Investigating potential light-duty efficiency improvements through simulation of turbo-compounding and waste-heat recovery systems

Conference · Fri Jan 01 00:00:00 EST 2010

DOI:https://doi.org/10.4271/2010-01-2209· OSTI ID:991673

Edwards, Kevin Dean ^[1]; Wagner, Robert M ^[1]; Briggs, Thomas E ^[1]

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1. ORNL

Modern diesel engines used in light-duty transportation applications have peak brake thermal efficiencies in the range of 40-42% for high-load operation with substantially lower efficiencies at realistic road-load conditions. Thermodynamic energy and exergy analysis reveals that the largest losses from these engines are due to combustion irreversibility and heat loss to the coolant, through the exhaust, and by direct convection and radiation to the environment. Substantial improvement in overall engine efficiency requires reducing or recovering these losses. Unfortunately, much of the heat transfer either occurs at relatively low temperatures resulting in large entropy generation (such as in the air-charge cooler), is transferred to low-exergy flow streams (such as the oil and engine coolant), or is radiated or convected directly to the environment. While there are significant opportunities for recovery from the exhaust and EGR cooler for heavy-duty applications, achieving similar benefits for light-duty applications is complicated by transient, low-load operation at typical driving conditions and competition with the turbocharger and aftertreatment system for the limited thermal resources. We have developed an organic Rankine cycle model using GT-Suite to investigate the potential for efficiency improvement through waste-heat recovery from the exhaust and EGR cooler of a light-duty diesel engine. The model is used to examine the effects of efficiency-improvement strategies such as cylinder deactivation, use of advanced materials and improved insulation to limit ambient heat loss, and turbo-compounding on the steady-state performance of the ORC system and the availability of thermal energy for downstream aftertreatment systems. Results from transient drive-cycle simulations are also presented, and we discuss strategies to address operational difficulties associated with transient drive cycles and balancing the thermal requirements of waste-heat recovery, turbocharging or turbo-compounding, and exhaust aftertreatment.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). National Transportation Research Center (NTRC)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 991673
• Resource Relation: Conference: 2010 SAE Powertrains, Fuels and Lubricants Meeting, San Diego, CA, USA, 20101025, 20101027
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
BRAKES
COMBUSTION
CONVECTION
DEACTIVATION
DIESEL ENGINES
EFFICIENCY
ENGINES
ENTROPY
EXERGY
HEAT EXCHANGERS
HEAT TRANSFER
LUBRICANTS
PERFORMANCE
RADIATIONS
RANKINE CYCLE
THERMODYNAMICS
TRANSIENTS
TURBOCHARGERS
WASTE HEAT
engine efficiency
organic Rankine cycle
turbo-compounding
exergy