A known installation of this type is used in a so-called turbomotor. The ratio of the volume flow through the compressor to that through the turbine is approximately 1, which is too low to generate sufficient compressed air as product with a single combustion chamber. For this purpose the said ratio would have to be at least 1.4.

The aim of the invention is to solve this problem and to provide an installation of the type mentioned in the preamble with which the quantity of compressed air as product can be arbitrarily raised within a limit determined by a maximum temperature in the turbine, using a single combustion chamber.

According to the invention the installation is to this end characterised in that the installation has two or more turbine-driven compressor units connected in parallel with a junction to which compressed air originating from the various turbine-driven compressors can be fed and from where, on the one hand, a compressed air line to the combustion chamber and, on the other hand, a product line with control valve branch off.

Preferably, a pressure sensor is arranged in the product discharge line-downstream of the said control valve-which pressure sensor is connected via a pressure signal line to a control unit, such as a PLC, which, in turn, is connected via a signal line to a pump for controlling the fuel feed to the combustion chamber on the basis of the desired consumer pressure.

One problem when starting up the installation according to the invention is the so-called "surge", that is to say that a compressor rotor rotates more rapidly than the air to be displaced.

As a consequence of the air slippage with respect to a compressor rotor, the compressor does not function or functions inadequately. This problem is known per se.

With the installation according to the invention the surge problem can be solved in that at least one nozzle is fitted in each of the compressors, which nozzle is connected to a source of compressed air which is able to supply compressed air to the blade wheel of the compressors, in that said control unit is programmed such that on starting up the installation compressed air originating from the source of compressed air is fed via the said nozzle to a first compressor and when a set pressure is reached in the discharge line of said first compressor compressed air originating from the source of compressed air is fed to a second compressor and, in the case of more than two turbine compressor units, this procedure is followed until the entire installation is in operation.

Instead of compressed air which is fed from the source of compressed air successively to the compressors, it is also possible, for example, to make use of electric motors to drive the compressors additionally in succession in order to solve the said surge problem.

What is important is a construction of said junction such that streams of compressed air originating from the various compressors can be added together without problems and can be mixed efficiently, whilst from said junction the said stream of compressed air can be branched off to the combustion chamber and the desired compressed air product stream with as few dust particles as possible in the compressed air product stream.

This can be achieved in that said junction consists of a cyclone having a number of tangential compressed air inlets, which number corresponds to the number of turbine-driven compressors, a first tangential outlet that leads to the combustion chamber and a second tangential outlet that joins onto the product discharge line, the said first tangential outlet being located upstream of the said second tangential outlet, viewed in the eddy direction in said cyclone.

A control valve that is able to regulate the ratio of the compressed air product stream and the compressed air stream to the combustion chamber is located in the product discharge line.

Said control valve preferably consists of a shut-off valve with an annular, fluid-filled chamber that delimits a passage, that at least partially is formed by a hose, the fluid chamber having at least one opening for supplying or discharging medium. The valve has an adjustable passage

through a venturi throat that can be accurately adjusted by supplying more or less fluid to the fluid chamber. The air resistance is particularly low.

The invention will now be explained in more detail with reference to the figures.

Figure 1 shows, diagrammatically, the installation according to the invention.

Figure 2 shows a view of a cyclone used in the installation according to Figure 1.

Figure 3 shows a cross-section through the control valve in the product discharge line of the installation according to Figure 1.

Figure 4 shows a view of one of the compressors according to Figure 1, partially in section.

The installation shown for generation of compressed air as product comprises a combustion chamber 1 and two turbine compressor units 2 and 3 connected in parallel. There can also be more than two turbine compressor units connected in parallel. For each of these units, the rotors of turbine 2a, 3a and compressor 2b, 3b are mounted on a single shaft. The combustion chamber 1 is supplied with fuel via a line 4 and with compressed air via a line 5. The compressed air line 5 branches off from a junction constructed as cyclone 6.

Two compressed air lines 7 and 8, connected, respectively, to the compressors 2b and 3b, open into the cyclone 6 and, moreover, two lines branch off from the cyclone 6, specifically the abovementioned compressed air line 5, which leads to the combustion chamber 1, and a compressed air line 9, which can be designated the product line. A control valve 10 by means of which the discharge of the product: compressed air can be controlled is arranged in said product line 9.

A PLC 11 is used to control the installation. A pump 12 for controlling the fuel supply via line 4 to the combustion chamber 1 is connected via a signal line 13 to the PLC 11. A pressure sensor 14, which is linked to the PLC 11 via a signal line 15, is arranged in the product discharge line 9-downstream of the valve 10.

The outlet from the combustion chamber 1 is connected to the inlet of the turbines 2a and 3a, respectively, via lines 16 and 17.

A compressed air line 18 and 19, respectively, which is connected to a compressed air vessel 20, opens into each of the compressors 2b and 3b. Control valves 21 and 22, respectively, are arranged in the lines 18 and 19. Said control valves are controlled by the PLC 11 via signal lines 23 and 24, respectively.

A pressure sensor 25, which is connected to the PLC 11 via a signal line 26, is arranged upstream of the control valve 10 in the product line 9.

As Figure 2 shows, the lines 7 and 8, which are positioned above one another, open tangentially via stubs 7a, 8a into the cyclone 6 and the lines 5 and 8 branch off, via stubs 5a and 8a, from the cyclone at a mutual angular spacing. Dust particles which move in the direction of the eddy arrow over the internal surface of the cyclone pass into the line 5 which leads to the combustion chamber 1 and not into the product discharge line 9.

Figure 3 shows a preferred embodiment of the control valve 10. The latter consists of an annular fluid chamber 27 which on the inside delimits a passage in the form of a hose 28.

Fluid can be supplied to the chamber 27 via a hole 29 in order to constrict the hose 28 to a greater or lesser extent in the form of a venturi and thus to increase or reduce the flow.

Each of the compressors 2b and 3b has a blade wheel 30 that is surrounded by a cylindrical casing 31, that part of which that faces towards the turbine 2a and 3 a, respectively, continuing in a diffuser flange 32 which extends perpendicularly to the axis of the casing 31 or of the rotary shaft of the blade wheel 30. The cylindrical casing 31 is fixed to the compressor housing by three radial fixed vanes 34 at a mutual angular spacing of 120°. A channel 35 that opens into a tangential opening in the transition rounding has been drilled through the fixed vanes 34 from the compressor housing to the transition rounding between cylindrical casing 31 and diffuser 32. The three channels 35 are connected to the compressed air vessel 20 via a line 18 and 19 respectively. The air inlet is indicated by 36 and the outlet for compressed air by 37. (A compressor of this type is also described in Netherlands Patent Application 1009679, filed on 17 July 1998). The said mutual angular spacings do not have to be identical

and can deviate from 120°.

The installation functions as follows: when operating at full capacity, the turbine compressor units 2 and 3 are running, the turbines 2a and 3a being driven by exhaust gases originating from the combustion chamber 1. The compressor rotors, which rotate with the turbines, draw in air via stub 36 and discharge compressed air via stub 37 and lines 7 and 8 respectively, which compressed air is fed through the tangential inlets into the cyclone 6. Part flows via line 5 into the combustion chamber 1 and the remainder is discharged as product discharge via line 9 and control valve 10.

The quantity of fuel which is supplied to the combustion chamber depends on the rev setting for the pump 12. This is controlled by the PLC 11 as a function of the desired consumer pressure measured by the pressure sensor 14. The exhaust gases which leave the turbines 2a and 3 a are discharged via the line 38.

On starting up the installation exhaust gases originating from the combustion chamber 1 are fed to the turbines 2a, 3a. To prevent surge, the control unit 11 is so programmed that the compressed air originating from the vessel 20 on start-up of the installation is fed via the channels 35 to the first compressor 2b. When a set pressure is reached in the discharge line from said first compressor, compressed air is fed from the source of compressed air to the second compressor 3b. In the case of more than two turbine compressor units this procedure is followed until the entire installation is in operation. The pressure produced by the compressor or compressors is measured by the sensor 25.