Primary Chamber Research Articles

Cavitation erosion of the damping piston in double damping system of hydraulic rock drill and its influencing factors

The fast response property of double damping system is beneficial to improve damping characteristics. However, the intense pressure fluctuation in damping chambers often leads to the cavitation erosion of damping piston and seriously affects the normal use of seal and rock drill. The coupling model including the damping piston, damping valve, damping accumulator and connecting pipelines was established considering the structural feature and dynamic characteristics of damping system. The cavitation erosion mechanism was revealed by the simulation results. Analysis suggested that the pipeline damping and oil flow velocity between the primary and secondary damping chamber were the critical influencing factors for the cavitation erosion. The influence on system cavitation of damping valve structure and connecting pipeline types was discussed, and the reasonable range of matching parameters was given. Pressure curves in the primary, secondary damping chamber and noise spectra of cavitation were obtained by the field rock drilling test. The simulation and experimental results had consistency. The system cavitation was detected by the high-frequency pulsating pressure signal and its power spectral density analysis. This detection method provides a new approach for studying the cavitation behavior of hydraulic rock drills.

Ultra-high heat flux dissipation with Piranha Pin Fins

The Microfluidic, Extreme heat flux, CMOS compatible, Heat-eXchanger (MECH-X) is an embeddable silicon-based reactor-style heat sink which has been experimentally studied by the authors. The 800 µm thick MEMS heat sink discretizes the working fluid into stacked primary and secondary chambers to enhance phase change heat transfer. Piranha Pin-Fin (PPF) microstructures—reported previously by the authors—have been employed in the primary reaction chamber. The PPF structures vent higher-enthalpy fluid into a secondary, or booster, chamber for additional heat transfer. The MECH-X system has been shown to dissipate heat loads exceeding 10,000,000 W/m2 with dielectric fluid HFE7000 while maintaining surface temperatures below 95 °C.The present work reports on flow boiling experiments performed to characterize system-level performance of the MECH-X heat sink at mass fluxes of 680, 1440, and 3350 kg/s/m2. HFE7000 was used as a coolant at ambient lab temperature (∼23 °C) and a system pressure of 377 kPa. A 3.95 mm2 heating element, which simulated a heat generating component, was maintained below 95 °C with heats loads exceeding 1 kW/cm2. Experiments were terminated at this heat flux due to saturating a 50 VDC laboratory power supply. Results are also presented at a system pressure of 239 kPa, and results are compared to first generation PPF heat sinks.

Numerical study on the operating characteristics of cryogenic loop heat pipes based on a one-dimensional heat leak model

The cryogenic loop heat pipe is an effective and reliable heat transfer system in the space technology. A global model of cryogenic loop heat pipe is developed by full consideration of the subcooled effect and the mass flow rate variation of the working fluid along the evaporator core. The heat leak is calculated on the basis of one-dimensional temperature distributions in the evaporator core. The calculation of the proposed model improves the prediction accuracy relative to traditional zero-dimensional models. The effects of filling pressure, parasitic heat load, auxiliary heat load, and use of bayonet on the CLHP performance are investigated. A normal “U-shape” of the evaporating temperature curve appears at a low filling pressure (1.45 MPa). At moderate and high filling pressures (1.465 MPa and 1.5 MPa, respectively), two new evaporating temperature curves with “flat bottom U-shape” and “L-shape”, which shows the unique operating characteristics of cryogenic loop heat pipes, are found. The two new profiles are attributed to the coupling of mass and energy between gas reservoir and primary compensation chamber. The determinant factor for the minimum working heat load is the void fraction of the primary compensation chamber. By contrast, the maximum working heat load is determined by the void fraction at a low filling pressure (below 1.4 MPa) and the maximum capillary pressure at a high filling pressure (above 1.4 MPa). The use of a bayonet can decrease the maximum vapor quality in the evaporator core and effectively avoid burnout.

Numerical study for the influences of primary steam nozzle distance and mixing chamber throat diameter on steam ejector performance

The geometry and operation parameters have important influences on the performance of steam ejectors. An axisymmetric two-dimensional mathematical model for transonic compressible flow inside a steam ejector has been established in this paper to investigate the flow characteristics inside steam ejectors aiming at optimizing primary steam nozzle exit section distance and mixing chamber throat diameter simultaneously. The results show that there are an optimum value for the primary steam nozzle distance ratio and an optimum diameter ratio of mixing chamber throat to primary nozzle throat at which the steam ejector acquires its best entrainment performance under the given design conditions. With the optimized primary steam nozzle distance, the optimization of the diameter ratio of the mixing chamber throat to primary nozzle throat is significant. In our case, the improvement of the entrainment ratio is as large as 25%. Deviation from its optimized value may result in a serious degeneration in the ejector performance. Therefore, to ensure the steam ejector performance, the primary steam nozzle distance should be designed at its optimum value and the diameter ratio of the mixing chamber throat to primary nozzle throat be within a narrow vicinity of its optimum value.

Fabrication of Magnetically Actuated Fluidic Drug Delivery Device Using Polyvinyl Chloride Adhesive Stencils.

In this paper, a polydimethylsiloxane (PDMS) fabrication method is introduced. It eliminates the need for conventional fabrication methods, such as photolithography and etching. Only a series of oxygen plasma treatments, silanization, and polyvinyl chloride (PVC) adhesive stencils were used to develop multi-layer designs. The fabrication method was applied to fabricate a PDMS-based drug delivery device with an actively controllable, magnetically actuated valve. Above all, this fabrication method eliminated the use of a power-consuming pump. Fluidic substances were injected into the circular shaped primary chamber through a syringe. A secondary chamber, similar to the primary chamber’s structure but with a smaller radius and thinner membrane, was connected via a microchannel to regulate the amount released. When actuated with a permanent magnet for one second, the volume in the secondary chamber first depletes. As the magnet is removed, the valve closes. Subsequently, the primary chamber replenishes the secondary chamber. This process can be repeated until the primary chamber reaches a saturation state that can no longer inflate the secondary chamber. The device could release a few microliters per actuation. Various combinations of size and thickness of primary, and secondary chambers can realize release rate of desired amount.

Development of secondary chamber for tar cracking–improvement of wood pyrolysis performance in pre-vacuum chamber

Energy crisis and global warming, in other words, climate change are critical topics discussed in various parts of the world. Global warming primarily result from too much emission of carbon dioxide (CO2) in the atmosphere. To mitigate global warming, or climate change and improve electrification in rural areas, wood pyrolysis technology is developed in a laboratory scale, of which gases are directly applicable to the gas engine generator. Our laboratory has developed a prototype of wood pyrolysis plant with a pre-vacuum chamber. However, tar yield was around 40 wt% of feedstock. This research aims to reduce tar yield by secondary tar cracking. For the secondary tar cracking, a secondary pre-vacuum chamber is installed after primary pre-vacuum chamber. Gases generated in the primary pre-vacuum chamber are lead into the secondary chamber that is heated up to 1000 K. This paper reports performance of the secondary chamber for secondary tar cracking in homogeneous mode and heterogeneous mode with char.

Enhancement of the air ejector performance: primary nozzle and mixing chamber investigation

Air ejectors are, practically, applicable devices used to remove air following a membrane integrity test (MIT). In the present work, investigations of the influence of geometrical parameters on the air ejector performance are performed numerically. Simulations have been performed by solving the steady compressible two-dimensional Reynolds-averaged Navier–Stokes together with realizable k-e turbulence model equations. A comparison of the computed results with the published experimental data exhibits agreement in terms of entrainment ratio. Increasing amount of the air that should be removed (secondary flow) and reducing energy consumption (primary flow) are considered in this work. To achieve these issues, the effects of geometrical parameters include mixing tube diameter, length of mixing tube, and primary nozzle diameter as well as operation condition which consists of primary flow pressure on the air ejector performance which are all studied. The results show that these changes could improve the entrainment ratio; it means that the secondary flow is increased or the primary flow is decreased. The optimal range of entrainment ratio for specific values of the primary nozzle diameter declares that the air ejector operates at its highest performance.

Influence of grid distribution on CFD model of compressible flow inside the primary nozzle and mixing chamber used in refrigeration application

In this study, the influence of grid distribution on CFD model of the primary nozzle and mixing chamber used in refrigeration application was primarily investigated. The only one geometry of primary nozzle and mixing chamber was modeled. The two different grid distributions, fine near-wall grid and regular grid with the identical total grid number, were simulated to investigate the flow phenomena inside the considered system. The appropriate boundary conditions and numerical methods were carefully employed. The simulated entrainment ratios obtained by two different grid arrangements were validated by comparing with the reliable experimental data. The results revealed that the Mach number distributions of these models were different. Further, the outlet total pressure predicted by fine near-wall grid was about 1.3% higher than that obtained by regular grid.

Bulk-Fill Restorative Materials in Primary Tooth: An Intrapulpal Temperature Changes Study.

Objectives:It was aimed to investigate the temperature changes in primary teeth pulp chamber during the curing/setting of bulk-fill restorative materials with different nanoparticle contents.Methods:Twenty-five extracted, primary mandibular second molars were prepared as a Class II cavity. Five bulk-fill restorative materials consisting of Equia Fil (HVGIC), glass carbomer (GC) cement, Sonic Fill (SF), X-tra Fil (XF), and Quix Fil (QF) were tested. The measurement of the pulp chamber temperature changes (starting temperature 37°C) during setting/curing was performed with a J type thermocouple. The data, differences between highest and initial temperature values, were recorded and analyzed by one-way ANOVA.Results:The temperature changes in the pulp chamber were in EF (2.81°C), GC (7.92°C), SF (3.33°C), XF (3.43°C), and QF (3.02°C). There were statistically significant differences between temperature changes in groups (P < 0.05).Conclusion:The tested bulk-fill resin composites and high-viscosity glass ionomer cement do not increase the intrapulpal temperature in primary teeth during the curing/setting.

Establishing IAEA TRS-457 diagnostic X-ray beam qualities at the Australian primary standard dosimetry laboratory.

This paper reports the process and findings in establishing the diagnostic beam qualities for the calibration of diagnostic dose meters in the Australian primary standard dosimetry laboratory at the Australian Radiation Protection and Nuclear Safety Agency, ARPANSA. A novel iterative method to achieve the RQR beam quality requirements described by IEC 61267 is presented. The correction factors for the primary standard free-air chamber and their uncertainties are reported. The calibration procedure with detailed uncertainty budget of a typical diagnostic ionisation chamber (model PTW 34060) is reported. Beam profile measurements and details of the use of an external monitor chamber (model PTW 34014) are also reported. The uncertainty in the ARPANSA calibration coefficients is estimated to be 1.2% at k = 2 for both RQR and RQA beam qualities. The laboratory is now able to provide calibration services for radiation detectors used in general X-ray radiography.

Vacuum System and Modeling for the Materials Plasma Exposure Experiment

Understanding the science of plasma-material interactions (PMI) is essential for the future development of fusion facilities. The design of divertors and first walls for the next generation of long-pulse fusion facilities, such as a Fusion Nuclear Science Facility (FNSF) or a DEMO, requires significant PMI research and development. In order to meet this need, a new linear plasma facility, the Materials Plasma Exposure Experiment (MPEX) is proposed, which will produce divertor relevant plasma conditions for these next generation facilities. The device will be capable of handling low activation irradiated samples and be able to remove and replace samples without breaking vacuum. A Target Exchange Chamber (TEC) which can be disconnected from the high field environment in order to perform in-situ diagnostics is planned for the facility as well. The vacuum system for MPEX must be carefully designed in order to meet the requirements of the different heating systems, and to provide conditions at the target similar to those expected in a divertor. An automated coupling-decoupling (“autocoupler”) system is designed to create a high vacuum seal, and will allow the TEC to be disconnected without breaking vacuum in either the TEC or the primary plasma materials interaction chamber. This autocoupler, which can be actuated remotely in the presence of the high magnetic fields, has been designed and prototyped, and shows robustness in a variety of conditions. The vacuum system has been modeled using a simplified finite element analysis, and indicates that the design goals for the pressures in key regions of the facility are achievable.

Control of the solids retention time by multi-staging a fluidized bed reactor

Fluidized bed reactors are often operated with particles of different size and density present simultaneously (e.g. inert bed material and fuel particles in fluidized bed combustion, or catalyst particles and polymer particles in fluidized bed polymerization). This paper presents a general concept to separate a single fluidized bed reactor into two reaction zones by introducing a primary chamber in the bed where flotsam particles are fed and spend a certain initial residence time. The feasibility of the concept is experimentally proven in a fluid-dynamically down-scaled unit, both in terms of functionality (ability to maintain two separate reaction regions and to avoid backflow from the secondary to the primary region of the solids fed) and of operability (ability to control the residence time distribution of the solids fed in the primary chamber through operational parameters such as pressure and bed height). Numerical simulations show that the residence time distribution is sensitive to the degree of segregation in the primary chamber, and that the heat transfer between the two reaction regions by means of bulk solids mixing is still sufficient to sustain an endothermic process in one zone by an exothermic process in the other.

Effect of Primary Rocket Jet on Thermodynamic Cycle of RBCC in Ejector Mode

AbstractThrust augmentation in ejector mode is important to improve engine performance so as to enable more propulsion applications of RBCC. Usually, the internal flow-path is configured mainly for combustion organization in ramjet and scramjet modes, thus the RBCC performance in ejector mode will mainly depend on the primary rocket operating parameters and jet expansion state. Considering such restrictions and requirements on the primary rocket, this paper studies the effects of the primary rocket jet on the thermodynamic cycle performance of ejector mode, in which incoming air is dominated by ejector-suction by the primary rocket jet at low flight Mach numbers. It is found that the engine performance in ejector mode will be improved by increasing the primary rocket chamber pressure and nozzle expansion ratio. Furthermore, for better design of primary rocket, primary rocket chamber pressure should be maximized on the basis of ensuring a complete expansion of primary rocket to the ambient pressure at the design point of flight conditions after 3-D CFD simulations for a full flow-path of RBCC including fore-airframe and aft-airframe of a flight vehicle. The results of 3-D numerical simulations show that the bypass ratio and specific impulse increase by 35.5 % and 12.5 % respectively at sea-level static condition.

CFD Modelling of the Condensation Inside a Supersonic Ejector Working with R134a

Abstract The present work is about CFD modelling of condensing flow inside a supersonic ejector. The geometry used for the simulations reproduces a small-scale prototype ejector chiller built at Georgia Institute of Technology (Atlanta). The working fluid is R134a, whose expansion inside the primary nozzle and mixing chamber can lead to non-equilibrium condensation phenomena. These alter the pressure and Mach profiles along the ejector, thus generating severe thermodynamic losses. The numerical analysis of non-equilibrium condensation requires modelling of the microscopic behaviour of the fluid with a high level of fidelity. In this study, the condensation of R134a is simulated by means of two in-house developed numerical models. The first considers equilibrium conditions between the phases whereas the latter reproduces the non-equilibrium behaviour of the phase transition. Comparisons are made to understand the limitations and advantages of both approaches.

Primary and Secondary Intraocular Lens Implantations in Children With Pediatric Cataract: Visual Acuity and Strabismus at the Age of 2 Years and Older.

To compare the visual outcomes of primary and secondary intraocular lens (IOL) implantations and to identify the risk factors for the development of strabismus in patients with pediatric cataract. The records of the pediatric patients who had undergone cataract surgery between January 1999 and November 2014 were reviewed retrospectively. The results of the cases with cataract extraction with primary IOL implantation (primary group) and cases with secondary IOL implantation (secondary group) were compared and the risk factors for the development of strabismus were investigated. This study included 220 eyes of 148 patients who had surgery for pediatric cataract. The mean age of the patients was 6.84 ± 3.45 years (range: 2 to 17 years) for the primary group at the time of cataract extraction and primary posterior chamber IOL implantation and 8.92 ± 5.12 years (range: 2 to 18 years) for the secondary group at the time of secondary IOL implantation (P = .118). Strabismus developed in 28 patients (23.73%) in the primary group and 9 patients (30%) in the secondary group (P = .702). At the last postoperative examination, Snellen visual acuity was 0.44 and 0.28 for the primary and secondary groups, respectively (P = .013). There was a negative relationship between visual acuity and the development of strabismus (P = .048), whereas there was a positive relationship between the follow-up period and the development of strabismus (P = .008). Optic rehabilitation of the pediatric cataract is an important factor in the development of strabismus. These cases should be monitored closely. [J Pediatr Ophthalmol Strabismus. 2017;54(2):97-102.].

Cataract Surgery with Primary Lens Implantation in Children with Chronic Uveitis

ABSTRACTPurpose: To evaluate the evolution of chronic uveitis in children undergoing cataract surgery with primary intraocular lens (IOL) implantation.Methods: Twelve children with chronic uveitis underwent cataract surgery with primary posterior chamber intraocular lens (IOL) implantation.Results: Fourteen eyes were implanted with a foldable hydrophobic acrylic IOL. The mean follow-up was 35.39 months (8.72–69.57). The mean BCDVA before surgery and at the end of follow-up was 1.11 (0.40–2.30; SD: 0.57) and 0.48 (0–3; SD: 0.77; p=0.007) respectively. The mean oral corticosteroids dosage after surgery and at the end of follow-up was 0.80 mg/kg/day (SD: 0.37) and 0.17 mg/kg/day (SD: 0.24; p=0.001) respectively. All patients except one were treated with methotrexate. Four patients (5 eyes) were additionally treated with anti-tumor necrosis factor agent.Conclusions: Cataract surgery with primary posterior chamber hydrophobic IOL implantation is possible and leads to a good visual recovery in cases of pediatric chronic uveitis. This surgery requires aggressive anti-inflammatory management with immunosuppressive drugs to control inflammation and reduce the corticosteroids dosage.

Phacoemulsification with Intraocular Lens Implantation in Pediatric Uveitis: A Retrospective Study

ABSTRACTPurpose: To analyze the outcome of phacoemulsification with primary posterior chamber intraocular lens (IOL) implantation without primary posterior capsulorhexis in older children with uveitis.Methods: Retrospective study of children with uveitis who underwent phacoemulsification with IOL implantation between January 2006 and May 2014.Results: Twenty-one eyes of 16 children were included. Mean age at cataract surgery was 10.9 years. Juvenile idiopathic arthritis was associated in 37.5%, tuberculosis in 18.7%, Vogt Koyanagi Harada disease in 6.2%, and idiopathic uveitis in 37.5%. Anterior uveitis occurred in 8/21 eyes, intermediate uveitis in 9/21 eyes, and panuveitis in 4/21 eyes. Mean follow-up was 29.9 months. Posterior capsule opacification occurred in 15 eyes, glaucoma in two eyes, choroidal neovascular membrane in one eye, and cystoid macular edema in five eyes. At the last follow up, 19/21 eyes had improved vision and 14 had 20/40 or better vision.Conclusion: Tight perioperative inflammatory control with immunosuppression may result in good vision after phacoemulsification and IOL implantation without posterior capsulorrhexis in older children with uveitic cataract.

The uropygial gland of the Southern Caracara (Caracara plancus; Falconidae: Falconinae): histological and histochemical aspects

AbstractThe uropygial gland of Southern Caracara is composed of two lobes with a conical papilla and 21 tuft feathers. The RGM recorded for this species was 0.057%. The capsule surrounding the gland and the medial septum is composed of dense connective tissue and has elastic and reticular fibres. The epithelium of the adenomers can be divided into different strata: germinative, intermediate, secretory and degenerative stratum. The adenomers can be divided into three zones; from zone III, adenomers lead to secondary chambers that converge into a primary storage chamber. Histochemical techniques showed that the uropygial gland synthesizes different types of mucins and it was also positive to some lectins demonstrating the presence of a variety of glycoconjugates. The RGM in this species is smaller than that found for other Falconidae. These differences may be attributed to a negative allometric relationship. The general histological description is similar to other birds. The histochemistry and lectin histochemistry analysis showed a variety of glycoconjugates as part of the uropygial gland. Uropygial secretions have been proposed to have protective functions against bacteria and fungi. The presence of carbohydrate residues is linked to glycoconjugates with antimicrobial functions in many vertebrates associating our results with this species′ habits.

Effect of endodontic sealers on bond strength of restorative systems to primary tooth pulp chamber

Background/purposeAlthough current literature suggests that root canal sealers affect the bonding ability of restorative systems to pulp chamber dentin of permanent teeth, primary teeth have not been investigated. This study intended to evaluate the microtensile bond strength (μTBS) of three restorative systems to pulp chamber dentin in primary teeth and to determine the effect of two different root canal sealers on the μTBS. Materials and methodsNinety primary molars were used in this study. The teeth were randomly divided into three main groups according to canal sealers: (1) control (without sealer); (2) Metapex; and (3) zinc-oxide eugenol. The main groups were further divided into three subgroups depending on the coronal restorative system: (1) compomer (Prime Bond NT + Dyract EXTRA); (2) composite (Clearfil Tri-S Bond + Clearfil Photo Posterior); and (3) resin-modified glass ionomer (Fuji II LC). After restoration, the buccal wall of the pulp chamber was sectioned to obtain sticks (1 mm × 1 mm). The μTBS was then measured. Data were analyzed with two-way analysis of variance, followed by a posthoc test. The interfacial morphology of the bonded space was evaluated using scanning electron microscopy. ResultsIn the control group, a significant difference was observed only for the μTBS of the composite (P < 0.05). Compared with the control groups, Metapex and zinc-oxide eugenol significantly reduced the μTBS of restorative systems (P < 0.05). ConclusionComposite materials seemed to bond to pulp chamber dentin in primary teeth with a higher strength than compomer and resin-modified glass ionomer. Metapex and zinc-oxide eugenol canal filling materials reduced the bond strength of all three restorative systems.

Second intraocular surgery after primary pediatric cataract surgery: indications and outcomes during long-term follow-up at a tertiary eye care center.

PurposeAlthough pediatric cataract surgery has become standardized and safe, further surgical interventions are not uncommon. The purpose of this study was to analyze the incidence of complications in children who required an intraocular intervention.MethodsA retrospective review of medical records of children (<7 years) with cataract who underwent cataract surgery with or without primary posterior chamber intraocular lens (IOL) placement between January 2006 and December 2014 was carried out. Data were collected regarding visual axis opacification (VAO), glaucoma, IOL decentration, intraocular infections, and other indications that required a second intraocular surgery.ResultsOut of 814 (570 pseudophakic and 244 aphakic) eyes of 620 operated children, 45 eyes of 40 children (5.5%, 45/814) needed a second surgery. The most common indication being VAO (2.9%, 24/814), followed by glaucoma (0.73%, 6/814). Incidence of complications was higher in children <1 year (VAO 6.1%, 19/308 and glaucoma 6%, 6/308). Among all children, repeat interventions and VAO were slightly less frequent in pseudophakics (4.91%, 28/570) vs aphakics (6.91%, 17/244) (P=0.31). As VAO was more common in pseudophakic eyes in infants, glaucoma was equally common in both groups. Best-corrected visual acuity improved from 1.6±0.56 LogMAR preoperatively to 0.80±0.50 LogMAR postoperatively.ConclusionsOur study suggests that overall incidence of second intraocular surgery is low after primary pediatric cataract surgery. VAO remains the most common indication followed by secondary glaucoma. Incidence of complications is higher in children <1 year of age at initial surgery.