An Advanced Method of Processing Liquid Crystal Video Signals From Transient Heat Transfer Experiments

1995 ◽  
Vol 117 (1) ◽  
pp. 184-189 ◽  
Author(s):  
Z. Wang ◽  
P. T. Ireland ◽  
T. V. Jones
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Film Cooling ◽  
Color Change ◽  
Transient Heat Transfer ◽  
Turbine Blade Cooling ◽  
Video Signals ◽  
Surface Heat Transfer Coefficient ◽  
Full Intensity ◽  
Cooling Passage

A new method of processing the liquid crystal color change data obtained from transient heat transfer experiments is presented. The approach uses the full-intensity history recorded during an experiment to obtain an accurate measurement of the surface heat transfer coefficient at selected pixels. Results are presented for a model of a turbine blade cooling passage with combined ribs and film cooling holes. The implementation of the technique and the advantages to be gained from its application are discussed.

An Advanced Method of Processing Liquid Crystal Video Signals From Transient Heat Transfer Experiments

1993 ◽  
Author(s):  
Zuolan Wang ◽  
Peter T. Ireland ◽  
Terry V. Jones
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Film Cooling ◽  
Colour Change ◽  
Transient Heat Transfer ◽  
Turbine Blade Cooling ◽  
Video Signals ◽  
Surface Heat Transfer Coefficient ◽  
Full Intensity ◽  
Cooling Passage

A new method of processing the liquid crystal colour change data obtained from transient heat transfer experiments is presented. The approach uses the full intensity history recorded during an experiment to obtain an accurate measurement of the surface heat transfer coefficient at selected pixels. Results are presented for a model of a turbine blade cooling passage with combined ribs and film cooling holes. The implementation of the technique and the advantages to be gained from its application are discussed.

A Technique for Processing Transient Heat Transfer, Liquid Crystal Experiments in the Presence of Lateral Conduction

2004 ◽  
Vol 126 (2) ◽  
pp. 247-258 ◽  
Author(s):  
John P. C. W. Ling ◽  
Peter T. Ireland ◽  
Lynne Turner
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Film Cooling ◽  
Cooling System ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Three Dimensions ◽  
Transient Heat Transfer ◽  
Adiabatic Wall ◽  
Full Intensity

New techniques for processing transient liquid crystal heat transfer experiment have been developed. The methods are able to measure detailed local heat transfer coefficient and adiabatic wall temperature in a three temperature system from a single transient test using the full intensity history recorded. Transient liquid crystal processing methods invariably assume that lateral conduction is negligible and so the heat conduction process can be considered one-dimensional into the substrate. However, in regions with high temperature variation such as immediately downstream of a film-cooling hole, it is found that lateral conduction can become significant. For this reason, a procedure which allows for conduction in three dimensions was developed by the authors. The paper is the first report of a means of correcting data from the transient heat transfer liquid crystal experiments for the effects of significant lateral conduction. The technique was applied to a film cooling system as an example and a detailed uncertainty analysis performed.

A Technique for Processing Transient Heat Transfer, Liquid Crystal Experiments in the Presence of Lateral Conduction

2003 ◽  
Author(s):  
John C. P. W. Ling ◽  
Peter T. Ireland ◽  
Lynne Turner
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Film Cooling ◽  
Cooling System ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Three Dimensions ◽  
Transient Heat Transfer ◽  
Adiabatic Wall ◽  
Full Intensity

New techniques for processing transient liquid crystal heat transfer experiment have been developed. The methods are able to measure detailed local heat transfer coefficient and adiabatic wall temperature in a three temperature system from a single transient test using the full intensity history recorded. Transient liquid crystal processing methods invariably assume that lateral conduction is negligible and so the heat conduction process can be considered one dimensional into the substrate. However, in regions with high temperature variation such as immediately downstream of a film-cooling hole, it is found that lateral conduction can become significant. For this reason, a procedure which allows for conduction in three dimensions was developed by the authors. The paper is the first report of a means of correcting data from the transient heat transfer liquid crystal experiments for the effects of significant lateral conduction. The technique was applied to a film cooling system as an example and a detailed uncertainty analysis performed.

Experimental Study of Heat Transfer Augmentation Near the Entrance to a Film Cooling Hole in a Turbine Blade Cooling Passage

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Gerard Scheepers ◽  
R. M. Morris
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Turbine Blade ◽  
Film Cooling ◽  
Surface Heat ◽  
Turbine Blade Cooling ◽  
Blade Cooling ◽  
Heat Transfer Augmentation ◽  
Cooling Hole ◽  
Cooling Passage

Film cooling is extensively used by modern gas turbine blade designers as a means of limiting the blade temperature when exposed to extreme combustor outlet temperatures. The following paper describes an experimental study of heat transfer near the entrance to a film cooling hole in a turbine blade cooling passage. Steady state heat transfer results were acquired by using a transient measurement technique in a 40 times actual rectangular channel, representative of an internal cooling channel of a turbine blade. Platinum thin film gauges were used to measure the inner surface heat transfer augmentation as a result of thermal boundary layer renewal and impingement near the entrance of a film cooling hole. Measurements were taken at various suction ratios, extraction angles, and wall temperature ratios with a main duct Reynolds number of 25,000. A numerical technique based on the resolution of the unsteady conduction equation, using a Crank–Nicholson scheme, is used to obtain the surface heat flux from the measured surface temperature history. Computational fluid dynamics predictions were also made to provide better understanding of the near-hole flow. The results show extensive heat transfer enhancement as a function of extraction angle and suction ratio in the near-hole region and demonstrate good agreement with a corresponding study. Furthermore it was shown that the effect of a wall-to-coolant ratio is of a second order and can therefore be considered negligible compared with the primary variables such as the suction ratio and extraction angle.o

Heat Transfer and Pressure Drop Correlations for Square Channels With 45 Deg Ribs at High Reynolds Numbers

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Huitao Yang ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Turbine Blade Cooling ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
High Reynolds ◽  
Cooling Passage

Systematic experiments are conducted to measure heat transfer enhancement and pressure loss characteristics on a square channel (simulating a gas turbine blade cooling passage) with two opposite surfaces roughened by 45 deg parallel ribs. Copper plates fitted with a silicone heater and instrumented with thermocouples are used to measure regionally averaged local heat transfer coefficients. Reynolds numbers studied in the channel range from 30,000 to 400,000. The rib height (e) to hydraulic diameter (D) ratio ranges from 0.1 to 0.18. The rib spacing (p) to height ratio (p/e) ranges from 5 to 10. Results show higher heat transfer coefficients at smaller values of p/e and larger values of e/D, though at the cost of higher friction losses. Results also indicate that the thermal performance of the ribbed channel falls with increasing Reynolds numbers. Correlations predicting Nusselt number (Nu) and friction factor (f¯) as a function of p/e, e/D, and Re are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+), p/e, and e/D.

scholarly journals Experimental Investigation of Heat Transfer in Two-Pass Coolant Passages With Ribs and Film Cooling Hole Ejection

2002 ◽  
Author(s):  
D. Chanteloup ◽  
A. Bo¨lcs
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Outer Wall ◽  
Reynolds Numbers ◽  
Thermochromic Liquid Crystal ◽  
Heat Transfer Characteristics ◽  
Surface Heat Transfer Coefficient ◽  
Staggered Arrangement ◽  
Cooling Hole ◽  
Surface Measurements

A study of flow in two stationary models of two-pass internal coolant passages is presented, which focuses on the heat transfer characteristics in the two-pass coolant channel. Heat transfer measurements were made with a transient technique using thermochromic liquid crystal technique to measure a surface temperature. The technique allows full surface heat transfer coefficient measurements on all the walls. The coolant passage model consisted of two square passages, each having a 20 hydraulic diameter length, separated by a rounded-tip web of 0.2 passage widths, and connected by a sharp 180 deg bend with a rectangular outer wall. Ribs were mounted on the bottom and top walls of both legs, with a staggered arrangement, and at 45 deg to the flow. The rib height and spacing were 0.1 and 1.0 passage heights, respectively. The measurements were obtained for Reynolds numbers of 25000, 50000 and 70000. One geometry is equipped with extraction holes to simulate holes for film cooling. Two series of holes are placed solely in the bottom wall, 4 holes are located in the bend, and 12 in the downstream leg. The global extraction through the holes was set to 30%, 40% and 50% of the inlet massflow. This paper presents new measurements of the heat transfer in the straight legs, and in the bend of the passage. It shows the influence of Reynolds number and extraction on full surface measurements and area averaged results.

Heat Transfer Analysis in a Modern DLN Combustor

2000 ◽  
Author(s):  
Giovanni Ferrara ◽  
Luca Innocenti ◽  
Giacomo Migliorini ◽  
Bruno Facchini ◽  
Anthony J. Dean
Keyword(s):  
Heat Transfer ◽  
Combustion Chamber ◽  
Film Cooling ◽  
Thermal Flux ◽  
Calculation Model ◽  
Heat Transfer Analysis ◽  
Turbine Blade Cooling ◽  
Air Flows ◽  
Critical Components ◽  
Cooling Air

The increasingly stringent emissions standards in recent years have mandated low gas turbine emissions and thus changed the approach to combustion chamber design. In particular, lean burners based on highly premixed fuel-air flows have become more important. These combustors, termed Dry Low NOx (DLN), can now achieve emissions of 25 ppm and below in commercial operation. This development together with the inlet turbine temperature increase has resulted in less cooling air for combustion chambers and turbine blade cooling systems. The designer now needs to optimise cooling air flows that control the wall temperature of the components that confine the hot gases. Moreover, much of the air coming from the compressor is used to premix the fuel and only a smaller fraction is now available for cooling processes. In annular combustor configurations the air available for cooling the combustion chamber walls sometimes also has to cool the first stage nozzle. So the pressure loss along the combustor cooling passages has to be limited in order to assure a suitable supply pressure for these downstream cooling passages. We analysed the cooling air flow around the liner of an annular combustion chamber and we investigated the thermal flux and friction losses. In this paper we show the development of a calculation model that allows the critical components heat transfer analysis of a typical annular combustion chamber. The code developed is based on the generalised 1–D flow treatment. We have used experimental correlations for convection, film cooling and impingement borrowed from works found in literature. The code is provided with a graphical interface that helps the user during the calculation. This code was used in practical application to optimize the PGT5B combustion chamber cooling.

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