Influence of geometry on the efficiency of convergent-divergent nozzles applied to Tesla turbines

摘要

Convergent-divergent (CD) nozzles were designed and manufactured to improve the injection efficiency of the working fluid in Tesla turbines. Ten nozzles have been designed using two different techniques: a one-dimensional approach and a two-dimensional approach with the method of characteristics. All nozzles had rectangular geometry at throat, while 3 had divergent section planar and 2 divergent section circular, considering each mass flow rate (55 and 70 kg h(-1)). Nozzles were analyzed using air as the working fluid. A nozzle exit to throat area ratio (NAR) of 1.35 was used in all nozzles, while the nozzle pressure ratios (NPR) ranged between 2.15 and 3.25. At planar nozzles an (x/H)(exit) of 2.1 was more suitable for decreased of total pressure losses, while at circular nozzles the shock waves were canceled inside of divergent section. (C) 2015 Elsevier Inc. All rights reserved.