Date Approved

10-31-2003

Embargo Period

5-5-2016

Document Type

Thesis

Degree Name

M.A. in Engineering

Department

Mechanical Engineering

College

Henry M. Rowan College of Engineering

First Advisor

Marchese, Anthony J.

Subject(s)

Diesel motor exhaust gas; School buses--Safety measures

Disciplines

Mechanical Engineering

Abstract

The New Jersey Department of Transportation (NJDOT) is currently sponsoring a research study at Rowan University to develop strategies for reducing diesel emissions from mobile sources such as school buses and class 8 trucks (classified as a heavy-duty truck of more than 33,000 lbs.). This thesis presents the results of an investigation performed to measure school bus idle emissions in a controlled environmental chamber. This thesis also presents the results of mobile school bus testing that has been performed to quantify the emission reduction capabilities of various alternative fuels, such as biodiesel, ultra low sulfur diesel, and a blend of the two, when used to fuel school buses that are representative of those currently in use in the state of NJ.

To measure emissions from school buses during idling conditions, three school buses equipped with an International T444E, an International DT466E, and a Cummins 5.9L B series engine were instrumented and tested at the Aberdeen Test Center at the Aberdeen Proving Grounds in Maryland. To simulate a wide variety of idling situations, tests were conducted at four different ambient temperatures (20°F, 40°F, 65°F and 85°F) and relative humidity ranging from 37 to 90%. In addition to quantifying school bus emissions during idling conditions, another objective of the school bus idling experiments was to develop a NOx humidity correlation for use in mobile school bus emissions testing, the first phase of which is presented herein. The results of the idle testing provide evidence that the measured CO emissions decrease from 10% to 40% with increasing ambient temperature. The measured NOx emissions under similar conditions vary by school bus and therefore a single correlation could not be developed that accurately corrects NOx emission for all three buses. Rather, an engine specific correction factor was developed for each school bus engine. The results also show that current NOx correction standards fail at lower temperatures suggesting that caution should be used when performing mobile emissions testing.

To ensure repeatability of testing under conditions that accurately reproduce actual school bus operating conditions, a new composite mobile school bus cycle was developed. The cycle was developed by acquiring Global Positioning System (GPS) data from actual school bus routes from 5 different municipalities within the state of New Jersey.

For both the mobile and idle tests, exhaust gas emission measurements were made using a Sensors Semtech-D to measure CO, CO2, NO2 , NO, O2, and HC, along with a Sensors PM-300 to measure Particulate Matter. In addition to the exhaust emissions measurements, operating parameters such as instantaneous vehicle speed, engine speed, percent load and fuel flow rate were acquired from the engine electronic control module (ECM) during testing.

The mobile emissions results presented in this thesis focus mainly on a comparison of alternative fuels on mobile emissions acquired during the new mobile test cycle that was developed as part of this study. The results of the mobile testing prove that the Rowan University Composite School Bus Cycle (RUCSBC) is a repeatable mobile test cycle when run during the same operating conditions. The results of mobile testing show a decrease in HC emissions for the alternative fuels tested for all buses of 7% to 43%. NOx emissions were only slightly affected by alternative fuels by 0% to 10%. A 20% biodiesel blend and ultra low sulfur diesel reduced CO and PM emissions by 30% to 40% for the T444E and Cummins, but showed no effect on the DT466E bus. The ultra low sulfur diesel and biodiesel blend provided significant reductions in CO and PM by 70% and 50%, respectively, for the T444E and a 22% reduction in PM for the DT466E.

Finally, in addition to the tests conducted at the Aberdeen Testing Center (ATC), a series of on-road tests were performed using school buses presently in service on actual operating routes. Specifically, four International DT466E school buses were tested at the Medford, New Jersey School District, a district that has been operating half of their school bus fleet on biodiesel for the past five years.

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