| Combustion and Emission Characteristics of a Natural Gas Engine under
Different Operating Conditions |
| Haeng Muk Cho1, and Bang-Quan He2† |
1Division of Mechanical Engineering and Automotive Engineering, Kongju National Univeristy, 276, Budae-Dong, Cheonan-City, Chungnam 330-717, Korea
2State Key Laboratory of Engines, Tianjin University, 92, Weijin Road, Nankai District, Tianjin 300072, PR China |
Corresponding Author:
Bang-Quan He ,Tel: +86-22-27406842-8011, Fax: +86-22-27383362, Email: bqhe@tju.edu.cn
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Received: October 15, 2008; Accepted: April 14, 2009. |
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| ABSTRACT |
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Natural gas is a promising alternative fuel of internal combustion engines. In this paper, the combustion and emission characteristics were investigated
on a natural gas engine at two different fuel injection timings during the intake stroke. The results show that fuel injection timing affects
combustion processes. The optimum spark timing (MBT) achieving the maximum indicated mean effective pressure (IMEP) is related to fuel injection
timing and air fuel ratio.
At MBT spark timing, late fuel injection timing delays ignition timing and prolongs combustion duration in most cases. But fuel injection timing
has little effect on IMEP at fixed lambdas. The coefficient of variation (COV) of IMEP is dependent on air fuel ratio, throttle positions and fuel injection
timings at MBT spark timing. The COV of IMEP increases with lambda in most cases. Late fuel injection timings can reduce the COV of IMEP
at part loads. Moreover, engine-out CO and total hydrocarbon (THC) emissions can be reduced at late fuel injection timing. |
| Keywords:
Natural gas | Emission | Lean burn | Combustion | Engine |
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