Fronts accelerating

A minimum flammable mass of 100 kgs (220 lbs.) is generally required flame front acceleration. 

There is general agreement that both fronts accelerate, and that the process is cumulative by virtue of their mutual interaction. This is promoted by turbulence, diffusion of hot particles ahead of the flame front, and passage of reflected shocks and rarefactions thru the "processed medium (Ref 3, p 130). Advance of the flame front thru it differs more and more from the initial laminar burning... 

D. Rae, Safety in Mines Res Estab, Res Rept 253 (1967) CA 69, 1140 (1968). The main characteristics of slow coal-dust explosions and their relation to the testing of barriers. The main characteristics of slow coal-dust explosions in the new gallery at Buxton are a const initial flame front acceleration from... 

The isohyets show that precipitation rates in excess of 30 mm. per six hours fell in northern California near the time of the frontal passage, but as the front accelerated southward through central California the precipitation amounts decreased substantially. Thus, south of Vandenberg, where the jet stream was observed to lose its strength, the frontal precipitation was mostly in form of drizzle and light intermittent rain. 

The surface frontal positions for the period Jan. 20-23, 1967 are presented in Figure 6 and show the front accelerating through central and southern California subsequent to a wave moving into Nevada on January 21. 

As the flame front accelerates, the amplitude of the compression wave increases. On reaching a sufficient intensity, this wave causes the deformation and destruction of the layer of explosive ahead of the flame front... 

For conservation of momentum, the pressure difference across the front accelerates the material according to... 

The main characteristics of slow coal-dust explosions in the new gallery at Buxton are a const initial flame front acceleration from... 

The idea that the processes, which occur during the combustion of a fuel in an engine cylinder, take place by a chain reaction mechanism comparable to that associated with the liquid phase autoxidation of benzal-dehyde, has led to the proposal that knock suppressors act by destroying the chains and reducing the rate at which the flame front accelerates. It is known that surfaces or solid bodies suppress chain reactions, in fact one of the criteria for a chain reaction in gaseous combustion processes is the decrease in rate of reaction caused by the increase in surface exposed to the gases. However, the mode by which the chains are broken or... 

Artificial lift systems are mostly required later in a field s life, when reservoir pressures decline and therefore well productivities drop. If a situation is anticipated where artificial lift will be required or will be cost effective later in a field s life, it may be advantageous to install the artificial lift equipment up front and use it to accelerate production throughout the field s life, provided the increased revenues from the accelerated production offset... 

The primary source energy can be switched between 6, 9 and 11 MeV. So it is possible to penetrate and examine up to 0.6 m solid steel objects. In front of the accelerator a collimator... 

The end or front of the plasma flame impinges onto a metal plate (the cone or sampler or sampling cone), which has a small hole in its center (Figure 14.2). The region on the other side of the cone from the flame is under vacuum, so the ions and neutrals passing from the atmospheric-pressure hot flame into a vacuum space are accelerated to supersonic speeds and cooled as rapid expansion occurs. A supersonic jet of gas passes toward a second metal plate (the skimmer) containing a hole smaller than the one in the sampler, where ions pass into the mass analyzer. The sampler and skimmer form an interface between the plasma flame and the mass analyzer. A light... 

On firings the gases from the propellant accelerate the piston that compresses the light gas in front of it. At a preestablished pressure, the projectile is propelled down the launch tube accelerated by the low molecular weight gas which follows the projectile to the mouth of the tube. The target material is placed in front of the launch tube, and appropriate instmmentation used to estabUsh the characteristics of the interface reaction between projectile and target (117-120). 

The plasma source implantation system does not use the extraction and acceleration scheme found in traditional mass-analy2ing implanters, but rather the sample to be implanted is placed inside a plasma (Fig. 4). This ion implantation scheme evolved from work on controlled fusion devices. The sample is repetitively pulsed at high negative voltages (around 100 kV) to envelope the surface with a flux of energetic plasma ions. Because the plasma surrounds the sample, and because the ions are accelerated normal to the sample surface, plasma-source implantation occurs over the entire surface, thereby eliminating the need to manipulate nonplanar samples in front of the ion beam. In this article, ion implantation systems that implant all surfaces simultaneously are referred to as omnidirectional systems. 

Deflagration to Detonation Transition A reaction front that starts out with velocities below the speed of sound and subsequently accelerates to velocities higher than the speed of sound in the unreacted material is said to have undergone a Deflagration to Detonation Transition. The possibility of transition is enhanced by confinement/turbulence generators in the path of the reaction front. 

The propagation of a shock wave from a detonating explosive or the shock wave induced upon impact of a flyer plate accelerated, via explosives or with a gun, result in nearly steady waves in materials. For steady waves a shock velocity U with respect to the laboratory frame can be defined. Conservation of mass, momentum, and energy across a shock front can then be expressed as... 

We assume that in (4.38) and (4.39), all velocities are measured with respect to the same coordinate system (at rest in the laboratory) and the particle velocity is normal to the shock front. When a plane shock wave propagates from one material into another the pressure (stress) and particle velocity across the interface are continuous. Therefore, the pressure-particle velocity plane representation proves a convenient framework from which to describe the plane Impact of a gun- or explosive-accelerated flyer plate with a sample target. Also of importance (and discussed below) is the interaction of plane shock waves with a free surface or higher- or lower-impedance media. 

This is expressed in terms of the particle acceleration immediately behind the shock front. Equation (A. 15) can be expressed in terms of the Lagrangian stress gradient (dff/dX), and the Lagrangian longitudinal sound speed Q =... 

An additional approximation can be used in the case when pCi = PqU and the acceleration behind the elastic shock front is small, so that... 

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