Review and status of heat-transfer technology for internal passages of air-cooled turbine blades

Selected literature on heat-transfer and pressure losses for airflow through passages for several cooling methods generally applicable to gas turbine blades is reviewed. Some useful correlating equations are highlighted. The status of turbine-blade internal air-cooling technology for both nonrotating and rotating blades is discussed and the areas where further research is needed are indicated. The cooling methods considered include convection cooling in passages, impingement cooling at the leading edge and at the midchord, and convection cooling in passages, augmented by pin fins and the use of roughened internal walls

Algorithms for a very high speed universal noiseless coding module

The algorithmic definitions and performance characterizations are presented for a high performance adaptive coding module. Operation of at least one of these (single chip) implementations is expected to exceed 500 Mbits/s under laboratory conditions. Operation of a companion decoding module should operate at up to half the coder's rate. The module incorporates a powerful noiseless coder for Standard Form Data Sources (i.e., sources whose symbols can be represented by uncorrelated non-negative integers where the smaller integers are more likely than the larger ones). Performance close to data entropies can be expected over a Dynamic Range of from 1.5 to 12 to 14 bits/sample (depending on the implementation)

Parameter dependence of phase and log amplitude scintillation

Parameter dependence of phase and log amplitude scintillation - Signal statistics of spherical wave emitted by transmitter through intervening slab of irregularitie

Comparison of heat-transfer test data for a chordwise-finned, impingement-cooled turbine vane tested in a four-vane cascade and a research engine

The heat-transfer characteristics of a chordwise-finned, impingement-cooled vane were investigated in both a modified J-57 research engine and a four-vane cascade. The data were compared by a correlation of temperature difference ratio with coolant- to gas-flow ratio and also by two modifications of this correlation. The results indicated that the cascade vane temperature data can generally be used to represent the engine vane temperature data. A discussion of engine and cascade gas-side heat-transfer coefficients is also presented. A redesign of the vane leading edge could significantly increase the potential turbine-inlet temperature operating limit

Universal vortex-state Hall conductivity of YBa2Cu3O7 single crystals with differing correlated disorder

The vortex-state Hall conductivity ([sigma][sub]xy) of YBa2Cu3O7 single crystals in the anomalous-sign-reversal region is found to be independent of the density and orientation of the correlated disorder. After the anisotropic-to-isotropic scaling transformation is carried out, a universal scaled Hall conductivity [sigma][bar][sub]xy is obtained as a function of the reduced temperature (T/T[sub]c) and scaled magnetic field strength (H[bar]) for five samples with different densities and orientation of controlled defects. The transport scattering times {tau], derived from applying the model given by Feigel'man et al (Feigel'man M V, Geshkenbein V B, Larkin A I and Vinokur V M 1995 Pis. Zh. Eksp. Teor. Fiz. 62 811 (Engl. Transl. 1995 JETP Lett. 62 835)) to the universal Hall conductivity [sigma bar](T/T[sub]c, H[bar]), are consistent in magnitude with those derived from other measurements for quasiparticle scattering, and are much smaller than the thermal relaxation time of vortex displacement and than the vortex–defect interaction time. Our experimental results and analyses therefore suggest that the anomalous sign reversal in the vortex-state Hall conductivity is associated with the intrinsic properties of type-II superconductors, rather than extrinsic disorder effects

On the optimality of code options for a universal noiseless coder

A universal noiseless coding structure was developed that provides efficient performance over an extremely broad range of source entropy. This is accomplished by adaptively selecting the best of several easily implemented variable length coding algorithms. Custom VLSI coder and decoder modules capable of processing over 20 million samples per second are currently under development. The first of the code options used in this module development is shown to be equivalent to a class of Huffman code under the Humblet condition, other options are shown to be equivalent to the Huffman codes of a modified Laplacian symbol set, at specified symbol entropy values. Simulation results are obtained on actual aerial imagery, and they confirm the optimality of the scheme. On sources having Gaussian or Poisson distributions, coder performance is also projected through analysis and simulation

Turbine vane coolant flow variations and calculated effects on metal temperatures

Seventy-two air-cooled turbine vanes were tested to determine coolant flow variations among the vanes. Calculations were made to estimate the effect of measured coolant flow variations on local vane metal temperatures. The calculations were based on the following assumed operating conditions: turbine inlet temperature, 1700 K (2600 F); turbine inlet pressure, 31 N/sq cm (45 psia); coolant inlet temperature, 811 K (1000 F); and total coolant to gas flow ratio, 0.065. Variations of total coolant flow were not large (about 10 percent from the arithmetic mean) for all 72 vanes, but variations in local coolant flows were large. The local coolant flow variations ranged from 8 to 75 percent, and calculated metal temperature variations ranged from 8 to 60 K (15 to 180 F)

Heat transfer results and operational characteristics of the NASA Lewis Research Center Hot Section Cascade Test Facility

The NASA Lewis Research Center gas turbine hot section test facility has been developed to provide a real-engine environment with well known boundary conditions for the aerothermal performance evaluation/verification of computer design codes. The initial aerothermal research data obtained are presented and the operational characteristics of the facility are discussed. This facility is capable of testing at temperatures and pressures up to 1600 K and 18 atm which corresponds to a vane exit Reynolds number range of 0.5x10(6) to 2.5x10(6) based on vane chord. The component cooling air temperature can be independently modulated between 330 and 700 K providing gas-to-coolant temperature ratios similar to current engine application. Research instrumentation of the test components provide conventional pressure and temperature measurements as well as metal temperatures measured by IR-photography. The primary data acquisition mode is steady state through a 704 channel multiplexer/digitizer. The test facility was configured as an annular cascade of full coverage filmcooled vanes for the initial series of research tests

Comparison of heat transfer characteristics of three cooling configurations for air-cooled turbine vanes tested in a turbojet engine

A comparison was made of the heat transfer characteristics of three air cooled vanes. The vanes incorporated cooling schemes such as impingement cooling, film cooling, and convection cooling with and without extended surfaces. A redesign study was made for two vanes to improve the cooling effectiveness. An average impingement heat transfer coefficient was calculated on the bases of experimentally determined temperatures at the leading edge and a one dimensional heat transfer calculation. This heat transfer coefficient was compared with existing impingement heat transfer correlations