Real Time Neutron Radiography Applications in Gas Turbine and Internal Combustion Engine Technology

Real Time Neutron Radiography (RTNR) is rapidly becoming a valuable tool for nondestructive testing and basic research with a wide variety of applications in the field of engine technology. The Phoenix Memorial Laboratory (PML) at the University of Michigan has developed a RTNR facility and has been using this facility to study several phenomena that have direct application to internal combustion and gas turbine engines. These phenomena include; 1) the study of coking and debris deposition in several gas turbine nozzles (including the JT8D), 2) the study of lubrication problems in operating standard internal combustion engines and in operating automatic transmissions (1, 2, 3), 3) the location of lubrication blockage and subsequent imaging of the improvement obtained from design changes, 4) the imaging of sprays inside metallic structures in both a two-dimensional, standard radiographic manner (4, 5) and in a computer reconstructed, three-dimensional, tomographic manner (2, 3), and 5) the imaging of the fuel spray from an injector in a single cylinder diesel engine while the engine is operating. This paper will show via slides and real time video, the above applications of RTNR as well as other applications not directly related to gas turbine engines.

Structural Design and its Improvements Through the Development of the XF3-30 Engine

The XF3-30 engine has been successfully completed its Qualification Test at March 1986 and the production has started as the powerplant for Japan Self Defence Force’s intermedeate trainer T-4. The first flight of the T-4 powered by two XF3-30 engine was made on the 29th July 1985. More than 500 test flights have been made in these two years and engine flight time has accumulated to over 1,500 hours. This XF3-30 engine has been imposed strict requirements of the structural integrity to meet the MIL-E-5007D specification. This paper describes the structural features of this engine and some structural problems encountered through the development. The improvements for these development problems are covered.

Porosity Determination of Thermal Barrier Coatings

Coating porosity is believed to be a critical factor for the thermal conductivity of thermal barrier coatings (TBC’s). A number of different techniques have been used to determine the porosities of thermal barrier coatings for diesel applications as part of a NASA/DOE sponsored study. A comparison is made between methods based on water immersion, optical microscopy, eddy current thickness measurements, and Archimedes principle for TBC porosity determination.

Whisker Orientation Measurements in Injection Molded Si3N4-SiC Composites

Hot pressed composites of Si3N4 containing 30% SiC whiskers have shown substantial improvements in strength and fracture toughness relative to monolithic silicon nitride. Injection molded samples made of this composite material distorted in a systematic manner during densification by hot isostatic pressing. Whisker orientation and aspect ratio measurements based on digitized SEM micrographs were used to evaluate microstructure with respect to injection molding direction. Results show definite orientation of whiskers during injection molding which can be related to the observed densification distortion.

The Oil-Free Shaft Line

This paper recalls the principles and main features of the active magnetic bearings and especially the advantages for turbomachines. Oil-free working and vibration control are part of them. Field experiences are described for different shaft line configurations. Step by step we are going to get totally rid of oil with the introduction of active magnetic bearings together with dry gas seals and gearless drive. Future machines will take the benefit of all this field experience. The trend of the design optimization is the active magnetic bearings in the process gas itself, for a length reduction of shafts. But at the present stage, the active magnetic bearing is a proven technology today.

The Measurement of Stress and Vibration Data in Turbine Blades and Aeroengine Components

Instrumentation utilizing the thermoelastic effect has become established in recent years as an important tool for experimental stress analysis. This instrumentation provides full field stress data in a digitized form that can be integrated with computer aided design methods for experimental optimization and validation of designs. More recently the same full field data acquisition techniques have been applied to vibration measurements. As a result stress and vibration data can be obtained from the same experimental set-up. The paper describes theoretical aspects of the thermoelastic effect upon which the stress measurements are based. It goes on to show how laser Doppler interferometric techniques can be incorporated into stress measuring instrumentation. Results from typical aerospace components are used to illustrate applications of commercially available instrumentation (Fig. 1).

A Turbine Wheel Design Story

A Jet Fuel Starter (JFS) is used to start the F100 main propulsion engines for the F-15 fighter aircraft. The JFS is a dual rotor machine which consists of a gas generator spool and a power turbine spool. The gas generator turbine wheel was designed to be contained within the turbine case in the event of a JFS overspeed. This is done by the inclusion of a containment ring in the turbine case. The initial power turbine wheel design was not able to be contained by its turbine case. A design decision was made to make this wheel frangible, that is, in an overspeed condition the wheel would break into small pieces which could be contained by the existing turbine case. An alternative design solution is proposed in this paper and an analytical proof-of-concept is presented.

Rotordynamic Coefficient and Leakage Test Results for Interlock and Tooth-on-Stator Labyrinth Seals

Test results (leakage and rotordynamic coefficients) are presented for an interlock and tooth-on-stator labyrinth seals. Tests were carried out with air at speeds out to 16,000 cpm and supply pressures up to 7.5 bars. The rotordynamic coefficients consist of direct and cross-coupled stiffness and damping coefficients. Damping-coefficient data have not previously been presented for interlock seals. The test results support the following conclusions: (a) The interlock seal leaks substantially less than labyrinth seals. (b) Destabilizing forces are lower for the interlock seal. (c) The labyrinth seal has substantially greater direct damping values than the interlock seal. A complete rotordynamics analysis is needed to determine which type of seal would yield the best stability predictions for a given turbomachinery unit.

The Effects of Gas Velocity and of Temperature on the Oxidative Response of Selected Sheet Superalloys

The ability of a range of sheet alloys to withstand oxidation has been assesed under static furnace conditions and under dynamic conditions. It was established that alloys showing considerable promise in the static environment degraded more rapidly during the dynamic burner rig test so that rankings were changed dramatically. Chromium depletion as a result of volatilisation of oxide species was believed to be responsible. A testing programme was instituted to study the effects of gas velocity and of temperature on oxide stability in Nimonic alloy 86, Haynes alloy 188 and Hastelloy X. Although the compositions of the alloys and hence of the oxides were complex, reduction in the Cr2O3 content of the oxide layer was observed following high velocity gas stream exposure when temperatures were as low as 750°C. A theory is proposed relating the response of the three alloys to the composition of each of the principal spinels.

Laser: A Gas Turbine Combustor Manufacturing Tool

Coordination of the latest manufacturing technologies to improve aircraft gas turbine combustor design has resulted in developing processes for machining and welding of combustor liners with laser. Major concerns were the cutting and drilling of chrome nickel alloys and ceramics to result in precise sizing with minimal or no burrs or slag which, if they existed, would disrupt airflow patterns, and welding which would neither contribute to distortion nor leave built-in cracks to propagate in fatigue loading. Laser machining has met these criteria with results superior to those of conventional punching, drilling, and welding techniques.