scholarly journals Determining the influence of structural and operational parameters of a double bearing on the thickness of its disc

2021 ◽  
Vol 3 (7 (111)) ◽  
pp. 68-73
Author(s):  
Vladimir Nazin
Keyword(s):  
Flow Rate ◽  
Power Plants ◽  
Bending Strength ◽  
Structural Parameters ◽  
Successive Approximations ◽  
Stable Operation ◽  
Centrifugal Forces ◽  
Total Load ◽  
Reynolds Equations ◽  
The Impact

This paper describes the main advantages of hydrostatic dynamic bearings of the double type, which have several lubricant films. It is indicated that they have an increased carrying capacity, by 1.8 times, and an extended range of stable operation, by 1.5 times, compared to conventional sleeve bearings with one lubricating film. The importance of determining the thickness of the bearing disk has been demonstrated, as it affects its durability. The goal was to investigate the impact of changes in the operational and structural parameters of a double bearing on the thickness of its disk. A sequence for determining the disk thickness has been proposed, including a joint solution to Reynolds equations, the balance of work fluid flow rate, as well as determining the loads acting on a bearing disk, which makes it possible to rationally assign the thickness of the bearing disk. The most common and effective methods of successive approximations have been used in the numerical implementation of Reynolds equations and flow rate balances. The action of centrifugal forces caused by the rotation of the disk has been taken into consideration in determining the total load acting on the bearing disk. The bending strength of the bearing disk was considered under its exposure to the total load. It was noted that due to the high flow rate of the working liquid pumped through the bearing, and the small change in the temperature of the liquid inside the bearing, the temperature deformations of the disk were not taken into consideration. The magnitude of change in the thickness of the double bearing disk has been determined, caused by the action of centrifugal forces in the examined range of angular speeds of the disk's rotation with the shaft. The reported results could be especially useful in the design of rotor supports for nuclear power plants where bearings have large dimensions, as well as for other units in power plants.

Design and Implementation of the Medium and Long-Term Time Scale System Frequency Fluctuations Simulation Platform

2013 ◽  
Vol 392 ◽  
pp. 656-659
Author(s):  
Ting Yu ◽  
Zhao Yu Jin ◽  
Ying Yun Sun ◽  
Jing Huai Lin ◽  
Tian Jiao Pu
Keyword(s):  
Mathematical Model ◽  
Wind Power ◽  
Power Plants ◽  
Frequency Control ◽  
Thermal Power ◽  
Clean Energy ◽  
Simulation Software ◽  
Stable Operation ◽  
Simulation Platform ◽  
The Impact

Large-scale wind power integrates in the grid to provide clean energy; however, it has a negative impact on the stable operation of the grid. To analysis the effect of wind power on frequency control, we need the help of simulation software. But, there has no frequency control mathematical model of wind farm in simulation software available for the user to choose. So this paper designs and establishes a frequency simulation platform, which provides the frequency control mathematical model of wind farms, hydroelectric power plants and thermal power plants. It can not only evaluate the impact of wind power fluctuations on frequency control, but also can quantitatively analysis of the system reserve capacity, as well as AGC performance monitoring function.

scholarly journals A Speed-Governing System Model with Over-Frequency Protection for Nuclear Power Generating Units

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 173 ◽  
Author(s):  
Li Wang ◽  
Wentao Sun ◽  
Jie Zhao ◽  
Dichen Liu
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Power Grid ◽  
Simulation Software ◽  
System Model ◽  
Total Power ◽  
Stable Operation ◽  
Thermal System ◽  
Governing System ◽  
The Impact

Overspeed is more likely to occur in the process of load rejection or large disturbances for nuclear steam turbines due to the large parameter range and low steam parameters, as well as the power of the low-pressure cylinder accounting for a high proportion of the total power. It is of great significance to study the overspeed characteristics of nuclear power plants (NPPs) to ensure the safe and stable operation of the unit and power grid. According to the characteristics of NPPs, the overspeed protection model and the super-acceleration protection model were established, which were added to the speed-governing system model. The response characteristics of the reactor, thermal system, steam turbine and speed-governing system in the process of load rejection or large disturbances of the power grid were analyzed and simulated. The results were compared using the simulation software personal computer transient analyzer (PCTRAN). The simulation results showed that quickly closing both the high and medium pressure regulating valves could effectively realize frequency control when load rejection or a large grid disturbance occurred. The over-acceleration protection cooperates with the super-acceleration protection to avoid the repeated opening/closing of the valves due to overspeed protection. This could effectively reduce the impact of large disturbances on the reactor, thermal system, and turbine.

scholarly journals A Theoretical and Experimental Study of a Piezoelectric Pump with Two Elastic Chambers

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5867
Author(s):  
Xiaolong Zhao ◽  
Dingxuan Zhao ◽  
Qinghe Guo
Keyword(s):  
Flow Rate ◽  
Dynamic Load ◽  
Structural Parameters ◽  
Experimental Tests ◽  
Maximum Output ◽  
Piezoelectric Pump ◽  
Piezoelectric Vibrator ◽  
Output Performance ◽  
Key Factor ◽  
The Impact

The paper is a continuation of our work on the dynamic load in piezoelectric pumps. In the study, the dynamic load of liquid in the pipelines was proposed as a key factor that limits the output performance of piezoelectric pumps. To decrease the dynamic load, a piezoelectric pump with two elastic chambers was proposed in our previous published work. In this paper, the performance and key parameters of the piezoelectric pump with two elastic chambers were studied through theoretical analyses and experimental tests. After establishing the mathematical model of the piezoelectric pump with two elastic chambers, the paper theoretically analyzed the performance of the pump and the effect of different structural parameters on the performance. Then prototypes with a range of structural parameters were developed and tested. As revealed from the test results, the elastic chamber effectively decreased the dynamic load of the liquid in the pipelines and the flow rate of the prototype with two elastic chambers was higher than that of the prototype with one or no elastic chamber. However, the elastic chamber did not lead to the increase in the maximum output backpressure of the prototype. Adopting an elastic diaphragm exhibiting a smaller stiffness or a larger diameter could help decrease the dynamic load of the liquid. The elastic chamber more significantly impacted the flow rate of the piezoelectric pump with long pipelines. The pump chamber height had a significant effect on the output performance of the piezoelectric pump with two elastic chambers, which is consistent with the conventional piezoelectric pump. At the height of 0.2 mm, the flow rate of the prototype with two elastic chambers was peaked at 7.7 mL/min; at the height of 0.05 mm, the output backpressure reached the highest of 28.2 kPa. The dynamic load could decrease the amplitude of the piezoelectric vibrator, whereas the prototype with two elastic chambers could effectively reduce the impact of dynamic load on the piezoelectric vibrator. The flow rate decreased almost linearly with the backpressure. Under the same backpressure, the flow rate of the prototype with two elastic chambers was higher than that of the prototype without elastic chamber, and the flow rate difference between the two prototypes gradually decreased with the backpressure.

Impact Of Transurethral Resection Of Prostate On International Prostate Symptom Score And Peak Urinary Flow Rate

2020 ◽  
Vol 16 (1) ◽  
pp. 11-15
Author(s):  
Md Waliul Islam ◽  
Md Abul Hossain ◽  
Md Nurul Hooda ◽  
Kazi Rafiqul Abedin ◽  
Husne Ara
Keyword(s):  
Flow Rate ◽  
Transurethral Resection ◽  
Urine Volume ◽  
T Test ◽  
Urinary Symptoms ◽  
Urinary Flow Rate ◽  
Transurethral Resection Of Prostate ◽  
Urinary Flow ◽  
Paired Student ◽  
The Impact

Objectives: To evaluate urinary symptoms and quality of life in patient with BPH before and after TURP. To determine the impact of TURP on the urinary symptoms (IPSS) and peak urinary flow rate. Methods: This study is prospective study carried out between 2010 and 2011 in the department of Urology, National Institute of Kidney Diseases & Urology. Total 102 cases were selected purposively according to selection criteria. Each patient was observed and followed up at 8 weeks (1st visit), 16 weeks (2nd visit) 24 weeks (3rd visit) after transurethral resection of prostate (TURP). IPSS score, QOL score also recorded and uroflowmetry was done to see the peak urinary flow rate (Qmax) of urine and voiding time. USG was done to see post voidal residual urine volume and DRE also done in selected cases. Data was complied and statistical analysis were done using computer based software, Statistical Package for Social Science (SPSS), using paired ‘t’ test. A P value <0.05 was taken as significance. Results: Before TURP, IPSS range 17-25 and mean 21.61+2.43, after TURP, range 0-7 and mean 4.27+1.71). Hence a significant improvement of IPSS was found from 2 months to 6 months follow up after TURP. The change was tested using “paired student ‘t’ test”. Before TURP Qmax range 7-12.2 and mean was 9.96+1.69, which became range 18-25 and mean was 22.61+2.28 after TURP and therefore change of mean Qmax was 12.64+2.69. The change was tested using “paired student ‘t’ test”. The change was found significant (P<0.001). Conclusion: Transurethral resection of prostate resolves obstructive symptoms, rapid improvement of urinary flow rate Bangladesh Journal of Urology, Vol. 16, No. 1, Jan 2013 p.11-15

Financial Risks of the Bank: Assessment and Mechanism of Neutralization

2020 ◽  
Vol 22 (1) ◽  
pp. 6-12
Author(s):  
Nelia Volkova ◽  
◽  
Alina Mukhina ◽  
Keyword(s):  
Risk Assessment ◽  
Financial Stability ◽  
Financial Risk ◽  
Stable Operation ◽  
Financial Risks ◽  
Negative Consequences ◽  
Conceptual Approach ◽  
Relevant Today ◽  
Banking Institution ◽  
The Impact

Abstract. Introduction. The issue of financial risk management of commercial banks is quite relevant today, because the activity of banks is the most risky of all. The presence of risks in banking can lead to unexpected losses, namely the loss of own resources. That’s why for the stable operation of the bank without loss the priority is to assess the financial risks, which is the basis for their further neutralization. Purpose. The purpose of the article is to develop conceptual provisions for assessment financial risks and justifying the need to neutralize them. Results. The article analyzes the impact of risks on the financial stability of a banking institution. The main methods of bank risk assessment are considered. All these include the statistical method, the analytical method, the expert method, the analogue method and the combined method. The necessity of neutralization of financial risks in order to avoid negative consequences is substantiated. Also the methods of bank risks neutralization are considered. It should be noted that these methods of neutralization can not only be used, but also supplement the list with new methods must be done, which in the future will protect the bank from the influence of undesirable factors. A conceptual approach to the assessment and neutralization of financial risks is proposed. This conceptual approach aims to ensure effective assessment of the level of risk with their subsequent neutralization Conclusions. Use of a conceptual approach will allow an effective risk assessment and decision-making to avoid or accept risk. Thanks to using this approach, the banking institution will be able to react swiftly to the presence of financial risks and to prevent the occurrence of negative consequences, which may lead to a violation of the financial stability of the bank.

Sign in / Sign up

Export Citation Format

Share Document