The non-isothermal oxidation of 2-methylpentane I. The properties of cool flames

1966 ◽  
Vol 293 (1434) ◽  
pp. 378-394 ◽  
Keyword(s):  
High Pressure ◽  
Pressure Rise ◽  
Isothermal Oxidation ◽  
Temperature Sensitive ◽  
Gaseous Mixtures ◽  
Cool Flame ◽  
Cool Flames ◽  
Slow Combustion ◽  
Subsequent Passage ◽  
Limiting Pressure

The conditions of pressure and temperature under which gaseous mixtures of 2-methylpentane with oxygen react non-iso thermally have been established. At temperatures greater than 307 °C, 1:2 fuel-oxygen mixtures of sufficiently high pressure ignite by a one-stage mechanism. At lower temperatures, the limiting pressure for ignition decreases and the resulting ignition is a two stage phenomenon, the passage of a cool flame preceding that of the hot flame. At similar temperatures but lower pressures, multiple and single cool flames propagate but do not lead to ignition. Correlation of the intensities of and rates of pressure rise due to cool flames with the limiting conditions for low temperature ignition has shown that cool flames affect profoundly the subsequent passage of a hot flame and that this effect is not purely thermal. The complexity of the limiting pressure/temperature relationship for cool flame propagation shows that the transition from slow combustion to cool flame is dependent upon several temperature-sensitive branching reactions. Moreover, the formation of periodic cool flames would appear to necessitate the participation, even under given conditions of pressure and temperature, of more than one branching agent.

A mathematical model of the cool-flame oxidation of acetaldehyde

1971 ◽  
Vol 322 (1550) ◽  
pp. 377-403 ◽  
Keyword(s):  
Mathematical Model ◽  
Negative Temperature ◽  
Isothermal Oxidation ◽  
Limited Range ◽  
Detailed Model ◽  
Cool Flame ◽  
Induction Periods ◽  
Cool Flames ◽  
Satisfactory Account ◽  
Flame Oxidation

A detailed mathematical model of the non-isothermal oxidation of acetaldehyde has been found to give a realistic simulation of (i) single and multiple cool flames, their limits, amplitudes and induction periods; (ii) two-stage ignition; and (iii) the negative temperature coefficient for the maximum rate of slow combustion. A simplified form of the model, valid over a limited range of conditions, has been subjected to mathematical analysis to provide interpretations of the effects simulated by the detailed model. It is concluded that cool flames are thermokinetic effects often, but not exclusively, of an oscillatory nature, and that a satisfactory account of cool-flame phenomena must necessarily take reactant consumption into account.

Alkylperoxy radical rearrangements during the gaseous oxidation of isobutene

1963 ◽  
Vol 273 (1354) ◽  
pp. 427-434 ◽  
Keyword(s):  
Methyl Ethyl Ketone ◽  
Peroxy Radical ◽  
Methyl Ethyl ◽  
Isotopic Tracer ◽  
Cool Flame ◽  
Cool Flames ◽  
Tracer Techniques ◽  
Slow Combustion ◽  
Flame Region ◽  
Subsequent Decomposition

Isotopic tracer techniques have been used to elucidate the mechanism of production of ketones in the gaseous oxidation of isobutane. Both acetone and methyl ethyl ketone are formed from this hydrocarbon, the former predominating in the products of slow combustion and the latter in the products of cool flames. Addition of [1,3- 14 C] acetone to reacting isobutane + oxygen mixtures has established that none of the methyl ethyl ketone formed in the cool-flame region and only 25% of that formed during slow combustion arises from further reactions of acetone. The formation of methyl ethyl ketone probably involves predominantly rearrangement and subsequent decomposition of the tert .-butyl peroxy radical and this indeed appears to be the almost exclusive fate of this radical under cool-flame conditions.

The non-isothermal oxidation of 2-methylpentane. II. The chemistry of cool flames

1967 ◽  
Vol 298 (1453) ◽  
pp. 204-237 ◽  
Keyword(s):  
Flame Temperature ◽  
Complex Mixture ◽  
Isothermal Oxidation ◽  
Qualitative Description ◽  
Cool Flame ◽  
Slow Combustion ◽  
Aldehydes And Ketones ◽  
Flame Region ◽  
Alkylperoxy Radicals ◽  
Liquid Chromatographic

The products of all the modes of non-isothermal oxidation of 2-methylpentane by molecu­lar oxygen and of the attendant slow combustion reactions have been analysed by gas-liquid chromatographic and chemical methods. Oxidation in the cool-flame temperature range produces more than forty molecular species, including O -heterocycles, peroxides, alkenes and saturated and unsaturated aldehydes and ketones. A good qualitative description of the mode of formation of this complex mixture and of its variation with temperature is afforded by the alkylperoxy radical isomerization theory. This theory is developed semi-quantitatively and is in reasonable agreement with the quantitative experimental results. It is concluded that chain propagation in the cool-flame region occurs predominantly by attack on the fuel by hydroxyl radicals; the resulting oxidation is rapid and unselective. In contrast, at temperatures too low for cool-flame formation alkylperoxy radicals are the likely chain-propagating species, whereas at temperatures above the upper cool-flame limit hydroperoxy radicals probably propagate the chain. The mechanism of chain branch­ing is not clear but it is established that, in the cool-flame region, peroxidic compounds are involved.

scholarly journals On detonation in gaseous mixtures at high initial pressures and temperatures

1927 ◽  
Vol 114 (767) ◽  
pp. 152-160 ◽  
Keyword(s):  
High Pressure ◽  
Maximum Rate ◽  
Initial Temperature ◽  
Initial Density ◽  
Pressure Rise ◽  
Gaseous Mixture ◽  
Gaseous Mixtures ◽  
Reaction Velocity ◽  
Maximum Value ◽  
Maximum Rate Of Rise

I. Detonation in Acetylene and Pentane Mixtures .— Observations on detonation in acetylene and pentane mixtures at ordinary pressures with the object of finding the position of detonation in a tube under set conditions, were described in the previous paper. The present paper extends this work, but at higher initial pressures and temperatures. Apart from the study of detonations in engines, and experiments in explosion bombs where the pressure rise is observed, very little appears to have been done to extend the work of Le Chatelier and of Dixon on rate of propagation of combustion to regions of high pressure. The highest pressure at which explosions were photographed by Le Chatelier and by Dixon were about one and a half to two atmospheres. Woodbury, Canby and Lewis using a bomb of 12 inches length succeeded in photographing explosions in acetylene air mixtures at pressures up to 4 atmospheres. They also investigated the effect of initial temperature (up to 125° C.). The results are referred to by Brown, Leslie and Hunn who find that for any initial density or pressure there should be a certain maximum value of the initial temperature to provide a maximum rate of rise of pressure on exploding a given gaseous mixture; decrease in density of charge on rise of temperature overcomes the effects of increase in reaction velocity.

Roles of vanes in diffuser on stability of centrifugal compressor

2019 ◽  
Vol 233 (14) ◽  
pp. 5380-5392
Author(s):  
Wangzhi Zou ◽  
Xiao He ◽  
Wenchao Zhang ◽  
Zitian Niu ◽  
Xinqian Zheng
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Centrifugal Compressors ◽  
Compression System ◽  
The Stability ◽  
Rotating Instability

The stability considerations of centrifugal compressors become increasingly severe with the high pressure ratios, especially in aero-engines. Diffuser is the major subcomponent of centrifugal compressor, and its performance greatly influences the stability of compressor. This paper experimentally investigates the roles of vanes in diffuser on component instability and compression system instability. High pressure ratio centrifugal compressors with and without vanes in diffuser are tested and analyzed. Rig tests are carried out to obtain the compressor performance map. Dynamic pressure measurements and relevant Fourier analysis are performed to identify complex instability phenomena in the time domain and frequency domain, including rotating instability, stall, and surge. For component instability, vanes in diffuser are capable of suppressing the emergence of rotating stall in the diffuser at full speeds, but barely affect the characteristics of rotating instability in the impeller at low and middle speeds. For compression system instability, it is shown that the use of vanes in diffuser can effectively postpone the occurrence of compression system surge at full speeds. According to the experimental results and the one-dimensional flow theory, vanes in diffuser turn the diffuser pressure rise slope more negative and thus improve the stability of compressor stage, which means lower surge mass flow rate.

scholarly journals Nozzle Wear and Pressure Rise in Heating Volume of Self-blast Type Ultra-high Pressure Nitrogen Arc

2019 ◽  
Vol 6 (1) ◽  
pp. 23-26 ◽  
Author(s):  
F. Abid ◽  
K. Niayesh ◽  
N. S. Støa-Aanensen
Keyword(s):  
High Pressure ◽  
Mass Loss ◽  
Pressure Rise ◽  
Filling Pressure ◽  
Electrode Gap ◽  
Ultra High Pressure ◽  
Unit Energy ◽  
Nozzle Wear ◽  
Type Switch ◽  
Current Zero

This paper reports on experiments with ultra-high pressure nitrogen arcs in a self-blast type switch design. The effect of filling pressure on nozzle mass loss and pressure-rise in the heating volume were investigated. An arc current peak of 130 A at 190 Hz and a fixed inter-electrode gap of 50 mm were used throughout the experiment. The arc burns inside a polytetrafluoroethylene nozzle with a gas outflow vent in the middle. Nitrogen filling pressure of 1 bar, 20 bar, and 40 bar was tested, which also covers the supercritical region. Moreover, to study the effect of vent size on blow pressure near current zero, three different vent dimensions were investigated. <span> By increasing the filling pressure, the energy deposited in the arc increases as a result of increased arcing voltage</span>. It was observed that the pressure-rise in the heating volume is linked to the filling pressure, while the vent size plays a crucial role in the blow pressure near current zero. The nozzle mass loss per unit energy deposited in the arc is found to be independent of the filling pressure.

scholarly journals Estimation of the combustion products from the cylinder of the petrol engine and its relation to "knock"

1935 ◽  
Vol 234 (744) ◽  
pp. 433-521 ◽  
Keyword(s):  
High Pressure ◽  
Experimental Evidence ◽  
Combustion Products ◽  
High Energy ◽  
High Pressure And Temperature ◽  
Engine Cylinder ◽  
Engine Knock ◽  
Slow Combustion ◽  
Set Up ◽  
Exhaust Valves

As a result of a variety of experiments it was suggested in 1928 that engine “knock” “appears to be due to inequality in the condition of the charge (in the engine cylinder) set up, particularly in regions of high pressure and temperature as in the neighbourhood of hot exhaust valves. This inequality provides regions of high energy containing molecules in high energy states where reaction can spread more quickly.” This view was a little vague, and was arrived at from indirect experimental evidence. It was with a view to obtaining more precise evidence that knock was occasioned in the flame as the result of processes of slow combustion occurring in the gaseous charge prior to its arrival that the present work was undertaken. Callendar and those working with him had simultaneously arrived at the conclusion that “knock” was occasioned in much the same manner, but they adopted the more definite view that peroxides of the hydrocarbons were formed and stored in the gas, and then suddenly detonated, so igniting a whole region of the gas simultaneously. This view had also been advanced by Moureu and Dufraisse.

Monounsaturated but Not Polyunsaturated Fatty Acids Are Required for Growth of the Deep-Sea BacteriumPhotobacterium profundum SS9 at High Pressure and Low Temperature

1999 ◽  
Vol 65 (4) ◽  
pp. 1710-1720 ◽  
Author(s):  
Eric E. Allen ◽  
Daniel Facciotti ◽  
Douglas H. Bartlett
Keyword(s):  
Fatty Acids ◽  
High Pressure ◽  
Fatty Acid ◽  
Low Temperature ◽  
Mutant Strain ◽  
Deep Sea ◽  
High Pressures ◽  
Unsaturated Fatty Acids ◽  
Temperature Sensitive ◽  
Pressure Sensitive

ABSTRACT There is considerable evidence correlating the production of increased proportions of membrane unsaturated fatty acids (UFAs) with bacterial growth at low temperatures or high pressures. In order to assess the importance of UFAs to microbial growth under these conditions, the effects of conditions altering UFA levels in the psychrotolerant piezophilic deep-sea bacterium Photobacterium profundum SS9 were investigated. The fatty acids produced byP. profundum SS9 grown at various temperatures and pressures were characterized, and differences in fatty acid composition as a function of phase growth, and between inner and outer membranes, were noted. P. profundum SS9 was found to exhibit enhanced proportions of both monounsaturated (MUFAs) and polyunsaturated (PUFAs) fatty acids when grown at a decreased temperature or elevated pressure. Treatment of cells with cerulenin inhibited MUFA but not PUFA synthesis and led to a decreased growth rate and yield at low temperature and high pressure. In addition, oleic acid-auxotrophic mutants were isolated. One of these mutants, strain EA3, was deficient in the production of MUFAs and was both low-temperature sensitive and high-pressure sensitive in the absence of exogenous 18:1 fatty acid. Another mutant, strain EA2, produced little MUFA but elevated levels of the PUFA species eicosapentaenoic acid (EPA; 20:5n-3). This mutant grew slowly but was not low-temperature sensitive or high-pressure sensitive. Finally, reverse genetics was employed to construct a mutant unable to produce EPA. This mutant, strain EA10, was also not low-temperature sensitive or high-pressure sensitive. The significance of these results to the understanding of the role of UFAs in growth under low-temperature or high-pressure conditions is discussed.

Infra-red spectra of gaseous mixtures under high pressure

1956 ◽  
Vol 22 ◽  
pp. 22 ◽  
Author(s):  
R. Coulon ◽  
L. Galatry ◽  
J. Robin ◽  
B. Vodar
Keyword(s):  
High Pressure ◽  
Gaseous Mixtures ◽  
Infra Red

The oxidation of hexane in the cool-flame region

1952 ◽  
Vol 212 (1110) ◽  
pp. 311-330 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
Chemical Nature ◽  
Complex Mixture ◽  
Cyclic Ethers ◽  
Reaction Products ◽  
Cool Flame ◽  
Oxidation Of Methane ◽  
Cool Flames ◽  
Flame Region ◽  
Considerable Support

The chemical nature of the cool flame of hexane at 300°C, maintained stationary in a flow system at atmospheric pressure, has been investigated. The relative intensities of cool flames obtained from mixtures of differing composition have been measured, using a photomultiplier cell, and correlated with analyses made of the complex mixture of reaction products. The stationary two-stage flames which may be obtained at either higher oxygen concentrations or higher pressures than the cool flame are also described, and investigated similarly. The results are examined in the light of a theory of combustion of the higher hydrocarbons via aldehydes and hydroxyl radicals, which is an extension of a mechanism derived for the oxidation of methane. This receives considerable support, particularly from the identification of the complete homologous series of saturated aldehydes which can result from the hexane molecule. Associated with these reactions are others due to the greater stability of peroxide radicals at 300°C than at the higher temperatures of methane oxidation. Thus the building up of a partial pressure of hydroperoxide sufficient to ignite in the presence of oxygen may initiate the cool flame, and considerable amounts of cyclic ethers have been found which probably had a peroxidic precursor.

Sign in / Sign up

Export Citation Format

Share Document