Inlet Configuration Research Articles

Experimental Investigation of Single-Ramp and Double-Ramp Internal Compression Inlet Models

Flow visualization experiments, pressure and particle image velocimetry (PIV) measurements were conducted in supersonic internal compression inlet models in a Mach 2 flow. In the first phase of the study, the inlet model having a single sharp-edged shock generator on the upper lip of the inlet was investigated. In the second phase, another ramp was added to the floor of the single-ramp inlet model in order to fully represent an internal compression inlet. A block piece is placed at the exit of the inlet channel to simulate the pressure condition caused by the presence of the diffuser and engine. Schlieren imaging method was used to obtain the multishock wave flow pattern within the models. Fluctuating pressure measurements were performed on the floor of the inlet models. Mean velocity field at the center plane section of the inlet is obtained by side-view PIV measurements. Moreover, mean total and static pressures were measured at the exit section of the models in order to assess the total pressure recovery and exit Mach distribution of the inlet configurations. Results show that in general the double-ramp model flow field exhibits relatively smaller unsteady pressure fluctuations and hence a better performance.

Effect of Different Inlet Configurations on Particle Concentration around a Patient in Cleanroom

Effect of Different Inlet Configurations on Particle Concentration around a Patient in Cleanroom

Fundamental studies on droplet throughput and the analysis of single cells using a downward-pointing ICP-time-of-flight mass spectrometer.

Capabilities of the downwardly oriented inductively coupled plasma mass spectrometer (ICP-MS) recently reported (Vonderach et al. 2021) were studied using a time-of-flight mass spectrometer (TOFMS) yielding benefits for the fast detection of short transient signals containing multi-element information. The previously reported sample inlet configuration for the analysis of microdroplets was equipped with two extra gas inlets for the supply of argon and helium, which enabled a more precise optimization of the sample introduction and operating conditions of the plasma. Furthermore, the sample supply system was operated at elevated temperatures to enhance the desolvation of the droplets prior to their introduction into the plasma. Transient droplet signals with frequencies of up to 1000 Hz were recorded for 74 μm (diameter) sized droplets. The upper detectable droplet size was limited by the droplet generator used and was measured at 93 μm (diameter). The droplets served as the transporter for biological cells so that the described setup could be used to analyze single cells. Mouse lung cells embedded into droplets were detected successfully according to their Cs droplet tracer, Ir nucleus marker, surface markers and the phosphorus content. Transient signals were recorded at a time resolution of 33 μs in order to investigate the signal structure of single droplet–cell events containing multiple elements. Signals between 200–400 μs (FW base) and ≤100 μs (FWHM) in duration were measured. To ensure that the droplet formation process did not affect the sampled cells, different types of cells were localized within the droplets using optical inspection directly after droplet formation and it was possible to observe that cells remained intact with random sampling. The results indicate that a downward-pointing ICP-MS in combination with the microdroplet-based approach can be considered as an alternative to commonly used ICP-MS systems for single cell analysis, and might be suitable for online coupling to flow cytometry.

Three-dimensional characterization of air infiltration using infrared thermography

The energy consumption in buildings is still very high despite its reduction in recent years. Buildings’ conditioning is the main cause of this energy consumption and, in this sense, air infiltration has a great impact. The control of air infiltration is essential to achieve thermal comfort and energy efficiency. The evaluation of the global airtightness of the building envelope based on pressurization tests has been broadly used to determine the airtightness of buildings, but it cannot define the shape of air leakages. The use of thermography in combination with pressurization tools could be very useful.This paper presents the laboratory experimental measurements to obtain a three-dimensional definition of the air temperature when passing through a controlled envelope gap. The method is based on the bidimensional temperature matrix, captured by infrared (IR) thermography, that the air leakeage produces close to the gap, and depending on the configuration of the air inlet and airflow. The temperature measurement was done using a non-continuous rendering surface in order to avoid the Coanda effect that opaque surfaces cause, achieving in this way a 42% increase in the measuring accuracy.

Geometry of natural and engineered tidal inlets

Tidal inlets are crucial landforms that control the exchange of water and sediment between the open sea and back-barrier basins. Despite the well-established relationship between tidal prism and inlet cross section area, some aspects of tidal inlet geometry remain unconstrained. What processes set their width to depth ratio (or aspect ratio)? What controls the presence of a single-thread versus a compound channel within the same inlet? Do these relationships change with engineering activities? These questions were investigated by compiling and analyzing a database with 226 inlets worldwide. We found that the aspect ratio has a weak dependency on tidal range and wave height. The aspect ratio varies by at least an order of magnitude, and this variability is likely associated with the variability in the widening process, e.g., the bank erodibility. Engineered inlets tend to have smaller widths and aspect ratios than natural inlets. Within natural inlets, multiple channels tend to form when the inlet width exceeds approximately 1 km. We developed an idealized barrier-inlet system using the detailed 2D hydro-morphodynamic model Delft3D to investigate the long-term morphological evolution of inlets. Two parameters greatly affect the aspect ratio: the transverse bed gradient factor for sediment transport (αbn) and the dry cell erosion factor (θsd), which allows for erosion of dry cells adjacent to a wet cell. Removing the dry cell erosion effectively “armors” the side of the inlets and thus produces inlets with a small aspect ratio, which resembles the geometry of engineered inlets. From model sensitivity analysis, we found that αbn = 5–10 and θsd = 0.3–1.0 provides inlet configurations that best agree with observations. Despite the dry cell erosion and the transverse transport parameters being a simplified representation of bank erosion processes, their calibration allows to reproduce realistic inlet aspect ratio.

Effects of surface morphological structure of a brown alga miyeok (Undaria pinnatifida) on sustainable drag reduction

Liquid-infused surfaces are a promising passive technique for frictional drag reduction. However, their practical application is limited by the easy depletion of the lubricant infused in the surface by external forces. Miyeok contains mucus on its surface, which induces a sustainable slippery surface under flow conditions. In this study, the effect of the surface morphological structures of miyeok on slippery characteristics was examined. The surface of miyeok has bump-like microstructures and tiny pores of mucilage gland cells with a re-entrant inlet configuration. A replica model of the miyeok surface was fabricated by adopting a molding process using polydimethylsiloxane. The miyeok replica model was dipped into a silicone oil solution to obtain a slippery surface property. The surface structures of fresh miyeok and the replica were checked by comparing their scanning electron microscopy images. A replica of a kelp surface was also fabricated by employing the same method. The heights of the surface microstructures of the miyeok replica were more uniform than those of the kelp replica. The sustainable drag reduction effect of the replica models’ surfaces was assessed by a sessile drop method. The liquid-infused miyeok replica surface (LIMRS) showed better sustainability than other surfaces. The slippery properties of the LIMRS were examined by measuring slip length and pressure drop. The drag reduction rates measured by the two methods were approximately 24% and 19%. The present results would be helpful for understanding the effects of the surface structure of natural miyeok on sustainable drag reduction and developing a biomimetic sustainable drag-reducing surface.

Numerical studies on the hydraulic and thermal performances of trapezoidal microchannel heat sink

The present work numerically studies the hydraulic and thermal performances of trapezoidal microchannel heat sink (TMCHS) with rectangular cross-sectional shape under the constant total channel volume. Considering the flow direction, channel arrangement direction and inlet location, TMCHSs with six different configurations are proposed to compare their hydraulic and thermal performances. The results demonstrate that the pressure drop of the six THCHSs always increases with the decreasing small-to-large end width ratio. For the thermal performance, only the two TMCHSs with Parallel Channel Parallel Flow Large Inlet (PCPFLI) and Reverse Channel Counter Flow Large Inlet (RCCFLI) configurations have improved thermal performances with the decreasing small-to-large end width ratio, including decreasing maximum temperature, decreasing thermal resistance and decreasing center zone temperature difference. On the basis of these, the effects of the channel height and inlet flowrate on the thermal performances of TMCHSs with PCPFLI and PCPFLI configurations are further studied. It is found that PCPFLI and RCCFLI configurations have lower thermal resistance and more uniform temperature distribution with increasing channel height and inlet flowrate. The TMCHS with RCCFLI configuration has the best thermal performances among the six TMCHSs. The findings reported in present work provide a simple method to improve the thermal performances of MCHS by changing the channel shape and configurations.

The Effects of Multiple Swirl Generator Inlets Circumferential Distribution to a Liquid Fuelled Ultra-High Swirl Flameless Combustion Characteristics

This paper presents the experimental results of a simple cylindrical shaped, liquid fuelled flameless combustor which utilizes ultra-high swirl flow in the combustion process. 4 different swirl generator inlet configurations were tested in this work. Ethanol fuel were used during flameless mode. The experiments were conducted at equivalence ratio (F=1), with the flow rate of fuel set at 4.48*104 kg/s, and flow rate of air at 3.854*103 kg/s. The results revealed that by using all 12 tangential air inlets (swirl generator injectors), the swirl strength was reduced through evenly distributing the position of the injectors circumferentially. As a result, the combustor successfully suppressed the emission of NOx and CO to zero ppm for both gasses. It was also reported that flameless mode was established in all configurations, regardless of the swirl strength.

Separate-effect experiments and modeling for two-phase flow under geometric restrictions

While significant efforts have been made to investigate two-phase flows in vertical upward channels, limited work has been performed to study the effects stemming from geometric configurations on two-phase flow transport, such as flow restrictions and change in flow orientation. This presents significant shortcomings in the application of predictive models to practical systems, including nuclear power reactors. It has been well observed that geometric restrictions (e.g., elbows, spacer-grid, and inlet configurations) and change in flow orientation (e.g., upward-to-horizontal, horizontal-to-downward) can cause significant effects on the hydrodynamics of two-phase flow. In view of these, high-resolution separate-effect experiments have been performed to establish a two-phase flow database that is accurate, extensive and good enough for multi-phase CFD codes development, to develop predictive models accounting for geometric effects, and to improve the performance of nuclear reactor system analysis codes. Recent studies on the effects of the vertical-upward and vertical-downward 90-degree elbows, spacer grid, inlet configurations, and change in flow orientation are summarized. Some of the major two-phase flow phenomena investigated in the present study include flow regime transition, pressure loss, two-phase flow parameters, flow development, and interfacial drag. To demonstrate the functionality of the newly developed models, the one-dimensional steady-state one-group interfacial area transport equation is employed to predict two-phase flow transport under geometric effects.

Effect of Inlet/Outlet Configuration on Water Quality in a Rainwater Harvesting Tank

Rainwater harvesting (RWH) has attracted global attention as a solution for the urban water crisis; however, the water quality can be impacted by particulate matter and soluble contaminants. Therefore, the inlet and outlet configurations of the storage tank should be designed to minimize bottom sediment resuspension and prevent the transport of soluble contaminants. Thus, this study investigated the effects of the inlet and outlet configurations of a rainwater storage tank on particle resuspension and residence time distribution for an instantaneous input of a conservative tracer. It was observed that J type inlets can reduce sediment resuspension by more than 50% while detaining and mixing a conservative pollutant, thus preventing the concentration from reaching the outlet as a plug flow. Although inlet height did not have a significant influence on the quality of water at the outlet, parameters such as inflow velocity and outlet height exerted a considerable influence on sludge resuspension and residence time distribution. The experiments also highlighted the importance of regulating the initial water level of the storage tank and regular flushing of bottom sediment to maintain the stored water quality.

Heat transfer and bed dynamics study on a swirling fluidized bed under various inlet configurations

The present paper aims to study the heat transfer from the wall to the bed in a laboratory-scale swirling fluidized bed with a blade distributor. The experiments were carried out in a swirling fluidized bed reactor with an internal diameter of 10 cm and a total length of 50 cm connected with two different blade-distributors, one with seven blades and another with twelve blades. The heat transfer process represented by the heat transfer coefficient and bed flow dynamics represented by the bed and distributor pressure drops were investigated at different designs and operating conditions, mainly the number of blades, using gas plenum, and using gas plenum with different central bodies. Sand particles (Geldart type D) with a mean diameter of 1.5 mm was used as a bed material fluidized by air. The experiments were carried out at different fluidization number of 2.8, 3.3,4.2, and 4.5 at minimum fluidization velocity of 0.8 m/s. Increasing distributor blades from seven to twelve blades resulted in enhancing the operation of a fluidized bed reactor due to increasing the heat transfer coefficient and reducing the bed and distributor pressure drop. Using gas plenum resulted in decreasing the bed and distributor bed pressure drop and also resulted in decreasing the heat transfer coefficient. Two central bodies with conical and cylindrical shapes were installed in the plenum. The two central bodies had a negative effect on the operation of the fluidized bed that leads to increasing both distributor and bed pressure drops and to decreasing the heat transfer coefficient. For all the cases were studies, the heat transfer coefficient in the horizontal direction had the same behavior; it increased near the walls and it was almost constant at the center region of the reactor. Also, the heat transfer coefficient increased at the lower bed heights and vice versa.

Thermal-hydraulic characteristics of purge gas in a rectangular packed pebble bed of a fusion reactor using DEM-CFD and porous medium analyses

The thermal-hydraulic characteristics of helium as a purge gas for the removal of the tritium from a spherical packed rectangular pebble bed reactor are studied in this paper using the DEM-CFDand porous medium approaches. Numerical models are developed for the two approaches considering radiation heat transfer, which are validated with the published experimental results. Further, a comparison is made between the porous medium and the DEM-CFD approaches for predicting the thermal and hydraulic characteristics of the helium. The heat transfer behaviour predicted by both the approaches is approximately the same. The DEM-CFD approach can capture the detailed and localized flow behaviour in the presence of pebble, whereas the porous medium approach can predict the average flow characteristics. Further, the effect of the location of the inlet and outlet on the uniformity of the fluid flow in the canister is studied by considering different combinations of inlet and outlet.It is found that the pebble bed with diagonally opposite inlet and outlet configuration has a higher tritium sweeping efficiency as compared to the existing design of the canister with inlet and outlet at the same face.

Systematic assessment of the anode flow field hydrodynamics in a new circular PEM water electrolyser

In this work, we investigated the key underlying flow characteristics of a circular unit cell proton exchange membrane (PEM) water electrolyser. In particular, we focused on investigating anode flow field design using computational fluid dynamics (CFD) tool. Transient, 3D single phase fluid flow simulation results were presented, and in-house experiments were conducted for validation against CFD simulation data identifying key performance parameters of the PEM water electrolyser: uniform water distribution, pressure drop and hydraulic retention time. The effects of the water flow rate, inlet and outlet sizing and different number of inlet and outlet configurations were considered. The main observation from the study was discussed to provide insight into the factors affecting the flow pattern. Among the studied flow field design cases, it was found that the average pressure drop decreased with increase in number of inlets, also flow profile can be grouped into different set, depending on number of inlets. The correlation between pressure drop and mean velocity profile for different inlet and outlet configurations provides a useful basis to properly design the high performance PEM water electrolyser.

A Thermal Investigation and Optimization of an Air-Cooled Lithium-Ion Battery Pack

An effective battery thermal management system (BTMS) is essential to ensure that the battery pack operates within the normal temperature range, especially for multi-cell batteries. This paper studied the optimal configuration of an air-cooling (AC) system for a cylindrical battery pack. The thermal parameters of the single battery were measured experimentally. The heat dissipation performance of a single battery was analyzed and compared with the simulation results. The experimental and simulation results were in good agreement, which proves the validity of the computational fluid dynamics (CFD) model. Various schemes with different battery arrangements, different positions of the inlet and outlet of the cooling system and the number of inlets and outlets were compared. The results showed that an arrangement that uses a small length-width ratio is more conducive to promoting the performance of the cooling system. The inlet and outlet configuration of the cooling system, which facilitates fluid flow over most of the battery pack over shorter distances is more beneficial to battery thermal management. The configuration of a large number of inlets and outlets can facilitate more flexible adjustment of the fluid flow state and can slow down battery heating to a greater extent.

Effect of hole feed system on the response of a squeeze film damper supported rotor

An experimental study on the effect of squeeze film clearance and oil inlet configuration on the displacement response of a Jeffcott rotor supported by squeeze film dampers (SFDs) is presented in this paper. Sealed and open-ended SFDs with three squeeze film clearances and three different oil inlet configurations are studied with different levels of unbalance applied to the system. Results show increased damping with smaller clearance and increased number of oil inlets, while the number and orientation of oil inlets also show an effect on the level of air ingestion into the SFD and some asymmetry in the rotor response.

Experimental Study of Square Inlets Effect on the Performances of Gas–Liquid Cylindrical Cyclone Separators (GLCC)

In the gas-oil field, the gas-liquid cylindrical cyclone (GLCC) separator has potentially replaced the traditional separator that is used over the century. It is also interesting for petroleum companies in recent years because of the effect of the oil world price. However, the behavior of phases in the equipment is very rapid, complex, and unsteady, which may cause the difficulty of enhancing the performance of the separation phases. The much research demonstrates that the geometry and the number of the inlet is probably the most important factor that impacts directly to the performance of separation of phases of the device. The main goal of the research paper is to deeply understand the effect of different geometrical configurations of the square inlet on hydrodynamics and performances for two phases flow (air-water). Two different inlet configurations are constructed, namely: One square inlet with the gradually reduced nozzle and two symmetric square inlets with the gradually reduced nozzle. As a result, the separation efficiency of the device will be higher when using two symmetric inlets, and we suggest the application of two symmetric square inlets type that is the same angle of inclination and the area of the nozzle with the unique inlet configuration to improve separation efficiency in GLCC. Such an inlet structure leads to lower swirl intensity decay than one inlet configuration. It also creates a more axis-symmetric flow at the centerline, which would improve the uplift of air bubbles in the performance of GLCC. Besides, this study can be viewed as a padding step to optimizing the operative parameters of GLCC in further study.

Experimental study of circular inlets effect on the performances of Gas-Liquid Cylindrical Cyclone separators (GLCC)

The gas-liquid cylindrical cyclone (GLCC) separators is a fairly new technology for the oil and gas industry. The current GLCC separator, a potential alternative for the conventional one, was studied, developed, and patented by Chevron company and Tulsa University (USA). It is used for replacing the traditional separators that have been used over the last 100 years. In addition, it is significantly attracted to petroleum companies in recent years because of the effect of the oil world price. However, the behavior of phases in the instrument is very rapid, complex, and unsteady, which may cause the difficulty of enhancing the performance of the separation phases. The multiple recent research shows that the inlet geometry is probably the most critical element that influences directly to the performance of separation of phases. Though, so far, most of the studies of GLCC separator were limited with the one inlet model. The main target of the current study is to deeply understand the effect of different geometrical configurations of the circular inlet on performances of GLCC by the experimental method for two phases flow (gas-liquid). Two different inlet configurations are constructed, namely: One circular inlet and two symmetric circular inlets. As a result, we propose the use of two symmetric circular inlets to enhance separator efficiency because of their effects.

Development of a fixed bed solar dryer: experimental study and CFD simulation

Facing the challenges to develop more efficient solar dryers, this work used the Computational fluid dynamics (CFD) to test different configurations of lateral air feeding in a fixed bed solar dryer. Through the simulations, it was found the best configuration of air inlet that provided a better fluid-particle contact. It was made a fixed bed solar dryer, which was tested using soybeans seeds and Moringa oleifera LAM leaves to evaluate the drying rate using two bed configurations: fully opened and partially opened inlets. The CFD results indicated that the air flow rate was more pronounced at the bed top, near the exhaust fan. This can explain the poor drying near the bottom for the experiments performed with all lateral inlets opened. According to the simulation results, the air velocity profile was more homogeneous when the air was fed only near the bottom. So, the use of a partially opened configuration led to a more homogenous solar drying, with a drying rate about 300% higher than the one using the fully opened inlets.

Investigation of variable orifice plate design for centrifugal compressor low-end performance improvement

In the present paper, a compressor with variable inlet configuration upstream of the compressor wheel was investigated to improve the compressor low-end performance. As a concept study, the variable inlet configuration was assumed to be a variable orifice plate which can reduce the compressor inlet flow area when it is activated. The compressor performance with and without the initial orifice plate was assessed quantitatively using both numerical and experimental methods. The results indicated that the initial orifice plate design can improve the compressor efficiency at low speed and flow rate condition. Different orifice plate designs with different setting angles to the compressor inlet main flow direction and different radial heights were also numerically studied. It was found that: (1) changing the orifice plate setting angle from 90° for the initial design to 67° can improve compressor efficiency about 0.56% at low flow rate condition; (2) increasing the orifice plate radial height from 16% of the compressor inlet radius for the initial design to 27% can improve the compressor efficiency by 1.78% at near surge condition and extend surge margin by 9%. The results indicated that the radial height has larger effects on compressor performance than the setting angle at near surge flow rate. While increasing the orifice plate height variation can further improve compressor low-end efficiency and surge margin, there is an increased complexity of the actuation and control system.

Experimental research and numerical simulations of a ceramic panel used for solar energy conversion

The paper presents the results of the laboratory testing and numerical simulations of ceramic solar panels. The experimental research was carried out in artificial (laboratory) operating conditions. Rise in temperature and pressure drop of the fluid flowing through the collector was measured. As a result of the tests, the linear relationship between efficiency and reduced temperature difference was determined. While the pressure drop was approximated by the exponential function. Another research method based on numerical modelling using Computational Fluid Dynamics (CFD) algorithms was applied in this study. The three-dimensional geometric model of the ceramic panel was developed using the application included in the Ansys v. 19.2 package. The data obtained from computer simulations were compared with the results of the experiment to validate the numerical model. In order to find potential opportunities to increase the efficiency and due to the fact that the ceramic panel can be made in various inlet and outlet configurations, three simulation cases were considered: diagonal, top – bottom, and left – right. As the results of numerical calculations showed, the largest flow irregularity occurred in the last configuration. Based on the analysis of the test results, it can be concluded that, in spite of some disadvantages, ceramic panels can compete with traditional solar collectors currently available on the market.