The future European trends for truck diesels include improvements to acceleration performance, economy and higher torque over a wider speed range (where maximum speeds are being reduced). A variable geometry turbocharger together with electronic control can combine the conflicting requirements of flexibility and economy in one engine. This thesis investigates the complete testing of a HOLSET turbocharger equipped with a variable area turbine (based on volute exit area and ring sleeve design) applied to an automotive type TL11 engine rated at 190 kW 2100 rev/min. Control was effected by a programmable digital controller and was extended to include variable injection timing and electronic governing functions. An optimal type control strategy was implemented. A description is included of the test facility and the features adopted such that the electronic control system could be developed effectively. An account on the control implementation is given together with details on the design and development of the control parameters. Different control algorithms both steady state and transiently were assessed and resulted in a torque back-up of 46% at 59% of rated speed compared with 21% at 62% of rated speed for the base. Significant improvements to part load efficiency were achieved e.g. .225 kg/kWh island increased by 25%. Boost scheduling controlled ring sleeve position and resulted in enhanced engine acceleration. The limitation to this work included mechanical, breathing and efficiency parameters. These were investigated theoretically. The practical and theoretical work indicated that with appropriate developments an SFC characteristic with better than .200 kg/kWh is readily attainable. Appropriate conclusions were drawn together with suggestions for further work.
|Date of Award||1984|