Dry electrostatic precipitators (ESPs) are widely used for purification of exhaust gases in industrial applications. Maintenance of their high efficiency depends primarily on periodical cleaning of the collecting electrodes (CEs). Dust removal (regeneration of CEs) is realized by inducing periodical vibrations of the electrodes. The paper presents results of vibration modelling of a system of CEs; the results were obtained by means of the finite element method, the hybrid finite element method, the finite strip method and a model formulated using Abaqus. Numerical results are compared with those obtained from experimental measurements. Conclusions concerning numerical effectiveness and exactness of the methods are formulated and reasons for differences are discussed.
The paper presents a model of a rapping system of an electrostatic precipitator. The rapping system consists of a set of collecting electrodes hanging on a suspension bar and braced together in a brushing bar. The suspension and brushing bars are modeled using the rigid finite element method, while the collecting plates are modeled using the hybrid method. The method combines the rigid finite element method with the classical finite element method. As a result, the mass matrix is diagonal. Some results of numerical simulations concerning free vibrations of the collecting plates and the influence of the number of elements, into which the plate is divided, on the vibrations of the rapping system are presented.
The rigid finite element method (RFEM) has been used mainly for modelling systems with beam-like links. This paper deals with modelling of a single set of electrodes consisting of an upper beam with electrodes, which are shells with complicated shapes, and an anvil beam. Discretisation of the whole system, both the beams and the electrodes, is carried out by means of the rigid finite element method. The results of calculations concerned with free vibrations of the plates are compared with those obtained from a commercial package of the finite element method (FEM), while forced vibrations of the set of electrodes are compared with those obtained by means of the hybrid finite element method (HFEM) and experimental measurements obtained on a special test stand.
The possibility of distinguishing and assessing the influences of defects in particular pump elements by registering vibration signals at characteristic points of the pump body would be a valuable way for obtaining diagnostic information. An effective tool facilitating this task could be a well designed and identified dynamic model of the pump. When applied for a specific type of the pump, such model could additionally help to improve its construction. This paper presents model of axial piston positive displacement pump worked out by the authors. After taking the simplifying assumptions and dividing the pump into three sets of elements, it was possible to build a discrete dynamic model with 13 degrees of freedom. According to the authors' intention, the developed dynamic model of the multi-piston pump should be used for damage simulation in its individual elements. By gradual change in values of selected construction parameters of the object (for example: stiffness coefficients, damping coefficients), it is possible to perform simulation of wear in the pump. Initial verification of performance of the created model was done to examine the effect of abrasive wear on the swash plate surface. The phase trajectory runs estimated at characteristics points of the pump body were used as a useful tool to determine wear of pump elements.
This paper presents a study on flowmeters oscillatory motion when subjected to periodical, enforced vibrations induced by vortex-shedding. The proposed mathematical modelling of flow was compared to corresponding numerical simulation, in form of modal analysis. The frequencies of vortices generation and detachment were calculated for a number of flow velocities in two different flowmeter profile variants. The performed modal evaluation enabled estimating their natural frequencies, and in consequence the acquired data helped us to determine flow velocity for which the analyzed structures were prone to resonant vibrations.
Two vibrating circular membranes radiate acoustic waves into the region bounded by three infinite baffles arranged perpendicularly to one another. The Neumann boundary value problem has been investigated in the case when both sources are embedded in the same baffle. The analyzed processes are time harmonic. The membranes vibrate asymmetrically. External excitations of different surface distributions and different phases have been applied to the sound sources’ surfaces. The influence of the radiated acoustic waves on the membranes’ vibrations has been included. The acoustic power of the sound sources system has been calculated by using a complete eigenfunctions system.