System Optimization for a 2-Stroke Diesel Engine with a Turbo Super Configuration Supporting Fuel Economy Improvement of Next Generation Engines

The objective of this paper is to present the results of the GT Power calibration with engine test results of the air loop system technology down selection described in the SAE Paper No. 2012-01-0831. Two specific boosting systems were identified as the preferred path forward: (1) Super-turbo with two speed Roots type supercharger, (2) Super-turbo with centrifugal mechanical compressor and CVT transmission both downstream a Fixed Geometry Turbine. The initial performance validation of the boosting hardware in the gas stand and the calibration of the GT Power model developed is described. The calibration leverages data coming from the tests on a 2 cylinder 2-stroke 0.73L diesel engine. The initial flow bench results suggested the need for a revision of the turbo matching due to the big gap in performance between predicted maps and real data. This activity was performed using Honeywell turbocharger solutions spacing from fixed geometry waste gate to variable nozzle turbo (VNT). New simulations results recommend VNT as it offers a higher potential to reduce BSFC with increase power and low end torque output than the original matching. For the high pressure stage the mechanical Roots type and the CVT superchargers have been assessed and the latter one has been identified having higher power adsorption than traditional positive displacement supercharger. This has allowed the supplier to work on an optimization of the units. Ultimately the VNT with CVT supercharger has been assessed on engine and it allowed confirming the validity and accuracy of the GT Power model after its calibration.