Subsonic speed

Deflagration a release of energy caused by a rapid chemical reaction in which the reaction front propagates by thermal energy transfer at subsonic 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. 

Original studies of gaseous detonations have shown no single sequence of events due primarily to what is now known as the complex cellular structure of a detonation wave. The primary result of an ordinary thermal initiation always appears to be a flame that propagates with subsonic speed. When conditions are such that the flame causes adiabatic compression of the still unreacted mixture ahead of it, the flame velocity increases. According to some early observations,... 

Deflagration An exothermic reaction that occurs particle to particle at subsonic speed. 

Nevertheless, the most typical general feature of a reaction is the existence of fronts of chemical transformation which are able to propagate, without being extinguished, in a hot mixture with a constant velocity at subsonic speed for a laminar flame (or deflagration front), at supersonic speed for a detonation wave (see below for a more detailed discussion of this paper). 

Deflagration or explosion—the flame front advances through a gaseous mixture at subsonic speeds. 

Combustion is understood to be a fast reduction-oxidation reaction between substances, capable of spreading in space at a subsonic speed and usually accompanied by flame and light. An oxidant and reducing agent are necessary for this reaction to occur. Combustion processes are as manifold as the chemical nature of compounds having oxidizing and reducing properties. 

Wallace (1975) calculated absorbed doses to passengers for a round trip, for both subsonic and supersonic transport between various city pairs. Some of these estimates are shown in Table 3.8. Doses for a round trip in supersonic aircraft are approximately 70% of those for subsonic speeds, because of the shorter flying time. However, the dose rates in supersonic aircraft are about twice as high as in subsonic aircraft. For a round trip across the Atlantic, the tissue-absorbed doses in passengers may be estimated to be about 2 10" Gy for an SST and 3 10 Gy for a subsonic aircraft, under average solar conditions. 

When a premixed gas-oxidant cloud is ignited, the flame can propagate in two different modes through the gas mixture—deflagration and detonation. Deflagrations propagate at subsonic speeds relative to the unburned mixture and the heat and mass are transported by conduction, diffusion, and convection. Gas mixture detonations propagate at speeds faster than the local sound speed of the unburned gas. In a gas mixture detonation, a shock wave is sustained... 

In materials with high dislocation mobility such as copper, dislocation patterns proceed through the rapid motion of dislocations in a very small volume of the specimen [36]. Under high strain rate deformation conditions, it is expected that the dislocations move at subsonic speed or even as fast as the shear wave velocity. The random motion of dislocations on their slip planes causes random changes not only in the local dislocation densities, but also in the dislocation velocities. 

Many applications of Eq. 7,16 involve jets. A jet is a stream of fluid which is not confined within a pipe, duct, or channel examples are the stream of water issuing from a garden hose and the exhaust gas stream from a jet engine. If a jet is flowing at a subsonic velocity, its pressure will be the same as the pressure of the surrounding fluid. If a jet enters or leaves a system or device at subsonic speed, it will enter and leave at the pressure of the surrounding fluid, although its pressure may be different inside the device. 

A deflagration occurs when a flame front propagates by transferring heat and mass to the unbumed air—vapor mixture ahead of the front. The combustion wave travels at subsonic speeds to unbumed gas immediately ahead of the flame front. Hame speeds range from 1 to 350 m/s at low speeds... 

Chemical reaction propagating through a material by a reaction front or zone travelling at subsonic speed. 

Schubauer s work on turbulence and airflow, and the development of instruments for measuring these phenomena, was vital to the development of the modem high-speed aircraft. In the 1950s, he studied the accuracy of the hot-wire anemometer at speeds up to twice the speed of sound. This instmment was previously a basis in aerodynamic research at subsonic speeds, but it was not known whether it could also be used at supersonic speeds. Schubauer was elected to the National Academy of Engineering in 1980 for the discoveiy of self-exited oscillations in laminar boimdaiy layers, giving a new direction for further inquiry into the origin of turbulent flows . He furthermore was the recipient of the 1988 Fluid Dynamics Prize from the American Physical Society APS. 

Perhaps the most frequent engineering application of nozzles is in propulsion systems for aircraft or spacecraft however, other important applications exist as well (e.g., spray nozzles and fluid atomization). Initial acceleration of a flow at subsonic speeds occurs in the convergent section, and for sufficiently high pressure ratios and nozzle area contraction, it is possible to accelerate a flow to sonic conditions at the... 

Inlet and Diffuser. The engine inlet is designed to capture the required airflow without causing flow separation. An aircraft flying at supersonic speeds has a supersonic inlet in which a series of shocks slows down the flow to subsonic speeds with minimal losses in pressure. Once the flow is subsonic, it is slowed further to the Mach number of about 0.4 needed at the fe.ce of the compressor or fen. A supersonic inlet and diffuser may lose 5 to 10 percent of the stagnation pressure of the incoming flow when used with aircraft flying in excess of Mach 2. 

Ramjet and Scramjet. Ramjets are used to power vehicles at speeds from about Mach 0.8 to 4. The diffuser slows the flow down to subsonic speeds, increasing the pressure so much that thrust can be generated without a mechanical compressor or turbine. Beyond Mach 4, the pressure loss in slowing down the flow to below Mach 1 is greater than the loss due to adding heat to a supersonic flow. In addition, if such a flow were decelerated to subsonic... 

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