The usage of turbocharging on internal combustion engines is indispensable to meet the latest power and emission requirements for large diesel and gas engines. In order to achieve
the required variability, the turbocharger can be designed with either by-passes and waste gates, or with fully variable turbine geometries (VGT). The usage of waste gates is detrimental to the turbocharger performance but provides a cost-effective and robust solution for the required variability. Conventional VGT systems require a large number of components in which each nozzle is moved independently by an actuation ring and sometimes by a lever arm.
Despite their complexity, VGT turbocharging does provide significant benefits compared to a fixed geometry turbocharger matched
either to full load, leaving a gap at part load applications, or matched at partial load and requiring a waste gate. The publication describes the requirement of having a nozzle that can displace axially to accommodate the presence of deposits and thermal expansion to prevent the blade from getting stuck. Conventional VGT systems have not been extensively applied to applications where high power, high reliability and long life are required due to cost and complexity reasons, and for this reason several developments have been conceived to achieve a VGT turbocharger with a simpler design and less moving components.
This work proposes a new concept of variable geometry turbocharger nozzle that can be applied to axial and radial turbocharger configurations. The concept offers a significant reduction in moving parts and therefore has the potential of reducing the cost of the turbocharger and increasing its reliability compared to conventional VGT designs. The concept consists of a main nozzle and a tandem nozzle. Each of these nozzles is a ring with the required number of vanes. By displacing one nozzle with respect to the other, it is possible to modify the exit flow angle of the nozzle, and modify the throat area in a way that a variation of the mass flow that passes through the nozzle can be achieved.
Reference
P. Jacoby, H. Xu and D. Wang, "VTG Turbocharging – avaluable concept for traction application," in CIMAC Paper No. 116, Shangai, China, 2013.
Post time: Jun-07-2022