Research on the performance of a hydrogen/methanol dual-injection assisted spark-ignition engine using late-injection strategy for methanol

摘要

A dual-fuel spark-ignition engine that was equipped with a hydrogen (H-2) port-injection and methanol direct-injection fuel-supply system was used to study the power, combustion and emission performances in a methanol late-injection strategy. The test was operated at a spark timing of a 20 degrees crank angle before top dead center, engine speed of 1200 rpm and 1800 rpm with a manifold absolute pressure of 70 kPa and 68 kPa, respectively, and H2 addition ratio of 0% and 3%, respectively, under different excess-air ratios. The indicated mean effective pressure decreased with an increase in excess-air ratio at an engine speed of 1200 rpm and 1800 rpm. H-2 enrichment could expand the lean-burn limits of a methanol engine without or with H-2 addition from excess-air ratio 1.6 to 2.2. H-2 addition could shorten the flame-development angle and rapid-burning angle, and advance the combustion central angle closer to top dead center. The coefficient of variation in the indicated mean effective pressure was increased significantly as the excess-air ratio was increased over 1.4 for no H-2 addition and 1.8 for H-2 addition from a 3% methanol engine at an engine speed of 1800 rpm. Brake-specific nitrogen-oxide emissions decreased as the excess-air ratio was increased. The BSNOx emissions for lean-burn conditions are average 90% lower than for excess-air ratio 1.0. The maximum soot emission for 3% H-2 addition at engine speed of 1200 rpm and 1800 rpm is 59% and 30% lower than for no H-2 addition, respectively.