What is clearance in turbine?
Clearance, the gap between the turbine blade tip and the encompassing shroud, increases as a result of wear mechanisms and rubbing of the turbine blades on shroud. Increases in clearance cause larger specific fuel consumption (SFC) and loss of efficient air flow.
What are two types of clearance in a turbine?
What are two types of clearance in a turbine? Answer: Radial – clearance at the tips of the rotor and casing. Axial – the fore-and-aft clearance, at the sides of the rotor and the casing.
What is blade clearance and what is its use?
Blade tip clearance is the distance between the tip of a blade and the casing. This clearance is an essential parameter in turbomachinery design: too little clearance and the rotor will rub against the casing; too much clearance and the turbomachine loses efficiency by allowing the gas path to bypass the blades.
What tool is used to check turbine blade tip clearance?
Chivers [1] originally developed the FM capacitance probe to measure average tip clearance over a gas turbine compressor or turbine’s blades.
What is turbine and types?
The two most common types of reaction turbines are Propeller (including Kaplan) and Francis. Kinetic turbines are also a type of reaction turbine. Propeller Turbine. A propeller turbine generally has a runner with three to six blades. Water contacts all of the blades constantly.
What is meant by degree of reaction?
From Wikipedia, the free encyclopedia. In turbomachinery, Degree of reaction or reaction ratio (R) is defined as the ratio of the static pressure drop in the rotor to the static pressure drop in the stage or as the ratio of static enthalpy drop in the rotor to the static enthalpy drop in the stage.
What is radial clearance?
Radial internal clearance is defined as the total distance that one ring can be moved, relative of the other ring or basically the amount of “play” in the bearing. In spherical roller bearings this can be measured using a feeler cage between the roller and the outer ring raceway surface.
What is the pressure inside the turbine casing?
As in case of impulse turbine pressure throughout turbine is constant and equal to atmospheric pressure, so only energy available for turbine is kinetic energy of fluid. There is no change in pressure energy as it takes place in reaction turbine.
What are the three types of turbines?
There are 3 main types of impulse turbine in use: the Pelton, the Turgo, and the Crossflow turbine. The two main types of reaction turbine are the propeller turbine (with Kaplan variant) and the Francis turbine.
What are the two main types of turbine?
A turbine is a work producing device. Production of power is achieved by expanding a fluid. Mainly, there are two different types of turbines, steam and gas turbines.
Which turbine has highest efficiency?
Large Francis turbines are individually designed for each site to operate with the given water flow and water head at the highest possible efficiency, typically over 90% (to 99%). In contrast to the Pelton turbine, the Francis turbine operates at its best completely filled with water at all times.
What is degree of reaction turbine?
In case of turbines, both impulse and reaction machines, Degree of reaction (R) is defined as the ratio of energy transfer by the change in static head to the total energy transfer in the rotor i.e. In pumps, degree of reaction deals in static and dynamic head.
What is the tip clearance of a gas turbine?
The narrow clearance between the rotor (first set of blades) and the casing is visible. Tip clearance is the distance between the tip of a rotating airfoil and a stationary part. ^ Boyce, Meherwan P. (2002). Gas turbine engineering handbook. Gulf Professional Publishing. p. 365. ISBN 0-88415-732-6. Retrieved 2009-03-16. gas turbine tip clearance.
How is the clearance between blade and turbine case maintained?
The air is routed to flow through tubes surrounding the casing at each turbine stage. This air expands or contracts the turbine case and in doing so, it maintains the accurate clearance between the turbine case and the blade tip. This clearance should be maintained accurately which is essential for the engine efficiency and its performance.
How does the turbine clearance control system work?
An engine’s turbine clearance control system (TCCS) relies on turbine clearance control valves (TCCVs) to control this tip clearance by managing the thermal expansion of the turbine case that surrounds the turbine stages of the engine.
How are the casings of a steam turbine affected?
During transient and steady state operations of HP and IP units, the turbine casings are subject to steam conditions which develop thermal gradients as described above. In addition to thermally induced stresses, the casings are subject to stresses arising from primary loads such as pressure and loads transmitted from mating parts.