Increasing the Accuracy of a Marine Diesel Engine Operation Limit by Thermal Factor

Abstract

When setting partial speed modes of the main diesel engine with gas turbine charging, an increase in thermal loads and incomplete combustion with increased exhaust gas opacity are observed. This frequently occurs due to the diesel load limiters being set to the universal limit constraint that has been used in less boosted designs. Often, to reduce the probability of thermal overloads, the universal limiting dependence is shifted in parallel towards the wider margin, but, in fact, this leads to underutilisation of the main engine power. To evaluate the efficiency of the linear limiting dependence used in the limiter by numerical modelling at partial modes of the main diesel engine HYUNDAI-MAN B&W 6G70ME-C9.2-TII of the large-capacity tanker GOLDWAY, the permissible fuel supply was determined at five steady running modes of the engine. The permissible values are those at which the temperatures of the gases on the expansion line do not exceed the design threshold values. The scientific novelty is determined by the fact that the temperature of the gases on the expansion line was taken as an integral criterion for limiting the fuel supply by thermal stress. The practical significance of the study is conditioned by the fact that the obtained limiting characteristic in terms of thermal stress facilitated the expansion of the diesel engine power range in steady modes without overloading.