Ed Proeschel offer heat transfer effectiveness of over 90% compared to 80% for earlier generation counter-flow heat exchangers.
The annular counter-flow heat exchanger can be adapted for operation in both open-cycle and closed-cycle gas turbine engines. Modern turbine blades made from ceramic material retains mechanical properties at 1400-degrees C or 2550-degrees F and allow combustion temperatures of 1200-degrees C without need to cool the turbine blades. While earlier generation heat exchangers were made from steel or stainless steel, there is evolving possibility of being able to make future heat exchangers from materials such as aluminium nitride and high-purity boron- arsenide that offer higher coefficients of thermal conductivity than that of steel, at much higher temperatures.
Upgraded Complex-Cycle Engine An upgraded complex-cycle gas turbine engine would include annular counter-flow heat exchangers installed downstream of both the low-pressure and high-pressure compressors, with computer-controlled fuel injection into combustion chambers placed upstream of both the high-pressure as well as power output turbine. The high-pressure turbine would operate on computer-controlled ultra-lean burn air-fuel ratio to assure sufficient oxygen in its exhaust gas to assure additional combustion to sustain operation of the power output turbine. Sensors connected to the
computer would continuously monitor properties of gases flowing from the high-pressure turbine, to assure optimal overall engine performance.
The power output of a future computer-monitored and computer-controlled complex-cycle gas turbine could rival that of the largest maritime diesel engines rated at over 100,000-horsepower and up to 50% thermal efficiency. To assure optimal turbine engine efficiency in cargo ship propulsion, the power output turbine could drive a variable pitch marine propeller via a planetary reduction gear system. While an optional electrical power transmission between power turbine and propeller would incur a reduction in overall engine efficiency, such a layout would be suitable for passenger cruise ship operation.
Bottom-cycle Steam Engine The complex-cycle gas turbine engine has 2-sources of reject heat to assist in the operation of a steam engine, preheating water flowing from the water pump to the boiler. Reject heat from the inter-cooler for the low-pressure compressor would provide primary preheating while turbine engine exhaust gas would provide a secondary source of heat that would further raise water temperature. Combustion of liquid or gaseous fuel would convert the preheated water to steam to operate a steam turbine engine at the equivalent of an elevated level of efficiency.
68 | ISSUE 110 | DEC 2024 | THE REPORT
If a gas turbine engine of
100,000-horsepower operates at near 50% thermal efficiency, its inter- cooler and exhaust would release the equivalent of 100,000-horsepower of thermal energy to preheat water to operate a bottom-cycle steam engine. A combined-cycle engine could operate at the equivalent of between 60% and 70% overall thermal efficiency on either liquid or gaseous fuel. The open-cycle turbine engine offers greater flexibility than a reciprocating engine, in the variety of competitively priced fuel that could sustain its operation. Higher overall thermal efficiency combined with lower fuel cost enhances the engine’s marketability.
Closed-Cycle Engine Externally heated closed-cycle gas turbine engines continuously recirculate the working gas by cooling it after leaving the power turbine. It replaces the combustion chambers of open-cycle engines with high-temperature heat exchangers, with low-pressure and high-pressure compressors and turbines rotating on a common shaft that drives either an electrical generator or reduction gearbox. Closed-cycle engines can be designed to operate with wide variation in the mass of gas that recirculates within the closed system. Such operation maintains high efficiency over a range of power output as turbines spin at maximum design RPM, with gas entering turbine at maximum temperature. A closed-cycle engine that delivers 40,000-horsepower with mean-average internal system
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