30-05-2012, 10:21 AM
AVIO FOR “GREEN” ENGINE”
green engine (2).pdf (Size: 1.58 MB / Downloads: 96)
For decades the aeronautics confronted it self with demands for propulsive
machines more and more efficient. It is normal by now for the technologists of the
aeronautical propulsion to feel to speak about 2 digit percentages of
improvement every 3 or 4 years on the power for unit of weight, thrust weight rate,
reliability indices or what other.
The today's thinking on evolution of the aero-engineering technology places the
absolute accent on the compatibility of a more and more efficient and reliable
propulsion with an acceptable by citizen and highly sustainable in the time.
If some years ago the emphasis were on the consumption in high quota for the
ozone threat, nowadays it is thought the pollution above all in proximity of the
earthly level or airports proximity needs to cure, pulling down drastically emissions
of gas injurious, reversible and not, as well as noise emitted from the propeller,
above all in the regimes in proximity of the airports.
Environmental impact for an engine that wants to become clean means first, emission of
injurious gas and second acoustic emission.
On first front the targets that we are chasing is the nitrogen oxide pulling down, not
reversible and highly harmful. The figure above illustrates in parallel to the pulling down of
specific consumption (SFC), proportional to the CO2 that we have already seen above, the
pulling down of nitrogen oxides (NOX), that continue the drastic evolution begun at
beginning of years 90, carrying such pulling down from - 30% of existing engines that
enter in service to - a 60% in 2008 and really to - a 80% in 2015.
The second improvement aspect is relative to the acoustic emissions (Noise) that,
cumulatively in the sensitive points of the engine mission, they must pull down the noise
levels from the existing levels (that they already moreover realize less 16 dB with
reference to the engines of first years 90) to - 32 dB in 2008 until quite to - 45% in 2015.
In the following figure is quoted in qualitative way the evolution of the acoustic emission
of a transport aircraft in the years (Boeing source). It is looked as looking forward to 2015
are those to halve the noise generated in all the flight envelope, regarding the present
values.
THE NEW ENGINE ARCHITECTURE
To have by pass ratio always increasing to limit specific consumption, as we said in the
first figure and at the same time make more efficient the components, it means to
decrease requirement of noise limitation on architectures more and more bold and difficult
to realize mechanically.
In the following figure are abstracted the more probable configurations that we think at
the moment for the future engines.
THE INNOVATIVE INNER SOLUTIONS
Besides the innovative engine architectures, on “green” engine a series of innovations, all
aimed to limit the energy waste
The turbo-engine founds its machine efficiency on good use of the energy stored under
warm air form in pressure. Every leak of flow rate of this most precious air, transforms it
in leakage of efficiency.
But on the other hand the engine cannot use other elements to work, if not the stored air:
the lubrication oil is held inside of zones to lubricate from the air in pressure, all the hot
zones is conditioned thermally from more `fresh' air and in addition to all this, air is
supplied also to the aircraft for the services and the pressurization of the cabin and for the
pneumatic control of all the accessories.
The future engine will have solutions on board that, if also difficult to develop, going to act
so as to minimize or cancel these leaks, will affect in substantial way the level of the
consumption.