机匣视窗折射对LDV聚焦的影响分析

为了分析激光束经过机匣视窗后聚焦状态的变化情况,发展了一套通用程序,可用于计算不同的测量条件下,激光束穿过不同尺寸机匣视窗时的折射情况,并对其结果的可信性进行了验证.利用所发展的程序,以二维LDV探头为例,分析了典型情况下蓝光、绿光焦点偏移情况,以及蓝光与绿光焦点之间偏移量的变化情况,并给出了确定焦点重合的计算准则.计算结果表明:如果不进行特殊的光学修正,LDV测量时必须要选取小的探头角度和浅的测点深度.

基于非线性约束模型的发动机部件性能衰退研究

引入流量因子和效率冈子，通过在稳态模型中修改流量因子和效率因子，模拟几种性能失效形式，分析了它们引起压气机和涡轮测量参数的变化。以发动机稳态模型为基础，构建优化部件性能参数的非线性约束模型，得到部件性能参数的衰退过程。在得到的性能参数基础上，代人到发动机稳态模型，得到对应的测量参数，同时滤掉噪声的干扰。又运用雅克比矩阵建立部件性能参数与测量参数的对应关系，得到的测量参数与非线性结果进行比较，证明了非线性约束模型计算发动机测量参数的优越性。

Measurement and Numerical Simulation of a Small Centrifugal Compressor Characteristics at Small or Negative Flow Rate

For centrifugal compressors used in automotive turbochargers, the extension of the surge margin is demanded because of lower engine speed. In order to estimate the surge line exactly, it is required to acquire the compressor characteristics at small or negative flow rate. In this paper, measurement and numerical simulation of the characteristics at small or negative flow rate are carried out. In the measurement, an experimental facility with a valve immediately downstream of the compressor is used to suppress the surge. In the numerical work, a new boundary condition that specifies mass flow rate at the outlet boundary is used to simulate the characteristics around the zero flow rate region. Furthermore, flow field analyses at small or negative flow rate are performed with the numerical results. The separated and re-circulated flow fields are investigated by visualization to identify the origin of losses.

Effects of Measuring Positions on the Measured Aerodynamic Performance of a Centrifugal Compressor

This paper performs a numerical simulation of three-dimensional flow field in a centrifugal compressor with long inlet and outlet pipes using CFX software.By arranging virtual probes at different positions in both inlet and outlet planes,the aerodynamic performance of the centrifugal compressor is measured and compared with each other.Then effects of measuring positions on measurement results are discussed.The results show that it will generate notable measuring errors of the pressure ratio and efficiency if the inlet total pressure is measured using a single-point probe.The inlet total pressure data can be accurate when they are measured using a 3-point rake.The outlet total pressure and total temperature data can not be accurate if they are respectively measured at one circumferential position even using a multi-point rake.Increasing tangential measuring positions at the outlet is effective to improve the test accuracy.When the outlet total pressure and total temperature are respectively measured at 3 tangential positions,the data can be almost accurate.

L2F Anemometry Measurements of the Inter-Row FlowField Within a Transonic Axial Compressor Providedwith Curved Windows

When measurements are performed in high speed, small-scale compressors, the use of curved glasswindows is required in order to avoid any mismatch between the measurement window and the casing. However, the glass curvature leads to optical distortions, which hinder acceptable measurementsand can even prevent the acquisition of any data. Thus, an original optical assembly, which consistsin inserting a simple and inexpensive corrective window between the frontal lens of the anemometerand the shroud window, is proposed. The way of determining the geometric characteristics and theposition of this corrective window, which restores very acceptable fool, is presented in the paper. Thereliability of this corrective optical assembly is highlighted by comparative measurements in a test case.Using such an optical setting, L2F measurements were realized along a section, downstream of the inletguide vane (IGV) of a transonic compressor stage. The spatial resolution leads to a good descriptionof the interaction of the wake with the oblique shock emanating from the leading edge of the rotor.A phenomenological study of the wake/shock interaction with a change of frame is realized using thestreamwise equation of the transport of vorticity.

Experimental Study on the Inlet Fogging System Using Two-Fluid Nozzles

Large-capacity compressors in industrial plants and the compressors in gas turbine engines consume a considerable amount of power. The compression work is a strong fimction of the ambient air temperature. This increase in compression work presents a significant problem to utilities, generators and power producers when electric demands are high during the hot months. In many petrochemical process industries and gas turbine engines, the in- crease in compression work curtails plant output, demanding more electric power to drive the system. One way to counter this problem is to directly cool the inlet air. Inlet fogging is a popular means of cooling the inlet air to air compressors. In the present study, experiments have been performed to investigate the suitability of two-fluid nozzle for inlet fogging. Compressed air is used as the driving working gas for two-fluid nozzle and water at am- bient conditions is dragged into the high-speed air jet, thus enabling the entrained water to be atomized in a very short distance from the exit of the two-fluid nozzle. The air supply pressure is varied between 2.0 and 5.0 bar and the water flow rate entrained is measured. The flow visualization and temperature and relative humidity measurements are carried out to specify the fogging characteristics of the two-fluid nozzle.