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The Ultimate Performance Potential of Compounded Diesel Engines for Heavy Vehicles
Published November 03, 1998 by Institution of Mechanical Engineers in United Kingdom
The paper is based on computer simulations for an 8-liter, 6- cylinder, 4-stroke DI diesel engine operating in any one of the following modes: a) single-stage turbocharged; b) compounded with a single-stage turbocharger; c) two-stage turbocharged; d) compounded with the geared power turbine in series with the HP and LP turbines of the 2-stage turbocharger.
Each system has been optimized by matching the compressors and turbines to achieve rated outputs at 2200 rev/min of approximately 300 kW for the systems with single-stage turbocharging and 490 kW for the system with 2-stage turbocharging.
The analysis shows that the improvements achieved by compounding are very much marked for the system with 2-stage turbocharging at BMEP levels of approximately 33 bar compared with single-stage turbocharging at approximately 20 bar, with efficiency improvements of the order of 3 percentage points for the former case as against only 1 percentage point in the latter. In addition, schemes with 2-stage turbocharging are characterized by very high torque back up over a wide speed range.
The paper does not deal specifically with emissions.