| Variable speed hydrodynamic coupling is widely used in many fields of industrialtransmission with its many excellent transmission performances and energy saving, and itsenergy efficiency is quite obvious. Accuracy and stability of variable speed control areimportant indicators to measure the performance of variable speed hydrodynamic coupling.However, owing to the complexities of its internal gas-liquid two phase flow status, it isdifficult to predict and grasp the performance of its dynamic output exactly. Meanwhile,hydraulic control system of variable speed hydrodynamic coupling has many characteristicssuch as hysteresis, time-varying and so on, it is hard to achieve high accuracy and stability.However, the current study on gas-liquid two phase flow fields of hydrodynamic coupling ismainly limited in static conditions, the study on characteristics of internal gas-liquid twophase flow fields under dynamic conditions hasn’t commenced, and the study on hydrauliccontrol system is also insufficient.In this thesis, the systematic study on variable speed hydrodynamic coupling is carriedout in terms of prediction of dynamic performance, hydraulic control system and variablespeed control performances with the matching requirements of aeration blower which isapplied to sewage disposal system for blowing. Based on three-dimensional multiphasetransient flow theory and computational fluid dynamics, the dynamic performances arepredicted by CFD numerical simulation method, which lays the foundation of the study onvariable speed control. The study on hydraulic control system through hydromechatronicsnumerical simulation method with the results of prediction of dynamic performance, itimproves the accuracy and stability of hydraulic control system. The study of this thesisprovides effective methods for prediction of dynamic performance and analysis on variablespeed control of hydraulic control system of variable speed hydrodynamic coupling, it has apartly engineered value. In this thesis, the transitive power, the input speed range and the variable speed controlrequirements of the variable speed hydrodynamic coupling are determined in the way ofmatching requirements of aeration blower. The torus diameter and the flow channelparameters are analyzed and determined as well as the scheme of variable speed controlmethod. The prototype of the variable speed hydrodynamic coupling which analyzes in thisthesis is designed. And the corresponding three-dimensional geometric models of flowchannel are established.The mesh models of full flow channel are established, the control equations whichdescribe the gas-liquid two phase flow in working chambers and the dynamic boundaryconditions are determined. The finite volume method is adopted to discrete the controlequations, and the SIMPLE algorithm and PISO algorithm are adopted to iterate the discreteequations. UDF method is adopted to define the dynamic conditions, the internal flow fieldsand output performances under dynamic conditions are predicted. The dynamic changes ofgas-liquid interface under dynamic conditions are analyzed, the prediction on dynamicranges of the conditions of gas-liquid two phase circulation is achieved, and base on thestudy above, the curve of variable speed control is fitted.Variable speed control principles, models of variable speed control, typical hydraulicsystems, structures and principles of actuators of variable speed hydrodynamic coupling areanalyzed in detail. The hydraulic system and the model of variable speed control are selectedwith the matching requirements of the aeration blower, also the PID controller, which usesparameters self-tuning algorithm is adopted to hydraulic control system. Pressure flowcharacteristics, flow continuity equation and spool dynamic equilibrium equations of therelief valve which is used as safety valve is analyzed minutely.Based on the hydraulic control system of variable speed hydrodynamic coupling, thehydromechatronics simulation model of variable speed control performance is established.The variable speed control performances under different operation mechanisms of theaeration blower are calculated. Based on the numerical calculation results, the startupprocess and the dynamic speed control performances under typical conditions of variablespeed control are analyzed. The results show that the hydraulic control system can stably adjust the output speed of the variable speed hydrodynamic coupling, and it always candynamically follow the rotational speed requirement of the aeration blower. The hydrauliccontrol system is evaluated by three performance indexes: starting time, maximum dynamicdeviation and rotational speed overshoot. The starting time under startup process and themaximum dynamic deviation and rotational speed overshoot under typical conditions areobtained. The results show that the hydraulic control system has a good performance ofvariable speed control. |
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