Managing Naval Gas Turbines Through a Memorandum of Understanding

This paper describes how four European navies have been able to work together for over twenty years in order to support their marine Tyne, Olympus and Spey gas turbines, used for surface ship propulsion, through two internationally agreed Memoranda of Understanding (MOUs). It shows how the MOUs came into existence, what their main aims are, how they are organised and how MOU business is conducted to achieve these aims. The final part of the paper discusses the merits of the existing MOUs and presents an insight into how they, and other MOUs currently under discussion, may develop in the future.

Endurance Testing of Marine Gas Turbines for the Royal Navy

Royal Naval policy since 1967 has been to employ gas turbines for major surface warship propulsion. In support of this policy, all new engines have been subject to endurance testing at DTEO Pyestock. Marinised Tyne and Olympus aero engines were tested during the 1960s and 70s which confirmed their initial suitability for RN service and uprated performance. Lessons learnt in formulating the test process were applied to the Spey SMIA engine programme in 1982. Further refinements, following comparison of sea operating experience with test bed results were applied to the 3000 hour endurance trial of the 18 MW Spey SMIC engine, which completed in 1993. The current testing at Pyestock is of the 21.6 MW Intercooled Recuperated (1CR) WR21 engine, presently under development for the USN in cooperation with the RN. The endurance trials being planned will require a further change in emphasis in order to address the unique operating regimes of an 1CR engine. The paper describes the evolution of endurance testing techniques, highlighting the particular requirements for complex cycle engines and discusses the opportunities that arose for piggyback trials during typical endurance testing regimes.

Inlet and Nozzle Technology for 21st Century Fighter Aircraft

The focus of propulsion integration technology in the 21st century will be economy. USAF inlet and nozzle technology goals translate into 50% weight reduction and 25% acquisition cost reduction metrics for new aircraft system. Innovative technology to enable these reductions over current state-of-the-art systems in weight and cost is required. For inlet systems, compact diffusers that reduce system volume by 50% will demand fewer parts and improved aerodynamic performance. Exhaust systems will be fixed with fewer parts, requiring a technology like fluidics, for example, to provide area control and thrust vectoring capabilities. Cooperative programs for both inlet and nozzle systems are in place to insure that technologies required to meet weight and cost reduction goals are matured by the year 2000.

A Nonintrusive Rotor Blade Vibration Monitoring System

A technique for measuring turbine engine rotor blade vibrations has been developed as an alternative to conventional strain-gage measurement systems. Light probes are mounted on the periphery of the engine rotor casing to sense the precise blade passing times of each blade in the row. The timing data are processed on-line to identify (1) individual blade vibration amplitudes and frequencies, (2) interblade phases, (3) system modal definitions, and (4) blade static deflection. This technique has been effectively applied to both turbine engine rotors and plant rotating machinery.

Development of Ceramic Gas Turbine Components for the CGT301 Engine

NGK Insulators, Ltd. (NGK) has undertaken the research and development on the fabrication processes of high-heat-resistant ceramic components for the CGT301, which is a 300kW recuperative industrial ceramic gas turbine engine. This program is under the New Sunshine Project, funded by the Ministry of International Trade and Industry (MITI), and has been guided by the Agency of Industrial Science & Technology (AIST) since 1988. The New Energy and Industrial Technology Development Organization (NEDO) is the main contractor. The fabrication techniques for ceramic components, such as turbine blades, turbine nozzles, combustor liners, gas-path parts, and heat exchanger elements, for the 1,200°C engine were developed by 1993. Development for the 1,350°C engine has been underway since 1994. The baseline conditions for fabricating of all ceramic components have been established. This paper reports on the development of ceramic gas turbine components, and the improved accuracies of their shapes as well as improved reliability from the results of the interim appraisal conducted in 1994.

Development of a Low-Emission Combustor for a 100-kW Automotive Ceramic Gas Turbine (III)

A low emission combustor, which uses a prevaporization-premixing lean combustion system for the 100 kW automotive ceramic gas turbine (CGT), has been subjected to performance tests. Now a second combustor prototype (PPL-2), which incorporates improvements intended to overcome a flashback problem observed in an initial combustor prototype (PPL-1), is tested. The PPL-2 has been designed and built, so that it will substantially expand the stable combustion range. The improvement is accomplished by increasing the air distribution ratio in the lean combustion region to avoid flashback, providing a uniform flow velocity through the throat area and also by diluting the boundary layer so as to suppress flashback. Test results of the PPL-2 combustor show that it expands the flashback limit without affecting the blow out limit and is able to cover the stable combustion range need for the 100kW CGT.

Status of the Automotive Ceramic Gas Turbine Development Program: Year Five Progress

Petroleum Energy Center of Japan has been carrying out a 7-year development program to prove the potential of an automotive ceramic gas turbine for five years with the support of the Ministry of International Trade and Industry. The ceramic gas turbine now under development is a regenerative single shaft engine. The output is 100kW, and the turbine inlet temperature (TIT) is 1350°C. All the ceramic components are now entering the 1350°C TIT test phase after completing 1200°C TIT evaluation tests, including durability tests, in various types of test rigs. The compressor-turbine combined test rig and the full assembly test rig which is the same as an actual engine and incorporates all the components are now going through 1200°C TIT function and performance evaluation tests. In the near future, we are planning to increase the TIT to 1350°C. In consideration of the current level of high-temperature, long-term strength available from the ceramic materials, we decided to change the rated speed to 100,000 rpm because the initial rated speed of 110,000 rpm, if unchanged, involves considerable risks. Then we reviewed mainly the designs of the compressor and turbine and revised the target values of the individual components to match the specifications that satisfy the target performance of the engine.

Creep Life of Ceramic Components Using a Finite Element Based Integrated Design Program (CARES/CREEP)

The desirable properties of ceramics at high temperatures have generated interest in their use for structural applications such as in advanced turbine systems. Design lives for such systems can exceed 10,000 hours. The long life requirement necessitates subjecting the components to relatively low stresses. The combination of high temperatures and low stresses typically places failure for monolithic ceramics in the creep regime. The objective of this paper is to present a design methodology for predicting the lifetimes of structural components subjected to creep rupture conditions. This methodology utilizes commercially available finite element packages and takes into account the time varying creep strain distributions (stress relaxation). The creep life of a component is discretized into short time steps, during which, the stress and strain distributions are assumed constant. The damage is calculated for each time step based on a modified Monkman-Grant creep rupture criterion. Failure is assumed to occur when the normalized accumulated damage at any point in the component is greater than or equal to unity. The corresponding time will be the creep rupture life for that component. Examples are chosen to demonstrate the CARES/CREEP (Ceramics Analysis and Reliability Evaluation of Structures/CREEP) integrated design program which is written for the ANSYS finite element package. Depending on the components size and loading conditions, it was found that in real structures one of two competing failure modes (creep or slow crack growth) will dominate. Applications to benchmark problems and engine components are included.

Thrust Reverser Catchers: Devices Which Enable Cyclic Testing Between Forward and Reverse Thrust

Cyclic operation of engines between forward and reverse thrust configurations is a requirement of testing for Extended Twin Operations (ETOPS) certification. When these tests are conducted inside enclosed test cells it is then necessary to redirect the exhaust gases in order to return them to the cell exhaust ducting. This is done by specially designed catcher ducts which have undergone many years of development, due to the complicated nature of the flow. The paper discusses the features that have eventually made these devices successful and as such is intended as an aid to design.

Predicting Marine Gas Turbine Engine Removals Using System Simulation

This paper evaluates System Simulation as a technique for predicting the removal of US Navy Marine Gas Turbine Engines. The Navy’s Allison 501K17 engine provided the data for this study. The Allison 501K17 is used for electric power generation by the Navy. A System Simulation Model was constructed using the programing language GPSS/H. Forecasts were developed using the model for fiscal years 1990 thru 1995. The model generated 21 forecasts for each year. The sample mode and mean were calculated for each year from this data. The Navy currently uses a statistical technique for forecasting engine removals. The Statistical Forecast, the System Simulation Sample Mode Forecast and System Simulation Sample Mean Forecast were compared with the actual number of removals for fiscal years 1990 thru 1994. A Chi-Square analysis was conducted to determine the goodness of fit of the forecast to the actual removals. The Chi-Square analysis showed that none of the forecasting techniques accurately predicted the removals. Additional study needs to be conducted to find a forecasting technique that accurately predicts engine removals.