Energy, Vol.82, 353-360, 2015
Effect of control strategy on performance and emissions of natural gas engine for cogeneration system
Because of the global increase in the consumption of low-calorie natural gas, and increasing awareness of the mid-to long-term problem with the decrease in the calorific value of natural gas, actions are needed to minimize the problems with gas appliances. Most natural gas engines for small distributed cogeneration systems operate with a lean fuel/air mixture and do not employ an excess air ratio control and optimized spark advance timing. The engine performance can be influenced by calorific value changes in the natural gas without the excess air ratio control. In the present study, the performance and emission characteristics of a natural gas engine were experimentally investigated under different HHV (higher heating value) of natural gas fuel. Nitrogen was introduced to simulate a decrease in the HHV, and the injection duration of the injector, spark advance timing, and throttle valve opening were maintained to realize the non-control of the excess air ratio at the baseline condition, where the HHV was 10,300 kcal/Nm(3). To recover the level of torque with the HHV baseline, the combustion and emission characteristics for each control strategy were analyzed, and the feasibility of lowering the HHV of the natural gas fuel in the field was also assessed. (C) 2015 Elsevier Ltd. All rights reserved.