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.

Material behaviors and mechanical features in friction stir welding process

Abstract: This paper presents the 3D material flows and mechanical features under different process parameters by using the finite element method based on solid mechanics. Experimental results are also given to study the effect of process parameters on joining properties of the friction stir welds. Numerical results indicate that the tangent flow constitutes the major part in the material flow. The shoulder can accelerate the material flow on the top half of the friction stir weld. The distribution of the equivalent plastic strain can correlate well with the microstructure zones. Increasing the angular velocity of the pin, the material in the nugget zone can be more fully mixed, which improves the joining quality of the two welding plates. The increase of speeds, including the rotational speed and the translational speed, can both accelerate the material flow, especially in front of the pin on the retreating side where the fastest material flow occurs. The contact pressure on the pin-plate interface is decreased with the increase of the angular velocity.

A conservative control strategy for variable-speed stall-regulated wind turbines

Abstract: Simulation models of a variable-speed, fixed-pitch wind turbine were investigated to evaluate the feasibility of constraining rotor speed and power output without the benefit of active aerodynamic control devices. A strategy was postulated to control rotational speed by specifying the demanded generator torque. By controlling rotor speed in relation to wind speed, the aerodynamic power extracted by the blades from the wind was manipulated. Specifically, the blades were caused to stall in high winds. In low and moderate winds, the demanded generator torque and the resulting rotor speed were controlled to cause the wind turbine to operate near maximum efficiency. Using the developed models, simulations were conducted of operation in turbulent winds. Results indicated that rotor speed and power output were well regulated. Preliminary investigations of system dynamics showed that, compared to fixed-speed operation, variable-speed operation caused cyclic loading amplitude to be reduced for the turbine blades and low-speed shaft and slightly increased for the tower loads. This result suggests a favorable impact on fatigue life from implementation of the proposed control strategy.

Prediction and optimization of process parameter of friction stir welded AA5083-H111 aluminum alloy using response surface methodology

Abstract: A systematic approach was presented to develop the empirical model for predicting the ultimate tensile strength of AA5083-H111 aluminum alloy which is widely used in ship building industry by incorporating friction stir welding (FSW) process parameters such as tool rotational speed, welding speed, and axial force. FSW was carried out considering three-factor five-level central composite rotatable design with full replications technique. Response surface methodology (RSM) was applied to developing linear regression model for establishing the relationship between the FSW process parameters and ultimate tensile strength. Analysis of variance (ANOVA) technique was used to check the adequacy of the developed model. The FSW process parameters were also optimized using response surface methodology (RSM) to maximize the ultimate tensile strength. The joint welded at a tool rotational speed of 1 000 r/min, a welding speed of 69 mm/min and an axial force of 1.33 t exhibits higher tensile strength compared with other joints.

Air conditioner and air speed control method thereof

Abstract: The invention discloses an air conditioner and an air speed control method thereof. Air scattering plates are arranged at the air outlet of an indoor unit so that the air outlet speed of the indoor unit can be decreased. Air guide plates are arranged so that the air outlet direction of the indoor unit can be regulated. The method includes the following steps that when the air conditioner runs in a refrigeration mode, if a non-air-feeling control instruction is received, the air conditioner is controlled to enter a non-air-feeling running mode; T1 is judged; if T1 is larger than Tw, the air scattering plates are controlled to be opened and are controlled to swing, or the air guide plates are controlled to move upwards, and the rotation speed of an indoor draught fan is controlled to be smaller than or equal to the first preset rotating speed; and if T1 is smaller than or equal to the difference between Tw and Tx, the air scattering plates are controlled to be closed, the air guide plates are controlled to be opened to the preset air outlet angle, the rotating speed of the indoor draught fan is controlled to be smaller than or equal to the second preset rotating speed, and meanwhile when phi is judged to be larger than phi w, the air conditioner is controlled to enter the dehumidification mode. By means of the air conditioner and the air speed control method of the air conditioner, the comfortable temperature environment can be provided, and meanwhile the comfortable indoor air speed environment can be provided and comfort is improved.

Thermal control variable speed DC brushless fan

Abstract: A thermal control variable speed DC brushless fan, especially a DC brushless fan which may change speed in accordance with the temperature sensed, includes a fan speed control circuit and a DC brushless fan. The fan speed control circuit is composed of drive ICs, operation amplifiers, transistors, diodes, capacitors resistors, and a thermal sensor. Under normal conditions, the change in the fan's rotation speed relation to the temperature is almost linear, but when the thermal sensor is open or shorted the speed control circuit of the fan causes the fan to operate at full speed to maintain a cooling effect.