Pressure Torque Research Articles

Processability and mechanical properties of extensively recycled high density polyethylene

In plastics industry it is a common practice to mechanically recycle waste material arising from production. However, while plastics are mechanically recycled, their mechanical properties change. These changes may affect material processing conditions and quality of the end products; therefore they need to be quantified. In this study, mechanical recycling of high density polyethylene (HDPE) was simulated by one-hundred (100) consecutive extrusions cycles. During extrusion, processability of virgin HDPE and its recyclates was studied by recording the processing conditions, i.e. melt pressure and extrusion torque, while after preparation of the recyclates, melt flow index measurements (MFI), small amplitude oscillatory shear tests (rheological properties), and differential scanning calorimetry measurements (DSC) of thermal properties were performed. Also, mechanical properties in solid state were characterized in terms of hardness and modulus measured by nanoindentation, and finally, shear creep compliance was measured to characterize the materials' time-dependent mechanical properties and its durability in solid state. In addition, gel permeation chromatography (GPC) and solubility tests were implemented to study changes in the material structure.The results on rheological and MFI measurements indicate significant structural changes in the material that occurred during the first 30 extrusion cycles. Those changes affect material processability which is as well supported by the recorded processing pressure and torque. On the other hand, processing did not significantly affect material thermal properties. Results on hardness and modulus show deterioration of the material mechanical properties after 10th reprocessing cycle. Similarly, shear creep compliance measurements showed an unfavourable effect of mechanical recycling on the time-dependent mechanical properties, particularly after the 30th extrusion cycle. In addition, results suggested chain branching as a dominating mechanism through first 30 extrusion cycles, domination of chain scission afterwards and also presence of cross-linking after 60th extrusion cycle.

Advance speed-based parametric study of greenfield deformation induced by EPBM tunneling in soft ground

For earth pressure balance machines advancing through soft ground, it is essential to control the mechanical driving parameters, such as skin friction, face pressure and cutter torque, to minimize the influence on the surrounding environment. A test at a greenfield site was conducted to determine the tunneling-induced soil deformation and the relationship between the mechanical driving parameters and advance speed. A method based on fuzzy statistics was proposed to calculate the standard values and deviations of the advance speed and mechanical driving parameters at the normal state of advancement. A finite element model verified by field measurements was employed to investigate the greenfield response and the effect of the mechanical driving parameters on soil deformation. Further, the response of soil deformation to the mechanical driving parameters was analyzed at the normal state of advancement. The results showed that at the normal state of deep advancement, the skin friction deviation had the greatest influence on the displacement of both the surface and subsurface. Increasing the skin friction increased the settlement above the tunnel and reduced the heave beneath the tunnel. The higher face pressure resulted in smaller settlement near the tunnel crown and heave near the tunnel invert. The larger cutter torque was only able to increase settlement near the tunnel crown. The combined effect of the mechanical driving parameter deviations was dominated by skin friction for the surface settlement. Regarding the subsurface vertical displacement near the tunnel, an offsetting or superimposed effect occurred at various advance stages. The mechanical driving parameter deviations based on a higher advance speed reduced the vertical displacement above the tunnel.

Topographic Coupling of the Atlantic Overturning and Gyre Circulations

AbstractThe vorticity dynamics associated with the mean and time-varying gyre and overturning circulations of the Atlantic Ocean are examined in a realistic ocean model hindcast simulation of the late twentieth century. Abyssal flow interaction with sloping bottom bathymetry gives rise to the bottom pressure torque (BPT) term of the vertically integrated vorticity equation. The dominance of this term in the closure of the barotropic gyre circulation noted in previous studies is corroborated here for both non-eddy-resolving and eddy-resolving versions of the Parallel Ocean Program (POP) model. This study shows that BPT is also a dominant term in the vorticity balance of the Atlantic meridional overturning circulation (AMOC) and therefore represents a key dynamical link between the overturning and gyre streamfunctions. The interannual variability of the Atlantic circulation over the last several decades, viewed in terms of time-varying integral vorticity balances, demonstrates the fundamental role played by BPT in coupling the large-scale barotropic and baroclinic flows. Forcing perturbation experiments show how flow–bathymetry interactions mediate buoyancy-driven changes in the gyre circulation and momentum-driven changes in the AMOC. Examples of topographic coupling of the overturning and gyre circulations that this analysis elucidates include the covariation of the high-latitude AMOC and subpolar gyre flows on decadal time scales, buoyancy-forced variance of the Gulf Stream, and large wind-driven variations in AMOC at subtropical latitudes.

Optimization of Steering System of Forklift Vehicle for Idle Performance

This paper presents an optimal design process for the steering system of a forklift vehicle. An efficient procedure for minimizing the engine-induced idle vibration is developed in this study. Reciprocating unbalance and gas pressure torque as two major sources of engine excitation are studied. Using the field vibration tests and FEM analysis, the cause and characteristics of steering system’s idle vibration are recognized. So as to distribute the characteristic modes based on the optimization strategy, global sensitivity analysis of the main parameters is also carried out to achieve the optimal combination of the optimization factors. Based on all analysis above, some structure modifications for optimization are presented to control the idle vibration. The effectiveness and rationality of the improvements are also verified through experimental prototyping testing. This study also makes it possible to provide a design guideline using CAE (computer aided engineering) analysis for some other objects.

급기가 프란시스 수차의 수압 맥동에 미치는 영향

In this study pressure and shaft torque pulsation were measured with variation of head and flow during the model test for a 15 MW Francis Turbine. Pressure pulsations were measured at the inlet of the spiral casing and 4 points in the cone of the diffuser and shaft torque pulsation at the upper position of the turbine. The maximum amplitude of pressure pulsation appeared 2.03% of the maximum rated head with the frequency of 25% of the rated revolution and at the guide vane opening of <TEX>$10^{\circ}$</TEX>. Shaft torque pulsation appeared 0.01% of the rated shaft torque, fairly low value. Air was admitted through the cone and pressure pulsation gradually decreased with increase of air flow and kept nearly constant after 5% of the rated flow. A new Francis turbine of which specific speed is 115 m-kW had been designed to rehabilitate the old one and the model test was performed at EPFL. The commercial code, STAR-<TEX>$CCM^+$</TEX> was used for numerical simulation of flow.

Combustion analysis of microalgae methyl ester in a common rail direct injection diesel engine

In this study, the biodiesel properties and effects of blends of oil methyl ester petroleum diesel on a CI direct injection diesel engine is investigated. Blends were obtained from the marine dinoflagellate Crypthecodinium cohnii and waste cooking oil. The experiment was conducted using a four-cylinder, turbo-charged common rail direct injection diesel engine at four loads (25%, 50%, 75% and 100%). Three blends (10%, 20% and 50%) of microalgae oil methyl ester and a 20% blend of waste cooking oil methyl ester were compared to petroleum diesel. To establish suitability of the fuels for a CI engine, the effects of the three microalgae fuel blends at different engine loads were assessed by measuring engine performance, i.e. mean effective pressure (IMEP), brake mean effective pressure (BMEP), in cylinder pressure, maximum pressure rise rate, brake-specific fuel consumption (BSFC), brake thermal efficiency (BTE), heat release rate and gaseous emissions (NO, NOx, and unburned hydrocarbons (UHC)). Results were then compared to engine performance characteristics for operation with a 20% waste cooking oil/petroleum diesel blend and petroleum diesel. In addition, physical and chemical properties of the fuels were measured. Use of microalgae methyl ester reduced the instantaneous cylinder pressure and engine output torque, when compared to that of petroleum diesel, by a maximum of 4.5% at 50% blend at full throttle. The lower calorific value of the microalgae oil methyl ester blends increased the BSFC, which ultimately reduced the BTE by up to 4% at higher loads. Minor reductions of IMEP and BMEP were recorded for both the microalgae and the waste cooking oil methyl ester blends at low loads, with a maximum of 7% reduction at 75% load compared to petroleum diesel. Furthermore, compared to petroleum diesel, gaseous emissions of NO and NOx, increased for operations with biodiesel blends. At full load, NO and NOx emissions increased by 22% when 50% microalgae blends were used. Petroleum diesel and a 20% blend of waste cooking oil methyl ester had emissions of UHC that were similar, but those of microalgae oil methyl ester/petroleum diesel blends were reduced by at least 50% for all blends and engine conditions. The tested microalgae methyl esters contain some long-chain, polyunsaturated fatty acid methyl esters (FAMEs) (C22:5 and C22:6) not commonly found in terrestrial-crop-derived biodiesels yet all fuel properties were satisfied or were very close to the ASTM 6751-12 and EN14214 standards. Therefore, C.cohnii- derived microalgae biodiesel/petroleum blends of up to 50% are projected to meet all fuel property standards and, engine performance and emission results from this study clearly show its suitability for regular use in diesel engines.

Effect of Distal Ulnar Collateral Ligament Tear Pattern on Contact Forces and Valgus Stability in the Posteromedial Compartment of the Elbow

Background: It is not known whether the pattern of ulnar collateral ligament (UCL) tear affects elbow biomechanics. Hypothesis: There will be a significant change in elbow biomechanics with 50% proximal but not 50% distal simulated rupture of the UCL. Study Design: Controlled laboratory study. Methods: Pressure sensors in the posteromedial elbow joint of 25 male cadaveric elbows (average age, 54.9 years; range, 26-66 years) were used to measure contact area, pressure, and valgus torque at 90° and 30° of elbow flexion. Thirteen specimens were tested with the UCL intact, then with proximal-to-distal detachment of 50%, and then with proximal-to-distal detachment of 100% of the anterior band of the UCL from the ulnar attachment. This method was repeated in the remaining 12 specimens in a distal-to-proximal direction. Results: With 50% proximal-to-distal detachment, contact area decreased significantly versus intact at 90° (91.3 ± 23.6 vs 112.2 ± 26.0 mm2; P < .001) and 30° (69.3 ± 14.8 vs 83.1 ± 21.6 mm2; P < .001) of elbow flexion; the center of pressure (COP) moved significantly proximally versus intact at 90° (3.8 ± 2.5 vs 5.4 ± 2.3 mm; P < .001) and 30° (5.9 ± 2.8 vs 7.4±1.9 mm; P < .001). With 50% distal-to-proximal UCL detachment versus intact, no significant change was observed in contact area, movement of the COP, or valgus laxity at either flexion position. With 100% proximal-to-distal and distal-to-proximal detachment, significant change in contact area, movement of the COP, and valgus laxity versus intact was found at 90° and 30° of elbow flexion (P < .05). No significant difference in contact pressure was observed in any test conditions. Conclusion: Significant change in contact area and proximal movement of the COP with 50% proximal UCL detachment and the lack of significant change with 50% distal UCL detachment suggest that the proximal half of the UCL ulnar footprint has a primary role in maintaining posteromedial elbow biomechanics. Clinical Relevance: The findings suggest that surgical reconstruction should aim to reestablish at least the proximal 50% of the UCL ulnar footprint.

Modeling and Simulation of Two-Stage Expansion Air-Powered Engine

Thermodynamic simulation of a two-stage expansion air-powered engine was established and working process simulation was conducted based on this model. The effects of inlet pressure (0.8Mpa-3.0Mpa), intake duration angle of second-stage (100°CA-160°CA) and cylinder diameter of second-stage (120mm-200mm) on the gas temperature, pressure and output torque were analyzed. The results show that effective power and output torque both increase with the increase of above three parameters, meanwhile effective gas consumption rate decreases.

Rocking motion of an optical wing: theory.

The intensity-dependent rocking frequency of an illuminated semicylindrical refractive rod (or "optical wing") on a flat, nonslip surface is investigated. Both longitudinal and transverse radiation pressure forces (scatter and lift forces), as well as radiation pressure torque, transform the mechanical system into one having a bistable potential energy above a critical intensity. The equation of motion may be written as a parametrically driven nonlinear bistable harmonic oscillator, resulting in complex rocking dynamics. The effects of linear and sinusoidal intensity modulation schemes are explored, and experimental conditions to verify these results are discussed.

Equilibration of the Antarctic Circumpolar Current by Standing Meanders

Abstract The insensitivity of the Antarctic Circumpolar Current (ACC)’s prominent isopycnal slope to changes in wind stress is thought to stem from the action of mesoscale eddies that counterbalance the wind-driven Ekman overturning—a framework verified in zonally symmetric circumpolar flows. Substantial zonal variations in eddy characteristics suggest that local dynamics may modify this balance along the path of the ACC. Analysis of an eddy-resolving ocean GCM shows that the ACC can be broken into broad regions of weak eddy activity, where surface winds steepen isopycnals, and a small number of standing meanders, across which the isopycnals relax. Meanders are coincident with sites of (i) strong eddy-induced modification of the mean flow and its vertical structure as measured by the divergence of the Eliassen–Palm flux and (ii) enhancement of deep eddy kinetic energy by up to two orders of magnitude over surrounding regions. Within meanders, the vorticity budget shows a balance between the advection of relative vorticity and horizontal divergence, providing a mechanism for the generation of strong vertical velocities and rapid changes in stratification. Temporal fluctuations in these diagnostics are correlated with variability in both the Eliassen–Palm flux and bottom speed, implying a link to dissipative processes at the ocean floor. At larger scales, bottom pressure torque is spatially correlated with the barotropic advection of planetary vorticity, which links to variations in meander structure. From these results, it is proposed that the “flexing” of standing meanders provides an alternative mechanism for reducing the sensitivity of the ACC’s baroclinicity to changes in forcing, separate from an ACC-wide change in transient eddy characteristics.

Elasto-dynamic analysis of a gear pump–Part III: Experimental validation procedure and model extension to helical gears

This work concerns external gear pumps for automotive applications, which operate at high speed and low pressure. In previous works of the authors (Part I and II, [1,2]), a non-linear lumped-parameter kineto-elastodynamic model for the prediction of the dynamic behaviour of external gear pumps was presented. It takes into account the most important phenomena involved in the operation of this kind of machine. The two main sources of noise and vibration are considered: pressure pulsation and gear meshing. The model has been used in order to foresee the influence of working conditions and design modifications on vibration generation. The model׳s experimental validation is a difficult task. Thus, Part III proposes a novel methodology for the validation carried out by the comparison of simulations and experimental results concerning forces and moments: it deals with the external and inertial components acting on the gears, estimated by the model, and the reactions and inertial components on the pump casing and the test plate, obtained by measurements. The validation is carried out comparing the level of the time synchronous average in the time domain and the waterfall maps in the frequency domain, with particular attention to identify system resonances. The validation results are satisfactory globally, but discrepancies are still present. Moreover, the assessed model has been properly modified for the application to a new virtual pump prototype with helical gears in order to foresee gear accelerations and dynamic forces. Part IV is focused on improvements in the modelling and analysis of the phenomena bound to the pressure evolution around the gears in order to achieve results closer to the measured values. As a matter of fact, the simulation results have shown that a variable meshing stiffness has a notable contribution on the dynamic behaviour of the pump but this is not as important as the pressure phenomena. As a consequence, the original model was modified with the aim at improving the calculation of pressure forces and torques. The improved pressure formulation includes several phenomena not considered in the previous one, such as the variable pressure evolution at input and output ports, as well as an accurate description of the trapped volume and its connections with high and low pressure chambers. The importance of these improvements are highlighted by comparison with experimental results, showing satisfactory matching.

Elasto-dynamic analysis of a gear pump–Part IV: Improvement in the pressure distribution modelling

This work concerns external gear pumps for automotive applications, which operate at high speed and low pressure. In previous works of the authors (Part I and II, [1,2]), a non-linear lumped-parameter kineto-elastodynamic model for the prediction of the dynamic behaviour of external gear pumps was presented. It takes into account the most important phenomena involved in the operation of this kind of machine. The two main sources of noise and vibration are considered: pressure pulsation and gear meshing. The model has been used in order to foresee the influence of working conditions and design modifications on vibration generation. The model experimental validation is a difficult task. Thus, Part III proposes a novel methodology for the validation carried out by the comparison of simulations and experimental results concerning forces and moments: it deals with the external and inertial components acting on the gears, estimated by the model, and the reactions and inertial components on the pump casing and the test plate, obtained by measurements. The validation is carried out by comparing the level of the time synchronous average in the time domain and the waterfall maps in the frequency domain, with particular attention to identify system resonances. The validation results are satisfactory global, but discrepancies are still present. Moreover, the assessed model has been properly modified for the application to a new virtual pump prototype with helical gears in order to foresee gear accelerations and dynamic forces. Part IV is focused on improvements in the modelling and analysis of the phenomena bound to the pressure distribution around the gears in order to achieve results closer to the measured values. As a matter of fact, the simulation results have shown that a variable meshing stiffness has a notable contribution on the dynamic behaviour of the pump but this is not as important as the pressure phenomena. As a consequence, the original model was modified with the aim at improving the calculation of pressure forces and torques. The improved pressure formulation includes several phenomena not considered in the previous one, such as the variable pressure evolution at input and output ports, as well as an accurate description of the trapped volume and its connections with high and low pressure chambers. The importance of these improvements are highlighted by comparison with experimental results, showing satisfactory matching.

A Total Flow Perspective of Atmospheric Mass and Angular Momentum Circulations: Boreal Winter Mean State

Abstract This paper reports a comprehensive diagnostic analysis of mass and angular momentum (AM) circulations and their budgets in boreal winter using the 32-yr daily NCEP–Department of Energy (DOE) reanalysis (1979–2010). The diagnosis is performed using instantaneous total flows before taking time and zonal average without decomposition of time mean and transient flows and separation of zonal mean and wavy flows. The analysis reveals that embedded in a broad hemispheric thermally direct meridional mass circulation in each hemisphere are three distinct but interconnected thermally direct meridional cells. They are the tropical Hadley cell, the stratospheric cell, and the extratropical zonally asymmetric Hadley cell. The tropical Hadley cell corresponds to the Hadley cell of the classic three-cell model whereas the extratropical Hadley cell and the stratospheric cell correspond to the eddy-driven extratropical residual circulation. The joint consideration of meridional mass and AM circulations helps to substantiate Hadley’s original view that the hemispheric-wide thermally direct meridional circulation can have broad surface easterly in the tropics and westerly in the extratropics. Because the mass circulation cannot have a net divergence anywhere in long time mean and the earth’s AM decreases toward the poles, the companion AM transport in the equatorward cold air branch inevitably has to be divergent. The downward transfer of westerly AM to the cold air branch by the pressure torque associated with westward tilted baroclinic waves dominates such divergence in the extratropics, explaining the prevailing surface westerly there. In the tropics and polar region where the meridional circulation is nearly zonally symmetric, the dominance of this divergence results in a surface easterly there.

Optimum design of a saw-tooth-shaped dental air-turbine using design of experiment

Air turbine high-speed handpieces have been used in dental cutting for more than 40 years. The air turbine is main part of the dental handpiece. High-pressure air enters the turbine and strikes the blades to drive the turbine rotor. The effects of the air-turbine blade configuration were investigated for the optimum air-turbine design by using ANSYS CFX. The objective of the research was to find an optimum design of the air-turbine blade configuration to increase the torque. Design of Experiments was used for the optimization process of the turbine. The airflow inside the air turbine was analyzed by changing the shape of the turbine blade using the blade tip width and angle of the turbine blade as the design variables. The variables of the turbine were generated by Minitab and evaluated by the torque. The pressure distribution and torque were obtained and analyzed for each blade shape. The influences of the design variables on the air-turbine performance were analyzed by Analysis of Variance. The blade shape was optimized by comparing the torque values of the various turbine blades. The optimum design variables were found when the blade tip width and angle of the blade were 0.2 mm and 80°, respectively.

大口径宽波段高能激光发射窗口的设计与测试

An automatic shutter-type mechanical window was designed for the multi-band, high-power and large-caliber laser launch system to meet the requirements of complex service environment for long interval emission and crystal window. The window is composed of two parts of the dust cover: pressing mechanism and driving mechanism. By using transmission links, such as screw, wire rope, and time synchronous belt, the pressing mechanism realizes multi-task driving of a single motor synchronously and the flexible hinges compensate installation errors. Then the relationship between wind pressure forced on dust cover and pressing force of the pressing mechanism was analyzed by nonlinear analysis methods and integral principles. The expression of wind pressure and motor torque was established by inverse method. According to the relationship of motor torque and frequency, the rotating speed range of the mechanism and the largest wind pressure of the dust cover were calculated. Experimental results show when the motor output torque is 0.341 Nm, the mechanism can resist the impact of wind of 10 m/s. The least intervals of the window are stably within 3 s no matter it is opened or closed. The relative calculation error of the expression between wind pressure and motor output torque is less than 15%, which satisfies working requirements of systems.

The control of the Southern Hemisphere Westerlies on the position of the Subtropical Front

In recent years the latitudinal position of the Subtropical Front (STF) has emerged as a key parameter in the global climate. A poleward positioned front is thought to allow a greater salt flux from the Indian to the Atlantic Ocean and so drive a stronger Atlantic Meridional Overturning Circulation. Here the common view that the STF aligns with the zero wind stress curl (WSC) is challenged. Based on the STF climatologies of Orsi et al. (1995), Belkin and Gordon (1996), Graham and De Boer (2013), and on satellite scatterometry winds, we find that the zero WSC contour lies on average approximate to 10 degrees, approximate to 8 degrees, and approximate to 5 degrees poleward of the front for the three climatologies, respectively. The circulation in the region between the Subtropical Gyres and the zero WSC contour is not forced by the WSC but rather by the strong bottom pressure torque that is a result of the interaction of the Antarctic Circumpolar Current with the ocean floor topography. The actual control of the position of the STF is crucially dependent on whether the front is regarded as simply a surface water mass boundary or a dynamical front. For the Agulhas Leakage problem, the southern boundary of the so-called Super Gyre may be the most relevant property but this cannot easily be identified in observations.

Calculation and Applied Research of Satellite Solar Radiation Pressure Torque

Satellite solar radiation pressure torque is one of the major long-term interference after the satellite finishes positioning and starts to working. However, there is no method to verify the calculation of solar radiation pressure torque. This paper is to analyze the in-orbit telemetry data of satellite DFH-3. Based on the results of data fitting and pressure torque calculation, the paper aims to test the accuracy of the calculation methods.

Study of Airship Stability Based on a Low Resistance Profile

Numerical simulation was conducted to investigate the external flow around airships with different tail layout, with the help of FLUENT 14.5, based on the incompressible Navier-Stokes equation and SST turbulent model. The aerodynamic information of the airships with different tail layout, such as pressure coefficient, torque coefficient and pressure distribution, were analyzed, and the numerical results showed the details of the airship surface flow and changes with different attack angle. According to the results, different tail layout had important influences on the aerodynamics and stability of airship. This will help to understand the aerodynamic characters around the tails of the stratospheric airship, and provide a reference in choosing tail layouts and the stability design of airships.

Logic Threshold Based Energy Control Strategy for Parallel Hydraulic Hybrid Vehicles

To improve the performance of a Parallel Hydraulic Hybrid Vehicle (PHHV), the operation of components in the hydraulic hybrid system of the vehicle should be well coordinated. This study introduces an energy control strategy based on the logic threshold methodology for PHHVs. The energy distribution of the PHHV can be controlled in real-time and the operation modes of the PHHV can be changed dynamically by means of this energy control strategy. A simulation model for the analysis of the whole vehicle dynamic performance is developed using the Simulink in MATLAB. The multi-objective Genetic Algorithm (GA) optimization method is employed to get the optimal working modes, the best energy distribution in different drive cycles and the optimal parameters of the control strategy. In this optimization, maximum fuel economy is the objective and the difference of engine optimal torque and active pressure torque and the pressure limit are the variables of the GA optimization. The simulation results show that the fuel economy of the PHHV can be improved and in addition, the dynamic performance of the vehicle can be enhanced with the proposed energy control strategy.

The Finite Element Analysis of a Shaft

Finite element method is a kind of method with the aid of computer engineering analysis of discretization numerical calculation. In the rotary steering drilling during the process of practical work, there was a great drilling pressure torque, space size limit strictly and requires a high efficiency and reliability .The working conditions are complex when drillings work underground and the working environment is harsh, there may has many unpredictable situations, the drilling tool may encounter the loose soil, or may be a hard rock, and these changes force is transmitted through the variation cardan shaft, so it is very necessary to check the strength of the variation cardan shaft. This article analyze the variation cardan shaft by ANSYS and provide a reference for actual use.