ABSTRACT
A new type of variable geometry turbine has been designed, analyzed using CFD, prototyped and tested. The design is based on a spiral track which a flexible wall can use to traverse from an “open” position to a “closed” position. The “open” position creates a full 360-degree volute with a large throat section. As the flexible wall traverses to the “closed” position, the volute throat section reduces as does the remainder of the 360-degree volute. The flexible wall traverses in a 720-degree track. The moving wall changes the throat section and controls which 360 section the flow stream will use.
Computational Fluid Dynamics (CFD) was used to analyze the corrected flow and efficiency and to improve those parameters. Additionally, a Rotordynamics analysis was used to determine the bearing friction, which was then combined with the CFD results to yield the “turbine mechanical efficiency”, which is commonly measured on turbocharger hot gas stands.
A protype unit was built utilizing 3D metal printing for the links that form the flexible wall. The unit was tested on a turbocharger hot gas stand which showed high efficiency and linear flow control. Another key advantage of the design is the elimination of the typical VGT “variable vanes”. The main undesirable characteristics of variable vaned units are eliminated, including high cycle fatigue, vane and actuating arm wear, variation in the throat section at fully closed due to manufacturing variability, actuation force reversal, sticking, and most importantly, poor performance when nearly closed.
