Walter Clauss

CARS thermometry in high pressure rocket combustors

Abstract Coherent anti-Stokes Raman spectroscopy (CARS) has been used to investigate high pressure cryogenic liquid oxygen/gaseous hydrogen (LOX/GH 2 ) flames at pressures up to 6.5 MPa. The method employs two synchronized broadband CARS systems to probe simultaneously H 2 and H 2 O. Temperature is deduced from the H 2 and H 2 O CARS profiles while the H 2 O concentration is deduced from the modulation from the resonant the H 2 O resonant signal superimposed on the nonresonant background signal. Details of the modeling of the CARS spectra at high pressure and the data reduction are discussed. Problems issued from the presence of liquid phase are also investigated. The results demonstrate the applicability and usefulness of CARS for investigating cryogenic combustion under representative rocket model combustor regimes where the pressure range is above the supercritical condition ( P >5.04 MPa).

Two wavelength-CARS thermometry of hydrogen

In this work, we present the results of two-wavelength (2λ)-CARS thermometry of hydrogen at temperatures from 300–1200 K. The choice of the pair of spectral lines for the 2λ-CARS thermometer with respect to optimal temperature sensitivity within a given temperature range was analysed. Software was developed to process the experimental data and calculate the temperature. In the experiments, temperature and density were measured in a heated cell using single-shot and averaged CARS intensities in the pure rotationalS branch. The accuracy achieved and its dependence on measured temperature values and on the number of averaged shots was analysed.

Temperature Field in a Cryogenic LOX/CH4 Spray Flame

To prepare for the application of CARS thermometry to LOX/methane spray ames CARS spectra have been recorded in a O2/CH4-burner at pressure up to 11 bar. Based on the experience obtained, potential probe molecules have been selected for the application of CARS to a LOX/CH4 spray ame. A CARS system allowing simultaneously the thermometry of the two probe molecules H2 and H2O was then used to map the temperature eld in a cryogenic rocket model combustor. The suitability of H 2-CARS thermometry in a LOX/CH4 ame is demonstrated and the results provide a quantitative data base for the validation of simulation tools.

CARS at a "hard-to-realize conditions": lineshape spectroscopy at high temperatures in a real flame

On the example of the study of the collisional broadening and shift of the hydrogen Q-branch lines due to collisions with water molecules in wide temperatures range [2000 K -3000 K], we display the use of single-short CARS-spectroscopy for lineshape analisys at experimental conditions in which the object naturally does not exist, but can be created due to some physical and/or chemical processes for some time, small in comparison with the time necessary for stationary laboratory researches. Importance of light statistics as well as some specific features of CARS spectroscopy, which are the most actual from the point of view of use of CARS as a tool for lineshape spectroscopy, are discussed.

Dual-broadband CARS thermometry in a H2/O2 atmospheric pressure diffusion flame

Dual-broadband coherent anti-Stokes Raman spectroscopy (CARS) of the Q-branch of H2 has been employed for thermometry in a laboratory atmospheric pressure hydrogen-oxygen flame. The aim was to investigate the applicability of the technique for single-shot temperature evaluation, to estimate its sensitivity and to analyze the accuracy of the measurements. The results are presented of single-shot temperature mapping of the flame in the temperature range of 700 - 3200 K. The achieved accuracy of single-shot measurements was 3 - 5%.

2lambda-CARS thermometry of hydrogen

In this work we present the results of two-wavelength rotational CARS thermometry (2(lambda) -CARS thermometry) of hydrogen at temperatures from 300 K to 1100 K. Experimentally, temperature was measured in a heated cell using single-shot and averaged CARS intensities in the rotational S-branch. Relative standard deviation for single-shot temperature values was approximately 1.5% at 296 K and approximately 8% at 1000 K. The accuracy achieved, its dependence on measured temperature, and possibility of their improvement were analyzed.