Abstract
A throttle can be installed on the intake pipe of a natural gas (NG)/diesel dual-fuel engine to control the excess air ratio of the air-fuel mixture by adjusting the air intake. Building on a previously proposed NG/diesel dual-fuel supply strategy using the adjustment of excess air ratio, this work further studied the effects of different injection timing schemes on output power, fuel efficiency, and pollutant emissions of a dual-fuel engine under low to medium load conditions. In the experiment, the engine was operated at a speed of 1600 r/min, under either low (27.1 N·m) or medium (50.6 N·m) loads, and the NG substitution rate was either 40%, 60%, or 80%. The effect of different injection timing schemes on the combustion performance of the engine under low to medium load conditions was studied based on in-cylinder pressure changes detected by a pressure sensor. Experimental results showed that under medium-speed low-load conditions and a NG substitution rate of 40%, setting the diesel injection timing to 27 °CA BTDC increased the engine output power by 9.03%, reduced the brake specific energy consumption (BSEC) by 13.33%, and effectively reduced CO, CO2, and HC emissions. Under medium-speed medium-load conditions with a NG substitution rate of 80%, setting the diesel injection timing to 25 °CA BTDC increased the engine output power by 14.62%, reduced the BSEC by 11.73%, and significantly reduced CO, CO2, and HC emissions.
Highlights
Natural gas (NG) is widely regarded as one of the most promising clean alternative fuels for internal combustion engines owing to its high hydrogen to carbon (H/C) ratio, high auto-ignition temperature, and affordable price
Building upon on a previously proposed NG/diesel dual-fuel supply strategy based on adjustment of the excess air ratio, this study further examined the effect of diesel injection timing (DIT)
Under the requirement of minimum retrofit on the engine provided by the cooperative enterprise, our previous work examined that it was possible for the target engine working under low to medium load conditions to achieve a higher substitution rates (SR) and to reduce nitrogen oxide (NOx ) emissions by controlling the excess air ratio, without the support of exhaust gas recirculation (EGR) and turbocharger [9]
Summary
Natural gas (NG) is widely regarded as one of the most promising clean alternative fuels for internal combustion engines owing to its high hydrogen to carbon (H/C) ratio, high auto-ignition temperature, and affordable price. The authors installed a throttle body on the original intake pipe of the diesel engine to control the air flow and to study the effects of different NG substitution rates (SR) on the performance of an engine working in the dual-fuel mode under low to medium load conditions [9]. Under the requirement of minimum retrofit on the engine provided by the cooperative enterprise, our previous work examined that it was possible for the target engine working under low to medium load conditions to achieve a higher SR and to reduce nitrogen oxide (NOx ) emissions by controlling the excess air ratio, without the support of EGR and turbocharger [9]. In this study as a successive work, an experiment was conducted to investigate the effect of DIT on the power output, fuel efficiency, and pollutant emissions of the target engine working under low to medium load conditions at NG/diesel dual-fuel mode. The findings of this study provide a basis for formulating effective fuel supply strategies for the target engine working under low to medium load conditions at dual-fuel mode with a minimum retrofit cost
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