US2930520A

US2930520A - Compressor bleed control

Info

Publication number: US2930520A
Application number: US656417A
Authority: US
Inventors: Robert N Abild
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1957-05-01
Filing date: 1957-05-01
Publication date: 1960-03-29
Anticipated expiration: 1977-03-29

Description

March 29, 1960 R. N. ABILD COMPRESSOR BLEED CONTROL Original Filed Nov. l5. 1952 ATTORNEY COMPRESSOR BLEED CONTROL Robert N. Abild, New Britain, Conn., assignor to United Y Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Continuation of application Serial No. 320,661, November 15, 1952. This application May 1, 1957, Serial No. 656,417

"5 Claims. (Cl. 230-114) This application is a continuation of my co-pending application Serial No. 320,661 filed November 15, 1952 for Compressor Bleed Control, now abandoned.

This invention relates to axial flow compressors, more particularly to controls for bleeding axial flow compressors.

Compressors of the axial ow type are made up of a plurality of bladed stages which aot to increase the pressure of gases flowing through the compressor, each succeeding stage further compressing the gases. By varying the number of stages, the pressure ratio, that is the ratio of compressor discharge pressure to compressor inlet pressure, can be controlled. A detrimental characteristic of axial flow compressors is the tendency to surge or pulsate at low speeds, sometimes resulting in physical damage to the compressor or its associated structure. This characteristic is due to the fact that the various Stages of the compressor are designed for maximum efficiency as a unit at one particular compressor speed. At a speed lower than the design speed the Various stages are not correctly matched for the volume of air flowing through the compressor. The tendency is for the rst stages to overpump the latter stages with the result that the first stages stall out and cause surging or pulsating of the compressor.

The speed at which an axial llow gas turbine power plant can be started is below the design speed of its compressor and, consequently, starting is very difiicult if surging or pulsating exists. It is known that by bleeding air from appropriate stages of the compressor at speeds below design speed the operating characteristics of the compressorcan be changed and the detrimental characteristics overcome. More is gained in compressor performance than is lost by dumping or wasting the gases which have been compressed and had work done on them.

Various methods have been used for bleeding axial flow compressors and for controlling the bleeding thereof. The subject of this invention is a control which regulates bleeding as a function of compressor speed and compressor inlet temperature.

An object of the invention is an axial flow compressor bleed control which closes compressor bleeds over a given speed range so as to obtain maximum performance from the compressor.

Another object of the invention is an axial flow compressor bleed control which provides stepped, reliable operation and which corrects for variations of temperature.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawing which illustrates an embodiment of the invention.

In the drawing:

Fig. 1 illustrates an axial ow gas turbine power plant having the compressor bleed control in accordance with this invention connected thereto.

' Fig. 2 illustrates the details of one of the compressor bleeds. l

l United States atent O i 2,930,520 ce Patented Mar. 29, 1960 Referring to the drawing in detail, 10 indicates an axial llow gas turbine power plant having inlet 12, compressor section 14, combustion section 16, turbine section 18 and exhaust nozzle 20. Casing 22 surrounds the compressor section and has mounted therein rotor 24 comprised of a plurality of discs 26, each disc having blades 28 about its periphery. Interspaced between each row of rotor blades 28 are rows of stator vanes 30 which serve to turn the gases flowing through the compressor so that they strike the succeeding rotor blades 28 at the most efficient angle. It is to be understood that the compressor can be comprised of any number of stages.

Mounted on the forward end of compressor shaft 32 is bevel gear 34 which drives bevel gear 36 connected to governor 38 through governor shaft 40. The governor shaft has Ia pair of yweights 42 mounted thereon which vare adapted to be displaced as a function of power plant speed. The principles of such a flyweight governor are well-known in the art. Displacement of the yweights is transmitted to link 44 through plate 46, bearing 48 being interposed between the link and the plate to permit relative rotational motion therebetween. Spring 50 forces link 44 to the left to resist displacing action of the flyweights. The right end of link 44 is connected to lever 52 such that displacement of the link tends to rotate the lever about pivot v54.

Y Pivot 54, the point about which lever 52 rotates, is shifted as a function of temperature changes in the gases entering inlet 12. Temperature responsive bulb 56 is mounted within inlet 12 and is connected through line 58 to expansible bellows `60. The bulb, line and bellows are filled with an lappropriate fluid which will respond to changes in compressor inlet temperature. One end of bellows 60 is fixed as at 62 and the opposite end is connected by link 64 to lever 52 at pivot 54. Changes in the temperature of the gases entering the compressor result in expansion or contraction of bellows 60 which in turn changes the position of pivot 54 to compensate for temperature variations.

The free end of link 52 has a pair of

sockets

66 and 68 thereon, each socket containing spring backed caps which successively cover a pair of Valves 70 and '72 as the link rotates in a counterclockwise direction about pivot 54.

Sockets

66 and 68 are identical in construction and comprise housing 74 having valve cap 76 therein loaded by spring 78, each cap being capable of limited axial movement within the housing. As lever 52 moves counterclockwise about pivot 54 due to displacing action of iiyweghts 42 caused by an increase in the speed of rotor 24, the valve cap in socket 66 will close valve 70 and, as counterclockwise motion of the link continues, the valve cap in socket 68 will close valve 72. Closing of the valves is sequential, the spacing between the sockets and the valves being such that one valve is closed before the other one. The result is a partial reduction in bleeding as compressor speed increases, with bleeding being com.- pletely terminated after the compressor has reached a predetermined speed.

A pair of piston operated, double balanced poppet valves and 82 control the gases which actuate the compressor bleeds.

Valves

80 and 82 are identical in construction and operation and, for the purpose of simplicity, the details of only one will be described. It is to be understood that while the valves function in the same manner they are set in operation at different times.

Valve 80 comprises housing 84 having bores 86, 88 and therein. Ported sleeve 92 is fixed within bore 8S and its end surfaces provide seating surfaces for a double balanced poppet plunger 94. Plunger 94 has at one end an enlargement 96 engaging with bore 86 and at its opposite end an enlargement 98 which is in engagement 3 with bore 90. Spring 100 interposed between enlargement 98 and the end wall of bore 90 tends to maintain plunger 94 in its extreme position to the left, against shoulder 102 on ported sleeve 92..

Compressor discharge pressure conducted by liner-104 'enters a chamber 106 to` the left of enlargement'96 through restricting orifice 108. Valve 70 is also connected to chamber 106 and pressure in the chamber is discharged through the valve when it is open. Compres sor bleeds 110, the number of which is determined by the volume oi gases to be bled, are connected by line 112 and port 114 in ported sleeve 92 to chamber 116 intermediate the plunger Venlargements 96 and 98. When valve 7i) is open, compressor bleeds 110 are also open lsince plunger 94 is in the position shown against shoulder 102, and since chamber 116 is connected to atmosphere through line 118. Line 118 is also connected to chamf ,ber 120 at the right end of plunger 94 within`which splring 100 is located, and vents the chamber to atmose p ere.

When valve 70 is closed by valve cap 76 in socket 66 the pressure within chamber 106 builds up and pushes on enlargement 96, shifting plunger 94 to the right until flange 122 on the plunger is in contact with the left end of ported sleeve 92. This cuts oi the connection between line 112 and line 1l8,'which connected chamber 116 to atmosphere. By means of passage 124 compressor dis# charge pressure line 104 is connected to annulus 126 in housing 84 surrounding plunger enlargement 98. When plunger 94 shifts to the right, the compressor discharge pressure in this annulus is admitted to chamber 116 and then to one or more compressor bleeds 110 through port l114 in ported sleeve 92 and line l112 connecting the valve and the bleed.

Details of the compressor bleeds are shown in Fig. 2. The compressor casing has two or more cylinders 128 mounted thereon in line with the compressor stage being bled. Holes 130 in compressor casing 22 connect the compressor stage to the interior of cylinders 128. These holes preferably are located in the area of stator vanes 30, between rotor discs 26. Each cylinder contains a piston 132 held by spring 134 in a position allowing compressor air to be bled to the atmosphere through openings 136.

When compressor discharge pressure is admitted to the top side of piston 132, as described above, piston 132 is forced down, closing oil? openings 136 and terminating the bleeding of compressor air through the openings.

Poppet valve 82 functions in the same manner as has been described for poppet valve 80 and, after valve 72 is closed by valve cap 76 on socket 68, poppet valve 82 acts to admitcompressor discharge pressure to a compressor bleed, or bleeds, connected to that poppet valve and close the bleed to further reduce or completely terminate the bleeding of compressor gases.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as dened by the following claims.

I claim:

l. A multi-stage axial llow compressor having a plurality of bleeds for bleeding said compressor between end stages, a pressure responsive closure in each of said bleeds for regulating the flow of compressor gases through said bleeds, a fluid connection between the compressor discharge and said bleeds for operating said closures by com pressor discharge pressure, a plurality of valves mounted in parallel in said fluid connection for controlling the admission of compressor discharge pressure to said bleeds, each valve controlling at least one of said compressor bleeds, and means responsive to compressor inlet tempera-V ture and compressor speed for controlling said valves.

2. A multi-stage axial dow compressor having a plu rality of bleeds for bleeding said compressor between end stages, a pressure responsive closure in each of said bleeds for regulating the ow of compressor gases through said bleeds, a duid connection between the compressor discharge and said bleeds for operating said closures by compressor discharge pressure, a plurality of valves mounted in parallel in said fluid connection for controlling the admission of compressor discharge pressure to said bleeds, each valve controlling at least one of said 4compressor bleeds, and means responsive to compressor inlet temperature and compressor speed for sequentially controlling said valves to give stepped operation of said bleeds.

3. A multi-stage axial dow compressor having a plu-- rality of bleeds forbleeding said compressor between end stages, a piston in each of said bleeds for regulating the flow of compressor gases through said bleeds, means nor mally positioning said pistons to permit maximum ow through said bleeds, a fluid connection between the compressor discharge and said bleeds for admitting compressor discharge pressure to said bleeds to overcome said positioning means and close said bleeds, a plurality of valves mounted in parallel in said fluid connection for controlling and admission of compressor discharge pressure to said bleeds, each valve controlling at least one of said compressor bleeds, compressor speed responsive means for sequentially controlling said valves to give a stepped reduction in bleeding as compressor speed increases, and temperature responsive means for compensating bleeding as a function of compressor inlet temperature.

4. A multi-stage axial ilow compressor having a plurality of bleeds for bleeding said compressor between end stages, a piston in each of said bleeds for regulating the ilow of compressor gases through said bleeds, a iluid connection between the compressor discharge and said bleeds for admitting compressor discharge pressure to close said bleeds, a valve mounted in said iluid connection for controlling the admission of compressor discharge pressure to at least one of said bleeds, compressor speed responsive means controlling said valve and the admission of compressor discharge pressure through said valve to its associated bleed, at least one additional valve in said fluid connection and connected to the remaining bleeds, said valve also being controlled by said speed responsive means, means for operating said valves sequentially to give stepped closing of said bleeds as compressor speed increases, and temperature responsive means for compensating bleeding for variations in compresor inlet temperature.

5. In combination, a multi-stage axial flow compressor comprising a rotor and stator having a casing surrounding the rotor, said stator casing having at least one port formed thereincommunicating interiorly with the compressor at a selected stage thereof, exhaust means for said port exhausting air from said selected compressor stage, valve means in said exhaust means, and control means including speed sensitive means controlling the position of said valve means over the compressor operating speed range, temperature sensing means responsive to compressor inlet temperature and means operatively connected with said temperature responsive means and said speed sensitive means uand affecting the point of operation of said exhaust valve means by said speed sensitive means vwith changes in compressor inlet temper- References Cited in the le of this patent UNITED VSTATES PATENTS