Turbocharging the I.C. EngineGuest Lecture for ME 444 Internal Combustion Engines Dr. Philip S. Keller BorgWarner Inc. Engine Systems Group
Outline • Introduction • Turbochargers • Thermodynamic Analysis • Compressor • Turbine • Intercoolers • Benefits • Challenges • New Developments • Conclusions
Introduction • History • 1885 and 1896, Gottlieb Daimler and Rudolf Diesel experiment with pre-compressing intake air • 1925 Swiss engineer Albert Buchi develops first exhaust gas turbocharger which increases power output by 40% • 1938 first commercial Diesel truck application by “Swiss Machine Works Sauer” • 1962 first production application of turbochargers in passenger cars - the Chevrolet Monza Corvair and the Oldsmobile Jetfire
Introduction • History • 1970’s – first oil crisis and increasingly stringent air emission regulations lead to demands for higher power density as well as higher air delivery. Outcome -> virtually all current truck engines are turbocharged. • 1978 Mercedes-Benz puts the 300 SD into production marking the appearance of the first turbocharged Diesel passenger car • 1994 VW introduces the variable geometry turbo in their TDI Diesel engine significantly improving the transient response of the Diesel engine.
Why boost? Definitions Introduction
Introduction Power is basically a function of three things: • Air density -> boosting • Swept volume • Engine speed
Introduction Types of Boosting Systems Exhaust Gas - Turbocharger Mechanical – Supercharger Main problem with supercharging is the parasitic loss of having to drive the compressor from the engine output shaft. This loss can be up to 15% of engine output.
Turbochargers • The vast majority of turbochargers consist of a centrifugal compressor and centripetal turbine mounted on a common shaft Turbine Compressor
TurbochargersThermodynamic Analysis • ~30-40% of the fuel energy is released as exhaust gas energy • Area bounded by points 415 is the theoretical energy available. This is sometimes referred to as blowdown losses Ideal cycle pressure-volume diagram for a naturally aspirated engine (Baines, 2005)
TurbochargersThermodynamic Analysis Schematic of engine with large exhaust volume (left) and minimal volume (right) (Baines, 2005) Ideal cycle pressure-volume diagram for a turbocharged engine (Baines, 2005)
Turbochargers - Thermodynamic AnalysisConstant Pressure and Pulse Turbochargers Constant Pressure Turbocharger • Lower backpressure at higher speeds • Primarily marine and industrial engines Pulse Turbocharger • More efficient use of exhaust energy • Better torque at low engine speeds
Turbochargers - Thermodynamic AnalysisPulse turbocharger for multi-cylinder engine • Pulse turbochargers need to have the exhaust piping segregated so that exhaust events don’t interfere with one another
TurbochargersCompressor • Consists of three elements • Compressor wheel • Diffuser • Housing • Compressor limits • Surge line • Choke line • Maximum Blade Speed
TurbochargersTurbine • Turbines consist of turbine wheel and housing
Intercooler Turbocharger TurbochargersIntercooler • Temperatures after the compressor can reach 180 C. Cooling the air can offer a significant performance increase. • Simultaneous improvement in output, fuel economy, and emissions