Supersonic speeds

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... 

The first commercial supersonic transport, the Concorde, operates on Jet A1 kerosene but produces unacceptable noise and exhaust emissions. Moreover, it is limited in capacity to 100 passengers and to about 3000 miles in range. At supersonic speed of Mach 2, the surfaces of the aircraft are heated by ram air. These surfaces can raise the temperature of fuel held in the tanks to 80 °C. Since fuel is the coolant for airframe and engine subsystems, fuel to the engine can reach 150°C (26). An HSCT operated at Mach 3 would place much greater thermal stress on fuel. To minimize the formation of thermal oxidation deposits, it is likely that fuel deflvered to the HSCT would have to be deoxygenated. 

Erosion. The abrasive is likely to be gas borne (as in catalytic cracking units), liquid borne (as in abrasive slurries), or gravity pulled (as in catalyst transfer lines). Because of the association of velocity and kinetic energy, the severity of erosion may increase as some power (usually up to the 3d) of the velocity. The angle of impingement also influences severity. At supersonic speeds, even water droplets can be seriously erosive. There is some evidence that the response of resisting metals is influenced by whether they are ductile or brittle. Probably most abrasion involved with hydrocarbon processing is of the erosive type. 

We have so far assumed that the atoms deposited from the vapor phase or from dilute solution strike randomly and balHstically on the crystal surface. However, the material to be crystallized would normally be transported through another medium. Even if this is achieved by hydrodynamic convection, it must nevertheless overcome the last displacement for incorporation by a random diffusion process. Therefore, diffusion of material (as well as of heat) is the most important transport mechanism during crystal growth. An exception, to some extent, is molecular beam epitaxy (MBE) (see [3,12-14] and [15-19]) where the atoms may arrive non-thermalized at supersonic speeds on the crystal surface. But again, after their deposition, surface diffusion then comes into play. 

Finally, we note that if the body is moving at speeds near and above the speed of sound (transonic and supersonic speeds), shock waves will occur that increase the pressure on the front portions of the body, contributing an additional source of pressure drag called wave drag. 

The dry ice blaster is an effective and mess-free method for in-place cleaning that eliminates the need to disassemble machinery before it is cleaned. Compressed air propels tiny dry ice pellets at supersonic speeds so they flash freeze and then lift grime, paint, rust, mold, and other contaminants from metal surfaces. Pellets vaporize quickly into the air, leaving no wastewater or solvents, only the soiled contaminant to be swept up. 

In a diffusion pump, the dense oil vapour produced by the boiler (see Fig. 1.12) is ejected into the vacuum at high (or even supersonic) speed through the nozzles. 

A detonation wave is a very rapid wave of chemical reaction which, once it is initiated, travels at a stable supersonic speed, called the detonation velocity, in a high explosive. Typically, detonation velocities for pressed or cast high explosives range from... 

Detonation a release of energy caused by an extremely rapid chemical reaction of a substance in which the reaction front propagates by a shock wave at supersonic speed. 

A combustible vapor explodes under a very specific set of conditions. There are two explosive mechanisms that need to be considered when evaluating combustible vapor incidents - detonations or deflagrations. A detonation is a shock reaction where the flames travel at supersonic speeds (i.e., faster than sound). Deflagrations are where the flames are traveling at subsonic speeds. 

Detonations produce much higher pressures than what be considered ordinary explosions. In most cases a process vessel or piping systems will be unable to contain detonation pressure. The only safe procedure is to avoid process system detonations is to preventing the formation of flammable vapor and air mixtures within vessels and piping systems. While the flame speed of explosions is at relatively slow speed, detonations travel at supersonic speeds and will be more destructive. 

When the tube is closed at one end and ignited there, the propagating wave undergoes a transition from subsonic to supersonic speeds. The supersonic wave is called a detonation. In a detonation heat conduction and radical diffusion do not control the velocity rather, the shock wave structure of the developed supersonic wave raises the temperature and pressure substantially to cause explosive reaction and the energy release that sustains the wave propagation. 

Both deflagrations and detonations can produce what a lay observer might describe as an explosion . Nonetheless, a detonation is a special type of explosion with specific physical characteristics. It is initiated by the heat accompanying shock compression it liberates sufficient energy, before any expansion occurs, to sustain the shock wave. The shock wave propagates into the unreacted material at supersonic speed, typically 1500—9000 m/s. We discuss the practical differences between the effects of detonation and deflagration in Chapter 11 on post-blast issues. 

An engine concept that utilizes a more efficient thermodynamic cycle that consumes less fuel, and is simple and capable of operation at both subsonic as well as supersonic speeds, would be an attractive alternative for future propulsion systems. Pulse detonation engines (PDE), in principle, can provide higher efficiency [9], and better performance over a wide range of operating conditions, with fewer moving parts. 

A fixed fuel-flow system is a simple set-up that is operated to maintain a constant fuel-flow rate. The fuel-rich gas flows out from the gas generator through a choked orifice that is attached at its aft-end. The mass generahon rate of the fuel-rich gas is therefore independent of the pressure in the ramburner. When a projectQe operated by a fixed-flow ducted rocket flies at a constant supersonic speed and at constant altitude, the airflow rate through the air-intake remains constant. Since the gas generahon rate in the gas generator is kept constant, the air-to-fuel raho also remains constant. Ophmized combustion performance is thereby obtained. This class of ducted rocket is termed a fixed fuel-flow ducted rocket . 

Sixties, mercury as the medium was almost completely replaced by oil. To obtain as high a vapor stream velocity as possible, he allowed the vapor stream to emanate from a nozzle with supersonic speed. The pump fluid vapor, which constitutes the vapor jet, is condensed at the cooled wall of the pump housing, whereas the fransported gas is further compressed, usually in one or more succeeding stages, before it is removed by the backing pump. The compression ratios, which can be obtained with fluid entrainment pumps, are very high if there is a pressure of 10 mbar at the inlet port of the fluid-entrainment pump and a backing pressure of 10 2 mbar, the pumped gas is compressed by a factor of 10 ... 

The 3rd stage, transition from deflagration to detonation (DDT), is the stage during which the reaction accelerates from the slow transport-determined steady state to supersonic speeds. In condensed explosives the velocity of propagation during transition must increase by a factor of about a million... 

WAVE IN. A shock wave is a violent disturbance moving with a loud bang along a medium (such as air, water, or earth), at a speed greater than that of sound ("supersonic speed ). Velocity of sound, c, in air is 331.9 m/sec (1088ft/sec) and the ratio of shock velocity to sonic velocity is known as Mach Number, M... 

Shock waves can be produced in a number of ways, such as movement of projectiles or other objects thru air at supersonic speeds, or pushing out of the air by the products of a detonation, which expand at many times the speed of sound. The latter type of shock wave is much stronger and is known as a blast wave (See under BLAST EFFECTS IN AIR, EARTH AND WATER in Vol 2 of Encycl, pp B180 to B184)... 

Although a shock wave may be attached to a projectile at its tip (Fig 3), detachment may occur at slower, though still supersonic, speeds. Or. the other hand, a shock wave of a slowly-moving body becomes attached if it accelerates beyond a certain critical speed which varies for different geometrical forms (Ref 50). When the wave... 

Since shock discontinuities move at supersonic speed into the fluid ahead, shocks overtake contact discontinuities and rarefaction waves. Since shocks move sub-sonically with respect to the fluid behind them, a shock will be overtaken by a shock or rarefaction behind it. When two shocks moving toward each other collide, two shocks moving away from each.other are produced together with two regions of different entropy separated by a contact discontinuity thru the point of collision. 

Detonation An exothermic reaction that propagates a shockwave through an explosive at supersonic speed (greater than 3300ft/sec). 

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