Propulsion Systems - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 129

Electronic speed regulation through the use of an automatic gear is important
for optimal operation of the transmission system. Automatic start and stop sys-
tems, and starter generators can save additional fuel.
In commercial vehicles, a 42 V main power supply produces higher energy
efficiency for the auxiliary components, e.g., for the heating and cooling of the
propulsion system's elements [ 38 ].
8.5.2 Propulsion of Airplanes
The main elements of an airplane's propulsion are the engine, the fuel supply
system, the bearing and the steering elements.
The integration of the engine and airframe results in the reduction of the air-
plane's weight and the installation of aerodynamic elements to avoid drag. New
propulsion systems have less noise and an increase in the bypass ratio from 12:1 to
15:1. These measures save fuel and lower the CO 2 emissions in the fan by up to
50%. The introduction of new turbofan and turboprop engine series depends on the
economical and environmental protection requirements. The most effective
measures are the use of open rotor technology, the application of contra-rotating
turbines, and new types of the combustion chamber. Certification of new fuels can
extend current market ranges.
Future technology will use even more intelligent and more sustainable pro-
pulsion systems with large turbofans and improved geared fans. An improvement
in the future propulsion system efficiency of about 1% fuel saving per annum can
be expected.
The open rotor technology burns fuel cleaner in the combustion chamber, and
consumes 15% less fuel and produces 20 dB(A) less noise compared with the
present systems. It can go into service approximately by 2015. By 2018, light-
weight construction, integration of the engine and the nacelle, and combination of
integrated airplane and engine design will decrease fuel consumption by another
20% [ 39 ].
8.5.3 Propulsion of Ships
A ship's propulsion system consists of the diesel engine, the steam or the gas
turbine, the diesel electric aggregate, the direct and the indirect operating trans-
mission elements, and the propeller.
Slower ships use a two-stroke or a four-stroke diesel engine and faster ships use
gas turbines as a propulsion. Electric motors and connected transmission systems
are common in submarines. Fuel cells and nuclear reactors are employed to propel
some warships and icebreakers.