bluuebunny/crossref_metadata_2025_split huggingface dataset:
Secondary Flow Response to Endwall Jets in a Low Pressure Turbine
Authors: Fletcher Nathan , Marks Christopher R. , Donovan Molly H. 
Published: January 2021

Abstract
Due to the significant losses contributed by the secondary flow features, an active flow control system was implemented in a low-pressure turbine linear cascade which consisted of localized endwall jets with small mass ratios to perturb the dominant passage vortex. Benefits included significant area-averaged total pressure loss reduction and improved exit angle deviations which help to open the design envelope to application of high-lift front-loaded blades. This report looks to reveal the impact of steady and pulsed endwall blowing on the secondary flow dynamics. High-speed stereoscopic particle image velocimetry for an in-passage measurement plane was utilized to investigate the time-dependent behavior of key flow features such as the passage vortex. At baseline conditions, the passage vortex is characterized by time-varying oscillatory motion in the pitchwise direction, streamwise undulation, bursting, and fluctuating strength. Upon actuation of endwall jets, some of these defining dynamics of key flow features were greatly affected. A complementary investigation of the endwall jets mounted outside of a turbine environment in order to study the emitted structures at varying conditions was used to explain the observations found in the turbine passage. Insights into the secondary flow responsiveness demonstrated that loss reduction was realized by inducing reduced coherence of the passage vortex. Despite pulsed blowing at discrete frequencies associated with the passage vortex, there was no indication that instability excitation was exploited. Rather, the endwall jets acted as a periodic shape-change to the endwall which weakened the passage vortex and forced it closer to the suction-surface.
A Numerical Approach to Centrifugal Compressor Stage Flow Path Design Synthesis and Optimization
Authors: Goldenberg Vlad , Gorman John M. , Simon Terrence , Sparrow Ephraim M. 
Published: January 2021

Abstract
This paper proposes geometry parameterization of a complete single centrifugal compressor stage and applies CFD-driven optimization using artificial neural networks and a Kriging surrogate model. Kinematic velocity triangle analysis is used to arrive at an initial design, which is then improved by using automated optimization algorithms and fundamental flow physics using CFD simulation. By allowing the design to evolve, guided by CFD, new and untested optimum designs are possible. This work deals specifically with design and optimization of the flow path. Design for structural aspects such as vibration, rotor dynamics and other mechanical aspects is outside the scope of this work.
The CAD parameterization enables robust specification of the flow path geometry while maintaining a sufficiently small set of parameters for practical design space exploration. The parameterization includes an impeller with optional splitter blades, a vaneless diffuser and volute. Steady-state, RANS-based CFD is employed in the analysis of both the rotationally-periodic components and the volute geometry.
Direct optimization and response surface optimization are demonstrated for rotationally periodic components to maximize design-point efficiency of the flow path using a multi-objective genetic algorithm (MOGA). Improvements in total-total isentropic efficiency of between 4 and 5 percent are achieved.
Optimization of the flow path of the volute is likewise demonstrated. In the case of the volute, a Kriging response-surface model is used and a 1.4 percentage point improvement is shown. Further research in the utilization various implementations of Artificial Intelligence (AI) machine learning techniques in conjunction with parameterized turbomachinery flow paths to enable enhanced designs to be generated effectively is proposed.
Experimental Investigation of Gas Turbine Axial Diffuser Performance: Part I — Parametric Analysis of Influential Variables
Authors: Brown Kenneth , Guillot Stephen , Ng Wing , Iksang Lee , Dongil Kim , Hong Giwon 
Published: January 2021

Abstract
An experimental investigation of the effect of inlet flow conditions and improved geometries on the performance of modern axial exhaust diffusers of gas turbines has been completed. As the first of a two-part series, this article concentrates on characterizing diffuser sensitivity to parametric variations in internal geometry and inlet flow conditions. Full-factorial experiments were carried out on five parameters including the inlet Mach distribution, shape of the support struts, shape of the oil-drain strut, diffuser hade angle, and the hubcap configuration. To enable an efficient sweep of the design space, experiments were performed in this initial study at a down-scaled turbine exit Reynolds number (ReH roughly 3% of the value for an H-class diffuser) and at a full-scale turbine exit Mach number. The study was accomplished in a continuous, cold-flow wind tunnel circuit, and tailored distributions of Mach number, swirl velocity, and radial velocity derived from on-design conditions of an industry diffuser were generated. Measurements included 5-hole probe traverses at planes of interest. Diffuser performance was most sensitive to the inlet Mach distribution with losses of 0.081 points of pressure recovery due to a nonuniform Mach distribution with higher velocity near the hub versus a uniform one. Detailed comparisons of axial flow variation for a top-performing configuration versus related configurations shed physical insight regarding the evolution of kinetic energy distortion into viscous loss in the wake, as well as highlight the benefit of uniform inlet profiles in practice despite the lower theoretical recovery of such cases. The results presented here isolate the inlet flow distribution as a parameter of high interest for further study which is carried out for both on- and off-design conditions in the companion article [1].
Application of Model Based Systems Engineering for the Conceptual Design of a Hybrid-Electric ATR 42-500: From System Architecting to System Simulation
Authors: Cappuzzo Federico , Broca Olivier , Vouros Stavros , Roumeliotis Ioannis , Scullion Calum 
Published: January 2021

Abstract
The progress in aerospace technology over the recent years led to the development of more sophisticated and integrated systems. To cope with this complexity, the aerospace industry is seeing a progressive trend towards adopting Model-Based Systems Engineering (MBSE) in various stages of the product development cycle. The ability to capture emerging behavior, mitigation of risk and improved communication among different stakeholders are some key benefits that MBSE provides over traditional methods for complex systems and processes. This paper attempts to bridge the gap between system architecting and system simulation activities by proposing a methodology to facilitate seamless flow of information between the two development aspects. This methodology was applied to the development of a parallel hybrid-electric version of the ATR 42–500. The use case was designed for a regional mission of 400 nautical miles with the ability to meet regulation requirement of carrying enough reserves for landing at an alternate airport. An integrated systems model, consisting of gas turbine engine, electric powertrain, and flight dynamics, was developed with Simcenter Amesim to analyze the dynamics performance of the aircraft throughout the whole mission. The key metrics evaluated were fuel consumption, take-off weight and the Energy Specific Air Range (ESAR) of the aircraft. As environmental regulations are becoming more stringent, pollutant and noise emissions were considered in the study. The most promising hybrid configurations are recognized, the potential benefits are quantified highlighting the strong potential of System Architecting and System Simulation to provide valuable insights early in the development cycle, reducing the time and cost of product development.
Pulsed Impingement Turbine Cooling and its Effect on the Efficiency of Gas Turbines With Pressure Gain Combustion
Authors: Neumann Nicolai , Peitsch Dieter , Berthold Arne , Haucke Frank , Stathopoulos Panagiotis 
Published: January 2021

Abstract
Performance improvements of conventional gas turbines are becoming increasingly difficult and costly to achieve. Pressure Gain Combustion (PGC) has emerged as a promising technology in this respect, due to the higher thermal efficiency of the respective ideal gas turbine cycle. Previous cycle analyses considering turbine cooling methods have shown that the application of pressure gain combustion may require more turbine cooling air. This has a direct impact on the cycle efficiency and reduces the possible efficiency gain that can potentially be harvested from the new combustion technology. Novel cooling techniques could unlock an existing potential for a further increase in efficiency. Such a novel turbine cooling approach is the application of pulsed impingement jets inside the turbine blades.
In the first part of this paper, results of pulsed impingement cooling experiments on a curved plate are presented. The potential of this novel cooling approach to increase the convective heat transfer in the inner side of turbine blades is quantified. The second part of this paper presents a gas turbine cycle analysis where the improved cooling approach is incorporated in the cooling air calculation. The effect of pulsed impingement cooling on the overall cycle efficiency is shown for both Joule and PGC cycles. In contrast to the authors’ anticipation, the results suggest that for relevant thermodynamic cycles pulsed impingement cooling increases the thermal efficiency of Joule cycles more significantly than it does in the case of PGC cycles. Thermal efficiency improvements of 1.0 p.p. for pure convective cooling and 0.5 p.p. for combined convective and film with TBC are observed for Joule cycles. But just up to 0.5 p.p. for pure convective cooling and 0.3 p.p. for combined convective and film cooling with TBC are recorded for PGC cycles.
Integration of Computational Fluid-Particle Dynamics Techniques for the Instantaneous Estimation of Particle Erosion Damage on Axial Fan Blade Sections
Authors: Castorrini Alessio , Venturini Paolo , Corsini Alessandro 
Published: January 2021

Abstract
In the last decade, the authors focused their research in the development and implementation of accurate numerical tools and methods able to predict the erosion and deposit on turbomachinery blades operating with particle-laden flows. These models and methods give complete three-dimensional description of the phenomenon, but their application is limited to a single working condition of the blade. The present paper covers the first step in the definition of a general methodology to extend the applicability of these tools to a full range of the machines operating conditions. The method aims to obtain an instantaneous prediction of the expected damage pattern for a blade section, given its local working condition in terms of relative fluid-particle flow. The final result is based on a precomputed database associated to the blade section, where the single element is obtained by computing the erosion damage using the aforementioned numerical tools.
This paper will show the methodology to obtain the database associated to the midspan section of an induced draft fan subjected to erosion due to coal ash particle. The final database is then used to predict the damage state of the section associated to a given point in the characteristic curve of the fan.
Analysis of Time-Wise Compressor Fouling Phenomenon on a Multistage Test Compressor: Performance Losses and Particle Adhesion
Authors: Vulpio Alessandro , Suman Alessio , Casari Nicola , Pinelli Michele , Kurz Rainer , Brun Klaus 
Published: January 2021

Abstract
The analysis of the performance losses of a multistage compressor concerning the air contaminant is not widespread in literature and, the mutual interactions of particle materials, air humidity, and compressor load are not well studied. The airborne micrometric particles that enter the compressor can deposit on the internal surfaces, causing the loss of performance of the machine.
In this paper, several experimental tests have been carried out on a multistage compressor unit. A detailed analysis has been carried out considering soil and soot ingestion, as well as the air relative humidity (ranging from 50 %RH to 80 %RH) and compressor rotating velocity. Several combinations of particle diameter, material, and operating conditions have been considered. The amount of contaminant at the compressor outlet has been measured and the capture efficiency of the whole machine has been determined. Over the exposure time, the capture efficiency ranges from 0.2 to 0.6 according to the powder type and compressor inlet conditions. The capability of the compressor to collect particles changes over time as a function of the condition, even if, several tested cases appear characterized by an almost constant capture efficiency trend.
In addition, the performance degradation has been monitored over time and, with the reference of the particle concentration, the present experimental campaign covers about 500 operating hours of an actual installation. After a detailed evaluation of experimental uncertainty, the performance losses due to particle contamination has been assessed. The losses in the compressor performance have been estimated by means of the pressure ratio of the axial stages. The maximum degradation has been estimated equal to 0.53 % per hour for the compressor pressure ratio. Soot particles appear stickier, especially in the presence of higher humidity and represent the most detrimental operating conditions for the compressor unit.
Contribution of Tip Shroud Cavity to Loss Generation in the Main Flow of a Low Pressure Turbine Using Steady and Unsteady Numerical Approach
Authors: Perini Maxime , Binder Nicolas , Bousquet Yannick , Schwartz Eric 
Published: January 2021

Abstract
A lot of studies on turbomachinery main flow optimisation have been performed in order to reach current efficiencies. To go further in the study of aerodynamic losses sources, a better understanding of technological effects is required. Tip shroud cavities in low pressure turbine is an example. Indeed, the by-pass flow causes additional pressure losses. In addition, interactions between main flow and cavity flows, as well as the re-entering flow, cause mixing losses and modifications of flow angle. This paper investigates the contribution of tip shroud cavities in a low pressure turbine stage on the overall performance and flow structures. The ability of a steady simulation to predict this kind of flow by comparison with time-resolved results is poorly documented in the literature, and is an objective of this paper. Computations are compared with experimental data from low speed turbine test rig. Entropy production shows that a large amount of additional losses comes from the cavities themselves whichever the steady or unsteady treatment of the simulation. Additional losses generated in the rotor are more dependent on the presence of the shroud or not than the unsteady feature of the simulations.
Conceptual Design and Energy Storage Positioning Aspects for a Hybrid-Electric Light Aircraft
Authors: Gkoutzamanis Vasilis G. , Srinivas Arjun , Mavroudi Doukaini , Kalfas Anestis I. , Kavvalos Mavroudis D. , Kyprianidis Konstantinos G. , Korbetis George 
Published: January 2021

Abstract
This work focuses on the feasibility of a 19-passenger hybrid-electric aircraft, to serve the short-haul segment within the 200–600 nautical miles. Its ambition is to answer some dominating research questions, during the evaluation and design of aircraft based on electric propulsion architectures. The potential entry into service of such aircraft is foreseen in 2030. A literature review is performed, to identify similar concepts that are under research and development. After the requirements definition, the first level of conceptual design is employed. Based on a set of assumptions, a methodology for the sizing of the hybrid-electric aircraft is described to explore the basis of the design space. Additionally, a methodology for the energy storage positioning is provided, to highlight the multidisciplinary aspects between the sizing of an aircraft, the selected architecture (series/parallel partial hybrid) and the energy storage operational characteristics. The design choices are driven by the aim to reduce CO2 emissions and accommodate boundary layer ingestion engines, with aircraft electrification. The results show that it is not possible to fulfill the initial design requirements (600 nmi) with a fully-electric aircraft configuration, due to the far-fetched battery necessities. It is also highlighted that compliance with airworthiness certifications is favored by switching to hybrid-electric aircraft configurations and relaxing the design requirements (targeted range, payload, battery technology). Finally, the lower degree of hybridization (40%) is observed to have a higher energy efficiency (12% lower energy consumption and larger CO2 reduction), compared to the higher degree of hybridization (50%), with respect to the conventional configuration.
A Nitrogen Oxides Emission Prediction Model for Gas Turbines Based on Interpretable Multilayer Perceptron Neural Networks
Authors: Huang Dawen , Tang Shanhua , Zhou Dengji 
Published: January 2021

Abstract
Gas turbines, an important energy conversion equipment, produce Nitrogen Oxides (NOx) emissions, endangering human health and forming air pollution. With the increasingly stringent NOx emission standards, it is more significant to ascertain NOx emission characteristics to reduce pollutant emissions. Establishing an emission prediction model is an effective way for real-time and accurate monitoring of the NOx discharge amount. Based on the multi-layer perceptron neural networks, an interpretable emission prediction model with a monitorable middle layer is designed to monitor NOx emission by taking the ambient parameters and boundary parameters as the network inputs. The outlet temperature of the compressor is selected as the monitorable measuring parameters of the middle layer. The emission prediction model is trained by historical operation data under different working conditions. According to the errors between the predicted values and measured values of the middle layer and output layer, the weights of the emission prediction model are optimized by the back-propagation algorithm, and the optimal NOx emission prediction model is established for gas turbines under the various working conditions. Furthermore, the mechanism of predicting NOx emission value is explained based on known parameter influence laws between the input layer, middle layer and output layer, which helps to reveal the main measurement parameters affecting NOx emission value, adjust the model parameters and obtain more accurate prediction results. Compared with the traditional emission monitoring methods, the emission prediction model has higher accuracy and faster calculation efficiency and can obtain believable NOx emission prediction results for various operating conditions of gas turbines.
Multi-Channel Spectral Analysis of Non-Synchronous Vibrations of Bladed Disks Measured by Blade Tip Timing
Authors: Carassale Luigi , Coletti Francesca , Guida Roberto , Marrè-Brunenghi Michela , Rizzetto Elena 
Published: January 2021

Abstract
The paper proposes a method for the processing of BTT data deriving from non-synchronous vibrations measured at constant rotor speed by a set of non-uniformly distributed sensors. The sampled data are interpreted as members of a vector space whose characteristics are determined by the signal itself and by sampling pattern. If the signal contains a single harmonic component, its frequency can be estimated through a method that has been named harmonic matching. On the contrary, when more than one harmonic component is present, due to a multi-modal response, a component separation processing is necessary. To this purpose, it is proposed a technique based on the Independent Component Analysis (ICA). This approach is limited to constant speed regime, but has the benefit of using statistical estimators that enable a strong resistance to noise. The method is illustrated using academic examples and is employed to study a flutter-like non-synchronous vibration of a bladed disk.
Development of Experimental and Numerical Methods for the Analysis of Active Clearance Control Systems
Authors: Da Soghe Riccardo , Mazzei Lorenzo , Tarchi Lorenzo , Cocchi Lorenzo , Picchi Alessio , Facchini Bruno , Descamps Laurent , Girardeau Julian , Simon Matthieu 
Published: January 2021

Abstract
The ever increasing performance requirements of modern aero-engines necessitate the development of effective ways to improve efficiency and reduce losses. Casing temperature control is particularly critical from this point of view, since thermal expansion directly affects the blade tip clearance and thus the associated leakages. To limit the turbine tip flows, Active Clearance Control (ACC) systems have been implemented over the last decades. These systems are usually based upon impingement cooling, generated by a series of perforated manifolds enclosing the turbine casing.
When dealing with aeroengine low pressure turbines, the current trend in increasing the engine by-pass ratio, so as to enhance the system propulsive efficiency, pushes the limits of ACC traditional design performance. The reduction of the pressure head at the ACC system inlet requires lower nozzle-to-target distances as well as denser impingement arrays to compensate the reduction of the jets’ Reynolds number. Literature correlations for the impingement heat transfer coefficient estimation are then out of their confidence range and also RANS numerical approaches appear not suitable for future ACC designs.
In this work, methodologies for the development of accurate and reliable tools to determine the heat transfer characteristics of low pressure ACC systems are presented. More precisely, this paper describes a custom designed finite difference procedure capable of solving the inverse conduction problem on the target plate of a test sample. The methodology was successfully applied to an experimental setup for the measurement of the thermal loads on a target plate of a representative low pressure ACC impinging system. The experimental data is then used to validate a suitable numerical approach. Results show that RANS model is not able to mimic the experimental trends, while scale-resolving turbulence models provide a good reconstruction of the experimental evidences, thus allowing to obtain a correct interpretation of flow and thermal phenomena for ACC systems.