Advanced Oxidation Protection System for Carbon-Carbon Composites

Carbon-carbon composites possess a number of desirable attributes including low density, high strength and stiffness at temperatures well beyond the capabilities of refractory alloys, low thermal expansion coefficient, tailorable orthotropic properties, absence of strategic materials, and resistance to thermal shock, fatigue, and brittle failures. However, for many applications of interest (such as aircraft and aerospace vehicle structure and engines) resistance to oxidation in high-temperature air or engine exhaust streams is a requirement which is not satisfied by unprotected carbon-carbon composites. The elements of an advanced oxidation protection system for carbon-carbon composites are described in this paper. The system is comprised of both an oxidation resistant coating intended to provide the primary barrier to oxygen ingress and inhibitors added to the matrix of the carbon-carbon composite to increase its oxidation resistance without significant losses in mechanical properties. The composite inhibition system is designed to be complementary to the coating and to enhance its long-term performance. A description of the principal elements of the system is presented along with recent test data and current research directions.

Current Status of Ceramic Gas Turbine R&D in Japan

The Japanese Ministry of International Trade and Industry (MITI) has started two nine-year national R&D projects for small-capacity ceramic gas turbines (CGTs) from 1988, following several preliminary investigations of the technical aspects and of the social impacts of CGTs. Planned 300kW industrial ceramic gas turbines are to be used for co-generation and mobile power generation. The goals are 42% and higher for the thermal efficiency at the turbine inlet temperature of 1350°C, and the emission from the exhaust gas should meet the regulatory values. Also ceramic components have the goals of 400MPa for the minimum flexure strength at 1500°C, and 15 MPam1/2 for the fracture toughness. New Energy and Industrial Technology Development Organization (NEDO) is the main contractor, and three groups of private industries are the subcontractors for 300kW industrial CGT project. Three national research institutes are involved in the projects to conduct supportive research of ceramic materials and engine components as well as to carry out assessment of the materials and engine systems developed by the private industries. The development of 100kW CGT for automotive use was also recommended in the above stated investigations and a two-year preliminary study started in 1988. The full-scale 100kW automotive CGT R&D project is scheduled to start in 1990 after the preliminary study. Japan Automobile Research Institute, Inc. (JARI) is the main contractor for 100kW automotive CGT project with the cooperation of three automobile companies.

Advanced Turbine Technology Applications Project (ATTAP): Overview, Status, and Outlook

The ATTAP aims at proving the performance and life of structural ceramic components in the hot gas path of an automotive gas turbine engine. This Department of Energy (DOE)-sponsored, NASA-managed program is being addressed by a General Motors (GM) team drawing expertise from the Advanced Engineering Staff (AES) and from Allison. The program includes design, process development and fabrication, rig and engine testing, and iterative development of selected key ceramic components for the AGT-5 engine. A reference powertrain design (RPD) based on this engine predicts acceleration, driveability, and fuel economy characteristics exceeding those of both current engines and the DOE goals. A low-apsect-ratio ceramic turbine rotor design has been successfully engine-demonstrated at 2200°F and 100% speed, including survival of impact and other hostile flow path conditions. Turbine flow path components have been designed for the 2500°F cycle, using improved monolithic ceramics targeted for Year 2 fabrication. Major development/fabrication efforts have been subcontracted at Carborundum, GTE Labs, Corning Glass, Garrett Ceramic Components, and Manville. Feasibility studies were initiated with Ceramics Process Systems and Drexel University.

A Variable-Geometry Power Turbine for Marine Gas Turbines

Gas turbines have been accepted in naval surface ship applications, and considerable effort has been made to improve their fuel consumption, particularly at part-load operation. This is an important parameter for shipboard engines because both propulsion and electrical-generator engines spend most of their lives operating at off-design power. An effective way to improve part-load efficiency of recuperated gas turbines is by using a variable power turbine nozzle. This paper discusses the successful use of variable power turbine nozzles in several applications in a family of engines developed for vehicular, industrial, and marine use. These engines incorporate a variable power turbine nozzle and primary surface recuperator to yield specific fuel consumption that rivals that of medium speed diesels. The paper concentrates on the experience with the variable nozzle, tracing its derivation from an existing fixed vane nozzle and its use across a wide range of engine sizes and applications. Emphasis is placed on its potential in marine propulsion and auxiliary gas turbines.

Desktop Failure Analysis on a Microcomputer Using Weibull, Lognormal and Renewal Data

Gas turbine components and parts are widely known to have many failure modes for which the failures correlate in either the Weibull or Lognormal probability distributions. This paper describes a typical case which is handled by the new computer programs now being used by the U. S. Navy. These programs have brought the capability to make such analyses directly to the designer or analysts desk instead of having to be sent off to a central computer to wait in line. The programs are interactive with the user and extremely user friendly. Uses are expanding to cover almost every area in the life cycle of gas turbines where it would be beneficial to forecast future failures. This makes the programs useful to managers, logisticians, life cycle cost analysts, and a host of others. Wide applicability of the methods assures usage outside of the gas turbine field.

Ceramic Composites for Gas Turbine Engines via a New Process

A new process for ceramic composites involves the growth of ceramic matrices through shaped preforms using directed oxidation reactions of molten metals. The preforms may consist of reinforcing fibers, whiskers, platelets, or particles, as needed to produce the desired properties in the finished component. This new technology is being developed by Lanxide Corporation and is being applied to gas turbine engine components by Du Pont Lanxide Composites Inc., a joint venture. The paper includes a description of the technology and a discussion of the status of its application to materials for gas turbine engine components.

United States Navy Gas Turbine Propulsion Machinery Systems Testing

Significant U.S. Navy controlled land based testing has been successfully conducted on gas turbines and gas turbine main propulsion systems since the early 1950’s. Through the success of these tested systems, largely as a result of successful land based testing, the demand for gas turbine powered main propulsion systems has been steadily increasing. Consequently, gas turbine technology, its applications, and required test capabilities are constantly being developed to meet future U.S. Navy requirements.

STOVL Hot Gas Ingestion Control Technology

A comprehensive wind tunnel test program was conducted to evaluate control of Hot Gas Ingestion (HGI) on a 9.2% scale model of the McDonnell Aircraft Company model 279-3C advanced Short Takeoff and Vertical Landing (STOVL) configuration. The test was conducted in the NASA-Lewis Research Center 9 foot by 15 foot Low Speed Wind Tunnel during the summer of 1987. Initial tests defined baseline HGI levels as determined by engine face temperature rise and temperature distortion. Subsequent testing was conducted to parametrically evaluate HGI control using: Lift Improvement Devices (LIDs), forward nozzle splay angle, combination of LIDs and forward nozzle splay angle, and main inlet blocking. The results from this test program demonstrate that HGI can be effectively controlled and that HGI is not a barrier to STOVL aircraft development.

Marine Gas Turbine Infra-Red Signature Suppression: Aerothermal Design Considerations

In recent years it has become evident that the Infrared (IR) Radiation given off by marine gas turbine exhaust systems is highly undesirable for naval vessels and commercial vessels traveling in areas of conflict. As a result, great interest has surfaced in the ways that IR signatures can be reduced. This paper presents an overview of some of the methods that can be used for engine exhaust IR signature suppression (IRSS). The methods considered here involve only ambient air addition for metal and plume cooling. The present paper describes various IRSS systems and discusses the basic technical criteria for system selection. Basic operating principles are also described. Aerothermal design considerations are discussed and areas requiring special care during the design are highlighted. Because of the confidential nature of the subject, direct quantitative performance comparisons cannot be made.

The Performance Prediction and Demonstration of a Centrifugal Compressor for the Multiple Purpose Small Power Unit (MPSPU)

This paper describes an analytical procedure for the prediction of the design point performance of a small centrifugal compressor. Results of a subsequent performance demonstration are presented. The geometry of the compressor was derived from an existing stage used in the PW200 engine, but rematched to 6:1 pressure ratio. Test data obtained from subsequent performance demonstration showed that the predicted performance had been achieved, but at 103% of design speed. A possible cause of this discrepancy is proposed.