Effect of Combustion Conditions and Blending Ratio on Aero-Engine Emissions

Abstract

The combustion chamber operating pressure, air inlet temperature, and bio-fuel blending ratio are the key factors affecting the emissions of aero engines. Numerical simulations were used to investigate the emission patterns of CO, CO2, NO and carbon soot at the combustion chamber outlet at different temperatures, pressures and blending ratios. The results show that the emission patterns of CO, CO2, NO and carbon soot vary greatly. With increasing working pressure and inlet air temperature of the combustion chamber, the CO2 emissions initially increase rapidly. However, when the working pressure exceeds 0.7 MPa and the inlet air temperature exceeds 450 K, the growth rate of CO2 emissions slows down. On the other hand, CO emissions show a relatively steady increase, but when the working pressure exceeds 0.5 MPa and the inlet air temperature exceeds 550 K, the CO emissions increase rapidly. The CO emissions decrease uniformly with an increase in the blending ratio, whereas the CO2 emissions are not significantly affected by the blending ratio when the bioethanol/aviation fuel ratio is less than 30%. However, when the blending ratio exceeds 30%, the CO2 emissions gradually decrease with an increase in the blending ratio. With increasing pressure, the distribution of NO in the combustion chamber shifts backward gradually, and the NO generation is related to the working pressure in a power function. The NO generation increases rapidly with an increase in the inlet air temperature, but it tends to slow down when the temperature reaches 550 K. The NO generation increases exponentially with an increase in the blending ratio. As the inlet air temperature increases, the soot emissions increase exponentially. The soot is concentrated in the head of the combustion chamber, and the maximum generation gradually decreases. When the biofuel blending ratio is 20%, the soot emissions show a trend of slowing down and then rapidly decreasing. Overall, the soot generation decreases gradually with an increase in the biofuel blending ratio.