US2529946A

US2529946A - Cooling device for the casings of thermic motors, including gas turbines

Info

Publication number: US2529946A
Application number: US612865A
Authority: US
Inventors: Imbert Roger Jean
Original assignee: Rateau SA
Current assignee: Rateau SA
Priority date: 1941-10-30
Filing date: 1945-08-27
Publication date: 1950-11-14
Anticipated expiration: 1967-11-14
Also published as: GB609028A; FR973663A; DE761677C

Description

Nov. 1-4, 1950 R. J. IMBERT 2,529,946

7 coouuc DEVICE FOR THE CASINGS 0F 'I'l-IERIIC QTORS, INCLUDING GAS TURBINES I 2 Sheets-Sheet 1 Filed Aug. 27. 1945 HIP-4 I {vve NTOR N. @W

CUM

Nov; 14, 1950 R. J. IMBERT 2,529,946

' coounc nsvxcz FOR THE CASINGS or mmuc MOTORS mcwnmc GAS TURBINES 2 Sheets-Sheet .2

Filed Aug. 27. 1945 IN 1/: NTOR Patented Nov. 14, 1950 COOLING DEVICE FOR THE CASINGS OF THEE-MIC MOTORS, INCLUDING GAS TURBIN ES Roger Jean Imbert, Paris, France, assignor to Societe Rateau Societe Anonyme), Paris, France,

a company of France 7 Application August 27, 1945, Serial No. 612,865

' In France October 30, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires October 30, 1961 3 Claims.

Thermic motors including gas turbines com- Drise chambers inside which gases are caused to circulate under pressure and at a high temperature, the pressure considered being of the order of 6 to 10 kgs. per cmfi, while the temperature may reach about 1000 C. The chief difliculty in the execution of the casings enclosing these cham bers resides in providing them with adequate resistance against mechanical and thermic strains. A particular solution of this problem is already known, in which each chamber is provided with a double casing inside which a cold fluid circulates which is in equilibrium as to pressure with the hot gases in the chamber. Thus the inner wall, which is broughtto a high temperature by the hot gases, is no longer submitted to any mechanical strain, provided it is allowed to expand free- 1y, while the outer wall which is cooled by the cooling fluid is submitted only to the mechanical strain due to the inner pressure exclusive of any thermic strain. It has already been proposed for executing such an arrangement to establish a circulation of cold air inside the space provided between the walls of the double casing, in particular for chambers intended for combustion under pressure, the air under pressure used for cooling the inner wall becoming hot and taking part in the combustive process. Similar arrangements have been proposed for passages and chambers through which the hot gases pass as they come out of the combustion chamber and before they enter the gas turbines, for instance. As', however, the cooling fluid becomes hot as it passes along its path, this results in an equal cooling of the outer casing which may lead'to an irregular expansion and consequently to a deformation of said casing. According to another known solution of the problem, the space between the double walls is filled with heat insulating material and is brought to a state of pressure equilibrium by means of holes or pipes communicating with the inner chamber; in such an arrangement the inner wall only allows a small flux of heat to pass but as it is only cooled to a small extent, it may then assume a very high temperature which may be detrimental for its good preservation.

The present invention has for its object a cooling device which removes this drawback. This device includes the provision inside the double casing of a system of continuous or fragmentary screens allowing a reduction and an adjustment of the amount of heat transmitted through convection and through radiation from the inner to the outer casing wall.

' It may comprise also a distribution of cooling air which ensures the flow of this air between the cold wall and the hot wall in a direction op- V ing device for the chambers containing gases under pressure at a high temperature.

Fig. 2 is a part cross-sectional view showing means known per se for producing a. circulation of fresh air under pressure inside a double casing.

Figs. 3, 4 and 5 illustrate forms of execution of the invention.

Fig. 6 is a detailed view corresponding to Fig. 5.

Fig. '7 illustrates a modification.

Fig. 8 shows a detail of said modification.

Fig. 1 illustrates the chief elements of a thermic motor including gas turbines and comprising a compressor a for the combustive air, an

auxi iary gas turbine b driving the compressor,

a, driving turbine 0 providing the useful power, a recuperator d heating the compressed air by means of the heat of the exhaust gases and a chambers for combustion under pressure provided with a burner h. The combustion chamber, the duct f connecting the combustion chamber with the turbine b and the turbine b itself form chambers containing not gases under pressure and the resistance of the walls of these chambers to the eifect of the pressure and. of the high temperature may be ensured by the known method consisting in the use of a double casing between the Walls of which fresh air under pressure is caused to circulate. To this end, the wall of the combustion chamber is constituted by a, hot inner sheet of metal I, and a cold outer sheet 2 which are connected respectively with the sheets la, 2a forming a double casing for the duct leading from the turbine b and for the body of said turbine. To ensure the circulation of fresh air required for cooling the space between said two walls, there is provided a branch connection 9 at. the delivery end of the air compressor a: a pressure substantially equivalent to the loss of head in the circuit of combustive air produced by its passage through the recuperator d is thus available as a driving pressure for the cooling air. The cooling air is progressively heated through its contacting with the inner wall of the turbine,

of the connecting duct f and of the combustion chamber e; it mixes then with the combustive air which has passed through the recuperator d and takes part in the combustion inside the chamber e fed with fuel by the burner h. Obviously the temperature of the fresh cooling air rises constantly along the path of said ai as it passes from the gas turbine into the combustion chamber; consequently the outer wall is not uniformly cooled and this may result in undesired expansions and deformations.

Fig. 2 is a detailed cross section of the usual form of execution of the inwardly cooled double casing: i designates the inner wall and 7 the outer wall; the hot gases, which may be say at 900 0., flow through the chamber k as shown by the arrow fl while the cold air advances between the two walls i and j as shown by the arrows i2; lastly the outer air is to be found at 3 on the outside of the arrangement. The cold air from the delivery end of the compressor is progressive ly heated as it advances, through conduction, convection and radiation from the wall i; the stream of cooling air flows generally with a certain turbulence which has for its result to mix the fluid elements and consequently to increase the heat transmission to, and thereby the temperature of, the outer wall.

According to one form of execution of the invention, it is possible to simultaneously reduce the convection and the heat transmitted by radiation; to this end and as shown in Fig. 3, there is arranged between the hot wall 1' and the outer wall a series of parallel screens el, e2, e3, e4 which subdivide into a plurality of sheets the flow of fresh air. The presence of these screens reduces first the convection as the air contained between the screens el and c2 which is heated very near the hot wall cannot mix with the air contained between the screens c2 and c3 and so on. Morea over only the air contained between the hot wall and the screen el may be submitted to the radiation of the hot wall. The air contained between the screens el and e2 is not submitted to any radiation, except that of the screen el the temperature of which is lower than that of the inner hot wall 1'. Of course, the spaces bounded by the intermediary screens are in equilibrium as to pressure with the hot spaces whereby the intermediary screens are submitted to no mechanical strains. Generally speaking the heat transmitted to the outer wall in accordance with the arrangement illustrated in Fig. 3 is always less than that received by the latter in the case of the arrangement of Fig. 2; thus the temperature of the outer wall is lowered and the thermic losses into the ambient atmosphere are reduced.

According to a second form of execution of the invention, both the radiation and the convection are limited, the former through the introduction of a plurality of sheets forming screens between the inner wall and the outer wall, while the convection is reduced through the cold air forming a flux the direction of which is opposed to the flow of heat from the hot wall to the cold wall.

To this end there are arranged, in the example illustrated in Fig. 4, a series of screens el, e2, e3, e4 between the two walls for ensuring the equilibrium in pressure with the hot chamber, said screens being provided with perforations Z. Moreover the cold air is brought to a plurality of points of the cold outer wall through pipes at, ,8, 7, etc. connected with the delivery end of the compressor. The cold air heated through radiation and convection. asses through the perforated screens and enters the hot chamber after it has passed through the ports a, p, 1'. adjustable if required, provided in the inner wall. Of course the pipes at, p, 'y may be replaced by a complemen- 5 tary casing surrounding the wall and leadins the cooling air to the holes provided in the wall 1 and opening into the space between the walls 1 and i.

Fig. 5 shows a modification according to which the superposed screen sheets are replaced by a filling of hollow bodies constituted by rings m of metal or refractory material forming a multiplicity of small sized screens reducing the radiation and allowing the cooling air to pass easily in the direction opposed to the flux of heat. One of these rings is shown alone in Fig. 6.

Lastly in Fig. '7, there is illustrated a further modification in transverse cross section wherein the screens are constituted by corrugated sheets 11 provided with holes, p, the corrugations being arranged along sloping helical lines having different directions whereby the successive sheets a are held at a distance from one another while allowing air to pass through the channels constituted by them.

a Fig. 8 shows the appearance of two sheets thus superposed.

The cooling air may be led as in the. above described case by a plurality of pipes on, p, 7 etc. or by a complementary casing surrounding the wall 7'.

It may also be led between the wall and a first corrugated sheet and it will flow towards the wall 1 in a direction opposed to the direction of the heat flux through the holes 1) provided in the successive sheets.

Obviously in this last described form of execution, the hot inner wall of the double casing containing gases under pressure is submitted only to thermic strains while the outer wall is submitted as uniformly as may be required to a temperature very near that of the cooling air. Moreover the heating of the air during its passage through the arrangement takes place in a direction opposite to the flux of heat whereby the heat capable of reaching the outer casing and elevating its temperature is reduced in an equivalent manner.

In the form of execution of Figs. 4 to 8, there 50 is provided in principle no circulation of air independent from that provided by the outer air pipes a, ,Bp It is however possible to superimpose on the circulation provided by the outer pipes at, p, 7 which is normal to the wall, a lon- 5 gitudinal circulation as in the known devices. This possibility of associating two cooling fluxes of which one is normal to and the other parallel with the walls may be of advantage in the case of Figs. 4, 5 and 6.

In the case of Fig. 3, the wall 1 may be provided with holes allowing a flow of fresh air towards the chamber is in a direction opposed to the flux of heat.

What I claim is:

1. In or for gas turbine plants, a device for cooling the pipes, burner casings and similar structures which are traversed by hot gases, said device comprising an inner heat resistant wall for enclosing the hot gases, an outer pressure resistant wall surrounding said inner wall and spaced therefrom, both said walls being provided with a plurality of substantially equally spaced ports, the ports of one wall being substantially opposite those of the other wall, openwork ma- 75 terial disposed in the space between the two said walls, and means for supplying cooling aeriform fluid under pressure at the said ports of the outer wall, whereby said cooling fluid is caused to flow through said ports and said openwork material and the ports of the inner wall, in a direction substantially opposed to the flow of heat dissipated by said inner wall.

2. In or for gas turbine plants, a device for cooling the pipes, burner casings and similar structures which are traversed by hot gases, said device comprising an inner heat resistant wall for enclosing the hot gases, an outer pressure resistant wall surrounding said inner wall and spaced therefrom, both said walls being provided with a plurality of substantially equally spaced ports, the ports of one wall being substantially opposite those of the other wall, openwork material in the form of at least one apertured screen disposed in the space between said walls, and means for supplying cooling aeriform fluid under pressure at the ports of the outer wall, whereby the cooling fluid is caused to flow through said ports, the apertures of said screen and the ports of said inner hot wall in a direction substantially opposed to the flow of heat dissipated by the said inner wall.

3. A'device according to claim 1, in which at least two apertured screens are disposed in the space between the two said walls, said screens being so formed and arranged so to cause a secondary circulation of cooling fluid, said secondary circulation being substantially parallel to said walls.

ROGER JEAN IMBERT.

REFERENCES CITED The following references are of record in the flie of this patent:

UNITED STATES PATENTS