汽车发电机冷却风扇旋转噪声预测方法

以汽车发电机冷却风扇为对象,针对其修改叶片分布角度前后的旋转噪声预测问题,提出一套较精确且节约计算机时的预测方法.该方法结合了声类比法和矢量合成方法,首先,用大涡模拟(LES)和Ffowcs-Williams和Hawkings(FW-H)方程相结合的声类比方法对原风扇总噪声和主要阶次旋转噪声幅值进行预测;然后,针对只改变叶片分布角度情况下,提出一种矢量合成方法,用于对修改叶片分布前后主要阶次旋转噪声变化量的预测;最后,得到修改后主要阶次旋转噪声的幅值.计算和实验结果表明,原风扇总噪声最大预测误差4.3dB,第12阶和第18阶主要阶次旋转噪声幅值预测误差为1.24dB和4.26dB;修改后风扇第12阶和第18阶主要阶次旋转噪声分别变小了9.3dB和10.5dB,其变化量预测误差分别为0.36dB和0.43dB.结果表明,这一整套对修改前后风扇旋转噪声进行预测的方法是可行的,且大大节省计算时间,为风扇叶片周向分布角度设计提供了很好的依据.      

An updated model of atomic oxygen redline dayglow emission

A comprehensive model is developed using the updated rate coefficients and transition probabilities to study the redline dayglow emission of atomic oxygen. The solar EUV fluxes are obtained from the Solar Irradiance Platform (SIP), and incorporated into the model successfully. All possible production and loss mechanisms of O(¹D) are considered in the model. The neutral number densities and temperature are adopted from the NRLMSISE-00 model. The ion and electron densities, and electron temperature are adopted from the IRI-07 model. The model results are validated with the help of measurements as provided by the Wind Imaging Interferometer (WINDII) on board Upper Atmosphere Research Satellite (UARS). The present results are found in better agreement with the measurements in comparison with the earlier model. The measured volume emission rate profiles are reproduced quite well by the present model. The model results show that the updated rate coefficients and transition probabilities are quite consistent and may be used in the aeronomical studies.     

空间探测原子磁强计的主动磁补偿实验

在空间探测过程中,采用高灵敏无自旋交换弛豫(SERF)原子磁强计在行星表面进行磁场测量是原位物质成分分析的有效手段之一。为了提高SERF原子磁强计的磁场测量灵敏度,必须减小外界磁场扰动对其原子自旋SERF态质量的影响,基于SERF原子磁强计的测量原理,设计了一套主动磁补偿系统。首先,通过测量驱动激光光强获得3个方向的磁场信息;在此基础上,控制电流源和线圈主动产生一个与外界磁场扰动大小相同、方向相反的磁场来补偿扰动,以提高原子自旋SERF态的质量;最后,结合现有的SERF原子磁强计实验平台进行了实验验证。实验结果表明,与手动补偿方式相比,采用本文所述的主动磁补偿系统,可以实时跟踪磁场补偿点,降低系统信号的噪声,补偿了外界磁场的扰动,验证了磁强计主动磁补偿技术的有效性,为后续样机的研制奠定了技术基础。     

组分变化对甲烷氧化特性影响

在射流搅拌反应器实验平台上针对温度范围850～1300K、常压条件下的甲烷氧化反应过程进行了实验研究,采用气相色谱仪测量了变组分条件下(当量比范围0.2～2、氧气体积分数2％～8％、二氧化碳体积分数0～20％、水蒸气体积分数0～20％)主要反应物(CH4、O2)、主要中间组分(C2H6、C2H4、C2H2、H2)和主要...     

Micro powder injection molding of boron carbide components with SiC-Al2O3-Y2O3 sintering additives

Sintering additives and micro-powder injection molding offer an effective method to densify boron carbide（B₄C） and make B₄C components with complex shapes. By adjusting the proportion of three kinds of powders（SiC, Al₂O₃ and Y₂O₃）, four kinds of sintering additives were prepared. The feedstock uniformity, debinding behavior, phase composition and microstructure of micro injection molded B₄C components with different sin...