Semester

Spring

Date of Graduation

2009

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Gregory J. Thompson.

Abstract

Heavy-duty diesel engines (HDDEs) typically burn hydrocarbon fuels and as a result their emissions cause harmful products of combustion to be emitted into the atmosphere. Due to these harmful emissions, the United States Environmental Protection Agency (EPA) has created strict emissions standards for these heavy-duty engine manufacturers to meet. Engine manufacturers strive to meet these stringent standards while maintaining performance requirements set forth by the consumer. The EPA currently mandates laboratory testing of all HDDE families on an engine dynamometer utilizing a standard testing procedure. One standard testing procedure that HDDEs must execute is commonly known as a Federal Testing Procedure (FTP).;The FTP is a transient test performed over a prescribed period of time governed by a set of engine speed and load points. For a test to be valid, the measured engine speed and loads during the FTP are compared to the prescribed, or set, engine speed and load points. There is some latitude between the actual and preset engine speed and load points which are confirmed through a regression analysis.;Currently, each laboratory conducting HDDE testing develops their own control algorithm to achieve the engine speed and load points prescribed by the FTP. This study investigated the effects that variations in accelerator pedal position control (APPC) have on emissions, performance, and tolerances of the FTP.;Five engines were utilized for this study including a 1991 DDC S60, 1992 DDC S60, 1992 rebuilt DDC S60, 1999 Cummins ISM, and a 2004 Cummins ISM engine. Three control algorithms were developed to control the accelerator pedal. However, initial investigations of throttle setting 2 of the control algorithms revealed that this APPC mimicked that of throttle setting 1 and was not further investigated.;Emissions varied significantly for most measured constituents for the two different APPCs. The older DDC engines saw the greatest response in regards to emissions when varying APPC. Of the three DDC's used for testing, the 1991 exhibited the greatest variations in the emissions. Oxides of nitrogen (NOx) were reduced by 2.4% under control of throttle 1, the more aggressive APPC setting. Total particulate matter (TPM) was reduced by 17.6% under guidance of throttle 3, the less aggressive APPC setting. Hydrocarbons (HC) were reduced by 15.0% under control of throttle 1 compared to the throttle 3. Carbon monoxide (CO) was reduced significantly by throttle 3, compared to the throttle 1, with a 29.0% reduction. Fuel consumption (FC) and work were both slightly elevated by the more aggressive throttle 1 compared to throttle 3.;Emissions responded more to the variations in APPC on the older engines due to lack of additional engine control devices, such as variable geometry turbochargers, as seen on the newer Cummins engines. The DDC engines experienced longer turbo-lag during transient conditions causing rich equivalence ratios during this time. Therefore, variations in transient load conditions led to different emissions results for the different APPCs. Both throttle 1 and throttle 3 provided valid transient tests under FTP regression requirements. It is suggested that these tolerances be tightened to better suit result comparisons from laboratory to laboratory.

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