Mainstream Temperature Research Articles

Sensitivity of the Overall Effectiveness to Film Cooling and Internal Cooling on a Turbine Vane Suction Side

The overall cooling effectiveness for a turbine airfoil was quantified based on the external surface temperature relative to the mainstream temperature and the inlet coolant temperature. This can be determined experimentally when the model is constructed so that the Biot number is similar to that of engine components. In this study, the overall cooling effectiveness was experimentally measured on a model turbine vane constructed of a material deigned to match Bi for engine conditions. The model incorporated an internal impingement cooling configuration. Overall cooling effectiveness and adiabatic film effectiveness were measured downstream of a single row of round holes positioned on the suction side of the vane. Experiments were conducted to evaluate the cooling effects of internal cooling alone, and then the combined effects of film cooling and internal cooling for a range of coolant flow rates. While the adiabatic film effectiveness decreased when using high momentum flux ratios for the film cooling, due to coolant jet separation, the overall cooling effectiveness increased at higher momentum flux ratios. This increase was due to increased internal cooling effects. Overall cooling effectiveness measurements were also compared to analytical predictions based on a 1D thermal analysis using measured adiabatic film effectiveness and overall cooling effectiveness without film cooling.

Automation Control Method of Time-Varying in Heat Conduction Coefficient and Pure Steam Output Interference

The relation curve of the raw water flow and main steam pressure under different main stream temperature is established by off-line experiments and expert experiences. For the time-varying in heat conduction coefficient, which is resulted by scaling and so on, water level need to be detected by installing float level gauge in every effect, and the curve can be corrected according to water level, so effective separation space of gas and water is ensured to avoid dry or flood pot. Because medical water distiller need to provide pure steam, by detecting the output flow of pure steam, correct the curve and inhibit the interference of production process due to pure steam output, then the production process of distilled water can be finished by automatically controlling the adjustable valves of raw water flow and main stream pressure. The method will improve the robustness of heat conduction coefficient time-varying and pure steam output interference.

Super-Heater Tube Wall Temperature Measurement Test and Analysis of 600MW Boiler

In order to precisely monitor the inner-flue tube wall temperature of the boiler platen super-heater, the temperature measurement test of inner-flue and outer-flue tube wall has been carried out. And the data of inner-flue and outer-flue tube wall temperature was acquired in real time. According to the experimental data, the correlative rule about inner-outer flue tube wall temperature was analyzed and researched. Moreover, the data was analyzed to get the relationship of wall temperature, load, water-coal ratio, main stream temperature between the inner-flue and outer-flue furnace. So the correlative formula which was based on the relation between inner-flue tube wall temperature and outer-flue tube wall temperature was built up and checked.

Material design of a film cooling system using experimental heat transfer data

The present study numerically calculates the temperature and thermal stress distributions near a normal cooling hole. We evaluate the effects of material properties on thermal damage by using local heat transfer data from previous experiments. The experimental results are converted into the surface’s heat transfer coefficients and the adiabatic wall temperature while using surface boundary conditions. The calculated results reveal that the thermal stresses depend on the main stream temperature and the material properties. To predict the maximum thermal stress near the normal cooling hole, we provide a single correlation consisting of the material properties and the main stream temperature.

Experimental investigations on overall cooling effect of ribbed channel with air bleeds

An experimental investigation on overall heat transfer performance of a rectangular channel, in which one wall has periodically placed oblique ribs to enhance heat exchange and cylindrical film holes to bleed cooling air, has been carried out in a hot wind tunnel at different mainstream temperatures, hot mainstream Reynolds numbers, coolant Reynolds numbers and blowing ratios. To describe the cooling effect of combined external coolant film with the internal heat convection enhanced by the ribs, the overall cooling effectiveness at the surface exposed in the mainstream with high temperature was calculated by the surface temperatures measured with an infrared thermal imaging system. The total mass flow rate of cooling air through the coolant channel was regulated by a digital mass flow rate controller, and the blowing ratio passing through the total film holes was calculated based on the measurements of another digital-type mass flow meter. The detailed distributions of overall cooling effectiveness show distinctive peaks in heat transfer levels near the film holes, remarkable inner convective heat transfer effect over entire channel surface, and visible conductive heat transfer effect through the channel wall; but only when the coolant Reynolds number is large enough, the oblique rib effect can be detected from the overall cooling effectiveness; and the oblique bleeding hole effect shows the more obvious trend with increasing blowing ratios. Based on the experimental data, the overall cooling effectiveness is correlated as the functions of Rem (Reynolds number of hot mainstream) and Rec (Reynolds number of internal coolant flow at entrance) for the parametric conditions examined.

Influence of material properties on temperature and thermal stress of thermal barrier coating near a normal cooling hole

The present study investigates numerical calculations of temperature and thermal stress distributions near a normal cooling hole. A normal injection cooling hole was applied to evaluate TBC delamination using the local heat transfer data, which were obtained by the previous experiments. Experimental results were converted into the surface heat transfer coefficients and the adiabatic wall temperature for surface boundary conditions. Calculated results reveal that the de-bonding stresses, which yield the TBC delamination, really depends on the main stream temperature and the TBC material properties. To predict the maximum de-bonding stress near the normal cooling hole, we obtained a single correlation consisting of the TBC material properties and the main stream temperature.

Main Stream Temperature Control System Based on Smith-PID Scheduling Network Control

This paper is concerned with the controller design problem for a class of networked main stream temperature control system with long random time delay and packet losses. To compensate the effect of time delay and packet losses, a gain-scheduling based Smith-PID controller is proposed for the considered networked control systems (NCSs). Moreover, to further improve the control performance of NCSs, genetic algorithm is employed to obtain the optimal control parameters for gain-scheduling Smith-PID controller. Simulation results are given to demonstrate the effectiveness of the proposed methods.

Comparison of Heat Transfer Measurement Techniques on a Transonic Turbine Blade Tip

The present study considers spatially resolved surface heat transfer coefficients and adiabatic wall temperatures on a turbine blade tip in a linear cascade under transonic conditions. Five different measurement and processing techniques using infrared thermography are considered and compared. Three transient methods use the same experimental setup, using a heater mesh to provide a near-instantaneous step-change in mainstream temperature, employing an infrared camera to measure surface temperature. These three methods use the same data but different processing techniques to determine the heat transfer coefficients and adiabatic wall temperatures. Two of these methods use different processing techniques to reconstruct heat flux from the temperature time trace measured. A plot of the heat flux versus temperature is used to determine the heat transfer coefficients and adiabatic wall temperatures. The third uses the classical solution to the 1D nonsteady Fourier equation to determine heat transfer coefficients and adiabatic wall temperatures. The fourth method uses regression analysis to calculate detailed heat transfer coefficients for a quasi-steady-state condition using a thin-foil heater on the tip surface. Finally, the fifth method uses the infrared camera to measure the adiabatic wall temperature surface distribution of a blade tip after a quasi-steady-state condition is present. Overall, the present study shows that the infrared thermography technique with heat flux reconstruction using the impulse method is the most accurate, computationally efficient, and reliable method to obtain detailed, spatially resolved heat transfer coefficients and adiabatic wall temperatures on a transonic turbine blade tip in a linear cascade.

Numerical modelling of film cooling with and without mist injection

Two-phase CFD calculations, using a Lagrangian model and commercial code Fluent 6.2.16, were employed to calculate the gas and droplet flows and film cooling effectiveness with and without mist on a flat plate. Two different three dimensional geometries are generated and the effects of the geometrical shape, size of droplets, mist concentration in the coolant flow and temperature of mainstream flow for different blowing ratios are studied. A cylindrical and laterally diffused hole with a streamwise angle of 30° and spanwise angle of 0° are used. The diameter of film cooling (d) hole, and the hole length to diameter ratio (L/d) for both of geometries are 10 mm and 4, respectively. Also the blowing ratio ranges from 1.0 to 2.0, and the mainstream Reynolds number based on the mainstream velocity and hole diameter (Red) is 6,219. The results are shown for different droplets diameters (1–10 μm), concentrations (1–5%) and mainstream temperatures (350–500 K). The centreline effectiveness and distribution of effectiveness on the surface of cooling wall are presented.

Comparison of Analytical and Superposition Solutions of the Transient Liquid Crystal Technique

The transient liquid crystal technique has been widely used in heat transfer measurement and, due to the nature of the transient test, the mainstream temperature changes over time. In many previous studies, the change of mainstream temperature was assumed as a series of step changes and Duhamel's superposition theorem was applied to evaluate the heat transfer coefficient. In this paper, the error in calculating the heat transfer coefficient by the series-of-step-changes assumption with Duhamel's superposition theorem is discussed and the analytical solution for the curve-fitted mainstream temperature with nth-order polynomials is presented. The solution using the series of step changes showed a high dependency on the size of the time step, thus on the sampling ratio of the mainstream temperature measurement, and higher error was induced for the higher heat transfer coefficient. It is recommended that the size of time step in the series of step changes should be minimized and that the use of an analytical solution would be a better choice in the transient liquid crystal test. It is expected that the presented analytical solution for the curve-fitted mainstream temperature with polynomials could be applied to many slow transient liquid crystal tests.

Film Cooling Measurements for Novel Hole Configurations

Experimental Procedure: •Blower is set appropriately for required mainstream velocity •Heater is turned on and allowed to heat the air to a desired mainstream temperature •The coolant air is provided from separate compressed air supply and is metered for flow measurement •The mainstream and coolant are triggered at the same instant when the IR system starts taking images and saving to hard drive at set intervals •Images are saved then processed to calculate the heat transfer coefficients and film effectiveness using the theory

Spatial and temporal stream temperature prediction: Modeling nonstationary temporal covariance structures

Stream temperature is a measure of water quality and directly influences both the biotic and abiotic dynamics within the aquatic system. Because of its importance, there is a need to find better methods of monitoring and modeling stream temperatures. Gardner et al. [2003] derived a networked geostatistical model to explain the spatial patterns of stream temperatures based on 72 temperature loggers recording stream temperatures hourly throughout the Beaverkill watershed network, New York, for a single time period. Because temperatures and temperature relationships between stream sections change over the season, the covariance structure of the system is likely also to change with time. The covariance structure of stream temperature data collected throughout the month of July was examined and found to be nonstationary temporally. However, the observed changes in the covariance structure were found to be highly dependent on main stem stream temperatures over time. Five nested correlation models were created and compared using Mallow's Cp. One model representing large‐scale variation in the sill as a linear function of the main stem temperature for each day was selected as the most parsimonious model.

Study of the influence of the number of holes rows on the convective heat transfer in the case of full coverage film cooling: Etude de l’influence du nombre de rangées de trous sur les échanges convectifs dans le cas du refroidissement par multiperforation

The protection of the combustion wall chamber of aeronautic propeller is assumed with a full coverage film cooling. In the case of 1–9 rows of eight staggered holes, we have measured several profiles of temperature in the mainstream perturbed by jets. Variations of wall temperatures T p have been measured simultaneously along the wall. Those experiences have been performed for three thermal cases, which are a function of the mainstream temperature T e, the injected temperature T i and the electrical density ϕ dissi. imposed at the wall. Three blowing rates M= ρ i U i/ ρ e U e are imposed too. The results are compared with the reference case without holes. The exam of the temperature profiles allows us to find a minimum number of rows to create a homogeneous cold layer. Two schemes of the convective heat transfer with two coefficients are presented and allow to represent each of the three thermal cases for the three blowing rates. Those models take into account of the three characteristic temperatures ( T e, T i and T p). One model is studied for 9 rows with infrared thermography. For five blowing rates, four zones of variations and an influence of M on the two coefficients are underlined.

99/00590 A diffusion layer model for steam condensation within the AP600 containment

Steam condensation in the presence of non-condensable gases is a dominating phenomenon inside a containment under LOCA scenarios. In numerical simulations, the basic diffusion boundary layer condensation model (BDBLM) has been proposed for containment thermal-hydraulics analysis. However, there are still some incompleteness such as the under prediction of heat transfer coefficient when the steam mass fraction is high. Besides, the effect of thermal diffusion (Soret effect) on condensation heat transfer has not been specified quantitatively. In order to compensate these shortcomings, a modified diffusion boundary layer model (MDBLM) was proposed and assessed in detail. In the modified condensation model, the under prediction of condensation heat transfer at high steam mass fraction conditions was modified by adding a suction effect parameter. The Soret effect was assessed by adding a new term including the temperature gradient, thermal diffusion coefficient, and steam mass fraction. The results indicate that the MDBLM could give a good prediction of heat transfer coefficient (HTC) at low air mass fraction conditions with deviations within 20%. The Soret effect takes less than 7% in the total mass transfer when the mainstream temperature is saturated and could be more than 80% when the mainstream temperature is superheated.

Adaptive simulation of boiler unit performance

Industrial boilers of a particular type will behave differently due to manufacturing or assembly tolerances. In addition, the performance of a boiler will vary at different times of its service life. The objective of the present study is to simulate a boiler unit. In the boiler model, heat transfer in the combustion chamber is simulated by the zone method; heat transfer in the secondary superheater, the reheater, the primary superheater, and the economizer is simulated by lump parameter analysis. One feature of the method used is that the models of the major components have been coupled sequentially according to the boiler configuration. Thus, it is assumed that this method may be applied to different boiler systems with different configurations. The uncertainty factors, such as water tube deposits, component deterioration and so on, are considered by modification factors which are determined from on-line measurements. Another feature of the boiler system simulation is that the major parts of the boiler system are simulated and coupled together to analyze some important operational parameters which impose a significant effect on boiler efficiency, such as main stream temperature, reheat temperature and reheat pressure drop. The boiler model has been tested and compared to on-line measurements data. The results are within a reasonable error range.

Characteristics of Combined Heat Transfer of Superheated Steam Drying. (Numerical Study on Coupled Convection and Gas Radiation Heat Transfer.)

A numerical study on a combined radiation and forced convection heat transfer of superheated steam, which is a radiation participating real gas, in thermally developing laminar flow through a parallel-plate channel has been conducted to investigate charactcristics of superheated steam drying. The integrodifferential energy equation was solved using an implicit finite-deference technique with a marching solution procedure and an exponential wide-band model for the treatment of the radiative transfer part. Comparison of results with and without gas radiation in various conditions shows that a fluid radiation decreases the temperature of main stream, but increases the total heat flux at a heat transfer surface. Furthermore, the results show that the fluid radiation decreases the inversion point temperature approximately to 150∼240°C with the increase of optical thickness. This numerical result agrees in the order of magnitude with the previous experimental studies, but is lower about 100K than that of former theoretical predictions without considering fluid radiation.

96/06405 Species measurements in a hypersonic hydrogen-air, combustion wake

A continuously sampling, time-of-flight mass spectrometer has been used to measure relative species concentrations in a two-dimensional, hydrogen-air combustion wake at mainstream Mach numbers exceeding 5. The experiments, which were conducted in a free piston shock tunnel, yielded distributions of hydrogen, oxygen, nitrogen, water and nitric oxide at stagnation enthalpies ranging from 5.6 MJ kg(exp -1) to 1.2 MJ kg(exp -1) and at a distance of approximately 100 times the thickness of the initial hydrogen jet. The amount of hydrogen that was mixed in stoichiometric proportions was approximately independent of the stagnation enthalpy, in spite of the fact that the proportion of hydrogen in the wake increased with stagnation enthalpy. Roughly 50 percent of the mixed hydrogen underwent combustion at the highest enthalpy. The proportion of hydrogen reacting to water could be approximately predicted using reaction rates based on mainstream temperatures.

Species measurements in a hypersonic, hydrogen-air, combustion wake

A continuously sampling, time-of-flight mass spectrometer has been used to measure relative species concentrations in a two-dimensional, hydrogen-air combustion wake at mainstream Mach numbers exceeding 5. The experiments, in a free piston shock tunnel, yielded distributions of hydrogen, oxygen, nitrogen, water, and nitric oxide at stagnation enthalpies ranging from 5.6 MJ kg −1 to 12.2 MJ kg −1 and at a distance of approximately 100 times the thickness of the initial hydrogen jet. The amount of hydrogen mixed in stoichiometric proportions was approximately independent of the stagnation enthalpy, despite the fact that the proportion of hydrogen in the wake was increased with stagnation enthalpy. Roughly 50% of the mixed hydrogen underwent combustion at the highest enthalpy. The proportion of hydrogen reacting to water could be approximately predicted using reaction rates based on mainstream temperatures.

112 冷却用空気吹出しのあるタービン直線翼列流路内の温度分布の可視化

To investigate mixing process with the main stream and behavior of the cooling-air in rotor cascade passages, an experiment was conducted with cooling-air ejection from blade leading-edges of the test cascade which was located downstream of another cascade simulating a stator cascade. In the present experiment, cooling-air was heated higher than the main stream temperature, and the temperature distribution of flow in the test cascade passage was measured in detail by a thermocouple. It was found that the behavior of the cooling-air ejected from the leading-edges were affected significantly by such as pressure gradients and passage vortices in the test cascade and by relative location between the upstream stator cascade and the downstream test rotor cascade.

Full-Coverage Discrete Hole Film Cooling: Investigation of the Effect of Variable Density Ratio

Experimental results of the overall and adiabatic cooling effectiveness for full-coverage discrete hole film cooling are presented for a range of practical geometries. The results are reported for various hot gas mainstream-to-coolant temperature (density) ratios, in the realistic range of 1.0–3.2. The variation of this ratio was achieved by increasing the crossflow mainstream temperature, over the range 300–930 K. For combustor wall film cooling applications, the overall cooling effectiveness increased significantly with the number of holes per unit wall surface area, over the range of 4306–26910 m−2 and with the hole size, in the range of 1.0–2.2 mm, due to the improvement in film cooling. The effect of varying the mainstream-to-coolant temperature ratio, in the present range of 1.0–3.2, on the film cooling performance was shown to be small and no consistent trends were established for various configurations, for the coolant mass flow rates per unit wall surface area, less than 0.4 kg/sm2. At a higher value of 0.89 kg/sm2, an increase in the temperature ratio improved the film cooling performance slightly.