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Heat Transfer

1981;():V003T09A001. doi:10.1115/81-GT-37.
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The combined heat transfer/heat conduction tests were performed by adopting brass and acrylic resin as a material for the full-coverage film-cooled wall. The 30 deg-slant injection holes are distributed in the staggered array with the two kinds of hole pitches, which are five and ten hole diameters in the streamwise and lateral directions. The free stream velocity was varied as 10 and 20 m/s, respectively, and the measurement of wall surface temperature was made with the help of liquid crystal as a temperature indicator. From these experiments, basic data are given for the head loss coefficient across the FCFC plate as well as the local and averaged cooling effectiveness for each material tested. Finally the heat transfer characteristics of FCFC are discussed from the heat balance of unit hole element and a technique for higher cooling effectiveness is demonstrated.

Topics: Cooling , Film cooling
Commentary by Dr. Valentin Fuster
1981;():V003T09A002. doi:10.1115/81-GT-38.
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The local heat transfer coefficient of full-coverage film-cooled wall has been measured by using the law of analogy to mass transfer. For this experiment, the technique of sublimation of naphthalene was used. The geometric shape of FCFC plate and the experimental condition were the same as those in Part 1. From these experiments, the effects of the mass flux ratio and non-dimensional injection wall temperature ratio on the local Stanton number are made clear and it is confirmed experimentally that the local Stanton number is a linear function of non-dimensional temperature ratio as expected from the analysis. Furthermore, the local heat transfer coefficient on the backside surface has been obtained and a technique for the improvement of cooling effectiveness is discussed.

Commentary by Dr. Valentin Fuster
1981;():V003T09A003. doi:10.1115/81-GT-75.
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Short pin fins are often used to increase the heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).

Commentary by Dr. Valentin Fuster
1981;():V003T09A004. doi:10.1115/81-GT-76.
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An analytical model for the prediction of cooling air flow characteristics (mass flow rate and internal pressure distribution) in gas turbine components is discussed. The model addresses a number of basic flow elements typical to gas turbine components such as orifices, frictional passages, labyrinth seals, etc. Static bench test measurements of the flow characteristics were in good agreement with the analysis. For the turbine blade, the concept of equivalent pressure ratio is introduced and shown to be useful for predicting (1) the cooling air flow rate through the rotor blade at engine conditions from the static rig and (2) cooling air leakage rate at the rotor serration at engine conditions. This method shows excellent agreement with a detailed analytical model at various rotor speeds. A flow calibration procedure preserving flow similarity for blades and rotor assemblies is recommended.

Commentary by Dr. Valentin Fuster
1981;():V003T09A005. doi:10.1115/81-GT-77.
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Two-dimensional arrays of circular jets of air impinging on a heat transfer surface parallel to the jet orifice plate are considered. The air, after inpingement, is constrained to exit in a single direction along the channel formed by the surface and the jet plate. The downstream jets are subjected to a crossflow originating from the upstream jets. Experimental and theoretical results obtained for streamwise distributions of jet and crossflow velocities are presented and compared. Measured Nusselt numbers resolved to one streamwise hole spacing are correlated with individual spanwise row jet Reynolds numbers and crossflow-to-jet velocity ratios. Correlations are presented for both inline and staggered hole patterns including effects of geometric parameters: streamwise hole spacing, spanwise hole spacing, and channel height, normalized by hole diameter. The physical mechanisms influencing heat transfer coefficients as a function of flow distribution and geometric parameters are also discussed.

Commentary by Dr. Valentin Fuster
1981;():V003T09A006. doi:10.1115/81-GT-88.
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Selected portions of the first-stage stationary inlet nozzle, shroud, and rotor of the AiResearch TFE 731-2 turbine were instrumented with thin-film heat-transfer gages and heat-flux measurements were performed using a shock tunnel as a source of high-temperature, high-pressure gas. Experiments were performed over a range of Reynolds numbers, based on mid-annular stator chord, from 1.6 × 105 to 3.1 × 105 and corrected speeds from approximately 70 to 106 percent. The full-stage heat-flux results are compared to our previous measurements obtained with a stator only, in the absence of a rotor. The previous results are in good agreement with the full-stage data for the tip end-wall region, but they are significantly less than the full-stage results for the stator airfoil. Pressure measurements were obtained throughout the model and these results are shown to be in excellent agreement with the steady-state rig data supplied to us by AiResearch for this turbine. Heat-flux measurements are also presented for the stationary shroud as a function of rotor mid-annular chord. The shroud heat flux data are shown to be in excess of the rotor blade results. Rotor-tip heat flux measurements are likewise shown to be slightly greater than the shroud results.

Commentary by Dr. Valentin Fuster
1981;():V003T09A007. doi:10.1115/81-GT-89.
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The two-dimensional, finite-difference boundary-layer code, STAN5, is the primary tool used at the NASA-Lewis Research Center for predicting turbine blade gas-side heat-transfer coefficients. A number of modifications have been made to the program to enhance its usefulness for these calculations. Experience in using STAN5 has identified some problems in the program that can be treated through program input, without modifying the program. These include the presence of a small separation bubble near the leading edge, and the effect of full-coverage film cooling on transition to turbulence. Some of the techniques used to treat these problems are described.

Topics: Boundary layers
Commentary by Dr. Valentin Fuster
1981;():V003T09A008. doi:10.1115/81-GT-90.
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The General Electric Company in conjunction with the Air Force Aero Propulsion Laboratory is involved in a program to more fully understand air-cooled turbine blade distress mechanisms. As part of this program, the tolerance effects of design parameters on the predicted blade temperature were evaluated. Turbine blade temperature predictions are based on the assumption that all blades conform to the nominal design intent in terms of blade geometry and operating conditions. Since the geometry and operating conditions of each blade may vary from these assumptions, the actual blade life may be significantly different from that calculated, based on the nominal design intent. This study analyzed the blade temperature sensitivity of a single stage high pressure turbine blade to variations in most of the design variables. The effect on blade metal temperature of each variable was assessed individually and the cumulative effect of changing several variables simultaneously was also determined. Finally, an equation was obtained from this study that can be used to predict the cumulative effect on blade temperatures in a given blade by knowing only the single-variable sensitivities.

Commentary by Dr. Valentin Fuster
1981;():V003T09A009. doi:10.1115/81-GT-91.
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Assuming the local adiabatic wall temperature equals the local total temperature in a low speed coolant mixing layer, integral conservation equations with and without the boundary layer effects are formulated for the mixing layer downstream of a single coolant injection hole oriented at a 30 degree angle to the crossflow. These equations are solved numerically to determine the center-line local adiabatic wall temperature and the effective coolant coverage area. Comparison of the numerical results with an existing film cooling experiment indicates that the present analysis permits a simplified but reasonably accurate prediction of the centerline effectiveness and coolant coverage area downstream of a single hole crossflow stream wise injection at 30-deg inclination angle.

Commentary by Dr. Valentin Fuster
1981;():V003T09A010. doi:10.1115/81-GT-92.
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An analysis is presented to investigate the time-mean characteristics of the laminar boundary layer near an axisymmetric stagnation point when the velocity of the oncoming flow relative to the body oscillates. Different solutions are obtained for the small and high values of the reduced frequency parameter. Numerical solutions for the velocity and temperature functions are presented and the wall values of the velocity gradients and temperature gradients are tabulated.

Commentary by Dr. Valentin Fuster
1981;():V003T09A011. doi:10.1115/81-GT-93.
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Commercially available elements of a composite consisting of a plastic sheet coated with liquid crystal, another sheet with a thin layer of a conducting material (gold or carbon), and copper bus bar strips were evaluated and found to provide a simple, convenient, accurate, and low-cost measuring device for use in heat transfer research. The particular feature of the composite is its ability to obtain local heat transfer coefficients and isotherm patterns that provide visual evaluation of the thermal performances of turbine blade cooling configurations. Examples of the use of the composite are presented.

Commentary by Dr. Valentin Fuster
1981;():V003T09A012. doi:10.1115/81-GT-94.
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In order to investigate the unsteady effect on transition in film cooling, an 11-m long Ludwieg Tube, consisting of a test section placed between the high pressure and low pressure sections of a shock tube, has been constructed. With this device, a controlled unsteady, low subsonic flow lasting for a period of several milliseconds is obtained. The transition Reynolds Number is determined from the output of thin film heat flux transducers having a response time of a fraction of a microsecond. The results indicate that, in the case of flow without gas injection into the boundary layer, the transition Reynolds Number is one order of magnitude smaller than the critical Reynolds Number for steady wedge flow with the same pressure gradient. With injection, the transition Reynolds Number is small near the injection slot; far downstream, it increases asymptotically to the value for flow without injection.

Commentary by Dr. Valentin Fuster
1981;():V003T09A013. doi:10.1115/81-GT-107.
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Detailed examination of flow measurements over concave pressure surfaces suggests that interaction of Taylor-Goertler vorticity with mainstream turbulent exerts only limited influence in enhancing laminar boundary-layer heat transfer. While transition is primarily controlled by the Launder laminarisation criterion, the Goertler number at which it subsequently occurs is not solely determined by turbulence intensity. Adoption of K >2.5.10 ± as a design criterion for the pressure surfaces of turbine blades would appear to have significant advantages in terms of reduced heat transfer, increased lift, and lower aerodynamic drag.

Commentary by Dr. Valentin Fuster

Electric Power

1981;():V003T10A004. doi:10.1115/81-GT-31.
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A new 100 MW gas turbine has been designed for electric power generation for either simple cycle or combined cycle applications. This paper describes the basis for design, new design features, performance, and test program.

Topics: Gas turbines
Commentary by Dr. Valentin Fuster
1981;():V003T10A005. doi:10.1115/81-GT-32.
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The Westinghouse 501D combustion turbine engine is the latest in a long line of Westinghouse designed and manufactured large single shaft heavy duty gas turbines designed especially for 60 Hz utility or industrial service. This 100 MW engine is described along with the design techniques utilized and the evolutionary changes made from previous engines. Also described are the component, shop, and field test conducted to bring the engine to fruition.

Commentary by Dr. Valentin Fuster
1981;():V003T10A007. doi:10.1115/81-GT-64.
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Combustion tests of methanol were conducted on a 26-MW gas turbine for a period of 523 total hours. The methanol fueled gas turbine was operated in tandem with an identical gas turbine fueled with distillate (Jet A). Emissions and performance data were recorded and hot section inspections were carried out on both machines periodically during the test program. A comparison of data recorded during the test program clearly indicates that methanol is a superior fuel for gas turbines.

Commentary by Dr. Valentin Fuster
1981;():V003T10A010. doi:10.1115/81-GT-155.
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A brief presentation of the basic heat transfer equations for blade cooling is presented. Various cooling schemes have been developed over the past twenty years utilizing air as the cooling fluid. The mathematical models have subsequently predicted cooling schemes for the air cooling with little consideration for two phase fluids. This paper is written to describe the research needs for utilizing steam as a cooling fluid in a reheat-gas-turbine combined cycle system. The basic heat transfer equations are derived and discussed with regard to implementing the steam blanket cooling mechanism. The steam injection and dispersion problem is discussed, along with the need for future research in using steam as a viable cooling technique.

Commentary by Dr. Valentin Fuster

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