共查询到20条相似文献,搜索用时 78 毫秒
1.
传统的电感式颗粒传感器输出的是电感或电压幅值的脉冲信号,本质为标量信号。可通过脉冲信号的正负性区分金属颗粒是磁性或非磁性,且只能在已知颗粒材质的情况下估计颗粒的粒径。但在含有多种金属颗粒的油液中,基于标量信号的颗粒识别方法将失效。为此,本文采用了一种双锁相放大电路,将颗粒产生的复数域信号转化为一对直流信号。提出一种基于模糊隶属度函数的信号处理方法,实现了在噪音干扰下多种颗粒的材质识别和粒径估计。本文搭建了三线圈传感器实验系统。利用五种金属颗粒构建了隶属度函数,并进行系统标定。最后选取两种颗粒对标定后的系统进行了验证。结果表明系统对颗粒材质的识别准确,粒径估计误差小于2%。 相似文献
2.
3.
《Flow Measurement and Instrumentation》2005,16(5):309-314
This paper presents a novel instrumentation system that uses a combination of electrostatic and digital imaging sensors. An inferential approach is adopted for the mass flow measurement of particles, velocity and volumetric concentration of particles being measured independently. The velocity of particles is determined by cross correlating two signals derived from a pair of electrostatic sensors and the volumetric concentration of particles is obtained using a novel digital imaging sensor, which also provides particle size distribution data. The basic principles and limits of operation of the imaging sensor are discussed and explained. Results obtained from a pneumatic conveyor are presented which demonstrate good performance of the measurement system for both mass flow metering (accurate to about ±6%) and particle sizing (reliable to around ±2.5%). Particle size distribution results are also included and the insensitivity of particle sizing to changes in velocity and concentration is assessed. In addition, on-line sizing results are compared to off-line results, measured using an accepted laser diffraction based instrument, and good agreement is observed. In general, the results obtained are encouraging and the system shows great promise. 相似文献
4.
5.
Acoustic emission (AE) technology is a promising approach to non-intrusively measure the size distribution of particles in a pneumatic suspension. This paper presents an experimental study of the AE sensing technology coupled with signal processing algorithms for on-line particle sizing. The frequency characteristics of the AE signals under different experimental conditions are studied and compared. Initially, the characteristics of the background noise and AE signals are compared in the frequency domain for different air velocities and particle feeding rates. Through short-term energy analysis the working features of the suction unit and the vibration feeder are revealed. To find the effective characteristic frequency band of the AE signals, a multiple scanning and accumulation method assisted with a Savitzky–Golay smoothing filter is used to denoise the power spectra of the signals. Wavelet analysis is also deployed to denoise the signals. The denoising performance of different wavelet parameters (wavelet function, decomposition level and thresholding) is compared in terms of signal-to-noise ratio and signal smoothness. Finally, particle size is predicted through a neural network with energy fraction extracted through wavelet analysis. Experimental results demonstrate that the relative error of the particle sizing system is no greater than 23%. 相似文献
6.
Recently, much attention has been given to the influence of airborne particles in the atmosphere on human health. Sliding contacts are a significant source of airborne particles in urban environments. Airborne particles may be generated by disc brakes and wheel-rail contacts. This paper presents a new model for determining the number of airborne particles generated by a sliding contact. Previously presented data from a pin-on-disc tribometer equipped with airborne particle counting instrumentation was used to verify the model. The derived particle rate is proportional to the load for the ball bearing steel material evaluated. Furthermore, the model incorporates three particle regimes with distinct number peaks; one with ultra fine particles with a peak around 0.08 μm, one with fine particles with a peak around 0.35 μm and one with coarse particles with a peak around 2 μm, that can be used to rank the number of generated particles from different material combinations and contact conditions. 相似文献
7.
When small airborne conducting particles and fibrils strike a conducting surface with an electric charge distribution on it, they acquire charge and are repelled from the surface. If the conducting surface is connected to a power supply of constant potential, a charging pulse is observed as each particle or fibril makes contact with the surface. A collection of such charging pulses can be processed by a pulse height analyzer to yield information about the size and frequency of conducting airborne particles. 相似文献
8.
9.
Airborne wear particles originating from disc brakes are one important contributor to the concentration of airborne particles
in urban environments. It is therefore of interest to improve the knowledge of these particles. The purpose of this article
is to investigate the concentration and size distribution of the airborne wear particles generated from the contact between
a low-metallic pad material and a grey cast iron disc at different load levels. This is done on model level with a pin-on-disc
machine that allows the cleanliness of the air surrounding the test specimens to be controlled, and thus the airborne portion
of the wear particles to be studied separately. The concentration and size of airborne wear particles were measured online
during testing with four particle instruments. In addition, airborne wear particles were collected on filters during the tests
and afterward analysed using SEM. Trimodal size distributions with peaks around 280, 350 and 550 nm were registered during
running-in for all load levels. After running-in bimodal size distributions with peaks around 350 and 550 nm were registered
for all load levels with the exception of the highest load level where multimodal size distributions were registered. At the
two highest load levels the concentration of ultrafine/fine particles showed an increase up to a factor hundred indicating
a change in wear mechanism. SEM images show ultrafine, fine and coarse airborne wear particles. 相似文献
10.
考虑传统动态光散射颗粒粒度分布测量用的反演算法复杂、精度不够、抗噪能力差,本文基于大数据思想,提出了一种动态光散射颗粒分布软测量方法。该方法通过调节颗粒粒度分布形状参数获得大量自相关函数及其对应颗粒分布的数据;使用这些数据对子学习机进行训练。最后,针对训练数据维数较高的特点对传统Bagging算法进行改进,并利用改进的Bagging集成算法集成子学习机以提高软测量模型的精度及泛化能力。通过模拟单峰数据和对300nm标准粒径进行软测量开展了验证实验。结果表明,该方法能够较好地测量出不同动态光散射颗粒分布的峰值及分布宽度,模拟单峰数据测量峰值精度可达1nm,300nm和503nm,标准粒径测量精度分别可达3nm和4nm,优于一般的反演算法。该软测量方法为动态光散射颗粒分布测量开辟了新的途径。 相似文献
11.
Alessandro Bastari Cristina CristalliRoberto Morlacchi Eraldo Pomponi 《Mechanical Systems and Signal Processing》2011,25(3):901-916
The present work introduces an innovative method for measuring particle size distribution of an airborne powder, based on the application of signal processing techniques to the acoustic emission signals produced by the impacts of the powder with specific metallic surfaces. The basic idea of the proposed methodology lies on the identification of the unknown relation between the acquired acoustic emission signals and the powder particle size distribution, by means of a multi-step procedure. In the first step, wavelet packet decomposition is used to extract useful features from the acoustic emission signals; the dimensionality of feature space is further reduced through multivariate data analysis techniques. As a final step, a neural network is properly trained to map the feature vector into the particle size distribution.The proposed solution has several advantages, such as low cost and low invasiveness which allow the system based on this technique to be easily integrated in pre-existing plants. It has been successfully applied to the PSD measurement of coal powder produced by grinding mills in a coal-fired power station, and the experimental results are reported in the paper. The measurement principle can also be applied to different particle sizing applications, whenever a solid powder is carried in air or in other gases. 相似文献
12.
激光散射法测量非球形粒子尺寸的方法 总被引:4,自引:0,他引:4
介绍了激光散射法粒度测量的基本原理。提出了非球形粒子,如线状、柱状粒子的测量方法。通过对几种尺寸粒子的计算机分析表明,用线形、矩形衍射数迭代上述粒子,可获得与实际情况一致的结果。 相似文献
13.
14.
单颗粒气溶胶质谱仪通常采用空气动力学透镜进样,通过测量透镜出口每一个颗粒物的速度来推算颗粒物的空气动力学直径。然而,颗粒物速度受透镜前端压力的影响较大,该压力发生微小变化就会导致颗粒物粒径检测发生偏差。本研究提出一种适用于单颗粒气溶胶质谱仪的自动粒径校正方法,预先记录几组一定透镜前端压力范围内的粒径校准参数,然后根据进样压力的变化,使软件自动通过插值算法拟合相应的粒径校正方程对颗粒物粒径测量值进行校正,从而保证在指定的压力波动范围内粒径测量结果的准确性。实验结果表明,当透镜前端压力在164.92~352.45 Pa范围变化时,该方法对于152~3100 nm颗粒物的测径偏差大部分都在10 nm以内。模拟结果表明,该方法能够保证仪器在海拔8 km范围内粒径测量的准确性,可以应用到所有采用空气动力学进样及激光颗粒物粒径测量的仪器中,能够极大地增加仪器对外界环境的适应性并提高数据结果的可靠性。 相似文献
15.
A novel test method was used to identify how contact conditions influence the wear modes and transitions for sliding steel-on-steel contacts. The test equipment was a pin-on-disc tribometer equipped with instruments for counting airborne particles. The results show that the dominant wear mode significantly influences the number of airborne particles generated from the contact. During mild wear few or no measurable airborne particles were generated. The transitional running-in process could also be identified by airborne particle measurement analysis. 相似文献
16.
17.
18.
In this paper, making the best use of the features of the electro-rheological (ER) valve, a two-port pressure control valve
using ER fluids is proposed and manufactured. The ER-Valve characteristics are evaluated by changing the intensity of the
electric field and the number of electrode. As only with electrical signal change to the ER-Valve in which ER fluid flowing,
ER fluid flow is controlled, so development of simple ER-Valves have been tried. The ER-Valves and pressure drop check method
are considered to be applied to the fluid power industry. Using the manufactured pressure control valve, a one-link manipulator
with FHA (Flexible Hydraulic Actuator) is driven. As a result, it is experimentally confirmed that the pressure control valve
using ER fluids is applicable to use in driving actuator. If it applies characteristics of the ER fluids, it will be able
to apply in the control system for the ER Valve which occurs from industrial controller. After having durability test, shear
stress increased regularly because of starch particles crushed by pump and particle size that was almost the same. Moreover,
Ra of copper electrode increased about 1.56 times rather than before those of performing durability test, and Rz increased
about 2.2 times. 相似文献
19.
M. LONGFILS M. RÖDING A. ALTSKÄR E. SCHUSTER N. LORÉN A. SÄRKKÄ M. RUDEMO 《Journal of microscopy》2018,269(3):269-281
Recently we complemented the raster image correlation spectroscopy (RICS) method of analysing raster images via estimation of the image correlation function with the method single particle raster image analysis (SPRIA). In SPRIA, individual particles are identified and the diffusion coefficient of each particle is estimated by a maximum likelihood method. In this paper, we extend the SPRIA method to analyse mixtures of particles with a finite set of diffusion coefficients in a homogeneous medium. In examples with simulated and experimental data with two and three different diffusion coefficients, we show that SPRIA gives accurate estimates of the diffusion coefficients and their proportions. A simple technique for finding the number of different diffusion coefficients is also suggested. Further, we study the use of RICS for mixtures with two different diffusion coefficents and investigate, by plotting level curves of the correlation function, how large the quotient between diffusion coefficients needs to be in order to allow discrimination between models with one and two diffusion coefficients. We also describe a minor correction (compared to published papers) of the RICS autocorrelation function. 相似文献
20.
Real-time single particle mass spectrometry, or continuous aerosol mass spectrometry, was originally developed in the 1970s for the purpose of identifying the chemical composition of airborne particulate matter in real-time. Although this technique has continued to evolve throughout the following decades, the fundamental characteristic of this method remains the same, involving the continuous introduction of solid particle or liquid droplets directly into the ion source region of a mass spectrometer. Continuous sample introduction allows for the chemical analysis of single airborne particles in real-time. A number of mass analyzers have been employed in real-time single particle mass spectrometry. The original real-time single particle mass spectrometer used a magnetic sector mass analyzer. Quadrupole, double-focusing, and ion trap mass spectrometers have also been utilized. The majority of the current real-time single particle mass spectrometry techniques use time-of-flight mass spectrometry. In the literature, a variety of general names have been applied to real-time single particle mass spectrometry methods. These names include direct-inlet mass spectrometry, on-line laser microprobe mass spectrometry, particle analysis by mass spectrometry, particle beam mass spectrometry, and rapid-single particle mass spectrometry. This review covers real-time single particle mass spectrometry techniques that were developed from 1973 through 1998, specifically for analyzing airborne particulate matter, including environmental aerosols, biological aerosols, and clean-room aerosols. Because the majority of the historical and current real-time single particle mass spectrometers have been employed for atmospheric aerosols, this topic is the primary focus of this review. This review does not include on-line mass spectrometry methods that are employed as a detector for other instrumental methods, such as liquid chromatography. 相似文献