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Low swirl burners present an effective approach to increase stability in lean premixed combustion. Effects of swirl number as a key parameter in the performance of these burners have been investigated in several studies with different conditions of pressure, bulk velocity equivalence ratio and geometrical specifications. Swirler distance from the exit, called recess length is another key parameter, which affects the performance of the burner and there are a few studies about its effects on the performance of the burner. In this study by design and fabrication of a low swirl burner and setup a rig test, several combustion parameters include flame temperature; flow rate, pressure and temperature of the air and fuel, and analysis of combustion products have been measured. And the effects of recess length and equivalence ratio variations on the performance of the low swirl burner have been studied. In addition, the exergy analysis has been done in order to investigate the performance of these burners. Results reveal that increasing recess length would result in wider range of lifted flame for different equivalence ratios. In addition, results also show that although low swirl combustion is working on lean condition, it has about 17 percent lower irreversibility ratio in comparison with diffusion flame from second law of thermodynamic point of view. Besides, the heat transfer ratio has been increased about 14 percent in the lifted flame in comparison with the attached flame.

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In this paper, numerical investigation was carried out for the sake of identifying optimum geometry for variable geometry ejector using in solar refrigeration system as the prerequisites to experimental tests. Variable geometry was made by using a movable primary nozzle and movable spindle in it. Vacuum tube collector was postulated as heat source and R600a used as working fluid. Condenser temperature based on Middle East area temperature and evaporator based on operative condition in HVAC system selected. Generator, condenser and evaporator operating temperatures have severe effects on the optimum geometry of ejector. Therefore, for maximum entrain ratio it is necessary to identify optimum geometry to cope with variations in operating condition. The results showed that using a variable geometry ejector is a requirement for cooling during the day. The following fluid structure was compared by entropy generation during mixing and shock phenomena. The results showed there is optimum back pressure to minimize fluid exit entropy. It coincides with critical back pressure. It was found that depending on back pressure maximum entropy generation happen by two reasons, mixing and shock phenomena.