Evaluation of HCCI Engine Potentials in Comparison to Advanced Gasoline and Diesel Engines

The objective of this program was to improve the HCCI combustion process on a single-cylinder VCR engine by calibrating engine and HCCI operation specific factors such as EGR flow rates, intake air pressure, intake air temperature, compression ratio, etc. Due to the large number of factors to be investigated, a statistical design of experiments method (DoE) was utilized in order to reduce the number of test combinations in the calibration test matrix and, thus, the duration of the engine calibration task. Upon completion of the HCCI engine calibration, the engine was operated through a steady-state test matrix representing vehicle certification test cycles. Weighting factors for each of the test points were applied to estimate the engine performance and emissions in respect to certification requirements. Additionally, mathematical correction models were developed to investigate possible engine performance improvements by means of Variable Valve Actuation and Miller combustion cycle application. A literature search for comparison of engine data from modern gasoline and diesel engines was conducted. Finally, the HCCI engine test results were compared to engine performance data from the literature search. The reported results include data plots illustrating the engine-to-engine comparison on an engine brake-specific basis (i.e. g/kwh) as well as charts estimating the performance of the HCCI combustion system in comparison to modern gasoline and diesel powered vehicles.