Abstract
The stable working window of a dual-fuel engine is narrow, and it is prone to knock during operation. The occurrence of knock limits the load and torque output of a dual-fuel engine, and even causes engine damage in severe cases. The existing volumetric model of marine dual-fuel engine has little research on the related problems of knock simulation. In order to analyze the causes of knock phenomenon and the influence of operating parameter changes on knock, under the Matlab/Simulink simulation environment, a quasi-dimensional model was established with MAN 8L51/60DF dual-fuel engine as the prototype, and the model was calibrated using the bench data. The knock intensity index coefficient (KI) was used as the evaluation index of knock intensity. Three parameters, the intake air temperature, compression ratio, and natural gas intake, were selected as variables to simulate the engine. According to the analysis of the simulation results, the influence of the parameter changes on the occurrence of engine knock phenomenon and knock intensity could be further studied. The results showed that the combination of the KI model and the quasi-dimensional model could effectively and accurately predict the engine performance and knock trend. The change of gas inlet quality, compression ratio, and inlet temperature could promote the occurrence of detonation, the engine knock could be avoided by controlling the intake air temperature below 336 K, compression ratio not exceeding 15 or the intake volume of natural gas per cycle not exceeding 11.25 g/cycle.
Highlights
Published: 30 March 2021With the aggravation of global energy shortage and the worsening of environmental problems, pollutant emission has become an important reason for the deterioration of the global atmospheric environment
The results showed that the combination of the knock intensity index coefficient (KI) model and the quasi-dimensional model could effectively and accurately predict the engine performance and knock trend
In order to ensure the reliability of the simulation analysis in this paper, the model was verified by bench test data, and the simulation results fit well, 5
Summary
With the aggravation of global energy shortage and the worsening of environmental problems, pollutant emission has become an important reason for the deterioration of the global atmospheric environment. Dual-fuel engines using natural gas as the main fuel developed rapidly and are gradually applied in the field of ship power plant. With the shortage of traditional oil resources and increasingly more stringent emission regulations issued by IMO [3], natural gas has the advantages of abundant reserves, high energy density, and green environmental protection, as compared to traditional fuels. Dual-fuel engines using natural gas as the main fuel de of 19 veloped rapidly and are gradually applied in the field of ship power plant. The dual-fuel engine has obvious advantages in emissions and other aspects, the pre-mixed natural gas dual-fuel engine will produce knock phenomenon under the conditions of excessive load high temperature thecombustion combustionchamber.
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