bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Engine System Approach to Improve Turbocharger Fatigue Life
Authors: Sun Harold , Hu Liangjun , Zhang Jizhong , Alashe Waheed , Hanna Dave , Curtis Eric , Yi James 
Published: September 2014

The ultimate goal of an advanced turbocharger development is to have a superior aerodynamic performance while having the turbocharger survive various real world customer applications. Due to the uncertainty of customer usage and driving pattern, the fatigue life prediction is considered one of the most ambiguous analyses in the entire design and analyses processes of the turbocharger. The turbocharger system may have various resonant frequencies, which may be within the range of turbocharger operation for automotive applications. A turbocharger may operate with excessive stresses when running near resonant frequencies. The turbocharger may experience fatigue failures if the accumulative cycles of the turbocharger running across the resonant frequencies exceeds a certain limit.
In this study, the authors propose an alternative approach to mitigate this kind of fatigue issues: i.e. engine system approach to improve turbocharger fatigue life via avoiding operating the turbocharger near resonant speeds for extended period of time. A preliminary numerical study was made and presented in this paper to assess the feasibility of such an engine system approach, which is followed by an engine dynamometer test for engine performance sensitivity evaluation when the turbocharger operation condition was adjusted to improve the high cycle fatigue life. The study shows that for a modern diesel engine equipped with electrically controlled variable geometry turbine and EGR for emission control, through the engine calibration and control upgrade, turbocharger operation speed can be altered to stay away from certain critical speeds if necessary.
The combined 1D and 3D numerical simulation shows the bandwidth of the turbine “risk zone” near one of the resonant speeds and the potential impact on engine performances if the turbocharger speed has to be shifted out of the “risk zone.”
Aerodynamic Robustness of End Wall Contouring Against Rim Seal Purge Flow
Authors: Regina K. , Kalfas A. I. , Abhari R. S. , Lohaus A. , Voelker S. , auf dem Kampe T. 
Published: September 2014

In the present study, the results of an experimental investigation are presented, which have been undertaken in the axial turbine facility LISA at ETH Zurich. The two test configurations consist of a one-and-a-half stage, unshrouded, highly loaded axial turbine with 3-dimensionally shaped blading representative of modern high pressure gas turbines. The two test configurations differ in the hub end walls: while one design has cylindrical end walls, the other design features non-axisymmetric end wall contouring (EWC).
Both turbine designs have not been especially designed for the unsteady and complex interaction mechanisms of the hub rim seal purge flow with the main annulus flow. However, these turbine designs have been subject to measurements without (nominal) and with purge flow (0.8% of the main mass flow) with the purpose of studying the aerodynamic robustness of the performance of the stages with respect to the rim seal purge flow. In order to further analyze the robustness of both turbine designs, also measurements at off-design conditions have been taken.
The steady and unsteady aerodynamic effects are measured, respectively, with pneumatic probes as well as with the in-house developed and manufactured Fast Response Aerodynamic Probe (FRAP) technology. With the aim of evaluating the aerodynamic performance and robustness of the end wall design, the one result of the experimental investigation is the quantification of the sensitivity of the stage efficiency with respect to the case with and without purge flow for both turbine designs. By means of the analysis of the time-resolved flow field and characterization of the secondary flow features, their reaction to the presence of purge flow is highlighted and used as an explanation for the efficiency deficits caused by the purge flow.
The measurements show a benefit in stage efficiency of +0.2% by using the end wall contouring in the nominal case, confirming the design intention and effectiveness of the contoured end walls. However, the beneficial impact of the end wall contouring is taken back by a higher sensitivity of the stage efficiency with respect to the purge flow, which causes the efficiency benefit to vanish with the investigated purge flow injection rate of 0.8%. The off-design measurements show that also the sensitivity of the stage with end wall contouring with respect to the reduction of stage loading factor is by 1/3 higher than the one of the cylindrical end walls.
The measurements imply that the cost of higher stage efficiency at nominal conditions by the use of end wall contouring is paid with a higher sensitivity of the stage to changes in the rotor incoming flow field and thus with a lower aerodynamic robustness of the turbine design.
Steam Turbine Valve Hard-Facings: Experience and Latest Developments
Authors: Brussk S. , Schrey A. , Barnikel J. , Weltersbach D. , Starwald H. 
Published: September 2014

The modern energy mix demands a flexible operation with an increased number of fast starts, and this results in enhanced requirements for the steam turbine and its components. Turbine admission valves, which are increasingly operated under instationary conditions to follow the changing power grid requirements, are mainly in charge. Therefore, continuous improvement of the tribological characteristics and oxidation resistance of valve components is required.
This paper discusses technical experience in steam turbine valve hard-facings over time, the current status and developments in this regard. Typical wear and crack findings of CoCr-based hard-facings are presented. The relevant investigations on the crack formation mechanism resulted in requirements and influences for the development of the current hard-facings. These concepts made for new products and service applications are introduced.
Furthermore, in consideration of a future increase in flexibility and efficiency demands, technical requirements for functional coatings are specified, and the development results of an integrated material concept are depicted.
The Influence of Transition on CFD Calculations of a Two-Stage Counter-Rotating Turbine
Authors: Akin M. Bugra , Sanz Wolfgang 
Published: September 2014

Accurate numerical simulations depend on the correct prediction of all relevant flow phenomena. For many aeronautical devices such as turbomachinery the behaviour of boundary layers, wall shear stress and wall heat transfer are significant for the performance. Turbulence and transition may influence such flow characteristics. Onset and the extent of transition can therefore be of high importance for the design process.
In this paper three-dimensional steady-state simulations of a two-stage turbine with and without modeling of transition are performed. The configuration consists of a transonic high pressure turbine stage followed by an S-shaped turning mid turbine frame and a counter-rotating low pressure turbine rotor. The in-house Reynolds-averaged Navier-Stokes solver has been applied to this configuration with the correlation based γ–Reθ transition model developed by Menter et al. which has been added to the SST turbulence model. Also, calculations without transition with the SST and the Spalart-Allmaras turbulence model have been performed. This configuration is also the subject of experimental investigations at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology, so that measurement data at two planes are used for the verification of the simulations. After verification and flow analysis, the results are also discussed to evaluate the effect of modeling transition phenomena. An analysis of the overall efficiency of the turbine and the efficiency losses in the blade and vane rows are finally presented.
On the Optimisation of a Geared Fan Intercooled Core Engine Design
Authors: Kyprianidis Konstantinos G. , Rolt Andrew M. 
Published: September 2014

Reduction of CO2 emissions is strongly linked with the improvement of engine specific fuel consumption, as well as the reduction of engine nacelle drag and weight. One alternative design approach to improving specific fuel consumption is to consider a geared fan combined with an increased overall pressure ratio intercooled core performance cycle. Thermal benefits from intercooling have been well documented in the literature. Nevertheless, there is little information available in the public domain with respect to design space exploration of such an engine concept when combined with a geared fan. The present work uses a multidisciplinary conceptual design tool to further analyse the option of an intercooled core geared fan aero engine for long haul applications with a 2020 entry into service technology level assumption. The proposed design methodology is capable, with the utilised tool, of exploring the interaction of design criteria and providing critical design insight at engine-aircraft system level.
Previous work by the authors focused on understanding the design space for this particular configuration with minimum specific fuel consumption, engine weight and mission fuel in mind. This was achieved by means of a parametric analysis, varying several engine design parameters — but only one at a time. The present work attempts to identify “globally” fuel burn optimal values for a set of engine design parameters by varying them all simultaneously. This permits the non-linear interactions between the parameters to be accounted. Special attention has been given to the fuel burn impact of the reduced HPC efficiency levels associated with low last stage blade heights.
Three fuel optimal designs are considered, based on different assumptions. The results indicate that it is preferable to trade overall pressure ratio and pressure ratio split exponent, rather than specific thrust, as means of increasing blade height and hence reducing the associated fuel consumption penalties. It is interesting to note that even when considering the effect of HPC last stage blade height on efficiency there is still an equivalently good design at a reduced overall pressure ratio. This provides evidence that the overall economic optimum could be for a lower overall pressure ratio cycle. Customer requirements such as take-off distance and time to height play a very important role in determining a fuel optimal engine design. Tougher customer requirements result in bigger and heavier engines that burn more fuel. Higher overall pressure ratio intercooled engine cycles clearly become more attractive in aircraft applications that require larger engine sizes.
An Experimental Investigation of a Tandem Stator Flow Characteristic in a Low Speed Axial Research Compressor
Authors: Tesch Alrik , Lange Martin , Vogeler Konrad , Ortmanns Jens , Johann Erik , Gümmer Volker 
Published: September 2014

A major goal in axial compressor development is to increase the efficiency and to reduce the weight of the module. In order to do so the power density has to be increased by raising the work per stage. Higher capability to do work can be achieved by increasing the circumferential velocity component of the fluid. Tandem stators might offer the ability to turn high swirling flow with lower losses compared to a single blade stator. In terms of higher aerodynamic loading the use of tandem vanes can be a key feature to allow the design of highly efficient and compact compressor modules.
This paper presents the design and experimental validation of a single stage low speed axial compressor with a tandem outlet guide vane, representative for a modern jet engine high pressure compressor. Additionally to the overall compressor performance the 3D flow field of the tandem stator has been measured with a five hole probe at different operating points. The results will be discussed in comparison with numerical results. Furthermore, oil flow pictures are used to get a deeper insight into flow conditions inside the vane passage and to validate the numerically predicted secondary flow structures.
Effects of the Steady Wake-Tip Clearance Vortex Interaction in a Compressor Cascade: Part II — Numerical Investigations
Authors: Busse Peter , Krug Andreas , Vogeler Konrad 
Published: September 2014

An important aspect of the aerodynamic flow field in the tip region of axial compressor rotors is the unsteady interaction between the tip clearance vortex and the incoming stator wakes. In order to gain an improved understanding of the mechanics involved, systematic studies need to be performed. As a first step towards the characterisation of the dynamic effects caused by the relative movement of the blade rows, the impact of a stationary wake-induced inlet disturbance on a linear compressor cascade with tip clearance will be analyzed. The wakes were generated by a fixed grid of cylindrical bars with variable pitch being placed at discrete pitchwise positions.
Part II of this two-part paper focuses on the numerical studies conducted with the scientific flow solver TRACE. Selected measurements, which are discussed in detail in the first part of this paper, are compared with steady state RANS simulation data to determine the validity of the computational model. For this purpose, the flow field obtained in the passage (PIV), at the cascade exit (five-hole probes) and the endwall pressure distributions were used. The presented numerical results show potentials and limitations of the steady state CFD for the prediction of the investigated flow phenomena. The computations provide the initial conditions for future unsteady calculations, and enable a separate depiction of potential effects of steady and unsteady wake-tip clearance vortex interaction.
Experimental Investigation Into the Performance of Shallow Aeroengine Off-Takes
Authors: Simmons Kathy , Chandra Budi 
Published: September 2014

Oil removal (scavenge) from aeroengine bearing chambers is an ongoing challenge for aeroengine designers. Effective scavenging of oil is necessary to avoid excessive heat generation, degradation of oil properties and deterioration in heat transfer functionality. However the task of oil removal is not trivial. Oil is entrained in a highly rotating environment induced by the rotating shafts. Simply removing a larger volume of fluid from the chamber with the scavenge pump can create higher air flowrates but lead to oil becoming trapped in the chamber and so no reduction in residence volume (the amount of oil present in the chamber during operation).
The University of Nottingham Technology Centre in Gas Turbine Transmissions Systems has been conducting experiments investigating two phase behaviour within a simplified aeroengine bearing chamber operating at ambient pressures with water as the working liquid. The rig is constructed from polycarbonate enabling good visual access. In the chamber offtake region a number of behaviours can be observed relating to the hydraulic uplift and general flow behaviour as gas and liquid exit the chamber. Chandra et al [1] reports a parametric study using a design of experiments approach into geometrical variants of a shallow offtake region defined by curved approaches and a small offtake volume. Phenomenlogical factors were quantified and used to identify the best performing geometry. Previous work at the UTC [2, 3] has used residence volume as the primary comparative performance parameter.
In this paper residence volume data is obtained for two sumps for which phenomenological data exists. The paper compares performance on the basis of these visual factors with performance on the basis of residence volume and concludes that although both frameworks have value, they do not lead to identical conclusions for all operating conditions. In film dominated cases significant hydraulic uplift usually corresponds to larger residence volume but for droplet dominated cases this is not necessarily so.
Numerical Investigation of an Integrated Impingement and Pin-Fin Cooling Configuration in a Wedge Duct
Authors: Feng Xiaoxing , Tian Shuqing , Bai Jiangtao , Zhang Hong , Wang Kefei , Wang Hui 
Published: September 2014

In the gas turbine blade cooling design, impingement insert and pin-fins arranged as an array in the trailing region are usually used to enhance the heat transfer. To investigate the heat transfer characteristics of the integrated impingement and the pin-fin cooling configuration in wedge channels, the numerical simulations with k-ε turbulence model and scalable wall function algorithm are carried out using a commercial CFD code.
To reveal the factors that enhance the heat transfer in the blade internal trailing channel, heat transfer characteristics of pin-fins with impingement slot are compared with that without impingement slot. The effect of the ratio of jet impingement distance to pin-fin diameter on the heat transfer is analyzed. The convergence angle of the channel is studied. The heat transfer characteristics of the integrated impingement and pin-fin cooling configuration in the wedge channels are evaluated.
The results reveal that the impinging jet enhances largely the heat transfer in the first two rows. In the studied range of L/D = 0.5∼2.0, the heat transfer of the pin-fins with impingement is about 20%∼25% higher than that without impingement. The averaged Nusselt numbers on the endwall surface, the pin surface, and the overall surfaces respectively in the wedge duct increase linearly with the increase of Reynolds number, decrease gradually with the increase of the impingement distance and increase with the increase of the convergence angle.
Design Optimization of Profiled Endwall in a High Work Turbine
Authors: Tang Huimin , Liu Shuaiqiang , Luo Hualing 
Published: September 2014

In this paper, a method based on non-uniform rational B-spline surface (NURBS) technique coupled with mesh deforming technique is implemented to design the profiled endwall of turbines. This method has the advantages of flexible geometry representation and automatic rapid remeshing. An optimization procedure has been implemented by integrating the in-house geometry manipulator, a commercial three-dimensional CFD flow solver and the optimization driver, IsightTM.
This procedure is applied to design the profiled endwalls of the first stage of a one-and-half stage high work axial flow turbine. Genetic Algorithm is used in the optimization process, and the aim is to minimize the total pressure loss.
The influences of the profiled endwalls on the secondary flow in the stator and rotor have been analyzed by steady simulation. The results indicate a 0.4% improvement in stage efficiency. The secondary loss as well as the profile loss has been significantly reduced, and the increase of the reaction which influences the turbine efficiency is also observed.
The unsteady simulations are also presented in this paper to confirm the improved performance of the optimum profiled endwalls.
Design and Flow Analysis of a Supersonic Small Scale ORC Turbine Stator With High Molecular Complexity Working Fluid
Authors: Uusitalo Antti , Turunen-Saaresti Teemu , Guardone Alberto , Grönman Aki 
Published: September 2014

In small scale and low temperature waste heat recovery systems, Organic Rankine Cycle (ORC) technology can be identified as a promising solution in converting low-grade heat into electricity. The principle of ORC is based on a conventional Rankine process but an organic working fluid is adopted instead of steam. The use of high molecular complexity working fluids enables the design of high efficiency ORCs and are characterized by dry expansion and high pressure ratios over the turbine, as well as low speed of sound, which typically leads to highly supersonic flows in the ORC turbine stator.
In order to design supersonic ORC turbines, the geometry of the turbine stator has to be based on design methods that accurately take into account the real gas effects of the working fluid during the expansion. In this study, a highly supersonic small scale ORC turbine stator using siloxane MDM as working fluid, is studied. The accurate real gas model was implemented in a CFD-flow solver in order to predict the flow field in the stator in design and in off-design conditions. The results of this study gives valuable information on realising small capacity ORC turbomachinery, characterized by highly supersonic stators, and on the off-design performance of supersonic radial turbine stator that has not been documented or discussed in the previous studies.
Development of New Engine Control for ETF40B Marine Turboshaft Engine
Authors: Luebs Alan 
Published: September 2014

Vericor Power Systems (Vericor), the manufacturer of the ETF40B turboshaft engine used on the US Navy Landing Craft Air Cushion (LCAC) vehicles, has introduced a new Full Authority Digital Engine Control (FADEC) to replace the original FADEC currently in service in the Navy LCAC fleet. After several attempts to improve the reliability of the original FADEC to meet an acceptable standard, the original FADEC has remained unreliable in service.
In 2008 Vericor initiated a self-funded development program to replace the original engine control. Alternative FADEC design approaches were considered and ultimately Safran Electronics Canada (SE-C) was selected to design and manufacture a single-channel purpose built embedded controller that would control ETF40B engine/LCAC application as well as other Vericor gas turbine engines.
The design effort began in August 2010 and the first on-engine tests occurred in July 2011. Environmental/EMI qualification testing was accomplished to aggressive temperature, shock, vibration and Mil-Std-461F requirements leading to field deployment in the spring of 2013. This paper describes the requirements for this FADEC, its design pedigree, and the development and testing of the unit leading to US Navy use on the ETF40B equipped LCACs.