The possibility of using CNG and diesel fuel in CI engine under dual-fuel mode by evaluation of performance and combustion characteristics at different coolant temperatures

experiments were conducted on a stationary four-stroke, naturally aspirated, water-cooled, single-cylinder, compression ignition engine to study the effects of blending CNG with neat diesel in dual-fuel operational mode and the variation in engine coolant temperature on performance parameters. For this study, factorial experiments in the form of a randomized complete block design with three replications were used to analyze the statistical status of the data. The studied parameters were fuel ratio, engine speeds and coolant temperatures. All experiments were conducted at the governor control mode. The results showed that, torque, brake power and brake mean effective pressure (BMEP) in diesel-CNG dual-fuel mode at all engine speeds significantly increased compared to pure diesel. At low engine speeds, increasing the coolant temperature reduced the brake specific fuel consumption (BSFC) and brake specific energy consumption (BSEC). Also, in the diesel-CNG dual-fuel mode compared to the engine with baseline diesel fuel, BSFC and BSEC were significantly lower. Brake thermal efficiency (BTE) also showed a significant increase at high speeds and when using dual-fuel operational mode. However, raising the coolant temperature increased the BTE. When using the engine in dual-fuel mode and increasing the temperature of the coolant, the volumetric efficiency showed a significant reduction.  Furthermore, raising the coolant temperature diminished the volumetric efficiency. Overall, it can be stated that the use of a diesel-CNG dual-fuel mode with a coolant temperature of 60 degrees Celsius at entire engine speeds has the best outputs on the performance and combustion characteristics of the engine.