Short Inlet Research Articles

Ultra-short columns for the chromatographic analysis of large molecules

Today, reverse phase liquid chromatography (RPLC) analysis of proteins is almost exclusively performed on conventional columns (100–150 mm) in gradient elution mode. However, it was shown many years ago that large molecules present an on/off retention mechanism, and that only a very short inlet segment of the chromatographic column retains effectively the large molecules. Much shorter columns - like only a few centimetres or even a few millimetres - can therefore be used to efficiently analyse such macromolecules.The aim of this review is to summarise the historical and more recent works related to the use of very short columns for the analysis of model and therapeutic proteins. To this end, we have outlined the theoretical concepts behind the use of short columns, as well as the instrumental limitations and potential applications.Finally, we have shown that these very short columns were also possibly interesting for other chromatographic modes, such as ion exchange chromatography (IEX), hydrophilic interaction chromatography (HILIC) or hydrophobic interaction chromatography (HIC), as analyses in these chromatographic modes are performed in gradient elution mode.

Study on the aerodynamic performance of nacelle inlet under crosswind

Flow separation will occur in the nacelle inlet under crosswind operation, which will result in engine intake distortion and even engine surge. To study the reference characteristics of the flow field of the short tank inlet separation under the influence of crosswind, this paper observed the cloud map of the total price loss coefficient by changing the flow deflection Angle and flow velocity, made a qualitative analysis of the total pressure distortion degree, then calculated the average total pressure loss coefficient and distortion index, and conducted a quantitative analysis to explore the improvement of the total pressure distortion under different flow field factors. The results show that the degree of total pressure distortion is improved with the increase of incoming flow velocity at a small inlet deflection Angle, but with the increase of incoming flow deflection Angle, the ability of incoming flow velocity to improve the total pressure distortion gradually weakens until it disappears. The inlet deflection Angle plays a decisive role in the improvement effect of incoming flow velocity on the total pressure distortion.

Cooling fan aerodynamic noise reduction with short inlet duct and its applicability

This paper presents experimental and numerical analyses of the noise-reduction method of applying short inlet ducts to axial-flow cooling fans. Far-field noise tests of three different-sized cooling fans with tip Mach numbers of 0.143, 0.156, and 0.174 demonstrated that tonal noise was the primary source of aerodynamic noise. Through the installation of short inlet ducts on these fans, the upstream propagation of tonal noise was reduced. The average total sound pressure levels were decreased by up to 3.5, 4.8, and 7.1 dBA, respectively. At the blade passing frequency, the dominant upstream-propagating azimuthal acoustic modes were suppressed. Full-passage unsteady computational fluid dynamics calculations revealed that the duct transforms multiple suction vortices into a single annular vortex structure and weakens the interaction with the rotor blades. In addition, the acoustic analogy was used to compute the reduction of far-field noise and the variations in the major acoustic modes. This revealed a noise-reduction trend similar to that seen in the experiments. Essentially, the duct restrains the non-uniform inlet flow to influence the various inlet–rotor–stator interaction modes. The application of this approach to various fan configurations confirmed that a duct with a parameter of L/D (duct length/duct inner diameter) equal to 0.08 can be recommended as a compact and efficient way to reduce noise.

Lagrange Optimization of Shock Waves for Two-Dimensional Hypersonic Inlet with Geometric Constraints

The present paper focuses on the Lagrange optimization of shock waves for a two-dimensional hypersonic inlet by limiting the cowl internal angle and inlet length. The results indicate the significant influences of geometric constraints on the configuration of shock waves and performances of an inlet. Specifically, the cowl internal angle mainly affects the internal compression section; the inlet length affects both the internal and external compression sections where the intensity of internal and external compression shock waves shows a deviation of equal. In addition, the performances of optimized inlets at off-design points are further numerically simulated. A prominent discovery is that a longer inlet favors a higher total pressure recovery at the positive AOA; conversely, a shorter inlet can increase the total pressure recovery at the negative AOA.

Liner Multiphysics Coupling Between Grazing Flow, Thermal Gradients, and Sound Pressure Levels

The evolution of turbofan engines has led to designs with larger fan diameters, shorter inlets, and thinner nacelle walls. This has forced the acoustic liners used therein to be placed closer to engine components that undergo significant thermal heating. This experimental study investigates the combined effects of important thermal gradients, grazing flow, and acoustic level on liners applied to the Long Elastic Open Neck Acoustic Resonator (LEONAR) liner concept. Previous studies have shown that a coupling between these three effects can exist. The objective is to compare such a liner concept to a classical equivalent single-degree-of-freedom liner and to highlight differences in this coupling behavior. Experiments are conducted in the grazing flow duct at ONERA (B2A), where the flow temperature can be accurately regulated and several types of acoustic excitation can be provided. A test section with a heating or cooling device is used to obtain a thermal gradient between the backplate and the perforated plate of the liner sample, and infrared thermography is used to measure the temperature distribution on the perforated plate. The measurement is conducted on several configurations to assess the behaviors of the LEONAR liner concept in the context of combined influence of grazing flow, thermal gradients, and high sound levels.

Effects of Inlet Types and Lengths on the Flow Field of Cyclone Separators

The effect of inlet type and length on the flow field was considered computationally for seven cyclone separators. The turbulent model was described by the Reynolds Stress Model (RSM). The air-water interface in underflow pipe and the spatial distribution of particles were tracked by the Volume of Fluid (VOF) model and Discrete Phase Model (DPM), respectively. Comparison investigations showed that inlet type and length had important impacts on flow field of cyclone. The instability flow field and back mixing phenomena were eliminated in symmetric double-inlet cyclone. The turbulent dissipation is obvious with a short inlet length. When it increased to 1.25D/2, the area and intensity of the turbulent dissipation tended to be stable. The optimum cyclone is the symmetric double-inlet with inlet length of 1.25D/2. When the particle diameter was larger than 5 μm, the complete separation could be realized.

The Comparisons of Real-time Ammonia Adsorption Measurement in Varying Inlet Tubes and the Different Ammonia Measurement Methods in the Atmosphere

Ammonia (NH3) is an important, albeit sticky, precursor for producing secondary inorganic aerosols (SIA), especially in the form of ammonium nitrate (NH4NO3) and ammonium sulfate ((NH4)2SO4). To reduce SIAs, many researchers have attempted to measure the concentration of ambient NH3 using real-time or passive methods. However, NH3 is a highly sticky gas and is therefore difficult to measure using real-time methods without incurring losses during measurement. In this study, four different tubing materials, semi seamless tubes, perfluoroalkoxy (PFA), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF), were used to ascertain the adsorption of NH3 in inlets using real-time instruments. Without heating sample tubes and at 0% relative humidity (RH), this study shows that PTFE had the least adsorption(i.e., 0% at 1 and 2m of sample tube), and semi-seamless tubes had the highest adsorption (i.e., 27.5% at 1 m of sample tube). To calculate the adsorption of NH3 under ambient conditions, at various inlet lengths, the RH of NH3 was varied from 20% to 80%, which showed that shorter inlets and higher RH lower NH3 adsorption at inlets (i.e., 1.74 ppb m−1 at 80% RH and 7.48 ppb m−1 at 20% RH). Additionally, inlet heating was effective in reducing the adsorption of NH3 as the RH decreased. Applying the inlet system (i.e., 2 m of PTFE tube with heating) showed excellent correlation (slope: 0.995 and coefficient: 0.992) between two different real-time measurements while measuring ambient air.

Research of the efficiency of using the Miller cycle of an internal combustion engine

The article is devoted to the study of the possibilities of improving the technical and economic indicators of an internal combustion engine (ICE) through the use of the Miller cycle with a shortened intake. A review of scientific works on the use of the Atkinson cycle and Miller cycle in an internal combustion engine is carried out. A comparative analysis of theoretical cycles: Otto cycle, Atkinson cycle and Miller cycle is carried out. Calculated studies of the influence of the expansion ratio and the pressure increase ratio on the efficiency of the Atkinson cycle have been carried out. The ratios are presented that allow using the Miller cycle with a short inlet to obtain the same theoretical efficiency of the cycle as that of the Atkinson cycle. At the same time, the implementation of the Miller cycle in a real engine design significantly exceeds the possibilities of using the Atkinson cycle. The results of the study showed that the use of the Miller cycle with a shortened intake is preferable, but it must necessarily increase the compression ratio and intake pressure through the use of boost. On the example of real data of the main parameters of the cycle, it is shown that the use of the theoretical Miller cycle can provide a significant up to 12.2% increase in the efficiency of the cycle compared to the Otto cycle. The ratios, conditions and recommendations are presented that allow the effective use of the Miller cycle with a shortened intake in a real engine design.

Improvement of impregnation quality on out-of-autoclave processed CFRP aircraft wing spar through resin flow simulation

Vacuum-assisted resin transfer molding (VaRTM) is becoming one of the most robust alternatives for autoclave processes. VaRTM, which applies the resin injection method in a vacuum environment, generally uses fiber reinforcement and a polymer matrix separately in the process. The VaRTM is mainly dominated by the characteristics of constituent materials, such as preform permeability and resin viscosity. Among them, process design with the arrangement of resin inlet/outlet locations is closely related to process defects, and inappropriate inlet/outlet layouts cause voids, etc, which has a decisive effect on quality degradation. Therefore, in this study, a highly curved and twisted spar structure was fabricated by the VaRTM, and both flow simulations using Programs for Applied Mechanics–Resin Transfer Molding software and experimental test parts built with three different inlet/outlet line conditions were performed and compared to predict and improve impregnation quality. There was good agreement between the simulation and built test specimen for the three cases that the shorter inlet and outlet length resulted in improved impregnation quality. It was verified that impregnation and inner quality could be improved through flow simulation analysis during the VaRTM process.

Surface temperature measurement of acoustic liners in the presence of grazing flow and thermal gradient

The development of turbofans with larger fan diameters, shorter inlets, and thinner walls forces the acoustic liners to be placed closer to the hot parts of engines. This experimental study investigates the combined effects of large thermal gradients, grazing flow and acoustic level on the impedance of liners. Previous studies have shown that a coupling between these three effects can exist. The objective is thus to understand the underlying coupled phenomena, in order to extract the driving parameters for a more accurate impedance modeling. In the ONERA B2A grazing flow acoustic liner facility, the flow temperature can be accurately regulated and several types of acoustic excitation can be provided. For the purposes of this study, a test section with a heating device is used to obtain a thermal gradient between the backplate and the perforated plate of the liner sample. Infrared (IR) thermography is used to measure the temperature distribution on the perforated plate. The measurement is conducted for several configurations, to determine in which conditions the coupling between thermal and acoustic dissipation effects exists. In particular, a possible control of surface temperature by high sound pressure level is highlighted.Graphic abstract

Morphodynamic Equilibria in Short Tidal Basins Using a 2DH Exploratory Model

AbstractA depth‐averaged (2DH) exploratory model is developed to identify morphodynamic equilibria in short mesotidal inlet systems with arbitrary planform geometries. The water motion is forced by an M 2 tidal constituent at the seaward entrance and is described by the depth‐averaged shallow water equations, whereas the depth‐integrated suspended sediment concentration follows from a diffusion equation, taking into account local inertia, horizontal eddy diffusion and topographically induced diffusive effects, erosion, and deposition. Based on a scaling analysis, it follows that the fine sandy bed evolution is dominated by the depth‐integrated diffusive sediment transport. The depth‐integrated advective contributions are one order smaller and therefore neglected. This observation also allows for the neglect of the advective terms in the governing equations. The associated morphodynamic equilibria are directly identified based on a continuation approach. By means of the exploratory model, the morphodynamic equilibria are studied in basins with a planform geometry characterized by width variations as a function of the distance to the seaward boundary. The model results show that in the case of a sufficient degree of widening in the landward direction, the equilibrium bed level exhibits significant lateral structures, characterized by shallow zones and deeper channels. The first channel bifurcation, as observed in many short tidal inlet systems, is forced by the planform geometry of the basin, and the associated physical mechanisms are explained. Furthermore, two mechanisms inducing asymmetric morphodynamic equilibria are investigated, of which the effect of an asymmetric basin planform seems to be dominant over that of the Coriolis force.

Dynamic flow behavior and performance of a reactor coolant pump with distorted inflow

In the operation of a nuclear plant system, a distorted inflow of a reactor coolant pump appears owing to the steam generator channel head and multi-bend, leading to the deterioration of pump performance and stability. In the present study, three-dimensional numerical calculations of three model geometries are carried out using block grid technology, with RNG k-ε and DDES model applied in the steady and transient simulation. The simulation results are validated with an experiment testing the pump with a short inlet pipe. As for the results, under the distorted inflow condition, the pump head and efficiency are reduced by 4% and 5.2% respectively at the nominal flow rate. Additionally, when the pump is coupled with upstream structures, the inlet flow becomes distorted and more chaotic, and the swirl and radial flow are produced by asymmetric pressure difference. Meanwhile, a pair of local vortices appears in the inlet section, forming re-distributed mass flow rates. As the distorted flow enters the pump, the blade inlet pressure and flow rate are unevenly distributed. Moreover, the evolution process of the vortex is accompanied with strong non-uniformity in the impeller channel, and thus asymmetric tangential force is imposed on the blades, increasing the risk of the fatigue breakdown of the impeller.

Effect of turbulent inlet conditions on the prediction of flow field and hemolysis in the FDA ideal medical device

Hemolysis is one of the most important issues of blood contacting artificial organs. Computational fluid dynamics, in conjunction with hemolysis models, has been widely used to predict the flow field and hemolysis during the development phase of these devices. It is widely accepted that hemolysis is related to flow field parameters, such as stress and energy dissipation. It is known that inlet boundary conditions such as turbulent intensity have important effects on flow fields. Nonetheless, the influence of inlet turbulent intensity on hemolysis is not yet clear. This study investigates the influence of turbulent intensity on the prediction of flow field and hemolysis in the FDA benchmark nozzle model. Three configurations are investigated: first is the original nozzle model (with a gradual contraction, throat, and sudden expansion); the second is composed only of the throat and sudden expansion; the third one is similar with the second, but with a shorter throat. Four turbulent intensities are considered, ranging from 1% to 20%. For the first configuration, the influence of turbulent intensity on both flow field and hemolysis is very small and limited prior to the gradual contraction, while for the other two configurations, the influence is considerable. The jet breaks down sooner with increased turbulent intensity. Both turbulence dissipation rate and Reynolds stress increase in the throat with increased turbulent intensity, but decrease after the jet breaks down. The influence of turbulent intensity is more considerable for the configuration with a shorter inlet. The influence of turbulent intensity on the prediction of hemolysis is up to 38.5%. This study shows that turbulent intensity can have considerable influence on the prediction of flow field and hemolysis in blood-contacting devices, thus should be taken in account when conducting blood compatibility design.

Flow and efficiency measurements with clamp-on ultrasonic equipment

There are several efficiency measurement methods to determine the performance of hydraulic turbines under various circumstances in hydropower plants. To do this, most of the measurement methods require precise determination of discharge. Any hydropower plant with complex pipe geometry and short water inlet near discharge measurement section complicates the use of traditional measuring techniques. Clamp-on ultrasonic flowmeter (USM) can be a good alternative in this situation as it is easy to install at very low cost compared to most of the volumetric flowmeters. Clamp-on USM can be used as index testing method that provides relative values of hydraulic efficiency by measuring the discharge.In this study, discharge measurements with a clamp-on USM were performed at three different positions away from a valve which was partially opened. The main objective was to study the repeatability of the measurements in each position.

Comparison of gas analyzers for eddy covariance: Effects of analyzer type and spectral corrections on fluxes

The eddy covariance technique (EC) is used at hundreds of field sites worldwide to measure trace gas exchange between the surface and the atmosphere. Data quality and correction methods for EC have been studied empirically and theoretically for many years. The recent development of new gas analyzers has led to an increase in technological options for users. Open-path (no inlet tube) and closed-path (long inlet tube) sensors have been used for a long time, whereas enclosed-path (short inlet tube) sensors are relatively new. We tested the comparability of fluxes calculated from five different gas analyzers including two open-path (LI-7500 A from LI-COR, IRGASON from Campbell), two enclosed-path (CPEC200 from Campbell, LI-7200 from LI-COR), and one closed-path (2311-f from Picarro) analyzers, which were all located on a single tower at an irrigated alfalfa field in Davis, CA. To effectively compare sensors with different tube characteristics we used three different spectral correction methods. We found that all sensors, regardless of type, can be used to measure fluxes if appropriate corrections are applied and quality control measures are taken. However, the comparability strongly depended on the gas (CO2 or H2O) and the correction method. Average differences were below 4% for CO2 fluxes using any spectral correction method, but for H2O average differences were between 4% and 13% for the different methods. The magnitude of corrections also varied strongly, especially for water vapor fluxes. This study does not identify the best sensor, but rather weighs the benefits and difficulties of each sensor and sensor type. Our findings show that enclosed and closed-path gas analyzers that measure water vapor with inlet tubes experience large high frequency attenuation and should be corrected with empirical correction methods. This information presented here about different the diverse sensors be considered by investigators when choosing a sensor for a site or when analyzing EC measurements from multiple sites.

Tonal Noise Prediction of a Modern Turbofan Engine With Large Upstream and Downstream Distortion

Ultra-high bypass ratio (UHBR) engines are designed as compact as possible and are characterized by a short asymmetric air inlet and heterogeneous outlet guide vanes (OGVs). The flow close to the fan is therefore circumferentially nonuniform (or distorted) and the resulting noise might be impacted. This is studied here at take-off conditions by means of a simulation of the unsteady Reynolds-averaged Navier–Stokes (URANS) equations of a full-annulus fan stage. The model includes an asymmetric air inlet, a fan, heterogeneous OGVs, and homogeneous inlet guide vanes (IGVs). Direct acoustic predictions are given for both inlet and aft noises. A novel hydrodynamic/acoustic splitting method based on a modal decomposition is developed and is applied for the aft noise analysis. The noise mechanisms that are generally considered (i.e., interaction of fan-blade wakes with OGVs and fan self-noise) are shown to be impacted by the distortion. In addition, new sources caused by the interaction between the stationary distortion and the fan blades appear and contribute to the inlet noise.

Study of burner geometry effects on non-premixed flame response under acoustic excitation

The study of the flame under the acoustic excitation contributes to the study of flame self-excited thermoacoustic instability. Although non-premixed combustion is widely used in industry, research on its combustion instability characteristics is relatively few. This paper experimentally studies the response of a non-premixed swirl flame under excitation. The geometry modifications are the length of the inlet section which is set to be 0.245 m, 0.345 m and 0.445 m and the installation of separation plates. Through the analysis of flame response behavior at different excitation frequencies, combined with the calculation of acoustic mode, we find that for the 0.245 m and 0.345 m inlet length cases, the maximum flame heat release fluctuation responds near 144 Hz. This mode is due to the resonance of the fuel pipe. For the 0.445 m inlet length cases, the maximum flame heat release responds near 134 Hz. This mode is a mixed mode of fuel pipe and combustion chamber. The maximum flame response occurs at the point where the pressure fluctuation reaches the maximum in the inlet section. The image analysis shows the same mode distinction trend between short and long inlet length. Besides, the removing of separation plates leads to a more stable response of the flame in low inlet airflow rate. However, at high airflow rate, the flame tends to be more unstable. Moreover, the higher acoustic forcing frequency than quarter-wave mode will cause the quarter-wave resonant frequency to appear. The results of our work can benefit the implications of thermoacoustic instability in non-premixed flame.

IGV position optimization for centrifugal blower

There is a need for centrifugal blowers to adapt to different operating conditions in order to meet the user requirements, in a high efficiency manner. Variable Inlet Guided Vanes (known as IGVs) are a simple solution which can lead to important energy savings. The IGV consists of wedge-shaped steel blades mounted around the inside circumference of a short length inlet pipe, with the purpose to restrict, or increase the inlet flow area, thus controlling the mass flow. The aim of this research is to determine the optimal distance between the IGV and the rotor in order to achieve maximum efficiency. The study will focus on the pressure losses and the separation of the boundary layer at the different lengths, for a fixed angle of the IGV of 45 degrees. For this study, the commercial CFD software Ansys CFX will be used to estimate the efficiency of the rotor for different set-ups, via a 3D steady-state numerical flow analysis. The end results of this study will help correlate the position of the IGV to the efficiency of the blower and to determine the optimal distance between the rotor and the IGV for an increased performance.

The influence of impeller eccentricity on centrifugal pump

In order to study the influence of the impeller eccentricity on the performance of centrifugal pump, the k–ε turbulence model was selected, and ANSYS CFX was provided for numerical simulation calculation of the centrifugal pump with impeller offsets of 0, 1, 3, and 5 mm. The results show that with the impeller eccentricity increasing, the head and efficiency become lower. Under the condition of rated flow, with the impeller eccentricity increasing, the area of low pressure at the suction surface of the short blade inlet become smaller gradually; however, the area of low pressure at the suction surface of the long blade inlet become larger, and the pressure at the impeller inlet and tongue become larger too. The corresponding critical net positive suction head increases in turn, as means that the cavitation performance of the pump becomes worse gradually. The bubble volume fraction in the impeller increases with the decrease of the static pressure at the inlet. The bubble first occurs at the inlet of the blade suction surface, and then extends gradually to the channel and even the outlet. Near the rated flow, radial force on the impeller and volute decreases with the increasing of flow, and the radial force characteristic becomes worse gradually with the increasing of the eccentricity.

Jahani Salt Diapir, Iran: hydrogeology, karst features and effect on surroundings environment

The Jahani Salt Diapir (JSD), with an area of 54 km2, is an active diapir in the Simply Folded Belt of the Zagros Orogeny, in the south of Iran. Most of the available studies on this diapir are focused on tectonics. The hydrogeology, schematic model of flow direction and hydrochemical effects of the JSD on the adjacent water resources are lacking, and thus, are the focus of this study. The morphology of the JSD was reevaluated by fieldwork and using available maps. The physicochemical characteristics of the springs and hydrometric stations were also measured. The vent of the diapir is located 250 m higher than the surrounding glaciers, and covered by small polygonal sinkholes (dolines). The glacier is covered by cap soils, sparse trees and pastures, and contains large sinkholes, numerous shafts, several caves, and 30 brine springs. Two main groups of caves were distinguished. Sub-horizontal or inclined stream passages following the surface valleys and vertical shafts (with short inlet caves) at the bottoms of nearly circular blind valleys. Salt exposure is limited to steep slopes. The controlling variables of flow route within salt diapirs are the negligible porosity of the salt rocks at depth more than about ten meters below the ground surface and the rapid halite saturation along the flow route. These mechanisms prevent deep cave development and enforce the emergence points of brine springs with low flow rates and small catchment area throughout the JSD and above the local base of erosion. Tectonics do not affect karst development, because the distributions of sinkholes and brine springs show no preferential directions. The type of spring water is sodium chloride, with a TDS of 320 g/l, and saturated with halite, gypsum, calcite and dolomite. The water balance budget of the JSD indicates that the total recharge water is 1.46 MCM (million cubic meter)/a, emerges from 30 brine springs, two springs from the adjacent karstic limestone, and flows into the Firoozabad River (FR) and the adjacent alluvium aquifer. The FR cuts through the northern margin of the salt diapir, dissolving the glacier salts at the contact with JSD, increasing the halite concentration of the 17.7 MCM/a of the FR from 100 mg/l to 12,000 mg/l. This is a permanent process because the active glacier flows rapidly down the steep slopes into the river gorge from the nearby vent. The possible relocation of the FR channel would enhance the FR water quality, but disrupt the natural beauty of the diapir.