Axial Hole Research Articles

Hydraulic Fracturing Effect on Filtration Resistance in Gas Drainage Hole Area in Coal

Features of stress state and jointing as well as their effect on hydraulic fracture propagation direction in coal seams are considered. The flow resistance in drainage areas is analyzed depending on hydrofracture orientation, thickness of seams and spacing of holes. The comparison of one-stage and multi-stage hydrofractures created in-plane and orthogonally to hole axes is given. In simulated reservoir conditions, permeability of dense coal is studied without a fracture and with a through propped fracture subjected to confining pressure. The recommendations are developed for improving efficiency of gas drainage in coal seams based on in-mine hydraulic fracturing.

Influences of effusion hole diameter on impingement/effusion cooling performance at turbine blade leading edge

This paper numerically investigates the effects of the film cooling hole diameter and the film cooling hole location on the impingement/effusion cooling performance inside a concave target channel. Three film cooling hole rows are established on the target surface under two arrangements. In the first arrangement, the inclined angle between the film cooling hole axis and jet hole axis is 0°, −60°, 60° respectively. In the second arrangement, the inclined angle is 0°, −30°, 30° respectively. In the first effusion hole arrangement, numerical simulations are conducted under three Reynolds numbers. In the second effusion hole arrangement, numerical simulations are only conducted under the middle Reynolds number. Four film cooling hole diameters of 0.4D, 0.6D, 0.8D, 1.0D are studied based on a fixed jet hole diameter of D = 10 mm. The heat transfer performance, pumping power and overall performance are evaluated and compared. Effusion air distribution and static pressure distribution are analysed. Flow development inside the target channel is compared and discussed. Nusselt number distribution is evaluated and compared. Results show that the effusion air mass flow rate and the flow development inside the target channel are obviously affected by the film cooling hole diameter and film cooling hole location. The heat transfer performance is also significantly affected by the film cooling hole diameter and film cooling hole location.

Design and optimization of dual-cycled cooling structure for fully-enclosed permanent magnet motor

For fully-enclosed permanent magnet motor (FEPM), the heat generated inside the rotor is difficult to dissipate, which can deteriorate the function of the permanent magnet and cause the motor performance degradation, especially during the field-weakening operation. A dual-cycled cooling structure is proposed for improving the inner heat transfer condition of the FEPM, which uses outer water and inner air as coolants. The 3D model of the FEPM equipped with water jacket is built and the temperature distribution is analyzed by thermal-fluid numerical analysis and its accuracy is verified by experiments. Based on the results, the rotor axial vent hole (RAVH), stator axial vent hole (SAVH) and air gap are chosen as internal cycled paths. The position of the internal cycled path is set according to the electromagnetic analysis. And the dimension of the internal cycled path is optimized by Taguchi method for better cooling effects which are evaluated through fluid-thermal coupled numerical analysis. The final optimization results indicate that the optimal dual-cycled cooling structure can reduce the maximum temperature inside the motor by 13.5 °C, which will suppress the internal temperature and improve the reliability of the FEPM in full operating range.

Combined processing of channels in ceramic parts

Abstract The paper examines the technology of manufacturing through and blind channels of various sections and axis profiles in ceramic filters and nozzles, applied in heat engines and current generator drives for supplying and purifying liquid fuel. The article presents the data on the manufacture of ceramic nozzles and filters, designed for preliminary and fine purification of liquid fuels, having increased thermal and chemical resistance when operating in the hot zone of aircraft and rocket engines. We show the possibility of their use in power machines and installations, operating at high pressure drops during the purification of corrosive media and in conditions of product vibration. New technological methods have been developed and implemented for combined manufacture of long channels with small sections, having various configuration and position of hole axes, which improve the performance parameters of parts. At the level of invention, new methods and devices have been created for combined processing of through and blind channels with anodic dissolution of metal inserts under the impact of an ultrasonic beam, locally amplifying the mass transfer from the zone of channel formation. The article shows the advantages of combined processing, using ultrasonic vibrations to intensify the process of manufacturing through and blind holes in ceramics, which successfully substitutes the previously applicable technological methods and means of technical equipment, and broadens the opportunities of technologists for manufacturing nozzles and filters, complying with the operational requirements for products of new-generation equipment, created and mastered by domestic industry. We disclose the ways of improving the structure and technology of combined processing of perspective types of ceramic products, with account of their use in mechanical engineering.

Experimental Investigation on the Tilt Helical Milling of Carbon Fiber Reinforced Plastics (CFRP)

Carbon fiber reinforced plastics (CFRP) has been widely used in various aircraft structural components. However, it is difficult for conventional methods such as drilling and helical milling to meet the requirements on high quality and efficient holes creation. Hence a so-called tilt helical milling (THM) method has been proposed. This new method is performed by replacing the revolving motion of the tool in conventional helical milling (CHM) with a conical pendulum motion, in which the tool axis is tilted towards the hole axis at a certain angle. As a step toward the establishment of the new method, in this work, the fundamental drilling characteristics of CFRP by the THM is elucidated by experimentally investigating the effects of tilt angle on thrust force and delamination factor. The obtained experimental results demonstrated that thrust force and delamination factor can be reduced with THM technique. In addition, THM can achieve better hole surface finish than CHM.

Proposal of a tilted helical milling technique for high-quality hole drilling of CFRP: analysis of hole surface finish

An innovative machining process, i.e., tilted helical milling (THM), was proposed previously by the authors for high-quality hole drilling of CFRP as an alternative technique to conventional helical milling (CHM). To further develop the THM technique, hole surface finish with THM is analyzed and compared to that finished with CHM in this article. Theoretical analysis results show that a large amount of fiber bending and fiber-matrix debinding in CHM will occur in the hole surface when instantaneous fiber cutting angle α lies in the range of 90° to 180° due to the tool pushing. This phenomenon can be mitigated in THM owing to a downward cutting force component along the hole axis, which makes fibers fracture easily. The theoretical analysis results are confirmed by CT scans and SEM results of surface morphology of holes, indicating THM is useful for obtaining high-quality hole surface finish. In addition, compared with CHM, damage generation, such as entrance split and exit delamination of the hole, can be restrained with THM technique.

Analysis of the stability bearing capacity of biaxial bending cellular steel column with circular hole

In order to promote the application and promotion of the cellular steel columns in practical engineering. Considering the geometric initial defect, geometric nonlinearity, material nonlinearity and residual stress. Using ABAQUS to analyze the effect of parameters of axial pressure, hole spacing, member length, hole size and flange width-thickness ratio on the stability bearing capacity of the cellular steel column, and get the influence of various parameters. The results show that with the increase of the axial pressure, member length and hole size, the stability bearing capacity of the cellular steel column decreases. With the increase of the hole spacing and flange width-thickness ratio, the stability bearing capacity of the cellular steel column increases. It is found that axial pressure, member length and flange width-thickness ratio have a great influence on the stability bearing capacity of cellular steel columns.

Evaluation of Rock Quality of Tunnel Wall Rock Based on Rough Set Theory and Unascertained Measurement Theory

A method for classification of the tunnel wall rock is established based on the rough set theory and unascertained measurement theory. The saturated uniaxial compressive strength, rock mass integrity index, structural surface condition, seepage measurement of groundwater, and the angle between the hole axis and main structural surface are selected as the evaluation indexes. The problem of weight coefficients for these evaluation indexes is converted into that of significance estimating on the attributes in the rough set theory. The proposed method is verified by the wall rock data of Yuanyanghui tunnel. The results show that the proposed method has an excellent performance in good agreement with the practical situation of wall rock and is feasible to classify the wall rock. Finally, the proposed method is applied to Xihualing tunnel of Zhu-Yong Expressway. The results are basically the same as those from Delphi-ideal point method, set pair analysis method, and the actual situation, which proves that the rough set theory and unascertained measurement theory are effective for classification of the wall rock.

Effects of film cooling hole locations on flow and heat transfer characteristics of impingement/effusion cooling at turbine blade leading edge

In order to investigate the effects of the film cooling hole locations on the flow and heat transfer characteristics of the impingment/effusion cooling, the film cooling holes are established on a concave target channel with three inclined angle (0°, 30°, 60° between film cooling hole axis and jet hole axis). The film cooling holes are both in-line and staggered arranged with jet holes when the inclined angle is 30° and 60° and only staggered arranged when the inclined angle is 0°. The film extraction flow distributions, static pressure development, total pressure drop, overall averaged Nusselt number and combined thermal performance are compared among different cases. The development of vortex and cross flow inside the target channel in different cases are studied and compared. The span averaged Nusselt number, Nusselt number contour on the target surface and Nusselt number distribution at several cross sections are studied and compared. Results show that the location of the film cooling holes affects the flow distributions of the film extraction air and the flow development inside the target channel. The heat transfer performance inside the target channel is affected by the impinging effect and the development of the cross flow and vortices.

COMPUTER MODELING AND ANALYSIS OF VIBRATIONS IN ANNULAR CONCENTRATOR OF ULTRASONIC SYSTEM

The paper provides substantiation on application of elastic annular concentrators of ultrasonic systems which allows to increase an intensity of tool vibrations. It has been shown that elastic elements are used as resonators and tools in a number of ultrasonic technological systems. However an application of the elastic elements as concentrators of ultrasonic vibrations has been insufficiently studied and requires research and development of recommendations for usage. For this purpose theoretical studies have been carried out and they have helped to perform modal and harmonic analysis of several variants for a computer model of a ring with outer diameter D = 50 mm. Models of rings with various hole sizes from 20 to 40 mm have been analyzed while changing hole axis position relative to ring axis. The paper shows modes of ring flexural vibrations which can be either flat or three-dimensional depending on frequency of forced oscillations. It has been pointed out that an increase in a ring internal diameter is accompanied by higher amplitude of bending oscillations in the thinnest ring section. The same effect is achieved by increasing eccentricity of a hole axis. The paper contains recommendations for determination of rational geometric parameters which allows to increase an oscillation amplitude gain ratio and it is determined as ratio of ring section thickness. It has been established that decrease in section thickness is accompanied by higher number of frequencies for ring resonance oscillations. So, if a concentric ring and a ring with small hole diameter have only one resonance frequency, then thin-walled rings with a variable cross-section have not less than three natural resonance frequencies of oscillations that makes it possible to increase a range of vibration frequencies and technological capabilities of the ultrasonic system. It has been also found that an intensity in fluctuations of the ultrasonic system is increased even more if at the same time a cross-section of a ring with variable stiffness is decreased as along thickness so across the width.

Influence of hole shape on sound absorption of underwater anechoic layers

A theoretical model is established to evaluate the sound absorption performance of underwater anechoic layers containing periodically distributed axial holes. Based on the concept for homogenized equivalent layer and on the theory of wave propagation in viscoelastic cylindrical tubes, the transfer function method is used to obtain the absorption coefficient of the anechoic layer adhered on the rigid plate. Three different types of axial holes are considered, the cylindrical, the conical and the horn shaped one. Results obtained with full finite element simulations are used to validate the model predictions. For each hole type, the vibration characteristics of the anechoic layer as well as the propagation of longitudinal and transverse waves in the layer are analyzed in detail to explore the physical mechanisms underlying its absorption performance. Furthermore, a three-dimensional finite element model for oblique incidence is developed to study the effect of hole shape at different incidence angles. The results show that two new absorption peaks appear since the oblique incidence excites two horizontal modes. Among the three hole types, the horn one achieves the best absorption performance at relatively low frequencies both in normal incidence and in oblique incidence.

The substantiation of parameters of sowing machine with adaptive dosing elements for seeding of corn

For sowing of corn precision seeders are used, one of the most complex and responsible details of which is a sowing machine. The purpose of this study is to substantiate the rational design and parameters of the dosing elements and the «superfluous» seeds seeder of the vacuum sowing device, which ensure an even increase in the supply of corn seeds to the furrow. A vacuum sowing machine is proposed for use in production, in which elongated suction holes are made on the sowing disk in such a way that their long axes are oriented to a radial direction at α angle. In addition, in the design of the sowing apparatus, the thickness of the first three projections of seeder for «superfluous» seeds is proposed to be made stepwise. Experiments carried out on the matrix of the orthogonal plan of the second order showed that the following parameters and tuning regimes of such a machine are rational for sowing corn seeds: width of suction holes tдэ = 3 mm; the smallest slot width in the vacuum chamber liner t = 3,0...3,5 mm; exhaustion in the vacuum chamber H = 5 kPa; thickness of the input edge of the working part of the “superfluous” seeds seeder h = 1,5 mm; angle of deviation of the longitudinal axes of the suction holes of the sowing disc from the radial direction α = 12...15 deg. Under laboratory conditions the machine provided the frequency of single seed feeds p1 = 99,0...99,5 %, which is close to the technological optimum. At the same time, the quality of seed dosing remained stable even with a significant increase in the angular velocity of the sowing disk.

DETERMINATION OF DIMENSIONAL PARAMETERS FOR ANNULAR CONCENTRATOR OF ULTRASONIC SYSTEM

Conventional ultrasonic systems contain concentrators of longitudinal type to amplify and transfer vibrations to a tool. Along with them, elastic rings with variable cross section thickness can be used effectively as concentrators for ultrasonic vibrations of acoustic systems. Their practical application requires a scientifically substantiated methodology for determination of geometric parameters. The paper provides substantiation of the method used to determine dimensions of annular concentrators with a variable cross section which can enhance effectiveness of the ultrasound equipment while performing various technological tasks. Visual analysis of acoustic waves radiated by annular concentrators has shown that the most intensive vibrations are produced in the most thin sections. Computer simulation of oscillations in rings with an external diameter of 50 mm and a variable cross section has demonstrated that the largest increase of vibration amplitude is achieved at a certain ratio of ring thicknesses and diameters. An analysis of numerical values for amplication factor of vibrational amplitude Kд has revealed that there is a limit boundary for the ratio of ring wall thicknesses which, in its turn, depends on the ratio of ring outer and inner diameters at certain values of hole axis eccentricity. The ratio of diameters is expressed quantitatively by the coefficient Kд. An analysis of the results concerning numerical calculations of amplitude amplification factor performed for the specified model of the ring having 50 mm diameter have illustrated that this ratio should lie between 1.3 > Kд > 1.15. The obtained results can be used in ultrasonic devices with annular concentrators in order to perform various technological tasks.

Experimental study on deep hole drilling of 17-4PH material

This paper uses 17-4PH material as the research object, according to the material characteristics of 17-4PH, designed and carried out deep hole drilling test. The purpose of the experiment is to study and discuss the three major problems of tool wear, chip shape and axial deviation of the hole in the process of deep hole drilling of 17-4PH materials. Through the deep hole drilling test of 17-4PH material, the variation of the chip shape and the deflection of the hole axis was obtained under different wear conditions.

Process-parallel center deviation measurement of a BTA deep-hole drilling tool

The BTA deep-hole drilling process is used to manufacture holes with a high length-to-diameter ratio of up to 100. A major quality criteria is the difference between the drilled hole axis and the desired, ideal straight hole axis, called center deviation. A novel measuring system is being investigated in order to measure the center deviation simultaneously to the drilling process. The deviation is determined by calculating the bending line of the boring bar using a newly developed algorithm. The measuring system consists of four subsystems: Optical fiber Bragg grating (FBG) sensors, four eddy current sensors, a rotary encoder and a displacement encoder. These subsystems enable a spatial measurement visualization of the bending line and the center deviation at the head of the boring bar. A major challenge is the separation of the bending strain from other undesired strain fractions. This is done by using an arrangement of two FBG sensors and a digital band pass filter. Experimental investigations show sufficiently good agreement between the calculated and the actual center deviation. Furthermore, drilling experiments reveal that the measurement setup can be used for additional process monitoring by using frequency analysis. Therefore, the investigated system is able to visualize and observe the center deviation. The visualization can be used to derive adequate countermeasures in order to ensure a better process control for the machine operator. The objective of the investigation is to increase the process reliability and productivity by preventing scrap parts. Within this paper, the investigated measuring system, the calculation of the center deviation and first experimental results are described.

Effect of an axial hole on natural convection heat transfer from a cylindrical pin fin attached to a horizontal plate

Heat transfer under laminar natural convection from a hollow cylindrical fin mounted on a horizontal base plate has been numerically studied. The flow outside the fin is much stronger than that inside the hole and as a consequence the rate of heat transfer from a hollow fin is primarily due to the contribution by the outer surface of the fin. Fortunately, the rate of heat transfer is not negatively affected by the presence of the hole at the fin centre. On the contrary, when the Grashof number is higher or the hole diameter is bigger, the inside surface contributes marginally to the heat transfer. A hollow fin saves material and weighs less compared to a solid fin. So, this feature may be exploited.

Method of axial adjustment for precessional transmissions

Axial adjustment method for precessional transmissions includes compensation error calculation, determination compensator groups, achieved in the form of base and auxiliary rings. The compensator has on the base ring axial canals in which can be placed clamping bolts but the auxiliary ring has axial holes for the screws. The auxiliary ring is formed from increasing sectors - the distance between auxiliary ring stairs and front side of body, from decreasing sectors - the distance between base ring and bottom place, and the closure element - the clearance between gear body and the front surface of the base ring. According to the method of group interchangeability is determined the deviation value of the upper and lower group tolerance and the clearance between lid and body. Then rotating one of the rings is ensured the dimension of the compensator which must match to compensation clearance value and then the compensator is adjusted to required value.

What Are “X-shaped” Radio Sources Telling Us? II. Properties of a Sample of 87

Abstract In an earlier paper, we presented Jansky Very Large Array multi-frequency, multi-array continuum imaging of a unique sample of low-axial ratio radio galaxies. In this paper, the second in the series, we examine the images to learn the phenomenology of how the off-axis emission relates to the main radio source. Inversion-symmetric offset emission appears to be bimodal and to originate from one of two strategic locations: outer ends of radio lobes (outer-deviation) or from inner ends (inner-deviation). The latter sources are almost always associated with edge-brightened sources. With S- and Z-shaped sources being a subset of outer-deviation sources, this class lends itself naturally to explanations involving black hole axis precession. Our data allow us to present a plausible model for the more enigmatic inner-deviation sources with impressive wings; as for outer-deviation sources these too require black hole axis shifts, although they also require plasma backflows into relic channels. Evolution in morphology over time relates the variety in structures in inner-deviation sources including XRGs. With features such as non-collinearities, central inner-S “spine,” corresponding lobe emission peaks, double and protruding hotspots not uncommon, black hole axis precession, drifts, or flips could be active in a significant fraction of radio sources with prominent off-axis emission. At least 4% of radio galaxies appear to undergo black hole axis rotation. Quasars offer a key signature for recognizing rotating axes. With a rich haul of sources that have likely undergone axis rotation, our work shows the usefulness of low-axial ratio sources in pursuing searches for binary supermassive black holes.

Вплив схеми базування на першій операції на величину припуску для розточування отворів в заготовках корпусних деталей на настроєних верстатах

Three variants of the scheme of basing the body part billet on the first machining operation are considered. The first two options solve the problem of providing dimensional communication between treated and untreated surfaces; the third option is the task of removing the minimum uniform allowance from the surface of the main hole. The aim of the work is to identify the influence of the base scheme in the first operation of the technological process of machining a batch of body parts on a tuned machine on the quantitative values of allowances for the main hole boring. The studies were carried out on the example of machining a workpiece of a part of the "Bearing housing" type under mass production conditions. To determine the allowances, the calculation and analytical method proposed by Professor V. M. Kovan was used. For the three variants of basing schemes, all elements of intermediate allowances, minimum, maximum and general allowances are calculated. It is established that the use of the first two variants of the base scheme causes the magnitude of the displacement of the hole axis in the initial billet relative to the technological bases for the operation of its boring approximately ten times greater than the use of the third variant of the base pattern. The magnitude of the offset of the axis of the hole in the original billet is determined by building the appropriate technological dimensional chains. An assessment of the possibility of using standard values of allowances, determined without taking into account the base scheme at the first operation, showed that if the value of the minimum start-up is significantly influenced by the offset value of the bore axis in the original billet relative to the technological bases, then for its full account in specific technological conditions should use the analytical method.

Surface quality and topographic inspection of variable compliance part after precise turning

The paper presents the problem of precise turning of the mould parts with variable compliance and demonstrates a topographic inspection of the machined surface quality. The study was conducted for the cutting tools made of cemented carbide with coatings, in a range of variable cutting parameters. The long shaft with special axial hole, made of hardened 55NiCrMoV6 steel was selected as a workpiece. The carried out study included the stiffness measurement of the machining system, as well as the investigation of cutting force components. In this context, the surface topography parameters were evaluated using the stylus profile meter and analysed. The research revealed that the surface topography, alongside the 3D functional parameters, and PSD influences the performance of the machined surface. The lowest surface roughness parameters values, equalled to Sa=1μm and Sz=4.3μm have been obtained during turning with cutting speed vc=90 m/min. The stable turning of variable compliance part affects the surface texture formation with a unidirectional perpendicular, anisotropic structure. Nevertheless, in case of unstable turning, the characteristic chatter marks are observed, and process dynamics has greater contribution in formation of surface finish than turning kinematics and elastic plastic deformation of workpiece.