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.

Investigation of the High Speed Rolling Bearing Temperature Rise With Oil-Air Lubrication

Abstract: The oil-air lubrication system has been widely used for rolling ball bearing. However, as the rotation speed increases, the temperature rise will increase dramatically, resulting in shortening the service life of the ball bearing. The existing literature has offered valuable fundamental data about the oil-air lubrication of rolling bearing; however, there are still some problems that concerned the oil-air lubrication, which are not addressed. In this study, an experiment setup to investigate the oil-air lubrication for the high speed ball bearing has been developed, and performance tests of hybrid ceramic and steel ball bearings under the extensive operating conditions including oil-air supply pipe length, bearing preload, lube interval, oil type, oil viscosity, nozzle design, and rotation speed have been conducted. The test results show that the bearing has the lowest temperature rise with the pipe length of 1.5 m. For the steel ball bearing, the proper preload decreases with increasing of the rotating speed, and the temperature rise of the hybrid ceramic ball bearing is not sensitive to the axial preload. There exists a proper amount of lubricant for the bearing at each rotational speed; and a larger amount of lubricant is required for the bearing as the rotating speed increases. The tested bearings under different speeds have almost the same lowest temperature rise under the lubricant with the viscosity of 100 cSt; a higher or lower viscosity will increase the bearing temperature rises. The nozzle design is an important factor to affect the temperature rise of the ball bearing, and the suitable geometric parameter of the nozzle is closely related to the cage landing method of the bearing. The temperature rise of tested bearings increases with the increase in the rotation speed; and the hybrid ceramic ball bearing always has a lower temperature rise than that of the steel ball bearing at the same operating conditions.

Characteristics of a two-stage counter-current rotating packed bed for continuous distillation

Abstract: A novel two-stage counter-current rotating packed bed (TSCC-RPB) was specially designed for and applied in continuous distillation. The hydrodynamic characteristics of the TSCC-RPB including gas pressure drop and flooding performance were studied with air–water system and air–glycerin solution system. The effects of rotational speed, gas flow rate, liquid flow rate and liquid viscosity on the pressure drop and flooding were examined. Continuous distillation experiments were carried out in the TSCC-RPB with an acetone–water system at atmospheric pressure. The separation efficiency is presented in terms of the number of theoretical plates (NT) and the effects of the operating parameters, such as rotational speed, feedstock temperature, feedstock concentration, and reflux ratio on the separation efficiency were investigated. Experimental results showed that the TSCC-RPB is an efficient gas–liquid contactor having a NT of 4.94–11.57 with a packing thickness of 200 mm.

Automatic speed ratio control system for stepless transmission of automotive vehicles

Abstract: An automatic speed ratio control system of the integration servo mechanism type for a stepless transmission of an automotive vehicle. Speed ratio is controlled by a hydraulic pump motor of variable displacement type, which in turn is controlled by an actuator having a piston and a cylinder to which hydraulic oil is supplied. The system comprises a target value generator which produces a target value for an engine speed corresponding to a throttle opening or an output torque of an engine, or which produces a target value for an engine output torque corresponding to a throttle opening or an engine speed; a detector for producing a signal indicative of an engine speed or an output torque of an engine; a control signal generator for comparing the signal from the detector against the signal from the target value generator to produce a control signal in accordance with a deviation therebetween; and a controller responsive to the control signal to drive the actuator to change a speed ratio of the stepless transmission. The system is characterized by further comprising means for controlling a gain of the alteration rate of the speed ratio in response to a rotational speed of an output shaft of the stepless transmission to increase the alteration rate when the rotational speed of the output shaft is low and decrease the alteration rate when the rotational speed of the output shaft is high.