| With the gradual improvement of emission regulations,the importance of natural gas in the ship field is therefore gradually increasing.At present,the development of natural gas fuels mainly affects the mid-speed engine market,especially in LNG ships,such as the Flex-DF engines of W?rtsil? and the ME-GI engines of MAN.This article will mainly study the W?rtsil? company’s Flex-DF engine,understand structure characteristics of the low-speed dual-fuel engine of low-pressure injection,and use the simulation technology to research the 40 DF lowspeed dual-fuel engine,build the simulation model and analysis the engine performance.On the basis of W?rtsil?’s RT-Flex50 DF,a 40 DF low-speed dual-fuel engine was developed.The relevant data of RT-Flex50 DF and X40-B low-speed dual fuel engines were collected,including structural parameter reports,test reports,etc.After fully understanding the engine’s structural features and working principles,a low-speed dual-fuel engine simulation model was established by using GT-POWER software,and diesel model and natural gas model simulations were realized.After the simulation model is established,comparing the RTFlex50 DF simulation results with the calibration parameters under different load conditions to verify the correctness of the model,the low-speed dual-fuel engine simulation model can be calculated and analyzed.Due to the lack of relevant experimental data for 40 DF low-speed dual-fuel engine,the performance parameters of the 40 DF were calculated by analyzing the similar engine in the GTD database,and the trend of performance parameters under various design conditions and different fuel modes under the same speed and power was analyzed and use the gray model to predict The approximate range of performance parameters of the 40 DF low-speed dual-fuel engine,and also provide a way to use Wiebe combustion model and Lyn combustion model to predict the performance of low-speed dual-fuel engine without a number of experimental data.Through comparison with two different combustion model simulation results,it can be found that the accuracy of the Wiebe combustion model and the Lyn combustion model simulation results is reliable.Compared with the Wiebe combustion model,the Lyn combustion model adjustment process is more simple.In combination with the parameters of RT-Flex50 DF and X40-B,a 40 DF simulation model was established.The simulation results and the grey prediction results were compared and analyzed.It was confirmed that the parameters were close and the development trend was consistent,which proved that the 40 DF simulation model was reasonable and reliable.Based on the 40 DF simulation model,the engine performance and emissions under the lean-burn combustion mode are studied.Because the fuel injection advance angle has a great influence on the gas consumption rate,and the excessive air coefficient has a great influence on the engine intake air amount,the effects of the injection advance angle and excessive air coefficient on engine performance,combustion and emissions under lean combustion are analyzed separately.The modulation strategy for overcoming environmental conditions in gas mode was studied.Through simulation calculations,the influence of different environmental conditions on engine performance was studied.On this basis,a modulation strategy to overcome environmental conditions was formulated.Through simulation calculation,it was verified whether the strategy was reliable. |
