Axial Slot Research Articles

Radiations from an Eccentric Coated Cylinder with N Slots

The transverse magnetic (TM) radiation characteristics are investigated for a cylinder with N infinite axial slots of arbitrary opening size and location. The cylinder is a thin circular conductor and coated by an eccentric material. Fields are found by applying the boundary conditions to the cylindrical wave functions. The addition theorem of Bessel functions is used to obtain an infinite series solution in Fourier–Bessel series form. Results are computed by shrinking the generated infinite series to a finite number of terms and compared to other available data. Numerical results in graphical forms for different values are also developed and discussed for small eccentricities.

Failure analysis of P110 tubing string in the ultra-deep oil well

A number of P110 carbon steel tubing, one of the very important parts of an oil well pipe system, suffered corrosion and scaling after being used for a relatively short times, which would result in the leakage of tubing string and the decrease of productivity. Optical metallographic microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (XRD), combined with the weight loss method and electrochemical characteristic technology were used to determine the most probable causes of the failure. The results showed that the composition and structure of tubing and coupling were in accordance with the related parameter requirements of API Spec 5CT standards, and the circumferential annular corrosion groove at the roots of male buckle side resulted from the crevice corrosion, while the axial corrosion wide slot at the outer surface of coupling and corrosion perforation of tubing were due to the reasons that the corresponding parts were mechanical damaged firstly and then suffered the severe local corrosion, in addition, the composition of corrosion products were mainly FeCO 3 and Fe 3O 4, and scaling layer were composed of the heavy components of the crude oil, CaCO 3 and a little of corrosion products. Finally, the proper annulus protection fluid, inhibitors and paraffin removers were advised to be used for preventing this type of failure from happening again in the further.

Investigation of Blade Tip Interaction With Casing Treatment in a Transonic Compressor—Part II: Numerical Results

A single stage transonic axial compressor was equipped with a casing treatment consisting of 3.5 axial slots per rotor pitch in order to investigate its influence on stall margin characteristics, as well as on the rotor near tip flow field, both numerically and experimentally. Contrary to most other studies, a generic casing treatment (CT) was designed to provide optimal optical access in the immediate vicinity of the CT, rather than for maximum benefit in terms of stall margin extension. The second part of this two-part paper deals with the numerical developments and their validation, carried out in order to efficiently perform time-accurate casing treatment simulations. The numerical developments focus on the extension of an existing coupling algorithm in order to carry out unsteady calculations with any exterior geometry coupled to the main flow passage (in this case a single slot), having an arbitrary pitch. This extension is done by incorporating frequency domain, phase-lagged boundary conditions into this coupling procedure. Whereas the phase lag approach itself is well established and validated for standard rotor-stator calculations, its application to casing treatment simulations is new. Its capabilities and validation will be demonstrated on the given compressor configuration, making extensive use of the detailed particle image velocimetry flow field measurements near the rotor tip. Instantaneous data at all measurement planes will be compared for different rotor positions with respect to the stationary slots in order to evaluate the time-dependent interaction between the rotor and the casing treatment.

Investigation of Blade Tip Interaction With Casing Treatment in a Transonic Compressor—Part I: Particle Image Velocimetry

A single-stage transonic axial compressor was equipped with a casing treatment (CT), consisting of 3.5 axial slots per rotor pitch in order to investigate the predicted extension of the stall margin characteristics both numerically and experimentally. Contrary to most other studies, the CT was designed especially accounting for an optimized optical access in the immediate vicinity of the CT, rather than giving maximum benefit in terms of stall margin extension. Part I of this two-part contribution describes the experimental investigation of the blade tip interaction with casing treatment using particle image velocimetry (PIV). The nearly rectangular geometry of the CT cavities allowed a portion of it to be made of quartz glass with curvatures matching the casing. Thus, the flow phenomena could be observed with essentially no disturbance caused by the optical access. Two periscope light sheet probes were specifically designed for this application to allow for precise alignment of the laser light sheet at three different radial positions in the rotor passage (87.5%, 95%, and 99%). For the outermost radial position, the light sheet probe was placed behind the rotor and aligned to pass the light sheet through the blade tip clearance. It was demonstrated that the PIV technique is capable of providing velocity information of high quality even in the tip clearance region of the rotor blades. The chosen type of smoke-based seeding with very small particles (about 0.5 μm in diameter) supported data evaluation with high spatial resolution, resulting in a final grid size of 0.5×0.5 mm2. The PIV database established in this project forms the basis for further detailed evaluations of the flow phenomena present in the transonic compressor stage with CT and allows validation of accompanying computational fluid dynamics (CFD) calculations using the TRACE code. Based on the combined results of PIV measurements and CFD calculations of the same compressor and CT geometry, a better understanding of the complex flow characteristics can be achieved, as detailed in Part II of this paper.

Longitudinally driven slotted cylinder transducer

A longitudinally driven slotted transducer has a tubular member with an axial slot extending from one end to the other end. A drive assembly is disposed across the inner wall of the tubular member and supported by journal bearing surfaces extending from opposing sides of the inner wall to locate the drive assembly in a position offset from the longitudinal central axis of the tubular member. The interface between the drive assembly and tubular member comprises a layer of solid lubricant material mounted on the journal bearing type surfaces.

EM-Wave Scattering by an Axial Slot on a Circular PEC Cylinder With an Eccentrically Layered Inner Coating: A Dual-Series Solution for TE Polarization

A dual-series approach is used to formulate scattering of a TE-polarized plane wave by a circular, PEC cylinder, having a longitudinal slot and enclosing two, eccentric, cylindrical dielectric layers. The dual-series equations are analytically regularized to a matrix Fredholm equation of the second kind by use of the Abel integral-transform method. The resulting infinite set of linear algebraic equations (i.s.l.a.e.) is truncated and solved numerically. The aforementioned analytical-numerical solution intrinsically takes into consideration the correct edge behavior of the field. Furthermore, the addition theorem of cylindrical wave functions is used to match the field components on any cylindrical interface. The numerical application manifests how the structure of the inner loading of this cylindrical cavity is imprinted on backscattering. Moreover, it is shown how the location of the innermost dielectric cylinder may contribute to the suppression or enhancement of resonances.

Tool Wear Mechanism in Interrupted Cutting Conditions

In this study the machinability of ductile iron having ferritic structure was examined in interrupted cutting conditions. For this purpose, cylindrical samples with 1, 2, and 4 axial slots were prepared. Uncoated cemented carbide cutting tool was used in this work. Two different cutting speeds, feed rate and depth of cut were chosen as cutting parameters. According to results, the number of slots seriously affects the tool wear. Increasing the number of slots results in a decrease in the dimension of chip. Another result observed during the tool wear experiments was that increasing the number of slots results in increase of flank wear. However, the cutting tool wears out rapidly at higher feed rate or depth of cut when one or two slotted workpiece are used. Scanning Electron Microscope (SEM) and Energy Dispersive X-ray microanalysis (EDX) of the worn tools showed that abrasive, adhesion and oxidation wear mechanisms are predominant in the machining of continuous and interrupted cutting of ductile iron.

Radiation of Hertzian Dipole in Cylindrical Cavity with Narrow Slots

Radiation of a Hertzian dipole placed within a cylindrical cavity with narrow slots is investigated. Narrow axial and transverse slots are considered. Scattered fields are expanded in terms of eigenfunctions and boundary conditions are enforced to obtain a set of simultaneous equations. Computations are performed to check the validity of the formulation.

Time Resolved Experimental Investigations of an Axial Compressor With Casing Treatment

A casing treatment with axial and radial skewed slots ending in a plenum chamber has experimentally been investigated at a highly subsonic axial compressor stage. The aim was to investigate the physical phenomenon of this treatment family that is responsible for the stabilization of the blade passage flow and the drop in efficiency mostly observed. The experimentally gained performance results of this configuration showed an extension of the operating range by approximately 50%, while the efficiency for design conditions is reduced by 1.4%. Apart from this, operating points at part load conditions have been observed nearly without any loss in efficiency. The detailed flow analysis is performed by means of results from a 3D pneumatic probe with temperature sensor and a dynamic total pressure probe. The focus of the investigations is on the incidence flow to the compressor rotor, the tip clearance vortex flow in combination with the wall stall separation region and the blade stall due to suction side separation. The casing treatment configuration is investigated with a special interest in detecting those effects which have an impact on the stability and the compressor overall efficiency, including the interaction of the rotor and the stator flow fields.

Ultrabroadband Wireless–Optical Transmission Links Using Axial Slot Leaky Feeders and Optical Fiber for Underground Transport Topologies

This paper describes a hybrid leaky feeder/fiber-optic transmission system for use in underground transportation networks. The system has a 1.6-Gb/s throughput and features an ultrawideband axial slot leaky feeder, which is based on a standard semirigid coaxial cable as a fixed antenna. Patch antennas with a 4-GHz center frequency and a 1-GHz, -10-dB bandwidth are proposed for the rolling stock. This highest reported data rate was achieved by combining two 800-Mb/s in-phase and quadrature (I and Q) phase-shift keying (PSK) modulated data streams. A specially designed carrier and data synchronization system provided a convenient interface to a 1.3/1.5-mum diplex single-mode fiber-remoting network. The measured 2.4- to 6-GHz leaky feeder bandwidth allows multiradio multiband wireless mesh networking and, therefore, low-contention gigabit rolling stock data communications.

Numerical Investigations of the Coupled Flow Through a Subsonic Compressor Rotor and Axial Skewed Slot

In order to advance the understanding of the fundamental mechanisms of axial skewed slot casing treatment and their effects on the subsonic axial-flow compressor flow field, the coupled unsteady flow through a subsonic compressor rotor and the axial skewed slot was simulated with a state-of-the-art multiblock flow solver. The computational results were first compared with available measured data, that showed the numerical procedure calculates the overall effect of the axial skewed slot correctly. Then, the numerically obtained flow fields were interrogated to identify the physical mechanism responsible for improvement in stall margin of a modern subsonic axial-flow compressor rotor due to the discrete skewed slots. It was found that the axial skewed slot casing treatment can increase the stall margin of subsonic compressor by repositioning of the tip clearance flow trajectory further toward the trailing of the blade passage and retarding the movement of the incoming∕tip clearance flow interface toward the rotor leading edge plane.

Structural Integrity Assessment of Steam Generator Tube by the Use of Heterogeneous Finite Element Method

Aging steam generator tubes have been experiencing a variety of degradations such as pitting, fretting wear, erosion-corrosion, thinning, cracking, and denting. To assist with steam generator life cycle management, some defect-specific flaw models have been developed from burst pressure testing results. In this work, an alternative approach; heterogeneous finite element model (HFEM), is explored. The HFEM is first validated by comparing the predicted failure modes and failure pressure with experimental measurements of several tubes. Several issues related to the finite element analyses such as temporal convergence, mesh size effect, and the determination of critical failure parameters are detailed. The HFEM is then applied to predict the failure pressure for use in a fitness-for-service condition monitoring assessment of one removed steam generator tube. HFEM not only calculates the correct failure pressure for a variety of defects, but also predicts the correct change of failure mode. The Taguchi experimental design method is also applied to prioritize the flaw dimensions that affect the integrity of degraded steam generator tubes such as the defect length, depth, and width. It has been shown that the defect depth is the dominant parameter controlling the failure pressure. The failure pressure varies almost linearly with defect depth when the defect length is greater than two times the tube diameter. An axial slot specific flaw model is finally developed.

Simulation of Casing Treatments ofa Transonic Compressor Stage

This article presents the study of casing treatments on an axial compressor stage for improving stability and enhancing stall margin. So far, many simulations of casing treatments on single rotor or rotor‐stator configurations were performed. But as the application of casing treatments in engines will be in a multistage compressor, in this study, the axial slots are applied to a typical transonic first stage of a high‐pressure 4.5‐stage compressor including an upstream IGV, rotor, and stator. The unsteady simulations are performed with a three‐dimensional time accurate Favre‐averaged Navier‐stokes flow solver. In order to resolve all important flow mechanisms appearing through the use of casing treatments, a computational multiblock grid consisting of approximately 2.4 million nodes was used for the simulations. The configurations include axial slots in 4 different variations with an axial extension ranging into the blade passage of the IGV. Their shape is semicircular with no inclination in circumferential direction. The simulations proved the effectiveness of casing treatments with an upstream stator. However, the results also showed that the slots have to be carefully positioned relative to the stator location.

Flow Inside a Solid Rocket Motor with Relation to Nozzle Inlet Ablation

Three-dimensional, single-phase (equilibrium two-phase) flows inside a solid rocket motor at three burn-back grain configurations are studied by computational fluid dynamics analyses of the Reynolds-averaged Navier-Stokes equations. The major concern is the relationship between the flowfield and the circumferentially periodic erosion pattern arising in the inlet region of the nozzle, which will be of help for better understanding of the surface recession mechanism. Obtained results for the first two cases show that, because the mass flux of the slot phase is notably large compared with that of the fin phase, a remarkable interphase gap in the amount of convection heating appears either in the throat or the exit cone. The peak heating rate appears, commonly to all cases, azimuthally in the slot phase and axially at the expansion ratio of about 0.9 upstream of the throat. The flow which comes out of a slot into a fin base region spreads toward the fin central part under the influence of the pressure gradient in the circumferential direction and forms a vortical flow tube of opposite rotation mutually with the flow which swirls out of the next slot At the fin phase, because the proportionality relation is accepted between the total mass recession per unit area and the total convective heat mass transfer per unit area, there is little mechanical erosion, and corrosion is considered to be dominant On the other hand, in the slot phase, surface recession which cannot be explained only by corrosion in a nozzle inlet nose exists. This surface recession has a very high possibility of having occurred by abrasion by the aluminum/alumina particles contained in the flow which comes out of the axial slot of grain and collides with the thermal protection system surface. It is expected that the periodic erosion pattern which synchronized with axial slots observed after the static-firing test is the result of such a mechanism ruling. In both the throat and the exit cone, it is thought irrespective of a phase that the effect of mechanical erosion is very small and corrosion or a so-called chemical attack is the dominant mechanism of surface recession.

Internal Thoracic Vessels Used as Pedicle Graft for Anastomosis With Vascularized Bone Graft to Reconstruct C7–T3 Spinal Defects

A report of 4 cases of primary bone tumors (3 cases) or infection (1 case) at the cervicothoracic junction treated with resection-reconstruction. To document a new technique using the internal thoracic vessels as recipient vessels for reconstruction of the cervicothoracic spine with free vascularized fibula grafts. The cervicothoracic junction is a difficult region in reconstructive spinal surgery. Although nonvascularized fibula grafts can be used to reconstruct the osseous defect, compared with free vascularized fibula grafts they are biomechanical weaker, incorporate less well, are less resistant to infection, and remodel incomplete in time. However, when using free vascularized bone grafts, the selection of suitable recipient vessels remains one of the most critical decisions. Four patients who had a primary tumor (3 cases) or a severe progressive kyphotic deformity and progressive neurologic symptoms due to tuberculosis (1 case) were treated by resection and vascularized reconstruction. In 3 patients, a staged anteroposterior en bloc resection of T1-T3 (2 cases) or T1-T2 (1 case) was performed; the ventral reconstruction of the osseous defect consisted of a vascularized fibula graft interposition between C7-T4 (2 cases) or C7-T3 (1 case). In another case, an axial slot was milled through the T1-T2 vertebral bodies to accept an osteotomized vascularized fibular graft. In all cases, a free vascularized fibula graft was used: the vascular anastomosis was performed between the peroneal and the dissected and rerouted internal thoracic vessels. The anterior construction was strengthened by a ventral plate-screw system. The resection-reconstruction procedures, including the dissection, rerouting, and anastomosis between the internal thoracic vessels and the peroneal vessels, were successfully performed. At present, all patients are alive, and there is no evidence of recurrent disease, unchanged, or improved neurologic with a mean follow-up of 28 months. All grafts are well incorporated. CONCLUSIONS.: A combined low anterolateral cervical and midsternal approach or a midline sternotomy allows not only a safe and excellent exposure to the cervicothoracic junction but also to the internal thoracic vessels. The internal thoracic vessels are appropriate donor vessels: its longevity, diameter, length, and rerouting capacity allow vascularized graft reconstruction of vertebral column defects of the low cervical (C6-C7) and/or upper thoracic (T1-T3) region.

Experimental and numerical investigation of a subsonic compressor with bend-skewed slot-casing treatment

On the basis of the test results of discrete axial and blade angle slot casing treatment, a new type of casing treatment was designed for a subsonic axial flow compressor rotor by optimizing various geometry parameters. To obtain a wide operating range and to minimize penalties in terms of isentropic efficiency, seven compressor configurations incorporating casing treatments of 0, 16.6, 33.3, 50, 66.6, 83.3, and 100 per cent rotor exposures were experimentally investigated. The results showed that significant improvements in stall margin are possible in all exposures and insignificant isentropic efficiency sacrifices are recorded in some exposures. Nearly 21.43 per cent stall margin improvement in terms of the corrected mass flow-rate was achieved with 33.3 per cent rotor blade tip axial chord exposure. The compressor built with 16.6 per cent rotor exposure was the best configuration in terms of maximum isentropic efficiency gain. The second issue of the paper was to offer a contribution to the understanding of the physical mechanism by which bend-skewed slot-casing treatment improves stall margin under subsonic conditions. By applying a concept similar to ‘Domain scaling’ approach (as often used in multistage turbomachinery flow-fields) to the interface between the rotor blade passage and end-wall treatments, a time-dependent three-dimensional numerical simulation was performed for the subsonic axial-flow compressor rotor with bend-skewed slot-casing treatment. The numerical results agreed well with the available experimental results. Detailed analyses of the coupled flow through bend-skewed slot-casing treatment and rotor blade passage under subsonic conditions led to some preliminary conclusions as to the flow physics involved in the stall margin improvements afforded by the use of bend-skewed slot-casing treatment.

Radiation from narrow axial slots on a conducting circular cylinder

The problem of radiation from narrow axial slots on a conducting circular cylinder with transverse electric (TE11, where the first 1 refers to the number of circumferential variation ad the second 1 refers to the number of radial variation) mode excitation was solved. The Fourier transform and mode matching were used to obtain a set of simultaneous equations. Fast convergent series solutions for radiation, transmission, and reflection coefficients were presented in terms of discrete modal coefficients. A 20‐slot antenna was fabricated, and its radiation patterns were measured. Our numerical results agree favorably with measured data.

Machining with chamfered tools

The application of chamfered tools in metal cutting is yet very much limited. Despite their better edge strength, relatively little research have been done so far to understand the effect of tool geometry on cutting variables and the mechanics of chip formation. The present study focuses on the performance of chamfered tools during continuous and interrupted turning of medium carbon low alloy steel. Several cutting tests were conducted in turning on a conventional lathe machine with cemented carbide chamfered solid tools and its performance with respect to cutting force, tool life and chip formation have been investigated. The tools were ground to different chamfer widths varying from 0.10 to 0.40 mm at a constant chamfer angle of 45° and to a varying main cutting edge chamfer angles ranging from 15° to 35° at a constant chamfer width of 0.20 mm. For the purpose of interrupted turning, four axial slots were milled on the cylindrical work material. It has been observed that both in continuous and interrupted turning, with the increase chamfer width, both the main cutting force and feed forces increases and the effect on the feed force is more significant. With the increase of chamfer angle, cutting forces increased but at the maximum chamfer angle, both main cutting force and feed force were low. The chip thickness was observed to decrease with increasing chamfer width. However the effect of chamfer angle on the chip thickness was insignificant. Shear angle increased with the increase of both width and angle of the chamfer.

Numerical and experimental modelling of gas flow and heat transfer in the air gap of an electric machine. Part II: Grooved surfaces

The study deals with the cooling of a high-speed electric machine through an air gap with numerical and experimental methods. The rotation speed of the test machine is between 5000–40000 r/min and the machine is cooled by a forced gas flow through the air gap. In the previous part of the research the friction coefficient was measured for smooth and grooved stator cases with a smooth rotor. The heat transfer coefficient was recently calculated by a numerical method and measured for a smooth stator-rotor combination. In this report the cases with axial groove slots at the stator and/or rotor surfaces are studied. Numerical flow simulations and measurements have been done for the test machine dimensions at a large velocity range. At constant mass flow rate the heat transfer coefficients by the numerical method attain bigger values with groove slots on the stator or rotor surfaces. The results by the numerical method have been confirmed with measurements. The RdF-sensor was glued to the stator and rotor surfaces to measure the heat flux through the surface, as well as the temperature.

Field Characteristics from an Eccentric Dielectric Coated Circular Cylinder with Two Axial Slots

The far field characteristics are investigated for a circular cylinder with two infinite axial slots coated by an eccentric dielectric material. Radiations are determined by applying the boundary-value method to the cylindrical wave functions of the fields in the Fourier–Bessel series form. The addition theorem and the orthogonality of Bessel and trigonometric functions are employed to find an infinite series solution. Numerical and graphical results are obtained by shortening the infinite series produced in the solution to a finite number of terms and compared to other published data.