Wyniki wyszukiwania - BazTech

1

Barometric calorimeter experiments with C4 charges

Kuhl A. L., Vandersall K., Howard W. M, Tringe J. W.

Archivum Combustionis

|

2013

|

Vol. 33 nr 1

41--56

EN

Experiments were conducted in our 506-liter barometric calorimeter, to characterize the reflected blast wave environment from C-4 explosions. Charges were constructed as a C4 hemi-sphere and boosted by a LX-10 hemi-sphere. The charge was placed in the center of the calorimeter and initiated by an SE-1 detonator. The blast wave was measured by Kistler piezo-electric pressure gauges, located at 8 radii on the chamber lid. Six experiments were conducted: three in air, and three in nitrogen (to eliminate combustion effects). Blast waves in air arrived earlier than those in nitrogen. Reflected pressure impulses were 7% larger for the air experiments than for those in nitthereby quantifying the effects than combustion has on C4 blast waves. Late-time chamber pressures were measured with a Kulite piezo-resistive gauge. Measured chamber pressures were 2 times larger for the air experiments than for those in nitrogen-thereby quantifying the effects that C4-air combustion has on late-time pressures. Results were fit with analytic functions to establish scaling laws that show how the reflected blast wave pressures and impulses depend on charge mass and height of burst.

2

Oppenheim's gasdynamic perspective of combustion and explosion phenomena

Kuhl A. L.

Archivum Combustionis

|

2011

|

Vol. 31 nr 3

135-138

EN

Perhaps the most important contribution of Antoni Kasimierz Oppenheim (Tony) to science was his gasdynamic perspective that he brought to the analysis of combustion and explosion phenomena. This perspective started with his two Ph.D. theses of 1944: "Investigation of High-Speed Flow of Gases in Channels [1]" (University of London) and "Some Applications of the Theory of Flow to Internal Combustion Engines [2]" (Imperial College of Science and Technology). The former provided a gas dynamic formulation for one-dimensional compressible flow of ideal gases (based on Busemann's Hand-Buch der Experimentalphyik), while the latter applied this theoretical formulation to improve the efficiency of internal combustion engines. This two-pronged theme dominated his research for more than 60 years.

3

Thermodynamic Analysis of Closed Explosion of Hexane-Air Mixtures

Kuhl A. L., Trzciński W. A., Wolański P.

Archivum Combustionis

|

2003

|

Vol. 23 nr 3-4

129-145

EN

The thermodynamic theory of combustion in an enclosure was applied to analyse the process of explosion of hexane vapour or hexane droplets - air mixtures in the chambers of different volumes. The relations between thermodynamic parameters and fuel consumption were determined. These relations and the overpressure histories taken from Ref.[1] were used to estimate the combustion rate and the final degree of hexane burned. Modified B.A. Khasainov's law of combustion of particles was applied to describe the process of combustion hexane droplets in air. The parameters of this equation were estimated.

4

Detonations of Hexane Vapor/Droplets-Air Mixtures Part III. Influence of droplet diameter

Kuhl A. L., Cudziło S., Wolański P.

Archivum Combustionis

|

2003

|

Vol. 23 nr 3-4

111-127

EN

The influence of droplet diameter on the detonation characteristics of hexane vapor/droplets-air mixtures was investigated. Hexane droplets were injected at the top of the test section with generators containing different numbers of needles of 0,5-, 0,8- and 1,2-mmin in internal diameter. The droplets were 1,3-, 1,9- and 3,2-mm in the average diameter, respectively. Detonative regimes (with velocities of 1600+-100 m/s and peak pressures rise of 2.5,3.0 MPa) can be initiated in each suspension. The hexane concentration at which the best conditions for detonation initiation and propagation were, as well as the upper limit of detonation increase with increasing droplet diameter.

5

Detonations of Hexane Vapor/Droplets-Air Mixtures Part II. Initiation and Parameterization

Kuhl A. L., Cudziło S., Trzciński W. A., Wolański P.

Archivum Combustionis

|

2003

|

Vol. 23 nr 3-4

95-109

EN

Detonation characteristics of hexane droplets/vapor-air mixtures were determinet on the basis of experiments in a vertical 13-m long detonation tube. Hexane droplets were injected at the top of the test section with generators containing different numbers of needles of 0,8-mm in internal diameter. The droplets moved down and - when first of them reached the bottom of the test section - a initiating shock wave (generated by detonation of oxygen-hydrogen-helium mixture) entered the tube. Pressure histories, shock wave and flame velocities in the hexane droplet suspension were determined on the basis of signals from pressure transducers, membrane switches and photodiodes located along the test section. The results obtained enabled us to state whether and under what conditions a detonation process of the droplet suspension occurs, what are the parameters (velocity and peak pressure) of the detonation wave and how are they affected by the suspension characteristics and the initiating shock wave pressure.

6

Detonations of Hexane Vapor/Droplets-Air Mixtures Part I. Preparatory Analyses and Tests

Kuhl A. L., Cudziło S., Trzciński W. A., Wolański P.

Archivum Combustionis

|

2003

|

Vol. 23 nr 1-2

3-11

EN

A system generating hexane sprays (with different concentrations) in a vertical 13-m long detonation tube is described. Applying results of a theoretical analysis of a liquid jet breakup, a droplet generator was designed. It was equipped with 0,8-mm needles and produced droplets of ca. 1,9 mm in the average diameter. The time-space characteristics of the droplet free motion in the tube were calculated and the theoretical results were verified experimentally.

7

Effects of confinement on combustion of TNT explosion products in air

Kuhl A. L., Ferguson R. E., Oppenheim A. K., Sum T-H.J., Reichenbach H., Neuwald P., Kuhl A. L., Ferguson R. E., Oppenheim A.

Archivum Combustionis

|

2001

|

Vol. 21 nr 1

3-25

EN

A numerical study of turbulent combustion following detonative explosions of TNT in geometrically similar cylinders filled with air reveals that the combustion rate depends significantly on the size of the chamber (confinement). The fluid-dynamic solution provides an insight into the evolution of combustion fields dominated by strong interactions between turbulence and shock waves. Time profiles of fuel consumption, extracted from this solution, demonstrate the dynamic (thermokinetic) features of the system, expressed by the rate of combustion (akin to velocity) and its change (akin to acceleration). Their evolution is described by means of bi-parametric life functions.

8

Gasdynamics of combustion of TNT products in air

Kuhl A. L., Ferguson R. E.

Archivum Combustionis

|

1999

|

Vol. 19 nr 1-4

67-89

EN

Effects of turbulent combustion induced by explosion of a 0.8-kg cylindrical charge ot TNT in a 17 m3 chamber filled with air, are investigated. The detonation wave in the charge transforms the solid explosiwe (TNT: C7H5N3O6) to gaseous products rich (`20% each) in carbon monoxide. The detonation pressure (`210 kb) thereby engendered causes the products to expand rapidly, driving a blast wave into the surrouding air. The interface between the products and air, being essentially unstable as a consequence of the strong acceleration inducted by the blast wave, evolves into a turbulent mixing layer - a process enhaced by shock reflections from the walls. Under such circumstances rapid combustion takes place where the expanded detonation products play the role of fuel. Its dynamic effect is manifested by the experimental measurement of ` 3 bar pressure increase in the chamber, in contrast to ` 1 bar attained by a corresponding TNT explosion in nitrogen. The experiments were modeled as turbulent combustion in an unmixed system at infinite Reynolds, Peclet and Damkohler numbers. The numerical solution was obtained by a high-order Godunov scheme using Adaptive Mesh Refinement to trace the turbulent mixing on the computational grid in as much detail as possible. The evolution of the calculared mass-fraction of fuel consumed by combustion began with a finite (non-zero) rate associated with strong initiation, followed by an exponential decay. Calculated pressures are in good agreement with measurements. The results thus reveal details of a combustion process that is controlled by fluid-mechanic transport in a higly turbulent field, in contrast to the conventional reaction-diffusion machanism of laminar flames.

9

Aerothermodynamics of closed combustion system

Oppenheim A. K., Kuhl A. L.

Archivum Combustionis

|

1999

|

Vol. 19 nr 1-4

15-65

EN

Fundamental concepts of two major subjects involved in the analysis of closed combustion systems: the aerodynamics of turbulence in the physical space (in Part 1), and the thermodynamics of exothermicity in the phase space (in Part 2), are exposed. Of principal significance to the former are the analytical properties of the principal two field elements: the rotational component of turbulence and the irrotational component of exothermicity. Direct implementation of this principle is provided by the random vortex method, illustrated here by solutions of simple two-dimensional, planar cases. Salient features of the latter are expressed in terms of the thermodynamics parameters, the thermostatics and the thermokinetics. Most instrumental for the first is the concept of the Le Chatelier diagram displaying the loci of states of the system components in terms of the relationships between the internal energy and the product of pressure and specific volume. The second provides a solution of the inverse problem in terms of an analytic expression for fuel consumption as a function of the measured pressure profile. The third furnishes a description of the system behavior in terms of its dynamic features: the amount (akin to displacement), rate (akin to velocity) and the change of rate (akin to acceleration).