Comprehensive investigation of injection parameters effect on a turbocharged diesel engine based on detailed exergy analysis

Abstract

In this study, the change rules and influence mechanism of injection pressure and timing on exergy terms at different working conditions are investigated based on a turbocharged diesel engine test platform, a multi-dimensional simulation model and subsequent theoretical calculation. To have a comprehensive analysis, the detail mechanism and distribution characteristic of exergy destruction were also studied at different injection parameters from the perspective of in-cylinder microscopic field. The results showing that first, adjusting injection pressure from 130 MPa to160 MPa, exergy efficiency and heat transfer exergy are positively correlated with injection pressure, while exhaust exergy and exergy destruction are negatively correlated with injection pressure, but the influence of injection pressure on heat transfer exergy and exergy destruction is relatively weak. Secondly, advancing injection timing from 1.7°CA BTDC to 6.7°CA BTDC, the exergy efficiency and heat transfer exergy increase significantly, while the exhaust exergy and exergy destruction decrease gradually, compared with injection pressure, injection timing has a greater impact on exergy terms. Third, variation of exergy terms occurs mainly in combustion process at different injection parameters. Fourth, the higher exergy destruction mainly concentrates in the region with equivalence ratio of 1–1.5 at different injection pressures, the EDR (exergy destruction rate) is proportional to HRR (heat release rate) in the same temperature range at different injection timing, the root influence causes of injection pressure and timing on exergy destruction are inhomogeneity of equivalent ratio and local temperature during combustion process, respectively. Finally, increasing exergy efficiency is accompanied by decrease of exergy destruction, reasonable adjustment of injection parameters of turbocharged diesel engine to enhance high-temperature and lean combustion characteristics during combustion process of in-cylinder mixture can effectively promote the exergy efficiency and restrain exergy destruction.