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A naturally aspirated, direct injection diesel engine was modified in order to be run on dimethyl ether (DME), with a conventional pump-line-nozzle system. The effects of various modifications to engine timing and the injection system as well as EGR were experimentally determined. Compared to the original diesel engine, the NOx emissions were reduced by over 70% through the use of suitable timing, lowered injector opening pressure and EGR. Particulate emissions were very low, and represent over a 90% reduction as compared to the original diesel version. The original pump-line-nozzle injection system was found to be not well suited to DME operation, CO and HC emissions were substantially higher due to secondary injections, caused by high pressure oscillations and residual pressure with the DME.

The paper presents a 2-dimensional model for the calculation of the regeneration process in a wall flow diesel particulate filter. The model includes heat transfer by conduction and convection, a model for particle combustion based on diffusive burning of individual particles, and flow through the channels and across the filter walls. It was found that only the pressure drop across the walls need be considered for normal regeneration conditions. Comparisons between model predictions and experimental results for spatial dependent temperature time histories, and integrated degree of regeneration are used to validate the model. The validations were carried out for a series of severe regenerations, where there are large changes in flow and temperature throughout the process. Relative magnitudes of energy flows due to combustion, convection, and conduction are presented, as well as parametric studies of the effects of temperature, oxygen concentration and soot loading.

Silicon Carbide (SiC) has been shown to have a high melting/decomposition temperature, good mechanical strength, and high thermal conductivity, which make it well suited for use as a material for diesel particulate filters. The high thermal conductivity of the material tends to reduce the temperature gradients and maximum temperature which arise during regeneration. The purpose of this paper is to experimentally investigate the thermal loading which arise under regenerations of varying severity. An experimental study is presented, in which regenerations of varying severity are conducted for uncoated SiC and Cordierite filters. The severity is varied through changes in the particle loading on the filters and by changing the flow conditions during the regeneration process itself. Temperature distributions throughout the filters are measured during these regeneration.

Recent studies have shown that SiC provides substantial advantages for use as the material for wall flow diesel particulate filters. In addition to very advantageous thermal properties, it has been shown that SiC based filter material has higher permeability than Cordierite. This paper presents a comparison of the basic flow characteristics of SiC based and Cordierite based wall flow filter material, expressed in terms of parameters which are basic materials properties that are independent of filter geometry. In addition, the flow characteristics of the particulate matter collected on the filter during engine operation are presented. The results show that the advantageous flow characteristics observed with the basic filter material are retained for loaded filters, up to very high loadings.

Lower proof ethanol is shown to be a viable alternate fuel for diesel engines. This type of ethanol can be manufactured economically in small distillation plants from renewable grain supplies. The effect of fumigation of ethanol proofs with a multipoint injection system on a turbocharged direct injection diesel engine at 2,400 rpm and three loads was studied. The addition of the water in the lower proofs reduced the maximum rate of pressure rise and peak pressure from pure ethanol levels. Both of these values were significantly higher than those for diesel operation. HC and CO emissions increased several times over diesel levels at all loads and also with increased ethanol fumigation. NO emissions were reduced below diesel levels for lower proof ethanol at all loads. The tests at this rpm and load with a multipoint ethanol injection system indicate that lower (100 or 125) proof provides optimum performance.

A study has been done to determine the effect of changes in diesel injection timing on engine performance using a multicylinder, turbo-charged diesel engine fumigated with ethanol. Tests at half load with engine speeds of 2000 and 2400 rpm indicated that a 4% increase in thermal efficiency could be obtained by advancing the diesel injection timing from 18 to 29 °BTDC. The effect of changes in diesel timing was much more pronounced at 2400 rpm. Advancing the diesel timing decreased CO and unburned HC levels significantly. The increase in NO levels due to advances in diesel timing was offset by the decrease in NO due to ethanol addition.

A complete non-steady intake and exhaust flow single cylinder computer simulation for spark ignition IC engines has been developed and is presented. The in-cylinder calculations include the use of a two-zone combustion model. The exhaust flow incorporated a quasi-steady heat transfer coefficient correlated from experimental data. Measurements from the experiment are compared to the results from the simulation. It was found that the quasi-steady heat transfer coefficient accurately models the temperature transients of the exhaust.

The availability and low price of personal computers with suitable interface equipment has made it practical to use such a system for cylinder pressure data acquisition. With this objective, procedures have been developed to measure and record cylinder pressure on an individual crank angle basis and obtain an average cylinder pressure trace using an Apple II Plus personal computer. These procedures as well as methods for checking the quality of cylinder pressure data are described. A simplified heat release analysis technique for an approximate first look at the data quality is presented. Comparisons are made between the result of this analysis, the Krieger-Borman heat release analysis which uses complete chemical equilibrium. The comparison is made to show the suitability of the simplified analysis in judging the quality of the pressure data.

The reaction of ethylene in engine exhaust gases has been studied using a turbulent plug flow reactor. The effects of ethylene, oxygen, and nitric oxide concentrations and of temperature on the reaction were investigated. Nitric oxide was found to be consumed in the reaction and partially converted to nitrogen dioxide. For temperatures up to 649 °C, little formation of carbon dioxide was measured for a reaction time of 140 ms. Increasing the oxygen concentration above 4% gave no increase in the oxidation rate. The Kinetics of the reaction were such that it was not possible to describe the reaction with a simple Arrhemus rate expression. The only other hydrocarbon found was a trace of acetylene at a reaction temperature of 649 °C.

A computer simulation of a three lobe, roots blower for use as a positive displacement supercharger has been developed. The simulation considers three to five control volumes existing at various times in the supercharger cycle, and numerically integrates continuity and energy equations for the control volumes throughout the cycle. Instantaneous properties for the control volumes and instantaneous flows throughout the supercharger are predicted. Comparisons between predicted and experimental performance show that the simulation can adequately model performance trends of the supercharger. Use of the simulation in providing a supercharger map and supercharger performance on an engine is shown.

A normally aspirated, four-stroke diesel engine was tested under operation with two alcohol containing fuel blends. The fuels contained ethanol, butanol, heavy virgin distillate, diesel Nos. 2 and 4, and a cetane improver. The proportions of the components were selected to give blends with properties within the range of diesel No. 2. The final blends contained 25 and 43.7 percent alchohols. Test results showed a loss in power due to the reduced heating value of the blends, and some deterioration of performance at light loads. At intermediate to heavy loads, satisfactory performance was obtained.

Experimental studies have been performed on a three-valve, single cylinder stratified charge engine in order to determine the effects of main chamber intake port injection and main chamber swirl on performance. Results indicate that injection timing affects hydrocarbon and carbon monoxide emissions but has little effect on NOx emissions and performance. Main chamber swirl, generated through the use of an intake port mask, resulted in increased power, lower fuel consumption, lower carbon monoxide emissions, and higher hydrocarbon emissions at a given level of NOx emissions. Changes in performance and emissions with swirl were attributed to improved mixing in the main chamber and an increased rate of combustion.

An experimental system has been constructed to study the heat transfer processes in the straight section of the exhaust port of a four-stroke, spark ignition engine. The effects of engine variables on the steady-state heat transfer rates have been studied at four locations in the exhaust port. It was found that the heat transfer rates have a significant dependence upon the location within the exhaust port. Data have been correlated in the form of a Nusselt-Reynolds number relationship for local and spatially averaged steady-state heat transfer. It has been shown that the use of conventional steady-state heat transfer relationships for developing steady-state turbulent flow in pipes predicts heat transfer rates which are lower than those experimentally observed.

A model has been developed for simulating the combustion in a three-valve stratified charge spark ignition engine. The conservation equations for mass, momentum, chemical species, and energy are numerically integrated for a one-dimensional flame using an empirical model for turbulent diffusivity. The chemical reaction of the fuel and air is modeled using simple kinetics in a one-step reaction and experimentally determined ignition delays are used. Nitric oxide emissions are calculated using a simple Zeldovich model with steady state atomic nitrogen and equilibrium atomic oxygen. Effects of various assumptions and parameters in the model are discussed and comparisons with experimental data from a single-cylinder engine are presented.

An analytical study has been performed to investigate the use of a one-dimensional combustion model for transient premixed flames under conditions similar to those occurring in a sparkignition internal combustion engine. The model consists of the numerical integration of the basic conservation equations for mass, momentum, energy, and species with the effects of turbulence modeled by the use of a turbulent diffusivity. In order to evaluate the effects of some of the assumptions and identify the significant parameters, a simplified system consisting of constant volume adiabatic combustion was considered. With simple chemical kinetics and constant turbulent diffusivity, there are three parameters in the problem: a non-dimensional speed of sound, a non-dimensional temperature rise due to combustion, and a Damkohler parameter relating diffusion and chemical reaction rate effects. Two types of flames were modeled, a flat flame in linear coordinates and a cylindrical flame.

One alternative to the problem of improving fuel consumption while reducing high exhaust emissions is the dual chamber stratified charge spark ignition engine. This paper describes the various phases of the research program now being conducted. Its purpose is to better understand the basic combustion process in this type of engine and the fundamental limitations involved. Typical results obtained in the initial phases of study are illustrated.

Methods used for the study of the kinetics of exhaust hydrocarbon reactions are reviewed, compared and contrasted. The isothermal plug flow reactor which allows the determination of time resolved concentration histories of reactants, intermediate products, and final products is suggested as, perhaps, the most desirable and versatile system for the study of moderate temperature hydrocarbon oxidation reactions. The isothermal plug flow reactor allows the gas phase reactions to be studied with kinetically well-defined, repeatable, homogeneous reaction conditions that are essentially free of heterogeneous interference. Due to the detailed data obtainable and the controlled reaction conditions, kinetic mechanisms can be studied and evaluated. Investigations that used this technique are reviewed and examples cited to demonstrate the unique capabilities of the plug flow reactor.

The purpose of this paper is to review the results of an experimental test program conducted on a commercial four cylinder spark ignition internal combustion engine. Corrected brake horsepower, corrected brake mean effective pressure and enthalpy efficiency are presented covering equivalence ratios from .42 through .63 at MBT timing under full load (or equivalently, wide open throttle) conditions. In addition, advanced cam timing was studied as a means of improving control of the hydrogen combustion rate and found to be ineffective. MBT timing characteristics suggest a marked increase in flame speed at full load operation for engine speeds above 1500 rpm, which is independent of equivalence ratio and cam timing.

This paper describes a method for studying reactions of hydrocarbons in S.I. engine exhaust gases. The reaction of ethane is described using an Arrhenius model (experimentally E = 86,500 cal/mole) for the rate of ethane diappearance and empirical correlations for distributions of the products carbon monoxide, ethylene, formaldehyde, methane, acetylene, and propane as a function of the fraction of ethane reacted. The results show that the nature of partial oxidation products from a nonreactive hydrocarbon may be less desirable from an air pollution viewpoint than the initial hydrocarbon.