US 4,815,294 AGranted

Gas turbine with external free-piston combustor

OwnerConstant V. Davidinventor

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Abstract

AN external-combustion gas turbine in which the fuel combustion takes place in a free-piston combustor. The gas turbine is the motor component of this type of engine and provides external power by means of its shaft. The gas turbine comprises an air compressor and a combusted gas expander both mounted on that same shaft. The compressed air output is directed to a storage-tank and heat-exchanger combination. The air is then admitted in the valve-less free-piston combustor and further compressed. Fuel is burned therein which further raises the pressure of the combusted gas resulting therefrom. The combusted gas is then directed to the storage tank where it exchanges some of its heat content with the compressed air. The combusted gas is then ducted into the turbine inlet and expands therein, providing energy to drive the compressor and yield shaft power. The coupling of motor, fuel combustion process and combusted-gas-pressure raising results in an engine that combines some of the advantages of Diesel engines, gas turbines and Otto-cycle engines, while eliminating some of the disadvantages of each one. This new external combustion engine operates totally differently from Diesel or Otto engines equipped with turbo-chargers and is not to be confused with either.

Claims23

Dependent claims

A gas turbine engine wherein the fuel combustion occurs pulsatingly in a combustor member including a free piston cooperating with two end closures of a sleeve in which said piston reciprocates for alternatively forming two combustion chambers in which fuel is intermittently injected and compressed air is timely and pulsatingly admitted from an air compressor member and from which combusted gas is continuously but unevenly delivered for expansion in a turbine member driving said compressor and a drive shaft for power usage externally to the engine, said engine comprising:

means for dampening pressuring fluctuations in the compressed air flowing from the compressor outlet to the combustor caused by the compressed-air pulsating admission into the combustor;
means for attenuating pressure variations in the combusted gas flowing from the combustor outlet to the turbine inlet caused by the unevenness of the combusted-gas delivery by the combustor;
means for timely injecting and igniting said fuel;
valving means controlled by the piston motion for admitting a set amount of compressed air into each combustion chamber sequentially and in one at a time, and for exhausting combusted gas out of each combustion chamber in a manner such that delivery of combusted gas is never interrupted when the engine operates;
and
means for enabling the mean pressure at which combusted gas is delivered by the combustor to exceed the mean pressure under which the compressed air is admitted therein;
whereby the pulsating nature of the fuel combustion is prevented from detrimentally affecting the operations of either one of the compressor member and the turbine member;
and
whereby combusted gas is enabled to be admitted into the turbine at a pressure higher than the pressure at which the compressor delivers compressed air.

6 more elements

A method of operating a gas turbine engine including air compressing means, fuel injecting and combusting means, means for expanding the combusted gas resulting from the fuel combustion in the compressed air, means for driving an external power shaft and control means for adjusting the level of the power delivered thereby, wherein the compressed-air admission in the fuel combusting means, the fuel injection thereinto, the combusted gas delivery thereby are of a pulsating nature, and wherein the compressed-air delivery by the compressor and the combusted-gas delivery to the turbine must both be continuous, whereas the compressed-air admission into the fuel combusting means must be discontinuous, said engine further including means for temporarily storing compressed air between the compressor outlet and the fuel combusting means, and means for temporarily storing combusted gas between the fuel combusting means and the turbine inlet, whereby:

(1) the flow of compressed air at the compressor outlet and the pressure fluctuations thereof, and (2) the flow of combusted gas into the turbine and the pressure variations thereof, can be dampened down to levels compatible with satisfactory operations of both the compressor and the turbine, said method comprising the steps of:
enabling the volume of a cavity located between the compressor outlet and the fuel combusting means inlet to vary so as to accommodate the compressed air flow and concomitant pressure variations caused by the pulsating nature of the compressed air admission into the fuel combusting means;
enabling the volume of a cavity located between the fuel combusting means outlet and the turbine inlet to vary so as to accommodate the combusted gas flow and concomitant pressure variations caused by the fluctuating nature of the combusted gas leathe fuel combusting means;
and
enabling the compressed air pressure and the combusted gas pressure to cooperate for urging both variable-volume cavities to adjust their volumes synchronously in a manner such that the ratio of the mean values of these two pressures can be adjusted and set by a regulated air pressure determined by the engine operating regime and power outlet level.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/085,359Filed 14 Aug 1987
Granted: 28 Mar 1989
Term ends: Not estimatedThe source records don’t support an estimate.

Classification12 codes

F02C 6/16
Gas-turbine plants having means for storing energy, e.g. for meeting peak loads: for storing compressed air
F02B 71/04
Free-piston engines; Engines without rotary main shaft: adaptations of such engines for special use; Combinations of such engines with apparatus…
F02B 75/04
Other engines: engines with variable distances between pistons at top dead-centre positions and cylinder heads
F02C 5/08
The working fluid being generated in an internal-combustion gas generated of the positive-displacement type having essentially no mechanical…