Masters Theses

Date of Award

12-2001

Degree Type

Thesis

Degree Name

Master of Science

Major

Mechanical Engineering

Major Professor

Ming Zheng

Committee Members

Jeffrey W. Hodgson, David K. Irick

Abstract

The Environmental Protection Agency (EPA) has set forth strict diesel emissions regulations that will take effect in 2004 and be totally phased in by 2007. For this action, the automotive industry has been compelled to assess new and current technologies to reduce diesel engine tailpipe emissions. Particulate matter (PM) and oxides of nitrogen (NOx) are the emissions of major distress. Both emissions are linked to cause damage to plant and animal ecosystems and adversely affect human health. For many years, several methods have been employed to reduce PM and NOx. Currently, the most widely used techniques to reduce these emissions are exhaust gas recirculation (EGR) and the particulate filter. NOx formation is heavily dependent on temperature and EGR reduces peak temperatures in the combustion chamber. PM emitted by diesel engines is primarily trapped by particulate filters and are removed from the filter by combustion or other similar methods. The purpose of this study is to investigate the dependence of NOx and PM emissions on EGR at various engine loads (0%, 25%, 50%, and 75% rated engine torque) and engine speed of 2000 rpm. The test cell used in this study employs a water brake dynamometer with a 2.4-L, five cylinder inline diesel engine. A vacuum driven system was implemented to control the EGR flow rate manually. For the purpose of this study, EGR rate was determined by the ratio of CO2 in the intake and exhaust. The measurements of the various exhaust quantities were determined by using the appropriate emission analyzers. The loading of the Microwave Regenerable Particulate Trap used in this study was expressed by the efficiency of the filter, which was determined by the measurement of smoke before and after the filter by the use of a smoke meter. This study shows that high levels of EGR are an effective method for the reduction of NOx, but increases the amount of PM emissions. For 75% engine load, NOx was lowered by 46% over the respective EGR range. Particulate emissions increased as EGR increased and for all loads and these emissions started to spike at "critical" EGR levels. PM spiked at 7% EGR for 75% engine load with appropriate increases for 25% and 50% engine loads. For the particulate trap used in the study, the effectiveness increased as EGR increased. Again, for 75% load, the efficiency of the filter varies from 50% at 0% EGR to 74.2% at roughly 10% EGR with the majority of the efficiency increase occurring beyond the "critical" EGR level.

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