An experimental study has been carried out to provide qualitative and quantitative insight into gas to wall heat transfer in a gasoline fueled Homogeneous Charge Compression Ignition (HCCI) engine. Fast response thermocouples are embedded in the piston top and cylinder head surface to measure instantaneous wall temperature and heat flux. Heat flux measurements obtained at multiple locations show small spatial variations, thus confirming relative uniformity of incylinder conditions in a HCCI engine operating with premixed charge. Consequently, the spatially-averaged heat flux represents well the global heat transfer from the gas to the combustion chamber walls in the premixed HCCI engine, as confirmed through the gross heat release analysis. Heat flux measurements were used for assessing several existing heat transfer correlations. One of the most popular models, the Woschni expression, was shown to be inadequate for the HCCI engine. The problem is traced back to the flame propagation term which is not appropriate for the HCCI combustion. Subsequently, a modified model is proposed which significantly improves the prediction of heat transfer in a gasoline HCCI engine and shows very good agreement over a range of conditions.

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New Heat Transfer Correlation for an HCCI Engine Derived from Measurements of Instantaneous Surface Heat Flux

The Calculation of Heat Release Energy from Engine Cylinder Pressure Data

An experimental investigation was conducted to determine the emissions characteristics of higher alcohols and gasoline (UTG96) blends. While lower alcohols (methanol and ethanol) have been ...

Combustion characteristics of higher-alcohol/gasoline blends

A First Law analysis based on the cylinder pressure variation during combustion is a commonly used diagnostic for determining actual spark-ignition engine burning rates. Both simple one-zone and more complex two-zone models have been developed for this purpose. It is shown that the fraction of the fuel's chemical energy which has been released and the fraction of fuel-air mixture burned, within the engine's cylinder, can be accurately estimated from a one-zone analysis if appropriate values for the “average ratio of specific heats”, y¯, of the one-zone contents are used. These values are determined by matching the output of the one-zone analysis to that of the more rigorous two-zone analysis of the same cylinder pressure data. Use of this one-zone burning rate analysis procedure is illustrated.

Estimating Heat-Release and Mass-of-Mixture Burned from Spark-Ignition Engine Pressure Data

Calculation of Heat Release in Direct Injection Diesel Engines

In analyzing the processes inside the cylinder of an internal combustion engine, the principal diagnostic at the experimenter's disposal is a measured time history of the cylinder pressure. This paper develops, tests, and applies a heat release analysis procedure that maintains simplicity while including the effects of heat transfer, crevice flows and fuel injection. The heat release model uses a one zone description of the cylinder contents with thermodynamic properties represented by a linear approximation. Applications of the analysis to a single-cylinder spark-ignition engine, a special square cross-section visualization spark-ignition engine, and a direct-injection stratified charge engine are presented.

F. E. Nelson

Papers

Heat Release Analysis of Engine Pressure Data