| The claw pole generator has the advantages of simple structure,economical application,and high-efficiency charging of the battery even at low speed of the engine.It is widely used in automobiles.As one of the main sources of automotive vibration and noise,the aerodynamic performance design and noise level control of claw pole generator structural parts is an important research topic at the moment.When the generator is operating at high speed,th e main part that affects its comprehensive noise level is aerodynamic noise.It is of great significance to study its flow field and sound field characteristics and noise reduction methods.Aiming at the problem that a certain type of claw pole generator has high aerodynamic noise and obvious order noise characteristics under high speed conditions,firstly,this paper explores the order noise characteristics at different speeds,and determines the types of noise sources in different speed ranges through experiments and theoretical analysis.And then,a model with a good fit to the test is established by numerical simulation methods.The flow field characteristics and sound field frequency spectrum characteristics are studied at different speeds.At the same time,the pressure distribution of the rotor surface under different orders is studied and the main order noise sources are analyzed by the method of removing components.Finally,the structural parameters of fan blades and claw poles are optimized and verified by noise test experiments on the optimized prototype.The main research contents of this paper include the following aspects:(1)Noise test platform are set up and,analysis of the noise test data of the prototype by applying the order analysis principle shows that 8,12,16,24,64,72,80 order are the main order noise in the top 100 orders.Based on the conclusions obtained by N.Curle through dimensional analysis o n the relationship between the fluid Mach number and the type of noise source,a linear fit of the noise test data of8000～12000r/min is performed.The results show that radiated sound power and airflow velocity are approximately 6th power relationship,and the dipole is the main type of noise source.(2)A numerical simulation model of the flow field and sound field are established.Based on the test data of the claw pole generator noise,the numerical simulation accuracy is compared under the two turbulence models of RNG k-ε and SAS-SST.the numerical simulation shows that the accuracy of major order noise is higher when using the SAS-SST turbulence model.(3)Based on the verified numerical simulation model,the flow field characteristics and sound field frequency spectrum characteristics of the generator under the conditions of 3000 r/min,8000r/min,and 12000r/min are researched.The pressure distribution of the rotor surface under different orders and the method of removing components are used to analyze the main order noise sources.It is found that the front fan blade has a greater impact on the 12 th and 16 th order noise,and the rear fan blade on the 6,8 and 10 th order noise.(4)The mathematical optimization model between the angle distribution of the front and rear blades and the relative sound pressure amplitude is established by the VCM method.The optimization results show that the angle of the front blades has already located in the optimal distribution,but the angle of the rear blades exists some optimization space.After numerical simulation and noise test verification,it is shown that when the average mass flow rate of the front and rear blades does not change more than 5%,the average noise of target optimization orders are reduced greatly,and the optimization effect is obvious.The feasibility of VCM optimization method is verified.(5)Experiments and numerical studies are conducted on the diversion trench of a certain type of claw pole generator.The test results show that the existence of the diversion trench can significantly improve high-order noise.At the same time,through numerical simulation research on the parameters of the diversion trench,it is found that when the depth and length of the diversion trench are decreased,the high-order noise can be reduced,but if the depth and length are increased too much,the noise value will increase.Therefore,a reasonable depth and length of the diversion trough can better lessen the corresponding high-order noise value. |
