bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Local Casing Features and External Dummy Flanges on Casing Contraction for Thermal Control of Blade Tip Clearance
Authors: Choi Myeonggeun , Gillespie David R. H. 
Published: November 2019

Abstract
Thermal closure of the engine casing is widely used to minimise undesirable blade tip leakage flows and thus improve jet engine performance. While this may be achieved using an external cooling scheme on the casing wall, the geometry of the casing itself may have considerable influence on the contraction. In this paper, key controllable design parameters such as the thickness of the casing, the extent (radial height) of the annular dummy flanges and their axial position have been examined to identify how the geometric features may be manipulated to obtain an optimised system for both contraction and weight. Finite element modelling has been used to simulate the contraction of a range of casing geometries using external cooling schemes, adapted previous work by the authors. The displacement-coolant exchange rate of each casing configuration is reported in mm / kg s−1. The results show the relative sensitivity of the contraction of the engine casing to the casing thickness, the radial height, and thickness profiling of the flanges, and also to the balance between jets impinging on the casing and towards the root of the flanges.
Combustion Instabilities Damping System Development for Dry Low NOx Emissions Operability Enhancement of a Heavy-Duty Gas Turbine
Authors: Cerutti Matteo , Giannini Nicola , Schuermans Bruno , Brenci Riccardo , Marini Alessandro , Ceccherini Gianni , Riccio Giovanni 
Published: November 2019

Abstract
This paper describes the development phases of a damping system for combustion instability reduction in an annular type combustor for heavy-duty gas turbine applications. As reported by the authors in a previous paper, the full scale annular test rig allowed for an extensive characterization of the combustor with realistic acoustic boundaries at engine-relevant conditions. Emissions and operability assessment over a wide range of load conditions was performed, allowing the evaluation of the response of the system near the thermo-acoustic instability onset.
The instability is quantified by its acoustic growth rate. This quantity is a crucial input in the design process of dampers. A methodology has been used to extract these growth rates form measured pulsation data.
Experimentally determined growth rates have been evaluated for different fuel flow rate split between the main and the pilot injections, providing input to dampers preliminary design. Given current combustor architecture constraints, a first attempt configuration has been proposed and performances evaluated in the full annular rig. Dampers have been equipped with dynamic sensors and thermocouples with the purpose of measuring the growth rate abatement and the consequent NOx emissions reduction. A dedicated numerical toolbox, in-house developed by GE Power, has been used for both dampers preliminary design and growth rate reduction evaluation. Fine tuning of dampers elements as well as design assumptions adjustments required additional experimental evaluations and design iterations.
Encouraged by the successful test in the concept phase, an optimized design for engine implementation was defined, that featured a significant increased damper volume, involving combustor parts re-design. The optimized configuration was finally tested in full annular rig and results demonstrated an important enhancement of operability while maintaining NOx emissions below the target levels.
Robust Active Flow Control of a Stator Cascade With Integer Control Functions and Sum-Up Rounding
Authors: Neuhäuser Karl , King Rudibert 
Published: November 2019

Abstract
This work is part of a research initiative that aims at increasing the overall gas turbine efficiency by means of constant volume combustion (CVC). For that purpose, flow control in the compressor becomes important, since unsteady combustion effects that may occur in a CVC are very likely to affect stability and efficiency of the compressor negatively due to flow disturbances.
Active Flow Control (AFC) often has to deal with uncertain flow conditions, e.g., due to turbulence, varying operating ranges, or simply environmental effects. By that, system parameters such as gain or time constants of the system model also become uncertain, making it difficult for control algorithms to ensure optimality or even stable behavior. Robust control in the sense of ℋ∞ control tackles these problems using an uncertainty description and a nominal model of the system. In this contribution, robust control applied to a linear stator cascade is addressed when only a binary control output from solenoid valves is available. Moreover, a surrogate control variable is proposed, describing the extent of the velocity deficit. By means of a principal component analysis, this control variable is reconstructed from a single measurement input.
AFC is realized via trailing edge blowing. In comparison to proportional valves, solenoid valves are cheaper and offer faster switching times with the drawback of a restricted range of the control output to integer or even binary values. Since the ℋ∞ controller, as well as most other control algorithms, results in a real-valued signal u(t) ∈ ℝ, a sum-up rounding strategy is applied to the controller output, forming a binary control output ub (t) ∈ {0, 1}. Although it is impossible for the two outputs to completely match, unless both are integer-valued, there is proof that the difference of real-valued to binary output is bounded in its integral value. The investigations show that a switching frequency of the valves of 100 Hz is sufficient to ensure that the control error via binary control matches its expected equivalent via real-valued control for the presented system.
Simultaneous TR-PIV and CH* Chemiluminescence During Combustion-Instability Triggered Flame-Flashback in a Backward Facing Step Combustor
Authors: Pancharia Pankaj , Ramanan Vikram , Nagarajan Baladandayuthapani , Chakravarthy S. R. 
Published: November 2019

Abstract
The present study is an experimental investigation of the nature of acoustically induced flashback in a lab-scale dump combustor. The control parameters varied include the inlet Reynolds number (Re) and the inlet turbulence intensity. The primary bifurcation plots of the combustor from stable to the unstable condition are seen to be significantly altered by the inlet turbulence intensity, with the latter delaying the onset of combustion instability to higher Re. The analysis of multivariate high-speed data acquisition and processing (viz. unsteady pressure, flame imaging and velocity field by means of PIV) reveals the role of low-frequency high amplitude acoustics in modulating the flame. It is seen that high amplitude oscillations are sustained by two mechanisms 1. Modulation of the flame by coherent structures shedding at the step and 2. The bulk flame motion in-and-out at the edge of the step. It is seen that flow reversal at sufficiently low frequencies provide enough duration for the hot products to ignite fresh reactants upstream of the duct, which in-turn reinforces the coherent unsteadiness in the system, thereby increasing the propensity of the mixture to be ignited more upstream with every cycle. This ultimately leads to the flame flashing back till the point of premixing. This work thus addresses and reforms the occurrence of flashback being an example of loss of static stability, whereby the overriding presence of dynamic combustion instability results in a flashback to behave in a dynamic manner.
Design, Testing, and Performance Impact of Exhaust Diffusers in Aero-Derivative Gas Turbines for Mechanical Drive Applications
Authors: Scotti Del Greco Alberto , Jurek Tomasz , Di Benedetto Daniele , Michelassi Vittorio , Ragni Giacomo , Beghini Enrico , Borghesi Maria Vittoria 
Published: November 2019

Abstract
The demand for gas-turbine (GT) based flexible power generation and mechanical drive is increasing due to the growing penetration of renewables and due to the need to quickly adjust production and operate at part load respectively. As efficiency operability low emissions, small footprint, availability and maintainability are of paramount importance, engine designers are leaning towards aircraft engine architectures that, with appropriate modifications mostly to the combustion system and turbine, can meet market needs. To leverage the large experience from aircraft propulsion, aero-derivative engines maintain the same architecture, with a high-speed shaft core, and a low-speed shaft driven by a multi-stage low-pressure turbine. While in aircraft engines power is adjusted by changing fuel rate and shaft speed, that go hand in hand, mechanical drive engines have more stringent needs that require changing the delivered power by keeping the shaft speed under control to guarantee the operation of the driven equipment (an LNG compressor or an electric generator). Therefore, the power turbine may deliver exit flow profiles and angles that put the turbine exhaust diffuser under severe off-design conditions, with the onset of large scale separations, large kinetic losses, and ultimately a significant drop on cycle performance. This paper describes Baker Hughes, a GE company experience in the CFD assisted design and scale-down testing of aero-derivative exhaust diffusers. The design incorporates the requirements of hot-end mechanical drive in multiple the power turbine operating conditions to determine the best compromise between peak design performance and off-design operability. The test in similitude conditions considered four relevant operating points. The inlet conditions matched with the power turbine exit profiles by the concerted action of swirl vanes and perforated plates, the design of which was heavily CFD assisted. Predictions matched measurements in terms of pressure recovery, kinetic losses, and exhaust velocity profiles. Different data post-processing and averaging were considered to properly factor in the diffuser losses into the overall turbine performance.
Simulation of the Deposit Evolution on a Fan Blade for Tunnel Ventilation
Authors: Castorrini Alessio , Venturini Paolo , Corsini Alessandro , Rispoli Franco 
Published: November 2019

Abstract
Fans used in tunnel ventilation operate for decades in an atmosphere that carries dust, soot, and other solid particles. The formation of deposit on the rotor blades, considering a so long time of exposition to this particle-laden flow, is highly probable. A not negligible quantity of deposited material can produce damages on the performance of the fan, but also mass unbalancing, which is potentially dangerous for the structural integrity of the fan components.
We applied our simulation tool to study a case of deposition on a large axial fan blade, used for tunnel ventilation. The outcome of the study is a parametric map of fouled blade geometries, obtained by simulating the deposition process over the increasing quantity of ingested particles mixture. The final map correlates the level and shape of deposit to the overall amount of particle ingested by the fan in its operating life. The same map can be easily used to predict the time needed in a specific application to reach any specific deposit thickness.
The evolution algorithm and simulation tools developed in the past years by the authors was applied to predict the modified geometry of eroded rotor blades. Here the same framework is updated to simulate the deposit problem. We use an integrated multiphase solver, coupled with a geometry update method. The solver can iteratively simulate the flow field, compute the particle tracking, dispersion and deposit processes, and modify the geometry (and mesh) according to the predicted deposit shape and rate.
Strongly Coupled Fluid-Structure Interaction Simulation of a 3D Printed Fan Rotor
Authors: Castorrini A. , Barnabei V. F. , Corsini A. , Rispoli F. 
Published: November 2019

Abstract
Additive manufacturing represents a new frontier in the design and production of rotor machines. This technology drives the engineering research framework to new possibilities of design and testing of new prototypes, reducing costs and time. On the other hand, the fast additive manufacturing implies the use of plastic and light materials (as PLA or ABS), often including a certain level of anisotropy due to the layered deposition. These two aspects are critical, because the aero-elastic coupling and flow induced vibrations are not negligible for high aspect ratio rotors. In this work, we investigate the aeroelastic response of a small sample fan blade, printed using PLA material. Scope of the work is to study both the structure and flow field dynamics, where strong coupling is considered on the simulation. We test the blade in two operating points, to see the aero-mechanical dynamics of the system in stall and normal operating condition. The computational fluid-structure interaction (FSI) technique is applied to simulate the coupled dynamics. The FSI solver is developed on the base of the finite element stabilized formulations proposed by Tezduyar et al. We use the ALE formulation of RBVMS-SUPS equations for the aerodynamics, the non-linear elasticity is solved with the Updated Lagrangian formulation of the equations of motion for the elastic solid. The strong coupling is made with a block-iterative algorithm, including the Jacobian based stiffness method for the mesh motion.
Estimation of the Hydraulic Losses in the Work Shaft of a Gas Turbine Engine of a Gas Compressor Unit Under Various Operating Conditions
Authors: Baturin Oleg , Krivtsov Aleksandr , Kolmakova Daria , Popov Grigorii 
Published: November 2019

Abstract
The paper presents the results of numerical simulation of air flow through a modernized variant of the inlet filter unit (IFU) of the gas compressor unit GPA-Ts-16. A feature of the IFU design is that to reduce the load on the filter unit, it is proposed to be as compact as possible, which determines its complex shape.
The goal of the study is to study the hydraulic losses and to develop the measures to reduce them, since it is found that every 100 Pa of losses in the inlet unit increases the consumption of fuel gas by 2.5 kg/h or reduces the engine power by 10.5 kW.
Calculations of hydraulic losses in IFU are carried out for cases of absence or presence of wind with a velocity from 0 to 35 m/s, blowing from 5 main directions (0°, 45°, 90°, 135°, 180°). Studies are also carried out on the effect of the weather shield shape, presence of baffles under it, and the rack in the shaft on the hydraulic losses.
As a result of the research, recommendations are provided for designing (changing the shape) of the inlet filter unit that eventually allow to propose a design that will reduce the hydraulic losses in IFU by 15% relative to the originally suggested variant.
Comparison of Different CFD Models for Predicting Emissions in an OPRA DLE Combustor
Authors: Ramaekers Wilhelmus J. S. , Tap Ferry A. , Bouten Thijs W. F. M. , Axelsson Lars-Uno 
Published: November 2019

Abstract
This paper presents a numerical investigation of natural gas combustion in an OPRA OP16 tubular DLE combustor operating in premixed mode. The aim of this study is to compare different CFD models for the accurate prediction of emissions. The numerical results are validated against experimental results obtained in an atmospheric combustion test rig.
A CFD workflow using AVL FIRE software has been devised enabling accurate CO and NOx emission calculations. Different turbulence models have been employed for adiabatic flow simulations at nominal load: the k-ζ-f turbulence model, PANS and LES-CSM model. Two detailed reaction mechanisms have been used to model combustion chemistry and thermodynamic properties: the DRM19 mechanism and the GRI 3.0 reaction mechanism. In the adiabatic simulations both the k-ζ-f and LES-CSM turbulence models perform well in combination with the GRI 3.0 reaction mechanism. In the non-adiabatic simulations heat exchange between combustor liner and cooling air is taken into account by using a wall temperature profile derived by scaling the experimentally obtained temperature profile such that the requirement of conservation of energy is satisfied.
Reactive flow simulations at nominal load using the k-ζ-f turbulence model and GRI 3.0 reaction mechanism resulted in accurate predictions for time-averaged combustor pressure drop, CO and NO emissions: the predicted CO value deviates less than 20% from its experimentally obtained value, for NO the deviation is less than 10%. Inclusion of heat exchange between combustor and cooling air liner reduces this deviation to less than 10% for CO and less than 2% for NO. At a load equal to 106% of its nominal value, non-adiabatic simulations result in less satisfactory CO and NO predictions: NO is over predicted by approx. 20% while CO is overpredicted by nearly a factor of four. The latter is caused by the fact that experimentally obtained CO emissions reduce significantly when the load is increased from 100% to 106%, while numerically obtained CO emissions just change by a few ppm.
Monitoring Fatigue of SiC/SiC Ceramic Matrix Composites With Acoustic Emission and Electrical Resistance
Authors: Han Zipeng , Morscher Gregory N. 
Published: November 2019

Abstract
Acoustic emission (AE) and electrical resistance (ER) have been effective methods to monitor damage in SiC/SiC composites for a variety of loading conditions. In this study, the change of ER and modal AE were monitored on woven silicon carbide fiber-reinforced silicon carbide (SiC/SiC) composite under cyclic loading (fatigue) conditions at room temperature. In particular, the AE activity will be emphasized in this work as it relates to ER and observed damage. Significant increase of ER and AE activities were observed during the “initial” and sometimes “final” parts of the experiments. For tests at higher fatigue frequency conditions, AE activity was significant near the end of the test which was correlated with damage predominant in the region that was ultimately the failure region. Most of these events occurred during the unload portion of the cycle, i.e., “valley” and inferred a compressive micro-fracture mechanism. Microscopy of polished sections showed increased damage very near the fracture surface, including longitudinal and shear cracking in the 90-tow region of the composite which corresponded to the “valley” AE events. For the lowest frequency fatigue condition (0.01 Hz), no valley events were observed. The compressive micro-fracture mechanism observed in this study is a new observation for progressive damage in these types of composites. More study is required to isolate the cause(s) of this behavior which are probably related to fatigue frequency, R ratio and/or porosity content.
A Framework for Optimization of Hybrid Aircraft
Authors: Zhao Xin , Sahoo Smruti , Kyprianidis Konstantinos , Sumsurooah Sharmila , Valente Giorgio , Rashed Mohamed , Vakil Gaurang , Hill Christopher Ian , Jacob Claire , Gobbin Andreas , Bardenhagen Andreas , Prölss Katrin , Sielemann Michael , Rantzer Jonatan , Ekstedt Edward 
Published: November 2019

Abstract
To achieve the goals of substantial improvements in efficiency and emissions set by Flightpath 2050, fundamentally different concepts are required. As one of the most promising solutions, electrification of the aircraft primary propulsion is currently a prime focus of research and development. Unconventional propulsion sub-systems, mainly the electrical power system, associated thermal management system and transmission system, provide a variety of options for integration in the existing propulsion systems. Different combinations of the gas turbine and the unconventional propulsion sub-systems introduce different configurations and operation control strategies. The trade-off between the use of the two energy sources, jet fuel and electrical energy, is primarily a result of the trade-offs between efficiencies and sizing characteristics of these sub-systems. The aircraft structure and performance are the final carrier of these trade-offs. Hence, full design space exploration of various hybrid derivatives requires global investigation of the entire aircraft considering these key propulsion sub-systems and the aircraft structure and performance, as well as their interactions.
This paper presents a recent contribution of the development for a physics-based simulation and optimization platform for hybrid electric aircraft conceptual design. Modeling of each subsystem and the aircraft structure are described as well as the aircraft performance modeling and integration technique. With a focus on the key propulsion sub-systems, aircraft structure and performance that interfaces with existing conceptual design frameworks, this platform aims at full design space exploration of various hybrid concepts at a low TRL level.
Uncertainty Quantification Analysis of a Pressurised Fuel Cell Hybrid System
Authors: Cuneo Alessandra , Giugno Andrea , Mantelli Luca , Traverso Alberto 
Published: November 2019

Abstract
Pressurised solid oxide fuel cell (SOFC) systems are a sustainable opportunity for improvement over conventional systems, featuring high electric efficiency, potential for cogeneration applications and low carbon emissions. Such systems are usually analyzed in deterministic conditions. However, it is widely demonstrated that such systems are affected significantly by uncertainties, both in component performance and operating parameters. This paper aims to study the propagation of uncertainties related both to the fuel cell (ohmic losses, anode ejector diameter and fuel gas composition) and the gas turbine cycle characteristics (compressor and turbine efficiencies, recuperator pressure losses). The analysis is carried out on an innovative hybrid system layout, where a turbocharger is used to pressurise the fuel cell, promising better cost effectiveness then a microturbine-based hybrid system, at small scales. Due to plant complexity and high computational effort required by uncertainty quantification methodologies, a response surface is created. To evaluate the impact of the aforementioned uncertainties on the relevant system outputs, such as overall efficiency and net electrical power, the Monte Carlo method is applied to the response surface. Particular attention is focused on the impact of uncertainties on the opening of the turbocharger wastegate valve, which is aimed at satisfying the fuel cell constraints at each operating condition.
Numerical Investigation of Vaneless Diffuser by Pinching and Rotation
Authors: Niveditha Porika , Prasad Bhamidi V. S. S. S. 
Published: November 2019

Abstract
Non-conventional diffuser designs are introduced to minimize the energy losses associated with diffusion and to enhance stable operating range of the diffusion system. This is achieved by reducing width of the diffuser by modifying a hub or shroud curves by keeping the diffuser diameter ratio constant which is often known as pinch. The comparison of modified compressor with base model is accomplished by using performance characteristics such as static pressure recovery coefficient, stagnation pressure loss coefficient, energy coefficient and isentropic efficiency. Simulations are performed at various hub pinch (5%–20%), shroud pinch (5%–20%) and combined hub and shroud pinch (5%–20%). Among all the cases shroud pinch of 10% shows best results in terms of stagnation pressure loss coefficient, static pressure recovery coefficient and energy coefficient. Further, simulations are carried out with forced rotating vaneless diffuser. It gives better results in terms of pressure rise with lower stagnation pressure losses. But there is a moderate decrement in isentropic efficiency of compressor when compared to the base model.