Project-1: Powertrain for aircraft in runways

EV BATCH17

AIM:To design a electric power train of Air Tug or Tractor for towing and pushing the aircraft in run ways.

INTRODUCTION:

• In an airport, tractor or tugs are used for pully or pushing back the heavy aircraft from its parking position to the runway or viceversa.
• Based the size and weight of an aircraft,we may require the tractor or tug to push or pull the aircraft.Table 1 shows the types of aircraft with their full weight.
• Small aircraft can be easily moved by the human or by use of landing gear or wing struts. Heavy or large aircraft cannot be by hand alone.
• (Answer 3:)Many aircrafts can move back on the ground by using the back/reverse thrust from engine.
• When the reverse thrust is used, the resulting jet blast would increase the noise, injure the airport staff and damage the terminal equipment as well as building due to high speed derbis.
• This derbis might also be sucked in by the aircraft engine which will causes the extensive wear of engine. So, it is not recommended to use aircraft engine power to move it on the ground at airport.
• (Answer 4:) To push or pull the heavy aircraft,tractor or tug are must.
• Pushback tug have a low profile design so that it can easily fit inside the nose of an aircraft.
• Figure 1 shows the tractor or tug used for the pulling or pushing the aircrafts.
• To provide high amount of traction, the tugs are generally heavy and its weight ranges around 54 Tones.
• Once the ground clearance is obtained pilot will communicate with the tractor driver to start the push back.
• Once the puwback is completed the tractor and aircrafts are disconnected.Now the aircraft can move forward by using its own power.

Table 1:Types of aircraft with their full weight (Answer :)

Figure(1) Airplane tugs

Lets Understand abit more about the aircrafts.

• (Answer2) Ground speed of the aircrafts is the speed of the aircraft relative to the surface of earth.
• While the air speed is the speed of the aircraft relative to the air it is flying in.It also has to be noted that when the aircraft is climbing vertically its ground speed is zero.
• So we are only considering the horizontal speed for the ground speed To sum of the ground speed is the sum of windspeed and airspeed.
• When wind is blowing at the same direction a the plane is travelling than the airspeed is less than the ground speed while when the airplane is moving in opposite direction to that of wind than the airspeed is more than the ground speed.

Figure(2) and Figure(3)

• Figure 3 shows the forces acting on the aircraft while flying.
• Lift acts in an upward direction which helps the airplane to fly. Weight of the aricraft is acted downward.
• Thrust force is used to propel the aeroplane and drag force is acting against the thrust force.
• Figure 2 shows the weight distribution for an aircraft.

(Answer 5):

• The aricraft tyre are not designed like a tyre for an automobile.
• The conditions where aircraft and automobile tyres are subjected are quite different.
• Aircrafts tyres are designed to withstand exteremely heavy load(During landing) for short duration of time while automobile tyres are designed to handle the load for longer duration of time.
• Aircraft tyre thread patterns are designed to provide the stability during cross wind condition as well as to channel the water for prevention of hydroplaning and for braking effect.
• Figure 4 a shows the thread pattern for aircraft tyre and 4b shows the internal construction for an aircraft tyre.

• Generally for an aircraft application, the tyre inflation pressure is more than 200 Psi 14 bars.
• This high pressure is for handling the large amount of the load produced by the aircrafts. The inflamation pressure for the landing gear is higher comparitively than other and is around 230 Psi.
• And the inflation pressure varies with type and size of an aircraft. The tyre is inflated by using nitrogen gas to minimize the expansion and contraction of the tyre.
• The aircraft tyres are generally replaced after 300 cycle of operation.
• For an aircraft,the braking is done by help of engine itself, wing spoiler and disc brakes at the wheels.
• The wing spoiler assit while braking an aircraft. When the plane is aproaching the runway,the pilot raise the spoiler to deaccelerate an aircraft.

Trailer Tire speed Ratings/Load capacity (65mph):

• Unlike automotive tires, all ST tires are tested and rated at by the DOT at 65MPH.
• This 65MPH test allows the tire to qualify as a high speed tire. Every ST Trailer Tire you see on the highway goes through this exact same test regardless of tire size or manufacturer.
• The advertised load capacity on the sidewall of the tire is approved at this speed with proper inflation.

outside Dia.(diameter) Measurements (In.):

The outside diameter figure specifies the height of the tire when inflated. This metric is paramount when determining the amount of clearance needed vertically once the tire assembly is installed.

Braking of aircraft:

• The raised wing spoiler results in a drag,which slows the aircraft to some extend with the wing spoiler air craft also uses the disc brakes when it is on the runaway.
• The disc brake is sirnilarte of the automobile brakes.
• The disc brakes mounted at the wheel grabs the wheel and slows it down.
• In the re thrust method, the direction of the thrust is reverese to stop the aircraft.
• In the figure 5 we can see that the se are raised and the engine is applying the reverse thrust.
• During flight the aircraft acolerates with the help of engine, when the necessary Speed is obtained by the aircraft, the pilot lowers down the spoiler which increas the pressure of air at the down region of a aircraft and lowers the pressure at the upper region as described bernouli principle.
• Due to this a force called as lift is created which enbles the aeroplane to fly.
• The litt force generated is greater than the weight of an alrcraft. The engine is propel by the help of thrust generated by the aircraft engine.
• While lowering the plane the spolier is adjusted in such a way that lift force is gradually decreased.

Electric aircraft:

• An electric aircraft is an aircraft powered by electricity, almost always via one or more electric motors which drive propellers. Electricity may be supplied by a variety of methods, the most common being batteries.
• Electrically powered model aircraft have been flown at least since the 1970s and were the forerunners of the small unmanned aerial vehicles(UAV) or drones, which in the twenty-first century have become widely used for many purposes.
• Although crewed flights in an electrically powered tethered helicopter go back to 1917 and in airships to the previous century, the first crewed free flight by an electrically powered aeroplane, the MB-E1, was not made until 1973 and most crewed electric aircraft today are still only experimental prototypes.
• Between 2015 and 2016, solar impulse completed a circumnavigation of the Earth using solar power.
• More recently, interest in electric passenger aircraft has grown, for both commercial airliners and personal air vehicle in part to limit the environmental impact of aviation.

assumptions:

• maximum speed of the aircraft tug is 10kmph.
• weight of tug =54,000kg
• coefficient for rolling friction for plane and tug be same as 0.01
• Grade=0
• Aircraft tug is pulling the vehicle at constant speed 2.77m/s for 2 minutes.
• Frontal area of tug =50 m^2
• Drag coefficient for the tug =0.63
• Considering the final drive ratio =23
• Radius of the wheel =0.38 m

Now,

• Total mass of the system =85000+54000=139000kg
• Total traction power is calculated by using the below formula,
• Tractive effort=Acceleration force +Drag force +Rolling resistance force
• mathematically,
• Ftrac= μrr *M*g *cosθ + 0.625 Af*Cd*v^2+ a+M*G*sinθ.
• where,
• Ftrac is the total tractive force μrr is the rolling resistance coefficient,Af is the frontal area of the aircraft,M is the total mass,η is the efficiency of the transmission system. G is the gear ratio, θ is the gradient.
• since the vehicle is travelling at a constant speed we can consider the acceleration force to be zero.with  0 Grade.
• we can consider the hill climbing force also zero.
• so, the above equation by using the Ms excel.

https://docs.google.com/spreadsheets/d/1DtVu0A_roApO7sxay_GBA-CWdSOsZkzB/edit?usp=sharing&ouid=112243400622031157726&rtpof=true&sd=true

modelling the above equation by using the simulink:

observe the results of simlink  compared with the excel spread sheet both results are same.

• power of approximately 40Kw and the tractive force is around 14KN.
• Torque requied =Ftr*r/G=228NM.
• 40kw is the continous power from the motor,so we have choose the motor higher power rating than 40kw lets take 60kw motor.
• energy/km =4 kwh/km.
• since the vehicle has to be operated at lower speed and high torque we can choose BLDC motor for out applicaton.
• motor specification
• power =60kw (peak)
• maximum torque =250 Nm
• mass =153kg 
• continuous power=35-45kw
• motor voltage=400v
• The voltage of the motor is around 400v as well as to design the battery in such a way that,our battery cutoff voltage should be higher than the rated voltage of the motor.
• current to the motor =150amps
• battery must be produce the 150amps current and the cutt off voltage should be 400v.I have consider the lithium-ion battery used in this case.
• No of cell in series for the battery= 400/2.75=146
• cells So the maximum voltage for the battery =4.2*146=614 V
• To deliver 150 Amphr of current the no of cell in parallel are =150/2.6=58 cells
• Now the capacity of battery for above condition=614*150 =92.1 Kwh
• By using above capacity, our aircraft tug can runupto=92.1/4=23 km by toying the plane.
• Duty cycle for the operation=0.5 -1 for rated voltage condition.

• In above figure we can see an electric powertrain for the aircraft tug.
• Based on the acclerator pedal and broker pedal postion a duty cycle is given to the inverter (Based on the motor control logic). Based on the duty cycle inverter will give the required frequency and voltage to the motor and motor will operates which inturn rotates the wheel.
• the below figure represent the block diagram of aircraft.

 Simulation of DC motor:

The below simulation is the DC motor of the air craft.

Soc:

State of charge drops from 100-0% while  Dc motor running.

Duty cycle:

Design parameters:

 conclusion:

a electric power train of Air Tug or Tractor for towing and pushing the aircraft in run ways design successfully by using the matlab.