| Co-Investigator(Kenkyū-buntansha) |
OHTA Yutaka Waseda University, Science and Engineering, Associate Professor, 理工学部, 助教授 (50211793)
TAJIMA Kiyohiro Waseda University, Science and Engineering, Professor, 理工学部, 教授 (60063335)
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| Research Abstract |
Development of technologies for extending the stable range of axial compressor operation by suppressing onset of rotating stall, or by recovering swiftly from stall, is one of the main subjects in improving the jet engine performance. This research aims at understanding mechanisms of rotating stall and of related unsteady flow phenomena through experiments and a numerical study of 2-D compressible Navier-Stokes equations.
In the numerical analysis, various aspects of unsteady flows generated by the relative motion of a rotor and a stator are presented with a special emphasis on features of vortical flow patterns in the cascades. With a rotor-stator cascades of a sufficiently large number of blades, it simulates a whole compressor characteristic from normal to deep-stall flow range, in the speed range up to transonic regime. For the subsonic case of rotor Mach number 0.3, comparisons are made on various flow data with measured data, whereas for the transonic case, total-pressure rise cha
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racteristics are compared to rig test data from an engine company.
On rotating stall structure, a twin-vortex cell structure is presented, which is formed by the collision of an incoming flow to the cascades with a high pressure stagnant zone produced in some portion of the cascade. The cell propagation speed as well as the induced reverse-flow velocity agree well with the data measured by hot-film probes. In the transonic regime, cell exhibits a structure slightly different from subsonic cases due to the presence of shock waves. Although the analysis is two-dimensional, it can be expected that, by focusing on this vortex system, dynamic model of the cell be established, and that, by introducing the model into a simplified three-dimensional analysis, some three-dimensional features of the stall cell be evaluated.
On the flow structure leading to stall inception, it can be prospected that, in such a highly loaded condition where the flow passing over the pressure surface of a blade rolls up to the suction surface, a blade-tip vortex stimulates this flow configuration, synchronized with the inlet distortion.
Various findings regarding stall behavior and cell structure, as well as some specific subjects for future study are obtained. These were applied to develop a stall control technique, and an improvement of 15% in stable flow range was attained up to this moment. It is noted that one of the papers on this project has received a 1995 Gas Turbine Society of Japan award. Less
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