Propulsion Systems
The propulsion systems generate the power and drive vehicles, airplanes, and ships. Although the operation mediums, i.e., the road surface, the air, and the water are physically and chemically very different, propulsion systems are similarly structured in
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Propulsion Systems
The propulsion systems generate the power and drive vehicles, airplanes, and ships. Although the operation mediums, i.e., the road surface, the air, and the water are physically and chemically very different, propulsion systems are similarly structured in all means of transportation. Parts of the propulsion are often called the transmission or drive chain.
8.1 Propulsion Elements in Road Vehicles The propulsion system contains all assemblies which are in the drive chain between the engine and driving wheels [1]. The elements of the power propulsion are: • Transmission system – Clutch gearbox, clutch, bridge, axis, drive shaft • Wheels and tires • Steering system – Steering wheel, steering gearbox, rods, cruise control • Braking system – Brake master cylinder, power lines, brake disc • Suspension – Spring shock absorber, spring column. The driving style and behavior significantly influences the propulsion efficiency.
M. Palocz-Andresen, Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation, Green Energy and Technology, DOI: 10.1007/978-3-642-11976-7_8, Springer-Verlag Berlin Heidelberg 2013
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8 Propulsion Systems
fuel consumption [l*(100 km)-1 *h]
14 1st gear 2nd gear 3rd gear 4th gear 5th gear 6th gear
12 10 8 6 4 0 0
50
100 speed [km*h-1]
150
200
Fig. 8.1 Influence of the gear choice on the fuel consumption in a mid-size car
8.2 Operating Functions of the Propulsion The most important operating functions of the propulsion system are: • • • • •
Starting and steering the vehicle; Interrupting the running engine; Changing the torque; Adjusting the speed of the driving wheels; and Operating the transmission system0 s elements [2].
Not only the engine technology, and internal and external resistances, but also the propulsion system significantly influences route fuel consumption: RFC ð1Þ ¼ f SFC; PEð2Þ ; DRð3Þ : ð8:1Þ (1)
RFC Route fuel consumption (2) Propulsion efficiency (3) Driving resistances There is a strong relationship between the propulsion efficiency and resistances while driving. Driving resistances mainly depend on the rolling, the air, the acceleration, the slope and the brake resistance [3].
8.2.1 Gear Choice Independently from the gear technology, fuel consumption can be reduced by 1–3% through increasing the number of gears due to increasing the transmission ratio in the final gear because the operating point of the engine is thereby shifted towards higher efficiency. For example with 7/8 gears instead of 6 gears in an automatic transmission, fuel savings of between 5 and 6% can be achieved (see Fig. 8.1) [4].
8.2 Operating Functions of the Propulsion
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Minimal energy consumption requires careful braking and accelerating when changing gears. Since the combustion engine operates most efficiently with relatively high loads at a low number of revolutions, minimum consumption is achieved with short and strong acceleration. In cars, it is useful to switch into third gear at 25–30 km h-1 (15.5–18.6 mph), into fourth gear from 35 to 40
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