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Technical Paper

Measurements of Instantaneous Heat Flux to Metal and Ceramic Surfaces in a Diesel Engine

The effects of surface materials and extent of insulation on the heat transfer to the head of an open-chamber diesel were studied. 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 are 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 is not as high as expected from conduction theory, but is 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.
Technical Paper

A Study of Diesel Cold Starting using both Cycle Analysis and Multidimensional Calculations

The physical in-cylinder processes and ignition during cold starting have been studied using computational models, with particular attention to the influences of blowby, heat transfer during the compression stroke, spray development, vaporization and fuel/air mixture formation and ignition. Two different modeling approaches were used. A thermodynamic zero dimensional cycle analysis program in which the fuel injection effects were not modeled, was used to determine overall and gas exchange effects. The three-dimensional KIVA-II code was used to determine details of the closed cycle events, with modified atomization, blowby and spray/wall impingement models, and a simplified model for ignition. The calculations were used to obtain an understanding of the cold starting process and to identify practical methods for improving cold starting of direct injection diesel engines.
Technical Paper

Analysis and In-Cylinder Measurement of Particulate Radiant Emissions and Temperature in a Direct Injection Diesel Engine

In-cylinder flame temperature and particulate concentration were measured in a Cummins single cylinder NH diesel engine by means of an optical radiation probe using the two-color theory. The radiation probe consists of a specially designed trifurcated fiber optical bundle and a sapphire rod window. A self-cleaning window was designed, which stays clean under steady state full load conditions. The engine was operated at various conditions for both standard cooled and simulated mini-cooled configurations. The heat release rate data and exhaust emissions, NO, NOx and CO are presented along with the radiant emission data. Increasing the coolant temperature gave slightly more exhaust soot production as well as in-cylinder soot production, because more late burning occurred at the higher coolant temperature. It is believed that increased late burning was caused by the delayed end of injection and lower injection rate perhaps due to thermal expansion effects in the injector.
Technical Paper

Mathematical Simulation of a Large Turbocharged Two-Stroke Diesel Engine

The multicylinder turbocharged engine was simulated by assuming each cylinder undergoes the same thermodynamic cycle. The model for the cylinder includes instantaneous heat transfer, homogeneous combustion burning rates, and a scavenging model which allows any intermediate mode between perfect scavenging and complete mixing. Metal surface temperatures are calculated by use of cyclic energy balances. The air receiver pressure is assumed constant and the exhaust manifold pressure is calculated by use of a filling and emptying process. The turbocharger turbine is analyzed on a quasi-steady basis with given mass flow-expansion ratio characteristics and efficiency-velocity ratio curves. Steady flow is assumed and experimental performance was used to model the compressor. Engine and turbocharger operating conditions are adjusted in the program until an energy balance is attained between the engine and the turbocharger.
Technical Paper

Geometry of the Fuel Cloud Created by Impingement of a Diesel Jet onto a Small Heated Target

The work presented was performed to increase the understanding of the important variables involved in the radial penetration of the droplet cloud formed by a liquid jet impinging on a target placed a short distance from the injector orifice. The experiments studied a spray produced in a high pressure, ambient temperature bomb by a Lucas CAV injector system with a Bosch pump. Three experimental procedures were performed. The first experiment used a laser interrupt method to determine the radial penetration of the impinged spray. The conclusions from these tests are that the important parameters are nozzle size, impingement distance, ambient density, and target diameter. The second experiment used high speed movies to determine the droplet cloud penetration and height at discrete time steps. This experiment yielded a series of diagrams which illustrate the development of the impinged spray. The third experiment determined the heat transfer from the heated target to the impinging liquid.