轴向间隙对纸浆泵性能的影响规律

Effect law of axial clearance on stock pump performance

为研究轴向间隙对纸浆泵水力性能的影响,应用计算流体动力学软件Fluent,采用标准k-ε湍流模型及SIMPLEC算法,分别以清水和悬浮液为介质,对半开式离心纸浆泵在3种轴向间隙下,0.7Q0～1.3Q0流量范围内进行三维湍流数值计算,得到浆泵的性能曲线.计算结果表明:介质为清水时,随着间隙的增大,泵扬程和效率下降;对于不同体积分数的介质,离心泵叶轮、间隙内速度分布与介质为清水时的分布基本一致;当浆料体积分数为2%时,流道内存在大量的低速区,流动混乱,提出了适当增大叶片出口安放角的改进方法;随着间隙的增大,间隙的刚性作用消失,泵整体性能下降.由于轴向间隙的作用,叶片吸力面与压力面间的压力、速度变化较大,对于一定体积分数的浆料,小的间隙值能增加泵的输送能力.通过试验和数值计算进行对比分析,结果表明间隙为1.0 mm时泵整体性能较好,试验结果与模拟结果相一致.

In order to research the effect of axial clearance on hydraulic performance of a stock pump,3D turbulent numerical simulation was carried out for a semi-open centrifugal stock pump with three kinds of axial clearances by the computational fluid dynamics software Fluent under the conditions of 0.7 to 1.3 times of design flow rate.The simulations were conducted on mediums of clean water and pulp fiber suspensions,respectively,and in which the standard k-ε turbulent model and SIMPLEC algorithm were adopted.The simulation results show that the head and efficiency both decrease with the increasing of clearance when taking clean water as media.The velocity distribution in impeller and clearance is in accordance with that of clean water when taking pulp fiber suspensions as medium.The method of properly increasing the blade outlet angle is proposed to reduce the low-velocity regions,while the latter causes flow distortion at the condition that the volume fraction of pulp fiber suspensions is of 2%.When the rigidity effect is of no more action due to the clearance increases,the overall performance of the pump would be decreased.Due to the impact of axial clearance,the pressure and velocity between the suction side and pressure side of blades are of great variation,and the transmission capacity will increase for a small axial clearance and a certain volume fraction of pulp fiber.Compared with test data,it shows that the semi-open pulp stock pump will work well when tip clearance is 1.0 mm,and the numerical simulated results agree with that of the tested.