Transient Pressure Measurements Research Articles

Asymmetry of oblique shock train and flow control

An oblique shock train generally forms an asymmetric structure in a Mach-2.7 flow field within a duct. To study the flow structure and interaction between oblique shock trains and upstream shocks, a ramp with equal width was installed inside a Mach-2.7 straight duct to generate an incident shock and an oblique shock train interaction. A Schlieren system, transient pressure measurements and particle image velocimetry were used to capture quantitative and qualitative shock structure information. Results show that the asymmetric separation deflection of the oblique shock train occurs randomly in the symmetrical straight duct. The separation deflection of the oblique shock train was steady with upstream shock interactions. Under backpressure conditions, the rate of movement of the oblique shock train increases rapidly when it passes through the separation regions generated by the ramp, and the deflection direction of the asymmetric separation may switch. Based on the characteristics of the oblique shock train and upstream shock interaction, a flow control method was used to generate asymmetric upstream flow conditions, providing active control of the oblique shock train deflection direction.

A Review on Pressure Transient Analysis in Multilayer Reservoir: South Iraq Case Study

Multilayer reservoirs are currently modeled as a single zone system by averaging the reservoir parameters associated with each reservoir zone. However, this type of modeling is rarely accurate because a single zone system does not account for the fact that each zone's pressure decreases independently. Pressure drop for each zone has an effect on the total output and would result in inter-flow and the premature depletion of one of the zones. Understanding reservoir performance requires a precise estimation of each layer's permeability and skin factor. The Multilayer Transient Analysis is a well-testing technique designed to determine formation properties in more than one layer, and its effectiveness over the past two decades has been demonstrated. In order to conduct MTA, a combination of rate profiles derived from production data and transient rate and pressure measurements at multiple surface rates is necessary. Numerous experimental and analytic approaches to calculating multilayer characteristics, performance, and flow behavior in multilayer systems have emerged. This technology was implemented at the Zubair oil field in southern Iraq. In the last four years, the number of wells producing under saturation pressure has been increased in the Zubair oil field, particularly for the Mishrif and Zubair reservoirs. In the design of secondary and tertiary recovery, the study of the reservoir in the form of an individual layer to determine the pressure, permeability, and damage of each layer with commingled formation is important. This research describes previously available methods, factors that affect Multilayer Transient Analysis an economic indicator of Multilayer Transient Analysis and a case study

Determination of the in situ hydraulic parameters of the Callovo–Oxfordian clay rock in a long-term hydraulic interference testing at Andra's Underground Research Laboratory (CMHM)

Abstract. Between 2009 and 2015, Andra has conducted a unique long-term hydraulic interference test in two parallel boreholes 1 m apart from each other and air core drilled in the undisturbed Oxfordian Clay rock at Andra's Underground Research Laboratory (CMHM) in Bure, France. The experimental set-up consisted of six test intervals positioned along the parallel boreholes drilled from a drift located within the Callovo–Oxfordian clay at around 500 m b.g.l. (below ground level). The 20 m boreholes were oriented around 30∘ downwards. The pressure sensors linked to six intervals of 1 m length each allowed for continuous pressure measurement over 6 years and a slanted borehole for the observation of rock displacements (see Fig. 1). Additionally, flow rates were measured during water injection tests that lasted weeks or months. This extensive set of hydraulic data allowed, for the first time, a precise determination of the in situ Callovo–Oxfordian clay rock permeability and anisotropy and its specific storage at the metre to decametre scale. It was achieved based on an automated calibration, using a 3D flow model and explicitly considering all the relevant hydraulic elements acting on the flow system (such as rock mass, borehole disturbed zone and sealing elements) and the drift acting as a steady sink due to the underground ventilation (see Fig. 2). The history matching was performed on the transient pressure measurements. The obtained numerical calibration results were in close agreement with the hydraulic parameter values of the Callovo–Oxfordian clay determined at a smaller scale (single borehole tests and rock core samples in the laboratory), therefore demonstrating the reliability of the very low permeability of the Callovo–Oxfordian clay at the metre to decametre scale. Furthermore, the modelling illustrated the impact of the measurement set-up and its details on the observed hydraulic behaviour. The analysis methodology and the main findings will be presented.

Experimental and numerical study on dynamic stall under a large Reynolds number

Dynamic stall under large Reynolds numbers and large reduced frequencies has a significant effect on the performance of the wind turbine blades, helicopter rotors, etc. So the dynamic stall physics of the NACA0012 airfoil under a large Reynolds number of Re = 1.5 × 106 was studied using experimental and numerical methods. The reduced frequency range was k = 0.035 – 0.1. The unsteady flow field in dynamic stall was studied in detail by using the transient pressure measurement and the numerical simulation based on the unsteady Reynolds-averaged Navier-Stokes (URANS) equation. And the time-frequency characteristics of the dynamic stall were studied using the wavelet analysis. The study showed that the aerodynamic performance during the dynamic stall was dominated by the shear layer vortex (SLV) and the leading edge vortex (LEV), and the phase difference between the SLV and the LEV was the key factor in the existence of the bimodal characteristics of the aerodynamic force/moment. There was a significant linear correlation between the negative peak of the vortex-induced Cp and the Cn in the reduced frequency range studied in this paper. During the convection of the near-wall LEV to the trailing edge, the high-frequency features firstly decay, and the multi-scale structures of the LEV become more significant as the reduced frequency gradually increases.

Assessment of experimental methods for measurements of the horizontal flow of fluidized solids under bubbling conditions

Dual fluidized bed systems are indispensable for future energy systems that require solids cycling between different atmospheres. However, controlling the residence time of solids in the reactor, which is crucial for controlling the heat and mass transfer of the fuel, is a significant challenge. This study investigates four experimental techniques to quantify the horizontal flow of solids fluidized under bubbling conditions: integral mass accumulation; differential mass accumulation; thermal tracing; and magnetic solids tracing. Integral mass accumulation entails collecting bed material using a defluidized box within a given time period. Differential mass accumulation measures the material accumulation rate in a section of the bed that is monitored using pressure measurements. Thermal tracing calculates the solids flow rate by solving the heat balance to match the temperature field captured by a thermographic camera. Magnetic solids tracing involves injecting a batch of magnetic tracer solids into the reactor and then measuring the residence time distribution using impedance coils.The experiments were conducted under down-scaled conditions that resemble large-scale operations with a length scaling factor of 0.12. For this study, three operational parameters were varied: the fixed bed height; the volumetric flow rate of the conveying air; and the fluidization velocity in the bed. The horizontal solids circulation rates achieved ranged from 1.7×10−4 to 10 kg/m·s, corresponding to 1.2×10−3 to 70 kg/m·s on a hot up-scaled basis, which is a relevant range to indirect biomass gasification in an industrial setting.The three selected operational parameters led to increases in the horizontal solids flow. While all four methods replicated the trends, quantitative variations in the measured circulation rates occurred due to the inherent characteristics of the methods. High circulation rates resulted in a continuous decrease in the solids inventory, leading to an underestimation of the circulation rate when using the integral mass accumulation method. The accuracy of the differential mass accumulation method relied on transient pressure measurements, which were less-effective at low solids flow rates. Conversely, the accumulation time required for pressure measurements was reduced at high circulation rates, resulting in uncertainties in the analysis. The accuracy of the thermal tracing method decreased drastically with higher solids circulation, resulting in an overestimation of the circulation rate. Moreover, low circulation rates adversely affected the accuracy of the magnetic solids tracing by producing barely discernible tracer concentration gradients.

Development of a retrofit layer with an embedded array of piezoelectric sensors for transient pressure measurement in maritime applications

Measurement of transient pressure distribution on maritime structures is important for the assessment of the hydrodynamic loads applied. The commonly used pressure sensors are mostly bulky, need to be bolted to the structure, and/or only provide point-wise measurements. In this paper, an elastic matrix layer with a network of embedded piezoelectric sensors is proposed to address these issues. For experimental validation, a 400 × 400 × 5 mm epoxy layer is fabricated embedding 25 piezoelectric sensors on a square grid in accordance with Gauss-Lobatto-Legendre points. A finite element based inverse procedure is developed to reconstruct the pressure field from the electric potentials measured by the piezoelectric transducers. Feasibility of the concept is evaluated by measuring and reconstructing the pressure field generated by a travelling wave in a water tank. Sensitivity of the layer is also investigated through the experiments. The results indicate that the retrofit layer is capable of pressure field reconstruction, and that the presence of disturbances on the sensing surface does not affect the measurements in a notable way, while non-ideal conditions of the mounting can have a significant impact on the accuracy of the measurements. The results highlight the potential of the concept in pressure distribution measurements.

Experimental evaluation of wind induced pressure fluctuations in cavity shaped open volumetric air receivers

In this study wind induced surface pressure fluctuations during operation of an open volumetric cavity receiver were investigated in wind tunnel experiments. Due to the process design of the open volumetric receiver, surface pressure fluctuations impact the receiver mass flow which is crucial for cooling the highly irradiated receiver. For this study a model of a solar tower was constructed under the concept of similitude which allows wind tunnel experiments at Reynolds numbers up to 13.17 × 106. Transient pressure measurements were conducted under 17 different flow directions to evaluate the impact of separation induced pressure fluctuations. The experimental design further allows a rotation of the model to evaluate the impact of changes in wind direction on the surface pressure at the receiver. For cases under a constant wind direction, a critical angle range could be identified in head on wind with a horizontal inclination of 45.0 to 78.8° relative to the central receiver axis. The results further show that surface pressure fluctuations are more sensitive to changes in wind direction as the amplitudes with maximum 20Pa for a Reynolds number of 13.17 × 106 are about one order of magnitude higher compared to the cases with a constant flow direction. Furthermore, a frequency analysis shows the shielding effect of the cavity design for side-wind as no peaks in the pressure spectrum appear. For flow directions within the critical range of 45.0 to 78.8° a main vortex shedding frequency under constant Strouhal numbers of 0.25 to 0.50 can be observed.

Influence of swirling flow parameters on frequency response of a simplified draft-tube in presence of cavitation

This paper focuses on investigating the influence of swirling flow parameters on frequency response of a simplified draft-tube under different cavitation numbers by using experimental approaches. The experiments are conducted for three swirl configurations featuring different swirl intensities conforming with the flow field in the draft-tube during high-load operation of a hydro-turbine. For this purpose, three stationary-blades swirl generators are used to generate axisymmetric swirling flows in a Venturi-tube with a diffuser resembling the draft-tube cone of a hydraulic turbine; and for each swirl configuration, the experiments are conducted over a wide range of cavitation numbers and flowrate values. Experiments include transient pressure measurements at different locations and high-speed visualization of cavitating flow in the Venturi. The results of transient pressure measurements are analyzed to identify the frequency spectrum of pressure fluctuations in the draft-tube. The first natural frequency of the draft-tube is identified for a wide range of operating conditions; and several correlations are established for its relationship with the flow parameters (cavitation number and swirl number). It is observed that the operating flowrate does not affect the natural frequency of the draft-tube. An unstable mode of cavitating flow is highlighted and a transition from stable to unstable modes is identified. Investigating the transition mechanism from the stable to the unstable modes of cavity led to identifying an excitation force for the onset of cavitation instability in the draft-tube. High-speed visualization of cavitation in the draft-tube is performed to capture the mean cavity volume and its fluctuations in time domain. The 1st natural frequency of the draft-tube is further predicted by analyzing the fluctuations of cavity volume. Furthermore, a 1D hydroacoustic model is also used to predict the local wave speed and the 1st natural frequency of the draft-tube. The obtained values of natural frequency from cavity visualization and 1D modelling are compared with the results of pressure measurements at the end.

Experimental investigation on the water hammer characteristic of stalling fluid in eccentric casing-tubing annulus

This study aims to analyze the water hammer characteristics of water hammer on tubing offset center in oil project for providing reference for water injection and well washing. An analysis is conducted by utilizing a test apparatus, particle image velocimetry, and a transient pressure measurement system. The characteristic of dynamic fluid loss is investigated in eccentric annulus flow channel and tubing and in flow line in terms of velocity, vorticity, and pressure field. Results show that water hammer occurs, and the pressure of oil casing annulus increases at the inside and outside walls with the increase in eccentricity. The water hammer pressure forms double imbalance in the internal and external walls of eccentric annulus tubing. With the increase in eccentricity, flow velocity decreases in the small flow passage, and flow velocity attenuation is fast at oil casing annulus.

Efficient estimation of aquifer intrinsic permeability anisotropy using perturbation theory

Inverse modeling of aquifer measurements aims at estimating the spatial distribution of rock properties that best fits the available measurements which, in turn, allows predicting water yields and pressures to an acceptable level of accuracy. Nonlinear automatic inverse methods require multiple solutions of the diffusion equation, also known as the groundwater flow equation. Although numerical solutions to the forward problems improve the understanding of complex groundwater flow systems, they are often computationally expensive, thereby rendering the inversion process inefficient. We introduce a gradient-based inversion algorithm that leverages perturbation theory to efficiently estimate the tensorial intrinsic permeability distribution of porous media from single-phase transient pressure measurements. With a maximum of two numerical simulations, the Joint Perturbation-Superposition (JPS) method allows one to compute flow-history-dependent Intrinsic permeability Sensitivity Functions (PSF) on the spatial-temporal domain. Regardless of the gradient-based iterative inversion technique, our method efficiently adapts the sensitivity functions yielded by perturbation theory to calculate the entries of the associated Jacobian matrix at every iteration. A two-dimensional synthetic model comprising multi-well conditions is examined for an anisotropic and spatially heterogeneous groundwater flow system. The perturbation method yields accurate and efficient parameter estimation by leveraging sensitivity functions for (1) the appropriate selection of input transient pressure measurements and (2) reducing the sequential calculation of Jacobian matrices. As a result, Monte Carlo uncertainties as low as <5% are obtained for the estimated tensorial intrinsic permeability distribution, with inversion times halved when compared to conventional techniques.

Steam cavity and explosion intensity of molten copper column interaction with water

The steam explosion is one of the most serious accidents in the metallurgical industry. In this paper, an experimental study on the interaction of molten copper column with cooling water was carried out using high-speed camera and transient pressure measurement system. The effects of temperature, falling height, diameter and mass of molten copper column on the interaction were investigated. The steam cavity phenomenon was observed in the interaction and the percentage of steam cavity volume affects the probability of fragmentation of molten copper column. The maximum percentage of steam cavity volume increases firstly and then decreases with the increase of temperature and falling height. It increases with the increase of diameter of molten copper column, but the mass has a weak effect. The pressure wave generated by the interaction of molten copper column with cooling water gradually increases with an increase in the temperature of molten copper column. The energy conversion rate in the interaction of molten copper column with cooling water was calculated. The rate of energy conversion from the thermal energy of molten copper column to the energy of pressure wave is low because most of the thermal energy is dissipated into the cooling water by heat transfer.

Experimental and numerical investigation on the effect of tip leakage vortex induced cavitating flow on pressure fluctuation in an axial flow pump

In this paper, the cavitating flow and pressure fluctuation in the tip region were simulated based on Delayed Detached Eddy Simulation (DDES). The high-speed photography and transient pressure measurements were employed to capture the cavitation structures and pressure fluctuation. The numerical results show a reasonable agreement with the available experiments. The maximum errors of head and efficiency are 2.9% and 2.2%. The impeller rotation dominants the tip pressure field, with some obvious high-frequency components induced by the cavitating flow. Increasing the flow rate from 0.8Qopt to 1.2Qopt, the amplitudes of the frequency domain in P2 decrease from 0.13 to 0.08. There are more harmonic-frequency components at 0.8Qopt, including 5BPF, 6BPF, 7BPF. Suction-side-perpendicular cavitating vortices (SSPCVs) appeared in severe cavitation conditions, which leads to the collapse of the triangular cavitation cloud. The spatial-temporal evolution of SSPCV was divided into three stages: Generating stage, Shedding stage, and Dissipating stage. The pressure fluctuates significantly in the flow passage caused by SSPCV. The amplitudes of dominant frequency in P3 vary from 0.031 to 0.089, as the cavitation number decreased from 0.582 to 0.231. In particular, there is an obvious low-frequency N∗ = 0.5 shown in the frequency domains of P2 and P3.

Experimental Investigation of the Transient Patterns and Pressure Evolution of Tip Leakage Vortex and Induced-Vortices Cavitation in an Axial Flow Pump

Abstract Cavitating flow is extremely complex in axial and mixed flow pumps, resulting in several adverse effects on pump performance. In this paper, the tip leakage vortex (TLV) cavitation patterns in an axial flow pump model were studied based on high-speed photography and transient pressure measurements. The TLV cavitation morphology and transient development of the induced suction-side-perpendicular cavitating vortices (SSPCVs) were investigated at multi-operating conditions. The time-domain of the transient pressure was employed to clarify the relationship between the tip cavitation and the pressure field. The results showed that cavitation inception occurred earlier with an unstable TLV cavitation shape at part-load conditions. Cavitation was more intense with a decrease of the cavitation number, presenting a larger area of triangular cavitation with the shedding of SSPCV. The inception of SSPCV was attributed to the tail of the shedding cavitation cloud originally attached to the suction surface (SS) of the blade, moving in the direction of the adjacent blade perpendicular to the SS, resulting in a flow blockage. With a further decrease in pressure, the SSPCVs grew in size and strength, accompanied by a rapid degradation in performance of the pump. The cavitation images and the corresponding circumferential pressure distributions showed that the lowest pressure point coincided with the SS corner. After this position, the pressure fluctuated as the cavitation intensity changed. The transient characteristics of SSPCV are a basis for revealing the instability mechanism of its evolution in the axial flow pump.

Study on connecting tube dynamics for transient pressure measurement

The present study evaluates the dynamic response of connecting tubes for transient pressure measurement. A systematic study is conducted to quantify the amplitude and phase distortion of connecting tubes of diameter 1, 2 and 3 mm with different lengths (10–50 cm). The experimental measurements and theoretical predictions have been carried out with both air and water as the working medium to cover a wide range of frequencies. The study highlights the underdamped nature of all the systems studied. The natural frequency of the system increases with an increase in the tube diameter and a decrease in tube length. The difference in natural frequency obtained from the experimental results and theoretical prediction is less for the smaller tube diameter (d = 1 mm) and more pronounced for the larger tube diameter. Larger tube diameters are recommended to avoid amplitude and phase distortion errors, especially in the low-frequency range. However, resonance effects are more pronounced for larger tube diameters. The phase response of larger tube diameters remains close to zero over a large range of frequency (0–0.8 times the natural frequency); hence, this range is more suitable for applications where phase information is more important than amplitude. This study is useful for compensating the amplitude and phase distortion error encountered in transient pressure measurements.

Experimental study of the molten tin column impacting on the cooling water pool

This paper presents the interaction between molten tin column and cooling water using the high-speed camera and the transient pressure measurement system. The effects of the molten tin column temperature, dropping height, diameter of molten tin column, and surrounding gas environment on the interaction of molten tin column with the water are examined. The results show that three modes of no explosion, product-outside explosion and product-inside explosion are observed. With the increase in the tin column temperature, no explosion is first shifted to product-outside explosion and then product-inside explosion with the maximum overpressure. The dropping height of the molten tin column promotes the intensity of the product-inside explosion. As the molten tin column diameter increases, the intensity of steam explosion first increases and then decreases. N2 atmosphere induces the stronger steam explosion than air.

Experimental and theoretical analysis of a pressure-driven logging piston during the liquid displacement process

Liquid displacement by a pressure-driven piston is a common phenomenon encountered in different industries. The main challenge of the displacement process is its inherent fast transient nature. The objective of the current work is to study such a process experimentally and to describe the hydrodynamic behavior of the system. An experimental facility was built to conduct transient measurements of pressure as well as piston and liquid slug velocities. Additionally, the piston itself was equipped with pressure and accelerometer sensors in order to conduct local measurements during its movement. The employed instrumentation was capable of sampling data at a frequency of 1000 Hz. The experiments were conducted for three initial pressure conditions and one liquid slug size. The core finding of the current study was the fact that piston and liquid slug velocities are different, which can be explained by the flow topology forming during the displacement process. It was also determined that the piston drag and friction forces are negligible for the studied conditions. A good agreement (within 10% error range) was observed between experimental velocity data and the solution of momentum and force balances.

Increasing confidence in estimating stimulated reservoir volume by integrating RTA and microseismic analysis

Rate Transient Analysis (RTA) and microseismic monitoring are gaining momentum in modelling Stimulated Reservoir Volume (SRV) in Multi-Frac Horizontal Wells (MFHWs) in unconventional reservoirs. From a behavioural perspective, RTA uses history matching and production data analysis to estimate fracture volume and productivity, and microseismic analysis maps frack-ing-induced micro-earthquakes to calibrate the fracture network from a spatiotemporal point of view. Defining the concepts of normalized rate, material balance time and pseudo-time, dynamic drainage volume, together with convolution, deconvolution and analytical models, make RTA a powerful and computationally efficient tool for modelling MFHWs (Blasingame et al., 1991; Agarwal et al., 1998, Mattar and Anderson, 2003). Poe (2005) proposed a rate-transient analysis method for evaluating the performance of wells with limited pressure data using the superposition theory and dimensionless parameters. Soliman and Adams (2010) estimated fracture properties by applying Flow Regime Identification (FRI) plots to early production data, followed by using analytical models derived for each distinct flow regime. Kuchuk et al. (2016) calibrated reservoir models by history-matching the transient flow rate and pressure measurements. Brown (2009), Stalgorova and Mattar (2012a, 2012b), Deng et al. (2015), and Yuan et al. (2015) divided the reservoir into a series of linear flow regions and derived analytical pressure transient models from the pressure diffusion equation, not only to confirm the validity of the identification, characterization and diagnostic analyses but also to provide production forecasts and carry out optimization studies. Clarkson et al. (2015) successfully applied RTA analytical and semi-analytical modelling techniques to a gas condensate MFHW in a Western Canadian Basin, highlighting the fact that building a predictive understanding of drainage volume dynamics is best started with physics-based analytical models rather than multi-phase numerical simulations. This is particularly important in unconventional reservoirs where the complex, small-scale physics and rock-fluid interactions significantly hinder gathering enough measurements to support the numerically added complexities.

Impact of sensor housing geometries on transient stagnation pressure measurements in impulse facilities

The measurement of transient stagnation pressure in impulse facilities, such as shock tubes and expansion tubes, is critical due to the limited experimental time window. In the present study, we investigate the characteristic behavior of pressure sensors shielded by blunt and conical housings, and evaluate the specific influence of the housing dimensions on the stagnation pressure measurement in distinct flow conditions. Pressure signals of piezoelectric sensors were acquired and schlieren images visualizing the wave dynamics were recorded. We conducted additional numerical simulations to support our hypotheses concerning the flow inside the housings. Results indicate that the pressure signal for conical housings exhibits longer rise time and more pronounced oscillations compared to that for blunt housings. Enlarging the borehole diameter and reducing the cavity depth both shorten signal rise time but enhance overshoots. Additional experiments on the sensitivity to assembly misalignment, the effect of gelatin-filled housings and the performance of exposed sensors complete the study.

Design, performance evaluation and analysis of the inlet tube of pressure sensor for chamber pressure measurement

PurposeIn Aerospace applications, the inlet tubes are used to mount strain gauge type pressure sensors on the engine under static test to measure engine chamber pressure. This paper aims to focus on the limitations of the inlet tube and its design aspects to serve better in the static test environment. The different sizes of the inlet tubes are designed to meet the static test and safety requirements. This paper presents the performance evaluation of the designed inlet tubes with calibration results and the selection criteria of the inlet tube to measure combustion chamber pressure with the specified accuracy during static testing of engines.Design/methodology/approachTwo sensors, specifically, one cavity type pressure sensor with the inlet tube of range 0-6.89 MPa having natural frequency of the diaphragm 17 KHz and another flush diaphragm type pressure sensor of the same range having −3 dB frequency response, 5 KHz are mounted on the same pressure port of the engine under static test to study the shortcomings of the inlet tube. The limitations of the inlet tube have been analyzed to aid the tube design. The different sizes of inlet tubes are designed, fabricated and tested to study the effect of the inlet tube on the performance of the pressure sensor. The dynamic calibration is used for this purpose. The dynamic parameters of the sensor with the designed tubes are calculated and analyzed to meet the static test requirements. The diaphragm temperature test is conducted on the representative hardware of pressure sensor with and without inlet tube to analyze the effect of the inlet tube against the temperature error. The inlet tube design is validated through the static test to gain confidence on measurement.FindingsThe cavity type pressure sensor failed to capture the pressure peak, whereas the flush diaphragm type pressure sensor captured the pressure peak of the engine under a static test. From the static test data and dynamic calibration results, the bandwidth of cavity type sensor with tube is much lower than the required bandwidth (five times the bandwidth of the measurand), and hence, the cavity type sensor did not capture the pressure peak data. The dynamic calibration results of the pressure sensor with and without an inlet tube show that the reduction of the bandwidth of the pressure sensor is mainly due to the inlet tube. From the analysis of dynamic calibration results of the sensor with the designed inlet tubes of different sizes, it is shown that the bandwidth of the pressure sensor decreases as the tube length increases. The bandwidth of the pressure sensor with tube increases as the tube inner diameter increases. The tube with a larger diameter leads to a mounting problem. The inlet tube of dimensions 6 × 4 × 50 mm is selected as it helps to overcome the mounting problem with the required bandwidth. From the static test data acquired using the pressure sensor with the selected inlet tube, it is shown that the selected tube aids the sensor to measure the pressure peak accurately. The designed inlet tube limits the diaphragm temperature within the compensated temperature of the sensor for 5.2 s from the firing of the engine.Originality/valueMost studies of pressure sensor focus on the design of a sensor to measure static and slow varying pressure, but not on the transient pressure measurement and the design of the inlet tube. This paper presents the limitations of the inlet tube against the bandwidth requirement and recommends dynamic calibration of the sensor to evaluate the bandwidth of the sensor with the inlet tube. In this paper, the design aspects of the inlet tube and its effect on the bandwidth of the pressure sensor and the temperature error of the measured pressure values are presented with experimental results. The calibration results of the inlet tubes with different configurations are analyzed to select the best geometry of the tube and the selected tube is validated in the static test environment.

Unsteady Flow Numerical Simulations on Internal Energy Dissipation for a Low-Head Centrifugal Pump at Part-Load Operating Conditions

Dredge pumps are usually operated at part-load conditions, in which the low-solidity centrifugal impeller could experience large internal energy dissipation, related to flow separation and vortices. In this study, SST k-ω and SAS-SST turbulence models were used, in steady and unsteady simulations, for a low-head centrifugal pump with a three-bladed impeller. The main focus of the present work was to investigate the internal energy dissipation in rotating an impeller at part-load operating conditions, related to flow separation and stall. The unsteady nature of these operating conditions was investigated. Performance experiments and transient wall pressure measurements were conducted for validation. A methodology for internal energy dissipation analysis has been proposed; and the unsteady pressure fluctuations were analyzed in the rotating impeller. The internal power losses in the volute and the impeller were mostly found in the centrifugal pump. The rotating stall phenomenon occurred with flow separation and detachment at the part-load operating condition, leading to a dissipation of the internal energy in the impeller. The rotating impeller experienced pressure fluctuations with low frequencies, at part-load operating conditions, while in the design operating condition only experienced rotating frequency.