Expansion Chamber Research Articles

Acoustic attenuation analysis of oval expansion chambers with extended single inlet and double outlets

A numerical mode matching (NMM) approach is developed to predict the acoustic attenuation performance of expansion chambers with extended single inlet and double outlets, and validated by comparing the transmission loss predictions from the NMM, three-dimensional finite element method (FEM) and 1-D analytical method. Then theNMMmethod is used to investigate the effects of extended lengths of inlet and outlets as well as higher order modes on the acoustic attenuation performance. The results demonstrated that the side-branch resonance may be produced only when the two extensions of outlets are nearly equal. Choosing the extensions of inlet and outlets reasonably may eliminate the pass frequencies and yield a broad band acoustic attenuation. The expansion chamber with symmetric outlets about the minor axis exhibits better acoustic attenuation performance than that with nonsymmetric outlets since the effects of some higher order modes may be eliminated by the symmetric outlets. © 2017 Institute of Noise Control Engineering.

Birch Bark Dry Extract by Supercritical Fluid Technology: Extract Characterisation and Use for Stabilisation of Semisolid Systems

Triterpene compounds like betulin, betulinic acid, erythrodiol, oleanolic acid and lupeol are known for many pharmacological effects. All these substances are found in the outer bark of birch. Apart from its pharmacological effects, birch bark extract can be used to stabilise semisolid systems. Normally, birch bark extract is produced for this purpose by extraction with organic solvents. Employing supercritical fluid technology, our aim was to develop a birch bark dry extract suitable for stabilisation of lipophilic gels with improved properties while avoiding the use of toxic solvents. With supercritical carbon dioxide, three different particle formation methods from supercritical solutions have been tested. First, particle deposition was performed from a supercritical solution in an expansion chamber. Second, the Rapid Expansion of Supercritical Solutions (RESS) method was used for particle generation. Third, a modified RESS-procedure, forming the particles directly into the thereby gelated liquid, was developed. All three methods gave yields from 1% to 5.8%, depending on the techniques employed. The triterpene composition of the three extracts was comparable: all three gave more stable oleogels compared to the use of an extract obtained by organic solvent extraction. Characterizing the rheological behaviour of these gels, a faster gelling effect was seen together with a lower concentration of the extract required for the gel formation with the supercritical fluid (SCF)-extracts. This confirms the superiority of the supercritical fluid produced extracts with regard to the oleogel forming properties.

Design of a helicon plasma source for ion–ion plasma production

A helicon plasma system is being designed and developed at CPP-IPR. The design parameters of the system are deduced from the dispersion relation of bounded helicon waves and the required magnetic fields are simulated by using Poisson Superfish code. The Helic code is used to simulate the power deposition profile for various conditions and to investigate the optimum values of chamber parameters for effective coupling of radio frequency (RF) power to plasma. The helicon source system is aimed at carrying out ion–ion plasma studies in electronegative gases such as Hydrogen, Oxygen and Chlorine. The system mainly consists of a source chamber in which helicon plasma will be produced by injecting RF power at a frequency of 13.56MHz through a right helical antenna in presence of a DC magnetic field followed by an expansion chamber in which it is expected to produce negative ions along with the positive ions. Installation of the various parts of the system is in progress. The details of the design and development of the system is presented in this article.

Investigation of the pulsation-reduction characteristics of an expansion chamber attenuator in a hydraulic system

This paper investigates the expansion chamber attenuator utilized in marine hydraulic systems to determine the pulsation-reduction characteristics in hydraulic deck machinery applications. First, the background is briefly introduced. Next, the advantages and disadvantages of investigation methods borrowed from the aerodynamic field are discussed with regard to hydraulic use. Insertion loss is eventually selected to evaluate the performance of the attenuator. Finally, attenuator prototypes and a test rig that simulates an actual marine hydraulic system in a vessel are manufactured, and the experimental conditions are introduced in detail to calculate and measure the insertion loss. As indicated by the investigation conclusion, mathematic computation generally fits the test results. A better choice of length–diameter ratio ranges and other characteristics are discussed. This paper provides theoretical and experimental evidence regarding design expansion chamber attenuator use in hydraulic systems.

Hydrodynamically reconfigurable optofluidic microlens with continuous shape tuning from biconvex to biconcave.

This paper presents an in-plane hydrodynamically reconfigurable optofluidic microlens, which is formed by the laminar flow of two streams of a low-refractive-index fluid and two streams of a high-refractive-index fluid in the two microchannels connecting to an expansion chamber where the microlens finally forms. In the expansion chamber, the stream of high-refractive-index fluid, acting as core, is sandwiched by the two streams of low-refractive-index fluid, acting as cladding. The interfaces between the streams can be flexibly manipulated by controlling the flow rate ratio between the two fluids in real time. Thus, the biconvex and biconcave microlens with different curvatures can be formed. By adjusting the microlens, the light beam can be continuously manipulated from focusing to collimation and then to divergence. In the experiment, a wide focus tuning range from 2.75 (focusing) to -1.21 mm (diverging) via collimation is achieved.

Investigation of droplet nucleation in CCS relevant systems – Design and testing of a CO2 branch of the mixture preparation device

A unique in-house designed experimental apparatus for investigation of nucleation of droplets in CCS relevant systems is being developed by our team. The nucleation is measured with the help of a rapid pressure drop within an expansion chamber. In this study, a CO2 branch representing an important part of the mixture preparation device (MPD) was designed, assembled and tested. MPD is intended for preparation of CO2 -rich mixtures in a sense of accurate setting of flow rates of individual gaseous components through the experimental section with the expansion chamber. In the CO2 branch, the saturated liquid CO2 coming from a cylinder with a dip tube is pressurized by a supercritical pump with a constant flow rate to the pressures of up to 340 bar. The required mass flow of the supercritical CO2 of up to 180 g/h at pressures between 74 bar and 150 bar is accurately tuned with a help of a set of stainless steel capillary tubes with inner diameter of 0.1 mm. Some of the tubes are submerged in a thermostatic bath set to a constant temperature of 70 °C in order to assure the supercritical flow conditions of CO2 . Needed lengths of the capillary tubes were determined with a help of a one-dimensional numerical model allowing prediction of both isothermal and adiabatic flow conditions.

Broadband noise attenuation using a variable locally reacting impedance.

Passive control of low-frequency duct noise remains a technical challenge. Traditional noise control devices are either overly bulky or too narrowband. A broadband attenuation mechanism inspired by the mammalian cochlea is presented in this theoretical study. It consists of a parallel arrangement of an array of multiple beams or stretched strips backed by a cavity. The structure vibrates strongly in response to the broadband incident noise and hence creates substantial reflection. If both the media in the cavity and the duct are air, the mass-like load from the fluid in the cavity suppresses the response of the structure and thus lowers the transmission loss. If helium, or some other gas with lower density than air in the duct, fills the cavity, the mass-like reactance of the cavity is reduced and the silencing performance is improved. Then such a silencer can achieve a satisfactory attenuation performance at low frequency range. Multiple adjacent resonant peaks are found in the transmission loss curve and such a silencer has superiority in size and acoustic performance over expansion chamber and duct lining.

Topology optimization of internal partitions in a flow-reversing chamber muffler for noise reduction

A topology-optimization-based design method for a flow-reversing chamber muffler is suggested to maximize the transmission loss value at a target frequency considering flow power dissipation. Rigid partitions for high noise reduction should be carefully placed inside the muffler to avoid extreme flow power dissipation due to a 180° change in flow direction from an inlet to an outlet. The optimal flow path for minimum flow power dissipation is well known to change depending on the Reynolds number, which is a function of the inlet flow velocity. To optimize the partition layout with an optimal flow path in an expansion chamber at a given Reynolds number, a flow-reversing chamber muffler design problem is formulated by topology optimization. The formulated topology optimization problem is implemented using the finite element method with a gradient-based optimization algorithm and is solved for various design conditions such as the target frequencies, rigid partition volumes, Reynolds numbers, non-design domain settings, and allowed amounts of flow power dissipation. The effectiveness of our suggested approach is verified by comparing the optimized partition layouts obtained by the suggested method and previous methods.

Scattering matrices in non-uniformly lined ducts

Sudden area expansion and sudden area contraction in an infinitely long duct with discontinuous locally reacting lining are defined by respective mixed boundary value problems. In the absence of a sudden area change, a separate problem with an infinite duct having bifid lining on its wall is described. Introducing Fourier transform along the duct axis boundary value problems is solved by the well-known Wiener–Hopf technique, and then, corresponding scattering matrices are constructed. To show the proper use of scattering matrices in the case of several discontinuities and also validation and comparison purposes, transmitted field in a duct with an inserted expansion chamber whose walls are treated by acoustically absorbent material is derived by the help of the relevant scattering matrices. A perfect agreement is observed when the transmitted fields are compared numerically with a similar work exists in the literature.

Macroscopic characteristics and internal flow pattern of dimethyl ether flash-boiling spray discharged through a vertical twin-orifice injector

This work is to investigate the macroscopic spray characteristics and internal flow pattern of dimethyl ether (DME) discharged through twin-orifice injectors. Transparent injectors were manufactured to study the effects of different diameters of discharge nozzles on the internal flow and atomization. Injection pressures of 4.0 MPa and 2.0 MPa were implemented to produce “stable” flash-boiling sprays vertically, and the ambient condition was atmospheric. Internal flow in the expansion chamber (EC) and external liquid atomization were observed simultaneously during the actuation. The relationship between the internal boiling flow in the EC and external flash-boiling spray were analyzed. Lower gas/liquid mass ratio in the EC generated larger external spray angles and lead to a sudden drop of spray angles when the supply valve closed. However, higher gas/liquid mass ratio (homogeneous bubbly flow) in the EC prolonged the stability of sprays when the solenoid valve was shutting down, but with smaller spray angles. The effect of expansion chamber volume was obvious at lower injection pressure. It is suggested to reduce the EC volume when the injection pressure is relatively low. This work provides a guide and reference for the port-fuel injection of DME engines.

Fast, hot electron production and ion acceleration in a helicon inductive plasma

A large, time-averaged, double layer-like plasma potential drop of 80 V over several hundred Debye lengths has been observed in the magnetic expansion region on the Madison Helicon eXperiment. It is operated in an inductive mode at 900 W and low argon operating pressures (0.12–0.20 mTorr) in the collisionless regime. The plasma space potential drop is due to the formation of a double layer-like structure in the magnetic expansion region and is much higher than the potential drop caused by a Boltzmann expansion. With the plasma potential drop, a locally negative potential ion hole region at lower pressures with a higher electron density than ion density has been observed just the downstream of the potential drop region. Two-temperature Maxwellian electron distributions with a warm (Te≈15 eV) and bulk (Te≈5 eV) components are observed just upstream of the double layer validated through a RF compensated Langmuir probe and an optical emission spectroscopy (OES) diagnostics. In the expansion chamber downstream of the double layer-like potential drop, a single warm (Te≈15 eV) Maxwellian electron distribution is observed via both the Langmuir probe and OES diagnostics. Ion beam energies of 65 eV are also observed downstream of the potential drop.

Time-domain CFD computation and analysis of acoustic attenuation performance of water-filled silencers

The multi-dimensional time-domain computational fluid dynamics (CFD) approach is extended to calculate the acoustic attenuation performance of water-filled piping silencers. Transmission loss predictions from the time-domain CFD approach and the frequency-domain finite element method (FEM) agree well with each other for the dual expansion chamber silencer, straight-through and cross-flow perforated tube silencers without flow. Then, the time-domain CFD approach is used to investigate the effect of flow on the acoustic attenuation characteristics of perforated tube silencers. The numerical predictions demonstrate that the mean flow increases the transmission loss, especially at higher frequencies, and shifts the transmission loss curve to lower frequencies.

A closer scientific look at foam bitumen

In the asphalt industry, a substantial interest is observed to find possibilities to reduce the production temperature of asphalt mixtures. In the context of this research, new methods for the visualisation of unstable bitumen foam, such as dynamic X-ray radiography, computed tomography (CT) and high-speed camera investigations, have been developed. Moreover, characterisation with empirical methods such as expansion ratio and half-life was determined accurately using ultrasonic measurements. This opens new possibilities to characterise bitumen foam (foaming process) for practical applications. Examination of the foam bitumen stream using a high-speed camera revealed that the foam bitumen contains fragmented pieces of bitumen, which resemble more a liquid than foam. This indicates that the foam is formed afterwards and not, as assumed, within the expansion chamber of the foam generator. In situ thermal imagery of the surface, during the hot foaming process, showed that the temperature distribution depends on the foaming water content (W.C.) and bubble size distribution. Higher W.C. results in more inhomogeneous temperature distribution as compared to lower W.C. (<2 wt%). The dynamic X-radiography results indicated that as the foam decays, the bubble size distribution becomes progressively larger with time for 160°C bitumen temperature. Furthermore, at the beginning of the foam formation, majority of the bubbles is small in cross-section size (0.2–10 mm2). At a later stage, the bubbles become polydisperse. Moreover, theoretical investigations based on the 3D X-ray CT scan data set of bubble merging show that the disjoining pressure increases as the foam film gets thinner with time and finally undergoes rupture. The speed of the bubbles also increases with time when the bubbles are getting closer to each other.

Application of RPMI 2650 nasal cell model to a 3D printed apparatus for the testing of drug deposition and permeation of nasal products

The aim of this study was to incorporate an optimized RPMI2650 nasal cell model into a 3D printed model of the nose to test deposition and permeation of drugs intended for use in the nose. The nasal cell model was optimized for barrier properties in terms of permeation marker and mucus production. RT-qPCR was used to determine the xenobiotic transporter gene expression of RPMI 2650 cells in comparison with primary nasal cells. After 14days in culture, the cells were shown to produce mucus, and to express TEER (define) values and sodium fluorescein permeability consistent with values reported for excised human nasal mucosa. In addition, good correlation was found between RPMI 2650 and primary nasal cell transporter expression values.The purpose-built 3D printed model of the nose takes the form of an expansion chamber with inserts for cells and an orifice for insertion of a spray drug delivery device. This model was validated against the FDA glass chamber with cascade impactors that is currently approved for studies of nasal products. No differences were found between the two apparatus.The apparatus including the nasal cell model was used to test a commercial nasal product containing budesonide (Rhinocort, AstraZeneca, Australia). Drug deposition and transport studies on RPMI 2650 were successfully performed.The new 3D printed apparatus that incorporates cells can be used as valid in vitro model to test nasal products in conditions that mimic the delivery from nasal devices in real life conditions.

The versatile size analyzing nuclei counter (vSANC)

ABSTRACTWe present a new field-deployable expansion chamber condensation particle counter—the versatile size analyzing nuclei counter (vSANC). The measuring principle, which was adopted from the classical SANC, was optimized regarding ranges of operating temperatures (−20°C to +40°C), inlet gas pressures (0.2–1.2 bar), inlet flow rates (1.6–9 l/min) and condensing liquids (alcohols, alcanes, water, etc.), all of which make vSANC applicable to a wide variety of environments. Precision determination of vapor supersaturation ratios allows estimating neutral cluster sizes without prior electrical-mobility based classification of the sample. Additionally, absolute number concentrations ranging from can be measured without referring to external calibration standards. This enables size-resolved number concentration measurements of nanoparticles. Laboratory studies using n-propanol as condensing liquid demonstrated that charged (NH4)2SO4 and WOx particles as small as 1.5 nm can be counted with an efficiency of 10...

덕트 밖에서 계산된 삽입 손실을 고려한 머플러 최적 설계

Abstract : In this study, we formulate an acoustical topology optimization problem to optimally design a partition layout inside the expansion chamber of a muffler. The lower-limit insertion loss value at a target frequency is constrained, and the partition volume is selected as an object function. In this study, we calculate the insertion loss outside the duct, while to determine the noise-attenuation performance, we use the insertion loss value calculated inside the duct or transmission loss value obtained in a previous study. We employ the finite-element model for acoustical analysis, and we determine the transmission of an incident acoustic wave through each finite element using the functions of design variables that change continuously between “0” and “1.” The rigid body elements, which totally reflect incident waves, build up partitions. Finally, we compare optimal topologies that depend on the target frequency and the allowed lower-limit value of insertion loss. § 이 논문은 대한기계학회 창립 70주년 기념 학술대회(2015. 11. 10-14., ICC제주) 발표논문임. † Corresponding Author, jinwoolee@ajou.ac.kr Ⓒ 2016 The Korean Society of Mechanical Engineers

Study on Analysis of Interrupting Characteristics for O-CO Operation of Self-blast Type Circuit Breakers

The function of high voltage circuit breaker is to clear the fault current and protect the equipment in a power network when the overload or short circuit is generated in the network. High voltage circuit breaker should interrupt short circuit currents not only under Open operation for minimum arcing time but also under Open-CloseOpen operation for maximum arcing time. Self-blast type high voltage circuit breaker often fails to interrupt the short circuit current under the Open-CloseOpen operation condition. In this study, analysis of arc extinction characteristics under the Open-CloseOpen operation for maximum arcing time has been conducted for the self-blast type high voltage circuit breaker. Arc extinction phenomena were analyzed by simulation that was developed based on computational fluid dynamics. Arc simulations for high voltage circuit breaker use compressible gas dynamic equations(e.g. Navier-Stokes equations) including Ohmic input, Lorentz force and radiation transport. Relevant Maxwell’s equations are included for the calculation of electromagnetic fields. The simulation results show that the arc extinction performance of the Open-CloseOpen operation is severely affected by the conditions of remaining thermal gas in the thermal expansion chamber after the first Open operation.

TRANSMISSION LOSS OF CYLINDRICAL MUFFLER WITH DIFFERENT LENGTH TO DIAMETER RATIO BY USING TWO LOAD METHOD AND SIMULATION TOOL

This paper shows the details of measurement of the acoustical transmission loss of single expansion chamber muffler with various lengths to diameter ratios of cylindrical chamber muffler. A muffler is an important noise control element for reduction of machinery exhaust noise, fan noise, and other noise sources involving the flow of gases. Mufflers are typically arranged along the exhaust pipe as the part of the exhaust system of an internal combustion engine to reduce its noise. Firstly simulation tool results (Comsol) are compared with experimentally then results are observed with various expansion ratio.

Dry powder nasal drug delivery: challenges, opportunities and a study of the commercial Teijin Puvlizer Rhinocort device and formulation

Purpose: To discuss the challenges and opportunities for dry powder nasal medications and to put this in to perspective by evaluating and characterizing the performance of the Teijin beclomethasone dipropionate (BDP) dry powder nasal inhaler; providing a baseline for future nasal products development.Methods: The aerosol properties of the formulation and product performance of Teijin powder intranasal spray were assessed, with a particular focus on particle size distribution (laser diffraction), powder formulation composition (confocal Raman microscope) and aerosol performance data (British Pharmacopeia Apparatus E cascade impactor, aerosol laser diffraction).Results: Teijin Rhinocort® (BDP) dry powder spray formulation is a simple blend of one active ingredient, BDP with hydroxypropylcellulose (HPC) carrier particles and a smaller quantity of lubricants (stearic acid and magnesium stearate). The properties of the blend are mainly those of the carrier (Dv50 = 98 ± 1.3 µm). Almost the totality of the capsule fill weight (96.5%) was emitted with eight actuations of the device. Using the pharmacopeia suggested nasal chamber deposition apparatus attached to an Apparatus E impactor. The BDP main site of deposition was found to be in the nasal expansion chamber (90.2 ± 4.78%), while 4.64 ± 1.38% of the BDP emitted dose was deposited on Stage 1 of the Apparatus E.Conclusions: The Teijin powder nasal device is a simple and robust device to deliver pharmaceutical powder to the nasal cavity, thus highlighting the robustness of intranasal powder delivery systems. The large number of actuations needed to deliver the total dose (eight) should be taken in consideration when compared to aqueous sprays (usually two actuations), since this will impact on patient compliance and consequently therapeutic efficacy of the formulation.

Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments

Abstract. Cloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather, and general circulation models. The detection of aerosol particles, liquid droplets, and ice crystals, especially in the small cloud particle-size range below 50 μm, remains challenging in mixed phase, often unstable environments. The Cloud Aerosol Spectrometer with Polarization (CASPOL) is an airborne instrument that has the ability to detect such small cloud particles and measure the variability in polarization state of their backscattered light. Here we operate the versatile Cosmics Leaving OUtdoor Droplets (CLOUD) chamber facility at the European Organization for Nuclear Research (CERN) to produce controlled mixed phase and other clouds by adiabatic expansions in an ultraclean environment, and use the CASPOL to discriminate between different aerosols, water, and ice particles. In this paper, optical property measurements of mixed-phase clouds and viscous secondary organic aerosol (SOA) are presented. We report observations of significant liquid–viscous SOA particle polarization transitions under dry conditions using CASPOL. Cluster analysis techniques were subsequently used to classify different types of particles according to their polarization ratios during phase transition. A classification map is presented for water droplets, organic aerosol (e.g., SOA and oxalic acid), crystalline substances such as ammonium sulfate, and volcanic ash. Finally, we discuss the benefits and limitations of this classification approach for atmospherically relevant concentrations and mixtures with respect to the CLOUD 8–9 campaigns and its potential contribution to tropical troposphere layer analysis.