Dynamic Pressure Measurements Research Articles

Static and Dynamic Pressure Measurement in Flight Test Application With Optical Fabry–Pérot Sensors

Conventional electrical pressure sensors show degradation of their performance in harsh environments because of their low overload protection, drawn back membrane, susceptibility to electromagnetic influences, and corrosion. Fiber-optic measurements overcome those challenges and promise to be a robust sensing solution for vigorous flight testing. We developed a passive fiber-optic Fabry-Pérot pressure sensor with a minimum thickness of 1.6 mm, natural frequency above 250 kHz, linear transfer characteristic, burst pressure resistance above >30 times full-scale, and without conductive corrosive materials. It can measure aerostatics, aerodynamics, and aeroacoustics down to 70-dB SPL. In combination with an industrialized edge filter measurement device, the fiber-optical sensor's simplified instrumentation is demonstrated on a microlight aircraft, performing dynamic maneuvers. The measurement data of near-stall flight situations demonstrate the monitoring capabilities of detached airflow in harsh environments.

A Model-Driven Scheme to Compensate the Strain-Based Non-Intrusive Dynamic Pressure Measurement for Hydraulic Pipe

Strain-based non-intrusive approaches for measuring the pressure of pipes have attracted widespread attention due to their great convenience and ability to avoid destroying the integrity of structures. However, the mentioned method usually measures the dynamic pressure based only on the static strain-pressure sensitivity coefficients (SSSCs) instead of the dynamic strain-pressure sensitivity coefficients (DSSCs) due to its complicated calibration, which will inevitably affect the accuracy significantly. To address this issue, a model-driven scheme with dual stages is proposed in the present study to compensate the dynamic pressure measurement. The DSSCs are analytically derived for the first time from the axial governing equations of the pipe, considering the general boundary conditions for the thin-wall pipe and thick-wall pipe simultaneously. In the first stage, the physical parameters involved in the DSSCs are calibrated by minimizing the residual of the experimental results and the theoretical counterparts. In the second stage, the DSSCs calculated from the calibrated analytical model are utilized to compensate the dynamic pressure based on the relationship between the DSSCs and the SSSCs. The proposed method is applied to an industrial hydraulic pipe system, and the experimental results show that the relative error is reduced greatly after the compensation is implemented, demonstrating the validity of the proposed compensation method.

Erratum to “Static and Dynamic Pressure Measurement in Flight Test Application With Optical Fabry–Pérot Sensors” [2021 Art. no. 7004611

Erratum to “Static and Dynamic Pressure Measurement in Flight Test Application With Optical Fabry–Pérot Sensors” [2021 Art. no. 7004611

Studies on electrospun polyvinylidene fluoride/aliphatic hyperbranched polyester (3rd gen) based piezoelectric sensors

Though many reports are available on polymer based piezoelectric sensor devices since the last decade, the novelty of the present work is to study the piezoelectric sensor characteristics of electrospun (a). Neat poly(vinylidene fluoride) (PVDF) and (b). PVDF/aliphatic hyperbranched polyester of 3rd generation (HBP-G3) blend (80/20 w/w) for energy-harvesting applications. Our work is segregated into two parts: In the first part, we synthesized aliphatic HBP-G3 using pentaerythritol (as core), dimethylol propionic acid (as monomer) and p-toluene sulphonic acid (as catalyst) using one-shot melt-polycondensation method, and characterized the final product using spectral and thermal measurements. Further, neat PVDF and PVDF/HBP (80/20 w/w) blend solutions were prepared by mixing with selected solvents and their electrospinning were carried out under controlled conditions. Upon characterizing the nanoweb samples using FTIR and XRD techniques, the blend nanoweb was confirmed to exhibit higher β-crystallinity than that exhibited by neat PVDF nanoweb. This serves as an evidence that it is possible to fabricate a piezoelectric sensor with higher output voltage using PVDF/HBP blend than that achieved using neat PVDF. Finally, dynamic-pressure measurements were carrried out to measure the peak-to-peak output voltage (Vp-p) data, which revealed higher Vp-p (+6.21 V) for blend sample compared to neat PVDF (Vp-p = +0.95 V).

ЭКСПЕРИМЕНТАЛЬНЫЕ ИССЛЕДОВАНИЯ УСЛОВИЙ РАСПЫЛА ЖИДКОСТЕЙ ПОСРЕДСТВОМ ВОЗДУШНОГО ПОТОКА

The processes of air movement in various types of air ducts are of great practical interest in terms of designing, manufacturing, and installing spraying devices used in agricultural production to create artificial fog with fi ne sprinkling and treat crops from pests and diseases. The authors analyze the existing methods of liquid spraying and reveal their main advantages and disadvantages. Under special attention is the pneumatic method. The study found that this method is used to spray contaminated liquids and the spray quality insignificantly depends on the liquid flow rate. It was revealed that one of the main factors affecting the quality indicators of spraying devices is the dynamic pressure of the gas medium acting on the liquid during its spraying. The research has determined that the dynamic pressure value of the airflow during the liquid movement in a horizontal duct depends on three factors: the presence of additional resistance, estimated by the value of the effective area duct, the position of the point at which the pressure was measured relative to the duct axis and the distance between the measurement point and the airflow source. The experimental data were tested for reproducibility using the Cochran criterion at the 5% signifi cancelevel, which proved the process reproducibility. The research has shown that the presence of additional resistance in the duct and the position of the dynamic pressure measurement point relative to the axis of the duct have the same effect on its value. The dynamic pressure of the airflow is primarily dependent on the remoteness of the measurement point from its source.

Experimental Study on Ramp Shock Wave Control in Ma3 Supersonic Flow Using Two-Electrode SparkJet Actuator

The control of a shock wave produced by a ramp (ramp shock) in Ma3 supersonic flow using a two-electrode SparkJet (SPJ) actuator in a single-pulse mode is studied experimentally. Except for schlieren images of the interaction process of SPJ with the flow field, a dynamic pressure measurement method is also used in the analysis of shock wave control. In a typical experimental case, under the control of single-pulsed SPJ, the characteristic of ramp shock changes from “short-term local upstream motion” in the initial stage to “long-term whole downstream motion” in the later stage. The angle and position of the ramp shock changes significantly in the whole control process. In addition, the dynamic pressure measurement result shows that the ramp pressure is reduced by a maximum of 79% compared to that in the base flow field, which indicates that the ramp shock is significantly weakened by SPJ. The effects of some parameters on the control effect of SPJ on the ramp shock are investigated and analyzed in detail. The increase in discharge capacitance helps to improve the control effect of SPJ on the ramp shock. However, the control effect of the SPJ actuator with medium exit diameter is better than that with a too small or too large one. In addition, when the SPJ exit is located in the separation zone and outside, the change in the ramp shock shows significant differences, but the control effect in the case of medium ramp distance is better when the SPJ exit is located outside the separation zone.

Visual experimental investigation on stable operating process of the plane-radial rotating detonation engine

Using visual observation methods, assisted by synchronous measurement of dynamic pressure and ion tracks, the flow field structures of stable operating modes in plane-radial rotating detonation engine (RDE) are revealed, and the influences of injection conditions on the RDE stable operating range are analyzed. The flow field structures of single-wave mode, symmetric dual-wave mode and triple-wave mode are observed. Typical structures such as rotating detonation wave (RDW), oblique shock wave, combustion products, deflagration surface and contact discontinuity are obtained in the flow fields. Obvious reactants pre-combustion ahead of detonation wave is found in the combustor, and low-frequency oscillation phenomenon is gained under specific conditions. With the increase of wave-head number in combustor, the detonation-wave height and parameters decrease. The RDW propagating velocity and pressure peak are higher in single-wave operating mode, but the flow fields in multi-wave mode are more stable. Both the RDW velocity and pressure peak increase generally with equivalence ratio. Keeping the equivalent ratio (ER) fixed, as the mass flow rate increases, the number of detonation wave in combustor increases, and the operating mode transforms from single-wave mode to multi-wave mode. Keeping the mass flow rate fixed, when the equivalent ratio deviates from stoichiometric ratio, the operating mode varies from multi-wave mode to single-wave mode. Additionally, with the mass flow rate increasing, the ER upper and lower limits of multi-wave mode decrease linearly, and the operating range of dual-wave mode remains unchanged. Mass flow rate has little influence on the ER lower limit of the RDE stable operation, which is approximately ER=0.55 in this structure.

사류펌프의 압력맥동특성 분석

The frequencies and amplitudes of the pressure pulsation caused by the model pump of the reactor coolant pump are obtained through the hydraulic test using the model pump of a reactor coolant pump. The relationship between the amplitude of the pressure pulsation and the head fluctuation of the model pump head is also obtained. The pressure pulsation amplitude of the rotational speed frequency is the biggest one, and the amplitudes of the blade passing frequencies (BPF) are smaller than that of the rotational speed. The amplitudes of the pressure pulsation above 6 BPF are gradually reduced to zero amplitude. The pump head fluctuation based on the dynamic pressure measurement is 0.72% of the rated head, and 0.63% based on the static pressure measurement. It is a meaningful result that the pump head fluctuation based on the dynamic pressure is almost the same the pump head fluctuation based on the static pressure. From this result, the amplitude of the pressure pulsation can be enveloped conservatively using the pump head fluctuation that can be measured easily from the static pressure at steady state condition.

Effect of forcing the tip-gap of a NACA0065 airfoil using plasma actuators: A proof-of-concept study

A proof-of-concept study is presented to understand the effect of continuous forcing by a dielectric-barrier-discharge (DBD) plasma actuator on the strength of the vortices formed in the tip-gap of a single NACA0065 airfoil. The airfoil was mounted with variable tip gaps in the test-section of a suction-type wind tunnel. Continuous forcing was generated by mounting a straight DBD actuator in the tip gap. The flow field was investigated experimentally by dynamic-pressure measurements, and stereoscopic-particle-image-velocimetry (SPIV). In addition, URANS was performed to investigate the flow field in the tip gap region, where SPIV could not be conducted. The results showed that the effectiveness of forcing decreased with increasing tip-gaps and free-stream velocity. The maximum cancellation of the vortex was observed when the blowing ratio was approximately 0.93, with a tip gap of 0.02c (c=chord) and free stream velocity of 2.7 m/s. Both experimental and numerical results showed that in this particular case, the DBD actuator created a strong reverse flow opposing the direction of tip flow. This reverse flow altered the pressure gradient in the tip gap region and canceled the vortex altogether.

Evaporation retardation by model tear-lipid films: The roles of film aging, compositions and interfacial rheological properties

A novel methodology for assessing evaporation (up to 48 h) through lipid-nanofilms in vitro was developed. The influence of lipid-mixture compositions on evaporation rates was studied. The evaporative fluxes and rheology of lipid-nanofilms were compared with those of human tear-lipid nanofilms in vitro.A sessile-drop technique with precise drop-volume control was adapted to measure evaporation rates at constant temperature of 36 °C and humidity of 75 %. Model lipid solutions were deposited on the surface of aqueous drops to create nanofilms of 10–100 nm. The measurements of dynamic surface pressure vs. nanofilm-thickness were performed under the same conditions. The lipid-mixtures compositions were chosen to mimic that of human tear lipids. Evaporation through lipid nanofilms decreased with film thickness and aging. Evaporation through 70-nm films was 2.5–3 time slower than through 10-nm-thick films. Nonpolar-lipid mixtures reduced evaporation by approximately 35 %. The optimized model-lipid mixtures containing polar phospholipids reduced evaporation by 70–75 %, matching the evaporation-reduction by human-lipid nanofilms in vitro. These model mixtures exhibited interfacial rheology similar to human tear lipids in vitro.This methodology substantiated that aged lipid-nanofilms significantly reduced evaporation in vitro. These findings contradict to the previous reports suggesting that model lipid and meibum films do not retard evaporation in vitro. Polar phospholipids enhance evaporative resistance close to the level observed for human tear-lipid films in vivo. We hypothesize that unique rheological properties of tear-lipid nanofilms are germane to the specific mono- and bi-layered structures formed by phospholipids at the lipid-air and lipid-aqueous interfaces.

Frequency and Spark Timing Effects on Thrust for Pulse Detonation Engine

An experimental study was performed on an ethylene/oxygen/air pulse detonation engine to examine the effect of frequency and spark delay time on the thrust output and efficiency. Reactants were mixed in a stainless-steel combustion chamber at frequencies ranging from 1 to 40 Hz. Dynamic pressure measurements were recorded throughout the system over the testing interval to determine exhaust velocities. Efficiency was evaluated based on the experimental average frequency and the experimental average velocity. Results on experimental thrust, detonation frequency, and Chapman–Jouguet velocities were analyzed. It was observed that average thrust increased exponentially with the increase of detonation frequency. For a spark delay time of 2 ms, maximum efficiency and thrust were achieved for given frequencies. As spark delay time increased beyond 6 ms, testing became erratic, with pulses misfiring, and a decrease in efficiency and thrust was observed until no combustion occurred beyond a spark delay time of 8 ms.

Enhancing effect of an open pipe exit on the precessing vortex core occurring in confined swirling flows

This paper investigates the effect of an open pipe exit on the dynamic behaviour of the helical precessing vortex core (PVC) occurring in a confined swirling flow after vortex breakdown. This is achieved by carrying out extensive particle image velocimetry and dynamic pressure measurements downstream of an air swirling flow generator in two pipes configurations at two values of swirl number $$S=0.7$$ and $$S=1.1$$ . The first pipe configuration features a diffuser followed by a straight pipe and an open exit. In the second configuration, the open exit is placed closer to the outlet of the swirl generator by removing the straight part. In both configurations, the PVC structural parameters are properly determined by phase-averaging of the instantaneous velocity fields. In the first configuration, a sudden change in the pitch of the helical vortex is observed at both swirl number values downstream of the connection between the diffuser and the straight part. Beyond this transition, the vortex trajectory starts widening as it is getting closer to the open exit of the pipe. The results in the second configuration confirm this enhancing effect of the open exit on the PVC: at both swirl numbers, the vortex trajectory is strongly widened and its radius continuously increases from the swirl generator outlet to the pipe exit, resulting in an increase in the Strouhal number and pressure fluctuations amplitude by 20 $$\%$$ and a factor up to 9, respectively, compared with the first configuration. Finally, based on a dimensional analysis, a linear relation between two dimensionless parameters including the vortex parameters and the pressure fluctuations amplitude is derived and supported by the data obtained in both pipe configurations.

Experimental study of heat transfer characteristics of finned-tube and circular-pore heat exchangers in oscillatory flow

This work is concerned with an experimental investigation of the thermal performance of two thermoacoustic heat exchangers characterized by different pore geometries, namely a circular-pore geometry and a finned-tube geometry. A standing wave engine, where the heat exchangers under test play the role of ambient HXs, is used as test-rig. Heat transfer rates measurements by standard energy balance techniques and dynamic pressure measurements are used to assess the impact of the two heat exchangers on the engine performance. The gas-side heat transfer coefficient, expressed as Nusselt number, is also determined for the finned-tube heat exchanger. The resulting values are compared to the heat transfer coefficients estimated in analogous experimental studies and by predictive models. Results show that the circular-pore heat exchanger reduces the performance of the engine compared to the finned-tube heat exchanger by about 23%, being affected by higher thermal and viscous irreversibility. Moreover, the boundary layer conduction model exhibits a better agreement with the measured heat transfer coefficients compared to other models. A new correlation law, based on regression of the experimental data, is also derived.

μ-Si strain gauge array on flexible substrate for dynamic pressure measurement

Low Temperature μ-Si layers have been deposited by Inductively Coupled Plasma Chemical Vapour Deposition (ICP-CVD) to produce strain gauges. These strain gauges performed on 25 μm thick flexible Kapton Polyimide (PI) were investigated in terms of Gauge Factor but also in dynamic mode through a homemade pneumatic test bench. Best strain gauge design has been identified and subsequently used to perform a 25 sensor array which was also tested using pulses and more complex signals. A simulation of blood pressure monitoring was performed to demonstrate the value of the technology.

Ignition of stoichiometric hydrogen-oxygen by water hammer

The potential of water hammer events for igniting hydrogen-oxygen mixtures was examined in an experimental study. Compression waves simulating water-hammer events were created by projectile impact on a piston in a water-filled pipe terminated by a test section filled with gas. Triangular wave forms with peak pressures up to 50 MPa propagated through the piping system and compressed the gas in the test section. Experiments were carried out with both air and hydrogen-oxygen gas mixtures using high-speed video of the transparent test section, dynamic pressure and spectroscopic measurements to examine the motion of the water-gas interface and determine ignition thresholds. The impulsive acceleration of the water-gas interface and deceleration created by the compression of the gas resulted in Richtmyer-Meshkov and Rayleigh-Taylor instabilities that grew to create large distortions of the initially planar and horizontal water-gas interface. The gas layer was compressed in volume by up to a factor of 50 and the gas pressures increased to as high as 20 MPa within 2 to 4 ms. The distortion of the water surface during compression resulted in a significant increase in interfacial area and ultimately, creation of a two-phase mixture of water and compressed gas. Some ignition events were observed, but the dispersion and mixing of water with the gas almost completely suppressed the pressure rise during the ignition transient. Only by eliminating the instability of the water interface with a solid disk between the water and gas were we able to observe consistent ignition with significant pressure rises associated with the combustion.

Combined measurement method for deep sea large pressure and its small fluctuation pressure.

A combined measurement method on the basis of liquid compressibility and the characteristics of deep sea pressure compensators and pistons is proposed to solve the difficulty in measuring the large pressure of several kilometers of water depth and the small fluctuation pressure of several centimeters of water depth in ocean pressure detection. First, the working principle of the proposed method is introduced. Second, the force of piston is evaluated under static and dynamic pressure measurement conditions, and the corresponding mathematical models are established. Third, the measurement accuracy of static and dynamic pressures is analyzed. Finally, a test platform is built. The results show that the maximum dynamic pressure of 0.025 bar is realized at a pressure changing speed of 0.2 bar/s, and the small fluctuation pressure of 2.8 × 10-3 bars is realized at a pressure of 20 bars. The measurement system can track the changing ambient pressure in real time, and the measurement accuracy of the small fluctuation pressure is only related to the characteristics of the measurement system itself but not to the external large pressure. The accuracy and feasibility of the proposed method are verified. This study provides a new approach for measuring deep sea large pressure and its small fluctuation pressure.

모사 가스터빈 연소기 내 동압 계측 특성 및 보정식 개발

본 연구에서는 가스터빈 연소기 내에서 연소 불안정을 진단하기 위해 주로 사용되는 동압 측정법의 타당성을 검증하고, 오차를 최소화하기 위한 보정식을 제안하였다. 비연소 상태에서 원기둥 형상의 캔형 가스터빈 모사 연소기의 일측에 부착된 스피커를 이용하여 50Hz~6,000Hz로 가진 주파수를 변경하였을 때, 라이너의 길이 방향으로 벽면 매설방식(flush mount type)으로 설치된 6개의 동압 센서를 이용하여 연소실 내 동압이 측정되었다. 일부 실험 조건에서 오측정 현상을 관찰되었고, 정상파 모드 분석을 통해 원인을 파악하였다. 이러한 계측 오차를 줄이고자 두 개의 보정식을 제안 · 검증하였고, 이 결과는 가스터빈 연소기 내 연소 동압 측정의 정확성을 향상시키고 연소 불안정 사고 위험성을 감소시킬 것으로 기대된다.

Advances in traceable calibration of cylinder pressure transducers

Accurate and reliable dynamic pressure measurements are needed for optimizing performance in modern combustion engines, manufacturing processes and aerospace applications. Besides fast pressure transients, these applications subject dynamic pressure transducers to elevated temperatures. Both of these quantities effect the sensitivity of transducers. Therefore, transducers should be calibrated at conditions that corresponds to the operating environment.To answer these needs, the National Metrology Institute VTT MIKES has developed its drop weight dynamic pressure primary standard further. Developments include improved control and measurement of the falling weight, extension of the pressure range to combustion engine pressures down to 3 MPa and a heating option for dynamic pressure transducers under calibration. These advances enable traceable calibration of cylinder pressure transducers at conditions relevant to engine applications. The overall uncertainty (k = 2) of calibration is estimated to be around 1.7%. The performance was demonstrated by calibrating a piezoelectric pressure transducer in the pressure and temperature range from 7 MPa to 30 MPa in 20 °C, 120 °C and 180 °C, respectively. As a result, traceable calibrations of dynamic pressure transducers can be performed at conditions relevant for engine applications. This improves the reliability and accuracy of in-cylinder pressure measurements.

Wall pressure unsteadiness in an over-expanded single expansion ramp nozzle

To evaluate the unsteady nature of wall pressure in an over-expanded single expansion ramp nozzle, under fixed nozzle pressure ratio (NPR) of 5.92, 6.55 and 7.19, an experimental investigation has been conducted based on focusing Schlieren techniques and dynamic pressure measurement. For all cases, the results show fully formed restricted shock separation (RSS) on the upper wall, which experiences flow reattachment on the wall downstream of separation resulting in the formation of a separation bubble. The separation mode is also RSS on the lower wall at [Formula: see text]. However, the lower wall pressure is randomly larger or lower than ambient pressure near the nozzle exit at [Formula: see text], the separated shear-layer can intermittently impinge on the lower wall, and the separation mode is partially restricted shock separation (pRSS). At [Formula: see text], the separation flow does not reattach downstream of the lower wall. That is, it occurs free shock separation (FSS).

Importance of Footwear Outsole Rigidity in Improving Spatiotemporal Parameters in Patients with Diabetes and Previous Forefoot Ulcerations.

We aimed to identify if any differences existed in spatiotemporal parameters during gait among different densities of rocker soles in patients with a history of neuropathic ulcerations and the differences in comfort between shoe conditions. This study was a cross-sectional study of 24 patients with diabetes and a history of neuropathic diabetic foot ulcers (DFUs). Spatiotemporal parameters (duration of stance phase (ms), stride length (cm), and step velocity (m/s)) were analyzed in barefoot, semirigid outsole, and rigid outsole footwear conditions. A dynamic pressure measurement system (Footscan® system, RSscan International, Olen, Belgium) was used to assess shoe conditions. We also analyzed differences in comfort between the shoe conditions using a visual analog scale. A Wilcoxon test for paired samples was used to assess gait differences. Result showed that a rigid outsole causes changes in the subphases of the stance phase (p < 0.001; Cohen d = 0.6) compared to a semirigid outsole. Stride length (p < 0.001; Cohen d = 0.66) and step velocity were significantly longer (p < 0.001; Cohen d = 2.03) with the use of rigid outsole footwear. A rigid rocker sole reduces the time of the stance phase, in addition to increasing the stride length and velocity of step in patients with a previous history of DFUs.