In more than 95 % of all motor vehicles, an internal-combustion reciprocating engine is used for propulsion. However, one should ignore the different propulsion concepts available for motor vehicles.
Following the invention of the automobile, the E-engine was very popular, but was quickly replaced by the combustion engine. Around the turn of the century already 15,000 electric passenger cars were registered in the USA.
Combustion engines can be distinguished into internal and external combustion engines. Internal combustion engines use a single working medium for heat and work transfer, whereas the external combustion engine uses two separate fluids. The Otto, Diesel and Wankel engines represent the common internal combustion engines, while the Stirling engine and the Steam engine represent external combustion engines.
So far the Stirling engine as well as the axial-piston engine, have not seen application, not only in the scope of automobiles, but also otherwise. The steam engine has to be considered as an antiquated form. In the following chapter the Compression Ignition (diesel) Engine, the Spark-Ignition (Otto) Engine will be considered in detail. As special cases, the Rotary (Wankel) Engine, the Gas Turbine, and the Electric Drive will be described in more detail. Finally, the different principles will be evaluated based on their suitability to motor vehicles.
Last but not least, are Hybrid Drives. A hybrid vehicle is one which is powered by a combination of a combustion engine and an electric motor. Alternative solutions also involve a combustion engine and an hydraulic accumulator or flywheel accumulator.
The Otto engine which represent one of the most widely used powerplants has the following characteristic features:
Spark ignition
External mixture formation (except for DI-Otto)
Mixture condensation (homogeneous mixture)
Quantity control (throttle valve)
λ ≈ const.