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.

Characterization and Modeling of Tensile Behavior of Ceramic Woven Fabric Composites

This paper examines the tensile behavior of SiC/SiC fabric composites. In the characterization effort, the stress-strain relation and damage evolution are studied with a series of loading and unloading tensile test experiments. The stress-strain relation is linear in response to the initial loading and becomes nonlinear when loading exceeds the proportional limit. Transverse cracking has been observed to be a dominant damage mode governing the nonlinear deformation. The damage is initiated at the inter-tow pores where fiber yarns cross over each other. In the modeling work, the analysis is based upon a fiber bundle model, in which fiber undulation in the warp and fill directions and gaps among fiber yarns have been taken into account. Two limiting cases of fabric stacking arrangements are studied. Closed form solutions are obtained for the composite stiffness and Poisson’s ratio. Transverse cracking in the composite is discussed by applying a constant failure strain criterion.

Dynamic Force Response of an Open Ended Squeeze Film Damper

The effects of whirl frequency and lubricant viscosity on the experimental pressure field and film forces in an open ended squeeze film damper test rig are presented. The measurements refer to circular centered journal motion of amplitude equal to one half the damper clearance (ε=0.5). The whirl frequency varied between 16Hz to 85Hz, while the lubricant temperature increased from 25°C to 45°C. The damper operated with levels of external pressurization which supressed lubricant cavitation. The experimental results show conclusivey that the radial film force is purely an inertial effect, i.e. it depends solely on the fluid density and the second power of the whirl frequency. The tangential film force shows a variation which depends on the viscous and inertial flow conditions in the squeeze film region. Correlation of experimental forces with conventional SFD models shows the radial force to be π times larger than the theoretical prediction, while the tangential force correlates well for low whirl frequencies and large lubricant viscosities.

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 Effects of Friction in Axial Splines on Rotor System Stability

An in depth parametric evaluation of the effects of Coulomb friction in an axial spline joint on the stability of the rotor-bearing system was conducted through time transient integration of the equations of motion. Effects of: spin speed, friction coefficient, spline torque, external damping, imbalance and side load as well as asymmetric bearing stiffnesses were investigated. A subsynchronous instability is present at the bending critical speed when the spin speed is above this critical. The limit cycle orbit is circular, is proportional to the product of the friction coefficient and spline torque (μT), is inversely proportional to the external damping and is independent of spin speed. When imbalance is applied to the rotor, beating between the subsynchronous natural frequency and the synchronous (spin speed) frequency occurs. The subsynchronous component of the orbit is proportional to μT, while the synchronous component is proportional to the imbalance. When a static side load is applied, the unstable node at the center of the orbitally-stable limit cycle grows into an elliptical orbitally-unstable limit cycle, separating stable - from unstable regions of the phase plane. Below a threshold value of side load, the transient motion approaches one of two asymptotic solutions depending on the initial conditions: the larger stable limit cycle or a point at the center of the smaller unstable limit cycle. Beyond the threshold value of side load the rotor-bearing system is stable and all motions decay to a point. Asymmetry in the bearing stiffnesses reduces the size of the subsynchronous whirl orbit.

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.