bluuebunny/crossref_metadata_2025_split huggingface dataset:
InterTurb: High-Pressure Turbine Rig for the Investigation of Combustor-Turbine Interaction
Authors: Wolf T. , Lehmann K. , Willer L. , Pahs A. , Rößling M. , Dorn L. 
Published: August 2017

This paper introduces a new 2-stage high-pressure turbine rig for aerodynamic investigations. It is operated by DLR Göttingen (Germany) and installed in DLR’s new testing facility NG-Turb. The rig’s geometrical size as well as the non-dimensional parameters are comparable to a modern engine in the small to medium thrust range. The turbine rig closely resembles engine hardware and features all relevant blade and vane cooling as well as secondary air-system flows. The effect of variations of each individual flow and different tip clearances on overall turbine efficiency will be studied. While the first part of the testing program will be based on uniform inlet conditions the second part will be run with a combustor simulator, which is based on electrical heaters and delivers a flow field similar to a rich-burn combustor. In order to find the optimum relative position for maximum turbine efficiency the combustor simulator can be rotated relative to the HPT inlet (clocking). For the same reasons the stators can also be clocked.
The paper gives a brief overview of the testing facility and from there on focuses on the HPT rig features such as aerodynamic design, cooling and sealing flows. The aerodynamic optimisation of the stator vanes and shroudless rotor blades will be outlined. Further topics are the aerodynamic design of the combustor simulator, a comparison with engine combustors as well as the implementation in the rig. The paper also describes the rig instrumentation in the stationary and rotating system which most importantly focuses on measurements of efficiency and capturing of traverse data. The topic of blade and vane manufacturing via direct metal laser sintering will be briefly covered. The discussion of test results and comparison with numerical simulations will be the subject of a follow-up paper.
Effects of Rotor Disc Growth on Flow and Heat Transfer Characteristics of Rim Seal
Authors: Jia Xingyun , Zheng Qun , Zhang Hai , Jiang Yuting 
Published: August 2017

Under actual operating conditions of gas turbine, centrifugal and thermal growth of disc in radial direction result in dislocation of inflow boundary at the disc mid-radius height, and a radial step of platform at high radius height. In this paper, flow and heat transfer characteristics in dislocated rim seal region are analyzed by the conjugate and thermal mechanical numerical methods.
The calculated radial growths of turbine discs reach approximately 14–20 % of turbine platform structure thickness. Dislocation of rim seal structure directly affects the flow characteristic of externally-induced (EI) ingress and rotationally-induced (RI) ingress, and aggravates overheat of stator disc due to induced hot gas ingestion, further affects the loss of mixture of mainstream gas and cooling sealant air flow in rim-seal and wheelspace regions. Radial step between rotor and stator platforms exacerbates the area and depth of hot gas ingestion in seal clearance, along with a 2–7 % decrease in seal efficiency.
Reconstruction and Analysis of the Acoustic Transfer Matrix of a Reheat Flame From Large-Eddy Simulations
Authors: Bothien Mirko , Lauper Demian , Yang Yang , Scarpato Alessandro 
Published: August 2017

Lean premix technology is widely spread in gas turbine combustion systems, allowing modern power plants to fulfill very stringent emission targets. These systems are, however, also prone to thermoacoustic instabilities, which can limit the engine operating window. The thermoacoustic analysis of a combustor is thus a key element in its development process. An important ingredient of this analysis is the characterization of the flame response to acoustic fluctuations, which is straightforward for lean-premixed flames that are propagation stabilized, since it can be measured atmospherically. Ansaldo Energia’s GT26 and GT36 reheat combustion systems feature a unique technology where fuel is injected into a hot gas stream from a first combustor, which is propagation stabilized, and auto-ignites in a sequential combustion chamber. The present study deals with the flame response of mainly auto-ignition stabilized flames to acoustic and temperature fluctuations for which a CFD system identification approach is chosen.
The current paper builds on recent works, which detail and validate a methodology to analyze the dynamic response of an auto-ignition flame to extract the Flame Transfer Function (FTF) using unsteady Large-Eddy Simulations (LES). In these studies, the flame is assumed to behave as a Single-Input Single-Output (SISO) or Multi-Input Single-Output (MISO) system. The analysis conducted in GT2015-42622 qualitatively highlights the important role of temperature and equivalence ratio fluctuations, but these effects are not separated from velocity fluctuations. Hence, this topic is addressed in GT2016-57699, where the flame is treated as a multi-parameter system and compressible LES are conducted to extract the frequency-dependent FTF to describe the effects of axial velocity, temperature, equivalence ratio and pressure fluctuations on the flame response.
For lean-premixed flames, a common approach followed in the literature assumes that the acoustic pressure is constant across the flame and that the flame dynamics are governed by the response to velocity perturbations only, i.e., the FTF. However this is not necessarily the case for reheat flames that are mainly auto-ignition stabilized. Therefore, in this paper we present the full 2 × 2 transfer matrix of a predominantly auto-ignition stabilized flame and hence describe the flame as a Multi-Input Multi-Output (MIMO) system. In addition to this, it is highlighted that in presence of temperature fluctuations the 2 × 2 matrix can be extended to a 3 × 3 matrix relating the primitive acoustic variables as well as the temperature fluctuations across the flame. It is shown that only taking the FTF is insufficient to fully describe the dynamic behavior of reheat flames.
Evaluation of Numerical Methods to Predict Temperature Distributions of an Experimentally Investigated Convection-Cooled Gas-Turbine Blade
Authors: Findeisen E. , Woerz B. , Wieler M. , Jeschke P. , Rabs M. 
Published: August 2017

This paper presents two different numerical methods to predict the thermal load of a convection-cooled gas-turbine blade under realistic operating temperature conditions. The subject of the investigation is a gas-turbine rotor blade equipped with an academic convection-cooling system and investigated at a cascade test-rig. It consists of three cooling channels, which are connected outside the blade, so allowing cooling air temperature measurements.
Both methods use FE models to obtain the temperature distribution of the solid blade. The difference between these methods lies in the generation of the heat transfer coefficients along the cooling channel walls which serve as a boundary condition for the FE model. One method, referred to as the FEM1D method, uses empirical one-dimensional correlations known from the available literature. The other method, the FEM2D method, uses three-dimensional CFD simulations to obtain two-dimensional heat transfer coefficient distributions. The numerical results are compared to each other as well as to experimental data, so that the benefits and limitations of each method can be shown and validated.
Overall, this paper provides an evaluation of the different methods which are used to predict temperature distributions in convection-cooled gas-turbines with regard to accuracy, numerical cost and the limitations of each method. The temperature profiles obtained in all methods generally show good agreement with the experiments. However, the more detailed methods produce more accurate results by causing higher numerical costs.
Experimental and Computational Study of the Effect of Momentum-Flux Ratio on High Pressure NGV Endwall Cooling Systems
Authors: Ornano Francesco , Povey Thomas 
Published: August 2017

High pressure nozzle guide vane endwalls are often characterized by highly three-dimensional flows. The flow structure depends on the incoming boundary layer state (inlet total pressure profile) and the (static) pressure gradients within the vane passage. In many engine applications this can lead to strong secondary flows. The prediction and design of optimized endwall film cooling systems is therefore challenging, and a topic of current research interest.
A detailed experimental investigation of the film effectiveness distribution on an engine-realistic endwall geometry is presented in this paper. The film cooling system was a fairly conventional axisymmetric double row configuration. The study was performed on a large-scale, low-speed wind tunnel using infrared thermography. Adiabatic film effectiveness distributions were measured using IR cameras and tests were performed across a wide range of coolant-to-mainstream momentum-flux and mass flow ratios. Complex interactions between coolant film and vane secondary flows are presented and discussed. A particular feature of interest is the suppression of secondary flows (and associated improved adiabatic film effectiveness) beyond a critical momentum flux ratio. Jet lift-off effects are also observed, and discussed in the context of sensitivity to local momentum flux ratio. Full coverage experimental results are also compared to three-dimensional, steady-state CFD simulations.
This paper provides insights into the effects of momentum flux ratio in establishing similarity between cascade conditions and engine conditions, and gives design guidelines for engine designers in relation to minimum endwall cooling momentum flux requirements to suppress endwall secondary flows.
On the Combination of Large Eddy Simulation and Phenomenological Soot Modelling to Calculate the Smoke Index From Aero-Engines Over a Large Range of Operating Conditions
Authors: Lamouroux Jean , Richard Stéphane , Malé Quentin , Staffelbach Gabriel , Dauptain Antoine , Misdariis Antony 
Published: August 2017

Nowadays, models predicting soot emissions are, neither able to describe correctly fine effects of technological changes on sooting trends nor sufficiently validated at relevant operating conditions to match design office quantification needs. Yet, phenomenological descriptions of soot formation, containing key ingredients for soot modeling exist in the literature, such as the well-known Leung et al. model (Combust Flame 1991). This approach indeed includes contributions of nucleation, surface growth, coagulation, oxidation and thermophoretic transport of soot. When blindly applied to aeronautical combustors for different operating conditions, this model fails to hierarchize operating points compared to experimental measurements.
The objective of this work is to propose an extension of the Leung model, including an identification of its constants over a wide range of condition relevant of gas turbines operation. Today, the identification process can hardly be based on laboratory flames since few detailed experimental data are available for heavy-fuels at high pressure. Thus, it is decided to directly target smoke number values measured at the engine exhaust for a variety of combustors and operating conditions from idling to take-off. A Large Eddy Simulation approach is retained for its intrinsic ability to reproduce finely unsteady behavior, mixing and intermittency.
In this framework, The Leung model for soot is coupled to the TFLES model for combustion. It is shown that pressure-sensitive laws for the modelling constant of the soot surface chemistry are sufficient to reproduce engine emissions. Grid convergence is carried out to verify the robustness of the proposed approach. Several cases are then computed blindly to assess the prediction capabilities of the extended model. This study paves the way for the systematic use of a high fidelity tool solution in design office constraints for combustion chamber development.
Correcting Turbocharger Performance Measurements for Heat Transfer and Friction
Authors: Schinnerl Mario , Ehrhard Jan , Bogner Mathias , Seume Joerg 
Published: August 2017

The measured performance maps of turbochargers which are commonly used for the matching process with a combustion engine are influenced by heat transfer and friction phenomena. Internal heat transfer from the hot turbine side to the colder compressor side leads to an apparently lower compressor efficiency at low to mid speeds and is not comparable to the compressor efficiency measured under adiabatic conditions.
The product of the isentropic turbine efficiency and the mechanical efficiency is typically applied to characterize the turbine efficiency and results from the power balance of the turbocharger. This so-called ‘thermo-mechanical’ turbine efficiency is strongly correlated with the compressor efficiency obtained from measured data.
Based on a previously developed one-dimensional heat transfer model, non-dimensional analysis was carried out and a generally valid heat transfer model for the compressor side of different turbochargers was developed.
From measurements and ramp-up simulations of turbocharger friction power, an analytical friction power model was developed to correct the thermo-mechanical turbine efficiency from friction impact.
The developed heat transfer and friction model demonstrates the capability to properly predict the adiabatic (aerodynamic) compressor and turbine performance from measurement data obtained at a steady-flow hot gas test bench.
A Comparison of Small-Scale Gas Turbine Control Schemes
Authors: Jaatinen-Värri Ahti , Backman Jari , Honkatukia Juha , Malkamäki Matti 
Published: August 2017

Throughout the world there is pressure to increase distributed energy generation. Driving factors include for example political and environmental concerns in developed countries and reliability in places where centralized grid does not either exist or is too unreliable. The energy generation based on renewable fuels such as biogas is also usually decentralized. To answer this demand, the number of small-scale gas turbine combined heat and power (CHP) installations have increased. Due to its nature, the required power output of distributed generation is highly variable. The power output of decentralized power plant needs to follow the local consumption power need and thus it needs to be efficiently controlled. Therefore, the requirement for variable output necessitates that small-scale gas turbines are often run at part-loads.
Previously, most of the installed small-scale gas turbines have been single-spool units with either fixed or variable speed shafts. Control schemes and part-load performance are somewhat different for the two setups. Recently, a two-spool gas turbine where the spools can be controlled independently has been proposed as a feasible alternative. The possibility to produce the desired power output with two spools, both having their own generator, which can be controlled independently of each other, offers significantly more possibilities for the control. Therefore, it might also offer better part-load performance.
In this paper, the control schemes of three different small-scale gas turbines are compared. Especially, the part-load electrical efficiency is studied. The studied gas turbines are: a single-spool fixed speed, a single-spool variable speed driven, and a two-spool variable speed driven gas turbine. The part-load performance of different machines is studied and then compared against each other. Furthermore, some estimations are given on how the part-load performance of each machine fares against certain load profiles.
Two-Phase CFD-Calculations for the Design of Water-Based Turbine Cleaning Systems for Turbochargers
Authors: Fischer Magnus , Weickgenannt Ansgar 
Published: August 2017

Turbochargers operated with heavy fuel oil are subjected to deposition of combustion residues on stator vanes, the turbine rotor and turbine casing. Without appropriate measures the turbine stage efficiency drops. Moreover, in severely contaminated turbine stages clogging of whole stator channels can occur, which results in unwanted turbine excitation and ultimately failure. To assure a constantly high level of efficiency and mechanical integrity turbochargers operated with critical fuels are equipped with an online turbine cleaning system that is based on the injection of water. The water is injected such that the whole stator is evenly wetted with water and ultimately cleaned.
The design of modern cleaning systems is based on two-phase computational fluid dynamics (CFD) simulations, where water-jets are tracked throughout the computational domain, commonly in a Lagrangian way. Multiple physical phenomena are considered, e.g. turbulent interaction with the gas phase and droplet break-up within the liquid spray, where the latter has a direct influence on spray penetration depth and finally the proper design of the cleaning system. This paper presents a validation of spray modeling in the relevant Weber and Reynolds number regime, with emphasis on the droplet break-up model. The numerical results are compared with LIF and laser diffraction measurements of the water spray in cross flow in terms of concentration and droplet size distribution. Finally, the validated and improved model is applied to re-calculate a real world application: the state-of-the-art cleaning system of a turbocharger again thoroughly validated against the test bench measurements.
Wet Gas Compression: Test Conditions and Similitude
Authors: Mæland Dagfinn , Bakken Lars E. 
Published: August 2017

Wet gas compression of gas/condensate/water provides a business opportunity for oil and gas producers. There are several opportunities of particular note: 1) As well tail-end production commences, the installation of sub-sea compressors will provide enhanced oil recovery and, if the subsea compressor is capable of handling liquids, the subsea process complexity can be dramatically reduced, thus decreasing capital investments and possibly operational costs. 2) Topside and Onshore projects can also be dramatically simplified. This is the case for both new installations and modification projects for which wet gas compression is a suitable solution.
However, there are several challenges that need to be addressed before wet gas compression, by means of centrifugal compressors, can be considered as a robust commercial solution for future projects. This relates to the robustness of the mechanical design, effects on electrical systems, and issues related to performance. This paper will focus on challenges related to performance prediction and testing.
For conventional dry gas compressor design, performance prediction is usually undertaken by the compressor manufacturer, utilising in-house know-how in impeller design and selection. This specialised knowledge is potentially unsuitable for predicting wet gas performance in the design phase; hence, a wet gas compressor design may not meet design requirements specified by the customer.
It is typical that agreements on performance testing of centrifugal compressors state that these are to be conducted according to an international standard such as ASME PTC10 or ISO 5389. These standards require that the compressed gas is dry.
However, for wet gas compressors, no such internationally established standards exist for performance evaluation. Several of the requirements stipulated in the standards are challenging to apply to wet conditions and they do not ensure similar conditions. Such parameters including the maximum permissible deviation in the specific volume ratio, Mach number and Reynolds number. It is clear that the path towards a standard for wet gas performance testing will require a substantial amount of effort in order to establish new requirements related to wet gas similarity. Based on wet gas compressor test experience, challenges and requirements related to low pressure inert fluid, compared with full pressure actual fluid tests, are analysed and discussed.
The Relevance of Damper Pre-Optimization and its Effectiveness on the Forced Response of Blades
Authors: Gastaldi Chiara , Berruti Teresa M. , Gola Muzio M. 
Published: August 2017

The paper presents a calculation procedure for the design of turbine blades with underplatform dampers. The procedure involves damper “pre-optimization” before the coupled calculation with the blades.
The pre-optimization procedure excludes, since the early design stage, all those damper configurations leading to low damping performance. Pre-optimization involves plotting a design “damper map” with forbidden areas, corresponding to poorly performing damper geometries and admissible design areas, where effective solutions for the damper shape can be explored. Once the candidate damper configurations have been selected, the damper equilibrium equations are solved by using both the multi-harmonic balance (MHB) method, and the direct time integration method (DTI). Direct time integration of the damper dynamic equations is implemented in order to compute the trend of the contact forces in time and the shape of the hysteresis cycles at the different contact points. Based on these trends, the correct number of Fourier terms to represent the contact forces on the damper is chosen. It is shown that one harmonic term together with the static term, are enough in the MHB calculation of a pre-optimized damper.
The proposed method is applied to a test case of a damper coupled with two blades. Experimental forced response functions of the test case with a nominal damper are available for comparison. The purpose of this paper is to show the effectiveness of the “damper maps” in excluding all those damper configurations, leading to undesirable damper behavior and to highlight the strong influence of the blades mode of vibration on the damper effectiveness. From the comparison of dampers with different geometrical parameters, the pre-optimized damper proved to be not only the most effective, in terms of damping capability, but also the one that leads to a faster and more flexible calculation of the damper, coupled with the blades.
Determining Stress in Turbocharger Impellers due to Component Machining Process
Authors: Barrans Simon M. , Tabriz Md Shams E. , Ellis Christian F. 
Published: August 2017

Turbocharger impeller wheels are traditionally manufactured using a casting process. However, with the improvement of multi-axial machining technology, machined impeller wheels are becoming popular among turbo machinery manufacturers due to their enhanced durability. Nonetheless, machining a complex impeller shape from a solid billet, results in tool marks being left on the component surface. As presented in this paper, repeatedly running a wheel to 5% beyond the design speed limit can result in fatigue failure initiating from the machining marks.
In this paper, the ‘as machined’ geometry of sample wheels has been determined using both CT scanning and optical surface measurement techniques. The data from these measurements has been used to generate solid CAD models suitable for finite element analysis to simulate the stress distribution of reverse engineered wheels. The maximum principal stress predicted is 15% higher than that obtained from the nominal CAD model. In order to model the measured geometry efficiently, a novel technique has been used to enforce cyclic symmetry on geometry that is not precisely cyclically symmetric.
The work has demonstrated that it is possible to predict the stress raising effect of the machining marks at the design stage. The analysis methodology presented in the paper will enable future integrated optimisation of both the design and manufacture of impeller wheels to ensure that wheels with a specified operating envelope are machined as efficiently as possible.