bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comprehensive Geometric Description of Manufacturing Scatter of High Pressure Turbine Nozzle Guide Vanes for Probabilistic CFD Analysis
Authors: Voigt Paul , Högner Lars , Fiedler Barbara , Voigt Matthias , Mailach Ronald , Meyer Marcus , Nasuf Alkin 
Published: August 2018

The increasing demands on jet engines require progressive thermodynamic process parameters, which typically lead to higher aerothermal loadings and accordingly to designs with high complexity. State of the art high pressure turbine (HPT) nozzle guide vane (NGV) design involves vane profiles with three-dimensional features including a high amount of film cooling and profiled endwalls (PEW).
Typically, the specific massflow, also called capacity, which governs the engine’s operation, is set by the HPT NGV. Hence, geometric variations due to manufacturing scatter of the HPT NGV’s passage can affect relevant aerodynamic quantities and the entire engine behavior. Within the traditional deterministic design approach, the influences of those geometric variations are covered by conservative assumptions and engineering experience. This paper addresses the consideration of variability due to manufacturing of HPT NGVs through probabilistic CFD investigations.
In order to establish a statistical database, 80 HPT NGVs are digitized with a high precision optical 3D scanning system to record the outer geometry. The vane profiles are parametrized by a section based approach. For this purpose, traditional profile theory is combined with a novel method that enables the description of NGV profile variability taking the particular leading edge (LE) shape into account. Furthermore, the geometric variability of PEWs is incorporated by means of principle component analysis (PCA).
On this basis, a probabilistic system assessment including a sensitivity analysis in terms of capacity and total pressure loss coefficient is realized. Sampling-based methods are applied in order to conduct a variety of 3D CFD simulations for a typical population of profile and endwall geometries. This probabilistic investigation using realistic input parameter distributions and correlations contributes to a robust NGV design in terms of relevant aerodynamic quantities.
Turbocharger-Based Hybrid Systems: Modeling and Validation of a Free Spool Subject to Compressor Surge
Authors: Abrassi Alessio , Traverso Alberto , Ferrari Lorenzo 
Published: August 2018

Compressor surge is one of the main problem that may affect fuel cell gas turbine hybrid systems, because of the energy stored in the volume containing the high temperature pressurized fuel cell stack. The problem becomes even more crucial because in such kind of system, the fuel cell is the most sensitive and costly component that has to be preserved by abrupt pressure changes.
In order to determine the behavior of a dynamic compressor in its whole range of operating conditions, a calculation model was implemented in TRANSEO, a software tool for transient and dynamic analysis of microturbine and fuel cell based-cycles (based on Matlab-Simulink environment). The modeling procedure has been derived from the Greitzer’s 1976 nonlinear dynamic approach; the resulting T-RIG1 model predicts the transient response of a compression system and is able to simulate both normal and instable transient conditions. Several investigations have been done in order to characterize the impact of different parameters and configurations on the system response. The validation, in the frequency domain, was performed comparing calculations with experimental data measured from a dedicated test rig, where a small size turbocharger has been operated in stable and unstable conditions. In particular, the present work demonstrates the capability of the T-RIG1 model to simulate a free shaft turbocharger performance and instability, with the future purpose to develop feasible strategies for surge detection and recovery, applicable to turbocharger-based hybrid systems.
On Deposit Sintering and Detachment From Gas Turbines
Authors: Casari Nicola , Pinelli Michele , Suman Alessio , di Mare Luca , Montomoli Francesco 
Published: August 2018

Solid particles ingestion can deteriorate performance and stability of gas turbines through the build-up of deposits on the aerofoils. In some cases, the effect is sufficient to require an engine shut-down or to cause a failure. The fouling phenomenon can be characterized by two different phases: particle sticking and deposit evolution. The sticking process of an impinging particle has been deeply studied with several models available in the literature, both deterministic and stochastic. A less investigated phase is the the evolution of the deposit over time. A deposit is subjected to several forces that either tend to make it sticking to the surface or to detach from it. In the hot section of the gas turbine, the forces that act on the build-up tending to make it to adhere to the surface can be traced back to the van der Waals forces and, possibly capillary force if a certain amount of liquid phase is present. On the other hand, the detaching mechanism is related to the component investigated: if the particle is deposited on a vane, the drag and the shearing force are the only forces that tend to detach the particle, if a rotor blade is investigated, the centrifugal forces must be considered as well.
On top of that, the deposit evolves over time in what is called sintering. During this process, the single particles deposited can melt together forming necks. If the temperature is sufficiently high, these necks increase in size until the former pores among particles are completely filled. This process is of paramount importance if the effect of the applied forces on the deposit needs to be investigated. The amount of material detached is indeed strongly dependent on the tension exchanged within various layers that constitute the build-up.
This article focuses on the prediction of the build-up evolution on an HPT nozzle. The sintering process is modeled and related to the resisting strength of the deposit: an increasing sintering time reduces the deposit porosity and thus increase its strength. In order to monitor the stability of the deposit, the balance among detaching and attaching forces is carried out. The evolution of the vane shape is taken into account by using a moving mesh technique.
Influence of Intrarow Interaction on the Aerodynamic Damping of an Axial Turbine Stage
Authors: Müller Tobias R. , Vogt Damian M. , Vogel Klemens , Phillipsen Bent A. 
Published: August 2018

The present numerical study aims at examining the influence of intrarow interaction effects in aerodynamic damping predictions of an axial turbine rotor. The investigated operating point corresponds to a resonance crossing associated with the fundamental engine order of the stator blade row. Accordingly, the pressure perturbations induced by the vibration of the rotor at its modal frequency are found to be coincident in frequency and thus superimpose with the pressure perturbations resulting from intrarow interaction phenomena. A methodology for extracting vibration induced pressure perturbations for the subsequent calculation of the vibration induced modal aerodynamic damping is established and applied within the scope of the present study.
Applying this methodology, both the influence of the underlying mean and transient flow field as well as the influence of acoustic wave reflections at the adjacent stator blade row is investigated on the predicted aerodynamic damping. In this context, the underlying mean flow field, which is found to be slightly altered in the presence of intrarow interaction phenomena, was proven to have a significant influence on vibration induced pressure perturbations. Moreover, acoustic wave reflections at the adjacent stator blade row are found to have the capability of influencing the aerodynamic damping depending on their actual phasing when impinging onto the turbine rotor.
Numerical and Experimental Investigation on an Effusion-Cooled Lean Burn Aeronautical Combustor: Aerothermal Field and Metal Temperature
Authors: Bertini D. , Mazzei L. , Puggelli S. , Andreini A. , Facchini B. , Bellocci L. , Santoriello A. 
Published: August 2018

Lean burn combustion is increasing its popularity in the aeronautical framework due to its potential in reducing drastically pollutant emissions (NOx and soot in particular). Its implementation, however, involves significant issues related to the increased amount of air dedicated to the combustion process, demanding the redesign of injection and cooling systems. A reduced coolant mass flow rate in conjunction with higher compressor discharge temperature negatively affect the cooling potential thus requiring the exploitation of efficient schemes such as effusion cooling.
This work describes the experimental and numerical final validation of an aeronautical effusion-cooled lean-burn combustor. Full annular tests were carried out to measure temperature profiles and metal temperature distributions at different operating conditions of the ICAO cycle. Such an outcome was obtained also with an in-house developed CHT methodology (THERM3D). RANS simulations with the Flamelet Generated Manifold combustion model were performed to estimate aerothermal field and heat loads, while the coupling with a thermal conduction solver returns the most updated wall temperature. The heat sink within the perforation is treated with a 0D correlative model that calculates the heat pickup and the temperature rise of coolant. The results highlight an overall good capability of the proposed approach to estimate the metal temperature distribution at different operating conditions. It is also shown how more advanced scale-resolving simulations could significantly improve the prediction of turbulent mixing and heat loads.
Effects of Endwall 3D Contouring on Film Cooling Effectiveness of Cylindrical Hole Injections at Different Locations on Vane Endwall
Authors: Chen Pingting , Gao Hongyu , Li Xueying , Ren Jing , Jiang Hongde 
Published: August 2018

With the development of gas turbine, the secondary flow loss in vane passage is getting higher. To reduce the strength of secondary flows within vane passage, endwall 3D contouring is an effective design. Endwall 3D contouring can lead to significant changes in the secondary flow vortices, which lead to changes on jet-to-secondary flow interaction and then changes on the film cooling effectiveness. Meanwhile, the geometry configuration of the contoured endwall, such as the rising and falling on the endwall, can also have an impact on film cooling performance. As a result, the film cooling performance on contoured endwall differs from that on flat endwall. Understanding the difference in film cooling characteristics on the contoured endwall and flat endwall may help to make better endwall contouring design and better endwall film cooling arrangement.
The present experiment compares the film cooling effectiveness of cylindrical hole injections at different locations on 3D contoured endwall versus flat endwall in an NGV (nozzle guide vane) passage. The measurement is performed in a low speed wind tunnel with a F-class annular sector NGV cascade. The cylindrical hole injections are located as 4 different rows at −30% axial chord, 30% axial chord, 50% axial chord and 70% axial chord. Endwall pressure distribution is measured with pressure taps by pressure sensor while film cooling effectiveness is measured using PSP (Pressure Sensitive Paint). Two density ratios with 1.0 and 1.5 and several average blowing ratios are investigated. Effects of endwall contouring, density ratio and blowing ratio on film cooling effectiveness are obtained and the results are presented and explained in this investigation.
Gas Temperature Measurement in Engine Conditions Using Uniform Crystal Temperature Sensors (UCTS)
Authors: DeVoe Jason , Thomas Anastasia , DeVoe Reagan , Ginzbursky Edward 
Published: August 2018

Validation and tuning methods for analytical algorithms used in modeling heat transfer for engine parts, such as turbine blades, require the direct comparison of calculated and experimental metal temperature measurement results. It is important to ensure that the geometric characteristics as well as the boundary condition parameters of the gas flow are held in common for both the physical experiment and the calculation. Unfortunately, the task of obtaining knowledge of the gas parameters such as the radial temperature profile at the turbine inlet is far from trivial. The authors will briefly survey commonly used methods and the uncertainties related to their application based on publicly available data. Among these techniques, a relatively new method of using Uniform Crystal Temperature Sensors (UCTS) for gas temperature measurement, may offer some advantages and will be analyzed in greater detail.
The authors use 3D Finite Element Analysis code to analyze sources of potential systematic error for gas temperature measurement using UCTS. A matrix of varying materials and configurations is evaluated. Recommendations drawn from this analysis will enable analytical designers and instrumentation engineers to optimize the application of this technique specific to their test requirements.
Advancements in H Class Gas Turbines and Combined Cycle Power Plants
Authors: Vandervort Christian 
Published: August 2018

The power generation industry is facing unprecedented challenges. High fuel costs combined with an increased penetration of renewable power has resulted in greater demand for high efficiency and operational flexibility. Imperative for a reduced carbon footprint places an even higher premium on efficiency. Power producers are seeking highly efficient, reliable, and operationally flexible solutions that provide long-term profitability in a volatile environment. New generation must also be cost-effective to ensure affordability for both domestic and industrial consumers.
Gas turbine combined cycle power plants provide reliable, dispatch-able generation with low cost of electricity, reduced environmental impact, and improved flexibility. GE’s air-cooled, H-class gas turbines (7/9HA) are engineered to achieve greater than 63% net, combined cycle efficiency while delivering operational flexibility through deep, emission-compliant turndown and high ramp rates. The largest of these gas turbines, the 9HA.02, exceeds 64% combined cycle efficiency (net, ISO) in a 1 × 1, single-shaft configuration. In parallel, the power plant has been configured for rapid construction and commissioning enabling timely revenue generation for power plant developers and owners.
The HA platform is enabled by 1) use of a simple air-cooling system for the turbine section that does not require external heat exchange and the associated cost and complexity, and 2) use of well-known materials and coatings with substantial operating experience at high firing temperatures. Key technology improvements for the HA’s include advanced cooling and sealing, utilization of unsteady aerodynamic methodologies, axially staged combustion and next generation thermal barrier coating (TBC). Validation of the architecture and technology insertion is performed in a dedicated test facility over the full operating range. As of February 2018, a total of 18 HA power plants have achieved COD (Commercial Operation).
This paper will address three topics relating to the HA platform: 1) gas turbine product technology, 2) gas turbine validation and 3) integrated power plant commissioning and operating experience.
Thermoacoustic Modes of Quasi-1D Combustors in the Region of Marginal Stability
Authors: Silva Camilo F. , Yong Kah Joon , Magri Luca 
Published: August 2018

It may be generally believed that the thermoacoustic eigenfrequencies of a combustor with fully acoustically reflecting boundary conditions depend on both flame dynamics and geometry of the system. In this work, we show that there are situations where this understanding does not strictly apply.
The purpose of this study is twofold. In the first part, we show that the resonance frequencies of two premixed combustors with fully acoustically reflecting boundary conditions in the region of marginal stability depend only on the parameters of the flame dynamics, but do not depend on the combustor’s geometry. This is shown by means of a parametric study, where the time delay and the interaction index of the flame response are varied and the resulting complex eigenfrequency locus is shown. Assuming longitudinal acoustics and a low Mach number, a quasi-1D Helmholtz solver is utilized. The time delay and interaction index of the flame response are parametrically varied to calculate the complex eigenfrequency locus. It is found that all the eigenfrequency trajectories cross the real axis at a resonance frequency that depends only on the time delay. Such marginally stable frequencies are independent of the resonant cavity modes of the two combustors, i.e. the passive thermoacoustic modes.
In the second part, we exploit the aforementioned observation to evaluate the critical flame gain required for the systems to become unstable at four eigenfrequencies located in the marginally stable region. A computationally-efficient method is proposed. The key ingredient is to consider both direct and adjoint eigenvectors associated with the four eigenfrequencies. Hence, the sensitivity of the eigenfrequencies to changes in the gain at the region of marginal stability is evaluated with cheap and accurate calculations.
This work contributes to the understanding of thermoacoustic stability of combustors. In the same manner, the understanding of the nature of distinct resonance frequencies in unstable combustors may be enhanced by employing the analysis of the eigenfrequency locus here reported.
Flutter Analysis of a Flexible UHBR Fan at Different Flight Conditions
Authors: Schuff Matthias , Reisberg Jannik 
Published: August 2018

A flexible UHBR fan is investigated at different flight conditions with a focus on static deflections and aeroelastic stability. Operating points at varying inlet conditions, which are comparable according to the Mach similarity principle, are investigated. However, not all the aerodynamic characteristics remain identical and aerodynamic damping of mode shape vibrations is changed.
When steady deformations of the fan blades are taken into account, the deviation between different inlet conditions increases further. This is mainly due to torsional deflections, changing the effective angle of attack and causing a general shift of the compressor map.
Even though the subsequent changes in flutter predictions are not severe for most parts of the compressor map, the behavior at the boundaries is sensitive to the real flight condition.
As shown, the Mach similarity principle is not suitable for investigating aeroelastic stability throughout the whole flight envelope, especially when the static blade deformation is not neglectable. The reason for this can be found in the complex interaction between dimension-less numbers (Mach, Reynolds), sized values (pressure difference or aerodynamic loading, natural frequency) and their dependency on each other.
Design, Modeling, and Implementation of an Electrically-Driven Seal Gas Booster
Authors: Garceau Sean W. , Bowen John S. 
Published: August 2018

This paper outlines the simulation, evaluation, and implementation of an electrically-driven seal gas booster in a tandem dry seal application. The electric boost compressor makes it feasible to supply seal gas to a process compressor’s seals during indefinite pressurized hold. Extended pressurized hold times reduce gas compressor station hydrocarbon emissions by reducing the number of unplanned compressor depressurization events. Traditional pneumatic seal gas boosters require regular depressurized maintenance intervals. The paper addresses the overall decrease in utility demand of the electric seal gas booster when compared to a pneumatic seal gas booster. The total cost difference between the two systems was determined for both initial investment and operational cost.
A steady-state simulation of a single impeller centrifugal boost compressor, within a package dry seal gas system utilizing differential pressure control to regulate seal gas flow, was conducted to evaluate overall system performance, design requirements, and constraints. The simulation validated a system design. The design was installed in an operational gas transmission compressor’s seal system for performance monitoring. The field testing data was compared to simulation output parameters to validate the simulation and confirm key performance characteristics. Additional process conditions and multi-body process compressor configurations were evaluated through simulation.
The use of differential pressure control, when compared to a flow control for seal gas regulation, has some key differentiating characteristics with regards to implementation of the electric seal gas booster in a package dry seal system [1, 2]. Seal gas source location, supplied internally or externally, is an important consideration for the system’s performance. Continuous operational with the electric seal gas booster requires additional control strategies to manage the process compressor case pressure.
Aerodynamic Optimization of Axial Fans Using the Adjoint Method
Authors: Bamberger Konrad , Carolus Thomas 
Published: August 2018

This paper discusses the aerodynamic optimization of low-pressure axial fans using adjoint Computational Fluid Dynamics (CFD).
In the first part, a typical CFD-based fan optimization problem is introduced. The focus is on the CFD model and potential objective functions.
The adjoint system of equations and the adjoint boundary conditions for this optimization problem are derived in the second part. Moreover, the software implementation in the open source CFD code OpenFOAM v3.0.x is described. The existing OpenFOAM solver “adjointShapeOptimizationFoam” serves as the basis and is customized to the optimization of fans. The code solves both the primal and the adjoint incompressible Reynolds-averaged Navier-Stokes (RANS) equations from which a sensitivity map of the objective function with respect to the grid topology can be derived. The main extension of the existing code deals with the consideration of a rotating frame of reference leading to additional source terms in both the primal and the adjoint RANS equations. Moreover, the implementation of new boundary conditions is performed to handle the distinct objective functions.
In the third part, the customized adjoint solver is applied to improve an existing baseline fan. Two adjoint simulations of the baseline fan are performed aiming at maximization of pressure and efficiency, respectively. The resulting surface sensitivities on the blade are used to modify the blade shape accordingly. Eventually, the performance of the two optimized fans is predicted by RANS to quantify the improvements. The first fan features a pressure rise which is 3.6 % higher as compared to the baseline fan. The second fan features an efficiency improvement of 0.1 percentage points as compared to the baseline fan. Hence, the functionality of the adjoint method is proven. A more substantial improvement would require further optimization loops with repeated adjoint simulations that, however, are not part of this paper.