Propulsion Systems - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 123

Table 8.1 Mid and long term predictions for saving fuel and decreasing emissions
Technology scenario
Year

Fuel efficiency LTO NO x level

2030 20-30% better than 2010 level 10-30% below current CAEP/2

2050 40-50% better than 2010 level 50-70% below current CAEP/2

• Using heat resistant materials; and
• Decreasing internal resistances [ 13 ].

The next generation of jet engines with a larger diameter and higher air
resistance could be placed over the wing instead of under it, because of the noise,
which spreads directly downward from engines placed under the wings. New
turboprop and especially contra-rotating fan engines emit a large amount of noise,
and endanger employees and residents near airports. However, over wing appli-
cation technology must be combined with improved mechanical and aerodynamic
measures, because placing the engines over the wings disadvantageously impacts
the elasticity and the inertness of the wings. Furthermore, over wing construction
of engines moves the load of the weight distribution upwards and thereby increases
the swinging of the wings at higher velocities [ 14 ].
The most important measure is to increase the bypass ratio of the engine from
12:1 to 15:1. This measure saves fuel, and lowers the CO 2 and pollutant emissions
in the fan by up to 50%. The application of a contra rotating fan and a new type of
combustion chamber can bring further advantages in the propulsion [ 15 ].
The long term predictions see an effective decrease in the fuel consumption and
exhaust gas emissions (see Table 8.1 )[ 16 ].

8.3.1 Integration of Airframe and Engine

The integration of engine and airframe would result in a reduction of the airplane's
weight and the installation of specific aerodynamic elements to avoid drag.
There are complex design problems in reducing interference drag caused by
flow interactions in the region of the wing pylon. Recent improvements in mod-
eling localize airflow and bring important benefits in reduced interference drag.
However, high bypass ratio engines with a higher front diameter lead to higher air
resistance and therefore higher specific fuel consumption. Nonetheless, the aero-
dynamic disadvantages are much lower than the benefits of the new high-bypass
technology.
Propulsion and airframe integration uses a large number of subsystems to
manage the airplane in flight. Optimal integration of the airframe and engine
allows lighter construction of the fuselage, the wing and the tail units and may
contribute to a lighter undercarriage. Further system integration and extending