Research on using EGR and ignition timing to control load of a spark-ignition engine fueled with methanol

Abstract

Using EGR and spark timing to control load of a spark-ignition methanol engine with wide open throttle (WOT) and stoichiometric mixture have been investigated experimentally, and its performance and emission characteristics were compared with the traditional control method by throttle. The methanol engine was modified from a diesel engine whose compression ratio was 18.0 and the methanol injectors were located in intake manifolds. The experimental results indicated that at engine speed of 1400 rpm and full load, the methanol engine can run stably without knock when the ignition timings are 18, 15 and 12°CA BTDC. The load range of the control method with variable of EGR and ignition timing was carried out from BMEP of 0.36 MPa to BMEP of 0.96 MPa. The ignition timings should be adjusted to acquire a better engine performance when the loads changed. Lower EGR rate should be applied at higher load, ignition timing should be delayed for avoiding knock; however, EGR rate is higher at lower load, ignition timing should be advanced to maintain good combustion quality and low cycle-by-cycle variations. With increasing of EGR rate and reducing of the engine load, ignition timing is required to be advanced appropriately in order to make the fuel economy of engine to optimality. Compared with the traditional load control mode by throttle, better performance and lower emissions were obtained for the control method with variable of EGR and ignition timing at higher load; whereas, BSFC and emissions of HC and CO become worse at lower load.