bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation on Influence Mechanism of Wall Coating on Infrared Radiation Signature of Serpentine Nozzle
Authors: Shi Jie , Zhou Li , Wang Zhanxue , Shi Jingwei 
Published: January 2021

Abstract
Stealth performance is one of the most important factors to evaluate the technical level of modern battleplane. Serpentine nozzle can block the direct radiation transmission path between the high-temperature components in exhaust system and the infrared detector, thus suppressing the infrared radiation signature. However, due to the reflection characteristics of nozzle wall, this method can also cause indirect transmission of infrared radiation through the wall reflection to form a local high radiation area. Motivated by previous researches on the application of serpentine nozzle wall coating in electromagnetic radiation suppression. Wall coating is applied to serpentine nozzle to suppress infrared radiation intensity in this paper. Aiming at the situation of turbofan engine using serpentine nozzle, the influence mechanism of coating position, area and emissivity of serpentine nozzle on infrared radiation signature is calculated and analyzed, and the scheme of wall coating which has the least coating area and can effectively suppress infrared radiation transmission is also studied. The results show that reducing wall coating emissivity will strengthen the indirect transmission of infrared radiation, then cause the increase of exhaust system infrared radiation intensity, while increasing wall coating emissivity will reduce wall coating reflectivity, and the local high radiation area caused by indirect radiation transmission can be effectively prevented. The research also found that the infrared radiation signature of exhaust system can be effected only when the emissivity adjustment of serpentine nozzle wall which can be detected directly by infrared detector. After adopting the optimized wall emissivity coating scheme, the infrared radiation intensity of serpentine nozzle for turbofan can be reduced by 51.3% on the original basis while the coating area only accounts for 25.1% of the nozzle area.
The Role of the Centerbody Wake on the Precessing Vortex Core Dynamics of a Swirl Nozzle
Authors: Mukherjee Arnab , Muthichur Nishanth , More Chaitali , Gupta Saarthak , Hemchandra Santosh 
Published: January 2021

Abstract
The precessing vortex core (PVC) phenomenon in swirling jets is a helical instability in the flow driven by the coherent precession of the vortex breakdown bubble (VBB) around the flow axis, resulting in the helical rollup of the shear layer. This instabilitty is driven mainly by flow processes in the region upstream of the VBB. Centerbodies, commonly employed in combustor nozzles create a central wake recirculation zone (CWRZ) that can interfere with VBB precession and hence suppress the PVC. We study this phenomenon in a swirl nozzle with a centerbody whose end face is flush with the nozzle exit plane, using large eddy simulations (LES) and linear hydrodynamic stability analysis for flow Reynolds numbers Re = 48,767 and 82,751, based on nozzle exit diameter and bulk flow velocity. For one of the Re = 82,751 cases the centerbody end face diameter is halved resulting in the onset of coherent VBB precession. Linear stability analysis reveals a marginally unstable mode in this case. The same mode is found to be stable in the nominal cases. Structural sensitivity analysis for these two cases, shows that the VBB precession eigenmode is sensitive to changes in the time averaged flow in the VBB-CWRZ merger region. This suggests that the reduction in CWRZ length due to halving the centerbody end face diameter is the reason for the onset of VBB precession. These results suggest that in general, spatial separation between the CWRZ and VBB can result in the onset of VBB precession and the emergence of PVC oscillations in swirl flows.
Consideration of Simplified Structural Models for Turbine Vane Modal Analysis
Authors: Korpics Natalie S. , Berdanier Reid A. 
Published: January 2021

Abstract
Modal analysis of jet engine hardware is a necessary analytical tool utilized by engineers to understand and predict the vibrational risks to the system. Whereas blades and disks are critically analyzed due to their failure modes and effects, turbine vanes also need to be evaluated with respect to their design modal criteria to minimize potential risks to the engine. Although full hoop models of the entire system are most accurate, the time required for modeling and solution processing is typically prohibitive. Through cyclic symmetry and the use of commercial contact techniques, an analytical model may be created that provides the behavior of the entire system with a fraction of the computing time. However, methods for model simplification, including vane-only models, have not been addressed, and the potential for simplified models to accurately predict system modes is of particular interest. Accordingly, this paper studies the finite element modeling procedures for turbine vane modal analysis using multiple contact methods and cyclic symmetry applied to a turbine vane. An emphasis is placed on evaluating vane-only modeling techniques and an abbreviated turbine casing model. Additional comparisons with a traditional assembly model assess finite element model solution accuracy and efficiency. Ultimately, formal recommendations are offered for structural modeling of turbine vanes, including assessments of accuracy, reduction of frequency prediction capability, and computational efficiency gain.
Multidisciplinary Design of a Low-Noise Propeller: Part I — Multi-Fidelity Design Methodology Leveraging on Acoustic Drivers
Authors: Dumont Chloé , Baert Lieven , Lepot Ingrid 
Published: January 2021

Abstract
High-fidelity numerical simulations have already contributed in a significant way to the emergence of state-of-the-art turbomachinery components but are still sparingly exploited due to their cost. It is hence relevant to continue the investigations on low-fidelity tools and their combination with higher fidelity methodologies especially when breakthrough technologies are studied. Multi-fidelity approaches are key in supporting turbomachinery engineers to quickly decide on the relevance of an innovative concept, and to accelerate optimisation processes.
This paper describes a low-noise propeller design methodology developed during the IRON project (Clean Sky 2). This methodology is driven by Calypso, a platform developed by Cenaero, which integrates machine learning strategies and multifidelity aerodynamic and acoustic solvers. Two key elements of this framework are detailed and validated in this paper. The first one is a low-fidelity tool that offers a fast estimation of the steady aerodynamic performance of a propeller blade using a lifting-surface method. The second one is a far-field tonal noise prediction solver, relying on an acoustic propagation performed with Farassat’s formulation 1A of the Ffowcs-Williams and Hawkings equation. Noise source can be either obtained after a CFD computation or after a low-fidelity aerodynamic evaluation.
The low and high-fidelity aero-acoustic methodologies have been applied on 600 samples. It is shown how data mining strategies available within Calypso pave the way to astutely combine both levels of fidelity within an optimisation to quickly and efficiently explore a large design space, and to identify the key design parameters as early as possible in the design process.
A Multi-Fidelity Aero-Thermal Design Approach for Secondary Air Systems
Authors: Amirante Dario , Hills Nicholas J. , Adami Paolo 
Published: January 2021

Abstract
The paper presents a multi-disciplinary approach for aero-thermal and heat transfer analysis for internal flows. The versatility and potential benefit offered by the approach is described through the application to a realistic low pressure turbine assembly. The computational method is based on a run time code-coupling architecture that allows mixed models and simulations to be integrated together for the prediction of the sub-system aero-thermal performance. In this specific application the model is consisting of two rotor blades, the embedded vanes, the inter-stage cavity and the solid parts. The geometry represents a real engine situation.
The key element of the approach is the use of a fully modular coupling strategy that aims to combine (1) flexibility for design needs, (2) variable level of modelling for better accuracy and (3) in memory code coupling for preserving computational efficiency in large system and sub-system simulations.
For this particular example Reynolds Averaged Navier-Stokes (RANS) equations are solved for the fluid regions and thermal coupling is enforced with the metal (conjugate heat transfer). Fluid-fluid interfaces use mixing planes between the rotating parts while overlapping regions are exploited to link the cavity flow to the main annulus flow as well as in the cavity itself for mapping of the metal parts and leakages. Metal temperatures predicted by the simulation are compared to those retrieved from a thermal model of the engine, and the results are discussed with reference to the underlying flow physics.
Numerical Analysis of Mass Flow Leakage Through Orifices for Supercritical CO2: Two-Phase Flow Effects
Authors: Vesely Ladislav , Khadse Akshay , Curbelo Andres , Kapat Jayanta S. , Petrungaro Luca 
Published: January 2021

Abstract
Supercritical CO2 (sCO2) holds a great promise as a future working fluid for power generating Brayton cycles. One of the challenging research areas in sCO2 power cycles is flow leakage and the design of seals on the compressor side of the cycle. Given the compact nature of sCO2 turbomachinery, even a minimal amount of leakage can lead to a significant power efficiency loss. Hence accurate prediction of mass flow leakage rate becomes important. However, on the compressor side of the cycle, operating conditions across the seal lead to two-phase flow. This makes flow modeling very challenging because conventional one-phase flow CFD models cannot be used. This paper is an attempt to understand the behavior of two-phase sCO2 flow going through circular and annular orifices. The focus is to utilize commercially available CFD scheme for modeling phase change and two-phase flow through constrictions. Since the pressure loss across constrictions is also accompanied with reduction in temperature, the flow becomes two-phase by entering the saturation dome. CFD simulation is performed using commercially available software STAR CCM+. 2D axisymmetric geometry is considered as the computational domain. Eulerian Multi-phase Mixture model is used in conjunction with the Two-Phase Thermodynamic Equilibrium implementation. This model is intended for applications that involve two phases of the same substance that are in thermodynamic equilibrium. Fluid properties are defined over a large range of temperatures and pressures, including both the liquid and vapor phases.
Development and Testing of a 10 MWe Supercritical CO2 Turbine in a 1 MWe Flow Loop
Authors: Moore Jeffrey , Cich Stefan , Day-Towler Meera , Mortzheim Jason 
Published: January 2021

Abstract
sCO2 power cycles offer improved cycle efficiencies compared with traditional steam Rankine cycles. However, the turbomachinery required to support such a cycle does not exist at a commercial scale and requires development. This paper describes a new 10 MWe scale sCO2 turbine was developed and demonstrated in an sCO2 closed-loop recompression Brayton cycle. Since this turbine was developed for Concentrating Solar Power (CSP) applications, a target inlet temperature of over 700°C was chosen using funding from the US DOE SunShot initiative and industry partners. However, it can be applied to traditional heat sources such as natural gas, coal, and nuclear power. Traditional Rankine steam cycle thermal efficiencies are typically in the 35–40% range, but can be as high as 45% for advanced ultra-supercritical steam cycles. The sCO2 cycle can approach 50% thermal efficiency using externally fired heat sources. Furthermore, this cycle is also well suited for bottoming cycle waste heat recovery applications, which typically operate at lower temperatures. The high-power density and lower thermal mass of the sCO2 cycle results in compact, high-efficiency power blocks that can respond quickly to transient environmental changes and transient operation, a particular advantage for solar, waste heat, and ship-board applications. The power density of the turbine is significantly greater than traditional steam turbines and is comparable to liquid rocket engine turbo pumps. This paper describes the design and construction of the turbine and provides additional testing of the 10 MWe turbine in a 1 MWe test facility including a description of rotordynamics, thermal management, rotor aero and mechanical design, shaft-end and casing seals, bearings, and couplings. Test data for the turbine is included, as it achieves its operational goal of 715°C, 250 bara, and 27,000 rpm.
A Prognostics Approach Connecting Oxidation Damage to Mechanical Criteria
Authors: Slottner Pontus 
Published: January 2021

Abstract
Oxidation of gas turbine parts is one of the damage mechanisms limiting firing rate and outage interval, thereby reducing potential efficiency and increasing operational cost. While oxidation isn’t an immediate integrity threat in itself, it has indirect impact by reducing load carrying cross sections, changing weight and stiffness distribution, causing cooling air leakages, changing material properties, changing parts aerodynamics characteristics et cetera. This in turn potentially results in shorter creep life, drifting eigenfrequencies, overheating of other parts, increased brittleness and performance loss. Since it is very complicated to analyze all these possible situations in detail, parts are often rejected because of their appearance rather than because of actually approaching a level of damage where it will have consequences on the operability of the turbine. Further, the rules tend to be general rather than customer specific, being set for the entire allowed operation envelope of the part rather than based upon the particular conditions of the unit where the part is in service. This paper presents a simple, first-step prognostics model that connects oxidation damage to local one-dimensional stress and stiffness and local cross-sectional force. An example is given where simple oxidation models are used to predict a detailed oxidation state with regard to multiple aspects. Herein, this oxidation state includes different aspects with regard to the type of oxidation and includes additional characteristics to be considered in the following. By connecting the model to measured characteristics instead of pure oxidation criteria it will be easier to: firstly, apply more relevant criteria that can be evaluated on a site-by-site basis. This will allow high-precision oxidation prognostics with criteria relevant for the operational safety of the equipment. Secondly, more accurately compare predictions to experiences, allowing more detailed operation experience evaluation as well as more relevant input to root cause investigations. This will allow more accurate root cause determination and will result in fewer data points needed to draw statistically sound conclusions from field experiences. Providing such possibility has a significant impact on corresponding applications, as it includes larger operation. Simultaneously, risks can be controlled and quantified better than today providing an important benefit for an application like gas turbines depending strongly on the reliability of the components utilized. The model is general in its nature and is formulated to allow application with any oxidation rule that can be formulated as a mathematical algorithm that is suitable for time integration. The main limitations are its restriction to one space dimension and the assumption of a constant temperature field. If the model is found useful, natural next steps are to extend the model to three space dimensions and a more complex temperature model. The model should also be tested with more accurate oxidation models.
Introduction of a Smartphone Application in an Aeroengine Technology Course
Authors: Aslanidou Ioanna , Gaitanis Aggelos , Kalfas Anestis I. 
Published: January 2021

Abstract
The main goal of an engineering course is for the students to achieve the defined educational goals, enhance their problem-solving capabilities and develop the essential engineering mindset. The continuous improvement of a course is essential to maintain its challenging nature while improving the course quality. Adapting the teaching methods used to new types of students can provide a significant improvement in student learning.
In that context, a digital tool is employed in an advanced course in Aeroengine Technology. A smartphone application that calculates gas turbine performance is introduced in the course to help students understand some of the key concepts. The purpose of the application is to provide the students with an interactive tool to understand the gas turbine thermodynamic cycle. An exercise regarding this application is assigned to note the performance of different engine technologies used in aircraft propulsion through the years. The assignment with the application is combined with a larger assignment on gas turbine performance. The application is also employed in the final exams of the course.
The purpose of this paper is to present the use of the application in the course and to address any challenges that arise in the implementation of the app in the learning process. The employed teaching methods received positive feedback from the students who indicated that the app assignment helped them understand some of the key concepts in the course. After all, the main aim of the use of novel teaching methods should be to make learning more interesting, so that students get more involved in a course.
Thermodynamic Analysis of a Novel Ammonia-Water Cogeneration System for Maritime Diesel Engines
Authors: Cheng Ziyang , Wang Yaxiong , Sun Qingxuan , Wang Jiangfeng , Zhao Pan , Dai Yiping 
Published: January 2021

Abstract
This paper proposes a novel cogeneration system based on Kalina cycle and absorption refrigeration system to meet the design requirements of China State Shipbuilding Corporation, which is efficiently satisfy the power and cooling demands of a maritime ship at the same time. Unlike most of the combined systems, this cogeneration system is highly coupled and realizes cogeneration without increasing the system complexity too much. The basic ammonia mass fraction of this novel system is increased, so that the ammonia concentration of ammonia-water steam from the separator can be higher, which contributes to lower refrigerating temperature and thus less heat loss in the distillation process. In addition, higher ammonia concentration solution makes overheating easier, which improves the thermal efficiency. Moreover, the system has two recuperators to make further improvement of the thermal efficiency. Thermodynamic models are developed to investigate the system performance and parametric analysis is conducted to figure out the effects of including working fluid temperature at the outlet of the evaporator, working fluid temperature at superheater outlet, mass fraction of ammonia in basic solution, turbine inlet pressure, temperature of cooling water at the inlet of condensers and the refrigeration evaporation temperature on the system performance. Furthermore, the cogeneration system is optimized with genetic algorithm to obtain the best performance, which achieves 333.00kW of net power output, 28.83 kW of cooling capacity and 21.81% of thermal efficiency. Finally, the performance of the proposed system is compared with an optimized recuperative organic Rankine cycle (ORC) system and an optimized Kalina cycle system 34 (KCS34) using the same heat source. The results show that the thermal efficiency and power output of the novel cogeneration system is 3.89% and 1.05% higher than that of the recuperative ORC system and KCS34 system respectively.
Study on Film Cooling Performance Improvement of NGV Leading Edge Subject to Distortion Profiles of Low NOx Combustor
Authors: Zhang Wenhao , Wang Zhihao , Wang Zhiduo , Feng Zhenping 
Published: January 2021

Abstract
Under the effect of inlet distortion profiles (including hot-streaks, total pressure profiles, and swirling flow angle patterns), the film cooling performance on the leading edge (LE) region of GE-E3 nozzle guide vanes (NGVs) has been numerically investigated in this paper. Firstly, the complicated inlet distortion profiles of a low NOx combustor chamber has been decoupled to single factors to explore the individual and the coupling effects on the film cooling performance of the NGV LE region (Case 1 to Case 4). Then the original and three modified film-hole configurations are compared and discussed under the quasi-real environment (Case 5 to Case 8). The results indicate that total pressure profile tends to draw more coolant toward the midspan and the residual swirl promotes turnover of the cooling film to the other side of NGVs near the enwalls of LE region. Under the combined effects of different distortion profiles, the cooling film is redistributed on the LE region with some area near the stagnation lines with poor coverage. The upwash or downwash of boundary layer fluid caused by the complicated vortex in passages draws the cooling film on NGV surfaces. And this effect will be strengthened or weakened by the injection angles of holes. Finally, the filmhole configuration in Case 8 with counter-inclined film-hole rows arranged along the stagnation lines shows the best film cooling performance, which has positive effects on the decrease of high temperature region induced by hot streak (HS), and results in more uniform temperature distribution.
Numerical Investigation on the Aerodynamic Performance of a Low-Pressure Steam Turbine Exhaust Hood Using DOE Analysis
Authors: Diurno Tommaso , Fondelli Tommaso , Nettis Leonardo , Maceli Nicola , Arcangeli Lorenzo , Andreini Antonio , Facchini Bruno 
Published: January 2021

Abstract
Nowadays, the rising interest in using renewable energy for thermal power generation has led to radical changes in steam turbine design practice and operability. Modern steam turbines are required to operate with greater flexibility due to rapid load changes, fast start-up, and frequent shutdowns. This has given rise to great challenges to the exhaust hood system design, which has a great influence on the overall turbine performance converting the kinetic energy leaving the last stage of LP turbine into static pressure.
The radial hoods are characterized by a complex aerodynamic behavior since the flow turns by 90° in a very short distance and this generates a highly rotational flow structure within the diffuser and exhaust hood outer casing, moreover, the adverse pressure gradient can promote the flow separation drastically reducing the hood recovery performance. For these reasons it is fundamental to design the exhaust system in order to ensure a good pressure recovery under all the machine operating conditions.
This paper presents a Design of Experiment analysis on a low-pressure steam turbine exhaust hood through CFD simulations. A parametric model of an axial-radial exhaust hood was developed and a sensitivity of exhaust hood performance as a function of key geometrical parameters was carried out, with the aim of optimizing the pressure recovery coefficient and minimizing the overall dimensions of the exhaust casing. Since hood performance strongly depends on a proper coupling with the turbine rear stage, such a stage was modeled using the so-called mixing-plane approach to couple both stator-rotor and rotor-diffuser interfaces. A detailed analysis of the flow field in the exhaust hood in the different configurations was performed, detecting the swirling structures responsible for the energy dissipation in each simulation, as well as correlating the flow field with the pressure recovery coefficient.