High Performance Turbine Engine Research Articles

Influences of a multi-cavity tip on the blade tip and the over tip casing aerothermal performance in a high pressure turbine cascade

In modern gas turbine, the over tip leakage flow is inevitably generated in the tip gap of the first stage turbine blade due to the freestanding airfoil. In order to obtain a higher thermal efficiency, the turbine inlet temperature is gradually increased. Therefore, the over tip leakage flow induces significant aerodynamic losses and the blade tip and the over tip casing endure high level of thermal load. In the pursuit of a high-performance turbine engine, cavity tips are widely implemented in the turbine blade to reduce the over tip leakage flow and the thermal load on the blade tip and over tip casing. In the current study, the influences of the multi-cavity squealer tip on the blade tip and the over tip casing aerothermal performance were numerically investigated. Three-dimensional (3D) Reynolds-Averaged Navier-Stokes (RANS) equations and standard k-ω turbulence model were solved to conduct the simulations. The results indicate that the flat tip attains the largest thermal load on the blade tip, over-tip casing and induces the largest total pressure loss. However, the case with a single tip cavity (1CST) achieves the smallest total pressure loss and heat transfer coefficient on the over-tip casing, which are 7.6% and 19.6% lower than the flat tip, respectively. The case with a multi-cavity tip obtains a decreasing heat transfer coefficient on the blade tip. The case with five tip cavities (5CST) achieves the smallest heat transfer coefficient on the blade tip among all simulated cases, which is decreased by 17.5% relative to the flat tip.

Reliability-based multidisciplinary design and optimization for twin-web disk using adaptive Kriging surrogate model

Compared with the conventional single web disk, the twin-web disk has been designed as the future trend of the high-pressure turbine disk by the US Integrated High Performance Turbine Engine Technology program due to its breakthrough in weight loss, strength, and heat transfer efficiency. However, as a crucial component, the high-pressure turbine disk of aerocraft needs a high reliability and a steady quality at the same time. The traditional deterministic multidisciplinary design of optimization method sometimes could not be able to satisfy both the two requirements and depends heavily on the selection strategy of safety factor. In this article, reliability-based multidisciplinary design optimization has been performed to find a proper shape of twin-web disk with the minimum weight. The structural strength reliability analysis is performed using Monte Carlo simulation and set as the constraints in order to ensure the stability and safety. Kriging approximation is performed to reduce the computational cost. Then, the optimal points obtained by reliability-based multidisciplinary design optimization and common multidisciplinary design optimization are compared. The results show that the reliability-based multidisciplinary design optimization can obtain a better performance and less weight, which could be a reference in designing the twin-web disk for industry.

Sensitivity of RF Sensors for Bearing Health Monitoring

Coated bearings in high-performance turbine engines have the potential to provide considerable improvement in engine reliability and service-life extension. One coating performance indicator is the level of vibration generated by rolling elements and their cage separators at high-speed bearing operation. This article introduces a nonintrusive, cage-mounted sensor that detects cage vibration and transmits wirelessly to a nearby receiver. The sensitivity of the cage-mounted sensor was compared to a housing-mounted accelerometer in the detection of seeded faults in coated and uncoated bearings. The smallest spall on an uncoated bearing that the sensor could detect was 28 μm deep × 3.2 mm wide, with a reliability of ∼40%. In contrast, the accelerometer consistently detected all levels of flaws, the smallest being 0.4 μm deep × 3.2 mm wide on the coated bearing, with a reliability of 55%. Despite the sensor having a detection rate less than the accelerometer, this research successfully demonstrated that the sensor could detect inner-race-bearing flaws and established its sensitivity level.

Technology for Jet Engines: Case Study in Science and Technology Development

This case study examines jet engine development from the 1960s through the establishment of IHPTET (Integrated High Performance Turbine Engine Technology program) in the late 1980s and its role in enabling continued U.S. leadership in air-breathing propulsion capabilities. It focuses on science and technology management principles employed during that period, and how they impacted the process by which technologies were introduced. For this case study, the Institute for Defense Analyses researched the documented history of aircraft engine development through the 1980s and interviewed a number of current and retired personnel from both Government (laboratory personnel to officials in the Pentagon) and the large engine companies (GE Aircraft Engines, Pratt & Whitney, Rolls-Royce and others).

Sheet gamma TiAl: Status and opportunities

Gamma TiAl alloys have attractive properties such as low density, high-temperature strength, and high modulus, oxidation, and burn resistance. As a result, these alloys have the potential to replace heavier superalloys in aircraft engine components. Gamma TiAl alloys were investigated in the 1950s but were too brittle for thermo-mechanical processing. However, interest in this class of material rekindled with several U.S. aerospace programs: the National Aerospace Plane, the Integrated High Performance Turbine Engine Technology, and Enabling Propulsion Materials/High Speed Civil Transport, as well as German hypersonic technology programs. Intense metallurgical and metal processing research during the last two decades led to significant progress in this area. As a result, gamma TiAl alloys are now available in all conventional product forms: ingots, forgings, extrusions, and sheets. This article reviews the current status of sheet gamma TiAl technology and its future opportunities.

Simultaneous Short and Long Wavelength Infrared Pyrometer Measurements in a Heavy-Duty Gas Turbine

Advanced thermal barrier coatings (TBCs) are increasingly being used in high-performance turbine engines. For optimized use of the coatings, accurate surface temperature measurements are required in the combustion environment. Current on-engine pyrometers, which use short infrared wavelengths to accurately measure the temperatures of metal surfaces, show increased uncertainties when used on TBCs. Studies have suggested that long infrared wavelengths are a suitable alternative. Therefore, to evaluate the response of both wavelength regions, simultaneous measurements with short and long wavelength infrared pyrometers have been accomplished in the first stage turbine of a Siemens V84.3A 60 Hz 180 MW engine at the Berlin Gas Turbine Development and Manufacturing Center.

Direct SLS Processing for Production of Cermet Composite Turbine Sealing Components

This paper presents the development to date of Selective Laser Sintering (SLS) technologies for production of cermet composite turbine sealing components, the particular application being an abrasive blade tip. The component chosen for the application is an integral part of the low pressure turbine in a. IHPTET (Integrated High Performance Turbine Engine Technology) demonstrator engine. Both indirect and direct SLS techniques are being developed. Initial trials and process development involved the use of fugitive polymeric binders. Sequential refinements were performed to develop a binderless direct SLS process. Results from mechanical testing indicate that acceptable microstructure and properties are attainable by SLS with substantial cost savings as compared to the currently employed production method. This is the first instance of direct Solid Freeform Fabrication (SIT) method applied to a functional component.

Thermal radiative properties and temperature measurement from turbine coatings

Recent studies have displayed the spectral radiative properties of ceramic thermal barrier coatings which are finding applications in high performance turbine engines. As a function of temperature, a region in the long wavelength infrared spectrum exhibits properties which will minimize the classical errors associated with temperature measurement by radiometric detection. Hollow sapphire waveguides transmit the portion of the long wavelength infrared spectrum which is optimum for radiometric temperature measurement from these materials, while the physical properties of the sapphire can withstand the combustion conditions within the engine. A prototype long wavelength infrared radiation thermometer was constructed to obtain surface temperature measurements from coated turbine blades subjected to high temperature combustion conditions.

Development and Tribological Properties of New Cyclotriphosphazene High Temperature Lubricants for Aircraft Gas Turbine Engines

A number of substituted aryloxycyclotriphosphazenes were synthesized and studied, with the objective of meeting the lubricant requirements of the Integrated High Performance Turbine Engine Technology (IHPTET) initiative. These compounds were evaluated for pour point, oxidative stability, and lubricity behavior. Further property evaluations were performed on a leading candidate fluid, bis(4-fluorophenoxy)-tetrakis(3-trifluoromethylphenoxy) cyclotriphosphazene, code-named X-1P. The results of this study are discussed, along with comparative data of other leading commercial high temperature fluids.

Advanced Technology Programs for Small Turboshaft Engines: Past, Present, Future

This paper addresses approximately 15 years of advanced technology programs sponsored by the United States Army Aviation Applied Technology Directorate and its predecessor organizations and conducted by GE Aircraft Engines (GEAE). Included in these programs is the accomplishment of (1) the 1500 shp demonstrator (GE12), which led to the 1700, and (2) the 5000 shp Modern Technology Demonstrator Engine (MTDE/GE27). Also included are several advanced technology component programs that have been completed or are ongoing through the early 1990s. The goals for the next generation of tri-service small advanced gas generator demonstration programs are shown. A prediction is thus made of the advancements required to fulfill the aircraft propulsion system established by the DoD/NASA Integrated High-Performance Turbine Engine Technology (IHPTET) initiative through the year 2000.

Magnetic repulsion bearings for turbine engines

A six-month feasibility study has shown that magnetic repulsion bearings (MRB) possess the load capacity and stiffness required by future high-performance turbine engines. The fundamentals of MRBs are presented, and the method of analysis used to determine bearing feasibility is described. It involved a magnetic finite-element analysis on a linear magnetic bearing, the results of which were applied to a radial geometry. >

Multivariable Quadratic Synthesis of an Advanced Turbofan Engine Controller

A digital controller for an advanced turbofan engine utilizing multivariate feedback is described. The theoretical background of locally linearized control synthesis is reviewed briefly. The application of linear quadratic regulator techniques to the practical control problem is presented. The design procedure has been applied to the F100 turbofan engine, and details of the structure of this system are explained. Selected results from simulations of the engine and controller are utilized to illustrate the operation of the system. It is shown that the general multivariable design procedure will produce practical and implementable controllers for modern, high-performance turbine engines.

High Performance Turbine Engines

“Thunder driven, they clanged ……'thwart a heaven Pldshy with flying lightnings round the spurn o’ their feet”Francis Thompson(1859–1907)If it implied anything in the context of high performance turbine engines, the mutilated quotation from “The Hound of Heaven” might conjure up a vision of afterburning turbojets, or turbo-ramjets, propelling second or third generation supersonic transports at very great heights. This would be a misleading picture, and it will probably emerge that the quotation has little to do with what follows, as this is largely concerned with subsonic flight—on which I believe the economic future of aviation will depend for many years.