The Design and Development of an Electrically Operated Fuel Control Valve for Industrial Gas Turbines

Industrial gas turbines operate over a wide range of combinations of loads and speeds. The fuel control valve must be designed to cover the entire range precisely. The design of an electrically operated fuel control valve is described and comparison between the predicted and measured performance characteristics is shown.

NDE Development for Ceramics for Advanced Heat Engines

Following an assessment of needs for NDT and characterization of ceramics for the DOE program, Ceramic Technology for Advanced Heat Engines (CTAHE), many NDT projects have been implemented under the sponsorship of CTAHE to address the needs. Tasks at Argonne National Laboratory have involved X-ray computed tomography and nuclear magnetic resonance imaging. The Oak Ridge National Laboratory has emphasized high-frequency ultrasonics, low-voltage radiography, and an advanced system for X-ray computed tomography. A brief investigation was made by Radiation Sciences, Inc., into the feasibility of synchrotron-computed tomography for ceramics. New programs recently initiated at Allison and Garrett integrate ultrasonics, radiography, and other methods into a major effort on life prediction. New programs at Norton and GTE on advanced processing of ceramics also place heavy emphasis on several methods of NDT for process development and control. Initial work on NDT standards has begun in ASTM Committees E-7 and C-28.

Progressive Damage in Unidirectional Ceramic Composites Under Transient Thermal Fatigue

The changes in stiffness properties for a CAS matrix-Nicalon fiber unidirectional composite resulting from cyclic heating and cooling are presented. The measurements are made using an ultrasonic pulse-echo technique. It is shown that a significant decrease in stiffness is observed after 30 cycles.

Development and Bench Test of High-Temperature Combustion Chamber With Structural Ceramic Components

The most effective method of increasing the thermal efficiency of a simple cycle gas turbine unit involves elevation of the gas temperature upstream of the turbine. This requires development of appropriate operational procedure principles and adequate combustion chamber design.

Development of Injection-Molded Gas Turbine Components: Investigation Into Toughening GTE PY6 Si3N4

GTE Laboratories has been supporting Allison Gas Turbine Division of General Motors under the current ATTAP program since early 1988. Injection-molding process development and component fabrication has been the emphasis of this effort, but material property enhancement studies have also been an important complement. Attempts to increase the resistance to foreign object damage have been made through parallel investigations of microstructural control and SiC whisker reinforcement. The research activities aimed at improving fracture toughness of GTE PY6 Si3N4 are discussed.

The Basics of Powder Lubrication in High-Temperature Powder-Lubricated Dampers

The objective of this investigation is to develop a novel powder-lubricated rotor bearing system damper concept for use in high-temperature, high-speed rotating machinery such as advanced aircraft gas turbine engines. The approach discussed herein consists of replacing a conventional oil lubrication or frictional damper system with a powder lubrication system that uses the process particulates or externally-fed powder lubricant. Unlike previous work in this field, this approach is based on the postulate of the quasi-hydrodynamic nature of powder lubrication. This postulate is deduced from past observation and present verification that there are a number of basic features of powder flow in narrow interfaces that have the characteristic behavior of fluid film lubrication. In addition to corroborating the basic mechanism of powder lubrication, the conceptual and experimental work performed in this program provides guidelines for selection of the proper geometries, materials and powders suitable for this tribological process. The present investigation describes the fundamentals of quasi-hydrodynamic powder lubrication and defines the rationale underlying the design of the test facility. The performance and the results of the experimental program present conclusions reached regarding design requirements as well as the formulation of a proper model of quasi-hydrodynamic powder lubrication.

A Procedure for Automated Gas Turbine Blade Fault Identification Based on Spectral Pattern Analysis

A method for diagnosing the existence and the kind of faults in blades of a Gas Turbine compressor is presented in the present paper. The innovative feature of this method is that it performs the diagnosis automatically, namely it gives a direct answer to whether a fault exists and what fault it is, without requiring the interpretation of results by a human expert. This is achieved by the derivation of the values of discriminants calculated from spectral patterns of fast response measurement data. A decision about the corresponding Engine status is then derived according to the values of these discriminants. In the paper, the procedure of examining the suitability of particular parameter discriminants and the constitution of a related knowledge base is described. The way of derivation of decisions by a computer, on what engine condition a particular measurement data set corresponds, is then described.

The Role of Carbide Phases in the Secondary Recrystallization of Nickel-Base ODS-Superalloys

In ODS nickel-base alloys with high γ′-content (e.g. MA760) the rate of heating to the recrystallization temperature plays an important role for the success of the recrystallization treatment. Previous results (Jongenburger et al., 1990) revealed the existence of a heating rate window for secondary recrystallization. While the lower limit of this window (Ṫmin) is well understood, an attempt is made in this paper to explain the upper limit (Ṫmax) by the influence of carbide phases. Furthermore it is shown that carbide phases may also influence the incipient melting temperature and consequently the width of the temperature window for successful secondary recrystallization.

Fracture Mechanics Approach to Creep Crack Growth in Welded IN738LC Gas Turbine Blades

Microcracks caused by hot cracking or strain age cracking mechanisms are very likely to be discovered in the weld repair zone of precision cast IN738LC gas turbine blades. The possibility of crack propagation under the operating conditions of the gas turbine thereby becomes a crucial issue for gas turbine designers. The creep crack growth rate in air of the hipped and fully heat treated IN738LC was measured at the service temperature experienced by the first stage turbine blade tip. The corresponding growth behaviour was also studied. The creep crack growth rate, da/dt, versus crack tip stress intensity factor, K1, a relation which exhibits the typical primary, secondary and tertiary behaviour, supports the applicability of K1 as an appropriate correlating parameter for the creep crack growth of this Ni-based superalloy under the loading conditions used in this study. Microstructural examination illustrated that the creep crack growth of IN738LC principally takes place by the nucleation, growth, coalescence and link-up of grain boundary microvoids and microcracks. An excellent approximation of the stress intensity factor under service loading conditions in the vicinity of the crack tip was obtained by using the Westinghouse WECAN finite element analysis. It is shown that the crack tip stress intensity factor under normal loading conditions will not be able to drive the transverse through-the-wall-thickness blade tip crack in this study.

Statistical and Mathematical Approach for Distribution Function Model for Low Probability of Failures

In probabilistic design it is common practice to use statistical models such as normal, lognormal, and Weibull to describe random design factors. However these distribution function models deviate in the lower tail, i.e. percentiles below 1%. The deviation is nonconservative in that since it predicts life longer than observed. A Statistical Distribution Function called Adaptive Distribution Function Model similar to Abelkis model was developed. It is compatible with the collected data, and it produces conservative designs at low tail ends. It is also relatively easy to use.