Typical Inlet Research Articles

Surface to sewer flow exchange through circular inlets during urban flood conditions

Abstract Accurately quantifying the capacity of sewer inlets (such as manhole lids and gullies) to transfer water is important for many hydraulic flood modelling tools. The large range of inlet types and grate designs used in practice makes the representation of flow through and around such inlets challenging. This study uses a physical scale model to quantify flow conditions through a circular inlet during shallow steady state surface flow conditions. Ten different inlet grate designs have been tested over a range of surface flow depths. The resulting datasets have been used (i) to quantify weir and orifice discharge coefficients for commonly used flood modelling surface–sewer linking equations and (ii) to validate a 2D finite difference model in terms of simulated water depths around the inlet. Calibrated weir and orifice coefficients were observed to be in the range 0.115–0.372 and 0.349–2.038, respectively, and a relationship with grate geometrical parameters was observed. The results show an agreement between experimentally observed and numerically modelled flow depths but with larger discrepancies at higher flow exchange rates. Despite some discrepancies, the results provide improved confidence regarding the reliability of the numerical method to model surface to sewer flow under steady state hydraulic conditions.

Preferred sampler inlet configurations for collection of aerosolized nano-scale materials

Due to the lack of standard industrial hygiene sampling protocols for collection of nano-scale materials, sampling inlet device selection is left to individual researchers and professionals. The objective of this study was to compare nano-scale aspiration efficiency for common inlet configurations with that of an open-ended sampler tube that is a commonly used inlet for direct reading instruments such as a condensation particle counter. A polydisperse aerosol was generated using an electric motor as the aerosol source. Typical aerosols generated by this method produced particles with geometric mean mobility diameters of approximately 30nm with geometric standard deviations of approximately 2. Comparison of raw particle counts in size ranges measured with a scanning mobility particle analyzer was made by determining the fractional difference between the selected inlet and that of the open-ended tube. Particle size distributions were nearly identical for all inlet types. The same held true for numbers of particles collected with the exception that the needle inlet was highly variable. When completing air monitoring for nano-scale materials, inlets on most collection devices (filters, tubing) do not impact aspiration efficiency. This means that it is not necessary to match inlet configurations when using multiple methods to collect and analyze nano-scale materials.

Assessing the Impact of the Inlet Total Pressure Distortion on the Turbofan Thrust

The paper considers techniques to develop a mathematical model using a method of «parallel compressors». The model is intended to estimate the impact of the air inlet distortion on the primary parameters of the aero-engine. The paper presents rated estimation results in the context of twin spool turbofan design for two typical cruiser modes of flight of the supersonic passenger jet. In estimation the base values σbase and the average values of the inlet ram recovery σave remained invariable. Thus, parametrical calculations were performed for each chosen relative value of the area of low-pressure region.The paper shows that an impact degree of the inlet distortion on the engine thrust for two modes under consideration is essentially different. In other words, if in the subsonic mode the impact assessment can be confined only to taking into account the influence of decreasing average values of the inlet total pressure, the use of such an assumption in the supersonic cruiser mode may result in considerable errors.With invariable values of the pressure recovery factor at the engine intake, which correspond to the speed of flight for a typical air inlet of external compression σbase, and average value σave, a parameter Δσuneven has the main effect on the engine thrust, and degree of this effect essentially depends on a difference between σave and σbase values.

Effects of Three-partitioned Horizontal Inlet and Clean Air on Collection Efficiency and Wall Loss of Slit Virtual Impactors

A numerical and experimental investigation comparing two configurations for a slit nozzle virtual impactor, one using a three-partitioned horizontal inlet and the other using a typical vertical inlet, was conducted to improve collection efficiency and reduce wall loss. All parameters, such as the length and width of the acceleration nozzle, the width of the collection nozzle, the distance between the two nozzles, and the inlet flow rate, were kept constant, and only the inlet configuration was changed. The ratio of the minor to the total flow rate was fixed at 0.1. Parametric analysis was performed to study the flow-rate influence of incoming clean air and aerosol on the performance of the three-partitioned horizontal inlet virtual impactor. The square root of the Stokes number, (Stk)1/2, was used to characterize the collection efficiency and wall loss of both configurations. It was observed that by using the three-partitioned horizontal inlet, the cut-off diameter was reduced from (Stk)1/2 = 0.80 to (Stk)1/2 = 0.41, and the wall loss near the cut-off diameter decreased from 25%–45% to below 4.5%. Moreover, using the three-partitioned horizontal inlet reduced the contamination by particles smaller than the cut-off size in the minor outflow section of the virtual impactor to almost 0%.

Efficient continuous biogas production using lignocellulosic hydrolysates as substrate: A semi-pilot scale long-term study

Traditional solid-state biogas production from lignocellulosic biomass has some issues such as relatively low methane yield, instability of fermentation system, etc., and these might be solved by changing solid-state mode to completely liquid-state mode using lignocellulosic hydrolysates as substrate for biogas production. However, the potential and possibility of this new technology for industrial application is still unclear. In this study, semi-pilot scale long-term biogas production using various lignocellulosic hydrolysates (acid hydrolysates of bagasse, rice straw, and corncob) as substrate was carried out in a 100L up-flow anaerobic bioreactor (internal circulation reactor, IC) for 76days. During operation, biogas was generated almost immediately when the substrate was pumped into bioreactor and the start-up can be finished in short period. Throughout the fermentation process, most COD (>85%) of lignocellulosic hydrolysates was utilized for biogas production. High biogas yield (0.549±0.058 m3/kg COD consumption), methane yield (0.381±0.043 m3/kg COD consumption) and CH4 content in biogas (69.6±5.6%) can be obtained respectively when the fermentation system was stable. Variations of inlet pH value and types of lignocellulosic hydrolysate showed little influence on the operation performance of this fermentation system. Overall, the fermentation scale, operation period, COD removal, biogas yield, CH4 content in biogas, and operation performance with various inlet pH value and different kinds of substrate shows that this technology has great potential and possibility of industrialization.

A numerical investigation of Helmholtz resonators in the presence of grazing flow by means of the lattice Boltzmann method

Helmholtz resonators remain widely used in noise control. In applications such as aircraft engines and exhaust systems, the presence of a grazing flow significantly changes their behavior, and a correct prediction of their acoustic properties is essential to improve noise reduction. With the purpose of understanding the physical phenomena associated with the acoustic-flow interaction, the simulation of a single 2D Helmholtz resonator was considered by means of an in-house numerical code based on the lattice Boltzmann method (LBM). The results have been validated against published data based on both experimental results and direct numerical simulation (DNS) for normally incident acoustic waves in the absence of flow. The investigations will proceed by taking into account grazing acoustic waves in the presence of a grazing flow, similarly to the conditions found in a liner test rig. Efforts will be focused on typical aircraft engine inlet conditions, i.e., high Mach numbers and SPL. Both experimental and numerical results will be compared in terms of absorption coefficient and impedance.

Study on flow characteristics in an open two-phase natural circulation loop

Flow characteristics are relevant to the safe operation of natural circulation systems. Experimental research on flow characteristics in an open natural circulation loop was conducted. It was shown that flashing and geysering are the two fundamental phenomena influencing the flow characteristics; in addition, flashing and geysering interact reciprocally: geysering weakens the impact of flashing on the flow, while flashing can suppress geysering. Six circulation modes were identified based on the weight of flashing and geysering, as well as typical inlet flowrate curve and experimental observations. As the heating power varies, so do the weights of flashing and geysering, which result in variable flow behavior and the evolution of circulation modes. Based on the theoretical analysis and the calculation of average circulation flowrate by taking into account the effects of subcooling, flashing and heat dissipation, suggestions for the operating and improvement of the system were proposed.

Pelvic Inlet Shape Is Not as Dimorphic as Previously Suggested.

It is well known that there are significant differences in the pelves of males and females due, in part, to differing constraints. The male and female pelves must be suitable for upright posture and locomotion, but the female pelvis must also be suitable for reproduction. These differing requirements lead to differences in the shape and size of various pelvic dimensions. These differences are reflected in the pelvic inlet, midplane, and outlet. Current research has documented dimorphisms in the posterior and anterior spaces in all three of these planes. One measure however, that is calculated from the relationship between the length of the anterior-posterior diameter (APD) and the transverse diameter (TD) of the inlet, is not as dimorphic as previously suggested. This computed value is used to describe four main categories of inlet shape: android, gynecoid, anthropoid, and platypelloid. Current textbooks in anatomy and midwifery describe these forms and identify the typical male inlet shape as android and the typical female inlet shape as gynecoid. In this study, however, using skeletonized pelves of 378 adult individuals from three identified skeletal collections, the most common inlet shape for both males and females was android. In addition, when examining shape as a continuous variable, inlet shape is not sexually dimorphic in two of the three populations examined in this study. Based on the results of this study, the inlet shape for males and females is less dimorphic than previously thought, and we need to discontinue using pelvic categories to describe typical inlet shape. Anat Rec, 300:706-715, 2017. © 2017 Wiley Periodicals, Inc.

Investigation on flow distribution of the fuel supply nozzle in the annular combustor of a micro gas turbine

The flow distribution of the fuel supply nozzle in the combustor of a 500 W micro gas turbine was investigated. Numerical simulation was performed. Numerical results for flow distribution of the fuel supply nozzle were validated from the corresponding experimental data. Based on the validated numerical model, the effects of the nozzle diameter, inlet mass flow rate, fuel temperature, and types of fuel on the flow distribution were examined. In order to quantitatively evaluate the non-uniformity of flow distribution, the relative flow non-uniformity parameter was introduced. Furthermore, the pressure drops between the inlet and outlet of the fuel supply nozzles were experimentally and numerically obtained. In the aspect of both the uniform flow distribution and lower power consumption of the pump, all nozzles with 500 μm in diameter are appropriate for the fuel supply nozzle of the micro gas turbine. In addition, a simple method was developed to determine the geometry of the fuel supply nozzle with variable nozzle diameters which could achieve the uniform flow distribution. Finally, it was confirmed that the uniformity of the flow distribution can be improved without the increase of the pressure drop by applying the variable nozzle diameters into the fuel supply nozzle design.

Exergy and entransy analyses in air-conditioning system part 2—Humid air handling process

Humid air handling process is an important component of the air-conditioning system. In the present study, air handling process between air and water or liquid desiccant are investigated from the perspectives of exergy and entransy analyses. Choosing typical inlet air states as examples, exergy destructions ΔEx,des and entransy dissipations ΔEn,dis are represented in the (1-T0/T)-Q diagram and the T-Q diagram respectively. Unmatched coefficient ξ is defined as the index to depict the uniformity of driving force (ΔT or Δω), which is always higher than or equal to 1. Reasons leading to ΔEx,des and ΔEn,dis are then clarified with the help of ξ. It’s indicated that dissipations or destruction occurred during the heat and mass transfer processes are mainly due to the limited transfer capability and the unmatched properties. The heat and mass transfer process approaching to the saturation line is recommended between air and water, with an unmatched coefficient approaching to 1 and a least destruction or dissipation resulted from ξ. Case studies are carried out with emphasis on reducing the unmatched exergy destruction. The water is recommended to be heated for humidification rather than the air in the humidifier and similarly the solution should be heated for regeneration, lowering the unmatched exergy destruction. The present research is beneficial for performance optimization of the humid air handling process in the air-conditioning system.

Gas-particle flows and erosion characteristic of large capacity dry top gas pressure recovery turbine

Based on the erosion rate model and the particle rebound model of blade material obtained through accelerated erosion test under high temperature, systematic numerical simulations of the complex gas-particle flows in inlet volute and cascade of a large capacity gas pressure recovery turbine are performed in this paper. The influence of inlet volute structure and cascade channel structure on the aerodynamic performance and erosion characteristics of turbine is first investigated. Results show that although mixing flows and vortex flows are formed in turbine intake volute, total pressure loss of volute is less than 0.7% because of low gas velocity. Erosion damage on the trailing edge of nozzles and rotating blades is mainly caused by high-speed cutting behavior of ash particles. The typical inlet volute structure results in an uneven erosion of first stage nozzles along circumferential direction. Nozzles located below the horizontal split are mainly eroded in blade root area, while erosion distribution of nozzles located above the horizontal split is irregular, and worse than the erosion degree of the lower half circle. Flow acceleration characteristics and cascade circumferential structure must be comprehensively considered so as to simultaneously improve the aerodynamic and anti-erosion performance of turbine.

Development of interception capacity equations according to grate inlet types

Development of interception capacity equations according to grate inlet types

Comparison of Chip Inlet Geometry in Microfluidic Devices for Cell Studies.

Micro-fabricated devices integrated with fluidic components provide an in vitro platform for cell studies best mimicking the in vivo micro-environment. These devices are capable of creating precise and controllable surroundings of pH value, temperature, salt concentration, and other physical or chemical stimuli. Various cell studies such as chemotaxis and electrotaxis can be performed by using such devices. Moreover, microfluidic chips are designed and fabricated for applications in cell separations such as circulating tumor cell (CTC) chips. Usually, there are two most commonly used inlets in connecting the microfluidic chip to sample/reagent loading tubes: the vertical (top-loading) inlet and the parallel (in-line) inlet. Designing this macro-to-micro interface is believed to play an important role in device performance. In this study, by using the commercial COMSOL Multiphysics software, we compared the cell capture behavior in microfluidic devices with different inlet types and sample flow velocities. Three different inlets were constructed: the vertical inlet, the parallel inlet, and the vertically parallel inlet. We investigated the velocity field, the flow streamline, the cell capture rate, and the laminar shear stress in these inlets. It was concluded that the inlet should be designed depending on the experimental purpose, i.e., one wants to maximize or minimize cell capture. Also, although increasing the flow velocity could reduce cell sedimentation, too high shear stresses are thought harmful to cells. Our findings indicate that the inlet design and flow velocity are crucial and should be well considered in fabricating microfluidic devices for cell studies.

Gas Flow Dynamics in Inlet Capillaries: Evidence for non Laminar Conditions.

In this work, the characteristics of gas flow in inlet capillaries are examined. Such inlet capillaries are widely used as a first flow restriction stage in commercial atmospheric pressure ionization mass spectrometers. Contrary to the common assumption, we consider the gas flow in typical glass inlet capillaries with 0.5 to 0.6 mm inner diameters and lengths about 20 cm as transitional or turbulent. The measured volume flow of the choked turbulent gas stream in such capillaries is 0.8 L·min(-1) to 1.6 L·min(-1) under typical operation conditions, which is in good agreement to theoretically calculated values. Likewise, the change of the volume flow in dependence of the pressure difference along the capillary agrees well with a theoretical model for turbulent conditions as well as with exemplary measurements of the static pressure inside the capillary channel. However, the results for the volume flow of heated glass and metal inlet capillaries are neither in agreement with turbulent nor with laminar models. The velocity profile of the neutral gas in a quartz capillary with an inner diameter similar to commercial inlet capillaries was experimentally determined with spatially resolved ion transfer time measurements. The determined gas velocity profiles do not contradict the turbulent character of the flow. Finally, inducing disturbances of the gas flow by placing obstacles in the capillary channel is found to not change the flow characteristics significantly. In combination the findings suggest that laminar conditions inside inlet capillaries are not a valid primary explanation for the observed high ion transparency of inlet capillaries under common operation conditions. Graphical Abstract ᅟ.

Inlet effects on vertical-downward air–water two-phase flow

This paper focuses on investigating the geometric effects of inlets on global and local two-phase flow parameters in vertical-downward air–water two-phase flow. Flow visualization, frictional pressure loss analysis, and local experiments are performed in a test facility constructed from 50.8mm inner diameter acrylic pipes. Three types of inlets of interest are studied: (1) two-phase flow injector without a flow straightener (Type A), (2) two-phase flow injector with a flow straightener (Type B), and (3) injection through a horizontal-to-vertical-downward 90° vertical elbow (Type C). A detailed flow visualization study is performed to characterize flow regimes including bubbly, slug, churn-turbulent, and annular flow. Flow regime maps for each inlet are developed and compared to identify the effects of each inlet. Frictional pressure loss analysis shows that the Lockhart–Martinelli method is capable of correlating the frictional loss data acquired for Type B and Type C inlets with a coefficient value of C=25, but additional data may be needed to model the Type A inlet. Local two-phase flow parameters measured by a four-sensor conductivity probe in four bubbly and near bubbly flow conditions are analyzed. It is observed that vertical-downward two-phase flow has a characteristic center-peaked void profile as opposed to a wall-peaked profile as seen in vertical-upward flow. Furthermore, it is shown that the Type A inlet results in the most pronounced center-peaked void fraction profile, due to the coring phenomenon. Type B and Type C inlets provide a more uniform distribution of the void fraction profile with a reduced coring effect.

Numerical simulation on geometrical parameters for closed sump

The closed sump is a typical inlet passage of middle and small pumping station. It has the characteristics of low channel height, small foundation excavation depth, simple structure, a single cross sectional shape changes, ease of construction and other features, so more and more attention and application has been paying on this closed sump in pumping station project. However the flowing pattern within the closed sump is complex, the design is not perfect in some respects, the structure size does not be optimized. Based on the background for renewal and transformation of a pumping station, according to the three-dimensional incompressible fluid Reynolds-averaged N-S equations, the RNG k-e model, the CFD technology. The study on the draught in closed sump might reduce the length of pump shaft to enhance the stability of the pump unit operation. The results reveal the effect of the change of the height of plate. The turbulence in back wall might cause vortex when the height is high. The height of plate had be recommended control in 0.65D-0.85D.The better parameter combination of geometry of closed sump had be given through comparing the results of the orthogonal test and the comprehensive test. The floor clearance should be control in 1.0D. (D is the diameter of flared pipe)

Rapid supersonic performance prediction for 2D ramjet inlets

A computational tool for quick estimation of mass-averaged throat performance for 2D ramjet inlets is presented. Based on the method of characteristics, coupled with unique corrections to the viscous flow and shock interactions associated with ramjet inlets, accurate predictions for the inlet throat are achieved. In comparison to viscous computational fluid dynamics simulation results, the absolute error for this rapid predictive tool is less than 3.5% over the working range of typical ramjet inlets, where the free-stream Mach number ranges from 2.2 to 4.0; the relative throat height ranges from 0.12 to 0.20, and the free-stream Reynolds number ranges from 3.20E+5 to 1.25E+7.

온라인 개방코드 OSCILOS를 이용한 모델 희박 예혼합 가스터빈 연소기의 연소불안정 해석 사례

Combustion instability is a major issue in design and maintenance of gas turbine combustors for efficient operation with low emissions. With the thermoacoustic view point the instability is induced by the interaction of the unsteady heat release of the combustion process and the change in the acoustic pressure in the combustion chamber. In an effort to study the combustion dynamics of gas turbine combustors, Morgans et al (2014) have developed OSCILOS (open source combustion instability low order simulator) code and it is currently available online. In this study the code has been utilized to predict the combustion instability of a reported case for lean premixed gas turbine combustion, and then its prediction results have been compared with the corresponding experimental data. It turned out that both the predicted and the experimental combustion instability results agree well. Further the effects of some typical inlet acoustic boundary conditions on the prediction have been investigated briefly. It is believed that the validity and effectiveness of the open source code is reconfirmed through this benchmark test.

Classification and analysis of candidate impact crater-hosted closed-basin lakes on Mars

We present a new catalog of 205 candidate closed-basin lakes contained within impact craters across the surface of Mars. These basins have an inlet valley that incises the crater rim and flows into the basin but no visible outlet valley, and are considered candidate closed-basin lakes; the presence of a valley flowing into a basin does not necessitate the formation of a standing body of water. The major geomorphic distinction within our catalog of candidate paleolakes is the length of the inlet valley(s), with two major classes – basins with long (>20km) inlet valleys (30 basins), and basins with short (<20km) inlet valleys (175 basins). We identify 55 basins that contain sedimentary fan deposits at the mouths of their inlet valleys, of which nine are fed by long inlet valleys and 46 are fed by short inlet valleys. Analysis of the mineralogy of these fan deposits suggests that they are primarily composed of detrital material. Additionally, we find no evidence for widespread evaporite deposit formation within our catalog of candidate closed-basin lakes, which we conclude is indicative of a general transience for any lakes that did form within these basins. Morphometric characteristics for our catalog indicate that as an upper limit, these basins represent a volume of water equivalent to a ∼1.2m global equivalent layer (GEL) of water spread evenly across the martian surface; this is a small fraction of the modern water ice reservoir on Mars. Our catalog offers a broader context within which results from the Mars Science Laboratory Curiosity rover can be interpreted, as Gale crater is a candidate closed-basin lake contained within our catalog. Gale is also one of 12 closed-basin lakes fed by both long and short inlet valleys, and so in␣situ analyses by Curiosity can shed light on the relative importance of these two types of inlets for any lacustrine activity within the basin.

Ammonia and greenhouse gas emissions from fattening pig house with two types of partial pit ventilation systems

To reduce the cost of the air purification system in cleaning the exhaust air from pig buildings, a concept of partial pit ventilation (PPV), which applies an extra pit exhaust extracting a part of air directly from emission source zone, was introduced. The objectives of this study are to quantify gaseous emissions from a fattening pig building with PPV, and to assess the performance of the PPV with two types of air inlets (ceiling air inlet, system-C; wall-jet air inlet, system-W). Two trials were carried out under summer and winter conditions. For each trial and in each type of PPV system, 32 fattening pigs were raised. Gas concentrations and climate data were continuously measured. Results showed that the average indoor concentrations were 2.1–3.4ppm for NH3, 0.4–0.6ppm for CH4, and 800–966ppm for CO2 in summer; and 4.2–4.3ppm for NH3, 5.0–5.6ppm for CH4, and 1491–1542ppm for CO2 in winter. N2O releases were rarely observed in the current set-up. The PPV system substantially improved the indoor air quality. Approximately half of the whole NH3 emission (47–63%) was driven through the pit exhausts. A combination of PPV and air purification system is considered to be a practical and efficient mitigation method for gaseous pollution from pig production. The two types of PPV systems resulted in two different kinds of airflow characteristics, which further affected the gaseous release processes. During summer, lower gas concentrations and emissions were found in system-C than in system-W. During winter, system-C gas concentrations were higher in room air and slightly lower in pit air than system-W. Both systems had similar values of emissions during winter. Higher gas concentrations were found in winter than in summer. On average, the winter trial had lower daily NH3 emissions but higher CH4 and CO2 emissions than the summer trial.