Method and apparatus avoiding blowdown losses in compound engines

Claim 2

A compound engine comprising: a first engine stage of the positive displacement internal combustion form having an air intake and at least one combustion chamber in which fuel is burned and having exhaust means for releasing pressurized exhaust gas from said combustion chamber and having output means for transmitting power to a rotary load, a second engine stage of the form driven by expansion of pressurized gas received at a gas inlet, exhaust gas conduit means connecting said first and second engine stages and forming an exhaust gas flow passage for transmitting said exhaust gas from said exhaust means of said first engine stage through said inlet of said second engine stage to operate said second engine stage by expansion of said exhaust gas therein, drive-transmitting means coupled to said second engine stage for obtaining supplemental output power from said second engine stage, and flow-regulating means for maintaining the pressure in said exhaust gas flow passage at a level substantially similar to the pressure which exists in said combustion chamber of said first engine stage at the time that said exhaust means thereof opens, wherein said flow-regulating means is adjustable to provide for variation of the size of said exhaust gas flow passage.

Claim 3

A compound engine as defined in claim 1 further comprising control means, connected between said first engine stage and said flow-regulating means, for reducing said exhaust gas flow passage when the pressure therein is less than the pressure which exists in said combustion chamber at the time that said exhaust means opens and for enlarging said exhaust gas flow passage when the pressure therein starts to rise above the pressure in said combustion chamber at the time that said exhaust means opens.

Claim 4

A compound engine as defined in claim 1 wherein said second engine stage includes at least one turbine and wherein said flow-regulating means is situated in the gas intake region of said turbine, and includes variable nozzle means for adjusting the size of the effective gas flow passage through said intake region of said turbine to maintain said exhaust gas flow pressure at said level.

Claim 5

A compound engine comprising: a first engine stage of the positive displacement internal combustion form having an air intake and at least one combustion chamber in which fuel is burned and having exhaust means for releasing pressurized exhaust gas from said combustion chamber and having output means for transmitting power to a rotary load, a second engine stage of the form driven by expansion of pressurized gas received at a gas inlet, exhaust gas conduit means connecting said first and second engine stages and forming an exhaust gas flow passage for transmitting said exhaust gas from said exhaust means of said first engine stage through said inlet of said second engine stage to operate said second engine stage by expansion of said exhaust gas therein, drive-transmitting means coupled to said second engine stage for obtaining supplemental output power from said second engine stage, flow-regulating means for maintaining the pressure in said exhaust gas flow passage at a level substantially similar to the pressure which exists in said combustion chamber of said first engine stage at the time that said exhaust means thereof opens, an air compressor coupled to said second engine stage and driven thereby and having a compressed air outlet communicated with said air intake of said first engine stage, first pressure signal generator means on said engine for producing a first pressure signal indicative of pressure within said exhaust gas flow passage, second pressure signal generator means on said engine for producing a second pressure signal indicative of the pressure which exists in said combustion chamber just prior to release of said exhaust gas therefrom, an actuator coupled to said flow-regulating means to vary said size of said exhaust gas flow passage in response to a control signal, and a control signal generator having inputs coupled to said first and second pressure signal generator means and having an output coupled to said actuator, said control signal generator having means for energizing said actuator to enlarge said exhaust gas flow passage when said first pressure signal exceeds said second pressure signal and for energizing said actuator to reduce said exhaust gas flow passage when said second pressure signal exceeds said first pressure signal.

Claim 6

A compound engine comprising: a first engine stage of the positive displacement internal combustion form having an air intake and at least one combustion chamber in which fuel is burned and having exhaust means for releasing pressurized exhaust gas from said combustion chamber and having output means for transmitting power to a rotary load, a second engine stage of the form driven by expansion of pressurized gas received at a gas inlet, exhaust gas conduit means connecting said first and second engine stages and forming an exhaust gas flow passage for transmitting said exhaust gas from said exhaust means of said first engine stage through said inlet of said second engine stage to operate said second engine stage by expansion of said exhaust gas therein, drive-transmitting means coupled to said second engine stage for obtaining supplemental output power from said second engine stage, flow-regulating means for maintaining the pressure in said exhaust gas flow passage at a level substantially similar to the pressure which exists in said combustion chamber of said first engine stage at the time that said exhaust means thereof opens, an air compressor coupled to said second engine stage and driven thereby and having a compressed air outlet communicated with said air intake of said first engine stage, first pressure signal generator means on said engine for producing a first pressure signal indicative of pressure within said exhaust gas flow passage, second pressure signal generator means on said engine for producing a second pressure signal indicative of the pressure which exists in said combustion chamber just prior to release of said exhaust gas therefrom, an actuator coupled to said flow-regulating means to vary said size of said exhaust gas flow passage in response to a control signal, and a control signal generator having inputs coupled to said first and second pressure signal generator means and having an output coupled to said actuator, said control signal generator having means for energizing said actuator to enlarge said exhaust gas flow passage when said first pressure signal exceeds said second pressure signal and for energizing said actuator to reduce said exhaust gas flow passage when said second pressure signal exceeds said first pressure signal.

Claim 7

A compound engine as defined in claim 4 wherein said control signal generator is a differential amplifier having first and second voltage signal inputs and having an output coupled to said actuator for transmitting control voltages thereto in response to voltage differentials at said first and second inputs, and wherein said first pressure signal generator means is a first transducer having a pressure sensitive element exposed to the pressure within said exhaust gas flow passage and having means for producing a first voltage signal indicative of said pressure therein, said second pressure signal generator means being a second transducer having a pressure sensitive element exposed to the pressure which exists within said combustion chamber just prior to opening of said exhaust means and having means for producing voltage pulses indicative of said pressure, first signal transmitting means coupled between said first transducer and said first input of said differential amplifier, and second signal transmitting means coupled between said second transducer and said second input of said differential amplifier, said second signal transmitting means including a peak voltmeter which transmits a voltage having a magnitude corresponding to the maximum magnitude of said voltage pulses.

Claim 10

The method of claim 6 further comprising: determining the pressure of exhaust gases passing from said combustion chamber to said gas expansion engine, determining the pressure within said combustion chamber at the time of release of said exhaust gas therefrom, enlarging said flow passage when said exhaust gas pressure exceeds said combustion chamber pressure, and reducing said flow passage when said exhaust gas pressure is less than said combustion chamber pressure.