Table of contents

September 5-8, 2017, Sumy State University, Sumy, Ukraine

PROCEEDINGS EDITED BY

Volodymyr MARTSYNKOVSKYY, Prof., Dr., Dr.h.c., Sumy State University

Igor TVERDOKHLEB, Ass. prof., Dr.-Ing., HMS GROUP

Andriy ZAHORULKO, Ass. prof., Dr.-Ing., Sumy State University

Serhii HUDKOV, Dr.-Ing., Sumy State University

Selected, peer reviewed papers from the XV International Scientific and Engineering Conference HERVICON+PUMPS-2017

FOREWORD

The Conference Proceedings devoted to problems of reliability and economy of pump and compressor equipment are offered to the attention of specialists. The book presents 58 papers of various authors, included in the Program of the XV International Scientific and Engineering Conference HERVICON+PUMPS-2017, which, since 1976, with an enviable constancy passes every three years in Sumy on the basis of the General Mechanics and Machine Dynamics Department of the Sumy State University. The main sponsor that provided holding of the current conference, as well as the previous one, was the HMS Group, demonstrating an effective interest in the technical progress development.

Published papers are grouped in five sections, which cover a wide range of issues of modern theory and practice of centrifugal machines. At the present stage of its development, the theory, thanks to the successes of computational mathematics and computer technology, is experiencing a period of prosperity. The possibility of numerical analysis of more perfect mathematical models of unsteady flows of real liquids and gases in flow channels has appeared. The existing solutions are specifying, the new physical processes laws accompanying the operation of pumps and compressors are finding. In the published papers, at least to a small extent, the present state of the theory of these machines is reflected. Part of the papers is devoted to the implementation of new design solutions. The results of experimental investigations and operational experience of the proposed designs are given (Sections 1 and 2).

Centrifugal pumps and compressors - rotary machines. The most critical units of these machines are bearings and seals, which are complex tribomechanical systems. The papers given in Section 3 and 4 are devoted to the problems of calculating and designing of bearing and seals, increasing of the wear resistance of friction pairs.

The unbalanced rotor of a centrifugal machine is the source of vibration disturbances, which determine the vibration state of the machine as a whole. At the same time, the level of vibration is one of the main indicators of reliability, therefore reliability problems are directly related to the rotor dynamics in the bearings and annular seals. The rotor dynamics are discussed in Section 5.

On behalf of the authors' team, I hope that the papers published in the book will awaken the interest of young research engineers and will be useful to experienced designers in creating new reliable and economical pumps and compressors. In addition, the technical personnel involved in the maintenance and repair of units, can to get useful information from the book.

Professor Volodymyr A. Martsynkovskyy

List of Scientific Committees and Chair members are available in this pdf.

All papers published in this volume of IOP Conference Series: Materials Science and Engineering have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

The article reveals the need for pump range charts development for different applications and describes main principles used by HMS Group. Some modern approaches to pump selection are reviewed and highlighted the need for pump compliance with international standards and modern customer requirements. Even though pump design types are similar for different applications they need adjustment to specific requirements, which gets manufacturers develop their particular design for each pump range. Having wide pump ranges for different applications enables to create pump selection software, facilitating manufacturers to prepare high quality quotations in shortest time.

The total energy consumption of various types of pumps is significant and the energy saving potential in this area is also huge. The transition from consideration of the characteristics of a separate pump to the features of its operation with a drive, taking into account the operation in different modes in conditions of a specific hydraulic network, allows obtaining a much greater potential for reducing energy consumption, significantly increasing the efficiency and reliability of pumping equipment.

The article deals with the effect of the vanes diffuser geometric components at the inlet (downstream of an impeller) and at the outlet (upstream of the impeller) on the shape and steepness of the Q-H-curve. Intermediate stage comparative curves based on centrifugal pump tests are given with corrections to the vanes diffuser components were made. This allows changing steepness of the Q-H-curve. Comparative tests of the intermediate stage with different types of vanes diffusers (with continuous crossover channels and discontinuous crossover channels) are shown.

Torque flow pumps are widely spread types of energy machines, which are used in majority of modern branches of industry for pumping of dirty media. The main task of researchers of torque flow pumps is increase of such pumps effectiveness for higher feed. Hydraulic losses for torque flow pumps are caused by working process of such pumps and are inevitable. Decrease of losses can be obtained by means of optimization of hydraulic flow part geometry.

Modern approach to design of pump outlet introduces new constructive solutions which can increase economy of torque flow pumps.

The aim of this research is increase of economy of torque flow pumps by means of application of spatial outlet and investigation of its geometry on pump characteristics.

Analytical and numerical methods of liquid flow research for hydraulic flow part of torque flow pump were used in this paper. Moreover, influence of hydraulic flow part geometry of different designs of "Turo" type torque flow pumps outlets on pump characteristics was investigated. Numerical research enabled to study process of energy transfer of torque flow pump and evaluate influence of geometrical dimensions of spatial spiral outlet on its characteristics. Besides numerical research confirmed introduced regularity of peripheral velocity distribution in outlet. Velocity moment distribution in outlet was obtained during implementation of numerical research.

Implemented bench tests of torque flow pump prototypes enabled to obtain real characteristics of pump and confirm effectiveness of spatial geometry of outlet application for such pump.

This work deals with improvements of the calculation and design methods of rotodynamic pump volutes taking into account viscous liquid flow. The research was performed with torque flow pump of "Turo" type. The analytical solution for the problem within the one-dimensional model of viscous liquid allowed to obtain a viscous liquid flow pattern in the volute. The law of velocity variation of viscous liquid flowing through the volute was obtained. There are numerical solutions of the problem concerning of viscous liquid flow in the pump with volute designed for traditional model of non viscous and viscous fluid.

The research results are given by means of head-capacity and power input curves. To estimate the results of numerical study the tests were performed on the test stand.

A comparative analysis of VS6 pump type in the range of specific speed n_q = 25...55 was carried out basing on information about analogous pumps produced by the world's leading manufacturers. The focus was made on mass-dimensional characteristics of the pump stages. It was found that rational design of a diffuser with radial vanes provides lower material consumption at similar hydraulic characteristics compared to using a semi-axial vanes diffuser in the stage.

The article deals with the analysis of cavitation processes in the flowing part of the double entry centrifugal pump. The analysis is conducted using numerical modeling of the centrifugal pump operating process in the software environment ANSYS CFX. Two models of the axial inlet device is researched. It is shaped by a cylindrical section and diffuser section in front of the impeller, which includes fairing. The walls of the axial inlet device rotate with the same speed as the pump rotor. The numerical experiment is conducted under the condition of the flow rate change and absolute pressure at the inlet. The analysis shows that the pump has the average statistical cavitation performance. The occurrence of the cavitation in the axial inlet device is after narrowing the cross-section of flow channel and at the beginning of the diffuser section. Additional sudden expansion at the outlet of the axial inlet diffuser section does not affect the cavitation characteristics of the impeller, however, improves cavitation characteristics of the axial inlet device. For considered geometric parameters of the axial inlet device the cavitation in the impeller begins earlier than in the axial inlet device. That is, the considered design of the axial inlet device will not be subjected to destruction at the ensuring operation without cavitation in the impeller.

The primary aim of the project was to increase cavitation performance of a big mixed–flow pump. The CFD software was used as a main research tool. The two kinds of numerical models were used to solve this problem – both were presented. The results were verified on the basis of comparison with experimental results obtained for real and model pumps. The interesting way of estimating cavitation performance was presented. The pump characteristics before and after the modernisation were shown.

The paper features the results of the fluid flow calculation in the channels of varying geometry of the centrifugal pump for the service water in the methanol production chain. Modeling of the flow in ANSYS CFX allowed developing recommendations on adjusting the impeller's profile, significantly decrease the cavitation wear and increase the lifetime by several times.

A numerical experiment performed by ECM based on different mathematic models and algorithms permits to investigate and evaluate internal and external dynamics of centrifugal pumps being operated in regimes of a flow without separation and separation one around bodies with excessive degree of reliability. This paper researches simulation of the flow within a centrifugal pump impeller by the method of hydrodynamic features. Streamlines and vortex lines were developed. Their relative positions were studied. Friction losses and losses induced by vortex dissipation have been evaluated in dependence to a flow rate.

On the basis of similarity in vortex chamber superchargers criteria of similarity are defined and their check by numerical researches is made. Vortex chamber superchargers have the big power efficiency of pumping, in comparison with classical jet pumps, at the expense of association of advantages of centrifugal and jet pumps on the basis of the vortex chamber. The concept of vortex chamber superchargers is based on a new principle of energy transfer in jet superchargers at the expense of hydrodynamic effects of rotating flows use. In consequence of pressure decrease near to an axis of the vortex chamber occurs intaking particles of a pumped over flow. Having got to the vortex chamber, particles get tangential velocity interact with a rotating flow at the expense of a momentum exchange. The received criteria take into account of three major factors of similarity: the geometrical sizes, pressure of an active stream on an input in the device, working medium density. Validity of the received criteria is confirmed by a finding of pressure-flow rate characteristics of similar operating modes of a supercharger and their further combination on one characteristic.

The article represents the research results of a centrifugal inducer stage with inducer bush. We determined the optimal inducer bush design that would improve the cavitation erosion characteristics without deteriorating the energy levels and preserving overall dimensions of the centrifugal inducer stage at the same time.

Static and dynamic characteristics of flow in technical practice are very important and serious problem and can be solved by experimental measurement or mathematical modeling. Unsteady flow presents time changes of the flow and water hammer can be an example of this phenomenon. Water hammer is caused by rapid changes in the water flow by means the closure or opening of the control valve. The authors deal with by hydraulic hammer at the multiphase flow (water and air), its one-dimensional modeling (Matlab SimHydraulics) and modeling with the use of the finite volume method (Ansys Fluent) in article. The circuit elements are defined by static and dynamic characteristics. The results are verified with measurements. The article evaluates different approaches, their advantages, disadvantages and specifics in solving of water hammer.

The article is devoted to the description of the theoretical foundations of the work of a new type of vortex three-phase separators for hydrocarbon processing plants. The expediency of using vortex flows in the technology of three-phase separation to improve the reliability of pumping and compressor stations is substantiated. The principle of operation of separators with a variable cross-sectional area of the working space and an inter-ring drain of the liquid is presented. A theoretical description of the hydrodynamic conditions for the separation of multiphase flows is given. A scheme for the installation of hydrocarbon feedstock processing using a three-phase vortex separator is proposed.

The article presents the results of experimental and numerical tests of a surface heating flow control system consisting of a distribution rail along with the fixed valve. The components were measured, their solid models were prepared and used to make a flow model. In a flow model geometry the measurements of the test stand elements were considered in order to compare the results.

The paper concerns axial water turbine of power equal to 1 kW. The example of axial water turbine constructional calculations was provided, as well as turbine rotor construction with NACA profile blades. The laboratory test rig designed and built to perform measurements on pico turbine was described. The turbine drove three-phase electrical generator. On the basis of highest efficiency parameters, pico turbine basic characteristics were elaborated. The experimental research results indicated that pico turbine can achieve maximum efficiency close to the values of larger water turbines.

Classification of multi-functional heat generating aggregates according to the function is considered in this article. Analysis of operating process mathematical model was implemented and methods for its refinement were proposed. Results of physical investigation of heat generating aggregate design and mode parameters influence on its power and head were presented.

The article presents the results of computing investigations of various construction arrangements of the VS6 type pumps. Variants of hydraulic parts differing in geometric parameters have been compared. Experimental performance curves, measured during the full-scale pump tests, corroborate the investigation results for two constructions of hydraulic parts.

The article presents the results of investigation of the effect of geometrics of a double-volute outlet hydraulic passage on the magnitude and direction of acting of the radial reaction forces in a between-bearings single-stage centrifugal pump with a double entry impeller. The investigation has been performed with the use of a computing experiment. Characteristic curves as well as values and directions of the radial thrust have been compared for three variants of outlet hydraulic passages differing in the width at their entrance.

At present, work on the use of vortex expansion machines for utilization of the expander installations is being carried out to solve energy saving problems. Significant radial load on the rotor arises at high pressures in the single-flow vortex stages. This problem can be solved by switching to a multi-flow scheme. In this connection, the flow and radial loads on the rotor in single- and multi-flow flow parts of the vortex expansion machine with an external peripheral channel were studied. As the result of applying the theory of experimental planning and optimization studies in the ANSYS software complex, the geometric and gas dynamic parameters of the studied flow parts are determined from the point of view of the efficiency.

The possibility of adjusting of the jet-reactive turbine's head parameters through changing of mass-flow of the working body with the help of adjustable feed-in nozzle is examined. The mass-flow coefficient of the feed-in nozzle is determined experimentally.

The article summarizes the results of analysis of data concerning the operation of turbocompressor packages at compressor stations for the natural gas transmission system of Ukraine. The basic requirements for gas turbine compressor packages used for modernization and reconstruction of compressor stations are considered. Using a 16 MW gas turbine package GPA-C-16S/76-1,44M1 as an example, the results of pre-design studies and some technical solutions that improve the energy efficiency of gas turbine compressor packages and their reliability, as well as its environmental performance are given. In particular, the article deals with the matching of performance characteristics of a centrifugal compressor (hereinafter compressor) and gas turbine drive to reduce fuel gas consumption; as well as application of energy efficient technologies, in particular, exhaust gas heat recovery units and gas-oil heat exchangers in turbocompressor packages oil system; as well as reducing emissions of carbon monoxide into the atmosphere using a catalytic exhaust system. Described technical solutions can be used for development of other types of gas turbine compressor packages.

The present study provides the overview of Maisotsenko Cycle (M-Cycle) applications for gas cooling in compressor systems. Various schemes of gas cooling systems are considered regarding to their thermal efficiency and cooling capacity. Preliminary calculation of M-cycle HMX has been conducted. It is found that M-cycle HMX scheme allows to brake the limit of the ambient wet bulb temperature for evaporative cooling. It has demonstrated that a compact integrated heat and moisture exchange process can cool product fluid to the level below the ambient wet bulb temperature, even to the level of dew point temperature of the incoming air with substantially lower water and energy consumption requirements.

The article is devoted to the theoretical bases of multistage (multi-level) utilization modules as part of chemical plants (on the example of the technological line for obtaining nitrogen fertilizers). The possibility of recycling production waste (ammonia vapors, dust and substandard nitrogen fertilizers) using ejection devices and waste heat using Maisotsenko cycle technology (Maisotsenko heat and mass exchanger (HMX), Maisotsenko power cycles and recuperators, etc.) is substantiated. The principle of operation of studied recycling module and prospects for its implementation are presented. An improved technological scheme for obtaining granular fertilizers and granules with porous structure with multistage (multi-level) recycling module is proposed.

The new methods of vibration and inertial gas-dynamic separation of gas-condensate and dusty flows and the corresponding separation devices are proposed in order to avoid emergencies and premature wear of parts and components of the compressor equipment. The formation of the gas flow and disperse particles in the curvilinear convergent-divergent channels are investigated. The optimizing hydrodynamic profiling of a geometrical configuration of curvilinear separation channels with rigid and flexible walls of baffles is carried out.

The article provides groundings for cleaning the gas flows of major pipelines from soild particles in order to improve the compressor operation reliability. One obtained formulas for determination of the dust level in the vertical and horizontal sections of the pipelines supplying gas to the booster compressor stations. Ways of structural modernization of vertical pipeline sections using the inbuilt separation devices for more efficient removal of dust particles from the gas flow are described.

The article deals with the basic methods of machine parts recovery. Advantages and disadvantages of these methods had been widely spoken. The effect of these methods on the surface properties had been analysed. The main reasons of the wear of screw compressor parts are described in short. The authors paid attention to the evaluation of the applicability of existing renovation methods in technology of screw compressors repairing. In choosing the optimal method of renovation the surfaces of screw compressor parts are guided by the criteria of RAMS: reliability, availability, maintainability and safety. Also, it is specially noted about the evaluation of the effect of renovation methods on the screw surface layer by the following criteria: adhesion, ecological safety, cost, wear resistance, hardness, roughness, layer thickness, capacity, hogging, porousness, surface preparation, changes in the structure and physical properties of the base metal and ease of use. The most appropriate method for the renovation of parts of screw compressors had been proposed.

The article describes the principle of jet thermal compression with reference to vacuum systems. We consider liquid-vapor ejectors, the working process of which is based on this principle, as an alternative to existing steam jet ejectors. The results of a theoretical and experimental investigations of the liquid-vapor ejector of a vacuum unit are presented. With the help of thermodynamic analysis of exergetic efficiency, the range of operation of the liquid-vapor ejector and the vacuum unit on its base is determined, at which its performance is at the maximum level. The efficiency of vacuum creation by such units is estimated by the example of various pumped media, such as saturated, superheated steam and steam-air mixture.

In this paper the 5/3-way pneumatic, proportional flow valve was designed and made. Stepper linear actuator was used to move the spool. The valve is controlled by the controlled based on a AVR microcontroller. Virtual model of the valve was created in CAD. The real element was made based on a standard 5/3-way manually actuated valve with hand lever, which was dismounted and replaced by linear stepper motor. All the elements was mounted in a specially made housing. The controller consists of microcontroller Atmega16, integrated circuit L293D, display, two potentiometers, three LEDs and six buttons. Series of research was also conducted. Simulation research were performed using CFD by the Flow Simulation addition to SolidWorks. During the experiments the valve characteristics of flow and pressure was determined.

The new measurement method of compressed air leakage flow rate in compressed air pipeline is proposed. In this method, the automatic measuring device is connected to a branch of the pipeline. The measuring device can be used to measure compressed air leakage in any place of compressed air pipeline: in main line, distribution line and connection line. The proposed measurement methods of compressed air leakage in pipeline are independent of receiver and compressor parameters, which is not the case with traditional method measuring leaks by emptying the receiver.

The present paper concerns the metrological measurements of the geometric structure of the faces of seal rings made of silicon carbide and carbon-graphite. Three different instruments, i.e. the stylus profilometer, the optical profilometer, and the atomic force microscope, were used to measure the geometric structure of surfaces. In the comparative analysis, an identical area of the ring surface which was mapped by three measuring instruments with different sampling densities resulting from their metrological characteristics was assumed. The measurements made show that for the silicon carbide ring, the surface texture measurements on an atomic force microscope and optical instruments more accurately represent the actual topography than the measurement determined by the stylus profilometer.

The non-contacting gas face seals are used in high-performance devices where the main requirements are safety and reliability. Compliance with these requirements is made possible by careful research and analysis of physical processes related to, inter alia, fluid flow through the radial gap and ring oscillations susceptible to being housed in the enclosure under the influence of rotor kinematic forces. Elaborating and developing mathematical models describing these phenomena allows for more and more accurate analysis results. The paper presents results of studies on stationary ring oscillations made of different types of materials. The presented results of the research allow to determine which of the materials used causes the greatest amplitude of the vibration of the system fluid film-working rings.

The paper presents an refined calculation of impulse face seals with a self-regulated gap. Unlike the existing methods of calculation, wherein, for the sake of simplicity, influence of the feeder conductance is neglected, this article describes conductance effect on the operating characteristics of the seal. Static calculation method of a face impulse seal of the high-speed pump is presented.

When formulating models of dynamic face seals, two issues are of essential importance. The first concerns the determination of the forces formed in the medium film in the gap formed by the faces of two rings, while the second refers to the model of the flexible housing of one of the seal rings. The first issue includes the analysis of the medium flow through a narrow slit, taking thermal phenomena and deformations of slit-forming surfaces into account. The second issue concerns the modeling of properties of seal structural components, especially the modeling of elastic-damping properties of the flexible seal ring housing. This paper presents the results of simple relaxation tests of elastomeric rings and the procedure for analyzing these results and evaluating the elastic-damping properties of the rings tested. Finally, experimental results will be compared with theory.

A mathematical model of the work of the mechanical seal with smooth rings made from cast tungsten carbide in the condition of liquid friction is drawn up. A special feature of this model is the allowance for the thermal expansion of a liquid in the gap between the rings; this effect acting in the conjunction with the frictional forces creates additional pressure and lift which in its turn depends on the width of the gap and the speed of sliding. The developed model displays the processes of separation, transportation and heat removal in the compaction elements and also the resistance to axial movement of the ring arising in the gap caused by the pumping effect and the friction in the flowing liquid; the inertia of this fluid is taken into account by the mass reduction method. The linearization of the model is performed and the dynamic characteristics of the transient processes and the forced oscillations of the device are obtained. The conditions imposed on the parameters of the mechanical seal are formulated to provide a regime of the liquid friction, which minimizes the wear.

Elastomeric plastics belong to a wide range of polymeric materials with special properties. They are used as construction material for seals and other components in many branches of industry and, in particular, in the biomedical industry, mechatronics, electronics and chemical equipment. The micromachining of surfaces of these materials can be used to build micro-flow, insulating, dispensing systems and chemical and biological reactors. The paper presents results of research on the effects of micro-machining of selected elastomeric plastics using a UV laser emitting picosecond pulses. The authors see the prospective application of the developed technology in the sealing technique in particular to shaping the sealing pieces co-operating with the surface of the element. The result of the study is meant to show parameters of the UV laser's performance when producing typical components such as grooves, recesses for optimum ablation in terms of quality and productivity.

In this paper are presented the recommendations for material's selections of the mechanical seals rings and basic productive and operating requirements. The system of a directional selection of technology that ensures the required quality of working surfaces of the mechanical seals rings covers their entire life cycle. The mathematical frictional model is proposed as an instrument for calculating a linear and weighing abrasion of the mechanical seals rings and helps to improve selection's criteria and the most rational method of strengthening.

The reliability of the magnetic fluid seals operation is reduced to an assessment of the quality control of a magnetic fluid associated with its stability in the working gap of the seal in many cases. The previously developed relatively simple method for express analysis of the quality of a magnetic fluid is supplemented by studying the dependence of the dynamic characteristics of a nanofluid on the size of magnetite particles. This method can be easily implemented in an industrial enterprise using devices with a magnetic fluid.

The resource of stuffing box seal is determined not only by the unit design and by the conditions of its operation, but also essentially depends on the correct choice of stuffing box packing. Not one of stuffing box packing manufacturers does not provide data on mechanical properties. Therefore, in this paper the results of experimental investigations on determining the mechanical properties of packings are presented. The obtaining mechanical characteristics allow to clarify existing methods of calculation and to increase sealing and durability of stuffing box packing seals.

This article shows the prediction method of conditions of flange joints depressurization during the assembly of pipelines using technological and standard fasteners.

The paper considers the procedure of constructing curves of dynamic equilibrium and problems of applicability of the procedure of linearization of lubricant film reactions around the equilibrium point for conical fluid-film bearings.

We consider the mathematical model of stabilization of the situation of a rotor is given in an active magnetic bearing. Also various options of control system are considered Investigated influence of the program movement and free controller parameters on quality of control process.

The article describes the perspectives of using active bearings in rotor-bearing systems. The principal scheme of a mechatronic tribotechnical system anв classification of actuators used in such system are shown. Piezo actuators are considered from the point of view of use as actuators in active bearings. The comparative characteristics of different types of actuators

The influence of the parameters of micro- and macrounevenness on the characteristics of a hybrid bearing with slotted throttling is considered in the present paper. The quantitative assumptions of calculation of pressure distribution, load capacity, lubricant flow rate and power loss due to friction in a radial hybrid bearing with slotted throttling are taken into account, considering the shape, dimensions and roughness of the support surfaces inaccuracies. Numerical simulation of processes in the lubricating layer is based on the finite-difference solution of the Reynolds equation using an uneven orthogonal computational grid with adaptive condensation. The results of computational and physical experiments are presented.

The present paper considers simulation of a rotor's dynamics behaviour on thrust foil gas dynamic bearings based on simultaneous solution of gas dynamics differential equations, equations of theory of elasticity, motion equations and some additional equations. A double-mass dynamic system was considered during the rotor's motion simulation which allows not only evaluation of rotor's dynamic behaviour, but also to evaluate the influence of operational and load parameters on the dynamics of the rotor-bearing system.

The present paper considers application of bi-metal materials and coatings to provide necessary strength and wear resistance of the surfaces of rigid and elastic gas dynamic bearings. Authors suggest using multi-layer foils with bimorph piezoelectric elements that operate in the generator regime to determine the deformation of elastic elements, and in the actuator regime to form an optimal shape of the surface of the bearing.

The main purpose of this paper is to define a methodology to determine the analytical approximate closed-form expression of probabilistic characteristics of load capacity of liquid-lubricated journal bearings in the case of a steady flow regime. Influence of random change of basic geometrical parameters of journal bearings (gap value and eccentricity) on the load capacity of bearing is considered. It is shown that the actual value of hydrodynamic force in bearing can substantially differ from a calculation one. The got results confirm the necessity of application of such approach at consideration both geometrical and operating parameters of bearing, for example, axes misalignment, deviation of surface form, roughness and others, which have casual nature too.

There is described a method for strengthening surfaces of heat-treated steel parts, which includes technological procedures of carburizing by electroerosive alloying process (CEEA) and also nitriding processes. The nitriding process is simultaneously carried out with the CEEA operation for a period of time sufficient to saturate the surface layer of a part with nitrogen to the depth of a heat-affected zone. Thus, the process of so-cold nitro-carburizing process performed by the EEL method (NCEEA) takes place. To reduce a surface roughness, the NCEEA process is carried out in at least two stages, with a decreasing a discharge energy value at each subsequent stage.

A new method for sulphiding steel and cast iron part surfaces by electroerosion alloying (EEA) with the use of a special electrode is proposed, which method is characterized in that while manufacturing the electrode, on its surface, in any known manner (punching, threading, pulling, etc.), there is formed at least a recess to be filled with sulfur as a consistent material, and then there is produced EEA by the obtained electrode without waiting for the consistent material to become dried.

There have been proposed new technical solutions including operations of applying coatings onto worn surfaces of steel and cast iron parts by electro-erosive alloying method (EEA). In this case, the EEA coatings are applied in two stages. At the first stage, there is applied a layer on the conditions providing the greatest thickness and continuity of the surfaces obtained. At the second stage, the operation is performed by the same electrode and on the conditions of the discharge energy and productivity corresponding thereto, which provide for the formation of the surface having a roughness value being about 2-4 times higher than that at the previous stage. At least one layer of a metal polymer material (MPM) is applied on the surface formed by the above said EEA method, with this layer having been reinforced by at least one wire reinforcement layer before polymerization.

There are represented the results of influence of the surface plastic deformation (SPD) methods, namely, diamond smoothing (DS) and ball-rolling surface roughness generation (BSRG) ones on the qualitative parameters (residual stresses, fatigue strength and wear resistance values) of the steel substrate surface layers formed by the electroerosive alloying (EEA) method. There are proposed the most rational methods of deformation and also the composition for electroerosive coatings providing the presence of the favorable residual compressive stresses in the surface layer, increasing fatigue strength and wear resistance values. There are stated the criteria for estimating the alternative variants of the combined technologies and choosing the most rational ones thereof.

Calculation of flexible coupling torsional stiffness is required when analyzing the torsional vibrations of the reciprocating machinery train. While having the lowest torsional stiffness of all the elements of the train, flexible coupling has a significant influence on the natural frequencies of torsional vibration. However, considering structural complexity of coupling, precise definition of its torsional stiffness is quite a difficult task. The paper presents a method for calculating the torsional stiffness of flexible disc coupling based on the study of its finite element model response under the action of torque. The analysis of the basic parameters that quantitatively and qualitatively affect the coupling torsional stiffness has been also provided. The results of the calculation as well as model adequacy, sufficient for practical application, have been confirmed at the experimental measurement of flexible disc coupling torsional stiffness. The obtained elastic characteristics (dependences of applied torque and torsional stiffness versus twist angle) are nonlinear in the initial stage of loading. This feature should be taken into account when creating reliable mathematical models of torsional vibrations of reciprocating machinery trains containing flexible disc couplings.

This research paper is aimed to investigating rotor dynamics of multistage centrifugal machines with ball bearings by using the computer programs "Critical frequencies of the rotor" and "Forced oscillations of the rotor," which are implemented the mathematical model based on the use of beam finite elements. Free and forces oscillations of the rotor for the multistage centrifugal oil pump NPS 200-700 are observed by taking into account the analytical dependence of bearing stiffness on rotor speed, which is previously defined on the basis of results' approximation for the numerical simulation in ANSYS by applying 3D finite elements. The calculations found that characteristic and constrained oscillations of rotor and corresponded to them forms of vibrations, as well as the form of constrained oscillation on the actual frequency for acceptable residual unbalance are determined.

The article deals with the effect of a bearing housing on rotor dynamics of a barrel casing centrifugal boiler feed pump rotor. The calculation of the rotor model including the bearing housing has been performed by the method of initial parameters. The calculation of a rotor solid model including the bearing housing has been performed by the finite element method. Results of both calculations highlight the need to add bearing housings into dynamic analyses of the pump rotor. The calculation performed by modern software packages is more a time-taking process, at the same time it is a preferred one due to a graphic editor that is employed for creating a numerical model. When it is necessary to view many variants of design parameters, programs for beam modeling should be used.

The article describes the elements of the theory of dynamic analysis of rotor systems. The mathematical model of a gyroscopic rotor as an elementary object on elastic-damping supports. The results of simulation of the trajectories of the rotor under kinematic loading with amplitude commensurate with the clearance in bearing assemblies of fluid friction.

The article presents static calculation of an automatic machine for unloading of rotor axial forces in a high-pressure and high-speed pump. Analysis of the rotor displacement influence to values of mass flow rate and pressure in the unloading chamber of the unloading system is given. The main geometric parameters of the system are obtained.

The article presents forced axial vibrations of the rotor with an automatic unloading machine in an oxidizer pump. A feature of the design is the use in the autoloading system of slotted throttles with mutually inverse throttling. Their conductivity is determined by a numerical experiment in the ANSYS CFX software package.

This article investigated the factors, which affect to the character of the head pulsations of a centrifugal pump. We investigated the dependence of the shape and depth of these pulsations from the operation mode of the pump. Was determined, that the head pulsations at the outlet of the impeller (pulsations on the blade passing frequency) cause head pulsations at the outlet of the pump, that have the same frequency, but differ in shape and depth. These pulsations depend on the design features of the flow-through part of the pump (from the ratio of hydraulic losses on the friction and losses on the vortex formation). A feature of the researches that were conducted is also the using of not only hydraulic but also electric modeling methods. It allows determining the values of the components of hydraulic losses.