Liquid temperature effect on the hydraulic shock wave velocity in polyethylene pipes

Introduction. Providing people with high quality drinking water has always come first. However, its transportation through pipeline systems was often associated with some problems, such as the temperature of the water and the environment, as well as the possibility of water hammer on certain pipe sections. This was especially true for systems that use polyethylene pipes. Temperature is a key factor affecting the flexibility properties of polyethylene pipes, and it affects not only the design, but also the investment in the development of water supply networks. The purpose of these studies was to study the effect of water and ambient temperature on the density, properties of the pipe material and the speed of propagation of a hydraulic shock wave in polyethylene pipes.Materials and Methods. In the experiments performed, the method of field research was used, when tests are carried out on specialized equipment on samples specially made for the pursued purposes. Here, samples of high-density polyethylene pipes were used, which were subjected to tensile tests on a tensile testing machine, and each experiment was carried out three times.In the course of the experiments, the samples were exposed to certain temperature regimes (both external and internal), while the influence of the hydrodynamic pressure of the liquid in the pipe was also investigated, as a result of the change in time of the liquid velocity in its sections. To do this, the samples were supplied with liquid under a certain pressure in order to find out the influence on the pipes of an effect known as water hammer.Results. In the course of the research, it was found that the value of the elastic modulus of high-density polyethylene PE100 decreases with increasing water temperature, and the decrease at a temperature of 60° C reaches 60.21% compared to its value at a water temperature of +4° C. Based on the results of experiments to determine the effect of the elastic modulus of polyethylene with increasing temperature, an exponential equation was derived to calculate the value of the polyethylene coefficient as a function of time E = 1.312e-0,01t with the correlation coefficient R2 = 0.988 ; and based on the results of the studies carried out to calculate the value of the propagation velocity of a hydraulic shock wave, an exponential equation was derived as a function of time C = 275.9e-0,01t with the coefficient correlation R2 = 0.987 .Discussion and Conclusions. In the course of the research, it was found that such a phenomenon as water hammer has a harmful effect on the pipe walls, which, if possible, should be avoided even at the design stage of the water supply network. During the experiments, it was found that with an increase in temperature, the values of the elastic modulus of polyethylene decreased with a simultaneous decrease in the values of the propagation velocity of the hydraulic shock wave.

Development and Parametric Analysis of Vibration System Controlled by Hydraulic Shock Rotary Vibrator

The improvement of the energy utilization rate of a hydraulic vibration-excitation system is critical to the research and development of hydraulic vibration equipment. In this paper, a hydraulic vibration-excitation system controlled by a new type of shock rotary vibrator is proposed. A system model considering the pipeline effect was established for the hydraulic shock phenomenon. In addition, the model was compared with the one that does not consider the pipeline effect. The effectiveness of the proposed model was verified experimentally. Finally, the shock phenomenon during the process of switching the working state of the vibrator and the influence of certain important parameters of the system on the vibration output were investigated based on the proposed model. The results showed that (1) the hydraulic shock phenomenon occurred when the working state of the hydraulic vibrator was switched and (2) the hydraulic shock wave could effectively improve the excitation force of the system. The excitation force increased with an increase in the oil supply pressure, spindle speed, and load. However, it was negatively correlated with the spring stiffness. The amplitude of the vibration waveform output was positively correlated with the oil supply pressure and negatively correlated with the spindle speed and load. The amplitude first increased and then decreased as the stiffness of the vibration spring increased. The only influence of the precompressed length of the spring on the system output was its alteration of the vibration center of the system output vibration.

Parameters control for the damping element hydraulic buffer of the vehicle suspension

The research investigates the impact coming from damping element hydraulic buffer of suspension on the vehicle smoothness. A change in the structural elements of hydraulic buffer for absorber rebound is considered in order to avoid hydraulic shock at the initial moment of its operation.

Comparing the physical principles of action of suspension damping devices based on their influence on the mobility of wheeled vehicles

This paper reports the comparison of two physical principles of action of suspension damping devices based on their influence on the mobility indicators for an 8×8 wheeled machine. A radical difference between these principles of action is the dependence of resistance forces on the speed of the relative movement of working bodies (internal friction: hydraulic shock absorbers) or on the relative movement of working bodies (external friction: friction shock absorbers). Widespread hydraulic shock absorbers have certain disadvantages that do not make it possible to further increase the mobility of wheeled or tracked vehicles without the use of control and recuperation systems. In turn, in friction shock absorbers, the use of new materials has eliminated many of their shortcomings and thus can provide significant advantages. It was established that the application of friction shock absorbers for a given wheeled vehicle did not significantly affect the speed compared to hydraulic ones. The main factor that prevented the implementation of the advantages of friction shock absorbers was the insufficient suspension travel. However, friction shock absorbers absorbed 1.76...2.3 times less power, which reduced the load on nodes and increased efficiency (autonomy). In addition, a more uniform load on suspensions was ensured, which improved their resource, and, due to the prevailing vertical oscillations of the suspended body over the longitudinal-angular ones, the geometric passability improved as well. The comparison of two physical principles of action of damper suspension devices in a wheeled vehicle has shown that the use of friction shock absorbers could provide significant advantages in resolving the task relates to improving the mobility and would fundamentally affect the choice of the suspension energy recuperation system if it is applied.

Hydraulic characteristics of integrated settler based biofilm reactor as onsite sanitation system

The present study identifies the hydraulic efficiency of a novel onsite sanitation system at variable hydraulic shock loading conditions. The system consisted of three chambers, each working as an up-flow anaerobic bioreactor, accommodated within a single unit. The hydraulic characteristics were identified with the help of residence time distribution (RTD) analysis by step feeding of lithium chloride (LiCl) solution into the system. The experiments were run at variable hydraulic loading conditions at different peak flow factors (PFF) of 1, 2, 4 and 6 while maintaining 24-h hydraulic retention time. As revealed in the RTD analysis, the biofilm reactor achieved a very good hydraulic efficiency that varied from 0.76 to 0.81 at PFF 1, 2 and 4. Although in the case of PFF6, it was comparatively low. It was noted that the dispersion number was always below 0.2 at variable hydraulic shock loading conditions under different PFFs, which indicated that the reactor behaved perfectly between mixed-flow and plug-flow reactor. The system was also able to achieve good pollutant removal efficiency for chemical oxygen demand (COD) and total suspended solids (TSS) under all PFFs, which was more than 68 and 75%, respectively.

Extrasystolic arrhythmia – an unaccounted risk factor of atherosclerosis development in main arteries?

Objectives to determine the hemodynamic changes within arterial vessels in different variants of extrasystole, to analyze whether extrasystole is an additional risk factor for the development of atherosclerosis. Material and methods. The study included 286 patients (175 men and 111 women) with extrasystole of more than 3000 per day and 88 patients with extrasystole of less than 3000 per day as a control group. When selecting eligible patients for the study, we tried to minimize the impact of traditional risk factors of atherosclerosis. The presence of cardiocerebral complications in medical history was also considered. The examination methods used in the study are electrocardiography, phonocardiography, 24-hour electrocardiography monitoring, Doppler ultrasound of the brachiocephalic vessels, lower extremities arteries, renal arteries, transthoracic or transesophageal echocardiography. Stress echocardiography was performed if indicated; as well as renal artery angiography, coronary angiography, computed tomography of the brain with angioprogram. When performing a biochemical blood test, the lipid spectrum and hemostasiogram were necessarily determined. All patients underwent left ventricular apexcardiography, as well as sphygmography, recorded on arteries of elastic type (a. Carotis communis) and muscular-elastic type (a. Tibialis posterior). The clinical examinations were confirmed and modeled using the original "Device for modeling of intra-arterial circulation", developed by us (RF patent No. 202780 dated 05.03.2021). Results. We determined an increase in the main parameters of the heart biomechanics and the kinetics of the main arteries in the 1st post-extrasystolic wave in patients with various types of extrasystole with the following pattern: the earlier extrasystole had appeared in the cardiocycle, the greater was the increase in the parameters under observation. A universal concept of hydraulic shock and possible cases of its formation were described. Conclusion. Extrasystole is an additional risk factor for the onset and progression of atherosclerosis. Hydraulic shock during the passage of the 1st post-extrasystolic wave is a powerful traumatic factor for the walls of the arteries, which can lead to the formation of an atherosclerotic process.

Modeling of restenosis of main arteries after the intravascular stenting interventions

Objectives to study the mechanism of restenosis after the intra-arterial stenting using the original device for modeling of intra-arterial blood flow. Material and methods. To perform the experiment, we have created the original device simulating the intra-arterial blood flow. A glass tube of rotameter was the imitation of the arterial vessel. The closed system was filled with the liquid imitating blood, specifically the solution of glycerin the same viscosity as the human blood plasma. Using our original model of intra-artetial blood flow, we were able to study the intra-arterial hemodynamics under different conditions of cardiovascular system functioning, including arrhythmias. Results. In extrasystolic arrhythmia, during the spread of the first post-extrasystolic wave, we observed the intensive impact of pressure wave (the indicator was the silk thread) on the vessel walls with forming of reflected and standing waves. Putting the piezo crystal probe of pressure inside the tube, we verified our observations. The increase of pressure during the spread of the first post-extrasystolic wave in multiple measurements had a mean value of 160% in comparison with the pressure during the regular heart rhythm. Conclusion. The hydraulic shock appears during the spread of the first post-extrasystolic wave in the arterial vessel. Its effect on hemodynamics grows in case of the frequent extrasystoles and allorhythmia. The mechanical impact of hydraulic shock in extrasystoles can be the starting point of the restenosis onset and progressing in the intra-arterial stent.

The influence of temperature on the damping characteristic of hydraulic shock absorbers

This paper presents the results of bench-tests and calculations assessing the influence of temperature on the performance of a two-pipe hydraulic shock absorber. The shock absorber prepared for the tests was cooled with dry ice to a temperature corresponding to that associated with the average winter conditions in a temperate climate. The temperature range of the shock absorber during testing was ensured via equipping it with a thermocouple and monitoring it with a thermal imaging camera. During testing, the shock absorber was subjected to kinematic forces of a selected frequency with two different, fixed displacement amplitudes. The results of the tests showed a direct correlation between the decrease of component resistance at lower temperatures. The rate of change in resistance was higher at lower temperatures. It was also found that the energy dissipated in one shock cycle decreased linearly with an increasing temperature. Finally, a method for determining the ideal use temperature of the shock absorber for the assumed operating conditions was also presented.