bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rotating Cavity With Axial Throughflow of Cooling Air: Flow Structure
Authors: Farthing P. R. , Long C. A. , Owen J. M. , Pincombe J. R. 
Published: March 2015

A rotating cavity with an axial throughflow of cooling air is used to provide a simplified model for the flow that occurs between adjacent corotating compressor discs inside a gas-turbine engine. Flow visualization and laser-Doppler anemometry are employed to study the flow structure inside isothermal and heated rotating cavities for a wide range of axial-gap ratios. G. rotational. Reynolds numbers, Reφ, axial Reynolds numbers, Rez, and temperature distributions.
For the isothermal case, the superposed axial flow of air generates a powerful toroidal vortex inside cavities with large gap ratios (G > 0.400) and weak counter-rotating toroidal vortices for cavities with small gap ratios. Depending on the gap ratio and the Rossby number, ε (where ε ∝ Rez/Reφ), axisymmetric and nonaxisymmetric vortex breakdown can occur, but circulation inside the cavity becomes weaker as ε is reduced.
For the case where one or both discs of the cavity are heated, the flow becomes nonaxisymmetric: cold air enters the cavity in a “radial arm” on either side of which is a vortex. The cyclonic and anti-cyclonic circulations inside the two vortices are presumed to create the circumferential pressure gradient necessary for the air to enter the cavity (in the radial arm) and to leave (in Ekman layers on the discs). The core of fluid between the Ekman layers precesses with an angular speed close to that of the discs, and vortex breakdown appears to reduce the relative speed of precession.
Three-Dimensional Wake Decay Inside of a Compressor Cascade and its Influence on the Downstream Unsteady Flow Field: Part I — Wake Decay Characteristics in the Flow Passage
Authors: Poensgen C. , Gallus H. E. 
Published: March 2015

A measuring technique based on multisensor hot-wire anemometry has been developed to determine the unsteady three-dimensional velocity vector and the structure of turbulent flows. It then has been applied to the passage and the exit flow of an annular compressor cascade, which is periodically disturbed by the wakes of a cylinder rotor, located about 50 percent of blade chord upstream. In part I of this paper the decay of the rotor wakes will be described first without stator and secondly through a stator passage. The time-dependent turbulent flow field downstream of this stator is discussed in Part II.
The rotor wakes have a major influence on the development of three-dimensional separated regions inside the compressor cascade, and this interaction will be addressed in both parts of this paper.
Mechanics on the Tip Clearance Loss of Impeller Blades
Authors: Senoo Yasutoshi 
Published: March 2015

For predicting the tip clearance loss of turbomachines, different equations are published in the literatures based on differnt principles. In 1986 the present author posturated a new theory where the pressure loss consisted of two parts, one was the pressure loss induced by the drag force of the leaked flow and the other was the pressure loss to support the axial pressure difference without blades in the tip clearance zone. There were comments such as the two losses were the same loss looked from two different view points, or at least a part of the former was included in the latter or vice versa.
In this paper the pressure loss due to the tip clearance is examined based on a macroscopic balance of forces and the two kinds of loss are derived. Furthermore, it is made clear that the former comes from the induced drag which is parallel to the blade while the latter comes from the missing blade force normal to the blade in the clearance zone. Because these two forces are mutually perpendicular, the two losses are entirely different in nature and they do not even partially overlap to each other. It is also made clear quantitatively, how the loss of the kinetic energy of leaked flow is related to the induced drag of the clearance flow.
Effects of Vortices With Different Circulations on Heat Transfer and Injectant Downstream of a Single Film-Cooling Hole in a Turbulent Boundary Layer
Authors: Ligrani P. M. , Subramanian C. S. , Craig D. W. , Kaisuwan P. 
Published: March 2015

Results are presented which illustrate the effects of single embedded longitudinal vortices on heat transfer and injectant downstream of a single film-cooling hole in a turbulent boundary layer. Attention is focussed on the changes resulting as circulation magnitudes of the vortices are varied from 0.0 to 0.15 m**2/s. Mean temperature results are presented which show how injectant is distorted and redistributed by vortices, along with heat transfer measurements and mean velocity surveys. Injection hole diameter is 0.952 cm to give a ratio of vortex core diameter to hole diameter of about 1.5–1.6. The freestream velocity is maintained at 10 m/s, and the blowing ratio is approximately 0.5. The film-cooling hole is oriented 30 degrees with respect to the test surface. Stanton numbers are measured on a constant heat flux surface with a non-dimensional temperature parameter of about 1.5. Two different situations are studied: one where the injection hole is beneath the vortex downwash, and one where the injection hole is beneath the vortex upwash. For both cases, vortex centers pass well within 2.9 vortex core diameters of the centerline of the injection hole.
To quantify the influences of the vortices on the injectant and local heat transfer, the parameter S is used, defined as the ratio of vortex circulation to injection hole diameter times mean injection velocity. When S is greater than 1.0–1.5, injectant is swept into the vortex upwash and above the vortex core by secondary flows, and Stanton number data show evidence of injectant beneath the vortex core and downwash near the wall for x/d only up to 33.6. For larger x/d, local Stanton numbers are augmented by the vortices by as much as 23 percent relative to film-cooled boundary layers with no vortices. When S is less than 1.0–1.5, some injectant remains near the wall beneath the vortex core and downwash where it continues to provide some thermal protection. In some cases, the protection provided by film cooling is augmented because of vortex secondary flows which cause extra injectant to accumulate near vortex upwash regions.
Gas Turbine Power Plant Possibilities With a Nuclear Heat Source: Closed and Open Cycles
Authors: McDonald Colin F. 
Published: March 2015

With the capability of burning a variety of fossil fuels, giving high thermal efficiency, and operating with low emissions, the gas turbine is becoming a major prime-mover for a wide spectrum of applications. Almost three decades ago two experimental projects were undertaken in which gas turbines were actually operated with heat from nuclear reactors. In retrospect, these systems were ahead of their time in terms of technology readiness, and prospects of the practical coupling of a gas turbine with a nuclear heat source towards the realization of a high efficiency, pollutant free, dry-cooled power plant has remained a long-term goal, which has been periodically studied in the last twenty years. Technology advancements in both high temperature gas-cooled reactors, and gas turbines now make the concept of a nuclear gas turbine plant realizable. Two possible plant concepts are highlighted in this paper, (1) a direct cycle system involving the integration of a closed-cycle helium gas turbine with a modular high temperature gas cooled reactor (MHTGR), and (2) the utilization of a conventional and proven combined cycle gas turbine, again with the MHTGR, but now involving the use of secondary (helium) and tertiary (air) loops. The open cycle system is more equipment intensive and places demanding requirements on the very high temperature heat exchangers, but has the merit of being able to utilize a conventional combined cycle turbo-generator set. In this paper both power plant concepts are put into perspective in terms of categorizing the most suitable applications, highlighting their major features and characteristics, and identifying the technology requirements.
The author would like to dedicate this paper to the late Professor Karl Bammert who actively supported deployment of the closed-cycle gas turbine for several decades with a variety of heat sources including fossil, solar, and nuclear systems.
Viscous Flow Field Calculations in High-Loaded Centrifugal Compressor Diffusers
Authors: Teipel Ingolf , Wiedermann Alexander 
Published: March 2015

The topic of this paper is the computation of transonic turbulent flow fields in high-loaded centrifugal compressor diffusers with a time-marching scheme. A thin-layer approximation is introduced into the time-dependent Navier-Stokes equations and the turbulent quantities are provided by a zero-equation eddy-viscosity model due to Baldwin and Lomax. For solving the governing equations an explicit-implicit MacCormack scheme is applied. The effect of the side wall boundary layer can be employed globally by variable stream sheet thickness.
The present code has been verified by comparison of calculated and measured data. Pressure and velocity fields as well as global results like diffuser efficiency have been considered. The code is very efficient at a CRAY-XMP vector computer. Hence, two-dimensional and quasi-three-dimensional turbulent flow fields can be obtained with a reasonable effort. However, one has to be very careful concerning the modelling of the effect of the side-wall boundary layer by variable stream sheet thickness.
Experimental and Computed Performance Characteristics of High Speed Silicon Nitride Hybrid Ball Bearings
Authors: Hosang George W. 
Published: March 2015

Development testing of hybrid bearings with M.50 rings and HIP’ed silicon nitride balls in small high speed turbojet engines was carried out for several minutes at speeds up to 110,000 rpm. The main rotor system comprised an overhung radial compressor and turbine monorotor assembly with a pair of preloaded 101–size bearings. Estimated aerodynamic thrust of up to 750 N (170 lb) was added to the 200 N (45 lb) preload on the bearing adjacent to the compressor. Some testing was carried out with MIL–L–7808 air/oil mist and some with JP–10 fuel supplied in a similar fashion.
After each test phase the bearings were removed for examination and re–used or replaced. Four of the bearings were submitted to inspection with special equipment to measure operating contact angles, as evidenced by the visible ball tracks, and any wear present.
Contact angles and other operating characteristics estimated with the Jones, “SHABERTH,” and “ADORE” computer codes were compared with the experimental data.
EJ200: The Engine for the New European Fighter Aircraft
Authors: Lane R. J. , Behenna J. 
Published: March 2015

This paper describes the concept and design of the EJ200 engine to meet the air staff targets for the European Fighter Aircraft.
The international collaborative arrangements to support the programme are shown and the lessons learnt from previous collaboration illustrated.
The excellent progress made in the programme during the first year since the signing of the development contract is described to illustrate confidence in the ability to meet the design targets within the programme timescales.
Dynamic Control of Centrifugal Compressor Surge Using Tailored Structures
Authors: Gysling D. L. , Dugundji J. , Greitzer E. M. , Epstein A. H. 
Published: March 2015

A new method for dynamic control of centrifugal compressor surge is presented. The approach taken is to suppress surge by modifying the compression system dynamic behavior using structural feedback. More specifically, one wall of a downstream volume, or plenum, is constructed so to move in response to small perturbations in pressure. This structural motion provides a means for absorbing the unsteady energy perturbations produced by the compressor, thus extending the stable operating range of the compression system.
In the paper, a lumped parameter analysis is carried out to define the coupled aerodynamic and structural system behavior and the potential for stabilization. First-of-a-kind experiments are then carried out to examine the conclusions of the analysis. As predicted by the model and demonstrated with experiment, a moveable plenum wall lowered the mass flow at which surge occurred in a centrifugal compression system by roughly 25% for a large range of operating conditions. In addition, because the tailored dynamics of the structure acts to suppress instabilities in their initial stages, this control was achieved with relatively little power being dissipated by the moveable wall system, and with no noticeable decrease in steady state performance. Although designed on the basis of linear system considerations, the structural control is shown to be capable of suppressing existing large amplitude limit cycle surge oscillations.
Computation of Heat Transfer in Rotating Cavities Using a Two-Equation Model of Turbulence
Authors: Morse A. P. , Ong C. L. 
Published: March 2015

The paper presents finite-difference predictions for the convective heat transfer in symmetrically-heated rotating cavities subjected to a radial outflow of cooling air. An elliptic calculation procedure has been used, with the turbulent fluxes estimated by means of a low Reynolds number k-ε model and the familiar ‘turbulence Prandtl number’ concept. The predictions extend to rotational Reynolds numbers of 3.7 × 106 and encompass cases where the disc temperatures may be increasing, constant or decreasing in the radial direction.
It is found that the turbulence model leads to predictions of the local and average Nusselt numbers for both discs which are generally within ± 10% of the values from published experimental data, although there appear to be larger systematic errors for the upstream disc than for the downstream disc. It is concluded that the calculations are of sufficient accuracy for engineering design purposes, but that improvements could be brought about by further optimization of the turbulence model.
Design and Development of a Research Combustor for Lean Blowout Studies
Authors: Sturgess G. J. , Sloan D. G. , Lesmerises A. L. , Heneghan S. P. , Ballal D. R. 
Published: March 2015

In a modern annular aircraft gas turbine combustor, the phenomenon of lean blow out (LBO) is of major concern. To understand the physical processes involved in LBO, a research combustor was designed and developed to specifically reproduce recirculation patterns and LBO processes that occur in a real gas turbine combustor.
A total of eight leading design criteria were established for the research combustor. This paper discusses the combustor design constraints, aerothermochemical design, choice of combustor configurations, combustor sizing, mechanical design, combustor light-off, and combustor acoustic considerations that went into the final design and fabrication. Tests on this combustor reveal a complex sequence of events such as flame lift-off, intermittency, and onset of axial flame instability leading to lean blowout. The combustor operates satisfactorily and is yielding benchmark quality data for validating and refining computer models for predicting LBO in real engine combustors.
The F109-GA-100 Engine Designed Specifically for Trainer Use
Authors: Maertins Hans F. W. , Bruce Thomas W. 
Published: March 2015

The F109-GA-100 (F109) engine, originally developed by Garrett under contract to the U.S. Air Force, is a state-of-the-art powerplant designed specifically for trainer use. The engine has been designed and demonstrated to be fully aerobatic capable, without limitations throughout the training envelope. To minimize student pilot workload, the engine features a full-authority digital electronic fuel control with automatic start and restart, automatic overspeed-/temperature-limiting, simple power management with no restrictions in operation and automatic thrust trim. Maintenance features include extensive built-in test and data logging to support effective life management. Designed for an 18,000-hour life to a duty cycle with a mission severity comparable to that of a fighter, the F109 has demonstrated exceptional durability and high reliability. This durability — coupled with excellent fuel efficiency that rivals a turboprop — resulted in extremely low life-cycle-cost (LCC) as demonstrated in accelerated mission testing.
This paper describes the design features of the F109 that establish this engine as a trendsetter for the 1990s and beyond.
A Simple and Reliable Combustion Control System
Authors: Becker B. , Bonsen F. , Simon G. 
Published: March 2015

The basis of a simple and reliable control system is a low number of components to be controlled. In order not to bend the outer casing of the turbomachinery components during transients a symmetric arrangement of the combustors is required. Two combustors are then the lowest possible number. For modern dry-low-Nox burner systems with different modes of operation in the load range, more than one fuel nozzle system and the air flow distribution in the combustors have to be controlled. A low number of combustors therefore leads to a low number of such control devices.
The second key to a simple control systems is the design of the fuel nozzles. A return flow pressure atomizing system eliminates the need for more than one fuel nozzle per burner and for an atomizing air system. Gas nozzles not exhausting directly into the combustion zone eliminate the need for a gas nozzle purging system. To further improve the reliability of the system, the components are designed for maximum safety.
Combustor Exit Temperature Distortion Effects on Heat Transfer and Aerodynamics Within a Rotating Turbine Blade Passage
Authors: Harasgama S. P. 
Published: March 2015

A numerical simulation of temperature distortion at inlet to a rotating turbine rotor has been performed. A 3D Navier-Stokes code the 2D boundary layer code - STAN5, have been used.
The results show that the hot gas is transported to the pressure surface of the blade and that hot gas also migrates to the blade pressure side tip. At locations greater than 50–60% axial chord the hot gas enters the tip-gap and emerges over the suction side. These computations are in agreement with previous experimental results.
The secondary flows within the turbine rotor are enhanced by the introduction of inlet radial temperature distortion and this is in accord with previous analytical work. It is shown that the heat flux near the tip region on the pressure side of the blade can be increased by up to 76% due to the re-distribution of the inlet temperature distortion.
Operating Experience in Refinery Application of the 13MW-Class Heavy Duty MF-111 Gas Turbine Engine
Authors: Masada J. , Fukue I. 
Published: March 2015

A new, 13MW class, heavy duty gas turbine, the “MF-111” was developed for use as a prime mover for cogeneration, combined cycle and repowering applications. The use of such equipment in refineries presents special challenges as regards the combustion of nonstandard fuels, tolerance of industrial environments, and accomodation of site-specific design requirements. Such circumstances add substantially to the tasks of proving and adjusting the design of a new gas turbine, meeting stringent emissions requirements and introducing to the world of industrial gas turbines the benefits of F-class (1250°C burner outlet temperature) levels of thermodynamic performance.
This paper describes how these challenges have successfully been met during the three calendar years and ten machine-years of MF-111 refinery-application experience accumulated to-late.
Industrial Design Optimization of Small and Large Size Axial Turbines
Authors: Massardo Aristide , Satta Antonio 
Published: March 2015

This paper discusses the possibility of integrating optimization techniques with the design and analysis codes normally utilized in the industrial turbine design works.
The mathematical minimization procedure presented by the Authors in previous works is coupled here with industrial design codes of multistage axial flow turbines (small and large size) utilized by two Italian Companies.
The new industrial optimization procedures allow increases in the efficiency of the turbines to be obtained without the need for modifications in the industrial technology normally utilized to build the machines. The assumed initial turbine design is generally coincident with the conventional — non mathematically optimized — industrial project. In all cases the optimization is achieved by utilizing the blade profiles or “Masters” of the Companies. The results obtained for the optimization of multistage turbines are presented; the advantages concerning the design time and the usefulness of the procedures are discussed.
Analysis of Experimental Time-Dependent Blade Surface Pressures From an Oscillating Turbine Cascade With the Influence-Coefficient Technique
Authors: Fransson T. H. 
Published: March 2015

A two-dimensional section of the last stage of a steam turbine has been investigated experimentally in an annular non-rotating cascade facility as regards to its steady-state and time-dependent aerodynamic characteristics at design and off-design conditions.
The unsteady experimental data obtained with the blades vibrating in the “travelling wave” mode indicate that one of the main reasons for the flutter susceptibility of the cascade lies in the high expansion and following shock wave close to the blade suction surface leading edge and the corresponding high unsteady loading. The decomposition of the experimental data into unsteady aerodynamic influence coefficients validates this conclusion and gives also that another reason for the flutter susceptibility can be found in the fact that the cascade is overlapped for a part of the blade surface where the local flow velocities are close to sonic.
The unsteady aerodynamic influence coefficients show that the instability arises because of the time dependent aerodynamic coupling effects between, essentially, the reference blade and its immediate suction surface and, to a lesser extent, pressure surface neighbors.
Three Dimensional Design of a High Speed Radial-Inflow Turbine by a Novel Design Method
Authors: Zangeneh M. 
Published: March 2015

This paper is concerned with the design of a high speed, 5 inch diameter radial-inflow turbine for medium-sized diesel engine turbocharger applications. The turbine was designed by a newly developed fully three dimensional compressible inverse design method, in which the blade shapes are computed for a specified distribution of rV¯θ. The designed blades had non-radial blade filaments and therefore the impeller was carefully analysed for its structural integrity. This was achieved by the iterative use of a three dimensional structural and vibration analysis program and the design method.
The impeller was made by a casting process. The performance of the new impeller was measured and then compared with three other impellers, one conventional and two experimental. The new impeller performed substantially better than all the baseline turbines and showed a 5.5% improvement in the total-to-static efficiency over the conventional turbine, 2.5% of which was attributable to the aerodynamically superior blade shape computed by the three dimensional inverse design method. The improvement in efficiency was not just confined to the design point and an appreciable improvement could be observed at off-design conditions.