Newsletter 2021.1 Index
Theme : "Mechanical Engineering Congress, 2020 Japan (MECJ-20)”
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Unsteady Flows in Turbomachines (What We Should Know and How We Can Apply to Designing)
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Abstract
This article begins with a kind of prophecy given by Prof. Ohashi, well-known scholar in turbomachinery community, that turbomachines are immortal. In fact, this is true under the condition that designers will be updating their methodologies by taking the full advantage of the state-of-the-art advancements of science and technologies.
Although turbomachinery is regarded as one of the well-developed or matured technologies and some people might say that very few new developments can be achieved, there still remains enough space for innovation. Based on findings in a number of previous studies, it is highly possible that breakthrough in turbomachinery designing can arise from the design that considers unsteady flow effects upon the aerodynamic performance, along with the usage of Machine Learning, the latest data analysis technologies like POD or DMD. The research group in Iwate University have been working on the project to find out a new methodology for designing high-lifting Low-Pressure Turbine (LPT) cascade with high efficiency by taking incoming wake effects into account, and some of the results obtained through the project are described in this article.
Fig. 1 shows tested cascades with different loading levels and deceleration rate over the suction surfaces (DR). Velocity and velocity-rms contours over 4 different airfoil suction surfaces under no wake condition are shown in Fig.2. Due to the existence of incoming wakes, as shown in Fig. 3, the separation bubble, which can be regarded as main cause of the high cascade loss, was considerably suppressed. This was also confirmed in the experiments (Fig. 4). Through these research efforts, our group have found a cascade loss map with respect to DR, a measure of the loading level, as shown in Fig. 5. This map clearly revealed that there exists a certain DR that gives the minimum loss value for each Reynolds number.
Key words
Aero-Engine, Low-Pressure Turbine, Aerodynamic Loss, Unsteady Flow Effects, Experiment
Figures
Fig. 1 Tested cascades with different loading levels and deceleration rate over the suction surfaces
Fig. 2 Velocity and velocity-rms contours over 4 different airfoil suction surfaces under no wake condition
Fig. 3 Velocity and velocity-rms contours over 4 different airfoil suction surfaces under no wake condition
Fig. 4 Velocity and velocity-rms contour over Design E (largest loading airfoil) suction surface under wake passing condition.
Fig.5 Normalized aerodynamic loss data for several cascades with different DR at three Reynolds number conditions