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Air Mixtures (air + mixture)

Distribution by Scientific Domains

Chemistry	54%
Engineering	36%

Selected Abstracts

Numerical Analysis of the Catalytic Combustion of Premixed Methane/Air Mixtures in Microtubes

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2008
J. Zhong
Abstract The combustion characteristics and extinction limits for the catalytic combustion of a methane/air mixture in a microtube are investigated computationally using the commercial CFD code FLUENT coupled to an external subroutine DETCHEM. The effects of the microtube dimensions, conductivities of wall materials, external heat losses and flow velocity on the combustion stability, are also studied. The numerical model is set as either adiabatic or non-adiabatic with a fixed exterior heat transfer coefficient. Numerical results indicate that thermal conductivity and wall thickness are vital to preheat the methane/air mixture through the conducting wall. Two types of extinction occur, i.e., thermal quenching and blow out. These extinction limits are characterized by wall surface temperature in the microtube and the ratio of Pt(s)/O(s). [source]

Self-sustained reformation of diesel fuel using a SiC block with penetrating walls

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2010
Min Kook Ko
Abstract Reformation of diesel fuel was performed using a silicon carbide (SiC) block with penetrating walls. The atomized fuel was spray injected to the electrically heated block. The fuel,air mixture was reformed by partial oxidation and changed to synthesis gas including CO, CO2, H2O, O2 and H2. The composition of the reformed gas was measured with varying fuel,air ratios. The degree of reformation or conversion changes with the temperature and a maximum conversion efficiency of ,90% is attained at around 850°C. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Performance and emission characteristics of turpentine,diesel dual fuel engine and knock suppression using water diluents

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2007
R. Karthikeyan
Abstract In the present work, a normal diesel engine was modified to work in a dual fuel (DF) mode with turpentine and diesel as primary and pilot fuels, respectively. The resulting homogeneous mixture was compressed to a temperature below the self-ignition point. The pilot fuel was injected through the standard injection system and initiated the combustion in the primary-fuel air mixture. The primary fuel (turpentine) has supplied most of the heat energy. Usually, in all DF engines, low-cetane fuels are preferred as a primary fuel. Therefore, at higher loads these fuels start knocking and deteriorating in performances. Usually, DF operators suppress the knock by adding more pilot-fuel quantity. But in the present work, a minimum pilot-fuel quantity was maintained constant throughout the test and a required quantity of diluent (water) was added into the combustion at the time of knocking. The advantages of this method of knock suppression are restoration of performance at full load, maintenance of the same pilot quantity through the load range and reduction in the fuel consumption at full load. From the results, it was found that all performance and emission parameters of turpentine, except volumetric efficiency, are better than those of diesel fuel. The emissions like CO, UBHC are higher than those of the diesel baseline (DBL) and around 40,45% reduction of smoke was observed at 100% of full load. The major pollutant of diesel engine, NOx, was found to be equal to that of DBL. From the above experiment, it was proved that approximately 80% replacement of diesel with turpentine is quite possible. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Investigation of the correlation of sensitivity vectors of hydrogen combustion models

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2004
Judit Zádor
A well-established method for the analysis of large reaction mechanisms is the calculation and interpretation of the sensitivity of the kinetic model output Yi to parameter changes. Comparison of the sensitivity vectors si = {, Yi/,p} belonging to different model outputs is a new tool for kinetic analysis. The relationship of the sensitivity vectors was investigated in homogeneous explosions, freely propagating and burner-stabilized laminar flames of hydrogen,air mixtures, using either calculated adiabatic or constrained temperature profiles, for fuel-to-air ratios , = 0.5,4.0. Sensitivity vectors are called locally similar, if the relationship si = ,ijsj is valid, where ,ij is a scalar. In many systems, only approximate local similarity of the sensitivity vectors exists and the extent of it can be quantified by using an appropriate correlation function. In the cases of adiabatic explosions and burner-stabilized flames, accurate local similarity was present in wide ranges of the independent variable (time or distance), and the correlation function indicated that the local similarity was not valid near the concentration extremes of the corresponding species. The regions of poor similarity were studied further by cobweb plots. The correlation relationships found could be interpreted by the various kinetic processes in the hydrogen combustion systems. The sensitivity vector of the laminar flame velocity is usually considered to be characteristic for the whole combustion process. Our investigations showed that the flame velocity sensitivity vector has good correlation with the H and H2O concentration sensitivities at the front of the adiabatic flames, but there is poor correlation with the sensitivity vectors of all concentrations in homogeneous explosions. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 238,252 2004 [source]

Kinetics of the reactions of OH with 3-methyl-2-cyclohexen-1-one and 3,5,5-trimethyl-2-cyclohexen-1-one under simulated atmospheric conditions

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 1 2002
James B. McQuaid
Relative rate coefficients for the reactions of OH with 3-methyl-2-cyclohexen-1-one and 3,5,5-trimethyl-2-cyclohexen-1-one have been determined at 298 K and atmospheric pressure by the relative rate technique. OH radicals were generated by the photolysis of methyl nitrite in synthetic air mixtures containing ppm levels of nitric oxide together with the test and reference substrates. The concentrations of the test and reference substrates were followed by gas chromatography. Based on the value k(OH + cyclohexene) = (6.77 ± 1.35) × 10,11 cm3 molecule,1 s,1, rate coefficients for k(OH + 3-methyl-2-cyclohexen-1-one) = (3.1 ± 1.0) × 10,11 and k(OH + 3,5,5-trimethyl-2-cyclohexen-1-one) = (2.4 ± 0.7) × 10,11 cm3 molecule,1 s,1 were determined. To test the system we also measured k(OH + isoprene) = (1.11 ± 0.23) × 10,10 cm3 molecule,1 s,1, relative to the value k(OH + (E)-2-butene) = (6.4 ± 1.28) × 10,11 cm3 molecule,1 s,1. The results are discussed in terms of structure,activity relationships, and the reactivities of cyclic ketones formed in the photo-oxidation of monoterpene are estimated. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 7,11, 2002 [source]

Condensation of steam in the presence of air on a single tube and a tube bank

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2003
Adrian Briggs
Abstract Data are presented for condensation of steam in cross-flow with and without the presence of air on the outside of a single tube and a bank of tubes. The tube bank consisted of ten staggered rows of two and one tubes per row. For pure steam the experimental results for both the single tube and tube bank gave good agreement with single-tube theory when account was taken of the reduction in vapour velocity due to condensation. There was some evidence, however, that condensate inundation may play a minor role in reducing heat-transfer coefficients on the lower tubes in the bank. For the case of condensation from steam,air mixtures, the single-tube data gave good agreement with theory. For condensation from steam,air mixtures on the bank of tubes, the data were significantly under predicted by single-tube theory, possibly because of mixing and re-circulation due to the complex flow pattern around the tubes. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Absorption Rate of Carbon Dioxide by K2CO3 -KHCO3 DEA Aqueous Solution

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2005
K. Takahshi
Gas absorption rates of carbon dioxide from CO2 -air mixtures into K2CO3, K2CO3 -KHCO3, DEA and K2CO3 -KHCO3 -DEA solutions have been measured by using a wetted wall column. The method to determine the enhancement factor of chemical absorption is confirmed by the absorption of carbon dioxide in NaOH solution. The enhancement factor was correlated with the potassium concentration [K+] (= 2[K2CO3 + [KHCO3]), the DEA concentration, and the CO2 -loading ratio of the absorbent. The chemical reaction for CO2, absorption has been expressed by an (m,n)th order irreversible-reaction model, where the reaction orders are m = 1 for CO2, n = 1.35 for DEA, n = 0.6 for K2CO3, and n = 0.6 and 1.35 for K2CO3 and DEA respectively. Experimental values of the enhancement factor were successfully reproduced by the calculations, where the reaction rate constants reflected the effect of loading ratio of the absorbent with carbon dioxide. [source]

A shock tube study of cyclopentane and cyclohexane ignition at elevated pressures

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2008
Shane M. Daley
Ignition delay times for cyclopentane/air and cyclohexane/air mixtures were measured in a shock tube at temperatures of 847,1379 K, pressures of 11,61 atm, and equivalence ratios of , = 1.0, 0.5, and 0.25. Ignition times were determined using electronically excited OH emission monitored through the shock tube endwall and piezoelectric pressure measurements made in the shock tube sidewall. The dependence of ignition time on pressure, temperature, and equivalence ratio is quantified and correlations for ignition time formulated. Measured ignition times are compared to kinetic modeling predictions from four recently published mechanisms. The data presented provide a database for the validation of cycloalkane kinetic mechanisms at the elevated pressures found in practical combustion engines. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 624,634, 2008 [source]

Numerical Analysis of the Catalytic Combustion of Premixed Methane/Air Mixtures in Microtubes

Anaesthetic management of a child with a positive family history of malignant hyperthermia for posterior fossa surgery in the sitting position

PEDIATRIC ANESTHESIA, Issue 4 2001
M.A. Wootton FRCA
A 6-year-old boy with a positive family history of malignant hyperthermia presented for posterior fossa craniectomy and excision of medulloblastoma. A nontriggering anaesthetic was therefore planned using infusions of propofol and remifentanil and a vapour free anaesthetic system delivering an oxygen/air mixture. The surgery was carried out with the child in the sitting position. [source]

Studies on heat processing and storage of seer fish curry in retort pouches

PACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2002
C. N. Ravi Shankar
Abstract Seer fish in curry medium packed in locally manufactured retort pouches, having a three-layer configuration of thickness 12.5,µm polyester/12.5,µm aluminium foil/80,µm cast polypropylene was processed in a steam/air mixture over a pressure retort. About 210,g fish curry, having 110,g fish slices, was packed in a retort pouch of size 17,cm,×,15.5,cm, each fitted with a thermocouple. Time,temperature data were collected during heat processing using an Ellab data recorder FO and cook value integrator. The heat penetration characteristics were determined using a mathematical method. The fh value was 25,min with a FO value of 11.5 and cook value of 95,min. These samples remained in good condition for up to 24 months at room temperature. Copyright © 2002 John Wiley & Sons, Ltd. [source]