过浓系数与对置活塞发动机的燃烧效率

Opposed-piston 2-stroke (OP2S) compress ignition engines have different fuel-air interactions compared with ordinary CI engines，while air utilization has proved inadequate in measuring fuel-air mixing in CI engines. In this study，the concept of coefficient of richness was proposed as an index of fuel-air mixing in OP2S engines to replace air utilization. Numerical simulation was carried out with CONVERGE software to study the effect of swirl ratio and injector yaw on combustion efficiency in OP2SCI. Results showed that the coefficient of richness was effective in representing fuel-air mixing regardless of average equivalence ratio. Larger swirl ratio could improve fuel-air mixing during injection while affecting radial distribution of fuel at end of injection. Fuel concentration near either cylinder axis or cylinder wall could hinder fuel-air mixing after injection，decreasing combustion efficiency. Combustion efficiency could vary between the range 0.6 and 1.0 of swirl ratio. Injector yaw may also impact radial distribution of fuel and in turn the combustion efficiency. This effect was taken into account jointly with that from swirl.