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De Laval Nozzle
A de Laval nozzle (or convergent-divergent nozzle, CD nozzle or con-di nozzle) is a tube which is pinched in the middle, with a rapid convergence and gradual divergence. It is used to accelerate a compressible fluid to supersonic speeds in the axial (thrust) direction, by converting the thermal energy of the flow into kinetic energy. De Laval nozzles are widely used in some types of steam turbines and rocket engine nozzles. It also sees use in supersonic jet engines. Similar flow properties have been applied to jet streams within astrophysics. History Giovanni Battista Venturi designed converging-diverging tubes known as Venturi tubes for experiments on fluid pressure reduction effects when fluid flows through chokes ( Venturi effect). German engineer and inventor Ernst Körting supposedly switched to a converging-diverging nozzle in his steam jet pumps by 1878 after using convergent nozzles but these nozzles remained a company secret. Later, Swedish engineer Gustaf de Lav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nozzle De Laval Diagram
A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe. A nozzle is often a pipe or tube of varying cross sectional area, and it can be used to direct or modify the flow of a fluid (liquid or gas). Nozzles are frequently used to control the rate of flow, speed, direction, mass, shape, and/or the pressure of the stream that emerges from them. In a nozzle, the velocity of fluid increases at the expense of its pressure energy. Types Jet A gas jet, fluid jet, or hydro jet is a nozzle intended to eject gas or fluid in a coherent stream into a surrounding medium. Gas jets are commonly found in gas stoves, ovens, or barbecues. Gas jets were commonly used for light before the development of electric light. Other types of fluid jets are found in carburetors, where smooth calibrated orifices are used to regulate the flow of fuel into an engine, and in jacuzzis or s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rocket Engine
A rocket engine is a reaction engine, producing thrust in accordance with Newton's third law by ejecting reaction mass rearward, usually a high-speed Jet (fluid), jet of high-temperature gas produced by the combustion of rocket propellants stored inside the rocket. However, non-combusting forms such as cold gas thrusters and nuclear thermal rockets also exist. Rocket vehicles carry their own oxidiser, unlike most combustion engines, so rocket engines can be used in a vacuum, and they can achieve great speed, beyond escape velocity. Vehicles commonly propelled by rocket engines include missiles, Rocket-assisted projectile, artillery shells, ballistic missiles and rockets of any size, from tiny Rocket (firework), fireworks to Rocket (weapon), man-sized weapons to huge Space vehicle, spaceships. Compared to other types of jet engine, rocket engines are the lightest and have the highest thrust, but are the least propellant-efficient (they have the lowest specific impulse). The ideal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reversible Process (thermodynamics)
In thermodynamics, a reversible process is a process, involving a system and its surroundings, whose direction can be reversed by infinitesimal changes in some properties of the surroundings, such as pressure or temperature. Throughout an entire reversible process, the system is in thermodynamic equilibrium, both physical and chemical, and ''nearly'' in pressure and temperature equilibrium with its surroundings. This prevents unbalanced forces and acceleration of moving system boundaries, which in turn avoids friction and other dissipation. To maintain equilibrium, reversible processes are extremely slow ( ''quasistatic''). The process must occur slowly enough that after some small change in a thermodynamic parameter, the physical processes in the system have enough time for the other parameters to self-adjust to match the new, changed parameter value. For example, if a container of water has sat in a room long enough to match the steady temperature of the surrounding air, for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ideal Gas
An ideal gas is a theoretical gas composed of many randomly moving point particles that are not subject to interparticle interactions. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics. The requirement of zero interaction can often be relaxed if, for example, the interaction is perfectly elastic or regarded as point-like collisions. Under various conditions of temperature and pressure, many real gases behave qualitatively like an ideal gas where the gas molecules (or atoms for monatomic gas) play the role of the ideal particles. Many gases such as nitrogen, oxygen, hydrogen, noble gases, some heavier gases like carbon dioxide and mixtures such as air, can be treated as ideal gases within reasonable tolerances over a considerable parameter range around standard temperature and pressure. Generally, a gas behaves more like an ideal gas at higher temperature and lower ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ambient Pressure
The ambient pressure on an object is the pressure of the surrounding medium, such as a gas or liquid, in contact with the object. Atmosphere Within the atmosphere, the ambient pressure decreases as elevation increases. By measuring ambient atmospheric pressure, a pilot may determine altitude (see pitot-static system). Near sea level, a change in ambient pressure of 1 millibar is taken to represent a change in height of . Underwater The ambient pressure in water with a free surface is a combination of the hydrostatic pressure due to the weight of the water column and the atmospheric pressure on the free surface. This increases approximately linearly with depth. Since water is much denser than air, much greater changes in ambient pressure can be experienced under water. Each of depth adds another bar (unit) , bar to the ambient pressure. Ambient-pressure diving is underwater diving exposed to the water pressure at depth, rather than in a pressure-excluding atmospheric diving suit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stagnation Pressure
In fluid dynamics, stagnation pressure, also referred to as total pressure, is what the pressure would be if all the kinetic energy of the fluid were to be converted into pressure in a reversable manner.; it is defined as the sum of the free-stream static pressure and the free-stream dynamic pressure. The Bernoulli equation applicable to incompressible flow shows that the stagnation pressure is equal to the dynamic pressure and static pressure combined.Clancy, L.J. (1975), ''Aerodynamics'', Pitman Publishing Limited, London. In compressible flows, stagnation pressure is also equal to total pressure as well, provided that the fluid entering the stagnation point is brought to rest Isentropic flow, isentropically. Stagnation pressure is sometimes referred to as pitot pressure because the two pressures are equal. Magnitude The magnitude of stagnation pressure can be derived from Bernoulli's principle, Bernoulli equation for incompressible flow and no height changes. For any two po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Choked Flow
Choked flow is a compressible flow effect. The parameter that becomes "choked" or "limited" is the fluid velocity. Choked flow is a Fluid dynamics, fluid dynamic condition associated with the Venturi effect. When a flowing fluid at a given pressure and temperature passes through a constriction (such as the throat of a convergent-divergent nozzle or a valve in a pipe (material), pipe) into a lower pressure environment the fluid velocity increases. At initially subsonic upstream conditions, the conservation of energy principle requires the fluid velocity to increase as it flows through the smaller cross-sectional area of the constriction. At the same time, the Venturi effect causes the static pressure, and therefore the density, to decrease at the constriction. Choked flow is a limiting condition where the mass flow cannot increase with a further decrease in the downstream pressure environment for a fixed upstream pressure and temperature. For homogeneous fluids, the physical point ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound
In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the brain. Only acoustic waves that have frequency, frequencies lying between about 20 Hz and 20 kHz, the audio frequency range, elicit an auditory percept in humans. In air at atmospheric pressure, these represent sound waves with wavelengths of to . Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges, allowing some to even hear ultrasounds. Definition Sound is defined as "(a) Oscillation in pressure, stress, particle displacement, particle velocity, etc., propagated in a medium with internal forces (e.g., elastic or viscous), or the superposition of such propagated oscillation. (b) Auditory sen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Entropy
Entropy is a scientific concept, most commonly associated with states of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the microscopic description of nature in statistical physics, and to the principles of information theory. It has found far-ranging applications in chemistry and physics, in biological systems and their relation to life, in cosmology, economics, sociology, weather science, climate change and information systems including the transmission of information in telecommunication. Entropy is central to the second law of thermodynamics, which states that the entropy of an isolated system left to spontaneous evolution cannot decrease with time. As a result, isolated systems evolve toward thermodynamic equilibrium, where the entropy is highest. A consequence of the second law of thermodynamics is that certain processes are irreversible. The thermodynami ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isentropic Process
An isentropic process is an idealized thermodynamic process that is both Adiabatic process, adiabatic and Reversible process (thermodynamics), reversible. The work (physics), work transfers of the system are friction, frictionless, and there is no net transfer of heat or matter. Such an idealized process is useful in engineering as a model of and basis of comparison for real processes. This process is idealized because reversible processes do not occur in reality; thinking of a process as both adiabatic and reversible would show that the initial and final entropies are the same, thus, the reason it is called isentropic (entropy does not change). Thermodynamics, Thermodynamic processes are named based on the effect they would have on the system (ex. isovolumetric: constant volume, isenthalpic: constant enthalpy). Even though in reality it is not necessarily possible to carry out an isentropic process, some may be approximated as such. The word "isentropic" derives from the proc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass Flow Rate
In physics and engineering, mass flow rate is the Temporal rate, rate at which mass of a substance changes over time. Its unit of measurement, unit is kilogram per second (kg/s) in SI units, and Slug (unit), slug per second or pound (mass), pound per second in US customary units. The common symbol is \dot (pronounced "m-dot"), although sometimes \mu (Greek language, Greek lowercase Mu (letter), mu) is used. Sometimes, mass flow rate as defined here is termed "mass flux" or "mass current". Confusingly, "mass flow" is also a term for mass flux, the rate of mass flow per unit of area. Formulation Mass flow rate is defined by the limit of a function, limit \dot = \lim_ \frac = \frac, i.e., the flow of mass \Delta m through a surface per time \Delta t. The overdot on \dot is Newton's notation for a time derivative. Since mass is a scalar (physics), scalar quantity, the mass flow rate (the time derivative of mass) is also a scalar quantity. The change in mass is the amount that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supersonic
Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times the speed of sound (Mach 5) are often referred to as hypersonic. Flights during which only some parts of the air surrounding an object, such as the ends of rotor blades, reach supersonic speeds are called transonic. This occurs typically somewhere between Mach 0.8 and Mach 1.2. Sounds are traveling vibrations in the form of pressure waves in an elastic medium. Objects move at supersonic speed when the objects move faster than the speed at which sound propagates through the medium. In gases, sound travels longitudinally at different speeds, mostly depending on the molecular mass and temperature of the gas, and pressure has little effect. Since air temperature and composition varies significantly with altitude, the speed of s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
