A Study on Performance and Combustion Characteristics for Valve Overlap Period Variation in a Hydrogen-fueled Engine with External Mixture

Abstract

In order to develop an external mixture type hydrogen engine with high performance, the characteristics of performance and combustion are investigated for various valve overlap period by using Hz engine installed a mechanical continuous variable valve timing system. In experiments, valve overlap periods are analogically varied for 0° to 400°CA by 10°CA with the same amount of supplied energy as valve overlap period of O°CA, fuel-air equivalence ratio of 0.3 to backfire limit equivalence ratio. The obtained results show that by using a similarly low supplied energy, the tendencies of the basic qualitative performance and combustion characteristics are similar to conventional engines using petroleum fuel, but quantitative results give a little difference. The backfire limit equivalence ratio (defined as the upper limit of fuel-air equivalence ratio just before backfire occurs) was also improved significantly with decrease of valve overlap period and/or for operating conditions with the same amount of supplied energy.