Effects of EGR, water/N2/CO2 injection and oxygen enrichment on the availability destroyed due to combustion for a range of conditions and fuels

This study was directed at examining the effects of exhaust gas recirculation (EGR), water/N2/CO2 injections and oxygen enrichment on availability destroyed because of combustion in simple systems like those of constant pressure and constant volume. Higher cooled EGR fractions lead to higher availability destruction for reactant temperatures less than 2000 K. The availability destroyed for 40% EGR at 300 K for constant pressure and constant volume combustion was 36% and 33%, respectively. Neglecting the chemical availability in the products, the equivalence ratio and reactant temperature that corresponded to the lowest availability destruction varied from 0.8 to 1.0 and 800 K to 1300 K, respectively, depending on the EGR fraction. The fraction of the reactant availability destroyed increased with the complexity of the fuel. The trends stayed the same for the different EGR fractions for the eight fuels that were analyzed. Higher injected water fractions lead to higher availability destruction for reactant temperatures less than 1000 K. The availability destroyed for a 40% injected water fraction at 300 K for constant pressure combustion was 36%. The product temperature ranged from 2300 K to 450 K at a reactant temperature of 300 K for injected fractions from 0% to 90%. For a 40% injected fraction at a reactant temperature of 300 K, water injection and cooled EGR resulted in the greatest destruction of availability (about 36%) with CO2 injection leading to the least destruction (about 32%). Constant volume combustion destroyed less availability compared to constant pressure combustion at a reactant pressure of 50 kPa. At a higher reactant pressure of 5000 kPa, constant pressure combustion destroyed less availability compared to constant volume combustion for reactant temperatures past 1000 K. Higher fractions of oxygen in the inlet lead to higher product temperatures that lead to lower availability destruction. For 40% oxygen in inlet, the product temperature increased to 2900 K and the availability destroyed dropped to 25% at a reactant temperature of 300 K for constant pressure combustion.