bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aeroacoustic Optimization of Radial Fans for Medical Applications
Authors: Stadler Michael , Grilliat Julien , Laufer Wolfgang , Schmitz Michael B. 
Published: September 2016

In recent years there is a growing number of patients suffering from pneumonia, chronic obstructive pulmonary disease or asthma. In these situations, the application of Continuous Positive Airway Pressure (commonly known as CPAP) is indicated by clinicians. It is a noninvasive means of healthcare used widely. As a more advanced technique, the positive airway pressure may follow a time-cycled change between two preset pressure values. This technique is known as BPAP (Bi-level Positive Airway Pressure).
The devices are used mainly during sleep at home. Hence the aeroacoustic requirements are critical. In addition the devices must be portable and compact. Furthermore, the high frequency of pressure change required in BPAP devices poses additional demands on the design. Due to the complexity of the overall design problem, it may be solved efficiently by multi objective optimization.
The pressure head in these devices is generated by radial fans. For the aerodynamic optimization, we utilize a RANS solver. For the aeroacoustic optimization we use the Lattice-Boltzmann Method (LBM). Both are operating on a parametric geometric model of the fan and housing. For the propagation of sound waves into the far-field, we develop algorithmic strategies for using the Ffowcs Williams-Hawkings (FW-H) equation with the LBM. The constrained multi objective optimization is driven by a variant of the NSGA-II algorithm.
We outline the complete optimization procedure for a BPAP device. Our numerical results are compared with physical tests. To analyze the contribution of selected geometric features to the emitted sound pressure, we perform a sensitivity study. The new algorithmic arrangement has shown to drastically cut development costs and time.
Modelling of Gas Turbine NOx Emissions Based on Long-Term Operation Data
Authors: Rudolf Christian , Wirsum Manfred , Gassner Martin , Zoller Benjamin Timo , Bernero Stefano 
Published: September 2016

The continuous monitoring of gas turbines in commercial power plant operation provides long-term engine data of field units. Evaluation of the engine performance from such data is challenging since, apart from variations of operating points and ambient conditions, the state of the engine is subject to change due to ageing of engine components. The installed measurement devices influence the analysis due to their accuracy, which may itself alter with time. Furthermore, the available measurements usually do not cover all necessary information for assessment of the engine performance. To overcome these issues, this paper describes a method to systematically evaluate long term operation data without the incorporation of engine design models that depict the design state of the engine, but do not cover performance changes when components are ageing. Key focus of the methodology is thereby to assess long-term emission performance in the most reliable manner.
The analysis applies a data reconciliation method to long-term operating data in order to model the engine performance including non-measured variables and to account for measurement inaccuracies. This procedure relies on redundancies in the data set due to available measurements and the identification of suitable additional constituting equations that are independent of component ageing. The resulting over-determined set of equations allows for performing a data set optimization with respect to a minimal cumulated deviation to the measurement values, which represents the most probable, real state of the engine. The paper illustrates the development and application of the method for analysing emission performance with long-term operating data of a commercial gas turbine combined cycle power plant.
Assessment of Solar Steam Injection in Gas Turbines
Authors: Kalathakis C. , Aretakis N. , Roumeliotis I. , Alexiou A. , Mathioudakis K. 
Published: September 2016

The concept of solar steam production for injection in a gas turbine combustion chamber is studied for both nominal and part load engine operation. First, a 5MW single shaft engine is considered which is then retrofitted for solar steam injection using either a tower receiver or a parabolic troughs scheme. Next, solar thermal power is used to augment steam production of an already steam injected single shaft engine without any modification of the existing HRSG by placing the solar receiver/evaporator in parallel with the conventional one.
For the case examined in this paper, solar steam injection results to an increase of annual power production (∼15%) and annual fuel efficiency (∼6%) compared to the fuel-only engine. It is also shown that the tower receiver scheme has a more stable behavior throughout the year compared to the troughs scheme that has better performance at summer than at winter. In the case of doubling the steam-to-air ratio of an already steam injected gas turbine through the use of a solar evaporator, annual power production and fuel efficiency increase by 5% and 2% respectively.
Laboratory Infra-Red Thermal Assessment of Laser-Sintered High-Pressure Nozzle Guide Vanes to De-Risk Engine Design Programmes
Authors: Kirollos Benjamin , Povey Thomas 
Published: September 2016

The continuing maturation of metal laser-sintering technology (DMLS) presents the opportunity to de-risk the engine design process by experimentally down-selecting HPNGV cooling designs using laboratory tests of laser-sintered — instead of cast — parts to assess thermal performance. Such tests could be seen as supplementary to thermal-paint-test engines, which are used during certification to validate cooling system designs.
In this paper, we compare conventionally cast and laser-sintered titanium alloy parts in back-to-back experimental tests at engine-representative conditions over a range of coolant mass flow rates. Tests were performed in the University of Oxford Annular Sector Heat Transfer Facility. The thermal performance of the cast and laser-sintered parts — measured using new infra-red processing techniques — is shown to be very similar, demonstrating the utility of laser-sintered parts for preliminary engine thermal assessments.
We conclude that the methods reported in this paper are sufficiently mature to make assessments which could influence engine development programmes.
Design of Compressor Endwall Velocity Triangles
Authors: Auchoybur Kiran , Miller Robert J. 
Published: September 2016

Near the endwalls of multi-stage compressor blade rows, there is a spanwise region of low momentum, high entropy fluid which develops due to the presence of annulus walls, leakage flows and corner separations. Off-design this region, known as the endwall flow region, often grows rapidly and in practice sets the compressor’s operating range. By contrast, over the operating range of the compressor, the freestream region of the flow is not usually close to its diffusion limit and has little effect on overall range. In light of these two distinct flow regions within a bladerow, this paper considers how velocity triangles in the endwall region should be designed to give a more balanced spanwise failure across the blade span.
In the first part of the paper, the sensitivity of the operating flow range of a single blade row to variations in realistic multistage inlet conditions and endwall geometry is investigated. It is shown that the operating range of the blade row is largely controlled by the size and structure of the endwall ‘repeating stage’ inlet boundary layer and not the detailed local geometry within the blade row.
In the second part of the paper the traditional design process is ‘flipped’. Instead of redesigning a blade’s endwall geometry to cope with a particular inlet profile into the blade row, the endwall region is redesigned in the multi-stage environment to ‘tailor’ the inlet profile into downstream blade rows. This is shown to allow an extra degree of freedom not usually open to the designer. This extra degree of freedom is exploited to balance freestream and endwall operating range, resulting in a compressor having an increased operating range of ∼20%. If this increased operating range is traded with reduced blade count, it is shown that a design efficiency improvement of Δη∼0.5% can be unlocked.
Investigations of the Actuation Effect of a Single DBD Plasma Actuator for Flow Separation Control Under Simulated Low-Pressure Turbine Blade Conditions
Authors: Pescini Elisa , Marra Fedele , De Giorgi Maria Grazia , Francioso Luca , Ficarella Antonio 
Published: September 2016

The present study intends to investigate the potentiality of the single dielectric barrier discharge plasma actuators (SDBDPAs) to reattach the separated flow, occurring at low Reynolds numbers. For this aim, a curved wall plate, which profile shape was designed to reproduce the suction surface of a low-pressure turbine (LPT) blade, was installed in the test section of a closed loop wind tunnel and a SDBDPA was placed in a groove made over it, at the front of the adverse pressure gradient region. The flow behavior in absence of actuation has been experimentally investigated by particle image velocimetry (PIV) and laser Doppler velocimetry measurements (LDV). Moreover, sinusoidal voltage excitation with amplitude of 8 kV and frequency of 2 kHz was applied to the SDBDPA and PIV measurements were also performed in presence of actuation. The applied voltage and the discharge current have also been recorded simultaneously, and they have been used for the determination of the device dissipated power.
Different wind tunnel free stream velocities were investigated, both in absence and presence of actuation. The effect of the active flow control was then studied in the entire measurement domain by analyzing the velocity fields, the turbulence intensity (Tu) values, the momentum coefficient (cμ) and the boundary layer shape factor (H12). In absence of actuation, a large reverse flow and a turbulence intensity up to ≈60% was observed in the separation region. Good agreement was found between the flow results obtained by the two velocity measurement techniques. Considering the actuated cases, it was found that, in all the tested operating conditions, actuation implied a reduction of the separated region and the turbulence intensity, even if a low flow control effect was noticed at the highest tested velocity.
Experimental Validation of an Innovative Metallic Tile Holder System for a Ceramic Combustor Liner
Authors: Becchi Riccardo , Burberi Emanuele , Facchini Bruno , Tarchi Lorenzo , Abba Luca 
Published: September 2016

In gas turbine, the enhancement of durability and the increase of reliability represent essential requirements. These issues become even more critical for components subjected to high thermal loads, as the combustion chamber, and go in parallel with the desire for higher efficiency, which resulted in a reduced amount of air that the cooling systems designers have available for the combustor liner.
This work presents the results of an experimental campaign aimed to evaluate the performance on a portion of the combustion chamber liner of the latest Ansaldo Energia AE64.3A+ gas turbine. In this configuration ceramic tiles replace the previous metallic heat shields, reducing coolant consumption up to 40%.
The designed test article is made up of two ceramic bricks, held on the shells by means of air cooled metallic tile holders, and is installed in a dedicated plenum chamber where is run over by an air flow from several angles of incidence in order to simulate some realistic turbine conditions.
A preliminary numerical study is conducted to estimate the test article surface pressure distributions in order to evaluate the mainstream flow impact on the tile holder cooling system behaviour. A novel application of Pressure Sensitive Paint (PSP) technique is applied to evaluate the air seal cooling of the brick holder system, essential to prevent hot gas ingestion. Furthermore, infrared (IR) thermography measurements on the liner are performed using an hot mainstream flow and reproducing typical cooling flow conditions. During the tests, several thermocouples, allocated on most critic brick holder components, continuously check the metal temperature.
Aerodynamic Loading Distribution Effects on Off-Design Performance of Highly Loaded LP Turbine Cascades Under Steady and Unsteady Incoming Flows
Authors: Berrino Marco , Simoni Daniele , Ubaldi Marina , Zunino Pietro , Bertini Francesco 
Published: September 2016

The present work is part of a continuous cooperation between GE AvioAero and the University of Genova aimed at understanding the detailed flow physics of efficient highly loaded LPT blades for aeroengine applications. In this paper the effects of the aerodynamic loading distribution on the performances of three different cascades with the same Zweifel number have been experimentally investigated under steady and unsteady incoming flow conditions. Measurements have been carried out for several Reynolds numbers (in the range 70000<Re<300000) with an incidence angle variation of ±9°, in order to cover the typical realistic LP aeroengine turbine working range on design and off-design conditions.
Profile aerodynamic loadings and total pressure loss coefficients have been evaluated for the different cases. Efficiency data clearly highlight that at nominal incidence an aft loaded cascade provides the lowest profile losses when the boundary layer is attached to the wall, as it occurs in the unsteady case or at high Reynolds numbers. Only at the lowest Reynolds number in the steady case, a front loaded profile is preferable since it helps to prevent a laminar boundary layer separation. Moreover, the aft loaded profile has also shown a better robustness to incidence angle variation, both for the steady and the unsteady inflow conditions. Indeed, the growth of profile losses with incidence is weaker for the aft loaded cascade with respect to the front and the mid loaded ones. However, irrespective of the loading distribution the loss trend vs incidence angle has been found to be completely different between the steady and the unsteady operations.
Results in the paper give a clear overview of the impact of the loading distribution on profile losses as a function of Reynolds number, as well as a detailed view of the influence due to the loading characteristics on incidence robustness under the realistic unsteady inflow case.
Analysis of Heavy Duty Gas Turbine Stator-Rotor Cavity Through 3D CFD-1D Fluid Network — Field Measurements Combined Approach
Authors: Bavassano Francesco , Mantero Marco , Gasnier Thibault , Ronconi Emanuele 
Published: September 2016

An effective design and development of the Secondary Air System of a heavy-duty gas turbine is crucial for many purposes, such as cooling and sealing air supply, pre-swirling features, leakages control, casings and rotor thermal state assessment and rotor axial thrust management. All of these features directly impact on the performances and integrity of the whole machine and accordingly require advanced design approaches.
The first stage stator-rotor turbine cavity of Ansaldo E-Class heavy-duty gas turbine AE94.2 underwent design modifications to adjust its internal pressure and consequently lower the global rotor axial load acting on the thrust bearing. This goal had to be reached while maintaining safety against hot gas ingestion from the turbine section main flow into the cavity, thus preserving the GT integrity.
A multi-purpose analysis was then carried out on the cavity Secondary Air System. This involved steady 3D CFD calculations with a computational domain comprising the first turbine stage and the corresponding stator-rotor wheelspace. A combined use of CFD and SASAC, the in-house Ansaldo 1D fluid network code, finally led to an upgraded design of the cavity. Two field measurement campaigns were subsequently carried out on an AE94.2 GT to validate both the baseline configuration and the upgraded one, by means of 6 pressure and temperature sensors in the cavity and 12 load cells/thermocouples on the thrust bearing.
The CFD model and results are presented, the fluid network tuning is discussed and the experimental setup and main outcomes of the two field campaigns are reported. Constant references to the definitive literature are made, with an effort to correlate at best research and industrial practice.
These integrated activities allowed to perform a reliable verification against hot gas ingestion into the stator-rotor cavity and to successfully develop an effective solution, which reduced the GT rotor residual axial thrust by up to 25% less.
Twin Shaft Gas Turbine Variable Area Turbine Nozzle: Analytical Modeling and Optimization of Kinematic Chain
Authors: Colantoni Simone , Tripoli Girolamo , Gorte Devidasa Pai , Franchini Francesco , Rossetti Fabio , Spagnolo Marco 
Published: September 2016

Some of twin shaft gas turbines models of GE are equipped with Variable Area Turbine Nozzle (VATN), also called Nozzle Guide Vane (NGV) as the first stator stage of Low Pressure Turbine (LPT). By varying the throat area, VATN controls the energy split between the High Pressure Turbine (HPT) and Low Pressure Turbine, allowing higher operational flexibility and higher efficiency at partial load/speed. This flexibility is an important requirement for gas turbine in mechanical drive applications.
This paper is focused on the design, development and optimization of a numerical Finite Element (FE) model of the kinematic chain implemented to actuate the variable area turbine nozzles, in order to evaluate the required force as input to size and design the actuator. The kinematic chain is composed of an arrangement of linkage components that transfer the load provided by the actuator to the VATN and achieve a desired rotation of VATN airfoil around its axis. The load provided by actuator has to balance the aerodynamic load taking into account the contribution of friction developed inside the kinematic chain. The FE model has been specifically developed to evaluate the effects of different parameters, such as manufacturing tolerances and assembly clearances, in terms of total actuation force requirement, stress/life of the components and friction distribution.
The additional scope of the detailed FE model is to represent an analytical validation criterion of the results obtained through a simplified spreadsheet-based tool which aims to be a reliable and quick responding system both for new product design phase and for implemented fleet issues resolution.
A Research on Waste-Gated Turbine Performance Under Unsteady Flow Condition
Authors: Deng Q. , Burke R. D. , Zhang Q. , Pohorelsky Ludek 
Published: September 2016

Turbochargers are key components of engine air-paths that must be carefully considered during the development process. The combination of fluid, mechanical and thermal phenomenon make the turbocharger a highly dynamic and non-linear modelling challenge. The aim of this study is to quantify the dynamic response of the turbocharger system across a frequency spectrum from 0.003Hz to 500Hz, i.e. for exhaust gas pulsation in steady state, load steps and cold start drive cycles, to validate the assumption of quasi-steady assumptions for particular modelling problems.
A waste-gated turbine was modelled using the dual orifice approach, a lumped capacitance heat transfer model and novel, physics-based pneumatic actuator mechanism model. Each sub-model has been validated individually against experimental measurements. The turbine inlet pressure and temperature and the waste-gate actuator pressure were perturbed across the full frequency range both individually and simultaneously in separate numerical investigations. The dynamic responses of turbine housing temperature, turbocharger rotor speed, waste-gate opening, mass flow and gas temperatures/pressures were all investigated.
The mass flow parameter exhibits significant dynamic behaviour above 100Hz, illustrating that the quasi-steady assumption is invalid in this frequency range. The waste-gate actuator system showed quasi-steady behaviour below 10Hz, while the mechanical inertia of the turbine attenuated fluctuations in shaft speed for frequencies between 0.1–10Hz. The thermal inertia of the turbocharger housing meant that housing temperature variations were supressed at frequencies above 0.01Hz.
The results have been used to illustrate the importance of model parameters for three transient simulation scenarios (cold start, load step and pulsating exhaust flow).
Optimizing Surge Margin and Efficiency of a Transonic Compressor
Authors: Goinis Georgios , Nicke Eberhard 
Published: September 2016

It has been shown in several cases that casing treatments can improve the surge margin of a compressor. The question that is often left unanswered when designing and optimizing a casing treatment for a given compressor stage is whether the casing treatment can still improve the performance and surge margin when used on an aerodynamically improved rotor.
The current work includes the influence of the rotor geometry and casing geometry in the analysis. Several optimizations with equal objectives, to improve surge margin and efficiency, were performed. First the different components were optimized separately. The possible impact of optimizing the rotor, the casing geometry and the casing treatment on surge margin and efficiency are compared in terms of global performance and aerodynamic effects. It is then analyzed how combinations of optimized geometries perform. Of particular interest is how the circumferential grooves perform when used in combination with the optimized blade geometry.
The optimizations were performed using state of the art CFD and optimization procedures. Constraints on boundary conditions, mass flow rates and stresses were applied in order not to change the behavior of the compressor at design point significantly or to deteriorate the structural mechanics.
Uncertainty Quantification of Thermocouple Air Temperature Measurement in Highly Radiative Environment: Application to Turbofan Engine Compartment
Authors: Sommerer Y. , Drouin V. , Nicolas X. , Trouette B. 
Published: September 2016

This paper focuses on thermocouple air temperature measurement uncertainty due to the radiative fluxes present in the engine compartment where engine case skin temperature can exceed 900 K. To really measure air temperature, the convective heat flux in the thermocouple bead must be predominant. This is why heat shields are used in order to reduce the radiative heat flux on the bead. However, in engine compartment, the heat shield orientation must be optimized since numerous hot walls surround the thermocouple.
In order to evaluate the impact of badly oriented heat shields and to provide a data bank for numerical simulation validations, a heated wind tunnel has been used. It has been shown that the uncertainty on the thermocouple temperature can reach dozens of degrees depending on the air speed and the heat shield orientation. Furthermore a specific 3D thermocouple model has been build and validated by comparison with the lab measurements. Then this thermocouple 3D model has been integrated in the whole engine compartment aero-thermal model in order to quantify the uncertainty of the thermocouple air temperature measurement in the real engine environment.