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Experimental research on engine and its components
UPDATETIME:2016-05-28 16:35:42 CLICK:

With the development of modern laser technology, optical diagnostic methods have been widely used in the test and research of engine and its components. These techniques can achieve in the engine of the temperature and the pressure of gas velocity component and concentration as well as fuel spray and spatial distribution of the two-phase flow measurement, engine parts debugging and validation of improved numerical calculation program to provide adequate data.

In the next few years, due to advances in optical electronic computer hardware and software, the main is increase in demand, prompted by laser velocimetry of turbomachinery flow field obtained data quantity and quality continues to improve. Through the turbine and compressor rotor and stator cascade and combustion chamber of a large number of studies, to deepen the understanding of turbine machinery and combustion chamber internal flow is good. Due to the need to laser beam in the measurement of the mechanical interior region, three-dimensional in the turbine mechanical testing has been a certain limit.

With the increasing need of 3D flow data, the development and application of 3D system has been greatly strengthened, and a great progress has been made. Laser Doppler velocimetry has many optical configurations that can be used to measure 3D velocity components. At present, three dimensional measurement is realized by three color laser, such as hydrogen ion laser. The measurement accuracy of the radial velocity component of this system is directly related to the radial angle. In order to reduce the measurement error, the proposed adjustment system is consistent with the direction of the system arrangement. The three dimensional tool system has been successfully applied to different turbine mechanical testing. The laser into the test zone usually uses the plane window. Because the shell of the turbine is curved surface, the plane window can not match with the shape of the shell, so as to cause the local distortion of the flow.

Practice proves that the system is not sensitive to the distortion of the light, because their light is not focused in the detecting area. The system can tolerate a sufficiently thin curved surface glass to produce a slight distortion of the light.

Research Center has been used for the flow field in the turbine components were detailed 3D measurement. The aim is to provide detailed experimental data for open centrifugal compressor and turbine on the primary flow and secondary flow date a year aviation engine the period of development. In the year of the development of a very complex three-dimensional system, it is the same as the two-dimensional system of laser into the human measurement area, in the form of the flow field in the turbine is more widely used. It applies a standard fringe pattern, and can be used to emit fluorescence of suspended particles to trace the axial and circumferential velocity component. The radial component is used a scanning confocal interferometer, Doppler frequency direct analysis of scattering light of particle generation shift obtained. Two configurations are combined into an optical system while running. The measurement method has been successfully applied to the annular turbine stator vane. But due to its complexity stability constraints and takes a long data acquisition time, cannot be applied to the rotor blade flow field measurements, in the study of the flow field of turbine machinery did not occupy very important position. It has also played a significant role in the study of the combustion chamber, which has already been accomplished in many meaningful measurements.

Because the laser is relatively easy to enter the measurement area in the non reactive flow, most of the measurements are done in the non reacting flow, and the measurement results are more accurate. The application of the reaction flow is very complex, mainly due to the difference of the refractive index of the component particles, so that the laser becomes uneven, the detection volume is distorted, so as to affect the quality and quantity of the measurement data. Even so, it has been successful to simplify the combustion chamber and the actual sector combustion chamber flame, but the experiment is not carried out under the condition of low pressure.

Establish the equipment can be carried out and three-dimensional measurement, test temperature up to pressure air mass flow when the pressure is reached, due to the fluctuations in the index of refraction, measurement of serious distortion. The standard of the laser two focus speed instrument is a two-dimensional measurement device, which measures the direction and size of the velocity component in the plane perpendicular to the optical axis. When the standard system is continuously measured in the flow field in different directions along the optical axis, the three-dimensional component can also be measured. Due to the inherent characteristics, it is mainly used in the large flow rate of high speed turbine mechanical measurement, such as the compressor and turbine. In such conditions, only the operation with a minimum fixed focus angle system can be used as ink three-dimensional velocity measurement. The usual system is composed of two independent two-dimensional systems.

This system is used by both the current market and European research institutions. The latest development of the three-dimensional system has been applied to analyze the unsteady flow of rotor blade interaction. It can measure the position of the shock wave and the characteristics of the three-dimensional flow. The newly developed system combines the frequency analysis of two dimensional measurement and scattered light, and the measurement of the frequency shift represents the velocity component of the optical axis of the optical head. A system has been established for the measurement of the flow field in the compressor and turbine. For the flow field of combustion test, the disturbance intensity is large, and the ability to resist disturbance is exceeded, so the system can not be used.

Coherent anti Stokes Raman spectroscopy is a very good method for measuring temperature. The detection area generation and similar, are produced by superposition of coherent signals of two or more different frequency beam. The actual system usually uses a double frequency laser, the pulse repetition operation. System application has encountered same question, namely laser how measurement region, also met to soot particle density and the variation of the refractive system problems, which limit the running under the condition of high pressure gas turbine combustion equipment in the application.

In the measurement, a substantial reduction in the amount of data in the critical position of the mixed strength is not even measured data, which indicates that the limit has been close to the month and measurement. Buried hot hair to restore it to measure the shoe almost all regions, even in the most complex test equipment. In addition to the combustion chamber operating at high pressure due to laser distortion can not be measured, the data provided by these measurement techniques used to verify the validity of the calculation program is sufficient. However, the time and cost of measuring the application of these techniques are very high. Digital particle image velocimetry digital particle image velocimetry is a powerful measuring device, in the field of research and application of a wide range of can as an alternative and complementary of laser Doppler velocimeter. It can be an attractive technique to obtain the transient planar measurement results in the complex flow field of turbine machinery. The same problem can be encountered in the flow field which is applied to the rotating machinery.