Search Results

The KIVA 3V code has been applied to predict combustion chamber heat flux in an air-cooled utility engine. The KIVA heat flux predictions were compared with experimentally measured data in the same engine over a wide range of operating conditions. The measured data were found to be approximately two times larger than the predicted results, which is attributed to the omission of chemical heat release in the near-wall region for the heat transfer model applied. Modifying the model with a simple scaling factor provided a good comparison with the measured data for the full range of engine load, heat flux sensor location, air-fuel ratio and spark timings tested. The detailed spatially resolved results of the KIVA predictions were then used to develop a simplified model of the combustion chamber temporally integrated heat flux using an artificial neural network (ANN).

Bulk gas temperature in an HCCI engine was measured using a novel optical sensing technique. A wavelength-agile absorption sensor using a fiber-coupled LED was used to measure the in-cylinder gas temperature. H2O absorption spectra spanning 1380-1420nm were recorded once every 63 μs using this sensor. The gas temperature was inferred from a least-squares fit of the integrated absorbance areas of H2O absorption features in this spectral region to those from simulated spectra. The primary source of the H2O was the humidity in the intake air. Measurements were made during the compression and early portion of the combustion phase of an n-heptane fueled HCCI engine. The measured pressure-temperature history was compared to kinetic calculations of the ignition delay, and showed the traversal of the negative temperature coefficient regime.