摘要:

An investigation of the projectile impact sensitivities of single, double and triple base propellants is described. The tests were conducted by firing different diameter, flat-ended brass projectiles into small cylinders of the propellant at various velocities and observing the impact reaction by appropriate sensors. It is shown that at large projectile diameters the impact velocity threshold for inducing detonation in the propellants is higher than for inducing burning (sustained ignition); whereas at small diameters the induced reaction is only detonation. These results are similar to those obtained earlier on a deflagratable composite explosive. They support the general validity of a previously postulated model, which was based on the view that the ignition and reaction buildup in an impacted propellant are independent processes.

ISSN:0010-2202    

DOI:10.1080/00102207908946890

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

An analytical study of the ignition of mixtures of methane and ethane has been carried out, using a numerical model consisting of 25 chemical species and 75 elementary chemical reactions. Computed ignition delay times and effective activation energies are compared with published experimental shock tube results. Initial conditions studied include temperatures from 1300-1900 K. and mixtures ranging from pure methane to pure ethane, with stoichiometric amounts of oxygen, diluted in argon. The analytical model reproduces experimental results for the effective activation energy and ignition delay time for both pure methane and pure ethane. Ignition delay times computed for mixtures of methane and ethane are found to lie between the pure methane and the pure ethane results. Addition of relatively small quantities of ethane to methane rapidly reduces the ignition delay time of the methane-ethane mixtures to values close to those of pure ethane. The chemical kinetic factors involved in the ignition of fuel mixtures are discussed in detail. The implications of these results for safety studies of liquified natural gas are also examined.

ISSN:0010-2202    

DOI:10.1080/00102207908946891

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The gas-phase ozone activated oxidation of n-butane is investigated in the temperature range 130-250 °C by means of a continuous stirred tank reactor. The reacting mixture (n-butane 66 percent, oxygen 33 percent, ozone 1 percent by volume) is fed to the reactor at mean residence times of 5 and 10 sec. The reaction progress is followed under steady state conditions by measuring the heat release rates and by performing the condensed products analysis at varying reaction temperatures. Results show the occurrence of a negative temperature coefficient of the reaction rate which can be interpreted on the basis of the increased rate of the ozone thermal decomposition in the reacting system at increasing reaction temperature. In this respect the n-butane behaviour appears to be very different from that previously observed in the case of i-butane under similar experimental conditions. The different behaviours are explained on the basis of the different structural characteristics of the two hydrocarbons. Analytical results allow one to elucidate the main reaction paths through which the oxidation process develops.

ISSN:0010-2202    

DOI:10.1080/00102207908946892

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The homogeneous gas phase reaction of NO-CH4-O2(-CO2)-Ar mixtures in high temperature is investigated by means of the molecular beam sampling method. The reaction species NO, CH4, HCN, CO, COk and N2are quantitatively analyzed with a mass filter system within a limit of 10 ppm. The species resulting from NO reduction are HCN, NH3and Na. The amount of HCN decreases with an increase in the ratio of O2to CH4. Both NO reduction and formation of HCN, NH3and N2are clearly enhanced by the addition of CO2. Conversely, the consumption of O2is retarded. In these reactions, it appears that oxidation of CH4initiates the NO reduction and, therefore, HCN, NH3and N2are progressively formed. Based on the experimental results, an overall kinetic equation for HCN behavior associated to NO reduction is derived as follows:

ISSN:0010-2202    

DOI:10.1080/00102207908946893

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The tips of two-dimensional premixed flames are analyzed for both plane and axisymmetric geometries. Using activation energy asymptotics and slender flame theory the problem of solving the model aerothermochemical equations is reduced to a generalized Stefan problem which is solved numerically. The qualitative nature of the solutions depends critically on the Lewis Number, L. For most values of L they correspond to closed tips, the most commonly observed laboratory situation. But for values of L significantly less than 1 solutions corresponding to open tips are formed, of the kind sometimes seen in the combustion of lean mixtures of hydrogen.

ISSN:0010-2202    

DOI:10.1080/00102207908946894

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Diffusion broadening spectroscopy has been used to make in situ size measurements of submicron aerosol particles in an acetylene-oxygen flame. Making use of the spectral broadening of scattered laser light due to random particle motion, this optical technique has been demonstrated to be suitable for application in unsteady high temperature environments of 2200 °K in flowing gases. Particle sizes were found to vary from 40 to 250 nm as the height above the burner varied from 0·5 to 3·0 cm. Little variation was found as a result of equivalence ratio changes from 2·5 to 5·0. Sizes measured from electron microscope photographs of soot particles collected from the flame show reasonable agreement with those determined from scattering measurements. A method to measure geometric mean diameter and standard deviation of the particle size distribution in a polydisperse aerosol is also presented, and experimental results described. Modifications necessary to account for polydispersity and noncontinuum flow effects are discussed.

ISSN:0010-2202    

DOI:10.1080/00102207908946895

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Temperature and species concentration profiles are presented for rich coal dust/oxygen/diluent flames burnt on a flat flame burner. Either argon or nitrogen was used as the diluent to study the fate of fuel nitrogen. 30-40 percent of the fuel nitrogen appears as HCN and NO with the leaner flames favoring NO. Experimental reaction rate profiles, which are compared to a simple model, indicate fuel nitrogen evolution occurs in two consecutive steps. The model assumes (1) only volatiles combustion occurs, (2) nitrogen is released early in the flame with the tar, (3) tar pyrolysis gives rise to HCN, (4) HCN oxidation produces NO, and HCN reaction with NO leads to N2, and (5) nitrogen is released later in the flame directly from the char as HCN. Reasonable qualitative agreement between measured and predicted rates is obtained. Quantitative agreement is precluded by uncertainties about the gas and particle temperatures and the rate constants for tar and char nitrogen release.

ISSN:0010-2202    

DOI:10.1080/00102207908946896

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The influence of wood fires in a 0·3 ×0·3 × 10 m duct on forced ventilation flow was studied in a model tunnel network by measuring tunnel gas mass flow rate, velocity, pressure, and temperature. Comparison of these measurements obtained before and during the fires at various ventilation air velocities provides useful information on the interaction between duct fires and ventilation flow in terms of fire throttling effects and reverse flow phenomena. Results show that duct fires essentially increase flow resistances of the passageways of a tunnel network by virtue of volatile fuel mass injection and high combustion temperatures. In the present tunnel network, the flow resistance in the fire zone was increased by a factor of 6, and upstream and downstream of the fire by ∼1·5. The ventilation air velocity was thus throttled to less than half of its initial value before the fire. Reverse flow occurred when the throttled air velocity was ∼0·6 m/s, which corresponds to a Froude number of ∼7 (based on duct height and ventilation air velocity). The experimental measurements were utilized in a flow network analysis to further elucidate the coupling process between duct fires and ventilation flow.

ISSN:0010-2202    

DOI:10.1080/00102207908946897

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A simple idea is proposed to produce an excess enthalpy flame by inserting a porous solid of high thermal conductivity into the one-dimensional flame zone. Heat is recirculated internally through the solid from the downstream high temperature region to the upstream low temperature region and large excess enthalpy is produced at the head of the reaction zone. The potentiality of the proposed artificially modified flame is analyzed on the basis of the simplified one-dimensional flame theory. It is found that in this flame the mass flow rate is not the eigenvalue but becomes a mere parameter. The heat transfer coefficient between the solid and the reacting gas is another parameter. With these additional two parameters the controllability over the flame characteristics increases remarkably. The analysis reveals several attractive characteristics of the flame and that the proposed idea is promising to burn mixtures of low heat content in a simple combustion system.

ISSN:0010-2202    

DOI:10.1080/00102207908946898

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor