CC BY
7Staryi Andrew Romanovich
graduate student of the Department of Mechanical Engineering Technology Khmelnytskyi National University Hordeev Anatoly Ivanovich
doctor of technical sciences, professor, professor of the Department of Mechanical Engineering Technology Khmelnytskyi National University
RESEARCH OF THE IMPACT ON PRODUCTIVITY OF PARAMETERS AND OPERATING MODES OF THE VIBRATION MACHINE DRIVE FOR CLEANING AND WASHING CONTAMINATIONS BY SUBMERGTD STREAM JET WITH SOLID PARTICLES
Старый Андрей Романович
аспирант кафедры технологии машиностроения Хмельницкого национального университета Гордеев Анатолий Иванович
доктор технических наук, профессор, профессор кафедры технологии машиностроения Хмельницкого национального университета
ИССЛЕДОВАНИЕ ВЛИЯНИЯ НА ПРОИЗВОДИТЕЛЬНОСТЬ ПАРАМЕТРОВ И РЕЖИМОВ РАБОТЫ ПРИВОДА ВИБРАЦИОННОЙ МАШИНЫ ДЛЯ ОЧИСТКИ И МОЙКИ ЗАГРЯЗНЕНИЙ ЗАТОПЛЕННОЙ СТРУЕЙ С ТВЕРДЫМИ ЧАСТИЦАМИ
DOI: 10.31618/ESSA.2782-1994.2021.1.68.13
Summary. Analyzed the methods of cleaning and washing, the design of machines with a vibration drive. The choice of a specific method of cleaning and washing is determined depending on the type and properties of contaminants, on the requirements for the cleanliness of products, and the type of production. The scheme of operation of a vibrating machine for cleaning and washing machine parts in a pulsating flow of liquid with solid particles is considered and parameters that affect its performance are determined. The results of studies of physical phenomena during the formation of a pulsating submerged jet are presented, and the influence of design parameters and modes of the drive robots on the maximum jet pressure is determined. An analytical dependence of the maximum instantaneous pressure of the jet has been obtained experimentally, which makes it possible to determine the optimal ratios of parameters when designing a vibration machine for cleaning and washing contaminants.
Аннотация. Проанализированы способы чистки и мойки, конструкции машин с вибрационным приводом. Выбор конкретного способа очистки и мойки определяется в зависимости от вида и свойств загрязнений, от требований, предъявляемых по чистоте изделий, типа производства. Рассмотрено схему работы вибрационной машины для очистки и мойки деталей машин в пульсирующем потоке жидкости с твердыми частицами и определены параметры, которые влияют на её производительность. Приведено результаты исследований физических явлений при формировании пульсирующей затопленной струи и определено влияние на максимальное давление струи конструктивных параметров, режимов роботы привода. Экспериментально получена аналитическая зависимость максимального мгновенного давления струи, которая дает возможность определять оптимальные соотношения параметров при проектировании вибрационной машины для очистки и мойки загрязнений.
Key words: cleaning, washing of contaminants, vibration machine, dynamic parameters of the process and machine.
Ключевые слова: очистка, мойка загрязнений, вибрационная машина, динамические параметры процесса и машины.
Formulation of the problem. On the surface of parts and assemblies in the process of their manufacture, operation of machinery and equipment, technological and industrial contaminants are formed. Qualitative cleaning of objects from pollution is achieved by a complex physico-chemical and mechanical impact on it, the first - is provided by the use of chemicals that affect pollution, the second - the use of mechanical energy of pollution (scrapers, brushes, liquid jets, abrasive jets). The emergence of new technological processes for the manufacture of parts, new requirements for the quality of repair of
various objects of technology leads to the search for new technologies and methods and the creation of new designs of jet-type installations for washing and washing parts, especially in small and single production types and equipment repair.
Analysis of recent research and publications. Qualitative cleaning of objects is achieved due to the complex interaction of physico-chemical and mechanical effects of the washing jet on pollution. Physico-chemical factor is provided by the use of heated detergents, which is associated with significant material costs for the acquisition and heating of these
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solutions with their adverse effects on the environment. Therefore, the development of technology to improve the quality of repair and maintenance of equipment, from the surface of parts and components must remove not only weakly and moderately bound contaminants (road dirt, oil and mud deposits, etc.), but also tightly bound (corrosion destruction products, old paintwork, etc.), which occupy about 10% of the total surface area of objects and have the greatest complexity of removal.
Improving the efficiency of cleaning and washing plants is achieved by increasing the mechanical action of the jet on pollution. The most promising and widespread of the existing technologies for cleaning and washing facilities are technologies using high-pressure water jets [1-4]. Recently, the increase in the efficiency of cleaning machines using jet cleaning technologies is achieved by increasing the kinetic energy of the jet by increasing the supply pressure of the washing liquid or adding abrasive material to it. As an increase in the mechanical factor, the use of abrasive is used, both separately (dry jets) and together with the cleaning solution (water-sandblasting) or increasing the pressure of the washing jet [5].
As a result of theoretical and experimental studies [5] it was found that hydroabrasive wear, which is similar in nature to the process of cleaning and washing, occurs under the impact of solid particles on the body surface. Depending on the properties of materials and the angle of attack of abrasive particles, wear can have the nature of brittle fracture (wear of silicate glass), micro-recognition (wear of copper), plastic extrusion, the emergence and growth of microcracks. The intensity of wear depends on the angle of attack [5], flow rate, concentration, size, hardness of abrasive particles, the ratio of surface hardness of the material and abrasive particles. As the angle of attack decreases, the magnitude of the shock pulse decreases, and the probability of microcutting the surface (contamination) increases. In order to clean a specific contaminant, it is necessary to develop cleaning and washing technologies that break down the contaminant under the action of additional stresses created in the flow of detergent by abrasive or polymer crumb particles. Known methods and designs of machines and devices with a vibrating drive for cleaning and washing parts and components for various contaminants that occur during the manufacture or repair of equipment and machinery [6,7]. As a result of analytical studies [6] it was found that the performance of the pulsating jet cleaning process is affected by the following parameters: velocity or pressure of the jet, mass of polymer crumb particles, frequency and amplitude of oscillations of the drive, ratio of pulsation chamber diameters and nozzle to the axis of the jet.
The purpose of the article. The aim of the work is to study the influence of drive modes and design parameters of the vibrating machine for cleaning and washing, using flooded pulsating jets of liquid with solid particles, to achieve optimal performance conditions of the cleaning and washing process. The
East European Scientific Journal #4(68), 2021 47 need to create special installations for the operation of cleaning and washing machine parts during repairs in small-scale production is an urgent scientific and technical task.
Selection of previously unsolved parts of the overall problem. Determining the optimal parameters of the drive of vibrating equipment with a pulsating working fluid based on a hydropulsator (GP) is constrained by the lack of experimental research in this area. This determines the relevance of the work.
Presenting main material. The modes of cleaning and washing the surface of the part by the flow of detergent (optimal technology) is determined based on the analysis of the hydrodynamic interaction of the detergent with particles with existing contamination on the parts, as well as on the analysis of experimental studies. Let's consider the mechanism of removal of pollution by the immersed pulsating stream of washing liquid with inclusions of firm particles. Without underestimating the importance of physicochemical factors due to the activity of the detergent medium, it is believed that the process of mechanical action of the liquid on the contamination is one of the main conditions that determines the efficiency of cleaning and washing. The process of cleaning and washing the surface of the product by the flow of liquid with solid particles can be divided into the following interconnected, elementary processes: the formation of a pulsating jet of liquid with solid particles, supply of liquid flow to the surface to be cleaned, separation of contaminants and their washing from the surface to be cleaned, the contaminants hang in the liquid stream, the contaminants are transported to the filter device. It is established [8,9] that turbulent pulsating flow of liquid with particles has more significant friction forces when spreading on the surface with contamination and the possible process of microcutting its solid particles and the main factor influencing the productivity of the process is the velocity of liquid flow capturing particles.
Pulsating jets of liquid are formed in the membrane GP (Fig.1), which works as follows: when the rod 4 with the membrane 3 down in the chamber 2 creates a vacuum and the liquid is drawn into the chamber through the nozzles 1. During the rod 4 and the membrane 3 up liquid and it is pushed under pressure through the nozzles 1 from the chamber 2. This produces a pulsating jet of liquid from the nozzle with a high degree of turbulence. It is established that when the liquid is drawn into the pulsation chamber through the nozzles at certain modes of fluid flow into the nozzle, an annular isolated cavity filled with gas is formed. When the annular insulated cavity is destroyed, dissolved air begins to be released from the liquid in the form of gas bubbles, which enter the pulsation chamber, which reduces the volume of liquid, which is then pushed through the nozzles and they act as a damper when compressing liquid in the pulsation chamber.
Fig. 1. The design of the membrane hydropulsator: 1 - nozzles; 2 - pulsation chamber;
3 - membrane; 4 - stock
Figure 2 shows a diagram of a vibrating machine for cleaning and washing machine parts in a pulsating flow of liquid with solid particles [10]. It consists of a bath 1 in which at the bottom is a pulsation chamber 2, which is connected by a rod with a vibrating actuator 4. It has a box 7 for collecting solid particles 11 with a grid 6 below the nozzle and on the side surfaces 9 for spreading fluid flow. In the box 7 above the grid 6 to which the jet is directed from the nozzle 5 is installed a nozzle 8 with a gap for solid particles on the grid 6, which are filled into the box 7. The vibrating machine works as follows. The part 12 to be cleaned is located on the nozzle 8 with a gap H (larger than the maximum size of the solid particle). The vibratory drive of the machine 4 is switched on. Due to the oscillations of the
diaphragm with disks 3 in the pulsation chamber 2 the fluid is alternately compressed when it moves upwards - a jet from the nozzle 5 appears, and when it flows down the liquid discharge - it is drawn through the nozzles 5 into the pulsation chamber. The jet from the nozzle 5 passes through the grid 6 and ejects the solid particles 11 and through the nozzle 8, the flow of the mixture strikes the surface12 to be cleaned. Solid particles 11, after interaction with the surface12, the liquid is thrown on the walls of the box7 and falls to its bottom. When the membrane with discs 3 moves downward, a liquid flow occurs, which draws solid particles 11 onto the mesh 6 under the nozzle 8. Then the cycle is repeated.
H
Fig.2. Scheme of operation of the vibrating machine for cleaning and washing of machine parts in a pulsating flow of liquid with solid particles: 1 - bath body; 2 - pulsation chamber; 3 - membrane with disks; 4 - vibratory drive; 5 - nozzles; 6 - grid; 7 - box for collecting solid particles; 8 -nozzle; 9 - grid; 10 - washing liquid; 11 - solid particles; 12 - the surface to be cleaned; H is the distance from the nozzle to the surface to be cleaned; dn - diameter of the nozzle; Dk is the diameter of the pulsation chamber; f is the oscillation frequency of the vibratory drive; And - the amplitude of vibrations of the vibratory drive
To determine the dynamic characteristics of the drive of the vibrating machine for washing and cleaning contaminants, an experimental setup was made to determine the visual process of forming a pulsating
fluid flow (Fig.3) and an experimental setup to determine the influence of drive modes and design parameters on the maximum pressure of the pulsating flooded fluid jet. (Fig.4).
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ItigSB
Fig.3. Installation of visualization of the formation of a pulsating jet offluid: 1 - vibrating drive: 2 - pulsation chamber;
3 - transparent nozzles; 4 - capacity for damping fluid oscillations
Installation for studying the value of the maximum pressure of the pulsating jet from the nozzle (Fig.4) consists of a frame on which is mounted an eccentric vibrating actuator driven by a DC motor. The change in the amplitude of oscillations occurs when changing the cams with an eccentricity of 0,5; 1,0; 2,0 mm. Changing the frequency from 0 Hz to 30 Hz is done by changing the voltage on the transformer of the control panel. The vibrating actuator is connected to the pulsation chamber by means of a rod. A bathtub with transparent walls for visual observations is fixed on the racks. A screw pair with a step of 0,75 mm is installed on the racks in the supports. In the case of a nut the rail transfer directed on an axis of movement of a stream is mounted. These means allow a fixed movement of the pressure sensor, which is fixed by means of a thread on the rail. The reciprocating movement of the liquid through the nozzles and the movement of the liquid in the pulsation chamber on the installation of Fig.3 was recorded by a digital video camera with further processing and conversion of information into a computer file.
As a result of researches of visualization of process of formation of a pulsating flooded stream the following results are received. With reciprocating oscillations of the membrane in the pulsation chamber
o
Fig.4. Installation for research of size ofpressure of a stream from a nozzle: 1- the vibrating drive: 2 -capacity for liquid; 3 - nozzles; 4 - pressure sensor; 5 - the control panel of frequency of fluctuations
of the vibrating machine, the following physical processes occur: when the membrane moves down in the pulsation chamber, the pressure drops below atmospheric and through the nozzles the liquid is drawn into the pulsation chamber at a rate depending on the membrane oscillation. At the entrance to the nozzles, the water current lines are distorted, and there is a narrowing of the flow (Fig.5,a, Fig.5,b). Simultaneously with the increase (frequency of oscillations) of the velocity through the nozzles there is a cavitation cavity at the entrance to the nozzles, which is filled with bubbles of gas dissolved in the liquid, which then break out of the cavitation cavity and enter the pulsation chamber (Fig.5, b). However, at significant speeds (oscillation frequencies) of liquid entrainment in the pulsation chamber, there is an avalanche increase in the volume of gas bubbles in the nozzle, resulting in a large gas bubble in the pulsation chamber and a smaller volume of water enters the pulsation chamber (Fig.5,c). As the membrane moves upward in the pulsation chamber, the pressure rises above atmospheric and the gas bubbles flatten, reducing the volume of liquid passing through the nozzles, which reduces the maximum speed and pressure force of the nozzle jet.
abc
Fig.5. The results of the visualization ofphysical processes during the reciprocating motion of the fluid through the nozzles in the pulsation chamber of the vibrating machine when changing the oscillation frequency of the drive: a - oscillation frequency 12 Hz; b - oscillation frequency 16 Hz;
c - oscillation frequency 22 Hz
It is established [11] that the productivity of the cleaning and washing process in the vibrating machine is determined by the formula:
Q =
(1)
Vt=An-f,
(2)
where A - is the amplitude of fluid oscillations in the pulsation chamber; f - frequency of fluid oscillations in the pulsation chamber; e- coefficient of narrowing of the flow into the nozzle; DK- the diameter of the pulsation chamber; dn - diameter of a nozzle; Dc -nozzle diameter; a - the angle of unilateral expansion of the jet from the nozzle, a = 120 40/; k0- the number of crumb particles involved in the processing; m -particle mass; H - the distance from the jet nozzle to the surface to be treated; kc - coefficient that takes into account the quenching of the jet velocity from the nozzle during the passage of the grid, k = 0,9.
From the analysis of dependence (1) it can be concluded that to increase the productivity of the cleaning process, the following parameters affect: the optimal ratio of particles in the jet at the smallest distance from the nozzle to the surface to be cleaned, reducing cutting stresses. But the main factor that affects the productivity of the process is the speed of
D2-A-f
the particle V = K 2 , which is captured and moves
£ ■ an
with the jet of liquid and has in formula (1) the third degree and its small change leads to a significant increase in productivity.
To measure the parameters of the pulsating jet from the nozzle, it is technically convenient to move from determining the value of the pulsating jet velocity to measuring the maximum pressure of the pulsating jet at its initial section at the exit of the nozzle. The pulsating jet of liquid from the nozzle is formed due to the oscillations of the vibrating drive of the machine, so the theoretical speed Vt of the liquid in the nozzle is determined by:
where An - the amplitude of oscillations of the liquid in the nozzle;
f - frequency of oscillations of the drive. Taking into account the reduction of speed in the nozzle due to the narrowing of the flow (local resistance), we can write the following dependence:
v = t-vt,
(3)
where V - jet speed taking into account local resistances; ^ - coefficient of local resistance ^ = 0,5;
Vt - theoretical speed.
In [9], the influence of the frequency of oscillations of the drive on the value of the maximum speed of the pulsating jet from the nozzle without taking into account the effect of hydraulic shock and the appearance of the gas phase in the pulsation chamber was obtained analytically. The obtained values, the values of the maximum jet velocity, can be converted into the maximum fluid pressure at the outlet of the nozzle at the initial section by the formula:
p = pH
2 '
(4)
where p - is the density of water, p = 1000kg/m3.
The search for the optimal operating modes of the drive of the vibrating machine was carried out experimentally on the installation (Fig.4) by measuring the sensor change the maximum pressure of the jet from the nozzle for the oscillation cycle of the drive. A pre-calibrated membrane strain gauge was used, which was mounted above the nozzle at a distance of 10 mm in the initial section of the flooded pulsating jet. To measure the instantaneous value of the hydrodynamic pressure of the fluid from the nozzle, a USB oscilloscope BM8020 is used, which is connected to a personal
3
computer via a USB port and is served by the software product «DiSco». In the experimental study, the change of the jet pressure in the form of oscillograms was recorded and during their processing the maximum pressure of the pulsating jet was determined under the following conditions: liquid temperature 200, amplitude of membrane oscillations A = 0.002 m; the diameter of the pulsation chamber Dk = 0.1 m, the diameter of the
nozzle dn = 0,01 m, the oscillation frequency f of the drive of the vibrating machine varied from 0 to 25 Hz.
After processing the obtained oscillograms on the grid of the pressure versus frequency graph obtained analytically (Fig.6, curve 1) [11], a graph of the change in the maximum pressure of the liquid jet from the nozzle was plotted (Fig.6).
PMPa
0,18 0,09 0M5
0.0225
/ A=0,002m; dH=0,01m: Dk=0, 1m, H=0,01m
/
5 10 15 20 25 30 f, Hz
Fig.6. Graphs of the maximum pressure of the pulsating jet of liquid from the nozzle on the oscillation frequency of the drive: 1 - analytical curve; 2 - experimental curve; A - amplitude of oscillations; Dk - diameter of the chamber; dh - diameter of the nozzle; H - is the distance from the cut nozzle to the sensor
In search experiments, it was found that the dependence of the maximum pressure of the pulsating liquid jet in the initial section (Fig.6, curve 2) on the frequency of the drive oscillations has the following curve change: in the initial section from 5 to 8 Hz, the maximum fluid pressure coincides with the analytical one, but with an increase in the frequency of oscillations of the drive in the range from 8 to 13 Hz, the value of the maximum pressure of the liquid jet increases due to the phenomenon of water hammer; with an increase in the frequency of oscillations of the drive in the range from 13 to 20 Hz, the value of the maximum pressure of the jet liquid decreases due to the appearance of a significant number of gas bubbles in the pulsation chamber.
The maximum fluid pressure of the jet from the nozzle is in the range of frequencies from 11 to 13 Hz, so the pulsating jet of fluid from the nozzle has a
maximum speed within these limits. To establish the optimal ratios of the design parameters of the pulsation chamber and the size of the nozzle depending on the modes of operation of the drive, a three-factor experiment of the central composite rotatable planning of the second order was carried out. For research, pulsation chambers measuring 60,120,180 mm with a 10 mm nozzle were made.
To establish the value of the maximum instantaneous pressure from the nozzle, the main variables that influenced the value of this parameter were determined: x1 - the ratio of the diameter of the pulsation chamber to the diameter of the nozzle (DK/dn), dH = 10mm; x2 - the oscillation frequency of the drive; x3- amplitude of oscillations of the drive. As a result of the experiments, the regression dependence was obtained as follows:
y = 0,2728 + 0,067x1 + 0,0091x2 - 0,052x3 - 0,01B6x1x2 - 0,0756x^3 -
-0,0339x12 - 0,00225*1 - 0,0203x|. (5)
After recoding and conversion of variables into natural values, the following regression dependence of the maximum instantaneous pressure of the pulsating fluid jet on the design parameters and modes of operation of the drive:
Pmax - 0,0000096D2 - 0,002/2 - 0,02642 (6)
Using the software product MatchCad, calculations were performed according to equation (6) and graphs of the dependence of the maximum instantaneous pressure of the liquid jet Pmax on the oscillation frequency and amplitude of oscillations Fig.7 and cross section of the response surface of the maximum instantaneous pressure Fig. 8.
a, mm
Fig. 7. Response surface of the dependence of the maximum instantaneous pressure of the liquid jet from the nozzle on the frequency and amplitude of oscillations for the pulsation chamber D = 100 mm
Conclusions
The analysis of the dependence of the productivity of the process of removing contamination from the surface of the part revealed the influence of various physical parameters of the vibrating machine on its performance, namely: the optimal ratio of particles in the jet at the smallest distance from the nozzle to the surface to be cleaned. with particles, which depends on the design parameters and modes of operation of the drive of the vibrating machine. It is experimentally established that the maximum pressure of the pulsating jet of liquid and the maximum productivity of the machine for cleaning and washing is achieved with the following design parameters: the ratio of the diameter of the pulsation chamber to the diameter of the nozzle 10mm; oscillation amplitude A = 2 mm and oscillation frequency of the drive from 11 to 13 Hz.
The obtained regression dependence (6) of the maximum instantaneous jet pressure on the design parameters and modes of operation of the drive and its graphical interpretation makes it possible to find the optimal ratios of frequency and amplitude of the drive for certain sizes of the pulsation chamber in the design. solid particles.
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