Diesel Engine NOx Reduction Using Charge Air Water Injection

Abstract

The Transportation Development Centre of Transport Canada, in collaboration with Environment Canada’s Emissions Research and Measurement Division, conducted a series of emissions tests onboard the Oceanex RoRo vessel MV Cabot operating between Montre´al, Quebec, and St. John’s, Newfoundland. The primary objectives were to verify emissions inventories and demonstrate the feasibility of installing affordable emissions reduction technology on marine vessels as well as compliance with future regulatory emissions limits. The tests also provided an opportunity for Canada to share information on emissions program and technology developments with U.S. regulatory authorities. This may lead to developing joint emissions reduction initiatives for existing marine vessels. This paper describes the field-testing of a water injection system (WIS) to reduce oxides of nitrogen (NOx) emissions from ocean-going vessels. Tests were conducted on a semi-dedicated basis during voyage and under steady-state conditions. The emissions measurements were taken in accordance with ISO 8178-4-E3 protocol and using both marine diesel oil and intermediate fuel oil, which enabled the evaluation of the impact of different fuel type and quality on emissions. An initial series of tests was carried out on the MV Cabot in March 2004, followed by a second series of tests on the same vessel in March 2005. These tests demonstrated the effectiveness of a low-cost WIS for reducing NOx emissions in marine diesel engines. They also showed that water injection reduces NOx at the expense of an increase in both particulate matter and carbon monoxide when using intermediate fuel oil. NOx reductions varied between 10 and 35 percent, and were most effective at high water injection ratios above 50 percent engine load. The test results showed no negative impact of the WIS on fuel consumption or engine operation and performance. This paper compares the results obtained from the consecutive series of tests in terms of the effectiveness of NOx reduction, and analyses the results in the context of other full-scale test results obtained from emissions control system vendors and engine suppliers. It also investigates the theoretical process and technology of water injection through charge air fumigation, and both direct water and fuel/water emulsion injection. In addition, the effects of water injection on engine emissions, operation and maintenance, and the optimization of water injection from a knowledge-based perspective are discussed. Further testing and development of the WIS are required to realize optimal emissions reduction potential and to determine the impact of water injection on fuel consumption, and engine operational performance as well as the impact of fuel quality on emissions.