Fixture design is an important issue in the process of manufacturing. As a critical design activity process, automation in fixture design plays an integral role in linking computer aided designs and computer aided manufacturing. This paper carries out a literature review of computer aided fixture design (CAFD) developments using intelligent methods that have been commonly utilized in automation in the last two decades. The first part of this review considers the steps of fixture design along with the significant researches and requirements of fixtures over time. After that, the paper presents important and relevant research carried out in the field of CAFD using intelligent approaches and the working principles surrounding this issue. The following section concentrates on the details of case based reasoning (CBR) approach, the most successful approach in CAFD. The examination of this approach is carried out based on applications, stages of CBR based systems fixture design, working principles, and pertinent proposed approaches. Lastly, the present drawbacks of the current methods and shortfalls in research are identified for future studies.
In this study, the turbulent non-premixed methane-air flame is simulated to determine the effect of air velocity on the length of flame, temperature distribution and mole fraction of species. The computational fluid dynamics (CFD) technique is used to perform this simulation. To solve the turbulence flow, k-ε model is used. In contrast to the previous works, in this study, in each one of simulations the properties of materials are taken variable and then the results are compared. The results show that at a certain flow rate of fuel, by increasing the air velocity, similar to when the properties are constant, the width of the flame becomes thinner and the maximum temperature is higher; the penetration of oxygen into the fuel as well as fuel consumption is also increased. It is noteworthy that most of the pollutants produced are NOx, which are strongly temperature dependent. The amount of these pollutants rises when the temperature is increased. As a solution, decreasing the air velocity can decrease the amount of these pollutants. Finally, comparing the result of this study and the other work, which considers constant properties, shows that the variable properties assumption leads to obtaining more exact solution but the trends of both results are similar.
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