Surface Heat Transfer Fluctuations on a Turbine Rotor Blade Due to Upstream Shock Wave Passing

1989 ◽  
Vol 111 (2) ◽  
pp. 105-115 ◽  
Author(s):  
A. B. Johnson ◽  
M. J. Rigby ◽  
M. L. G. Oldfield ◽  
R. W. Ainsworth ◽  
M. J. Oliver
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Shock Waves ◽  
Rotor Blade ◽  
Transfer Rate ◽  
Turbine Rotor ◽  
Surface Heat ◽  
Transfer Rates ◽  
Surface Heat Transfer ◽  
Turbine Rotor Blade

A theoretical model to explain observed rapid large-scale surface heat transfer rate fluctuations associated with the impingement of nozzle guide vane trailing edge shock waves on a transonic turbine rotor blade is described. Experiments were carried out in the Oxford Isentropic Light Piston Cascade Tunnel using an upstream rotating bar system to simulate the shock wave passing. High-frequency surface heat transfer and pressure measurements gave rapidly varying, large, transient signals, which schlieren photography showed to be associated with the impingement of passing shock waves on the surface. Heat transfer rates varying from three times the mean value to negative quantities were measured. A simple first-order perturbation analysis of the boundary layer equations shows that the transient adiabatic heating and cooling of the boundary layer by passing shock waves and rarefactions can give rise to high-temperature gradients near the surface. This in turn leads to large conductive heat transfer rate fluctuations. The application of this theory to measured fluctuating pressure signals gave predictions of fluctuating heat transfer rates that are in good agreement with those measured. It is felt that the underlying physical mechanisms for shock-induced heat transfer fluctuations have been identified. Further work will be necessary to confirm them in rotating experiments.

Short Duration Measurements of Heat-Transfer Rate to a Gas Turbine Rotor Blade

1982 ◽  
Vol 104 (3) ◽  
pp. 542-550 ◽  
Author(s):  
H. Consigny ◽  
B. E. Richards
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Gas Turbine ◽  
Rotor Blade ◽  
Transfer Rate ◽  
Turbine Rotor ◽  
Turbulence Level ◽  
Flow Angle ◽  
Turbine Rotor Blade

The paper describes the results of an experimental study of the effect of Mach number, Reynolds number, inlet flow angle, and free-stream turbulence level on heat transfer rate to a gas turbine rotor blade. The measurements were made in the VKI short-duration isentropic light piston tunnel using thin film heat transfer gages painted on a machinable ceramic blade of 80 mm chord and 100 mm height. The tests were performed for three cascade inlet Mach numbers: 0.62, 0.92, 1.15; inlet unit Reynolds number was varied from 0.3 × 107 m−1 to 1.2 × 107 m−1; the inlet flow angle from 30 to 45 deg (for an inlet blade angle of 30 deg); the turbulence level from 0.8 percent to approximately 5 percent. The effect of changing these parameters on boundary layer transition and separation, on leading edge and average heat transfer to the blade was examined. For typical situations, experimental blade heat distributions were compared with boundary layer predictions using a two-equation closure model.

Liquid Crystal Visualization of Surface Heat Transfer on a Concavely Curved Turbulent Boundary Layer

1984 ◽  
Vol 106 (3) ◽  
pp. 619-627 ◽  
Author(s):  
J. C. Simonich ◽  
R. J. Moffat
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Large Scale ◽  
Surface Heat ◽  
Transfer Rates ◽  
Surface Heat Transfer ◽  
Experimental Heat ◽  
Surface Heat Transfer Coefficient ◽  
Transfer Measurement

An experimental heat transfer study on a concavely curved turbulent boundary layer has been performed. A new, instantaneous heat transfer measurement technique utilizing liquid crystals was used to provide a vivid picture of the local distribution of surface heat transfer coefficient. Large scale wall traces, composed of streak patterns on the surface, were observed to appear and disappear at random, but there was no evidence of a spanwise stationary heat transfer distribution, nor any evidence of large scale structures resembling Taylor-Gortler vortices. The use of a two-dimensional computation scheme to predict heat transfer rates in concave curvature regions seems justifiable.

Effect of Flow Exit Angle and Blade Height on the Temperature Distribution of a Typical Gas Turbine Rotor Blade

2012 ◽  
Vol 452-453 ◽  
pp. 502-506
Author(s):  
Esmail Poursaeidi ◽  
Maryam Mohammadi ◽  
Seyed Sina Khamesi
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Heat Transfer Rate ◽  
Direct Effect ◽  
Rotor Blade ◽  
Transfer Rate ◽  
Turbine Rotor ◽  
Exit Angle ◽  
Blade Height ◽  
Turbine Rotor Blade

One of the major factors which have important effects in turbine blade designing is temperature distribution and its heat transfer rate. The temperature distribution in blades depends on many factors; one of the most important ones is the geometry of the blades. In this paper by continuing some previous findings about the geometry[1], an optimized blade and a real one are compared from the thermally aspect view. Flow exit angle of the rotor blade and the blade height are two parameters which have direct effect on the heat transfer rate. The presented temperature distribution is solved based on the new flow exit angle of rotor blade. By optimizing the flow exit angle for the first time, the blade height is computed. By solving mathematically and thermodynamically relations and writing a solving code based on the finite volume method, the temperature and the heat transfer rate are computed numerically. These results shows the direct effect of flow exit angle on temperature distribution which can be used for upgrading the turbine efficiency.

scholarly journals Entropy Generation Measurement in a Laminar Turbine Blade Boundary-Layer

1997 ◽  
Author(s):  
John D. Wallace ◽  
Mark R. D. Davies
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Rate ◽  
Turbine Blade ◽  
Entropy Generation ◽  
Transfer Rate ◽  
Surface Heat ◽  
Entropy Generation Rate ◽  
Blade Surface ◽  
Surface Heat Transfer

This paper demonstrates a method of calculating the entropy generation rate in an incompressible laminar turbine blade boundary-layer from measurements of surface heat transfer rate. It is shown that the entropy generated by fluid friction in an incompressible blade boundary-layer is significantly less than that generated by heat transfer at engine representative temperature ratios. The centre blade in a low-speed linear cascade is electrically heated and isolated from the airflow with a bypass valve. Upon opening the valve the blade is transiently cooled and thin film heat transfer gauges, painted on machinable glass ceramic inserts mounted into the surface of the blade, are used to record blade surface temperature and surface heat transfer rate signals; local Nusselt numbers are then calculated. Non-dimensional temperature distributions are derived across the boundary-layer using the blade surface heat transfer rate and a similarity condition. The equation describing the local entropy generation per unit volume is then integrated through the boundary-layer at each chordwise measurement point on the blade surface.

Non-similar solutions for mixed convection along a wedge embedded in a porous medium saturated by a non-Newtonian nanofluid

2014 ◽  
Vol 24 (7) ◽  
pp. 1471-1486 ◽  
Author(s):  
Ali J. Chamkha ◽  
M. Rashad ◽  
Rama Subba Reddy Gorla
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Friction Factor ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Surface Heat ◽  
Content Type ◽  
Transfer Rates ◽  
Surface Heat Transfer

Purpose – The purpose of this paper is to present a boundary layer analysis for the mixed convection past a vertical wedge in a porous medium saturated with a power law type non-Newtonian nanofluid. Numerical results for friction factor, surface heat transfer rate and mass transfer rate have been presented for parametric variations of the buoyancy ratio parameter Nr, Brownian motion parameter Nb, thermophoresis parameter Nt, Lewis number Le and the power law exponent n. The dependency of the friction factor, surface heat transfer rate (Nusselt number) and mass transfer rate on these parameters has been discussed. Design/methodology/approach – This general non-linear problem cannot be solved in closed form and, therefore, a numerical solution is necessary to describe the physics of the problem. An implicit, tri-diagonal finite-difference method has proven to be adequate and sufficiently accurate for the solution of this kind of problems. Therefore, it is adopted in the present study. Variable step sizes were used. The convergence criterion employed in this study is based on the difference between the current and the previous iterations. When this difference reached 10−5 for all the points in the η directions, the solution was assumed to be converged, and the iteration process was terminated. Findings – The results indicate that as the buoyancy ratio parameter (Nr) and thermophoresis parameter (Nt) increase, the friction factor increases whereas the heat transfer rate (Nusselt number) and mass transfer rate (Sherwood number) decrease. As the Brownian motion parameter (Nb) increases, the friction factor and surface mass transfer rates increase whereas the surface heat transfer rate decreases. As Le increases, mass transfer rates increase. As the power law exponent n increases, the heat and mass transfer rates increase. Research limitations/implications – The analysis is valid for natural convection dominated regime. The combined forced and natural convection dominated regimes will be reported in a future work. Practical implications – The approach used is useful in optimizing the porous media heat transfer problems in geothermal energy recovery, crude oil extraction, ground water pollution, thermal energy storage and flow through filtering media. Originality/value – The results of the study may be of some interest to the researchers of the field of porous media heat transfer. Porous foam and microchannel heat sinks used for electronic cooling are optimized utilizing the porous medium. The utilization of nanofluids for cooling of microchannel heat sinks requires understanding of fundamentals of nanofluid convection in porous media.

The Effects of Localized Blade Endwall Suction on Secondary Flows and Heat Transfer

2010 ◽  
Author(s):  
Rebecca Hollis ◽  
Jeffrey P. Bons
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
High Surface ◽  
Surface Heat ◽  
Secondary Flows ◽  
Surface Shear Stress ◽  
Mean Velocity ◽  
Surface Shear ◽  
Surface Heat Transfer ◽  
High Heat Transfer

Two methods of flow control were designed to mitigate the effects of the horseshoe vortex structure (HV) at an airfoil/endwall junction. An experimental study was conducted to quantify the effects of localized boundary layer removal on surface heat transfer in a low-speed wind tunnel. A transient infrared technique was used to measure the convective heat transfer values along the surface surrounding the juncture. Particle image velocimetry was used to collect the time-mean velocity vectors of the flow field across three planes of interest. Boundary layer suction was applied through a thin slot cut into the leading edge of the airfoil at two locations. The first, referred to as Method 1, was directly along the endwall, the second, Method 2, was located at a height ∼1/3 of the approaching boundary layer height. Five suction rates were tested; 0%, 6.5%, 11%, 15% and 20% of the approaching boundary layer mass flow was removed at a constant rate. Both methods reduced the effects of the HV with increasing suction on the symmetry, 0.5-D and 1-D planes. Method 2 yielded a greater reduction in surface heat transfer but Method 1 outperformed Method 2 aerodynamically by completely removing the HV structure when 11% suction was applied. This method however produced other adverse effects such as high surface shear stress and localized areas of high heat transfer near the slot edges at high suction rates.

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