谷子单纵轴流脱粒分离理论模型的建立与验证

Rotating electrodes can effectively improve the processing performance of micro-electrical discharge machining (micro-EDM), but there is still a lack of systematic research on the specific effects of electrode rotation and rotational speed changes. In this paper, the effects of electrode rotation and rotational speed on the discharge channel, debris stress, and debris motion in micro-EDM were analyzed theoretically. An AISI304 sheet was used as the workpiece and helical tungsten carbide alloy as the electrode. The through-hole drilling experiments of micro-EDM were carried out at low and high discharge energy and different electrode rotational speeds. In terms of processing efficiency, the effects of electrode rotation and rotational speed on material removal rate (MRR), relative tool wear ratio (RTWR), and short circuit number were analyzed. The results show that MRR increases first and then decreases, RTWR and short circuit number decrease first and then increase. In the aspect of processing precision, the impacts of electrode rotation and rotational speed on taper angle and overcut were analyzed. The results show that the electrode rotational speed has little effect on the change of the taper angle. In addition, when the electrode rotational speed is small, there is no obvious change in overcut. When the speed is too high, the overcut increases obviously and shows a trend of continuous increase. Finally, by comparing the experimental results, the optimal electrode rotational speeds of micro-EDM with two kinds of discharge energy were determined. The final experimental results also verify the correctness of the previous theoretical analysis.

Dynamics of a powered disk in clay soil

Friction drilling is a non-conventional process that generates heat through the interaction between a rotating tool and a workpiece, forming a hole with a bushing. In this study, the effect of the preheating temperature, rotational speed, and feed rate on the induced temperature during the friction drilling of A356 aluminum alloy was investigated. This study aimed to analyze the influence of friction-drilling parameters on the thermal conditions in the induced bushing, where it focused on the relationship between preheating and the resulting heat generation. The analysis of variance (ANOVA) approach was carried out to optimize the friction-drilling parameters that contributed most to the induced temperature during the friction-drilling processing. Experiments were conducted at various preheating temperatures (100 °C, 150 °C, 200 °C), rotational speeds (2000 rpm, 3000 rpm, 4000 rpm), and feed rates (40 mm/min, 60 mm/min, 80 mm/min). The induced temperature during the process was recorded using an infrared camera, where the observed temperatures ranged from a minimum of 154.4 °C (at 2000 rpm, 60 mm/min, and 100 °C preheating) to a maximum of 366.8 °C (at 4000 rpm, 40 mm/min, and 200 °C preheating). The results show that preheating increased the peak temperature generated in the bushing during friction drilling, especially at lower rotational speeds. The rotational speed rise led to an increase in the induced temperature. However, the increase in the feed rate resulted in a decrease in the observed temperature. The findings provide insights into optimizing friction-drilling parameters for enhanced thermal management in A356 aluminum alloy.

A new ultrahigh speed micro-spindle has been developed for micromachining that can be used at rotational speeds as high as 500,000 rpm. Since conventional ball bearings or fluid lubricated journal bearings cannot be used at speeds beyond 300,000 rpm for any extended period of time, the new spindle uses a set of journal and thrust foil bearings. The micro-spindle was integrated with a 3-axis micro-milling machine. Cutting experiments were performed on an aluminum alloy at speeds greater than 300,000 rpm using 50 and 300 micron end-mills. The increase in rotational speed to 450,000 rpm in micro-milling of aluminum alloy allowed an increase in feed rate to nearly 800 mm/min (the maximum feed rate available by the positioning stage), thus increasing the material removal rate by more than two orders of magnitude. The dimensional accuracy of several straight cuts made at different feed rates and depths of cut was measured. Theoretical models and research on machining of industrial ceramics have shown that high-speed machining allows for smaller depths of cut by each diamond grit, thus reducing the contact forces and resulting in a reduced possibility of detrimental chipping and subsurface machining damage. Therefore, micro-grinding was performed on dental ceramics to evaluate the feasibility ultrahigh speed machining. In these studies several ceramics used for preparation of dental restorations were cut with diamond tools. The propensity for generation of machining-related damage, such as surface and subsurface microcracks, were greatly reduced by machining at ultrahigh speeds and high feed rates. Micro-machining at such high speeds, and in combination with high feed rates, has never been achieved before.

Turbocharger surge remains an area of concern for the automotive industry as it limits the permissible operating range on the compressor map, while also adversely impacting the compressor’s pressure rise, efficiency, and acoustics. The present study uses Stereoscopic Particle Image Velocimetry (SPIV) to investigate the flow field at the inlet of an automotive turbocharger compressor without a recirculating channel. Experiments were carried out at four different speeds, including 80, 100, 120, and 140 krpm, which represent a substantial portion of the compressor map. The mass flow rates investigated ranged from choke to deep surge, thus spanning the entire mass flow regime at each rotational speed. The current work aims to characterize how the compressor inlet velocity field varies with rotational speed, with a specific emphasis on surge. The qualitative nature of the flow field (radial dependence of axial and tangential velocity profiles), over the choke to mild surge range, was observed to be nearly independent of rotational speed for comparable operating conditions (for example, comparison of mild surge at different rotational speeds). A quantitative comparison of the velocity profiles at the choke or mild surge operating points showed an increase in the velocity magnitudes with increasing rotational speed. The flow field at deep surge, however, was observed to change substantially from 80 krpm to 140 krpm. At 80 krpm, the character of the flow field at different times (at different points on the surge cycle) was observed to be similar: the core flow near the center of the duct was always directed into the impeller, whereas the reversed flow occupied an annular region near the periphery in nearly all time instances. However, as the rotational speed was increased to 140 krpm, the variation in the flow field at different instances within a deep surge cycle increased. At 140 krpm, the negative flow rate (where the cross-sectional average flow is directed out of the inducer back into the inlet duct) portion of the surge cycle was still similar to the overall surge flow field at 80 krpm, but over a substantial part of the positive flow rate (cross-sectional average flow is directed into the impeller) portion of the surge cycle, there was no sign of reversed flow within the visualization domain. As the rotational speed was increased, the surge loop (obtained by combining the PIV and pressure transducer data) extended over a wider portion of the compressor map with higher maximum (positive) and minimum (negative) flow rates, along with higher amplitude pressure fluctuations. The mean amplitude of mass flow rate and pressure ratio fluctuations at deep surge increased in nearly a quadratic fashion with rotational speed. The deep surge frequency did not change substantially over the range of rotational speeds examined in this study.

Despite the rapid development of alternative energy sources, the role of hydrocarbons in the global fuel and energy balance remains significant. For their transportation and further processing, pre-processing is carried out using a set of equipment. In this case, the mandatory devices are separators. In terms of specific energy consumption and separation efficiency, methods based on the action of inertia forces are optimal. However, standard designs have common disadvantages. A method of dynamic separation is proposed to eliminate them. The proposed devices are automatic control systems. The object of regulation is hydraulic resistance, and elastic forces are the regulating actions. Aerohydroelastic phenomena accompany the operation of dynamic separation devices. Among them, the most interesting are flutter and buffeting. Oscillations of adjustable baffles accompany them. It is necessary to conduct a number of multifactorial experiments to determine the operating parameters of dynamic separation devices. In turn, physical experiments aim to identify patterns and features of processes occurring during vibration-inertial separation (i.e., the dependence of various parameters on velocity). Therefore, the article proposes a methodology for carrying our physical experiments on dynamic separation and a designed experimental setup for these studies. As a result, the operating modes of separation devices for different thicknesses of baffle elements were evaluated. Additionally, the dependences of the adjustable element’s deflections and oscillation amplitudes on the gas flow velocity were determined for different operating modes of vibration separation devices.

The shifted flow separation point on an airfoil wall must be predicted with a high accuracy over a time series in order to precisely analyze the unsteady flow around the moving airfoil. Pressures on the wall of the cylindroid, which was rotated in a uniform flow, were measured in order to obtain the test data for developing the numerical analysis method for flows including unsteady flow separation phenomena. From the results, when the rotational speed was low, the pressure on the suction side near the leading edge was significantly lowered. On the other hand, the pressure lowering was insignificant at high rotational speeds. Results suggest that the air flows along the wall around the leading edge in the case of low rotational speeds, whereas flow separation occurs at the leading edge in the case of high rotational speeds as a result of the large centrifugal force in the boundary layer.

To investigate the performance of engine cooling water pump in automobile with variable rotating speed, experimental tests and numerical simulation are carried out on an engine cooling water pump under the rotating speed of 2650, 2960, 3700, and 4300 r/min. The hydraulic performance under 3700 r/min rotating speed and the cavitation performance under 340 L/min flow rate are tested and analyzed. The predicted results agree well with the experimental results, indicating that the simulation has high accuracy. The results show that the head of engine cooling water pump increases gradually and the best-effective region moves toward high flow rate condition with the increase in rotating speed. The augment of rotating speed would deteriorate the internal flow fields and causes more energy losses, which is due to the increase in tip leakage flow and enhancement of rotor–stator interaction effects. And, the rotor–stator interaction effect is sensitive to the temperature under various rotating speeds. Furthermore, the required net positive suction head increases with the increase in rotational speed and anti-cavitation performance is weakened during cavitation conditions.

The paper presents the numerical investigation results of the gyroscopic moments’ influence on the dynamic behavior of a transmission shaft, specifically on the change in its natural oscillation frequencies with varying rotational speeds and direction. Systems that include shafts are often operated at different rotational speeds. If a shaft is represented as an elastic rod, it can perform natural and forced oscillations. The natural frequencies of the shaft depend on its rotational speed. This behavior is caused by precession motion. Therefore, the oscillatory motion of the shaft is considered in space, accounting for gyroscopic and other inertial forces. As a result, the dependences of the natural oscillation frequencies in the inertial and rotating coordinate systems, plotted using developed software for studying the dynamics of elastic shafts, are shown. The numerical values of the natural oscillation frequencies for an unmoved shaft and its critical rotational speeds for direct and reverse precession are also presented. An analysis of the results and conclusions regarding the possibility of operating the shaft in certain frequency ranges have been made. It is noted that the natural frequencies of elastic shafts during rotation are dependent on the influence of gyroscopic moments. An important parameter is the natural oscillation frequency in the rotating coordinate system, as it is directly related to the elastic body. As the diagrams show, the change in the natural frequency in the rotating and inertial coordinate systems occurs with different intensity when the rotational frequency changes: slowly in the inertial system and rapidly in the rotational system. In addition, when the rotational speed increases in the range up to critical values, the natural oscillation frequency in the rotating coordinate system decreases. With a further increase in rotational speed beyond the critical value, the natural oscillation frequency begins to grow, and the precession movement occurs in the reverse direction.

Many celestial bodies in our Solar System, such as the Moon, Mars and small bodies, are covered with a layer of regolith. Numerous current and upcoming space missions aim to interact with these surfaces such as the IDEFIX rover of the Martian Moons eXploration (MMX) mission [1] and the Hera mission [2]. Some instruments, such as the instrument InSight HP³ mole, have even failed to perform as expected [3], highlighting the importance of understanding the geotechnical behavior of regolith surfaces. Due to the limited accessibility and high cost of in situ missions, laboratory experiments using regolith simulants are crucial for the preparation of surface operations like landing, mobility, and sampling. Different extraterrestrials simulants have been developed and characterized regarding the mineralogical, granulometric and some geotechnical properties [e.g., 4-7]. Here we present the results of additional characterisation experiments focussing on the dynamic angle of repose and the cohesive properties of the simulants. A rotating drum experiment has been developed to measure bulk properties of different planetary simulants in low consolidation conditions. The setup is presented in Figure 1. The simulant is placed in a cylinder container of 4 cm diameter and 5 cm depth so that the container is half full with the granular material. Two PMMA windows are mounted on the front and back of the container, to be able to see through the system. The sample container is attached to a drive shaft which allows it to rotate around its axis. A CCD camera (mvBlueFox-120aG) is fixed facing the front window to image the granular material. An LED panel illuminates the experiment from behind allowing a shadometry image analysis to be performed. The rotational speed of the motor is controlled by an Arduino card. The gear ratio between the motor and the container allows it to rotate between 10 and 70 rotations per minute (RPM).Figure 1: The rotating drum experiment at ISAE-SUPAERO.The motor rotational speed is varied and 10 images are taken for each speed with a frame rate of 20 Hz. A binarization of the image is performed followed by an edge detection which automatically detects the surface of the material. This process is shown in Figure 2 for glass beads at two different rotational speeds. It is performed on the 10 images, and for each rotational speed, as illustrated in Figure 3.Figure 2: Surface detection for glass beads at two different rotational speeds.Figure 3: Surface profiles for 10 images at different rotational speeds for glass beads.By measuring the surface slope close to the center of the drum, the dynamic angle of repose for each rotational speed can be determined. This result is presented in Figure 4 for three different granular materials: quartz sand with a mean particle diameter of 500 µm, glass beads with a diameter between 90 and 150 µm and Mars Global (MGS-1) High-Fidelity Martian Regolith Simulant. Figure 4: Dynamic angle of repose as a function of the rotational speed. The error bars represent the standard deviation of the angle of repose measured in 10 different images at each rotation speed.This experimental set-up also allows for a characterisation of the cohesive properties of the granular material. The rugosity of the surface at each rotational speed can be used to compute the cohesive index, an adimensional number directly linked to the total cohesive force [8]. This gives a comparative measurement of the cohesion of the different simulants.In summary, we have developed a rotating drum experiment to characterise different planetary simulants. Two main material parameters can be extracted: a cohesive index, which is an adimensional number directly linked to the total cohesive forces, and the dynamic angle of repose. The set-up has already been tested with three different materials (glass beads, quartz sand and Mars Global (MGS-1) High-Fidelity Martian Regolith Simulant). The results of the rotating drum characterisation of the Exolith planetary simulants - Lunar Highlands (LHS-1) High-Fidelity Regolith Simulant, Lunar Mare (LMS-1) High-Fidelity Regolith Simulant, Carbonaceous Chondrite (CI-E) High-Fidelity Asteroid Regolith Simulant and Carbonaceous Chondrite (CM-E) High-Fidelity Asteroid Regolith Simulant - will be presented during the conference.

The carotid bifurcation is found to be a major site of Atherosclerotic plaque formation and intima-media thickening. In the present study, oxygen mass transfer in the human carotid bifurcation has been numerically investigated, focusing on effects of the bifurcation angle and the volumetric flow ratio between the internal carotid artery (ICA) and the external carotid artery (ECA) on the magnitudes and distributions of the oxygen wall flux. Three-dimensional models of bifurcations with two different bifurcation angles mimicking the real bifurcation anatomy were constructed to perform simulations of steady blood flow under the wall boundary condition of a constant oxygen concentration. Results reveal that the axial flow separation at the outer common-internal carotid wall can significantly alter the distribution and the magnitude of the oxygen wall flux, depending strongly on the bifurcation angle. The magnitude of the lowest Sherwood (Sh) number (non-dimensional oxygen wall flux) at the ICA sinus, where Atherosclerotic plaque is likely to develop, is sensitive to the change in the value of the volumetric flow ratio rather than the change in the bifurcation anatomy.

A Study of Mechanical and Micro Structural Properties of Friction Stir Welded Aluminium Alloy

This work investigates the microstructure evolution during the rotary friction welding (RFW) of Inconel 718 alloy. A cellular automata (CA) approach is implemented to evaluate a cylindrical component (at weld center and edge wall), predicting dynamic recrystallization (DRX) and grain size of friction welds. The input variables for RFW were rotational speed (500, 1000, and 1200 rpm), feed rate (2 mm/s), and feed distance (3.6 mm). The CA model is based on the Laasraoui-Jonas model and explains intricate grain transformation in terms of microstructure, temperature, strain, and strain rate. Calculated grain consists of very fine grain structure at the stir zone followed by the thermo-mechanical affected zone, where partial recrystallized microstructure was present. The average grain size was 2.5 µm, which is comparable to reported experimental values. The grain analysis revealed that temperature and strain are most affecting factors to attain a refined microstructure. The strain rates predicted for both center and edge locations of the weld were found to be higher as rotational speed increased. A steady strain distribution is noted at greater temperature for all the rotational speeds. The results of this work contribute toward the understanding of microstructure and mechanical response for RFW of Inconel 718.

Experimental investigation of blade number and design effects for a ducted wind turbine

Effects of pressure ratio and rotational speed on the leakage flow and cavity pressure characteristics of the rotating staggered labyrinth seal were investigated by means of experimental measurements and numerical simulations. The rotating seal test rig with turbine flowmeter and pressure measuring instruments was utilized to investigate the leakage flow of the staggered labyrinth seal at eight pressure ratios and five rotational speeds. The repeatability of the experimental data was demonstrated by three times measurements at different pressure ratios and fixed rotational speed. The three-dimensional Reynolds-averaged Navier–Stokes equations and standard k-ε turbulent model were also applied to study the leakage flow characteristics of the staggered labyrinth seal at the experimental conditions. The validation of the numerical approach was verified through comparison of the experimental data. The detailed flow field in the staggered labyrinth seal was illustrated according to the numerical simulations. The experimental and numerical results show that the leakage flow coefficient increases with increasing pressure ratio at the fixed rotational speed and is more sensitive to the smaller pressure ratio. The influence of rotational speed on the leakage flow coefficient is not obvious in the present rotational speed limitations. The cavity pressure coefficient in the staggered labyrinth seal decreases and is significantly influenced by the cavity structure along the flow direction.