DESIGN AND DEVELOPMENT OF WAUKESHA'S, STOICHIOMETRIC, COOLED EGR ENGINE FOR THE CALIFORNIA ARICE PROGRAM

摘要

Waukesha Engine, Dresser, Inc., (Waukesha) entered into a program with the California Energy Commission (CEC) to develop and demonstrate a 500 kWe ultra-low emission, Advanced Reciprocating Internal Combustion Engine (ARICE) for power generation. The purpose of the program was to demonstrate a natural gas fueled engine with emissions control technology that could achieve the following ARICE goals: Reduce specified emissions by 90%; Increase thermal efficiency by 10%; Reduce installed costs of Distributed Generation (DG) systems by 10%; Maintain engine durability. All changes are with respect to current levels defined at the time the program began. To work towards meeting these program goals Waukesha partnered with two primary subcontractors, Southwest Research Institute (SwRI) and MIRATECH Corporation. The program was originally defined in two phases. In Phase I Waukesha would develop and demonstrate a cooled EGR system. In Phase II further enhancements would be applied to the cooled EGR system with the intent of achieving still further gains in efficiency and reductions in emissions. A cooled Exhaust Gas Recirculation (EGR) system was installed on a base Waukesha H24GSI engine. The diluent properties of the EGR added to the stoichiometric fuel-air charge reduce peak cylinder combustion temperature. The lower combustion temperatures result in lower NO{sub}x values without the need for excess air which would yield oxygen in the exhaust gas. The lack of oxygen in the exhaust gas allows the use of an efficient, cost-effective, three-way catalyst (TWC) to reduce all three primary emittants -NO{sub}x, CO, and unburned hydrocarbons. This paper describes the Phase I design and development of an ultra-low emission, natural gas engine operating at stoichiometric conditions with cooled EGR and a TWC. Hardware modifications to incorporate the cooled EGR system on the base engine are covered. The TWC and control system developed are briefly described. The EGR engine with control system and three-way catalyst successfully completed a 500 hour durability test at SwRI. Stable control of the engine across the load range and acceptable load response by the unit have been demonstrated. Very low emissions of the three primary pollutants were measured downstream of the catalyst both before and after the 500 hours of durability testing. The phase I emissions goals were easily met. Emission levels near the Phase II goals were achieved. The Phase I engine efficiency was increased 12% and BMEP was increased 33% compared to the baseline engine. Examination of the engine and systems after the 500 hour run did not show signs of unusual wear or deposits. The potential for a cooled EGR system to produce significantly reduced NO{sub}x in a reciprocating natural gas engine was demonstrated. Remaining challenges include the demonstration of consistent, long term emissions performance and the long term durability of engine systems and components operating with EGR.