Mass Flow Rate Measurement Research Articles

Evaluation of off-design scaling methods of supercritical CO2 compressor with experimental data

A compressor off-design performance prediction is one of the issues related to load following operation of the S–CO2 cycle. Normally, a compressor performance map produced at the design conditions is used to predict off-design performance under specific inlet temperature and pressure conditions, and that has been the case for an air compressor. The variation of temperature and pressure from the design conditions can be corrected easily for the measured mass flow rate and rotational speed when using the compressor performance map produced at the design conditions for air. In contrast, the validity of the similitude model for an S–CO2 compressor is not confirmed experimentally previously. Since S–CO2 have been repeatedly reported to have strong real gas effect, the most appropriate similitude model is yet to be determined. Using the selected data from existing S–CO2 test facilities, various similitude models are compared and the validity is checked. The results show that most similitude models predict better with enthalpy rise rather than pressure ratio for the S–CO2 compressor's off-design performance predictions. Among the compared models, ideal gas model based compressibility modified (IGZ) model for predicting enthalpy rise of the compressor at different inlet conditions showed the best prediction within the tested data.

Balanced multiphase mixing through a narrow gap

Mixing of a two-phase flow through a gap connecting adjacent channels was investigated for a variety flow rates and two gap heights. The mixing was characterized by the amount of gross liquid and net gas mass transfer from one channel to the other. The liquid mixing through the gap was calculated based on the measured mass flow rates and dye tracer concentrations at the inlet and outlet of each channel. The gas net transfer, phase fraction distributions, bubble size distributions, and gas interface velocity were measured using dual-plane wire mesh conductivity sensors at both inlets and outlets. Additionally, imaging of the fluorescent tracer dye and air bubbles were used together with Spectral Proper Orthogonal Decomposition (SPOD) to further characterize the mixing mechanisms. The water inlet Reynolds number was varied from 4 to 10×104 and the volumetric gas quality from 0 to 0.35 which resulted in gas volume fractions up to 15%. All conditions were in the bubbly flow regime. Air was introduced by a needle array producing nominally monodispersed bubbles at lower gas flow rates with broader bubble size distributions at higher gas flow rates. The Sauter mean diameter varied from 3 to 8 mm, depending on flow rates. For these balanced flows large coherent structures dominated the mixing. However, even mere O(5%) volumetric quality gas injection could significantly suppress the coherent structures reducing mixing by over 50%.

Evaluation of correlations for mass flow rate of refrigerant through electronic expansion valve in air—water heat pump system using R32

To measure mass flow rate of R32 through EEVs under real operating conditions, a commercially available air-water heat pump (AWHP) system was operated in as wide a range as possible. Measurements showed that the effect of oil circulation on the refrigerant mass flow rate of the test system was negligible. To examine whether they were able to predict refrigerant mass flow rate of R32 in a real operating heat pump systems, previous empirical correlations available in the open literature were compared against these measured data. Previous empirical correlations, except for those of Park et al. (2007), showed poor agreement with the present experimental data, with mean absolute percentage error (MAPE) from 9.1% to 334.5% for EEV#1 (D: 2.40 mm) and from 24.1% to 122.2% for EEV#2 (D: 1.65 mm). These large differences were caused by differences in internal geometry of flow passage and operating conditions due to different refrigerants. A new empirical correlation was developed considering these aspects. The valve opening ratio was considered in terms of the valve flow coefficient variation. The thermodynamic state of refrigerant at the EEV inlet was represented by the enthalpy difference, so as to avoid discontinuity of the mathematical expression at the saturated liquid point. The new correlation showed good agreement with mass flow rate measured through both EEVs, with MAPE values of 9.3% and 14.5% for EEV#1 (D: 2.40 mm) and EEV#2 (D: 1.65 mm), respectively.

3D micro-structures for rarefied gas flow applications manufactured via two-photon-polymerization

In this work, the two-photon-polymerization (TPP) fabrication technique was employed to manufacture three-dimensional (3D) micro-structures suitable for confined rarefied gas flows. Four different micro-tubes of simple geometry have been tested in vacuum conditions. The geometry of the micro-tubes was characterized via a focus-variation 3D optical measurement microscope, a digital microscope and an X-ray μ-tomography. Mass flow rate measurements of pressure-driven rarefied gas flows of nitrogen in slip and transition regimes were compared to theoretical values obtained via the kinetic theory of gases. The experimental measurements were realized via the constant volume technique. The good agreement obtained between experimental and numerical results proves the feasibility of using this fabrication technique to create well controlled 3D shaped microsystems for rarefied gas flows applications.

Gravitational mass flow measurements of various granular materials in relation to an extended Bond number

Uniaxial die pressing is a commonly used shaping technique in powder metallurgy. The initial step within the compression cycle is the filling process of the cavity with granular materials. Here, the goal is to have a reproducible cavity filling to manufacture compressed parts of consistent quality. Besides effects linked to the geometry of the cavity and the mechanisms of filling, the flowability of the granular material plays a major role. Therefore, a deeper understanding of the flow behaviour is in the centre of the present study. In order to assess the flowability, two different experimental methods are used. Granular materials of the same composition but different granular size distributions are characterised by angle of repose (AOR) and mass flow rate measurements. The two methods deliver a set of parameters that are compared using the granular Bond number. Based on the empirical findings, a modification of the granular Bond number is suggested.

Mass Flow Rate Measurement of Pneumatically Conveyed Solids in a Square-Shaped Pipe Through Multisensor Fusion and Data-Driven Modeling

Mass Flow Rate Measurement of Pneumatically Conveyed Solids in a Square-Shaped Pipe Through Multisensor Fusion and Data-Driven Modeling

The monolithic coupling of straight tube Coriolis mass flowmeter with liquid hydrogen

The Coriolis mass flowmeter (CMF) has the advantages of a simple structure and direct measurement of fluid mass flow rate. This paper numerically simulates the fluid-structure interaction (FSI) of a straight tube CMF based on the monolithic coupling methods of hydrodynamics and structural mechanics with liquid hydrogen (LH2) as the working fluid. The simulated time lag for the CMF with water is firstly compared with the results from the published experiment and the iterative partitioned coupling method to validate the model. The comparison shows that the results of the monolithic coupling are closer to the experimental results. Then the monolithic coupling method is used to analyze the FSI characteristics of the CMF with LH2. And the general flow-induced vibration results with LH2 are presented for the straight tube CMF, including the dry and wet vibration modes. The velocity and the detector positions on the time lag are specially discussed. The results reveal the FSI characteristics of the straight tube CMF with LH2.

Sub-millimetre wave range-Doppler radar as a diagnostic tool for gas-solids systems - solids concentration measurements

Current non-intrusive measurement techniques for characterising the solids flow in gas-solids suspensions are limited by the low temporal or low spatial resolution of the sample volume, or in the case of optical methods, by a short range of sight. In this work, a sub-millimetre wave range-Doppler radar is developed and validated for non-intrusive sensing of solids concentrations in a gas-solids particle system with known characteristics. The radar system combines favourable features, such as the ability to see through at optical frequencies opaque materials, to measure the local solids velocity and the reflected radar power with a spatial resolution of a few cubic centimetres over distances of a few metres. In addition, the radar hardware offers flexibility in terms of installation. After signal processing, the output of the radar is range-velocity images of the solids flowing along the radar’s line-of-sight. The image frame rate can be close to real-time, allowing the solids flow dynamics to be observed.While the well-established Doppler principle is used to measure the solids velocity, this paper introduces a method to relate the received radar signal power to the solids volumetric concentrations (cv) of different particulate materials. The experimental set-up provides a steady stream of free-falling solids that consist of glass spheres, bronze spheres or natural sand grains with known particle size distributions and with particle diameters in the range of 50–300 µm. Thus, the values of cv found using the radar measurements are validated using the values of cv retrieved from closure of the mass balance derived from the measured mass flow rate of the solids stream and the solids velocity. The results show that the radar system provides reliable measurements of cv, with a mean relative error of approximately 25 % for all the tested materials, particle sizes and mass flow rates, yielding values of cv ranging from 0.2 × 10-4m3/m3 up to 40 × 10-4m3/m3 and solids velocities within the range of 0–4.5 m/s. This demonstrates the ability of the radar technology to diagnose the solids flow in gas-solids suspensions using a unique combination of penetration length, accuracy, and spatial and time resolution. In future work, the radar technique will be applied to study non-controlled solids flow at a larger scale, and to understand flow conditions relevant to industrial reactor applications, e.g., fluidised bed, entrained flow, and cyclone units.

Control Approach to Fault Disambiguation

To ensure resilience, systems must be endowed with capabilities for rapid detection, response, and recovery to disruptiveevents. In this paper we focus on faults as disruptive events and use a diagnosis engine for their detection and isolation. In particular we use model-based diagnosis, where the diagnosis engine is provided with a model of the system, nominal values of the parameters of the model and values of some of its inputs and outputs. However, there is no guarantee that the information measured by sensors is sufficient to distinguish between multiple root-causes. We address this challenge using an optimal control approach: we design control inputs such that the similarity between outputs in ambiguous fault modes is reduced. We show that under certain assumptions on the system model, minimizing a similarity metric in terms of outputs is equivalent to increasing the diagnosis certainty. We use an optimization-based approach to input design, where the system model acts as a constraint. We show that by using a surrogate model expressed with constructs endowed with differential operators, we improve the time efficiency of the optimal control problem. We demonstrate our approach on a fuel line system, where feedback control is used to ensure the mass flow rate at the engine follows a prescribed reference. We consider leak faults that affect the fuel lines. We show that under the control inputs generated by the nominal controller, mass flow rate measurements are not enough to accurately isolate leaks. We demonstrate that by using custom inputs that minimize the similarity between the outputs in the ambiguous faults modes, the diagnosis uncertainty is eliminated.

A novel coriolis mass flowmeter signal processing method based on adaptive notch filter and Hilbert transform

Coriolis mass flowmeter has been widely used in the energy field, and the key of mass flowrate measurement is to calculate the frequency and phase difference of the signal accurately. Aiming at the poor measurement precision problem in Coriolis mass flowmeter, a novel Coriolis mass flowmeter signal processing method is presented based on adaptive notch filter and Hilbert transform. Firstly, the long time continuous frequency tracking and accuracy problem of adaptive notch filter is effectively solved, by introducing the idea of negative feedback control. Then, the frequency estimation results are used to judgment whether the whole data will be extended or not, which makes the length of data sequence close to or equal to an integer multiple of the period. And then, Hilbert transform is conducted to the extended signals. Finally, the phase difference can be obtained by utilizing the sinusoidal functions. Simulation results show that the proposed method has high frequency and phase difference estimation accuracy, and it can be used for real time flowrate measurement of flowmeter. Experimental tests validate that the precision of this method is less than 3‰, which is more than 2 times of that of the traditional method.

Influence of needle electrode arrangement on gas transportation performance of the multi-needle ionic wind pump

The ionic wind pump with multi-electrode arrangement is helpful in enlarging its application. However, the arrangement has an inherent mutual interference among the electrodes during discharging process, which have a vital influence on the transportation performance of the ionic wind pump. Meanwhile, the relevance between the mutual interference and the intensity of the ionic wind has not been clearly revealed. In this study, the gas transportation experiments of the multi-needle electrode ionic wind pump are conducted. The intensity variation of the ionic wind with mutual interference is observed in the experiments. A simulation model based on the plasma transportation is proposed to describe the multi-needle discharging process with mutual interference effect. The EHD force is used as the indicator parameter for the intensity of the ionic wind. The experimental results show that the measured mass flow rate of the ionic wind pump is enhanced under dual-row needles and weakened under triple-row needles. Based on the simulation results, the above phenomenon is attributed to variations of the space charge and electric field induced by multi-needle discharging. The added needle electrodes reduce the electric field intensity per needle while increasing the net negative charge in the space. Due to the discharging interference among the needles, the increment of the net negative charge is not proportional to the number of needles. As a result, comparing the three arrangements from the simulations, the electrohydrodynamic (EHD) force of each needle, which is the electric field intensity multiplying by space charge density, increases approximately 45.8% under dual needles and decreases approximately 38.1% under triple needles. The conclusions obtained in this paper can help to guide the design and optimization of the multi-needle ionic wind pump.

Investigation of a High-Pressure Turbine Stage in a High-Speed Rotating Transient Test Facility for Rotor Tip Study and a Parametric Study for Improved Heat Transfer Calculation

Abstract The first part of the paper presents commissioning of a single-stage high-pressure (HP) turbine employed in a series of extensive experiments to study the aerodynamics and heat transfer on the rotor surface and casing liner. The Oxford Turbine Research Facility (OTRF), a high-speed rotating transient test facility has the capability to take unsteady aerodynamic and heat transfer measurements at engine representative conditions with a variety of inlet temperature profiles including radial distortion and swirl. A temperature profile survey was conducted at the inlet of the HP nozzle guide vane (NGV). Static and total pressure and temperature measurements have been taken at various locations on the rig including NGV surface, inlet and exit, and rotor exit to establish rig operating conditions. Detailed description of mass flow rate measurements along with calculation of heat loss factor in the rig is presented. The second part of the paper presents a parametric study performed to improve heat transfer measurement calculations from high-frequency response thin-film gauges. The effect of parameters like material properties and thickness of substrate on heat flux has been studied. A detailed uncertainty analysis for heat flux is also presented. A thermal model calibrated with analytical solutions has been developed to optimize thin-film gauge configurations and to study side-conduction effects.

Mass flow prediction in a refrigeration machine using artificial neural networks

Measuring mass flow rate in refrigeration systems with flow meters can be expensive when taking into account the cost of the equipment itself and the costs related to installation and maintenance. A mode based on Artificial Neural Networks can be used to predict the value of the mass flow, at a low cost, through easily observed and measured parameters, like temperatures. Additionally, well-known correlations to calculate parameters that directly influence the mass flow rate can be used as input data for the model to improve its accuracy. Within this context, the present study aims to develop a Multilayer Perceptrons model to predict the mass flow rate of a refrigeration systems. The model developed was optimized using one hidden layer with four neurons, Adam as the optimizer and softplus as the activation function. Later, it is presented an alternative mass flow rate meter, using an Artificial Neural Network model programmed in a microcontrolled circuit with only three temperatures as inputs. To develop the model, experimental data were collected in a refrigeration machine at several operating points. Step disturbances were introduced in the mass flow rate to produce transient data. Two different data sets were considered in the training process. The first data set contained only steady-state data and in the second data set, there were steady-state plus transient data. The mass flow rate estimated through the proposed model presented an average error of 0.79 % when considering steady-state and transient data in the training process, and 0.81 % when considering only steady-state data in the training procedure. The final embedded system developed predicted the mass flow rate with an average error of 1.22 %.

Measurement of Instantaneous Mass Flow Rate of Polypropylene Gasification Products in Airflow

A simple semi-empirical gas-dynamic approach for measuring the instantaneous mass flow rate of gasification products of low-melting solid material (polypropylene) in a flow-through gas generator with ambient-temperature air as gasifying agent is proposed. The approach is validated experimentally in the direct-connect facility allowing for the short-term (~0.5 s) heating of incoming air up to ~1700 K by hydrogen injection and ignition or by pyrotechnic charge activation. The application of the proposed method for processing experimental data for 9 (of over 100) selected typical test fires showed that the time-averaged total yield of polypropylene gasification products varied from 43 to 120 g/s, while the air-to-gasification product mass ratio was 2.3–2.9. The results of all conducted experiments confirm the applicability of the proposed approach for determining the mass flow rate of gasification products. The universality of the proposed approach is confirmed by applying two different schemes of gas generator: one with hydrogen ignition and another with pyro-charge ignition.

A gas-flow funnel system to quantify advective gas emission rates from the subsurface

The estimation of greenhouse gas emission rates from the subsurface into the atmosphere is an important part of climate-related research activities and associated efforts concerning the global carbon cycle. For the direct quantification of gas emission rates from the subsurface to the atmosphere a large variety of gas detection and flux quantification techniques exists. With the goal of measuring advective CO2 gas exhalations circumventing limitations of available systems such as e.g. accumulation-chamber systems or eddy-flux covariance methods, we developed a simple, robust, and low-cost gas-flow funnel system. The device allows for the continuous measurement of mass flow rates with a free, unrestricted gas flow from advectively dominated gas exhalation spots. For the design of the gas-flow funnel we used custom-made, though easy-to-produce components, and sensors that are typically already available when working at such sites. Our general design can easily be applied at sites with focused, advectively driven gas exhalation like volcanic areas, shale-gas seeps, landfills, and open boreholes. For the proof-of-concept we tested the system during three field campaigns at a site with natural CO2-bound emissions associated with a geologic fault in southwestern Germany. The measurements showed to be comparable and repeatable throughout the three campaigns, and are consistent with findings from other field sites with comparable CO2 exhalations.

Simulation and validation of the gas flow in close-coupled gas atomisation process: Influence of the inlet gas pressure and the throat width of the supersonic gas nozzle

The effectiveness of a close-coupled gas atomisation process largely depends on the operational and the geometric variables. In this study, Computational Fluid Dynamics (CFD) techniques are used to model and simulate the gas flow in the melt nozzle area for a convergent-divergent, close-coupled gas atomiser in the absence of the melt stream. Firstly, a reference case, in which the atomisation gas is nitrogen at 50 bar and a supersonic gas nozzle with a throat width of L0 has been modelled, is presented. Then, the influence of both the inlet gas pressure and this design parameter are investigated, comparing the numerical results provided by simulations varying the inlet pressure from 5 to 80 bar and modelling different convergent-divergent gas nozzles with throat widths of 0.29∙Lo, 0.5∙Lo, 0.77∙Lo and 2∙Lo respectively. The simulation results show how similarly these two parameters modify gas mass flow rates, gas velocity fields, aspiration pressures in the melt delivery tube or the size of the recirculation zones below the melt nozzle. Therefore, it can be stated that this geometric variable of the gas nozzle may be as relevant as the inlet pressure in the atomisation process. The most important novelty of this study is related to experimental validation of the numerical results using the Particle Image Velocimetry (PIV) technique and through direct measurements of gas mass flow rates, with a clear correlation between simulated and measured data. Moreover, some results obtained with experimental atomisations using copper and nitrogen are also presented. The experimental results show that finer powders are produced by increasing the atomising pressure or the throat width of the supersonic gas nozzle, which can be directly related to the gas flow dynamics calculated numerically.

Free Suspended Thin-Walled Nickel Electroplated Tubes for Microfluidic Density and Mass Flow Sensors

In this paper, a novel fabrication method is proposed for microfluidic tubes with a large diameter, circular cross-section, and thin wall. These properties make the tubes especially suitable for density sensors and Coriolis mass flow sensors, because of the resulting low tube mass, low-pressure drop, and low pressure-dependence of the tube shape. A demonstrator sensor was fabricated and the first measurement results of fluid density and mass flow are presented. The low-cost fabrication method is based on electroplating technology and results in tubes with a near-perfect circular cross-section. Diameters ranging from 120 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> to 1 mm and wall thicknesses from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8~\mu \text{m}$ </tex-math></inline-formula> to 60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> have been achieved. For the demonstrator sensor presented in this paper a freely suspended tube was realized with a total length of 37 mm, a diameter of 600 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> , and a wall thickness of 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> . Density measurements were performed using various gases, liquids, and liquid mixtures at 21°C to 23°C lab temperature. The accuracy of the measured densities of gases such as nitrogen, argon, and helium is 5%. For liquids including DI water, isopropyl alcohol (IPA), and their various mixtures an accuracy of 0.5% was obtained. Preliminary mass flow rate measurements were performed with water and isopropyl alcohol up to 30 g/h with less than 30 mbar pressure drop thanks to the large tube diameter. [2021-0179]

Leak diagnostics in natural gas pipelines using fault signatures

Most of the oil and natural gas resources are transported via pipelines. However, due to unavoidable factors such as corrosion and earthquakes, these pipelines frequently experience faults such as leaks. In the past, undetected leaks in pipelines resulted in massive human and material losses. Though, it is possible to timely and accurately detect leaks or other faults in pipelines by improvising existing fault detection and diagnostics (FDD) methodologies. In this study, fault signatures are used to identify a leakage as well as a leaking section in a natural gas pipeline. A long transportation pipeline (up to 150 km) is simulated under transient conditions for the leak detection and diagnostics (LDD) study. Under normal operating conditions, mass flow rate measurements are used to estimate pipeline models based on autoregressive exogenous (ARX) model. Mass flow rate limits under leak-free conditions are defined by calculating adaptive thresholds. The models are tested for leakage at several locations; a minimum detectable leak with zero false alarm was 0.084 m in diameter (around 6% of the total diameter). Finally, the indicated leakage started the algorithm to identify the leaking section. Identification of a leaking section is based on a fault signature from three locations in a pipeline. The leaking section was detected by comparing a specific fault signature with a defined diagnostics matrix in the presence of 0.5% white noise.

Low-pressure gas flow properties of sintered stainless steel microporous media

The gas flows through the low permeable porous media are of great interest, especially in vacuum technology for filtering, separation processes, protection, and flow control. They can combine a high mass flow rate and a high level of rarefaction. The transient experimental technique, developed previously for the mass flow rate measurements through the microchannels [Rojas Cardenas et al., Phys. Fluids 23, 031702 (2011)], is generalized to obtain the permeability and conductance directly from the pressure variation measurements. The present experimental methodology, allowing for step by step data verification, leads to higher accuracy than the similar and commonly used method such as “pulse-decay” techniques [W. F. Brace and R. J. Martin, Int. J. Rock Mech. Min. Sci. 5, 415–426 (1968)]. The measured data are fitted according to the exponential function with the pressure relaxation time as a single fitting parameter. The permeability and conductance of the sintered stainless steel microporous medium are measured for different gases. By using the methodology proposed by Johansson et al. [Int. J. Heat Mass Transfer 142, 118412 (2019)], the characteristic pore size of the sample was determined to be equal to 1.5 micrometers. It was found that free molecular flow constant conductance is achieved at a pressure below 30 mbar for helium. This property makes this kind of porous media particularly suitable as a leak element by taking advantage of the constancy of conductance in the free molecular flow regime, for example, for calibration of ionization gauges or mass spectrometers [Yoshida et al., Measurement 45(10), 2452–2455 (2012)].

Gas pipeline safety management system based on neural network

AbstractThe risk of leakage poses a grave threat to natural gas pipeline safety. The high compressibility of gases combined with unsteady boundary conditions makes detecting leaks in pipelines a challenging endeavor. To date, in the literature, only a limited number of studies have focused on leak detection and diagnostics in gas mixture pipelines. The present study provides a system for detecting, locating, and estimating the size of small gas leaks from a compressible and dynamic natural gas flow in pipelines with improved accuracy. As a case study, a long natural gas pipeline of 80 km is simulated with leak sizes of 0%, 2%, and 5%. The safety system is developed using mass flow rate, temperature, and pressure measurements. Six classes for faulty cases and one class for no fault case were considered for the study. A shallow neural network classifier (SNNC) is trained to identify a specific fault class. The SNNC is based on a two‐layered network with 20 and 7 neurons. An input vector of 15 variables is provided to the system, and the output is one of the seven possible classes. Leakage as low as 2% at various locations are correctly diagnosed with more than 99% correct classification rate.