Maintenance, Reliability and Condition Monitoring
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Research on IGOA-LSSVM based fault diagnosis of power transformers
Get PDFPower transformer is an important part of power equipment, and its functionality affects the proper operation of the whole power network. In order to diagnose power transformer faults effectively, the authors propose a fault diagnosis strategy based on an improved locust optimization algorithm for least squares vector machines (IGOA-LSSVM). Firstly, it was required to address the problem that the diagnostic prediction accuracy of the least squares vector machine is reduced due to its parameters. So this paper introduces the locust optimization algorithm with simple algorithm structure and good performance for optimizing the parameters. And at the same time, the authors generate an improved locust optimization algorithm with self-learning factors, proportional weight coefficients and Levy flight strategy. Secondly, the improved locust optimization algorithm is used for optimizing the least squares vector machine parameters. Finally, in the simulation experiments, the results of the benchmark test function illustrate that the IGOA algorithm has better performance, and the test results of a fault samples diagnosis of the power transformer equipment illustrate that the IGOA-LSSVM has good prediction effect and improves the fault identification accuracy compared with ACO-LSSVM and PSO-LSSVM in five types of fault diagnosis
Study on the extraction method of the friction-induced vibration signal of rotary compressors
Get PDFThe operation noise level of air conditioners has been a main concern to consumers. The friction-induced vibration and noise have a contribution to the overall operation noise level of air conditioners. In this paper, two rotary compressors were tested to measure the vibration and noise of the compressors. The friction-induced vibration signals were extracted using a combination of the harmonic wavelet transform and the envelope spectrum analysis. The two rotary compressors were disassembled to check whether the compressor parts have been worn after testing. Results show that when the crankshaft was worn, the friction-induced vibration of compressors is strong. At low rotational speeds of the rotary compressor, the friction-induced vibration is easily excited, which is probably attributed to the boundary lubrication at the interface between the crankshaft and bearing. At high rotational speeds of the rotary compressor, the friction-induced vibration is not easy to be excited, which is probably attributed to the aerodynamic lubrication at the interface between the crankshaft and bearing
Determining the position of two cracks in a cantilever beam using artificial neural networks
Get PDFDuring functioning time, structures such as beams are subjected to a variety of loads caused by the working conditions and environment, which can lead to the development of cracks. The current research is concerned with detecting the presence and location of two transverse breathing cracks, in cantilever beams. Starting from the known fact that damages produce a stiffness degradation in structures altering their dynamic parameters, we performed modal simulations of damaged beams to determine their natural frequencies. By using the simulation data, we trained an artificial neural network (ANN), using the feedforward backpropagation algorithm, that is capable to detect the presence of the cracks, their position and for the case when the damages are in proximity, the model can determine if the cracks occur on the same face or opposite faces
A study of numerical simulation on extreme flexural stress of ice plate
Get PDFIce plate is general construction component in the cold region and the flexural stress governs its failure pattern. As per the stress equations which were proposed by Westgaard and Masterson, they explained the generic empirical methods to evaluate the extreme and effective flexural stress of ice plate. Based on these equations, most of consequent experiments and simulations referred them directly. Despite of this, there are not any demonstrations about the limitations of these equations by numerical modeling, therefore, it is possible to find the differences between the simulation values and theoretical calculation values by the deployment of numerical simulations from ‘Finite Element Analysis’ perspective, and based on these comparisons, author proposed some assumptions about the limitations of these equations. In the meantime, the simulation process can enhance the understanding of the applications of these equations
Use of gas reduction energy at a gas distribution station
Get PDFThe issue of utilization of excess energy of throttled natural gas is still relevant today. To solve it, various devices are used, based on such principles as on the Ranque-Hilsch vortex effect, temperature stratification using the Leontief tube, expander-generator sets and devices based on the Hartmann-Sprenger effect. One of the most common devices at gas distribution stations (gas gate station) is the turboexpander. The principle of its operation is based on the expansion of the gas flow with the performance of external mechanical work. Taking into account the increased interest in hydrogen fuel in connection with the course announced by the UN for decarbonization of production by 2050, the modern gas transmission system can become a secondary source of electricity for hydrogen production, thereby solving the problem of excess pressure energy utilization at gas distribution stations. The technological solution for using this energy is the installation of turboexpanders and electrolysis of water at gate stations in order to produce hydrogen
Experimental study on the effect of particle gradation on dewatering performance of geotubes
Get PDFTo clarify the effect of particle gradation of filling soil on the dewatering and consolidation performance of geotubes, the content of four-particle size classes (powder, fine, medium, and coarse) which are commonly used in engineering as the research object was taken. The dewatering rate, soil infiltration and solid-liquid mixing pressure in the bag with time when filling soil with different particles were studied, and the soil loss of the hanging bag was analyzed from the perspective of seepage soil gradation. The research results show that the dewatering process could be divided into the quick dewatering stage, silting stage, and stable stage according to the dewatering rate. According to the performance of soil conservation, it could be divided into the loss stage and reverse filtration stage. Further, based on the effects of powder content, non-uniformity coefficient, and curvature coefficient of soil on the dewatering rate of the hanging bag, a formula for calculating the dewatering rate of geotubes is summarized
On the use of a network of trunk pipelines to compensate for the shortage of water resources at the expense of the country’s deep Siberian rivers
Get PDFThe paper discusses topical issues and problems of water supply in scarce and arid regions of the country, including the redistribution of water flows from high-flowing Siberian rivers, which are heavily overflowing during the flood period. In particular, an overview of world experience in solving water supply problems is given, both through desalination of sea water and the use of underground sources, and through the construction of canals and main water pipelines, from futuristic ideas to projects that have already been implemented and have many years of positive operating experience. Special attention is paid to the domestic union experience, plans to turn large rivers to supply the Central Asian republics, the world’s first nuclear plants for desalination of sea water and a main water conduit to supply the Mangyshlak Peninsula. Based on the results of the analysis performed, the main disadvantages, areas, limitations and advantages of various water supply options are identified, which make it possible to draw a conclusion about the possibility of involving unclaimed capacities of main oil and gas pipelines to solve the problems of compensating for the shortage of water resources at the expense of the country's deep Siberian rivers
Recent advancements of signal processing and artificial intelligence in the fault detection of rolling element bearings: a review
Get PDFA rolling element bearing is a common component in household and industrial machines. Even a minor fault in this section has a negative impact on the machinery's overall operation. As a result, the industry suffers significant financial losses, and this damage can potentially result in catastrophic failures. Therefore, even a little fault in the rolling element bearings must be recognized and remedied as soon as possible. Many ways for detecting REB defects have been created in recent years, and new methods are being introduced on a daily basis. This article will provide a summary of such methods, with a focus on vibration analysis techniques. The newest advancements in this field will be recognizable to readers of this article. Anyone interested in defect diagnostics of rolling element bearings can utilize this material
Influence of floating support on the dynamic characteristics of compound planetary gear set
Get PDFDue to a large number of components, complex meshing relations and high requirements for assembly accuracy, the dynamic characteristic of compound planetary gear, such as vibration, impact, periodic motion and load sharing, are more easily affected by internal excitation than those of simple planetary gear set and parallel shafting gear set. To improve the load sharing behavior and the resistance of Chaos motions in the compound planetary gear set, in this work, by introducing the floating support into the center gear and planet gear, a lumped-parameter dynamic model of the compound planetary gear set is built based on the lumped parameter method and Lagrange kinematics equation. The steady response is calculated by numeric method to investigate the influence of floating support from different components on loading sharing behavior and periodic motion. The results indicate that, the increase of the floating value of all components improves the instantaneous load-sharing behavior, and single floating of planet gear reduces the load sharing behavior. To avoid the system being in quasi-periodic motion and Chaos motions under the condition of floating support, the input speed should be avoided away from the range of 3201 r/min-5069 r/min
Squeak and Rattle recognition based on speaker recognition
Get PDFSqueak and Rattle problems seriously affect the quality of the vehicles. In the adjustment stage of the automobile development process, engineers mainly rely on subjective evaluation to diagnose squeak and rattle noises, which is prone to misjudgment, missed judgment and time-consuming problems. There are gaps in relevant objective evaluation methods. This article proposed that speaker identification is used to identify squeak and rattle noises from the audio recorded in the test, to achieve objective and accurate results. In this paper, four kinds of squeak and rattle noise audios are used as samples, Mel Frequency Cepstrum Coefficient is extracted as feature vector to construct target Gaussian mixture models (GMM). The expectation, variance and correlation coefficient of the Gaussian mixture model can be calculated to describe the difference of multiple squeak and rattle noises. Using samples to judge accuracy rate, the results indicated that the acceptance accuracy rate reaches 100 %, and the rejection accuracy rate reaches more than 95 %