Sathiro

Solo disponible en BuenasTareas
• Páginas : 47 (11575 palabras )
• Descarga(s) : 0
• Publicado : 5 de marzo de 2011

Vista previa del texto
1
Introduction: Dimensional Analysis—Basic Thermodynamics and Fluid Mechanics

1.1 INTRODUCTION TO TURBOMACHINERY
A turbomachine is a device in which energy transfer occurs between a ﬂowing ﬂuid and a rotating element due to dynamic action, and results in a change in pressure and momentum of the ﬂuid. Mechanical energy transfer occurs inside or outside of the turbomachine, usually in asteady-ﬂow process. Turbomachines include all those machines that produce power, such as turbines, as well as those types that produce a head or pressure, such as centrifugal pumps and compressors. The turbomachine extracts energy from or imparts energy to a continuously moving stream of ﬂuid. However in a positive displacement machine, it is intermittent. The turbomachine as described above covers awide range of machines, such as gas turbines, steam turbines, centrifugal pumps, centrifugal and axial ﬂow compressors, windmills, water wheels, and hydraulic turbines. In this text, we shall deal with incompressible and compressible ﬂuid ﬂow machines.

1.2 TYPES OF TURBOMACHINES
There are different types of turbomachines. They can be classiﬁed as: 1. Turbomachines in which (i) work is done bythe ﬂuid and (ii) work is done on the ﬂuid.

Figure 1.1 Types and shapes of turbomachines.

2. Turbomachines in which ﬂuid moves through the rotating member in axial direction with no radial movement of the streamlines. Such machines are called axial ﬂow machines whereas ifthe ﬂow is essentially radial, it is called a radial ﬂow or centrifugal ﬂow machine. Some of these machines are shown in Fig. 1.1, and photographs of actual machines are shown in Figs. 1.2 –1.6. Two primary points will be observed: ﬁrst, that the main element is a rotor or runner carrying blades or vanes; and secondly, that the path of the ﬂuid in the rotor may be substantially axial,substantially radial, or in some cases a combination of both. Turbomachines can further be classiﬁed as follows: Turbines: Machines that produce power by expansion of a continuously ﬂowing ﬂuid to a lower pressure or head. Pumps: Machines that increase the pressure or head of ﬂowing ﬂuid. Fans: Machines that impart only a small pressure-rise to a continuously ﬂowing gas; usually the gas may be considered tobe incompressible.

Figure 1.2

Radial ﬂow fan rotor. (Courtesy of the Buffalo Forge Corp.)

Figure 1.3 Centrifugal compressor rotor (the large double-sided impellar on the right is the main compressor and the small single-sided impellar is an auxiliary for cooling purposes). (Courtesy of Rolls-Royce, Ltd.)

Figure 1.4Centrifugal pump rotor (open type impeller). (Courtesy of the IngersollRand Co.)