Boosted HCCI operation on multi cylinder V6 engine

This paper is an extension of work done with boosted 1-cyl Homogenous Charge Compression Ignition (HCCI) engine. As has been proven in the authors’ laboratory on a single cylinder research engine, applying boosting can enable an increased load range with a decreased NOx emission. During the tests which are covered in this paper, a Jaguar V6 research engine with a negative valve overlap facility has been used. The engine is equipped with a mechanically coupled supercharger, which supplies the required amount of air. The introduction of a higher amount of air allows the cylinder mixture to be kept on a highly diluted level; this enables autoignition to be controlled and improves NOx emission. Finally, more air introduced into the cylinder enables more fuel to be injected, which in turn provides for a higher load. This fact is useful as one method to increase the upper load limit for HCCI. Boosted HCCI operation is very sensitive to exhaust gas residuals. It has been proven that valve operation, whether advancing or retarding away from the optimum point will affect NOx emission. Th6is paper will demonstrate that the optimisation of valve timing in connection with lambda value and boost pressure can produce lower NOx emission for the same or even a higher load.