发动机轴流风扇流场与声场测量及分析

Measurement and analysis of airflow field and acoustic field in engine axial fan

为探索发动机冷却风扇变转速气流场、声场和噪声传播特性,建造了发动机冷却系统试验台和研制了465Q型发动机轴流风扇。首先,通过调节6挡风扇转速,对风扇轴功率、散热器正面不同半径10测点静压强、总压强和噪声声压级进行了测量,同时完成护风圈出口不同半径6测点静压强、总压强和噪声声压级,以及散热器外不同半径3个方向6测点噪声声压级的测量。然后,计算出风扇变转速流量、全压和效率等特性参数,绘制了风扇变转速散热器正面和护风圈出口气流场和声场压强、风速、声压级分布曲线及风扇变转速性能曲线。最后,根据试验数据拟合出转速-风量、转速-效率等经验计算公式,给出噪声声压级与位移半径和转速之间约束方程式,验证发动机轴流风扇变转速噪声声压级换算满足对数比例定律。通过比较日本机械工程师学会实验统计数据,本研究最大比声压级为37.8 dB在其所测21~38 dB范围内,证明本研究结果达到较高的精确度。经过综合分析阐明了发动机冷却风扇流场与声场主要特征及流动和传播规律,提出了高效低噪风扇优化设计改进的具体措施。本研究结果可为发动机冷却风扇的优化配套设计提供参考。

In order to probe into the characteristics of variable-speed airflow field,acoustic field and noise propagation in engine cooling fan,an engine cooling system test-bed was built and the 465 Q engine axial fan was developed.Firstly,by adjusting 6 fan rotational speeds,the fan’s performance and airflow parameters were measured,such as its shaft power together with the static pressure,the total pressure and the sound pressure level of 10 measuring points with different radii on the front of the radiator,as well as the static pressure,the total pressure and the sound pressure level of 6 measuring points with different radii on the wind duct outlet,in addition to the sound pressure level of 6 different-radius measuring points situated outside of the radiator from 3 directions.Then,such characteristic parameters of the fan as variable-speed flow,total pressure and efficiency were obtained through calculations,giving rise to the distribution curves of pressure,velocity and sound pressure level in the airflow field and the acoustic field on the front and on the wind duct outlet of the variable-speed radiator along with its variable-speed performance curve.Finally,the tests data and curves contributed to fitting of a few experience formulas,such as rotational velocity-flow and rotational velocity-efficiency,as well as constraint equations among sound pressure level of the noise,displacement radius and rotational speed,verifying that conversion of sound pressure level meets the law of logarithmic proportion for the variable-speed noise of the engine axial fan.Compared with the statistical data of Japanese Society of Mechanical Engineers experiment,the specific sound pressure level in the study peaks at 37.8 dB,still within the range of its measurements from 21 to 38 dB.It is proved that the study has achieved high accuracy.The comprehensive analysis sheds light on main characteristics of the airflow field and the acoustic field in the engine cooling fan as well as the laws of flowing and circulation,proposing specific measures for optimizing the design of the high-efficiency and low-noise fan.The results can provide a reference for the optimal matching design of the engine cooling fan.