Jaeha Ryi

A Rotating Balance Design and Performance Estimation for a Rotor Test Jig

In this study a 3-component rotating balance, which is designed to measure the thrust (Fz) and two moment components (Mx, My) simultaneously for a rotor test jig, is designed and its performance is validated experimentally. The low voltage signal from the strain gages mounted on the balance is amplified with a rotating amplifier, which is then fed through a slip-ring unit into the data acquisition system. In order to validate the accuracy of the calibration matrix obtained from a static calibration test, an additional reaction type balance is used to measure the thrust from a model rotor simultaneously, and shows very good result. Finally, the expanded uncertainty value, which is obtained from ISO method is estimated to be , and the balance turns out to be reliable.

Estimation method to achieve a noise reduction effect of airfoil with a serrated trailing edge for wind turbine rotor

This article describes a wind tunnel experiment that was undertaken to investigate the changes in the aerodynamic performance of a wind turbine due to the inclusion of a 2D airfoil with a serrated trailing edge designed to reduce the noise caused by a wind turbine rotor blade. The restrictive condition for the serrated trailing edge equipped with the use of a 2D airfoil was examined through the use of a wind tunnel experiment after studying existing restrictive condition and analyzing prior research on serrated trailing edges. The study was conducted according to Howes theory, which is a cornerstone of the study of noise reduction effects produced by a serrated trailing edge. For the serrated trailing edge equipped on a 2D airfoil, the wake distribution and the relation to noise were analyzed in order to determine the restrictive condition in accordance with Howes theory. The results indicated that an empirical formula or a theoretical approach should consider changes in the boundary layer thickness of a 2D airfoil, so an empirical noise prediction formula is suggested for the serrated trailing edge. Also, a comparison and an analysis of the prediction and the experimental results for the noise produced by the NACA0012 or the baseline airfoil equipped with a serrated trailing edge suggested a novel formula for a 2D airfoil. Finally, it is confirmed that 2D airfoil noise data are compared with wind tunnel test data by using an empirical formula estimationmethod.

An Experimental Study on Flapping Motion of Forward Flight Condition used to Articulated Hub Rotor

In this paper, wind tunnel test and analytical prediction are compared for result of flapping motion in helicopter forward flight condition. Tests were performed at low speed wind tunnel at Chungnam National University, test section of wind tunnel has 1.8 by 1.8 meter open-jet test section area. According to the results of measured data for aerodynamic performance of model rotor in forward flight. It has to observed the difference of analytical and measured results of power coefficient for fixed thrust coefficient. And calculated and measured data of helicopter rotor flapping angles in forward flight are compared for a model rotor in a wind tunnel. A test was conducted to verify the measured data of coning and lateral/longitudinal flapping angle with predicted values.

Validation of Noise Prediction Theory Using Scaled Rotor Experiment for Hovering Condition

In this paper, a series of experiment is performed for a scaled hovering rotor in a semi-anechoic chamber and the results are compared to the noise spectra predicted by using Lowsons loading noise equation and FW-H equation. It was founded that the sound directivity pattern for both experiments and predictions are similar in their trend. Meanwhile the FW-H equation showed better agreement with experiments in the near-field noise spectra, but at the far-field the Lowsons equation performed better. The discrete noise are known to be proportional to the loading on the blades, which can be controlled by collective pitch angle of the blades. It was founded that the predicted spectra with FW-H equation come close to the measured noise spectra in low collective pitch, but in high collective pitch angles the Lowsons equation be more reliable.