Research On Low Frequency Excitation Characteristics And Transfer Path Analysis Of Typical Auxiliary Equipment

Various mechanical equipments in the engine room will inevitably generate vibrations while working.At present,the research on the vibration characteristics of the main engine is relatively mature,and its vibration has also been controlled.The vibration of the auxiliary equipment has become increasingly prominent and gradually attracted by researchers.In a variety of auxiliary engines,the number of centrifugal pumps is the largest and the most versatile.In the course of operation,the vibration of the ship's shell is caused,which in turn radiates noise to the surrounding fluid,which is detrimental to the acoustic stealth of ships.Researching the vibration characteristics of the centrifugal pump and analyzing the transmission path have important guiding significance for the vibration and noise reduction of the ships.In this paper,fluid-solid coupling method is used to calculate the flow field of IS100-65-315 single-stage single-suction horizontal centrifugal pump under different operating conditions.The vibration characteristics of the machine feet are analyzed.Then the finite element power flow method was used to analyze the transmission path of double floor frame under centrifugal pump excitation.The main contents include:(1)Centrifugal pump structure and fluid three-dimensional model and finite element model are respectively established.The flow field of steady flow under rated condition is calculated and analyzed,and the test bench is set up to carry out the test.The established model is verified from three aspects of machine vibration,efficiency and head.(2)Based on the ANSYS Workbench collaborative simulation platform,the flow and structural vibrations of the centrifugal pump at 30,40,50,60,and 70 m~3/h are simulated and calculated using the fluid-solid coupling method.The vibration characteristics of the three feet are analyzed.The results show that the vibration of the feet on the side of the volute of the centrifugal pump at the blade frequency and double blade frequency is stronger than that at the rotating frequency.For the side of the volute side of the foot,the vibration of the foot away from the centrifugal pump outlet side is stronger than the exit side of the machine feet.In addition,the change of the vibration of the machine foot in the rotating frequency and the blade frequency is larger than that of the double blade frequency.(3)The finite element model of double-deck floor structure is established,and the modal analysis is carried out.Then the acceleration excitation of the machine feet under the rated condition of the centrifugal pump is applied.The harmonic response computation and analysis show that the vibration response of outsole at 33 Hz is the maximum.(4)The program of generating the structural intensity vector data of shell element is compiled and validated with examples.Then the component and the contribution of the structural intensity of each bottom girder and the plate floor at 33 Hz is calculated and the important transfer paths are determined.Their structural intensity vector diagrams are drew to identify that the main transmission path at 33 Hz under the single excitation is in a“?”shape and is located directly under the base of the centrifugal pump.(5)The centrifugal acceleration and the simulated exciter excitation are applied to the double floor frame structure.The harmonic response analysis under multi-excitation is carried out.The results show that the vibration response of the outsole at 87 Hz is the maximum under multi-excitation.Then the power flow contribution quantification method is used to conduct the transfer path analysis.It is recognized that the main transmission paths at 33 Hz and 87 Hz under dual excitations are distributed on both the damping base side and the centrifugal pump base side of the double-floor frame structure,and the distribution is wider and more even at 33 Hz than single excitation.(6)The vibration resistance mass band is installed on the main transmission path at 87Hz under multi-excitation,and the vibration response and radiation sound field of the outsole are calculated.After comparison and analysis,it is found that the structural intensity of the important transmission path,the vibration response and radiated sound power of outsole are significantly reduced before and after vibration damping.