Dynamic Pressure Sensors Research Articles

Turbulent flame propagation in corn dust clouds formed in confined and open spaces

Flame propagation stages in a corn dust cloud in a large room size confinement investigated. The clouds ignited by a weak heat source. The mass of the dust identified to be influenced the flame acceleration. Dust in the clouds burnt rapidly through several fluid dynamic mechanisms. Four types of instabilities contributed to fast flame development. Landau–Darrieus and Kelvin–Helmholtz instabilities increased the flame speed in the initial stages of the fireball. In the intermediate and final stages, corrugated and the wrinkled flame structure originated through Rayleigh–Taylor instabilities. In addition to flow aspects and instabilities, the shock waves also enhanced the flame speed. The shock overpressure measured with a dynamic pressure sensor. These shock waves induced Richtmyer–Meshkov instability in the fireball and developed turbulent flames. Density gradients across the fireball (due to higher temperature gradients) caused perturbations. Further, this gradient increased by the shock waves. The crosswind speed through the confinement windows was slower, therefore it has not enhanced the flame speed. Corn dust dispersed quickly to a wider area by the shock waves, established large dust clouds, and lead to explosions. The maximum surface temperature of the fireball predicted as 1384 K. The preheat zone around the fireball identified by an image processing tool. The turbulence parameters at the fireball obtained from qualitative and quantitative methods and analyzed. The clouds of a small quantity of corn dust lead to the formation of larger fireballs due to higher kinematic viscosity than the energy dissipation rate.

Leak monitoring and localization in baghouse filtration system using a distributed optical fiber dynamic air pressure sensor

• Distributed optical fiber dynamic air pressure sensor is proposed to identify and locate broken bags in baghouse filtration systems in cement industry. • Detection of broken bags with hole diameters of 0.3 cm is achieved using ADA-SVM algorithm without the interference of electromagnetic field. • The technique can be potentially used for dust emission control in environment protection field. Coherent Rayleigh backscattering noise produced by the detection of the dynamic airflow applied to a standard optical fiber is proposed to monitor and locate the potential broken fabric bags within a baghouse filtration system with a sensing distance of 2 km. The optical fiber cable hangs freely inside the fabric bags with small leak holes. Experimental results demonstrated that the proposed distributed optical air pressure sensor is capable of identifying broken bags via the measurement of airflow perturbation applied onto the optical fiber cable. Field test at a baghouse filtration test platform was conducted and results showed that the location accuracy of the system is less than ±5 m with a detectable hole diameter of 0.3 cm and a recognition rate of ~87.6% measured by Adaboost-Support Vector Machine (ADA-SVM) method. A false alarm rate of 9% for this particular leak diameter is achieved.

Effects of Air Cavity in Dynamic Pressure Sensors: Experimental Validation.

An air-backed diaphragm is the key structure of most dynamic pressure sensors and plays a critical role in determining the sensor performance. Our previous analytical model investigated the influence of air cavity length on the sensitivity and bandwidth. The model found that as the cavity length decreases, the static sensitivity monotonically decreases, and the fundamental natural frequency shows a three-stage trend: increasing in the long-cavity-length range, reaching a plateau value in the medium-cavity-length range, and decreasing in the short-cavity-length range, which cannot be captured by the widely used lumped model. In this study, we conducted the first experimental measurements to validate these findings. Pressure sensors with a circular polyimide diaphragm and a backing air cavity with an adjustable length were designed, fabricated, and characterized, from which the static sensitivities and fundamental natural frequencies were obtained as a function of the cavity length. A further parametric study was conducted by changing the in-plane tension in the diaphragm. A finite element model was developed in COMSOL to investigate the effects of thermoviscous damping and provide validation for the experimental study. Along with the analytical model, this study provides a new understanding and important design guidelines for dynamic pressure sensors with air-backed diaphragms.

Experimental investigation on bed shear stress distribution in the roughened compound channel

The roughness in the floodplains in a compound canal and its impact on hydraulic parameters such as the shear stress and their estimation are one of the problems that have attracted the attention of engineers. In this research, the aim is to investigate the effect of artificial on the floodplain of the compound channel on hydraulic parameters. In experiments, slope of channel bed was 0.0015 and three different discharges have been used. The four types of rigid roughness were used to investigate the effect of these parameters. These roughness elements were arranged with zigzag state with two distances of 4 k and 8 k (k is the height of roughness) in the floodplain. A Preston tube with an external diameter of 3 mm that equipped with dynamic pressure sensors was used to compute the shear stress. The Patel calibration curve was used in order to convert the difference between the static and dynamic pressure measured by the Preston tube to the shear stress values. The results showed that for the zigzag arrangement with the density of 4 k, the shear stress is reduced due to the high roughness density and the greater roughened area. In a rough bed, the shear stress in floodplain was significantly higher than smooth bed, and the stress distribution is such that it has descending trend from the main channel toward the wall of the floodplain. The shear stress increase for roughness with a spacing of 8 k is 22–36% higher than the similar hydraulic condition in a smooth bed and the shear stress for condition with the presence of a cylinder with D = 3 cm and roughness spacing of 8 k was 14–18% higher than the shear stress of bed without a cylinder and the same roughness density. The shear stress for condition of the presence of a cylinder with D = 6 cm and roughness spacing of 4 k is 24–30% more than the roughened plain with distances of 4 k.

Study on the suitability of ZnO thin film for dynamic pressure sensing application

Abstract ZnO thin films were prepared by RF reactive magnetron sputtering on phynox substrate at room temperature for four different thicknesses by varying deposition duration. The structural and morphological properties and composition of these films were characterized using XRD, SEM, and EDS, respectively. Suitability of these films for dynamic pressure sensing applications and the effect of film thickness on dynamic pressure sensing were evaluated experimentally using a shock tube equipment. Shock tube test results show the pure dynamic behavior of ZnO films with fast rise and discharge. Sensors with higher film thickness showed improved sensitivity which is on par with commercially available dynamic pressure sensors. This work demonstrates that the cost-effective sensors based on ZnO thin film are capable of sensing dynamic pressures for different pressure ranges.

Analysis of Model Tests of Rainfall‐Induced Soil Deposit Landslide

A large number of deposit landslides are induced by rainfall, and those with different weak layers may be subject to catastrophic failure. This research investigates the rainfall infiltration effect on the stability of deposit landslides with a weak layer at different slope angles. Four rainfall physical model tests were conducted with fixed double penetration artificial rainfall technique and dynamic sensor technologies by using the rainfall test methods as modified in the paper. Deformation and mechanics parameters, as well as water content parameters in the key position in the deposit landslide, were monitored by means of various displacement monitoring sensors, dynamic soil pressure sensors, pore water pressure (PWP) monitoring sensors, and water content sensors. The results show that, under the same rainfall conditions, the rule of displacement and mechanical changes of deposit slope with different angles are similar, that the displacement, soil pressure, and PWP are characterized by two stages of rising and falling, and that the displacement of deposit slope with weak layer remains creep after rainfall. In addition, the displacement at the rear edge of the slope with a small angle is larger than that at the front of the steep slope, but the displacement in the front of the slope is opposite. Furthermore, the slope with a smaller angle is prone to form a tensile crack in the back of the slope, and its deformation and failure have the characteristics of a progressive and thrust‐type landslide. While the failure in front of a steep slope (slope angle more than 60°) occurred first, the slope failure was characterized by sudden and retrogressive modes. The mathematical analysis of the model is also conducted which shows that deformation and failure can be divided into three stages, i.e., creep inoculation, accumulation uplift, and speed‐up sliding. The test results can provide a reference for the investigation, design, and assessment of similar deposit slopes.

Evaluation of Printed P(VDF-TrFE) Pressure Sensor Signal Quality in Arterial Pulse Wave Measurement

In this contribution, we evaluate the performance of an additively fabricated piezoelectric poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) based dynamic pressure sensor in non-invasive arterial pulse wave (PW) measurement. Additively fabricated piezoelectric sensors have high potential for the realization of affordable and unobtrusive PW measurement systems which could enable the long-term monitoring of patients with cardiovascular diseases (CVDs). However, the accuracy and reliability of such sensors have not been extensively studied before. We propose an additive fabrication process for a P(VDF-TrFE) PW-sensor, measure PW from the radial artery at the wrist from 22 healthy volunteer subjects, calculate clinically relevant parameters based on the PW waveform and compare their values to the values obtained from concurrent measurement with an electromechanical film (EMFi) based reference sensor, used earlier in several clinical studies. We show that the signals recorded with the two sensors, as well as the radial augmentation index (rAIx) and the stiffness index (SI) calculated from them, are in good agreement with each other. These results demonstrate that the additively fabricated P(VDF-TrFE) PW sensors can reach a suitable level of accuracy and reliability for clinical use.

Investigating the effect of chemical ingredient modifications on the slow cook-off violence of ammonium perchlorate solid propellants on the laboratory scale

ABSTRACTRocket propellants that contain ammonium perchlorate (AP) often have a violent response during slow heating. Two laboratory tests have been developed to determine the reaction violence of these materials. The first test was the Combustion Rate Analysis of a Slowly Heated Propellant (CRASH-P) test, which used dynamic pressure sensors to quantify the violence of the reaction. The second test used x-rays to measure physical changes in the propellants before ignition and their reaction violence through the deformation speed of the sample container. For this study, four propellant formulation modification categories were investigated. The propellants were investigated for their reaction violence and sample expansion before ignition.

Optimization of an impulse pressure generator based on the drop-weight method.

An optimized impulse dynamic pressure generator based on a drop-weight method was developed as a secondary standard. The impulse pressure generator was characterized in detail using various parameters in order to obtain a proper reference dynamic pressure, to calibrate a dynamic pressure sensor. Both a hardware filter and a software filter were successfully employed to eliminate unavoidable noise when the impulse pressure was generated. Five variables were considered to optimize the system. A larger effective area piston-cylinder assembly should be used to obtain a faster impulse pressure. To control the peak pressure using a variable drop height is easier rather than drop weight because the change is linearly proportional to the impact speed associated with the drop height. An increase in drop weight causes an increase in duration as well as an increase in peak pressure. In addition, the pressure transmission medium is very important for generating the optimized impulse pressure, so an appropriate fluid choice is required. The viscosity and bulk modulus among the fluid properties are considered as design variables. High viscosity fluids with high bulk modulus can achieve high peak pressures without jittering. The drop weight based impulse pressure generator design and implementation method is proposed based on the detailed characterizations in this study.

Verification of Calculation Procedure for Unsteady Aerodynamic Forces on a Launch Vehicle

Unsteady aerodynamic forces on large, slender aerospace structures are established in wind-tunnel tests that employ a limited number of dynamic pressure sensors and use a correlation-based approach that, so far, cannot be directly verified. This paper describes a robust procedure based on frequency-specific correlation lengths, and it provides validation from an experiment on a generic, space vehicle model. The model was coated with unsteady pressure sensitive paint, which provided time histories of pressure fluctuations on a large number of points. At first, the entire dataset was integrated to determine the “true” unsteady forces. In the next step, progressively fewer points were used as “virtual sensors,” and the correlation-based procedure was applied to determine the “modeled” forces. By comparing the time histories and power spectra, it was observed that as few as 16 virtual sensors (four rings, with each containing four sensors and separated by half a diameter) were able to replicate the true fluctuations on a model segment with a reasonable accuracy. The modeled levels were typically higher, and they approached the true levels with an increase in the number of the virtual sensors. The procedure showed better agreement when pressure fluctuations were more coherent over a buffet zone.

Simulations and Experimental Investigations on the Acoustic Characterization of Centrifugal Pumps of Different Specific Speed

Subject of discussion are simulations and experimental investigations on the acoustic characterization of three single stage centrifugal pumps of different specific speed. In operation, these pump-types generate pressure pulsation at blade passing frequency, primarily due to rotor-volute-interaction. In order to determine the acoustic excitation it is necessary to know about the pumps’ acoustic transmission parameters. In this paper, a one-dimensional numerical model for transient time-domain simulation is presented, which takes into account the pump geometry as well as the volutes’ structural behaviour by means of the local effective speed of sound. Numerical results for the transmission characteristics of the three different pumps are shown in terms of scattering matrices and evaluated against parameters calculated from measurement results. The experimental analyses are carried out using dynamic pressure sensors in both the suction and the discharge pipe. Assuming solely plane wave propagation, the complex acoustic field on each side is evaluated independently. The so called “two source” method is then used to determine the transmission parameters of the pumps in standstill for a range of frequencies experimentally. Subsequently, the acoustic excitation at varying rotational speed is evaluated by means of measurements at the pumps in operation and presented as monopole and dipole source types for cavitation-free conditions.

Understanding the dynamic response in ferroelectret nanogenerators to enable self-powered tactile systems and human-controlled micro-robots

Self-powered pressure sensors are critical devices in IoT sensing networks. Continuous efforts have been made in the community to improve the device performances by optimizing the materials selection and structural configurations. Therefore, a design platform for understanding the device-machine interface is imperative. This work presents a comprehensive study that uses the fundamental working principles of dipole moments in ferroelectret polymers to describe the energy conversion mechanism. The study addresses discrepancies in voltage measurements caused by instruments with different internal resistances and sampling rates. A lumped parameter model is also proposed and validated to explain the impedance mismatch at the device-machine interface. Applications including control of MEMS microactuator through static response and dynamic pressure sensor array for impact distribution sensing have also been demonstrated.

Advances in pressure sensing for vapour phase soldering process monitoring

Purpose The purpose of the paper is to improve the control of vapour phase soldering (VPS). To enable better productivity and assembling quality, the industry needs to provide precise control and measurements during assembling. In the paper, a special monitoring method is presented for VPS to enable improved process control and oven state identification. Design/methodology/approach The work presents the investigation of the workspace with dynamic and gage type pressure sensors in fusion with thermocouples. Different sensors were evaluated to find an appropriate type. The relation between the temperature and the pressure was investigated, according to the setup of the oven. The effect of inserting a printed circuit board (PCB) on the pressure of the vapour inside the oven was also investigated with the pressure/power functions. Findings It was found that the novel gage-type sensors enable better precision than solutions seen in previous literature. The sensors are able to monitor the decreasing vapour concentration when a PCB is inserted to the workspace. It was found that there is a suggested minimum power to sustain a well-developed vapour column for soldering in saturated vapour. An inflexion point highlights this in the pressure/power function, in accordance with the temperature/power curve. Originality/value The research presents original works with aspects of a novel sensor fusion concept and work space monitoring for better process control and improved soldering quality.

On the observation of high-order, multi-mode, thermo-acoustic combustion instability in a model gas turbine combustor firing hydrogen containing syngases

This paper explicates the characteristics of high-order multi-mode combustion instability generated in a model GE7EA combustor that has a partially premixed flame, which can prohibit flashback when firing fast-burning hydrogen-containing fuels. Five test cases varying both the fuel composition and heat input were selected, which generates a high multi-mode without a fundamental mode. Multi-mode instability phenomena were observed by 11 dynamic pressure sensors in both the time and frequency domains and by OH planar laser induced fluorescence (PLIF) images, which were time-synchronized with a dynamic pressure signal. A distortion in pressure waves, which resulted from the superposition of several harmonic modes of combustion instability, was observed, whereas distortion in heat release was not clearly observed. PLIF images and their statistical analysis showed scientific clues that proved the dependency of the flame location and movement on the combustion instability. The driving source of the combustion instability of the longitudinal mode was not only the longitudinal variations but also the radial variations in the center of intensity (COI) of the flame images so the Pythagorean addition of the interquartile ranges of both longitudinal and radial directions was suggested as a good indicator of the size of the longitudinal mode's combustion instability. The time series trajectory of the COI also provided meaningful information on the combustion instability mechanism. A linear and longer COI trajectory was likely to generate more intense instability because the one-way movement of the flame can be more effective in driving instability by transferring consistent force in the same direction.

Empirical findings on the transmission of draft tube instabilities along the penstocks of hydraulic plants

On EDF hydraulic production plants equipped with Francis turbines, there have been related some cases of significant pressure fluctuations detected in the upper parts of the penstock when units were operating in the high load pressure surge zone. There was no decrease of the Peak-to-Peak pressure fluctuations along the penstock in the upstream part as it could be expected. To understand the phenomenon, on site tests have been carried out using innovative non-intrusive dynamic pressure sensors in many points along the penstock allowing the analysis of upward and downward waves and their “interferences”. These interferences cause in some cases standing waves for which the envelope of pressure oscillations along the penstock exhibits nodes and anti-nodes whose positions are relatively fixed along the penstock for a given operating point of the turbine. It appears that the ratio [Frequency of surge]/[Natural frequency of the penstock] conditions directly the number of nodes. This point is important because upper zones of the penstock close to the surge tank have generally not been designed to withstand high values of pressure fluctuations. For high number of ratio (3, 5, 7…), long term operation may induce mechanical fatigue of the penstock. A statistical approach was performed based on the dynamic signal databases of EDF and GE comprising data analysis of 21 occurrences of strong axial pressure surges of high load. It seems that certain values of the frequency ratio favour this resonance. This emphasizes the role of water exchanges between the rope and the penstock (complementarily with the draft tube) in establishing the conditions of resonance.

Ultralight, Superelastic, and Fatigue-Resistant Graphene Aerogel Templated by Graphene Oxide Liquid Crystal Stabilized Air Bubbles.

Graphene aerogel (GA) has attracted great attention due to its unique properties, such as ultralow density, superelasticity, and multifunctionality. However, it is a great challenge to develop superelastic and fatigue-resistant GA (SFGA) with ultralow density because it is generally contradictory to improve the mechanical properties with reducing density of GA. Herein, we report a simple and efficient approach to prepare ultralight SFGA templated by graphene oxide liquid crystal (GOLC) stabilized air bubbles. The thus-prepared ultralight SFGA (∼2 mg cm-3) exhibits superelasticity (rapid recovery from >99% compression) and unprecedented fatigue-resistant performance (maintaining shape integrity after 106 compressive cycles at 70% strain and 5 Hz). The ultralow density and excellent dynamic mechanical properties of SFGA are mainly associated with the "volume exclusion effect" of the air bubbles as well as the highly ordered, closely packed, and uniform porous structure of the resultant GA, respectively. This study provides a green and facile strategy for preparing high-performance ultralight SFGA, which has great potential in various applications, including ultrafast dynamic pressure sensors, soft robot, and flexible devices.

Experimental research on rotating detonation with liquid hypergolic propellants

This paper describes experimental research into the initiation and propagation of rotating detonation for liquid Nitrogen TetrOxide (NTO) and liquid MonoMethylHydrazine (MMH). An annular rocket-type combustor without nozzle was designed to investigate detonation combustion. The propellants were injected through unlike impingement injectors. The combustion flame fronts and pressure waves were detected using optical diagnostics and dynamic pressure sensors, respectively. The propagation of rotating detonation was established spontaneously by increasing the mass flow rate of propellants. The velocity of propagation of the flame fronts and pressure waves was nearly equal and reaches supersonic speed. Two different detonation combustion patterns are present, single wave mode and double waves mode. And in double waves mode, the two detonation waves are always counter-rotating. The possibility of rotating detonation initiation in a combustor with nozzle was also checked. Stable rotating detonation can be initialized and sustained at similar operating conditions.

The effect of the throat width of plug nozzles on the combustion mode in rotating detonation engines

Rotating detonation engines have been studied due to their better theoretical propulsion performance than that of deflagration-based engines. In this experimental study, the Laval nozzle throat width was varied to study combustion features in rotating detonation engines with different air flow rates and equivalence ratios. The detonation channel had an outer diameter of 100 mm and an inner diameter of 80 mm. Air and hydrogen were injected into the combustor from 60 cylindrical orifices each of 2 mm in diameter and a circular channel with a width of 1 mm, respectively. Four different widths of the plug nozzle were used: 2, 4, 6, and 8 mm. Three dynamic pressure sensors were used to obtain the detonation pressure. A standard speed camera was used to observe the exhaust from the combustion process. The results show that rotating detonation never occurred for a throat width of 4 mm. Rotating detonation waves with high speeds above 2300 m/s were obtained for a throat width of 2 mm. The mode of combustion in the engine was highly dependent on equivalence ratio and throat width. Probabilities of occurrences of longitudinal pulsed detonation increased first and then decreased with the decreased throat width.

Double-Layer Rotator Cuff Repair: Anatomic Reconstruction of the Superior Capsule and Rotator Cuff Improves Biomechanical Properties in Repairs of Delaminated Rotator Cuff Tears

Background: Delamination in rotator cuff tears has been identified as a prognostic factor for negative outcome after repair, with a reported prevalence between 38% and 88%. Purpose: To compare biomechanical properties of 3 repair techniques for delaminated rotator cuff tears. Study Design: Controlled laboratory study. Methods: Eighteen fresh-frozen cadaveric shoulders were used to evaluate rotator cuff footprint reconstruction, contact area and pressure, displacement under cyclical loading, and load to failure of 3 double-row repair configurations: double-row suture repair with medial row knots (medially knotted bridge, mkB); knotless double-row repair using suture tapes (knotless bridge, klB); and knotless double-row, double-layer-specific repair (double-layer, DL). Dynamic pressure sensors were used to assess contact patterns at the footprint region in 0°, 30°, and 60° of glenohumeral abduction and 5 rotational positions (0°, 30° of internal rotation, 30° of external rotation, 60° of internal rotation, 60° of external rotation). Optical markers were used to document whole tendon and individual layer displacement after rotator cuff repair under cyclical loading for 200 cycles (10 N to 100 N at 1 Hz). Specimens were then loaded monotonically to failure at a rate of 33 mm/min. Results: Mean contact area and footprint restoration were highest in the DL group at 60° of glenohumeral abduction for all rotational positions (mkB mean ± SD, 195.4 ± 54.3 mm2, 66.7% ± 19.7%; klB, 250.6 ± 34.9 mm2, 76.2% ± 10.3%; DL, 318.4 ± 36.6 mm2, 109.1% ± 24.0%; P < .001). The double-layer-specific repair showed the least displacement under cyclical loading (mkB mean ± SD, 0.53 ± 0.18 mm; klB, 0.79 ± 0.37 mm; DL, 0.31 ± 0.24 mm; P = .029), most closely resembling the native tendon. Peak loads at failure were comparable between repair groups (mkB mean ± SD, 366.92 ± 70.59 N; klB, 280.05 ± 77.66 N; DL, 398.35 ± 109.04 N; P = .083). Conclusion: Anatomic restoration of the superior capsular and tendon insertion in delaminated rotator cuff tears with a double-layer-specific repair configuration demonstrated superior footprint restoration with increasing abduction, while providing construct displacement comparable to the native tendon under cyclical loading. Peak load at failure was comparable between repair constructs. Clinical Relevance: The prevalence and clinical importance of delaminated rotator cuff tears have long been underestimated. Anatomically correct individual reconstruction of the superior capsule and rotator cuff could restore near-native biomechanics and potentially reduce the risk of rotator cuff repair failure.

Snapshot POD analysis of transient flow in the pilot stage of a jet pipe servo valve

ABSTRACTThe spatial evolution of a turbulent flow in the pilot stage of a jet pipe servo valve at the inlet pressure and deflection angle of the jet pipe is investigated using a large eddy simulation (LES). The pressure of the same flow field is measured by a high frequency dynamic pressure sensor in the experiments and is compared with the results of the LES, as well as their root-mean-square (RMS) and fast Fourier transform (FFT) results. The results of experiments and LES are in good agreement, indicating that LES is able to predict the flow dynamics. Velocity datasets based on LES are utilised to conduct the snapshot proper orthogonal decomposition (snapshot POD) technique. The snapshot POD analysis results of the first 4 modes show a full ability to directly visualise details of the coherent structures. The influences of the inlet pressure and deflection angle of the jet pipe are also discussed. Under different inlet pressures, the velocity eigenfunctions of the first mode are similar, while the locations and strengths of the vortices in high modes are different. The Lamb-Oseen vortices that affect the trajectory of jet streams are observed in the vicinity of the entrances of receiver channels only in the first mode, and several spindly vortices appear in the region of −5 < y/n < −2 in the higher modes and act in opposite directions between adjacent vortices. The flow becomes more turbulent with increasing inlet pressure, and the turbulent structures of the high modes become ineffective from a deflection angle of 0.4° onward.