GB2169967A - Radial flow gas turbine engines - Google Patents

Abstract

An internal combustion gas turbine engine of the inward radial flow type comprises two concentric turbine rotors 3,4 respectively powering a centrifugal compressor 6 and an output power shaft (not shown). Rotary valves control admission and exhaust of gas into and from peripheral combustion chambers 2. The chambers 2 may include a spark ignition 20 to facilitate cold start up of the engine and the exhaust may be used to preheat the air intake (Figures 7 and 8 not shown). <IMAGE>

Description

SPECIFICATION Centripedal flow gas turbine with independant collinear and concentric drive and compressor turbines, designed to run at low speeds with the use of rotary valves This invention relates to gas turbine engines.

For certain applications the gas turbine is preferred to the internal combustion engine due to the higher power-to-weight ratio and general simplicity. However, these engines can only be effective and obtain their power from high compressor and output shaft speeds. The use of gas turbines on motor vehicles has been limited partly due to the complexity of reduction gearing required from the output shaft to the final drive. The object of this invention is to obtain low speed/high torque characteristic of a gas turbine engine by applying some of the features of internal combustion engines.

According to this invention the combustion chambers, power turbine and compressor turbine are concentric and collinear. The two turbines are independant but driven from the same body of gas. The engine is designed so that a fuel/air mixture is burnt in a number of independent combustion chambers that encircle the two turbines.

Centripedal flowing gas will produce a net torque on each turbine. The power turbine is geared to an output shaft while the compressor turbine drives a compressor via a simple shaft. The compressor feeds air through a series of short manifolds to the combustion chambers. A rotary valve is used, geared from the compressor shaft to seal and open the combustion chambers from the turbines to the intake manifolds. Hot gases that emerge from the compressor turbine along the axis of the engine are fed through a number of exhaust manifolds corresponding to the number of intake manifolds.

Each exhaust manifold is wrapped around an intake manifold to exchange its heat energy to the compressed air. Fuel is either injected into the air while in the intake manifold or directly into the combustion chamber and burnt in a number of ways described herein.

An example of this engine will be described and will refer to a number of drawings in which: Figure 1 shows a side elevation sectioned along the axis of the engine illustrating the main components, collinear combustion chambers, power turbine, and compressor turbine.

Figure 2 shows a cut-away end elevation along X-X on Figure 1 concentric combustion chambers, power turbine and compressor turbine. The gas flow is indicated by the solid arrows with the structure of each turbine and resultant torque shown.

Figures 3-6 are diagrams illustrating the cycle of operations.

Figure 7 shows the structure of the heat exchanger as seen in the section Y-Y of Figure 1.

Figure 8 shows the heat exchanger as seen in the section Z-Z of Figure 7.

Figure 9 shows an end elevation illustrating the exhaust manifold arrangement to the heat exchanger and finally to the exhaust pipes.

Figure 10 shows an alternative manifold arrangement.

According to the present invention the engine burns gas in combustion chambers outermost in the engine 2. When the gas has reached its maximum pressure, a passage is made available for it to escape from the combustion chamber to the atmosphere. From the combustion chamber the gas rapidly accelerates centripedally through the annular shaped power turbine 3. The vanes built into the power turbine are so shaped as to obtain the maximum torque from a given quantity of fuel burnt. The jets of gas that emerge at the centre of the power turbine are directed by the vanes to act almost tangentially on the impeller vanes of the compressor turbine 4. Work done on the power turbine is geared to an output shaft (not shown), whereas the work done on the compressor turbine will drive the compressor shaft 5.This engine may use any form of compressor, illustrated here is a centrifugal blower type 6, which compresses air into a common casing 7, to distribute to a number of intake manifolds 8. The number of intake manifolds will correspond to the number of combustion chambers assuming one manifold per combustion chamber.

A feature of this engine is the use of rotary valves to obtain a satisfactory torque at comparatively low compression pressures. For the present, the valve gear is driven from the compressor shaft at a suitable reduction ratio using a combination of worm and wheel gears 9. The valve gear consists of two perpendicular plates which are joined to a common disc 10. These plates form the limit of the combustion chamber. At different attitudes of the disc relative to the combustion chambers the valve may open the combustion chamber to the intake manifold port 11, and close it to the power turbine port 12, and vice-versa.

The cycle of operations follows: the intake manifold which is charged with compressed air 13, begins to flood the combustion chamber when the vertical plate opens the intake manifold port 14, the horizontal valve closes the power turbine port 15 The momentum of air rushing along the manifold will produce a pressure wavefront in the combustion chamber. When the pressure in the combustion chamber exceeds that in the intake manifold the vertical plate will close the intake manifold port. For a specified time this body of air will be contained in the combustion chamber with both plates closing the ports.

During this time a quantity of fuel is injected into the combustion chamber 16. During normal running the temperature of the air will be sufficient to burn the fuel, otherwise some form of igniter may be used. When the fuel air has burnt to its maximum pressure the horizontal plate opens the power turbine port 17. With the vertical plate still closing the intake manifold port, the reaction of the gas will be to accelerate through the turbines 18.

The vanes in the power turbine as so shaped to produce a net torque as previously described and direct emerging gas to act almost tangentially on the impeller vanes of the compressor turbine. The burnt gas is then fed through the master exhaust manifold.

An alternative method for burning the fuel/air mixture is to let it ignite as it comes in contact with the hot vanes of the power turbine. Both these methods of igniting the fuel /air mixture would only work under warm running conditions so provision would have to be made for cold starting.

Figure 1 shows the location for a cold start injector 19. Since it is positioned in the intake manifold the atomised fuel has a longer period to evaporate and therefore combustion is made easier. Ignition during cold starting is done by electric spark located in an ideal position in the combustion chamber 20.

Therefore in cold start situations the torsion spark and cold start injectors would be used instead of the direct fuel injectors.

During the latter stages of the combustion when most of the gas has been expelled through the turbine, the pressure in the combustion chamber will fall below that in the intake manifold which has become more and more charged with air when the intake manifold port is closed. When this occurs the vertical plate will open the intake manifold port and fresh charge will again flood the combustion chamber. For a short period both ports will be open so the fresh charge can scavenge the remaining gas in the combustion chamber through the turbines 21, this is the period of valve overlap.

The valve timing requirement will depend upon how quickly the charge can flood the combustion chamber to the maximum pressure, how quickly the fuel/air mixture burns to its maximum pressure, how quickly the pressure in the combustion chamber drops to below that in the intake manifold, and how quickly the fresh charge can scavenge the burnt gas remaining in the combustion chamber.

Assuming all these factors depend upon the intake pressure, the valve gear may be geared at a suitable ratio to the compressor shaft. The speed of the compressor shaft determines the compression pressure.

On contemporary gas turbine engines there is an option to use a heat exchanger to transfer heat away from the exhaust to the compressed air so as to reduce the quantity of fuel required for a given temperature/pressure rise in the combustion chamber.

Figures 7 and 8 shows a form of heat exchanger used to perform this function. The inlet manifold 22, is shrouded by the exhaust manifold 23, so that exhaust flowing along the gas passages 24, can give up its heat to the surfaces it comes in contact with. The heat will be transferred by conduction through the intake manifold and given up to the compressed air flowing through it.

In order to make this process more effective the exhaust and intake manifolds are constructed with internal fins 25, to increase the surface area in contact with the gases.

The exhaust gas is directed to the heat exchanger via an exhaust manifold arrangement seen in Figure 9. In this example the exhaust is divided into six independant manifolds 26, from one master manifold 27. Each manifold directs the exhaust gas to the heat exchanger 28 and finally to an exhaust pipe 29.

Different combinations of manifolds may be used and in the main the number of manifolds in an engine will depend upon the number of combustion chambers. Figure 10 illustrates an alternative arrangement by which an exhaust manifold exchanges heat to an intake manifold supplying two combustion chambers.

Claims (6)

1. A gas turbine engine comprises of two independant power and compressor turbines, the power turbine being annular and encircling the compressor turbine, combustion chambers fed via intake manifolds encircle both turbines and controlled by plate valves joined to a common rotating disc geared from the compressor shaft and the engine provided with a type of heat exchanger.

2. A gas turbine as claimed in Claim 1 where torque is obtained on both turbines by gas being burnt and centripedally accelerated perpendicular to the axis of the engine.

3. A gas turbine engine as claimed in Claim 1 or 2 where gas is burnt in any number of combustion chambers which are independant from each other.

4. A gas turbine engine as claimed in Claim 1 which uses rotary valves consisting of perpendicular plates forming the limits of the combustion chambers to perform a continuous cycle of operations.

5. A gas turbine engine as claimed in Claim 1 or 4 whose rotary valves are geared at a required reduction from the compressor shaft.

6. A gas turbine under this specification that harnesses additional energy from the exhaust.

6. A gas turbine engine as claimed in Claim 1 with a heat exchanger comprising an exhaust manifold arrangement whereupon exhaust is directed around an intake manifold structure with internal fins.

7. A gas turbine engine as claimed in Claim 1 or Claim 6 where combustion chambers are supplied with compressed air via a number of intake manifolds connecting the combustion chambers and a compressed air case.

Amendments to the claims have been filed, and have the following effect: Claims 1-7 above have been deleted. New claims have been filed as follows:

1. A gas turbine engine comprising turbines and combustion chambers mounted concentrically, the turbines obtaining torque from radially flowing gases.

2. A gas turbine as claimed in claim 1 where concentric turbines consist of one mounted centrally and the other, being annular, encircling the former.

3. A gas turbine as claimed in claim 1 and 2 where the vanes on the annular turbine direct gas so as to obtain torque on the central turbine.

4. A gas turbine as claimed in claim 1 with combustion chambers which direct gas so as to obtain torque on the annular turbine.

5. A gas turbine as claimed in claim 1 with a valve system which comprises a rotating disc with apertures opening and sealing compustion cham bers.