离心式消防泵内流特性

为了研究离心式消防泵外特性、内流特性及空化特性,基于RNG k-ε湍流模型对某一比转数为24.7的离心式消防泵不同工况下的内部非定常流动进行数值模拟.结果表明:在关死点工况下,离心泵消防泵叶轮内部产生大量的失速旋涡,尤其在叶轮出口位置出现面积较大且极高湍动能的涡核分布,严重影响流道的通流能力,且造成较大的能量损失;随着流量增大,流道内的旋涡逐渐消失,流场趋于稳定,涡核分布基本保持稳定且对称;随着流量持续增大,离心式消防泵轴向力逐渐增大,在极小流量和极大流量工况下的轴向力波动相对较强;随着流量增大,径向力逐渐降低,且不同工况下径向力的矢量分布均呈现六齿形分布;随着流量的增大,离心式消防泵扬程特性曲线受空化的影响更加明显,随扬程曲线开始下降时的NPSHR也逐渐增大,但下降速度相对较慢.

Internal flow characteristics of centrifugal fire pump

In order to study the external characteristics, internal flow characteristics and cavitation characteristics of the centrifugal fire pump, numerical analysis was carried out based on the RNG k-ε turbulence model to compare the internal unsteady flow of the centrifugal fire pump with a specific speed of 24.7 under different working conditions. The results show that under the shut-off condition, a lot of stall vortices are generated in the impeller of the centrifugal fire pump, especially the vortex core distribution with large area and extremely high turbulent kinetic energy appears at the outlet of the impeller, which seriously affects the flow passage capacity and causes a lot of energy loss. With the increase of flow rate, the vortex in the channel disappears gradually, the flow field tends to be stable, and the distribution of vortex core basically fixed and symmetrical. With the continuous increase of flow rate, the axial force of centrifugal fire pump increases gradually, and the fluctuation of axial force is relatively strong under the conditions of minimum flow rate and maximum flow rate. With the increase of flow rate, the radial force decreases gradually, and the vector distribution of radial force under different working conditions presents a six tooth distribution. With the increase of flow rate, the influence of cavitation on the head characteristic curve of centrifugal fire pump is more obvious. When the head curve begins to decline, the NPSHR increases gradually, but the decline speed is relatively slow.