21 research outputs found
Optimization of a single-stage double-suction centrifugal pump
In this study, the objective of the optimization of a double-suction pump is the
maximization of its hydraulic efficiency. The optimization is performed, by means of the
modeFRONTIER optimization platform, in steps. At first, by means of a DOE (Design of
Experiments) strategy, the design space is explored, using a parameterized CAD representation
of the pump. Suitable metamodels (surrogates or Response Surfaces), which represent an
economical alternative to the more expensive 3D CFD model, are built and tested. Among
different metamodels, the evolutionary design, radial basis function and the stepwise regression
models seem to be the most promising ones. Finally, the stepwise regression model, trained on
a set of 200 designs and constructed with only five the most influential input design parameters,
was chosen as a potentially applicable metamodel
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Multi-Objective Optimisation of A Centrifugal Compressor for a Micro Gas Turbine Operated by Concentrated Solar Power
Solar powered micro-gas turbines (MGTs) are required to work over a wide range of operating conditions due to the fluctuations in the solar insulation. This means that the compressor has to perform efficiently over a wider range than in conventional MGTs. To be able to extend the efficient operating range of a compressor at the design stage, both impeller blades and diffuser passage need to be optimised. Vaneless diffusers could offer more flexibility to extend the operating range than typical diffuser vanes. This paper presents a methodology for the design and optimisation of a centrifugal compressor for a 6 kW micro-gas turbine intended for operation using a Concentrated Solar Power (CSP) system using a parabolic dish concentrator. Preliminary design parameters were obtained from the overall system specifications and detailed cycle analysis combined with practical constraints. The compressor’s geometry optimisation has been performed using a fast and computationally efficient method, which involves the Latin hypercube Design of Experiment (DoE) technique coupled with the response surface method (RSM) in order to build a regression model through CFD simulations. Three different RSM techniques were compared with the aim to choose the most suitable technique for this specific application and then a genetic algorithm was applied. The CFD analysis for the optimised compressor showed that the high efficiency operating range has increased compared to the baseline design. Cycle analysis for the plant has been performed in order to evaluate the effect of the new compressor design on the system performance. The simulations demonstrated that the operating range of the plant was increased by over 30%
Two-Dimensional-Based Hybrid Shape Optimisation of a 5-Element Formula 1 Race Car Front Wing under FIA Regulations
Front wings are a key element in the aerodynamic performance of Formula 1 race cars. Thus, their optimisation makes an important contribution to the performance of cars in races. However, their design is constrained by regulation, which makes it more difficult to find good designs. The present work develops a hybrid shape optimisation approach to obtain an optimal five-element airfoil front wing under the FIA regulations and 17 design parameters. A first baseline design is obtained by parametric optimisation, on which the adjoint method is applied for shape optimisation via Mesh Morphing with Radial Basis Functions. The optimal front wing candidate obtained outperforms the parametric baseline up to a 25% at certain local positions. This shows that the proposed and tested hybrid approach can be a very efficient alternative. Although a direct 3D optimisation approach could be developed, the computational costs would be dramatically increased (possibly unaffordable for such a complex five-element front wing realistic shape with 17 design parameters and regulatory constraints). Thus, the present approach is of strong interest if the computational budget is low and/or a fast new front wing design is desired, which is a frequent scenario in Formula 1 race car design.The authors want to acknowledge the financial support from the Ramón y Cajal 2021 Excellence Research Grant action from the Spanish Ministry of Science and Innovation (FSE/AGENCIA ESTATAL DE INVESTIGACIÓN), the UMA18-FEDERJA-184 grant, and the Andalusian Research, Development and Innovation Plan (PAIDI—Junta de Andalucia) fundings. Partial funding for open access charge: Universidad de Málag
Pengujian Karakteristik Turbin Francis Pikohidro dengan Variasi Tiga Jenis Shroud Impeller Pompa Sentrifugal sebagai Runner Turbin
Indonesia sebagai negara kepulauan memiliki sumber daya air yang
berlimpah yang dapat dimanfaatkan sebagai sumber energi listrik. Namun,
kenyataannya pemanfaatan sumber daya air ini masih terbilang sangat minim jika
dibandingkan dengan kebutuhan energi listrik penduduknya yang tinggi. Turbin
francis pikohidro dapat menjadi solusi dalam memaksimalkan pemanfaatan
sumber daya air ini. Namun, masih perlu dilakukan pengujian untuk mendapatkan
sumber energi yang optimal. Salah satu cara yang dilakukan adalah dengan
memodifikasi runner turbin dengan memanfaatkan tiga jenis shroud impeller
pompa sentrifugal. Untuk mendapatkan jenis shroud manakah yang dapat
menghasilkan sumber energi yang optimal, maka dilakukanlah pengujian karakteristik turbin francis pikohidro dengan variasi tiga jenis shroud impeller
pompa sentrifugal pada runner turbin ini.
Pengujian dilakukan di Limau Manis, Kecamatan Pauh, Kota Padang,
Provinsi Sumatera Barat. Dimana daya air yang diperoleh berasal dari aliran
irigasi pada daerah tersebut dengan head konstan. Pengujian dilakukan dengan
memberikan variasi tiga jenis shroud impeller pompa sentrifugal pada runner
turbin untuk mendapatkan karakteristiknya.
Hasil pengujian karakteristik ini didapatkan turbin francis pikohidro
dengan runner shroud closed impeller memiliki efisiensi sebesar 68,88 %, dengan
runner semi-open shroud impeller memiliki efisiensi sebesar 49,27 % dan runner
open shroud impeller memiliki efisiensi sebesar 43,30 %. Hal ini menunjukkan
bahwa turbin francis pikohidro dengan runner closed shroud impeller memiliki
efisiensi paling optimal
Development of a multi-objective optimization algorithm based on lichtenberg figures
This doctoral dissertation presents the most important concepts of multi-objective optimization and a systematic review of the most cited articles in the last years of this subject in mechanical engineering. The State of the Art shows a trend towards the use of metaheuristics and the use of a posteriori decision-making techniques to solve engineering problems. This fact increases the demand for algorithms, which compete to deliver the most accurate answers at the lowest possible computational cost. In this context, a new hybrid multi-objective metaheuristic inspired by lightning and Linchtenberg Figures is proposed. The Multi-objective Lichtenberg Algorithm (MOLA) is tested using complex test functions and explicit contrainted engineering problems and compared with other metaheuristics. MOLA outperformed the most used algorithms in the literature: NSGA-II, MOPSO, MOEA/D, MOGWO, and MOGOA. After initial validation, it was applied to two complex and impossible to be analytically evaluated problems. The first was a design case: the multi-objective optimization of CFRP isogrid tubes using the finite element method. The optimizations were made considering two methodologies: i) using a metamodel, and ii) the finite element updating. The last proved to be the best methodology, finding solutions that reduced at least 45.69% of the mass, 18.4% of the instability coefficient, 61.76% of the Tsai-Wu failure index and increased by at least 52.57% the natural frequency. In the second application, MOLA was internally modified and associated with feature selection techniques to become the Multi-objective Sensor Selection and Placement Optimization based on the Lichtenberg Algorithm (MOSSPOLA), an unprecedented Sensor Placement Optimization (SPO) algorithm that maximizes the acquired modal response and minimizes the number of sensors for any structure. Although this is a structural health monitoring principle, it has never been done before. MOSSPOLA was applied to a real helicopter’s main rotor blade using the 7 best-known metrics in SPO. Pareto fronts and sensor configurations were unprecedentedly generated and compared. Better sensor distributions were associated with higher hypervolume and the algorithm found a sensor configuration for each sensor number and metric, including one with 100% accuracy in identifying delamination considering triaxial modal displacements, minimum number of sensors, and noise for all blade sections.Esta tese de doutorado traz os conceitos mais importantes de otimização multi-objetivo e uma revisão sistemática dos artigos mais citados nos últimos anos deste tema em engenharia mecânica. O estado da arte mostra uma tendência no uso de meta-heurÃsticas e de técnicas de tomada de decisão a posteriori para resolver problemas de engenharia. Este fato aumenta a demanda sobre os algoritmos, que competem para entregar respostas mais precisas com o menor custo computacional possÃvel. Nesse contexto, é proposta uma nova meta-heurÃstica hÃbrida multi-objetivo inspirada em raios e Figuras de Lichtenberg. O Algoritmo de Lichtenberg Multi-objetivo (MOLA) é testado e comparado com outras metaheurÃsticas usando funções de teste complexas e problemas restritos e explÃcitos de engenharia. Ele superou os algoritmos mais utilizados na literatura: NSGA-II, MOPSO, MOEA/D, MOGWO e MOGOA. Após validação, foi aplicado em dois problemas complexos e impossÃveis de serem analiticamente otimizados. O primeiro foi um caso de projeto: otimização multi-objetivo de tubos isogrid CFRP usando o método dos elementos finitos. As otimizações foram feitas considerando duas metodologias: i) usando um meta-modelo, e ii) atualização por elementos finitos. A última provou ser a melhor metodologia, encontrando soluções que reduziram pelo menos 45,69% da massa, 18,4% do coeficiente de instabilidade, 61,76% do TW e aumentaram em pelo menos 52,57% a frequência natural. Na segunda aplicação, MOLA foi modificado internamente e associado a técnicas de feature selection para se tornar o Seleção e Alocação ótima de Sensores Multi-objetivo baseado no Algoritmo de Lichtenberg (MOSSPOLA), um algoritmo inédito de Otimização de Posicionamento de Sensores (SPO) que maximiza a resposta modal adquirida e minimiza o número de sensores para qualquer estrutura. Embora isto seja um princÃpio de Monitoramento da Saúde Estrutural, nunca foi feito antes. O MOSSPOLA foi aplicado na pá do rotor principal de um helicóptero real usando as 7 métricas mais conhecidas em SPO. Frentes de Pareto e configurações de sensores foram ineditamente geradas e comparadas. Melhores distribuições de sensores foram associadas a um alto hipervolume e o algoritmo encontrou uma configuração de sensor para cada número de sensores e métrica, incluindo uma com 100% de precisão na identificação de delaminação considerando deslocamentos modais triaxiais, número mÃnimo de sensores e ruÃdo para todas as seções da lâmina
Análisis de falla operacional de un sistema hidroneumático en instalación hospitalaria
Introducción: El trabajo presenta el estudio de la falla operacional de un sistema hidroneumático destinado al suministro de agua a una institución hospitalaria. Objetivo: Determinar la o las causas de interrupción del suministro de agua del sistema hidroneumático a la edificación. MetodologÃa: Se trazó la caracterÃstica hidráulica del sistema de tuberÃa y se comparó con la caracterÃstica hidráulica del sistema hidroneumático, comprobando que satisfacÃa plenamente las solicitudes de carga y flujo requeridas por la edificación. Dada la presencia de ruidos y vibraciones en la tuberÃa de succión se realizó la comparación del NPSH requerido con el NPSH disponible, determinando que el actual diseño de la tuberÃa de succión es la causa de la falla del sistema hidroneumático. Resultados: Se proponen tres variantes de modificación al diseño de la tuberÃa de succión que eliminan el fenómeno de la cavitación. Ello evita poner en operación una bombea auxiliar que incrementa el consumo energético en 8760 kWh/año con un costo de 1839,6 /year and the insecurity in the water service.Conclusions−The selected hydro-pneumatic equip-ment satisfactorily meets the requirements of the instal-lation, except for the design of the suction pipe where the available NPSH is lower than the NPSH required at flow rates higher than 900 l/min, hence, producing the cavitation phenomenon and causing the output of system’s service
Progettazione multidisciplinare ottimizzata nelle microturbine a gas
Optimized multidisciplinary design in micro-gasturbine
Numerical modelling of bidirectional dry gas face seals
The optimization of the geometrical parameters of the aerodynamic lift features and the
analysis of the fluid flow in the seal interface are inter-twined. Any small changes in the
geometrical parameters of the aerodynamic lift features significantly affect the performance
of a non-contacting gas face seal.
For a gas face seal to function with optimum performance requires that the optimum
geometrical parameters be identified. This can be achieved through a lengthy trial and error
process, often heavily dependent on the designer’s depth of insight, itself dependent on
experience, or can be achieved through automated numerical methods.
The purpose of this research was to develop a reliable numerical model that can serve
as a design tool for simulating the performance of both unidirectional and bidirectional
dry gas face seals. This was achieved in three steps. The first approach consisted in
developing a 2D numerical model that employed the Reynolds equation for seals operating
at very low rotating speeds and low pressure differentials. In the second step a 3D-CFD
model was assembled and the practicability of using CFD, in a seal design loop, for seals
operating in wide range of operating conditions, was investigated. This model employed a
commercial CFD package (ANSYS CFX version 11). For last approach both models were
incorporated into an automatic optimization tool that can generate optimal seal geometries
with a minimum of human intervention.
An extensive set of results from the analysis of dry gas face seals spanning across different
operating conditions and geometrical seal face profiles, with the inclusion of convergent
radial taper, are presented and discussed in this thesis. The results obtained from the
Reynolds equation and 3D CFD models are compared and critically analysed. Results
obtained with both models are validated against test data obtained from AESSEAL plc,
the sponsor of this research. The 3D CFD model predictions showed a better agreement
with the test data on the seal leakage than the Reynolds equation model. The leakage rates
and fluid film thickness predictions illustrate how the 3D CFD model can be used for seal
design while overcoming some of the shortcomings of the Reynolds equation based models.
The major limitation of the 3D CFD model is that it is computationally expensive.
An automatic optimization tool which can be used for the design of dry gas face seals has
been presented. The improvements achieved from the optimization of a spiral groove face
seal utilising the automatic optimization tool are: 4.8% increase of opening force, 13.2%
reduction of seal leakage, 20.7% increase of design efficiency parameter, 28.3% increase of
axial film stiffness and 15.9% reduction of power consumption. A proposed new design of
dry gas face seal capable of bidirectional operation has been presented. This type of seal
outperformed the spiral groove face seal, in reverse rotation of the sealing shaft, in terms of
opening force and positive axial film stiffness
Metamodel-based design optimization in industrial turbomachinery
Fans and Blowers community is experiencing, during those years, an incredible push in rethinking design approaches and strategies. The change in regulations on minimum efficiency grades and market requirements on even more customized products demand a changing in the way design in fan technology is perceived. In this context, even if synthetic approaches for fan design and analysis are still valuable tools, they need to be flanked by metamodels in order to overcome the limitations and criticism introduced by empirical relationships developed in the past for specific applications. In addition, by replacing computation-intensive functions with approximate surrogate models, it is possible to adopt advanced and nested optimization methods, such as those based on Evolutionary Algorithms, drastically improving the overall optimization computational time. Surrogate-based Optimizations based on Evolutionary Algorithm should become common practice in design optimization because of their capability of find optima in the design space, thanks to their intrinsic balance between exploitation and exploration.
This work proposes methods for interweave elements of metamodeling techniques and multi-objective optimization problems with the synthetic approaches classically developed by the turbomachinery community. The entire Thesis can be ideally divided into two parts; the first gives a brief survey on the classical fan design and analysis approaches and reports two synthetic in-house codes for axial fan performance prediction. The second part present the state-of-the-art in metamodeling and optimization techniques, underlining the role of metamodeling in supporting design optimization and focusing in the more reliable and accurate framework for multi-objective optimization in fans engineering design
CFD Modeling of Complex Chemical Processes: Multiscale and Multiphysics Challenges
Computational fluid dynamics (CFD), which uses numerical analysis to predict and model complex flow behaviors and transport processes, has become a mainstream tool in engineering process research and development. Complex chemical processes often involve coupling between dynamics at vastly different length and time scales, as well as coupling of different physical models. The multiscale and multiphysics nature of those problems calls for delicate modeling approaches. This book showcases recent contributions in this field, from the development of modeling methodology to its application in supporting the design, development, and optimization of engineering processes