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The quest for achieving more efficient gas turbine engine systems (GTESs) has led the researchers to try getting into many new dimensions of research. Simple Brayton cycle-based GTESs were coupled with recuperators, regenerators and reheaters to avoid/recoup heat energy from being wasted and these were designated as complex GTESs. Multistage compression (multi-casing) in axial compressors and multistage (two-cylinder) expansions in turbines paved the path to optimize the plant design for greater thrust to weight ratio and greater efficiency of the GTESs. Since the increase in efficiency of any power plant is directly or indirectly related to temperatures at which the plant cycle is being operated, this thermodynamic constraint had led to the development of high temperature materials such as single crystal nickel-based superalloys.

Automotive power packs have been the focus of research over a long period of time. Among various power packs when we consider internal combustion engines, there is an ample opportunity in developing systems that can make optimal utilization of all the energy streams related to the automotive engine. In this regard utilization of internal combustion engine exhaust waste heat and environmental pollution have been the focus of research in the recent past. About 35% of the automotive input fuel energy is converted to useful crankshaft work and about 30% energy is expelled with exhaust. This leaves about one-third (35%) of the total energy that must be transmitted from the enclosed cylinder through the cylinder walls and head to the surrounding. The exhausted energy from engine results in entropy elevation and solemn environmental pollution. So it is desired to utilize waste heat to the extent possible.