Investigation of the effects of intake manifold pressure on performance and combustion characteristics in an HCCI engine

Abstract

Homogeneous charge compression ignition (HCCI) engines have significant advantages over spark ignition (SI) and compression ignition (CI) engines due to their high thermal efficiency and low NOx emissions. However, it is difficult to control the start of combustion. In this study, the effects of the intake manifold pressure on HCCI combustion were investigated experimentally at 373 K intake temperature in a four cylinders HCCI engine, which was transformed from the SI engine. It was observed that there was an advance in the start of combustion as the manifold pressure increased. It was also observed that the change in octane number had significant effects on the start of combustion. The highest thermal efficiency was recorded as 46.38% at 120 kPa manifold pressure using RON40 fuel. The increase in the volumetric efficiency that depends on the increase in manifold pressure provided an increase in maximum cylinder pressure and heat release. Figure A. In-cylinder pressure and heat release rate variations Purpose: This study aims to investigate the effects of the intake manifold pressure on HCCI combustion. Theory and Methods: A single cylinder, four stroke, port injection SI-HCCI engine was used in the experiments. Reference fuels which were RON0, RON20 and RON40 used in this study. Experimental study was performed at 1000 rpm engine speed, constant lambda 3 and constant 373 K inlet air temperature at different inlet air pressure of 100 kPa, 110 kPa, 120 kPa and 140 kPa in order to observe the controlling of HCCI combustion. Results: Since the increase in intake manifold pressure increases volumetic efficiency, maximum heat release and in-cylinder pressure also increase. Increasing the octane number delayed the combustion. Increasing the manifold pressure increased the rate of chemical reaction in the cylinder. Therefore, combustion starts at earlier crank angles. The highest indicated thermal efficiency was obtained as 46.38% with RON40 fuel at 120 kPa manifold pressure. At 140 kPa manifold pressure, most of the combustion occurs before TDC. This situation negatively affected the combustion efficiency. Under these conditions, increasing the octane number of the fuel made the combustion more controlled and slower. Conclusion: The manifold pressure directly affects the CA10. CA10 is advanced at the manifold pressure of 140 kPa and CA10 is delayed at 100 kPa and 110 kPa manifold pressure. In this study, it can be stated that the ideal manifold pressure is 120 kPa.