bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation of a 1-1/2 Axial Turbine Stage at Quasi-Steady and Fully Unsteady Conditions
Authors: Aubé Martin , Hirsch Charles 
Published: July 2014

The analysis and design methods used for turbomachinery components are mostly based on steady aerodynamics, neglecting the important unsteady nature of the flow field. An improvement in performance can however be achieved with a prior understanding, evaluation and modeling of the main unsteady loss sources generated in rotor/stator interactions, through new advanced experimental data coupled to systematic and controlled numerical simulations performed at the full unsteady level of approximation. But such calculations are even nowadays challenges to the CFD community, due to their high requirement in computer resources.
To investigate the importance of unsteady loss mechanisms, a 1-1/2 axial turbine stage has been resolved at both quasi-steady and fully unsteady levels of approximation. In order to reduce the demand on computer resources, a scaling procedure can be applied to retrieve equal pitch distance on both sides of each rotor/stator interface. The space and time flow periodicity are then uncoupled and the unsteady flowfield may be resolved on a reduced number of blade passages per row without having to consider any time periodicity in the boundary treatment. The grid scaling however affects the turbine total pressure ratio and the position and strength of secondary flows, as the pitch-to-chord ratio is not kept constant. This effect is analyzed in the paper, with the objective to assess the associated approximation errors.
Steady and unsteady numerical simulations are compared with the experimental data along three measuring stations placed downstream of each blade row. Even if steady results are in good agreement and allow capturing the main flow structures of the turbine stage, only the fully unsteady calculation resolves the complex loss mechanisms encountered mainly in the rotor and downstream stator components. These unsteady interactions are observed through time variations of the entropy, absolute flow angle and static pressure.
Centrifugal Compressor Blade Trimming for a Range of Flows
Authors: Rodgers C. 
Published: July 2014

Centrifugal impeller blade trimming has long been used in the turbocharger industry to adapt a single impeller casting to a series of flow capacities, but surprisingly little published literature exists on the effects of trimming to compressor performance.
This paper is presented as partial remedy, and describes the performance characteristics of a single stage centrifugal compressor designed and tested to cover a range of flow requirements by impeller blade and diffuser vane trimming.
Stage and component test performance characteristics are presented for five trimmed flowpath contours covering a flow capacity range of approximately five to one at a DeLaval number of 0.75.
The impeller tip diameter was 356mm, and the highest overall stage efficiency measured was 84.8% at an (air) pressure ratio of 1.5.
Short and Long Length-Scale Disturbances Leading to Rotating Stall in an Axial Compressor Stage With Different Stator/Rotor Gaps
Authors: Inoue M. , Kuroumaru M. , Yoshida S. , Furukawa M. 
Published: July 2014

The transient processes of rotating stall evolution have been investigated experimentally in a low-speed axial compressor stage with three stator-rotor gaps. The pressure traces at 8 circumferential locations on the casing wall near the rotor leading edge have been analyzed by the wavelet transforms. With the appropriate mother wavelets, the evolution of short and long length-scale disturbances leading to the stall can be captured clearly.
Behavior of these disturbances is different depending on the stator-rotor gap. For the large and middle gap, the stall inception is detected by a spiky short length-scale disturbance, and the number of spiky waves increases to generate the high frequency waves. They becomes the short length-scale part-span stall cells at the mild stall for the large gap, while they turn into a big stall cell with growth of a long length-scale disturbance for the middle gap. In the latter case, therefore, the stalling process was identified with ‘high frequency stall inception’. For the small stator-rotor gap, the stalling process is identified with ‘long wave-length stall inception’, and supported the recent computational model for the short wave-length stall inception by showing that closing the rotor-stator gaps suppressed the growth of short length-scale disturbances.
From the measurement of the pressure field traces on the casing wall, a hypothesis has been built up that the short length-scale disturbance should result from a separation vortex from a blade surface to reduce circulation. The processes of the stall evolution are discussed on this hypothesis.
Computational Analysis of Passive Stall Delay Through Vaned Recess Treatment
Authors: Ghila A. , Tourlidakis A. 
Published: July 2014

This paper presents a computational investigation of flows in a single axial flow fan with and without casing treatment. It analyses the effect of the recess casing treatment on stall margin improvement as well as its influence on global performance parameters. The paper seeks to offer a contribution to the understanding of the physical processes occurring when approaching stall and the working mechanism by which casing treatments improve stall margin.
A Reynolds-Averaged Navier-Stokes CFD code was used for the analysis and the numerical investigation of the overall performance, efficiency and work-input characteristics of the fan were found to agree very well with previously reported experimental results. The effect of casing treatment was investigated using two types of configurations, vaneless and vaned casing. The vaneless casing treatment produced a sizeable stall margin improvement with negligible loss of efficiency. The recess was fitted later with vanes and was shown to offer both a further stall margin improvement and an increase in the pressure rise coefficient without any significant drop in efficiency at design conditions.
Turbomachinery Blade Design Using 3-D Inverse Design Method, CFD and Optimization Algorithm
Authors: Ashihara Kosuke , Goto Akira 
Published: July 2014

An optimization approach for improving turbomachinery performance was proposed based on a three-dimensional inverse design method, a Computational Fluid Dynamics (CDF) and optimization algorithm. By combining the three-dimensional inverse design method and CFD predictions, the blade loading parameters which is the major inputs for the three-dimensional inverse design method were treated as design variables and the impeller performance predicted by CFD was treated as an objective function of the optimization problem.
Firstly, to clarify the effects of optimization algorithm, mixed-flow pump impellers (Ns400), with a specific speed of 400 (m3/min,m,min−1) or 0.155 (non-dimensional), were optimized to improve the impeller efficiency by using several optimization algorithm. From these results, it was confirmed that turbomachinery optimization using the three-dimensional inverse design method is a multi-peak problem and it is essential to use exploratory techniques such as Simulated Annealing. Then, a mixed-flow pump impeller (Ns1350), with a specific speed of 1350 (m3/min,m,min−1) or 0.523 (non-dimensional), was optimized to improve the impeller efficiency with constraints for suction performance by Simulated Annealing. Reasonably high efficiency and high suction performance were confirmed by comparing the CFD results with those for the previous design which employed manual optimization.
Performance of Zero Emissions Integrated Gasification Hydrogen Combustion (ZE-IGHC) Power Plants With CO2 Removal
Authors: Cau Giorgio , Cocco Daniele , Montisci Augusto 
Published: July 2014

This paper concerns a performance evaluation of advanced zero emissions (NOx, SOx, CO and particulate, but also CO2), coal gasification integrated power plants with hydrogen combustion (ZE-IGHC). In ZE-IGHC power plants the hydrogen is produced through CO shift conversion and subsequent CO2 separation. The hydrogen is burned using pure oxygen in an internal combustion steam power plant with double combustion and thermodynamic regeneration. As a result of raw gas cleaning, CO2 separation and hydrogen combustion with oxygen, the ZE-IGHC power plant eliminates pollutant and greenhouse gas emissions.
A comparative study of ZE-IGHC plant configurations based on different gasifiers and raw gas cooling options indicated that net efficiencies of up to about 50% can be achieved by resorting to configurations based on dry-feed gasifiers and raw gas cooling heat recovery with steam production. The simpler and cheaper plant configurations based on wet-feed gasifiers and raw gas quench systems give an efficiency penalty of about 3-4 % points.
The ZE-IGHC power plant presented here can be a very attractive option for a near term, coal-fired power generation system. What is more, its major components are already adopted in conventional power plants and only the hydrogen combustors and the high temperature turbine require technology development.
Flame Transfer Function Calculations for Combustion Oscillations
Authors: Zhu M. , Dowling A. P. , Bray K. N. C. 
Published: July 2014

Combustors with fuel-spray atomisers are particularly susceptible to a low-frequency oscillation at idle and sub-idle conditions. For aero-engine combustors, the frequency of this oscillation is typically in the range 50-120Hz and is commonly called ‘rumble’. The mechanism involves interaction between the plenum around the burner and the combustion chamber. Pressure variations in the plenum or the combustor alter the inlet air and fuel spray characteristics, thereby changing the rate of combustion. This in turn leads to local ‘hot spots’ which generate pressure oscillations as they convect through the downstream nozzle.
In order to eliminate the combustion oscillations, it is essential to determine which fuel atomisers are particularly likely to lead to instability by quantifying their sensitivity to flow perturbations. This can be done by identifying the system through understanding the transfer function, which represents the relationship between the unsteadiness of combustion and the inlet fuel and air. In the present work, various types of signals are applied to produce a small change the inlet fuel and air flow rates, the response in the rate of heat release caused downstream was calculated and stored for subsequent analysis. Afterwards, the system transfer function is calculated by determining the coefficients of an IIR filter (Infinite Impulse Response) for which the output signal is the downstream heat release rate and the input signal is the inlet flow rate. The required transfer function then follows from the Fourier transform of this relationship. The resulting transfer functions are compared with those obtained by the forced harmonic oscillations at a fixed given frequency. Suitably chosen input signals accurately recover the results for harmonic forcing at a single frequency, but also give detailed information about the combustor response over a wide frequency range. There are two distinct forms to the low-frequency quasi-steady response. In the primary zone, the rate of combustion is influenced by the turbulence and is enhanced when the inlet air velocity is large. Near the edge of combustion zone, the rate of combustion depends on the mixture fraction and is high when the mixture fraction is close to the stoichiometric value. This generates ‘hot spots’ which convect into the dilution zone. At higher frequencies, the combustion lags this quasi-steady response through simple lag-laws and the relevant time delays have been identified.
The Integration of Atmospheric Molten Carbonate Fuel Cells With Gas Turbine and Steam Cycles
Authors: Campanari Stefano , Macchi Ennio 
Published: July 2014

The exploitation of the high-temperature-fuel-cell technology, actually being developed by many companies involved in the gas turbine market, could allow outperforming performance of conventional prime movers based upon fossil fuel combustion.
This paper investigates the integration of molten carbonate fuel cells (MCFCs) working at atmospheric pressure with some representative cycle configurations based either on steam and gas turbine cycles.
Detailed energy balances of the most promising cycle configurations are presented; fuel cell and conventional components working parameters and technological issues are described and discussed.
It is shown that efficiencies well above 60% can be achieved by combining MCFCs either with recuperative gas turbine or steam cycles.
Degradation Effects on Combined Cycle Power Plant Performance: Part 2 — Steam Turbine Cycle Component Degradation Effects
Authors: Zwebek A. , Pilidis P. 
Published: July 2014

This is the second paper exploring the effects of the degradation of different components on Combined Cycle Gas Turbine (CCGT) plant performance.
This paper investigates the effects of degraded steam path components of steam turbine (bottoming) cycle have on CCGT power plant performance. Areas looked at were, steam turbine fouling, steam turbine erosion, heat recovery steam generator degradation (scaling and/or ashes deposition), and condenser degradation. The effect of gas turbine back-pressure on plant performance due to HRSG degradation is also discussed.
A general simulation Fortran code was developed for the purpose of this study. This program can calculate the CCGT plant design point performance, off-design plant performance, and plant deterioration performance. The results obtained are presented in a graphical form and discussed.
Computational Design and Experimental Evaluation of Using a Leading Edge Fillet on a Gas Turbine Vane
Authors: Zess G. A. , Thole K. A. 
Published: July 2014

With the desire for increased power output for a gas turbine engine comes the continual push to achieve higher turbine inlet temperatures. Higher temperatures result in large thermal and mechanical stresses particularly along the nozzle guide vane. One critical region along a vane is the leading edge-endwall juncture. Based on the assumption that the approaching flow to this juncture is similar to a two-dimensional boundary layer, previous studies have shown that a horseshoe vortex forms. This vortex forms because of a radial total pressure gradient from the approaching boundary layer.
This paper documents the computational design and experimental validation of a fillet placed at the leading edge-endwall juncture of a guide vane to eliminate the horseshoe vortex. The fillet design effectively accelerated the incoming boundary layer thereby mitigating the effect of the total pressure gradient. To verify the CFD studies used to design the leading edge fillet, flow field measurements were performed in a large-scale, linear, vane cascade. The flow field measurements were performed with a laser Doppler velocimeter in four planes orientated orthogonal to the vane. Good agreement between the CFD predictions and the experimental measurements verified the effectiveness of the leading edge fillet at eliminating the horseshoe vortex. The flowfield results showed that the turbulent kinetic energy levels were significantly reduced in the endwall region because of the absence of the unsteady horseshoe vortex.
Component Management Programs for Reliable Life Extension
Authors: Cooke Lloyd A. 
Published: July 2014

Conventional maintenance schedules and scheduling techniques are typically based on the manufacturer’s guidelines and applied to all engines of a certain make and model. This approach does not always address the specific operating environment and requirements for each operator.
An alternative to this conventional “one schedule suits all” approach is the Component Management Program described in the paper. This type of program is designed to tailor maintenance requirements to suit the specific operating environment of the operator’s engine or fleet of engines. The program is intended to extend and optimize maintenance intervals and at the same time ensure reliability of the components. The paper outlines the metallurgical analysis and other techniques that are incorporated into a Component Management Program, the tracking systems used to schedule maintenance, and some case studies where these programs have been used to extend component life and reliability.
Aerodynamic Design of a New Five Stage Low Pressure Turbine for the Rolls Royce Trent 500 Turbofan
Authors: Ulizar I. , González P. 
Published: July 2014

Almost a decade ago, ITP (Industria de Turbo Propulsores, S.A.) started to participate in Low Pressure turbine design supported by Rolls-Royce. The Trent 500 LP turbine aerodynamic design is the most challenging and extensive design work carried out to the moment.
The Trent 500 is part of the Rolls Royce Trent family. It has been designed to enter in service in the Airbus 340-600. This engine has very aggressive targets in terms of cost, performance, weight and noise. An optimization process was carried out during the preliminary and detailed design phases to accomplish these targets.
This paper describes the most outstanding characteristics of the LP turbine, how the previous experience and Research and Technology results have been employed in this design and also some of the new advanced features, e.g. the introduction of spoon aerofoils.
Boundary Layer Development in the BR710 and BR715 LP Turbines: The Implementation of High Lift and Ultra High Lift Concepts
Authors: Howell R. J. , Hodson H. P. , Schulte V. , Schiffer Heinz-Peter , Haselbach F. , Harvey N. W. 
Published: July 2014

This paper describes a detailed study into the unsteady boundary layer behaviour in two high lift and one ultra high lift Rolls-Royce Deutschland LP turbines. The objectives of the paper are to show that high lift and ultra high-lift concepts have been successfully incorporated into the design of these new LP turbine profiles.
Measurements from surface mounted hot film sensors were made in full size, cold flow test rigs at the altitude test facility at Stuttgart University. The LP turbine blade profiles are thought to be state of the art in terms of their lift and design philosophy. The two high lift profiles represent slightly different styles of velocity distribution. The first high-lift profile comes from a two stage LP turbine (the BR710 cold-flow, high-lift demonstrator rig). The second high-lift profile tested is from a three-stage machine (the BR715 LPT rig). The ultra-high lift profile measurements come from a redesign of the BR715 LP turbine: this is designated the BR715UHL LP turbine. This ultra high-lift profile represents a 12% reduction in blade numbers compared to the original BR715 turbine.
The results from NGV2 on all of the turbines show “classical” unsteady boundary layer behaviour. The measurements from NGV3 (of both the BR715 and BR715UHL turbines) are more complicated, but can still be broken down into classical regions of wake-induced transition, natural transition and calming. The wakes from both upstream rotors and NGVs interact in a complicated manner, affecting the suction surface boundary layer of NGV3. This has important implications for the prediction of the flows on blade rows in multistage environments.
Flight Test and Refinement of a Nacelle Ventilation Inlet Partially Submerged in Boundary Layer
Authors: Lundy Brian F. , Sylvester Thomas G. , Catt Jeffrey A. 
Published: July 2014

Efforts to develop, test, and refine a nacelle ventilation inlet for the F-16 Fighting Falcon are presented in this work. The nacelle inlet was developed to support retrofit of existing F-16 aircraft with an ejector nozzle.
The F-16 is equipped with a ventilated nacelle that inhibits ignition sources and accumulation of flammable vapors in the engine bay. When integrating the ejector nozzle, Lockheed Martin Aeronautics Company (LM Aero) and GE Aircraft Engines (GEAE) took advantage of this feature to redirect nacelle ventilation air (which is typically dumped overboard) to the exhaust nozzle for cooling. This system dramatically extends nozzle divergent flap and seal life and reduces operational and support (O&S) costs.
GEAE’s ejector nozzle produces higher nacelle ventilation exhaust pressures than the existing system, prompting the need to redesign the nacelle inlet to maintain nacelle ventilation capability. Fire protection and nozzle cooling goals drove the need for higher nacelle pressure, while structural design limited the maximum pressure within the nacelle. The design space was bound by these contrasting requirements. To complicate matters, the nacelle inlet also had to manage the thick boundary layer generated by the aircraft fuselage.
A flight test was performed to manage uncertainties in the system and mitigate the risks of installing a new nacelle inlet on the F-16. The flight test revealed the influence of shock wave / boundary layer interaction (viscous interaction) on inlet pressure recovery. These findings resulted in several recommendations for improving the inlet design, the most significant being the inclusion of a boundary layer diverter. An overview of inlet development and the results obtained from the risk management tasks are presented in this work.
Improvement of the Accuracy in Gas Turbine Health Determination
Authors: Pinelli M. , Venturini M. 
Published: July 2014

Health Monitoring Systems (HMS) based on operating state determination techniques that make use of field measurements are subjected to inaccuracies arising from measurements unreliability due to various kinds of uncertainties (such as sensors faults, measurements inaccuracies, etc.).
In this paper, some techniques to improve the accuracy of gas turbine health state determination are presented:
- a measurement conditioning technique based on the expected and trend values of measurements;
- the evaluation of the best measurements/health parameters combination that should be used with respect to the gas turbine operating state determination.
Development of High-Speed Gas Bearings for High-Power-Density Micro-Devices
Authors: Ehrich F. F. , Jacobson S. A. 
Published: July 2014

A 4.2 mm diameter silicon rotor has been operated in a controlled and sustained manner at rotational speeds greater then 1.3 million rpm and power levels approaching 5 W. The rotor, supported by hydrostatic journal and thrust gas bearings, is driven by an air turbine. This turbomachinery/bearing test device was fabricated from single crystal silicon wafers using micro-fabrication etching and bonding techniques. We believe this device is the first micro-machine to operate at a circumferential tip speed of over 300 meters per second, comparable to conventional macro-scale turbomachinery, and necessary for achieving high levels of power density in micro-turbomachinery and micro-electrostatic/ electromagnetic devices.
To achieve this level of peripheral speed, micro-fabricated rotors require stable, low friction bearings for support. Due to the small scale of these devices as well as fabrication constraints that limit the bearing aspect ratio, the design regime is well outside that of more conventional devices. This paper focuses on bearing design and test, and rotordynamic issues for high-speed high-power micro-fabricated devices.