A Comparison of Thermal Efficiency of Carbureted and Injection Methanol Engines by Means of Thermodynamic Cycle Simulation

Thermal efficiency of carbureted and injection engine was compared through thermodynamic cycle simulation. When the compression ratio is the same, the combined control carbureted engine in which the A/F ratio control method is used in the high load range and the throttling method is used in the low load range shows the highest thermal efficiency followed by the injection engine and the throttling carbureted engine. The thermal efficiency of the injection engine is lower than that of combined control carbureted engine because the temperature of gases in cylinder does not rise much due to stratified charge combustion. When the compression ratio of these engines is optimized, the thermal efficiency is the highest for the injection engine followed by the combined control carbureted engine. The thermal efficiency of the combined control carbureted engine is lower than that of the injection engine at high and low loads, but they are in the same level at intermediate loads.