| New energy vehicles have gradually begun to occupy the market,with the absence of noise sources such as internal combustion engines,the noise of the air-conditioner blower system has become one of the main factors affecting the comfort of the occupants in the passenger compartment.The traditional automotive air-conditioner blower is a centrifugal structure fan,which has some problems,such as low operation efficiency and prominent aerodynamic order noise.The main research purpose of this thesis is to design and optimize a new automotive air-conditioner blower impeller with high efficiency and low noise.The multistage impeller is an impeller structure that is widely used in high-efficiency impeller machinery such as aviation compressors,and its efficiency and aerodynamic performance are excellent.Therefore,the design of a centrifugal tandem impeller and the law analysis of the influencing factors are proposed in the design of the new impeller.Firstly,by analyzing the problems existing in the power,efficiency and aerodynamic noise of the single-stage impeller of the original air-conditioner blower,it is found that the obvious impact loss at the inlet of the original impeller,the large low-speed fluid accumulation area on the hub surface and the phenomenon of strong vortex are the key reasons for the low efficiency and poor noise of the original impeller.Based on the analysis results of flow field and sound field,the common flow loss types in the fan are considered through the flow loss theory,and the mathematical relationship between the main structural parameters and operating parameters of the impeller and the optimal value of the performance theory is established with the goal of minimizing the flow loss.The key parameters of the new impeller model are determined through the verification of cyclic hypothesis,and a new tandem impeller model is established in the impeller design software.The effectiveness of the numerical simulation method is determined by comparing the noise test data of the original blower with the numerical simulation data.Based on the new impeller model,the flow field and sound field distribution laws of four different reaction degree models are simulated and analyzed.The results show that the static pressure difference between the pressure surface and suction surface of the model with high reaction degree is significantly higher,the work ability of its blades is stronger,the velocity in the second stage blade passage is relatively higher,and the turbulent kinetic energy in the passage is stronger.The outlet speed of this type of impeller is mainly tangential speed,and the axial speed and radial speed are small.The outlet speed of the model with high reaction is higher than that of the model with low reaction.The air flow obtains more kinetic energy in its blade passage,resulting in higher efficiency.The sound power intensity in the passage of the low reaction model is high,and it is mainly concentrated near the blade surface and the impeller outlet.The noise performance of the model with reaction degree of 0.3 is the best.The influence law of four models with different blade numbers is analyzed,the results show that the flow passage of the model with 28 blades is small,the inelt is congested and the flow condition is not well.The model with 16 blades has strong turbulence in the volute passage,resulting in flow loss.The model with the highest efficiency is the model with 20 blades,and the model with the lowest noise is the model with 24 blades.The influence law of the models with different first and second stage blade spacing is analyzed,the results show that there is a transverse pressure gradient in the model passage with 12 mm spacing,there are obvious backflow and vortex at the inlet.Disturbed by the wake of the previous stage blade,a large amount of low-speed fluid accumulates in the passage,which reduces the efficiency of the impeller.The most efficient model is the 10 mm spacing model,and the lowest noise model is the 8 mm spacing model.Through the orthogonal test,the influence weights and laws of three structural parameters including the number of blades,the spacing between the first and second blades and the inlet angle of the second blades on the efficiency and noise of the impeller are analyzed and compared.Using the double-objective optimization evaluation method of efficiency and noise,the best combination of structural parameters to achieve a better balance between the efficiency and noise performance of the impeller is found.Compared with the original impeller model,the efficiency of the final optimized impeller model is improved by 0.97%,the total sound pressure level at the two noise monitoring points is reduced by 0.85 d B and 1.08 d B respectively.The prominent order noise of the original impeller has reduced,which has reduced by 1.10 d B and 1.61 d B at the two monitoring points respectively.In the optimized impeller model,the sound energy is redistributed,and the contribution of the prominent order is reduced.Under the high speed condition of 4250 r/min,the optimized model improved the efficiency by 2.03% compared with the original model,and the total sound pressure level decreased by 1.82 d B and 2.04 d B at the POS1 and POS2 noise monitoring points respectively.As for 5000 r/min,the optimized model improved the efficiency by 2.53%compared with the original model,and the total sound pressure level decreased by 2.13 d B and2.43 d B at the POS1 and POS2 noise monitoring points respectively.In summary,this thesis carries out the design of the new tandem impeller of the automotive air-conditioner blower,studies the distribution law of the flow field and sound field of the impeller under different factors,and optimizes the optimal structural parameter combination of the impeller with the double objectives of improving efficiency and reducing aerodynamic noise through orthogonal test.The above has certain theoretical significance and reference value for the design and optimization of the impeller of the automotive airconditioner blower. |
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