Effects of HCCI combustion on performance of the heavy-duty diesel engine fueled with natural gas fuel

Homogeneous charge compression ignition (HCCI) is one of the alternatives to reduce significantly engine emissions for future regulations. This new alternative combustion process is mainly controlled by chemical kinetics in comparison with the conventional combustion in internal combustion engines. In this paper, a heavy duty diesel engine is modeled in the GT-Power engine simulation software. After calibration of model, the outputs of the simulated model were compared with the available experimental data. The comparison showed that the results of a simulated engine and experimental data were in good agreement.

Then, the HCCI combustion of the considered engine with the natural-gas fuel was simulated by a variable volume computation including the piston motion into the chemical reaction design, CHEMKIN, package. The SENKIN code used in order to simulate the in-cylinder combustion. A single-zone zero-dimensional model was used in order to simulate the combustion phenomena. The chemical kinetic mechanism incorporated the GRI-3.0 mechanism that considers 53 species and 325 reactions together. Finally, these combustion results were transferred into an overall model of the considered engine in GT-Power software in order to calculate the engine performance characteristics. The computational model was validated by available experimental data. The results showed that the calculated data were relatively in good agreement with the experimental data. In contrast with the diesel engine, in HCCI combustion, the peak pressure is increased suddenly. The BMEP and output power in HCCI engine are also less than the BMEP and output power in diesel engine in the identical engine velocity. Also, the BSFC in HCCI engine is by far less than the diesel engine. The brake thermal efficiency in HCCI engine is a little less than the ones in diesel engine. The average amount of NO_x concentration in HCCI engine is by far less than the diesel engine.