Durability of zirconia thermal-barrier ceramic coatings on air-cooled turbine blades in cyclic jet engine operation

Thermal barrier ceramic coatings of stabilized zirconia over a bond coat of Ni Cr Al Y were tested for durability on air cooled turbine rotor blades in a research turbojet engine. Zirconia stabilized with either yttria, magnesia, or calcia was investigated. On the basis of durability and processing cost, the yttria stabilized zirconia was considered the best of the three coatings investigated

Temperature in a J47-25 Turbojet-engine Combustor and Turbine Sections During Steady-state and Transient Operation in a Sea-level Test Stand

In order to determine the conditions of engine operation causing the most severe thermal stresses in the hot parts of a turbojet engine, a J47-25 engine was instrumented with thermocouples and operated to obtain engine material temperatures under steady-state and transient conditions. Temperatures measured during rated take-off conditions of nozzle guide vanes downstream of a single combustor differed on the order of 400 degrees F depending on the relation of the blades position to the highest temperature zone of the burner. Under the same operation conditions, measured midspan temperatures in a nozzle guide vane in the highest temperature zone of a combustor wake ranged from approximately 1670 degrees F at leading and trailing edges to 1340 degrees F at midchord on the convex side of the blade. The maximum measured nozzle-guide-vane temperature of 1920degrees at the trailing edge occurred during a rapid acceleration from idle to rated take-off speed following which the tail-pipe gas temperature exceeded maximum allowable temperature by 125 degrees F

Brayton heat exchanger unit development program (alternate design)

A Brayton Heat Exchanger Unit Alternate Design (BHXU-Alternate) consisting of a recuperator, a heat sink heat exchanger, and a gas ducting system, was designed and fabricated. The design was formulated to provide a high performance unit suitable for use in a long-life Brayton-cycle powerplant. Emphasis was on double containment against external leakage and leakage of the organic coolant into the gas stream. A parametric analysis and design study was performed to establish the optimum component configurations to achieve low weight and size and high reliability, while meeting the requirements of high effectiveness and low pressure drop. Layout studies and detailed mechanical and structural design were performed to obtain a flight-type packaging arrangement, including the close-coupled integration of the BHXU-Alternate with the Brayton Rotating Unit (BRU)

Welcher Weg? A trajectory representation of a quantum Young's diffraction experiment

The double slit problem is idealized by simplifying each slit by a point source. A composite reduced action for the two correlated point sources is developed. Contours of the reduced action, trajectories and loci of transit times are developed in the region near the two point sources. The trajectory through any point in Euclidian 3-space also passes simultaneously through both point sources.Comment: 12 pages LaTeX2e, 9 figures. Typos corrected. Author's final submission. A companion paper to "Interference, reduced action, and trajectories", quant-ph/0605120. Keywords: interference, Young's experiment, entanglement, nonlocality, trajectory representation, determinis

Neurospora crassa qa-2 gene fragment.

Neurospora crassa qa-2 gene fragment

A key to the females of the genus Oxyethira (Trichoptera: Hydroptilidae) from the southern United States

Associations of females with the males for most species of the genus Oxyethira known from the southern United States has made possible the construction of a key to females of that region. Illustrations for 24 of the 27 species are provided along with a discussion of the general morphology of the genital segments of females of the genus

Obituary - Edwin Wallace King

Dr. E.W. King was a highly respected scientist and teacher whose enthusiasm for entomology and general biology has inspired students toward excellence in our discipline for more than 30 years. On December 10, 1984, Dr. King died suddenly of complications associated with cancer

A New Species of Ceraclea (Trichopterma:Leptoceridae) Preying on Snails

Ceraclea joannae, new species, feeds on the freshwater snail Somatogyrus virginicus Walker (Hydrobiidae). Our study is the first report of prey other than sponges for a Ceraclea species and the first report of snail predation by Trichoptera larvae in North America. Ceraclea joannae larvae and adults resemble those of C. diluta (Hagen); however, the larva of the new species has a dark head, sickle-shaped mandibles, and a dark pronotum except for a pair of unique, conspicuous, oblique, white bands; the male differs in the slightly longer superior appendages, more nearly straight ventral margins of tergum X, slightly stouter inferior appendages, and the more-tapered apex and less-pronounced ventral notch of the phallus. This new species of Ceraclea is known from only 3.2 km of the Little River (Montgomery County, North Carolina, USA), downstream of the developing town of Asheboro. Because of its rarity and limited distribution, Ceraclea joannae may be highly vulnerable to changes in water or habitat quality

An Experimental Investigation of Hollow Turbine Blades for Expandable Jet Engines

An experimental investigation was made to determine the feasibility of using hollow turbine blades in engines designed for short service life. Airfoils were fabricated from sheet material and techniques of welding and brazing attachment were investigated. The airfoils were not intended to be cooled. A principal objective was the reduction of strategic material requirements primarily as a function of direct weight reduction. The materials considered were in the density range of 0.28 to 0.31 pound per cubic inch. Three materials were used for airfoils: N-155, Inconel-X and L-605. These were attached to J47 turbine blade bases and operated to destruction at maximum service conditions of turbine speed and temperature. It was found that L-605 airfoils brazed to suitable bases satisfied the requirements for expendable engines. Service life varied from 11 to 40 hours