Conference article

The efficiency of internal combustion engines and gas turbine processes are free from Carnot limitations as they are not performing cycle processes – the initial state of the thermodynamic system is the fuel with air; whereas the final state is the flue gas; whose chemical composition is different than fuel and air. Therefore; as we show here; the theoretical thermodynamic efficiencies of ideal combustion engines and gas turbine processes can be very high; the same as it is for fuel cells. The entropy generation analysis; what we have done for the internal combustion engines and gas turbines; shows that they suffer for relatively low efficiencies because of the exergy losses in the combustion processes; i.e. for the reason that the combustion reaction takes place quite far from the equilibrium state. We have studied several different combustion processes in the Exergyproject of MIDE-program to find a method for decreasing the entropy generation in the combustion. If the entropy generation can be reduced; by any means; then as a “reward”; we get the outlet pressure of the flue gas higher than the inlet air pressure without using any compressor which in turn would then increase the efficiency essentially. We present here a theoretical description of a membrane combustion method which; with the aid of gasification; suits for bioenergy. Shortly; it can be described as a molecular scale oxygen gas compressor driven by the combustion reaction; where the affecting force is amplified by the electric field across the membrane.

Entropy; exergy; combustion; membrane; efficiency; combustion engine; gas turbine process