How shroud presence/absence at turbine rotary influences onto its appearance and efficiency loss

Аuthors

Krylov B. A.^*, Barykin I. Y.^**

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: agulnik@mai.ru
**e-mail: igor6fhsrby@yandex.ru

Abstract

The way for calculating of how gaps and several parameters influence on to an efficiency loss of shroud-free turbine is presented. The mean diameter of the turbine is varied by (20 times, blades height by (36 times, profile chord by (5 times, other parameters are varied in a wide range.
Graphical and mathematical relationships between efficiency loss and reduced complex parameter are presented for the shroud-free rotary.
We try to apply the relationship obtained for shroud-free rotary to the rotary with the shroud, but our attempt is failed.
We analyze works performed by K.M. Popov, M.Kh. Mukhtarov, et al., (CIAM) where it is examined of how reduced radial gap influences onto efficiency loss under shroud presence/absence at turbine rotary. It is shown that such approach describes improperly the picture for flows and efficiency loss in the turbines.
By using the results of experiment-calculated investigations for turbines rotary with/without the shroud we develop the procedure for considering of how shroud presence/absence influences onto stage appearance and efficiency losses in it. The procedure is based on the existed generalized relationships according to two parameters: efficiency loss and complex reduced parameters, if admission is equal to 1.
By means of the presented procedure it is shown that shroud presence/absence at the turbine rotary varies efficiency loss and complex reduced parameter.
On the base of the regression equations generated for the blade of constant height, we reveal the relationships for efficiency loss in the turbine stage for a rotary with/without shroud. It is shown that during calculations the limit (choking) gap should be considered.

Keywords:

axial turbine stages, rotary with/without shroud, gaps

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