Analysis of metering scheme for compressed air flow

Abstract: The analysis information of the compressed air flow meter metering scheme is provided by the excellent flow meter and flow meter production and quotation manufacturers. Abstract: During the engine test, a measuring rake is usually installed between the outlet of the intake port and the inlet of the engine to measure the total static pressure parameters of the section, and then obtain the compressed air flow at the engine inlet. Considering the influence of the boundary layer, a new type of boundary is adopted. More flowmeter manufacturers choose models and price quotations. You are welcome to inquire. The following is the details of the analysis article of the compressed air flowmeter metering plan. During the engine test, a measuring rake is usually installed between the outlet of the intake port and the inlet of the engine to measure the total static pressure parameters of the section, and then obtain the compressed air flow at the engine inlet. Taking into account the influence of the boundary layer, a new type of pressure combined measuring rake of the boundary layer was used for measurement. At the same time, the different measurement schemes for obtaining the cross-sectional flow field pressure are analyzed, and combined with the test data, the errors caused by the different measurement schemes are analyzed. The results show that the combined pressure measurement rake can accurately obtain the compressed air flow at the engine inlet, and the pressure difference sensor is used to obtain the cross-sectional flow field pressure, which can significantly reduce the measurement error of the engine inlet compressed air flow and the boundary layer. 1. Introduction The compatibility of the intake port and the engine is an important assessment index for the comprehensive evaluation of the aircraft propulsion system. Compressed air flow is an important measurement parameter in the air intake and engine compatibility test. In the engine performance test, the thrust measurement is particularly important, and the compressed air flow is an important measurement parameter in the thrust measurement. Therefore, obtaining the compressed air flow of the engine is an important part of the engine test, which is of great significance to the design of aero-engines. During the test, reasonable and clever planning of the measurement scheme can effectively reduce the measurement error. During the flight test, a measuring rake is generally installed in the transition section between the outlet of the intake port and the inlet of the engine to measure the flow field information of the section and obtain the compressed air flow at the engine inlet. The research on the measurement and calculation of engine compressed air flow abroad is earlier, and it has accumulated rich engineering experience. The testing technology and theory are relatively advanced, and in the measurement of engine gas path pressure, the United States has designed and error analysis of the measuring rake and the sensing part. Detailed standards have been developed. The measurement and calculation of the compressed air flow of the engine has also been carried out in engineering research and application in China. The China Gas Turbine Research Institute has carried out detailed research on the design and error analysis of the engine gas path pressure measurement rake and the sensing part. China flight test research The institute also measured the compressed air flow during the engine test flight, and achieved certain results. In the measurement of cross-sectional flow field, the measurement of pressure is more critical, and different measurement methods will lead to large differences in the results. At present, absolute pressure sensors and differential pressure sensors are mainly used for measurement. In this paper, when measuring the compressed air flow at the engine inlet, a combined pressure measuring rake of the boundary layer is used. Combined with the test results of the engine, the compressed air flow is obtained by calculation, and the errors when the absolute pressure sensor and the differential pressure sensor are used to measure the pressure are calculated. analysis. 2. Measurement scheme The flow area of ​​gas in the intake duct can be divided into the mainstream area that is not affected by viscosity and the boundary layer area that is affected by viscosity. The measurement of parameters in the mainstream area is easy to implement and has various methods. The precise measurement of the boundary layer region has always been difficult in engineering due to the influence of viscosity. Although my country has carried out actual engineering research and application in the measurement and calculation of the boundary layer, the engineering experience is still relatively lacking, the measurement method is also traditional, and the measurement result has a large error. In the test of a certain type of engine, according to the flow characteristics of the main flow area and the boundary layer of the flow field, on the basis of the development and engineering application of the previous measuring rake, combined with the boundary layer measurement rake, a new method that can measure the flow in the main flow area is designed. The combined measurement rake can obtain the information of the flow field in the boundary layer, as shown in Figure 1. The 4 sensing parts at the front end of the measuring rake are the sensing parts of the total static pressure of the pitot tube for measuring the flow field information in the mainstream area, and the 10 sensing parts near the root are the sensing parts for measuring the total pressure of the boundary layer. During the test, the measuring rake was installed in the transition section between the outlet of the intake port and the engine inlet. A total of 6 pressure rakes were installed in this section, 3 of which were combined pressure measuring rakes of the boundary layer, and 3 were no boundary layer. The pressure measuring rake of the measuring point (the pitot tube measuring point near the root is located in the boundary layer); at the same time, three temperature rakes are installed, which are evenly distributed along the circumference of the measuring section. The installation of the measuring rake and the distribution of measuring points are shown in Figure 2. In the measurement and calculation of compressed air flow, the total pressure and static pressure of the measurement section are very important. Due to the variety of pressure measurement methods, the pressure measurement methods are studied from the perspective of sensor selection, and two measurement schemes of absolute pressure sensor and differential pressure sensor are used respectively.The pressures in the main flow area and the boundary layer are measured. Measurement plan 1: Directly use absolute pressure sensor to measure the total pressure, static pressure and total pressure of the boundary layer in the mainstream area. Measurement plan 2: The method of directly testing the total static pressure difference is adopted, that is, the pressure in the mainstream area is measured by the absolute pressure sensor and the differential pressure sensor respectively, and the total pressure of the boundary layer is measured indirectly by the differential pressure sensor. The cabin pressure is used as the reference pressure during measurement. In order to prevent airflow disturbance, the cabin pressure sensor is placed in a fixed iron box in the engine compartment.

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