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Electrical and Mechanical Sensor-Based Mass Flow Rate Measurement System: A Comparative Approach
Abstract
Gas-Solid flow finds its application in various industries such as chemical and food processes, pharmaceuticals, automobile and power generation. The precise measurement and real-time monitoring of the flow process has garnered a lot of attention in the modern industrial era. The effective utilization, with high efficiency, of resources has compelled researchers to investigate the Gas-Solid flow monitoring and measurement process for the last two decades. Efforts are extended to design instruments for flow pattern visualization and quantification of mass flow rate. Generally, volumetric flow concentration and velocity profile of solid particles are required to find the mass flow rate in the case of non-invasive measurement techniques. This paper proposes a novel non-invasive mass flow rate measurement system for solid particles where electrical and mechanical sensors are simultaneously used to compensate each other's associated drawbacks. The solid particles are allowed to slide along an insulated inclined channel under the effect of gravity. The velocity profile and volumetric flow concentration are calculated using electrical sensors. Furthermore, a load cell serves as a second sensor to calculate the mass flow rate. The experimental results from both the sensors are compared to investigate the accuracy and relative errors of both the sensors under different conditions.
... These designed sensors apply for calculating the MFR of solid particles. There are two kinds of techniques: (1) indirect and (2) direct methods of calculation [15]. These methods are explained in subsequent sections. ...
... M(t) = ρ s AV s (t)β s (t) (1) where M is the MFR of the solid particles, A is an area in the cross-section of the channel through which the particles flow, the average concentration of volumetric flow is depicted by β s (t), whereas the mean velocity of particles is V s (t) and for the density of the following particles, ρ s is employed [14,15]. ...
... This algorithm is known as cross-correlation. Abrar et al. [15] have illustrated phenomena of cross-correlation flow utilizing capacitive sensors. ...
Gas-solid flow is used in the chemical industry, food industry, pharmaceuticals, vehicles, and power generation. The calculation of flow has aroused great interest in contemporary industry. In recent decades, researchers have been seeking to build an effective system to monitor and calculate gas-solid flow. Attempts have been extended from computational modeling to the creation of flow pattern visualization methods and mass flow (MFR) quantification. MFR is usually studied by volume flow concentration (VFC) and velocity distribution of solid particles. A non-invasive device is used for testing MFR, in which electronic and mechanical sensors are used to balance the shortcomings related to each other. This study investigates the simulation of flow patterns to demonstrate the behavior of solid particles as they pass through the channel. The particles are allowed to slide longitudinally in the insulated tending channel. This slippage is due to the influence of natural gravity. Electronic sensor components are used to measure the velocity distribution and concentration of volumetric flow. The load cell is used as an auxiliary sensor for measuring MFR. In addition, ANSYS fluent is used to analyze streaming queries. The experimental results are related to evaluating the accuracy and relative error of the data collected from various sensors under different conditions. However, the simulation results can help explain the movement of the gas-solid mixture and can understand the cause of pipeline blockage during the slow movement of solid particles.
... Many sectors, such as food processing, wood processing, pharmaceuticals, and surface finishing industries, could benefit immensely from an improved efficiency, output, and quality of their final products. Various methods are available to detect the mass flow, including mechanical [1], electrostatic [2], ultrasonic [3], and optical [4] techniques and more. This study focuses on microwave-based flow sensors only. ...
This paper presents a novel technique for the mass flow rate determination of particulate solids called the “Sliding Mass Technique”. The mass flow rate is a measure of the mass of a substance that passes through a given cross-sectional area per unit time. Its calculation requires simultaneous detection of the concentration and velocity of the Material Under Test. A novel measurement technique is designed for determining the concentration of the mass flow without the necessity for density evaluation. The mass flow rate is determined by fusing the established concentration results with velocity results obtained from “Microwave Spatial Filtering Velocimetry”. A new metamaterial-based mass flow sensor for particulate solids was designed, realized and measured in an industrial environment. A Software-Defined Radio (Ettus Research™’s USRP B210) was utilized as a sensor electronic system for DAQ purposes. A MATLAB app was developed to operate the SDR. Measurements were carried out on-site using a state-of-the-art wood pellet heating system with wood pellets with different moisture contents. The measurement results were found to be in very good agreement with the expected results, which strengthens the feasibility of this newly proposed measurement technique.
... Generally, an ECT sensor is typically fitted with the variable number of electrodes uniformly arranged around a pipeline or vessel, for example, in a gas-solid CFB. e electrode and a grounded screen have an isolating sheet among them. A picture of the setup used is shown in Figure 3. e specification and data acquisition are provided in [33]. ...
Electrical capacitance tomography (ECT) has been used to measure flow by applying gas-solid flow in coal gasification, pharmaceutical, and other industries. ECT is also used for creating images of physically confined objects. The data collected by the acquisition system to produce images undergo blurring because of ambient conditions and the electronic circuitry used. This research includes the principle of ECT techniques for deblurring images that were created during measurement. The data recorded by the said acquisition system ascends a large number of linear equations. This system of equations is sparse and ill-conditioned and hence is ill-posed in nature. A variety of reconstruction algorithms with many pros and cons are available to deal with ill-posed problems. Large-scale systems of linear equations resulting during image deblurring problems are solved using iterative regularization algorithms. The conjugate gradient algorithm for least-squares problems (CGLS), least-squares QR factorization (LSQR), and the modified residual norm steepest descent (MRNSD) algorithm are the famous variations of iterative algorithms. These algorithms exhibit a semiconvergence behavior; that is, the computed solution quality first improves and then reduces as the error norm decreases and later increases with each iteration. In this work, soft thresholding has been used for image deblurring problems to tackle the semiconvergence issues. Numerical test problems were executed to indicate the efficacy of the suggested algorithms with criteria for optimal stopping iterations. Results show marginal improvement compared to the traditional iterative algorithms (CGLS, LSQR, and MRNSD) for resolving semiconvergence behavior and image restoration.
In coal-fired power plants, the coal is pulverised and pneumatically conveyed to the burners. It is essential to measure and control pulverised fuel (PF) to improve combustion efficiency, reduce pollution and lower operating costs. Unlike single-phase flow, where flow density is generally considered to be uniform, air–solids two-phase flow in pneumatic conveying systems can undergo inhomogeneous concentration distributions across a given pipe cross-sectional area, especially around bends and bifurcators or trifurcators. The “roping” flow regime is an extreme example of inhomogeneous solids distribution, where highly concentrated solids form a column-like (rope-like) flow.
Two-phase flow is important in an increasing number of applications and industries. For example, the safety analysis codes for the nuclear energy industry require closure relations for the vapor-liquid interfacial transfer terms, while accurate two-phase pressure drop models are necessary to design the piping systems in the oil and gas industry. Also, two-phase flow occurs in heat exchangers, steam generators, chemical reactors, oil transportation and many other process equipments. In addition, development of accurate and suitable instrumentations for on-line monitoring and measurement of the solids concentration and velocity in gas-solid two-phase flows has proven to be a challenging problem with many scientists and engineers worldwide developing novel techniques for this application. This paper presents a review on the electrical-based measurement techniques for gas-solid and gas-liquid two-phase flows along with the most recent patents developed for two-phase flow measurements. Also, development of a novel method for the design of capacitance sensors for void fraction measurement and flow pattern identification was presented in detail.
There are a lot of different noncontact methods for measuring the electric charges carried on solid particles, the mass flow rate, concentration, volume loading, mean flow velocity, and other flow electrical and mechanical parameters in the two- and multiphase gas-solid flows as those in pneumatic conveyance, in the air, etc. One of the methods is that based on the phenomenon of electrostatic induction. The nonintrusive probes, sensors, detectors, and transducers of different shapes are used as the first parts of measuring systems built to measure the aforementioned quantities, which are strictly related to the flow of charged particles, without any disturbance to them. The method presented here employs a ring-shaped metal electrode called a probe. The flow itself produces the electrostatic flow noise that is induced on the inner surfaces of sensing devices in the form of charge or potential or both whose values are proportional to the quantities measured. The signals obtained at the output of the sensing devices are a source of information about the flow of particulates. The very first information about the method, its metrological description, and practical application to the charge measurement was published for the first time 50 years ago, and this is the reason why the author has decided to present the method's evolution and historical development, along with its many different aspects over that period.
This chapter covers the electronics for micromechanical and bioelectrical interface circuits. Therefore, standard techniques are reviewed, and recent research and development issues are outlined based on several integrated circuit designs. Interface electronics for micromechanical sensors range from open loop, purely switched capacitor (SC) circuits to closed loop, partially force feedback as well as time-continuous concepts. Interface circuits for functional electrical stimulation (FES) as well as bioelectrical recording take the step toward massively parallel circuits that allow hundreds of parallel channels, providing much more flexibility and functionality as before. Additionally, by taking advantage of modern high-voltage (HV) technologies for stimulation as well as extremely sensitive readout circuits for monitoring, a wide range of biomedical applications becomes available. The presented issues are explained in detail by exemplary circuit designs for linear and angular accelerometer and a retinal implant.
Dense phase pneumatic conveying of pulverized fuel particles under high pressure is one of the key techniques in large scale gasification of coal and petroleum coke. The real time and continuous measurement of dense phase gas–solid flow parameters such as particle velocity, concentration and mass flow rate has great significance for the in-depth understanding of particle flow dynamic behaviors and the optimized design of the conveying system. In this paper, an integrated electrostatic sensor is designed and used to explore the flow characteristics of anthracite and petroleum coke particles on a dense phase pneumatic conveyor. The ring electrodes in the integrated sensor are capable of measuring the “mean” velocity of solid particles over the whole cross-section of the pipeline, while the arc electrodes are employed to determine the local velocity of particles near them. The experimental results on a dense phase pneumatic conveyor under high pressure demonstrate that the flow characteristics depend on the physical properties of solid particles and carrying gas. Petroleum coke particles are much easier to be suspended in the gas flow than the anthracite particles, but its flow stability is worse. The local velocities from the arc electrode pairs mounted on the top of the pipeline are usually higher than those from the arc electrodes on the bottom for a stratified flow. The velocity from the ring electrode pair, indicating the mean velocity of particles over the whole cross-section, is usually higher than the local velocities from the arc electrode pairs for a suspension flow. In addition, the relationship between the mass flow rate and charge level of dense phase pneumatically conveyed solid particles is very complicated due to the complexity of the particle flow and the charge level cannot be used to measure particle concentration or mass flow rate.
Electrostatic sensors have a simple but robust structure, which can detect the electric charge from moving charged particles. Measurement of the dry particle mass flow rate, velocity, and concentration in a conveyor are the main areas of sensor application. This paper considers the measurement methods and techniques that utilize electrostatic sensors for instrumentation. The most significant applications of the sensor are reviewed and a newly developed technique in particle sizing using the spatial filtering method is explained. The results of the study re-emphasize the flexibility, reliability and cost-effective features of the electrostatic sensor for industrial applications.
The accuracy of local particle mean velocity measurement with spatial filtering method based on an electrostatic sensor matrix (ESM) is closely related to its sensitivity and spatial filtering characteristics. In this paper, the three-dimensional electrostatic field generated by a point charge in the sensing zone of the ESM is solved by using a finite element method to obtain the spatial sensitivity distributions of the ESM. Further a dimensionless calculation model for the sensitivity of the ESM is suggested based on a Cosine function. The numerical results demonstrate that the spatial sensitivity has a periodic distribution along the axial direction and its spatial periodicity is determined by the axial spacing between two adjacent electrodes. The sensitivity over the central cross-section is localized. The spatial filtering characteristics of the ESM are also investigated and verified by experiments on a gravity-fed rig. These results provide a basis for the optimized design of the ESM.
Particulate process measurement presents challenges because it often involves multiphase flow. Due to its advantages over other tomography modalities, electrical capacitance tomography (ECT) is widely applied in monitoring and measuring particulate processes. This paper presents a review on the application of ECT in particulate process measurement, including the monitoring of flow regime and solids distribution, solids flow velocity measurement, and fluidized bed dryers. The electrostatic phenomenon and the effect of electrostatics on the performance of ECT systems are also addressed. Finally, the challenges to ECT for particulate process measurement are given.
Based on tunable diode laser absorption spectroscopy, the combustion gas temperature distribution was reconstructed using the algebraic iterative reconstruction technique. The effects of the projected angle and number of rays on the temperature reconstruction results for both fan beam and parallel beam were investigated. The flow field information was shown in detail. The reconstruction quality increased with increased ray number for both parallel- and fan-beam projections. The trend tended to be smooth when the total number of beams exceeded 100. A virtual ray method combined with the reconstruction algorithms was proposed. The virtual ray method is effective to improve the accuracy of reconstruction results for the symmetric and non-axisymmetric temperature distributions. Moreover, the temperature reconstruction of an infrared gas-field furnace is demonstrated, showing the virtual ray method can be applied to the combustion diagnostics.
A novel spatial filtering velocimeter for solid particle velocity measurement in gas-solid flow system is presented based on a Linear Electrostatic Sensor Array (LESA) in the paper. The fundamental spatial filtering principle of the LESA is theoretically described, and a differential filter based on two LESAs is further proposed to remove the pedestal component of the output signal from the LESA. Thus solid particle velocity can be measured by determining the central frequency of the periodic output signal of the differential filter. A spatial filtering velocimeter consisting of a measurement head, seven-channel differential amplifiers and a computer-based data acquisition and processing system is designed and its performance is evaluated on a purpose-built gravity-fed particle flow rig and a belt rig, respectively. Experimental results show that the system repeatability is within ±5.4% over the velocity range of 1.72–3.91 m/s for a particle concentration range 0.011–0.163 m3/m3.
A novel capacitive system for the concentration measurement of gas–solid flow in pneumatically conveyed pulverized fuel at power stations has been developed. The capacitance sensor for measuring the concentration uses source-grid sensing electrodes. An active sensor and a dummy sensor are used to form a differential configuration. In order to eliminate baseline drift, to be immune to stray capacitance, and to ensure accurate measurement under very low solids/air mass flux ratio conditions, a correlated double sample (CDS) technique and lock-in detector with closed loop are used in the interface circuit. A laboratory scale pneumatically conveyed pulverized fuel loop system incorporating facilities for calibration has been fabricated for this purpose. The test section is a vertical ceramic tube of diameter 100 mm with an upward flow direction and pulverized fuel has been used as the solid phase. Results demonstrate that the system is capable of achieving linearity within ±5% at different temperatures or moisture content.
Theoretical and experimental studies of cross correlation techniques applied to non-restrictive velocity measurement of pneumatically conveyed solids using ring-shaped electrodynamic flow sensors are presented. In-depth studies of the electrodynamic sensing mechanism, and also of the spatial sensitivity and spatial filtering properties of the sensor are included, together with their relationships to measurement accuracy and the effects of solids' velocity profiles. The experimental evaluation of a 53 mm bore sensing head is described, including trials using a calibrated pneumatic conveyor circulating pulverized fuel and cement. Comparisons of test results with the mathematical models of the sensor are used to identify important aspects of the instrument design. Off-line test results obtained using gravity-fed solids flow show that the system repeatability is within +or-0.5% over the velocity range of 2-4 m s-1 for volumetric concentrations of solids no greater than 0.2%. Results obtained in the pilot-plant trials demonstrate that the system is capable of achieving repeatability better than +or-2% and linearity within +or-2% over the velocity range 20-40 m s-1 for volumetric concentrations of solids in the range 0.01-0.44%.
This paper describes a measurement system for mass flow measurement in a pneumatic pipeline. The system mainly consists of a volumetric concentration sensor and a velocity sensor. The concentration sensor is an electrical capacitance sensor which has eight electrodes; the velocity sensor is based on cross-correlating two signals derived from a pair of capacitance sensors. A cyclone is employed in this system where the sensors are placed in order to compensate the inhomogeneity of the sensor sensitivity. Experimental results obtained on a pneumatic conveyer circulating coal ash demonstrate that this system is capable of detecting various velocity profiles and solids distributions and providing an absolute mass flow rate of solids within a good agreement with the reference reading from load cells.
An accurate, reliable, on-line, continuous and non-invasive measurement of solids’ mass flow rate in pneumatic conveying pipelines has been a technically challenging area, which becomes increasingly significant to achieve efficient utilization of energy and raw materials and to reduce waste. Energy and environmental regulation and legislation, and efficiency and waste reduction are two most powerful drivers in the academic research and industrial applications for solids’ mass flow meters. In this paper, a review is presented on the recent measurement techniques of solids’ mass flow rate measurement in pneumatic conveying systems. On basic principle and configuration of each technique, performances and limitations of these techniques in industrial applications are analyzed and compared from different views to demonstrate the recent developments in the field and the possible approaches which may provide solutions to the solids’ mass flow measurement problem.
This paper presents a method for measuring the flow velocity of two-phase cryogenic flows. The proposed sensing principle is based on a multi-electrode structure that increases the sensitivity to dielectric permittivity variations compared to a simple two-electrode structure while preserving the ability to detect small perturbations. The principle may be applied for the non-invasive measurement of the volume flow of cryogenic fuels inside conveyor pipes. Measurements conducted to evaluate the applicability of the principle were performed using liquid hydrogen.
This work describes the first application of a non-invasive capacitance tomographic technique to monitoring the behaviour of industrial-scale pneumatic conveyors. Dynamic images of the solids distribution within a pipe have captured the movement of slugs in dense-phase solids conveying, and the presence of saltation in dilute-phase conveying. It has also been possible to acquire images downstream of a pipe bend and to use this information to establish a suitable location for obtaining a representative sample of a material stream. The information provided by cross-sectional images facilitates the validation of theoretical models and ultimately will allow improved design as the sensitivity and resolution of the technique are enhanced. A study of particle (sea salt) attrition is reported using a conveying line 32 m in length. It is demonstrated that particle breakage can be described as a function of the conveying velocity and solids-gas loading factor. Particle breakage is described in terms of the mass-specific surface area, and is seen to increase with conveying velocity. Particle breakage rates are found to be inversely related to the solids loading factor.
Processes involving biomass are of growing interest, but handling and conveying biomass particles are challenging due to the unusual physical properties of biomass particles. This paper reviews recent work on pneumatic conveying of biomass particles, especially agricultural particles and pulp fibres. Experimental work has been mainly carried out to determine a range of parameters, such as pressure drop, particle velocity, flow regime and electrostatic charging for both horizontal and vertical conveying. Models ranging from empirical to CFD models are also being developed. Difficulties in representing turbulence and interactions among biomass particles and between the particles and fluid have so far limited the success of advanced modeling. Further work is needed to improve understanding of multiphase biomass pneumatic conveying and to assist in the development of biomass energy and conversion processes.
The development and performance of a PC-based instrumentation system for measuring the mass flow rate of gas-solid flow in a pneumatically conveying system have been discussed in this paper. A laboratory scale pneumatic conveyor incorporating facilities for calibration has been fabricated for this purpose. The test section is a vertical plexiglass tube of diameter 12.7 mm with an upward flow direction and sand has been used as the solid phase. The principle of measurement is based on inferential technique. Instantaneous velocity and concentration of the bulk solids are measured using a pair of electrodynamic sensors and a capacitance sensor, respectively. Several modifications of the existing technique of measurement have been suggested.
Summary Due to the unparalleled simplicity of its sensor elements, its versatility due to a plurality of applicable materials and
the availability of small and fairly low cost monolithic sensor interfaces, the acceptance of capacitive technology has constantly
increased during the last years. This work addresses the design of a versatile sensor interface for capacitive sensors usable
for automotive and industrial measurement problems. The interface is implemented in a 0.25 µm CMOS technology and provides
mechanisms in order to cope with front end parasitic effects and external electromagnetic compatibility disturbers. The presented
interface is used to evaluate the coupling capacitances of a spatial filtering sensor for flow velocity determination of liquid
hydrogen.
Capacitive technologies play an increasingly important role in the fields of industrial and automotive sensors. The non-contact working principle, on the one hand, is the main advantage of this technology, on the other hand the sensor may be sensitive to electromagnetic disturbances. This paper gives an overview of capacitive sensors which can reliably be operated in harsh industrial and automotive environments summarizing the author's work on this topic.