A temperature measurement model of radiation thermometry for the surface covered by participating media was developed. The model was based on the radiation heat transfer of participating media and principles of radiat...A temperature measurement model of radiation thermometry for the surface covered by participating media was developed. The model was based on the radiation heat transfer of participating media and principles of radiation pyrometers, and solved by integral formulation of discrete ordinate method on spectral waveband. The influence of water mist on the indicated temperature of Raytek MR1SB one/two color pyrometer was discussed. Mie theory was used to calculate the radiative properties of water mist. In order to verify the model, a laboratory temperature measurement experiment was executed. The result shows that temperature of radiation thermometry is sensitive to the spectral response wavelength of pyrometer, and the simulated temperature of pyrometer agrees well with the experimental measurements on a suitable wavelength. The simulated temperature was lower than the real temperature of surface for one-color pyrometer, and it could be higher or lower than the real one for two-color pyrometer with the influence of participating media.展开更多
The Boltzmann equation(BE)for gas flows is a time-dependent nonlinear differential-integral equation in 6 dimensions.The current simplified practice is to linearize the collision integral in BE by the BGK model using ...The Boltzmann equation(BE)for gas flows is a time-dependent nonlinear differential-integral equation in 6 dimensions.The current simplified practice is to linearize the collision integral in BE by the BGK model using Maxwellian equilibrium distribution and to approximate the moment integrals by the discrete ordinatemethod(DOM)using a finite set of velocity quadrature points.Such simplification reduces the dimensions from 6 to 3,and leads to a set of linearized discrete BEs.The main difficulty of the currently used(conventional)numerical procedures occurs when the mean velocity and the variation of temperature are large that requires an extremely large number of quadrature points.In this paper,a novel dynamic scheme that requires only a small number of quadrature points is proposed.This is achieved by a velocity-coordinate transformation consisting of Galilean translation and thermal normalization so that the transformed velocity space is independent of mean velocity and temperature.This enables the efficient implementation of Gaussian-Hermite quadrature.The velocity quadrature points in the new velocity space are fixed while the correspondent quadrature points in the physical space change from time to time and from position to position.By this dynamic nature in the physical space,this new quadrature scheme is termed as the dynamic quadrature scheme(DQS).The DQS was implemented to the DOM and the lattice Boltzmann method(LBM).These new methods with DQS are therefore termed as the dynamic discrete ordinate method(DDOM)and the dynamic lattice Boltzmann method(DLBM),respectively.The new DDOM and DLBMhave been tested and validated with several testing problems.Of the same accuracy in numerical results,the proposed schemes are much faster than the conventional schemes.Furthermore,the new DLBM have effectively removed the incompressible and isothermal restrictions encountered by the conventional LBM.展开更多
基金The support of this work by the National Natural Science Foundation of China under Grant No.50074006 is gratefully acknowledged.
文摘A temperature measurement model of radiation thermometry for the surface covered by participating media was developed. The model was based on the radiation heat transfer of participating media and principles of radiation pyrometers, and solved by integral formulation of discrete ordinate method on spectral waveband. The influence of water mist on the indicated temperature of Raytek MR1SB one/two color pyrometer was discussed. Mie theory was used to calculate the radiative properties of water mist. In order to verify the model, a laboratory temperature measurement experiment was executed. The result shows that temperature of radiation thermometry is sensitive to the spectral response wavelength of pyrometer, and the simulated temperature of pyrometer agrees well with the experimental measurements on a suitable wavelength. The simulated temperature was lower than the real temperature of surface for one-color pyrometer, and it could be higher or lower than the real one for two-color pyrometer with the influence of participating media.
基金This work is supported by the ITC of Hong Kong Government through ITF under Contract No.GHP/028/08SZ.
文摘The Boltzmann equation(BE)for gas flows is a time-dependent nonlinear differential-integral equation in 6 dimensions.The current simplified practice is to linearize the collision integral in BE by the BGK model using Maxwellian equilibrium distribution and to approximate the moment integrals by the discrete ordinatemethod(DOM)using a finite set of velocity quadrature points.Such simplification reduces the dimensions from 6 to 3,and leads to a set of linearized discrete BEs.The main difficulty of the currently used(conventional)numerical procedures occurs when the mean velocity and the variation of temperature are large that requires an extremely large number of quadrature points.In this paper,a novel dynamic scheme that requires only a small number of quadrature points is proposed.This is achieved by a velocity-coordinate transformation consisting of Galilean translation and thermal normalization so that the transformed velocity space is independent of mean velocity and temperature.This enables the efficient implementation of Gaussian-Hermite quadrature.The velocity quadrature points in the new velocity space are fixed while the correspondent quadrature points in the physical space change from time to time and from position to position.By this dynamic nature in the physical space,this new quadrature scheme is termed as the dynamic quadrature scheme(DQS).The DQS was implemented to the DOM and the lattice Boltzmann method(LBM).These new methods with DQS are therefore termed as the dynamic discrete ordinate method(DDOM)and the dynamic lattice Boltzmann method(DLBM),respectively.The new DDOM and DLBMhave been tested and validated with several testing problems.Of the same accuracy in numerical results,the proposed schemes are much faster than the conventional schemes.Furthermore,the new DLBM have effectively removed the incompressible and isothermal restrictions encountered by the conventional LBM.
