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This work has focused on studying the in-cylinder pressure fluctuations caused by rapid HCCI combustion and determine what they consist of. Inhomogeneous autoignition sets up pressure waves traversing the combustion chamber. These pressure waves induce high gas velocities which causes increased heat transfer to the walls or in worst case engine damage. In order to study the pressure fluctuations a number of pressure transducers were mounted in the combustion chamber. The multi transducer arrangement was such that six transducers were placed circumferentially, one placed near the centre and one at a slight offset in the combustion chamber. The fitting of six transducers circumferentially was enabled by a spacer design and the two top mounted transducers were fitted in a modified cylinder head. During testing a disc shaped combustion chamber was used. The results of the tests conducted were that the in-cylinder pressure experienced during rapid HCCI-combustion is inhomogeneous.

This study examines fuel auto-ignitability and shows a method for determining fuel performance for HCCI combustion by doing engine experiments. Previous methods proposed for characterizing HCCI fuel performance were assessed in this study and found not able to predict required compression ratio for HCCI auto-ignition (CRAI) at a set combustion phasing. The previous indices that were studied were the Octane Index (OI), developed by Kalghatgi, and the HCCI Index, developed by Shibata and Urushihara. Fuels with the same OI or HCCI Index were seen to correspond to a wide range of compression ratios in these experiments, so a new way to describe HCCI fuel performance was sought. The Lund-Chevron HCCI Number was developed, using fuel testing in a CFR engine just as for the indices for spark ignition (research octane number and motor octane number, RON and MON) and compression ignition (cetane number, CN).