Analysis of Sequential Turbocharger Systems for Diesel Engines Rob Stalman, Vanco Smiljanowski, Uwe Späder, Ford Research & Advanced Europe October 24 th 2011, Ford Forschungszentrum Aachen GmbH, All rights reserved
Contents: Introduction & motivation Comparison of Sequential Turbocharging Systems Switching of a parallel sequential system Summary Page 2
Contents: Introduction & motivation Comparison of Sequential Turbocharging Systems Switching of a parallel sequential system Summary Page 3
Introduction Specific Power of Passenger Car Diesel Engines in Europe. 100 Specific Power [kw/l] 90 80 70 60 50 40 30 20 10 Naturally Aspirated Turbocharged Turbocharged & Intercooled Sequential Systems 0 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 Year [-] Page 4
Introduction 30 25 20-80% PM PM [mg/km] 15 10-56% NO x -28% NO x 5 0 EU6 EU5 EU4 0 50 100 150 200 250 300 NO x [mg/km] Page 5
Contents: Introduction & motivation Comparison of Sequential Turbocharging Systems Switching of a parallel sequential system Summary Page 6
Sequential Boosting Systems Layout Parallel Sequential Series Sequential TC1 Turbine Shutoff Valve Compressor Bypass Valve TC2 wastegate Compressor Recirc Valve Turbine Bypass Valve TC1 TC2 Page 7
Sequential Boosting Systems Layout Parallel Sequential Series Sequential Page 8
Compressor Maps Parallel Sequential Compressor 1 Compressor 2 Pressure ratio Druckverhältnis Pressure ratio Druckverhältnis Mass flow Mass flow Massenstrom Massenstrom 07.11.2006 07.11.2006 Page 9
Compressor Maps Parallel Sequential Compressor 1 Compressor 2 first operating point parallel (twin turbo) Pressure ratio Druckverhältnis Full load single turbo Pressure ratio Druckverhältnis first operating point parallel (twin turbo) Mass flow Mass flow Massenstrom Massenstrom 07.11.2006 07.11.2006 Page 10
Compressor Maps Parallel Sequential Compressor 1 Compressor 2 Pressure ratio Druckverhältnis Full load parallel Pressure ratio Druckverhältnis Full load parallel Mass flow Mass flow Massenstrom Massenstrom 20.11.2006 07.11.2006 20.11.2006 Page 11
Compressor Maps Series Sequential Druckverhältnis Pressure ratio C:\users\hkindl\CTI\2stufig2.ipw Massenstrom flow 02.11.2006
Full Load Performance & Emissions Range Single VNT Series Sequential Series Sequential + VNT Parallel Sequential Torque FTP75 & US06 Application with lowest weight 1000 Engine Speed 4000 Page 13
Comparison Package: Series Sequential general has a very big TC2 which is a challenge to package. Parallel Sequential is more compact and flexible to package. All are more complex to package than single VNT. Aftertreatment / Emissions: Series sequential turbine side has a high thermal inertia that impacts temperature available for the aftertreatment system.. The boosting systems in general compete for the same package space as parts of the aftertreatment system. This can lead to unfavourable compromises. Transient & driveability: Both sequential systems have better transient behaviour than single VNT Parallel has slightly better transient behaviour. Series Sequential is more suited to extend engine rpm range Page 14
Comparison Fuel economy over NEDC slightly better for parallel sequential Longer design lead time for complex boosting systems, special care must be taken in case of series sequential. Series Sequential usually involves a big exhaust manifold casting including one of the turbine stages, requiring design effort Turbine side valves are critical for both (leakage, DP, response, robustness). Both systems cost more than a single VNT. Mode switching performance critical. Mode switch of parallel sequential discrete, serial sequential much more smooth Switching with EGR? Page 15
Contents: Introduction & motivation Comparison of Sequential Turbocharging Systems Switching of a parallel sequential system Summary Page 16
Parallel Sequential Switching - Valves Open 100 80 Parameter [%] 60 40 Turbine shut-off valve 20 Closed 0 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 Time [sec] Page 17
Parallel Sequential Switching - Valves Open100 80 Parameter [%] 60 40 Turbine shut-off valve Compressor bypass valve Recirculation valve 20 Closed 0 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 Time [sec] Page 18
Parallel Sequential Switching - Valves Open 100 80 Parameter [%] 60 40 20 Turbine shut-off valve Compressor bypass valve Recirculation valve Turbine VNT position Closed 0 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 Time [sec] Page 19
Parallel Sequential Switching - Valves Open 100 80 Parameter [%] 60 40 20 Turbine shut-off valve Compressor bypass valve Recirculation valve Turbine VNT position Dashed: measured signals Closed 0 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 Time [sec] Page 20
Parallel Sequential Switching - Measured TC speed [rpm] 240000 180000 120000 60000 0 Speed TC1 Speed TC2 110 Torque Boost Pressure Pressure ds TC1 Pressure ds TC2 100 90 80 70 60 50 40 Torque, Pressure (rel) [%] 110 30 Signal [%] 90 70 50 30 VT2 VNT Position Compressor Shut Off Valve Recirculation Valve 10-10 2.00 2.20 2.40 2.60 2.80 3.00 time [s] Page 21
Parallel Sequential Switching - Measured Switch from single turbo to biturbo, high partload, measured. Video courtesy of L. Bartsch Page 22
Contents: Introduction & motivation Comparison of Sequential Turbocharging Systems Switching of a parallel sequential system Summary Page 23
Summary Both Parallel Sequential and Series Sequential offer the potential to increase specific power and torque, with Series Sequential more suitable for engine rpm increase. This increase can either be used to increase performance or allow downsizing. Both systems face a number of constraints: package cost complexity High thermal inertia is a risk for series sequential Step-wise switching poses a challenge for parallel sequential Correct system choice depends entirely on the application (In-Line or V-engine, vehicle, duty cycle etc...) Page 24