DIESEL ENGINE CYLINDER GAS-SIDE HEAT TRANSFER TO A CERAMIC SURFACE.

摘要

This dissertation contains two parts. The first part is a study of the effects of swirl and injection parameters on direct injection engine in-cylinder heat transfer. The second part is a study of the effects of surface materials and extent of insulation on the heat transfer to the head of an open-chamber diesel.; In the first study, engine parameters varied were the injection pressure, nozzle geometry and air swirl level. Two heat flux transducers were installed in a research head instrumentation plug to provide measurement of heat transfer rates to the head surface one over the bowl and the other over piston squish lip.; The effect of increased injection pressure was found to increase the peak heat flux, to advance the timing of this peak and to generally increase the time-averaged heat flux. Increasing the swirl level decreases the heat flux level. Trends of the heat flux are mostly similar for the three different nozzle geometries tested. Surface heat fluxes measured at the transducer over the piston bowl are higher than those measured over the piston squish lip.; In the second study, a large instrumentation plug designed to incorporate plates of various materials on the gas-side surface was utilized with a special research head. Instantaneous rates of heat transfer to the plate gas-side surface were measured. Measurement results obtained with a zirconia plate and an insulated metal plate were compared to data for an uninsulated metal plate.; The insulation of the metal plate increased its gas-side surface temperature over the uninsulated case by about the same amount achieved with a 6.35-mm-thick zirconia plate. The magnitude of the surface temperature swing for zirconia was not as high as expected, but was substantially higher than that for the uninsulated metal. Significant reductions of steady state heat fluxes were achieved with both the zirconia and the insulated metal compared to the uninsulated metal. However, peak values of surface heat fluxes for the insulated metal were found to be higher than those for the uninsulated metal. Substantial reductions in peak values of surface heat flux were achieved with zirconia over the uninsulated metal. Surface temperature levels for zirconia were not as high as possible because of limitations placed on the thermal loading by the design of the research engine head.