Rotational speed

About: Rotational speed is a research topic. Over the lifetime, 23327 publications have been published within this topic receiving 151696 citations. The topic is also known as: speed of revolution & revolution rate.

Power tool anti-kickback system with rotational rate sensor

Abstract: A control system is provided for use in a power tool The control system includes: a rotational rate sensor having a resonating mass and a controller electrically connected to the rotational rate sensor The rotational rate sensor detects lateral displacement of the resonating mass and generates a signal indicative of the detected lateral displacement, such that the lateral displacement is directly proportional to a rotational speed at which the power tool rotates about an axis of the rotary shaft Based on the generated signal, the controller initiates a protective operation to avoid further undesirable rotation of the power tool The controller may opt to reduce the torque applied to shaft to a non-zero value that enables the operator to regain control of the tool

Effects of rotational direction and rotation-to-revolution speed ratio in planetary ball milling

Abstract: The rotational direction of a pot in a planetary ball mill and its speed ratio against revolution of a disk were studied in terms of their effects on the specific impact energy of balls calculated from the simulation on the basis of the Discrete Element Method (DEM) and structural change of talc during milling. The specific impact energy of balls is measured as a significantly large value, and the structure of talc is transferred into an amorphous state quickly when the mill pot is rotated in the counter direction against the revolution. In both rotation–revolution relationships, the specific impact energy increases with an increase in the rotation-to-revolution speed ratio in the initial stage and then falls around the critical speed ratio, which can be calculated by the balance equation based on the centrifugal forces acting on a ball due to the combination of the rotation and revolution. The highest value in the specific impact energy of balls during milling can be achieved effectively around this critical speed. This critical speed would, therefore, be a key condition in milling for designing suitable and optimum mechanical milling performance.

Characteristics of flow over a rotationally oscillating cylinder at low Reynolds number

Abstract: Effects of rotary oscillation on unsteady laminar flow past a circular cylinder have been investigated in this study. Numerical simulations are performed for the flow at Re=100 in the range of 0.2⩽Ω⩽2.5 and 0.02⩽Stf⩽0.8, where Ω and Stf are, respectively, the maximum rotational speed and forcing oscillation frequency normalized by the free-stream velocity and cylinder diameter. Results show that the rotary oscillation has significant effects on the flow. The lock-on frequency range becomes wider as the rotational speed increases. In a non lock-on region, modulations in the velocity, lift and drag signals occur and the modulation frequency is expressed as a linear combination of the forcing frequency and vortex-shedding frequency. Also, the mechanism for the modulation phenomenon is presented in terms of the vortex merging process. Finally, it is found that the mean drag and amplitude of the lift fluctuations show local minima near the boundary between the lock-on and non lock-on regions.