Effects of Four Types of Pre-swirls on the Leakage, Flow Field, and Fluid-Induced Force of the Rotary Straight-through Labyrinth Gas Seal

The labyrinth seal in turbomachinery is a key element that restricts leakage flow among rotor-stator clearances from high-pressure regions to low-pressure regions. The fluid-induced forces on the rotor from seals during machine operation must be accurately quantified to predict their dynamic behavior effectively. To understand the fluid-induced force characteristics of the labyrinth seal more fully, the effects of four types of pre-swirls on the leakage, flow field, and fluid-induced force of a rotary straight-through labyrinth gas seal (RSTLGS) were numerically investigated using the proposed steady computational fluid dynamics (CFD) method based on the three-dimensional models of the RSTLGS. The leakage, flow field, and fluid-induced force of the RSTLGS for six axial pre-swirl velocities, four radial preswirl angles, four circumferential positive pre-swirl angles, and four circumferential negative pre-swirl angles were computed under the same geometrical parameters and operational conditions. Mesh analysis ensures the accuracy of the present steady CFD method. The numerical results show that the four types of pre-swirls influence the leakage, flow field, and fluid-induced force of the RSTLGS. The axial pre-swirl velocity remarkably inhibits the fluid-induced force, and the circumferential positive pre-swirl angle and circumferential negative pre-swirl angle remarkably promote the fluid-induced force. The effects of the radial pre-swirl angle on the fluid-induced force are complicated, and the pressure forces and viscous forces show the maximum or minimum values at a specific radial pre-swirl angle. The pre-swirl has a negligible impact on the leakage. The four types of pre-swirls affect the leakage, flow field, and fluidinduced force of the RSTLGS to varying degrees. The pre-swirl is the influence factor affecting the leakage, flow field, and fluid-induced force of the RSTLGS. The conclusions will help to understand the fluid-induced force of labyrinth seals more fully, by providing helpful suggestions for engineering practices and a theoretical basis to analyze the fluid–structure interaction of the seal-rotor system in future research.

A Three-Terminal Quantum Well Heat Engine with Heat Leakage

We propose a model for a three-terminal quantum well heat engine with heat leakage. According to the Landauer formula, the expressions for the charge current, the heat current, the power output and the efficiency are derived in the linear-response regime. The curves of the power output and the efficiency versus the positions of energy levels and the bias voltage are plotted by numerical calculation. Moreover, we obtain the maximum power output and the corresponding efficiency, and analyze the influence of the heat leakage factor, the positions of energy levels and the bias voltage on these performance parameters.

Fluid filtration and dye leakage testing of Resilon/Epiphany and guttapercha/Pulp Canal Sealer root canal fillings

The aim of the present study was to compare sealing abilities of Resilon/Epiphany (R/E) with those of guttapercha and Kerr Pulp Canal Sealer EWT (GP/PCS). 50 single rooted teeth were randomly divided into 2 groups (n = 22) (R/E;GP/PCS), and 2 control groups (n = 3) (Positive, Negative). Fluid flow rate through the filled roots was measured using a fluid filtration device. The same specimens were immersed in a 2% Methylen Blue Solution. Roots were embedded in clear epoxy resin and cross sectionet at 1 mm intervals along the length of the root. Circumferential dye penetration was evaluated at 40× magnification. Fluid filtration of teeth obturated with the R/E system (0.085 [0.057, 0.113] μL·min-1), and dye penetration test showed no statistically significant difference compared to those obturated with GP/PCS (0.113 [0.057, 0.141] μL·min-1). Within the limits of the present study, there is no statistically significant difference between R/E and GP/PCS sealing abilities.

Influence of Internal Combustion Engine Parameters on Gas Leakage through the Piston Rings Area

In this work, the influence of internal combustion engine parameters (cylinder-piston clearance, piston head height, the first segment position, gap of the first piston ring and gap of the second piston ring, piston rings’ axial clearance, intake valve debit coefficient) gas leakage from the combustion chamber through the piston rings’ area was investigated. This influence was studied by making an initial forming operation over gas leakage in the analyzed area.

Fluid Leakage in Submerged Offshore Pipeline: An Analysis of Oil Dispersion in Seawater

Leakages in oil pipelines can cause financial losses and several environmental damages, where large-scale offshore oil and gas exploration results in large releases of oil and gas into ocean waters. In the event of oil leakage, an immediate and adequate response is required to reduce environmental damage, such as containment barriers, for example, which depends on the agglomeration of oil particles, velocity and tendency to propagation. Thus, the understanding of the fluid flow behavior around of subsea pipeline at different depths is crucial. On the other hand, the knowledge of interfacial phenomena of immiscible liquids allows the process of adjective migration in submarine pipelines. Consequently, this science enables the prediction of the behavior and the geometric shape of the water-oil interface and provides a phenomenological foundation concerning the theories of perturbation, the stability criteria and mathematical modeling, as well as the flow patterns in the neighborhoods and submerged pipelines. From this perspective, this work aims to study the oil dispersion in sea water caused by leakage in a submerged pipeline. Here, a two-dimensional mathematical model based on the mass and linear momentum conservation equations and the standard k-ε turbulence model, was developed. The dynamic behavior of the oil and water phases is evaluated by pressure fields, surface velocity, volumetric fraction and velocity vectors. Simulation results show the presence of oil flux from the pipe to the marine stream and vice-versa. Further, the increase in oil velocity at the pipe inlet leads to an increase in pressure drop.

Individualized Sellar Floor Reconstruction Method and Nursing Strategy for the Intraoperative Cerebrospinal Fluid Leakage Caused by Neuroendoscopic Transsphenoidal Pituitary Adenoma Resection

Objective: To explore the clinical effect of and the method and nursing strategy for sellar reconstruction for intraoperative cerebrospinal fluid (CSF) leakage in pituitary adenoma resection under neuroendoscopy. Methods: The data from 20 cases of intraoperative CSF leak caused by transsphenoidal pituitary adenoma resection were retrospectively analyzed. Six patients were treated with mucosal flap and artificial dural reconstruction of sellar (simple sellar floor reconstruction). In 45 patients, autologous fat, fascia lata, and artificial dura were used to repair and reconstruct the sellar floor (multilayer sellar floor reconstruction). After the operation, all patients underwent follow-up for 6 - 24 months. Results: Fifty patients were followed up without CSF leakage. One patient was cured after leakage of CSF through the lumbar cistern 1 month after discharge. Conclusion: For patients with CSF leakage during neuroendoscopic transsphenoidal pituitary adenoma resection, individualized sellar floor reconstruction should be adopted according to the degree of CSF leakage and the size of the sellar floor defect. Strict nursing measures can effectively prevent CSF leakage and reduce postoperative complications.

Erratum to:“An Approximate Method for Calculating the Fluid Force and Response of A Circular Cylinder at Lock-in” [China Ocean Engineering,22(3),2008,371-384]

Because of my carelessness,Eq.（1）in the paper "An approximate method for calculating the fluid force and response of a circular cylinder at lock-in"(China Ocean Engineering,22（3）,2008,pp.373)should be f’-1.0/U’-5.0=f’;-1.0/5.75f’;-5.0,not f’=U’/5.75. My apology is hereby given.

MANAGEMENT OF CEREBROSPINAL FLUID LEAKAGE FOLLOWING CERVICAL SPINE SURGERY

Objective To investigate the management and outcome of cerebrospinal fluid leakage(CSFL)after cervical surgery.Methods Medical records of 642 patients who underwent cervical surgery between December 1999 and December 2005 at our hospital were retrospectively reviewed.Five patients complicated by CSFL after surgery were enrolled,of which 4 cases were complicated after ossified posterior longitudinal ligament or posterior vertebral osteophyte resection directly injuring the dura,and 1 case after posterior cervical double-door laminoplasty without observed dural injury during surgery.Of the 5 CSFL cases,4 cases occurred at 1-3 days after operation and 1 case at 9 days after operation.All 5 postoperative CSFL cases were treated through wound drainage removal,wound sutures,prophylactic antibiotics,and continuous subarachnoid drainage in the elevated head position.Results All 5 CSFL cases experienced leakage cessation within 1-3 days and wound healing within 4-8 days,and subarachnoid drainage lasted 11-16 days with an average volume of 320 mL(range,150-410 mL).Four cases experienced headache,nausea and vomiting,1 case suffered from somnolence and hyponatremia,and symptoms subsided after symptomatic treatment and intravenous fluid administration.All patients were followed up for an average of 32 months(range,22-50 months).No occurrence of cerebrospinal fluid cyst or wound infection was observed.CSFL produced no significant negative effects upon neuromuscular function recovery.Conclusion Continuous subarachnoid cavity drainage in combination with elevated head position is a simple and safe non-surgical method in treatment of CSFL following cervical surgery.

Theoretical Investigation on Internal Leakage and Its Effect on the Efficiency of Fluid Switcher-Energy Recovery Device for Reverse Osmosis Desalting Plant

这个工作为反向的渗透(RO ) 集中于一台最新发达的飞行员规模液体开关精力恢复设备(FS-ERD ) 的内部漏的理论调查系统。为增加 FS-ERD 效率并且减少 RO 的操作费用的目的，在底层控制内部漏被要求。在这个工作，在不同的漏差距和 retentate 盐水压力的内部漏率被计算液体动力学(CFD ) 调查方法和验证实验。内部漏与有漏差距的规模的 retentate 盐水压力和一种多项式关系有一种线性关系，这被发现。现在的工作的结果暗示那低内部漏和高 retentate 盐水压力带好处完成高 FS-ERD 效率。

Mineralization of the Liwu large-scale stratiform copper deposits in Sichuan Province, China: Constraints from fluid inclusions

The Liwu stratiform copper deposit is located in the northwestern Jianglang dome,western China.Current studies mainly focus on the genetic type and mineralization of this deposit.Detailed fluid inclusion characteristics of metallogenic period quartz veins were studied to reveal the ore-forming fluid features.Laser Raman analysis indicates that the ore-forming fluids is a H_(2)O-NaCl-CH_(4)(-CO_(2))system.Fluid inclusions microthermometry shows a homogenization temperature of 181-375°C and a salinity of 5.26%-16.99%for the disseminated-banded Cu-Zn mineralization;but a homogenization temperature of 142-343°C and a salinity of 5.41%-21.19%for the massive-veined Cu-Zn mineralization.These features suggest a medium-high temperature and a medium salinity for the ore-forming fluids.H-O isotopic data indicates that the ore-forming fluids were mainly from the metamorphic and magmatic water,plus minor formation water.And sulfur isotopic data indicates that sulfur was mainly derived from the formation and magmatic rocks.Metallogenesis of the disseminated-banded mineralization was mainly correlated with fluid mixing and water-rock reaction;whereas that of the massive-veined mineralization was mainly correlated with fluid boiling.The genetic type of the deposit is a medium-high temperature hydrothermal deposit related to magmatism and controlled by shear zones.This study is beneficial to understand the stratiform copper deposit.

3D fluid model analysis on the generation of negative hydrogen ions for negative ion source of NBI

A radio-frequency(RF) inductively coupled negative hydrogen ion source(NHIS) has been adopted in the China Fusion Engineering Test Reactor(CFETR) to generate negative hydrogen ions.By incorporating the level-lumping method into a three-dimensional fluid model,the volume production and transportation of H^(-) in the NHIS,which consists of a cylindrical driver region and a rectangular expansion chamber,are investigated self-consistently at a large input power(40 k W) and different pressures(0.3–2.0 Pa).The results indicate that with the increase of pressure,the H^(-) density at the bottom of the expansion region first increases and then decreases.In addition,the effect of the magnetic filter is examined.It is noteworthy that a significant increase in the H^(-) density is observed when the magnetic filter is introduced.As the permanent magnets move towards the driver region,the H^(-) density decreases monotonically and the asymmetry is enhanced.This study contributes to the understanding of H-distribution under various conditions and facilitates the optimization of volume production of negative hydrogen ions in the NHIS.

Subdural fluid collection rather than meningitis contributes to hydrocephalus after cervical laminoplasty:A case report

BACKGROUND Hydrocephalus following dural tear after spinal surgery is rare.Although a few cases of obstructive hydrocephalus caused by subdural fluid collection and communicating hydrocephalus associated with meningitis have been reported,the mechanism remains uncertain.Herein we describe a patient complicated with hydrocephalus after cervical laminoplasty in whom subdural fluid collection in the cervical spine and posterior cranial fossa rather than chronic meningitis was the main mechanism.CASE SUMMARY A 45-year-old man underwent cervical laminoplasty for cervical spondylotic myelopathy at a local hospital.Ten days postoperatively,a high fever occurred and magnetic resonance imaging(MRI)showed cerebrospinal fluid(CSF)leakage.Pseudomeningocele liquid test showed high levels of protein and white blood cell(WBC)count with negative bacterial culture.The patient was treated with shortterm intravenous antibiotic and discharged with normal body temperature.The patient was uneventful during the first 8 mo follow-up although repeated MRI showed persistent pseudomeningocele.At the 9th mo postoperatively,the patient gradually presented with dizziness and headache accompanied by recurrent weakness of his left arm.Imaging examinations demonstrated hydrocephalus and a cystic lesion around the cervical spinal cord.CSF test from lumbar puncture indicated chronic meningitis.MRI on 1 d after pseudomeningocele drainage showed a significant decrease in the cystic volume,suggesting that the cystic lesion would be subdural fluid collection rather than adhesive arachnoiditis.After dural defect repair,the patient’s symptoms completely resolved and hydrocephalus gradually disappeared.CSF analysis at the 21-mo follow-up revealed significantly decreased protein level and WBC count.CONCLUSION Subdural fluid collection rather than meningitis contributes to the hydrocephalus formation after cervical laminoplasty.

Cerebrospinal Fluid Leakage after Thoracic Decompression

Objective： The objective of this study is regular and special features. to review cerebrospinal fluid leakage （CSFL） after thoracic decompression and describe its Data Sources： Literature cited in this review was retrieved from PubMed and Medline and was primarily published during the last 10 years. ＂Cerebrospinal fluid＂, ＂leakage＂, ＂dural tears＂, and ＂thoracic decompression＂ were the indexed terms. Relevant citations in the retrieved articles were also screened to include more data. Study Selection： All retrieved literature was scrutinized, and tbur categories were recorded： incidence and risk factors, complications, treatment modalities, and prognosis. Results： CSFL is much more frequent after thoracic decompression than after cervical and lumbar spinal surgeries. Its occurrence is related to many clinical factors, especially the presence of ossified ligaments and the adhesion of the dural sac. While its impact on the late neurological recovery is currently controversial, CSFL increases the risk of other perioperative complications, such as low intracranial pressure symptoms, infection, and vascular events. The combined use of primary repairs during the operation and conservative treatment postoperatively is generally effective for most CSFL cases, whereas lumbar drains and reoperations should be implemented as rescue options for refractory cases only. Conclusions： CSFL after thoracic decompression has not been specifically investigated, so the present study provides a systematic and comprehensive review of the issue. CSFL is a multi-factor-related complication, and pathological fators play a decisive role. The importance of CSFL is in its impact on the increased risk of other complications during the postoperative period. Methods to prevent these complications are in need. In addition, though the required treatment resources are not special for CSFL after thoracic decompression, most CSFL cases are conservatively curable, and surgeons should be aware of it.

Diagnostic value of drain amylase for detecting intrathoracic leakage after esophagectomy

AIM:To investigate the value of elevated drain amylase concentrations for detecting anastomotic leakage(AL) after minimally invasive Ivor-Lewis esophagectomy(MIILE).METHODS:This was a retrospective analysis of prospectively collected data in two hospitals in the Netherlands. Consecutive patients undergoing MI-ILE were included. A Jackson-Pratt drain next to the dorsal side of the anastomosis and bilateral chest drains were placed at the end of the thoracoscopic procedure. Amylase levels in drain fluid were determined in all patients during at least the first four postoperative days. Contrast computed tomography scans and/or endoscopic imaging were performed in cases of a clinically suspected AL. Anastomotic leakage was defined as any sign of leakage of the esophago-gastric anastomosis on endoscopy,re-operation,radiographic investigations,post mortal examination or when gastro-intestinal contents were found in drain fluid. Receiver operator characteristic curves were used to determine the cut-off values. Sensitivity,specificity,positive predictive value,negative predictive value,risk ratio and overall test accuracy were calculated for elevated drain amylase concentrations.RESULTS:A t o t a l o f 8 9 p a t ie n t s w e re in c lu d e d between March 2013 and August 2014. No differences in group characteristics were observed between patients with and without AL,except for age. Patients with AL were older than were patients without AL(P = 0.01). One patient(1.1%) without AL died within 30 d after surgery due to pneumonia and acute respiratory distress syndrome. Anastomotic leakage that required any intervention occurred in 15 patients(16.9%). Patients with proven anastomotic leakage had higher drain amylase levels than patients without anastomotic leakage [median 384 IU/L(IQR 34-6263) vs median 37 IU/L(IQR 26-66),P = 0.003]. Optimal cut-off values on postoperative days 1,2,and 3 were 350 IU/L,200 IU/L and 160 IU/L,respectively. An elevated amylase level was found in 9 of the 15 patients with AL. Five of these 9 patients had early elevations of their amylase levels,with a median of 2 d(IQR 2-5) before signs and symptoms occurred.CONCLUSION:Measurement of drain amylase levels is an inexpensive and easy tool that may be used to screen for anastomotic leakage soon after MI-ILE. However,clinical validation of this marker is necessary.

Research on cigarette during smoking based on reverse engineering and numerical simulation

The three-dimensional(3 D)model of cigarette was accurately constructed through reverse engineering as the research object of numerical simulation.The combustion process of cigarette was studied with computational fluid dynamics(CFD).Standard Laminar models with species transport approach were applied,and numerical simulation of the cigarette was analyzed with semi-implicit method for pressure–velocity coupling.The results showed that the model could predict velocity of cigarette smoke,the distributions of temperature and pressure at different times.In order to verify the correctness of model,it was found that the relationship between the velocity of smoke and pressure according to Darcy’s law on z position(x=4 mm,y=0,0 mm≤z≤50.61 mm).

Numerical analysis of reactive turbulent flow in the thrust chamber of RD-108 engine rocket

Combustion chamber modeling and simulation of the liquid propellant engine with kerosene as fuel and liquid oxygen as an oxidizer in the turbulent flow field are performed by CFD technique.The flow is modeled as Single-phase in steady state and using RNG k-ε turbulence model.Simulation results are validated by experimental data of thrust,special impulse and combustion chamber pressure.By comparing t.^wo reaction models of finite rate chemistry and frozen model with experimental data,it is concluded that finite rate chemistry has acceptable results.The optimum value of equivalence ratio(oxidizer to fuel ratio)per reaction and operational parameters of the engine which maximize thrust and special impulse are determined.

Numerical Analysis and Verification of the Gas Jet from Aircraft Engines Impacting a Jet Blast Deflector

The process of the gas jet from aircraft engines impacting a jet blast deflector is not only a complex fluid–solid coupling problem that is not easy to compute, but also a safety issue that seriously interferes with flight deck envi?ronment. The computational fluid dynamics(CFD) method is used to simulate numerically the impact e ect of gas jet from aircraft engines on a jet blast deflector by using the Reynolds?averaged Navier?Stokes(RANS) equations and turbulence models. First of all, during the pre?processing of numerical computation, a sub?domains hybrid meshing scheme is adopted to reduce mesh number and improve mesh quality. Then, four di erent turbulence models includ?ing shear?stress transport(SST) k-w, standard k-w, standard k-ε and Reynolds stress model(RSM) are used to compare and verify the correctness of numerical methods for gas jet from a single aircraft engine. The predicted values are in good agreement with the experimental data, and the distribution and regularity of shock wave, velocity, pressure and temperature of a single aircraft engine are got. The results show that SST k?w turbulence model is more suitable for the numerical simulation of compressible viscous gas jet with high prediction accuracy. Finally, the impact e ect of gas jet from two aircraft engines on a jet blast deflector is analyzed based on the above numerical method, not only the flow parameters of gas jet and the interaction regularity between gas jet and the jet blast deflector are got, but also the thermal shock properties and dynamic impact characteristics of gas jet impacting the jet blast deflector are got. So the dangerous activity area of crew and equipments on the flight deck can be predicted qualitatively and quantitatively. The proposed research explores out a correct numerical method for the fluid–solid interaction during the impact process of supersonic gas jet, which provides an e ective technical support for design, thermal ablation and structural damage analysis of a new jet blast deflector.

New high-resolution 2D seismic imaging of fluid escape structures in the Makran subduction zone,Arabian Sea

Seabed fluid escape is active in the Makran subduction zone,Arabian Sea.Based on the new highresolution 2D seismic data,acoustic blanking zones and seafloor mounds are identified.Acoustic blanking zones include three kinds of geometries:Bell-shaped,vertically columnar and tilted zones.The bellshaped blanking zone is characterized by weak and discontinuous reflections in the interior and upbending reflections on the top,interpreted as gas chimneys.Vertically columnar blanking zone is interpreted as side-imaged gas chimneys associated with focused fluid flow and topped by a seafloor anomaly expressed as a localized reflection discontinuity,which may together serve as a vent structure.Tilted acoustic blanking zone could be induced by accretionary thrust activity and rapid sedimentation surrounding slope.Seafloor mounds occur at the sites of bell-shaped acoustic blanking zone and may be associated with the material intrusion.Bottom simulating refectors(BSRs)are widely distributed and exhibit a series of characteristics including diminished amplitude,low continuity as well as local shoaling overlapping with these acoustic blanking zones.The large amount of gases dissociated from the gas hydrates migrated upwards and then arrived at the near-seafloor sediments,followed by the formation of the gas hydrates and hence the seafloor mound.

Experimental Investigation and Semi-Active Control Design of A Magnetorheological Engine Mount

In this paper;the dynamic characteristics of a semi-active magnetorheological fluid(MRF)engine mount are studied.To do so,the performance of the MRF engine mount is experimentally examined in higher frequencies(50~170 Hz)and the various amplitudes(0.01~0.2 mm).In such an examination,an MRF engine mount along with its magnetically biased is fabricated and successfully measured.In addition,the natural frequencies of the system are obtained by standard hammer modal test.For modelling the behavior of the system,a mass-spring-damper model with tuned PID coefficients based on Pessen integral of absolute error method is used.The parameters of such a model including mass,damping ratio,and stiffness are identified with the help of experimental modal tests and the recursive least square method(RLS).It is shown that using PID controller leads to reducing the vibration transmissibility in the resonance frequency(=93.45 Hz)with respect to the typical passive engine mount by a factor of 58%.The average of the vibration transmissibility decreasing is also 43%within frequency bandwidth(50~170 Hz).

Design of a Transverse-flux Permanent-magnet Linear Generator and Controller for Use with a Free-piston Stirling Engine

Transverse-flux with high efficiency has been applied in Stirling engine and permanent magnet synchronous linear generator system,however it is restricted for large application because of low and complex process.A novel type of cylindrical,non-overlapping,transverse-flux,and permanent-magnet linear motor（TFPLM） is investigated,furthermore,a high power factor and less process complexity structure research is developed.The impact of magnetic leakage factor on power factor is discussed,by using the Finite Element Analysis（FEA） model of stirling engine and TFPLM,an optimization method for electro-magnetic design of TFPLM is proposed based on magnetic leakage factor.The relation between power factor and structure parameter is investigated,and a structure parameter optimization method is proposed taking power factor maximum as a goal.At last,the test bench is founded,starting experimental and generating experimental are performed,and a good agreement of simulation and experimental is achieved.The power factor is improved and the process complexity is decreased.This research provides the instruction to design high-power factor permanent-magnet linear generator.