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Abstract

Electrostatic prccipitators (ESP) arc the most commonly used devices for gas cleaning in the power industry. From the beginning of ESP usage on a commercial scale, it has been said that all swirls and turbulences should be eliminated from the gas flow, approaching uniform gas distribution in an ESP chamber. Application of CFO (Computer Fluid Dynamics) methods in electrostatic precipitation caused radical changes in views on the role of the gas flow. Series of non-uniform gas flows was then indicated, causing an increase in ESP efficiency. This paper is a review of the gas flow distributions used in ESP and their influence on ESP efficiency. The results of computer analysis presented in this paper show that diversification of gas velocity in the ESP chamber leads to efficiency improvement for shorter zones; however, for longer zones it causes an efficiency drop. The efficiency raise owing to diversification of gas flow profile is a consequence of exponential gas velocity - efficiency dependence.
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Authors and Affiliations

Beata Sładkowska-Rybka
Marian Sarna
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Abstract

The accuracy of vehicle speed measured by a speedometer is analysed. The stress on the application of skew normal distribution is laid. The accuracy of measured vehicle speed depends on many error sources: construction of speedometer, measurement method, model inadequacy to real physical process, transferring information signal, external conditions, production process technology etc. The errors of speedometer are analysed in a complex relation to errors of the speed control gauges, whose functionality is based on the Doppler effect. Parameters of the normal distribution and skew normal distribution were applied in the errors analysis. It is shown that the application of maximum permissible errors to control the measuring results of vehicle speed gives paradoxical results when, in the case of skew normal distribution, the standard deviations of higher vehicle speeds are smaller than the standard deviations of lower speeds. In the case of normal distribution a higher speed has a greater standard deviation. For the speed measurements by Doppler speed gauges it is suggested to calculate the vehicle weighted average speed instead of the arithmetic average speed, what will correspond to most real dynamic changes of the vehicle speed parameters.

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Authors and Affiliations

Jonas Skeivalas
Eimuntas Paršeliūnas
Raimundas Putrimas
Dominykas Šlikas
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Abstract

In recent times, the concept of hard turning has gained awareness in metal cutting as it can apparently replace the traditional process cycle of turning, heat treating, and finish grinding for assembly of hard, wear-resistant steel parts. The major apprehension in hard turning is the tool vibration, which affects the surface finish of the work piece, has to be controlled and monitored. In order to control tool vibration in metal cutting, a magnetorheological fluid damper which has received great attention in suppressing tool vibration was developed and used. Also an attempt has been made in this study to monitor tool vibration using the skewness and kurtosis parameters of acoustic emission (AE) signal for the tool holder with and without magnetorheological damper. Cutting experiments were conducted to arrive at a set of operating parameters that can offer better damping characteristics to minimize tool vibration during turning of AISI4340 steel of 46 HRC using hard metal insert with sculptured rake face. From the results, it was observed that the presence of magnetorheological damper during hard turning reduces tool vibration and there exist a strong relationship between tool vibration and acoustic emission (AERMS) signals to monitor tool condition. This work provides momentous understanding on the usage of magnetorheological damper and AE sensor to control and monitor the tool condition during turning of hardened AISI4340 steel.

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Authors and Affiliations

P. Sam Paul
Mohammed Jazeel
A.S. Varadarajan

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Abstract

This paper takes a 50 kW interior permanent magnet brushless DC motor as an example, and explores the influence of the degree of stator slot skew on the overall motor magnetic density and air gap magnetic density; then reveals the influences of stator slot skewed structure on a series of key electromagnetic properties like no-load back electromotive force (B-EMF), cogging torque, electromagnetic torque, torque fluctuation, electromagnetic loss, input power, output power and operating efficiency. On this basis, a relatively best range of the skew degrees is obtained. The research work in this paper has direct reference value for the further improvement of design and manufacture, operation and maintenance, control and protection of such motors.
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Authors and Affiliations

Xue-gui Gan
1
ORCID: ORCID
Zhen-nan Fan
1
ORCID: ORCID
Jing-can Li
2
ORCID: ORCID

  1. The Key Laboratory of Fluid and Power Machinery, Ministry of Education, Xihua University, Chengdu, China
  2. State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing, China
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Abstract

A numerical analysis of the process of single-pass rolling of AZ31 magnesium alloy bars in the three-high skew rolling mill has been carried out in the study. Based on the obtained investigation results, the effect of rolling speed on the band twist and the state of stress and strain occurring in the rolled band has been determined. From the obtained results of the numerical studies it has been found that with the increase in rolling speed the unit band twist angle θ, increase, which translates into an increase in the value of tangential stress in the axial zone of the rolled bar. This contributes directly to an increase in redundant strain in the rolled bar axial zone, which brings about a structure refinement. To verify the effect of rolling speed on the flow pattern and the stress and strain state, experimental tests were carried out. It has been found from the tests that the band twist (flow pattern) contributes to obtaining a bimodal structure in the bar cross-section.

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Authors and Affiliations

A. Stefanik
P. Szota
S. Mróz

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