Numerical and experimental study of variable speed automobile engine cooling water pump

Dynamics of a powered disk in clay soil

The affinity law is widely used in pump design and experiments. The applicability of the affinity law in an emergency drainage pump at different rotating speeds was studied. Experiments and numerical simulation through ANSYS CFX (Computational Fluid Dynamics X) 15.0 software were used to research the affinity law characteristics. Results show that the simulation of characteristics is basically consistent with the experimental curves. In small flow rate conditions, due to the existence of obvious differential pressure between the pressure side and the suction side in the impeller blade tip area, the leakage flow occurs at the tip clearance, which collides with the main stream at the inlet and generates vortices at the leading edge of the impeller. The tip leakage flows of the pump at four different rotating speeds were compared, and it was found that the tip leakage increased with increasing rotation speed, and at the same rotation speed, the tip leakage flow was large in the small flow rate condition, which led to the simulation value of the characteristics being greater than the scaling value. As the flow rate increased, the anti-cavitation performance of the pump became worse and the hydraulic loss was larger, so the pump’s performance curve deviated from the scaling curve.

Compared with conventional high-specific-speed axial flow pump, better cavitation performance and compact size have been achieved in contra-rotating axial flow pump, where the rear rotor is employed additionally to the front rotor to convert the swirling flow to the pressure rise. Meanwhile, significantly deteriorated performance has also been observed at well off-design flow rates with design rotational speed. The rotational speed control (RSC) of front and rear rotors has been experimentally proved to be effective to enhance the performance. However, thorough investigations are necessary to find the optimum rotational speeds of rotors. It may be done by computational fluid dynamics (CFD) simulations, whereas it is time-consuming to cover the wide ranges of rotational speeds. Therefore, in the present paper, a fast and effective performance prediction model is established by considering radial equilibrium condition, conservation of rothalpy and mass, empirical deviation angle, bladerows interaction and empirical losses. Experimental and CFD results are employed to validate the proposed prediction model. It is found that the proposed model shows good enough accuracy in predicting performances of contra-rotating axial flow pump under RSC in broad flow rate range. Furthermore, an energy saving application of the proposed model is also illustrated for two typical system resistances. Compared with the traditional valve control under the design rotational speed operation, the RSC method can well modify the pump head to satisfy the system resistance at wide flow rate range with the significantly improved energy performance.

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

A test stand to determine the performance of a dynamic-static rotor separator is described. An experimental study has been conducted of the separator at different air flow rate and rotor rotating speeds with pulverized coal serving as a raw material. Experimental results indicate that either an increase of the rotor rotating speed or a decrease of the air flow rate can increase the fineness of the pulverized coal at the outlet of the separator, whose value of R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">45</sub> can be as low as 0. As the rotor rotating speed increases, the comprehensive separation efficiency decreases in general, but it fluctuates at high rotational speed. The comprehensive separation efficiency rises as the air flow rate increases. In gas-solid two-phase flow, there is the minimum pressure drop as the rotational speed increases and the pressure drop has an accelerative increase as the air flow rate increases.

The two phase program addresses long-term developments in deep well and hard rock drilling. TerraTek believes that significant improvements in drilling deep hard rock will be obtained by applying ultra-high rotational speeds (greater than 10,000 rpm). The work includes a feasibility of concept research effort aimed at development that will ultimately result in the ability to reliably drill ''faster and deeper'' possibly with smaller, more mobile rigs. The principle focus is on demonstration testing of diamond bits rotating at speeds in excess of 10,000 rpm to achieve high rate of penetration (ROP) rock cutting with substantially lower inputs of energy and loads. The significance of the ultra-high rotary speed drilling system is the ability to drill into rock at very low weights on bit and possibly lower energy levels. The drilling and coring industry today does not practice this technology. The highest rotary speed systems in oil field and mining drilling and coring today run less than 10,000 rpm--usually well below 5,000 rpm. This document details the progress to date on the program entitled ''Smaller Footprint Drilling System for Deep and Hard Rock Environments: Feasibility of Ultra-High-Speed Diamond Drilling'' for the period starting 1 October 2004 through 30 September 2005. Additionally, research activity from 1 October 2005 through 28 February 2006 is included in this report: (1) TerraTek reviewed applicable literature and documentation and convened a project kick-off meeting with Industry Advisors in attendance. (2) TerraTek designed and planned Phase I bench scale experiments. Some difficulties continue in obtaining ultra-high speed motors. Improvements have been made to the loading mechanism and the rotational speed monitoring instrumentation. New drill bit designs have been provided to vendors for production. A more consistent product is required to minimize the differences in bit performance. A test matrix for the final core bit testing program has been completed. (3) TerraTek is progressing through Task 3 ''Small-scale cutting performance tests''. (4) Significant testing has been performed on nine different rocks. (5) Bit balling has been observed on some rock and seems to be more pronounces at higher rotational speeds. (6) Preliminary analysis of data has been completed and indicates that decreased specific energy is required as the rotational speed increases (Task 4). This data analysis has been used to direct the efforts of the final testing for Phase I (Task 5). (7) Technology transfer (Task 6) has begun with technical presentations to the industry (see Judzis).

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.

The effects of rotor speed (417 to 1000 rev/s) on yarn quality were investigated. The following parameters were also varied: rotor diameter and configuration, card type, cotton-fiber properties, and type of takeoff navels. The strength of a 49 mg/m yarn increased as rotor speed increased to 667 rev/s, and then decreased, whereas the strength of 25 mg/m yarn decreased with increased rotor speed. A latively fine, strong-fibered cotton was necessary for spinning at high rotor speeds. However, the difference in strength between yarns from a carded cotton and yarns from a combed cotton was less at high rotor speeds, evidently as a result of more wrappers and greater fiber breakage with longer fibers. Any factor that increased the twisting torque to the yarn-formation point in the rotor, such as large-diameter rotors, fast rotor speeds, and grooves in the takeoff navel, produced yarns with poorer fiber orientation and short-term uniformity. Also, high rotor speeds reduced the fiber parallelazation of the fiber ring in the rotor.

The study of flow field characteristics inside the tip clearance is essential for understanding tip leakage flow (TLF) generation mechanisms. This paper investigates the TLF flow field in a single-stage axial compressor using a particle image velocimetry visualization system, alongside proper orthogonal decomposition and omega vortex identification methods, to analyze the flow at the mid-axial cross section under varying rotational speeds. The results reveal that the time-averaged flow field inside the clearance can be divided into four distinct regions, largely unaffected by speed variations: the high-speed region at the blade leading edge, the diverting and steering region of TLF, the TLF and main stream convergence region, and the trailing edge low-velocity region. Notably, two distinct directions of TLF are observed. At the blade leading edge, TLF flows directly from the upstream field to the lower blade, with a maximum velocity of approximately 2.2 times that of the main flow. Between 30% and 40% of the blade length, radial vortices dominate the diverting and steering of the main flow, forming a precessing vortex structure. Subsequently, TLF from the pressure side accelerates upstream, intersecting with the main flow to form a low-velocity tip leakage vortex region, obstructing the upstream flow. As rotational speed increases, the diverging and steering region shifts downward, and the disturbances in the internal and upstream flow fields further intensify. Furthermore, TLF from the downstream field bypassing the tip is observed between blades. These findings offer valuable data to improve understanding and optimize control strategies of TLF.

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

A 6061-T6 aluminum alloy was self-reacting friction stir welded by using the specially designed tool with unequal shoulder diameters at a constant welding speed of 150 mm/min to investigate the effect of rotation speed on microstructure and mechanical properties of the joints. Excessive flash on the bottom surface of the joint and groove defects on both surfaces of the joint were formed when the lower shoulder diameter was much smaller. The suitable shoulder sizes were determined as 16 and 18 mm in lower shoulder diameter and upper shoulder diameter, respectively. The grain size and the dislocation density in the weld nugget zone (WNZ) increased with increasing rotation speed. The tensile strength of joints first increased with increasing rotating speed and then decreased remarkably as a result of the formation of void defect. The joints welded at lower rotation speeds were fractured in the thermal mechanically affected zone (TMAZ). However, the fracture locations of the defect-free joints were changed to the heat affected zone (HAZ) at higher rotation speeds.

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.

In this article, a numerical investigation was performed on a quadrotor UAV propeller with the aim of examining effects of airspeed and rotational speed on thrust coefficient, which is one of the most important parameters on propeller aerodynamic performance. In that purpose, Computational Fluid Dynamics (CFD) analyses of an 11-inch propeller were carried out at different airspeeds and rotational speeds in vertical climbing flight condition. In order to have optimum number of mesh elements in computational domain, mesh independence analyses were also conducted. In conclusion, results of the analyses with k-ω SST turbulence model were shown that, increase in rotational speed was leaded to higher turbulent kinetic energy. Furthermore, higher rotational speeds also resulted in higher differences between numerical estimations and experimental data, but found to become more independent from airspeed.

In order to avoid the high cycle fatigue which leads to the failure of turbine blades, friction structural damping has been widely used in turbine blade designs to reduce vibratory stresses by energy dissipation. A method is developed here to analyze the influence of friction structural damping on the vibration characteristics of turbine blades. Vibratory responses of a long steam turbine blade with shroud and snubber are studied. Finite element contact analysis of the steam turbine blades which are modeled in 3-D solid elements is conducted to obtain the normal contact force on the shroud contact surface and snubber contact surface of adjacent blades under five different rotational speeds (2100rpm, 2200rpm, 2413rpm, 2600rpm and 3000rpm). A rig for the tests of non-rotating turbine blade with friction damping structure is built. The normal contact forces of the shroud and snubber are applied to the blade according to numerical results. The response curves and modal damping ratios of the blade under different normal contact forces, which each one is related to a different rotational speed, are obtained. The experimental results show that with increases in rotational speed, modal damping ratio of the blade experiences an increasing period followed by a decreasing period while the resonance amplitude decreases first and then increases when there is only shroud contact. The effects are similar when there are both shroud and snubber contact. The modal damping ratio of the blade is basically identical with that of the uncoupled blade for the rotational speed above 2600rpm. For this range of rotational speed, the resonance frequency increases with the increase of rotational speed, and the changes of the resonance frequency are very trivial.

To investigate the influence of Coriolis force on vibration characteristics of mistuned bladed disk, a bladed disk with 22 blades is employed and the effects of different rotational speeds and excitation engine orders on the maximum forced response are discussed considering the effects of Coriolis forces. The results show that if there are frequency veering regions, the largest split of double natural frequencies of each modal family considering the effects of Coriolis forces appears at frequency veering region. In addition, the amplitude magnification factor considering the Coriolis effects is increased by 1.02% compared to the system without considering the Coriolis effects as the rotating speed is 3000 rpm, while the amplitude magnification factor is increased by 2.76% as the rotating speed is 10000 rpm. The results indicate that the amplitude magnification factor may be moderately enhanced with the increasing of rotating speed. Moreover, the position of the maximum forced response of bladed disk may shift from one blade to another with the increasing of the rotational speed, when the effects of Coriolis forces are considered.