Cylinder Cavity Research Articles

Analysis on plasma and electric field property of TM<sub>011</sub> mode MPT and its tuning experiment

Microwave plasma thruster (MPT) is a kind of electrothermal thruster. Inside its cylindrical cavity, the plasma process, microwave electric field distribution, and TM<sub>011</sub> mode resonant state are important factors affecting the performance of MPT seriously. According to previous MPT formed through continuous regulation in the resonant sate of cylindrical cavity, the research is needed on a newly fixed and simple MPT, which will simplify the resonant state regulation and lays an important foundation for further study. Therefore the plasma process is analyzed to find the optimal gas discharge condition, and the microwave electric field intensity and power density distribution inside the cavity running in TM<sub>011</sub> resonant sate are calculated to analyse how the parameters are influenced by the cavity dimensions. The resonant state is finely regulated to study how it is influenced by the dimensions of cylindrical cavity and microwave coupling probe with ball and half ball structure. The results of theoretical analysis and calculation show that the discharge power of helium gas is the lowest under the condition of 489 Pa and when the ratio of length to diameter is greater than 1, the microwave electric density distribution inside the cavity is beneficial. Owing to the appropriate length and radius of microwave coupling ball probe, the experiment on resonant state regulation shows that the shortest cylinder cavity is in the optimal resonant sate, with a resonance frequency very close to 2.45 GHz. The helium discharge experiment proves that the cavity and matching ball probe enable high microwave utilization and easy helium gas discharge, and the structure scheme is correct and reliable.

Nonlinear force transfer characteristic analysis of active suspension for emergency rescue vehicles

This paper presents a nonlinear force transfer model for active suspension. First of all, according to the motion analysis of Mcpherson suspension, the force transfer characteristics between the three-dimensional force on tire contact point and the output force of suspension cylinder was studied. Then the friction force between the piston rod and the cylinder body was analyzed. Combined with the force transfer characteristics and the friction force, the nonlinear force transfer model was established which expressed the relationship between the pressure of cylinder cavities and the three-dimensional force at the tire contact point. Finally, the test is carried out on the three-axis emergency rescue vehicle, and the results show that, compared with the simplified active suspension model the ME and RMSE values of the force transfer model are reduced by 93.97%, and 78.31%, respectively. The nonlinear force transfer model can provide more accurate data support for the operation and control of active suspension system.

Circular rotation of different structures on natural convection of nanofluid-mobilized circular cylinder cavity saturated with a heterogeneous porous medium

The incompressible smoothed particle hydrodynamics (ISPH) method is utilized for studying the circular rotations of three different structures, circular cylinder, rectangle and triangle centered in a circular cylinder cavity occupied by Al2O3 nanofluid. The novelty of this work is appearing in simulating the circular rotations of different solid structures on natural convection of a nanofluid-occupied a circular cylinder. The circular cylinder cavity is suspended by heterogeneous/homogeneous porous media. The embedded structures are taken as a circular cylinder, rectangle and triangle with equal areas. The first thermal condition considers the whole structure is heated, the second thermal condition considers the half of the structure is heated and the other is cooled and the third thermal condition considers the quarter of the structure is heated and the others are cooled. The outer boundary of cylinder cavity is cooled. Due to the small angular velocity ω=3.15 (low rotational speeds), then the natural convection case will be considered only. The results are representing the temperature, velocity fields. The simulations revealed that the presence of the inner hot/cold structures affects on the velocity distributions and temperature field inside a circular cylinder cavity. The triangle shape has introduced the highest temperature distributions and maximum values of the velocity fields compare to other shapes inside a circular cylinder cavity. The homogeneous porous level reduces the maximum values of velocity field by 25% compared to the heterogeneous porous level.

Optical-thermal-stress analysis of an ultra-high-temperature solar receiver combining a secondary concentrator and a tungsten cavity

This work proposes an ultra-high-temperature cavity-type solar receiver that integrates a secondary concentrator and a double-deck tungsten cavity, utilizing molten tin as the heat transfer fluid. A coupled numerical model is developed and validated to analyze the optical-thermal-stress characteristics of the receiver. Firstly, to strike a balance between performance and safety, the receiver design with a cavity cylinder length of 200 mm is recommended. Subsequently, the influences of operating parameters on receiver performance are examined, finding that an increased flow rate of tin enhances receiver efficiency and mitigates thermal stress. Moreover, the receiver efficiency can reach 61.5%–89.5% within a wide inlet temperature range of 573∼1573 K and an incident power range of 200∼800 kW. Additionally, thermal stress analysis confirms that the designed receiver remains within safe limits even under the most extreme condition. This study provides valuable insights for the development of efficient and reliable ultra-high-temperature solar thermal systems.

Numerical simulation of the dynamical behavior of a spinning cylinder partially filled with liquid

The flow pattern and transient response of a spinning cylinder partially filled with fluid are investigated in this paper. A two-dimensional finite element model of the fluid domain in the cylinder cavity is developed via the structured tetrahedral element. By using the volume of fluid model, the flow pattern of the liquid is examined numerically. Also, the effects of fluid type, rotating speed, and liquid height on the flow pattern are investigated. Then, the obtained fluid pressure exerted on the inner wall of the cylinder is considered as the input load, and transient dynamic analysis of the spinning liquid-filled cylinder is carried out. Finally, a comprehensive parametric study is conducted to evaluate the effects of liquid type, spinning speed, and fluid height on the dynamical behavior of the system. The results show that these parameters greatly influence the fluid flow pattern and dynamic characteristics of the spinning liquid-filled cylinder system.

Microstructure and mechanical properties of 7075 aluminum alloy parts formed by semi-solid thixoextrusion

Hot-extruded 7075 aluminum alloy was used to form deep cavity cylinders by thixoextrusion. The effects of isothermal temperature and soaking time on the microstructure and mechanical properties of the formed parts were analyzed. The parameters of T6 heat treatment were optimized by orthogonal test, and the influence of T6 heat treatment on the microstructure and mechanical properties of the formed parts was studied. The results indicated that the deep cavity cylinder with a smooth surface could be successfully formed through thixoextrusion. The forming temperature and heating time had remarkable effects on the metallographic structure of the formed components. T6 heat treatment could greatly enhance the mechanical properties of the deep cavity cylinders. The optimum parameters of T6 heat treatment were achieved as: solution at 465 °C for 16 h and aging at 150 °C for 16 h. When semi-solid billets were heated at 600 °C for 10 min, the formed deep cavity cylinder had the best mechanical properties with the ultimate tensile strength of 573.57 MPa, the elongation of 13.44%, and the microhardness of HV 187.12.

ANALYSIS OF DYNAMICS OF VOLUME HYDRAULIC POWER STEERING SELF-PROPELLED TRACTOR CHASSIS

Goal. Analysis of the dynamics of the hydraulic fluid power steering drive of the wheeled tractor self-propelled chassis СШ2540 by simulating the operation of a hydraulic cylinder with a one-sided rod for moving the steering trapezoid when turning the wheels and studying the change in the pressure of the working fluid and the movement of the hydraulic cylinder rod under different load modes. Research methodology. The method of simulation modeling is used, when the variables describing the behavior of the steering hydraulic cylinder are determined by certain load algorithms and operating fluid flows, and are described by differential equations. The differential equations that determine the pressure of the working fluid in the cavities of the hydraulic cylinder and the movement of its rod when the working fluid is fed into the piston or rod cavity are based on the laws of mechanics, the principle of the continuity of the flow of the working fluid and its compressibility. The VisSim package of application programs was used for modeling according to the proposed methodology. The changes of the parameters in the hydraulic cylinder of turning the wheels when they are shifted from the task of the control action in the form of an increase in the external load and the flow of the working fluid in the output channels of the metering pump overcome by the hydraulic cylinder were studied. The influence of the modulus of elasticity of the working fluid, which decreases when it is saturated with undissolved air, was also investigated. The results. When starting the hydraulic steering drive, i.e. when turning the steering wheel from its neutral position, depending on the external load and the intensity of the driver's work at the wheel, oscillatory processes take place in the hydraulic cylinder cavities, which can significantly exceed the working pressure. The results of the research give a reason to conclude that it is necessary to study the nature of the increase in the flow rate and pressure of the working fluid on a full-scale sample of the tractor chassis metering pump, i.e. by replacing the flow rate simulation with its actual value. Setting the loading time and flow rate of the working fluid using the map-VisSim unit is more convenient than setting it with analytical expressions, as it makes it possible to simulate different acceleration rates of the hydraulic cylinder and, if necessary, to control the stationary mode of the steering wheel in the neutral position.

Experimental study on wall heat transfer from diesel spray flame in two-dimensional combustion chamber operated with rapid compression and expansion machine (RCEM)

Heat transfer phenomenon in internal combustion diesel engine is one of problems to be solved. This study was conducted to investigate the relationship between diesel spray impingement, combustion processes, and heat loss using a rapid compression and expansion machine (RCEM). Furthermore, spray combustion and heat transfer processes were investigated using multiple injection strategies with a 6-holes injector. The amounts of diesel fuel used in the pilot, pre-injection, and main injection sprays were 3.964, 0.747, and 11.205 mg, respectively. Variations in common rail pressure conditions (30, 120, and 180 MPa) were applied to properly investigate spray evaporation, air–fuel mixture formation, and heat transfer in the combustion chamber. In addition, a local wall heat flux sensor was installed in the cylinder (head and liner) and piston cavity (upper lip, lip, and bottom) to measure the heat flux distribution, and a diffused backlight illumination method was used to visualize the spray and flame behavior in the combustion chamber and 2D piston cavity. The results showed that the impingement flame surrounding the cylinder head contributed to the highest magnitude and longest duration of the heat flux on the cylinder side owing to the spray flame velocity, impingement, and residence time. Meanwhile, the highest different temperature at cavity bottom induced more heat flux on the cavity side than that on the squish side. In addition, the higher injection pressure increased the spray momentum and spray tip penetration which led to a better air–fuel mixture, better evaporation rate, and less flame residence that contributed to reduce the accumulated heat loss in combustion chamber. Furthermore, a low common rail pressure was found to induce a greater difference in the accumulated heat flux ratio than a high common rail pressure which is owing to longer flame residence time in the combustion chamber. They were approximately 14% and 6% greater than that compared to the baseline common rail pressure which mean that a high common rail pressure contributes for the improving thermal efficiency in spray combustion.

Cooling and heat transfer efficiency of a Newtonian fluid in a vented duct

Mixed convection is studied numerically to investigate the performance of the better heat transfer and also the effective cooling in a vented cylinder cavity, which is covered by two rotating discs. An external airflow enters the enclosure through an opening in the bottom vertical side and exits from another opening in the top of the opposite vertical one. The bottom disc is kept at a constant temperature, while the other sides are adiabatic. CFD code is used to solve the governing equations (continuity, momentum, and energy equations). The calculus is carried out for different values of Ri = Gr/Re² (0.1 ≤ Ri ≤ 20). Nusselt numbers, velocity and temperature profiles, and heat transfer rate are presented and compared to the literature.

DYNAMICS OF PNEUMATIC DRIVE. LECTURE CYCLE. THE INFLUENCE OF THE ADOPTED FRICTION MODEL ON THE STABILITY OF THE TRANSIENT PROCESSES OF THE SERVO PNEUMATIC DRIVE

The paper considers the main features of the servo pneumatic actuator with throttle control, the design features of the drive and the element for its control are given. Two design schemes of the pneumatic drive are described and are given: an “integrated” scheme and a “spaced” scheme. The advantages and disadvantages of each of the schemes are determined. The principle of operation of each element of a servo pneumatic drive consisting of a pneumatic cylinder with feedback, a feedback sensor (position), pro-portional to the distributor is considered. The characteristic of the transition process and the criteria for estimating the transition process is given, and the static characteristic of the throttle control pneumatic actuator obtained by experimentally is given. A mathematical model of the servo pneumatic drive is given. The equations describe to unambiguously establish the connection between the desired physical quantities: the pressure level in the pneumatic cylinder cavities and the developed force of te pneumatic servo drive. The paper generates the classification of the friction models currently used to study the dynamic characteristics of the developed drives. The equations of each of the considered friction models are given. An example of constructing a friction model using a flowchart method, where connection between blocks in the diagram is real physical quantities. The charts obtained as a result of mathematical modeling of transient processes and their quality indicators for the servo pneumatic actuator, applying different contemplated friction models. An assessment of the quality of transient processes received, their analysis and the effect of the considered friction models on the stability of the drive operation. The scientific novelty of the work includes the formulation of the task of studying the sustainability of the work of the servo pneumatic actuator under different types of friction models, as well as the provision of practical recommendations to specialists engaged in the development of esign of servo pneumatic actuators and their operation. In addition, this work is based and is implemented as a course of lectures of the “Dynamics of the Pneumatic Drive”, is red by the author in MSTU named after N. E. Bauman at the department “Hydromechanics, hydromachins and hydropneumoautomatics” (E10), as part of the training of masters in the specialty 05.04.13 – hydraulic machines and hydropneumatic drives.

FLUID–STRUCTURE COUPLING SIMULATION OF EXPLOSIVE FLOW FIELD IN HETEROGENEOUS POROUS MEDIA BASED ON FRACTAL THEORY

In this paper, through finite difference and finite element coupling algorithms with structured grid, the fluid–structure coupling problems of the pressure of the fluid as well as stress and strain of the heterogeneous porous medium under the initial pressure of MPa magnitude are calculated, respectively. The porous medium is a cavity cylinder with fractal characteristics. The parameters of porosity, elastic modulus and Poisson’s ratio of porous media with different fractal dimensions ([Formula: see text], 2.4 and 2.5) are obtained by theoretical calculation. Through theoretical derivation, the amplitude of WM function is expressed by the fractal parameter porosity, which can predict the uneven characteristics caused by the nonuniformity of pore size distribution after explosion. The results show that with the increase of fractal dimensions, the porosity increases, and both the elastic modulus and the Poisson’s ratio decrease. The Poisson’s ratio has a linear relationship with porosity, which is well consistent with the modified formula in the literature. Under the same initial pressure, the stress and strain values of the material without fractal characteristics are much larger than those of the material with fractal feature which has an obvious fluctuation by extracting the average values. It indicates that the fractal porous media with rough surface can effectively reduce the pressure wave peak at the wall surface, and reduce the size of the stress and strain concentrations to prevent the vibration of the cylinder. As expected, if the initial pressure increases with an equal fractal dimension, the stress and strain values of the fluid–structure coupling will increase too. When the initial pressure is equal, the peak value of pressure in wall decreases gradually with the increase of fractal dimension, and the stress and strain values also decrease.

Investigation on the heat transfer and energy-saving performance of microchannel with cavities and extended surface

Microchannel heat sinks (MCHSs) are widely used in microelectronic systems and are one of the most effective heat sinks in the 21st century. In this work, the fluid flow and heat transfer performance of different extended surfaces (cylindrical fins, rectangular fins, water droplets) of triangular combined cavity, 90° fan-shaped and triangular combined cavity were investigated. The comprehensive performance in microchannels were analyzed and evaluated in detail by different aspects, including flow characteristics, heat transfer characteristics, pressure drop characteristics, comprehensive thermal strengthening performance and thermal strengthening performance aimed at energy saving. The result indicated that the microchannel with the triangular combined cavity exhibited the best heat transfer performance at a low Reynolds number. However, as the Reynolds number gradually increasing, the microchannel with 90° fan-shaped and triangular combined cavity presented more obvious advantages. Furthermore, the microchannel is evaluated by the comprehensive thermal enhancement performance and the enhanced performance evaluation aiming at energy-saving. When Re<144.6, the comprehensive heat transfer performance of the microchannel with triangular combined cavity cylinder fins was the best, and the energy-saving effect was excellent. The microchannel of the 90° fan-shaped and triangular combined cavity cylindrical fins at Re>144.6 had better comprehensive heat transfer performance and energy-saving effects. Because of the combined effect of the boundary layer redevelopment and the cold and heat exchange of the fluid in the channel, the microchannel with cavity and the extended surface has better heat transfer and energy-saving performance than that of the traditional rectangular microchannel.

Numerical investigation of the melting process in a half horizontal cylinder with radial fins

In the present study, the melting phenomenon in a half horizontal cylinder cavity with rectangular heat sources is investigated using numerical lattice Boltzmann method. The cylinder is modeled two dimensionally and its boundaries are insulated. Also, the high temperature rectangular heat sources with constant area are located in radial position on cavity. The enthalpy-based lattice Boltzmann method is used for simulating the phase change problem in the cavity. Melting of lead with Stefan number of 0.86 and Prandtl number of 0.0236 is simulated in the cavity. The effects of pertinent parameters such as the aspect ratio of the fins 1,2.5,5,7.5, the Rayleigh number 103,104,105 and the angular position of the heat sources 0,15,45 are studied on the melting phenomenon. The results show that increasing the aspect ratio of the fin with constant area reduces the melting time and increases the liquid fraction at the same time. Also higher value of the Rayleigh number improves the natural convection effect and raises the rate of melting. Finally, it is observed that the highest rate of melting is obtained when two fins are positioned at 45 degrees with aspect ratio of 7.5 at Rayleigh number of 105.

Numerical study of free-fall cylinder water entry using an efficient three-phase lattice Boltzmann method with automatic interface capturing capability

The realistic three-phase water entry of a free-fall cylinder is investigated in this paper using an efficient lattice Boltzmann method (LBM) with automatic interface capturing capability implemented in an in-house FORTRAN 90 code. The numerical method takes advantage of automatic interface capturing, using a real equation of state (EOS), and considering the surface tension and gas phase compared to the free-surface LBM used for water entry simulations in a few previous LBM works. Simulation results are first compared with other numerical and experimental data with good agreements. Variation of the cylinder trajectory and cavity diameter is presented, and effects of the Froude number, solid density, and surface wettability are investigated. Data analysis shows that the non-dimensional cavity diameter vs. non-dimensional time is independent of the Fr number, or impact velocity, and obeys a power-law trend almost the same as the one reported for variation of the non-dimensional crown diameter for the droplet impact on a liquid film or a deep liquid. The penetration depth during time is almost linearly increased with the impact velocity and solid density. As the surface wettability increases, the penetration depth is reduced, and the deviation of different wettability curves increases with time.

The Calculation of Electric Field Caused by Distributed Charge

The potential and electric field responses in cylinder cavity with ceramics slice caused by distributed charge in X-ray environment were simulated with finite difference method. The numerical results indicate that the distributed charge in ceramics’ middle section is negative or positive, and positive of both sides. For the photon energies from 30 keV to 1 MeV with same fluence, distributed charge and electric field were decreased at first and then increased. Electrode has great effect to the potential and electric field responses. For different plating thickness, there exists minimum to the electric field amplitude, and for the plating, there exist optimal diameter and thickness. Distributed charge is calculated using Monte-Carlo particle transport code.

Layout Experimental Study of Dynamic Parameters of an Asymmetrical Self-Oscillating Hydraulic Drive

The article describes the developed asymmetric self-oscillating hydraulic drive and a stand for determining its dynamic characteristics. The design feature of the self-oscillating drive is that the switching of the working fluid in the cylinder cavity is made by two spools mounted inside the piston, while the working fluid is supplied to the spools by the hollow rod. The test stand is based on the principle of throttling the working fluid when it flows from one cavity of the loaded hydraulic cylinder to another. Stand tests of the developed drive have shown its reliability at different values of the piston stroke and at different operating pressures. The paper presents the characteristics of the drive when operating under load and at idle..

Effect of secondary electrons on SGEMP response

It is difficult to effectively shield the system generated electromagnetic pulse (SGEMP), which can significantly affect the performance of important electronic devices and infrastructure, such as low-orbit spacecraft. Numerical simulation is an essential way to study the SGEMP response. However, many previous studies ignored or simplified the effect of secondary electron emission in their models. In this paper, a three-dimensional electromagnetic particle-in-cell numerical simulation model is developed to evaluate the effect of secondary electrons on the SGEMP response of two typical structures (external SGEMP and cavity SGEMP, respectively) under different current densities (0.1–100 A/cm&lt;sup&gt;2&lt;/sup&gt;) and different materials (Al, Cu and Au). A right cylinder or cylindrical cavity with a length of 100 mm is used. The photoelectrons produced by the interaction between the X-ray photon and metal are emitted from one end of the system and assumed to be monoenergetic. The photoelectron pulse follows a sine-squared distribution, and its full width at half maximum is 1 ns. Some important parameters of secondary electrons are discussed and summarized, including the emission coefficients of elastically and inelastically backscattered electrons, as well as the probability density functions of emission angles and energies. The results show that ignoring the secondary emission in the simulation model leads the peak electric field to be underestimated by twice-thrice, and the duration of electric field response by more than 10%. The oscillation frequency and the amplitude of the second peak of the tangential magnetic field are also increased, with the secondary electrons considered. Among various types of secondary electrons, backscattered electrons have a dominant effect on the change of SGEMP. The effect of true secondary electrons is about 1/5 of that of backscattered electrons. The effect of secondary electrons on SGEMP response increases with a higher atomic number of the material used in the system, mainly due to higher backscattering emission coefficient and a high ratio of high energy inelastically backscattered electrons. The secondary electrons will influence the response of the external SGEMP only when the space charge effect is strong (high X-ray fluence). While the response of the cavity SGEMP is more easily affected by the secondary electrons even at a relatively low X-ray fluence. This paper helps to better obtain the SGEMP response of a specific device under strong radiation through numerical simulation.

Different closure patterns of the hollow cylinder cavities with various water-entry velocities

The vertical water-entry processes of a hollow cylinder with three different velocities are investigated both numerically and experimentally. Three different closure patterns and flow characteristics of the air-entraining cavities induced by water-entry processes are discovered and discussed. Our results show that three different closure patterns appear with the increase of entry velocity, the deep-closure, the surface closure on the through-hole jet and on the geometry wall. Three high-speed regions also appear during the water entry process and their characteristics are different with various closure patterns. Besides, with the increase of water entry velocity, the velocity variation will vary from increase to decrease, but their water depths all increase linearly due to the short time and small variations of velocities.

Heat transfer hybrid nanofluid (1-Butanol/MoS2–Fe3O4) through a wavy porous cavity and its optimization

PurposeThe purpose of this paper is to investigate natural convection in a porous wavy-walled enclosure that is including a cylinder cavity in the middle of it and filled with a hybrid nanofluid contains 1-Butanol as the base fluid and MoS2–Fe3O4 hybrid nanoparticles.Design/methodology/approachThe domain of interest is bounded by constant temperature horizontal corrugated surfaces and isothermal vertical flat surfaces. The numerical outputs are explained in the type of isotherms, streamline and average Nusselt number with variations of the Rayleigh number, Hartmann number, nanoparticle shape factor and porosity of the porous medium. For solving the governing equations, the finite element method has been used.FindingsThe results show that Nuave is proportional to Rayleigh and nanoparticle shape factor directly as well as it has an inverse relation with Hartmann and porosity. The obtained results reveal that the shape factor parameter has a significant effect on the heat transfer performance, which shows a 55.44% contribution on the average Nusselt number.Originality/valueAs a novelty, to maximize the heat transfer performance in a corrugated walls enclosure, the optimal parameters have intended by using the response surface and Taguchi methods. Additionally, an accurate correlation for the average Nusselt number is developed with sensibly great precision.

A Function Reconfigurable Antenna Based on Liquid Metal

To meet the demands of maritime transportation on ships, including satellite positioning, wireless communication, and radio frequency identification (RFID) for cargo handling management, a function reconfigurable antenna based on liquid metal is proposed in this paper. The antenna is composed of 3-D-printed hollow cavities, a two-step impedance feeding sheet, and two feeding probes. The 3-D-printed hollow cavities contain a big hollow helix cavity, a hollow cone loaded cylinder cavity, four hollow cylinder cavities, and four small hollow helix cavities. By filling the liquid metal into different hollow cavities, reconfigurable functions are generated, including right-handed circular polarization (RHCP), omnidirectional linear polarization (O-LP), pattern reconfigurable circular polarization, and omnidirectional left-handed circular polarization (O-LHCP). To illustrate this, a prototype is fabricated using 3-D-printed photopolymer resin and etching technology. The measurement results agree well with the simulated ones in terms of return loss, radiation pattern, gain, and axial ratio (AR). For the five reconfigurable states, the measured relative bandwidths for |S11| &lt; −10 dB are 44.7%, 41.7%, 30.4%, 28.1%, and 10.8%, respectively, which covers the bands of a global navigation satellite system (GNSS), wireless communication system, and RFID communication system. Attributing to the advantages of its compact structure, flexible conversion, and good performance, the proposed antenna is a good candidate for maritime transportation applications.