bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multi-Physics Simulations With OpenFOAM in the Re-Design of a Commercial Combustor
Authors: Konle Marco , de Guillebon Ludovic , Beebe Christopher 
Published: August 2018

The numerical description of combustion provides a good understanding of the thermal boundary conditions of a combustor already in the early design phase. With an accurate simulation, the thermal load on the combustor wall as well as the turbine inlet profile can be estimated and potentially tailored to the structural requirements.
At MTU Aero Engines AG, the authors set up a multi-physics solver in OpenFOAM to support the development process for combustors. This article shows the activities for a redesign of a commercial engine combustor and the successful numerical description of all related physical aspects. The comparison of combustor liner temperatures predicted via Conjugate Heat Transfer (CHT) with thermal paint results show excellent agreement. The numerical results allow the evaluation of different redesign options with respect to maximum liner temperatures and impact on turbine inlet temperature profiles.
The application of a multi-physics solver to real engine combustor designs is limited to the availability of computational power and acceptable running time. The applicability of the presented approach to complex engine designs is not only shown by the successful simulation results. The choice of an open source code allows the usage of massive parallelization. A parallelization up to 1024 CPUs was tested to evaluate the potential of speeding up the simulations. The results are encouraging and show that complex meshes with ∼15 million cells can be simulated within acceptable calculation time.
A Critical Analysis on Low-Order Simulation Models for Darrieus VAWTs: How Much Do They Pertain to the Real Flow?
Authors: Bianchini Alessandro , Balduzzi Francesco , Ferrara Giovanni , Persico Giacomo , Dossena Vincenzo , Ferrari Lorenzo 
Published: August 2018

To improve the efficiency of Darrieus wind turbines, which still lacks from that of horizontal-axis rotors, Computational Fluid Dynamics (CFD) techniques are now extensively applied, since they only provide a detailed and comprehensive flow representation. Their computational cost makes them, however, still prohibitive for routine application in the industrial context, which still makes large use of low-order simulation models like the Blade Element Momentum (BEM) theory. These models have been shown to provide relatively accurate estimations of the overall turbine performance; conversely, the description of the flow field suffers from the strong approximations introduced in the modelling of the flow physics.
In the present study, the effectiveness of the simplified BEM approach was critically benchmarked against a comprehensive description of the flow field past the rotating blades coming from the combination of a two-dimensional unsteady CFD model and experimental wind tunnel tests; for both data sets, the overall performance and the wake characteristics on the mid plane of a small-scale H-shaped Darrieus turbine were available. Upon examination of the flow field, the validity of the ubiquitous use of induction factors is discussed, together with the resulting velocity profiles upstream and downstream the rotor. Particular attention is paid on the actual flow conditions (i.e. incidence angle and relative speed) experienced by the airfoils in motion at different azimuthal angles, for which a new procedure for the post-processing of CFD data is here proposed. Based on this model, the actual lift and drag coefficients produced by the airfoils in motion are analyzed and discussed, with particular focus on dynamic stall. The analysis highlights the main critical issues and flaws of the low-order BEM approach, but also sheds new light on the physical reasons why the overall performance prediction of these models is often acceptable for a first-design analysis.
A Biogas Fuelled Micro Gas Turbine Using Dual-Fuel Approach
Authors: Calabria Raffaela , Chiariello Fabio , Massoli Patrizio , Reale Fabrizio 
Published: August 2018

In this study, research activity concerning the utilization of biogas into a commercial micro gas turbine (MGT) Ansaldo Turbec T100P is presented. The use of biogas in MGT has been already quite explored in literature. However, conflicting and not yet fully comprehensive results highlight the need for further scientific investigations. Although several authors have demonstrated, through numerical studies, the possibility of using biogas with amounts of CO2 up to 40–50% in volume in commercial MGT, experimental evidences of this condition are not yet present in literature. In fact, the CO2 concentration limit experimentally validated in literature, after which phenomena of detachment and instability of the flame happen, is considerably lower (∼12%). The utilization of biogas in micro gas turbines generally requires structural adaptations, often invasive and expensive, to the fuel compression unit and control valves. Not infrequently a partial redesign of the combustor is often necessary. Costs associated with the modifications significantly reduce the benefits of a rational and sustainable exploitation of energy resources of lower value as the biogas.
Aim of this activity is to overcome these issues, by identifying a non-invasive and cost-effective technical solution to increase the CO2 concentration in the fuel and to extend the operation domain when low calorific value fuels are used. It has been studied, implemented and tested an innovative management strategy of fuel feeding and combustion. Experimental layout and preliminary results of this novel approach are shown and discussed.
Near-Wing Multi-Sensor Diagnostics of Jet Engine Components
Authors: Frackowiak W. , Barton S. , Reimche W. , Bruchwald O. , Zaremba D. , Schlobohm J. , Li Y. , Kaestner M. , Reithmeier E. 
Published: August 2018

Engine maintenance and repair is a large part of the total airplane operating cost. Routine maintenance is essential for providing a positive impact on lifetime, engine performance and reliability. The sector of on-wing and near-wing maintenance is growing because of its potential to reduce the expenses and inspection time, with diagnostics taking place close to the airplane or inside a hangar on the airport. Due to the high complexity of modern jet engines, this task creates special needs towards the measurement systems regarding flexibility and robustness.
This paper describes four design approaches of such measurement systems to determine the engine parts’ health status with complex geometries in narrow or occluded spaces between blades and individual discs. The utilized nondestructive technologies are endoscopic fringe projection for geometry measurement, adapted low coherence interferometry to determine surface microstructures, high frequency inductive thermography with an optical mirror and miniaturized high frequency eddy current testing for inspection of the protection coating system and for the detection of subsurface cracks and defects. The inspection information obtained by all these techniques can be further used for regeneration process simulations and functional simulations to predict the optimal overhaul strategy.
Digital Geometry and Morphing to Support Analysis and Design
Authors: Meah N. , Hunt M. , Evans R. , Racz T. , Verdicchio J. , Kudryavtsev A. , Dawes Bill 
Published: August 2018

This paper describes the application of geometry morphing, integrated with meshing and flow simulation, to the topological optimisation of gas turbine film cooling holes.
Using a Genetic Algorithm to manage the digitally represented geometry a wide range of novel cooling hole shapes can be generated and useful improvements in film cooling effectiveness are observed. The simulations suggest that modified vortical flow structures are responsible for improved coolant distribution and coverage at hole exit.
Impact Analysis of Pocket Damper Seal Geometry Variations on Leakage Performance and Rotordynamic Force Coefficients Using CFD
Authors: Griebel Clemens 
Published: August 2018

In this paper, different notch and partition wall arrangements of a fully partitioned pocket damper seal (FPDS) are investigated using Computational Fluid Dynamics (CFD).
The CFD model is derived for a baseline FPDS design reflecting the full sealing configuration with a structured mesh. Steady-state simulations are performed for eccentric rotor position and different operational parameters. The results are validated using experimental cavity pressure measurements.
In transient computations, rotor whirl is modeled as a circular motion around an initial eccentricity using a moving mesh technique. Different whirl frequencies are computed to account for the frequency-dependent behavior of damper seals. The stiffness and damping coefficients are evaluated from the impedances in the frequency domain using a Fast Fourier Transform.
The validated model is then transferred to varying designs. In addition to the baseline design, six different notch arrangements with constant clearance ratio were modeled. Moreover two partition wall design variations were studied based on manufacturability considerations. Predicted leakage as well as frequency-dependent stiffness and damping coefficients are presented and the impact of geometry variations on these parameters is discussed. The results suggest that a single centered notch is favorable and indicate considerably higher effective damping for a design with staggered partition walls. A rounded partition wall design with significantly eased manufacturing reveals good performance.
Gas Turbine Fouling: A Comparison Among One Hundred Heavy-Duty Frames
Authors: Aldi Nicola , Casari Nicola , Morini Mirko , Pinelli Michele , Spina Pier Ruggero , Suman Alessio 
Published: August 2018

Over recent decades, the variability and high costs of the traditional gas turbine fuels (e.g. natural gas), have pushed operators to consider low-grade fuels for running heavy-duty frames. Synfuels, obtained from coal, petroleum or biomass gasification, could represent valid alternatives in this sense. Although these alternatives match the reduction of costs and, in the case of biomass sources, would potentially provide a CO2 emission benefit (reduction of the CO2 capture and sequestration costs), these low-grade fuels have a higher content of contaminants. Synfuels are filtered before the combustor stage, but the contaminants are not removed completely. This fact leads to a considerable amount of deposition on the nozzle vanes due to the high temperature value. In addition to this, the continuous demand for increasing gas turbine efficiency, determines a higher combustor outlet temperature. Current advanced gas turbine engines operate at a turbine inlet temperature of (1400–1500) °C which is high enough to melt a high proportion of the contaminants introduced by low-grade fuels. Particle deposition can increase surface roughness, modify the airfoil shape and clog the coolant passages. At the same time, land based power units experience compressor fouling, due to the air contaminants able to pass through the filtration barriers. Hot sections and compressor fouling work together to determine performance degradation.
This paper proposes an analysis of the contaminant deposition on hot gas turbine sections based on machine nameplate data. Hot section and compressor fouling are estimated using a fouling susceptibility criterion. The combination of gas turbine net power, efficiency and turbine inlet temperature (TIT) with different types of synfuel contaminants highlights how each gas turbine is subjected to particle deposition. The simulation of particle deposition on one hundred (100) gas turbines ranging from 1.2 MW to 420 MW was conducted following the fouling susceptibility criterion. Using a simplified particle deposition calculation based on TIT and contaminant viscosity estimation, the analysis shows how the correlation between type of contaminant and gas turbine performance plays a key role.
The results allow the choice of the best heavy-duty frame as a function of the fuel. Low-efficiency frames (characterized by lower values of TIT) show the best compromise in order to reduce the effects of particle deposition in the presence of high-temperature melting contaminants. A high-efficiency frame is suitable when the contaminants are characterized by a low-melting point thanks to their lower fuel consumption.
Reaction Model Development for Synthetic Jet Fuels: Surrogate Fuels As a Flexible Tool to Predict Their Performance
Authors: Kathrotia Trupti , Richter Sandra , Naumann Clemens , Slavinskaya Nadezhda , Methling Torsten , Braun-Unkhoff Marina , Riedel Uwe 
Published: August 2018

In the last years, the development of synthetic aviation jet fuels has attracted much interest, to provide alternatives to crude-oil based kerosene. Synthetic jet fuels can be produced from a variety of feedstocks and processes. To limit possible harmful effects on the environment when burning a jet fuel, discussions are attributed to the effects of the specific composition of a synthetic fuel on its performance and its emission pattern. A numerical tool, if available, would also be helpful within the specification process any aviation jet fuel must pass.
The present work contributes to the studies and efforts how to design a synthetic jet fuel to match predefined properties, e.g. the energy content or a less harmful emission characteristics compared to Jet A-1. The approach of a generic fuel will be followed in order to design a synthetic jet fuel with pre-defined chemical properties: A chemical kinetic reaction mechanism will be elaborated capable predicting the fundamental combustion properties of the generic fuel for each possible mixing ratio of the components included.
In this work, a generic mixture serving as an innovative synthetic jet fuel was studied, with n-dodecane, cyclohexane, and iso-octane chosen as single fuel components; no aromatics were added to reduce the concentration of soot precursors. Then, their fundamental combustion properties, i.e. laminar burning velocity and ignition delay time, were measured in a burner test rig and applying the shock tube technique, respectively. These experimental data were used for the validation of the reaction mechanisms developed for each single fuel component, which were then combined to the reaction mechanism for the generic fuel under consideration. To allow a comparison of the combustion behavior of the synthetic jet fuel directly, with the same reaction mechanism, to Jet A-1, toluene was added as a model component for aromatics. A reduced surrogate reaction model was produced, too.
All the reaction mechanisms elaborated are shown to reasonably predict the fundamental combustion properties within the parameter range considered. The compact reduced surrogate model can serve as a virtual jet fuel within numerical simulations. Thus, ultimately, an estimation of the suitability of an innovative synthetic jet fuel as a blending component to crude-oil kerosene is enabled. As a result, CFD simulations can be run efficiently tackling the combustion of a synthetic fuel in a jet engine under practical conditions and by taking into account the interaction between turbulence and chemistry.
A Methodology for Quantifying Distortion Impacts Using a Modified Parallel Compressor Theory
Authors: Pokhrel Manish , Gladin Jonathan , Garcia Elena , Mavris Dimitri N. 
Published: August 2018

Efforts to achieve NASA’s N+2 and N+3 fuel burn goals have led to various future aircraft concepts. A commonality in all these concepts is the presence of a high degree of interaction among the various disciplines involved. A tightly integrated propulsion/airframe results in distortion in the flow field around the engine annulus. Although beneficial in terms of propulsive efficiency (due to boundary layer ingestion), the impact of distortion on fan performance and operability remains in question for these concepts. As such, rapid evaluation of the impacts of distortion during the conceptual design phase is necessary to assess various concepts. This is especially important given the expansion of the design space afforded by turbo-electric and hybrid-electric distributed propulsion concepts, in which the gas turbine generator and propulsive devices can be decoupled in space.
A simple and rapid methodology to assess operability of compressors is the theory of Parallel Compressors (PC). PC theory views the compressor as two compressors in parallel, one with a uniform high Pt and the other with a uniform low Pt, both operating at the same speed and exiting to a common static pressure. The assumption of two compressors exiting at the common static pressure is not entirely true, especially when the distortion is high. In this paper, the development of a modified parallel compressor model with parametric boundary condition that can capture the impact of non-uniform inflow on fan performance is introduced and validated. Unlike classical PC model, the modified approach introduces a boundary condition dependent on the intensity of distortion (DPCP) at the Aerodynamic Interface Plane (AIP). Additionally, the concept of PC is also extended to Multi-Per Revolution (MPR) distortion.
A modeling environment which follows this methodology is created in PROOSIS, an object oriented 0-D cycle code. The model was created using the “compressor” components acting in parallel and a procedure for implementing both design mode and off-design mode solutions was created using the PROOSIS toolset. The example problem was implemented to demonstrate two capabilities — i) the ability of quantifying impacts on thrust and performance of a ducted fan propulsion system, and ii) the ability of predicting loss in stability pressure ratio. The results clearly show the ability of the tool to quantify distortion related losses.
The work described in this paper can be integrated to a Multi-Disciplinary Design and Optimization (MDAO) framework along with other disciplines and can be used to evaluate the viability of design space offered by novel aircraft configurations.
OH* Chemiluminescence Imaging of the Combustion Products From a Methane-Fueled Rotating Detonation Engine
Authors: Tobias J. , Depperschmidt D. , Welch C. , Miller R. , Uddi M. , Agrawal A. K. , Daniel Ron 
Published: August 2018

Pressure gain combustion (PGC) has been conceived to convert fuel’s chemical energy into thermal energy and mechanical energy, thereby reducing the entropy production in the process. Recent research has shown that the rotating detonation combustion or combustor (RDC) can provide excellent specific thrust, specific impulse, and pressure gain within a small volume through rapid energy release by continuous detonation in the circumferential direction. The RDC as a PGC system for power generating gas turbines in combined cycle power plants could provide significant efficiency gains. However, few past studies have employed fuels that are relevant to power generation turbines, since RDC research has focused mainly on propulsion applications. In this study, we present experimental results from RDC operated on methane and oxygen-enriched air to represent reactants used in land-based power generation. The RDC is operated at a high pressure by placing a back-pressure plate downstream of the annular combustor.
Past studies have focused mainly on probe measurements inside the combustor, and thus, little information is known about the nature of the products exiting the RDC. In particular, it is unknown if chemical reactions persist outside the RDC annulus, especially if methane is used as the fuel. In this study, we apply two time-resolved optical techniques to simultaneously image the RDC products at framing rate of 30 kHz: (1) direct visual imaging to identify the overall size and extent of the plume, and (2) OH* chemiluminescence imaging to detect the reaction zones if any. Results show dynamic features of the combustion products that are consistent with the probe measurements inside the RDE. Moreover, presence of OH* in the products suggests that the oblique shock wave and reactions persist downstream of the detonation zone in the RDC.
Effects of Effusion Cooling Pattern Near the Dilution Hole for a Double-Walled Combustor Liner: Part 1 — Overall Effectiveness Measurements
Authors: Shrager Adam C. , Thole Karen A. , Mongillo Dominic 
Published: August 2018

The complex flowfield in a gas turbine combustor makes cooling the liner walls a challenge. In particular, this paper is primarily focused on the region surrounding the dilution holes, which is especially challenging to cool due to the interaction between the effusion cooling jets and high-momentum dilution jets. This study presents overall effectiveness measurements for three different cooling hole patterns of a double-walled combustor liner. Only effusion hole patterns near the dilution holes were varied, which included: no effusion cooling; effusion holes pointed radially outward from the dilution hole; and effusion holes pointed radially inward toward the dilution hole. The double-walled liner contained both impingement and effusion plates as well as a row of dilution jets. Infrared thermography was used to measure the surface temperature of the combustor liners at multiple dilution jet momentum flux ratios and approaching freestream turbulence intensities of 0.5% and 13%.
Results showed the outward and inward geometries were able to more effectively cool the region surrounding the dilution hole compared to the closed case. A significant amount of the cooling enhancement in the outward and inward cases came from in-hole convection. Downstream of the dilution hole, the interactions between the inward effusion holes and the dilution jet led to lower levels of effectiveness compared to the other two geometries. High freestream turbulence caused a small decrease in overall effectiveness over the entire liner and was most impactful in the first three rows of effusion holes.
Increase of Glucose Uptake in Human Bone Marrow With Increasing Exercise Intensity
Authors: Heinonen Ilkka , Kemppainen Jukka , Fujimoto Toshihiko , Knuuti Juhani , Kalliokoski Kari K. 
Published: August 2018

Human bone marrow is a metabolically active tissue that responds to acute low-intensity exercise by having increased glucose uptake (GU). Here, the authors studied whether bone marrow GU increases more with increased exercise intensities. Femoral bone marrow GU was measured using positron emission tomography and [18F]-fluorodeoxyglucose in six healthy young men during cycling at intensities of 30% (low), 55% (moderate), and 75% (high) of maximal oxygen consumption on three separate days. Bone marrow GU at low was 17.2 µmol·kg−1·min−1 (range 9.0–25.4) and increased significantly (p = .003) at moderate (31.2 µmol·kg−1·min−1, 22.9–39.4) but was not significant from moderate to high (37.4 µmol·kg−1·min−1, 29.0–45.7, p = .26). Furthermore, the ratio between bone and muscle GU decreased from low to moderate exercise intensity (p < .01) but not (p = .99) from moderate to high exercise intensity. In conclusion, these results show that although the increase is not as large as observed in exercising skeletal muscle, GU in femoral bone marrow increases with increasing exercise intensity at least from low- to moderate-intensity effort, which may be important for bone and whole-body metabolic health.