Gas Intake Experimental And Simulation Study On Multi-Point Sequential Injection Of LNG/Diesel Dual Fuel Ngine

Compared with less and less storage capacity of coal and oil resources,natural gas is still rich in storage on earth.The natural gas energy density is lower and storage is more difficult when comparing with coal and oil.The application of natural gas in internal combustion engine is far less than the oil fuel.Because some of the products produced by the burning of petroleum fuels are seriously polluting the environment.And countries around the world have issued more and more stringent emission regulations.So the cleanliness of natural gas is widely valued.With the progress of natural gas low temperature storage technology,more and more internal combustion engine researchers have begun to study the use of high quality,clean and efficient liquefied natural gas(LNG)to replace petroleum fuel as fuel for engines.It can reach the requirements of the emission regulations and can reduce the cost of fuel.For inland river ships,LNG is mostly used in the LNG diesel dual fuel engine which is modified by the original diesel engine.Early "oil to gas" pilot ships which are implemented in inland river choose a simple modification way of outside the cylinder single point air intake.Single point air intake of the dual fuel engine can reduce the fuel costs of the engine to a certain extent.But when the engine is running,it produced higher hydrocarbon emissions which will cause energy waste and environment pollution.So it becomes the concerned problems of shipowners.The Zibo 6170 diesel engine which is widely used in the river ship is selected to be converted into LNG/diesel multi-point sequential jet fuel engine.The modified engine is studied to compare with the single-point intake dual-fuel engine to analyze whether the modified engine can achieve multi-point injection expected economic performance and emission performance or not.So that the optimization of the single-point injection dual-fuel engine can be completed.The single cylinder intake test bed which is in accordance with the original engine under the conditions of the intake law is used to complete the intake air simulation test.According to the test results to inspect whether the LNG gas supply system and the original machine can reach the theoretical requirement of the original machine in the propelling characteristic or not.And through the test results to verify whether the control system can accurately control the injection time or not.When the original engine is modified,the natural gas intake line is installed in the intake manifold.And a set of LNG gas supply system that can store gasification,pressure and supply enough natural gas is designed for the prototype.The modified engine was selected to carry out the dual fuel test under the 50% load.Grouping tests were carried out according to the same injection starting point different jet duration angle and the different injection starting point same jet duration angle.The hydrocarbon emissions and equivalent fuel consumption rate are respectively selected as evaluation index of emission performance and economic performance.By comparing and analyzing the engine emission performance and economic performance at different injection starting points and at different injection sustaining angles,the optimal injection starting point and the optimum injection duration angle of the engine under the working conditions can be obtained.The three-dimensional inlet model is established and divided the grid.And the Fluid calculation software Fluent is adopted to analyze the flow field in the intake airway when the engine enters the air intake.The residual amount of natural gas in the inlet is calculated at the same injection starting point and different jet duration angle when the valve overlap angle is avoided.Residual natural gas in the inlet will greatly affect the engine HC emissions.According to the test and simulation results,a jet scheme is proposed for this condition.It can reduce the engine's hydrocarbon emissions without changing the original structure.