bluuebunny/crossref_metadata_2025 huggingface dataset:
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

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

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

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

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

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

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

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

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

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.
Atmospheric Tests of a Full Scale Gas Turbine Burner Fed With Blast Furnace Gas and Coke Oven Gas
Authors: Bertolotto Edoardo , Amato Alberto , Guoqiang Li
Published: November 2019

The present paper describes atmospheric experimental tests of a new Ansaldo Energia full scale burner which was designed to burn fuels byproduct of steel making processes (mixtures of Blast-Furnace Gas (BFG) and Coke-Oven Gas (COG)), characterized by very low heating values (LHV∼2–3.5 MJ/kg) and very low stoichiometric air/fuel ratios (∼0.5–1 kg/kg). In particular, flame stability and blow-out margins were assessed for different burner variants and fuel compositions such as pure BFG, blends of BFG with increasing content of COG, and also a synthetic mixture of natural gas, hydrogen and nitrogen (NG/H2/N2). Except for pressure, all burner inlet conditions were simulated as in the actual gas turbine engine. The best performing burner among those tested demonstrated an excellent burning stability behavior over a wide operating range and stably burned pure BFG without any supplementary fuel. Furthermore, considering that in most operating concepts gas turbine engines for Ultra-Low BTU applications require a back-up fuel (such as oil, propane or natural gas) to ignite and ramp up or to perform load-rejections, the present atmospheric tests also assessed maneuvers to switch from natural gas operation to syngas operation. Also in this type of dual-fuel operation the burner demonstrated a wide flame stability range.
Theoretical and Experimental Investigation of a Small-Scale, High-Speed, and Oil-Free Radial Anode Off-Gas Recirculation Fan for Solid Oxide Fuel Cell Systems
Authors: Wagner Patrick H. , Van herle Jan , Schiffmann Jürg
Published: November 2019

The Laboratory for Applied Mechanical Design (LAMD) designed, manufactured, and experimentally tested a novel recirculation fan for a 10 kWe solid oxide fuel cell (SOFC). The fan uses oil-free bearings, more specifically herringbone-grooved journal and spiral-grooved thrust gas bearings. The radial inducer-less fan with a tip diameter of 19.2 mm features backward-curved prismatic blades with constant height. Prior to coupling the recirculation fan with the SOFC, the fan was experimentally characterized with air at 200 °C. At the nominal point of 168 krpm, the measured inlet mass flow rate is 4.9 kgh−1, the total-to-total pressure rise 55 mbar, the isentropic total-to-total efficiency 55 %, and the power 18.3 W. This paper compares the experimental data towards a computational fluid dynamic simulation of the full fan impeller and volute suggesting an excellent correlation at the nominal point what validates the numerical approach. However, the heat flows crossing the fan fluid domain, have an increased effect at off-design conditions, thus the experimental results need careful consideration. The fan backface leakage has negligible impact on the measurements.
Validation of a Turbine Blade Component Test With Frictional Contacts by Phase-Locked-Loop and Force-Controlled Measurements
Authors: Schwarz Stefan , Kohlmann Lukas , Hartung Andreas , Gross Johann , Scheel Maren , Krack Malte
Published: November 2019

In this paper, a validation approach for a turbine blade component test with frictional contacts is presented. The investigated system is derived from a high cycle fatigue test setup, where a turbine blade is base-excited in the clamped blade foot. The setup has been extended by laser scanning vibrometry, a force measurement platform and feedback-controllers for both force level and phase. At first, a conventional validation of a linearized model of the system is performed at low amplitudes to ensure the correct modal basis for model reduction. After that, the nonlinear behavior around the fundamental mode is analyzed in detail. Frequency responses for different excitation levels and backbone curves are measured and assessed regarding repeatability and robustness of the measurement chain. Among other effects, overhanging branches of the frequency response were encountered. Nonlinear, amplitude-dependent modal frequencies and damping ratios are identified from the backbone curves. This data forms the validation basis for a reduced-order model of the system considering nonlinear friction in the blade foot. The correlation of measurement and simulation is investigated and advantages and shortcomings of the different validation metrics are discussed.
Large-Eddy Simulations of Heat Transfer Within a Multi-Perforation Synthetic Jets Configuration
Authors: Esnault Soizic , Duchaine Florent , Gicquel Laurent
Published: November 2019

Synthetic jets are produced by devices that enable a suction phase followed by an ejection phase. The resulting mean mass budget is hence null and no addition of mass in the system is required. These particular jets have especially been considered for some years for flow control applications. They also display features that can become of interest to enhance heat exchanges, for example for wall cooling issues. Synthetic jets can be generated through different mechanisms, such as acoustics by making use of a Helmholtz resonator or through the motion of a piston as in an experience mounted at Institut Pprime in France. The objective of this specific experiment is to understand how synthetic jets can enhance heat transfer in a multi-perforated configuration. As a complement to this experimental set up, Large-Eddy Simulations are produced and analysed in the present document to investigate the flow behavior as well as the impact of the synthetic jets on wall heat transfer.

The experimental system considered here consists in a perforated heated plate, each perforation being above a cavity where a piston is used to control the synthetic jets. Placed in a wind tunnel test section, the device can be studied with a grazing flow and multiple operating points are available. The one considered here implies a grazing flow velocity of 12.8 m.s−1, corresponding to a Mach number around 0.04, and a piston displacement of 22 mm peak-to-peak at a frequency of 12.8 Hz. These two latter parameters lead to a jet Reynolds number of about 830.

A good agreement is found between numerical results and experimental data. The simulations are then used to provide a detailed understanding of the flow. Two main behaviours are found, depending on the considered mid-period. During the ejection phase, the flow transitions to turbulence and the formation of characteristic structures is observed; the plate is efficiently cooled. During the suction phase the main flow is stabilised; the heat enhancement is particularly efficient in the hole wakes but not between them, leading to a heterogeneous temperature field.
New Methods for Secondary Flow Phenomena Visualization and Analysis
Authors: Straccia Mattia , Hofmann Rodolfo , Gümmer Volker
Published: November 2019

This work focuses on presenting new techniques for the visualization of Secondary Flow Phenomena (SFP) in transonic turbomachinery. Here, Rotor 37 has been used to develop and apply these techniques in order to study vortices, shocks and secondary flows. They are also used to provide a comparison between turbulence models in Ansys CFX environment, here the Spalart-Allmaras (SA) and Shear Stress Tensor (SST) turbulence models. The scope of this paper is to give an improved understanding of SFP and how their onset and evolution are influenced from the turbulence model.

The analysis is based on results of three-dimensional steady-state RANS simulations, for operating points between design point and near-stall condition, achieved by varying the outlet static pressure radial equilibrium distribution at the rotor exit. The new visualization techniques highlight important flow field features less investigated in previous research works, in particular secondary weak strength vortices. They will give a better visualization of and insight to the interaction of the passage shock and the tip leakage vortex, the interaction between vortices and boundary layers and the interaction of the shock wave and endwall boundary layers.
Humidified Micro Gas Turbine for Range Extended Electric Vehicles: Thermodynamic Performance Assessment
Authors: De Paepe Ward , Montero Carrero Marina , Pappa Alessio , Bricteux Laurent , Contino Francesco
Published: November 2019

To reduce the emission of greenhouse gases, there is nowadays a strong focus on the electrification of transportation, especially personal vehicles. One of the main limitations of this trend is the limited range of Electrical Vehicles (EVs) due to the rather low energy density of batteries compared to liquid fossil fuels. Adding a range extender allows for a significant increase of the vehicle driving range. Typical range extenders are Internal Combustion Engine (ICE) based. Although micro Gas Turbines (mGTs) are not adequate for continuous change of load, as would be the case when used as direct power source, operating them as range extender offers large potential, especially given their higher power-to-weight ratio than ICEs, but also due to their lower emissions, vibration levels and maintenance requirements. The main drawback of the mGT compared to the ICE is its lower electrical efficiency. Humidification of the mGT cycle allows boosting its performance and by doing so making it more compatible.

In this paper, we investigate the feasibility of applying a (humidified) mGT as a range extender in EVs. In this investigation, we considered a small vehicle for use in urban area. The option of using an mGT as range extender (standard and humidified) is compared to the standard ICE based range extender. Aspen plus is used to assess the engines performance, showing that the humidified mGT has the highest potential in terms of fuel consumption reduction and range extension. Moreover, the humidified mGT presents similar performance compared to an ICE, leading to the same specific energy consumption. In addition, different pathways to compensate for the water consumption (exhaust gas condensation) are studied and discussed, revealing that the vehicle does not need external input of water.
Surrogate-Assisted Modeling and Robust Optimization of a Micro Gas Turbine Plant With Carbon Capture
Authors: Giorgetti Simone , Coppitters Diederik , Contino Francesco , De Paepe Ward , Bricteux Laurent , Aversano Gianmarco , Parente Alessandro
Published: November 2019

The growing share of wind and solar power in the total energy mix has caused severe problems in balancing the electrical power production. Consequently, in the future, all fossil fuel-based electricity generation will need to be run on a completely flexible basis. Micro Gas Turbines (mGTs) constitutes a mature technology which can offer such flexibility. Even though their greenhouse gas emissions are already very low, stringent carbon reduction targets will require them to be completely carbon neutral: this constraint implies the adoption of post-combustion Carbon Capture (CC) on these energy systems. To reduce the CC energy penalty, Exhaust Gas Recirculation (EGR) can be applied to the mGTs increasing the CO2 content in the exhaust gas and reducing the mass flow rate of flue gas to be treated. As a result, a lower investment and operational cost of the CC unit can be achieved. In spite of this attractive solution, an in-depth study along with a robust optimization of this system has not yet been carried out. Hence, in this paper, a typical mGT with EGR has been coupled with an amine-based CC plant and simulated using the software Aspen Plus®. A rigorous rate-based simulation of the CO2 absorption and desorption in the CC unit offers an accurate prediction; however, its time complexity and convergence difficulty are severe limitations for a stochastic optimization. Therefore, a surrogate-based optimization approach has been used, which makes use of a Gaussian Process Regression (GPR) model, trained using the Aspen Plus® data, to quickly find operating points of the plant at a very low computational cost. Using the validated surrogate model, a robust optimization using a Non-dominated Sorting Genetic Algorithm II (NSGA II) has been carried out, assessing the influence of each input uncertainty and varying several design variables. As a general result, the analysed power plant proves to be intrinsically very robust, even when the input variables are affected by strong uncertainties.
Gas Turbine Co-Firing of Steelworks Ammonia With Coke Oven Gas or Methane: A Fundamental and Cycle Analysis
Authors: Hewlett S. G. , Valera-Medina A. , Pugh D. G. , Bowen P. J.
Published: November 2019

Following on from successful experimental trials employing ammonia/hydrogen blends in a model gas turbine combustor, with favorable NOx and unburned fuel emissions, a detailed numerical study has been undertaken to assess the viability of using steelworks by-product ammonia in gas turbines. Every metric ton (tonne) of steel manufactured using a blast furnace results in approximately 1.5 kg of by-product ammonia, usually present in a vapor form, from the cleansing of coke oven gas (COG). This study numerically investigates the potential to utilize this by-product for power generation. Ammonia combustion presents some major challenges, including poor reactivity and a propensity for excessive NOx emissions. Ammonia combustion has been shown to be greatly enhanced through the addition of support fuels, hydrogen and methane (both major components of COG). CHEMKIN-PRO is employed to demonstrate the optimal ratio of ammonia vapor, and alternatively anhydrous ammonia recovered from the vapor, to COG or methane at equivalence ratios between 1.0 and 1.4 under an elevated inlet temperature of 550K. Aspen Plus was used to design a Brayton-Rankine cycle with integrated recuperation, and overall cycle efficiencies were calculated for a range of favorable equivalence ratios, identified from the combustion models. The results have been used to specify a series of emissions experiments in a model gas turbine combustor.
A Novel Solid-State Additive Manufacturing Technology in Support of Turbomachinery Sustainment
Authors: Cox Chase D. , Hardwick Nanci
Published: November 2019

Maintenance, repair, and overhaul activities are necessary and critical, often repeated, operations which occur during the lifecycle of turbomachinery components and assemblies. The ability to extend the life and performance of parts via sustainment type activities currently in service offers a significant and beneficial financial impact for both the manufacturers of these components as well as their end-users. Additive manufacturing not only enables manufacturers the ability to “print” complex geometries in a wide array of materials including metals but, in some instances, also offers a novel opportunity for the repair and overhaul of existing components. The MELD process is quickly becoming an established AM technology which has repeated demonstrated success in additive manufacturing, repair, coating, and joining operations. The MELD process creates fully-dense products with near wrought properties, and reduced distortion, at very high deposition rates. MELD is a solid-state process, which yields parts with superior mechanical properties as compared to those produced by liquid-state metal deposition or spray forming processes. It is an open atmosphere process, allowing for extreme scalability. By the nature of the process all depositions, repairs, and coatings are fully dense and do not require any additional processing for densification such as sintering or HIP. Potential disadvantages include the inability to construct complex, finely featured products. The MELD process is well suited for the fabrication, repair, and overhauling of large-scale components as it is not restricted to space restrictive powder beds or vacuum chambers. In addition, the MELD process carries a lower operating cost (comparable to a CNC mill) and requires less infrastructure than traditional melt-based AM technologies. In this presentation, the MELD process will be explored as a viable method for additive manufacturing, coating, repair, and joining operations. Unique attributes will be considered along with resulting advantages and disadvantages. Specific high-level real-world examples presented will include MELD applications which highlight the repair of a cast non-fusion weldable Mg helicopter gearbox housing, the joining and repair operations of simulated damage (holes and cracks) using 2XXX and 7XXX series aluminum alloys, the application of nickel-based super-alloy coatings on high-strength low alloy steels, and the additive manufacture and repair of titanium alloys.
Methodology to Optimize and Predict the Measurement Point Distribution for Compressor Mapping on the Hot-Gas Test Bench
Authors: Mai Holger , Kaufmann André , Vogt Mathias
Published: November 2019

Current and future legal requirements for internal combustion engines (ICE) are increasing the complexity of modern charging systems. Test system manufacturers are facing high demands in terms of hardware specifications and methods for turbocharger testing on a hot-gas test bench. Innovative test systems and methodologies help to improve the quality of the turbocharger and engine matching process and significantly optimize the operating strategy in engine process simulation, especially in the early development and design phase.

The compressor and turbine characteristic maps are the most important sources of information in order to quantify the performance of the turbocharger. This is achieved in practice by thermodynamically evaluating turbochargers on the hot-gas test bench under test conditions that are as close as possible to real engine operation conditions. Turbocharger compressor mapping relies on the measurement of pressure and temperature upstream and downstream of the compressor at designated operating points. For use in the turbocharger matching process, mostly equidistant points on the operation line between surge and choke are required. Comparison to Computational Fluid Dynamics (CFD) requires a higher density of measurement points, especially in the vicinity of maximum compressor efficiency to analyze different geometries. The requirement to measure different point distributions at fixed rotational speed is the logical consequence.

The primary objective of this paper is to develop and evaluate a methodology that allows different operating point distributions of compressor speed lines for the compressor mapping on the hot-gas test bench. The secondary objective deals with the prediction of the measurement points with respect to pressure ratio and volume flow rate at a fixed rotational speed. This facilitates the pre-selection of settings on the hot-gas test bench.
An Experimental Study of Impingement Cooling on Latticework in a Wide Channel
Authors: Xu Jin , Lu Ruishan , Zhang Ke , Lei Jiang , Wu Junmei
Published: November 2019

Previous researches on latticework were focused on the convective heat transfer performance on pressure and suction sides of a blade model. Besides, it has an effect on leading edge by impingement. Thus, the present study provides heat transfer enhancement and pressure loss of jet impingement of a latticework on side wall in a wide channel (AR = 4). Two latticework configurations with impingement effects are employed in this study. Three kinds of sub-channel models are used in this experiment, which is according to different cooling designs. The angle of the rib is 45° and the numbers of subchannel are 4, 6 and 8, respectively. Reynolds number range is from 10000 to 30000 with an increment of 10000. The wall temperature is obtained by using wide band liquid crystal technique, and then the heat transfer coefficients on the target surface of the channel are achieved. Pressure drop of the latticework channel is also measured by pressure taps. The result shows that these two latticework models have different flow and heat transfer characteristics. The Nusselt number distribution is not similar to that of traditional jet array impingement. The range of Nusselt number enhancement is 2.3 to 6.4 compared to that of a smooth convective channel (the Nusselt number is based on the channel hydraulic diameter). The jet-to-target distance could reduce the overall averaged heat transfer on side wall. But it could also lead to a high Nu region. To the normal lattice model, more sub-channels there are, more pressure loss it has. To the novel lattice model, sub-channel number cannot affect the pressure loss, but the jet-to-target distance could affect the friction factor obviously.
Vibration Characteristics of Rotor System Considering Gear Meshing
Authors: Hong Jie , Xu XiRu , Jiang LiMing , Ma YanHong
Published: November 2019

Spiral bevel gears are essential units in the accessories system of the aero-engine. The rotor transmits torque to the accessories system through the spiral bevel gears, which also change the direction of rotation. With the wide application of elastic support and the reduction in the number of bearing frames, the fulcrum stiffness and the rotor shaft stiffness is on the same order of magnitude of the gear meshing stiffness. For these multi-axis gear transmission systems, the effects of time-varying relative displacement between the gear meshing points and its additional constraint on the dynamic characteristics of the rotor ought be considered. In this paper, a coupled mechanical model of the bevel gear-coupled two-shaft rotor system is established. Besides, the coupled vibration mode of the gear-rotor system is studied. Finally, the influence of nonlinearity relative displacement and its additional constraint on the vibration characteristics of the rotor system are analyzed. The results show that the driven gear will produce elastic additional constraint on the rotor under the specific vibration mode. When the gear meshing stiffness is on the same magnitude as the support stiffness of the rotor, and the relative vibration displacement between the driving and driven gears is large enough, it is necessary to consider the influence of additional constraints on the rotor dynamics. The analysis in this paper provide a reference for dynamic optimization designs, fault monitoring and diagnosis of gear-rotor systems.
Using Optimization in Industrial Multi-Point Radial Compressor Design: Map Correction
Authors: Childs Edward P. , Deserranno Dimitri , Bagi Akshay
Published: November 2019

The application of Surrogate-Based Optimization (SBO) to the industrial design process for a radial compressor with two operating points is described. The design specification includes two operating points at mass flow rates differing by a factor of three, and efficiency and pressure ratio targets for each point. The base case, while roughly sized from 1D analysis, fails to achieve the pressure ratio targets. In this paper, the optimization focusses on correcting the two speed-line map of total to static pressure ratio vs. mass flow rate. “Smart parameterization”, combining independent and dependent geometric parameters, and yielding reasonable geometries for most input combinations, coupled with efficient SBO, with separate models for response surface modeling and failure prediction, yields a design achieving the targets in just 57 CFD runs. FINE/Turbo [1] is used as the CFD analysis code and FINE/Design3D [2] and MINAMO [3] as the multi-objective optimizer.
Unsteady Heat Transfer Assessment of Supersonic Turbines Downstream of a Rotating Detonation Combustor
Authors: Liu Zhe , Inhestern Lukas Benjamin , Braun James , Paniagua Guillermo
Published: November 2019

The supersonic outlet conditions from a rotating detonation combustor exhibit fluctuations in temperature and pressure that exceed 200% of their mean level. Such unsteady conditions will induce a large convective heat loading onto a downstream supersonic turbine. Hence, the precise evaluation of the thermal load to the vane and rotor is essential to the design of adequate cooling strategies. In this paper, a numerical framework is proposed to compute the convective heat transfer on two types of supersonic turbines: axial and radial outflow. The fluctuations imposed at the turbine inlet were obtained from a nozzle coupled to a rotating detonation combustor. Both radial and axial turbines were designed and subsequently analyzed with full stage unsteady simulations using an Unsteady Reynolds Averaged Navier–Stokes solver. The inlet boundary conditions to the turbine are based on CFD results from a rotating detonation combustor. The unsteady adiabatic convective heat transfer coefficient was obtained from two simulations performed at a fixed homogeneous wall temperature. The heat flux variation in span-wise and stream-wise direction is analyzed in detail. Budgeting of the unsteady heat flux mechanism was performed to identify the driving contributor of the heat transfer within the turbine and finally both designs are compared.
Experimental Investigation of Forced Convection Enhancement by Acoustic Resonance Excitations in Turbulated Heat Exchangers
Authors: Gendebien S. , Kleiman A. , Leizeronok B. , Cukurel B.
Published: November 2019

The present research deals with enhancing thermal performance of turbulated heat exchangers through application of sound pressure waves at acoustic resonance frequencies. Extending the findings of prior wind tunnel studies, where a standing wave greatly improved the forced convection in reattaching flows, this paper exploits such a phenomenon in a practical heat exchanger setting. The current experiments are conducted in representative turbulated plate and double pipe heat exchanger geometries, mounted in a dedicated facility. After identifying the inherent acoustic resonance frequencies of the passageways, the impact of excitation is studied in various sound pressure levels, blockage ratios, as well as Strouhal and Reynolds numbers. The acoustic resonance excitation resulted in heat transfer enhancement of 20% and 10% in the plate and double pipe designs respectively, absent of additional pressure penalties. To the best knowledge of the authors, this is the first demonstration of acoustic forced convection enhancement in turbulated heat exchanger geometries. Such a technology can pave the way towards future designs that require low pressure losses, minimal form factor and/or process controllability.
Study of Dynamical Instabilities in Siemens Liquid Spray Injectors Using Complementary Modal Decomposition Techniques
Authors: Ajisafe Adesile , Talibi Midhat , Ducci Andrea , Balachandran Ramanarayanan , Parsania Nishant , Sadasivuni Suresh , Bulat Ghenadie
Published: November 2019

Liquid fuel spray characterisation is essential for understanding the mechanisms underlying fuel energy release and pollutant formation. Careful selection of operating conditions can promote flow instabilities in the fuel spray which can enhance atomisation and fuel mixing, thereby resulting in more efficient combustion. However, the inherent instabilities present in the spray could have adverse effect on the combustor dynamics. Hence, it is important to better understand the dynamical behaviour of the spray, and particularly at representative operating conditions. This work describes an experimental investigation of dynamical behaviour of pressure-swirl atomisers used in Siemens industrial gas turbine combustors, at a range of chamber pressures and fuel injection pressures, using high speed laser planar imaging. Two modal decomposition techniques — Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) — are applied and compared to assess the spray dynamics. Results indicate that both POD and DMD are able to capture periodic structures occurring in the spray at different spatial length scales. The characteristic frequencies estimated from both the methods are in good agreement with each other. Both techniques are able to identify coherent structures with variable size, shape and level of staggering, which are observed to be dependent on the pressure difference across the atomiser and the chamber pressure. The spatio-temporally resolved data and the results could be used for spray model development and validation. Furthermore, the methods employed could be applied to other fuel atomisers, and more complicated conditions involving cross flow and higher chamber temperatures.
Assessment of Power Plant Components With Flaws and Defects Operating in the Long-Term Creep Range
Authors: Speicher Magdalena , Bender Thorben , Klenk Andreas , Mueller Falk , Kontermann Christian , Ewald Juergen
Published: November 2019

Originating from defects and flaws in high temperature components crack initiation and crack propagation under service conditions can occur. Fracture mechanics data and procedures are needed to study crack problems and to support an advanced remnant life evaluation.

During subsequent research in the past 35 years, data were determined for different high temperature materials. Methodologies and concepts taking into account the specific material behavior were developed in order to be able to describe crack initiation and crack growth and have appropriate assessment methods available. For creep crack initiation two criteria principles were used and for creep crack growth assessment based on the integral C* parameter were applied.

Furthermore, a method for determination of critical crack length was developed allowing decisions whether modified stress analysis methods are sufficient or more complicated fracture mechanics methods are needed.

To provide data and methodologies in a user-friendly way, a program system combining data and methods was implemented. The paper describes developed features and shows comparisons to other methods. The methods can be applied for design purposes as well as remnant life assessments.
Tip-Shroud Labyrinth Seal Effect on the Flutter Stability of Turbine Rotor Blades
Authors: Corral Roque , Greco Michele , Vega Almudena
Published: November 2019

The effect of the tip-shroud seal on the flutter onset of a shrouded turbine rotor blade, representative of a modern gas turbine, is numerically tested and the contribution to the work-per-cycle of the aerofoil and the tip-shroud are clearly identified. The numerical simulations are conducted using a linearised frequency domain solver. The flutter stability of the shrouded rotor blade is evaluated for an edgewise mode and compared with the standard industrial approach of not including the tip-shroud cavity. It turns out that including the tip shroud significantly changes the stability prediction of the rotor blade. This is due to the fact that the amplitude of the unsteady pressure created in the inter-fin cavity, due to the motion of the airfoil, is much greater than that of the airfoil. It is concluded that the combined effect of the seal and its platform tends to stabilise the rotor blade for all the examined nodal diameters and reduced frequencies. Finally, the numerical results are shown to be consistent with those obtained using an analytical simplified model to account for the effect of the labyrinth seals.