PREDICTION OF CARRY- OVER COEFFICIENT FOR FLUID FLOW THROUGH TEETH ON ROTOR LABYRINTH SEALS USING COMPUTATIONAL FLUID DYNAMICS

Ahmed, Dr.SabaYassoub; Abass, Dr.BasimAjeel; Hamza, NehadAbd-Allah

	PREDICTION OF CARRY- OVER COEFFICIENT FOR FLUID FLOW THROUGH TEETH ON ROTOR LABYRINTH SEALS USING COMPUTATIONAL FLUID DYNAMICS
Iraqi journal of mechanical and material engineering
Article 1, Volume 14, Issue 3, 2014, Pages 346-366
Authors
Dr.SabaYassoub Ahmed; Dr.BasimAjeel Abass; NehadAbd-Allah Hamza
Abstract
The design of the labyrinth seals depends on two main factors, namely, the reduction of leakage loss and the avoidance of rotor system instability. The most important parameter affecting the prediction of leakage mass flow rate of fluid through the labyrinth seal, namely, the carry over coefficients. Hence the computational fluid dynamics (CFD) and model has been used to predict the carry-over coefficient of flow through teeth on rotor straight through labyrinth seal. The mathematical model proposed through this work has been solved using the finite volume technique using a FLUENT commercial computer program. The effect of turbulence, seal geometry such as (teeth width, clearance, and pitch cavity) and shaft rotational speed have been taken into consideration. A prediction equation for the carry-over coefficient of the labyrinth seal has been proposed through this work. The prediction equation of carry over coefficient has been found to be a function of (C/S), (W/S) and Reynolds number. It can be concluded from the results that obtain here that the carry over coefficient which describe the labyrinth seal efficiency is highly affected by clearance to pitch ratio (C/S) , while the tooth with to pitch ratio (W/S) has a secondary effect on carry over coefficient. The results obtained show that the carry over coefficient is increased about 42% with increasing of the (C/S) from (0.0075 to 0.0375). While this coefficient is decreased by 9% at Reynold’s number more than 8000 with increasing of (W/S) from ( 0.0075) to (0.5). The effect of rotation has been studied on the carry over coefficient; therefore, the results showed that the carry over coefficient decreases with 10% after a certain value of rotation which is equal to (10000 rpm).Verification for the prediction models of the present work has been carried out by comparing some of the results obtained through this work with the experimental results published by Scharrer (1988) , Eser (2004) and the CFD analysis of Vamshi (2011). The results obtained through the present work found to be in a good agreement with the results of other workers.
Keywords
Labyrinth seal; Carry; over coefficient; CFD

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