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开展了可压缩流体中热线探针校准方法的研究,以满足其在各种速度测量场合的使用需求。研究了对数校准数学模型,发现校准系数求解过程中存在矩阵奇异性过强的问题,导致在速度小扰动条件下方程求解稳定性差。对对数校准数学模型进行了参数无量纲化及添加正向偏置的改进,建立了无量纲化对数校准数学模型。在马赫数为0.3~0.5,引射压力为150~300 k Pa范围内进行了校准实验,利用对数校准数学模型对实验数据进行拟合,拟合优度为0.997 61,拟合速度平均偏差为1.378 m/s,校准系数求解过程中系数矩阵条件数为1.595×108,矩阵奇异性过强,加入速度小扰动(1 m/s)后,拟合优度为0.379 74,拟合速度平均偏差为43.81 m/s,方程求解稳定性差。利用无量纲化对数校准数学模型对实验数据进行拟合,拟合优度为0.998 95,拟合速度平均偏差为1.203 m/s,校准系数求解过程中系数矩阵条件数为3.655×102,且无量纲化方法不受速度小扰动影响。对流体速度进行不确定度分析,速度平均不确定度为3.168 m/s,无量纲化拟合速度平均偏差明显小于速度平均不确定度。实验结果证明了无量纲化对数校准数学模型应用于可压缩流体热线探针校准的可行性。
A study of hot wire probe calibration methods in compressible fluids has been conducted to meet their needs for use in a variety of speed measurement applications. The mathematical model of logarithmic calibration is studied. It is found that the matrix singularity is too strong in solving the calibration coefficients, which leads to the poor stability of the equation under small speed disturbance. The calibration of logarithmic calibration model has been improved with the non-dimensional parameters and the addition of forward bias, and a mathematical model of logarithmic calibration has been established. The calibration experiment was carried out with the Mach number of 0.3-0.5 and the injection pressure of 150-300 kPa. The logarithm calibration mathematical model was used to fit the experimental data. The goodness of fit was 0.997 61, and the average deviation of the fitting speed Is 1.378 m / s, the coefficient matrix condition number is 1.595 × 108, the matrix singularity is too strong, the fitting goodness is 0.379 74 after adding the small disturbance speed (1 m / s), the average of the fitting speed The deviation is 43.81 m / s and the equation is poorly resolved. The non-dimensional logarithmic calibration mathematical model was used to fit the experimental data. The goodness of fit was 0.998 95 and the average speed of fitting was 1.203 m / s. The number of coefficient matrix in solving the calibration coefficient was 3.655 × 102 The non-dimensional method is immune to small velocity disturbances. Uncertainty analysis of fluid velocity, the average velocity uncertainty of 3.168 m / s, the average deviation of non-dimensional fitting speed was significantly less than the average speed uncertainty. The experimental results show that the non-dimensional logarithm calibration mathematical model is applicable to the feasibility of compressible fluid probe.