Working - Fluid Injector for a Piston Steam Engine

Abstract

An injector for injecting the working fluid of a piston vapour-engine. It incorporates an injector nozzle with injector nozzle-needle, needle actuating plunger and a solenoid controlled valve. It is characterised by the working fluid being supplied continuously to a working-fluid reservoir (4), while fluid for servocontrol purposes is supplied continuously to a servo-fluid reservoir (10). The injector nozzle-needle (1) is connected to the plunger (2) which passes through the working-fluid reservoir (4) and also through the servo-fluid reservoir (10). The top of the plunger (2) is capped by a plunger pressure-face (6), which is located in the servo-control chamber (11). The servo-control chamber (11) is connected by means of a feed-orifice (12) to the servo-fluid reservoir (10). The plunger (2) has a pressure-shoulder (7) located in the servo-fluid reservoir (10). The servo-control chamber (11) is connected by means of a bleed-orifice (15) to the bleed-valve (13), which releases the servo-fluid to the spill chamber (21).

Description

BRIEF DESCRIPTION OF DRAWINGS

The injector of the working-fluid of the piston steam engine according to the invention is represented in its best form in the attached drawing, in which

FIG. 1 represents the injector in sectional schematic form and

FIG. 2 represents a timing diagram showing start and duration of injection of working-fluid, in this case hot water, into the flash-chamber.

BEST MODE FOR CARRYING OUT THE INVENTION

The injector, according to the invention, incorporates in its lower part a nozzle 3 and an injector nozzle-needle 1, which is sealed against the seat of the injector nozzle 3 by a plunger spring 8. The injector nozzle-needle is connected to the plunger 2 by means of a special knuckle joint, which allows for small misalignments of the injector nozzle-needle 1 and plunger 2 caused by thermal expansion of the hot materials during operation. The plunger 2 of the injector located in the injector body passes through the hot water (working-fluid) reservoir 4, the upper part of the injector body in which it is sealed by hot water seal 19 and also through the cold water (servo-fluid) reservoir 10. At its top end, the plunger 2 is capped by a pressure-face 6 whilst below the pressure-face 6 the plunger has a collar 7 forming a pressure-shoulder located within the cold water reservoir 10. The cold water reservoir 10 is connected to the control chamber 11 of the servo-system by means of a calibrated feed-orifice 12 located above the plunger pressure-face 6 of the control chamber 11. The control chamber 11 is connected at the top of the injector by a calibrated bleed-orifice 15 with a bleed-valve 13 the needle of which is controlled by a solenoid 14. The outflow of the bleed-valve 13 spills into the spill-chamber 21 connected by spill-connector 16, which returns used servo spill-water to a cold water tank. Temperature and pressure sensors 18 are located in the hot water reservoir 4 and these continuously monitor temperature and pressure in the hot water reservoir. A nozzle-needle 1 position-sensor 17 is located in the cold water reservoir 10. The nozzle-needle position-sensor 17 comprises a permanently fixed coil and an armature fixed to the plunger 2. Movements of the plunger 2 are detected as changes in magnetic field in the coil 17 of the sensor. Outputs from the temperature and pressure sensors 18 and the position sensor 17 of the injector nozzle-needle 1 are sent to an electronic control unit (ECU) with the objective of optimising the operation of the engine.

Hot water under pressure continuously supplies the hot water reservoir 4 through connection 5 with the objective of replacing injected water and maintaining pressure within the reservoir at a level sufficient to prevent vaporisation of the water.

Axial movements of the plunger 2 and the nozzle needle 1 of the injector are induced by means of differential hydraulic pressure acting on the plunger pressure face 6 of the plunger 2 and on the pressure shoulder 7 of the plunger 2 in combination with spring pressure of the plunger spring 8. The servomechanism by which this takes place comprises of cold pressurised water connector 9, which supplies the cold water (servo-fluid) reservoir 10. The cold water reservoir 10 feeds the control chamber 11 of the servomechanism through the feed-orifice 12. When the bleed-valve 13, controlled by the solenoid 14 is closed, pressure in the control chamber 11 of the servo mechanism is close to or equal to the pressure in the cold water reservoir 10 and the pressure on the pressure-face 6 of the plunger 2 is equal to the pressure on the pressure-shoulder 7 of the plunger 2. When the bleed-valve 13 is open, the control chamber 11 of the servomechanism releases water through the bleed-orifice 15.

The feed-orifice 12, as well as the bleed orifice 15, are so calibrated that the outflow of cold water through the bleed-orifice 15, is greater than the inflow of water through the feed-orifice 12. This is the reason for the fall in water pressure in the control chamber 11 of the servo mechanism, and this in turn lowers the pressure on the pressure face 6 of the plunger 2 which causes the movement of the plunger 2 together with the nozzle-needle 1 of the nozzle 3 of the injector and the opening of the nozzle 3 of the injector. Each time the nozzle 3 is opened a metered quantity of pressurised water is released from the hot water reservoir 4 and this water is injected into the flash-chamber or directly into the working cylinder in the form of highly atomised droplets. Water released through the bleed-valve 13 is led away to a cold water tank by means of the spill connector 16.

The start point of injection or series of injections is measured in relation to the top dead centre (TDC) of the piston and may vary between 20 degrees before top dead centre (TDC) to 10 degrees after top dead centre (TDC). The duration of injection or series of injections is measured in degrees of crankshaft angular displacement and may vary between 0 degrees to a maximum of 160 degrees. The actual start point and duration change in accordance with power demand and torque requirements of the engine.

The injector is fitted with temperature and pressure sensors 18, which continuously monitor conditions in the hot water reservoir 4, and also a nozzle-needle 1 position-sensor 17 which comprises a fixed stationary coil and an armature fixed to the plunger 2. Movements of the plunger are, by this means, detected as changes in magnetic field in the coil of the sensor 17. Outputs of these sensors are fed to the electronic control unit (ECU) in order to optimise the operation of the engine.

The plunger 2, connected to the nozzle-needle 1 of the nozzle 3 of the injector passes through three sectors of the injector: hot water reservoir 4, cold water reservoir 10 and the control chamber 11 of the servo mechanism. The hot water seal 19 and cold water seal 20 provide effective isolation between these three sectors.

The flow of cold water, apart from supplying the servomechanism also protects the hot water seal 19 from high temperatures in the adjacent hot water reservoir 4. This is achieved by appropriate location of the seal 19. The cold water also acts as a cooling medium for the electrical elements (needle position sensor coil 17 and also the solenoid 14 located in the injector and protects them from the hot external elements which surround the injector.

The operation of the injector may be divided into five phases:

1. Engine not operating—injector is closed: since the engine is not operating, the water pump is not operating and therefore no hydraulic pressure exists within the system. The only pressure source operating on elements of the injector is the pressure of the plunger spring 8 and the pressure of the solenoid spring 22.

2. Engine operating—injector is closed: since the engine is operating, the water pump is supplying hot pressurised water to the hot water reservoir 4 and pressurised cold water to the cold water reservoir 10. The solenoid is not activated, therefore the bleed valve 13 closes off the bleed orifice 15. At this time the pressure in the servo control chamber 11 is close to equal the pressure in the cold water reservoir 10. Pressure exerted on the pressure-face 6 of the plunger 2, together with the pressure exerted by the plunger spring 8 on the plunger 2 overcomes the pressure exerted on the pressure-shoulder 7 and keeps the nozzle 3 closed. Nozzle 3 therefore remains closed.

3. Engine operating—injector opening—start of injection: the solenoid 14 is supplied with high initial current from the electronic control unit (ECU), which ensures that the force developed by the solenoid 14 overcomes the force of the solenoid spring 22 and the bleed valve opens immediately. The high initial current is reduced almost immediately to a level sufficient for the solenoid 14 to hold the armature. Such a reduction in current is made possible by the fact that after activation, the solenoid's magnetic air-gap is considerably smaller. When the bleed-orifice 15 is open, cold water flows from the control chamber 11 via the bleed-valve into the overspill chamber 21 and from there via the spill connector 16 to return to the water (servo-fluid) tank. The opening of the bleed-orifice 15 causes the pressure in the servo control chamber 11 to fall below the pressure exerted on the pressure-shoulder 7 of the plunger 2. The differential pressure between the pressure-face 6 of the plunger 2 and the pressure-shoulder 7 of the plunger 2 is sufficient to overcome the pressure exerted by the plunger spring 8 of the plunger 2. Injector nozzle-needle 1 of the nozzle 3 opens and injection of hot water into the working cylinder or flash chamber begins.

4. Engine operating—injector is fully open: Speed of opening of the injector nozzle 3 is controlled by the difference between the flows through the bleed orifice 15 and the feed-orifice 12. The plunger 2 of the injector moves upwards until stopped by a cushion of water, which is, formed by the flow between the bleed-orifice 15 and the feed-orifice 12. The nozzle 3 of the injector is now completely opened and hot water is injected into the flash-chamber or working cylinder at a pressure close to the pressure in the hot water reservoir 4 and in the hot water supply system.

5. Engine operating—injector closed—end of injection: As soon as electric current ceases to flow through the solenoid 14, the solenoid spring 22 causes the bleed valve nozzle-needle 23 of the bleed-valve 13 to move downwards, the bleed-valve 13 closes the bleed-orifice 15. The closing of the bleed-orifice 15 causes an increase in pressure in the servo-control chamber 11 resulting from an inflow of water from the cold water reservoir 10 via the feed-orifice 12. When the pressure in the servo control chamber 11 again rises to a level sufficient to overcome the sum total of the opposing forces acting on plunger 2 (from plunger spring 8 of plunger 2 and hydraulic pressure acting on the pressure shoulder 7 of plunger 2), the injector nozzle-needle 1 of the nozzle 3 of the injector closes and injection ends.

INDUSTRIAL APPLICABILITY

The injector of working-fluid for piston steam engines, according to the invention, has industrial applications in external combustion piston steam engines—in particular in piston steam engines intended for powering land vehicles, marine vessels and aircraft, as well as piston steam engines intended to power machines—self-powered, portable and stationary.

Claims

1. An injector for the working-fluid of a piston vapour-engine, intended particularly for high efficiency flash-steam piston engines incorporating an injector nozzle with injector nozzle-needle, plunger controlling the nozzle-needle and a solenoid controlling a valve, said is characterised by: working-fluid under high pressure and at a high temperature being supplied in a continuous manner to a working-fluid reservoir (4) while servo-fluid is supplied in a continuous manner to servo-fluid reservoir (10), while injector nozzle-needle (1) closes nozzle (3) of the injector is connected with a plunger (2) which passes through working-fluid reservoir (4) as well as servo-fluid reservoir (10) and is capped by a pressure-face (6) located in servo-control chamber (11) which is connected by a feed-orifice (12) to servo-fluid reservoir (10), also the plunger (2) has a pressure-shoulder (7) located in the servo-fluid reservoir (10) and the servo-control chamber (11) is connected by a bleed-orifice (15) to bleed-valve (13) which leads away servo-fluid to spill-chamber (21) connected to servo-fluid spill connector.

2. An injector according to claim 1 in which the start of injection of working fluid into the flash-chamber or working-cylinder is initiated by the difference in hydraulic pressure between the servo control chamber (11) and that in the servo-fluid reservoir (10).

3. Injector according to claim 2 in which the difference in hydraulic pressure between the servo control chamber (11) and servo-fluid reservoir (10) is caused by the closing or opening of a bleed-valve (13) which connects the bleed-orifice (15) with the spill chamber (21) connected by spill connector (16) to the servo-fluid tank (not shown).

4. Injector according to claim 2 or claim 3 where bleed-valve (13), connects bleed orifice (15) with spill chamber (21) via bleed valve nozzle-needle (23) of the bleed valve (13) which is controlled by solenoid (14),

5. Injector according to claims 1 or 2 or 3 or 4 characterised by having temperature and pressure sensors (18) located in the working-fluid reservoir (4).

6. Injector according to claims 1 or 2 or 3 or 4 characterised by having a position sensor (17) for the injector nozzle-needle (1).

7. Injector according to claim 6 characterised by the position sensor (17) of the injector nozzle-needle (1) being located in the servo-fluid reservoir (10).

8. Injector according to claims 1 or 2 or 3 or 4 or 5 or 6 or 7 characterised by outputs from the temperature and pressure sensors (18) and injector nozzle-needle (1) position-sensor (17) being fed to an electronic control unit (ECU) which controls the operation of the engine.

9. Injector according to claim 8 characterised by the electronic control unit (ECU) sending control signals to the solenoid (14).

10. Injector according to claim 9 characterised by the electronic control unit (ECU) regulating the timing of start of injection or series of injections of working-fluid in the range 20 degrees before top dead centre (TDC) to 10 degrees after top dead centre (TDC) of the engine's working piston.

11. Injector according to claim 9 characterised by the electronic control unit (ECU) regulating the duration of injection or series of injections of working-fluid within the range 0 degrees to 160 degrees of crankshaft angular displacement.

12. Injector according to claim 1 characterised by the plunger (2) being sealed in the body of the injector by the working-fluid seal (19) located in the central part of the body of the injector below the servo-fluid reservoir (10).

13. Injector according to claim 1 characterised by the plunger (2) being sealed in the body of the injector by the servo-fluid seal (20) located in the upper part of the injector body between the upper part of the plunger (2) and the upper body of the injector.