Numerical Analysis of Single-Particle Motion Using CFD-DEM in Varying-Curvature Elbows

Centrifugal pumps are the critical components in deep-sea mining. In order to investigate the particle motion in the curved channel of the impeller, three different types of curvature conform to blade profile to simplify the impeller design of pumps. A numerical study is conducted to investigate the flow field in a varying-curvature channel for solid-liquid two-phase flow. The flow of particles within the varying curvature channel is studied by combining the discrete element method (DEM) with computational fluid dynamics (CFD) and a comparison with Particle Image Velocimetry (PIV) test results. The results show that a polyhedral mesh with a small mesh number yields very accurate results, which makes it very suitable for CFD-DEM. Based on this method, the movement of a single particle is compared and analyzed, and the particle-motion law is obtained. The effects of the curvature ratio Cr and area ratio Ar on the motion law for a single particle are studied, and the simulation results are analyzed statistically. The results show that the effect of Cr on both the particle slip velocity and the turbulent kinetic energy only changes its strength, while the distribution law does not change significantly. Compared with the curvature ratio Cr, the area ratio Ar has a greater impact on the particles, and its distribution law becomes clearly different. As the area ratio Ar increases, the arc radius and length of the corresponding particle trajectory decrease.

THE IMPACT OF SELECTED PARAMETERS ON PRESSURE DISTRIBUTION IN THE FACE THROTTLE OF A CENTRIFUGAL PUMP AUTOMATIC BALANCING DEVICE

Face throttles are a necessary functional element of non-contact face seals and automatic balancing devices of centrifugal pumps of different constructions. To calculate the hydrodynamic forces and moments acting on the rotor and fluid flow through the automatic balancing device, it is necessary to know the pressure distribution in the cylindrical and face throttle when considering all important factors which predetermine fluid flow. The face throttle surfaces are moving, which leads to unsteady fluid flow. The movement of the walls of the face throttle causes an additional circumferential and radial flow, which subsequently leads to the additional hydrodynamic pressure components. The paper analyses viscous incompressible fluid flow in the face throttle of an automatic balancing device taking into account the axial and angular displacements of throttle’s surfaces and the inertia component of the fluid. The effect of local hydraulic losses as well as random changes in the coefficients of local hydraulic resistance at the inlet and outlet of the throttle is analysed.

Training of simple fire installation for security guard at Samarinda State Polytechnic

The Samarinda State Polytechnic has a hydrant that does not work, because the installation is damaged and is 35 years old. Currently, a simple fire fighting water installation has been made at three points with a length of 257 meters for 16 buildings, which utilizes lake water inside the Samarinda State Polytechnic campus. Therefore, this service activity is intended to provide skills for security guard in the Samarinda State Polytechnic regarding the use of hydrants. The specifications of the equipment used are portable centrifugal pumps with a maximum capacity of 700 liters/minute, a horizontal reach length of 40 meters, a vertical height of 12 meters and a pump pressure of ±5 bar. The results of this activity revealed that all security guard at the Samarinda State Polytechnic were able to operate a simple fire extinguisher installation. In addition, security personnel also have the ability to maintain a fire pump engine.

Research on stator current characteristics of centrifugal pumps under different mechanical seal failures

Mechanical seal failure has a great negative impact on the operation of a centrifugal pump system. A method to analyze the stator current characteristics of the motor in a centrifugal pump system is proposed to monitor the internal flow of the centrifugal pump and to identify the failure status of the mechanical seal. Experiments were conducted under different mechanical seal states. Based on sensorless technology, the stator current signal of the motor is collected, processed by windowing function, anti-aliasing filter, singular value decomposition, Hilbert–Huang transform, and the marginal spectrum of correlation quantity is drawn. The results show that according to the external characteristic curve of the centrifugal pump, after the failure of the mechanical seal, the head and efficiency of the centrifugal pump decrease, and the head is greatly affected by the degree of failure, while the degree of mechanical seal failure has little effect on the shaft power of the centrifugal pump; the centrifugal pump has good operation stability under design conditions or near slightly large flow; the stability of centrifugal pump operation decreases with the aggravation of mechanical seal failure; the corresponding maximum amplitude in the marginal spectrum can be used as an index to diagnose the damage degree of the mechanical seal.

A New Prediction Method for the Complete Characteristic Curves of Centrifugal Pumps

Complete pump characteristics (CPCs) are the key for establishing pump boundary conditions and simulating hydraulic transients. However, they are not normally available from manufacturers, making pump station design difficult to carry out. To solve this issue, a novel method considering the inherent operating characteristics of the centrifugal pump is therefore proposed to predict the CPCs. First, depending on the Euler equations and the velocity triangles at the pump impeller, a mathematical model describing the complete characteristics of a centrifugal pump is deduced. Then, based on multiple measured CPCs, the nonlinear functional relationship between the characteristic parameters of the characteristic operating points (COPs) and the specific speed is established. Finally, by combining the mathematical model with the nonlinear relationship, the CPCs for a given specific speed are successfully predicted. A case study shows that the predicted CPCs are basically consistent with the measured data, showing a high prediction accuracy. For a pump-failure water hammer, the simulated results using the predicted CPCs are close to that using the measured data with a small deviation. This method is easy to program and the prediction accuracy meets the requirements for hydraulic transient simulations, providing important data support for engineering design.

Increasing wear resistance of the protective sleeve of the centrifugal pump made of gray cast iron by surface hardening

One of the weak spots that reduce the guaranteed operating time of centrifugal pumps is the assembly that includes the seal and protective sleeves. The main purpose of the bushings in the rotor kit is to protect the shaft from corrosion, erosion and wear. The sleeve operates under abrasive wear conditions by packing elements and abrasive particles that get into the liquid pumped by the pump. The protective sleeves made of gray cast iron do not meet the service life in connection with accelerated surface wear. Goal. The purpose of the work is to ensure high wear resistance of cast iron pump parts by heat treatment. Method. The chemical composition was determined on a portable laser analyzer Laser Z200 C +. The structure was studied using an optical microscope. The wear was investigated by the roller-block method on a friction machine. Surface quenching was carried out with a high-frequency lamp generator in a single-turn inductor. Results. The microstructure of gray cast iron as cast consists of pearlite, ferite, double phosphide eutectic and inclusions of lamellar graphite. Microhardness of small-lamellar pearlite is Н50 = 1550–2220 MPa, microhardness of phosphide eutectic is Н50 = 6500–8000 MPa. Surface induction quenching by high-frequency currents followed by low tempering is an effective way to increase the wear resistance of cast iron products of small cross-section and does not cause warping. Cast iron for surface quenching should have a pearlite structure, and graphite should be contained in the form of small inclusions. The optimal heating temperature for induction hardening was determined as 900 °С, which made it possible to obtain the microstructure of the hardened layer – martensite, double phosphide eutectic and graphite. Scientific novelty. The developed modes of surface quenching make it possible to preserve a double phosphide eutectic in the structure of the surface layer, which makes it possible to obtain high hardness and wear resistance of the hardened layer. Practical significance. Surface induction quenching with low tempering of cast gray iron increased its wear resistance by 2,4 times. The previous normalization had practically no effect on the durability of cast iron, since its structure contains less than 10% ferrite.

Influence of Blade Type on the Flow Structure of a Vortex Pump for Solid-Liquid Two-Phase Flow

Vortex pumps have good non-clogging performance owing to their impellers being retracted into retraction cavities, but they are much less efficient than ordinary centrifugal pumps. In this paper, numerical simulations were performed on a model of the 150WX200-20 vortex pump for four different blade types, and the influence of blade structure on pump performance was determined. The simulations revealed the existence of axial vortices in the flow passage between the blades in the impeller region. The geometric characteristics of these axial vortices were more regular in two-phase solid-liquid flow than single-phase liquid flow. The presence of the solid phase reduced the vortex strength compared with the single-phase flow and suppressed the increase in size of the secondary circulation vortex. It was found, however, that the blade shape had a greater influence on the circulating flow than the presence of the solid phase. The flow state of the medium flowing out of the impeller domain had a direct effect on the circulating flow with this effect being related to the law governing the flow of the medium in the flow channel between the blades. It was found that the performance of a front-bent blade was the best and that of a curved blade the worst. This influence of blade type on the internal flow structure was used to further explain the relationship between the internal flow structure and the external characteristics of the vortex pump, the understanding of which is crucial for blade selection and hydraulic optimization.

Pressure Fluctuation Characteristics of High-Speed Centrifugal Pump with Enlarged Flow Design

The pressure fluctuations of high-speed centrifugal pumps are the hotspot in pump research. Pressure fluctuations is differ for different structural designs and flow structures. High-speed centrifugal pumps are usually designed to increase efficiency with an enlarged flow design at a low specific speed, which changes the structure of the pump. In order to analyze the pressure fluctuations of a high-speed centrifugal pump with an enlarged flow design, the pressure was measured, and the flow field of the pump was simulated with different flow rates. Through analysis, we found that pressure fluctuations varied periodically and was consistent with the blade frequency. The pressure fluctuations at the guide vane and the interference region were also closely related to the vortices at the impeller outlet, which changed differently at different flow rates. The results showed that the high-speed centrifugal pump with an enlarged design had better performance at a large flow rate. The results in this paper can provide reference for the design of a pump that should be designed with the enlarged flow method.

Submersible pumps - application practice, technical requirements, development paths

Проанализировано применение погружных (плавающих) насосов в насосно-рукавных комплексах. Рассмотрены их преимущества перед центробежными насосами, устанавливаемыми в мобильной пожарной технике. На основе практики применения и технических характеристик погружных насосов, производимых ведущими зарубежными фирмами, сформулированы технические требования для разработки отечественного погружного насоса. Кроме того, технические требования могут стать основой разработки национального стандарта для этого типа пожарно-технической продукции. The article analyzes the results of operation of a relatively new type of centrifugal pump - a submersible (floating) centrifugal pump with a hydraulic drive. These pumps have a number of significant advantages over centrifugal pumps installed on mobile fire fighting equipment - they can be used to pump liquid from a mark up to minus 30 m. Since the suction pipe of such a pump is located directly in the pumped liquid (below the liquid mirror level), the phenomenon of cavitation is practically excluded. Submersible pumps are used to supply water in case of fire and for water disposal during the elimination of hazardous hydrological phenomena, both independently and in conjunction with centrifugal pumps installed on mobile fire fighting equipment (supply to pumping). All submersible pumps included in the set of hose-pumping complexes are of foreign production. The demand for such pumping units causes the need to develop domestic samples in order to get away from import dependence in the manufacture of pumping and hose systems and their operation. Based on the practice of using submersible pumps and the technical characteristics of submersible pumps produced by leading foreign companies, the following technical requirements for the development of a domestic submersible pump have been formulated. Pump delivery is 170-180 l ∙ s from the mark to minus 30 m. Water intake is possible both in equipped (adapted) and unequipped (unsuitable) places. In addition, the requirements for the hydraulic drive, weight and size characteristics, and some components have been formulated. In conclusion, some directions for the further development of pumping and hose systems and submersible pumping stations are considered.