The flow quality of the linear cascade tests for compressor airfoils is always poor under high-load conditions, it is necessary to improve flow quality of linear cascade by adjusting methods to ensure the availability of test data. A passive control scheme of adjustable tailboard was designed based on a subsonic linear cascade wind tunnel. The effect of tailboard angle on flow quality and performance of cascade was investigated, and compared with the results of active control scheme of upper end-wall suction previously studied. The results indicate that the tailboards adjust the flow quality by changing the exit static pressure distribution. As the tailboard angle decreases, the exit static pressure near the upper tailboard decreases while it increases near the lower tailboard, leading to an improvement in the cascade flow quality. However, if the tailboard angle is decreased beyond a certain limit, the uniformity of the inflow and the periodicity of the outflow will decline. Therefore, to achieve the best overall flow quality, the tailboard angle needs to be controlled within a specific critical range. And the outlet flow angle shows the best periodicity due to the isolating effect of tailboard, with a periodicity index less than one. The flow quality of cascade declines when the tailboard angle is over the critical value. The improvement of inflow quality of cascade by upper end wall suction is better than that of tailboard. Due to the difference of control mechanism and flow quality between these two methods, the outlet flow angle of cascade adjusted by tailboard is about 2° smaller than that of upper end wall suction, and the loss is about 0.02 larger than that of upper end wall suction. The difference of static pressure ratio and distribution of isentropic Mach number between the two methods is small.

The standard model for linear cascade wind tunnel is the key to the construction of axial compressor design systemand the standardization of linear cascade testing technique. The standard model of compressor cascade with a typical controlled diffusion airfoil is designedand tested based on the linear cascade wind tunnel of Northwestern Polytechnical University. The flow quality of the standard cascade including inflow precision, flow periodicity, and two-dimensionality is adjusted by a self-established integrated control system. On the basis of ensuring the flow quality, the performance of the standard cascade is measured, including the features of incidenceand axial velocity density ratio, as well as the distributions of surface isentropic Mach numberand wake, and is then compared to the reference cascade data published by DLR. The results show that the standard cascade exhibits good flow periodicityand accuracy, including a uniform region over four successive blade passages upstreamand a periodicity range over two successive blade passages downstream, and the periodicity index of outflow is less than 2. The deviation of the inlet Mach numberand axial velocity density ratio in the measuring blade passage is no more than 0.005and 0.02, respectively. The comparison with the reference cascade data shows that the variation laws of the loss, exit flow angleand static pressure ratio with the inlet flow angle are essentially the same between the standard cascadeand reference cascade at the design inlet Mach number of 0.62. The lossand exit flow angle of the standard cascade are larger than those of the reference cascade due to the difference of measuring position downstream of cascade, but the static pressure ratio is basically the same. The distributions of the surface isentropic Mach numbers for the two sets of cascades are highly consistent. In general, the test data for the established standard cascade are comprehensiveand reliable.

Reconstruction of 3D pressure is crucial for Pressure-Sensitive Paint (PSP) measurements. We propose a method for three-dimensional pressure reconstruction combining binocular digital image correlation technology. The PSP measurement results are mapped to the reconstructed three-dimensional point cloud pixel by pixel to realize the three-dimensional pressure reconstruction without relying on the geometric parameters of the measured model. The method involves creating random speckle patterns on the PSP coating surface and using two cameras to synchronously capture PSP images. By integrating cross-correlation analysis and the principles of binocular stereo vision in PSP data processing, we achieve precise reconstruction of the 3D pressure on the measured surface. This method has been successfully applied to the 3D pressure measurement on the surface of a compressor cascade, and a comparative analysis with pressure tap data has shown that the relative deviation of the PSP data is within 1.2%. Furthermore, the accuracy of the measurement results has been verified by comparing the reconstructed 3D point cloud with a CAD model, with an average deviation of 0.17 mm.

Reliable and comprehensive compressor cascade test data are essential for establishing high-load compressor design systems and verifying the accuracy of numerical methods. In response to the demand for standard cascade test data of high-load compressor blade roots, the absence of authoritative test data of China, the inadequacy of publicly available data for high-load design needs, and the issue of data misuse due to the lack of flow field quality detection, the National Science and Technology Major Project Group conducted extensive research and discussions. With the support of the research results from Northwestern Polytechnical University on the influence mechanisms and regulation strategies of planar cascade wind tunnel flow field quality, the independently designed modern high-load compressor standard model cascade NPU-28 (with a blade camber angle of 43.5°, solidity of 1.72, and diffusion factor of 0.5) was established. This study obtained extensive experimental data, including cascade attack angle characteristics, isotropic Mach number on the blade surface, total pressure loss coefficient at the cascade channel exit, and exit flow angle for nine operating conditions within the inflow Mach number range of 0.4 and attack angle range of −10.9° to 5.1°. The data also provide flow field quality parameters, such as inflow Mach number uncertainty, axial velocity density ratio, and exit periodic index, along with measurement positions, test conditions, and inflow turbulence intensity, offering complete test information.

The complex three-dimensional configuration and thin-walled structure of compressor blades lead to great difficulty in their manufacturing, and uncertainty of blade geometric deviation is very prominent in the machining process. As the aerodynamic loading of the compressor continues to rise and the geometric size continues to decrease, its working environment and internal flow characteristics become worse and more complex. The harsh working environment amplifies the influence of machining uncertainty. This leads to the high dispersion of the aerodynamic performance for the same batch of compressors and the frequent occurrence of severe performance degradation in service, resulting in substandard performance and even failure problems. In recent years, a lot of research work has been carried out on uncertainty quantification of compressor blade machining deviation at home and abroad. In this paper, the research progress in this field is reviewed in terms of geometric modeling, probabilistic model characterization, uncertainty quantification method, and uncertainty effect. Finally, the key problems and research prospects of uncertainty quantification on compressor blade machining deviation are summarized.

The issue of geometric uncertainty of compressor blade machining is very prominent. As the input of the uncertainty quantification system, the accurate expression of its statistical distribution is particularly important for the system output. According to the statistical analysis of leading-edge radius errors at the same blade height section of 100 compressor rotor blades, it is found that the distribution is left-skewed and in a peak condition, with significant non-normality. Then, to overcome the limitations of the normal distribution, the expectation conditional maximization either method is used to obtain the error distribution with skewness and kurtosis, which fits the error data better than the normal distribution. Finally, the leading-edge radius error fitting the two distributions are used as the uncertainty quantification input separately, and the total pressure loss coefficient and static pressure ratio of the cascade are used as the response. Comparison of the quantification results shows that the total pressure loss coefficient and static pressure ratio mean variable values, the mean variable values of the total pressure loss coefficient and static pressure ratio corresponding to different statistical distribution are less than 1%, which can be negligible, while the scatter difference is significant. Besides, the variation of the total pressure loss coefficient is larger than that of the static pressure ratio, about 20% at most. In addition, if the normal distribution is input, the influence of the uncertainty of the leading-edge radius error on the scatter of the cascade aerodynamic performance and the performance variation range are significantly overestimated, while the possibility of performance deterioration is underestimated. This research illustrates the necessity of considering skewness and kurtosis characteristics of machining errors to provide more accurate reference for blade fine machining.

In the actual processing of the cascade blade, the leading edge is prone to exceeding the tolerance, while other parts of the blade are not. The discrepancy in processing tolerance results in a deterioration of the aerodynamic performance consistency of compressor cascades. This paper proposes a mathematical model that incorporates random deliations in blade processing across the entire arc length of the blade profile coupled with the leading-edge over tolerance. This study examines the impact of processing deviation uncertainties on the aerodynamic performance consistency of a high subsonic diffuser cascade. A non-intrusive polynomial chaos expansion method based on sparse grids was employed to achieve this. The results show that the consistency of the blade loss coefficient and static pressure ratio is optimal at the design angle of attack, while it is lowest at large positive angles of attack. The poor performance consistency can be attributsd to the fact that the leading edge deviations result in an increase in the mean and root-mean-square values of flow loss within the boundary layers around the blade leading edge. When using ±5% deviation from the design blade as the criterion to measure the blade loss coefficient, the probability of blade profile performance consistency is 99% at the design angle of attack and 79.4% at large positive angles of attack.