O. M. Stelmakh

On the influence of electronically excited oxygen molecules on combustion of hydrogen–oxygen mixture

This communication reports on the experimental observation of the shortening of the induction zone length in a premixed mode of combustion in a subsonic H2–O2 low pressure flow due to the presence of oxygen molecules excited to the singlet a 1Δg electronic state. The low pressure electric glow discharge was used to produce singlet oxygen molecules. The analysis showed that even a small number of O2(a 1Δg) molecules (~1%) in the H2–O2 mixture allows one to noticeably reduce the ignition delay length and to ignite the mixture at a lower temperature. The results obtained exhibit the possibility to intensify the combustion of a hydrogen–oxygen mixture by means of excitation of O2 molecules by electrical discharge at low pressure (P = 10–20 Torr).

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 diagnostics of the burning of H{sub 2} - O{sub 2} and CH{sub 4} - O{sub 2} mixtures at high temperatures and pressures

Coherent anti-Stokes Raman scattering (CARS) spectroscopy is used to determine the parameters of gaseous combustion products of hydrogen and hydrocarbon fuels with oxygen at high temperatures and pressures. The methodical aspects of CARS thermometry, which are related to the optimal choice of molecules (diagnostic references) and specific features of their spectra, dependent on temperature and pressure, are analysed. Burning is modelled under the conditions similar to those of real spacecraft propulsion systems using a specially designed laboratory combustion chamber, operating in the pulse-periodic regime at high temperatures (to 3500 K) and pressures (to 20 MPa) of combustion products.

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.