Gas Flow Sensor Research Articles

Self-powered, multi-angle gas flow sensing based on photovoltaics with porous graphite electrodes

A self-powered, multi-attack angle gas/air flow sensor without azimuth directional constraints has been designed and developed in this study. Two essential components, the porous graphite cathode and the perovskite photovoltaics, work synergistically in the device. The gas flow penetrates the bulky porous cathode, causing the pressure differences between the upper and lower sides of the nano/micro sheets, leading to the micro lift-force (Bernoulli theory) or dynamic pressure, consequently breaking or forming the electrically conductive paths among the nano/micro sheets. Therefore, the altered electrical conductivity of the cathode prompts a change in the output photocurrent of the perovskite photovoltaic unit. The thin film photovoltaic device design eliminates the requirement for external power sources, enabling multi-attack angle sensing without any azimuth directional limitations.It's important to highlight the scarcity of micro airfoil structures in the gas flow sensing domain by utilizing the nano/micro graphite sheets as the electrode and the thin film photoelectrical device as the power source, which challenges the conventional design typically based on macro-mechanical theory. It is expected that this study could provide researchers with a fresh and distinct perspective for designing and advancing the next generation of multi-angle gas-flow sensors.

Reliability of Domestic Gas Flow Sensors with Hydrogen Admixtures.

Static flow sensors (e.g., thermal gas micro electro-mechanical sensors-MEMS-and ultrasonic time of flight) are becoming the prevailing technology for domestic gas metering and billing since they show advantages in respect to the traditional volumetric ones. However, they are expected to be influenced in-service by changes in gas composition, which in the future could be more frequent due to the spread of hydrogen admixtures in gas networks. In this paper, the authors present the results of an experimental campaign aimed at analyzing the in-service reliability of both static and volumetric gas meters with different hydrogen admixtures. The results show that the accuracy of volumetric and ultrasonic meters is always within the admitted limits for subsequent verification and even within those narrower of the initial verification. On the other hand, the accuracy of the first generation of thermal mass gas flow sensors is within the limits of the verification only when the hydrogen admixture is below 2%vol. At higher hydrogen content, in fact, the absolute weighted mean error ranges between 3.5% (with 5%vol of hydrogen) and 15.8% (with 10%vol of hydrogen).

Development of PMUT-Based High Sensitivity Gas Flow Sensor

Development of PMUT-Based High Sensitivity Gas Flow Sensor

A high sensitivity and low noise thermal gas flow sensor based on silicon-doped thermocouples

A high sensitivity and low noise thermal gas flow sensor based on silicon-doped thermocouples

Advances in Triboelectric Flow Sensor

AbstractWith the rapid development of advanced materials and manufacturing technologies, flow sensors have made significant progress in the field of mechanical engineering, which could cater to the development trend of the Internet of Things (IoT) and the ongoing Fourth Industrial Revolution. However, traditional power supply modes such as lithium batteries require regular recharging or replacement, which greatly causes too much inconvenience and maintenance consumption, and may also pose potential risks to the marine environment. The triboelectric nanogenerators (TENGs), based on the coupling effect of contact electrification and electrostatic induction, have been demonstrated to convert mechanical movements of the fluid into electrical signals with various features such as flexibility, conformability, and user‐friendliness. This review systematically summarizes for the first time the fundamental working mechanism, rational structural design, and analysis of practical application scenarios of triboelectric flow sensor as an emerging technology for flow monitoring of the Industrial IoT. According to the different fluid objects monitored, the latest representative achievements of triboelectric flow sensors can be divided into gas flow sensors, liquid flow sensors, and two‐phase flow sensors. Finally, the current challenges and future development directions of triboelectric flow sensors are examined, which can promote the further development of the field of the flow sensors.

A Thermopile-Based Gas Flow Sensor with High Sensitivity for Noninvasive Respiration Monitoring.

In this work, a N/P polySi thermopile-based gas flow device is presented, in which a microheater distributed in a comb-shaped structure is embedded around hot junctions of thermocouples. The unique design of the thermopile and the microheater effectively enhances performance of the gas flow sensor leading to a high sensitivity (around 6.6 μV/(sccm)/mW, without amplification), fast response (around 35 ms), high accuracy (around 0.95%), and mood long-term stability. In addition, the sensor has the advantages of easy production and compact size. With such characteristics, the sensor is further used in real-time respiration monitoring. It allows detailed and convenient collection of respiration rhythm waveform with sufficient resolution. Information such as respiration periods and amplitudes can be further extracted to predict and alert of potential apnea and other abnormal status. It is expected that such a novel sensor could provide a new approach for respiration monitoring related noninvasive healthcare systems in the future.

Monitoring the Stability of Oxygen Flow Analyzer on Oxygen Station in the Hospital

Oxygen therapy besides having benefits also has certain dangers and side effects. For this reason, oxygen therapy must be given at the proper dose by monitoring the patient regularly and adjusting the oxygen flowmeter. The accuracy of flowmeter under standard conditions is guaranteed by manufacturer. With time and use the precision may change and the flow accuracy given in a hospital setting may differ from the original value. Thepurpose of this research is to conduct further research on Oxygen flow analyzer which focuses on discussing the accuracy and stability of the oxygen flow sensor against the gold standard. Contribution of this study is to increase the range of oxygen flowrate measurement to 15 liters per minute (LPM). This research uses Arduino Mega while the gas flow sensor used is legris flow sensor. The measurement results are displayed on TFT LCD equipped with SD Card data storage. The gas flowrate is regulated using a flowmeter (GEA). Meanwhile the comparison tools using Oxygen Analyzer and 1 m3 oxygen gas cylinder. At the testing stage, the sensor reading value on the module that appears on the TFT LCD is compared with the resultsf a comparison tool with a measurement range of 1 LPM to 15 LPM 6 times at each point. The conclusion from these results is that the calibrator module has a relative error is still within the allowable tolerance limit of ±10%.
 INDEX TERMS Calibration, Oxygen Flow Analyzer, Flowmeter, TFT Display

Cross Correlation-Based Ultrasonic Gas Flow Sensor With Temperature Compensation

Cross Correlation-Based Ultrasonic Gas Flow Sensor With Temperature Compensation

Low-Power Transit Time-Based Gas Flow Sensor with Accuracy Optimization.

In this paper, a fully designed ultrasonic transit time-based gas flow sensor is presented. The proposed sensor has been optimized in terms of accuracy, sensitivity, and power consumption at different design stages: mechanical design of the sensor pipe, piezoelectric transducer configuration and validation over temperature, time of flight detection algorithm, and electronics design. From the optimization and integration of each design part, the final designed gas flow sensor is based on the employment of 200 kHz-piezoelectric transducers mounted in a V-configuration and on the implementation of a cross-correlation algorithm based on the Hilbert Transform for time-of-flight detection purposes. The proposed sensor has been experimentally validated at different flow rates and temperatures, and it fully complies with the accuracy specifications required by the European standard EN14236, placing the proposed design into the state of the art of ultrasonic gas flow sensors regarding cost, accuracy, and power consumption, the latter of which is crucial for implementing smart gas meters that are able to autonomously operate as IoT devices by extending their battery life.

Highly accurate differential pressure FBG gas flow sensor

In this paper, the limitations of traditional electronic-type gas flow sensors for flow measurements in practical engineering applications such as flammable and explosive gas environments are discussed. Further, the importance and uncertainty of gas flow measurements in critical parts of industrial equipment are also discussed. In this work, a high-precision differential-pressure FBG gas flow and a temperature sensor with an embedded nozzle were designed using a long-diameter nozzle-type throttle tube with a fiber optic Bragg grating and an elastic-sensitive diaphragm composite strain mechanism. It was observed that the pressure difference between the two sides of the nozzle leads to the deformation of the elastic-sensitive diaphragm, and it results in a wavelength drift of the strain grating that is attached to the elastic diaphragm. Further, it also enables real-time monitoring of the gas flow value. Moreover, the temperature compensation grating which was attached to the side wall of the gas chamber was used to eliminate the cross-sensitivity of the strain grating as well as to improve measurement accuracy while implementing a temperature monitoring system. The experimental results showed that the Bragg wavelength drift in the fiber grating gas flow sensor acts as a quadratic curve with respect to the gas flow, and the experimental results were found to be highly compatible with the results of the theoretical analysis.

Design and Fabrication of a Novel Poly-Si Microhotplate with Heat Compensation Structure.

I Microhotplates are critical devices in various MEMS sensors that could provide appropriate operating temperatures. In this paper, a novel design of poly-Si membrane microhotplates with a heat compensation structure was reported. The main objective of this work was to design and fabricate the poly-Si microhotplate, and the thermal and electrical performance of the microhotplates were also investigated. The poly-Si resistive heater was deposited by LPCVD, and phosphorous doping was applied by in situ doping process to reduce the resistance of poly-Si. In order to obtain a uniform temperature distribution, a series of S-shaped compensation structures were fabricated at the edge of the resistive heater. LPCVD SiNx layers deposited on both sides of poly-Si were used as both the mechanical supporting layer and the electrical isolation layer. The Pt electrode was fabricated on the top of the microhotplate for temperature detection. The area of the heating membrane was 1 mm × 1 mm. Various parameters of the different size devices were simulated and measured, including temperature distribution, power consumption, thermal expansion and response time. The simulation and electrical-thermal measurement results were reported. For microhotplates with a heat compensation structure, the membrane temperature reached 811.7 °C when the applied voltage was 5.5 V at a heating power of 148.3 mW. A 3.8 V DC voltage was applied to measure the temperature distribution; the maximum temperature was 397.6 °C, and the area where the temperature reached 90% covered about 73.8% when the applied voltage was 3.8 V at a heating power of 70.8 mW. The heating response time was 17 ms while the microhotplate was heated to 400 °C from room temperature, and the cooling response time was 32 ms while the device was recovered to room temperature. This microhotplate has many advantages, such as uniform temperature distribution, low power consumption and fast response, which are suitable for MEMS gas sensors, humidity sensors, gas flow sensors, etc.

Self-Powered and Robust Marine Exhaust Gas Flow Sensor Based on Bearing Type Triboelectric Nanogenerator

Exhaust gas flow takes a vital position in the assessment of ship exhaust emissions, and it is essential to develop a self-powered and robust exhaust gas flow sensor in such a harsh working environment. In this work, a bearing type triboelectric nanogenerator (B-TENG) for exhaust gas flow sensing is proposed. The rolling of the steel balls on PTFE film leads to an alternative current generated, which realizes self-powered gas flow sensing. The influence of ball materials and numbers is systematically studied, and the B-TENG with six steel balls is confirmed according to the test result. After design optimization, it is successfully applied to monitor the gas flow with the linear correlation coefficient higher than 0.998 and high output voltage from 25 to 106 V within the gas flow of 2.5–14 m/s. Further, the output voltage keeps stable at 70 V under particulate matter concentration of 50–120 mg/m3. And the output performance of the B-TENG after heating at 180 °C for 10 min is also surveyed. Moreover, the mean error of the gas flow velocity by the B-TENG and a commercial gas flow sensor is about 0.73%. The test result shows its robustness and promising perspective in exhaust gas flow sensing. Therefore, the present B-TENG has a great potential to apply for self-powered and robust exhaust gas flow monitoring towards Green Ship.

Novel Micro flow Sensor for Air Purge Method to Monitor the State of Charge of Lead Acid Battery

The foremost aim of the present research study is to measure specific gravity of lead-acid batteries and further know batterys state-of-charge (SoC). In this article, air purge method is used to monitor the status of a battery; back differential pressure is measured using MPX4006 DP MEMS pressure sensor. In air purge method, it is essential to adjust the rate of bubbles in acid. This can be achieved by controlling the compressors speed or controlling the air flow by controllers. When air purge tubes are inserted through a batterys cap, it is difficult to observe bubbles produced in the acid as the battery is nontransparent. If the bubble rate is too slow, the system lowers the output signal and hence stops working. During the calibration of the instrument, air flow measurement through the pipe is of prime importance. In this method, FS1012 MEMS gas flow sensor is used to monitor the discharged air flow. FS1012 is based on the thermo-transfer principle. Compared to the resistive technique, this flow sensor consists of a thermopile for air flow sensing whose signal-noise ratio is exceptional. The output of the sensor is exponential; signal conditioning circuit has been designed to get linear output 0 to 3.3 V standard range. The amplified output of signal conditioning circuit is monitored using TM4C123GXL arm controller. FS1020 is first time proposed to monitor the air flow of a small air purge probe used to monitor the state of charge of a lead-acid battery. FS1020 ensures an ideal flow of the air bubbler system, which improves the performance of the battery charge monitoring system. Conventional flow sensors for example, rotameter cannot be used for very low flow measurement; they are costlier as well as bulky. The minimum flow required to produce sufficient bubbles in acid is 0.50 liter per minute (LPM) which is measured by FS 1012.

Non-Dispersive Near Infrared Gas Flow Cell Design for Oxygenator-Exhaust Capnometry

Non-dispersive near-infrared technique is widely used nowadays for the detection of gases, especially in harsh environments. In this study, an optical gas cell was designed for oxygenator exhaust capnometry. A computer-based simulation was used for the analysis of air flows for model selection. ANSYS Discovery 2020 R2 was used for model simulation. The gas flow cells were tested using a custom-made gas rig to measure the fraction absorbance of carbon dioxide gas at the detector. Two gases were used, nitrogen gas as a reference gas (0%) and 9% carbon dioxide. Three gas cells with the following optical path lengths were tested: 31mm, 36mm, and 40mm. The results showed that all gas flow cells produced laminar flow and small pressure drop across the inlet and outlet of the cell (11~12 Pa). Further, the minimum velocity is obtained in the 40mm gas flow sensor and it is located at the gas outlet path away from the effective optical gas path. The simulation and experimental results indicate that the gas flow cell of 40mm optical path length is more suitable for the intended application as it offers a maximum effective absorption path compared to the stagnation areas, and as a result, it provides the maximum fraction absorbance.

Design and Implementation of High-Precision Panel for Multichannel Micro-Flow Gas Monitoring in Oil Exploitation

Gas leakage is a common occurrence in crude oil exploitation, and may cause devastating effects or at least put the health of workers at stake if not managed properly. To address this issue, a type of high-precision panel for multichannel micro-flow gas monitoring was proposed in this paper, which can be applied to a range of scenarios including the monitoring of gas leakage in oil exploitation. Different channels for gas-flow sensors are provided on the panel, to monitor the gas flow in multiple places at the same time. The menu is enhanced with a multilevel design, which makes it possible for the functions to be customized. The research method of this paper followed these procedures: First, hardware design was illustrated. Next, the software solution was specified in the paper. Finally, based on theoretical analysis, laboratory experiments were successfully carried out, which demonstrated that the performance of this design was in line with our scheme. Overall, this design can help conduct early warning in the case of gas leakage and remind the operators to take timely response, which can significantly ensure the safety of crude oil exploitation.

A gas flow velocity sensor fabricated with femtosecond laser using 4 μm ultra-thin glass sheet

Here we proposed a gas flow sensor enabled by a 4 μm ultra-thin glass sheet with high-integration capability for applications in the fields of industry and medicine/health. The sensor was fabricated with femtosecond laser processing in a time of several minutes, which can measure the gas flow velocity by detecting the displacement (0.4 μm to 3 μm) of the ultra-thin glass sheet in a large range of 4 m s−1 to 36 m s−1 with a sensitivity of 8.21 mV m s−1. Furthermore, changing geometric parameters of the sensor, such as aspect ratio and thickness can adjust the sensitivity and dynamic range of the sensor.

Highly Accurate Differential Pressure Fbg Gas Flow Sensor

Highly Accurate Differential Pressure Fbg Gas Flow Sensor

Enhancing the mediated electrochemical reduction process combined with developed liquid-gas electrochemical flow sensors for sustainable N2O removal at room temperature

New electrocatalysts with high reduction efficiency are needed to upgrade the mediated electrochemical reduction for real applications. In addition, automation is required to quantify active electrocatalysts in alkaline media and air pollution. In this study, N2O was removed sustainably by electrogenerated low valent nickel(I) phthalocyanine tetrasulfonate [Ni(I)TSPc] in 1 M KOH using an electroscrubbing system. Ni(I)TSPc electro generation and N2O removal were automated by two (liquid/gas) electrochemical flow sensors, respectively. The Ni(I)TSPc was generated electrochemically up to 95% in 1 M KOH, and high removal efficiency (100%) was observed for 5 ppm N2O and 90% for 10 ppm N2O. A limiting potential change in the in-situ LSV of the chemically synthesized Ni(I)TSPc was taken and derived from the calibration plot and validated by an ex-situ potentiometric titration using an oxygen reduction potential electrode. Using the obtained calibration plot, electrogenerated Ni(I)TSPc allowed a direct determination in a liquid flow cell. The gas flow sensor developed using a KOH/Ni(II)CN4 (TCN (II))-fabricated silver solid amalgam electrode showed an excellent response to N2O concentrations up to 32 ppm. A calibration plot with known concentration was derived and validated by gas chromatography. The response time and sensitivity obtained were approximately 500s and −0.012 mA ppm−1 cm−2, respectively. The sensor stability test confirmed its good stability. Finally, the developed in-situ electrochemical flow sensors were applied to the sustainable automation of N2O pollutant removal.

Real-time monitoring of chlorobenzene gas using an electrochemical gas sensor during mediated electrochemical degradation at room temperature

The stable molecular structure of chlorobenzene makes it difficult to detect at room temperature. In this study, potassium hydroxide and tetracyanonickelate (II) ([Ni(CN)4]2−) fabricated nickel foam was synthesized using a dip-coating method and monitored the chlorobenzene in the gas phase. The morphology and structure of the as-prepared sample were characterized by X-ray diffraction, field-emission scanning electron microscopy, dispersive energy spectrum, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The gas-sensing test showed that the presence of KOH enhanced the sensing performance of the tetracyanonickelate (II) layer. The KOH/tetracyanonickelate (II)-fabricated nickel foam showed a good response to low chlorobenzene concentrations ranging from 1 to 50 ppm with −0.0016 mA ppm−1 cm−2 sensitivity. In contrast, KOH and the tetracyanonickelate (II) separately fabricated nickel foam showed no response to chlorobenzene. The response time of the sensor was approximately 250 s. The mechanism for the enhanced sensing of tetracyanonickelate (II) was discussed. The sensor stability test confirmed the good stability of the sensor in measuring the chlorobenzene gas concentration. The developed electrochemical gas flow sensor effectively monitored the exit chlorobenzene gas during the electrochemical degradation process; the concentration was calculated using a calibration plot with 98.5% accuracy.

Design and Modeling of a New MEMS Capacitive Microcantilever Sensor for Gas Flow Monitoring

A new capacitive microelectromechanical system (MEMS) microcantilever gas flow sensor is introduced for application in industrial gas flow measurement pipelines. The chip encompasses microcantilevers with different lengths (50, 100, 250, and 400 μm) and the same thickness and wideness of 2 and 50 μm, respectively. Besides MEMS sensor development, we have designed a customized bypass channel based on the orifice principle for the placement of the MEMS sensor chip. Accordingly, a minibypass has been designed, which alleviates the harsh flow condition on the sensor that will be placed in the flowmeter housing. Simulations and the experimental study revealed that the sensor is capable of measuring airflows from 0 to 25 m/s with a sensitivity of 2 x 10⁻⁴ pF/m/s, and this can be expanded to other gas flow measurements with a certain bandwidth. This measurement allows us to apply this sensor for measuring moderate flows up to ~200 m/s in ~10-cm diameter pipes based on the current design for bypass. According to experimental results, the sensor output capacitance varied from 3.3445 to 3.350 pF for a range of airflow between 0 and 25 m/s. We have shown that capacitive microcantilever MEMS flow sensors could be used for flow measurements in heavy-load industrial applications.