Modification of the Internal Flows of Thermal Propulsion Systems using Local Aerodynamic Inserts

Abstract

Modern thermal propulsion systems (TPS) as part of hybrid powertrains are becoming increasingly complex. They have an increased number of components in comparison to traditionally powered vehicles leading to increased demand in packaging requirements. Many of the components in these systems relate to achieving efficiency gains, weight saving and pollutant reduction. This includes turbochargers and diesel or gasoline particulate filters for example and these are known to be very sensitive to inlet boundary conditions. When overcoming packaging requirements, sub-optimal flow distributions throughout the TPS can easily occur. Moreover, the individual components are often designed in isolation assuming relatively flat and artificially quiescent inlet flow conditions in comparison to those they are actually presented with. Thus, some of the efficiency benefits are lost through reduced component aerodynamic efficiency. Using local aerodynamic modification devices, StreamVane^TM, to eliminate excessive secondary velocity components prior to TPS component inlet boundaries is considered one solution to this. This type of device has been previously demonstrated to be effective at generating a wide range of secondary velocity profiles. With minor modifications, it should be possible to use these devices to instead remove secondary velocities. As a demonstration, a vane-pack designed to generate a counter-rotating vortex pair in a duct from a uniform flow is considered. An investigation is then carried out using Reynolds-Averaged Navier-Stokes (RANS) numerical simulation to assess the effectiveness of the same device in removing vorticity and secondary velocity components when presented with its design outflow in reverse, i.e. producing uniform flow when presented with a complex inlet flow. Results presented demonstrate clear potential for a vane pack to be used to produce a uniform flow thereby addressing the TPS packaging problem. Without any design modification for reverse flow, the insert reduced the mean secondary velocity magnitude by around 75% without a notable increase in system pressure loss. Consequently, proof-of-concept has been achieved and the use of a generic vane pack design process provides a realistic solution worthy of further development