Bjoern Schenk

Oxidation Behavior of Prospective Silicon Nitride Materials for Advanced Microturbine Applications

Various laboratory tests have shown that high-pressure water vapor environments combined with elevated temperatures and intermediate gas velocities (current facilities limited to about 50 m/s) can cause grain boundary degradation and material recession in silica formers. Recent tests include burner rig testing conducted by NASA [1], Honeywell Engines & Systems [2], Siemens Power Generation [3], CRIEPI in Japan [4, 5], “Keiser rig” testing at Oak Ridge National Laboratory (ORNL) [6], and engine testing in the Allison 501K industrial gas turbine [7]. This paper presents a summary of oxidation test data of candidate silicon nitride materials for advanced microturbine applications. These data are of interest to microturbine component designers in order to determine the limits of safe unprotected component operation with respect to the given turbine environment, as well as to understand the behavior of ceramic microturbine components once local spallation of the protective environmental barrier coating has occurred.This paper intends to give materials and engine development engineers some guidance with respect to the different test facility capabilities and the prevailing oxidation/recession mechanisms to better understand/interprete the oxidation test results when developing new ceramic material compositions and environmental barrier coating systems.Copyright

Development and Evaluation of a High-Resolution Turbine Pyrometer System

Optical pyrometers provide many advantages over intrusive measuring techniques in determining the spatial and time varying temperature distribution of fast rotating components in gas turbines. This paper describes the development and evaluation of a versatile high-resolution pyrometer system and its application to radial turbine rotor temperature mapping as has been done in a R&D project at the Technical University Berlin under funding from Siemens Power Generation (KWU). The development goal was a pyrometer system with a temporal resolution of 1 μs, a minimum field of view of 1 mm, and a measurement range from 600 to 1500°C. A prototype of the pyrometer system has been built and tested at the small gas turbine test facility of the Technical University Berlin. The system yielded excellent results with respect to measurement uncertainty, resolution, and reliability. Finally, measurement results obtained with the new system on a radial turbine rotor and on a heavy duty industrial gas turbine are compared with measurements conducted with a commercially available turbine pyrometer system.

Ceramic/Metal-Shaft/Hub Connection for Applications in Small High Temperature Ceramic Gas Turbine Rotors

The paper provides a synopsis of the research activities currently pursued at the Technical University Berlin, Hahn-Meitner-Institut Berlin and Honeywell Engines & Systems with respect to ceramic/metal joining concept for small ceramic high temperature gas turbine rotors. The objective was to design an interference fit type joint that can be cost effectively produced and reliably transmit torque at elevated temperatures (up to 800°C). Experimental and numerical investigations have been carried out to examine two slightly different designs which both utilize the same basic principle of a shrink fit connection that is able to compensate the thermal expansion mismatch between ceramic and metal and therefore is capable of keeping the contact pressure at the ceramic/metal interface nearly constant over a wide operating temperature range. The joints have been tested under torsional load at isothermal conditions in order to determine the static coefficient of friction and the torque carrying capability, as well as to optimize the joint geometry. The stress distribution inside the joint has been determined by FEA and subsequently evaluated by measuring the residual stress state of the joint in the ceramic by neutron diffraction.© 2000 ASME

Ceramic Turbine Engine Demonstration Project — A Summary Report

Honeywell Engines & Systems has successfully addressed critical concerns that are slowing commercialization of structural ceramics in gas turbines. The U.S. Department of Energy (DoE) sponsored Ceramic Turbine Engine Demonstration Project (CTEDP) had the mission of advancing ceramic gas turbine component technology toward commercialization. The thrust of the program was to “bridge the gap” between ceramics in the laboratory and near-term commercial heat engine applications. Most of this mission has been achieved. The 331-200[CT] auxiliary power unit (APU) test bed featured ceramic first-stage nozzles and blades. Fabrication of ceramic components provided manufacturing process demonstration scale-up to the minimum levels needed for commercial viability. Through this program, design methods refinement and the development of new design methods unique to ceramic turbine components have been supported and validated in rig and development engine testing. Over 6800 hours of on-site endurance tests demonstrated component reliability. Additional field testing in APUs onboard commercial aircraft and stationary industrial engines has been initiated and will continue beyond completion of this program.Copyright