Soheil Jafari

Bio: Soheil Jafari is an academic researcher from Cranfield University. The author has contributed to research in topics: Control theory & Control system. The author has an hindex of 12, co-authored 59 publications receiving 517 citations. Previous affiliations of Soheil Jafari include Iran University of Science and Technology & University of Sussex.

The Impact of Ice Formation on Wind Turbine Performance and Aerodynamics

Abstract: Wind energy is the world's fastest growing source of electricity production; if this trend is to continue, sites that are plentiful in terms of wind velocity must be efficiently utilized. Many such sites are located in cold, wet regions such as the Swiss Alps, the Scandinavian coastline, and many areas of China and North America, where the predicted power curves can be of low accuracy, and the performance often deviates significantly from the expected performance. There are often prolonged shutdown and inefficient heating cycles, both of which may be unnecessary. Thus, further understanding of the effects of ice formation on wind turbine blades is required. Experimental and computational studies are undertaken to examine the effects of ice formation on wind turbine performance. The experiments are conducted on a dynamically scaled model in the wind turbine test facility at ETH Zurich. The central element of the facility is a water towing tank that enables full-scale nondimensional parameters to be more closely matched on a subscale model than in a wind tunnel. A novel technique is developed to yield accurate measurements of wind turbine performance, incorporating the use of a torquemeter with a series of systematic measurements. These measurements are complemented by predictions obtained using a commercial Reynolds-Averaged Navier―Stokes computational fluid dynamics code. The measured and predicted results show that icing typical of that found at the Guetsch Alpine Test Site (2330 m altitude) can reduce the power coefficient by up to 22% and the annual energy production (AEP) by up to 2%. Icing in the blade tip region, 95―100% blade span, has the most pronounced effect on the wind turbine's performance. For wind turbines in more extreme icing conditions typical of those in Bern Jura, for example, icing can result in up to 17% losses in AEP. Icing at high altitude sites does not cause significant AEP losses, whereas icing at lower altitude sites can have a significant impact on AEP. Thus, the classification of icing is a key to the further development of prediction tools. It would be advantageous to tailor blade heating for prevention of ice buildup on the blade's tip region. An "extreme" icing predictive tool for the project development of wind farms in regions that are highly susceptible to icing would be beneficial to wind energy developers.

The effect of emerging green market on green entrepreneurship and sustainable development in knowledge-based companies

Abstract: Environmental concerns, as well as consumers’ awareness of buying green or environmentally-friendly products, has a positive impact on the emergence of the green market. The emerging green market brings many opportunities in different fields. Today, the issue of green entrepreneurship and sustainable development aim at producing environmentally-friendly products. This is indeed welcomed in the emerging green market. The publicly available research studies that investigate how green entrepreneurship, sustainable development, and emerging green markets are interconnected with each other are limited. More specifically, the impact of the green market on green entrepreneurship and sustainable development has not yet been studied completely. Therefore, a comprehensive research model has been developed in this paper based on the literature. The developed model is then tested using IBM SPSS Statistics for Windows, Version 19. IBM Corp.: Armonk, NY, USA and Smart-PLS Version 2 based on the data collected via a survey from a sample of knowledge-based companies in the Science & Technology Park of Tehran University. The results of the research indicate a positive and significant effect of the emergence of the green market on green entrepreneurship and sustainable development in knowledge-based companies. Moreover, the impact of the green entrepreneurship structure on sustainable development has been studied and the result presents that green entrepreneurship has a positive and significant effect on sustainable development.

Evolutionary Optimization for Gain Tuning of Jet Engine Min-Max Fuel Controller

Abstract: AS turbine aero engines (GTEs) have played a significant role in the expansion of the flight capabilities of modern aircraft. For a GTE, stable and safe operation of the engine components must be ensured in order to operate at the operability and performance level for which it is designed. The thrust response is also of great importance for an aircraft, both in terms of the speed of response and accomplishment of the adequate thrust [1]. Hence, an appropriate control system has always been an essential part of the GTEs to provide both regulation and management. The main task of a GTE control system is to provide the required performance while maintaining safe and stable operation [2]. The safetyconsiderationsincludethe flowinstability,highheatloads,and high cyclic stresses. In other words, the GTE control requirements include amainfuel controlforsetting andholdingsteady-state thrust (steady-state control mode) and fuel acceleration and deceleration schedules to provide limit protection (physical limitation control mode) and rapid time response for gas turbine engine (transient control mode) [3]. AsurveyonGTEcontrolstrategiesshowsthatvariousfuelcontrol methods have been used for GTE fuel control in the last two decades [4–16]. These studies show that the complexity of the engine control comes from the need to operate the engine as close as possible to its limits. In other words, the design of the control system for a gas turbine aero engine results in a series of single input single output controllers. Many methods such as PID, LQ, LQG, and H1 are used as one of the single feedback control loops of the GTE control system. In this case, the design method is based on a selection approach between various control loops. This strategy is named “min-max selection strategy,” as the selection of the control loops is based on a min-max approach between transient control loops. Minmax approach is an industrial method for the design of the GTE fuel control system. However, in order to provide an improved engine performance as well as the engine protection against the physical limitations, one of the most common complexities of the min-max selection strategy is controller gain tuning. Taking the nonlinearity and switching nature of this control strategy into account, gradient-based optimization methods have weak performance for gain tuning. As a result, this problem requires a non gradient optimization technique on the basis of the evolutionary algorithms. In this paper, application of an evolutionary algorithm for optimization of the min-max fuel controller parameters is presented. For this purpose, the control requirements and constraints for a gas turbine aero engine are first explained. The min-max fuel control strategy is then described and an initial min-max fuel controller is designed. Subsequently, using the genetic algorithm (GA), the parameters of the initial min-max fuel controller is tuned so that the engine requirements and constraints are satisfied. In optimization process, the fitness function is defined to minimize the settling time andfuelconsumption,wheretheweightfactorsaresetwithrespectto the importance of each function. In addition, a computer simulation programisdevelopedtoinvestigatetheeffectivenessoftheapproach for a single-spool jet engine. The results of simulation are validated by experimental data in both steady-state and transient modes to support the simulation model. Finally, the results are provided to investigate the performance of the optimized controller and to evaluate the effectiveness of the approach.

Thermal management systems for civil aircraft engines: review, challenges and exploring the future

Abstract: This paper examines and analytically reviews the thermal management systems proposed over the past six decades for gas turbine civil aero engines. The objective is to establish the evident system shortcomings and to identify the remaining research questions that need to be addressed to enable this important technology to be adopted by next generation of aero engines with complicated designs. Future gas turbine aero engines will be more efficient, compact and will have more electric parts. As a result, more heat will be generated by the different electrical components and avionics. Consequently, alternative methods should be used to dissipate this extra heat as the current thermal management systems are already working on their limits. For this purpose, different structures and ideas in this field are stated in terms of considering engines architecture, the improved engine efficiency, the reduced emission level and the improved fuel economy. This is followed by a historical coverage of the proposed concepts dating back to 1958. Possible thermal management systems development concepts are then classified into four distinct classes: classic, centralized, revolutionary and cost-effective; and critically reviewed from challenges and implementation considerations points of view. Based on this analysis, the potential solutions for dealing with future challenges are proposed including combination of centralized and revolutionary developments and combination of classic and cost-effective developments. The effectiveness of the proposed solutions is also discussed with a complexity-impact correlation analysis.

Heat and Mass Transfer

Abstract: Thermophysical Properties Research Literature Retrieval Guide Edited by Y. S. Touloukian, J. K. Gerritsen and N. Y. Moore Second edition, revised and expanded. Book 1: Pp. xxi + 819. Book 2: Pp.621. Book 3: Pp. ix + 1315. (New York: Plenum Press, 1967.) n.p.

Doing business in a green way: A systematic review of the ecological sustainability entrepreneurship literature and future research directions

Abstract: In line with an intensified call for conducting business in a greener and more sustainable way, sustainability-related entrepreneurship has become an important subfield of entrepreneurship research. The variety of terms, such as "sustainable entrepreneurship", "ecopreneurship", "environmental entrepreneurship/enviropreneurship", and "green entrepreneurship", reflects the fragmented and inconsistent findings of this research field. Based on the one-pillar model of sustainable development, i.e., ecological sustainability, we present the first systematic review of the literature on ecological sustainable entrepreneurship. This analysis of 114 scientific articles reveals a strong focus on the drivers of engagement in ecological sustainable entrepreneurship, the drivers of conducting business in an ecological sustainable way, the strategic actions taken by ecological sustainable enterprises, and the outcomes, enabling factors and challenges of ecological sustainable entrepreneurship. Based on this thematic clustering, we develop an integrative framework for ecological sustainable entrepreneurship and a coherent agenda for future research. This work may help researchers to take stock of the existing literature and advance this research field.

Aircraft Engine Design

Abstract: From Introduction: "The subject of this paper is so broad in scope that a large volume might be devoted to it. In a short paper of this kind it is possible simply to sketch in the high lights of aircraft engine design showing the development to date, the possibilities of the future, and the underlying fundamental principles. Summarizing this development and referring to the graph (Fig.1), we that there is now a water-cooled engine in every power from 150 to 800 HP. and an air-cooled engine in the 200 to 400 HP. classes."

An Immersed Boundary Method for the Weather Research and Forecasting Model

Abstract: This paper describes an immersed boundary method that facilitates the explicit resolution of complex terrain within the Weather Research and Forecasting (WRF) model. Mesoscale models, such as WRF, are increasingly used for high-resolution simulations, particularly in complex terrain, but errors associated with terrain-following coordinates degrade the accuracy of the solution. The use of an alternative-gridding technique, known as an immersed boundary method, alleviates coordinate transformation errors and eliminates restrictions on terrain slope that currently limit mesoscale models to slowly varying terrain. Simulations are presented for canonical cases with shallow terrain slopes, and comparisons between simulations with the native terrain-following coordinates and those using the immersed boundary method show excellent agreement. Validation cases demonstrate the ability of the immersed boundary method to handle both Dirichlet and Neumann boundary conditions. Additionally, realistic surface forcing can be provided at the immersed boundary by atmospheric physics parameterizations, which are modified to include the effects of the immersed terrain. Using the immersed boundary method, the WRF model is capable of simulating highly complex terrain, as demonstrated by a simulation of flow over an urban skyline.

Handbook Of Metaheuristics

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