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61.
高速加工机床及其关键技术 总被引：29，自引：3，他引：29
介绍了高速加工机床的发展现状。对高速机床的几个主要关键技术—高速主轴单元、高速主轴支撑轴承、直线电机进给驱动系统、高速机床控制系统以及高速加工刀具进行了讨论。 相似文献
62.
根据陕西锌业有限公司对外夹式超声波液体流量计的应用实践,对这种非接触式的流量计在湿法炼锌系统的液体流量测量中的应用效果以及标定、维护方法进行了介绍。 相似文献
63.
主要针对棒线材短应力线轧机十字万向接轴的翘头现象影响现场换辊效率这个问题,通过大量现场调研,对十字万向接轴的翘头原因进行分析,并结合万向接轴和接轴托架各自的结构特点,提出三种改进方案,从根本上解决了翘头问题,提高现场生产效率. 相似文献
64.
Accurate measurement of water flow rates in large diameter pipelines is a challenge for water companies that need to produce, transport and distribute increasing quantities of water. To a large extent, this challenge results from the impossibility of recalibration of the flow meters within the periodicity established in the metrological regulations since the removal of a large size flow meter from its site of operation in the field and its transport to a calibration laboratory is in most cases technically and economically impracticable. Because of this scenario, this paper presents the pitometry technique as an interesting alternative to solve problems related to the validation of water flow measurements performed by flow measurement systems installed in large diameter conduits. The technique is based on the determination of the water flow rate by mapping the velocity profile of the water flow inside the pipe by means of Cole type Pitot tubes. The water flow rate is determined in a cross section of the pipe located near and in series to the flowmeter to be evaluated. Based on the results obtained in a great number of water flow measurements already performed by applying the pitometry technique in large diameter pipelines in the field, it is possible to conclude that this methodology is perfectly applicable in the validation of the performance of flow meters installed in these conduits solving satisfactorily the issues related to its operation. 相似文献
65.
Ultrasonic gas flowmeters (UGFM) are extensively used in petroleum, chemical, natural gas and other fields because of their distinctive measurement advantages. As the core technology of the UGFM, digital signal processing technology determines its measurement accuracy and stability. This paper systematically reviews the signal processing methods for measuring the TOF (time of flight) based on the principle of time difference method. According to the stability of the feature information extracted by different digital signal processing methods, the advantages and disadvantages of each method are analyzed. Aiming at the problems of serious energy attenuation, weak echo signal amplitude, and low signal-to-noise ratio (SNR) when ultrasonic signal propagate in the gas, different signal processing methods are evaluated and compared from the aspects of calculation accuracy, response speed, anti-interference ability and sensitivity to parameter changes. Finally, some improvement ideas and directions for further research are proposed according to the analysis results. 相似文献
66.
A venturi device is commonly used as an integral part of a multiphase flowmeter (MPFM) in real-time oil-gas production monitoring. Partial flow mixing is required by installing the venturi device vertically downstream of a blind tee pipework that conditions the incoming horizontal gas-liquid flow (for an accurate determination of individual phase fraction and flow rate). To study the flow-mixing effect of the blind tee, high-speed video flow visualization of gas-liquid flows has been performed at blind tee and venturi sections by using a purpose-built transparent test rig over a wide range of superficial liquid velocities (0.3–2.4 m/s) and gas volume fractions (10–95%). There is little ‘homogenization’ effect of the blind tee on the incoming intermittent horizontal flow regimes across the tested flow conditions, with the flow remaining intermittent but becoming more axis-symmetric and predictable in the venturi measurement section. A horizontal (blind tee) to vertical (venturi) flow-pattern transition map is proposed based on gas and liquid mass fluxes (weighted by the Baker parameters). Flow patterns can be identified from the mean and variance of a fast electrical capacitance holdup measured at the venturi throat. 相似文献
67.
The shortcomings traditional phase difference extraction algorithms have such as being susceptible to noise interference, requiring full cycle conditions, leads to a decrease in phase difference extraction accuracy. To improve the accuracy of the phase difference extraction, two improved correlation analysis methods are proposed in this paper, one of which is based on the relationship between the extreme value of the cross-correlation function and the time difference, the other of which combines correlation analysis method with Hilbert transform. A simulation and experiment were set up to explore the influence of sequence length and signal-to-noise ratio on the extraction accuracy, as well as the influence of Kalman filtering. An experiment is set to compare the extraction mean error and variance of different algorithms under different phase differences. Experimental result shows that the improved algorithms have higher accuracy and stability. The feasibility of the two improved algorithms is verified. 相似文献
68.
Ultrasonic flowmeters are currently used in the measurement of large natural gas flow. However, their high sensitivity to noise signals can cause measurement errors and direct economic losses. Particle image velocimetry (PIV) measurement technology has several advantages, including convenient installation and maintenance, and strong anti-interference ability, thereby presenting an innovative idea for its application in the field of flow measurement. In this paper, a cyclic integration method is proposed for the application of PIV technology in flow measurement of natural gas. The results show that PIV flowmeter and ultrasonic flowmeter are basically consistent, and the maximum deviation is about 2%. confirming the feasibility of the PIV flowmeter. Therefore, this study provides a theoretical and technical reference for the development of a PIV flowmeter for natural gas. 相似文献
69.
Ultrasonic clamp-on flowmeters (USCF) are popular among measurement technologies due to the versatility of applications, increasing accuracy, and easy, non-intrusive mounting, with the sensors being mounted directly on the external surface of the pipe. In industrial applications, installation space is usually restricted and therefore, flowmeters must be mounted often directly downstream of flow disturbances (FD). A major issue of USCF is the long inlet run needed downstream of FD to achieve a measurement within the specified accuracy. A configuration of two V-paths is proposed, axially rotated 90° relative to each other, that compensates for the flow error introduced due to disturbed flow conditions, independent of the rotational position of the flowmeter. Flow disturbance compensation (FlowDC) is achieved, i.e., accurate measurements within the specification of 2% flow rate accuracy, when the flowmeter is mounted as close as 2 pipe diameters (D) downstream of a FD. Computational fluid dynamics (CFD) are employed to generate rotationally independent correction factors that compensate for the error introduced from disturbed inlet conditions. An automated simulation method is developed to generate correction factors for 90° bend, out-of-plane bend, expansion, and contraction, at mounting distances from 2D to 100D, several flow rates, and rotational positions 0°, 90°, 180°, 270°. This study would be practically impossible with non-automated simulations or solely with measurements. In-house experiments were performed with an industrial clamp-on device at selected distances from the FD with the aim of verifying the simulation results. An independent field-test is presented that showcases the value of FlowDC in USCF applications. The automated simulations have the capability to simulate further FDs on-demand, with the aim of creating a database for the needs of the respective application in industry. 相似文献
70.
科里奥利质量流量计在能源和化工品等领域的贸易结算中应用较广,其具有测量效率高、精度准确和运行稳定可靠的特点。目前,人们对科里奥利质量流量计的使用提出了更高的精度要求,因此有必要进行其检定误差的消除处理。以万华(宁波)化学有限公司2019年的大修项目为例,在阐述流量计检定准确性影响因素的基础上,就项目检定与误差分析过程进行深入分析,指出科里奥利质量流量计检定误差处置办法,期望能进一步提升科里奥利质量流量计检定精度,继而为相关行业贸易实现和经济发展提供有效保证。 相似文献