Pressure Fluctuation Reduction of a Centrifugal Pump by Blade Trailing Edge Modification

Abstract

The pressure fluctuation inside centrifugal pumps is one of the main causes of hydro-induced vibration, especially at the blade-passing frequency and its harmonics. This paper investigates the feature of blade-passing frequency excitation in a low-specific-speed centrifugal pump in the perspective of local Euler head distribution based on CFD analysis. Meanwhile, the relation between local Euler head distribution and pressure fluctuation amplitude is observed and used to explain the mechanism of intensive pressure fluctuation. The impeller blade with ordinary trailing edge profile, which is the prototype impeller in this study, usually induces wake shedding near the impeller outlet, making the energy distribution less uniform. Because of this, the method of reducing pressure fluctuation by means of improving Euler head distribution uniformity by modifying the impeller blade trailing edge profile is proposed. The impeller blade trailing edges are trimmed in different scales, which are marked as model A, B, and C. As a result of trailing edge trimming, the impeller outlet angles at the pressure side of the prototype of model A, B, and C are 21, 18, 15, and 12 degrees, respectively. The differences in Euler head distribution and pressure fluctuation between the model impellers at nominal flow rate are investigated and analyzed. Experimental verification is also conducted to validate the CFD results. The results show that the blade trailing edge profiling on the pressure side can help reduce pressure fluctuation. The uniformity of Euler head circumferential distribution, which is directly related to the intensity of pressure fluctuation, is improved because the impeller blade outlet angle on the pressure side decreases and thus the velocity components are adjusted when the blade trailing edge profile is modified. The results of the investigation demonstrate that blade trailing edge profiling can be used in the vibration reduction of low specific impellers and in the engineering design of centrifugal pumps.

Influence of the Trailing Edge Shape of Impeller Blades on Centrifugal Pumps with Unsteady Characteristics

“…The mainstream approach to blade edge modifications involves employing similar offset and cutting operations from the shroud to the hub [2][3][4][5][6][7]. Some scholars have also modified the trailing edge unilaterally.…”

“…Zhang et al [2] conducted cutting operations on the pressure side of the blade trailing edge, effectively improving the uniformity of the blade exit. Similarly, Huang et al [3] implemented unilateral pressure-side cutting to reduce the exit angle of the impeller's pressure surface, thereby adjusting the velocity component at the impeller exit and influencing the pressure pulsations within the pump. Some researchers have attempted to simultaneously modify both the pressure and suction sides.…”

Influence of Blade Trailing-Edge Filing on the Transient Characteristics of the Centrifugal Pump during Startup

“…The results showed that EPS (ellipse on pressure side) and EBS (ellipse on both sides) can both reduce the eddy current intensity at the trailing edge of the blade, significantly improve the efficiency of the pump, and reduce the pressure pulsation. Huang et al [25] found that filing the trailing edge of the blade reduces the outlet angle of the blade, leading to an increase in head and a decrease in pressure pulsation.…”

Study on the inner flow mechanisms and unsteady force distribution of side channel pump

“…[2][3][4] Periodic pressure fluctuations may force the impeller to vibrate, and resonance may occur when the frequency of pressure fluctuation approaches the natural frequency of pump components. 5 On the other side, unbalanced axial and radial force generate higher vibration amplitudes which affect the life cycle of the pump's shaft and bearing. The generation of these pressure fluctuations and unsteady axial and radial forces consequently affect the mechanical integrity of the pump.…”