Papers by Keyword: Pitch Angle

Abstract: The Savonius and Darrieus are vertical-axis wind turbines. This turbine has resistance on one side of the blade that makes it difficult for the shaft to rotate resulting in reduced efficiency. However, the vertical shaft turbine type provides the advantage of being able to accept wind speeds from any direction without an additional tail. Savonius and Darrieus turbines show different characteristics in terms of their performances. Savonius turbine has a high power coefficient (CP) in the range of low tip speed ratio (TSR), when its TSR increases the CP will fall. In contrast to Darrieus, high CP is achieved if the TSR is also high but the CP achievement will fall at a low TSR. If it is compared to Savonius, Darrieus has higher power efficiency although it is difficult to self-start. In contrast to Savonius, Darrieus has a better self-starting ability but a lower efficiency. This study aims to improve the performance of vertical shaft wind turbines by creating a new design combination of Darrieus and Savonius turbines with deflectors to produce CP achievement on a wide TSR. The combination of the Darrieus-Savonius turbine is to improve efficiency to make self-start easier. The research method uses numerical simulation by employing CFD Ansys software. On the airfoil with a deflector angle of 70 deg, it shows that there is an increase in speed in several parts of the Darrieus blade airfoil. The increase in speed causes the decrease of static pressure in the area. The pressure difference between the sides of the airfoil surface causes a force. The direction of the force causes the turbine shaft to rotate. The deflector acts as a directional headwind, increasing the local flow velocity to counter the resistance on one side of the rotor blades The average torque produced at an angle of 70 deg is 0.5 Nm. Whereas, at an angle of 90 deg, the average torque generated is lower by around 0.15 Nm.

Abstract: Vertical Axis Wind Turbine (VAWT) can perform better than Horizontal Axis Wind Turbine (HAWT) because VAWTs are relatively simple, quiet, and easy to install. It can take wind from any directions, and operate efficiently in urban areas where turbulent wind conditions usually happen. The weakest point for its configuration, however, is its low efficiency so more intensive research is required.Actual VAWT performance can be predicted based on a determination of the forces acting on blades that produce the turbine’s torque. Thus, this paper proposed a new model of force analysis for calculation of VAWT’s performance and a way to enhance the efficiency of VAWT through proper variations of the pitch angles. Additionally, in order to increase the efficiency of the VAWT for a given tip speed ratio, the solidity in term of blade’s number can be adjusted.Results show that right changes in the value of pitch angles and proper selection of the number of blades can considerably increase the efficiency of the turbine and reduce amplitude of turbine’s torque variation. The new model of force analysis can be helpful for aerodynamic analysis of the VAWT turbine for its better design.

Abstract: This paper concerns a simplified 7 DOF model for car vertical vibrations. The classical 7 DOF of the considered 3D vertical model are: the vertical displacement of the gravity center of the car body, the roll and pitch angles of the car body and the four vertical displacements of the wheels centers. Using the x-y-z sequence of rotations parameterization, the Euler’s rotation equations concerning the roll and pitch angle are easily obtained. Small differences are observed between our car body rotation equations concerning the two pitch and roll angles and the same equations provided by Demić et al. [6]. For small pitch and roll angles, no differences were observed with respect with [6]. Also, no differences were observed concerning the other 5 dynamics equations of the 7 DOF model, the ones for the vertical displacements.The simplified 7 DOF car vertical dynamics model, comprising two rotation equations (for pitch and roll angles) and five dynamics equations concerning vertical displacements/accelerations, were integrated/simulated in Matlab. For small pitch and roll angles (a rather flat and smooth straight road profile was considered in our case study), the results obtained using the in-house 7 DOF model Matlab simulator are in very good agreement with the results provided by CARSIM.

Abstract: The paper analyzes the effect of airfoil thickness, camber and blade pitch angle on the performance of the three-bladed Darrieus wind turbines. The research results show that the increase of airfoil thickness, camber and pitch angle of blade, can improve power coefficient when the wind turbine tip speed ratio between zero and four. The increase of thickness and camber of the airfoil leads to running tip speed ratio range of wind turbine get narrowed, and reduces the power coefficient when wind turbine runs in high tip speed ratio range. When the pitch angle of blade is 1˚, power coefficient reaches the maximum value. Negative pitch angle has a bad impact on power coefficient and even creates negative power coefficients.

Abstract: The aerodynamic performance and the bypass flow field of a vertical axis wind turbine under self-starting are investigated using CFD simulations in this paper. The influence of pitch angle variations on the performance of the wind turbine during self-starting is presented. A two-dimensional model of the wind turbine with three blades is employed. A commercial software FlowVision is employed in this paper, which uses dynamic Cartesian grid. The SST turbulence model is used for turbulence modeling, which assumes the flow full turbulent. Based on the comparison between the computed time-dependent variations of the rotation speed with the experimental data, the time-dependent variations of the torque are presented. The characteristics of self-starting of the wind turbine are analyzed with the pitch angle of 0^o、-2^o and 2^o. The influence of pitch angle variations on two-dimensional unsteady viscous flow field through velocity contours is discussed in detail.

Abstract: The influence which is brought by the variation law of the whole machines center of gravity position when the telescopic boom and fixed boom at different pitch angles during shipping is been given by using ANSYS and MATLAB. Meanwhile, the influence which the swing arms different pitch angles bring to the safety of the ship loaders own structure is also being analyzed in this paper. Finally, the best placement angle of the ship loaders swing arm is given based on the comprehensive analysis of all factors.

Abstract: The difference between the attitude angle and the rotation angle will cause the modeling error of DTG. The accurate calculation model of azimuth is established according to the relationship between the attitude angle and rotation angle. The error between the accurate calculation model and the traditional model is analyzed by simulating. The simulation show that the modeling error is proportional to the tilt angle and the pitch angle, when the change of the tilt angle and the pitch angle is 1°, the max change of the modeling error will be 3.6701.

Abstract: Wind turbine pitch control need a higher demand due to the random changes in wind speed, this paper proposes using adaptive neural fuzzy inference system to control wind turbine pitch, and constructs a mathematical model of the wind turbine. Consider the error between the measured and the actual value of generator speed as the input to the controller. Take a simulation analysis to the adaptive neural fuzzy inference system controller under random wind speed. The simulation results show that the adaptive neural fuzzy inference system control strategy has good robustness and dynamic performance, to improve wind turbine pitch control is feasible and effective.

Abstract: At the base of development of ordnance, the study of model machine of controllable micro emitter definitive direction angle and pitch angle is advancing, which definitive direction angle and emissive angle is very important. By theoretical and empirical equation analysis, it may deduce dynamics equations about load flux of micro fluid controlling direction angle and emissive angle in micro emitter. After linearization, transfer function may be calculated. When deviation is very small, output and input control present good linear relation. So make emissive process control easy.

Abstract: We present a study of the feasibility of controlling the pitch angle of a high velocity ground vehicle in ballistic phase by accelerating or decelerating its wheels. The vehicle performed several jumps, and various wheel acceleration commands were sent to it while it was airborne. Images were recorded using a high-speed video camera, and the trajectories of markers placed on the vehicle were analyzed in order to measure the relationship between the changes in angular velocities of the chassis and the wheels. It appeared that it was possible to achieve pitch righting through the modification of the angular velocities of the wheels with adequate performance, thus opening the road towards automated control of pitch, then later yaw and roll angles.