Parameters Optimization Matching And Verification Study Of High Efficiency Propeller Propulsion System Of High Altitude Airship

Electric propulsion system,the last energy conversion system of the High Altitude Airship(HAA),is the power source of HAA.Propeller propulsion system is composed of motor,gearbox and propeller,which involves different subsystems,and this inevitably leads to the existence of the strong coupling and nonlinear characteristics of the system performance and system design parameters.To make sure the propulsion has high efficiency and works well in near space,this paper mainly focus on the research and analysis of the propeller propulsion system parameters matching and testing.Firstly,the optimal power uint of the propulsion system is studied in order to increase the payload of the HAA,and this will improve the efficiency of the propulsion system indirectly.Based on graphic method,the method of parameters matching is studied to improve the efficiency of propulsion system directly;then,the dynamic performance of the system is studied based on the simulation model.At last,load simulator is introduced to test the performance of the propulsion system.Main contents of this paper are as follows:(1)Proposing the method of improving the efficiency of the propulsion system1)Proposing a novel concept of propulsion system for a HAA called optimum power unit(OPU),to achieve the lowest propulsion system and energy system weight for a HAA.The paper represents an optimization model of the OPU for HAA.Firstly,the Optimal Latin Hypercube Design method is applied to obtain the sample points of the distributed low power propulsion system.Secondly,the surrogate model,which is used to establish the optimization model,is obtained by responding surface method based on these sample points.Finally,the Multi-Island Genetic Algorithm is used to find the OPU for a typical HAA.The results show that,under OPU,weight is reduced by 11.5%.In addition,experiment design method is used to find the most significant performance index of the energy system and propulsion system,the pareto figure shows that the efficiency of the propulsion system is the most significant performance index,which accounts for 35% of the total index.2)Parameter matching design method of the propulsion system is put forward by traditional graphic method.First,the characteristics of permanent magnet brushless DC motor and propeller is analyzed.Then basic principle and detail steps for parameter matching design is proposed.Then,propeller under 6.8 meters diameter with 30 kw power is calculated by CFD method,and its performance is obtained.Finally,based on the motor characteristic curve and the propeller performance curve,the parameter matching design is finished through utilizing the graphic method.The result shows the speed with maximum efficiency of the motor and propeller is close to the rated speed.Besides,the performance of propulsion system with different rated condition are taken into consideration,this will help understand the importance of reasonable parameter matching design,and a well matched propulsion system will not only make good use of the energy but also can guarantee good performance of the propulsion system.(2)Putting forward the validation method for propulsion system's dynamic characteristics1)Simulation model of the propulsion system is established to analyze the performance of the propulsion system.Besides,a new scheme of the propulsion system based on variable ratio reducer is put forward.Using the MATLAB/Simulink and the classical PID controller to establish the simulation model of the rare-earth permanent magnet brushless DC motor.Dynamic simulation model is established according to the motion equation of the propeller.Simulation model of propulsion system is sestablished by integrating these two subsystems according to its torque and speed mathching.With the integrate simulation modules,working performance and parameters of all the parts of the propulsion system are obtained.Besides,the simulation results and their analysis show preliminarily that deceleration ratio of the propulsion system decreases while altitude increases.Thus we obtain the optimal deceleration ratio of the propulsion system at different altitudes.2)To test the properties of the pulsion system on the ground,a new kind of load simulator is proposed,which can imitate propeller's three load properties at the same time comparing with existent load simulator which can only imitate single load property.Limited by the output torque of the motor,propeller on the ground can't reach the rated angular speed when propeller works at high altitude,so it's difficult to carry on rotation test on the ground,and the performances of the propulsion system can't be tested.In this paper,different loading actuators are evaluated and the conceptual design of the load simulator is accomplished: Inertia is simulated by flywheel and electric inertia;thrust is simulated by electric cylinder and torque is simulated by torque motor.Load simulator is establiehed according to the conceptual design;its measurement and control software is compiled through virtual instrument software Labview.3)Debugging the test bed to improve the loading accuracy,including coaxiality adjusting,friction torque and inertia measurement.Meanwhile,the simulator is validated through the result of propeller experiment and simulation.Firstly the coaxiality of the simulator is adjusted by level gauge and coaxial display.Then,based on the balance torque method through virtual instrument measurement system,the friction torques under variable velocities are obtained.Besides,the total inertia of the simulator is adjusted by acceleration and deceleration method,this will help correcting loading aerodynamic torque and inertia compensation torque.Eventually,the effectiveness and universality of the simulator is validated by simulation and experiment results which were obtained before,and the loading accuracy is 5%.5)Based on the load simulator,the performance of the propulsion system is verified.Besides,ANFIS(Adaptive neural fuzzy inference system)is introduced to demonstrate and predict the performance of the propulsion system under different working situations.First,performance of the propulsion system is tested in consideration of different working conditions.Finally,perfomance indentification of the propulsion system is achieved by the load simulator and experimental data acquisition system: performance of propulsion system(motor current,voltage,input power,output power,efficiency of motor,and the efficiency of the system)under varied altitudes,wind velocities and rotate velocities is analyzed by using ANFIS.The study of the relationship between the operating conditions and the performance of the motor is accomplished by ANFIS.This thesis focuses on the high efficiency and dynamic properties test of the HAA's propulsion system.The method designed in this thesis can be applied on the near space airship propulsion system parameter matching design and system test.Meanwhile,the load simulator has been introduced to test the performance of some relevant driving motors,which indicates the achievements of this thesis has big values for engineering application.