Method and device for simultaneously measuring sound velocity and refractive index of fluid

Abstract

The invention discloses a method and device for simultaneously measuring the sound velocity and the refractive index of fluid. Plane mirrors are respectively arranged in the normal direction and the symmetrical direction of probe light so as to adjust the receiving angle of scattered light; two scattered light beams with different scattering angles pass through a focusing lens and two diaphragms and then respectively enter a Fabry-Perot interferometer with a function generator for filtering, and are then received by the photoelectric detector with a shading cylinder and are converted into TTL pulse signals for Rayleigh-Brillouin spectrum analysis. Rayleigh-Brillouin scattering spectrums at different angles are used for decoupling the refractive index and the scattering angle, the influence of the scattering angle and noise interference on sound velocity and refractive index measurement is fundamentally eliminated through a scanning type measurement method, and the method has the characteristics of non-contact measurement, irrelevance with body size precision, easiness in high-temperature measurement and the like, and method and device have important application prospects in the fields of energy chemical industry, national defense military industry, industrial production, scientific research and the like.

Description

technical field [0001] The invention belongs to the technical field of measuring fluid thermophysical properties, and in particular relates to a method and a device for simultaneously measuring fluid sound velocity and refractive index. Background technique [0002] The speed of sound and refractive index are the basic physical parameters of fluids, which play an important role in the fields of energy and chemical industry, national defense and military industry, industrial production and scientific research. For example, the speed of sound is very important in constructing the state equation, deriving thermodynamic properties such as specific heat capacity, virial coefficient, and compressibility coefficient, as well as in the design of thermodynamic systems; the refractive index and its temperature coefficient are closely related to the performance of fuel, and are often used to correlate with density, Parameters such as flash point and cetane number were correlated. Sinc...

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Problems solved by technology

Due to the mutual coupling between the refractive index and the scattering angle in Bragg's law, the current research object of the Rayleigh-Brillouin light scattering method is mainly the gas with a relatively small refractive index, and the difference in refractive index between the fluid to be measured and the ambient gas is often ignored during the experiment , for other fluids, a small angle measurement is generally used to minimize the influence of the scattering angle, but an error of about 0.35% will still be introduced

H.Bohidar, Brillouin scattering study of pressure dependence of hypersonicsound velocity in binary liquids, J.Phys.D: Appl.Phys.22 (1989) 1252-1256 designed a 45° angle incident, -45° angle to receive scattered light The experimental body completely eliminates the influence of the scattering angle on the sound velocity measurement, but the incident angle cannot be adjusted in different sound velocity ranges to match the Brillouin frequency shift with the free spectral region of the Fabry-Perot interferometer

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