Simulation of HCNG Engine Based on Negative Valve Overlap EGR Strategy
Author(s): YUAN Junyong, HE Yituan, ZHOU Lei, WANG Yafang, JI Wenxiao, SHAO Yiming
Pages: 65-69,75
Year: 2015 Issue: 3
Journal: Vehicle Engine
Keyword: hydrogen engine; compressed natural gas (CNG ) engine; negative valve overlap; exhaust gas recirculation (EGR); simulation;
Abstract: In order to reduce NOx emission of hydrogen‐enriched compressed natural gas (HCNG) engine ,3D simulation of intake and combustion process under different intake valve open (IVO) timings was conducted with AVL‐Fire software based on EGR strategy of negative valve overlap (NVO) .The simulation results show that the EGR strategy can not only avoid the backfire but also guarantee a certain intake mass flow and charging efficiency when the IVO timing is 380° and the exhaust valve closure (EVC) timing is 340° .EGR concentration shows a gradient distribution of low value near the spark plug at the late of compression stroke by using NVO ,which is beneficial to ignition and flame propagation .Moreover ,the NVO can decrease the maximum in‐cylinder pressure and temperature ,but reduces the fresh working gas with the loss of engine power .In addition , NVO can realize internal EGR with NOx reduction ,but leads to difficult ignition by slowing the combustion .Ignition delay and combustion duration shortens by improving the ignition energy ,and then the combustion accelerates .
Pages: 65-69,75
Year: 2015 Issue: 3
Journal: Vehicle Engine
Keyword: hydrogen engine; compressed natural gas (CNG ) engine; negative valve overlap; exhaust gas recirculation (EGR); simulation;
Abstract: In order to reduce NOx emission of hydrogen‐enriched compressed natural gas (HCNG) engine ,3D simulation of intake and combustion process under different intake valve open (IVO) timings was conducted with AVL‐Fire software based on EGR strategy of negative valve overlap (NVO) .The simulation results show that the EGR strategy can not only avoid the backfire but also guarantee a certain intake mass flow and charging efficiency when the IVO timing is 380° and the exhaust valve closure (EVC) timing is 340° .EGR concentration shows a gradient distribution of low value near the spark plug at the late of compression stroke by using NVO ,which is beneficial to ignition and flame propagation .Moreover ,the NVO can decrease the maximum in‐cylinder pressure and temperature ,but reduces the fresh working gas with the loss of engine power .In addition , NVO can realize internal EGR with NOx reduction ,but leads to difficult ignition by slowing the combustion .Ignition delay and combustion duration shortens by improving the ignition energy ,and then the combustion accelerates .
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