100F10_Propulsion and Fans_Update

100F10_Propulsion and Fans_Update - Hovercraft Fluid...

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Hovercraft Fluid Mechanics: Fan Levitation & Propulsion Fall 2010 Dr. Ken Kiger Department of Mechanical Engineering Dr. Chris Cadou Department of Aerospace Engineering Revised by Evandro Valente
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Levitation Review – Previously… Vehicle hovers when pressure force = vehicle weight D A Mg p = W p1 A D skirt hga p pe 2 2 = gap h Q p ρ - = 2 2 2 2 1 2 V gap e h V Q = e p p p - = 1 V1 p2, V2 2 1 e V p p - 0 pe, Ve Berno ulli Mass Conservation
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Levitation Review - Previously Hover height set by vehicle weight, geometry, and fan characteristic curve: D o A W Q p gap h 2 2 gap Q p h ρ ∆ = ( 29 ( 29 o gap gap h h < ( 29 ( 29 o gap gap h h ( 29 o gap h D A W D A W Increasing W lowers hgap Decreasing W increases hgap Fan Characteristic Skirt Characteristic
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Hovercraft Levitation & Propulsion Design Perspective General Knowledge about fans Fan characteristics Types of fans Axial fans Centrifugal fans When to use a centrifugal or axial fan Levitation based on Characteristic curves provided by manufacture Using your vehicle parameters to dictate axial or centrifugal Levitation based on Custom Propeller and Motor Set up Using your design parameters to guide your prop and motor choices Estimate Thrust for Propulsion Using a given prop and motor to see if it fits your design Levitation based on Custom Impeller and Motor Setup Using your design parameters to size your impeller and motor Centrifugal Fan Construction Some words about Motors Testing Set Up
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Definition: Fan, Blower, Pumps A fan or pump is defined as a device that Increases the energy of a fluid stream Through an increase in pressure and/or kinetic energy Commonplace Examples Pumps usually refer to a liquid working medium Fans & Blowers refer to air (what you will use with hovercraft) For this class, you are mainly interested in two types Axial fans Centrifugal fans
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Given a fan with fixed size and rotational velocity: How much pressure and flowrate can it produce? This is referred to as the “fan characteristic” curve Fan Characteristics
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Fan Characteristics Other important items: Power How much energy is consumed for fan to do its work? How much electric power (Pin ) is converted to mechanical power (Pout ) Efficiency Determines the best operating point for given design Work done on fluid/ work required to turn impeller
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System Characteristics What is the operation point of a fan when it is placed in a “system”? A system is taken to be the device through which the flow is forced The system provides the resistance to the moving fluid Pressure created by the fan is used to move the fluid The system “resistance” is caused by: acceleration of fluid Frictional losses For example, the hovercraft: ρ p h V A Q gap exit exit = = 2 2 2 = gap h Q p
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This note was uploaded on 10/05/2010 for the course ENES 100 taught by Professor Jacob during the Spring '08 term at Maryland.

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100F10_Propulsion and Fans_Update - Hovercraft Fluid...

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