Comparative analysis of various combustion phase control methods in a lean-burn H2/methanol fuel dual-injection engine

The combustion phase of the maximum in-cylinder pressure (theta(pmax)) and 50% heat release rate position (CA50) are often used to evaluate the reasonableness of the engine combustion. Spark timing is a decisive parameter that influences theta(pmax) and CA50 of spark-ignition engine. A H-2 port-injection and methanol direct-injection dual-fuel engine was adopted to study the adjustment spark timing under low engine speed, lean-burn and methanol late-injection strategy by application constant theta(pmax) and CA50 combustion center. The performances of the adjustment spark timing by constant theta(pmax) and CA50 combustion center was compared with performances of maximum brake torque (MBT) spark timing under equivalence ratio 1.0. The results show that using constant theta(pmax) 16 degrees CA ATDC combustion center, the optimal spark timing was advanced as decreasing equivalence ratio. Using constant CA50 of 10 degrees CA ATDC combustion center, the optimal spark timing was also advanced as decreasing equivalence ratio. The higher the H-2 addition ratio is, the later the optimal spark timing will be at same equivalence ratio. The optimal spark advance for addition H-2 is smaller than that of pure methanol, and the optimal spark advance for 6% addition H-2 is smaller than that of 3% addition H-2. The adjustment spark timing by theta(pmax) 16 degrees CA ATDC has good regularity. The adjustment spark timing by CA50 10 degrees CA ATDC is almost random. Using adjustment spark timing by theta(pmax) could achieve the best compromise of engine performance for with/without H-2 addition methanol engines.