acd505 session 09
DESCRIPTION
Thrust 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.TRANSCRIPT
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Session Speaker Dr. H. K. NarahariSession 09Aircraft Flight Dynamics 1 M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologySession ObjectivesAt the end of this session, student will be able to: Describe the axes and notation for the analysis of dynamic stability of an aircraftDerive the generalised set of equations of motion for a rigid aircraftConstruct the linearised form of equations of motion
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyDynamics : Trivial ExampleConsider a canon fires mortar 500 m/s from the edge of the cliff (figure) questions we ask are :How long will the mortar be in air?how far away will it fall? Does it depend on the initial height?
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyDynamics ExampleOnce the mortar leaves the canon, only gravitational force is acting (ignoring drag)So vertical velocity V and distance P is given byVo is initial velocity =o, and Po is cliff height 100mThe mortar will be in air for 4.52 secs, notice P0 is used to get this height is important. Place your canons as high as possible
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyNotations and ConventionsThe axes and notation for the analysis of dynamic stability of an aircraft are given in Figure and follow a logical order.Once the x, y and z-axes are defined we have translation along them.Then we have rotations about these axis,L, the rolling moment about the x-axis, M the pitching moment about the y-axisN and the yawing moment about the z-axis respectively.M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyNotations and ConventionsThe axis system uses what are known as body axes.This axis system is not locked in position in space, but moves with the aircraft.The origin of the axis system is at the centre of gravity of the aircraft, since all rotations take place about the c.g.A rigid aircraft has six degrees of freedom. Three translationsThree rotationsM. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyNotations and ConventionsFor computations, these equations are simplified when performing analysis of the dynamic modes of an aircraft. These degrees of freedom are expressed as perturbation quantities in relation to steady straight flighti.e. velocity perturbations u, v and w and rotational velocities p ,q and r M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyNotations and Conventions
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEquations of Motion
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEquations of Motion
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEquations of MotionThe basic rule is apply Newtons second law of motion for each of the six degrees of freedom which simply states that,mass acceleration = disturbing force i.e. m*a = FFor the rotary degrees of freedom the mass and acceleration become moment of inertia and angular acceleration respectively whilst the disturbing force becomes the disturbing moment or torque.I * = torqueM. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEquations of MotionThe static stability analysis presented earlier is good for the preliminary design of aircraftAircraft flight is a dynamic phenomenon:Excitation internal or external results in a dynamic responseThe response may have a single or multiple componentsThe response may be damped (stable) or undamped (unstable)The modelling of this dynamic response necessitates the derivation of the full equations of motion of the aircraftM. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEquations of MotionHere is a definition of the degrees of freedom of an aircraft and the forces and moments acting on it.All degrees of freedom are relative to the aircrafts centre of gravity and use aircraft geometrical axes.M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEquations of Motion
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEquations of Motion
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEquations of Motion
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEquations of Motion
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEOM : Total Local Velocities
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEquations of MotionThe above equations are generalized set of equations and apply to any rigid aircraft.These EOMs are non-linear and if we replace the RHS with respective equations, many of the terms are difficult to evaluate. Hence these are linearised by perturbation studiesM. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEOM : Local Accelerations
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEOM : Total Accelerations
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEOM : Total Local Accelerations
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEOM : Total Local Accelerations
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEOM Example
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEOM : Solution
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyEOM : Solution
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyGeneralised Force Equations
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyGeneralised Force Equations
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyGeneralised Moment Equations
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyGME : X Axis
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologyGME : X Axis
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & TechnologySummaryIn this session following topics were discussed:Axes and notation for the analysis of dynamic stability of an aircraftGeneralised set of equations of motion for a rigid aircraftLinearised form of equations of motion
M. S. Ramaiah University of Applied Sciences#Faculty of Engineering & Technology