Project-1: Powertrain for aircraft in runways
Project 1: Power Train for Aircraft Engines:
1) Total weight of various types of aircrafts.
Types of aircraft weights are the following:
1) Manufatures empty weight:
It includes the weight of aircraft of the entire flight with its intergal working parts,but excludes baggage ,passenger and fuels.
2) zero fuel weight:
It includes total weight of aeroplanes including unuseable fuels but excludes total weight of useable fuel at board.
3) Payload:
It is load carrying capacity of an aircraft which includes passenger ,cargo and fuels,But if it is in the case of cargo flight it determines the total load of logistics weight of the container which it needs to transport.
4) Maximum take off weight:
This is the maximum weight at which the aircraft would be made to takeoff .
5) Regulated take off weight:
Depending on different factors (flap setting,altitude,lenght of runway),RTOW varies for each take off,but can never be high for MTOW.
6) Maximum landing weight:
It is maximum weight at which an aircraft is permitted to land.
7) Maximum Ramp weight:
It is the maximum weight used for manuevering (towing) aircraft on the ground.
Listed below are the types of aircraft with its weight:
Category MTOW(kg) MLW(tons)
Boeing 747-8F 447,700 346.091
Airbus A380-800 575,000 394
Concorde 185,000 111.1
Antonov An225 640,000 91.7
Vickers VC10 152,000 151.9
Fokker 100 46,000 39.95
Embraer 175(19) 37,500 32.8
Avro RJ-85 42,000 36.47
Tupolev Tu-154M 104,000 80
Boeing 777-300 299,370 237.683
2) Difference between ground speed and Air speed:
Ground speed:
1) Ground Speed is the airplane speed which related to ground.
2) Ground speed which determine how fast airplane will reaches its detination.
3) Ground Speed is calculated by sum of airspeed and windspeed.
Air speed:
1) Air Speed refers to the speed to which is relative to air it is flying in.
2) It determines whether there is enough airflow around an aircraft to make it lift.
3) Air Speed is independent of ground speed.
The above figure refers to the relative velocity with respect to aircraft reference and ground reference.
Wind speed is the vector difference between ground and air speed. if the wind speed is zero and it is equal to the ground speed.
If the measured air speed is greater than the observed ground speed the wind speed becomes positive.
3) Why it is not recommended to use aircraft engines to move it on the gorund at airport?
Generally, most of the airplane can move itself in reverse manner in use of reverse thrust technology. But in the most of the practical, it is not possible because when airplanes start using reverse thrust it will consume lot of fuels as well as causes lot of noise and also hazardous for the people working near by.
The another for not using reverse thrust is that the jet blast can cause damage to terminal buildings or its equipments. Since the engine is also close to the ground it will blow off the sand and debreis forward and sucks it to the engine and causes damage to it.
To solve this kind of issue we use a towing vehicle which helps to tow the vehicle in reverse dierection and it eill be tugged until it reaches a safe place and from there onwards airplane will move by itself for further take off.
4) Taxiing is the movement of an aircraft on the ground, under its own power, in contrast to towing or push-back where the aircraft is moved by a tug.
The aircraft usually moves on wheels, but the term also includes aircraft with skis or floats (for water-based travel). The power for taxiing comes from the engines itself.
If it is a propeller powered aircraft, the propeller provides thrust and pulls the aircraft, like it would in air.
If it is a jet engine, the exhaust air that comes out of the engine creates a forward force due to Newton's third law and moves the airplane.
5)
Take off Performance :
Take off performance can be predicted using a simple measure of the acceleration of the aircraft along the runway based on force equilibrium.
The forces involved will be,
T – Thrust of propulsion system pushing aircraft along runway.
D – Aerodynamic Drag of vehicle resisting the aircraft motion.
F – Rolling resistance friction due to the contact of wheels or skids on the ground.
During take-off run the imbalance in these forces will produce an acceleration along the runway.
he procedure for take-off will be that the vehicle will accelerate until it reaches a safe initial flying speed. The pilot can then rotate the vehicle to an attitude to produce climb lift and it will ascend from the ground. The determination of this safe flying speed or rotation speed, VR, is a critical factor in determining take-off performance.
For safety reasons VR is usually determined as being 1.1 × VSTALL
VSTALL : is the lowest speed that the aircraft can be flown before the airflow starts to separate from wings as the angle of attack becomes too great. The wing is assumed in this case to be in take-off configuration or "clean".
Tyre design of an aircraft:
-An aircraft tyre are deisgned to withstand extreme heavy loads by absording shocks during and there by providing cushioning effect.
-The number of tires required for an aircraft depends on the total weight of aircraft as the weight needs to be distributed evenly.
-Aircraft tyre are designed to facillitate stability in high crosswind condition,to chanalize the water away for preventing skidding and helps to give a good braking effect.
-Aircraft tires are usually inflated by nitrogen air inorder to reduce expansion and contraction from extrerme changes in ambient pressure and tempurature.This type of inert gases will eliminate the possibilty of tire explosion.
-Aircraft tire design are set into an aircraft based on its application and also suffeicient clearance with the ground for allowing tyre growth which happens when centrifugal force is at high speed.
*Rolling Resistance:
-Rolling resistance or rolling drag is the force resisting the motion when the body rolls on a surface and it is mainly caused by non elasticity that is not all the energy needed for deformation of wheel is recovered when the pressure is removed.
-The rolling resistance equation can be defined by the folowing equation:
-Usually aircrafts have a very low rolling resistance coeffiecient of 0.06. Some other examples are as follows:
*Tyre Pressure:
-Aircraft tyres are designed to withstand heavy loads and shocks durong landing and take off and also needs to distribute weight evenly.
-As per research and testing it is found that aircraft tyres are able to sustain pressure upto 800 psi.Generally to note the tyre pressure of an aircraft a special type of sensors are used,its daigram is given below:
-There are 2 primary parameters which is hazardous to the aircraft tires:
I)Deflation:
Here the tire deflates in a controlled ma-nner with minimum dierect consequence to other system.
II)Explosive breakup:
In this case the tire deflates or bursts in an uncontrolled manner with a probablity of causing damage to other secondary system,which further can cause a major crash landing incidents.
*Brake forces:
-Braking an aircraft is a challenging job for most of the pilots especially during landing in a rainy and cross wind environment.
-Inorder to encounter this kinds of problem pilots usually make use of spoilers and reverse thust method inorder to have a safe landing so that the energy required to apply brakes on tires can be reduced and henceforth they do not skid.
-Now there is method which determines the brake force for aircrafts and they are as follows:
K = 0.5*m*v^2where m= mass of aircraft and v=velocity of aircraft.A typical commercial landing speed will range between 150 to 165 MPH.And for passenger flight it is about 166 to 172mph.
6) Force and power required to pull or push an aircraft by a towing vehicle:
Considering:
Total mass of ther aircraft (including payload) for airbus a380 = 575,000kg.
Mass of the push back: 1000kg (assumed)
Rolling Resistance (Frr):
Coefficient of rolling resistance (Crr) = 0.002 (on tarmac)
Rolling resistance force is given by
For the aircraft:
For the Towing Vehicle:
As the towing vehicle resistance is so less compared to the Aircraft because this is a heavy aircraft these can be neglected
Aerodynamic resistnace (Far):
Drag coeffcient(Cd): 0.025
Air Density (ρ) = 1.125kg/m^3
Frontal Area (A): 150m^2.
Velocity (v) = 14.5kmph or 4m/s.
As the vehicle and Plane is moving at very low speed Aerodynamic resistance can be neglected
Hill Climb Resistnace:
Runways are constructed flat so Gradient resistance/ hill climb force is neglected.
Total Resistance:
Power Required:
The min power required by the tow vehicle is 45.26kW to taxi a heavy air craft at 4m/s.
B. Develop the model for the calculated force and power using Simulink.
Simulink Model:
7) A: Design an electric powertrain with type of motor, Duty cycle, PArameters and simulink model:
Estimation of Duty Cycle:
The Power Required for towing of the aircraft is 45.26kW.
Let us consider Motor for the drive train is REB 90
Technical Data:
| Type | Voltage | Continuous / Peak power | RPM | Max torque | Weight | Cooling |
| REB 90 | 400–800 V | 60–70 kW / 80 kW | 1500–4000 rpm | 300 Nm | 22 000 g |
Air / Hybrid (air + fluid) |
Considering 60kW as continuous power, so the voltage will be 400V
Battery power is considred to be 550v
Duty cycle is given by Vo/Vb
where Vo is motor required voltage
Vb is battery voltage.
As there will be losses due to the resistance of FET and Inductance.
Correction factor is considred to be 90%
As there is 10% loss, the voltafge demanded by the motor should be 10% more than required
so the voltage demand should be around 440V from the battery.
| Assumed Parameters | ||
| Mass of aircraft | 575000 | kg |
| Mass of the push back truck | 1000 | kg |
| Coefficient of Rolling Resistance | 0.002 | |
| Drag Coefficient | 0.025 | |
| Air density | 1.125 | kg/m^3 |
| Frontal Area | 150 | m^2 |
| Velocity | 4 | m/s |
| Uphill gradient | 0 | deg |
| Battery Voltage | 550 | V |
| Correction Factor | 0.8 | |
Block Diagram of Power Train:
Simulink Model:
7) B: Excel Calculation:
The power required by the propulsion is calcukated in excel sheet as shown below:
