Laser Diagnostic Development and Measurement and Modeling of Turbulent Flowfields of Jets and Wakes. Part 3. The Development of a Two-Channel CW Time-Resolved Laser Raman Spectroscopy (TiLaRS) System for Measurements in Gas Flowfields


Book Description

The design and performance of a photon counting, two-channel spectroscopic system using the 6-W, 448-nm line of a cw argon ion laser is described. The two channels are formed by use of cylindrical optics and special slit mirrors set up following the exit slit of a conventional double spectrometer. The system is capable of dynamic, simultaneous measurements of either the concentrations of two gas species in cold flow or the temperature and concentration of a single gas species, such as N2, in a flame. Measurements are accomplished by recording the intensities of two spontaneous rotational Raman lines with spectral bandwidths between 0.04 and 0.08 nm. Up to 4096 samples (or reads from each of the two channels) can be recorded by a dedicated minicomputer at rates up to 10 kHz. Studies of a CH4 diffusion flame at sampling rates of 20 to 100 Hz and a room-temperature, axisymmetric C02 jet at rates up to 2.0 kHz were carried out. Analysis of the data from these studies include mean and rms profiles, probability density functions (pdf's), power spectral density functions, autocorrelation functions, cross correlation functions, and determinations of skewness and kurtosis in the pdf's and the C02 fluctuations.




Laser Diagnostic Development and Measurement and Modeling of Turbulent Flowfields of Jets and Wakes


Book Description

The design and performance of a photon counting, two-channel spectroscopic system using the 6-W, 448-nm line of a cw argon ion laser is described. The two channels are formed by use of cylindrical optics and special slit mirrors set up following the exit slit of a conventional double spectrometer. The system is capable of dynamic, simultaneous measurements of either the concentrations of two gas species in cold flow or the temperature and concentration of a single gas species, such as N2, in a flame. Measurements are accomplished by recording the intensities of two spontaneous rotational Raman lines with spectral bandwidths between 0.04 and 0.08 nm. Up to 4096 samples (or reads from each of the two channels) can be recorded by a dedicated minicomputer at rates up to 10 kHz. Studies of a CH4 diffusion flame at sampling rates of 20 to 100 Hz and a room-temperature, axisymmetric C02 jet at rates up to 2.0 kHz were carried out. Analysis of the data from these studies include mean and rms profiles, probability density functions (pdf's), power spectral density functions, autocorrelation functions, cross correlation functions, and determinations of skewness and kurtosis in the pdf's and the C02 fluctuations.




Laser Diagnostic Development and Measurement and Modeling of Turbulent Flowfields of Jets and Wakes


Book Description

Finite-difference numerical computations are presented to predict the isothermal, turbulent, recirculating flowfields in a centerbody combustor configuration which involves confined dual coaxial jet mixing in the near-wake region of an axisymmetric bluff body. Calculations based upon the Reynolds-averaged Navier-Stokes equations and the k-epsilon turbulence model consider the influence of the annular and central flow rates on the nature of the flowfield downstream of the bluff body. The reported isothermal modeling calculations are performed with the 'Teaching Elliptic Axisymmetrical Characteristics Heuristically' (TEACH) Code. Numerical results show the influence of the annular and central jet flow rates on the distributions of the mean and rms velocity fields and centerline locations of stagnation points. The sensitivity of the predicted results to several aspects of the modeling is considered. The predicted results demonstrate the complexity of flowfield interactions in the near-wake region and refine the understanding of the centerbody combustor flowfields. The character of the recirculating flowfield emerging from the numerical predictions when the near-wake is dominated by the annular jet is in conformity with experimental observations.




Laser Diagnostic Development and Measurement and Modeling of Turbulent Flowfields of Jets and Wakes


Book Description

Finite-difference numerical computations are presented to predict the isothermal, turbulent, recirculating flowfields in a centerbody combustor configuration which involves confined dual coaxial jet mixing in the near-wake region of an axisymmetric bluff body. Calculations based upon the Reynolds-averaged Navier-Stokes equations and the k-epsilon turbulence model consider the influence of the annular and central flow rates on the nature of the flowfield downstream of the bluff body. The reported isothermal modeling calculations are performed with the 'Teaching Elliptic Axisymmetrical Characteristics Heuristically' (TEACH) Code. Numerical results show the influence of the annular and central jet flow rates on the distributions of the mean and rms velocity fields and centerline locations of stagnation points. The sensitivity of the predicted results to several aspects of the modeling is considered. The predicted results demonstrate the complexity of flowfield interactions in the near-wake region and refine the understanding of the centerbody combustor flowfields. The character of the recirculating flowfield emerging from the numerical predictions when the near-wake is dominated by the annular jet is in conformity with experimental observations.