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The diesel/natural gas engine configuration provides a potential alternative solution for PM and NOx emissions reduction from typical diesel engine operations. However, their engine operations suffer from high NMHC/methane emissions and poor engine performance, especially at light loads. By increasing the diesel pilot quantity, the performance and reduction of NMHC/methane emissions can be improved but the emission levels are still very high. Clearly, a typical DOC is not good enough to treat NMHC/methane emissions. Methane has been known as one of most stable species that is difficult to catalytically oxidize in lean burn environment and low exhaust temperatures. An aftertreatment system exclusively designed for treating methane emissions from DDF operations is therefore necessary. The current work is aimed to establish an effective computational tool in order to study the newly proposed catalytic converter system concept on treating methane from DDF operations.

A Texaco L-163S TCCS (Texaco Controlled Combustion System) engine was operated with pure methanol to investigate the origin and mechanism of unburned fuel (UBF) and formaldehyde emissions. The effects of engine load, speed and coolant temperature on the exhaust emissions were studied using both continuous and time-resolved sampling methods. Within the range studied, increasing the engine load resulted in a decrease of the exhaust UBF emissions and an increase in the formaldehyde emissions. Engine speed had little effect on both UBF and formaldehyde emissions. Decreasing the engine coolant temperature from 85°C to 45°C caused the exhaust UBF emissions to approximately double and the formaldehyde emission to increase approximately 20 percent. It is hypothesized that both fuel impingement and spray tailing are responsible for the high UBF emissions. In-cylinder formation of formaldehyde was found to be the major source of the exhaust aldehyde emissions in this experiment.

Diesel particulate samples were collected from a light duty engine operated at a single speed-load point with a range of biodiesel and conventional fuel blends. The oxidation reactivity of the samples was characterized in a laboratory reactor, and BET surface area measurements were made at several points during oxidation of the fixed carbon component of both types of particulate. The fixed carbon component of biodiesel particulate has a significantly higher surface area for the initial stages of oxidation, but the surface areas for the two particulates become similar as fixed carbon oxidation proceeds beyond 40%. When fixed carbon oxidation rates are normalized to total surface area, it is possible to describe the oxidation rates of the fixed carbon portion of both types of particulates with a single set of Arrhenius parameters. The measured surface area evolution during particle oxidation was found to be inconsistent with shrinking sphere oxidation.

Ethanol has been injected through an atomizing nozzle into the intake manifold of a four cylinder turbocharged diesel engine. It was found that to avoid liquid droplet impingement on the compressor blades the injector needed to be located downstream of the compressor, in the high pressure section of the inlet manifold. 160 proof and 200 proof alcohols were investigated with a series of percentage substitutions at different speeds and loads. The fumigation of ethanol resulted in a slight improvement in thermal efficiency at high loads and a small reduction at light loads. The ignition delay and rate of pressure rise also increased significantly when ethanol was added to the engine. A change in the proof of ethanol from 160 to 200 did not produce any noticeable change in engine performance. Emission measurements were also made and are discussed. The problem of obtaining uniform cylinder to cylinder distribution of alcohol has been encountered.

Diesel Dual Fuel (DDF) operation is a promising alternative engine operating mode. Previous research studies have reported a DDF engine operating under low load conditions suffers from high HC emissions, mostly Methane. The current study investigated the use of a multiple direct injection strategy for improvement of low-load DDF operation in a commonrail direct injection single-cylinder diesel engine. Natural gas was supplied at 70% of energy replacement ratio. Results indicated that depending on engine conditions, a double-pulse injection had potential for combustion control and provided an effective way to reduce NOx and methane emissions. Moreover, the double-pulse injection helped improve the combustion stability, reduce the pressure rise rate, and decrease the maximum cylinder pressure, compared to DDF operation with a single pulse injection.

This article presents nondestructive neutron computed tomography (nCT) measurements of Diesel Particulate Filters (DPFs) as a method to measure ash and soot loading in the filters. Uncatalyzed and unwashcoated 200cpsi cordierite DPFs exposed to 100% biodiesel (B100) exhaust and conventional ultra low sulfur 2007 certification diesel (ULSD) exhaust at one speed-load point (1500 rpm, 2.6 bar BMEP) are compared to a brand new (never exposed) filter. Precise structural information about the substrate as well as an attempt to quantify soot and ash loading in the channel of the DPF illustrates the potential strength of the neutron imaging technique.

A model developed to predict outoignition is used with data from a premixed charge, spark-ignition engine. A detailed chemical kinetics mechanism is used to predict the reactions which occur in the end-gas and lead to autoignition. Experimental pressure data from a CFR engine are used in the model to determine end-gas temperatures. The initial temperature at the time of spark must be increased above the bulk temperature for the predicted time of outoignition to agree with the observed time. A method for estimating the initial temperature based on an adiabotic compression from the time of intake valve closing is presented. The predictions of the model are examined over a range of engine speeds and fuel-air equivalence ratios. The magnitude by which the initial temperature must be increased above the bulk temperature decreases with increasing engine speed. This magnitude follows a trend which can be related to a heat transfer correlation.

A constant volume combustion simulation has been used to compute the ignition delays of pure fuels and binary fuel mixtures in air. Minima in the ignition delays were predicted by a comprehensive chemical kinetic mechanism for binary fuel mixtures with methane. A model has been developed to predict the occurrence of autoignition in a spark ignited engine. Experimental pressure data from a CFR engine were used in the model to simulate the temperature-pressure history of the end gas and to determine the time when autoignition occurred. Comprehensive chemical kinetic mechanisms were used to predict the reactions in the end gas. Methanol, methane, ethane, ethylene, propane and n-butane were used as fuels. The initial temperatures in the model were adjusted to give agreement between predicted and observed autoignition. Engine data for methane-ethane mixtures indicated a problem with the kinetic mechanism.