Swirl stabilised combustion is one of the most successful technologies for flame stabilisation in gas turbine combustors. Lean premixed combustion systems allow the reduction of NOx coupled with fair flame stability. The swirl mechanism produces an aerodynamic region known as central recirculation zone (CRZ) providing a low velocity region where the flame speed matches the flow velocity, thus anchoring the flame whilst serving to recycle heat and active chemical species to the root of the former. Another beneficial feature of the CRZ is the enhancement of the mixing in and around this region. However, the mixing and stabilisation processes inside of this zone have shown to be extremely complex. The level of swirl, burner outlet configuration and combustor expansion are very important variables that define the features of the CRZ. The complex fluid dynamics and lean conditions pose a problem for stabilization of the flame. The problem is even more acute when alternative fuels are used for flexible operation. Therefore, in this paper swirling flame dynamics are investigated using computational fluid dynamics (CFD) with commercial software (ANSYS). A new generic swirl burner operated under lean-premixed conditions was modelled. A variety of nozzles were analysed using isothermal case to recognize the the behavers of swirl. The investigation was based on recognising the size and strength of the central recirculation zones. The dimensions and turbulence of the Central Recirculation Zone were measured and correlated to previous experiments. The results show how the strength and size of the recirculation zone are highly influenced by both the shear layer surrounding the Central Recirculation Zones (CRZ) and outlet configurations
A concentrating photovoltaic thermal system is composed of multiple concentrator modules which designed with wide acceptance angle such (Hyperbolic Profile) to collect high illumination flux that can be used for building integrated applications, in order to produce electrical and thermal energy, as well as to reduce gained solar radiation of the sun and enhancing natural day lighting in buildings. In this study many stages have been taken into consideration to achieve the optimum design. The system has been divided into two sections, first section is consisted of PMMA configured with Longitudinal Aluminum Plates and second section is considered as one piece of Flat Aluminum Plate. The results of the comparison between two sections with constant flow rate regarding temperature difference at the section of Flat Aluminum Plate is slightly higher than that in the section of PMMA plus Longitudinal Aluminum Plates.
The solar-assisted combined ejector was configured with the basic cycle of solar absorption refrigeration system to evaluate the performance of this cycle which using LiBr/H2O as a working fluid and operating under steady-state conditions. In this paper, the improvement of the system is achieved by utilizing the potential kinetic energy of the ejector to enhance refrigeration efficiency. However, the first and the second law of thermodynamics are used to analyze the performance of a single-stage water-lithium bromide absorption refrigeration system (ARS), whereas some working parameters are varied. Moreover, a mathematical model based on the exergy method is introduced to evaluate the system performance, exergy loss of each component and total exergy loss of all the system components. As well as, Parameters connected with performance of the cycle-circulation ratio (CR), coefficient of performance (COP), exergetic efficiency are calculated from the thermodynamic properties of the working fluids at various operating conditions. In addition, Minimum generator temperature that required to operate the system was evaluated. The results showed that, the evaporator, condenser loads and post-addition of the ejector are found to be permanently higher than that in the basic cycle. As well as, The COP of the modified cycle is improved by up to 60 % compared with that in the basic cycle at the given condition.
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