With the development of modern laser technology, optical diagnosis method has been more and more widely used in the experimental research of engine and its components. These technologies can realize the measurement of gas velocity, temperature and pressure components and concentration, the spatial distribution of fuel mist and two-phase flow field in the engine, and provide sufficient data for the debugging of engine components and verification of improved numerical calculation programs.

In the years that followed, advances in optical computer hardware and software, and above all an increase in demand, led to a continuous improvement in the quality and quantity of data obtained from using laser velocimeters to study turbine-machine flow fields. 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 turbine-machinery and the flow in combustion chambers. 3D has been limited in turbomachinery testing due to the need to focus laser light on the measuring area inside the machine.

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. A laser Doppler velodrometer has many optical configurations that can be used to measure three-dimensional velocity components. Currently, three dimensions are achieved using three-color lasers to generate three dimensional measurement areas, such as hydrogen ion lasers. The accuracy of measuring radial velocity component is directly related to radial declination 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. The 3D tool system has been successfully applied to various turbomachinery tests. A flat window is usually used when the laser enters the measuring area. Because the turbine-machinery shell is curved, the plane window cannot match the shape of the shell, resulting in local flow distortion. Therefore, the circumferential dimension of the observation window is limited.

It turns out that the systems are not as sensitive to the distortion of light as the systems, because their light is not focused extremely precisely in the detection area. The system tolerates a thin enough curved glass to produce tiny distortions of light.

The research Center has carried out detailed three-dimensional measurements of the flow field within the turbine components in order to provide detailed experimental data for the first and second flow of the open centrifugal compressor and turbine in the first year of the development of the aero-engine phase. In 2005, a rather complex three-dimensional system was developed, which has the same way of laser penetration into the measurement area as the two-dimensional system, and is more widely used in the flow field formed by turbine-machinery. The axial and circumferential velocity components are measured using a standard fringe configuration and a tracer of fluorescing suspended particles. The radial component is obtained by scanning with a confocal-interferometer and directly analyzing the Doppler shift of the scattered light produced by the particles. The two configurations are combined into an optical system that operates simultaneously. This method has been successfully applied to the measurement of turbine ring stator blades. However, due to the limitation of complexity and stability and the 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 study of turbine-machinery flow field. It has also played a huge role in the study of combustion chambers, 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 measurements are done in the non-reactive flow, and the obtained measurement results are more accurate. The application situation in the reaction flow is very complicated, mainly due to the difference in the refractive coefficient of the component particles, so that the laser becomes uneven, the detection volume is distorted, thus affecting the quality and quantity of the measured data. Even so, success has been achieved by measuring simplified combustion chambers and actual fan-shaped combustion chamber flames, but the experiments have been carried out either under low pressure conditions or on small-scale experimental equipment.

Set up the equipment that can carry out and three-dimensional measurement, test temperature up to pressure air mass flow When the pressure reaches, due to the fluctuation of the refraction coefficient, the measurement is seriously distorted. The laser difocal velocimeter is a two-dimensional measuring device that measures the direction and magnitude of the velocity component in a plane perpendicular to the optical axis. Three-dimensional components can also be measured when the standard system is continuously measured point by point in the flow field in different directions along the optical axis. Due to its inherent characteristics, it is mainly used in turbomachinery measurements with large flow rates and high speeds, such as compressors and turbines. Under such conditions, only the inkstone system operating at a very small fixed focal Angle can be used for three-dimensional velocity measurement. A typical system is composed of two independent two-dimensional systems.

This system is currently available on the market and used by research institutions in Europe. Recently developed 3D systems have been applied to the analysis of unsteady flows caused by rotor blade interactions. It can measure the position of shock waves and three-dimensional flow characteristics. The newly developed system combines two-dimensional measurements with frequency analysis of scattered light, and the measured frequency shift represents the velocity component in the direction of the optical axis. Systems have been established in most turbomachinery laboratories for the measurement of compressor and turbine flow fields. For the flow field of combustion test, the system cannot be applied because of the high disturbance intensity, which exceeds the ability of anti-disturbance measurement.

Coherent anti-Stokes Raman spectroscopy is a good method to measure temperature. The detection region is similar in that it produces coherent signals by superimposing two or more beams of different frequencies. The actual system usually uses a double frequency laser, running in repeated pulses. The application of the system encountered the same problem, that is, how to enter the measurement area of the laser, but also encountered the problem of not adapting to the density of soot particles and the change of the refraction system, which limited 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 the limit of monthly measurement is close. The burning heat of the burial plies its wish to measure almost all areas, even within the most complex test equipment. The data provided by these measurement techniques are sufficient to verify the validity of the calculation program, except that the combustion chamber operating under high pressure cannot be measured due to laser distortion. But the time and expense required to make measurements using these techniques is high. The digital particle image velocimeter is a powerful measuring device, which can be used as an alternative and supplement to the laser Doppler velocimeter in a wide range of applied research fields. Transient plane measurements can be obtained in complex flow fields created by turbomachinery, making it an attractive technique. The same problem is encountered when applied to the flow field generated by rotating machinery.