Fluid Characteristics Analysis of the Lubricating Oil Film and the Wear Experiment Investigation of the Sliding Bearing

The sliding bearing is an important component in machines. The characteristics of the oil film fluid of the sliding bearing is the key factor affecting lubrication, which will affect the wear and reliability of the sliding bearing. Herein, the lubricating oil of the sliding bearing is studied, the oil film flow model considering the cavitation effect is established, the pressure and temperature distribution of the oil film under different rotational speeds is explored, and its influence on oil film pressure and temperature are analyzed. Furthermore, wear tests are carried out to measure the wear amount of the bearing bush under different rotational speeds, and the influence of the fluid characteristics of the lubricating oil film on bearing wear is explored. The simulation and experimental study in this paper can provide a reference for the design of sliding bearings.

Research on Cavitation Characteristics of Two-Throat Nozzle Submerged Jet

Ship fouling not only increases ship resistance and fuel consumption but is equally a type of biological invasion, which causes severe ecological damage. Submerged cavitation jet cleaning is an environmentally friendly, high-efficiency, and energy-saving cleaning method. The nozzle structure has an essential influence on the cleaning effect. Thus, a two-throat nozzle was designed for application in submerged cavitation jet cleaning. To investigate the cavitation characteristics of the two-throat nozzle, a high-speed photographic visualization experiment and an erosion experiment concerning the submerged cavitation jet were carried out in this study. The frame-difference method (FDM) was used to analyze the dynamic changes in the cavitation cloud in a single period. The dynamic changes in the cavitation cloud and the characteristics of the submerged cavitation jet were investigated under different inlet pressures. The sample mass loss and the macroscopic and microscopic changes in surface morphology were used to evaluate the cavitation intensity of the two-throat nozzle submerged jet. The experimental results demonstrate that the two-throat nozzle has a good cavitation effect, and the cavitation cloud of the submerged jet has obvious periodicity. With the increase in inlet pressure, the length, width, and area of the cavitation cloud continue to increase, and the shedding frequency of the cavitation cloud continues to decrease. The intensity of cavitation erosion is related to target distance and impact time. There is an appropriate target distance by which to achieve the optimal cavitation effect. The collapse of cavitation bubbles near the sample surface is related to the erosion distribution on the sample surface. Moreover, the magnitude of the absolute values of the root-mean-square surface roughness and surface skewness increase with cavitation intensity. The results in this paper are helpful for a better understanding of the cavitation characteristics of the two-throat nozzle submerged jet.

Разработка инновационной энергосберегающей технологии очистки резервуаров путем диспергирования отложений

An obvious global trend in recent years is the increase in the proportion of viscous and heavy oils featured by high density and content of asphalt-resin-paraffin deposits. Due to the deterioration of the rheological properties of oil, the processes of its extraction, preparation in the fields, further transportation and subsequent processing have been made more difficult. The object of the study is the cleaning of oil and petroleum products storage tanks from the accumulated bottom sediments. The existing methods of tanks cleaning have been analyzed, the most promising methods and technical means for removing sediment and reducing the volume of sediment formation have been identified. The urgency of the development and implementation of innovative technologies enabling minimization of accumulation of deposit to reduce the scope of work in tank cleaning has been established. In this regard, experimental laboratory studies were conducted to determine the effectiveness of ultrasonic exposure with the occurrence of cavitation on the rheological properties of oil. The obtained results are indicative of a positive effect of ultrasound treatment of high-paraffin oil, such effect been expressed in decreased oil viscosity. A method is proposed for cleaning the tank from bottom sediments with the use of hydraulic washout system and ultrasonic plant. That method is based on the use of the cavitation effect caused by high-frequency waves, which makes it possible to temporarily adjust the rheological properties of oil and sludge deposit, reduce the deposit deposition rate and thereby slow down the process of sediment deposition during the storage of oil and petroleum products in large-volume tanks. Очевидной тенденцией последних лет в мире является увеличение доли вязких и тяжелых нефтей, характеризующихся высокой плотностью и содержанием асфальтосмолопарафиновых отложений. Вследствие ухудшения реологических свойств нефти затрудняются процессы ее добычи, подготовки на промыслах, дальнейшей транспортировки и последующей переработки. Объектом исследования является очистка резервуаров для хранения нефти и нефтепродуктов от образующихся донных отложений. Проанализированы существующие способы очистки резервуаров, выявлены наиболее перспективные методы и технические средства для удаления осадка и снижения объема образования отложений. Установлена актуальность вопроса разработки и использования инновационных технологий, позволяющих минимизировать выпадение осадка с целью уменьшения объема работ при очистке резервуаров. В этой связи проведены экспериментальные лабораторные исследования для определения эффективности ультразвукового воздействия с возникновением кавитации на реологические свойства нефти. Полученные результаты свидетельствуют о положительном эффекте обработки ультразвуком высокопарафинистой нефти, который выражается в снижении ее вязкости. Предложен способ очистки резервуара от донных отложений с применением гидравлической системы размыва и ультразвуковой установки. Он основан на использовании эффекта кавитации, вызываемой посредством высокочастотных волн, что позволяет провести временную корректировку реологических свойств нефти и осадка нефтешлама, снизить скорость выпадения осадка и таким образом замедлить процесс образования отложений при хранении нефти и нефтепродуктов в резервуарах большого объема.

Hydrodynamic activation of heavy oil residues

Objectives. Recently, there has been a tendency to increase the volume of high-viscosity heavy oils in the total volume of oil produced. The processing of these oils requires new technological approaches. This task is closely related to the need to increase the depth of oil refining. Among the approaches proposed to solve these problems, mechanochemical activation, which is based on the cavitation effect produced by ultrasonic or hydrodynamic methods, has been suggested. This study evaluated the effects of cavitation in increasing the depth of oil refining.Methods. Straight-run and “secondary” oil products were used as raw materials: vacuum gas oil, catalytic cracking gas oil, and fuel oil. Activation was carried out in a high-pressure disintegrator. The principle of operation was to compress the oil product and then pass it through a diffuser. When the oil was passed through the diffuser, there was a sharp pressure release to atmospheric pressure, which caused cavitation in the hydrodynamic flow. The pressure gradient on the diffuser and the number of processing cycles ranged from 20 to 50 MPa and 1 to 10, respectively. The density, refractive index, and the fractional composition of petroleum products were determined using standard and generally accepted methods.Results. This paper reports the influence of mechanochemical activation of petroleum products on their physical and chemical characteristics. An increase in the pressure gradient and the number of processing cycles leads to a decrease in the boiling point of the petroleum products and their density and an increase in the yield of fractions that boil off below 400 °C. The yield of the fractions with boiling points of 400–480 °C and the remainder were reduced. The density and refractive index of fractions with boiling points up to 480 °C decreased, and the density of the residue increased. The effects of cavitation (an increase in the yield of fractions with boiling points up to 400 °C and a decrease in the density of the petroleum products) increased with increasing pressure gradient and the number of processing cycles.Conclusions. The changes in the density, boiling point, and the yield of fractions increased with increasing the pressure from 20 to 50 MPa and the number of hydrodynamic cavitation cycles from 1 to 5. Increasing the number of processing cycles to more than five had little additional effect. The effects of cavitation increased with increasing initial density of the oil product. The average molecular weight of these fractions was estimated from the densities and boiling points of individual fractions of the petroleum products. The calculation confirmed the assumption regarding the course of cracking reactions of petroleum products under the influence of cavitation and indicates the course of the compaction processes.

Research of the influence of acoustic load on a piezoelectric emitter to control the cavitation erosion of materials

The paper analyzes the possibilities of research the cavitation erosion of materials that are subjected to cavitation effect. The study is carried out by a system for controlling the magnitude of the acoustic load on the piezoelectric emitter of the ultrasonic vibrating system. The analysis of the processes of interaction between the ultrasonic emitter and the processed environment was carried out on the basis of a research of the model, which was created on the basis of a system of electromechanical analogies. The analysis made it possible to reveal the dependence of the electrical impedance of the ultrasonic vibrating system on the magnitude of the acoustic load. The revealed dependencies made it possible to propose and develop a control system. It is able to provide a study of the properties that are located near the emitting surface of the ultrasonic emitter of materials influenced to cavitation ultrasonic, including under abnormal conditions (high temperatures and pressures).

Insight into friction and lubrication performances of surface-textured cylinder liners and piston rings

The effects of surface-texture technology on the friction and lubrication mechanism of cylinder liner-piston rings (CLPR) were explored in this study. An inclined groove texture was machined on the CL of a S195 diesel engine and dimples designed on the gas ring. Friction and wear tests of nontextured (NT), CL textured (CLT), and PR textured (PRT) conditions were performed on a CLTR friction and wear tester under different temperatures. First, the characteristics of friction and lubrication at different temperatures were analyzed by examining friction and contact resistance. Then, the wear characteristics were analyzed by examining surface morphology parameters of the CL and the PR wear mass after testing. Finally, the friction and lubrication mechanisms of NT, CLT, and PRT were studied by analyses of real-time friction and contact resistance in one cycle. The results showed that, under the same temperature, CLT and PRT increased oil film thickness, improved the lubrication state, and reduced friction, with CLT better than PRT in these respects. With increased temperature, the wear degree of CL liners became larger. The existence of surface texture reduced CL wear, yielded CL surface morphology not excessively changed by temperature, and improved its supporting performance and oil storage capacity. The inlet suction effect, structural effect, micro-wedge action, balancing wedge action, squeezing effect, and cavitation effect should be taken into account together when exploring the mechanism of the influence of surface texture on friction pairs. This study provided a method for scholars to explore the friction and lubrication mechanism of different texture types and provided an experimental basis for improving the performance of CLPR friction pairs.

Microstructure and Wear Property of ZrO2-Added NiCrAlY Prepared by Ultrasonic-Assisted Direct Laser Deposition

For improving the wear properties of NiCrAlY, the 10 wt %, 20 wt % and 30 wt % ZrO2-added NiCrAlY samples were prepared by ultrasonic-assisted direct laser deposition, respectively. The results showed that the ultrasonic-assisted direct laser deposition can realize the ZrO2-added NiCrAlY preparation. Furthermore, due to the cavitation effect and agitation of the ultrasound in the molten pool, ultrasonic-assisted could make the upper surface of the samples smoother and flatter, and it also improved the microstructural homogeneity. The microstructure was mainly composed of columnar dendrites, and most of ZrO2 particles were located in the intergranular regions. The principal phase constituents were found to contain γ-Ni and t-NiZr2, and the amorphous (Ni, Zr) intermetallic phase generated, because of more rapid solidification after ultrasound assisted. The microhardness was improved slightly with the increase of ZrO2 contents, rising from 407.9 HV (10% ZrO2) to 420.4 HV (30% ZrO2). Correspondingly, wear mass loss was decreased with the maximum drop 22.7% of 30% ZrO2 compared to that of 10% ZrO2, and wear mechanisms were mainly abrasive wear with slightly adhesive wear. After applying ultrasound, the oxide islands in samples disappeared, and more ceramic particles were retained. Thus, the hardness and wear performance of the samples were improved.

Neointimal hyperplasia regression using combined paclitaxel- mediated confocal dual pulse shock wave sonoporation therapy and catheter- based 90Y- mediated brachytherapy

Background and aims Intimal hyperplasia refers to proliferation and migration of vascular smooth muscle cells primarily in the tunica intima, resulting in arterial wall thickening and decreased arterial lumen size. Neointimal hyperplasia is the major cause of restenosis after percutaneous carotid interventions such as stenting or angioplasty. The aim of this study was to investigate the effect of combined shock wave enhanced sonoporation therapy and catheter-based 90Y-mediated β-brachytherapy on neointimal hyperplasia regression in an animal model, wherein diagnostic B-mode ultrasound is combined with therapy system, with a goal of increased safety. Methods Endothelial balloon catheter denudation of the abdominal aorta of golden Syrian hamsters was performed. Histopathologic evaluation confirmed neointimal hyperplasia formation in all of the hamsters' arteries. The treatment group underwent intravenous lipid-based encapsulated paclitaxel nanoparticles (10mg/kg)-mediated extracorporeal confocal dual pulse low-level focused electrohydraulic shock wave (V=15 kV, F=2 Hz, Impulses = 50 and V=10 kV, F=0.2 Hz, Impulses = 150) enhanced sonoporation therapy accompanied by catheter-based 90Y-mediated β-brachytherapy (90Y, 15 Gy), guided by simultaneous B-mode ultrasound imaging. Results B-mode ultrasound guided combined shock wave enhanced sonoporation therapy and β-brachytherapy was feasible and appeared safe for the targeting of stenosis in the aorta artery. Furthermore, pathological results showed a significant reduction in the mean value for smooth muscle hyperplasia cells density, lumen wall thickness and percentage of luminal cross- sectional area of stenosis in the treatment group compared with the other groups (p<0.05). Conclusions Enhanced toxicity effect of paclitaxel, induced by enhanced sonoporation effect of shock wave therapy, due to inertial cavitation effect of collapsed capsules and dual pulse system application accompanied by apoptotic effect of brachytherapy, can cause to neointimal hyperplasia regression. Combined shock wave enhanced sonoporation therapy and β-brachytherapy is significantly associated with reduced aorta artery stenosis in hamsters. The mechanism may relate to reduced smooth muscle hyperplasia cells and inflammation in the tunica intima. FUNDunding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Mehrad Research Lab

Investigation of Inertial Cavitation of Sonosensitive and Biocompatible Nanoparticles in Flow - Through Tissue- Mimicking Phantoms Employing Focused Ultrasound

A promising approach to drug delivery applications for chemotherapeutics is the use of drug carriers to reduce the total amount of cytostatics, minimizing side effects. In addition, the carriers, loaded with the drug, can be guided to the tumorous tissue via the vascular system, which enables a local drug release (LDR). In our case, LDR is activated due to the sonosensitive behavior of the nanocapsules by inertial cavitation (IC) caused by focused ultrasound (FUS). Thereby, IC is excited by employing sound pressures within the recommended limit allowed for diagnostic ultrasound. In order to verify this drug delivery approach for its clinical suitability, a tissue-mimicking flow -through phantom, containing a small vessel, is used. Investigations have shown that the drug releasing cavitation effect associated with the sonosensitive and biocompatible nanocapsules also occurs in fine vessel structures, even in the case of moving particles and vessel diameters dc smaller than the wavelength λ.