Analysis of ship emission characteristics under real-world conditions in China

The actual emission characteristics of CO, THC, NOx, and PM from 50 ships were tested by a portable emission measurement system. Statistical analysis of emission data was carried out based on model years and engine types. The results show that with the increase of the model year, the specific emissions of pollutants increase gradually, that is, the stage I ships (before 2000 years) emit more pollutants. For CO, the specific emissions for stage Ⅱ ships (between 2001 and 2010 years) increase by 3.99%–26.39% compared with those for stage Ⅲ ships (between 2011 and 2016 years), and for stage I and Ⅱ ships, the maximum specific emissions increase by 25.34%–36.95 under the same operating modes; The specific emissions of THC are similar to those of CO. The specific emissions of THC increase by 45.84%–52.97% for stage I and Ⅱ ships and the weighted emissions of stage Ⅱ ships are 9.37% higher than that of stage Ⅲ. For NOx, the specific emissions of stage I, Ⅱ and Ⅲ ships are gradually reduced by 1.64%–13.44% and 6.83%–23.19% respectively, and the specific emissions under cruise condition are increased by 16.15%–36.47% compared with maneuvering condition. Due to the limitation of fuel products and test methods, PM emission characteristics are slightly different from other pollutants for different stage ships, but weighted emissions considering errors are reduced by 22.49%–25.59%. For different engine types, the specific emissions of high speed engines are higher than those of medium speed engines, especially for CO and THC pollutants, which are 16.05%–36.61% and 6.52%–73.31% higher respectively; On the contrary, for NOx, the emissions for each stage ships are reduced by 8.21%–8.82% compared with those for other stages, and PM has no consistent trend. At the same time, compared with foreign experimental data (European, USA, Sweden, et al.), the emissions of domestic ships, traveling on major routes (Yangtze river basin and Shandong coastal area and so on) in China, are about 1.1–5.11 times than that of other countries.