The WORKING PReSSuRe ReSeARCh OF PISTON PuMP RN-3.8

The research of working pressure of one-piston pump with a combined compensator of pressure pulsations during the operating cycle is carried out. One of the basic gas law in an isothermal process, namely the law of Boyle-Marriott is employed. The law of piston motion which is driven from the crank-connecting rod mechanism (the axis of the crank shaft is made offset downwards relative to the axis of the piston to reduce the magnitude of lateral forces) is used. The piston drive crank rotation angle, the primary pressure in the compensator are taken into account. The research is needed to ensure a stable high-pressure feed of medium (solution) pumped by the pump, with a reduced level of pulsation. The quantitative dependences of the solution volume in the compensator on the piston movement, the solution feed pressure relative to the crank shaft rotation angle, the minimum required amount of total given volume of combined compensator air (it is 0.02m 3 ) are defined. Practical significance of the obtained results of the research is to develop a piston pump design. It provides a stable feed pressure, moderate pulsation level of the solution, which is pumped.


introduction
The mortar pumps were used for transportation of building mortar mixes directly to jobs in the initial phase of implementation.The surface treatments of buildings and structures were performed manually in the next step.The mortar solutions have been of large mobility at the same time.They were fed with significant pulsation (pressure fluctuations), which had no impact on the technology, because there was only filling in the working tanks.There is a gradual transition from manual application of mortar solutions on the buil dings and structures working sur faces to mechanized.Labour productivity increased several times.The nozzles are used in mechanized application.They have mouth pieces that are located at the end of the pressure pipeline.Pulsation affects the quality of performed work.Its impact has become the dominant factor that hindered the development of treatment processes by a nozzle.
Methods of finishing external and internal surfaces of buildings and structures with panels of different materials are in widespread use nowadays.But the process of plas tering is still relevant until now.It has a relatively low cost and satisfactory quality.
Also, the mortar pumps can be used for the feed and laying of cement-sand mixtures when performing a self-levelling floor screed, filling under pressure a hard mortar for joints and seams between concrete structures for grouting and also for pumping of whitewashing compounds with a large scope of work.
Piston pumps have found application not only in construction but also in mining, oil, gas, petrochemical and other industries where all the main processes are connected with pumping of sand-clay mortar, oil, petroleum products, liquefied gases, water, chemicals, construction-soluble compounds, etc. by pipelines [1][2][3].They are simple and reliable.
The problem of ways searching to reduce the feed pulsation magnitude of mortar pumps is still relevant.

literature review and problem statement
Piston pumps remain the most common currently.They have a direct impact of the working body (piston) on the working environment.
The authors [4] made a review of modern equipment designs.It is used for transportation and preparation of building mortars on the basis of pumping equipment of various designs.The piston pump is characterized by simplicity of design, ease of maintenance and repair even in field conditions.
The complex of requirements for mortar pumps design for the modern mechanized technology of surface plastering is noted in [5].Properties of the pumped mortar have been summarized.Attention is paid to the issue of equipment reliability.The requirements were written for pumps modern designs generally.Their advantages and disadvantages are noted.The essence of the problem of the feed pressure pulsation is disclosed.One of the problems is its stability when piston pumps are used.But ways of its reduction or elimination are not proposed.
The author of the work [6] writes, that the mortar feed pressure pulsation in the pressure pipe is certainly a harmful factor.This factor degrades the technical-economic indicators of the work of the grouting pump by increasing resistance to movement of mixtures through pipelines, and increases back bounces off the surfaces that are processed if you perform nozzle processing.The registration method of indicators of mortar mixture pressure and displacement of the working mortar body on a PC at the same time has been described in the work.It will give the opportunity to compare the pressure recorded on different sections of the pressure line or pump chambers at a specific point in the operating cycle.Unfortunately, the specific ways of pulsation reducing are also not suggested.
The pumping workflows have been investigated in [7].The authors suggested laboratory load test.It is designed to test pumps.Its advantages and disadvantages were described.The feed uniformity is one of important characteristics during the working cycle.The main theme of this publication is to study the issue of energy consumption, volumetric efficiency and reverse leakage of mortar mix through the valve nodes.The work has not paid enough attention to the problem of feed pulsation.
Study of pumping equipment progressive structure is given in [8].Its effectiveness is proven.But the design complexity plays a main role during decision making about the use of equipment of this type in the field conditions.
Study of a new, progressive pump with elastic pipeline was performed in the publication [9].The pump has no valves and seals.The design is complex.Its scope is severely limited.
The designs of one-piston mortar pump RN-3.8 with a combined pressure pulsations compensator are presented in [10].It is a partial solution to the problem of ensuring feed stability.Piston pump RN-3.8 with a combined pressure pulsations compensator (Fig. 1) has undergone a long production test.It was used both separately and as part of the universal mobile mortar-mixer URZ-3.8 (Fig. 2, 3) [10].
Graphic dependence has been obtained during a series of theoretical and experimental studies.They show the influence of feed pressure of the sandy-clay solution on the degree of pressure pulsation of one-piston pump when pre-pressure of comressed air in a closed chamber 0.5; 0.7 and 1.0 MPa.They describe only its maximum deviation from the average [10] and don't allow seeing how pressure will change during the working cycle of one-piston pump.
So, the piston pumps are simple and reliable.The stable feed high-pressure of the pumped medium with a low level of pulsation is an actual problem.

setting of the task
The goal of this work is to provide a stable high-pressure feed of the pumped medium (solution), with a reduced level of pulsation.This is to determine a minimum value of a given volume of air in the pump combined compensator.
The tasks were set to achieve the goal: -the motion law of the piston (installed with an offset) for mortar pump with a combined compensator of pressure pulsations must be written; -the compressed air volume change in the compensator while changing the crank rotation angle j must be determined; -the dependence of feed pulsation on the pressure initial value must be determined; -on the basis of obtained theoretical dependences of the compressed air volume change in the compensator and the feed pressure depending on the angle j of crank rotation to carry out the calculations for pump RN-3.8.The recommendations regarding the modes of its practical use on the base of calculations results must be given.

materials and methods of the study of changes in pressure of solution feed
The calculations of changes in the solution feed pressure during the cycle with piston motion law and combined pressure pulsations compensator action need to be done (Fig. 1).
The piston pump is driven by the crank mechanism.In this mechanism, the axis of the crank shaft is offset downward relative to the piston axis, by the magnitude of e (Fig. 4).It is calculation condition.
The law of motion of the piston (point B) will be determined.First, let's write x and y coordinates of the point A when j is an angle of rotation of the crank shaft: Connecting rod AB will change the angle of its inclination to the horizontal when you rotate the crank.Its where R -crank radius; l -connecting rod length; e -displacement of crank axis by height relative to the piston axis.The piston stroke (point B, Fig. 4) will be (solution injection during the entire pump work cycle, j = 0…2π): one part of solution will be squeezed in the pipeline to the stroke of injection, another part will fill the compensator air chamber and reduce the volume of this chamber.The pressure changes in injection strokes and intake strokes occur in the same range.The jet of solution during pump operation with a pressure combined compensator is almost uniform at the exit of the injection pipeline.We accept the following.The feed of mortar does not change during the cycle.Then, the volume change of compressed air in the compensator will be when changing the angle j:  3), in the stroke of injection (j = 0…π) depending on the angle j; h p -full piston stroke, h p = х 1 max -х 1 , determined by the equation (3), this value will be slightly different from 2R due to the crank shaft axis displacement relative to the piston axis; x π -х 1 value when j = π.

According to the Boyle
Where we have where V j -current volume of compressed air in the compensator at an angle j; V g -given to normal conditions (p = 0.1 MPa) volume of air in the compensator; p jcompressed air pressure (and solution) at an angle j, MPa.
As you know, V j = V 0 -ΔV.So, according to the equation (4), we have: where V 0 -volume of compressed air in the compensator if where p 0 -compressed air pressure at the beginning of the pump cycle, MPa; x 1 -piston stroke in the stroke of injection, determined by the equation (3).After inserting x 1 value according to the equation (3): So, the dependence is obtained.It will determine the pump working pressure during the operating cycle (stroke of injection, intake stroke).

the results of studies of changes in pressure of solution feed
The change in pressure of the solution feed can be determined by the equations (8) during the pump operation cycle.The R, l, e, F p , V g , р 0 parameters are known.
The pump (Fig. 1) has the following design parameters: crank radius R = 0.04 m; length of connecting rod l = 5R = 0.2 m; offset value e = 0.5R = 0.02 m; piston area (it has a diameter of 0.09 m) F p = (π ⋅ 0.092)/4 = 0.006 m 2 ; given air volume in both chambers of combined pressure compensator = + ⋅ =0 026 3  ., where V f -free air volume in the first compensator chamber, V f = 0.005 м 3 ; V с -closed chamber volume filled with compressed air, V с = 0.003 м 3 ; p c -air pressure in a closed chamber before the pump operation.It is taken for calculations p c = 0.7 MPa.The volume of solution and compressed air will vary in combined compensator chambers during the pump full cycle.Consider this.
This process is shown in Fig. 5 clearly.
Curve 1 shows feed of solution in the first compensator chamber from the piston in the stroke of injection.This feed is determined by the equation F p ⋅x 1 .
The second curve characterizes the change of solution volume in the first chamber from the solution feed in the injection pipeline.It is determined by the equation  Fig. 6 shows graphs of pressure of the solution, which is pumped.It takes place during the full operation cycle.Graphics were obtained with PC help.Also, the equations (8) are used.Initial pressure p 0 = 1; 2; 3 and 4 MPa.Numerical values of these calculations are presented in the table 1.  8) for given total air volume V g = 0.01; 0.02; 0.03 м 3 at an initial pressure p 0 = 2 MPa.This initial pressure level was chosen due to the fact that the feed pressure of 2.0...2.5 MPa is the most common.So, specific values of pressure and feed pulsations were obtained during the working cycle of the piston pump RN-3.8 with combined compensator.The real pump design parameters and the above-obtained theoretical dependence were taken.

Discussion of results of researches of change of pressure of the solution feed
The benefits of research are to monitor pressure changes of the combined compensator and pressure during the working cycle of one-piston mortar pump.
The air pressure (and solution) in the compensator starts to grow during the stroke of injection (j = 0…π).It reaches the maximum level even for some time before the end of the stroke of injection.The pressure then begins to decline.
The air pressure in the compensator only gradually decreases during the intake stroke (j = π…2π).The degree of pressure increase in the stroke of injection depends on the level of initial pressure.So, at the initial pressure of 1 MPa pressure pulsation is 13.5 %, but if p 0 = 2 MPa is already 26 %, i. e. almost twice as much.
The shift of maximum in the curves of pressure change to the left of the angle j = π is explained as follows.The piston speed is reduced substantially in the stroke of injection at the end of its stroke.It does not provide the level of average feed per cycle after some time.The solution feed in the injection pipeline is not only due to injection from the piston, starting now.The compressed air in the compensator expands and is affected also.This leads to a reduction of air pressure.The same phenomenon is observed in the initial moment of the stroke of injection, when the piston stroke speed is low and it does not provide the desired level of the solution feed.The areas of some reductions in pressures appear on the curves of pressure change in the initial period of the stroke of injection in this regard.They are especially noticeable on curves with a high initial pressure (p 0 = 3...4 MPa).
The researches are especial.The calculations are not only theoretical but have practical implementation.They complete the studies cycle of one-piston mortar pump RN-3.8 with the combined compensator.It has a stable performance.The results can be used to develop a parametric series of similar pumps.

summary
1. Functional dependence in the form of a trigonometric equation is obtained.It describes the law of pump piston motion according to constructional features of the drive link and crank rotation angle depending on the operation stroke of one-piston mortar pump.
2. The given air volume in the compensator should be less than 0.02 m 3 .This will provide a moderate level of solution feed pulsation.
3. The feed pulsation depends on the pressure initial level in the compensator.It can range from 13.5 % to 57 % at p 0 from 1 to 4 MPa, respectively.

V . Z a k h a r c h e n k o
Assistant* Е-mail: victoriaIT@ukr.net

introduction
Today design automation of technical objects is an important factor for the increase of the designers' labor productivity.However, it isn't developed enough.Nowadays achievements in this area are rather insignificant in comparison with achievements in mechanical engineering in general.In the work [1] Petrenko observed that in the twentieth century the labor productivity in mechanical engineering increased much more, than the labor productivity of developers, who designed new equipment.
It is noted that complexity and volumes of projects tend to double every 10 years.Developers use rather old and wellknown design methods for the automation of only separate design operations, which doesn't significantly contribute to the increase of their labor productivity.The latter depends on the use of traditional design methods, which aren't optimized, and the job management, which isn't controlled enough and doesn't provide the optimization of non-manufacturing actions.All these are reasons of the designers' lagging behind the general increase of the industrial manufacturing.Therefore, there is an urgent need to solve this complex problem and to develop the full-function system for design works automation.Further, under the system for design works automation (CAD system) we will consider the set of programming and information means, which help to exclude the expert from a contour of the design process management.According to requirements of an integrated approach, not only separate components of the system, but also their interaction have to be the subject of improvement.Based on this provision it is necessary to automate the whole design process from the development of Terms of Reference to the formation of the completed project and its transferring to the client, but not only separate design operations, as it takes place nowadays.Such full-function CAD system would provide both the design automation of technical objects and the job management of the whole design process.In consequence, it will increase the designers' labor productivity.This determines the topicality of the CAD system development for the management of the performance of all kinds of works at design organizations and design subdivisions of industrial enterprises.

ΔV 1 -
volume change of compressed air in the compensator during the piston injection stroke relative to the volume of compressed air, j = 0…π; ΔV 2 -the same in the intake stroke of the piston, j = 0…2π; F p -piston area, diameter; х 1 -law of piston motion, determined by the equation ( 9) where V r.w.-real working piston volume.The third curve shows the real change of the solution volume.The change occurs in the compensator chamber during the pump operation cycle.It causes changes in the compressed air pressure and the solution feed pressure in the compensator.

Fig. 6 .
Fig. 6.Dependence of solution pressure (solution is pumped) on the angle of shaft crank rotation: 1 -p 0 = 1 МPа; 2 -p 0 = 2 МPа; 3 -p 0 = 3 МPа; 4 -p 0 = 4 МPа Fig. 7 shows variation graphs of air pressure in the compensator during the cycle.It depends on the total given volume of air contained in the combined compensator.These graphs are constructed by the equation (8) for given total air