Research on erosion characteristics of a novel cavitation nozzle under nonsubmerged condition

When a cavitating jet enters the atmosphere directly, its cavitating effect weakens rapidly, and the erosion energy it produces cannot be fully utilized. Regarding the problem that existing cavitation nozzles are only used in submerged condition, methods to improve the erosion ability of cavitation jets under nonsubmerged condition are studied. The nozzle is visually simulated using Fluent software, and the results show that the dynamic submerged environment at the outlet effectively expands the nearby low-pressure cavitation area. The enhancement effect of the annular cavitation nozzle on the jet cavitation effect in the atmosphere domain is verified by measuring the impact force curve of the jet and through erosion tests on brass surface. Cleaning and derusting tests show that the annular cavitation nozzle has stronger derusting ability than the high-pressure nozzle under nonsubmerged condition and under the same pressure, demonstrating that the cleaning and derusting effect mainly comes from the collapse of cavitation bubbles.

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The Clean pilot study: evaluation of an environmental hygiene intervention bundle in three Tanzanian hospitals

Antimicrobial Resistance and Infection Control ◽

10.1186/s13756-020-00866-8 ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Giorgia Gon ◽

Abdunoor M. Kabanywanyi ◽

Petri Blinkhoff ◽

Simon Cousens ◽

Stephanie J. Dancer ◽

...

Keyword(s):

Pilot Study ◽

Study Design ◽

Low Income ◽

High Volume ◽

Surface Cleaning ◽

Low Income Countries ◽

Training Period ◽

Future Research ◽

Environmental Hygiene ◽

The Impact

Abstract Background Healthcare associated infections (HAI) are estimated to affect up to 15% of hospital inpatients in low-income countries (LICs). A critical but often neglected aspect of HAI prevention is basic environmental hygiene, particularly surface cleaning and linen management. TEACH CLEAN is an educational intervention aimed at improving environmental hygiene. We evaluated the effectiveness of this intervention in a pilot study in three high-volume maternity and newborn units in Dar es Salaam, Tanzania. Methods This study design prospectively evaluated the intervention as a whole, and offered a before-and-after comparison of the impact of the main training. We measured changes in microbiological cleanliness [Aerobic Colony Counts (ACC) and presence of Staphylococcus aureus] using dipslides, and physical cleaning action using gel dots. These were analysed with descriptive statistics and logistic regression models. We used qualitative (focus group discussions, in-depth interviews, and semi-structured observation) and quantitative (observation checklist) tools to measure why and how the intervention worked. We describe these findings across the themes of adaptation, fidelity, dose, reach and context. Results Microbiological cleanliness improved during the study period (ACC pre-training: 19%; post-training: 41%). The odds of cleanliness increased on average by 1.33 weekly during the pre-training period (CI = 1.11–1.60), and by 1.08 (CI = 1.03–1.13) during the post-training period. Cleaning action improved only in the pre-training period. Detection of S. aureus on hospital surfaces did not change substantially. The intervention was well received and considered feasible in this context. The major pitfalls in the implementation were the limited number of training sessions at the hospital level and the lack of supportive supervision. A systems barrier to implementation was lack of regular cleaning supplies. Conclusions The evaluation suggests that improvements in microbiological cleanliness are possible using this intervention and can be sustained. Improved microbiological cleanliness is a key step on the pathway to infection prevention in hospitals. Future research should assess whether this bundle is cost-effective in reducing bacterial and viral transmission and infection using a rigorous study design.

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Numerical simulation and experimental research of cavitation nozzle based on equation curve

Water Science & Technology Water Supply ◽

10.2166/ws.2021.058 ◽

2021 ◽

Author(s):

Lifu Wang ◽

Dongyan Shi ◽

Zhixun Yang ◽

Guangliang Li ◽

Chunlong Ma ◽

...

Keyword(s):

Numerical Simulation ◽

Reynolds Number ◽

Flow Field ◽

High Speed ◽

Quadratic Equation ◽

Outer Contour ◽

Study Results ◽

Fluent Software ◽

The Impact ◽

Better Than

Abstract To further investigate and improve the cleaning ability of the cavitation nozzle, this paper proposes a new model that is based on the Helmholtz nozzle and with the quadratic equation curve as the outer contour of the cavitation chamber. First, the numerical simulation of the flow field in the nozzle chamber was conducted using FLUENT software to analyze and compare the impact of the curve parameters and Reynolds number on the cleaning effect. Next, the flow field was captured by a high-speed camera in order to study the cavitation cycle and evolution process. Then, experiments were performed to compare the cleaning effect of the new nozzle with that of the Helmholtz nozzle. The study results demonstrate that effective cavitation does not occur when the diameter of the cavitation chamber is too large. For the new nozzle, with the increase of the Reynolds number, the degree of cavitation in the chamber first increases and then decreases; the cleaning effect is much better than that of a traditional Helmholtz nozzle under the same conditions; the nozzle has the best cleaning effect for the stand-off distance of 300 mm.

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The mechanism of edge cutting machining of rolled iron from oxide scale

Science intensive technologies in mechanical engineering ◽

10.30987/2223-4608-2021-11-12-19 ◽

2021 ◽

Vol 2021 (11) ◽

pp. 12-19

Author(s):

Albert Korolev ◽

Anastasia Panfilova ◽

Boris Iznairov ◽

Olga Reshetnikova ◽

Viktorya Pavlova

Keyword(s):

Boundary Conditions ◽

Oxide Scale ◽

Cutting Tool ◽

Impact Force ◽

Mechanical Action ◽

Surface Cleaning ◽

Tool Support ◽

The Impact ◽

Rolled Surface ◽

Edge Tool

A new purifying method of metal surface cleaning from oxide scale using a special rotating edge tool is described, which allows to solve the problem of increasing the extent of surface purification from oxide scale more efficiently, reliably and effectively. The process of the surface cleaning of flat- rolled products used for the manufacture of hollow sheres from oxide scale by mechanical action of a cutting tool on various layers of oxide scale is simulated. The force required to shift an oxide scale and the boundary conditions of the ratio hold-down pressure of the tool to the workpiece, the friction force in the tool support and the impact force of the scale on the tool, at which it is possible to remove the scale from the rolled surface, are determined.

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Dynamic Simulation of the Meshed Gears Based on ADAMS

Materials Science Forum ◽

10.4028/www.scientific.net/msf.800-801.708 ◽

2014 ◽

Vol 800-801 ◽

pp. 708-711

Author(s):

Bo Zhu ◽

Xi Chen ◽

Liang Zhou

Keyword(s):

Dynamic Simulation ◽

Simulation Method ◽

Mechanical Analysis ◽

Force Curve ◽

Effective Dynamic ◽

Impact Parameters ◽

Definition Of ◽

Contact And Impact ◽

Design And Manufacture ◽

The Impact

Gears are widely used in engineering machinery. Mechanical analysis of the gears matters more much than motion analysis when they are used in heavy machinery or equipment. Dynamic simulation of the meshed gears is based on the theory of contact and impact concerning with the definition of the impact parameters and the model in ADAMS, so the dynamic simulation process is often complicated. In this paper, an effective dynamic simulation method of meshed gears was proposed by analyzing the physical significance of the impact parameters and the calculation method of the impact, and the force curve of the meshed gears was simulated. This result can provide basis for the design and manufacture of the gear.

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Investigation of Material Deformation by the High-Speed Water Slugs

Fluids Engineering ◽

10.1115/imece2002-33782 ◽

2002 ◽

Cited By ~ 3

Author(s):

O. Petrenko ◽

E. S. Geskin ◽

G. A. Atanov ◽

B. Goldenberg ◽

A. Semko

Keyword(s):

Shock Waves ◽

Nozzle Exit ◽

High Speed ◽

Numerical Models ◽

Water Pressure ◽

Experimental Studies ◽

Surface Cleaning ◽

Water Velocity ◽

Material Deformation ◽

The Impact

Water constitutes an attractive manufacturing tool It is readily available and clean. The waterjets are conventionally used for surface cleaning, material removal, and surface modification. The intrinsic shortcomings of such an application are the need in the use of expensive and heavy pumping facilities and, what are more important, peculiarities of the waterjet-substrate interaction which limit material deformation by the incoming jet. These shortcomings are eliminated if the workpiece is impacted by the array of the water slugs, generated by the direct injection of high-intensity energy pulses into the water vessel (barrel) and ejection the portion of the water via the nozzle attached into the barrel. Such a device (barrel-nozzle combination) will constitute an effective and versatile manufacturing tool. Understanding of the phenomena that occur in the course of the energy injection into the water is necessary for the design of the desired device. The phenomena in question are determined by the ratio between the speed of the water in the barrel in the course of the energy injection and the speed of the shock waves in the water. If this ratio is much less than unity, the exit velocity is determined by the ratio between the cross section areas of the nozzle exit and the barrel. If the ratio in question approaches the unity, the water velocity at the nozzle exit is determined by the impact pressure. The device utilizing this principle is termed the water extruder. If however, the ratio is much more than unity the exit water velocity is determined by the superposition of shock waves developed in the fluid. This device termed the water cannon is able to accelerate the water slug to the speed far exceeding 1,000 m/sec. The numerical and experimental studies of water extruder were carried out. The numerical models were constructed and the variation of the water velocity and the water pressure in the barrel were investigated. Experimental setup for the study of the water extruder was constructed by the modification of Remington power tool. The experiments involved the piercing of metal strips. The effect of operational conditions on the maximal depth of the piecing was determined. Another series of experiments involved the study of the slug impact on plastic (lead) and brittle (concrete) materials. The effect of the stand off distance on the removal of both kinds of material was investigated. As the result the suggestions about the way of construction of the water extruders and their practical applications were made.

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COVID-19 Outbreak and Dental Health Care Provision in Nigeria – A National Survey

10.21203/rs.3.rs-286938/v1 ◽

2021 ◽

Author(s):

Timothy Olukunle ALADELUSI ◽

Foluso Ayobami ATIBA ◽

Shakeerah Olaide GBADEBO ◽

Yewande Isabella ADEYEMO ◽

Adeola Adenike OLUSANYA ◽

...

Keyword(s):

Dental Health ◽

Healthcare Providers ◽

Dental Service ◽

Surface Cleaning ◽

Common Features ◽

Study Population ◽

The Common ◽

The Impact ◽

Preventive Methods ◽

Self Administered Questionnaire

Abstract Background: The impact of the COVID-19 pandemic on the world is unprecedented, posing greater threats to vulnerable healthcare systems, especially in developing countries. This study aimed to assess the knowledge of dental healthcare providers in Nigeria about the disease and evaluate their responses to the preventive measures necessitated by the disease.Methods: This was an online self-administered questionnaire-based study conducted among Dentists practicing in Nigeria. A message containing the link to the survey was sent widely via social medial platforms and electronic mails to dentists practicing in Nigeria. The data collection was done between the 2nd of June and 3rd of July, 2020.Results: A total of 314 responses was recorded. Fever was the most commonly specified generalized symptom (97.5%), while the use of masks (100%), hand hygiene (99.7%), social distancing (97.7%) and surface cleaning (99.4%) were the most commonly employed general preventive methods. The main identified risk of transmission in the clinic was aerosol generating procedures (98.7%).Conclusion: The general knowledge of dental personnel in our study population appears to be adequate on the common features of COVID-19 but less adequate regarding the less common features. The COVID-19 pandemic has also modified some aspects of dental service delivery but more needs to be done in this regard.Preventive measures against the transmission of COVID-19 in dental practice settings include proper utilization of teledentistry, clinical triage, preprocedural 1% hydrogen peroxide oral rinses, and the use of appropriate PPEs which should always be encouraged.

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Dynamic Performance of Partially Orifice Porous Aerostatic Thrust Bearing

Micromachines ◽

10.3390/mi12080989 ◽

2021 ◽

Vol 12 (8) ◽

pp. 989

Author(s):

Muhammad Punhal Sahto ◽

Wei Wang ◽

Ali Nawaz Sanjrani ◽

Cheng Xu Xu Hao ◽

Sadiq Ali Shah

Keyword(s):

Thrust Bearing ◽

Dynamic Stiffness ◽

Dynamic Performance ◽

Research Work ◽

Analysis Model ◽

Thrust Bearings ◽

Damping Characteristics ◽

Fluent Software ◽

Perturbation Frequency ◽

The Impact

The aerostatic thrust bearing’s performance under vibration brings certain changes in stiffness and stability, especially in the range of 100 to 10,000 Hz, and it is accompanied by significant increase in fluctuations due to the changes in frequency, and the size of the gas film damping. In this research work, an analysis is carried out to evaluate the impact of throttling characteristics of small size orifice on stiffness and stability optimization of aerostatic thrust bearings. There are two types of thrust bearing orifices such as: partial porous multiple orifice and porous thrust bearings and their effects on variations in damping and dynamic stiffness are evaluated. A simulation based analysis is carried out with the help of the perturbation analysis model of an aerostatic thrust bearing simulation by using FLUENT software (CFD). Therefore, two models of aerostatic thrust bearings—one with the porous and other with partial porous orifice are developed—are simulated to evaluate the effects of perturbation frequencies on the damping and dynamic stiffness. The results reveal a decrease in the amplitude of dynamics capacity with an increase in its frequency, as well as a decrease in the damping of partial porous aerostatic thrust bearings with an increase in the number of orifices. It also reveals an increase in the radius of an orifice with an increment of damping of bearing at the same perturbation frequency and, with an increase in orifice height, a corresponding decrease in the damping characteristics of bearings and in the dynamic stiffness and coefficient of damping of bearing film in the frequency range less than 100 Hz.

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Weak feature extraction of rolling element bearing based on self-adaptive blind de-convolution and enhanced envelope spectral

Journal of Vibration and Control ◽

10.1177/10775463211050726 ◽

2021 ◽

pp. 107754632110507

Author(s):

HongChao Wang ◽

WenLiao Du ◽

Haiyi Li ◽

Zhiwei Li ◽

Jiale Hu

Keyword(s):

Feature Extraction ◽

Vibration Signal ◽

Rolling Element Bearing ◽

Enhancement Effect ◽

Minimum Entropy ◽

Rolling Element ◽

Element Bearing ◽

Repetitive Impact ◽

The Impact ◽

Fault Feature Extraction

As the most commonly used support component in engineering, rolling element bearing is also the most prone-to-failure part. The vibration signal of faulty bearing will take on repetitive impact and modulation characteristics, and the two features are often difficult to be extracted by conventional fault feature extraction methods such as envelope spectral. The main reasons are due to the influence of strong background noise, the signal attenuation of the acquisition path, and the early weak failure characteristics. To solve the above problem, a weak fault feature extraction method of rolling element bearing by combing improved minimum entropy de-convolution with enhanced envelope spectral is proposed in the paper. The enhancement effect of improved minimum entropy de-convolution on impact features and the satisfactory extraction effect of EES on repetitive impact and modulation features are utilized comprehensively by the proposed method. Firstly, improved minimum entropy de-convolution is used to filter the vibration signal of faulty bearing to enhance the impact characteristics, and the influence of signal acquisition path on the attenuation of the signal characteristics is also weakened at the same time. Then, enhanced envelope spectral is performed on the filtered signal, and the repetitive impact and modulation characteristics of vibration signal are extracted synchronously. In order to solve the shortcomings of the current commonly used de-convolution methods, an improved minimum entropy de-convolution method based on D-norm is proposed, which can solve the interference caused by random impulsive signals effectively. In addition, compared with the conventional method such as envelope spectral, the enhanced envelope spectral method could extract the repetitive impact and modulation characteristics of the faulty signal simultaneously much more effectively. Effectiveness and superiority of the proposed method are verified through simulation, experiment, and engineering application.

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Water Injection Pipeline Repair Offshore Angola Enhances Production

10.4043/31015-ms ◽

2021 ◽

Author(s):

Kamil Sobolewski

Keyword(s):

Water Injection ◽

Surface Cleaning ◽

Second Phase ◽

Element Analysis ◽

Reduced Pressure ◽

Area Survey ◽

Coating Removal ◽

Multiple Challenges ◽

Mechanical Tool ◽

The Impact

Abstract An international operating company detected a leak during an annual ROV inspection of a water injection (WI) pipeline offshore Angola in the Gulf of Guinea. The pipeline owner made the decision to repair the damaged line using clamps, but there were multiple challenges involved in executing the repair. First was the depth of the pipeline, which was on the seabed across an area that ranged from 1,170 m to 1,410 m (3,839 ft – 4,626 ft). Additional challenges included potential complications for clamp installation because of the location of the pipe welds and the physical condition of the pipe, which had experienced considerable wall thinning in multiple areas. Bringing the pipeline back into safe service required repairs to the aging pipe within a scope of work that included site preparation, the installation of two 12-in clamp connectors, and inspection services following clamp placement to verify proper installation. Because there were welds in the WI pipeline, there was a risk that the clamp installation site would correspond with an area of the pipe that was welded, which would impact the ability of the clamps to fit snugly over the damaged area. Survey data were cross-referenced with the client's data to determine that the weld locations would not interfere with the installation. Coating removal was critical, so a purpose-built mechanical tool was designed to prepare the pipeline for clamp installation. The project also required finite element analysis (FEA) to confirm that the pipeline could withstand the seal load applied by the repair clamps. The project was carried out in three steps. The objective of the first step was to prepare and stabilize the seabed to ensure it could bear the weight of the clamp installation frame and the impact of the ROV working nearby. The second phase focused on preparing the repair locations for installation of the clamps, a process that included coating removal and surface cleaning to return the WI pipeline to bare metal finish in the clamp areas. The third phase was the preparation and installation of the 12-in repair clamps. This included the inspection and spot cleaning of pipeline surfaces, clamp installation, and clamp seal verification. The two clamps were successfully installed and passed pressure testing in February 2020, enabling the operator to bring the WI line back online and functioning safely at reduced pressure. This repair employed the highest-pressure clamp of this type installed to date (138 bar / 2,000 psi).

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