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Earlier work has shown that the in-cylinder flow in internal combustion engines can be modelled, with reasonable accuracy, as the sum of an ensemble averaged mean component, a non-stationary ‘turbulence’ component and a ‘cycle-to-cycle’ variation component, the latter being phase-locked to the engine cycles. The development of the LDA technique has enabled direct measurements of the in-cylinder velocity field to be taken, either at a single position in space over the engine cycle, or over a range of spatial positions, at effectively one point in the engine cycle (scanning LDA). Previously, different approaches have been developed for separating the various flow components in the model described above, dependent on the type of data acquired. In this paper a single ‘unified’ method is presented, based on the computation of autocorrelation functions and a completely parametric representation of the various components in the flow model.

To gain a better understanding of the exhaust emissions impact of olefins in a low aromatic, full boiling range gasoline, an evaluation of the before and after catalyst emissions of three highly olefinic refinery streams and three highly paraffinic refinery streams, blended 50/50 in motor alkylate, was conducted using a 3.1 L GM engine. The test fuels were also selected to consider the effects of volatility in addition to olefin concentration. The fuels were evaluated under three steady state engine operating conditions. The results of the tests indicate essentially only small differences in the before and after catalyst total hydrocarbons (THC) between the pairs of highly olefinic streams and the highly paraffinic streams at relatively the same volatility level, for two of the test conditions (2400RPM-light and moderate/heavy loads. The ozone forming potentials (OFP) for these fuels, across all three speed and load conditions, also show relatively small differences.