Computational Analysis of the Blade Loading on Tip Clearance Effects
Limin Wang,
Yadong Liu,
Chengqin Li
Issue:
Volume 6, Issue 4, December 2020
Pages:
95-107
Received:
27 June 2020
Accepted:
26 October 2020
Published:
16 November 2020
Abstract: Gas turbines normally have the rotating and stationary parts. The rotational blades always need clearance to rotation. Blade tip clearance is one of the important parameters affecting performance, safety and stability of a gas turbine engine. However, it is difficult to measure the tip clearance accurately during the tests. The numerical studies are important methods to study the tip clearance effects. Tip clearance effects have been studied for a long time. However, there are still many aspects that are not fully understood and industries still don’t have a good way to perform design with minimum tip clearance losses. In the gas turbine design, the tip clearance considerations are very critical for both performance and reliability. In this paper, we perform the numerical study on the tip clearance impacts during the aerodynamic design, especially the blade loading through blade counts. The study found that the proper blade loading could reduce the tip clearance sensitivity and reduce the tip clearance losses. In the cases of reasonable number of blades, the effect of clearance on the total pressure loss and efficiency had a linear relationship. But in the cases of small number of blades, the effect of clearance on the total pressure loss and efficiency is no longer linear. The study helped turbine designers to consider blade loading and tip clearance together during the turbine design.
Abstract: Gas turbines normally have the rotating and stationary parts. The rotational blades always need clearance to rotation. Blade tip clearance is one of the important parameters affecting performance, safety and stability of a gas turbine engine. However, it is difficult to measure the tip clearance accurately during the tests. The numerical studies ar...
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Impact Mechanism of Interfacial Polymer Film Formation in Aqueous Quenchants
Logvynenko Peter,
Moskalenko Anatoly
Issue:
Volume 6, Issue 4, December 2020
Pages:
108-123
Received:
8 October 2020
Accepted:
9 November 2020
Published:
23 November 2020
Abstract: The results of studies of the cooling ability, rheological and surface-active properties of aqueous solutions of polyalkyleneglycol, sodium salt of carboxymethyl cellulose and polyacrylamide are presented. The choice of polymers is due to the problem of studying the mechanism of the cooling process in aqueous solutions of polymers. Comparison of the results of complex studies and video surveillance made it possible to propose a substantiated version of the mechanism of heat transfer during cooling of a metal sample in aqueous solutions of polymers. At the moment of shock boiling, a substance is formed in the wall layer, which is a nanosol (for PAG solutions) or a nanogassuspension (for Na-CMC and PAA). Under the action of a shock wave, it is directed from the heated metal surface to the interface between the polymer solution-vapor film, forming an interfacial polymer shock film. One of the stages of the shock mechanism of the formation of a polymer film is the adsorption increase in the polymer concentration on the surface of the bubbles formed during shock boiling; the next stage, the polymer shell of the bubbles, is spent on the formation of an interfacial polymer film. Heat fluxes and heat transfer coefficients are presented as a function of polymer concentration and surface temperature. The research results can be useful for assessing the effect of an interfacial polymer film on the ratio of the initial, first qcr1 and second qcr2 critical heat fluxes density, which determines the passage of heat transfer stages in water-polymer quenching media (WPQM).
Abstract: The results of studies of the cooling ability, rheological and surface-active properties of aqueous solutions of polyalkyleneglycol, sodium salt of carboxymethyl cellulose and polyacrylamide are presented. The choice of polymers is due to the problem of studying the mechanism of the cooling process in aqueous solutions of polymers. Comparison of th...
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Effect of Anisotropic Permeability on Thermosolutal Convection in a Porous Cavity Saturated by a Non-newtonian Fluid
Yovogan Julien,
Fagbemi Latif,
Koube Bocco Sèlidji Marius,
Kouke Dieudonné,
Degan Gérard
Issue:
Volume 6, Issue 4, December 2020
Pages:
124-131
Received:
13 November 2020
Accepted:
30 November 2020
Published:
16 December 2020
Abstract: In this paper, an analytical study is reported on double-diffusive natural convection in a shallow porous cavity saturated with a non-Newtonian fluid by using the Darcy model with the Boussinesq approximations. A Cartesian coordinate system is chosen with the x- and y- axes at the geometrical center of the cavity and the y’-axis vertically upward. The top and bottom horizontal boundaries are subject to constant heat (q) and mass (j) fluxes. The porous medium is anisotropic in permeability whose principal axes are oriented in a direction that is oblique to the gravity vector. The permeabilities along the two principal axes of the porous matrix are denoted by K1 and K2. The anisotropy of the porous layer is characterized by the permeability ratio K*=K1/K2 and the orientation angle φ, defined as the angle between the horizontal direction and the principal axis with the permeability K2. The viscous dissipations are negligible. Based on parallel flow approximation theory, the problem is solved analytically, in the limit of a thin layer and documented the effects of the physical parameters describing this investigation. Solutions for the flow fields, Nusselt and Sherwood numbers are obtained explicitly in terms of the governing parameters of the problem.
Abstract: In this paper, an analytical study is reported on double-diffusive natural convection in a shallow porous cavity saturated with a non-Newtonian fluid by using the Darcy model with the Boussinesq approximations. A Cartesian coordinate system is chosen with the x- and y- axes at the geometrical center of the cavity and the y’-axis vertically upward. ...
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