In this paper, we explore the redesign of a transonic compressor using the 3D inverse design method. In the inverse design approach, the pressure loading, blade thickness distribution and stacking axis are specified and the camber surface is calculated accordingly.
Fig. Comparison of pressure distribution and streamlines on the blade suction side at the design point.
The design of transonic and supersonic axial compressors strongly relies on the ability to control the shock strength, location and structure. The use of an inverse design method enables the designer to act directly on the aerodynamic parameters, like the blade loading and provides an efficient tool to control the shock wave and its interaction with the secondary flows and the tip clearance vortex.
In this process, the blade loading distribution is controlled in a parametric way. The impact of the design parameters used to control the blade loading on the rotor performance is explored using a systematic approach. CFD analysis is performed in order to assess the effect of the design modifications on the aerodynamic flow field and on the design and off-design performance of the rotor.
The following performance parameters are analyzed:
- Peak efficiency value.
- Design point efficiency at three span locations (50%, 75% 95% of the span).
- Choke margin.
- Slope of the efficiency characteristic curve at the operating condition Mcorr=0.87, which is close to the rotor stall.
The characteristic curves are reported in this report and the operating range has increased: the rotor is characterized by a higher choke margin and better ‘performance trend’, at all the rotational speeds. As expected, the peak efficiency value has dropped.
The operating condition at 95% of the design speed is the one that benefits most from the design modification, since it is characterized by the widest improvement in operating range at the lowest cost in peak efficiency (around 0.2%).
As a result, it is possible to develop some design guidelines, which can be exploited for similar design applications.
An example is reported in this paper.