15-12-2012, 05:05 PM
ACTIVE CONTROL TECHNOLOGY FOR ENHANCED PERFORMANCE OPERATIONAL CAPABILITIES OF MILITARY AIRCRAFT, LAND VEHICLES AND SEA VEHICLES
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ABSTRACT
This paper describes the technical features of the Thrust
Vectoring Nozzle (TVN) developed by ITP and its
advantages for modern military aircraft. It is presented in
conjunction with two other papers by DASA (Thrust
Vectoring for Advanced Fighter Aircraft High Angle of
Attack Intake Investigations) and MTU-München (Integrated
Thrust Vector Jet Engine Control) respectively.
Thrust Vectoring: advantages and technology
Thrust Vectoring is a relatively new technology which has
been talked about for some time, and it can provide modern
military aircraft with a number of advantages regarding
performance (improved manoeuverability, shorter take-off
and landing runs, extended flight envelope, etc...) and
survivability (control possible in post-stall condition, faster
reaction in combat, etc...).
Additionally, as a byproduct of Thrust Vectoring, there is
also the capacity to independently control the exit area of the
nozzle, which allows to have always an “adapted” nozzle to
every flight condition and engine power setting. This means
an improvement in thrust which in cases can be as high as
7%.
There are several types of Thrust Vectoring Nozzles. For
example, there are 2-D (or single-axis; or Pitch-only) Thrust
Vectoring Nozzles, and there are 3-D (or multi-axis; or Pitch
and Yaw) Thrust Vectoring Nozzles. The ITP Nozzle is a full
3-D Vectoring Nozzle. Also, there are different ways to
achieve the deflection of the gas jet: the most efficient one is
by mechanically deflecting the divergent section only, hence
minimizing the effect on the engine upstream of the throat
(sonic) section.
ITP Design
The ITP concept consists of a patented design featuring the
so-called “Three-Ring-System”, which allows all nozzle
functions (Throat Area, Exit Area, Pitch Vectoring and Yaw
Vectoring) to be performed with a minimum number of
actuators, which, in turn, leads to an optimized mass and
overall engine efficiency.
The nozzle is controlled by four independent hydraulic
actuators, each one with its own servovalve and position
transducer. The level of redundancy will depend on the exact
application.
There is also, only at design level, a simplified variant of the
nozzle, with three actuators only, which has basically the
same functions of the 4-actuator one, except the independent
exit area control. This variant would be a little lighter, but it
misses the thrust improvement capability.
The reaction bars of the ITP nozzle present an arrangement
which allows for high deflection angles, without the risk of
petal overlapping and/or disengagement. The present
prototype has demonstrated deflections up to 23º, but studies
have been performed of variants of the nozzle with deflection
angles of up to 30-35º.
BACKGROUND
The Thrust Vectoring Nozzle developed by ITP was initially
designed to fit and be compatible with an EJ200 engine,
which powers the European Fighter Aircraft EF2000. This
aircraft is developed by the European consortium
Eurofighter, constituted by the companies British Aerospace
(UK), DASA (Germany), Alenia (Italy) and CASA (Spain).
Similarly, the above engine EJ200 is developed by the
European consortium Eurojet, constituted by the companies
Rolls-Royce (UK), MTU (Germany), Fiat Avio (Italy) and
ITP (Spain).
The current EJ200 engine is equipped with a variablegeometry
Convergent-Divergent (Con-Di) Nozzle, developed
by ITP. This nozzle can modify the area to match the engine
running point and afterburner setting, but it has no vectoring
capability.
Through a dedicated R&D programme, ITP have now
introduced a new Thrust Vectoring Nozzle which could be
applied to EJ200 to significantly enhance the capabilities of
EF2000 Aircraft.
Introduction to Military Aircraft Nozzles
In a military aircraft engine with reheat (also called
afterburner or augmentor), the nozzle presents a convergent
section, which has the task to accelerate the gas jet in order
to generate thrust, yet with the characteristic that it must be
capable of varying the throat area according to the
requirement of the engine running point. These are called
“variable geometry convergent” nozzles.
Some nozzles, additionally, comprise a divergent section
downstream of the convergent section, which overexpands
the jet between the throat area and the exit area in order to
extract yet some extra thrust.