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Nozzle; النوزل شرح مبسط

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    الصورة الرمزية حسن هادي
    حسن هادي
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    Nozzle; النوزل شرح مبسط

    باستدراج تتابعي نكتب موضوع النوزل كونه البوابة العملية لمرور المائع لتغير بعض الخواص *وكما اسلفنا بالمواضيع ذات الشان والارتباط كالتوربينات وبهدف التنويه والاشارة الى التقاطع العلمي بين هذه المواضيع *نرفق لكم طيا ما وجدناه في صفحات النت حول هذا الموضوع وسنضع ما لدينا من ملفات كمرفقات لنسهل عملية البحث للاخوة الاعضاء *
    ومن الله التوفيق*
    ************************************************** ******

    Introduction
    Nozzles are used to determine a fluid's flowrate through a pipe. The ISA 1932 nozzle was developed in 1932 by the International Federation of the National Standardizing Associations (later succeeded by the International Organization for Standardization or ISO). The ISA 1932 nozzle is commonly used outside of the USA (ASME, 1971). The long radius nozzle is a variation of the ISA 1932 nozzle. The venturi nozzle is a hybrid having a convergent section similar to the ISA 1932 nozzle and a divergent section similar to a classical venturi tube flowmeter. The venturi nozzle shown above is called a "truncated" venturi nozzle because the divergent section does not extend smoothly to the pipe diameter (ISO, 1991). The divergent portion of a "non-truncated" venturi nozzle is longer and extends smoothly all the way to the pipe diameter. The discharge coefficients are the same for both types of venturi nozzles.
    Differential pressure is the pressure difference P1 - P2 shown in the above diagrams. For exact geometry and specifications for nozzles, see ISO (1991) or ASME (1971). Nozzles are typically used in 5 to 50 cm diameter pipes. The ASME (American Society of Mechanical Engineers) and ISO have been working on guidelines for nozzles since the early 1900s. The organizations have the most confidence in nozzle accuracy when the Reynolds number is in the range of 104 to 107 as discussed below. The calculation above is for liquids. Gas flow calculations have an additional factor called expansibility.
    Equations
    The calculations on this page are for nozzles carrying a liquid as described in ISO (1991) and ASME (1971). The ISO reference has a more complete discussion of nozzles than the ASME reference, so the ISO equations are used in our calculations.


    k = Equivalent Roughness of the pipe material [L]. Click for k values.
    w is the static pressure loss occurring from a distance of approximately D upstream of the nozzle to a distance of approximately 6D downstream of the nozzle. It is not the same as differential pressure. Differential pressure is measured at the exact locations specified in ISO (1991) (shown in the above figures). Km is computed to allow you to design pipe systems with nozzles and incorporate their head loss. Head loss is computed as h=KmV2/2g where V is the pipe velocity

  2. [2]
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    Discharge Coefficients
    For each type of nozzle, a graph of Discharge Coefficient vs. ReD or d/D is shown. Each graph is followed by the equation used to form the graph. The equations are from ISO (1991).

    ISA 1932 Nozzle Discharge Coefficient Equation:
    C = 0.9900 - 0.2262(d/D)4.1 - [0.00175(d/D)2 - 0.0033(d/D)4.15][106/ReD]1.15
    Valid for: 5 cm <= D <= 50 cm
    and 0.3 <= d/D < 0.44 having 7x104 <= ReD <= 107
    and 0.44 <= d/D <= 0.8 having 2x104 <= ReD <= 107
    and k/D <= 3.8 x10-4 generally for all d/D

    Long Radius Nozzle Discharge Coefficient Equation:
    C = 0.9965 - 0.00653[(106)(d/D)/ReD]0.5
    Valid for: 0.2 <= d/D <= 0.8, 104 <= ReD <= 107, 5 cm <= D <= 63 cm
    and k/D <= 10-3 generally.


    Venturi Nozzle Discharge Coefficient Equation:
    C = 0.9858 - 0.196(d/D)4.5
    Valid for: 0.316 <= d/D <= 0.775, 1.5x105 <= ReD <= 2x106,
    6.5 cm <= D <= 50 cm, d >= 5 cm, and k/D <= 3.8x10-4 generally

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  3. [3]
    حسن هادي
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    عضو متميز
    الصورة الرمزية حسن هادي


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    لتسليط الضوء بصورة اكثر دقة*على النوزل ومن خلال موسوعة الويكابيديا *


    Nozzle

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    Rocket nozzle.



    Water nozzle.


    A nozzle is a mechanical device designed to control the characteristics of a fluid flow 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, and/or the pressure of the stream that emerges from them.

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  4. [4]
    حسن هادي
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    عضو متميز
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    Purposes of nozzles

    High velocity nozzles
    Frequently the goal is to increase the kinetic energy of the flowing medium at the expense of its pressure energy and/or internal energy.
    Nozzles can be described as convergent (narrowing down from a wide diameter to a smaller diameter in the direction of the flow) or divergent (expanding from a smaller diameter to a larger one). A de Laval nozzle has a convergent section followed by a divergent section and is often called a convergent-divergent nozzle.
    Convergent nozzles accelerate subsonic fluids. If the nozzle pressure ratio is high enough the flow will reach sonic velocity at the narrowest point (i.e. the nozzle throat). In this situation, the nozzle is said to be choked.
    Increasing the nozzle pressure ratio further will not increase the throat Mach number beyond unity. Downstream (i.e. external to the nozzle) the flow is free to expand to supersonic velocities.
    Divergent nozzles slow fluids, if the flow is subsonic, but accelerate sonic or supersonic fluids.
    Convergent-divergent nozzles can therefore accelerate fluids that have choked in the convergent section to supersonic speeds. This CD process is more efficient than allowing a convergent nozzle to expand supersonically externally.
    Since greater thrust is obtained with the same mass flow with a higher exhaust velocity supersonic aircraft also very typically use a con-di nozzle despite the weight and cost penalties. Jet aircraft like rockets can exceed the velocity of the engine exhaust jet however for aircraft because they take in high velocity stream of air, to the extent that jet velocity does not exceed the airspeed it produces a net thrust only due to the fuel which is added to the consumed air. Supersonic jet engines, like those employed in fighters and SST aircraft (e.g. Concorde), indeed have relatively high nozzle pressure ratios. For best energy efficiency at lower velocities is lower velocity jet's use. Therefore subsonic jet engines employ relatively low exhaust velocities, require only subsonic exhaust and thus have modest nozzle pressure ratios and employ simple convergent nozzles.
    Rocket motors use convergent-divergent nozzles, to maximise thrust and exhaust velocity and thus extremely high nozzle pressure ratios are employed.
    Note that the Mach 1 can be a very high speed for a hot gas; since heat significantly raises the speed of sound. Thus the absolute speed reached at a nozzle throat can be far higher than the speed of sound at sea level. This fact is used extensively in rocketry where hypersonic flows are required

    Magnetic nozzles
    Magnetic nozzles have also been proposed for some types of propulsion, in which the flow of plasma is directed by magnetic fields instead of walls made of solid matter.

    [edit] Spray nozzles

    Many nozzles atomise liquids.
    • Air-Aspirating Nozzle-uses an opening in the cone shaped nozzle to inject air into a stream of water based foam (CAFS/AFFF/FFFP) to make the concentrate "foam up". Most commonly found on foam extinguishers and foam handlines.
    • Swirl nozzles inject the liquid in tangentially, and it spirals into the center and then exits through the central hole. Due to the vortexing this causes the spray to come out in a cone shape.

    [edit] Vacuum nozzles

    Vacuum cleaner nozzles come in several different shapes.

    [edit] Shaping nozzles

    Some nozzles are shaped to produce a stream that is of a particular shape. For example Extrusion molding is a way of producing lengths of metals or plastics or other materials with a particular cross-section. These nozzles are typically referred to as a die.

    [edit] Other meanings

    In some areas of Scotland, the nozzle can refer to the nose.
    It can also be used as an insult meaning something between 'jerk' and 'idiot'. This use was made popular by the character Al Calavicci on the science-fiction television show Quantum Leap

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  5. [5]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
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    رقم الماك او الماخ كما يسميه بعض اخواننا Mach number ولما قد دخلنا في في موضوع النوزل وددت الى ان اشير الى هذا الموضوع ولو اني اعتقد انه يحتاج الى موضوع خاص ولكن حتى تكتمل الصورة نشير اليه في موضوع النوزل وذلك لغرض الترابط * وتقبلو تحياتي
    ************************************
    Mach number

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    An F/A-18 Hornet at transonic speed and displaying the Prandtl-Glauert singularity just before breaking the sound barrier.


    Mach number (Ma) (pronounced: [mɑːk], [mɑx], [m&aelig;k], see IPA) is a dimensionless measure of relative speed. It is defined as the speed of an object relative to a fluid medium, divided by the speed of sound in that medium:
    where
    is the Mach number is the velocity of the object relative to the medium and is the velocity of sound in the medium Mach number is the number of times the speed of sound an object or a duct, or the fluid medium itself, move relative to each other. It is named after Austrian physicist and philosopher Ernst Mach.*********************************************

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    حسن هادي
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    Overview
    The Mach number is commonly used both with objects travelling at high speed in a fluid, and with high-speed fluid flows inside channels such as nozzles, diffusers or wind tunnels. As it is defined as a ratio of two speeds, it is a dimensionless number. At a temperature of 15 degrees Celsius and at sea level, Mach 1 is 340.3 m/s (1,225 km/h, 761.2 mph, or 661.7 kts) in the Earth's atmosphere. The speed represented by Mach 1 is not a constant; it is temperature dependent. Hence in the stratosphere it remains about the same regardless of height, though the air pressure changes with height.
    Since the speed of sound increases as the temperature increases, the actual speed of an object travelling at Mach 1 will depend on the fluid temperature around it. Mach number is useful because the fluid behaves in a similar way at the same Mach number. So, an aircraft travelling at Mach 1 at sea level (340.3 m/s, 1,225.08 km/h) will experience shock waves in much the same manner as when it is travelling at Mach 1 at 11,000 m (36,000 ft), even though it is travelling at 295 m/s (654.632 MPH, 1,062 km/h, 86% of its speed at sea level).
    It can be shown that the Mach number is also the ratio of inertial forces (also referred to aerodynamic forces) to elastic forces.
    High-speed flow around objects
    High speed flight can be classified in five categories:
    (For comparison: the required speed for low Earth orbit is ca. 7.5 km·s-1 = Ma 25.4 in air at high altitudes)
    At transonic speeds, the flow field around the object includes both sub- and supersonic parts. The transonic period begins when first zones of Ma>1 flow appear around the object. In case of an airfoil (such as an aircraft's wing), this typically happens above the wing. Supersonic flow can decelerate back to subsonic only in a normal shock; this typically happens before the trailing edge. (Fig.1a)
    As the velocity increases, the zone of Ma>1 flow increases towards both leading and trailing edges. As Ma=1 is reached and passed, the normal shock reaches the trailing edge and becomes a weak oblique shock: the flow decelerates over the shock, but remains supersonic. A normal shock is created ahead of the object, and the only subsonic zone in the flow field is a small area around the object's leading edge. (Fig.1b)
    (a)(b)
    Fig. 1. Mach number in transonic airflow around an airfoil; Ma<1 (a) and Ma>1 (b).
    When an aircraft exceeds Mach 1 (i.e. the sound barrier) a large pressure difference is created just in front of the aircraft. This abrupt pressure difference, called a shock wave, spreads backward and outward from the aircraft in a cone shape (a so-called Mach cone). It is this shock wave that causes the sonic boom heard as a fast moving aircraft travels overhead. A person inside the aircraft will not hear this. The higher the speed, the more narrow the cone; at just over Ma=1 it is hardly a cone at all, but closer to a slightly concave plane.
    At fully supersonic velocity the shock wave starts to take its cone shape, and flow is either completely supersonic, or (in case of a blunt object), only a very small subsonic flow area remains between the object's nose and the shock wave it creates ahead of itself. (In the case of a sharp object, there is no air between the nose and the shock wave: the shock wave starts from the nose.)
    As the Mach number increases, so does the strength of the shock wave and the Mach cone becomes increasingly narrow. As the fluid flow crosses the shock wave, its speed is reduced and temperature, pressure, and density increase. The stronger the shock, the greater the changes. At high enough Mach numbers the temperature increases so much over the shock that ionization and dissociation of gas molecules behind the shock wave begin. Such flows are called hypersonic.
    It is clear that any object travelling at hypersonic velocities will likewise be exposed to the same extreme temperatures as the gas behind the nose shock wave, and hence choice of heat-resistant materials becomes important

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    Calculating Mach Number
    Assuming air to be an ideal gas, the formula to compute Mach number in a subsonic compressible flow is derived from the Bernoulli equation for M<1:[1]


    where:
    is Mach number is impact pressure and is static pressure.
    The formula to compute Mach number in a supersonic compressible flow is derived from the Rayleigh Supersonic Pitot equation:
    where:
    is now impact pressure measured behind a normal shock

    As can be seen, M appears on both sides of the equation. The easiest method to solve the supersonic M calculation is to enter both the subsonic and supersonic equations into a computer spreadsheet. First determine if M is indeed greater than 1.0 by calculating M from the subsonic equation. If M is greater than 1.0 at that point, then use the value of M from the subsonic equation as the initial condition in the supersonic equation. Then perform a simple iteration of the supersonic equation, each time using the last computed value of M, until M converges to a value--usually in just a few iterations.[1]

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  8. [8]
    ابو الباسل الألمعي
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    موضوع رائع

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  9. [9]
    شكرى محمد نورى
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    مشرف


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    وسام الاشراف

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    الأخ حسن هادي .

    تحية طيبة .

    النوزل ويسمى ايضا البوق والابواق اشكالها مختلفة منها البوق المخروطي من الداخل والبوق مستقيم

    الحافة يكون مخروطي من الداخل ثم يستقيم وايضا الاخير يسمى بوق الحريق يكون متقارب الاقواس

    الى فتحة المنفذ .

    موضوع اكثر من رائع ومذهل .

    ماشاء الله عليك انجزته بكل همة واندفاع واصرار .

    الله يكون بعونك وجزاك الله خير جزاء واحسان .

    البغدادي

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  10. [10]
    حسن هادي
    حسن هادي غير متواجد حالياً
    عضو متميز
    الصورة الرمزية حسن هادي


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    اقتباس المشاركة الأصلية كتبت بواسطة شكرى محمد نورى مشاهدة المشاركة
    الأخ حسن هادي .

    تحية طيبة .

    النوزل ويسمى ايضا البوق والابواق اشكالها مختلفة منها البوق المخروطي من الداخل والبوق مستقيم

    الحافة يكون مخروطي من الداخل ثم يستقيم وايضا الاخير يسمى بوق الحريق يكون متقارب الاقواس

    الى فتحة المنفذ .

    موضوع اكثر من رائع ومذهل .

    ماشاء الله عليك انجزته بكل همة واندفاع واصرار .

    الله يكون بعونك وجزاك الله خير جزاء واحسان .

    البغدادي
    اعتز بهذه المداخلة يا اخي يا ابا احمد * ووفقنا الله واياكم لما فيه الخير /اخوكم حسن العراقي

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