230510254Thrust is the force which moves any aircraft through the air. Propulsion system is the machine that produces thrust to push the aircraft forward through air. Different propulsion systems develop thrust in different ways, but all thrust is generated through some application of Newton's third law of motion. A gas (working fluid) is accelerated by the engine, and the reaction to this acceleration produces the thrust force. Further, the type of power plant to be used in the aircraft depends on four important factors, namely: the aircraft mission, over all weight, flying range and endurance and altitude of flight. This assignment work was partitioned into three different parts (A, B and C respectively). In Part-A, a debate was made on the viability of implementation of twin engine propulsion system for long range civil aircrafts. Logical arguments based on literatures collected from various internet and text book sources were made and the conclusion of the usage of twin engine propulsion system for long range civil aircrafts was drawn. In Part-B, for the given mission of the aircraft, suitable power plant was chosen (Turbo fan engine) and corresponding cycle analysis calculations was done. The calculations were repeated for a range of flying altitudes and performance plots drawn were critically examined. Also, for the given Turbo prop engine data, cycle analysis calculations were done. The calculations were repeated for a set of Mach numbers and performance plots drawn were critically examined. The different engine installation techniques for a turboprop engine was also discussed. In Part-C, flow over an axial gas turbine cascade was analysed in Ansys-FLUENT software package. The blade geometry was created in Ansys-BladeGen and then imported to CATIA to create the flow domain. Meshing of the geometry was done in Fluent-ICEMCFD. The total momentum thrust and propulsion efficiency for the selected turbofan engine for the extreme altitudes of 4km & 18km was estimated as 73541N & 9375N and 47% & 40% respectively. The percentage of cold thrust generated at 4km & 18km was 60% & 45% respectively. Both momentum thrust and propulsion efficiency of the engine was observed to decrease with increase in altitude. The propeller thrust and power for the given turboprop engine for flight Mach corresponding to 0.1 & 0.8 was estimated to be 191669N & 25546N and 6074467W & 6477144W respectively. With increasing Mach number of flight, propeller thrust and power was observed to decrease and increase respectively. For the flow analysis over the axial turbine cascade, maximum static pressure value occurs for +150 (2.67*105 Pa) and minimum for 00 (2.5*105 Pa) flow incidence angles respectively. The maximum Mach number value occurs for +150 (1.89) and minimum for -150 (1.57) flow incidence angles respectively. Further the pressure loss was observed to be minimum for -150 (0.1118) flow incidence angle and maximum for +150 (0.2538) flow incidence angle.
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Session Speaker M. SivapragasamSession 08Aircraft
ManoeuvrabilityM. S. Ramaiah University of Applied Sciences#Faculty
of Engineering & TechnologySession ObjectivesAt the end of this
session, student will be able to: Define manoeuvrability of an
aircraftExplain the handling characteristics of an aircraftEstimate
control surface effectivenessEstimate hinge momentsEstimate stick
forcesDescribe control reversal
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyManoeuvrabilityManoeuvre is an airplane
executing aerobatics in a the sky Or multiple airplanes engaged in
aerial combat Generally Manoeuvres are difficult to quantify,
especially in an analytical framework.Basically, most manoeuvres
are comparatively mundane and simply involve changing from one
trimmed flight condition to another.M. S. Ramaiah University of
Applied Sciences#Faculty of Engineering &
TechnologyManoeuvrabilityWhen a pilot wishes to manoeuvre away from
the current flight condition he applies control inputsThis upsets
the equilibrium trim state by producing forces and moments to
manoeuvre the aeroplane toward the desired flight condition.The
temporary out of trim forces and moments cause the aeroplane to
accelerate in a sense determined by the combined action of the
control inputs.Manoeuvring flight is also referred to as
accelerated flight Airframe during such flight is subjected to
temporary, or transient, loads M. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & TechnologyManoeuvrabilityThe
main aerodynamic force producing device in an aeroplane is the
wing,Wing lift acts normal to the direction of flight in the plane
of symmetry. Normal manoeuvring involves rotating the airframe in
roll, pitch and yaw to point the lift vector in the desired
direction Simultaneous adjustment of both angle of attack and speed
enables the lift force to generate the acceleration to manoeuvre.M.
S. Ramaiah University of Applied Sciences#Faculty of Engineering
& TechnologyManoeuvre ExampleDuring turning flight the
aeroplane is rolled to the desired bank angle Horizontal component
of lift causes the aeroplane to turn in the desired direction.
Simultaneous increase in pitch is required to generate more lift
such that the vertical component is sufficient to balance the
weight of the aeroplane.to maintain level flight in the turn.
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyManoeuvre ExampleWhen the pilot pulls
back stick the aeroplane pitches up to generate an increased lift
force this results in out-of-trim normal acceleration the pilot
senses the change in acceleration.The pilot senses what appears to
be an increase in the weight through increase g and is said to be
pulling g.If the increased acceleration is in the direction of
existing acceleration , then it is called +gIf it is against then
it is called -gPilots can withstand larger +g ( 6-8) than -g
(2-3)M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyManoeuvre stabilityStandard definition
of stability implies that when aircraft is disturbed from Trim it
should recover Trim conditionHowever, during manoeuvre pilot
deliberately causes it to go out of trim.Accelerations are
continually varying in all directions, the analysis becomes very
involvedHence analytical formulations have been developed where the
acceleration is constant.Manoeuvres which can be flown at constant
normal acceleration are the inside or outside loop and the steady
banked turn.M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyManoeuvre stabilityFor the purpose of
analysis the loop is simplified to a pull-up,This is just a small
segment of the circular flight path.Since the steady acceleration
is constrained to the plane of symmetry the problem simplifies to
the analysis of longitudinal manoeuvre stabilityThe motion is
steady, hence the analysis is a simple extension of that applied to
longitudinal static stabilityM. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & TechnologyHandling Analysis
leads to the concept of the longitudinal manoeuvre margin,the
stability margin in manoeuvring flight,And control parameters like
stick movement per g and stick force per g.Manoeuvrability of an
airframe is a critical factor in its overall flying and handling
qualities. Large manoeuvre stability means that large control
displacements and forcesLow value could lead to the pilot
overstressing the airframeM. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & TechnologyPhases of
Flight
Radial Force = m* v 2 / r ; accn = v2 / r = n*g
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologySteady Pull-up Manoeuvre An aeroplane
flying in level flight at speed V0 is subject to a small elevator
input which causes it to pull up with steady pitch rate q. (see
figure below)
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologySteady Pull-upIn order to sustain
flight in the vertical circle it is necessary that the lift L
balances not only the weight mg but the centrifugal force alsoLift
is greater than the weight and L = nmg, where n is the normal load
factor.This load factor quantifies the total lift necessary to
maintain the manoeuvre and in steady level flight n=1.M. S. Ramaiah
University of Applied Sciences#Faculty of Engineering &
TechnologySteady Pull-upThe centrifugal force balance is therefore
given by L mg = mV0qIncremental normal load factor is : n = (n 1) =
V0q / gAircraft is pitching up steadily the tail plane experiences
an increase in incidence T due to the pitch manoeuvre (see
figure)For perturbations and eliminating q we get
n*m*g m*g = m *V0* q m*g(n-1) = m* V0* qM. S. Ramaiah University
of Applied Sciences#Faculty of Engineering & TechnologyEffect
on Tail plane
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyManoeuvrabilityIn steady level flight
velocity V 0 is to usual variables C L w lift coefficient etc
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyPitching moment equation
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & Technology
Pitching moment equation M. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & Technology
Pitching moment equation M. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & Technology
Pitching moment equation M. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & TechnologyStick Fixed
Manoeuvre point
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyStick Fixed Manoeuvre Stability
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyCoupled Effects
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyDutch RollSome of our Gliders show this
!!
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyStability Derivatives
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyControl Surface Deflections
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyControl Surface Effectiveness : Flap
Example
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyHinge Moments
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyEstimation of Stick Forces
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyStick Fixed and Stick Free
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyFixed and Free Margin
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyStick Force
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyControl Issues : Aileron Reversal
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyControl Types
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyTypes of Control Systems
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyDeviations from our assumptionsAssumed
linear aerodynamicsLift coefficient CL depends on linearlyNot valid
for higher AOAIgnored compressibility effectsNowhere dependence on
Mach number includedFor M> 0.7 has to be consideredAssumed
aircraft as a rigid bodyNo deformation of aircraft components under
all load conditionsM. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & TechnologyHigh speed
effectsLift curve slope a varies drastically near M=1Aerodynamics
centre a.c shifts backwardsCm0 becomes more +ve while for zero lift
increases
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyAero-elastic effectsEffect of aero
elasticity is to reduce lift curve slope, proportional to dynamics
pressureCombined M and aero elastic effects are shown above
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyFly-By-Wire BasisIf the computer has
final authority on the commands sent to the control system. The
pilots inputs should be limited by the computer (hard limits or
protections) to prevent exceeding the physical design limits of the
aircraft (e.g., angle of attack, g loads, etc.) to protect the
integrity and dynamics of the aircraft.If the pilot has final
authority of the commands sent to the control system.The computer
should monitor the pilots inputs for limits (soft limits) and warn
when they exceed the physical design limits of the aircraftBut
carry out the commands even if that would endanger the aircraft
integrity or flight.M. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & TechnologyStability and
Controllability
M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyHandling QualitiesControls must feel
right to pilotControl parameters (gains, damping, etc.) are unique
to each aircraft and thus must be tuned typically through wind
tunnel and flight testsM. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & TechnologyHigh AOA
ProblemsModern combat aircraft fly at very high AOA and these are
associated with some issues which need to be addressed.Wing Rock
Roll and Yaw DivergenceM. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & TechnologyWing RockWing rock
phenomenon is manifested by a limit cycle oscillation predominantly
in roll about the body axis.This self-induced rolling oscillation
is highly annoying to the pilot and poses serious limitation to the
combat effectiveness.The maneuvering envelope of an aircraft
exhibiting this behavior is also seriously restricted maximum angle
of attack (AOA) is often limited by the onset of wing rock before
the occurrence of stall.In addition, the wing rock can be a safety
problem during landing. M. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & TechnologyWing RockThe final
state is generally stable and characterized by both large roll
attitudes and coupling with directional modes.Handling qualities
are obviously compromised and the maneuvering capabilities degrade
in terms of the maximum achievable angle of attack.Moreover the
presence of wing rock in the approach or landing phase can have
very serious consequences on the operational safety of the
aircraft.This phenomenon, arising from a nonlinear aerodynamic
mechanism.M. S. Ramaiah University of Applied Sciences#Faculty of
Engineering & TechnologyWing RockHas been documented in flight
at a high angle of attack.On configurations with slender forebodies
and highly swept wing plan forms combined with leading edge
extensionsHigh speed civil transport and combat aircraft can fly
under conditions where this self-induced oscillatory rolling motion
is observed.The aerodynamic regime on these configurations is
dominated by vortical flows. During wing rock oscillations, the
normal position in the cross-flow plane of vortex cores is affected
by hysteresis.M. S. Ramaiah University of Applied Sciences#Faculty
of Engineering & TechnologyRoll and Yaw DeparturesThe roll
reversal phenomenon is one in which the aircraft rolls in the
opposite direction to aileron input.The roll due to adverse yaw
overpowers the proverse roll due to ailerons. The directional
instability/directional departure may cause the aircraft to depart
from controlled flight and enter into a spin. Whether the aircraft
can develop a steady spin depends on the balance between the
inertial and aerodynamic momentsM. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & TechnologySummaryIn this
session following topics were discussed:Manoeuvrability of an
aircraftHandling characteristics of an aircraftEstimation of
control surface effectivenessEstimation of hinge momentsEstimation
of stick forcesControl reversalM. S. Ramaiah University of Applied
Sciences#Faculty of Engineering & Technology
