JPH037054B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention focuses a laser beam for gas velocity measurement and a laser beam for temperature and component concentration measurement onto a single point within the gas to be measured, thereby obtaining these measured values at the same point. This invention relates to a measuring optical device that can perform

2. Description of the Related Art Conventionally, laser anemometers have been known that measure the speed of airflow by focusing a laser beam onto a single point within a gas. This current meter mixes fine particles on the order of microns into a moving gas, and when incident light hits these fine particles, so-called elastically scattered light, which is scattered at the same frequency as the incident light without giving or receiving energy, is used. (Mie) The speed of airflow is determined by detecting the shift frequency due to the Doppler effect caused by the movement of particles using scattered light.

On the other hand, in recent years, Raman scattering spectroscopy has been developed that can measure the temperature and concentration of a gas by focusing a powerful laser beam into the gas. This focuses on specific molecules contained in a gas, such as N ₂ and O ₂ , and a laser beam of a specific wavelength is incident on them, and energy is exchanged between the incident light and these molecules. It takes advantage of the phenomenon of inelastic scattering, so-called Raman scattering, in which light with different wavelengths is emitted.

Both of these devices have the same feature in that they focus a laser beam into a gas, but their measurement principles are completely different.
Therefore, since the intensity and properties of the laser beams used are different, they have been used as separate devices.

Combustion phenomena observed in aircraft engines, automobile combustors, industrial furnaces, etc. are complex phenomena involving chemical reactions, heat transfer, and fluid motion.
Scientifically, this is an area that is largely unexplored. For this reason, the development of improvements to these combustion devices has largely depended on experience.

To understand such combustion phenomena more scientifically, it is necessary to simultaneously measure velocity, temperature, and component concentration at the same point in the combustion region and analyze the data.

The above-mentioned laser velocimeter and Raman scattering spectroscopy can be used to measure velocity, temperature, and component concentration at a single point in the combustion region of a gas, but if these are used as separate devices, they cannot be measured at the same point. In order to measure the gas velocity, temperature, and component concentration of the two devices, it is necessary to match the focal points of the laser beams of both devices, and adjusting the two devices is a time-consuming and difficult task.

The present invention focuses a laser beam for a laser anemometer and a laser beam for a Raman scattering spectrometer using the same condensing lens, thereby concentrating the laser beams from both devices on the same point, and converging the laser beams in the gas. Flow velocity, temperature, and concentration that can be measured simultaneously at one point
The purpose is to obtain a device for simultaneously measuring concentration.

A detailed explanation will be given below with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of the optical system of the present invention and its optical path configuration.
6 and 7 are focused by a common condensing lens 1 to a point 8 in the airflow to be measured. Divergent light from the measurement point 8, non-scattered light, Mie scattered light containing velocity information, and Raman scattered light containing temperature/concentration information are similarly focused by a common condensing lens 2 and sent to the analyzer. I am guided.

The laser for speed measurement is, for example, a continuous oscillation light of a He-Ne laser, but the laser for temperature and concentration measurement is
For example, the giant pulse of a YAG laser,
Phase matching at focal point 8 to cause Raman scattering,
It is necessary to satisfy quantum mechanical properties such as conservation of momentum.

Since these light beams are condensed at the same focal point 8 by the common condensing lens 1, the velocity, temperature, and concentration at the same point can be measured simultaneously.

FIG. 2 shows another embodiment, in which the laser beam 5 for measuring temperature and concentration is only one beam along the optical axis. In the embodiment shown in FIG. 3, the beams 3 and 4 for measuring the flow velocity are arranged offset from the optical axis,
Priority is given to signal intensity by Raman scattering method over flow velocity measurement. On the contrary, FIG. 4 shows an example in which the signal intensity of Mie scattered light is prioritized over the Raman scattering method, and in this way, an appropriate beam arrangement can be made depending on the purpose of measurement.

[Brief explanation of drawings]

1 to 4 are schematic diagrams of beam arrangements in the optical system of the present invention, respectively. 1, 2: Condenser lens, 3, 4: Laser beam for current meter, 5, 6, 7: Laser beam for temperature/concentration measurement.

Claims (1)

[Claims] 1. Converging a continuous wave laser beam for measuring the flow velocity of gas containing particulates and a separate giant pulse laser beam for measuring temperature and concentration onto one point in the measurement space using a common condensing lens. Features: Simultaneous measurement device for flow velocity, temperature and concentration.