WO1990001627A1

WO1990001627A1 - Starter for a turbine engine including a combined oxidant storage and combustion vessel

Info

Publication number: WO1990001627A1
Application number: PCT/US1989/002768
Authority: WO
Inventors: Roy W. Vershure
Original assignee: Sundstrand Corporation
Priority date: 1988-07-29
Filing date: 1989-06-23
Publication date: 1990-02-22

Abstract

A starting system for a turbine engine (10) includes a pressure vessel (14) capable of withstanding extremely high internal pressures and combustion temperatures, contains a charge of oxidant and is provided with a fuel injector (30) and a fuel igniter (32) whereby fuel may be combusted within the vessel (14). The vessel (14) is provided with a regulated outlet (36) including a valve (38) whereby combustion gases may be directed to a starter (12) for the turbine engine (10).

Description

STARTER FOR A TURBINE ENGINE INCLUDING A COMBINED OXIDANT STORAGE AND COMBUSTION VESSEL

Field of the Invention

This invention relates to method and apparatus fo starting turbine engines.

Background of the Invention

In so-called fly-by-wire aircraft, aircraft contro surfaces are not linked to the controls by mechanical means Rather, the linking is via electrical or hydraulic circuits Consequently, in the event of an electrical power of hydrau lic failure, the aerodynamic configuration of the aircraf cannot be altered under the control of the pilot until powe is restored. As a result, such aircraft require an emer gency power unit (EPU) which is capable of responding to power failure by providing a sizable quantity of electrica and/or hydraulic energy in very short order so the contro of the aircraft can be returned to the pilot.

These aircraft, like other aircraft of more than basi simplicity, may also require an auxiliary power unit (APU for providing electrical and/or hydraulic energy as well a bleed air when the main engine or engines of the aircraf are not in use. In most cases, emergency power units and/o auxiliary power units include a gas turbine engine that i coupled to a generator and/or a hydraulic pump.

In the commonly assigned, copending application Seria No. 001,818 filed January 8, 1987 in the name of Vershure e al and entitled, "Integrated Power Unit", the details o which are herein incorporated by reference, there is dis closed a combined auxiliary power unit and emergency powe unit (APU/EPU) that may be used in such aircraft. Tha application points out that because in the typical case th turbine engine is an air breathing turbine, at high alti tudes, the density of the air may be insufficient to provid the required quantity of oxidant to readily start th turbine and rapidly bring the same up to a speed at which i will operate at that altitude to produce emergency power.

To meet this and other problems, United States Letter Patent 4,092,824 issued June 6, 1978 to Friedrich disclose a turbine for use in aircraft which is operable in a emergency mode that does not require the presence of air This patent includes a supply of hydrazine which is capabl of undergoing an exothermic decomposition reaction. Accord ing to the Friedrich patent, the heat from this reaction i utilized to vaporize aircraft fuel to provide gas to driv the turbine in an emergency situation.

While the Friedrich solution does solve a number of t previously specified problems, it also creates a few n ones. In particular, the decomposition products of hydr zine can accumulate much like soot within the turbin something that will decrease turbine efficiency when oper ted conventionally. Furthermore, soot-like material brea ing free from its point of deposition during operation the turbine may cause erosion of turbine parts and there shorten the life of the turbine. Perhaps more signif cantly, because the basis of the system is that of exothermic decomposition reaction, it necessarily follo that the fuel, such as hydrazine, must be sufficient unstable as to rapidly undergo decomposition. Obviousl the presence of such a fuel that is not stable in a conve tional sense can present hazards of its own.

Still another difficulty resides in the fact th hydrazine and proper storage facilities therefor may not available at all locations. Thus servicing of a system whose hydrazine fuel charge has been partially or wholly consumed becomes a problem. Moreover, hydrazine is toxic and therefore is not easily handled.

To avoid these problems, in the previously identified copending application of Vershure et al, there is proposed a system wherein an oxidant as stored air may be fed to an auxiliary combustion chamber to support the combustion of fuel. The resulting hot gases of combustion from the auxiliary combustion chamber are then directed against the turbine wheel of the turbine engine to accelerate the same and bring the same up to a speed whereat it can operate on its own.

The present invention is directed to improving on the Vershure et al system.

Summary of the Invention

It is the principal object of the invention to provide a new and improved starting system for a turbine engine. More specifically, it is an object of the invention to provide a new and improved starting system of the type that utilizes a stored oxidant and a method of starting such an engine.

An exemplary embodiment of the invention achieves the foregoing object in a starting system including a pressure vessel capable of withstanding an internal pressure of several thousands of pounds per square inch and formed of a material capable of withstanding combustion temperatures. A charge of oxidant is disposed in the vessel at an elevated pressure substantially less than the internal pressure and means are provided for injecting fuel into the vessel to mix with the oxidant therein. Means are also provided in the vessel for igniting injected fuel therein to produce high pressure combustion gas. The vessel is provided with regulated outlet which includes a valve that is normall closed to maintain the charge in the vessel and which may b selectively opened to allow high pressure combustion gas t flow from the vessel through the outlet. The outlet is the adapted to be connected to the starter of a turbine engine. As the result of the foregoing, a single element, th pressure vessel, serves the dual function of storing th oxidant and housing the combustion reaction. Through th use of a single element to perform both functions, a weigh savings, critical in aircraft, is achieved.

In a preferred embodiment, the vessel is spherical an in a highly preferred embodiment, the material of which th vessel is made includes titanium or is, for example, made o a composite construction such as a titanium liner surrounde by a carbon filament wound outer casing.

The vessel preferably includes an oxidant charge inle along with valve means for closing the inlet. Typically the inlet valve means will be a check valve which allow oxidant to flow into the vessel through the inlet whil preventing flow of fluid from the vessel through the inlet.

The invention contemplates that the starting system b in combination with a turbine engine having a starter wit the starter being connected to the outlet.

A preferred embodiment of the invention also contem plates that means be provided for introducing fuel as diluent into the high pressure combustion gas exiting th outlet. This increases the volume of gas that is fed to th turbine engine as well as reduces the temperature of the ga to one whereat it may be satisfactorily applied to th starter of the turbine engine.

The invention also contemplates a method of starting turbine engine which includes the step of storing an oxidan at an elevated pressure in a pressure vessel capable of withstanding an internal pressure of several thousands of pounds per square inch and capable of withstanding combus¬ tion temperatures. Included in the method is the step of injecting fuel into the vessel and igniting the same therein to produce high pressure combustion gas.

The method then contemplates that the resulting high pressure combustion gas be fed to the starter of a turbine engine to drive the same, such feeding being in a regulated manner.

According to a preferred embodiment of the method, the high pressure combustion gas is diluted with excess fuel for the purposes mentioned previously.

Other objects and advantages of the invention will become apparent from the following specification taken in conjunction with the accompanying drawings.

Description of the Drawinσ

The Fig. is a somewhat schematic illustration of a turbine engine embodying a starting system made according to the invention.

Description of the Preferred Embodiment

An exemplary embodiment of a turbine engine utilizing a starting system made according to the invention is illus¬ trated in the Fig. The turbine engine is generally desig¬ nated 10 and includes a starter 12 of the type that requires receipt of gas under pressure. By way of example, the turbine engine 10 and starter 12 may be that disclosed in the previously identified Vershure et al application, the starter 12 being provided by the dual nozzle connection to the auxiliary combustor therein. According to the invention, there is provided a pres sure vessel 14. The pressure vessel 14 is preferabl spherical and includes a spherical interior surface 16. Th construction is such that the pressure vessel 14 can with stand an internal pressure of several thousand pounds pe square inch acting against the surface 16. The value may b eight thousand, ten thousand or even more pounds per squar inch, the actual number being dependent upon the pressure generated during rcombustion of fuel within the vessel 14 a will be seen.

The material of which the vessel 14 is formed must b capable of withstanding combustion temperatures at th pressures of concern and for this reason, the vessel 14 wil typically be formed of a strong material such as titaniu which is also preferred for its relatively low density sinc the system will typically be employed in aircraft.

The vessel 14 may be provided with a conventiona pressure relief valve 20 which will open to discharge ga from the interior of the vessel 14 if a predetermine pressure is exceeded.

The vessel 14 also includes an oxidant charge inl shown schematically at 22. Oxidant is introduced into t vessel 14 through the inlet 22. In the usual case, th oxidant employed will be air or oxygen enriched air, b other oxidants may be utilized if desired.

The inlet 22 includes a check valve 24 that is co figured to allow oxidant to flow into the vessel 14 b prevent back flow. A charge air source 26 is indicated the Fig. and may include a reciprocating compressor or t like for compressing air and driving the same through t inlet 22 into the interior of the vessel 14.

In the usual case, such a compressor should be capab of compressing the air to a pressure on the order of 15 psi so that the charge of oxidant in the vessel 14 will be at that pressure.

The system includes a source of fuel 28. The fuel source 28 is connected to the turbine engine 10 to provide fuel for normal operation of the same. It is also connected to a fuel injector 30 by which fuel may be injected into the interior of the vessel 14. Because of pressure of the stored oxidant within the vessel 14, the injector 30 will preferably be a piston or plunger type of injector such as may be utilized in, for example, a diesel engine and which will inject fuel into the vessel 14 at pressures well in excess of, say, 10,000 psi, to mix with the stored air charge therein.

Also located within the vessel in proximity to the injector 30 is a spark ignition or pyrotechnic ignition device 32 connected to an ignition circuit 34. Upon injection of fuel into the vessel 14, the igniter 32 is utilized to ignite the fuel which will then combust with the stored oxidant therein.

This burning of fuel within the vessel 14 will result in a substantial elevation of the pressure therein, from about the 1,500 psi pressure of the stored oxidant to perhaps as high 10,000 psi or more and as noted previously, the vessel 14 is designed to withstand these pressures.

The vessel 14 is also provided with a high pressure combustion gas outlet shown schematically at 36. The outlet 36 is provided with a regulating valve 38 which may be in the form of a high speed stepper operated valve. The same is adapted to control the flow of the combustion gas along a line 40 to the starter 12 in a way that operation of the starter 12 is optimized to rapidly bring the turbine 10 up to a selfsustaining speed irrespective of altitude or other

/ * factors that may i.nhi.bi.t ease of starting. Optionally, the system may include a line 44 extendin from the fuel source 28 to the outlet 36 by which fuel i excess of the stoichio etric amount required for complet combustion within the vessel 14 may be added to the exitin high pressure combustion gas. The fuel in the line 44 wil be vaporized by the hot gas thereby increasing the volume o gas ultimately delivered to the starter 12. The vaporiza tion of the excess fuel, of course, reduces the temperatur of the high pressure gas and this is frequently desirable i that it brings down the temperature of the stream of ga applied to the starter 12 to a value whereat damage will no occur. Thus, such fuel serves as a diluent.

It will be appreciated that the starting system of th invention is ideally suited for use in an emergency situa tion since a source of high pressure gas needed for startin a turbine engine is quickly provided by combustion withi the vessel 14.

After use, it is only necessary to again connect th inlet 22 to a charge air source 26 to again introduc oxidant into the vessel 14 for storage therein at an eleva ted pressure. Thus, the invention provides all the advan tages of the system of the previously identified Vershure e al patent application and one additional advantage as well In the Vershure et al application, two vessels are required one for storing the oxidant, and the other one for housi the combustion reaction. According to the present inve tion, one vessel serves both purposes allowing a reducti in weight of the system.

Claims

1. A starting system for a turbine engine comprising: a pressure vessel capable of withstanding an internal pressure of several thousands of pounds per square inch and formed of a material capable of withstanding combustion temperatures; a charge of oxidant in said vessel at an elevated pressure substantially less than said internal pressure; means for injecting fuel into said vessel to mix with the oxidant therein; means in said vessel for igniting injected fuel in said vessel to produce high pressure combustion gas; and a regulated outlet from said vessel including a valve that is normally closed to maintain said charge in said vessel and which may be selectively opened to allow high pressure combustion gas to flow from said vessel through said outlet, said outlet being adapted to be connected to the starter of a turbine engine.

2. The starting system of claim 1 wherein said vessel is spherical.

3. The starting system of claim 2 wherein said vessel material includes titanium.

4. The starting system of claim 1 wherein said vessel includes an oxidant charge inlet and valve means for closing said inlet.

5. The starting system of claim 4 wherein said inle valve means comprises a check valve for allowing oxidan flow into said vessel through said inlet while preventin flow of fluid from said vessel through said inlet.

6. A turbine engine including a starter and th starter system of claim 1, said outlet being connected t said starter. r

7. The starting system of claim 1 further includin means for introducing fuel as a diluent into high pressur combustion gas exiting said outlet.

8. A turbine engine including a starter operable t start the turbine engine upon receipt of gas under pressure a spherical pressure vessel capable of withstanding a internal pressure of several thousand pounds per square inc and formed of a titanium containing material capable o withstanding combustion temperatures; an oxidant char inlet to said vessel including a check valve for allowi oxidant flow into the vessel through said inlet whil preventing the flow of fluid from the vessel through th inlet; a charge of oxidant in said vessel at an elevat pressure substantially less than said internal pressure means for injecting fuel into said vessel to mix with t oxidant therein and means operable with said injection mea for igniting injected fuel within the vessel to produce hi pressure combustion gas; a regulated outlet from said vess including a valve that is normally closed to maintain sa charge in said vessel and which may be selectively opened allow high pressure combustion gas to flow from said vess through said outlet, said outlet being connected to sa starter; and means for introducing fuel as a diluent in said high pressure combustion gas exiting said outlet to increase the volume of gas being delivered to said starter while lowering the temperature thereof.

9. A method of starting a turbine engine including a starter operable upon receipt of gas under pressure com¬ prising the steps of:

(a) storing an oxidant in a pressure vessel capable of withstanding internal pressure of several thousand pounds per square inch and formed of material capable of with¬ standing combustion temperatures; (b) introducing fuel into said vessel while igniting the same to generate high pres¬ sure combustion gas within said vessel; and releasing the high pressure combustion gas from the vessel at a controlled rate and flowing the same to the turbine starter.

10. The method of claim 9 further including the step of introducing fuel as a diluent into the high pressure com¬ bustion gas as it flows to the starter.

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