Project-1: Powertrain for aircraft in runways
1.
Total weight of various types of aircraft has been categorized into several names.For example Manufacturer's EmptyWeight(MEW), Zero Fuel Weight(ZEW),Operating Empty Weight(OEW),Maximum Take Off Weight(MTOW),Maximum Landing Weight(MLW), Maximum Ramp Weight(MRW) etc.Below is a list of four aircraft's Maximum TakeOff Weight.
Airbus A380 575000 Kg
Boeing 747-8 443613 Kg
Boeing 747-400ER 412770 Kg
Antonov An 225 640000 Kg
2.
Air speed is the vector difference between ground speed and wind speed.On a reasonably still day air speed will be equal to ground speed.However, if the wind is blowing in the same direction that the aircraft is moving air speed will be less than the ground speed.
3.
Though many aircrafts are capable of moving in backward using reverse thurst the resulting jet blast or propwash might cause damage to the Terminal Building and Equipment.Engine close to ground may also blow sand and debris forward and then suck them into the engine causing damage to it.That is why it is recommended not to use aircraft engine power to move it on the ground at airport.
4.
A so called pushback Truck reverses the aircraft into taxiing position pushing it with a towbar attached to the nose wheel strut or in the most modern versions by actually lifting the wheel.This process speeds up coupling and decoupling.The aircraft taxis to the runway to depart at the ground time.
5.
Take off power is the power allowed to an engine to produce for a limited period of time for the purpose of take off.The use of take off power is usually limited to 5 min for reciprocating engines and 2.5 min for gas turbine engines.But this may not always be the case.
Aircraft tyres were of Bias design in earlier days.But now Radial design is extensively used.The design involves Overlay,Belt Plies,Casing Plies and Chipper.Overlay is nothing but reinforcing Rubber coating.Best Plies uses a composite structure for stifening purpose while Casing Plies and Chipper uses Rubber coated fabrics.
Co efficient of Rolling Resistance is a dimensionless number signifying ratio of two forces.Thus mathematically
RR co-efficient=F/G where F is a force necessary to pull the axle of a tyre horizontally in the direction of travel and G is the vertical load on the tyre which is assumed to roll on a flat horizontal surface.
Aircraft tyres are generally operated at high pressures upto 200 psi or 14 bar and even higher for business jets.Large aircraft tyres are filled with Nitrogen gas.
While landing brke forces act on the wheels of an aircraft.An Electrical signal is sent from the flight deck to the hydraulic actuators near the main landing gear.Here hydraulic fluid at 3000 pounds per sq inch pressure is used to force the brake unit against the wheel thus slowing it down.Boeing 787 has one brake unit on each of the 8 wheels.The brake units are powered by the hydraulic system.
6.
The force to move an aircraft on an absolute flat runway with no wing at constant low speed is given by the formula
F=CRRX MXg
where CRR is Coefficient of Rolling Resistance,M is mass of the aircraft and g is acceleration due to gravity.
We know that g=9.81 m/s2.So taking M=40000Kg and CRR=0.02 we get F= 7848 N
Tanking velocity of movement as 1.5 m/s we find that Power is
P=FXv=7848X1.5 i.e.11772 Watts or 11.772 KW
For calculation of Force and Power a Simulink model has been developed vide the model Airplane attached.The same calculation was done by running simulation also.
7.
Electric Powertrain has been designed to fulfill aircraft towing application vide Simulink Model P_train attached herewith.Duty Cycle estimation is done below.
The motor input power is the output power of the towing vehicle.Thus to obtain maximum speed the Duty Cycle calculation will be as under.
Duty Cycle=Output Power/Input Power=(84.54/90)X100% i.e.93.9%.This is the Duty Cycle range to control the aircraft speed from zero to the maximum.
TableIV shows the power calculation while TableV shows a list of assumed parameters.Table VI shows a block diagram.