Project-1: Powertrain for aircraft in runways
Part A:
1. Search and list out the total weight of various types of aircrafts.
The aircraft gross weight (also known as the all-up weight and abbreviated AUW) is the total aircraft weight at any moment during the flight or ground operation.
An aircraft's gross weight will decrease during a flight due to fuel and oil consumption. An aircraft's gross weight may also vary during a flight due to payload dropping or in-flight refuelling.
At the moment of releasing its brakes, the gross weight of an aircraft is equal to its takeoff weight. During flight, an aircraft's gross weight is referred to as the en-route weight or in-flight weight.
The following image depicts takeoff weight components.
1
MTOW-Maximum Take off weight
MLW-Maximum Landing Weight
|
Type |
MTOW [kg] |
MLW [tons] |
|
640,000 |
591.7 |
|
|
589,670 |
589.67 | |
|
575,000 |
394 |
|
|
447,700 |
346.091 |
|
|
443,613 |
306.175 |
|
|
412,770 |
295.742 |
|
|
Antonov An-124-100M |
405,060 |
330 |
|
396,900 |
295.742 |
|
|
381,000 |
288.417 |
|
|
377,840 |
285.700 |
|
|
377,840 |
260.320 |
|
|
371,950 |
240 |
|
|
367,400 |
256 |
|
|
347,800 |
260.816 |
|
|
351,800 |
251.29 |
|
|
347,450 |
223.168 |
|
|
340,200 |
265.300 |
|
|
308,000 |
233.5 |
|
|
299,370 |
237.683 |
|
|
297,550 |
213.00 |
|
|
276,700 |
190 |
|
|
273,300 |
185 |
|
|
270,000 |
175 |
|
|
270,000 |
195.04 |
|
|
256,280 |
183 |
|
|
254,000 |
192.777 |
|
|
254,000 |
201.849 |
|
|
253,500 |
181 |
|
|
250,000 |
175 |
|
|
242,000 |
185 |
|
|
242,000 |
180 |
|
|
231,300 |
166.92 |
|
|
228,000 |
172.365 |
|
|
211,400 |
||
|
208,000 |
175 |
|
|
204,000 |
158.758 |
|
|
192,000 |
140 |
|
|
187,000 |
136.08 |
|
|
185,000 |
111.1 |
|
|
163,000 |
138 |
|
|
159,000 |
136.078 |
|
|
157,000 |
124 |
|
|
152,000 |
151.9 |
|
|
151,000 |
97.5 |
|
|
151,000 |
112.1 |
|
|
147,000 |
||
|
142,000 |
123 |
|
|
141,000 |
122 |
|
|
140,000 |
||
|
125,000 |
||
|
124,000 |
101.6 |
|
|
117,000 |
86.3 |
|
|
116,000 |
89.9 |
|
|
106,000 |
79.5 |
|
|
104,000 |
79.5 |
|
|
104,000 |
80 |
|
|
104,000 |
87.5 |
|
|
87,500 |
||
|
85,000 |
66.36 |
|
|
85,000 |
71.35 |
|
|
84,000 |
70.1 |
|
|
Airbus A321-100[17] |
83,000 |
77.8 |
|
79,000 |
65.32 |
|
|
78,000 |
68.1 |
|
|
73,000 |
63.28 |
|
|
72,500 |
62.4 |
|
|
72,500 |
62.4 |
|
|
71,000 |
64.41 |
|
|
70,700 |
||
|
70,000 |
58.06 |
|
|
Airbus A320-100[17] |
68,000 |
66 |
|
68,000 |
54.9 |
|
|
68,000 |
||
|
67,000 |
||
|
66,000 |
54.66 |
|
|
65,000 |
57.61 |
|
|
65,000 |
||
|
64,000 |
62.5 |
|
|
63,000 |
51.7 |
|
|
60,000 |
49.9 |
|
|
59,000 |
50.80 |
|
|
59,000 |
57.5 |
|
|
55,000 |
47.174 |
|
|
55,000 |
||
|
54,000 |
||
|
50,000 |
46.265 |
|
|
50,000 |
||
|
48,600 |
||
|
48,500 |
||
|
48,000 |
43 |
|
|
46,000 |
||
|
46,000 |
39.95 |
|
|
44,000 |
||
|
42,000 |
36.74 |
|
|
39,000 |
||
|
37,500 |
32.8 |
|
|
36,500 |
33.345 |
|
|
36,000 |
32.8 |
|
|
33,000 |
30.39 |
|
|
33,000 |
||
|
30,400 |
||
|
28,000 |
28.01 |
|
|
23,000 |
21.319 |
|
|
22,800 |
22.35 |
|
|
22,800 |
21.5 |
|
|
22,000 |
19.3 |
|
|
18,600 |
18.3 |
|
|
13,150 |
12.930 |
|
|
11,500 |
11.25 |
|
|
10,890 |
10.570 |
|
|
9,752 |
8.709 |
|
|
8,300 |
7.665 |
|
|
8,150 |
7.65 |
|
|
7,765 |
7.605 |
|
|
7,761 |
7.103 |
|
|
7,000 |
7.000 | |
|
4,800 |
4.43 |
Maximum taxi weight (MTW)
The maximum taxi weight (MTW) (also known as the Maximum Ramp Weight (MRW) is the maximum weight authorized for maneuvering (taxiing or towing) an aircraft on the ground as limited by aircraft strength and airworthiness requirements. It includes the weight of taxi and run-up fuel for the engines and the APU (Auxillary Power Unit).
It is greater than the maximum takeoff weight due to the fuel that will be burned during the taxi and runup operations.
The difference between the maximum taxi/ramp weight and the maximum take-off weight (maximum taxi fuel allowance) depends on the size of the aircraft, the number of engines, APU operation, and engines/APU fuel consumption, and is typically assumed for 10 to 15 minutes allowance of taxi and run-up operations.
Maximum takeoff weight (MTOW)
The maximum takeoff weight (also known as the maximum brake-release weight) is the maximum weight authorised at brake release for takeoff, or at the start of the takeoff roll.
The maximum takeoff weight is always less than the maximum taxi/ramp weight to allow for fuel burned during taxi by the engines and the APU.
In operation, the maximum weight for takeoff may be limited to values less than the maximum takeoff weight due to aircraft performance, environmental conditions, airfield characteristics (takeoff field length, altitude), maximum tire speed and brake energy, obstacle clearances, and/or en route and landing weight requirements.
Maximum landing weight (MLW)
The maximum weight authorised for normal landing of an aircraft.The MLW must not exceed the MTOW.
The operation landing weight may be limited to a weight lower than the Maximum Landing Weight by the most restrictive of the following requirements:
- Aircraft performance requirements for a given altitude and temperature:landing field length requirements,approach and landing climb requirements
- Noise requirements
If the flight has been of short duration, fuel may have to be jettisoned to reduce the landing weight.
Overweight landings require a structural inspection or evaluation of the touch-down loads before the next aircraft operation.
Maximum zero-fuel weight (MZFW)
The maximum permissible weight of the aircraft less all usable fuel and other specified usable agents (engine injection fluid, and other consumable propulsion agents). It is the maximum weight permitted before usable fuel and other specified usable fluids are loaded in specified sections of the airplane.
2. Is there any difference between ground speed and air speed?
There is a difference between ground speed and air speed to understand this we should take in to account wind speed too.
Wind Speed
For a reference point picked on the ground, the air moves relative to the reference point at the wind speed. Notice that the wind speed is a vector quantity and has both a magnitude and a direction. Direction is important. A 20 mph wind from the west is different from a 20 mph wind from the east. The wind has components in all three primary directions (north-south, east-west, and up-down). In this figure, we are considering only velocities along the aircraft's flight path. A positive velocity is defined to be in the direction of the aircraft's motion. We are neglecting crosswinds, which occur perpendicular to the flight path but parallel to the ground, and updrafts and downdrafts, which occur perpendicular to the ground.
Ground Speed
For a reference point picked on the ground, the aircraft moves relative to the reference point at the ground speed. Ground speed is also a vector quantity so a comparison of the ground speed to the wind speed must be done according to rules for vector componsation.
Airspeed
The important quantity in the generation of lift is the relative velocity between the object and the air, which is called the airspeed. Airspeed cannot be directly measured from a ground position, but must be computed from the ground speed and the wind speed. Airspeed is the vector difference between the ground speed and the wind speed.
Airspeed = Ground Speed - Wind Speed
On a perfectly still day, the airspeed is equal to the ground speed. But if the wind is blowing in the same direction that the aircraft is moving, the airspeed will be less than the ground speed.
Difference between Ground speed and Air speed
| GROUND SPEED | AIR SPEED |
| 1. Ground speed is the speed of the aeroplane relative to the earth surface. |
1. Air speed is the speed of aeroplane relative to the air it is flying in. |
| 2. Ground speed determines how fast an aircraft will get to its destination. |
2. Air speed determines whether there is enough airflow around an aircraft to make it fly. |
| 3. Ground speed is the sum of air speed and wind speed. |
3. Air speed is independent of ground speed. |
Fig- Ground Speed
In calculation of Ground speed and Air speed , the wind speed is the main factor. Depending on the direction and magnitude of Wind speed the relative ground speed and Air speed is calculated.
For Example- If Air speed of an aircraft is 500km/h, where as the wind speed is 100km/h in the same direction of air speed. Then the ground speed will be (500+100)= 600km/h, which is explained in Fig-2. But if the wind speed of 100km/h is in the opposite direction of air speed , then the ground speed will be (500-100)= 400km/h, which is explianed above in Fig-1.
3. Why is it not recommended to use aircraft engine power to move it on the ground at Airport?
For movement on the ground the aircraft uses it own engine power, which is called taxing.
Although many aircrafts are capable of moving in backward using reverse thrust, as result the jet blast or prop wash might cause damage to the terminal building or equipment. Engine close to ground may also blow sand and debris forward and then suck them into the engine, causing damage to the engine. Therefore there are pushback trucks in the airport. A pushback truck lifts the front weel of the aircraft, their role in most airports is to move the aircraft away from the parking spot on to the taxiways, which is called towing.
Unwanted consequences mainly arising from the unintended movement of the aircraft during engine running.
i)Effectively a loss of control can happen, especially during high power engine running. Damage can occur to the aircraft itself, other aircraft nearby or to airside structures.
ii)There is a risk of injury to ground support personnel who may be in relatively close proximity to the aircraft.
iii)It is easier for truck driver to see the surroundings better than the pilot sitting in the cockpit with limited window. The pushback driver knows the airport better than the pilot.
iv)It also saves fuel. virgin Atlantic had proposed a new system in which pushback truck will move the aircraft all the way to runway to save fuel and reduce impact of environment.
v)The plane engines are very loud. When more than one plane will add up their sound, than it will not be pleasent for passangers and others near airport.
vi)The risks which may arise from engine ground running relate to the potential for loss of control of the aircraft by those persons occupying the pilot seats in the flight deck.
vii)The extensive noise arises from the engine power also dangerous for humans and other living things around the vicinity.
Hence for the above reasons it is not recommended to use engine power to move on the ground.
4. How an aircraft is pushed to runway when its ready to take off?
In aviation, pushback is an airport procedure during which an aircraftis pushed backwards away from an airport gate by external power. Pushbacks are carried out by special, low-profile vehicles called pushback tractors or tugs.
Although many aircraft are capable of moving themselves backwards on the ground using reverese thrust (a procedure referred to as a powerback), the resulting jetblast or propwash might cause damage to the terminal building or equipment. Engines close to the ground may also blow sand and debris forward and then suck them into the engine, causing damage to the engine. A pushback is therefore the preferred method to move the aircraft away from the gate.
Pushbacks at busy aerodromes are usually subject to ground control clearance to facilitate ground movement on taxiways. Once clearance is obtained, the pilot will communicate with the tractor driver (or a ground handler walking alongside the aircraft in some cases) to start the pushback. To communicate, a headset may be connected near the nose gear.
Since the pilots cannot see what is behind the aircraft, steering is done by the pushback tractor driver and not by the pilots. Depending on the aircraft type and airline procedure, a bypass pin may be temporarily installed into the nose gear to disconnect it from the aircraft's normal steering mechanism.
Once the pushback is completed, the towbar is disconnected, and any bypass pin removed. The ground handler will show the bypass pin to the pilots to make it clear that it has been removed. The pushback is then complete, and the aircraft can taxi forward under its own power.
5. Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.
i)Takeoff power:-
Takeoff is the phase of flight in which an aircraft leaves the ground and becomes airborne. For aircraft that take off horizontally, this usually involves starting with a transition and moving along the ground on a runway. For light weight aircraft, usually full power is used during takeoff. Large transport catagory (airliner) aircraft may use a reduced power for takeoff, where less than full power is applied in order to prolong engine life, reduce maintenance costs and reduce noise emissions. In some cases, the power used can then be increased to increase the performance. Before takeoff, the engines, particularly piston engines are routinely run up at high power to check for engine-related problems.
An airplane is motionless at the starting of a runway. This is denoted by location O. The pilot releases the brakes and pushes the throttle to maximum takeoff power, and the airplane accelerates down the runway. At some distance from its starting point, the airplane lifts into the air. The distance the airplane cover along the runway before it lifts into the air is called the ground roll (sg). The total takeoff distance also includes the extra distance covered over the ground after the airplane is airborne but before it clears an obstacle of 50 ft for military aircraft and 35 ft for commercial aircraft. This is denoted by sa. The sum of sg and sa is the total takeoff distance.
The aircraft is permitted to accelerate to rotation speed (often referred to as Vr). The term rotation is used because the aircraft pivots around the axis of its main landing gear while still on the ground, usually because of gentle manipulation of the flight controls to make or facilitate this change in aircraft attitude (once proper air displacement occurs under / over the wings, an aircraft will lift off on its own; controls are to ease that in).
The nose is raised to a nominal 5°–15° nose up pitch attitude to increase lift from the wings and effect liftoff. For most aircraft, attempting a takeoff without a pitch-up would require cruise speeds while still on the runway.
ii)Tyre design:-
An aircraft tire is designed to withstand extremely heavy loads for short duration of time. The number of tires required for aircraft increases with the weight of the aircraft, as the weight of the airplane needs to be distributed more evenly. For example -A Boeing 737NG & 737MAX uses 6 wheels, Boeing 787 uses 10 wheels, Boeing 777 uses 14 wheels and Airbus A380 uses 22 wheels.
Aircraft tires also include fusible plugs (which are assembled on the inside of the wheels), designed to melt at a certain temperature. Tires often overheat if maximum braking is applied during an aborted takeoff or an emergency landing. The fuses provide a safer failure mode that prevents tire explosions by deflating in a controlled manner, thus minimizing damage to aircraft and objects in the surrounding environment.
Designing aircraft tires is a very intense undertaking. Carcass plies are used to form the tire. They are sometimes called casing plies. An aircraft tyre is constructed for the purpose it serves.
- They support the weight of an aircraft while it is on the ground.
- It also provides the necessary traction for braking and stopping of an aeroplane.
- Tyre also helps to absorb the shock of landing and provide cushioning the roughness of takeoff, roll-out, and taxi operations.
Once an aircraft manufacturer goes to the tire manufacturer with the size and weight requirements, the tire manufacturer begins the process of designing a tire that meets the needs of the aircraft manufacturer as well as all regulatory requirements — including foreign regulations in many cases. Engineers are challenged with designing tires with cool running, heat-resistant materials while simultaneously exceeding tire service requirements.
Two types of tires are used in aircraft applications — bias-ply tires and radial tires. Although both types of tires share some similarities in design, there are difference between a radial tyre and bias (cross-ply) tyre is the lay of the plies within the tyre carcass. The remainder of the tyre is very similar in construction in both.
- Breakers: Breakers are reinforcing plies of rubber-coated fabric placed under the buff line cushion to protect casing plies and strengthen and stabilize the tread area. They are considered an integral part of the casing construction.
- Tread: The tread is made of rubber mixed with other additives to obtain the desired level of toughness, durability, and resistance to wear. The tread pattern is designed to aircraft operational requirements, with the ribbed tread design used widely due to its good traction under varying runway conditions.
- Sidewalls: The sidewall is a protective layer of rubber that covers the outer casing ply. It extends from the tread edge to the bead area.
- Casing Plies: Alternate layers of rubber-coated fabric (running at opposite angles to one another) provide the strength of the tire
- Chafers: A protective layer of rubber and/or fabric located between the casing plies and wheel to minimize chafing.
- Ply Turnups: The casing plies are anchored by wrapping them around the wire beads, thus forming the ply turnups.
- Flippers: Layers of rubberized fabric that help anchor the bead wires to the casing and improve the durability of the tire.
- Wire Beads: Hoops of high tensile strength steel wire that anchor the casing plies and provide a firm mounting surface on the wheel. The outer edge of the bead that fits against the wheel flange is called the bead heel. The inner bead edge is called the bead toe.
- Apex Strip: A wedge of rubber affixed to the top of the bead bundle.
- Bead toe: It is the inner edge of the bead.
- Bead heel: It is the outer edge of the heel.
- Inner Liner: In tubeless tires, the liner is a layer of low permeability rubber that acts as a built-in tube and restricts gas from diffusing into the casing plies. In tube-type tires, a thinner liner is used to prevent tube chafing against the inside ply.
- Caroass Plies: Layers of rubber-coated fabric piles which have the cords running from bead to bead. These provide the tire with strength in the sidewall area.
- Tread Reinforcing Ply: One or more layers of fabric that strengthens and stabilizes the tread area for high-speed operation. It also serves as a reference for the buffing process when tires are retreaded.
- Buff Line Cushion: The buff line cushion is made of rubber compound to enhance the adhesion between the tread reinforcing ply and the breakers or casing plies. It is of sufficient thickness to allow for the removal of the old tread when the tire is retreaded. Tubeless tyres are more advantageous over tube-type. There is no longer the use of tube-type tyre in recent aviation.
Aircraft tyres must have an approved speed and load rating and have sufficient clearance when retracted through landing gear to allow for tyre growth. Tyre growth is the increase in the size of the tyre due to centrifugal forces at high speed.
- Retreading – Retreading is methods of restoring a worn tyre by renewing the tread area or by renewing the tread area plus one or both sidewalls. Repairs are included in the tyre retreading process.
- Load Rating – Load rating is the maximum permissible load at a specified inflation pressure.
- Ply Rating – Ply Rating is used to identify the maximum recommended load rating and inflation pressure for a specified tyre. It is an index of tyre strength.
- Speed Rating – The speed rating is the maximum takeoff speed to which the tyre has been tested.
- Skid Depth – Skid depth is the distance between the tread surface and the deepest groove as measured in the mould.
Today’s tyres are conductive. Aircraft tyre are manufactured with tread rubber with conducting compounds to permit earthing of static charges.In early days when tyres were not sufficiently conductive, aircraft used to have a conductive strip hanging down from the axle of the landing gear. Upon landing, this strip would be the first part of the aircraft to touch the earth. This discharges any static electricity accumulated on the outer surfaces of the aircraft.
iii)Rolling resistance:-
In addition to the familier forces like thrust, weight, lift, drag there is a rolling resistance force Fr caused by friction between tyre and ground. When aircraft is towing or taxing to pushed it into runway or when take off roll is happenning, the rolling resistance force act against the traction force of the aircraft.This rolling resistance force depends on many factors like surface of the road, roughness of the road, dry or wet condition of the road, tyre pressure, tyre material, tyre temperature, thread pattern of the tyre etc, which determines the rolling resistance force.
Rolling resistance force = Fr in Newton
Rolling resistance co-efficient = urr(It varries for different types of environment)
| urr Typical Values For Aircraft- | ||
| SURFACE | BRAKES OFF | BRAKES ON |
| Dry concrete/ asphalt | 0.03-0.05 | 0.3-0.5 |
| Wet concrete/ asphalt | 0.05 | 0.15-0.3 |
| Icy concrete/ asphalt | 0.02 | 0.06-0.10 |
| Hard turf | 0.05 | 0.4 |
| Firm dirt | 0.04 | 0.3 |
| Soft turf | 0.07 | 0.2 |
| Wet grass | 0.08 | 0.2 |
Rolling resistance force Frr = urr*m*g
Where m = total mass of the aircraft(Actual mass+Pay load) in kg
g = gravitational constant, that is 9.8 m/s^2 .
iv)Tyre pressure:-
The pressure generally is vert high in an aircraft tire to reduce the rolling resistance and to withstand the weight.
Aircraft tires are usually inflated with nitrogen to minimize expansion and contraction from extreme changes in ambient temperature and pressure experienced during flight. Dry nitrogen expands at the same rate as other dry atmospheric gases (normal air is about 80% nitrogen), but common compressed air sources may contain moisture, which increases the expansion rate with temperature.
Tests of airliner aircraft tires have shown that they are able to sustain pressures of maximum 800 psi (55 bar; 5,500 kPa) before bursting. During the tests the tires have to be filled with water, to prevent the test room being blown apart by the energy that would be released by a gas when the tire bursts.
The main landing gear on the Concorde was typically inflated to 232 psi (16.0 bar), whilst its tail bumper gear tires were as high as 294 psi (20.3 bar). The high pressure and weight load on the Concorde tyres were a significant factor in the loss of Air France flight 4590
According to U.S. Federal Aviation Administration(FAA) Technical Standard Order TSO-C62c, the maximum allowable tire pressure loss is 5% per day.
For example-A Boeing 777 fully loaded weighs around 700,000 pounds and has fourteen tires. Therefore, if each of those tires is reacting roughly the same force, then that is 50,000 pounds per tire. The tire pressure is 200 psi. Therefore there should be 250 square inches of surface contact area for each tire with the ground (250 * 200 = 50,000).
v)Break force when landing:-
Stopping an aircraft landing at 180-200 mph requires a lot of braking force. To do this, the aircraft has brake unit on each of the wheels on the main gear assembly. On landing, pilots should use aerodynamic braking by applying extra back-pressure on the stick or yoke. Extreme caution should be used when applying brakes at any significant speed, and only when the end of the runway is quickly approaching. Never step on the brakes to make a runway exit. Applying the brakes at too high a speed could burn the tires, wear out the brakes, or result in a ground loop or swerve.
In general, when the wheels touch the ground, a set of spoilers raise up quickly, which kills the lift provided by the wings. (There are two sets seen in the image below: ground spoilers that only deploy on landing, and spoilers that are used in flight as speed brakes as well as on landing.) While the spoilers provide some drag, their primary purpose is to stop the plane from actually flying, putting all of the weight on the landing gear and in turn making the brakes that much more effective.
Aircraft have highly-engineered, multi-disc brakes made of a carbon-steel material. Manufacturers include Honeywell and Goodrich, part of Collins Aerospace. In general, the brakes are composed of discs that rotate with the wheel and separate discs that are fixed. When pressure is applied—and below you see pressure applied from the right fixed disc on all of the discs—the entire assembly compresses to create the braking action. Carbon brakes are standard today; they cool faster than steel brakes (their predecessor) and can weigh up to 700 pounds less. That represents a significant weight saving for airlines.
Auto Brakes:
Wheel brakes are usually selected to engage automatically after landing. These are called “autobrakes”.that all airliners have several levels of autobrake “severity”. The crew will decide which is the most appropriate to use for every landing depending upon factors like the length of runway, if it is wet or dry, or if the pilots want to exit the runway at a particular point. “For a short wet runway you might select autobrake 3, or MED on the Airbus. For a long dry runway you might select autobrake 1 or LOW on the Airbus".
Part B:
6. A. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle.
For this question, the Towing vehicle specifications is shown below
Length: 8,100 mm
Width: 3,450 mm
Height: 2,050 mm
Thus, frontal area is calculated to be:7.07m2
Dry weight: 15,000 kg
Working speed: 10kmph to 30kmph
The Airbus has the following specifications:
Length 33.8m
Wingspan 35.8m
Height 11.8m
Maximum take-off weight 64,000 – 75,500 kg
Weight of Aircraft 35,000 kg
Drag Coefficients (Cd):0.3
The frontal area for the can estimated as
Area = (Width)*(Height)
= (2*2.54)*(2*2.38)
= 24.18m2
The area of the wings can be estimated to be
Area = Width*Height
(35.08-(2*2.54))*(0.3)
=30.72*0.3
=9.2118m2
Hence, the total frontal area to be considered for the aircraft and tow truck will be
=Frontal Area of tow truck + Frontal Area of Aircraft
= Frontal Area of tow truck + (Frontal Area of Wings + Frontal Area of cabin)
= 7.07 + 9.2118 + 24.18
=40.46m2
The forces to be taken into consideration while calculating the traction power required are
- Frr = μrr mg
Where, Frr is the Rolling Resistance Force in N
μrr is the Coefficient of Rolling Resistance=0.02
m is the total mass of vehicle in kg
g (g=9.81) is the acceleration due to gravity in m/s2
- Fad =0.5*rho*A*Cd*V2
Where, Fad is the Aerodynamic Drag Force in N
rho is the Air Density=1.25
A is the Frontal Area of vehicle in m2
Cd is the Drag Coefficient=0.3
V2 is the velocity in m/s
So,the Total force(Ft)=Frr+Fad
for V=2.77m/sec(10kmph)
Ft=0.02*50000*9.81+0.5*1.25*40.46*0.3*2.77^2=9810+58.2=9868.2N
for V=5.44m/sec(20kmph)
Ft=0.02*50000*9.81+0.5*1.25*46.46*0.3*5.44^2=9810+224.5=10034.5N
The summation of all the forces multiplied by the vehicle velocity will give the required power.
Total Power for 2.77m/s=F*V=9868.2*2.77=27334.9=27.3kW
Total Power for 5.44m/s=F*V=10034.5*5.44=54587.7=54.6kW
B. Develop the model for the calculated force and power using Simulink.
the simualtion is done for V=2.77m/sec(10kmph)
7. A. Design an electric powertrain with type of motor, it’s power rating, and energy requirement to fulfill aircraft towing application in Simulink. Estimate the duty cycle range to control the aircraft speed from zero to highest. Make all required assumptions. Prepare a table of assumed parameters. Draw a block diagram of powertrain.
(Hint :DC7 Block)
| Assumtion For Powertrain Design- | |
| Aircraft Mass | 35000 Kg |
| Towing Vehicle Mass | 15000 Kg |
| Rolling Resistance Co-efficient | 0.02 |
| Air Density | 1.25 kg/m^3 |
|
Towing Vehicle Drag Co-efficient |
0.3 |
| Aircraft Drag Co-efficient | 0.3 |
| Frontal area | 40.46 m^2 |
| Tyre Pressure | 203 PSI/14 bar |
| Towing Velocity(V) |
20km/h=2.778m/s |
| Towing Time(t) | 10min |
| Radius of the towing vehicle wheel |
0.30m |
Power required for the Towing vehicle is 54.6kW
Required Energy(E) for towing application based on the assumed time, that is E = P * t
E=54.6*10min=54.6*10/60=9.1kWh
before choosing wright motor its necessary to find torque requiered for the vehicle
T=F*r
F total force
r radius of the wheel
T=10034.5*0.3=3010.4Nm
lets choose 3Phase Induction motor for this application
Specifications of the motor is
rated power=60kW
rated voltage=220V
efficiency=95%
rated torque=3000Nm
The motor needs to generate 54.6kW of output power.assuming the motor is 95%efficient
Pi=Pout/efficiency=54.6k/0.95=57473.68W
So 57473.68 is the input power should given from the battery
Full load current=Pi/rated voltage=261.2A
Consider input voltage as 220V and Power as 60kW
P= Vi*Ii
60000=220*Ii
Ii=272.7A
The efficiency is calculated as
η=57473.68/60000
=0.95
From the above power equation
Vo*Io=η*Vi*Ii
Vo*272.7=0.95*220*272.7
Vo=209V
So the Duty ratio=Output Voltage/Input voltage
=209/220=0.95
the duty cycle range to control the aircraft speed from zero to highest is 0 to 0.95
Block Diagram of Powertrain for Towing Vehicle- 
Electric Vehicles, consist of a battery, connected to an electric motor (either AC or DC) via an inverter and a motor controller. As automotive batteries generally operate on DC current, while the gird operates AC, a converter is needed to transfer power to the battery.One of the key advantages of an EV is its much higher levels of energy efficiency. Typically an EV will achieve a system efficiency of 80% from battery to wheel (roughly 60% from grid to wheel), while with a conventional IC engine it’s more like 15-25%. This is largely due to the fact that an IC engine is a “heat engine” (i.e. it has to burn fuel and produce heat to operate) and much of all that heat is simply wasted.
Now we will use DC7 block by placing the enrgy capcity and battery voltage inside the battery block
This the design of DC7 block with battery block
The motor is coupled to load, which means that the mechanical torque of the load is Torque=24.7+0.0051Wm^2
The speed reference is set at 500 rpm at t = 0 s. Observe that the motor speed follows the reference ramp accurately (+500 rpm/s) and reaches steady state around t = 1.3 s.
The armature current follows the current reference very well.
For proper system behaviour, the instantaneous pulse values of IGBT devices 1 and 4 are opposite to those of IGBT devices 2 and 3. This generates the average armature voltage needed to obtain the desired armature current. In order to limit the amplitude of the current oscillations, a smoothing inductance is placed in series with the armature circuit.
Here we can see the battery SOC,Current and Voltage ratings
