Study on evaluation method of flow characteristics in steady flow bench(7) - Torque distribution along radial direction(1)

This paper is the seventh investigation on the methods of evaluating flow characteristics in a steady flow bench. In previous studies, solid rotation assumptions used in the steady flow bench were examined. Then, the impulse swirl meter(ISM) measurement was compared with a particle image velocimetry(PIV) evaluation after comparing the plane velocity distribution based on the valve angle and measurement plane. In this study, the effect of the tangential velocity distribution along the radial direction on the measured torque was quantitatively evaluated. For this purpose, the effects of the evaluation center setting and axial velocity at 1.75B, or 1.75 times of the bore position apart from the bottom of the head, and 3.00B downstream plane were investigated, leading to the following conclusions. The tangential velocity distribution is mainly influenced by the valve angle in the case of the cylinder center, and the change according to the lift is not large, but the swirl center is highly irregular due to the wall effect when the radius is increased. Next, the sum of torques of the same radius does not show a significant difference below the non-dimensional radius of 0.2 regardless of the axial speed and the center setting, but it increases rapidly after the radius of 0.8, considering axial velocity. The cumulative torque increases in a very simple form, close to the theoretical curve for the cylinder center, and asymptotic for the swirl center, while this torque is quite small, up to a radius of 0.4, with virtually no impact on the final value. At the same time, torques up to a radius of 0.8 are also theoretically less than 40 % of the final value, and the actual measured value is smaller. Finally, the cumulative torque increases significantly after a radius of 0.8, and this ratio is further increased after considering axial speed, so that the torque, which is far from the center, has a dominant effect on the final torque value.