05-05-2011, 03:21 PM
ABSTRACT
A turbomachine is a device in which energy transferoccurs between a flowing fluid and a rotating elementdue to dynamic action, and results in a change inpressure and momentum of the fluid. Mechanicalenergy transfer occurs inside or outside of theturbomachine, usually in a steady-flow process.Turbomachines include all those machines that producepower, such as turbines, as well as those types thatproduce a head or pressure, such as centrifugal pumpsand compressors. The turbomachine extracts energyfrom or imparts energy to a continuously movingstream of fluid. However in a positive displacementmachine, it is intermittent.The turbomachine as described above covers a widerange of machines, such as gas turbines, steam turbines,centrifugal pumps, centrifugal and axial flowcompressors, windmills, water wheels, and hydraulicturbines. In this text, we shall deal with incompressibleand compressible fluid flow machines.In turbomachine problems (that its part rotates withhigh velocity in fluid domain), pressure, force values offluid flow on blades are so important for design. Whendesigners have a model of turbine blade, they want toknow how it will work, specially the moment andpropulsive force values supplied by it in fluidenvironment. More, they also want to learn thebehaviour of these turbine blades in fluid for theiroptimal design. Normally, engineers often do manyexperiments with some blade models for testing.Nowadays, with the development of numerical methodsand digital computer, we can simulate this kind ofproblem so fast and comfortably.
KEY WORDSPropeller, turbomachine, fan, pump, turbine.
BODY TEXT
1. Introduction
In this paper, we want to present a problem thatsimulates the behaviour of a propeller in fluidenvironment. For this purpose, finite element method(FEM) be used to analyse. With ANSYS/CFX software,the results obtained such as velocities, forces, moments,pressure are used for blades design and optimizationwork.The turbomachine as described above covers a widerange of machines, such as gas turbines, steam turbines,centrifugal pumps, centrifugal and axial flowcompressors, windmills, water wheels, and hydraulicturbines. Basing on this simulation method,turbomachine applications can be analyzed and appliedfor design optimization.
2. Description
2.1. Turbomachines Introduction
There are different types of turbomachines. They can beclassified as:• Turbomachines in which (i) work is done by the fluidand (ii) work is done on the fluid.• Turbomachines in which fluid moves through therotating member in axial direction with no radialmovement of the streamlines. Such machines arecalled axial flow machines whereas if the flow isessentially radial, it is called a radial flow orcentrifugal flow machine. Some of these machinesare shown in Fig. 1.1. Two primary points will beobserved: first, that the main element is a rotor orrunner carrying blades or vanes; and secondly, thatthe path of the fluid in the rotor may be substantiallyaxial, substantially radial, or in some cases acombination of both. Turbomachines can further beclassified as follows:o Turbines: Machines that produce power byexpansion of a continuously flowing fluid to alower pressure or head.o Pumps: Machines that increase the pressure orhead of flowing fluid.o Fans: Machines that impart only a smallpressure-rise to a continuously flowing gas;usually the gas may be considered to beincompressible.o Compressors: Machines that impart kineticenergy to a gas by compressing it and thenallowing it to rapidly expand. Compressors canbe axial flow, centrifugal, or a combination ofboth types, in order to produce the highlycompressed air.
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