Characterisation of planetary simulants using a rotating drum experiment

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

Band formation (axial segregation) and subsequent coarsening of bidisperse mixtures in long circular tumblers is well documented for the case where the cylinder is at a single fill level and the interstitial fluid is air. However, little information is available for a range of fill levels, nor is the effect of rotational speed on segregation clear. Moreover just a handful of studies have focused on slurry systems, where the interstitial fluid is a liquid. This is precisely the parameter space covered in this study. Experiments are conducted using a 2:1 mixture of 882 and 272 mum glass beads with water as the interstitial fluid. Several different phenomena are uncovered. Results indicate that bands are less likely to form at low rotational speeds and low fill levels. As the fill level and rotational speed increase, more bands form and they form more quickly. However, at fill levels near 50% and high rotational speeds the bands contain a mixture of particles rather than being relatively pure. Furthermore, the evolution of the core of small beads that forms deep in the bed depends on the fill level and the rotational speed. For certain fill levels and rotational speeds, the core remains prominent as bands form, while in other cases the core disappears entirely between bands. Finally, when the tumbler is tilted so that the fill level varies from 14% at one end to slightly more than half full at the other end, the bands and core that form locally qualitatively correspond with those that would form for the corresponding fill level in a horizontal cylinder.

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.

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.

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.

Determining the optimal features that are invariant under changes in the rotational speed variations of rolling element bearings is a challenging task. To address this issue, this paper proposes an acoustic emission (AE) analysis-based bearing fault diagnosis invariant under fluctuations of rotational speeds using envelope spectrums (ES) and a convolutional neural network (CNN). The ES extracted from the raw AE signals provides valuable information about the characteristic defect frequency peaks and variations to bearing rotational speeds when faults appear on a bearing. The proposed method employs CNN to automatically extract high quality features and classify bearing defects. In the experiment, a CNN trained on a dataset corresponding to one revolutions per minute (RPM) is used to detect patterns from datasets corresponding to other RPMs to verify that the classification is accurate and invariant under rotation speed fluctuations. The efficacy of the proposed method is verified on AE-based low-speed bearing data under various rotational speeds. The experimental results show that the proposed method is effective at detecting bearing failures, provides an average classification accuracy of about 86% under fluctuating RPM, and outperforms other state-of-the-art algorithms.

The operational rotational speeds of hydroturbines change arbitrarily within a small range, and the friction power consumption caused by the asymmetric curl represents a technical difficulty in magnetofluid sealing. In this study, the pressure-withstanding value and equations for the asymmetric curl of a magnetofluid sealing device under different rotational speeds were deduced. By considering the magnetofluid sealing device characteristics with Halbach magnetic arrays, temperature fields under a static field and low rotational speed were calculated for determining the Halbach magnetofluid sealing device with the best sealing performance. Comparisons and analyses were performed with the friction power consumption and sealing pressure-withstanding value of the selected structure under high (3000 r/min), medium (1500 r/min), and low (300 r/min) rotational speeds and alternating work conditions of ±3, ±6, and ±9. The results indicated that changes in magnetic moment caused by changes in the external magnetic field are the primary cause of friction power consumption. Heat generation occurs concurrently with the friction power consumption. Consequently, the pressure-withstanding value of the magnetofluid sealing is reduced; the friction power consumption of the magnetofluid is directly proportional to the magnetic field strength, rotational speed, and alternating amplitude. Unstable states and asymmetry of the external magnetic field lead to nonlinear increments in the friction power consumption of the magnetofluid. A stable and symmetrical magnetic effect, with a smaller rotational speed and alternating amplitude leads to lower friction power consumption, resulting in a more ideal sealing effect.

Experimental investigation on the effects of rotation and the blowing ratio on the leading-edge film cooling of a twist turbine blade

We studied the influence of the rotational speed and eccentricity of the ring image on the severity of the stereokinetic effect (SE) in a group of 36 children aged 8 to 16 years with partial optic atrophy and in the control group of 44 age-matched children with a normal fundus. Four variants of the ring image with the eccentricity of 0.2, 0.4, 0.6 or 0.8 were used as a test image. The rotational speed of the ring image was 2, 10, 30, 60 or 90 rpm. It was found that the stereokinetic effect was absent in the majority of children (63.9%) with optic atrophy at a combination of eccentricity of 0.2 and a rotational speed of 2 rpm, in contrast to the control group, where the stereokinetic effect was only absent in 9.1% of children under the same conditions of stimulus presentation. The stereokinetic effect was observed with all eccentricities when the speed of rotation of the test image was 30–90 rpm in children with optic atrophy and 10–90 rpm in children from the control group. The number of children with alternate perception of the virtual cone and the virtual funnel was significantly higher in the control group than in the group of children with optic atrophy at all the test image eccentricities and rotational speeds used. The binocular figure size estimates were equal to the monocular estimates in the group of children with optic atrophy for all the image eccentricities and rotation speeds in contrast to the control group with a general tendency for the virtual cone size estimate to increase under the monocular conditions of observation. An increase in the test image rotation speed from 2 to 60 rpm was accompanied by an increase in the size of a virtual figure and a significant decrease in the duration of alternate dominance of virtual cone and virtual funnel perception in both groups of subjects with all the eccentricities used. The difference between the results obtained in the group of children with POA and in the control group may be explained by reduction of afferent visual information flow. These differences are partially offset by increased speed and increased eccentricity of the test image.

To evaluate the effect of rotational speed and the angle and radius of curvature of root canals on the fracture of two types of nickel-titanium rotary instruments: K3 and ProTaper. A total of 240 root canals of extracted human maxillary and mandibular molars were divided into two groups of 120, according to the angle of the canal curvature (group A: <30 degrees, group B: >30 degrees). Each group was then divided into two subgroups of 60 canals in order to perform instrumentation using K3 and ProTaper rotary instruments at three different rotational speeds: 150, 250 and 350 r.p.m. (20 canals at each rotational speed). Each instrument was used a maximum of 20 times and at one rotational speed only. The angle and radius of canal curvature were measured in the only group in which fractures actually took place (group B). There were a total of 22 instrument fractures; all of these occurred in canals with curves >30 degree. In a multivariate analysis, it was demonstrated that the files used at a rotational speed of 350 r.p.m. were more likely to fracture than those used at 250 r.p.m. (OR: 1113.88; 95% CI: 2.36-526420.05) and than those used at 150 r.p.m. (OR: 13531.33; 95% CI: 5.37-34120254.00). A decrease in the angle of curvature of the canal also significantly reduced the likelihood of fracture (OR: 0.2083; 95% CI: 0.068-0.6502). These relationships remained significant after being adjusted for the potential interactions between the remaining variables. No significant differences were found between the files or the radii of the canals. Instrument fracture was associated with rotational speed and the angle of curvature of the canal.

Microstructure and mechanical characterization of continuous drive friction welded grade 2 seamless titanium tubes at different rotational speeds

Introduction: The origins of Mars' moons, Phobos and Deimos, remain uncertain, with two main hypotheses under consideration: formation from debris following a high-energy impact between Mars and an asteroid [1], or capture of primitive asteroids [2]. To address this, JAXA's Martian Moons eXploration (MMX) mission aims to return samples from Phobos by 2031 [3]. The characterisation of these samples will determine the origin of Phobos.To ground-truth remote observations of Phobos, we have used X-ray diffraction (XRD), and Fourier transform infrared (FTIR) reflectance spectroscopy to characterise the bulk mineralogy and IR spectral properties of ureilites, carbonaceous and ordinary chondrites, the composition of which could be indicative of a captured asteroid [4], and Martian meteorites that could represent a collisional formation. By acquiring XRD and IR data from the same material, mineral abundances can be directly correlated with features in reflectance spectra [5]. When MMX reaches Phobos, meteorite data collected in the laboratory will play a crucial role towards interpreting the mineralogy and composition of materials on its surface.Methods: We have characterised the mineralogy and spectral properties of six CM (Mighei-like) carbonaceous chondrites, Tarda (C2-ung), the CO (Ornans-like) chondrite Kainsaz, a range of shock darkened ordinary chondrites (mostly falls) including L4-6, and H5-6, four CR2 chondrites, four ureilites, Martian meteorites Nakhla and Tissint, and a Tagish Lake (C2-ung) based simulant created by the University of Tokyo, known as UTPS-TB [6]. For the meteorites, chips of approximately 200 mg were ground to produce powders with grain sizes of less than 40 microns. The UTPS-TB sample came in a powdered form which was ground to the same grain size as the meteorites.Diffuse reflectance spectra (1.7 - 50 μm) were collected using a Bruker VERTEX 70V FTIR spectrometer at the University of Oxford Planetary Spectroscopy Facility. Spectra were calibrated at the start of each measurement day and between measurements of samples using a gold standard. The powdered sample was measured under a vacuum to reduce terrestrial atmospheric contributions.XRD patterns of the same powders were collected using an INEL X-ray diffractometer with a position-sensitive detector at the Natural History Museum, London. Around 50 mg of powdered sample was measured for 16 hours to achieve good signal-to-noise. Measurements of well-characterised standard minerals were collected for 30 minutes and compared with meteorite patterns to identify minerals and quantify their abundance in the sample [e.g. 7].Results &amp; Discussion: The mineralogical and spectral characteristics of meteorites in this investigation are compared the reflectance spectra of Phobos’ surface. The CR chondrites are primitive, containing both anhydrous silicates (e.g. olivine and pyroxene) and aqueous alteration phases such as phyllosilicates, carbonates, magnetite, and sulfides. Their albedo is ~3-5% reflectance with a weak red slope in the visible to near-infrared (VNIR). The CRs have a 3 μm hydration band, due to partial aqueous alteration. Their low VNIR reflectance, red-sloped continuum, and weak 3 μm spectral absorption feature is like that of Phobos, supporting the captured asteroid origin theory. The CM chondrites share similar spectral features but have a lower albedo and a stronger μm hydration band, corresponding to a higher phyllosilicate composition. The ureilites are achondritic ultramafic meteorites containing olivine, pyroxene and carbon phases. These samples have a low albedo (~6-15% in VNIR) due to their opaque carbonaceous composition. However, their VNIR spectra are blue-sloped, inconsistent with Phobos’ red-sloped spectra. Ureilites are also anhydrous and therefore lack the 3 μm hydration band seen in Phobos spectra. Their low reflectance and feature-poor spectra could resemble Phobos, however there is a significant difference in spectral slope and hydration features. Therefore, Phobos were composed of ureilitic material, its surface would need to be significantly modified by space weathering.Martian meteorites Nakhla (a nakhlite) and Tissint (a shergottite) have mineralogical and spectral features consistent with their basaltic origin. XRD measurements of these meteorites are dominated by pyroxene (augite, pigeonite), and olivine, consistent with their origin in the Martian crust. Their reflectance spectra have relatively high albedo, mafic absorption bands at ~1 and 2 μm, and a lack of hydration features. These features are inconsistent with the spectra of Phobos, which lack 1 or 2 μm bands and show significantly lower reflectance.CR and CM chondrites are the closest spectral match to Phobos from the samples studied. Their low albedo, red-sloped, hydrated spectra are consistent with surface measurements of Phobos. Ureilites share low reflectance but differ significantly in slope and hydration, while Martian meteorites differ in more spectral characteristics. These results support the interpretation that Phobos is composed of primitive, carbon-rich material, likely of outer solar system origin, and favour a capture scenario over a collisional formation from Martian ejecta. The similarities between the carbonaceous chondrites and Phobos indicates that the Martian moons may be captured asteroids and further demonstrates the importance of the MMX mission sample return for solving the mystery of their origin definitively.