Research on Numerical Simulation of Vibration Reduction of Marine Centrifugal Pumps WANG Xin-hai DU Hua 2, MU Yan 3, CHEN Jian 2 (1. Naval Military Representative Office Huludao 431, Huludao 125004, China; 2. Wuhan Second Ship Design Institute, Wuhan 430064; 3. Naval Warship Supporting Military Representative Office in Shenyang, Shenyang 110031) The characteristics of the heart pump, combined with engineering practices, suggest possible causes for excessive vibration of the equipment. Based on the modern design method of CFD performance prediction, a modified vibration-reducing design of the pump was performed. The CFD performance prediction results of the improved scheme show that the instability of the flow in the pump has been significantly improved.
Centrifugal pumps are used extensively in ships' air conditioning cold water systems, bilge ballast systems, circulating water systems, fire fighting systems, drainage systems, and domestic water systems. Marine centrifugal pumps are prone to large vibration noise due to improper design, processing, and operating conditions, which pose a threat to the safe use of the equipment and cause damage to the health of the operation and management personnel.
According to statistics, centrifugal pumps have become the main source of mechanical radiation noise. In addition, due to the vibration of the water pump, the efficiency of the water pump and the head and flow rate will also be reduced. In order to make the centrifugal pump run smoothly and reduce cabin noise, it is urgent to develop a low-vibration centrifugal pump for ships.
This article takes a certain type of marine centrifugal pump as an example, analyzes the current status and causes of the vibration of the pump, proposes the main improvement measures, and verifies the improved scheme with the numerical simulation analysis method.
1 Overview The object of this study is a marine centrifugal pump used to transport air-conditioning refrigerant water for all ships. The pump is mainly composed of a pump body, a bearing, a pump shaft, an impeller and a motor. The outline diagram is as shown.
The main parameters of a marine centrifugal pump are its flow parameters: flow rate 100t/h; head 53m out of 0; necessary NPSH 4.9m; motor speed 2980r/min; motor power 22kW. The sum is the typical vibration spectrum of the pump foot.
Unit Foot Vibration Typical Line Spectrum Unit Foot Vibration Typical 1/3 Octave Spectrum 2 Cause Analysis Centrifugal pumps are rotary fluid machines that vibrate for a variety of reasons during operation. When a marine centrifugal pump is operated, it will be affected by two kinds of vibrations, one is self-excited vibration and the other is environmental vibration. Spectral analysis based on spectrograms is an effective way to analyze vibration violations.
2.1 Spectrum Analysis The pump's rated speed is 2980r/min, so the rotor's rotation frequency is: /=2980/60=49.67(Hz). From the sum can be found: 1) in the high frequency range (4kHz ~ 10kHz range) The vibration of the pump is very high and it is growing. Therefore, the main source of the vibration of the pump is the fluid excitation vibration; 2) At the integral multiple frequency of the rotor rotation frequency, the peak of the vibration acceleration spectrum appears, the reason for this phenomenon is that the rotor rotation is unbalanced; 3) exists on the spectrogram. There are some peaks that are not significantly related to the rotor speed frequency.
This may be due to other reasons, such as poor bearing housing structure, insufficient strength of the base plate, rough manufacturing of the impeller and pump, installation problems, and the like.
2.2 Possible causes of excessive vibration. Water Pump Technology, 2008(3):20-24. Wu Renrong. Operational vibration and deduction measures for marine centrifugal pumps. Li Ting, Lu Shuwang, Long Shiyi. Frequency spectrum analysis of motor vibration. The history of Hu Shihong, Dai Yan. Research on Vibration Problems of High Speed ​​Pumps . Contemporary chemical industry, Zhang Hao. Centrifugal pump vibration analysis and preventive measures. Chemical equipment Wu Renrong, Chen Wenyi. Hydraulic design to reduce the vibration of the centrifugal pump Huai Huimei, Zhu Xiaohui. Causes of pump vibration and countermeasures. Mechanical engineering (on page 71 of the previous page) should pay attention to accurately obtain the propeller's radial moment of inertia, pole moment of inertia, moment of inertia, and the coefficient of attached water.
The calculation of the cyclonic vibration is a necessary work for the determination of the niobium bearing in the shafting design. In the multi-support shafting system, the greatest impact on the swirling vibration is the bearing spacing, which increases the bearing spacing and reduces the critical speed. In addition, for the controllable propeller propulsion shafting, increasing the hollowness of the shafting can increase the critical rotational speed and thus leave the resonance region.
4 Conclusions The design of the propeller propulsion shaft of the ship's controllable pitch propeller is a very complex comprehensive project. The design of the plan directly determines the pros and cons of the ship's power plant. When designing pitch-adjusting propeller shafting systems, the coordination of various internal and external interfaces and the determination of various technical parameters need to be repeatedly coordinated with marine engineers and hull engineers, and balanced and reasonable arrangements must be made in an integrated manner in order to design a safe, reliable, process-friendly system. Ship shafting.
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