Experimental Investigations into Combustion Characteristics of Natural Gas-Gasoline Dual-Fuel Engines

To investigate the feasibility and advantage of natural gas-gasoline dual-fuel combustion in modern engines,the combustion characteristics of natural gas-gasoline dual-fuel with different engine loads,excess air coefficients and substitute rates of natural gas were studied on a turbocharged direct-injection engine with port-injection of natural gas and direct-injection of gasoline.It was found that at low loads with constant torque output,peak pressure increases,combustion advances,and cyclic variation decreases with the increase of natural gas mass flow,especially at lean combustion conditions.The combustion at medium load conditions shows a similar trend to that at low loads,and with the increase of natural gas mass flow effective thermal efficiency is greatly improved at high natural gas substitute rates and lean combustion cases.At large load conditions with fully-opened throttle engine knock is effectively delayed,knocking intensity is significantly decreased and combustion is advanced even though there is some decrease in the maximum torque output.Since insufficient engine power output can be compensated by supercharging,the natural gas-gasoline dual-fuel engines,therefore,have a good application prospect.