R&D Journal最新文献

{"title":"XFOIL Performance Validation for Medium-Scale Variable Pitch UAV Rotor Systems","authors":"B Nielsen, M Gilpin","doi":"10.17159/2309-8988/2023/v39a2","DOIUrl":"https://doi.org/10.17159/2309-8988/2023/v39a2","url":null,"abstract":"This study focuses on experimentally validating the performance of XFOIL, a sophisticated software airfoil analysis tool used for approximating lift and drag coefficients. XFOIL output data was incorporated into a theoretical model simulating a variable pitch rotor system operating in a hovering state. The output of the Blade Element Momentum Theory (BEMT) rotor model is compared to thrust and power output performance data collected from a constructed rotor test bench and analysed in MATLAB. Using XFOIL as input, the BEMT rotor model was observed to yield good robust results when compared to experimental data, but demonstrated sensitivity to airfoil performance characteristics, laying the groundwork for future empirical validation. In comparing BEMT model performance, it was interesting to find that thrust performance remained within tolerance in contrast to an overprediction of rotor power output resulting from XFOIL drag at high blade pitch angles. Upon further interrogation by means of variable isolation, XFOIL demonstrated instability resulting from sensitivity to variability of model constraints. Modification of rotor geometry definitions or environmental constants beyond the test environment framework showed simulated systems may not necessarily behave reliably nor enhance output performance. This highlights the critical importance and utility of experimentation for understanding theoretical model behaviour or validating simulation output performance.","PeriodicalId":299970,"journal":{"name":"R&D Journal","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135360519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Monte Carlo Simulation of Supply and Demand for Payload Limited Routes","authors":"Stefan Poprawa, L. Dala","doi":"10.17159/2309-8988/2019/V37A1","DOIUrl":"https://doi.org/10.17159/2309-8988/2019/V37A1","url":null,"abstract":"ABSTRACT Large commercial aircraft by design are typically not capable of transporting maximum fuel capacity and maximum payload simultaneously. Beyond the maximum payload range, fuel requirements reduce payload capability. Varying environmental conditions further impact payload capability noticeably. An airline's commercial department requires prior knowledge of any payload restrictions, to restrict booking levels accordingly. Current forecasting approaches use monthly average performance, at, typically, the 85% probability level, to determine such payload capability. Such an approach can be overly restrictive in an industry where yields are marginal, resulting in sellable seats remaining empty. Monte Carlo simulation principles were applied to model the variance in environmental conditions, as well as in the expected payload demand. The resulting forecasting model allows the risk of demand exceeding supply to be assessed continually. Payload restrictions can then be imposed accordingly, to reduce the risk of demand exceeding supply to a required risk level. Additional keywords: Fuel, payload, forecasting, performance, environment.","PeriodicalId":299970,"journal":{"name":"R&D Journal","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127023064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigating an Inverse Finite Element Approach for Characterising Soft Materials","authors":"F. Bresler, Franciena Helena","doi":"10.17159/2309-8988/2021/V37A9","DOIUrl":"https://doi.org/10.17159/2309-8988/2021/V37A9","url":null,"abstract":"ABSTRACT Soft materials, such as soft biological tissue and soft silicone rubber, are non-linear materials which require the classical uniaxial and biaxial tensile testing methods for characterisation. Unfortunately, in special cases, such as for soft biological tissue, the samples are smaller than 10 mm χ 10 mm in size and these classical tensile testing methods produce unwanted stress and strain gradients due to the fastening techniques associated with these methods. Micro-indentation is proposed as an alternative method for characterising soft materials. Using inverse Finite Element (FE) analysis and a known Mooney-Rivlin three parameter material model, six different micro-indentation tests were proposed. A theoretical approach was used to determine which indentation test best characterised a silicone sample, by using two FE models. The results showed that microindentation is capable of characterising a soft material in ideal conditions with a cylindrical indenter applied in a diagonal orientation over the sample, as the best indentation method. Finally, it was observed that the material model can either match the displacements with the smallest objective function or the stress vs. stretch curve can be matched to 99 % over the whole stretch range but not both simultaneously. Additional keywords: Inverse Finite Elements analysis, Micro-indentation, Gradient optimisation, Mooney-Rivlin hyper-elastic material model.","PeriodicalId":299970,"journal":{"name":"R&D Journal","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126282422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Performance Enhancement of an Induced Draught Axial Flow Fan Through Pressure Recovery","authors":"G. Bekken, C. Meyer, S. V. D. Spuy","doi":"10.17159/2309-8988/2021/V37A5","DOIUrl":"https://doi.org/10.17159/2309-8988/2021/V37A5","url":null,"abstract":"ABSTRACT This study illustrates that downstream diffusers can significantly aid the performance of an induced draught axial flow fan. Two conical diffusers of length 0.2 and 0.4 times the fan diameter and an annular diffuser with a length equal to the fan diameter are tested. At the design flow rate of the fan, the short conical diffuser increases the available static pressure by 17.6 % and the static efficiency by 8.9 %. The medium-length conical diffuser increases it by 21.9 % and 11.7 %, respectively. The long annular diffuser produces a 28.2 % pressure increase and a 14.2 % efficiency increase. The paper also compares the obtained pressure recovery coefficients of the different discharge diffusers using two-dimensional axisymmetric and three-dimensional computations. It shows that the pressure at the outlet of the fan cannot be assumed to be equal to atmospheric pressure, as is prescribed by the fan testing standards. A new method of measuring pressure recovery from two-dimensional computations is proposed. Additional keywords: Pressure recovery, axial flow fan, diffuser.","PeriodicalId":299970,"journal":{"name":"R&D Journal","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123777729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Performance Optimisation of Coal-fired Boiler Control using Flownex® Simulation Environment and AI","authors":"L. V. D. Westhuizen, I. Gorlach","doi":"10.17159/2309-8988/2019/V37A2","DOIUrl":"https://doi.org/10.17159/2309-8988/2019/V37A2","url":null,"abstract":"ABSTRACT The inherent variability of renewable energy sources, pump storage plants and combined cycle gas turbines implies that coal-fired plants designed for continuous base load generation in South Africa must now be used for variable load. This has a negative effect on the overall efficiency and life expectancy of these plants. The challenge is, therefore, to balance the network demands with the power station operation, its thermal efficiency, availability and extended plant life expectancy. The focus of the current research is to monitor and optimise the efficiency of the boiler operation and control through modelling of the boiler subsystems during transient states. Flownex® Simulation Environment was used to model a generic boiler and a boiler control system in order to simulate thermo-fluid processes and critical boiler controllers. The developed model was evaluated based on plant data and optimised afterwards by means of PID controllers and Machine Learning algorithms. The process parameters obtained from the Machine Learning algorithms outperform that of the PID controllers for the selected controllers, such as: boiler load control and steam pressure control. Additional keywords: Power generation, boiler control, boiler modelling.","PeriodicalId":299970,"journal":{"name":"R&D Journal","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124371286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A parametric design and optimization approach to enhance the fatigue life of a male pyramid socket adapter","authors":"P. Roux, R. Laubscher","doi":"10.17159/2309-8988/2019/v35a6","DOIUrl":"https://doi.org/10.17159/2309-8988/2019/v35a6","url":null,"abstract":"","PeriodicalId":299970,"journal":{"name":"R&D Journal","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116093698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Over-attemperation and Short-term Overheating in Pendant-type Superheaters","authors":"N. Basson, W. F. Fuls","doi":"10.17159/2309-8988/2021/V37A7","DOIUrl":"https://doi.org/10.17159/2309-8988/2021/V37A7","url":null,"abstract":"ABSTRACT A water-wedge is often suspected to be the root cause for short-term overheating in fossil-fuelled boiler superheaters. However, it can be argued that evaporation of the water-wedge would cool the tube sufficiently and prevent overheating. This study aims to determine if the thermo-physical conditions occurring at low loads support this claim by studying the transient behaviour of a representative superheater segment under postulated conditions. A flow model was constructed to facilitate direct comparison with a boiler pendant superheater of a full-scale fossil-fuelled power plant. Several scenarios of water-wedges sustained by attemperation spraywater were simulated at low load operating conditions. The temperature evolution of the tube wall was tracked and, together with calculated equivalent stresses including thermal stress, was compared to the yield strength of the material. The results show that the stresses exerted over the tube wall and throughout the tube length are not sufficient to overcome the yield strength of the tube material, even for an aged tube under severe process conditions of boiler overfiring. Evaporation of the water-wedge provides sufficient cooling to the superheater tube to prevent failure. It was concluded that water-wedging alone is unlikely to be the root cause of short-term overheating at low boiler loads. Additional keywords: Short-term overheating; water-wedge; boiler superheater tube; attemperation; thermal stress, evaporation.","PeriodicalId":299970,"journal":{"name":"R&D Journal","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122765857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A computational study on additively manufactured welding electrodes","authors":"D. Kirkman, J. Pillay, J. Padayachee","doi":"10.17159/2309-8988/2019/v35a5","DOIUrl":"https://doi.org/10.17159/2309-8988/2019/v35a5","url":null,"abstract":"R & D Journal of the South African Institution of Mechanical Engineering 2019, 35, 38-46 http://dx.doi.org/10.17159/2309-8988/2019/v35a5 http://www.saimeche.org.za (open access) © SAIMechE All rights reserved. 38 Abstract: Advances in additive manufacturing technology present new design opportunities for metal parts that would otherwise be infeasible with subtractive manufacturing technologies. Clifford Machines & Technology (Pty) Ltd is an international producer of large mesh welding machines. The research was conducted with the aim of investigating the advantages that can be provided through the redesign of the mesh welding electrodes, for production using additive manufacturing. Simulation studies were applied in order to evaluate the performance of the redesigned electrodes and the results were compared to the existing electrodes. The results show that the electrodes designed for additive manufacturing achieved mass reductions of up to 58.2%. The electrodes were also able to support increases of current density by up to 98%, while operating at a lower temperature than the original electrodes. The study has identified the high initial cost of production and increased power consumption to be the disadvantages of additively manufactured electrodes.","PeriodicalId":299970,"journal":{"name":"R&D Journal","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129119415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simulating Turbulent Air Flow Past a Hemispherical Body","authors":"M. Meas, J. Bruwer, M. Combrinck, T. M. Harms","doi":"10.17159/2309-8988/2021/v37a10","DOIUrl":"https://doi.org/10.17159/2309-8988/2021/v37a10","url":null,"abstract":"ABSTRACT The flow of air past a smooth surface-mounted hemisphere is investigated numerically using six common RANS turbulence models and seeking steady flow solutions. Where possible, the turbulence models are applied using standard wall functions, resolving the viscous sublayer, and the enhanced wall treatment option in ANSYS Fluent. Results of the simulations are compared against measurements taken in a wind tunnel experiment. The comparison shows that enhanced wall treatment and resolving the boundary layer on a low Reynolds number mesh yields superior accuracy compared to standard wall functions or resolving the boundary layer on a high Reynolds number mesh, for all the turbulence models considered. The RNG k - ε model with enhanced wall treatment applied is found to yield the most accurate prediction of the static pressure distribution across the surface of the hemisphere model. Conversely, the Reynolds Stress model and the standard k - ω model are found to give the least accurate predictions, irrespective of the near-wall modelling approach applied. It is found that good agreement with the experimental data for this case offlows can be attained using each of the near-wall modelling techniques if a well-suited turbulence model is used. Keywords: hemisphere, wind tunnel, turbulence modelling, computational fluid dynamics, steady flow","PeriodicalId":299970,"journal":{"name":"R&D Journal","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126233116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modelling of a Heated Gas-solid Fluidised Bed using Eulerian Based Models","authors":"A. Potgieter, M. Bhamjee, S. Kruger","doi":"10.17159/2309-8988/2021/V37A6","DOIUrl":"https://doi.org/10.17159/2309-8988/2021/V37A6","url":null,"abstract":"ABSTRACT An Eulerian-Eulerian granular model was used to simulate the flow and heat transfer through a heatedgassolid fluidised bed. The primary objective of the study was to determine whether the Eulerian-Eulerian granular model adequately predicts the chamber pressure drop, temperature, and bed expansion through the bed. The model predictions were assessed and validated for various flow-regimes, namely the fixed-bed, smooth, bubbling fluidisation, and the maximum fluidisation regimes. This was done on an experimental scale heated gas-solid fluidised bed. However, the results are generalisable for heated gas-solid fluidised beds when the flow is laminar. Numerical models were created using Computational Fluid Dynamics (CFD). The CFD-model predictions were investigated, analysed, and compared to experimental results. Basic experiments were carried out to obtain varying hydrodynamic characteristics. The results showed a slight overprediction of pressure drop and bed expansion, however, the results were still in close agreement with the experiment. In contrast, underprediction of chamber temperatures were obtained. Based on the results of this study, it is recommended that the Eulerian model be used to predict dynamic flow behaviour. Before minimum fluidisation, when in a fixed bed regime, pressure drop in the chamber increases with no increase in bed height. No visible bubbles were present in the fixed bed regime. When fluidisation has been reached, the bed height rises whereas the pressure drop tends to a constant value. Bubble size increases with chamber height and increased superficial velocities. Bubble speed increased with increased chamber height. With increased superficial velocity, the chamber temperatures increase to a maximum temperature of326.65 K with an initial heating element temperature of373.15 K. However, when excessive heat is present in the gas-solid fluidised bed, other methods that sufficiently incorporate particle-particle interactions and bubble-bubble interactions, are recommended. An investigation should be lent to bubble-bubble interactions in the fluidised beds with relation to heat transfer. Additional keywords: Heated fluidised bed, computational fluid dynamics, CFD, Eulerian, granular, fluidisation, gas-solid","PeriodicalId":299970,"journal":{"name":"R&D Journal","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130705911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}