Takao Tsuboi

Shock tube study on homogeneous thermal oxidation of methanol

Abstract Homogeneous thermal oxidation of methanolue5f8oxygen mixtures, highly diluted with argon, was studied in shock waves by following infrared emission of various species during the course of the reaction. The equivalence ratio φ = 1.5 [CH 3 OH] [O 2 ] was varied from 0.2 to 2.0. The total density extended from 1 × 10 −5 to 2 × 10 −4 mol/cm 3 . For mixtures of methanol and oxygen between 0.05 and 1.0%, the following expression describes the induction period: r i = 1.4 × 10 −16 [ CH 3 >OH ] −0.1 [ O 2 ] −O.19 [ Ar ] −O.62 X exp (201 kJ/mol /RT) s. For very dilute mixtures, the experiments indicated a decrease of the power dependency of argon density. In order to obtain the mechanism for the oxidation of methanol, profiles of some species were obtained from the numerical integration of 57 reactions and were compared with the measured results. The calculated induction periods agreed well with the measured ones. The argon density strongly influences the induction period in the mixtures with less than 1% CH 3 OH since the decomposition of H 2 O 2 plays an important role during the induction period.

Light Absorption by Hydrocarbon Molecules at 3.392 µm of He-Ne Laser

The decadic molar extinction coefficients of various hydrocarbon molecules at the wavelength of 3.392 µm of the infrared He-Ne laser were measured at temperatures between 292 and 1100 K using the shock-tube technique. Methane, ethane, propane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, iso-octane, methanol, ethanol, butanol, acetone and benzene absorbed the laser light. No Doppler-or pressure-broadening of these molecules was observed except in the case of methane and ethane. The values of the decadic molar exctinction coefficients give information on a temperature-measurement technique which utilizes Beer-Lamberts law.

Thermal Decomposition of Methanol behind Shock Waves

The thermal decomposition of methanol in argon behind incident and reflected shock waves is studied. The reaction was followed by ultraviolet (UV) absorption between 1900 and 2200 A and by infrared (IR) emission of methanol at wavelengths 2.4–2.9 µm, 3.1–3.9 µm and 4.8–5.2 µm and of formed species at wavelengths 2.7 µm, 3.6 µm and 4.9 µm. The temperature and the density dependences of the decomposition rate constants were observed at temperatures from 1500 to 1900 K, at total densities from 10-5 to 2×10-4 mol/cm3 and at concentrations from 0.01% to 1.0% methanol. The experimentally-determined signals are compared with the calculated values and the density-dependent rate constants of the unimolecular reaction of methanol are obtained.

Temperature, density, and perturber dependences of absorption of the 3.39 µm He-Ne laser by methane

We present an experimental and theoretical study of the absorption of the IR He–Ne laser (3.39 µm) by Ch4. Shocktube measurements were made for mixture of CH4 with Ar, N2, and O2 in wide density and temperature ranges. Calculations were made by using the available spectroscopic data on CH4 absorption lines. Comparison between experiments and calculations show that the theoretical predictions are accurate for all densities up to the temperature of 1200 K. At 2000 K, the calculations fail, probably due to insufficient knowledge of hot-band lines. Furthermore, the present study shows that mixture of CH4 with Ar, O2, and N2 lead to absorptions which are similar (within experimental error), as is confirmed by the theoretical model.

Measurement of heat loss due to thermal radiation of liquid spray flames using shock tube technique

A single-compression, “tailored” interface shock tube was used to measure thermal energy radiating from diesel combustion. The fuel (light oil) was injected through a throttle nozzle (pintle diameter: 1 mm) into air behind a reflected shock wave, 37, 78, and 120 mg of fuel were injected at pressures of 15 and 20 MPa. Monochromatic emission at wavelengths of 0.6328, 0.9, 1.1, 1.45, 2.5, 3.56, 3.92, and 4.2 μm was followed with IR-detectors at different distances from the injection nozzle. These signals were obtained simultaneously, together with pressure and nozzle lift sensor signals. In another experiment, time histories of the flame radius at diffrent distances from the injection nozzle were determined by observing light signals of near-IR detectors set radially with relation to the shock tube. Heat loss due to thermal radiation was calculated using the time histories of both monochromatic emission and the flame radius. Soot concentration profiles were also obtained using this data. Results were as follows: (1) Heat loss per injection is approximately proportional to the injection pressure. (2) Heat loss is also proportional to the amount of fuel. (3) The ratio of thermal radiation to the lower calorific value of light oil is about 5 to 10%. (4) The volume concentration of soot increases gradually near the ejection nozzle and decays rapidly. At points far from the injection nozzle, soot increases rapidly and decays gradually. The maximum volume concentration of soot is about 10 −4 cm 3 soot/cm 3 gas.

High-temperature absorption by pure CO 2 far line wings in the 4 μm region

We present, for the first time, shock-tube measurements of the absorption of infrared radiation by pure CO2 near 4 µm up to the temperature of 1200 K. The experimental values are in good agreement with previous determinations up to 800 K. These results demonstrate the interesting point of this new measurement technic and the investigated temperature and pressure ranges are extended toward those of the combustion media. Comparisons with calculations confirm the strongly sublorentzian behavior of the far wings of CO2 absorption lines; the accuracy of previously published models based on empirical corrections to the Lorentzian profile is also shown.

Optische Messungen der Dichte der von Azetylen Gebildeten Rußteilchen

The density of acetylene-soot was obtained by making measurements using light extinction at 3.392 µm with an infrared He-Ne laser. Acetylene-soot was produced behind a reflected shock wave using a tailored-interface shock tube. The obtained value was 0.9± 0.2 g/cm3 at temperatures from 1500 to 2000 K. This value agreed with the value of benzene-soot which was measured using the same optical system with a normal shock tube. The wavelength dependence of the emission intensities due to soot particles, produced behind the reflected wave, agreed well in the visible and infrared regions with that of grey-body radiation.

Further study on temperature, density, and perturber dependences of absorption of 3.39 μm He-Ne laser by methane

In order to supplement the information on the perturber dependence of absorption at 3.39 µm of the He–Ne laser by methane, the decadic molar extinction coefficients of methane diluted with helium, hydrogen and carbon dioxide have been measured. The broadening data S γl( CH4–X)/ S γl( CH4–Air) and βl( CH4–X) for He, H2 and CO2, which are available in a wide range of temperature (300–1000 K), are proposed.

On Induction Periods of Shock-Heated Methane-Oxygen-Argon-Mixtures

The induction periods of shock-heated methane-oxygen-argon-mixtures were measured over a wide range of mixture ratios. The methane decay behind the reflected shock wave was monitored using an InSb-photodiode at a wavelength of 3.43 µm. Both the measured induction periods and the observed emission profiles were compared with the values obtained from computer simulation using reaction kinetics. The results were as follows: (1) The emission intensity at 3.43 µm in-creased during the induction period in a mixture less diluted with argon, while that of a mixture highly diluted with argon remained constant. If the reaction step CH3+O2=CH2O+OH is replaced with the step CH3+O2=CH3O+O in the methane oxidation mechanism developed in the authors laboratory, the calculated induction periods agree well with the measured ones over a wide range of mixture ratios.

Deformation of Needle in the High Temperature Gas behind Detonation Wave

Deformation of needle-points in burning gas behind H2-O2 and natural gas-O2 detonation has been investigated experimentally. Three typical cases of deformation are observed: (1) melting of the needle-point; (2) burning of the needle; and (3) breaking of the needle. The kind of deformation depends on the setting place of the needle in the detonation tube as well as on the mixture ratio.