Generation Of Hot Vapor

Abstract

A method of and apparatus for generating a hot vapor at high pressure, wherein primary water is sprayed into air during compression thereof and the compressed air with the entrained water as superheated steam is delivered into a combustion chamber where fuel is injected and burned continuously, a secondary water supply being sprayed simultaneously into the combustion chamber and at a rate which determines the temperature of the efflux from said chamber.

Description

This invention is concerned with the generation of hot vapor at high pressure, one use of such vapor being for the actuation of expansion motors. In this instance, the vapor generator and an expansion motor together constitute a prime mover, the vapor generator being analogous to the evaporator (boiler) in a conventional steam powerplant.

In powerplants used for propulsion of road vehicles, the demand for power fluctuates rapidly and frequently, but contemporary steam powerplants have considerable inherent thermal inertia and in order that they may comply adequately with sudden demands for power, they must include, as a reservoir of energy, a suitable volume of steam stored under pressure. Thus the volume of the pressure or storage vessel is a function of the thermal inertia of the evaporator.

In contemporary steam powerplants, even those of the lowest thermal inertia, the amount of energy which must be stored in this manner is unacceptable for a road vehicle, (a) because of the bulk of the associated pressure vessel, (b) because of the excessive time required to develop working pressure in the system from a cold start, and (c) because, with captive energy in this form, there is always the risk of its violent escape in the event of damage to the pressure vessel, as might occur in a collision of vehicles.

In conventional evaporators there is a metal barrier between the heat source at low pressure and the water at high pressure. The thermal inertia of this metal barrier is the major cause of the slow response of such evaporators to change of demand, in either direction, for steam. The faster the boiler is required to generate steam, the greater becomes the temperature drop between the heat source and the steam.

The present invention provides an improved method of and means for generating hot vapor at high pressure without the interposition of a barrier between the heat source and the water thereby achieving minimal thermal inertia.

According to the invention there is provided a method of generating hot vapor under pressure which comprises compressing air and delivering it into a combustion chamber, injecting fuel into said chamber and burning it therein, and spraying water into said chamber during the combustion of the fuel whereby there is discharged from the combustion chamber a hot vapor consisting of a mixture of steam, products of combustion and uncombined air, the water being metered into said chamber at a rate such as to control or determine the temperature at which the generated vapor leaves the chamber.

Preferably, a single stage air compressor is used and water in a finely atomized spray is also injected into the compressor cylinder during the compression of air therein whereby a mixture of compressed air and superheated steam is delivered to the combustion chamber. The latter chamber may be relatively small because of the high density of the mixture, the fuel being sprayed by an injector at a rate compatible with the mass flow of air so that the air/fuel ratio exceeds stoichiometric, initial ignition being provided by a glow plug or the equivalent. The hot vapor produced in this manner is free of hydrocarbons, carbon monoxide, oxides of nitrogen and other pollutants in any objectionable concentration, and it is not necessary to use leaded fuels since combustion is continuous and at a constant pressure.

The invention also provides an apparatus or generator for carrying out the improved process, such apparatus comprising a compressor operable to deliver compressed air to a combustion chamber, primary pump and injector means for introducing water into the compressor cylinder, means for injecting fuel into the combustion chamber, means for initiating ignition of the injected fuel, secondary pump and injector means for introducing an additional water supply to the combustion chamber, and means for metering the secondary water supply to control the outlet temperature of the efflux from said combustion chamber, part of the efflux from said combustion chamber being used to actuate an expansion motor used to drive the compressor.

The expansion motor for driving the compressor will be referred to hereinafter as the "auxiliary" expansion motor in order to distinguish it from such other expansion motor or motors as might be served by the external output of the hot vapor generator.

Modulation of the external output is effected by changing the speed at which the compressor is driven by the auxiliary expansion motor. This speed change is made through the medium of any one of the known suitable speed governing devices which regulates the flow of hot vapor to the auxiliary expansion motor, the governor speeder control being actuated by a pressure-responsive servomechanism whereby, between prescribed high and low limits of system pressure, known as the "control range," the governor holds compressor speed at minimum or "idle" speed when system pressure is at its high limit and at maximum permissible or "full power" speed when system pressure is at its low limit.

The controls provide that, in the event of system pressure tending to fall below the low limit due, for instance, to excessive external demand, an overriding control acts to restrict outflow from the vapor generator to the external circuit to such a value as the generator can satisfy at "full power" speed of the compressor without causing system pressure to drop below the low limit of the control range.

When the external demand is zero, system pressure rises to the high limit and the pressure-responsive governor speeder sets the compressor at idle speed, this state being maintained until external demand causes system pressure to fall below the high limit when the governor speeder instantly causes the compressor to accelerate and meet the demand. It is to be understood that the primary water pump and the fuel supply pump act in unison with the compressor.

The manner in which the objects of the invention are achieved will be more readily understood from the following detailed description of the apparatus illustrated schematically in the accompanying drawing.

In the drawing there is shown a reciprocatory type air compressor, indicated generally at 11, the crank 13 of which is driven by the crank 14 of an auxiliary expansion motor indicated generally at 12. The compressor is provided with a valve-controlled air inlet port 15 and with a valve-controlled discharge port 17 through which compressed air is delivered to a combustion chamber 19, the discharge port 20 of the latter leading by way of an admission valve 18 to the cylinder of auxiliary expansion motor 12 which has an exhaust port 16. The discharge port 20 of the combustion chamber has a branch 21 leading at 61 to an external circuit, and between the discharge port 20 and the admission valve 18 is interposed means 47 for controlling admission of vapor to auxiliary expansion motor 12, said means 47 being actuated by a governor indicated generally at 42. Governor 42 is driven from crankshaft 14 of auxiliary expansion motor 12, the speeder spring 43 thereof acting on sleeve 44 which is engaged by one end of lever 45 connected at its other end by link 46 to vapor admission control means 47.

Compressor 11 is provided with primary water injector 22 to which water is delivered by conventional cam-actuated jerk pump 51. Combustion chamber 19 is provided with fuel injector 23, secondary water injector 24, electric glow plug 25 and temperature sensor 26. Fuel is delivered to injector 23 by conventional cam-actuated jerk pump 52 and secondary water is delivered to injector 24 by conventional cam-actuated jerk pump 53. Quantity control levers 68 of jerk pumps 51, 52 and 53 all swing clockwise, as indicated by the arrows, to increase delivery rate and are spring-biased to shut-off position. As shown in the drawing, sensor 26 is located at the efflux end of the combustion chamber at which region combustion of the mixture moving through the chamber is complete, so that there is little or no difference in temperature between the region of sensor 26 and the interior of efflux discharge port 20 and therefore sensor 26 is sensitive substantially to the temperature of the efflux from the combustion chamber.

Temperature sensor 26 is connected to temperature-responsive servo 28 which actuates camshaft 39 in clockwise direction with increase of temperature. Camshaft 39 is provided with lobes 40 and 41, lobe 40 acting on tappet 54 and, through rocker 55, provides an overriding control of the delivery rate of jerk pump 52 whilst lobe 41 acts directly on control lever 68 of jerk pump 53 to control the delivery thereof.

Discharge port 17 of compressor 11 is piped to pressure-responsive servo 27 which actuates camshaft 34 in counter-clockwise direction with increasing pressure. Since there is virtually no pressure drop between ports 17 and 20 at opposite ends of the combustion chamber, sensor 27 as indicated in the drawing is responsive substantially to pressure in the combustion chamber. Camshaft 34 is provided with lobes 35 and 36 which, through levers 68, control the quantitative output of jerk pumps 51 and 52 respectively, with lobe 38 which controls the tension of speeder spring 43 and with lobe 37 which controls means 50 for regulating the vapor flow rate to a point 61 leading to an external circuit, lobe 37 actuating means 50 by way of lever 48 and link 49. A further means 59 for controlling the vapor flow rate to the external circuit is provided downstream of means 50 but, unlike the latter which is adjusted in response to system pressure changes acting on servo 27, means 59 is actuated by any desired control means through lever 60.

Camshaft 29, driven by crankshaft 14 of auxiliary expansion motor 12, is provided with lobes 30 and 33 which actuate admission valve 18 of auxiliary expansion motor 12 and jerk pump 53 respectively. Camshaft 69, driven by crankshaft 13 of compressor 11, is provided with lobes 31 and 32 which actuate jerk pumps 51 and 52 respectively. Cranking motor 56 is provided for starting the vapor generator. Solenoid 57 also acts on lever 45 of governor 42 by way of link 58 and effects closure of vapor admission control means 47 when the vapor generator is being cranked for starting.

An electric switch, indicated generally at 62 and comprising terminals 63 and 64 and contact bridge 65, is connected in series with the winding of solenoid 57; switch 62 is actuated through pushrod 66 and spring seat 67 by speeder spring 43 under control of lobe 38 of camshaft 34.

To start the vapor generator, cranking motor 56 is energized; at the same time current is supplied to glow plug 25 and, through switch 62, to solenoid 57 which then sets means 47 to isolate auxiliary expansion motor 12 from combustion chamber 19.

As pressure in combustion chamber 19 rises during pump-up, pressure-responsive servo 27 rotates camshaft 34 until primary water pump 51 and fuel pump 52 begin to deliver. Fuel sprayed from injector 23 is ignited by glow plug 25 and the pressure in combustion chamber 19 rises further. When pressure reaches the prescribed high limit, camshaft 34 is rotated by pressure responsive servo 27 to such degree that spring seat 67 is allowed to move under the action of spring 43 to open switch 62 through pushrod 67. Thus solenoid 57 is de-energized, allowing means 47 to admit vapor to auxiliary expansion motor 12 and the vapor generator becomes self-sustaining. Cranking motor 56 is switched off and the vapor generator settles at idle speed and maintains this until means 59 is actuated to meet an external circuit demand at 61.

As vapor is delivered to the external circuit the pressure in combustion chamber 19 drops, pressure-responsive servo 27 rotates camshaft 34 clockwise and lobe 38 compresses speeder spring 43, resulting in admission of more vapor to auxiliary expansion motor 12 with consequent acceleration of compressor 11 and generation of vapor at a higher rate.

Should the temperature of the vapor leaving combustion chamber 19 rise, temperature-responsive servo 28 rotates camshaft 39 clockwise and, through lobe 41, increases the delivery rate of secondary water pump 53. But, if the temperature of the vapor leaving combustion chamber 19 rises above high limit, further clockwise rotation of camshaft 39, through lobe 40, reduces the delivery rate of fuel pump 52.

When the pressure in combustion chamber 19 falls to the low limit, pressure responsive servo 27 rotates camshaft 34 clockwise to such degree that speeder spring 43 is compressed so as to govern at maximum permissible speed. If, at this maximum permissible speed the pressure falls below low limit, camshaft 34 will rotate further in the clockwise direction so that lobe 37 acts to close vapor control means 50 until low limit pressure is restored.

If, under any circumstances, pressure exceeds high limit, counter-clockwise rotation of camshaft 34 by pressure responsive servo 27 causes lobe 36 to reduce the rate of delivery of fuel pump 52.

Should the vapor temperature drop below the low limit, camshaft 39 will be rotated counter-clockwise by temperature responsive servo 28 so that lobe 41 reduces the delivery rate of secondary water pump 53.

The working pressure at compressor outlet 17 is of the order of 600 p.s.i. and the temperature at this point is of the order of 300.degree. C. The temperature at combustion chamber outlet 20 is of the order of 450.degree. C.

From the foregoing it will be apparent that this invention provides a hot vapor generator characterized by fast response to change of demand, with concomitant minimal storage of energy.

Claims

I claim:

1. Means for generating hot vapor under pressure comprising a compressor having a piston and a cylinder, a combustion chamber to which air under pressure is delivered from the compressor, primary pump and injector means for introducing water into the compressor cylinder, means for injecting fuel into the combustion chamber, means for initiating ignition of the injected fuel, secondary pump and injector means for introducing an additional water supply to the combustion chamber and means responsive substantially to the temperature of the efflux from said chamber for metering the secondary water supply.

2. In combination, means for generating hot vapor under pressure comprising a compressor having a piston and a cylinder, a combustion chamber to which air under pressure is delivered from the compressor, primary pump and injector means for introducing water into the compressor cylinder, means for injecting fuel into the combustion chamber, means for initiating ignition of the injected fuel, secondary pump and injector means for introducing an additional water supply to the combustion chamber, means responsive substantially to the temperature of the efflux from said chamber for metering the secondary water supply, an expansion motor connected to be driven by part of the efflux from the combustion chamber and having driving connection with the compressor, and servo mechanism responsive substantially to the pressure in said combustion chamber and operable through a governor device to control the speed of said expansion motor and thereby the output of the compressor.

3. Means as claimed in claim 2 and wherein said pressure responsive servo mechanism is effective to maintain the operation of the compressor within a specific speed range, including an over-riding control mechanism operable to restrict the efflux from the combustion chamber to an external circuit should the demand on the system result in the system pressure falling below a lower limit.

4. Means as claimed in claim 2, including a solenoid under control of switch mechanism actuated by the pressure responsive servo mechanism and operable when starting the compressor to isolate the expansion motor from the combustion chamber until an operating pressure has been established in said chamber.

5. Means for generating hot vapor under pressure comprising a compressor, primary injector means for introducing water into the cylinder of said compressor, a combustion chamber to which air under pressure from the compressor together with entrained water as superheated steam is delivered, means for injecting fuel into said combustion chamber at the inlet end, means for initiating ignition of the injected fuel, secondary injector means for introducing water into the combustion chamber downstream of said fuel injector means, a branched outlet from said combustion chamber, one branch leading to an expansion motor in driving connection with the compressor and the other branch leading via a control means to an external circuit, pumps driven by said compressor and operable to supply respectively the primary water injection means and the fuel injection means, a further pump driven by said expansion motor and operable to supply the secondary water injection means, servo means responsive substantially to pressure in said combustion chamber and operable to control the delivery of the primary water and fuel pumps and the discharge of efflux from the combustion chamber to the expansion motor, further servo means responsive substantially to the temperature at the delivery end of said combustion chamber and operable to control the delivery of the secondary water pump and to provide an additional control over the delivery of the fuel pump, and governor mechanism under control of said pressure responsive servo means and operable to control the flow of said efflux to the expansion motor in dependence on the pressure in said combustion chamber.

6. Apparatus for the controlled generation of hot vapor comprising an air compressor having a space into which air is introduced and compressed, means for introducing water directly into said space during air compression, means responsive to the discharge pressure of said compressor for controlling said injection of water into the compressor space during compression, means defining a combustion chamber, means connecting said space to discharge the pressurized mixture from said space into said combustion chamber, means for introducing fluid fuel into said combustion chamber, ignition means for said combustion chamber, means for introducing water directly into said combustion chamber during combustion, and means for controlling the temperature at which hot vapor may leave the combustion chamber comprising means for metering admission of water into the combustion chamber and means connecting said metering means to be automatically responsive to the temperature of the hot vapor within said combustion chamber.

7. Apparatus for the controlled generation of hot vapor comprising an air compressor having a space into which air is introduced and compressed, means for introducing water directly into said space during air compression, means defining a combustion chamber, means connecting said space to discharge the pressurized mixture from said space into said combustion chamber, ignition means for said combustion chamber, means for introducing water directly into said combustion chamber during combustion, means for controlling the temperature at which hot vapor may leave the combustion chamber comprising means for metering admission of water into the combustion chamber and means connecting said metering means to be automatically responsive to the temperature of the hot vapor within said combustion chamber, and means automatically responsive to the temperature of the hot vapor within said combustion chamber for controlling the rate of admission of fuel into said combustion chamber.

8. In the apparatus defined in claim 7, said means for controlling the rate of admission of fuel into the combustion chamber comprising a variable pump connected to an injection nozzle in the combustion chamber, said means for metering admission of water into the combustion chamber comprising a variable pump connected to an injection nozzle in the combustion chamber and means operatively connected to temperature sensing means in said combustion chamber and connected to actuate said pumps in predetermined relation.

9. Apparatus for the controlled generation of hot vapor comprising an air compressor having a space into which air is introduced and compressed, means for introducing water directly into said space during air compression, means defining a combustion chamber means connecting said space to discharge the pressurized mixture from said space into said combustion chamber, means for introducing fluid fuel into said combustion chamber, ignition means for said combustion chamber, means for introducing water directly into said combustion chamber during combustion, means for controlling the temperature at which hot vapor may leave the combustion chamber comprising means for metering admission of water into the combustion chamber and means connecting said metering means to be automatically responsive to the temperature of the hot vapor within said combustion chamber, and means driven by the compressor for injecting said water into the compressor space.

10. In the apparatus defined in claim 9, means responsive to the pressure in said combustion chamber for controlling said injection of water into said compressor space.

11. Apparatus for the controlled generation of hot vapor comprising an air compressor having a space into which air is introduced and compressed, means for introducing water directly into said space during air compression, means defining a combustion chamber, means connecting said space to discharge the pressurized mixture from said space into said combustion chamber, means for introducing fluid fuel into said combustion chamber, ignition means for said combustion chamber, means for introducing water directly into said combustion chamber during combustion, means for controlling the temperature at which hot vapor may leave the combustion chamber comprising means for metering admission of water into the combustion chamber and means connecting said metering admission of water into the combustion chamber and means connecting said metering means to be automatically responsive to the temperature of the hot vapor within said combustion chamber, and means driven by said compressor for injecting said fuel into the combustion chamber.

12. In the apparatus defined in claim 11, means responsive to the pressure in said combustion chamber for controlling said injection of fuel into the combustion chamber.

13. In the apparatus defined in claim 12, means responsive to the temperature of the hot vapor in said combustion chamber for controlling said injection of fuel into the combustion chamber.

14. Apparatus for the controlled generation of hot vapor comprising an air compressor having a space into which air is introduced and compressed, means for introducing water directly into said space during air compression, means defining a combustion chamber, means connecting said space to discharge the pressurized mixture from said space into said combustion chamber, means for introducing fluid fuel into said combustion chamber, ignition means for said combustion chamber, means for introducing water directly into said combustion chamber during combustion, means for controlling the temperature at which hot vapor may leave the combustion chamber comprising means for metering admission of water into the combustion chamber and means connecting said metering means to be automatically responsive to the temperature of the hot vapor within said combustion chamber, and means driven by the compressor for injecting water into the combustion chamber.

15. In the apparatus defined in claim 14, means responsive to the temperature of the hot vapor in the combustion chamber for controlling injection of said water into the combustion chamber.

16. Apparatus for the controlled generation of hot vapor comprising an air compressor having a space into which air is introduced and compressed, means for introducing water directly into said space during air compression, means defining a combustion chamber, means connecting said space to discharge the pressurized mixture from said space into said combustion chamber, means for introducing fluid fuel into said combustion chamber, ignition means for said combustion chamber, means for introducing water directly into said combustion chamber during combustion, means for controlling the temperature at which hot vapor may leave the combustion chamber comprising means for metering admission of water into the combustion chamber and means connecting said metering means to be automatically responsive to the temperature of the hot vapor within said combustion chamber, an expansion motor connected to drive said air compressor, passage means between said combustion chamber and motor containing valve means, and means responsive to the pressure in said combustion chamber for opening said valve means when the pressure of said mixture attains a predetermined value.

17. In the combination defined in claim 16, speed responsive means driven by the motor connected for variably controlling the opening of said valve means to regulate the hot vapor being supplied to the motor.

18. In the combination defined in claim 16, a further passage connecting said combustion chamber to discharge into an external hot vapor circuit, valve means in said further passage, and means responsive to the pressure of said mixture for controlling said valve means to control the pressure in said combustion chamber.

19. Means for generating hot vapor under pressure comprising a compressor having a piston and a cylinder, a combustion chamber to which air under pressure is delivered from the compressor, primary pump and injector means for introducing water into the compressor cylinder, means for injecting fuel into the combustion chamber, means for initiating ignition of the injected fuel, secondary pump and injector means for introducing an additional water supply to the combustion chamber, means responsive substantially to the temperature of the efflux from said chamber for metering the secondary water supply, and an over-riding control mechanism operably connected to said fuel injection means to regulate delivery of fuel to the combustion chamber to prevent an excessive rise in temperature of the efflux from the said chamber.