The vitiation effects of water vapor and carbon dioxide on the autoignition characteristics of kerosene

Water vapor and carbon dioxide species measurements in narrow channels

Effect of water vapor on ignition and combustion of boron lumps in an oxygen stream

The past several decades have seen a significant rise in atmospheric carbon dioxide levels resulting from the combustion of hydrocarbon fuels. A solar energy based technology to recycle carbon dioxide into readily transportable hydrocarbon fuel (i.e., a solar fuel) would help reduce atmospheric CO2 levels and partly fulfill energy demands within the present hydrocarbon based fuel infrastructure. We review the present status of carbon dioxide conversion techniques, with particular attention to a recently developed photocatalytic process to convert carbon dioxide and water vapor into hydrocarbon fuels using sunlight.

Analysis of the long term NOAA carbon dioxide flask sample records to examine the exchange among the continental Antarctic air mass and other air masses shows a meteorological variation of carbon dioxide concentration. There is an inverse relation between the seasonal variation of carbon dioxide concentration and water vapor at all stations examined. Well established diffusion coefficients indicate an interaction of water and carbon dioxide vapor on the molecular scale. Laboratory experiments using a Fourier transform spectrometer show carbon dioxide to be removed from an airstream in proportion to water vapor precipitated. We propose that interaction of carbon dioxide and water vapor in the atmosphere provides temporary sinks that can influence the balance of the carbon dioxide budget.

A method of computation of the direct absorption of solar radiation by the near infra‐red bands of water vapour and carbon dioxide in a cloudless, non‐scattering atmosphere using recent laboratory data compiled by Howard, Burch and Williams (1955) is described.Three applications of this computation are discussed:(i) Heating rates in an atmosphere whose water‐vapour distribution is given by radiosonde or aircraft observations.(ii) Instantaneous heating rates as a function of solar zenith angle, altitude and precipitable water vapour.(iii) A climatological study of heating rates in a cloudless atmosphere integrated over a 24‐hr period as a function of latitude, season, altitude and precipitable water vapour. The relative contributions to heating by water vapour and carbon dioxide are assessed between 10 and 1,000 mb.The mixing ratio of carbon dioxide was assumed constant throughout the atmosphere, while idealized vertical distributions of water vapour mixing ratio were used in (ii) and (iii).

Study on lubricating characteristic and tool wear with water vapor as coolant and lubricant in green cutting

Water vapor and carbon dioxide are the most dominant greenhouse gases directly contributing to the Earth's radiation budget and global warming. A performance evaluation of an airborne triple-pulsed integrated path differential absorption (IPDA) lidar system for simultaneous and independent monitoring of atmospheric water vapor and carbon dioxide column amounts is presented. This system leverages a state-of-the-art Ho:Tm:YLF triple-pulse laser transmitter operating at 2.05 μm wavelength. The transmitter provides wavelength tuning and locking capabilities for each pulse. The IPDA lidar system leverages a low risk and technologically mature receiver system based on InGaAs pin detectors. Measurement methodology and wavelength setting are discussed. The IPDA lidar return signals and error budget are analyzed for airborne operation on-board the NASA B-200. Results indicate that the IPDA lidar system is capable of measuring water vapor and carbon dioxide differential optical depth with 0.5% and 0.2% accuracy, respectively, from an altitude of 8 km to the surface and with 10 s averaging. Provided availability of meteorological data, in terms of temperature, pressure, and relative humidity vertical profiles, the differential optical depth conversion into weighted-average column dry-air volume-mixing ratio is also presented.

Water vapor effects on fire extinguishment are studied using a tubular flame burner and a CHEMKIN program. Methane/air mixtures with water vapor and carbon dioxide suppressant are studied on the basis of flammability limit. A 353 K water vapor is mixed with methane/air and is burned in a tubular flame. The whole mixture is kept at the constant temperature by heating up the mixture line. Although the heat capacities of water vapor and carbon dioxide are different each other, the methane flammability areas for both cases in the methane/suppressant coordinate are almost the same. Numerical analysis using a CHEMKIN program shows the same results which certifies both experimental and numerical results. Three suppressants, water vapor, carbon dioxide, and halon, are compared to clarify their suppression effects on methane/air premixed flame. From this good agreement with experiments, the CHEMKIN calculation is worth doing to see the flammability limit, even probably for higher hydrocarbon flames and many suppressants. This result enables water to be a good suppressant for fire.

Mass transfer properties of fibre network and coated paper are essential for understanding the barrier properties of the products and further advance in their application. In this study, different unmodified and coated papers, e.g., (Poly lactic acid (PLA), zein grafted paper) were prepared and characterized with regard to mass transfer properties. Water vapor, carbon dioxide (CO2) and oxygen (O2) transmission rates through the cellulose paper films were measured and the results discussed. The effects of sample film thickness and samples were found to be strongly dependent on the temperature and the relative humidity difference (mass transfer driving force). On the other hand water vapor permeabilities relative humidity. Water vapor diffusivities of the samples were also measured from the uptake rate measurements using Fickian diffusion slab model for a wide range of relative modified samples were found to be generally low compared to unmodified (reference) paper sample. Among the investigated samples, PLA/polyhedral oligomeric silsesquioxane POSS-bentonite modified paper sample showed higher mass transfer resistance to water vapour and the gases investigated in this study (CO2and O2). It showed lower water transmission rate (104 g/m2.day) compared to PLA-coated paper (130 g/m2.day), zein coated paper (179 g/m2.day) and control sample (359 g/m2.day) at the relative humidity gradient RH=74% and temperature of 25 oC. The oxygen transmission rate for PLA/(POSS-Bentonite) coated paper was found to be lower than for the other modified papers. Zein grafted paper showed better barrier property for water vapor than oxygen. Water vapor permeation through paper films shows an Arrhenius type of dependency with temperature, indicating activated process. The activation energies reveal diffusion dominated process for all paper samples investigated in this study, according to the solution-diffusion mechanism used to describe the permeation processes.

Permeability of polylactide nanocomposite films for water vapour, oxygen and carbon dioxide

Measurements of ignition delay times in cornstarch dust-air mixture

A review of the effects of hydrogen, carbon dioxide, and water vapor addition on soot formation in hydrocarbon flames

According to the present data, KA zeolite, which can adsorb only water vapor, helium, and hydrogen, has the greatest selectivity in drying. The feasibility of using this zeolite in devices for selective drying of gases used in gas-analysis systems was studied. The results of the experiments were approximated by the thermal equation of the theory of bulk filling of micropores. The limiting value of the adsorption depends on the temperature, and it can be calculated according to the density of the adsorbed phase and the adsorption volume. The critical diameters of the water and carbon dioxide molecules are close to the dimensions of the KA-zeolite pores, something that determines the activated nature of the adsorption of these substances. Experiments on coadsorption of water vapor and carbon dioxide by a fixed bed of KA-zeolite under dynamic conditions showed that the adsorption of these substances has a frontal nature. The time of the protective action of the layer of zeolite during adsorption af water vapor exceeded by more than an order the time of the protective action during adsorption of carbon dioxide. The results showed that this adsorbent can be used for selective drying of gas mixtures containing carbon dioxide in batch-operationmore » devices. Beforehand, the adsorbent should be regenerated with respect to moisture, and then it should be saturated with carbon dioxide by blowing the adsorbent with a gas mixture of the working composition until the equilibrium state is reached.« less

Sensitivity of an infrared gas analyzer used in the differential mode, to partial gas pressures of carbon dioxide and water vapor in the bulk air

Atmospheric water vapor and carbon dioxide are important greenhouse gases that significantly contribute to the global radiation budget on Earth. A 2-micron triple-pulse, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric carbon dioxide and water vapor concentration measurements using direct detection was developed at NASA Langley Research Center. This active remote sensing instrument provides an alternate approach with significant advantages for measuring atmospheric concentrations of the gases. A high energy pulsed laser transmitter approach coupled with sensitive receiver detection provides a high-precision measurement capability by having a high signal-to-noise ratio. This paper presents the concept, development, integration and testing of the 2-micron triple-pulse IPDA. The integration includes the various IPDA transmitter, receiver and data acquisition subsystems and components. Ground and airborne testing indicated successful operation of the IPDA lidar.