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The methyl ester of soybean oil, known as biodiesel, is receiving increasing attention as an alternative fuel for diesel engines. Biodiesel is a nontoxic, biodegradable, and renewable fuel with the potential to reduce engine exhaust emissions. However, previous results have shown that biodiesel-fueled engines produce a higher fraction of soluble organic material (SOF) in their exhaust particulate matter than when petroleum-based diesel fuel is used even when the total particulate emissions are lowered. Most researchers have also observed that unburned hydrocarbon (HC) emissions decrease with biodiesel. In this project, the formation of SOF in exhaust particulates under different measurement conditions and the possibility of deposition of HC vapor in the sampling lines of the HFID detector were studied experimentally and theoretically when the diesel engine was fueled with biodiesel.

The methyl esters of soybean oil, known as biodiesel, are receiving increasing attention as renewable fuels for diesel engines. Biodiesel has a high cetane number, and offers the potential of emission reduction. The properties of biodiesel vary depending on its composition, and this may affect engine performance and emissions. In this project, biodiesel fuels were prepared from feedstocks with modified compositions including the methyl esters of a low palmitic soybean oil, a partially transesterified soybean oil, a synthetic blend of saturated esters, and a commonly used methyl soyate. These esters were blended with No. 2 diesel fuel in 20% and 50% concentrations. The blended fuels were then tested in a diesel engine to investigate the effect of biodiesel composition on performance, combustion characteristics, and emissions.

The methyl esters of vegetable oils and animal fats, known as biodiesel, are receiving increasing attention as an alternative fuel for diesel engines. Although the production of biodiesel involves a relatively simple chemical process, there is potential for various contaminants to be present in the fuel. These contaminants include water, free glycerin, bound glycerin, alcohol, free fatty acids, soaps, catalyst, unsaponifiable matter and the products of oxidation. As interest in this fuel grows, quality standards and specifications are being developed. These standards place limits on the amounts of contaminants that may be present in biodiesel. The objective of this project was to develop a database of property data to provide a basis for setting realistic specification values for biodiesel. Small amounts of these various contaminants were added to biodresel and their impact on the properties and performance of the biodiesel was measured.

The alkyl esters of plant oils and animal fats are receiving increasing attention as renewable fuels for diesel engines. These esters have come to be known as biodiesel. One objection to the use of the methyl and ethyl esters of soybean oil as a fuel in diesel engines is their high crystallization temperature. One solution to this problem is to use the isopropyl esters of soybean oil which have significantly lower crystallization temperatures. Another method to improve the cold flow properties of esters is to winterize them to sub-ambient temperature. This is accomplished by cooling the esters and filtering out the components that crystallize most readily. Previous work has shown that when methyl, isopropyl and winterized ester blends were compared with No.2 diesel fuel, the isopropyl and winterized methyl esters had at least the same emission reduction potential as the methyl esters, with similar engine performance.

A computer model has been developed to predict diesel engine particulate emission during transients in speed and torque. The computer model consists of a quasi-steady-state engine combustion model, a dynamic engine model, and a dynamic turbocharger model. The model uses information developed from steady-state tests to predict the transient particulate emissions. The computer model accurately predicts engine airflow rate, turbocharger speed, and instantaneous engine equivalence ratio. The fuel consumption given by the model is within 3% of the experimental measurement over the EPA transient cycle. The brake-specific particulate emission during the transient cycle is also accurately predicted by the model. The predicted particulate emission is within 5% of the averaged experimental data over the EPA transient cycle.

Adaptive control techniques have been applied to the problem of diesel engine torque control. Adaptive control has the potential of greater versatility than classical control techniques. Three adaptive control strategies are tested and compared to each other: self-tuning control with one-shot parameter identification and controller design, self-tuning gain-scheduling control, and self-tuning control with continuous adaptation of system and controller parameters. A continuous-time parameter identification approach, namely the Poisson moment functional (PMF) method, is employed because of its superior noise rejection capability. In order to ensure the applicability of time delay systems, a Smith predictor is employed. The controller design is implemented by using a new pole-zero placement algorithm to ensure closed-loop stability. Comparisons with constant parameter controllers reveal that adaptive control provides equal or better torque control than a constant parameter controller.

Second law analyses of both spark-ignition and diesel engines are presented using two-zone models. The analyses include descriptions of the evaluation of the various terms in the availability balance. Chemical and thermomechanical availability are separated using a definition which allows the portion of the fuel availability that can be extracted by a combustion engine to be distinguished from that which requires interaction with the reference environment. The chemical availability must be calculated correctly in order to obtain an availability balance. The diesel model includes a parameter that allows the effect of fuel-air mixing rates to be simulated. The analyses for the spark-ignition and diesel models are applied in a parametric study of the effects of equivalence ratio, fuel-air mixing, residual fraction and combustion duration on the chemical and thermomechanical availability and the irreversibility.

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.