipe 30 to the fuel tank 28. The bleed valve is shown in Figure 3 in its closed position and may be of any suitable form and operate in any convenient way. In Figure 3, the valve 29 is shown as a simple piston valve arranged to be opened by a solenoid actuator 31 by an electrical control circuit 32 including contacts 33 arranged to be opened and closed periodically.In the case where the fuel injection valve is to be used in a fuel injection engine, the contacts 33 would be opened and closed by an engine-driven timing device 34.

Assuming that the differential piston is initially in the position shown in Figure 1 and the bleed valve 29 is closed, liquid fuel will have filled the cylinder portion 23, the cylinder 5 and the chamber 11 and the spring 10 will have returned the differential piston to the position shown in Figure 1 and the needle valve will have been moved to its closed position by the spring 16. The pressure intensifying device is ready to commence spraying liquid fuel immediately the bleed valve 29 is opened. When the bleed valve 29 is opened in response to an electro-mechanical, electronic, hydraulic, pneumatic or other signal, the pressure at 6 within the combustion chamber will displace the differential piston to the left, as viewed in Figure 1, and the spring 10 will be compressed.This movement of the differential piston will start to increase the pressure of the liquid fuel within the cylinder 5 in the ratio of the effective areas of the piston portions 2A and 2B. Thus if the pressure within the combustion chamber at 6 is P and the diameters of the two piston portions are, for example, in the ratio of 3:1, the pressure in the cylinder 5 will be 9P. The effective area on which the liquid fuel pressure in the chamber 11 acts on the needle valve 12 is designed to be greater than the effective area at the end 43 of the needle valve stem 14 and thus as the pressure of the liquid fuel in the cylinder 5 increases so the resultant fluid force on the needle valve in opposition to the spring force 16 will increase.When the resultant fluid force on the needle valve exceeds the spring force 16, the needle valve will open and spraying will commence of liquid fuel at substantially the high pressure within the cylinder 5. When the differential piston has been moved to the left toward or fully into the position shown in Figure 2 in which the portion 2A abuts the adjacent end of the block 3, spraying will cease because the entrance to throughway 17 will become closed and the needle valve will also be closed by the spring 16. The distance the differential piston moves to the left is determined by the timing of the movement of the bleed valve 29 in accordance with the quantity of liquid fuel required according to the operating conditions of the engine.

When the bleed valve 29 is closed, liquid fuel at low pressure introduced through the fuel inlet 18 will then refill the cylinder portion 23 and the cylinder 5 and the differential piston will be returned to the initial position shown in Figure 1 and be held in that position by the spring force 10.

The pressure intensifying device will then be ready to inject a fresh supply of liquid fuel when the bleed valve 29 is opened again and permits low pressure liquid fuel to be displaced from the cylinder portion 23 by the differential piston being displaced under the pressure in the combustion chamber at 6.

Where the pump 26 is provided with a return flow by-pass controlled by a pressurerelief valve responsive to pressure downstream of the valve in the pipe 25, the return pipe 30 would not be required. Instead, the valve 29 would connect the fuel inlet and the bleed outlet 24 together and liquid fuel would be returned to the fuel tank 28 through the pipes 25 and 27 using a fuelrelief valve 45 and by-pass 46 around the pump 26. This arrangement is shown in Figure 4. A similar result could be obtained by using a diaphragm pump in place of the gear pump 26 illustrated in Figure 4.

The device described and shown in Figures 1 and 2 therefore enables liquid fuel to be introduced into the combustion chamber at a high pressure produced by the device without the need for a high pressure fuel pump. Furthermore as the fuel nozzle itself is formed in the end cap 8 of the larger diameter portion 2A of the differential piston, no high pressure ducting leading to the fuel nozzle is required. However it would be possible for the fuel nozzle to be mounted elsewhere in the combustion chamber provided suitable ducting or a passageway is provided between the cylinder 5 and a pressure-openable, non-return valve leading to the fuel orifice.

Although the fluid used for controlling the movement of the differential piston, that is the fluid admitted to the cylinder portion 23, is low pressure liquid fuel provided from the same source as the low pressure liquid fuel admitted initially to the cylinder 5 for pressure intensification, a separate control fluid may be provided.

WHAT WE CLAIM IS: 1. A pressure intensifying device for use with a combustion chamber and to supply liquid fuel under pressure to the combustion chamber, the device comprising a first piston means movable in a first cylinder and arranged to be subjected, in use, at one end face thereof adjacent one end of the first cylinder to the internal pressure of the combustion chamber, the first cylinder having an inlet thereto controlled by a nonreturn valve for the admission into the first cylinder of a low pressure fluid to be applied to an end face of said piston means remote from said one end face thereof and a valve-controllable outlet for the removal from the first cylinder of said low pressure fluid, and a second piston means of smaller effective area than said first piston means and movable in a second cylinder having an inlet thereto controlled by a non-return valve through which liquid fuel is introduced into said second cylinder, in use, at a low pressure and an outlet leading to a spray orifice controlled by a pressure-openable valve, said spray orifice communicating, in use, with the combustion chamber, the pressure-openable valve being movable relatively to said first and second piston means, and the two piston means being so arranged that movement of said first piston means will effect corresponding movement of said second piston means. whereby, in use, on opening of the valve-controllable outlet from said first cylinder. the internal pressure in the combustion chamber will effect displacement of said first piston means, which will thereby effect corresponding displacement of said second piston means and hence increase the pressure of fuel in said second cylinder, the increase in the pressure of fuel moving the pressure openable valve to open said spray orifice to permit fuel within said second cylinder to be discharged therefrom through said spray orifice into the combustion chamber, and, on closing of the valve-controllable outlet from said first cylinder, the discharge of fuel from said second cylinder will cease, whereby the internal pressure in the combustion chamber will fall sufficiently to permit said first and second piston means to return to their initial positions and the pressureopenable valve to move relatively to said first and second piston means to close said spray orifice, low pressure fluid and low pressure fuel being admitted to said first and second cylinders respectively during the return movement of said first and second piston means.

2. A device as claimed in Claim 1 in which the low pressure fluid applied to said first piston means is liquid fuel from the same supply as that introduced to said second cylinder.

3. A device as claimed in Claim 1 or 2 in which said first and second piston means are portions of different effective areas of a single differential piston, each portion being movable in a respective cylinder portion, constituting respectively said first and second cylinders, of a housing containing the differential piston.

4. A device as claimed in Claim 3 in which the fuel discharged from said second cylinder passes through the differential piston to a chamber therewithin containing the pressure-openable valve which is moved relatively to said first and second piston means by the increase in the pressure of fuel discharged through the differential piston to the chamber therein to open said spray orifice, said spray orifice being provided in the portion of the differential piston constituting the said first piston means and communicating through a duct in said first piston means with the chamber in the piston.

5. A device as claimed in Claim 4 in which the pressure-openable valve is a needle valve mounted in the chamber in the piston and urged by spring means into engagement with a seat formed in the chamber in the piston to close the duct leading to said spray orifice.

6. A device as claimed in Claim 5 in which the needle valve has a hollow stem which is slidable in the differential piston and forms a throughway leading from said second cylinder to the chamber in the piston.

7. A device as claimed in any one of Claims 3-6 in which the portion of the piston constituting said first piston means is slidably sealed in the respective cylinder portion of the housing by a roll-sock having its annular ends secured to the piston and the housing respectively, an annular space being provided partly by an annular recess in the outer peripheral wall of the piston portion and partly by an annular recess in the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. without the need for a high pressure fuel pump. Furthermore as the fuel nozzle itself is formed in the end cap 8 of the larger diameter portion 2A of the differential piston, no high pressure ducting leading to the fuel nozzle is required. However it would be possible for the fuel nozzle to be mounted elsewhere in the combustion chamber provided suitable ducting or a passageway is provided between the cylinder 5 and a pressure-openable, non-return valve leading to the fuel orifice. Although the fluid used for controlling the movement of the differential piston, that is the fluid admitted to the cylinder portion 23, is low pressure liquid fuel provided from the same source as the low pressure liquid fuel admitted initially to the cylinder 5 for pressure intensification, a separate control fluid may be provided. WHAT WE CLAIM IS:

1. A pressure intensifying device for use with a combustion chamber and to supply liquid fuel under pressure to the combustion chamber, the device comprising a first piston means movable in a first cylinder and arranged to be subjected, in use, at one end face thereof adjacent one end of the first cylinder to the internal pressure of the combustion chamber, the first cylinder having an inlet thereto controlled by a nonreturn valve for the admission into the first cylinder of a low pressure fluid to be applied to an end face of said piston means remote from said one end face thereof and a valve-controllable outlet for the removal from the first cylinder of said low pressure fluid, and a second piston means of smaller effective area than said first piston means and movable in a second cylinder having an inlet thereto controlled by a non-return valve through which liquid fuel is introduced into said second cylinder, in use, at a low pressure and an outlet leading to a spray orifice controlled by a pressure-openable valve, said spray orifice communicating, in use, with the combustion chamber, the pressure-openable valve being movable relatively to said first and second piston means, and the two piston means being so arranged that movement of said first piston means will effect corresponding movement of said second piston means. whereby, in use, on opening of the valve-controllable outlet from said first cylinder. the internal pressure in the combustion chamber will effect displacement of said first piston means, which will thereby effect corresponding displacement of said second piston means and hence increase the pressure of fuel in said second cylinder, the increase in the pressure of fuel moving the pressure openable valve to open said spray orifice to permit fuel within said second cylinder to be discharged therefrom through said spray orifice into the combustion chamber, and, on closing of the valve-controllable outlet from said first cylinder, the discharge of fuel from said second cylinder will cease, whereby the internal pressure in the combustion chamber will fall sufficiently to permit said first and second piston means to return to their initial positions and the pressureopenable valve to move relatively to said first and second piston means to close said spray orifice, low pressure fluid and low pressure fuel being admitted to said first and second cylinders respectively during the return movement of said first and second piston means.

2. A device as claimed in Claim 1 in which the low pressure fluid applied to said first piston means is liquid fuel from the same supply as that introduced to said second cylinder.

3. A device as claimed in Claim 1 or 2 in which said first and second piston means are portions of different effective areas of a single differential piston, each portion being movable in a respective cylinder portion, constituting respectively said first and second cylinders, of a housing containing the differential piston.

4. A device as claimed in Claim 3 in which the fuel discharged from said second cylinder passes through the differential piston to a chamber therewithin containing the pressure-openable valve which is moved relatively to said first and second piston means by the increase in the pressure of fuel discharged through the differential piston to the chamber therein to open said spray orifice, said spray orifice being provided in the portion of the differential piston constituting the said first piston means and communicating through a duct in said first piston means with the chamber in the piston.

5. A device as claimed in Claim 4 in which the pressure-openable valve is a needle valve mounted in the chamber in the piston and urged by spring means into engagement with a seat formed in the chamber in the piston to close the duct leading to said spray orifice.

6. A device as claimed in Claim 5 in which the needle valve has a hollow stem which is slidable in the differential piston and forms a throughway leading from said second cylinder to the chamber in the piston.

7. A device as claimed in any one of Claims 3-6 in which the portion of the piston constituting said first piston means is slidably sealed in the respective cylinder portion of the housing by a roll-sock having its annular ends secured to the piston and the housing respectively, an annular space being provided partly by an annular recess in the outer peripheral wall of the piston portion and partly by an annular recess in the

adjacent inner peripheral wall of the housing.

8. A device as claimed in Claim 7 in which the two annular recesses have equal radial depth.

9. A pressure intensifying device incorporating a fuel nozzle constructed and arranged substantially as described herein and shown in Figures 1 and 2 of the accompanying drawings.

10. A fuel system incorporating the pressure intensifying device according to Claim 9 and substantially as described herein with reference to Figure 3 or Figure 4 of the accompanying drawings.