医用风机启动及瞬态变工况运行特性分析

Analysis of Start-up and Transient Operating Characteristics of Medical Fan

基于CFD三维全流场数值模拟分析,对呼吸机医用风机在启动和变工况运行过程瞬态流动特性进行详细分析。根据仿真计算结果可知,风机快速启动过程湍动能随转速增加而增加,而叶轮靠近隔舌的流道处湍动能强度最小,转速越快此处影响越明显。在变速运行过程中,由于风机惯性和动静干涉作用导致风机出口压力变化存在波动,同时变化频率落后于转速变化频率。风机停机过程中,转速不断降低,叶轮压力侧先发生脱流然后向整个流道发展;叶轮停机后,由于回流现象,叶轮会出现扭矩负值,相反,叶轮停机后,叶轮出口湍动能和静压由于惯性和涡流的存在仍然大于0。

Based on three-dimensional CFD numerical simulation analysis,the transient flow characteristics of respirator medical fan in the process of start-up and variable operating conditions are analyzed in detail.According to the simulation results,the turbulent kinetic energy increased with the increasing speed during the fast start-up of the fan,and the turbulent kinetic energy intensity at the flow path of the impeller near the spacer was the smallest,and the faster the speed,the more obvious the effect here.During variable speed operation,the fan inertia and rotor-stator interaction led to fluctuations in the fan outlet pressure change,while the change frequency lagged behind the speed change frequency.In the process of fan shutdown,the rotational speed decreased continuously,and the impeller pressure side firstly occurred the deliquescence and then developed to the whole flow channel.After the impeller shutdown,the impeller will have negative torque due to the backflow phenomenon.On the contrary,after the impeller shutdown,the turbulent kinetic energy and static pressure at the impeller outlet were still greater than 0 due to the existence of inertia and vortex.