Installation Position Research Articles

A Domain Adaption ResNet Model to Detect Faults in Roller Bearings Using Vibro-Acoustic Data.

Intelligent fault diagnosis of roller bearings is facing two important problems, one is that train and test datasets have the same distribution, and the other is the installation positions of accelerometer sensors are limited in industrial environments, and the collected signals are often polluted by background noise. In the recent years, the discrepancy between train and test datasets is decreased by introducing the idea of transfer learning to solve the first issue. In addition, the non-contact sensors will replace the contact sensors. In this paper, a domain adaption residual neural network (DA-ResNet) model using maximum mean discrepancy (MMD) and a residual connection is constructed for cross-domain diagnosis of roller bearings based on acoustic and vibration data. MMD is used to minimize the distribution discrepancy between the source and target domains, thereby improving the transferability of the learned features. Acoustic and vibration signals from three directions are simultaneously sampled to provide more complete bearing information. Two experimental cases are conducted to test the ideas presented. The first is to verify the necessity of multi-source data, and the second is to demonstrate that transfer operation can improve recognition accuracy in fault diagnosis.

Research on Liquid Flow Measurement Method Based on Heat Transfer Method

Thermal flowmeters are used more and more widely in liquid flow measurement. In this paper, the mechanical shape of the thermal flowmeter is designed, and the optimal installation position of the thermal probe is determined. In the aspect of measurement mechanism research, three heating methods of the thermal probe are deduced: constant voltage heating method, constant current heating method, and constant power heating method. After reasoning, the constant current heating method is determined to be ideal, so the constant current heating method is selected to heat the speed-measuring probe in the experiment. By analyzing the power factor of convection heat transfer and residual heat source of the heating probe, it is concluded that the measurement range of the thermal flowmeter is 0.5–15 m3/d, the flow in this range is proportional to the electrical signal, and the relative error of measurement is within ±5.8%. According to the analysis of the experimental results, the thermal flowmeter has a simple mechanical structure and no redundant moving parts, which can prolong its service life when used on site. When considering industrial applications, the error may be greater than the laboratory error.

Transient modeling of plunger lift with check valve for gas well deliquification in horizontal well

ABSTRACT To improve the plunger gas lift efficiency, a modified plunger was developed by adding a check valve to the downhole positioner in the Changqing Gas Field. However, the transient flow behavior of the plunger lift with check valve is unclear owing to the lack of a reliable method. Therefore, in this study, a simplified transient mechanistic model based on the law of conservation of momentum and mass is proposed to simulate the comprehensive dynamic process of a plunger-lift system. The results of the proposed method exhibited a high coincidence with that of the accumulated gas and liquid production of gas Well-1 in one cycle, and the relative errors were 2.11% and 4.29%, respectively. The calculation results demonstrate that the plunger lift with check valve can effectively prevent the flow of liquid to the bottom of the well, reduce the bottom hole flow pressure, and increase the productivity of gas well during the shut-in period. The efficiency of the plunger lift with check valve was enhanced with an increase in the volume of the accumulated liquid unloaded from the bottom of gas wells. Additionally, for the plunger lift with check valve, the production peak value was higher and the instantaneous gas production peak value was lower in comparison with the conventional plunger. After the plunger reached the wellhead, the instantaneous fluid production of the conventional plunger was relatively unstable than that of the plunger lift with check valve. A certain distance should be maintained from the bottom of the well in the case of the positioner with check valve. If the positioner is placed at the bottom of the tubing, the difference between the lift efficiency of the plunger with check valve and conventional plunger is small, and lower than that of the conventional plunger. The installation position of the downhole positioner in a gas well should be below the accumulated liquids level and should maintain a certain distance between the positioner and bottom of the well (200 m). The results of this study enhance the understanding of the operation mechanism of the plunger lift with check valve, and unloading of the accumulated liquids from the bottom of gas wells.

Effectiveness of High-Damping Rubber (HDR) Damper and Tuned Mass—HDR Damper in Suppressing Stay-Cable Vibration

High-damping rubber (HDR) dampers have the advantages of convenience for various shapes of pressure blocks, aesthetic installation, easy maintenance, temperature stability, etc.; thus, they present good application prospects in the vibration reduction of stay cables. Hence, a model of a taut cable equipped with two types of HDR damper—i.e., HDR damper and tuned mass–high-damping rubber damper (TM-HDR-D)—is established herein. Then, based on this theoretical model, the effect of each damper acting alone and in combination on the cable’s additional modal damping is studied. Finally, an actual cable of a cable-stayed bridge is used to study the effectiveness of two dampers for practical engineering. The results show that, when the TM-HDR-D has a small mass, the total additional modal damping of the cable approximates the superposition of the respective effects of the two dampers. The damping effect of HDR mainly depends on its stiffness and installation position; meanwhile, the damping contribution of TM-HDR-D is mainly related to its tuning frequency and installation position. In practical engineering, the smaller installation mass of TM-HDR-D can make up for the lack of damping enhancement of the cable-end HDR damper.

Analysis and design of a novel cubic WPT system in a metal environment for an enclosed sensor scenario

AbstractThis paper proposes a novel cubic WPT system for an enclosed sensor scenario, and its transmission characteristics in a metal environment have been analyzed. In addition, stable and high transmission efficiency can be normally achieved in all positions. The proposed quasi‐double D coil structure is composed of two pairs of transmitting coils; each transmitting coil pair is placed face to face and connected serially. Through current amplitude modulation, magnetic flux can flow towards the centre of the receiving coil and keep the system high efficiency when the rotation angle of the receiving coil changes. However, the installation position of the receiving coil is not fixed in the switch cabinet application, and an irregular iron wall and the metal shell of sensors could also lead to inconsistent iron loss of multiple transmitters. To overcome the resulting disturbances in efficiency, the improved current amplitude control method and the optimal load have been theoretically deduced in the case of the position variation of the receiving coil in a metal environment. Finally, experimental results in two‐dimensional space verify the omnidirectional transmission capability of the proposed quasi‐double D coil, and efficiency disturbances are effectively alleviated.

A Novel Method Applicable to Large-Scale Active Magnetic Shielding System which Effectively Compensates Gradient Magnetic Fields Originated from the Surrounding Buildings

We propose the novel magnetic compensation method which is suitable to compensate gradient magnetic fields. The method is to be applied to a conventional large-scale, tri-axial active magnetic shielding system such as spacecraft magnetic testing facility. The essences of this method are adoption of compensation coils which have degrees of freedom in their coil orientations, and their installation position, which is chosen to have certain distances from the center of the shielding area. The method works with at least 4 compensation coils. In this research, we actually demonstrated the method with scaled-down experiment. Disturbance magnetic field (B) at the target zone was suppressed from 21.33nT to -1.54nT and magnetic field uniformity (ΔB) within the test zone was improved from 2.3nT to 0.015nT. In terms of magnetic field gradient, improvement from over 4nT/m to below 0.5 nT/m was achieved.

Weakly Aligned Multimodal Flame Detection for Fire-Fighting Robots

Flame detection is a key module of fire-fighting robots, especially for autonomous fire suppression. To effectively tackle the fire-fighting tasks, fire-fighting robots are usually equipped with multimodal vision systems. On the one hand, cameras of different modalities can provide complementary visual information. On the other hand, the differences in installation position and resolution between different cameras also result in weakly aligned image pairs, that is, the positions of the same object in different modal images are inconsistent. Directly fusing the image features of different modalities is difficult to meet the accuracy and false alarm requirements of fire-fighting robots. Therefore, we propose a multimodal flame detection model based on projection and attention guidance. First, we use projection to obtain the approximate position of the flame in the thermal image and employ a neighbor sampling module to detect flames around it. Second, we design an attention guidance module based on index matching, which applies the attention map generated by the thermal modality to optimize the regional feature of the color modality. Experiments on multimodal datasets collected by an actual fire-fighting robot validate that the proposed method is effective in both fire and nonfire environments.

Influence of different testing positions of sensors on the dynamic response of load sensing hydraulic systems

This paper first introduced the load sensing hydraulic system and elaborated on its load feedback, pressure cut-off, and constant power control principles. Moreover, based on the response hysteresis of the load sensing hydraulic system in the actual commissioning of the project, this paper proposed the possible influence of the sensor on the response of the hydraulic system through troubleshooting analysis. Third, experiments were conducted to obtain the system dynamic response curves given different sensor positions and to prove the hypothesis. Meanwhile, the influence mechanism and improvement measures were analyzed. Finally, the optimal installation positions of the sensor based on different operating conditions were discussed.

A Systematic Stability Enhancement Method for Microgrids With Unknown-Parameter Inverters

With massive electronic inverters, microgrids are threatened by the instability problems caused by the impedance interactions among inverters and the network. For the microgrids with black-box inverters (whose parameters are unknown due to industry secrets), it is hard to assess, much less enhance, the stability of such systems. This article proposes a systematic impedance-based stability assessment and enhancement method for the microgrids with black-box inverters. First, the return-ratio matrix <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">net</sub> of the system with both current-controlled and voltage-controlled inverters is formulated based on the nodal admittance matrix. And then, the sensitivities of the critical eigenvalues of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">net</sub> are calculated with respect to individual admittances/impedances of inverters, which can identify the “trouble maker(s).” Moreover, the low voltage active damper (LVAD) is proposed for the stability enhancement of the system. An eigenvalue perturbation sensitivity analysis method is presented to calculate the sensitivities of the critical eigenvalues with respect to nodal parallel admittances, which identifies the optimal installation position for LVAD, and accordingly provides the guidance for the design of LVAD. The effectiveness of the proposed method is verified using a modified IEEE 6-bus system in PSACD/EMTDC and RT-Lab platforms.

Optimize the Rectifier Structure to Improve the Accuracy of Gas Ultrasonic Flowmeter Under Low Flow Conditions

With the promotion of the coal-to-gas policy, the consumption of civil natural gas in China is increasing rapidly. Improving the measurement accuracy of the flowmeter is of great significance in reducing transportation costs. Computational fluid dynamics software (FLUENT) was used for simulation, the upstream choke model of a single elbow pipe was established, and the flow field in the urban pipe network’s transition area was analyzed and optimized to improve the existing commercial flow Conditioner. The effects of the Reynolds number, the installation location of the ultrasonic gas flowmeter, and aperture depth on measurement accuracy were investigated. The results show that installing the flow Conditioner can improve the velocity distribution of the flow field in the pipeline. Optimizing the flow Conditioner can shorten the installation position of the flowmeter. The optimum thickness of the flow Conditioner is 0.25D. The research results provide important theoretical significance and application value for improving the industry’s ultrasonic gas flowmeter measurement accuracy.

Research on wind direction measurement of wind turbine based on fluid simulation

For horizontal-axis wind turbines, wind turbines typically alignment nacelle to the wind using yaw system, realizing max energy capture. If the wind turbine’s nacelle has a large error to the wind, the captured wind energy loss will be large, and it will also cause an increase in the load of the unit, which will pose a major risk to the safety of the wind turbine. Affecting the wind measurement error in addition to the performance of the sensor itself, the installation position of the wind measurement equipment also accounts for an important factor, this paper on the basis of the calculation of fluid dynamics simulation results, through the lateral and longitudinal comparison of the simulation results, pointed out the best installation location of the wind direction sensor, optimize the loss caused by wind measurement error of wind turbine in design, and provide guidance for the installation of the wind direction sensor on site.

Single-sensor-based dynamic response reconstruction of blades under base excitation

Blades in the turbo-machinery are inevitably excited by base excitation in addition to unbalanced excitation of the rotor during operation. Accurate measurements of the dynamic response under base excitation are especially critical, which feasibly provides essential guidance on vibration fatigue analysis and remaining life prediction of blades. However, due to some practical factors such as the restriction of the sensor installation position and the inability to directly obtain the external load information, there are still significant challenges in obtaining dynamic response of blades at critical positions under base excitation. In this paper, a novel method is proposed to reconstruct the dynamic response of blades under base excitation, where the measurement of only one sensor is adopted. The method comprises mostly of two steps. The measured signal is first divided into single-frequency response components using empirical mode decomposition with intermittency criteria (EMDIC), and the response components are then classified into two groups depending on whether the frequency is the blade's natural frequency. Then, by combing the time-domain and frequency-domain response transmissibility matrices under base excitation (RTMBE) derived in this paper, the dynamic response of the blade can be reconstructed, whether the blade is in the resonant or non-resonant state. This paper presents numerical simulation and experimental research on a titanium alloy fan blade. The effects of single-and multi-frequency excitation, measurement noise, and measuring point selection on the results of response reconstruction are all investigated. The results demonstrate the feasibility of the response reconstruction method presented in this work for the dynamic response reconstruction of blades under base excitation.

Effect of impeller installation position on unsteady flow characteristics of a vortex pump

PurposeThe purpose of the paper is to disclose the effect of the relative position (d) between the impeller and non-vane cavity on the hydraulic performance and unsteady characteristics of vortex pump.Design/methodology/approachThree groups of vortex pump models with different impeller installation positions were analyzed and studied by combining experimental and CFD (Computational Fluid Dynamics) numerical calculations.FindingsThe steady numerical results show that as the width (d) of the impeller moves into the non-vane cavity increases, the proportion of circulation flow in the non-vane cavity is reduced and both the pump head and efficiency are on the rise. The unsteady numerical results and the Enstrophy analysis show that the dynamic and static interference between the circulation flow and the volute tongue is the main reason for the pressure pulsation with a frequency of 2fn in the vortex pump. With the increase of the d value, the dynamic and static interference between the circulation flow and the volute tongue is enhanced. The pulsation amplitude at the volute tongue of the d = 16.5 mm model increases about six times compared with the d = 0 mm model; the distribution of the vortex core in the non-vane cavity is closely related to the position of the impeller, and the peak of the Enstrophy of the circulation flow vortex belt always appears at the top of the impeller.Originality/valueThe research results provide a theoretical foundation for the optimization and improvement of the vortex pump.

Numerical simulation of the spatial and temporal distributions of the downwash airflow and spray field of a co-axial eight-rotor plant protection UAV in hover

The downwash airflow of a multi-rotor unmanned aerial vehicle (UAV) in hover can improve the penetration rate of droplets in the canopy of fruit trees, but the uncertain distribution of the downwash airflow can also lead to the generation of uneven distribution of droplets. With a co-axial eight-rotor plant protection UAV as the research object, the computational fluid dynamics (CFD) method is adopted in this study to establish the coupled flow field model of the downwash airflow and the two-phase flow model of airflow-droplets in hover. The spatial and temporal distribution law of the downwash airflow is analyzed, and the impact of the motion law of the droplets in the spray field is investigated. The results show that the downwash airflow shifts from an unsteady state to a steady state over time. Various wind vortices such as wake vortex, ground diffusion airflow, and vortex ring are generated during the evolution process, with a “negative velocity channel” of downwash airflow velocity identified in the central region under the rotors. The farther the airflow is from the rotor, the larger the area field of wake vortex airflow. Consequently, there is a gradual coupling of the left and right adjacent wake vortices from mutual independence, with the “spiral effect” of the downwash wind field offset by the mutual coupling of the upper and lower rotors of the UAV. When the installation position of the nozzle falls within the below-rotor region, the distribution of droplet deposition becomes more penetrative than the central axis installation position of the nozzle. It indicates that the below-rotor installation position of the nozzle can prevent droplets from entering into the coupling region of the trailing vortex, which reduces droplet drift. According to the field test, the measurement and simulation results of the downwash air velocity are consistent, with the minimum and maximum relative error reaching 4% and 29%.

Grounding fault location method of overhead line based on dual-axis magnetic field trajectory

To address the challenges in fault location in distribution networks, the distribution of magnetic field under overhead line and its relationship with three-phase currents are explored in this paper. At the same time, considering the influence of sensor installation position, line sag and galloping on magnetic field, a grounding fault location method of an overhead line based on dual-axis magnetic field trajectory is proposed. The analytical expressions of the magnetic field on the x-axis and y-axis under the overhead line are obtained by least squares fitting. The Lissajous figure synthesized by dual-axis is then compared with the general equation of an ellipse, and the characteristic quantity expression characterizing the magnetic field trajectory structure is obtained. Finally, a fault location criterion is constructed using the difference of the characteristic quantities of the ellipses synthesized by x-axis and y-axis magnetic fields upstream and downstream of the fault point, i.e., the difference of the length of the major axis and the minor axis, and the sign for the ratio of the cosine value of the inclination angle. Compared with other location methods based on electrical quantity, the principle of this method is simpler and it can locate faults more quickly and accurately. A large number of simulation results show that the proposed method is suitable for different types of fault conditions.

High precision and real-time acquisition system for interface stress measurement in bridge bearing

Since the damage of the bridge structure may cause great disasters, it is necessary to monitor its health status, especially the bridge bearing, the important connecting component of the bridge's upper and lower structures. Nowadays, manual inspection is the main method to get the information of the bridge bearings’ work status. However, occasional damage of bridge bearing may not be detected in time, and sometime the installation position of the bearing makes the manual inspection on bridge bearing difficult and even impossible. Therefore, in order to know the work status of the bridge bearings timely, an intelligent remote monitoring system for the bridge bearing is developed. A 32-channel real-time acquisition system is designed by using an AD7768-1 analog-to-digital converter and Xilinx Spartan-6 Field Programmable Gate Array for interface stress continuously acquired in the bridge bearing. To assure the good linearity and low noise performance of the monitoring system, the data acquisition card is meticulously designed to reduce noise from both hardware and software and realize high-precision acquisition. Through the establishment of the monitoring server, the compressive stress data can be displayed synchronously and the overpressure situation can be alarmed in real-time. The experimental results show that the accuracy of the calibrated sensor is within 1.6%, and the detection error of the acquisition board is less than 200 μV. The acquisition system is deemed to have considerable advantages in accuracy and applicability.

Effect of the Position of Overflow Pipe with Mixed Spiral Structures on the Separation Performance of Hydrocyclones

Overflow pipes are important components of hydrocyclones. The overflow products can carry huge amounts of residual energy when being discharged. In order to take full advantage of the residual energy and enhance hydrocyclone separation performance, this research designed a novel hydrocyclone by adding static mixing units with spiral elements in the overflow pipe. This study performed numerical simulations to investigate the effects of the install position of the spiral structure on the separation performance and inner flow field of the hydrocyclone. It can be concluded that both tangential velocity and pressure are first enhanced and then reduced by the elevation of the spiral structure. When the spiral structure is installed 30 mm away from the overflow pipe bottom, because of the hindrance of spiral elements, the discharge of coarse particles with the overflow are fully decreased and the quality of overflow products are enhanced.

Experiment on the influence of downhole drill string absorption & hydraulic supercharging device on bottom hole WOB fluctuation

Large amplitude and high frequency WOB (weight on bit) fluctuation will lead to problems such as low rock breaking efficiency, short service life and slow drilling speed. This problem is particularly prominent in hard and difficult to drill formation and multi interlayer formation. The development of drilling string damping and pressurization device provides an idea for the utilization of vibration energy. Theoretically, the installation of downhole drill string absorption & hydraulic supercharging device can ensure the smooth operation of the bit. However, up to now, the influence of the characteristic parameters and application methods of downhole drill string absorption & hydraulic​ supercharging device on the WOB fluctuation at the bit is not clear. Based on the drill string dynamics experimental device, the influence of downhole drill string absorption & hydraulic supercharging device on WOB fluctuation at the bit is tested and analyzed. The results show that whether the downhole drill string absorption & hydraulic supercharging device can stabilize the bit WOB is related to its elastic stiffness, installation position, bit speed and WOB; When the WOB remains unchanged, the elastic stiffness of the elastic element of the downhole drill string absorption & hydraulic supercharging device increases, and the fluctuation range of the WOB at the bit increases; Increasing the rotating speed and increasing the WOB is conducive to controlling the WOB fluctuation of the bit. Under the condition of high rotating speed, shortening the distance between the downhole drill string absorption & hydraulic supercharging device and the bit is conducive to restraining the WOB fluctuation. The research results provide a reference for the design, development and application of damping elements of drilling string damping and pressurization device.

Multimode vibration control of stay cables using pseudo negative stiffness MR damping system

At present the vibration control of stay cable suffers from low damping effectiveness in single mode vibration caused by the limitation of damper installation position as well as the poor modal compatibility, that is, a rapid degradation performance when the actual mode deviates from the designed optimal mode. In this paper, one practical semi-active magnetorheological (MR) damper based control solution is proposed to address the problems faced in multi-modal vibration control of stay cables. The semi-active pseudo negative stiffness (PNS) control strategy takes full account of the MR damper’s mechanical characteristics and the demands of the stay cable vibration control. Compared with the linear equivalent model, the proposed time-varying model exhibits more details of the damping force and the nonlinear response of the damped stay cable, which shows its essential role in the optimal design of MR-PNS scheme. Then the optimal design method of MR-PNS multi-modal vibration control for stay cable is summarized by taking the first three modes vibration control of the J20 cable in Nanjing Baguazhou Yangtze River Bridge as simulation examples. The simulations of cross-modal, multi-modal and wind-induced vibration cases are conducted respectively, while the results show that the optimal designed multi-modal MR-PNS scheme can simultaneously exceed the passive maximum modal damping ratio within first three modes. The advantages of the proposed MR-PNS method in high damping efficiency and modal compatibility could be verified by comparing with the passive multi-modal damping solution.

Applying the Crow Search Algorithm for the Optimal Integration of PV Generation Units in DC Networks

This paper presents an efficient master–slave methodology to solve the problem of integrating photovoltaic (PV) generators into DC grids for a planning period of 20 years. The problem is mathematically formulated as Mixed-Integer Nonlinear Programming (MINLP) with the objective of minimizing the total annual operating cost. The main stage, consisting of a discrete-continuous version of the Crow search algorithm (DCCSA), is in charge of determining the installation positions of the PV generators and their corresponding power ratings. On the other hand, at the slave level, the successive approximation power flow method is used to determine the objective function value. Numerical results on 33- and 69-bus test systems demonstrate the applicability, efficiency and robustness of the developed approach with respect to different methodologies previously discussed in the scientific literature, such as the vortex search algorithm, the generalized normal distribution optimizer and the particle swarm optimization algorithm. Numerical tests are performed in the MATLAB programming environment using proprietary scripts.