HIGH STIFFNESS IMPELLER
Publication Date: 2017-Jan-12
The IP.com Prior Art Database
Stiffness of the baseline impeller is increased by introducing a set of struts (circular or elliptical in cross section) between hub and shroud. Hub and shroud is extended in the upstream direction to accommodate these newly introduced struts. Because of this additional support between hub and shroud, impeller stiffness increases and compressor can be operated at much higher speed. This idea helps to increase the pressure ratio of each stage and thereby reduces the overall size of the compressor.
High stiffness impeller
In the centrifugal compressor industry, having smaller compressor footprint is one of the essential requirements. To achieve this, impellers should be able to run at very high speed but with less stress levels, in other words impeller should have higher stiffness. However, the mass of the shroud for a closed impeller causes higher stresses at higher rotational speeds. These stresses are located near the leading edges at both hub and shroud sides. At the same time, to remove the shroud, as in the case of open impellers, would induce large leakage losses, thus reducing the performance of the impeller.
BRIEF DESCRIPTION OF DRAWINGS
In the following picture “high stiffness impeller” concept is shown.
Figure 1&2 shows the introduction of stiffening rods on the extended portion of hub and shroud.
Figure 3-7 shows few options to improve the aerodynamic losses due to struts.
This invention proposes a design concept of increasing baseline impeller stiffness. In the new design concept, hub and shroud walls are extended upstream (very close to upstream return channel exit) and struts are introduced between these walls to increase the stiffness. By this new approach, the CG of the baseline impeller is moved closer to the shaft axis and this helps to reduce impeller deflection which reduces the stress at the joints. With this new design approach impeller stiffness can be increased so that it can be operated at higher speed to achieve high pressure ratio. The main advantage of this new design concept is that, baseline design of impeller is not a...