US2556161A - Gas diffusers for air supplied to combustion chambers - Google Patents

Description

June 12, 1951 w. BAILEY ETAL 'GAS DIFFUSERS FOR AIR SUPPLIED T0 GOMBUSTION CHAMBERS Filed March 20, 1945 Attorney:

Patented June 12, 1951 GAS DIFFUSERS FOR AIR SUPPLIED T COMBUSTION CHAMBERS Wilfred Bailey, Fleet, and James Roy, South Farnborough, England, assignors to Power Jets (Research and Development) Ltd., London, England, a British company Application March 20, 1945, Serial No. 583,7 70 In Great Britain March 21, 1944 Claims. 1

This invention relates to gas diffusers such, for example, as may be employed for reducing the velocity of air delivered into the primary zone of the combustion chamber of an internal combustion turbine power unit of the axial flow type; the chief object being to provide a diffuser which will enable diffusion of a gas how to be obtained rapidly and efficiently.

In order to obtain efficient diffusion in a simple diffuser in the form of a diffuser passage of progressively increasing cross-sectional area from the inlet to the outlet, the taper or rate of. change of cross-section of the diffuser passage must be small so as to preserve a uniform distribution of the gas throughout the passage and prevent the flow breaking away from the Walls thereof. The deceleration of the gas fiow is consequently gradual and the use of a long diffuser passage is entailed if the velocity is required to be reduced considerably.

In the design of certain apparatus a long diffuser of simple taper form is difiicult to accommodate; this is particularly the case in the design of internal combustion turbine power plants for aircraft where there are limitations upon the overall length and lateral dimensions of the power unit which can be installed.

According to the invention, the diffuser is adapted to divide the flow into two or more streams before any diffusion commences and to lead or direct said streams each into a separate diffusion passage having a diifusion angle between 4 and 12, the number of diffusion passages being suflicient to obtain the requisite rate of diifusion.

Optimum diffusion efficiency has been found to obtain with a diffusion angle of 6.

The invention will now be described more particularly with reference to the accompanying drawing in which Figs. 1, 2 and 3 are fragmentary radial sections illustrating different embodiments of diiiuser as applied to an internal combustion turbine power plant of the axial flow type, the diffuser in each embodiment being employed for reducing the velocity of air delivered into the combustion chamber.

Referring to the embodiment illustrated in Fig. 1, an axial flow compressor, comprising a rotor with rows of blades 2 inter-digitating with rows of stator blades 3 on a stator casin 4, discharges compressed air directly from its convergent flow annulus into a, divergent annular diffusion chamber defined by outer and inner walls 5, 6, respectively. The diffusion chamber is divided internally by an annular member 1 of hollow wedge section to afford between it and the outer and inner walls 5, 6 outer and inner diffusion passages 8, 9, respectively. The wedge shaped member T has its pointed end or leading edge located at the junction of the diffusion chamber inlet with the supply conduit or inlet accelerator constituted by the convergent flow annulus of the compresser, and the said wedge shaped member l extends throughout the length of the diffusion chamber so that the diffusion passages 8, 9 discharge into the secondary zone of the combustion chamber l0. Annular partitions Ii serve in conjunction with the walls l2, It of the combustion chamber to lead the air to the secondary zone, whilst the annular space between said partitions is bridged on the upstream side by a perforated dished ring 14 so as to constitute a flame chamber or primary zone it in which fuel is injected a and burnt by burner jets It (only one of which is shown). Primary air to support the combustion of the fuel injected into the flame chamber or primary zone i5 is supplied through axially disposed ports H, which lead from the diffusion passages 8, 9 into the interior of the wedge shaped member 7, and by the perforations in the ring it.

Radial webs i8 locate and support the wedgeshaped member l in the diffuser chamber.

Each diffusion passage t, 9 has a diffusion angle between 4 and 12, and preferably an angle of 6 with which aerodynamic losses are found to be a minimum.

Referring now to the embodiment illustrated in Fig. 2, in which like references to those in Fig. 1 indicate like or analogous features, the modification consists in the inlet end of the diffusion chamber being forined as a continuation of the supply conduit or inlet accelerator and the provision on the forward portion of the wedgeshaped member l of a plate-like extension P with a sharp leading edge located at the junction of the diffusion chamber inlet with the discharge end of the flow annulus of the compressor.

In the embodiment illustrated in Fig. 3, in which like or analogous features to those .in Fig. 1 are again indicated by the same reference numerals, the divergence between the walls 5, 6 of the diffusion chamber is equal to the sum of the angles of diffusion of the two diffusion passages 8, 9, the division in this instance being made by a centrally located plate ill which extends throughout the length of the diffusion chamber and has a sharp leading edge at the junction of the diffusion chamber inlet and the discharge end of the flow annulus 'of the compressor.

3 in each of the three embodiments above described, the air fiow is divided into two streams, by the leading edge of the wedge (Fig. 1), platelike extension (Fig; 2), or dividing plate (Fig. 3), at or in advance of the point'where diffusion commences.

ing for the separate diffusion of each stream; as above described, the degree and efilcie'ncy" of; dire fusion through each passage is the same as obtains with a simple diffuser: consequently with a split diffuser affording two diffusion passages the same amount of diffusion as in a simple diff fuser can be obtained in half the overall length with little increase in aerodynamicsloss,

It will, of course, be understood thati the' num ber of diffusion passages provided in, any in:- stance will be in accordance with therat'eo'fdiffusion required and any limitations imposed on the overall length, and that, whereas the in v'ention has been described more particularly in relation to its application to-internal combustion turbine power plants, it is ofgeneral-application to various types or kinds of apparatus whichrequire for their satisfactory operation or design that the gases are diffusedrap'idly and efiiciently.

What weclaim as our invention and desire to secure by Letters Patent is:

1'. Gas diffuser means comprising wall means defining'an' upstream non-diffusing gas passage and wall means defining a plurality of down,- stream diffusing gas passages arranged" in parallel and having a-- common inlet connected" with the outlet of said: upstream passage, the total cross-sectional area of the downstream passages at'their common inlet beingequal to that of the upstream passage at its outlet, each downstream passage having an effective diffusion angle between 4" and 12 and an upstream'extension of the wall means defining'said downstream passages, said extension being so constructed and arranged as to divide the total gas flow into the downstream passages before diffusion takes place.

2. Gas diffuser means comprising an inner wall of frustoconical form, an outer wall of frustoconical form coaxial and corresponding in axial length with said inner wall; said'wa'lls'diverging from theirupstream ends, toward their downstream ends, wall forming means supported coaxially between said inner and" outer walls defining therewith a plurality of diffuser passages having effective diffusion angles of between 4 and 12, combustion means arranged, to receive air from said difiuser passages, said wall forming means bein provided with passages therethrough so located as to supply air from saiddiifuser passages to said combustionmeans prior to complete diffusion.

3. Gas diifuser means comprising an inner wall of frustoconical form, an outer wall of frustoconical form coaxial and corresponding in axial length with said inner wall,-said walls'diverging from their upstream ends towardtheir downstream ends, wall formingmeans supported coaxially between. saidinner and outerwalls defining therewith a plurality of diffuser pas. sages having effective diffusion angles ofbetween 4 and 12, said wall forming means comprising a structure of wedge sectionand annular-in form.

4. Gas diffuser means according to claim 2 wherein the air prior to complete diffusion is led into the primary combustionzone, of said combustion means.

5. A gas generator for a gas turbine that com- It has been found that by splitting the flow before diffusion commences and provid prises a compressor to supply air having means defining an outlet, combustion means, and connecting means between said combustion means and-i the" outlet of said' compressor, said combustion means includin an inner and outer annular spaced partition defining a primary zone, and an inner annular wall spaced from said inner annular partition; and an outer annular wall spaced; from said outer annular partition defining a secondary zone, said connecting means including a co'n't inuous tapered extension of said partitions to form in lengthwise section a hollow wedge, and a continuous extension of said walls defining with the extension of said partitions a plurality of passages communicatin between the outlet'ofsaid compressor and said secondary zone'to transmit air therebetween, the extension of said partitions having openings communicating between said passages and its interior, and said connecting means constituting a diffusion chamber,

6; A gas generator for a gas turbine that comprises a compressor to supply air having means defining an outlet, combustion means, and connecting means between said' combustion means and the outlet of said compressor, said combustion means including an inner and outer annular spaced partition defining a primary zone, and an inner annular wall spaced from said inner annular partition and an outer annular wall spaced from said outer-annular partition defining a secondary zone, said connecting means including" a continuous tapered extension of said partiticnsto form in lengthwise section a hollow wedge having openings, and a continuous extension of said walls" defining with the extension of saidpartition's a plurality of passages communicating between the outlet of said compressor and said secondary zone to'transinit air therebetween, each of said plurality of passages having an effective diffusion angle between 4 and 12, and said openings'communicating between said passages and the inside of said hollow wedge.

7. A gas generator for a gas turbine according to claim 5 wherein the extension of said walls includes a non-tapered continuation defining a common inlet for air from the outlet of said compressor and a plate-like extension on said hollow wedge extending into said'common inlet so that air fromsaid compressor is divided be fore diffusion takes place.

8; A gas generator for a gas turbine that comprises a; compressor to supply air having means defining an outlet, combustion means, and connecting'means between said combustion means and the outlet of said compressor, said combustion means including partition means defining a primary zone, and an inner annular wall spaced from said partition means and an outerannular wall spaced from said partition means, said: walls defining, thereb'etween a secondary zone; said connecting means including an annular member forming inlengthwise section a nollow wedge, the.

interior of said member communicating with saidprimary zone and a'continuous extensionof said walls-spaced from a'nddefining. withsaid' annular member a plurality'of passages communicating between the; outlet of said'c'ompress'orand said secondary-zonetotransmit air therebetween, said annular member havingopenings communicating betweensaidpassages and the interior of said member, and said connectingmeans constituting a'difiusio'n-chamber'.

9: A' gas generator for argasturbine that com:

prises a compressor to supply air having means 5 defining an outlet, combustion means, and connecting means between said combustion means and the outlet of said compressor, said combustion means including partition means defining a primary zone, and an inner annular wall spaced from said partition means and an outer annular wall spaced from said partition means, said walls defining therebetween a secondary zone, said connecting means including an annular member forming in lengthwise section a hollow wedge having openings, the interior of said member communicating with said primary zone, and a continuous extension of said walls spaced from and defining with said annular member a plurality of passages communicating between the outlet of said compressor and said secondary zone to transmit air therebetween, each of said plurality of passages having an effective diffusion angle not greater than 12, and said openings communicating between said passages and the hollow wedge extending into said common inlet so that air from said compressor is divided before difiusion takes place.

WILFRED BAILEY. JAMES ROY.

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

UNITED STATES PATENTS Number Name Date 23,589 Latta Apr. 12, 1859 506,335 Pearson Oct. 10, 1893 610,072 Mink Aug. 30, 1898 884,326 Emery Apr. 7, 1908 1,827,727 Blizard Oct. 20, 1931 2,326,072 Seippel Aug. 3, 1943 2,332,866 Mfiller Oct. 26, 1943 2,402,377 Davenport June 18, 1946 2,405,723 Way Aug. 13, 1946 FOREIGN PATENTS Number Country Date 227,825 Great Britain Apr. 8, 1926

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