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.

Turbulent spot flow topology and mechanisms for surface heat transfer

2008 ◽  
Vol 612 ◽  
pp. 81-105 ◽  
Author(s):  
D. R. SABATINO ◽  
C. R. SMITH
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Surface Heat ◽  
Heated Plate ◽  
Surface Shear Stress ◽  
Turbulent Spot ◽  
Flow Topology ◽  
Turbulent Spots ◽  
Surface Heat Transfer

The properties of artificially initiated turbulent spots over a heated plate were investigated in a water channel. The instantaneous velocity field and surface Stanton number were simultaneously established using a technique that combines particle image velocimetry and thermochromic liquid crystal thermography. Several characteristics of a spot are found to be similar to those of a turbulent boundary layer. The spacing of the surface heat transfer streak patterns within the middle or ‘body’ of a turbulent spot are comparable to the low-speed streak spacing within a turbulent boundary layer. Additionally, the surface shear stress in the same region of a spot is also found to be comparable to a turbulent boundary layer. However, despite these similarities, the heat transfer within the spot body is found to be markedly less than the heat transfer for a turbulent boundary layer. In fact, the highest surface heat transfer occurs at the trailing or calmed region of a turbulent spot, regardless of maturity. Using a modified set of similarity coordinates, instantaneous two-dimensional streamlines suggest that turbulent spots entrain and subsequently recirculate warm surface fluid, thereby reducing the effective heat transfer within the majority of the spot. It is proposed that energetic vortices next to the wall, near the trailing edge of the spot body, are able to generate the highest surface heat transfer because they have the nearest access to cooler free-stream fluid.

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.

The Research on the Key Factor Affect the Precision in Stress Analysis for the Rotor of Steam Turbine

2013 ◽  
Vol 275-277 ◽  
pp. 83-86
Author(s):  
Chun Lin Zhang ◽  
Nian Su Hu ◽  
Wen Yang ◽  
Jian Mei Wang ◽  
Min Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Numerical Calculation ◽  
Transfer Coefficient ◽  
Stress Analysis ◽  
Surface Heat ◽  
Flow State ◽  
Surface Heat Transfer ◽  
Surface Heat Transfer Coefficient ◽  
Key Factor

With the development of the power grid, the proportion of large capacity unit is increasing rapidly. It requires a more in-depth study on the reliability of the unit, especially for the unit adjusting the peak. This paper concerned on the research of the surface heat transfer coefficient, which is the key factor affect the precision in thermal stress analysis. The surface heat transfer coefficient is obtained via the numerical calculation for the steam’s flow state and the transient heat transfer between rotor. This paper mainly describes the steam’s flow state and the transient heat transfer with the steam seal, and the results show that the direct numerical calculation is resultful in this subject.

scholarly journals An Experimental Study on the Aerodynamics and the Heat Transfer of a Suction Side Film Cooled Large Scale Turbine Cascade

1999 ◽  
Author(s):  
Wolfgang Ganzert ◽  
Leonhard Fottner
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Film Cooling ◽  
Total Pressure ◽  
Large Scale ◽  
Suction Side ◽  
Surface Heat ◽  
Two Dimensional ◽  
Turbine Cascade ◽  
Surface Heat Transfer

As a part of a more complex research program systematic isothermal investigations on the aerodynamics and heat transfer of a large scale turbine cascade with suction side film cooling were carried out. The film cooling through a row of holes at forty percent chord length on the suction side was supplied by a large plenum chamber. Two injection geometries were hitherto tested and evaluated: cylindrical holes with thirty respectively fifty degrees axial inclination angle and no lateral inclination. Typical engine conditions for the Mach and Reynolds number as well as the inlet turbulence level were maintained. The aerodynamic studies are based on steady state pressure measurements. The static profile pressure distribution together with oil-and-dye flow visualisation gives information on the surface flow conditions and boundary layer development especially in the near hole region. The measured data also comprise local and integral total pressure loss coefficients obtained by pressure probe traversing at mid span downstream of the cascade. The heat transfer examination set-up is based on the steady state liquid crystal technique using a compound of a thermochromic sheet combined with an electrical surface heating layer attached on an adiabatic blade corpus. Two dimensional pseudo colour plots are used for the documentation of the local surface heat transfer coefficient distribution and hot spot estimation. Laterally averaged and statistically analysed data of the surface heat transfer is applied in overall heat transfer examinations. All this data is used for a joint aerodynamic flow and surface heat transfer optimisation of a blowing configuration in suction side film cooled turbine cascade. The most important conclusions can be summarised as follows: Aiming at an optimised design of cylindrical film cooling configurations the axial inclination of the holes should be kept low thus diminishing the suction peak value at the cooling position in the profile pressure distribution and decreasing the mainstream deceleration area upstream of the jets. This also leads to reduced total pressure losses. Through the high influence of the blowing on the aerodynamics the flow in the near hole mixing region is highly three-dimensional. This shows significant effects in the two-dimensional surface distribution and the laterally averaged heat transfer coefficient. Oil-and-dye pictures confirm the observations qualitatively.

Sign in / Sign up

Export Citation Format

Share Document