Prediction And Application Of Vibration Response Of Low-Speed Two-Stroke Dual-Fuel Engine

Diesel engine,the power source of ship,is the main factor causing ship vibration and noise,of which vibration extent directly affects the vibration and noise.At present,large diesel engines,especially low-speed ones,can only be rigidly mounted with the body of the ship due to weight and size constraints.Therefore,how to predict and reduce diesel engine vibration is the key technology to effectively reduce the vibration.In the thesis,the research of vibration response prediction of low-speed two-stroke engine is carried out to provide technical support for the vibration optimization design of low-speed diesel engine.The main research work of the thesis is as follows:Taking a two-stroke low-speed dual-fuel engine as the research object,the thesis establishes the finite element model of the whole engine,which calculates the natural frequency of the engine,and modifies the finite element model by measuring the vibration response of the whole engine with variable rotate speed.In the thesis,through the dynamic analysis of the moving parts of the crankshaft and connecting rod,the excitation force in the cylinder under the condition of uniform speed is obtained;In the thesis,the instantaneous axis of rotation characteristics are obtained according to the torsional vibration test results,and the characteristics of the internal excitation force of the cylinder under the actual working conditions are analyzed.In the thesis,the whole machine vibration prediction model is established by loading the internal excitation force of the cylinder in the finite element model,in addition,the engine vibration response is calculated,and the accuracy of the finite element model are verified through the vibration test results.Based on the model,the optimization scheme of exhaust reflux pipe structure is proposed,the validity of the scheme is verified by ship measurement;By calculating the torsional vibration response of shafting,the influence law of flywheel inertia on instantaneous speed fluctuation and the vibration of the engine is obtained;In the thesis,the sensitivity analysis of installation stiffness and vibration of the whole machine is carried out by simplifying ship propulsion shafting,which provides reference for reducing the vibration of the engine.