NOx emission characteristics of large bore 2 stroke diesel engines in area of layout diagram

摘要

The marine large bore 2 stroke diesel engines have their own layout diagram defined by the certain range of mean effective pressure P{sub}me and also of the engine speed n. The customers can select voluntarily any combination of power and speed in this layout diagram as the MCR point of his engine. In relation to the exhaust emission regulation by IMO, it is very important and urgent subject to clarify the NO{sub}x emission characteristics of the engines in the layout diagram.In this paper, the behavior of the maximum gas temperature in cylinder T{sub}max in the layout diagram was analyzed and also the many NO{sub}x emission data on the shop trials were investigated. Consequently, the following facts have been clarified.The NO{sub}x emission values on the E3 mode in the IMO Technical Code coincide relatively well with those on 100% load. Therefore the evaluation and analysis of the NO{sub}x emission characteristics can he executed by means of the NO{sub}x emission values on 100% load.The value of the degree of explosion p{sub}max/p{sub}c correlates closely with T{sub}max, and also T{sub}max correlates closely with the NO{sub}x emission values. One of the cause of the relatively large dispersion of the NO{sub}x emission values is thescattering of the p{sub}max/p{sub}c on the shop trials.In case of the P{sub}me derating in the layout diagram, if the slope of p{sub}s/p{sub}me to P{sub}me/p{sub}me0 is set to be approx. -0.11, then the value of p{sub}s/p{sub}me is made to increase along with the decrease of p{sub}me/p{sub}me0 by the matching and the value of T{sub}max is kept to be almost same, subsequently the value of NO{sub}x is kept also almost same.