CA2061169A1

CA2061169A1 - Gas turbine group

Info

Publication number: CA2061169A1
Application number: CA002061169A
Authority: CA
Inventors: Rolf Althaus
Original assignee: Individual
Current assignee: ABB Asea Brown Boveri Ltd
Priority date: 1991-03-12
Filing date: 1992-02-13
Publication date: 1992-09-13
Also published as: EP0503277A1; JPH04320718A; DE4113680A1

Abstract

ABSTRACT OF THE DISCLOSURE

In a gas turbine group essentially comprising a compressor (1), a high pressure turbine (3), a low pressure turbine (4) and a generator (5), a pressure wave machine (2) located between the compressor (1) and the high pressure turbine (3) is provided as combustion chamber. The pressure wave machine (2) includes a cell rotor whose rotor cells form the actual combustion volume. By means of auxiliary devices, the rotor cells are continuously filled with a mixture of compressor air and fuel, which mixture is subsequently ignited.
Since the rotor cells filled with the mixture are of fixed volume, constant volume combustion takes place after ignition. Because of this fact - that combustion takes place in a closed cell at constant volume the efficiency of the plant can be significantly increased.
Both the delivery of the compressor air (7) to the pressure wave machine (2) and the delivery of the driving gases (8, 9) to the respective turbine sections (3, 4) occur directly, without the need to resort to a pipework system.

(Fig. 1)

Description

-`` 2 ~ 9 Bo 12.3.91 91/012 TITLE OF THE INVENTION

Gas turbine group s BACKGROUND OF T~E INVENTION

Field of the Invention The present invention concerns a gas turbine group in accordance with the preamble to claim 1. It also concerns a method of operating such a gas turbine group.

Discussion of Backqround Gas turbine groups consist essentially of a com-pressor, a combustion chamber, a turbine and a gener-ator. In conventional technology, the air compressed in the compressor is thermally treated in a constant pressure combustion chamber; the hot gas is sub-sequently admitted into the turbine, which in turn drives a generator for the production of electricity.
The constant pressure combustion chambers are per se voluminous structures, most of which operate mounted vertically between compressor and turbine. In order to increase the compactness of the turbine groups, the introduction of so-called annular combustion chambers has already been proposed. These function on the same constant pressure combustion principle, the combustion volume being moved - fundamentally - from the vertical to the horizontal. Insofar as the horizontal combus-tion volume now overlaps in the axial plane of both the compressor and the turbine, a certain vertical and horizontal compactness is achieved. This, of course, is regularly accompanied by penalties with regard to the flow path of the compressed air from the compressor into the combustion chamber and of the thermally treated gases from the combustion chamber into the turbine. The working gas must therefore be redirected - 2 - 2~

within a restricted space, both from the compressor into the combustion chamber and from the combustion chamber into the turbine. This is inevitably accompanied by losses which, in the end, depress the S efficiency. With combustion chambers of this kind, great attention must always be paid to the prevention of excessive NOx emissions from the combustion process.
This can frequently only be achieved by means of specifically targeted measures.

SUMMARY OF THE INVENTION
Accordingly, one object of this invention (as defined in the claims) is to provide a novel means of integrating a combustion chamber in a compact manner between compressor and turbine. A further object o~
the invention is to arrange the combustion process ln this combustion chamber in such a way that it takes place with maximized efficiency and minimized pollutant emlsslons.
The essential advantages of the invention can be seen in the fact that the complete turbine group i5 a very compact unit, the combustion chamber occupying approximately the same vertical extent as the com~
pressor and turbine. Moreover this combustion chamber occupies an axial extent which is no greater than the space requirement ~or the inlet and exhaust flows of a conventional vertically mounted combustion chamber. In the present case, the combustion chamber introduced between compressor and turbine is a pressure wave machine, which consists of a cell wheel in which the individual cells, in the course of their rotational movement about a center line which preferably coincides with the compressor and turbine center line, continu-ously form a fixed, defined volume for the combustion of an air/fuel mixture. In the above configuration with a single center line, this takes place if, for example, the cell wheel rotates together with the rotor of the compressor or the turbine, the cells rotating ~$1.~

past the outlet flow of compressed air from the compressor being continuously filled with the above-mentioned combustion mixture (fuel and compxessor air).
Displaced in phase from this location, the casing contains at least one outlet flow to at least one turbine. Ignition of the mixture takes place in the individual cells between the two locations. The result is a hot gas which, as the cell wheel rotates, flows -at the above-named, phase-displaced outlek flow opening - to the turbine and is admitted to the latter.
Obviously this sequence of events also occurs if the cell wheel does not in fact rotate but the delivery of the mixture and the extraction of the hot gases takes place by means of rotating inlet flow and outlet flow devices, corresponding to the number of process cycles per revolution. Since the mixture ignites within a respective closed space of fixed, defined volume, combustion takes place at constant volume, thus permitting much higher temperatures - similar to those found in a piston engine. Because combustion takes place in a closed cell and therefore (as stated) at constant volume, the efficiency of this combustion process proves to be higher than in the case of classic constant pressure combustion chambers.
The object matter of the invention is dis-tinguished, moreover, by a whole range of further advantages:
A first advantage is to be seen in that the com-pression process which takes place in the cells leads to a more intensive degree of mixing of the media forming the mixture.
Moreo~-er, since the fuel added to the mixture is protected from the flame, i.e. the mixing process is shielded from the flame radiation, a very good premix can be anticipated and, since vaporized fuel absorbs practically no further flame radiation during the subsequent process, the danger of premature ignition of the mixture is avoided.

Furthermore, another advantage of the invention is to be seen in that the cell wheel does not require the provision o~ any special cooling precautions (as is usually the case in constant pressure combustion cham~
bers) because the continuing intake of compressed air continuously cools the cells in which combustion has previously taken place.
Finally, mention should be made of a further advantage of the invention which arises from the con-figuration of the respective inlet and outlet flows to and from the cell wheel. The inlet flow to the cells is at the compressor end and the inlet flow to the turbine is at the turbine end. If reference is made to inlet flows, this is because it is readily possible with the subject matter of the invention, to provide low pressure admission as well as high pressure admi~sion to the turbine. On this last point, it may be generally stated that the turbine group does not require an extensively branched pipe system and, in consequence, many design problems simply do not arise.
Advantageous and expedient extensions of the invention are given in the further claims.

BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation o~ the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying draw-ings, wherein:

Fig. 1 shows a diagrammatic representation of the gas turbine group with an integrated pressure wave machine as combustion chamber;
Fig. 2 shows a diagrammatic development of the cell wheel, subsequently also called the cell rotor, in which may be seen the progress of the s pressure wave process and the combustion at constant volume;
Fig. 3 shows an axial section through the gas turbine group;
Fig. 4 shows a control disk downstream of the com-pressor and upstream of the pressure wave machine; and Fig. 5 shows a control disk downstream of the pressure wave machine and upstream of the turbine. 0 DESCRIPTION OF_T~E PREFERRED EMBODIMENTS
Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, wherein only those lS elements essential for understanding the invention are shown and wherein the flow direction of the various media is denoted by arrows, Fig. 1 shows a diagrammatic representation of the gas turbine group into which is integrated a pressure wave machine. The gas turbine group comprises a compressor 1~ a high pressure turbine 3, a low pressure turbine 4 and an electrical generator 5 connected to the turbine group. The pressure wave machine 2 acts as combustion chamber and is placed between the compressor 1 and the high pressure turbine 3. The induced air 6 is converted into compressor air in the compressor 1. The compressor air first flows into a pre-mixing passage 7, in which a fuel 11 is mixed with the air before the resultant mixture 12 flows into the pressure wave machine 2. ~ process, to be described in more detail with re~erence to Fig. 2 and which results in the creation of a high pressure driving gas and a low pressure driving gas, takes place in the pressure wave machine 2. While the high pressure driving gas is admitted into the high pressure turbine 3 via a high pressure gas ~uct ~, the remainder of the partially-expanded hot gas is directed as low pressure driving gas (via a low pressure driving gas duct 9, preferably separate) to the low pressure - 6 ~ $ ~

turbine 4; the latter can be a low pressure stage of the total turbine. The expanded driving gases -then flow as exhaust gases 10 out of the final turbine stage, where the potential that they still contain, in particular their heat potential, can be made available for the production of live steam to drive a steam turbine mounted downstream of the gas turbine group;
this makes it possible to provide a combined cycle plant, with or without additional firing.
Fig. 2 shows a diagrammatic development of the cell rotor 13 of the pressure wave machine 2, to the extent necessary for the explanation of the pressure wave process and the constant volume combustion process; in the present case, it is assumed that the cell rotor 13 rotates. Only individual cells 13a of the cell rotor 13 are represented or visible; in the present case, these extend at right angles to the direction of rotation 13b of the cell rotor 13. These cells can, of course, also be arranged at an angle to the direction of rotation of the cell rotor - as described for example in EP-B1-0 212 181. (For any further clarification necessary on this point, reference should be made to the description given in that publication.) The cell rotor 13 itself runs with very small clearance within a casing 19, 20, which is only indicated, the two faces of the casing 19, 20 adjacent to the rotor being pierced by various passages 7, ~, 9. Fig. 2 shows a single process diagram-matically; it is intrinsicall~ possible to accommodate a number of processes per revolution of the cell rotor 13. In order to obtain a uniform temperature distribution in the cell rotor 13, it is advantageous to accommodate at least two symmetrically arranged processes. Accordingly, only one c~cle of the process is described in what follows. The compressor air coming from the compressor 1 undergoes fuel addition 11 in the pre-mixing passage 7 before this fuel/air mixture 12 reaches the operating region of the rotor cells 13a. This mixture 12 therefore passes through the outlet of the pre-mixing passage 7 to enter the cells 13a. The cells 13a rotating past the pre-mixing passage 7 take up a certain quantity of the mixture 12 S available there, the mixture being composed of compressor air and fuel. For the purpose of ensuring a constant quantity, the charging o~ the cells 13a is determined by the closing edge l9a of the pre~mixing passage 7 in the casing 19. The line joining the latter closing edge l9a and the other closing edge 20a of the casing 20 represents the path of the shock wave 18, which defines the boundary of the compression A.
Ignition of the mixture held at constant volume in the cells 13a occurs subsequently along the cell rotor 13, lS which is closed at its end faces by the body of the casing 19, 20, and this ignition can advantageously take place by means of a series of ignition loops, which are not shown. Other ignition devices can also, of course, be provided. In the following part of the cycle the driving gas, created in each cell 13a at constant volume as a result of the combustion process B
initiated, reaches the high pressure turbine 3 via a high pressure driving gas duct 8 (on this point, cf.
Fig. 1). This high pressure turbine admits part of the total quantity of driving gas available between the two expansion waves 14 and lS, corresponding to the high pressure region C. As far as the opening edges l9b and 20b in the corresponding parts of the casing, the driving gas expands between the expansion waves 15 and 16 from a pressure p2 to a pressure pl, as is symbolized by the streamlines becoming less dense in the expansion region D. This partially expanded driving gas then flows through the low pressure driving gas duct 9 to the low pressure turbine 4 (cf. Fig. 1).
This low pressure region E is bounded by the media boundary 17, which extends from the opening edge l9b of the pre-mixing passage 7 to the closing edge 20a of the low pressure driving gas duct 9. A new phase then begins by the rotating cells 13a being filled via the pre-mixing passage 7 with the ~uel/air mixture 12 in a manner similar to that stated above. Each of the individual cells 13a therefore represents a "mini S combustion chamber" characterized by a constant volume, preferably designed in such a way that the driving gases produced in it at gas turbine group maximum load do not exceed the maximum permissible limiting temperature for the blading at inlet to khe high pressure turbine. It is preferable to provide a circuit or arrangements allowing the partially-expanded and correspondingly cooled driving gas behind the high pressure turbine to be mixed, as requirad, with the driving gas for the low pressure turbine, and to do lS this in such a way that the resultant thermally-enhanced driving gas mixture in turn never exceeds the limiting temperature of the first stage of the low pressure turbine. No such circuit or arrangements for this purpose are represented in Fig. 2. If the qas turbine should also happen to contain an intermediate pressure section, admission to that particular section of the gas turbine would be achieved in an analogous manner, in accordance with the preceding considerations. The ultimate aim of such designs will always be to achieve for the gaz turbine a rough approximation to the isothermal expansion of the Carnot cycle process.
Fig. 3 shows a section through the gas turbine group, in which may be seen the compressor 1, the pre-mixing passage 7 together with the fuel supply 11, thecell rotor 13 with one cell 13a and, downstream of the cell rotor 13, the high pressure turbine 3 and the low pressure turbine 4. In contrast to the initial position of Fig. 2, the configuration represented here shows a design with a fixed~ non-rotating cell rotor 13. Delivery of the compressor air to the individual cells 13a is undertaken, downstream o the compressor l, by a rotating control disk 21 which has a number of 2 ~

ports forming, in the flow direction, part of khe pre-mixing passages 7, the number corresponding to the number o~ process cycles, as already explained in the context of Fig. 2. Another rotating control disk 22 operates downstream of the cell rotor 13 and this also has a number of ports through which the drlving gas ~lows to the respective turbi~e. Obviously, this control disk 22 must have a number of ports per process cycle to suit the turbines connected downstream. It is, furthermore, obvious that the ports which ~orm part of the high pressure driving gas duct 8 or the low pressure driving gas duct 9 must be dimensioned such that the driving gas quantity requirement for admission to each turbine is satisfied. Moreover, the ~igure lS shows how admission to the individual turbines is achieved without a pipework system. The ports in the control disk 22 have opposite flowpath inclinations so that each port communicates with the flow inlet to the respective turbine. As previously explained, it is intrinsically possi~le to provide control disks that are fixed. In such a case, the cell rotor 13 would rotate, as described in the context of Fig. 2; the process itself does not alter with respect to pressure waves and combustion technology.
Fig. 4 shows the control disk 21 which operates upstream of the pressure wave machine; two ports 21a, 21b can be seen, corresponding to the fact that in this case, two process cycles occur per developed view of the cell rotor 13. The dimensioning of the ports ~ollows from the ~uantity of gas re~uired per cell 13a;
it obviously also depends on other parameters specific to the ~low, such as rotational speed of the ce]l rotor, compressor air and driving gases mass flow rates, etc.
Fig. 5 shows the other control disk 22, which operates downstream of the pressure wave machine. The ports 22a and 22b are directed towards the high pressure driving gas ducts 8 and the ports 22c and 22d correspondingly towards the low pressure driving gas ducts 9. The mode of operation is the same as that described above.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

Claims

1. A gas turbine group, essentially comprising at least one compressor, at least one combustion chamber, at least one turbine and at least one generator, wherein the combustion chamber is a pressure wave machine located between compressor and turbine, wherein the pressure wave machine essentially comprises a cell rotor with a number of rotor cells arranged in the circumferential direction, a casing enclosing the cell rotor circumferentially and on its end faces and wherein the casing is connected via at least one passage to the compressor and via at least one other passage to the turbine.

2. The gas turbine group as claimed in claim 1, wherein the cell rotor can be rotated about a common axis of the compressor and/or the turbine, wherein a fixed control disk is located at each end of the cell rotor, on both the compressor side and the turbine side and wherein the control disks have ports in the plane of the rotor cells.

3. The gas turbine group as claimed in claim 1, wherein the cell rotor is fixed, wherein a rotatable control disk is located at each end of the cell rotor on both the compressor side and the turbine side and wherein the control disks have ports in the plane of the rotor cells.

4. The gas turbine group as claimed in claims 2 and 3, wherein the number of ports in the case of either a fixed or a rotatable control disk agrees with the number of process cycles per cell rotor developed view at the compressor end and with the number of process cycles multiplied by the number of coupled turbines at the turbine end.

5. A method for operating a gas turbine group as claimed in claim 1, wherein the air processed in the compressor is mixed with a fuel before entry into the pressure wave machine, wherein the fuel/air mixture is introduced into the rotor cells, wherein the fuel-air mixture is ignited in a condition of constant volume indicated by the size of the individual rotor cells and wherein the turbine admits a driving gas formed from the combustion process in the rotor cells.