Experimental and numerical investigation of flow characteristics of a novel tubeless vortex reducer with integrated deswirl nozzles

A novel tubeless vortex reducer with integrated deswirl nozzles is proposed to suppress the non-monotonic flow characteristics of the traditional vortex reducer. The flow characteristics of this vortex reducer are investigated through numerical simulations and experiments. The integrated nozzles consist of two types of nozzles: the main nozzles and the auxiliary nozzles, which have distinct geometric shapes. Utilizing the distinctions in flow characteristics between two varieties of nozzles, differing flow distribution ratios are achieved at varying flow rates. At low flow rates, the auxiliary nozzles are effectively “closed” due to the fact that virtually no fluid is passing through them. This enhances the deswirl effect, thereby reducing the pressure drop at the lower knee of the vortex reducer's flow characteristic curve. The deswirl effect at the upper knee is reduced as a result of the auxiliary nozzles being “opened” at high flow rates. Consequently, the pressure drop range of the unstable multi-solution region is significantly reduced by 57.3% from the numerical simulation and 32.5% from the experiment. Conversely, the pressure drop and flow rate at the design point can be independently altered by adjusting the flow area of the main nozzles and the auxiliary nozzles, respectively. This prevents the issue of traditional vortex reducers increasing the bleed air flow rate at the expense of increased pressure drop. The structural robustness advantage of this tubeless vortex reducer is preserved by this innovative design, which does not incorporate any additional structures or mechanisms.