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Vehicles and Their Powerplants: Energy Use and Efficiency
Vehicles and Their Powerplants: Energy Use and Efficiency PHILLIP S. MYERS and DAVID FOSTER University of Wisconsin at Madison Madison, Wisconsin, United States
1. 2. 3. 4. 5. 6. 7.
History of Ground Vehicle Power Plants Use Classification of Ground Vehicles Constraints Past Trends Energy Sources for Ground Vehicles Prognosis for the Future Considerations and Problems in Reducing Fuel Consumption
Glossary absolute pressure (P) Pressure measured relative to total vacuum—or zero pressure. absolute temperature (T) Temperature measured in Kelvin or Rankine. Carnot cycle An external combustion engine whose compression and expansion strokes are ideally accomplished without heat transfer and for which the heat addition and rejection processes occur at different but constant temperatures. The Carnot cycle engine achieves the maximum theoretical efficiency possible for an external combustion engine operating between the temperatures at which heat addition and heat rejection take place. Its thermal efficiency is given by Z ¼ (ThighTlow)/Thigh. For a Carnot cycle, or any external combustion engine, to achieve an efficiency of 100% would require that either Thigh ¼ N or Tlow ¼ 0 (absolute zero). enthalpy (H) Defined as H ¼ U þ PV. entropy (S) A measure of disorder. external combustion engine An engine in which heat transfer from combustion occurring outside the engine is transferred across the boundary of the system to the working fluid of the engine (e.g., a steam engine). Gibb’s Free Energy (G) Defined as G ¼ HTS. heat (Q) Energy transferred across the boundary of a system because of a temperature difference. higher heating value (HHV) Heat transferred out of a constant pressure system in which complete combustion
Encyclopedia of Energy, Volume 6. r 2004 Elsevier Inc. All rights reserved.
occurs and the products are brought back to the original temperature, with any resulting water being condensed to liquid. internal combustion engine An engine in which the working fluid is initially an air-fuel mixture and, after combustion and until exhausted, the products of combustion. It is different from an external combustion engine. The maximum work obtainable from a given amount of fuel is the Gibbs free energy. High temperature is not required to achieve high thermal efficiency. The Carnot cycle limitation of thermal efficiency does not apply to an internal combustion engine. The ideal thermal efficiency for any internal combustion engines is 100%. internal energy (U) Total energy in a defined closed system. thermal efficiency (g) The ratio of the work out to the input fuel HHV.
Rapid transportation of persons and material is a critical component of modern society. Internal combustion engines, using petroleum as fuel, are the principle energy converter used in transportation. Consequently, transportation is a major consumer of petroleum. Because of increasing use and rapid growth of developing countries, petroleum will undoubtedly increase in cost and the supply is finite. The desirable results of rapid transportation are accompanied by undesirable air pollution, safety issues, and other problems. This article reviews the past trends of emissions, fuel economy, and safety together with customer preferences as well as techniques for minimizing the amount of petroleum needed to continue to meet society’s desires for mobility.
1. HISTORY OF GROUND VEHICLE POWER PLANTS Humans have always valued the capability of transporting themselves and possessions to desired
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1. 2. 3. 4. 5. 6. 7.
History of Ground Vehicle Power Plants Use Classification of Ground Vehicles Constraints Past Trends Energy Sources for Ground Vehicles Prognosis for the Future Considerations and Problems in Reducing Fuel Consumption
Glossary absolute pressure (P) Pressure measured relative to total vacuum—or zero pressure. absolute temperature (T) Temperature measured in Kelvin or Rankine. Carnot cycle An external combustion engine whose compression and expansion strokes are ideally accomplished without heat transfer and for which the heat addition and rejection processes occur at different but constant temperatures. The Carnot cycle engine achieves the maximum theoretical efficiency possible for an external combustion engine operating between the temperatures at which heat addition and heat rejection take place. Its thermal efficiency is given by Z ¼ (ThighTlow)/Thigh. For a Carnot cycle, or any external combustion engine, to achieve an efficiency of 100% would require that either Thigh ¼ N or Tlow ¼ 0 (absolute zero). enthalpy (H) Defined as H ¼ U þ PV. entropy (S) A measure of disorder. external combustion engine An engine in which heat transfer from combustion occurring outside the engine is transferred across the boundary of the system to the working fluid of the engine (e.g., a steam engine). Gibb’s Free Energy (G) Defined as G ¼ HTS. heat (Q) Energy transferred across the boundary of a system because of a temperature difference. higher heating value (HHV) Heat transferred out of a constant pressure system in which complete combustion
Encyclopedia of Energy, Volume 6. r 2004 Elsevier Inc. All rights reserved.
occurs and the products are brought back to the original temperature, with any resulting water being condensed to liquid. internal combustion engine An engine in which the working fluid is initially an air-fuel mixture and, after combustion and until exhausted, the products of combustion. It is different from an external combustion engine. The maximum work obtainable from a given amount of fuel is the Gibbs free energy. High temperature is not required to achieve high thermal efficiency. The Carnot cycle limitation of thermal efficiency does not apply to an internal combustion engine. The ideal thermal efficiency for any internal combustion engines is 100%. internal energy (U) Total energy in a defined closed system. thermal efficiency (g) The ratio of the work out to the input fuel HHV.
Rapid transportation of persons and material is a critical component of modern society. Internal combustion engines, using petroleum as fuel, are the principle energy converter used in transportation. Consequently, transportation is a major consumer of petroleum. Because of increasing use and rapid growth of developing countries, petroleum will undoubtedly increase in cost and the supply is finite. The desirable results of rapid transportation are accompanied by undesirable air pollution, safety issues, and other problems. This article reviews the past trends of emissions, fuel economy, and safety together with customer preferences as well as techniques for minimizing the amount of petroleum needed to continue to meet society’s desires for mobility.
1. HISTORY OF GROUND VEHICLE POWER PLANTS Humans have always valued the capability of transporting themselves and possessions to desired
347