Academic literature on the topic 'Robust low-order modelling'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Robust low-order modelling.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Robust low-order modelling"
1
Messenger, Andrew, and Thomas Povey. "Calibrated Low-Order Transient Thermal and Flow Models for Robust Test Facility Design." Journal of the Global Power and Propulsion Society 4 (July 3, 2020): 94–113. http://dx.doi.org/10.33737/jgpps/122270.
Full textAbstract:
This paper describes an upgrade to high temperature operation of the Engine Component AeroThermal (ECAT) facility, an established engine-parts facility at the University of Oxford. The facility is used for high-TRL research and development, new technology demonstration, and for component validation (typically large civil-engine HP NGVs). In current operation the facility allows Reynolds number, Mach number, and coolant-to-mainstream pressure ratio to be matched to engine conditions. Rich-burn or lean-burn temperature, swirl and turbulence profiles can also be simulated. The upgrade will increase the maximum inlet temperature to 600 K, allowing coolant-to-mainstream temperature ratio to be matched to engine conditions. This will allow direct validation of temperature ratio scaling methods in addition to providing a test bed in which all important non-dimensional parameters for aero-thermal behaviour are exactly matched. To accurately predict the operating conditions of the upgraded facility, a low order transient thermal model was developed in which the air delivery system and working section are modelled as a series of distributed thermal masses. Nusselt number correlations were used to calculate convective heat transfer to and from the fluid in the pipes and working section. The correlation was tuned and validated with experimental results taken from tests conducted in the existing facility. This modelling exercise informed a number of high-level facility design decisions, and provides an accurate estimate of the running conditions of the upgraded facility. We present detailed results from the low-order modelling, and discuss the key design decisions. We also present a discussion of challenges in the mechanical design of the working section, which is complicated by transient thermal stress induced in the working section components during facility start-up. The high-temperature core is unusually high-TRL for a research organisation, and we hope both the development and methodology will be of interest to engine designers and the research community.
2
Jones, Bryn Ll, P. H. Heins, E. C. Kerrigan, J. F. Morrison, and A. S. Sharma. "Modelling for robust feedback control of fluid flows." Journal of Fluid Mechanics 769 (March 25, 2015): 687–722. http://dx.doi.org/10.1017/jfm.2015.84.
Full textAbstract:
This paper addresses the problem of designing low-order and linear robust feedback controllers that providea prioriguarantees with respect to stability and performance when applied to a fluid flow. This is challenging, since whilst many flows are governed by a set of nonlinear, partial differential–algebraic equations (the Navier–Stokes equations), the majority of established control system design assumes models of much greater simplicity, in that they are: firstly, linear; secondly, described by ordinary differential equations (ODEs); and thirdly, finite-dimensional. With this in mind, we present a set of techniques that enables the disparity between such models and the underlying flow system to be quantified in a fashion that informs the subsequent design of feedback flow controllers, specifically those based on the$\mathscr{H}_{\infty }$loop-shaping approach. Highlights include the application of a model refinement technique as a means of obtaining low-order models with an associated bound that quantifies the closed-loop degradation incurred by using such finite-dimensional approximations of the underlying flow. In addition, we demonstrate how the influence of the nonlinearity of the flow can be attenuated by a linear feedback controller that employs high loop gain over a select frequency range, and offer an explanation for this in terms of Landahl’s theory of sheared turbulence. To illustrate the application of these techniques, an$\mathscr{H}_{\infty }$loop-shaping controller is designed and applied to the problem of reducing perturbation wall shear stress in plane channel flow. Direct numerical simulation (DNS) results demonstrate robust attenuation of the perturbation shear stresses across a wide range of Reynolds numbers with a single linear controller.
3
TOUBER, EMILE, and NEIL D. SANDHAM. "Low-order stochastic modelling of low-frequency motions in reflected shock-wave/boundary-layer interactions." Journal of Fluid Mechanics 671 (March 7, 2011): 417–65. http://dx.doi.org/10.1017/s0022112010005811.
Full textAbstract:
A combined numerical and analytical approach is used to study the low-frequency shock motions observed in shock/turbulent-boundary-layer interactions in the particular case of a shock-reflection configuration. Starting from an exact form of the momentum integral equation and guided by data from large-eddy simulations, a stochastic ordinary differential equation for the reflected-shock-foot low-frequency motions is derived. During the derivation a similarity hypothesis is verified for the streamwise evolution of boundary-layer thickness measures in the interaction zone. In its simplest form, the derived governing equation is mathematically equivalent to that postulated without proof by Plotkin (AIAA J., vol. 13, 1975, p. 1036). In the present contribution, all the terms in the equation are modelled, leading to a closed form of the system, which is then applied to a wide range of input parameters. The resulting map of the most energetic low-frequency motions is presented. It is found that while the mean boundary-layer properties are important in controlling the interaction size, they do not contribute significantly to the dynamics. Moreover, the frequency of the most energetic fluctuations is shown to be a robust feature, in agreement with earlier experimental observations. The model is proved capable of reproducing available low-frequency experimental and numerical wall-pressure spectra. The coupling between the shock and the boundary layer is found to be mathematically equivalent to a first-order low-pass filter. It is argued that the observed low-frequency unsteadiness in such interactions is not necessarily a property of the forcing, either from upstream or downstream of the shock, but an intrinsic property of the coupled system, whose response to white-noise forcing is in excellent agreement with actual spectra.
4
Bianchi, Fernando D., Marcela Moscoso-Vásquez, Patricio Colmegna, and Ricardo S. Sánchez-Peña. "Invalidation and low-order model set for artificial pancreas robust control design." Journal of Process Control 76 (April 2019): 133–40. http://dx.doi.org/10.1016/j.jprocont.2019.02.004.
Full text
5
Shishkin, G. I. "ROBUST NOVEL HIGH-ORDER ACCURATE NUMERICAL METHODS FOR SINGULARLY PERTURBED CONVECTION‐DIFFUSION PROBLEMS." Mathematical Modelling and Analysis 10, no. 4 (2005): 393–412. http://dx.doi.org/10.3846/13926292.2005.9637296.
Full textAbstract:
For singularly perturbed boundary value problems, numerical methods convergent ϵ‐uniformly have the low accuracy. So, for parabolic convection‐diffusion problem the order of convergence does not exceed one even if the problem data are sufficiently smooth. However, already for piecewise smooth initial data this order is not higher than 1/2. For problems of such type, using newly developed methods such as the method based on the asymptotic expansion technique and the method of the additive splitting of singularities, we construct ϵ‐uniformly convergent schemes with improved order of accuracy. Straipsnyje nagrinejami nedidelio tikslumo ϵ‐tolygiai konvertuojantys skaitmeniniai metodai, singuliariai sutrikdytiems kraštiniams uždaviniams. Paraboliniam konvekcijos‐difuzijos uždaviniui konvergavimo eile neviršija vienos antrosios, jeigu uždavinio duomenys yra pakankamai glodūs. Tačiau trūkiems pradiniams duomenims eile yra ne aukštesne už 2−1. Šio tipo uždaviniams, naudojant naujai išvestus metodus, darbe sukonstruotos ϵ‐tolygiai konvertuojančios schemos aukštesniu tikslumu.
6
Abouorm, Lara, Maxime Blais, Nicolas Moulin, Julien Bruchon, and Sylvain Drapier. "A Robust Monolithic Approach for Resin Infusion Based Process Modelling." Key Engineering Materials 611-612 (May 2014): 306–15. http://dx.doi.org/10.4028/www.scientific.net/kem.611-612.306.
Full textAbstract:
The aim of this work is to focus on the Stokes-Darcy coupled problem in order to propose a robust monolithic approach to simulate composite manufacturing process based on liquid resin infusion. The computational domain can be divided into two non-miscible sub-domains: a purely fluid domain and a porous medium. In the purely fluid domain, the fluid flows according to the Stokes' equations, while the fluid flows into the preforms according to the Darcy's equations. Specific conditions have to be considered on the fluid/porous medium interface. Under the effect of a mechanical pressure applied on the high deformable preform/resin stacking, the resin flows and infuses through the preform which permeability is very low, down to 10-15 m2. Flows are solved using finite element method stabilized with a sub-grid scale stabilization technique (ASGS). A special attention is paid to the interface conditions, namely normal stress and velocity continuity and tangential velocity constraint similar to a Beaver-Joseph-Saffman’s condition. The originality of the model consists in using one single mesh to represents the Stokes and the Darcy sub-domains (monolithic approach). A level set context is used to represent Stokes-Darcy interface and to capture the moving flow front. This monolithic approach is now perfectly robust and leads to perform complex shapes for manufacturing process by resin infusion.
7
Kim, Young Chol, and Lihua Jin. "Robust identification of continuous-time low-order models using moments of a single rectangular pulse response." Journal of Process Control 23, no. 5 (2013): 682–95. http://dx.doi.org/10.1016/j.jprocont.2013.03.002.
Full text
8
Semiletov, Vasily A., and Sergey A. Karabasov. "Similarity scaling of jet noise sources for low-order jet noise modelling based on the Goldstein generalised acoustic analogy." International Journal of Aeroacoustics 16, no. 6 (2017): 476–90. http://dx.doi.org/10.1177/1475472x17730457.
Full textAbstract:
As a first step towards a robust low-order modelling framework that is free from either calibration parameters based on the far-field noise data or any assumptions about the noise source structure, a new low-order noise prediction scheme is implemented. The scheme is based on the Goldstein generalised acoustic analogy and uses the Large Eddy Simulation database of fluctuating Reynolds stress fields from the CABARET MILES solution of Semiletov et al. corresponding to a static isothermal jet from the SILOET experiment for reconstruction of effective noise sources. The sources are scaled in accordance with the physics-based arguments and the corresponding sound meanflow propagation problem is solved using a frequency domain Green’s function method for each jet case. Results of the far-field noise predictions of the new method are validated for the two NASA SHJAR jet cases, sp07 and sp03 from and compared with the reference predictions, which are obtained by applying the Lighthill acoustic analogy scaling for the SILOET far-field measurements and using an empirical jet-noise prediction code, sJet.
9
Liu, Bin, Chang-Hong Wang, Wei Li, and Zhuo Li. "Robust Controller Design Using the Nevanlinna-Pick Interpolation in Gyro Stabilized Pod." Discrete Dynamics in Nature and Society 2010 (2010): 1–16. http://dx.doi.org/10.1155/2010/569850.
Full textAbstract:
The sensitivity minimization of feedback system is solved based on the theory of Nevanlinna-Pick interpolation with degree constraint without using weighting functions. More details of the dynamic characteristic of second-order system investigated, which is determined by the location of spectral zeroes, the upper boundγofS, the length of the spectral radius and the additional interpolation constraints. And the guidelines on how to tune the design parameters are provided. Gyro stabilized pod as a typical tracking system is studied, which is based on the typical structure of two-axis and four-frame. The robust controller is designed based on Nevanlinna-Pick interpolation with degree constraint. When both friction of LuGre model and disturbance exist, the closed-loop system has stronger disturbance rejection ability and high tracking precision. Numerical examples illustrate the potential of the method in designing robust controllers with relatively low degrees.
10
Flinois, Thibault L. B., and Aimee S. Morgans. "Feedback control of unstable flows: a direct modelling approach using the Eigensystem Realisation Algorithm." Journal of Fluid Mechanics 793 (March 14, 2016): 41–78. http://dx.doi.org/10.1017/jfm.2016.111.
Full textAbstract:
Obtaining low-order models for unstable flows in a systematic and computationally tractable manner has been a long-standing challenge. In this study, we show that the Eigensystem Realisation Algorithm (ERA) can be applied directly to unstable flows, and that the resulting models can be used to design robust stabilising feedback controllers. We consider the unstable flow around a D-shaped body, equipped with body-mounted actuators, and sensors located either in the wake or on the base of the body. A linear model is first obtained using approximate balanced truncation. It is then shown that it is straightforward and justified to obtain models for unstable flows by directly applying the ERA to the open-loop impulse response. We show that such models can also be obtained from the response of the nonlinear flow to a small impulse. Using robust control tools, the models are used to design and implement both proportional and $\mathscr{H}_{\infty }$ loop-shaping controllers. The designed controllers were found to be robust enough to stabilise the wake, even from the nonlinear vortex shedding state and in some cases at off-design Reynolds numbers.
Dissertations / Theses on the topic "Robust low-order modelling"
1
Lombardi, Edoardo. "Low order modelling for flow simulation, estimation and control." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14000/document.
Full textAbstract:
L’objectif est de développer et de tester des instruments peu côuteux pour la simulation, l’estimation et le contrôle d’écoulements. La décomposition orthogonale aux valeurs propres (POD) et une projection de Galerkin des équations sur les modes POD sont utilisées pour construire des modèles d’ordre réduit des équations de Navier-Stokes incompressibles. Dans ce travail, un écoulement autour d’un cylindre carré est considéré en configuration bidimensionnelle et tridimensionnelle. Des actionneurs de soufflage/aspiration sont placés sur la surface du cylindre. Quelques techniques de calibration sont appliquées, fournissant des modèles précis, même pour les écoulements tridimensionnels avec des structures tourbillonaires compliquées. Une méthode d’estimation d’état, impliquant des mesures, est ensuite mise au point pour des écoulements instationnaires. Une calibration multi-dynamique et des techniques d’échantillonnage efficaces sont appliquées, visant à construire des modèles robustes à des variations des paramètres de contrôle. Nous amorçons une analyse de stabilité linéaire en utilisant des modèles d’ordre réduit linéarisés autour d’un état d’équilibre contrôlé. Les techniques présentées sont appliquées à écoulements autour du cylindre carré à des nombres de Reynolds compris entre Re = 40 et Re = 300<br>The aim is to develop and to test tools having a low computational cost for flow simulation, estimation and control applications. The proper orthogonal decomposition (POD) and a Galerkin projection of the equations onto the POD modes are used to build low order models of the incompressible Navier-Stokes equations. In this work a flow past a square cylinder is considered in two-dimensional and three-dimensional configurations. Two blowing/suction actuators are placed on the surface of the cylinder. Calibration techniques are applied, providing stable and rather accurate models, even for three-dimensional wake flows with complicated patterns. A state estimation method, involving flow measurements, is then developed for unsteady flows. Multi-dynamic calibrations and efficient sampling techniques are applied to build models that are robust to variations of the control parameters. A linear stability analysis by using linearized low order models around a controlled steady state is briefly addressed. The presented techniques are applied to the square cylinder configuration at Reynolds numbers that range between Re = 40 and Re = 300
Conference papers on the topic "Robust low-order modelling"
1
Cui, Jiahuan, Rob Watson, Paul Tucker, and Mark Wilson. "Low Order Modelling for Fan and Outlet Guide Vanes in Aero-Engines." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75660.
Full textAbstract:
Intakes of reduced length have been proposed with the aim of producing aero-engines with higher efficiency and reduced weight. As the intake length decreases, it is expected that stronger effects of the fan on the flow over the intake lip will be seen. If the effects of the fan cannot be ignored, a low-cost but still accurate fan model is of great importance for designing a short-intake. In this paper, a low order rotor/stator model — the immersed boundary method with smeared geometry (IBMSG), has been further developed and validated on a rig test case. The improved IBMSG is more robust than the original. The rig test case used for validation features a low-pressure compression system with a non-axisymmetric inflow, which is representative of the inlet condition of an aero-engine at its cruise condition. Both the fan and the Outlet Guide Vanes (OGV) are modelled using IBMSG. Detailed analysis is carried out on the flow both upstream and downstream of the fan. After validating the IBMSG method against the rig test case, a short-intake case, coupled with a fan designed for the next generation of aero-engines, is further investigated. It is found that, compared with the intake-alone case, the inflow distortion at the fan face is significantly reduced by the presence of fan. Due to this increased interaction between the fan and the flow over the intake lip, accounting for the effects of the downstream fan is shown to be essential when designing a short intake.
2
Povey, Thomas, and Andrew Messenger. "Calibrated Low-Order Transient Thermal and Flow Models for Robust Test Facility Design." In GPPS Beijing19. GPPS, 2019. http://dx.doi.org/10.33737/gpps19-bj-206.
Full textAbstract:
This paper describes the high temperature upgrade of the Engine Component Aero Thermal (ECAT) facility, an established engine-parts facility at the University of Oxford. The facility is used for high technology readiness level research and development, new technology demonstration and for component validation. The current facility has a modular working section which houses a full annulus of engine nozzle guide vanes (typically HP NGVs from a large civil jet-engine, but reconfigurable for smaller core sizes) which can be run at engine conditions of Reynolds number, Mach number and coolant-to-mainstream pressure ratio. The facility has a combustor simulator, which is used for combustor-turbine interaction studies with either rich or lean-burn temperature, swirl and turbulence profiles. The ECAT facility is capable of highly accurate measurements of capacity, aerodynamic loss, and metal effectiveness. The facility can operate in either semi-transient blow-down mode (typically used for capacity characteristics) or steady-state regulated mode (typically used for aerodynamic traversing). For metal effectiveness measurements, a coolant-to-mainstream temperature ratio range of 1.00-1.28 can be achieved by heating the mainstream with two 1 MW heaters. Although ECAT can be run at very close to engine conditions, the limitation on temperature ratio capability leads to imperfectly matched specific heat capacity flux ratio and compressibility effects (ratio of recovery temperature ratio to coolant-to-mainstream temperature ratio). The development described in this paper (foreseen as a requirement when ECAT was developed) addresses this scaling mismatch. This paper is about the design and optimisation of increased temperature capability for the ECAT facility, a system which will increase the mainstream inlet temperature to 600 K (327 °C), allowing coolant-to-mainstream temperature ratio to be matched to engine conditions. This is desirable as it will allow direct validation of temperature ratio scaling methods in addition to providing closer engine similarity. This is a critical development for engine designers as it allows higher technology readiness level testing to be achieved than has previously been possible, providing a test bed in which all important non-dimensional parameters for aero-thermal behaviour can be exactly matched to engine conditions. The aim is reduced engine development times, by providing earlier and higher fidelity testing than has previously been possible. As the technology matures it is possible to foresee that engine development testing (as opposed to Pass-Off testing) may be avoided with a test vehicle of this type. To accurately predict the operating conditions of the facility, a low order transient thermal model was developed in which the air delivery system and working section are modelled as a series of distributed thermal masses. Nusselt number correlations were used to calculate convective heat transfer to and from the fluid in the pipes and working section. The correlation was tuned and validated with accurate and extensive experimental results taken from test campaigns conducted in the existing facility. This modelling exercise informed a number of high-level facility design decisions to be taken, and will provide an accurate estimate of the running conditions of the facility. We present detailed results from the low-order modelling, and discuss the key design decisions. We also present a discussion of challenges in the mechanical design of the working section, which is complicated by transient thermal stress induced in the working section components during start-up of the facility. This analysis is benchmarked with directly measured boundary conditions from the existing working section, scaled appropriately to upgraded facility conditions. The staged development of the ECAT test-bed allows robust component analysis during the design phase. The high-temperature core for the ECAT test-bed has unusually high TRL capacity for a research organisation, and it is expected that the development and underlying methodology will be of interest to both engine designers and the research community. The facility will contribute to accelerated development time of novel engine technology in addition to further enabling fundamental research to be carried out engine representative environments.
3
Mucchi, Emiliano, Gabriele Tosi, Roberto d’Ippolito, and Giorgio Dalpiaz. "A Robust Design Optimization Methodology for External Gear Pumps." In ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-24775.
Full textAbstract:
This work addresses the topic of external gear pumps for automotive applications, which operate at high speed and low pressure. In previous works of the authors, a hybrid lumped-parameter/finite-element model has been developed, in order to foresee the pump dynamic behaviour in terms of gear and casing acceleration. The model includes the main important phenomena involved in the pump operation and it has been validated on the basis of experimental data. In this research, an original optimization process has been applied to such a hybrid model in order to reduce the pump vibration level, i.e. the acceleration of the external casing. The set up of the optimization process comprises a single objective (case accelerations) and some operational and geometrical input variables (oil viscosity, oil Bulk modulus, relief groove dimension and radial clearance in the journal bearings). This paper compares three optimization methodologies for the optimization of the pump vibration level. In particular common optimization processes based on simulations are compared with a combined analysis based, firstly, on Design Of Experiments (DOE) and Response Surface Modelling (RSM) and, secondly, on the application of evolutionary algorithms to reach the optimal variable combination. The different methodologies are compared in terms of time efficiency and accuracy in the solution. Finally, a robust design process has been carried out in order to consider the manufacturing tolerances of the real pump and assess their effect on the performance of the component. The results offer important information and design insights that would be very difficult to obtain without such procedures.
4
Pinelli, Lorenzo, Federico Vanti, Lorenzo Peruzzi, et al. "Aeromechanical Characterization of a Last Stage Steam Blade at Low Load Operation: Part 2 — Computational Modelling and Comparison." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-15409.
Full textAbstract:
Abstract This paper is part of a two-part publication that aims to experimentally and numerically evaluate the aerodynamic and mechanical damping of a last stage ST blade at low load operation. A three-stage downscaled steam turbine with a snubbered last stage moving blade LSMB has been tested in the T10MW test facility of Doosan Skoda Power R&D Department in the context of the FLEXTURBINE European project (Flexible Fossil Power Plants for the Future Energy Market through new and advanced Turbine Technologies). Aerodynamic and flutter simulations of different low load conditions have been performed. The acquired data are used to validate the unsteady CFD approach for the prediction of the aerodynamic damping in terms of logarithmic decrement. Numerical results have been achieved through an upgraded version of the URANS CFD solver, selecting appropriate and robust numerical setups for the simulation of very low load conditions, such as increased condenser pressure at the exhaust hood outlet. The numerical methods for blade aerodamping estimation are based on the computation of the unsteady pressure response caused by the row vibration. They are usually classified in time-linearized, harmonic balance and non-linear approaches both in frequency and time domain. The validation of all these methods historically started in the field of aeronautical low-pressure turbines and has been gradually extended to compressor blades and steam turbine rows. For the analysis of a steam turbine last rotor blade operating at strong part load conditions, non-linear methods are recommended as these approaches are able to deal with strong nonlinear phenomena such as shock waves and massive flow separations inside the domain. Experimental data have been used to separate the contributions of mechanical and aerodynamic damping, extrapolating to zero mass flow the total measured damping. Finally, the comparisons between the aerodynamic damping coming from measurements and CFD results have been reported in order to highlight the capability to properly predict the last stage blade flutter stability at low load conditions. Such comparisons confirms the flutter free design of the new snubbered LSMB blade.
5
Trasino, Francesco, Michele Bozzolo, Loredana Magistri, and Aristide F. Massardo. "Modelling and Performance Analysis of the Rolls-Royce Fuel Cell Systems Limited: 1 MW Plant." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59328.
Full textAbstract:
This paper is focused on the performance of the 1MW plant designed and developed by Rolls-Royce Fuel Cell Systems Limited. The system consists of a two stage turbogenerator coupled with pressure vessels containing the fuel cell stack, internal reformer, cathode ejector, anode ejector and off gas burner. While the overall scheme is relatively simple, due to the limited number of components, the interaction between the components is complex and the system behaviour is determined by many parameters. In particular two important subsystems such as the cathode and the anode recycle loops must be carefully analyzed also considering their interaction with and influence on the turbogenerator performance. The system performance model represents the whole and each physical component is modelled in detail as a sub-system. The component models have been validated or are under verification. The model provides all the operating parameters in each characteristic point of the plant and a complete distribution of thermodynamics and chemical parameters inside the SOFC stack and reformer. In order to characterise the system behaviour, its operating envelope has been calculated taking into account the effect of ambient temperature and pressure as described in the paper. Given the complexity of the system various constraints have to be considered in order to obtain a safe operating condition not only for the system as a whole but also for each of its parts. In particular each point calculated has to comply with several constraints such as stack temperature distribution, maximum and minimum temperatures and high and low pressure spool maximum rotational speeds. The model developed and the results presented in the paper provide important information for the definition of an appropriate control strategy and a first step in the development of a robust and optimized control system.
6
Gallee, Sébastien, Vincent Robin, Florence Gommez, et al. "Numerical Welding Simulation of a Vessel Head Adapter: Influence of Modelling Assumptions." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63517.
Full textAbstract:
In nuclear industry, most of heavy components and reactor coolant lines have a large thickness and their manufacturing processes require multi-pass welding. When low-alloy steel components are concerned, the assembly process is often performed in several stages, such as a cladding, a buttering and a Post Weld Heat Treatment (PWHT) before joining two materials without phase transformations. The distortions induced by the welding operation might be an issue and residual stresses could be significant and play a role on the weldability. For these reasons, AREVA has placed a lot of effort to improve the reliability of numerical simulation of its welding processes, in order to have a better understanding of the involved phenomena and also to predict the residual stress state through the structure [1], [2] and [3] because this numerical simulation can be used to select the manufacturing process in the early phase of welded component design. The aim of the simulations presented in this paper is the investigation of the final residual state of a nozzle placed at the central position of the vessel head. The computations are performed according a robust methodology packaged in AREVA OSS tool [4] which is based on SYSWELD™ Finite Element solver [5]. Two welding configurations are investigated. The first one is a mock-up with an “open” narrow gap, the groove filling being performed by a manual welding process using electrode coatings. The second one is a mock-up with a “closed” narrow gap, the groove filling being performed by an automatic TIG process. After the comparison of these two configurations, a special investigation is performed on the “open” narrow gap mock-up. The influence of the vessel head buttering before the groove filling is investigated, as well as the efficiency of the PWHT performed after the buttering operation.
7
Alfonso-Solar, David, Paula Bastida-Molina, Lina Montuori, and Carlos Vargas-Salgado. "Monitoring and evaluation of thermal comfort in urban areas: application to Valencia city." In CARPE Conference 2019: Horizon Europe and beyond. Universitat Politècnica València, 2019. http://dx.doi.org/10.4995/carpe2019.2019.10198.
Full textAbstract:
In this paper, it is presented preliminary results of a methodology for thermal comfort monitoring and evaluation in urban areas based on local metering of ambient conditions and Rayman model application. In the framework of GROWGREEN European project it was installed six monitoring stations for data acquisition of air temperature, relative humidity, wind speed, solar radiation and black globe temperature. Data of first 5 months of monitoring and modelling of one location with Rayman model to calculate PET (physiological equivalent temperature) is presented. Based on PET it was calculated the percentage of hours with thermal comfort per month, and it was made a comparison between PET and black globe temperature (GT) in order to evaluate the suitability of GT as a single, low cost and robust indicator of thermal comfort in urban areas.
8
Legnani, Giovanni, Giovanni Incerti, Roberto Pagani, and Matteo Gheza. "Modelling and Evaluation of the Friction in Robotic Joints Considering Thermal Effects." In ASME 2019 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/detc2019-97545.
Full textAbstract:
Abstract The paper presents a second order friction model for the joints of industrial robot manipulators that takes into account temperature effects. A solution based on a polynomial description of the friction is proposed. The theoretical analysis and the experimental measurements have shown that friction decreases with increasing temperature, which in turn depends on the working cycle of the manipulator. The mathematical model here proposed allows to foresee the friction variation during extensive working cycles and it does not require the use of a transducer for the measurement of the joint internal temperature; therefore it is well suitable for low-cost industrial applications, to improve the control performance or to predict the energy consumption. Experimental tests performed on a commercial 6 DOF manipulator show that the model is effective in estimating the joint temperature and the friction torque during the robot operations.
9
Pampaloni, Daniele, Pier Carlo Nassini, Antonio Andreini, Bruno Facchini, and Matteo Cerutti. "Numerical Investigations of Pollutant Emissions From Novel Heavy Duty Gas Turbine Burners Operated With Natural Gas." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91365.
Full textAbstract:
Abstract A numerical investigation of pollutant emissions of a novel dry low-emissions burner for heavy-duty gas turbine applications is presented. The objective of the work is to develop and assess a robust and cost-efficient numerical setup for the prediction of NOx and CO emissions in industrial gas turbines and to investigate the pollutant formation mechanisms, thus supporting the design process of a novel low-emission burner. To this end, a comparison against experimental data, from a recent experimental campaign performed by BHGE in cooperation with University of Florence, has been exploited. In the first part of this work, a RANS approach on both a simplified geometry and the complete domain is adopted to characterize the global flame behavior and validate the numerical setup. Then, unsteady simulations exploiting the Scale Adaptive Simulation (SAS) approach have been performed to assess the prediction improvements that can be obtained with the unsteady modelling of the flame. For all simulations, the Flamelet Generated Manifold (FGM) model has been used, allowing the reliable and cost-efficient application of detailed chemistry mechanisms in CFD simulation. However, FGM typically faces issues predicting flame emissions, such as NOx and CO, due to the wide range of time scales involved, from turbulent mixing to pollutant species oxidation. Specific models are typically used to predict NOx emissions, starting from the converged flow field and introducing additional transport equations. Also CO prediction, especially at part-load operating conditions could be an issue for flamelet-based model: in fact, as the load decreases and the extinction limit approaches, a super-equilibrium CO concentration, which cannot be accurately predicted by FGM, appears in the exhaust gases. To overcome this issue, a specific CO burn-out model, following the original idea proposed by Klarmann, has been implemented in ANSYS Fluent. The model allows to decouple the effective CO oxidation term from the one computed by FGM, defining a post-flame zone where the source term of CO is treated following the Arrhenius formulation. In order to support the design process, an in-depth CFD investigation has been carried out, evaluating the impact of an alternative burner geometrical configuration on stability and emissions and providing detailed information about the main regions and mechanisms of pollutants production. The outcomes support the analysis of experimental results, allowing an in-depth investigation of the complex flow-field and the flame-related quantities, which have not been measured during the tests.
10
Dash, Ranjita, Anurag R. Chandnani, Arash Tourki Samaei, and Ramuel Safarkoolan. "Advance Model for Capturing Real Life Human Gait Process." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-66893.
Full textAbstract:
Human gait represents a highly coordinated multi-dimensional and energy efficient process involving complex precision control mechanisms. Several attempts have been made in the literature to capture every minute detail of this process and develop accurate models. Although available state of art neuromuscular models demonstrate higher degrees of accuracy, the extent to which the shoulder muscles actively drive the arms, their effect on stability and economy during gait are not well established till date. Most of these models are sufficiently accurate to replicate the human gait in upright position, but fail to capture the energy efficiency and analysis while in a bent position such as the start-up posture just before a running event. Moreover performance of existing models degrade while capturing motions around a smooth turn. The prime objective of this work is to clearly bring out the effect of arm swing and posture on the energy efficiency of human gait process. This work can be a potential enhancement to performance of existing state of art neuro-musculoskeletal models, thereby reducing energy expenditure by approximately 7.89%. In this work we present a simple and systematic methodology for deriving the control system model of human gait considering the challenges faced in previous models and includes advanced effects encountered in real life. Although the single inverted pendulum is widely accepted as an adequate model of bipedal motion, but creates accuracy as well as stability issues and is less likely to capture advance dynamics of the human gait process. In addition to the motion of ankle joints, human gait often involves the motion of hip and knee joints for improved balancing, increased flexibility in face of the multitude external disturbances and robustness in terms of fail safe. For optimized results, a multi-pendulum model with forward dynamics approach has been considered in this work. In order to achieve real time performance with good controllability, LQR controller with state feedback techniques has been adapted in the model. Typical observations like swinging of hands out of phase with respect to legs, effect of posture prior to a running event are also analyzed and included into the model. We investigate the control and function of arm swing in human gait process to test three competing hypotheses i.e. (1) The arms are actively driven by shoulder muscles, (2) The arms are passively powered by movement of the lower body, (3) During few initial steps of gait arm movement is actively driven by shoulder muscles and consequently by passive dynamic effect of the thorax, inertia and gravity. Effects of removing arm swing that create stability problems during walking and especially running, resulting in greater variability in footfall positions are also analyzed. A comparative analysis between distance covered, maximum velocity achieved, effort on foot for the same input torque at the hip joint, and energy efficiency computations (work done per step per meter) is carried out for the above mentioned cases with and without hand motion during the gait process. This work finds potential application in development of energy efficient automated robots usually employed in industries, biomimetic, prosthetic, neuro-rehabilitation engineering and sports biomechanics where the energy efficiency and performance under varying postures are at priority. It drives gait modelling methodology towards an advanced low constrained multidimensional approach as is required by modern high end systems and compromise between energy efficiency and speed. This model can be cleverly utilized to suggest the best initial posture for different athletes having different body structures to obtain maximum speed efficiently. Strategic approach towards the development of a flexible and an accurate gait model are analyzed and discussed in detail.