With the development of modern laser technology, optical diagnostic methods have been more and more widely used in the experimental research of engines and their components. These technologies can realize the measurement of the gas velocity, temperature and pressure components and concentration in the engine, the spatial distribution of fuel mist and the two-phase flow field, and provide sufficient data for the debugging of engine components and the verification and improvement of numerical calculation programs.
In the following years, due to the advancement of optical and electronic computer hardware and software, *the main thing is the increase in demand, which promotes the continuous improvement of the quality and quantity of data obtained by using laser speedometers to study the flow field of turbomachinery. A large number of studies on turbine and compressor rotors and stator cascades and combustion chambers are of great benefit to deepening the understanding of the flow in turbomachinery and combustion chambers. Due to the need to shoot the laser into the measurement area inside the machine, three-dimensional has been subject to certain limitations in turbomachinery testing.
With the increasing demand for 3D flow data, the development and application of 3D systems have been greatly strengthened, and considerable progress has been made. There are many optical configurations of laser Doppler velocimeters that can be used to measure three-dimensional velocity components. At present, three-dimensionality is achieved by using three-color lasers to generate three-dimensional measurement areas, such as hydrogen ion lasers. The accuracy of this system to measure the radial velocity component is directly related to the radial deflection angle. In order to reduce the measurement error, it is recommended to adjust the direction of the system layout to be consistent with the flow vector. Such a three-dimensional knife system has been successfully applied to different turbomachinery tests. The plane window is usually used when the laser enters the measurement area. Since the casing of the turbomachinery is curved, the plane window cannot conform to the shape of the casing, which may cause local distortion of the flow. Therefore, the circumferential size of the observation window is restricted.
Practice has proved that the system is not as sensitive to the distortion of light as the system, because their light is not focused extremely accurately in the detection area. The system can tolerate small light distortion caused by sufficiently thin curved glass.
The Research Center has carried out detailed three-dimensional measurements on the flow field in the turbine components. The purpose is to provide detailed experimental data for the development of the first-year aero-engine phase of the open-type centrifugal compressor and turbine. In 2005, a rather complex three-dimensional system was developed. It has the same way that laser enters the measurement area as the two-dimensional system, and is more widely used in the flow field formed by turbomachinery. It uses a standard stripe configuration and uses fluorescent suspended particles as a tracer to measure the axial and circumferential velocity components. The radial component is obtained by scanning with a confocal interferometer and directly analyzing the Doppler frequency shift of the scattered light generated by the particles. The two configurations are combined into an optical system and operate simultaneously. This method has been successfully applied to the measurement of turbine annular stator blades. However, due to its complexity and stability limitations and the need for a long data acquisition time, it cannot be applied to the flow field measurement of rotor blades, and it does not occupy a very important position in the research of turbomachinery flow field. It has also played a huge role in the research of the combustion chamber, and many meaningful measurements have been completed.
Since it is easier for the laser to enter the measurement area in the non-reactive flow, most of the measurements are completed in the non-reactive flow, and the measurement results obtained are more accurate. The application situation in the reaction flow is very complicated, mainly due to the difference of the refractive index of the component particles, which causes the laser to become non-uniform, and the detection volume is distorted, which affects the quality and quantity of the measurement data. Even so, the combustion chamber with simplified measurement and the actual fan-shaped combustion chamber flame have been successful, but the experiment was carried out either under low pressure conditions or on small-sized experimental equipment.
Set up equipment that can perform and three-dimensional measurement. When the test temperature reaches the pressure air mass flow rate, when the pressure is reached, the measurement is seriously distorted due to the fluctuation of the refractive index. The standard of the laser two-focus velocity meter is a two-dimensional measuring device, which measures the direction and size of the velocity component on a plane perpendicular to the optical axis. When the standard system is continuously measuring point by point in the flow field along the optical axis in different directions, it can also measure the three-dimensional component. Due to its inherent characteristics, it is mainly used in the measurement of large flow and high speed turbomachinery, such as compressors and turbines. Under such conditions, only inkstone systems operating at a very small fixed focal angle can be used for three-dimensional velocity measurement. The usual system consists of a combination of two independent two-dimensional systems.
Currently on the market and European research institutions are using this system. *The newly developed three-dimensional system has been applied to analyze the unsteady flow formed by the interaction of rotor blades. It can measure the position of the shock wave and the three-dimensional flow characteristics. The newly developed system combines two-dimensional measurement and frequency analysis of scattered light, and the measured frequency shift represents the velocity component in the direction of the optical axis of the optical head. Systems have been established in most turbomachinery laboratories for the measurement of compressor and turbine flow fields. For the flow field of the combustion test, the system cannot be applied due to the high disturbance intensity, which exceeds the ability of anti-disturbance measurement.
Coherent anti-Stokes Raman spectroscopy is a good method of measuring temperature. The generation of the detection zone is similar to that of generating coherent signals by superimposing two or more beams of different frequencies. Practical systems usually use double-frequency lasers, which run repeatedly with pulses. The application of the system encounters the same problem, that is, how does the laser enter the measurement area, and also encounters the problem of not adapting to the high density of soot particles and the large change of the refraction system, which limits the application of gas turbine combustion equipment operating under high pressure conditions. .
In the measurement, the amount of data is greatly reduced, and even no data can be measured at the critical position of high mixing intensity, which indicates that it is close to the limit of monthly measurement. Buried hot hair resumes its measurement in almost all areas, even within the most complex test equipment. Except for the inability to measure the combustion chamber operating under high pressure due to laser distortion, the data provided by these measurement techniques is sufficient to verify the validity of the calculation program. However, the time and expense required to apply these technologies for measurement are very high. Digital particle image velocimetry digital particle image velocimetry is a powerful measuring device, which can be used as a substitute and supplement for laser Doppler velocimetry in a wide range of application research fields. Transient plane measurement results can be obtained in the complex flow field formed by turbomachinery, making it an attractive technology. The same problem can also be encountered in the flow field generated by the rotating machinery. For automotive parts and parts machining, PTJ Shop offers the highest degree of OEM service with a basis of 10+ years experience serving the automotive industry. Our automotive precision shop and experts deliver confidence. We have perfected the art of producing large component volumes with complete JIT reliability, backed by the quality and long-term reliability our customers expect.
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