Study on Characteristics of Gasoline Fueled HCCI Using Negative Valve Overlap

Gasoline fueled Homogeneous Charge Compression Ignition (HCCI) combustion with internal exhaust gas re-circulation using Negative Valve Overlap (NOL) was investigated by means of calculation and experiment in order to apply this technology to practical use with sufficient operating range and with acceptable emission and fuel consumption. In this paper we discuss the basic characteristics of NOL-HCCI with emphasis on the influence of intake valve timing on load range, residual gas fraction and induction air flow rate. Emission and fuel consumption under various operation conditions are also discussed.

A water-cooled 250cc single cylinder engine with a direct injection system was used for this study. Three sets of valve timing were selected to investigate the effect of intake valve opening duration. Experimental results demonstrated that an engine speed of approximately 2000rpm yields an NMEP (Net Mean Effective Pressure) range from 200kPa to 400kPa. Operation with high engine speed, up to 4800rpm, was possible with the widest intake valve opening duration, while operation at low engine speed was less stable than with narrower intake valve opening duration. NOx emission was affected by AFR with wider intake valve opening duration showing less NOx emission at the same load.