Static Pressure Drop Research Articles

Comparative study of analytical models with linear and quadratic pressure drop conditions on a perforated plate in water waves

Proper pressure drop conditions are essential in predicting hydrodynamic performance of perforated structures in the framework of a potential flow theory. In this study, we investigate water waves passing through a perforated plate with various pressure drop models to examine how pressure drop conditions affect the hydrodynamic performance of perforated structures. We derive the analytical solutions of waves across the perforated plate by adopting three commonly pressure drop conditions, including one linear pressure drop condition (LPDC), and two quadratic pressure drop conditions (QPDCs). A series of laboratory experiments are conducted to validate the present theoretical results. We compare the hydrodynamic performance between the experimental data and the theoretical solutions with the three different pressure drop models, typically for wave reflection coefficients, dynamic pressures, and velocity fields measured by the technique of particle image velocimetry in the experiments. It is found that the existing pressure drop models can predict well wave reflection coefficients, dynamic pressure, and velocity profiles at certain conditions. However, the linear wave solutions associated with LPDC or QPDCs generally underpredict the amplitude of particle velocity near the free surface on the perforated plate. This underestimation increases largely as the wave steepness increases. The LPDC performance relies much on the selection of empirical coefficients. For the QPDCs, the analytical models show deviated results from the experimental data for wave reflection coefficients when the wave steepness is relatively low.

Rigorous design and economic optimization of reactive distillation column considering real liquid hold-up and hydraulic conditions of industrial device

The liquid hold-up in a reactive distillation (RD) column not only has a significant impact on the extent of reactions, but also affects the pressure drop and hydraulic conditions in the column. Therefore, the liquid hold-up would be a critical design factor for RD columns. However, the existing design methods for RD columns typically neglect the influence of considerable amount of liquid hold-up in downcomers owing to the difficulties of solving a large-scale nonlinear model system by considering downcomer hydraulics, resulting in significant deviations from actual situation and even operation infeasibility of the designed column. In this paper, a pseudo-transient (PT) RD model based on equilibrium model considering tray hydraulics was established for rigorous simulation and optimization of RD plate columns considering the liquid hold-up both in downcomers and column trays, and a steady-state optimization algorithm assisted by the PT model was adopted to robustly solve the optimization problem. The optimization results of either ethylene glycol RD or methyl acetate RD demonstrated that assuming all the liquid hold-up of a stage belonged to the tray will cause significant deviations in the column diameter, weir height, and the number of stages, which leads to not meeting the separation requirements and even operation hydraulic infeasibility. The rigorous model proposed in this study which considers the liquid hold-up both on trays and in downcomers as well as hydraulic constraints can be applied to systematically design industrial RD plate columns to simultaneously obtain optimal operating variables and equipment structure variables.

Experimental and numerical investigation of water flow in different media models at multiple scales

ABSTRACT The study of the flow behavior in pores, fractures, and pore-fracture dual media plays a crucial role in understanding the mechanisms of sudden water inrush and sand flow. In this study, laboratory experiments were conducted using a custom-made transparent porous model to investigate the flow characteristics of fluids in complex media. Additionally, finite element simulations were employed to explore the flow features at multiple scales. A detailed analysis at the micrometer scale was conducted to examine the variations in the water velocity, volumetric flow rate, Reynolds number, flow field, and permeability under different porosity and pressure drop conditions. The results indicate that within the studied range of flow velocities and pressures, the fluid flow in all the media models adhered to Darcy’s law. The improvement in structural connectivity in the random pore model has made the flow channels of fluids in the random pore network more diverse, resulting in an increase in the peak water flow velocity from 4.89E–5 m/s to 4.19E–4 m/s. The fluid accelerated while bypassing the protruding solid particles, resulting in the formation of high-velocity zones in the vicinity. As the pressure drop increases, the volume flow rate of the random dual-medium model with a porosity of 0.6 can increase to 1.01E–9 m3/s, with the highest growth rate. We also simulate the fluid flow of a regular dual-medium model at different porosities and find that the permeability rapidly increases from 5.65E–13 m2 to 1.01E–11 m2, demonstrating that the presence of fractures can significantly improve the permeability performance of the medium. The research findings deepen our understanding of the migration behavior of water in complex geological environments and provide theoretical guidance for groundwater resource protection and underground engineering.

Experimental Study of High-Diodicity Inlet Effects On Rotating Detonation Combustor Performance and Operability

Abstract Implementing high-diodicity inlets is critical to reduce backflow and mitigate the pressure loss across the injector in RDCs. Experiments on air injection diodicity were conducted in a non-premixed RDC for both cold-flow and reacting conditions. The introduction of a Tesla-like diode impacted operating modes and injector dynamics, but the extent of that effect depended on the throat-to-combustor area ratio. A smaller ratio mitigated the impact of the diode on detonation characteristics, while a larger ratio extended the operating range of stronger wave modes. The diode stabilized RDC operation through an increased static pressure drop, but limited performance most likely due to poor reactant mixing and local equivalence ratio distribution. Cold-flow tests showed a higher diodicity for the diode, which may contribute to higher pressure gain in reacting experiments. A modified diodicity formulation based on reacting flow measurements was introduced, suggesting that a multi-metric approach can be useful to assess injector performance. High-diodicity air inlets could be useful tools for reducing total pressure loss and controlling operating modes, but careful consideration is required to limit adverse effects on processes like reactant mixing.

Centrifugal failure mechanism analysis for ferrofluid seals based on a bidirectional coupled multi-physics model

In this paper, we propose a bidirectional coupled multi-physics (BCM) model to study the centrifugal failure mechanism of ferrofluid seals, employing a hybrid finite volume–finite element method. In this model, the evolution of the flow field is described by the two-phase incompressible Navier-Stokes (NS) equations with Kelvin force. The volume of fluid (VOF) method is used to capture the gas-ferrofluid interface. Magnetic scalar potential is introduced to solve for the magnetostatic field. We conducted secondary development on the OpenFOAM and Elmer software packages, which are based on the finite volume method (FVM) and finite element method (FEM), respectively, to calculate the flow field and magnetic field in ferrofluid seals. By developing interpolation methods between FEM and FVM grids based on the parallel bidirectional coupler EOF-Library[1], field information exchange between the flow field and magnetic field is achieved. The BCM model executes iterative computations on the flow and magnetic fields in an alternating way, continuously synchronizing the information of each, thus facilitating bidirectional coupling between the FVM and FEM frameworks. We employ the BCM model to investigate the failure mechanisms of ferrofluid seals under different conditions, including various load pressure and rotational velocity. The results indicate that the ferrofluid will leave the surface of the shaft along the pole teeth under the action of centrifugal forces, with the highest radial velocity occurring at the boundary of the liquid film. Under varying conditions of rotational velocity and pressure drop, the centrifugal failure modes of ferrofluid seals exhibit distinct differences. Moreover, two dimensionless numbers are proposed to quantitatively evaluate the effects of load pressure and centrifugal force, thereby augmenting the efficacy of seal design.

A novel optimization model for tackling capacity challenges in natural gas gathering systems

In the layout optimization of natural gas gathering pipeline network, a lot of work has been done, but few scholars focus on the capacity optimization of gas gathering station (short for station). The structural relationship parameters of dendritic pipeline network and the flow parameters of pipeline network are complicated, which makes it difficult to establish the model, and at the same time, the existence of nonlinear term causes the difficulty of solving the problem. In the current two stage star-dendritic natural gas gathering pipeline network, pipeline sizes and station capacity are not well taken into account for the optimization of pipeline network layout at the same time. In this paper, a consideration station capacity and pipeline sizes: Two-stage star-dendritic network layout optimization model (SCPSTSDLO-Model) is constructed by integrating the factors of site discrete characteristics, station capacity and pipeline sizes, and considering the hydraulic pressure drop conditions of the network, and a solution framework based on the nonlinear processing is proposed, which can obtain the optimization results of optimal affiliation, station type, station site and pipeline sizes at the same time. Five cases are used to verify the validity and accuracy of the model and algorithm, compare the sensitivity analysis and solution algorithm, compare the hydraulic pressure drop conditions, and analyze the application in different forms of pipeline networks. The results show that the SCPSTSDLO-Model and the solution method established in this paper can obtain the optimal solutions under different topologies according to the application requirements, taking into account the capacity of stations and pipeline sizes.

MFiX-TFM simulation of hydrodynamics of a dual fluidized bed system

The abundance and replenishable nature of biomass make it a suitable fuel for power generation. Among the various technologies, dual fluidized bed gasification (DFBG) is a suitable technology to generate high-quality syngas from biomass. However, the complexity of hydrodynamics and heat transfer with bed geometry, flow conditions as well as feedstock demands effective research for the design of such system. This study, therefore, focuses on the simulation of hydrodynamics of a dual fluidized bed gasification system. The 2-D two-fluid model (TFM) simulations were performed using Multiphase Flow with Interphase eXchanges (MFiX) software by varying the superficial air velocities for both the gasifier and riser. The influence of superficial air velocity on static pressure, pressure drop, axial and radial voidage, solid velocities, and granular temperature was evaluated. From the simulations, it was observed that with the increase in superficial air velocities, there was an increase in the effective height of pressure drop (66%), voidage, and solid velocities of the gasifier. For the simulation of the riser, similar trends in the profile of hydrodynamic parameters were also observed. The optimum velocity for the gasifier and riser has been suggested to be between 0.15 and 0.35 m/s and 6–7 m/s, respectively.

Investigation of the Static Pressure Drop and Production that Occurs due to Flow Patterns in a Perforated Horizontal Wellbore

This study examined the intricate interaction between flow patterns and production within a perforated horizontal wellbore. The study precisely assessed the behavior of static pressure drop by utilizing an array of flow regimes encompassing bubble, dispersed bubble, transitional bubble/slug, slug, stratified, transitional slug/stratified wave, and stratified wave. Remarkably, an upward trend in static pressure drop was observed with increasing water phase presence, while the converse was true for the air phase. Besides, the air phase superficial velocity exhibited a direct correlation with the magnitude of pressure drop fluctuations. The liquid production demonstrated a peak during bubble and slug flow regimes, followed by a descent during the transition to stratified and stratified wave flow. This decline can be attributed to mixing pressure drops localized during the perforations. Furthermore, an upward trend in average liquid production was observed with increasing mixture superficial velocity, primarily due to the dominant presence of the water phase. Additionally, the percentage of liquid production was positively associated with the water's superficial velocity when the air's superficial velocity was held constant. While the experimental and numerical results were in agreement for slugs and structured flows, there were discrepancies in the behavior of static pressure for bubbles, small bubbles, and structured waves.

Modelling the far-field effect of drag-induced dissipation in wave–structure interaction: a numerical and experimental study

In the interaction of water waves with marine structures, the interplay between wave diffraction and drag-induced dissipation is seldom, if ever, considered. In particular, linear hydrodynamic models, and extensions thereof through the addition of a quadratic force term, do not represent the change in amplitude of the waves diffracted and radiated to the far field, which should result from local energy dissipation in the vicinity of the structure. In this work, a series of wave flume experiments is carried out, whereby waves of increasing amplitude impinge upon a vertical barrier, extending partway through the flume width. As the wave amplitude increases, the effect of drag – which is known to increase quadratically with the flow velocity – is enhanced, thus allowing the examination of the far-field effect of drag-induced dissipation, in terms of wave reflection and transmission. A potential flow model is proposed, with a simple quadratic pressure drop condition through a virtual porous surface, located on the sides of the barrier (where dissipation occurs). Experimental results confirm that drag-induced dissipation has a marked effect on the diffracted flow, i.e. on wave reflection and transmission, which is appropriately captured in the proposed model. Conversely, when diffraction becomes dominant as the barrier width becomes comparable to the incoming wavelength, the diffracted flow must be accounted for in predicting drag-induced forces and dissipation.

Numerical and experimental study on the performance of novel type of separation element based on Coanda effect

This study proposes a new separator based on the Coanda effect to address the issue of low separation efficiency in traditional separators at low gas velocity. The study investigates the impact of inlet velocity on streamlines, pressure drop, and separation efficiency through numerical simulation. Additionally, an experimental platform was constructed to measure the application effect of the new separator using PDPA. Then the following conclusions were drawn: (1) The separation mechanism of WAS is a comprehensive process that utilizes the Coanda effect, supplemented by collision and centrifugation. (2) The inlet gas velocity has little impact on streamlines and droplet attachment, and the mass separation efficiency is 99.9 % when the velocity is between 1–12 m/s. (3) Within the gas velocity range mentioned above, PDPA was used to monitor droplet size information at the outlet. The results showed that droplet sizes were mainly between 0 and 20 μm, with droplets larger than 20 μm being almost completely separated. The droplet size distribution curves at the outlet were consistent, with peak values of 6.5 μm. This results are consistent with the numerical simulation results, verifying the accuracy of the simulation and indicating that WAS has high separation efficiency and a wide range of gas velocities. (4)The main flow loss occurs between the jet nozzle and the outlet of the separation element. At this stage, the total pressure drop accounts for 96 % of the entire process, and the static pressure drop accounting for 56 % of the entire process. Then the correlation formula between pressure drop and inlet velocity was obtained by fitting the experimental results.

A shock loss reduction method for the low-pressure rotor of a vaneless counter-rotating turbine using circulation redistribution

This paper proposes the circulation redistribution for the low-pressure (LP) rotor of a highly-loaded vaneless counter-rotating turbine (VCRT) to reduce the LP shock losses. The method is to decrease the mid-span circulation and increase the tip circulation at the exit of the LP rotor with unchanged high-pressure (HP) and LP power output. The LP Blade-to-Blade flow field can be considered as a Laval nozzle model. And the high static pressure drop from the throat to the exit results in strong trailing edge (TE) shocks near the LP mid-span. Also, the suction side TE shock (ST) and the reflected shock of the pressure side TE shock (RPT) near the LP mid-span merge into a relatively strong shock very close to the TE. These two factors result in high shock losses. To reduce the shock losses under the design condition, decreasing the stagger angle and the blade exit angle near the LP mid-span are adopted to reduce the LP mid-span exit circulation. This changes the throat area to exit area ratio near the LP mid-span, prompting the actual static pressure drop from the throat to the exit to be reduced and closer to the theoretical value, so that the TE shock strength is reduced. Besides, the intersection of the RPT and the ST is delayed owing to the improved flow angle distributions near the TE, further contributing to the LP mid-span shock loss reduction. Since the LP power output is decreased and the LP tip-leakage flow (TLF) losses are far lower than the HP TLF losses, increasing the stagger angle and the blade exit angle in LP tip regions are employed to increase the LP exit circulation and decrease the HP exit circulation in tip regions. Then the HP and LP efficiency are both raised with unchanged HP and LP power output after optimizing the blade profiles near the mid-span and in tip regions of the LP rotor. The remarkable thing is that the TE shock strength in LP tip and root regions are both reduced after improved because of the decreased ratio of the exit area to the throat area. And the intersection of the RPT and the ST in LP tip and root regions are also both delayed, leading to reduced shock losses. The reduced TE shock losses along the whole LP span appreciably raise the LP and VCRT efficiency by 0.96% and 0.32% respectively.

Numerical modeling and experimental validation of air-side forced convection on a Wire-on-tube condenser for a domestic refrigerator

In this study, the effects of various parameters on the air-side performance of a condenser used in a domestic refrigerator were investigated numerically and experimentally. A new condenser design with streamlined eye and kammtail tube shapes was studied to delay flow separation. The kammtail form was utilized in a wire-and-tube heat exchanger for the first time in this work instead of traditional round or elliptical geometry. Different design parameters were studied for the outer tube height (3, 3.5, 4, 4.5, and 5 mm), aspect ratio of the tube (1.5, 2, and 2.5), tube pitch (20 and 15 mm), tube arrangement (inline and staggered), and tube shapes (eye, kammtail, and ellipse forms) to improve the air-side performance. The model was validated using experimental data based on a performance test setup and wind tunnel measurements conducted at different air velocities. The impact of tube shape and tube dimensions on the convection coefficient and pressure drop were found to be dominant due to delayed flow separation and reduction in the recirculation area. The results showed that, for a similar heat-transfer rate, the total tube surface area was reduced by 7%, the convection coefficient was increased by 9.4%, and the static pressure drop was decreased by 27% with the new Kamm tail-form design of 3 × 6 mm compared to the respective values of the original condenser. In addition, for a similar air-side performance, decreasing the tube pitch from 20 to 15 mm resulted in subsequent decreases of up to 30% in the heat exchanger volume. When the tube arrangement was changed from inline to staggered, the convective coefficient increased by 23% and the pressure decreased by 14%. The numerical results were in good agreement with the experimental results, showing errors of less than 10% for air pressure drop and less than 9% for heat-transfer capacity.

Consideration of surface roughness during the design of internal structures for fluid transport produced by additive manufacturing of PEEK

Additive manufacturing offers new possibilities for the design of structural components used in fluid transport. Sections of hydraulic manifolds or hydraulic blocks, parts of fluid pumps or hydraulic motors can now be manufactured with details which were not achievable with conventional manufacturing technologies, e.g., optimization of internal bends to minimize pressure drops or decrease peaks in velocity fields of fluids. However, as geometric features influence operational conditions of structural elements, pressure drop and velocity field also depend on the wall roughness of internal bends. This feature thus also has to be taken into account when designing the internal structure for the given fluid and operating conditions. In this paper, a study on surface roughness produced with additive manufacturing of polyether ether ketone (PEEK) is presented. PEEK is known for its excellent thermal and mechanical properties, resistance to wear, chemicals, and temperature which makes it an exciting material choice for structural elements with exceptional performance characteristics. First, flow of water and oil through a round pipe produced with additive manufacturing has been simulated. Two models have been used in simulations, a simplified pipe with a prescribed wall roughness and a detailed pipe with modeled surface roughness. Pressure losses and velocity fields in the pipe were then calculated. Finally, an experiment has been set to measure the pressure losses which are compared to the simulated values.

Numerical analysis of the heat transfer and pressure drop of a wavy fin and Kammtail tube condenser: An investigative study

The aim of this study was to numerically investigate the factors affecting the air-side performance of an innovative condenser for a domestic refrigerator. Novel condenser with a smooth Kammtail tube form was investigated due to delaying flow separation. For the first time in the literature, the kammtail form was used instead of round or ellipse geometry in a finned tube heat exchanger, and the advantages of this form was demonstrated both experimentally and numerically. This study incorporated design parameters such as air velocity (0.5, 0.7, 1 m/s), number of tube rows (4 or 5), tube arrangement (inline, staggered), fin pitches (5, 7, 10, 5–7, 5–10, 7–10 mm), and fin arrangement (homogeneous or hybrid). The findings indicated that, for identical fin types and fin surface areas, the proposed Kammtail shape of 3 × 6 mm exhibited 19% lower pressure drop and 9% higher heat-transfer coefficient compared to the original circular tube profile. Furthermore, decreasing the fin pitches resulted in a 32.9–97% increase in static pressure drop, while the heat-transfer coefficient decreased by about 4.7–11.7%. The examination of two new designs revealed a marked reduction of 7–20.4% in the static pressure drop, a decline in air flow rate of 30%, an increase in heat transfer of 5.6–12.2%, and a corresponding decrease in the volume of the condenser of 20%. The numerical results of this study are in good agreement with experimental results, with deviations of less than 10%.

Design of a flow channel with vortex generators for performance improvement of flow-electrode capacitive mixing under low pressure drop conditions

Salinity gradient power generation is a novel renewable energy technology that generates electricity by exploiting the disparity in salt concentration between bodies of water with high and low salt content, using techniques such as capacitive mixing with flow electrodes (F-CapMix). In this research, we conducted a comprehensive numerical analysis to examine the fluid dynamics and particle behavior of saline water and activated carbon within a flow electrode system equipped with vortex generators on the inner walls of the flow channels. The maximum and net power densities of the F-CapMix for a flow channel with vortex generators were evaluated experimentally. On average, the introduction of vortex generators into the flow channel resulted in a 35.6 % increase in the maximum power density of the F-CapMix compared to a plain channel. Furthermore, when a vortex generator was incorporated, the net power density, considering the pumping power, showed an average enhancement of 26.3 % at flow rates of 15 ml/min or less. Therefore, we anticipate that the flow channel with integrated vortex generators can be effectively utilized in the F-CapMix electrode system with a negligible impact on the pressure drop.

Flow investigation of two-stand ultrasonic flow meters in a wide dynamic range by numerical and experimental methods

The enhancement of two-stand ultrasonic flow meters relies upon obtaining a precise understanding and prediction of their complex flow physics throughout their entire dynamic range of operation. This study provides a comprehensive numerical and experimental investigation of the flow physics of a typical two-stand ultrasonic flow meter by industry standards. Predictions based on computational fluid dynamics simulations are employed to obtain numerical results, which are validated through experiments based on laser Doppler velocimetry and static pressure drop. Results indicate that no qualitative changes occur beyond an inflow Reynolds number of 104 in terms of coherent structures and flow dynamics. Analysis of the static pressure distribution across cross-sections reveals that the stands are the most influential areas contributing to pressure drop. In cases with turbulent inflow, there is a noticeable recovery of static pressure following significant pressure gradients across the stands, while such recovery is absent in scenarios with laminar inflow. Both numerical and experimental approaches yield excellent agreement in outcomes, accurately estimating the axial velocity within the flow meter’s measurement volume and the pressure drop across it, with deviations within experimental uncertainty ranges of 2 standard deviations. The developed numerical methodology demonstrates its potential to accurately evaluate complex internal-flow systems with similar flow features and Reynolds number ranges. The flow dynamics for a wide dynamic range of operation in two-stand ultrasonic flow meters are shown in detail in both laminar and turbulent flow regimes, displaying rolling vortices, detached flow, and recirculation zones.

EXPERIMENTAL AND THEORETICAL CHARACTERIZATION OF TWO-PHASE FLOW DISTRIBUTION IN UNBALANCED FLOW NETWORKS

This study investigates the two-phase flow distribution of R-1234yf into two-branched channels. The effect of unbalanced pressure drop and tube diameter on the flow distribution was especially characterized and modeled. The experiments were conducted for a mass flux ranging from 393 kg/m<sup>2</sup>s to 1179 kg/ m<sup>2</sup>s, and the inlet quality was fixed at 0.2. The flow distribution was mainly governed by the pressure drop ratio between two branched channels. The mal-distribution under the unbalanced pressure drop condition was mitigated by increasing mass flux, whereas sustained mal-distribution was observed under unbalanced tube diameter conditions. Correspondingly, a theoretical representation of the phenomenon based on the principle of minimum entropy production was developed and adopted to predict two-phase flow distribution in an unbalanced flow network. The characteristics of the experimental data were clearly and quantitatively reflected in the prediction results. Under the unbalanced pressure drop condition, the predictions agreed well with the experimental data, maintaining the maximum deviation within ± 30%, whereas it exceeded ± 30% under the unbalanced tube diameter condition. The analysis of such theoretical formulation suggests the necessity of appropriate pressure drop models of flow impact, contraction, and merging at the outlet channel, which are compatible with the extremization of entropy production for further improving the prediction accuracy without compromising its generality.

Orthogonal Pattern Louver Mixer for Two-Dimensional Air Mixing in HVAC Applications: Performance and Design Optimization

This article focuses on the investigation of the mixing and hydraulic performance of an orthogonal pattern louver mixer in a square duct. The investigation includes various configurations, including the following parameters: mixer spacing and louver pattern orientation for a pair of mixers, as well as louver angle and louver array size were for both a single and a pair of mixers. Additionally, operational parameters such as mixing length, total flow rate, and flow rate ratio between cold and warm air were considered. Experimental testing was conducted to assess the performance of the orthogonal pattern louver mixer across various parameter combinations. Additionally, a numerical model was developed to enhance understanding of the mixing pattern and flow behavior. Numerical results highlighted that the two-dimensional mixing flow, characterized by multiple vortices generated through the unique louver design, significantly contributed to rapid and robust mixing, effectively reducing maldistribution within a short mixing length. The performance of the orthogonal pattern louver mixer from the experimental results was compared to other mixer types, such as orifice type mixers and ASHRAE Standard 41.2-based “cheese grater” baseline louver mixers. The orthogonal pattern louver mixer was found to be outstanding, with a maximum mixing effectiveness of 88 % for a mixing length of 2.0 Dh. Although it caused a higher static pressure drop than the baseline louver mixers, it was still acceptable for industrial use. The findings indicate that the orthogonal pattern louver mixer is a promising option due to its simple design, easy fabrication, high mixing performance with low pressure drop, and two-dimensional mixing. The orthogonal pattern louver mixer was also less sensitive to flow rate and velocity maldistribution than orifice-type mixers. This article provides useful guidelines for designing and selecting the best mixer type for HVAC applications, considering factors such as cost-effectiveness, mixing performance, pressure drop, and sensitivity to flow rate and velocity maldistribution. In addition, the article offers valuable insights into the performance characteristics of single or dual-use orthogonal pattern louver mixers, as well as the importance of carefully selecting the louver angle and array size when configuring the mixer.

Aerodynamic performance test and flow visualization for reducing acoustic liner drag in grazing flow

We aim to reduce aerodynamic drag over an acoustic liner, which comprises of a perforated plate, a honeycomb core, and a rigid backplate, for aero-engine applications through both performance testing and flow visualization. Whereas the acoustic liner can attenuate engine noise, the structural characteristic of the liner surface causes the additional drag in grazing flow, resulting in deterioration of engine fuel efficiency. In this work, acoustic liner test pieces with various hole geometries are tested in the flow duct rig capable of generating sound wave and grazing air flow inside the duct. The static pressure drop measurement reveals that the perforation in the grazing flow direction wound increase the drag despite the same overall perforation for all test pieces. We further conduct the flow visualization using the test rig designed for water flow to be analogous to the air flow of the flow duct rig, and the analogy is based on Reynolds number defined with the friction velocity and the representative size of an acoustic liner. The result via particle image velocimetry represents the flow patterns causing the drag.

Flow characteristics of radial inflow in impeller rear cavity with baffle plate

The research purpose of this paper is to explore the influence of the baffle plate on the airflow in the rear cavity of the centrifugal impeller and optimize the performance of the secondary air system's air bleed section. In this paper, a comprehensive experimental study was carried out on the flow characteristics in the impeller rear cavity with baffle plate. The windage torque, flow structure and pressure drop between inlet and outlet were measured respectively. The experiment was carried out with the condition that the range of rotational Reynolds number was from 8.33 × 105 to 22.2 × 105 and the range of mass flow rate coefficient was from 0.92 × 104 to 2.92 × 104. The results show that the static cavity and the narrow stator-rotor cavity formed by the baffle plate effectively suppress the overall swirl coefficient in the cavity. Thus, the static pressure and total pressure drop in the rotor–stator cavity were reduced. The influence of the baffle plate on the windage torque of the rotary disk is related to the turbulence parameters. Under large turbulence parameters, the windage torque would be reduced with baffle plate, while under small turbulence parameters, the baffle plate would increase with baffle plate. In general, the baffle plate can improve the flow capacity and optimize the bleed air performance with proper structure and operation conditions.