The velocity profile of water flow in a pelton turbine bucket can be assumed to have a velocity similar to the velocity profile of flow over circular cylinder with a free stream velocity u. The stage velocity triangles are shown in fig 1, which also includes the case of a 50% reaction turbine for comparison. Very simple kaplan turbine design durham university. Velocity triangles for the jet striking the bucket from the impulsemomentum theorem, the force with which the jet strikes. Velocity diagram for axial flow turbines watch more videos at videotutorialsindex. The fluid is accelerated by a row of rotating airfoils or blades the rotor and diffused by a row of stationary blades the stator. A centrifugal pump impeller has an external diameter of 12 inches and a discharge area of 1. In turbomachinery, a velocity triangle or a velocity diagram is a triangle representing the various components of velocities of the working fluid in a turbomachine. It is not uncommon to have pressure ratios in industrial gas turbines in the 17 to 20. Evolution from francis turbine to kaplan turbine wikipedia. The moving blades of impulse turbines do not have a change in flow area.
Now, let this turbine be made up of parsons stages. Boyce, in gas turbine engineering handbook fourth edition, 2012. Velocity triangle for moving blade of an impulse turbine. At exit from the runner, the flow is shown leaving the runner without a whirl velocity, i. The shape of the moving blades however is not the same for impulse and reaction turbines. In this case the tangential load of the blade is created by impulsive force leading to the specification of impulse stage. Velocity triangles in moving curved plate duration. The gas is turned by the rotor and exits, relative to the rotor, at velocity v r2. The analysis will be carried out at the mean height of the blade. An axialflow compressor compresses its working fluid by first accelerating the fluid and then diffusing it to obtain a pressure increase chapter 7.
Velocity triangles are used to illustrate flow conditions. The turbine rotor then extracts work from the flow by removing the kinetic energy associated with the swirl velocity. Elementary analysis of axial turbines too begins with velocity triangles. Velocity triangle showing the notation and conventions used in this work. The principal disadvantages of the freevortex approach to turbine design are that the model is. Gas with an absolute velocity c 1 making an angle a 1, angle measured from the axial. Fundamentals of fluid mechanics chapter 12 pumps and turbines. It adds swirl to the flow, converting internal energy into kinetic energy. Velocity triangles in fluid mechanics and machinery unsymmetrical vane. In the second blade row, swirling kinetic energy is extracted from the. That is, the blade pushes and turns the fluid in the direction of the blade motion, thereby doing work on the fluid.
The appropriate velocity triangles are shown in figure 12. Velocity triangles example april 12, 2012 mechanical and aerospace engineering department florida institute of technology d. Velocity triangles turbine dynamics mechanics free. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. The inlet velocity triangle the outlet velocity triangle at the inlet there is no component of absolute velocity in the direction of rotation. Velocity triangles example velocity triangles example april 12, 2012. Velocity triangles in turbomachinery linkedin slideshare. The torque and hence the power is proportional to the change in the tangential component of the absolute velocity. Figure 3 velocity triangle v1, v2 absolute velocities at inlet and outlet. Fundamentals of fluid mechanics chapter 12 pumps and. Let this be the entry velocity of steam in a given stage refer to comment no. Figure 2 depicts typical velocity triangles in turbine mode. Classification of turbines the hydraulic turbines can be classified based on type of energy at the inlet, direction of flow through the vanes, head available at the inlet, discharge through the vanes and specific speed. Velocity triangles for turbine and compressor design.
Velocity triangle for moving blade of an impulse turbine 1. Gas exits the stationary turbine nozzle guide vanes at absolute velocity v a1. The relative velocity w or v of the fluid these velocities are related by the following wellknown vector equation. Combining v 1 with blade velocity u 1 gives relative velocity v r1 at inlet, inclined at angle. Now let the jet glides over the inside surface and leaves the blade at d, as shown in fig. Now different turbines arrangements are taking place especially for large and medium size turbines. Velocity triangles can be used to calculate the basic performance of a turbine stage. With this background, now calculate the generation of velocity in each stage. Impulse turbines are simple devices where the steam expands in or through the nozzle, and the heat released through the pressure drop associated with the nozzle or comparable device imparts velocity to the steam.
What is the difference in velocity triangles of impulse. Pdf day 25 solved important velocity triangles and. Very simple kaplan turbine design grant ingram 30th january 2007 nomenclature b blade height g gravitational acceleration h head k loss coe. Herewith we have shared the important gate civil engineering notes pdf for the topic of velocity triangles and specific speed of pumps and turbines download pdf, 399kb share this.
How to draw a velocity triangle for various pumps or. That is, the blade pushes and turns the fluid in the direction of the blade motion, thereby doing. Velocity triangles for both impulse and reaction turbines and the force on the blades references for impulse and reaction turbines with worked examples. In the last lecture we discussed the basic mechanisms of energy exchange in compressors and drew some simple velocity triangles to show how we go from the stationary coordinate system to one in the moving blades. Relative to the rotor, the velocity of the gas as it impinges on the rotor entrance is v r1. In the turbine, inlet passage area is greater than the outlet. Velocity triangles example velocity triangles example april 12, 2012 mechanical and aerospace engineering department 2. We can apply the same analysis techniques to a turbine, figure 12. Analytical study on flow through a pelton turbine bucket. First steam turbine and history of steam turbines historically, the first steam turbine of which we have proof was built by heron of alexandria around 175 bc, which consisted of a metal sphere with two nozzles at their poles and oriented in the same direction where the steam escaped. Based on the velocity triangles at the entrance or exit. This relationship is illustrated in the velocity parallelogram of a liquid particle.
Velocity triangles may be drawn for both the inlet and outlet sections of any turbomachine. Boyce, in combined cycle systems for nearzero emission power generation, 2012. Thus the process in turbine blades can bedescribedas anaccelerating. Velocity triangles turbine physical sciences free 30. After considering the results of these first calculations, a. How to draw a velocity triangle for various pumps or turbines quora. Velocity triangles two reference frames to use for fluid velocity engines blades. Study on turbines with different inlet width for an orc process with an electrical work output of 3. The velocity diagram will show clear symmetry in the relative frame. The velocity triangles for a turbomachine contain the following three components. The turbine rotor then extracts work from the flow by removing the kinetic energy associated with the swirl. Consider a steam jet entering a curved blade after leaving the nozzle at c.
Vu1, vu2 tangential component of absolute velocities at inlet and outlet. Francis turbine is a mixed hydraulic turbine the inlet velocity has radial and tangential components while the kaplan turbine is an axial hydraulic turbinethe inlet velocity has only axial velocity component. The corresponding status of the flow is described by the flow velocities. Lec11 basic concept of turbine, velocity diagram duration. Herewith we have shared the very important previous year gate civil engineering solved questions with detailed solutions. They do not therefore change the velocity of the steam but only change its direction. Combination turbines in the past it was either reaction or impulse turbines. Air approaches rotor blade with absolute velocity v 1 at an angle. The opposite occurs in the compressor, as shown infig. Velocity triangles free download as powerpoint presentation.
The peripheral whirl tangential velocity u of a rotor blades 2. The impulse turbine is the simplest type of turbine. Velocity of water at outlet of runner is very high 315% of net working head, for high specific speed it is 45% in case of kaplan turbine, by employing draft tube recovers this wasted ke is utilized which increases efficiency of the turbine. Velocity diagram for axial flow turbines watch more videos at lecture by. The blades are bent backwards so that the direction of the relative velocity at the discharge surface makes an angle of 145 degrees with the tangent to this surface drawn in the direction of the impeller rotation. Preliminary design and optimization of axial turbines. The magnitude and direction of the absolute velocity at exit from the rotor c 3 at an angle a 3 are found by vectorial addition of u to the relative velocity v 3. The velocity triangle is the vectorial representation of kinematic movement.
Turbines are sometimes differentiated on the basis of the type of inlet flow, whether the inlet velocity is in axial direction, radial direction or a combination of both. Curtis stage tworow velocitycompounded impulse followed by series of rateau pressurecompounded impulse stages. Velocity triangles and specific speed of pumps and turbines fluid mechanics. Axialflow compressors an overview sciencedirect topics.