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An experimental study was conducted using the dumping technique (total cylinder sampling) to produce cylinder mass-averaged nitric oxide histories. Data were taken using a four stroke diesel research engine employing a quiescent chamber, high pressure direct injection fuel system, and simulated turbocharging. Two fuels were used to determine fuel cetane number effects. Two loads were run, one at an equivalence ratio of 0.5 and the other at a ratio of 0.3. The engine speed was held constant at 1500 rpm. Under the turbocharged and retarded timing conditions of this study, nitric oxide was produced up to the point of about 85% mass burned. Two different models were used to simulate the engine run conditions: the phenomenological Hiroyasu spray-combustion model, and the three dimensional, U.W.-ERC modified KIVA-II computational fluid dynamic code. Both of the models predicted the correct nitric oxide trend.

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.

The objective of this study was to observe and attempt to understand the effects of equivalence ratio and simulated exhaust gas recirculation (EGR) on the exhaust emissions and performance of a L-head single cylinder utility engine. In order to isolate these effects and limit the confounding influences caused by poor fuel mixture preparation and/or vaporization produced by the carburetor/intake port combination, the engine was operated on a premixed propane/air mixture. To simulate the effects of EGR, a homogeneous mixture of propane, air, and nitrogen was used. Engine measurements were obtained at the operating conditions specified by the California Air Resources Board (CARB) Raw Gas Method Test Procedure. Measurements included exhaust emissions levels of HC, CO, and NOx, and engine pressure data.

A theoretical model was developed to better understand the lubrication of piston rings. Models like this are important for studying oil consumption and its contribution to emission. The model suggests that temperature gradients and viscous heating in the oil film can be neglected if it is assumed the oil is the same temperature as the cylinder wall. A simple model suggests that vibrations will not affect the calculated film thickness significantly. Oil film thickness was measured in a Cameron Plint wear test rig and in a diesel engine. Evidence of oil starvation was observed in both tests. Measured and predicted film thickness correlated well on the wear test rig. Engine tests showed some unexpected trends, however the theory predicts oil film thicknesses of the same order of magnitude as the measured results. Measured results showed that separation occurs at the rear boundary of the ring. For modelling, the Reynolds boundary condition has the best correlation with experimental data.

A new method has been developed for measuring the oil films on cylinder walls in engines that offers benefits in improved understanding of oil transport and consumption. The unique aspect of this work is that fiber optics and laser induced fluorescence are combined to measure the oil film thickness. As a result the system is much less intrusive than previous methods using windows to observe the fluorescence. Static tests were used to demonstrate the characteristics of the technique. Dynamic tests, performed on a Cameron Plint wear tester, showed the capability of the system to measure thin films under dynamic conditions and at high loads and temperatures. Finally, the system was installed in a diesel engine and used to measure oil film thicknesses under fired conditions.

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.

An investigation into factors influencing top-ring oil film thickness at TDC, in a diesel engine, was carried out using capacitance probes and surface thermocouples installed in the liner. Short term and long term trends in the data were observed, and many unexpected features were found. Significant, consistent differences in the film thickness around the cylinder were detected, and the thermocouples showed that for this engine, the top ring unexpectedly cools the wall for a short time near TDC. Due to irreproducibility of the data, two different data acquisition techniques were used. Acquiring consecutive cycles, for a short period of time, provided a “high resolution snapshot” of the process. This method however, was not sufficient to characterize the data, and it was found that taking non-consecutive cycles, over a longer period of time, provided much more knowledge about the long term trends in the data.

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.

This paper reviews previous work on spark assisted diesel engines and then goes on to discuss the results of investigations carried out at U.W. Results are given for two Army referee fuels and compared to D2 fuel results. The data concentrates on starting and low load running of Type I fuel which is a broadcut fuel with a cetane number of 20. Results are given for both two stroke and four stroke open chamber engines modified for spark ignition. The best results were obtained by directing one fuel spray at a raised central portion of the piston and spark igniting the resulting fuel cloud at a position 12 mm from the head and near the cylinder axis.

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.

A single cylinder TACOM-LABECO open chamber diesel engine with a special research head, which incorporates an American Bosch Electronic Fuel Injection System, was used to study the effects of air swirl, injection pressure and nozzle geometry on exhaust particulates, NOx emissions, ignition delay, heat release and local heat flux measured at two positions on the head. Air swirl was varied from 0.8 to 4.5 swirl ratio by use of a shrouded intake valve. Peak injection pressure was varied from 35-114 MPa. Five different nozzle geometries were tested. All data were taken at a fixed engine operating condition of 2000 rpm and 0.5 equivalence ratio with an inlet pressure of 1.5 atm and nominal inlet temperature of 340°K.

Experimental histories of major species total concentrations in the cylinder were obtained for a single cylinder TACOM-LABECO diesel engine by using a dumping technique to quench the cylinder gas rapidly at various selected crank angles during the combustion and expansion process. Performance data using both an eight-hole and four-hole nozzle were taken for a range of swirl ratios, exhaust gas recirculation percentages and injection timings at medium load and 1000 RPM. Seven dumping histories were obtained all at 1000 RPM and 0.5 equivalence ratio for selected combinations of two injection timings (15 and 25), two EGR values (0 and 10%), two swirl ratios (2.5 and 4), and two nozzle tips (4 and 8 hole). These histories show cylinder-averaged values of NOx, CO and H2 as a function of crankangle.

A computer program which rapidly calculates the equilibrium mole fractions and the partial derivatives of the mole fractions with respect to temperature, pressure and equivalence ratio for the products of combustion of any hydrocarbon fuel and air is described. A subroutine is also given which calculates the gas constant, enthalpy, internal energy and the partial derivatives of these with respect to temperature, pressure and equivalence ratio. Some examples of the uses of the programs are also given.

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.

A method of calculating mass burning rates for a single cylinder spark-ignition combustion engine based on experimentally obtained pressure-time diagrams was used to analyze the effects of fuel-air ratio, engine speed, spark timing, load, and cyclic cylinder pressure variations on mass burning rates and engine output. A study of the effects on mass burning rates by cyclic pressure changes showed the low pressure cycles were initially slow burning cycles. Although large cyclic cylinder pressure variations existed in the data the cyclic variations in imep were relatively small.

A detailed mathematical simulation of a single cylinder, open chamber, naturally aspirated diesel engine was used to predict changes in performance caused by changing various engine design parameters. The computations have in some cases, been used to obtain the parameter values which give optimum performance. Among the parameters studied are: bore-stroke ratio, valve timing, intake and exhaust valve size, heat release patterns, compression ratio, and atmospheric temperature and pressure. The results are discussed and evaluated in terms of the assumptions used in the calculations.

Recently engineers from various companies have attempted to further the study of engine simulation. This paper considers how the cycle analysis works and gives a brief and qualitative description of it. It also considers cycle analysis in terms of how well it fulfills the designer's needs. Cycle simulation can be used for design studies, it can predict trends, it can serve as a diagnostic tool, it can give more complete data than normally obtained from experiments, and it helps in understanding of complex processes. A brief discussion of the simulation techniques for compression, combustion, exhaust, and intake processes is presented.