bluuebunny/crossref_metadata_2025_split huggingface dataset:
Automated Design Space Exploration of Advanced-Shaped Film Cooling Holes Using the SHERPA Algorithm
Authors: Kusterer Karsten , Dickhoff Jens , Campana Noël T. , Sugimoto Takao , Tanaka Ryozo , Kazari Masahide , Bohn Dieter 
Published: September 2016

In modern gas turbines, the film cooling technology is essential for the protection of hot parts. Today, shaped holes are widely used, but besides others, the NEKOMIMI-shaped cooling holes have shown that there is still potential to increase the film cooling effectiveness significantly by generation of Anti-Counter-Rotating Vortices (ACRV). As a result, the cooling air remains close to the wall and spreads in lateral direction along the surface. The ACRV result from the specialized shape of the expanding hole exits (NEKOMIMI-shape). Thus, the design parameters have a crucial impact to the film cooling effectiveness behind the hole.
In the present study the design parameters are varied and in order to explore the design space for a defined test case with respect to the maximum achievable averaged adiabatic film cooling effectiveness. This illustrates the capabilities of the technology. Additionally, the design space of a laidback fan-shaped film cooling configuration is explored and compared to the result obtained with the NEKOMIMI-shaped geometry. In order to show the robustness of the configurations with respect to compound angles of the cross flow, two advanced configurations — one NEKOMIMI and one shaped hole — are analysed with compound angles up to 16°.
Low Frequency Distortion in Civil Aero-Engine Intake
Authors: Carnevale Mauro , Wang Feng , di Mare Luca 
Published: September 2016

The main role of the intake is to provide a sufficient mass flow to the engine face and sufficient flow homogeneity to the fan. Intake-fan interaction off design represents a critical issue in the design process because intake lines are set very early during the aircraft optimization.
The off-design operation of an aero-engine, strictly related to the intake flow field, can be mainly related to two different conditions. When the plane is in near ground position, vorticity can be ingested by the fan due to crosswind incidence. During the flight, distortions occur due to incidence. In these conditions, the windward lip is subjected to high acceleration followed by strong adverse pressure gradients, high streamline curvature and cohabitation of incompressible and transonic flow around the lip. All these features increase the risk of lip stall in flight at incidence or in crosswind near ground operation and increase the level of forcing seen by the fan blades because of the interaction with non-uniform flow from the intake.
This work deals with the study of two sources of distortions: ground vortex ingestion and flight at high incidence conditions. A test case representative of a current installation clearance from the ground has been investigated and the experimental data available in open literature validated the CFD approach. An intake, representative of a realistic civil aeroengine configuration flying at high incidence, has been investigated in powered and aspirated configurations. Distortion distributions have been characterized in terms of total loss distributions in space and in time. The beneficial effect of the presence of the fan in terms of distortion control has been demonstrated. The mutual effect between fan and incoming distortion from the intake has been assessed in terms of modal force and distortion control. CFD has been validated by means of comparisons between numerical results and experimental data have been provided. Waves predicted by CFD have been compared with an actuator disk approach prediction. The linear behavior of the lower disturbance frequency coming from distortion and the waves reflected by the fan has been demonstrated.
Numerical Analysis of Turbulent Jets in Quiescent Medium
Authors: Singh Ritik , Gyuro Marton L. 
Published: September 2016

Jet fans produce a highly anisotropic turbulent flow regime and cause severe entrainment of the ambient fluid. Additionally, the placement of jet fans near or away from walls has a significant impact on throw and spread of the fan. This paper proposes a RSM based numerical technique to accurately predict the throw and spread of jet fans in an industrial setting while accounting for both the near wall effects and anisotropic nature of turbulence. The RSM based numerical technique described in this study allows for accurate prediction of the axial throw termination distances for jet fans in an industrial setting. The RSM approach also overcomes the limitations imposed by the free jet theory by accounting for wall effect on flow as well as other physical or temporal limitations imposed by various numerical methods such as RANS and SRS.
The Free Jet Theory proposes a classification method for turbulent jet decay problems, where the jet decay domain is classified into three flow domains and one terminal region. The terminal region of turbulent jet decay is not understood well physically and is neglected for the purpose of throw and spread calculations. The technique put forth in this paper draws from the fundamentals presented by the free jet theory and is then modified and applied to account for Coanda effects seen due to the proximity of walls to the flow when the jet fan is mounted close to the ceiling. Finally, experimental data is recorded by placing the jet fan in proximity with the floor in a closed room. The data thus generated is subsequently used to validate numerical results.
Numerical and Experimental Results From a Common-Source High-G Ultra-Compact Combustor
Authors: Cottle Andrew E. , Polanka Marc D. 
Published: September 2016

Ultra-Compact combustion presents a novel solution to address the demand for increasingly compact, efficient, and low weight aircraft gas turbine engine propulsion systems. An Ultra-Compact Combustor (UCC) operates by diverting a portion of the compressor exit flow into a cavity about the engine outer diameter. Injection into the cavity can be done at an angle in order to induce bulk circumferential swirl. Swirl velocities in the cavity then impart a centrifugal load of approximately 1000g0. This high-g UCC concept has been investigated by The Air Force Institute of Technology with the goal of incorporating a common upstream flow source to distribute the simulated compressor exit flow into separate core and combustion cavity flow paths.
Experimental results from this test rig are presented, with particular emphasis on establishing the design flow split through the diffuser into the circumferential cavity. The implementation of a core channel plate was instrumental in control of the mass flow splits. Computational Fluid Dynamics (CFD) supplement the experiments and enable a more detailed understanding of the interactions within the diffuser and the interactions between the air injection jets and the fuel jets. A range of cavity equivalence ratios was studied and combustion within the cavity was shown to be a strong function of cavity loading, which was in turn a function of the total mass flow. Varying the orientation of the channel plate with respect to guide-vane leading edges caused a change in the core flow development which then had a secondary effect of aiding the combustion process within the cavity.
Exhaust Gas Recirculation to Improve Part Load Performance on Combined Cycle Power Plants
Authors: Jonshagen Klas 
Published: September 2016

The common approach for part load operation of a combined cycle power plant is to maintain the turbine inlet temperature as high as possible without exceeding the temperature limits of the gas turbine exhaust. High part load firing temperature will give high cycle efficiency and low HC and CO emissions. The common approach is to reduce the flow by decreasing the compressor inlet flow-angle by turning the compressor variable guide vanes. This is done to control the turbine inlet temperature while the load is reduced by decreasing the fuel flow. However, using the variable guide vanes to reduce the flow renders in an offset of the compressor stage loading which has a negative impact on the efficiency.
Compressors are basically volumetric flow machines and if operated on a fixed speed, a change in inlet gas density will alter the mass-flow. This means that if the inlet air is heated, the mass-flow and hence load will be reduced if turbine inlet temperature is kept constant. Thanks to the more or less maintained volume flow the compressor is operated closer to its design point and efficiency remains high. A heat exchanger, preferably with water or steam from the bottoming cycle on the hot side, would be a simple solution to heat the inlet gas. A better use of the available energy would be to semi-close the cycle by recirculating a part of the exhaust gas flow.
Semi-closing the cycle means that less oxygen will be available in the combustion process and this will be one of the limiting factors for the recirculation rate. However, the fuel to air ratio decreases at part load and hence the oxygen surplus increases. Therefore, higher recirculation rates may be acceptable at part load compared to full load. The results from this thermodynamic study are very promising and show that a 40% recirculation rate can improve part load efficiency by as much as 4.1%.
Predicting Flashback Limits of a Gas Turbine Model Combustor Based on Velocity and Fuel Concentration for H2-Air-Mixtures
Authors: Utschick Matthias , Eiringhaus Daniel , Köhler Christian , Sattelmayer Thomas 
Published: September 2016

This study investigates the influence of the fuel injection strategy on safety against flashback in a gas turbine model combustor with premixing of H2-air-mixtures. The flashback propensity is quantified and the flashback mechanism is identified experimentally.
The A2EV swirler concept exhibits a hollow, thick walled conical structure with four tangential slots. Four fuel injector geometries were tested. One of them injects the fuel orthogonal to the air flow in the slots (jet-in-crossflow-injector, JICI). Three injector types introduce the fuel almost isokinetic to the air flow at the trailing edge of the swirler slots (trailing edge injector, TEI). Velocity and mixing fields in mixing zone and combustion chamber in isothermal water flow were measured with High-speed-Particle-Image-Velocimetry (PIV) and Highspeed-Laser-Induced-Fluorescence (LIF). The flashback limit was determined under atmospheric pressure for three air mass flows and 673 K preheat temperature for H2-air-mixtures. Flashback mechanism and trajectory of the flame tip during flashback were identified with two stereoscopically oriented intensified high-speed cameras observing the OH* radiation.
We notice flashback in the core flow due to Combustion Induced Vortex Breakdown (CIVB) and Turbulent upstream Flame Propagation (TFP) near the wall dependent on the injector type. The Flashback Resistance (FBR) defined as the ratio between a characteristic flow speed and a characteristic flame speed measures the direction of propagation of a turbulent flame in the flow field. Although CIVB cannot be predicted solely based on the FBR, its distribution gives evidence for CIVB-prone states.
The fuel should be injected preferably isokinetic to the air flow along the entire trailing edge in oder to reduce the RMS fluctuation of velocity and fuel concentration. The characteristic velocity in the entire cross section of the combustion chamber inlet should be at least twice the characteristic flame speed. The position of the stagnation point should be tuned to be located in the combustion chamber by adjusting the axial momentum. Those measures lead to safe operation with highly reactive fuels at high equivalence ratios.
Development of Next Generation Gas Turbine Combined Cycle System
Authors: Yamazaki Hiroyuki , Nishimura Yoshiaki , Abe Masahiro , Takata Kazumasa , Hada Satoshi , Masada Junichiro 
Published: September 2016

Tohoku Electric Power Company, Inc. (Tohoku-EPCO) has been adopting cutting-edge gas turbines for gas turbine combined cycle (GTCC) power plants to contribute for reduction of energy consumption, and making a continuous effort to study the next generation gas turbines to further improve GTCC power plants efficiency and flexibility.
Tohoku-EPCO and Mitsubishi Hitachi Power Systems, Ltd (MHPS) developed “forced air cooling system” as a brand-new combustor cooling system for the next generation GTCC system in a collaborative project. The forced air cooling system can be applied to gas turbines with a turbine inlet temperature (TIT) of 1600deg.C or more by controlling the cooling air temperature and the amount of cooling air. Recently, the forced air cooling system verification test has been completed successfully at a demonstration power plant located within MHPS Takasago Works (T-point). Since the forced air cooling system has been verified, the 1650deg.C class next generation GTCC power plant with the forced air cooling system is now being developed. Final confirmation test of 1650deg.C class next generation GTCC system will be carried out in 2020.
Effect of Buoyancy-Induced Rotating Flow on Temperatures of Compressor Discs
Authors: Tang Hui , Owen J. Michael 
Published: September 2016

Calculation of the clearances between the blades and casing of the high-pressure-compressor rotors in aeroengines involves calculating the radial growth of the corotating compressor discs. This requires the calculation of the thermal growth of the discs, which in turn requires a knowledge of their temperatures and of the Nusselt numbers and the flow structure in the cavity between the discs. The authors have recently published a theoretical model of the buoyancy-induced flow in rotating cavities, and approximate solutions were obtained for laminar Ekman-layer flow on the discs; the equation for the Nusselt numbers, which includes two empirical constants, depends strongly on the Grashof number and on the radial distribution of disc temperature.
In this paper, Nusselt numbers and disc temperatures predicted by the buoyancy model are compared with values obtained from published experimental data. For most of the 19 test cases, with Grashof numbers up to nearly 1012, mainly good agreement was achieved between the theoretical and experimental distributions of Nusselt numbers and disc temperatures. This suggests that, owing to Coriolis effects, the laminar model of buoyancy-induced rotating flow could be valid even at the high Grashof numbers found in the compressor rotors of aeroengines. As predicted by the model, for a constant Grashof number increasing the rotational Reynolds number can cause a decrease in the Nusselt number.
This is the first time a theoretical model (rather than CFD) has been used to predict the temperatures of a compressor disc, and the model takes only seconds to predict disc temperatures that would take days or even weeks to predict using CFD. More experimental data is required if the model is to be used by the designers of compressor rotors, and suggestions for future research are given in the paper.
Experimental and Numerical Investigations on the Aerodynamic Performance of the Three-Stage Turbine With Consideration of the Leakage Flow Effect
Authors: Chen Yang , Li Jun , Tian Chaoyang , Zhong Gangyun , Fan Xiaoping , Kong Xianglin 
Published: September 2016

The aerodynamic performance of three-stage turbine with different types of leakage flows was experimentally and numerically studied in this paper. The leakage flows of three-stage turbine included the shroud seal leakage flow between the rotor blade tip and case, the diaphragm seal leakage flow between the stator blade diaphragm and shaft, as well as the shaft packing leakage flow and the gap leakage flow between the rotor blade curved fir-tree root and wheel disk.
The total aerodynamic performance of three-stage turbine including leakage flows was firstly experimentally measured. The detailed flow field and aerodynamic performance were also numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and S-A turbulence model. The numerical mass flow rate and efficiency showed well agreement with experimental data. The effects of leakage flows between the fir-tree root and the wheel disk were studied. All leakage mass flow fractions, including the mass flow rate in each hole for all sets of root gaps were given for comparison. The effect of leakage flow on the aerodynamic performance of three-stage was illustrated and discussed.
Influence of Mach Number on Profile Loss of Axial-Flow Gas Turbine Blades
Authors: Kibsey M. D. , Sjolander S. A. 
Published: September 2016

The current profile loss prediction methods for axial turbine blades usually predict a monotonic increase in profile losses at outlet Mach numbers above 1.0, while linear cascade testing in the literature has revealed a more complex behaviour. An objective of this investigation was to help clarify the flow features that are most influential on the profile losses in the transonic and supersonic regimes. Four linear cascades of turbine blades were investigated both experimentally and computationally, at design incidence. Measurements were carried out over an outlet Mach number range of roughly 0.5 to 1.4, and a Reynolds number range of about 5 × 105 to 1.4×106.
It was found that the profile losses of the four cascades exhibited a loss “plateau”, where the total pressure loss coefficient became approximately constant over a range of outlet Mach numbers spanning the low supersonic range. Cascades of different geometries exhibited different extents of this loss plateau, and a commonly used Mach number correction for profile losses did not capture the behaviour.
In the literature, a relationship has been observed between the base pressure and the profile losses. The base pressure was linked to the losses in the trailing edge wake and in the trailing edge shock system. For this reason, base pressure data were obtained from blades instrumented with a static tap at the trailing edge, and also from computational fluid dynamics (CFD). The results provided insight into the role of the base pressure in the profile losses through the transonic regime. It was concluded from this study that an accurate prediction of the base pressure may serve as a basis for a revised Mach number correction to be applied to the profile loss correlation in the transonic and supersonic flow regimes.
Comparison of Numerical Combustion Models for Hydrogen and Hydrogen-Rich Syngas Applied for Dry-Low-NOx-Micromix-Combustion
Authors: Funke H. H.-W. , Beckmann N. , Keinz J. , Abanteriba S. 
Published: September 2016

The Dry-Low-NOx (DLN) Micromix combustion technology has been developed as low emission combustion principle for industrial gas turbines fueled with hydrogen or syngas. The combustion process is based on the phenomenon of jet-in-crossflow-mixing. Fuel is injected perpendicular into the air-cross-flow and burned in a multitude of miniaturized, diffusion-like flames. The miniaturization of the flames leads to a significant reduction of NOx emissions due to the very short residence time of reactants in the flame.
In the Micromix research approach, CFD analyses are validated towards experimental results. The combination of numerical and experimental methods allows an efficient design and optimization of DLN Micromix combustors concerning combustion stability and low NOx emissions.
The paper presents a comparison of several numerical combustion models for hydrogen and hydrogen-rich syngas. They differ in the complexity of the underlying reaction mechanism and the associated computational effort.
For pure hydrogen combustion a one-step global reaction is applied using a hybrid Eddy-Break-up model that incorporates finite rate kinetics. The model is evaluated and compared to a detailed hydrogen combustion mechanism derived by Li et al. including 9 species and 19 reversible elementary reactions. Based on this mechanism, reduction of the computational effort is achieved by applying the Flamelet Generated Manifolds (FGM) method while the accuracy of the detailed reaction scheme is maintained.
For hydrogen-rich syngas combustion (H2-CO) numerical analyses based on a skeletal H2/CO reaction mechanism derived by Hawkes et al. and a detailed reaction mechanism provided by Ranzi et al. are performed.
The comparison between combustion models and the validation of numerical results is based on exhaust gas compositions available from experimental investigation on DLN Micromix combustors.
The conducted evaluation confirms that the applied detailed combustion mechanisms are able to predict the general physics of the DLN-Micromix combustion process accurately. The Flamelet Generated Manifolds method proved to be generally suitable to reduce the computational effort while maintaining the accuracy of detailed chemistry.
Especially for reaction mechanisms with a high number of species accuracy and computational effort can be balanced using the FGM model.
Automatic Detection of Defects in a Swirl Burner Array Through an Exhaust Jet Pattern Analysis
Authors: Hartmann Ulrich , Hennecke Christoph , Dinkelacker Friedrich , Seume Joerg R. 
Published: September 2016

A significant challenge in improving the regeneration process of jet engines is the reduction of engine down-time during inspection. As such, early defect detection without engine disassembly will speed up the regeneration process. Defects in the engines hot-gas path (HGP) influence the density distribution of the flow and lead to irregularities in the density distribution of the exhaust jet which can be detected with the optical Background-Oriented Schlieren (BOS) method in a tomographic set-up.
The present paper proposes a combination of tomographic BOS measurements and supervised learning algorithms to develop a methodology for an automatic defect detection system. In a first step, the methodology is verified by analyzing the exhaust jet of a swirl burner array with a non-uniform fuel-supply of single burners with tomographic BOS measurements. The measurements are used to implement a Support Vector Machine (SVM) pattern recognition algorithm.
It is shown that the reconstruction quality of tomographic BOS measurements is high enough to be combined with pattern recognition algorithms. The results strengthen the hypothesis, that it is possible to automatically detect defects in jet engines with tomographic BOS measurements and pattern recognition algorithms.