The Travelling Cascade, Constant Volume Heat Exchanger in a Gas Turbine Lead Combined Cycle

Abstract

When a gas enclosed in a cavity is heated or cooled, its pressure changes with its temperature as well. If a set of two countermoving “driven” cavity cascades employs the same free wall, then the system will operate as a countercurrent heat exchanger. At the exit points of the heat exchanger the two gases can be brought back to their original (atmospheric) pressure by isentropic processes thus producing useful work. The entire set of thermodynamic processes forms a double Lenoir cycle. The exhausts from the two Lenoir cycles may drive two more sets of corresponding cycles, thus allowing for the cascading of the process, until the added useful work becomes insignificant. When this idea is employed as a bottoming cycle in a Gas Turbine lead Combined cycle, employing four sets of Lenoir cycles, the achievable total thermal efficiencies rise to the 75 to 82 % level, athough the amount of heat transferred in all these processes is about 50 % more than that in a modern Brayton-Rankine combined cycle.