An approach of experimental study on HCCI engine

Spark ignition engine (S.I) and compression ignition engine (CI) development is reached to peak stage from the last decades even it may have the substantial advantages in efficiency and exhaust emissions still it may need to go for further advancement by research activities for the day to day changes for the future requirements. The CI engine has a fuel efficiency advantage over the SI engine due to higher thermodynamic efficiency and lower pumping losses. In regard to the exhaust emissions the SI engine holds an advantage over the CI engine. From researches the new combustion concept is the homogenous charge compression ignition (HCCI), is a promising technology that combines elements of the diesel and gasoline engine. Engine operations in HCCI mode for the advanced reciprocating internal combustion engine allows for improvement of thermal efficiency and substantial reduction NOx emission. The attractive properties are increased fuel efficiency due to reduced throttling losses, increased expansion ratio and higher thermodynamic efficiency. The most production feasible solution for gasoline HCCI engine is application of exhaust gas recirculation. This technique increases thermal energy of a mixture, thus allowing for autoignation at moderate compression ratios. However, high exhaust gas recirculation rate decreases be applied in order to improve volumetric efficiency and extend high load limit. However increase the amount of intake air can lead to reduction of start of compression temperature via decreases of residuals in a mixture.in order to achieve HCCI mode of combustion, temperature of start of compression must be kept within narrow limits. HCCI is a way to increase the efficiency of the gasoline engine. With the advantages there are some mechanical limitations to the operation of the HCCI engine. The implementation of homogenous charge compression ignition (HCCI) to gasoline engines is constrained by many factors. The main drawback of HCCI is the absence of direct combustion timing control. Therefore all the right conditions for auto ignition have to be set before combustion starts In this experimental study investigations and modeling are studied. Experiments were carried out using four stroke single cylinder and six cylinder research engines. The single cylinder engine was equipped with fully variable valve train and direct gasoline injection. Application of mechanical boosting allowed for widening achievable load range in HCCI mode of operation. Numerical calculations allowed for determination of admissible valve train setting and intake pressure, which guarantee proper temperature of start of compression.