US2982095A - Gas generating device - Google Patents

Description

May 2, 1961 P. B. CAMPBELL GAS GENERATING DEVICE Filed Jul 9, 1959 INVENTOR PHILLIP B. CAMPBELL GAS GENERATING DEVICE Phillip B. Campbell, Kansas City, Mo., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed July 9, 1959, ser. N 826,043 -7 Claims. c 60-3914) This invention relates to gas generating devices, more particularly togas generating devices wherein a combustible charge is disposed within a housing and ignited to provide a flow of hot gaseous combustion products for an interval of time, and has for an object to provide an improved device of this character.

It is a further object of the invention to provide a gas generating device of the above type, wherein 'the hot gaseous products formed upon ignition of a primary combustible charge are directed through a first passageway for utilization in one portionof a reaction engine and, wherein after a preselected period of time, the hot gaseous products are directed through a secondary passageway 'for utilization in another portion of the reaction engine, a and including means providing a second combustible charge for initially blocking the secondary passageway fl d States Patent but unblocking the secondary passageway when consumed.

Briefly, the invention provides a gas generating device comprising a pressure tighthousing having a primary and a secondary outlet, a primary combustible charge disposed within the housing, a secondary combustible charge of solid form disposed in and blocking the secondary passageway, and means forigniting the primary and secondary charges The secondary charge is disposed in a manner to be ignited concomitantly with the primary charge. Accordingly, upon ignition of the primary charge, a large volume of hot gaseous products of combustion are rapidly generated and directed from the housing through the primary passageway.

The secondary charge is also ignited at the same time as the primary charge. After the secondary charge is completely consumed, it unblocks the secondary passageway and flow of the hot gaseous products therethrough is initiated. The proper selection of the material and axial length of the secondary charge consistent with the time required for complete consummation of the secondary charge may be predetermined with a high degree of accuracy, so thatthe time delay between initiation of gas flow through the primary passageway and the secondary passageway may be accurately predetermined.

Although the device mentioned above may conceivably have wide utility, it is especially suited for controlling the starting of a gas turbine engine. As well known in the art, gas turbine engines are notself-starting and their rotors must be driven by external means to a critical speed necessary for self-sustaining operation of the engine. Many devices have heretofore been proposed for accelerating the turbine rotor to the critical starting speed. However, after the rotor is accelerated to the critical speed by such prior art devices, ignition of the fuel is attained by a suitable, but highly complex engine control.

With this invention, both the rotor acceleration step and the fuel ignition step are attained in an exceedingly simple, yet highly reliable, manner, by connecting the primary gas passageway to the turbine rotor blading to c 2,982,095 Patented May2, 196-1 provide motive gases for acceleration purposes, and by subsequently unblocking the secondary gas passageway to the fuel combustion section for ignition.

Accordingly, a more specific object of the invention is to provide an auxiliary'gas generating device-including a primary combustible charge for providing hot gaseous products of combustion for initially cranking a gas turbine engine and bringing the rotor of the engine to a speed at which the engine may be fired to become selfsustaining, and having a secondary passageway for delivering a portion of the hot gaseous products to the fuel combustion apparatus of the engine for ignition, after the rotor of the engine has attained the above speed.

The foregoing and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying' drawing, forming a part of this application, in which:

Fig. 1 is a longitudinal elevational view of an aviation turbojet engine equipped with a gas generating device formed in accordance with the invention;

Fig. 2 is a sectional view, on a larger scale, taken on lines IIII of Fig. 1;

Fig. 3 is a view similar to Fig. 2, but enlarged to show further details of the gas generating device;

Fig. 4 is an enlarged transverse sectional view taken on lines IVIV of Fig. 2; and,

Fig. 5 is a fragmentary sectional View taken on line V-V of Fig. 3.

Referring to the drawing in detail, in Fig. 1 there is shown an aviation turbojet engine 10 equipped with a gas generating device 12 formed in accordance with the invention. The turbojet engine 10 forms no part of the invention and may be of any suitable type. Accordingly, it has been shown in somewhat schematic form. As well known in the art, the engine comprises a tubular outer shell or housing 13 defining a forwardly directed air intake opening 14- and a rearwardly directed exhaust nozzle 15. Within the shell 13 there are disposed in the following order, an air compressor section 16 including a bladed rotor 17, an annular air passageway 18 extending from the outlet of the compressor section 16 to the inlet of a gas turbine section 19 having a bladed rotor 20, and fuel combustion structure 22 disposed within the air passageway 18. The turbine rotor 20 is drivingly connected to the compressor rotor 17 by a suitable shaft.

The fuel combustion structure 22'includes a foraminous fuel combustor 23 of annular shape provided with a plurality of fuel injection nozzles 24 connected by a suitable manifold 25 to a source of fuel supply (not shown).

As is well known in the art, engines of the above type are not self-starting and must be provided with means for cranking the rotor structure 17 and 20 to a sufficiently high speed before the combustible fuel and air mixture formed in the fuel combustor 23 is ignited to provide hot motive gases for driving the turbine rotor 20. This speed may be on the order of about 40 percent of the maximum rated speed of the engine. For example, in an engine which has a maximum rotational speed of 10,000 r.p.m., the rotors must be initially rotated by a supplementary source of power to a speed of about 4,000 rpm. before the fuel combustion structure 22 may be fired. Many devices have heretofore been utilized in the prior art to initially rotate the rotor structure to the speed at which self-sustained operation may be obtained by the engine. However, after initial rotation to the speed at which self-sustained operation may be obtained, it has heretofore been necessary to ignite the fuel and air mixture by separately actuated ignition means.

In accordance with the invention, the gas generating device 12 comprises a pressure tight tubular shell or housing 27' of elongated shape having a nozzle structure 28 attached to one end thereof and having an end closure cap 29 disposed at the opposite end.

The nozzle structure 28, as best shown in Figs. 2, 3 and 4, has a plurality of exit nozzles 30 extending through the engine shell 13 and registering with an annular row of lant charge 34 is snugly received within the housing 27 and is preferably of discrete form with its longitudinal bore 33 preferably formed with a plurality of radially outwardly extending surface portions 35 to provide a large burning area. In the illustrated embodiment, the surface portions 35 impart a generally star-shaped cross section to the bore, as best shown in Figs. 4 and 5.

An ignitor squib 36 is threadedly received in the end cap 29 and extends therethrough into the longitudinal bore 33, as best shown in Fig. 3. The squib 36, as well known in the art, may comprise a casing 37 of tubular shape having a readily ignitable material 38 contained therein and disposed in encompassing relation with an electrical filament 39 which may be heated to incandescence by directing an electrical current therethrough from any suitable electrical supply, for example, a battery 40, when a switch 41 is moved to the circuit making position. The

' casing 37 is provided with .a plurality of outlets 42 disposed in registry with the bore 33.

Adjacent the forward end, that is the end adjacent the squib 36, there is provided a tubular member 43 defining a radially outwardly extending passageway 44 and connected to the interior of the fuel combustor 23 by a suitable conduit 45, as shown in Fig. 3. The conduit 45 is tightly attached to the housing 27 at one end and to the engine shell 13 adjacent its opposite end by suitable fittings 46 and 47, respectively. The conduit 45 further extends through the air passageway 18 and has its outlet end 48 snugly received in the wall structure of the fuel combustor 23.

Within the radially extending passageway 44, there is provided a solid propellant plug or charge 49 of discrete form which is snugly received therein and held in position by the fitting 46 in such a manner that it blocks gas flow therethrough. The plug 49 has an exposed end surface portion 50 disposed adjacent the bore 33 and readily ignitable.

The gas generating device 12, when ignited, automatically provides the cranking or starting impulse to the rotors 17 and 20 and acceleration of the same to the starting speed, and subsequently automatically ignites the combustible fuel and air mixture in the combustor 23.

To initiate the cranking operation of the engine, the switch 41 is moved to the circuit making position, thereby connecting the filament 39 of the squib to the electrical power source 40. The filament 39 is thus rapidly heated to incandescence and causes ignition of the charge 38 in the squib. The ensuing highly heated gaseous products of combustion and incandescent particles are violently ejected through the squib outlets 42 into the bore 33 of the primary propellant charge, thereby causing ignition of the same along the surfaces 35 of the bore. Hot gaseous products of combustion are thereby formed at a high rate and pressure and ejected in a steady stream through the passageway 32 and nozzles 30 in the nozzle structure 28 against the turbine blades 31 with sufficient force to drive the turbine rotor 20 with a rapidly accelerating effect.

Since the turbine rotor 20 is connected to the compressor rotor 17, air is drawn into the engine through the air intake opening 14, pressurized as it flows through the compressor section 16 and thence directed through the passageway 18 into the fuel combustor 23, wherein it is mixed with fuel being admitted by injector nozzles 24 to provide a combustible fuel and'air mixture.

Concomitantly with ignition of the primary propellant charge 34, the propellant plug 49 is ignited. When the propellant plug 49 is substantially totally consumed, the hot gaseous products generated by the primary propellant charge are bled through the conduit 45 and into the combustor 23 to ignite the fuel and air mixture therein. Accordingly, the engine is thus automatically fired when the speed of the rotors is sufiicient to permit self-sustaining operation and the primary charge is subsequently consumed. Thereafter the engine will continue to operate without further assistance of the gaseous products from the gas producing device 12.

The gas producing device 12 may be attached to the engine shell 13 in any suitable manner and, since it is relatively small, presents only a small weight penalty on the engine during flight. Accordingly, it may be left attached to the engine after the engine is started, if so desired.

The propellant plug 49 is preferably of considerably less mass than the primary charge 34, but may be of any suitable propellant material and may be of any crosssectional shape. However, it is desirable to form the plug 49 of sufficient length to provide a predetermined time interval between the initial ignition of the main propellant charge and complete consumption of the plug, since the burning rate of the plug 49 is a direct function of its axial length.

Further, the axial length and the burning rate of the plug 49 must be of such a nature that the passageway 44 is opened before the main propellant is completely consumed, so that sufficient hot gaseous products of combustion may be directed through the conduit 45 into the combustor 23 to eifect ignition of the fuel and air mixture.

The gas generating device 12 may be employed repeatedly by replacing the consumed squib 36 and inserting another primary charge 34 and plug 49.

It will now be seen that the invention provides a gas generating device which combines several functions in a highly simple and straightforward manner. More par; ticularly, with the invention, the gaseous products of combustion formed by the main propellant charge are first directed through one outlet passageway to energize one portion of the engine and subsequently, after a delayed time interval, are ejected through another passageway to assist or initiate a second function of the engine. Although in the embodiment shown the gas generating device is employed in conjunction with a turbojet engine and the starting thereof, the invention may be provided in other apparatus wherein two successive and properly timed functions are required.

Although the invention has considerably wide utility, it is particularly suited for starting a guided missile wherein such starting is effected by remote control. For example, the invention is highly advantageous for use in an airborne missile which may be carried aloft by a mother aircraft and launched therefrom after the desired altitude is attained.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What is claimed is:

1. A gas generating device comprising a housing, a primary combustible charge disposed within said housing, means defining a primary gas passageway extending outwardly from said housing and communicating with said charge, means defining a secondary gas passageway extending outwardly from said housing and communicating with said charge, a second combustible charge disposed in blocking relation with said second passageway, and means for concomitantly igniting said primary charge and said second charge, said primary charge forming gaseous combustion products, said second combustible charge initially blocking flow of said gaseous combustion products through' said second passageway but-being con- 2. A gas generating device comprising a housing, a

primary combustible charge of discrete form disposed within saidhousing, said charge having an opening, means for igniting said primary charge and initiating generation of gaseous combustion products, means defining a primary gas passageway extending outwardly from said housing and communicating with the opening in said charge, means defining a secondary gas passageway extending outwardly from said housing and communicating with the opening in said charge, and a second combustible charge of discrete form disposed in said second passageway, said second charge being disposed adjacent said primary charge and being ignitable jointly therewith, said second combustible charge initially blocking flow of gaseous combustion products through said second passageway but being consumable within a predetermined length of time after ignition of said primary charge by said igniting means to unblock said second passageway and initiate flow of said combustion products therethrough.

3. A gas generating device comprising a housing, a primary combustible charge of discrete form disposed within said housing, means defining a primary gas passageway extending outwardly from said housing and communicating with said charge, means defining a secondary gas passageway extending outwardly from said housing and communicating with said charge, a second combustible charge of discrete form disposed in said second passageway, and means for concomitantly igniting said primary and secondary charges, said primary charge forming gaseous combustion products upon ignition, said second combustible charge initially blocking flow of said gaseous combustion products through said second passageway but being consumable within a predetermined period of time after ignition to unblock said second passageway and initiate flow of said combustion products therethrough, said primary charge having a longer burning period than said secondary charge.

4. A gas generating device comprising a housing, a primary combustible charge of solid form enclosed within said housing, said charge having an axial passage extending from end-to-end defined by an internal surface portion of said charge, means disposed in communication surface portion of said charge, thereby to initiate formation of gaseous combustion products, means defining a primary gas ejection passageway communicating with said axial passage and extending outwardly from said housing, means defining a secondary gas ejection passageway communicating with said axial passageway and extending outwardly from said housing, and a secondary charge of combustible solid material disposed in and obdurating said secondary passageway, said secondary charge having an end surface portion disposed adjacent said axial passage and ignitable substantially concomitantly with said primary charge, said secondary charge being consumable within a predetermined period of time after ignition and of shorter duration than the consumption period of said primary charge, and initiating flow of said gaseous combustion products through said secondary passageway after said predetermined period, said secondary charge being of smaller mass than said primary charge.

5. In a gas turbine power plant having a bladed turbine rotor, a compressor rotor connected thereto, and fuel combustion structure; the combination therewith of an auxiliary hot gas generating device comprising a pressure tight housing, a primary charge of combustible solids enclosed within said housing, said charge having an internal surface portion defining an elongated passage,

means disposed in communication with said passage for "igniting the internal surface portion of said charge,

thereby to initiate formation of pressurized hot gaseous combustion products, means including a nozzle structure communlcating with said elongated passageway for conducting said gaseous products from said housing to one of the rotors to effect initial rotation of said turbine rotor, means defining a secondary passageway communicating with said elongated passageway for conducting said gaseous products from said housing to said combustion structure to effect ignition of the fuel in said fuel combustion structure, and a secondary combustible charge disposed in and blocking said secondary passageway, said secondary charge being of predetermined axial length and having a surface portion in communication with said elongated passageway, said secondary charge being consumable within a predetermined time interval after ignition of said primary charge and being effective to unblock said secondary passageway and initiate flow thereto.

6. In a gas turbine power plant having a turbine rotor, an air compressor rotor connected to said turbine rotor, and fuel combustion structure interposed between said rotors for providing hot motive gases to said turbine rotor; the combination therewith of an auxiliary hot gas generating device comprising a pressure tight housing, a primary charge of combustible solids enclosed within said housing, said charge having an internal surface portion defining an elongated passage, means disposed in communication with said passage for igniting the internal surface portion of said charge, thereby to initiate forma tion of pressurized hot gaseous combustion products, means including a'nozzle structure communicating with said elongated passage for conducting said gaseous products from said housing to one of the rotors to effect initial rotation of said turbine rotor, means defining a secondary passageway communicating with said elongated passage for conducting said gaseous products from said housing to said fuel combustion structure to effect ignition of the fuel in said fuel combustion structure, and a solid combustible plug disposed in and blocking said secondary passageway, said plug being of predetermined axial length and having a surface portion in communication with said elongated passage, said plug being consumable within a predetermined time interval after ignition of said primary charge to unblock said secondary passageway and initiate flow of said gaseous products therethrough.

7. In a gas turbine power plant having a bladed turbine rotor, a compressor rotor connected thereto and a fuel combustion structure for providing hot motive gases to said turbine rotor; the combination therewith of an auxiliary hot gas generating device comprising an elongated pressure tight housing, a primary charge of combustible solids enclosed within said housing, said charge having an internal surface portion defining an elongated central bore, means disposed in communication with said bore for igniting the internal surface portion of said charge, thereby to initiate formation of pressurized hot gaseous combustion products, means including a tubular nozzle member communicating with said bore, said nozzle member being disposed in registry with said turbine rotor and being efiective to conduct said gaseous products from said housing to eifect initial rotation of said turbine rotor, means defining a secondary passageway communicating with said bore and extending radially therefrom, said last mentioned means further including a conduit disposed in communication with said fuel cornbustion structure and being effective to conduct said gaseous products from said housing to effect ignition of the fuel in said fuel combustion structure, and a solid combustible plug disposed in and blocking said secondary passageway, said plug being of predetermined axial 7 T8 length and having a surface portion in communication 1 References Cited inthe file of this patent 2155312225? aizi 'g i ta bl j c fin i 31 11 5%;225213 UNITED STATES PATENTS 1 11 1 charge, said plug being consumable withinapredeter- 'gg Wheeler et 1949 mined time intervalafter ignition and being effective :5 37269 71950 to unblock said secondary passageway and initiate flow .of said gaseous products therethrough.

2,850,976 Seifert Sept. 9, 1958

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