MEE 121 INTRODUCTION TO MECHANICAL ENGINEERING. Prepared by- Md Ferdous Alam, Lecturer, MEE, SUST

Transcription

1 MEE 121 INTRODUCTION TO MECHANICAL ENGINEERING Prepared by- Md Ferdous Alam, Lecturer, MEE, SUST

2 Hello Class

3 Radiator Radiator is the application of the heat exchanger which is the part of the engine cooling system.

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5 Purpose of a radiator Remove excessive heat produced by the engine during combustion and by friction Degree Celsius temps. could seriously damage engine parts.

6 Types of Cooling Systems Air cooling system Liquid cooling system

7 Air cooling system Its design of air-cooled engine is simple. It is lighter in weight than water-cooled engines due to the absence of water jackets, radiator, circulating pump and the weight of the cooling water. It is cheaper to manufacture. It needs less care and maintenance.

8 No risk of damage from frost, such as cracking of cylinder jackets or radiator water tubes. This system of cooling is particularly advantageous where there are extreme climatic conditions in the arctic or where there is scarcity of water as in deserts.

9 Some older cars, motorcycle and very few modern cars, are air-cooled. Instead of circulating fluid through the engine, the engine block is covered in aluminum fins that conduct the heat away from the cylinder. A powerful fan forces air over these fins, which cools the engine by transferring the heat to the air.

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11 Liquid cooling system Uniform cooling Volumetric efficiency is this type of engine is higher This system requires more maintenance Compact design of engine is possible

12 Some important components

13 Clutch The clutch allows the driver to engage or disengage the engine and manual transmission.

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15 Shaft vs axle

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17 CV Joint Constant-velocity joints (AKA homokinetic or CV joints) allow a drive shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction. A constant velocity joint is a coupling that connects two rotating shafts, an input shaft and an output shaft, at an angle. A constant velocity joint, by design, ensures that both the input and output shaft rotate at the same speed, regardless of the angle of the joint. They are mainly used in front wheel drive vehicles,

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20 Universal Joint (UJ) A universal joint (universal coupling or Hooke's joint) is a joint or coupling in a rigid rod that allows the rod to "bend" in any direction, and is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges located close together, oriented at 90 to each other, connected by a cross shaft. The universal joint is not a constant-velocity joint.

21 At each end of the shaft there is a universal joint (UJ), which allows the rear axle to move up and down in relation to the gearbox without bending or snapping the shaft.

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24 Differential

25 A differential is a gear train with three shafts that has the property that the angular velocity of one shaft is the average of the angular velocities of the others, or a fixed multiple of that average.

26 The differential allows the outer drive wheel to rotate faster than the inner drive wheel during a turn. This is necessary when the vehicle turns, making the wheel that is traveling around the outside of the turning curve roll farther and faster than the other The average of the rotational speed of the two driving wheels equals the input rotational speed of the drive shaft. An increase in the speed of one wheel is balanced by a decrease in the speed of the other.

27 FWD A transmission system that provides power to the front wheels of a motor vehicle. Hence, Front wheel drive (FWD)

28 This arrangement is extremely popular in modern vehicles: Smaller drivetrain: Instead of the engine, transmission, and differential running from the front to the back of a vehicle, a front-wheel drive vehicle has the entire drivetrain in the front. Less weight: Because of the compact drivetrain, frontwheel drive vehicles weigh less than the equivalent rear-wheel or all-wheel drive vehicle.

29 More traction than rear-wheel drive: With most of the vehicle s weight near or above the drive wheels, frontwheel drive vehicles tend to have more traction than rear-wheel drive vehicles. This is especially helpful when the road is slippery or wet. Most fuel efficient type of drivetrain: Due to the light weight and more efficient use of power, front-wheel drive vehicles get more miles out of every gallon compared to the equivalent all-wheel drive or rear-wheel drive vehicle.

30 Ford Focus ST

31 RWD RWD means that the power from the engine is delivered to the rear wheels and the rear wheels push the car forward. The front wheels do not receive any power and are free to manoeuvre the vehicle. Due to the weight of a RWD vehicle being more evenly spread than a FWD vehicle, creates a better balance of weight. The disadvantage of a RWD vehicle are that they do not perform well in poor weather conditions such as rain or snow because they are more prone to loss of traction on slick roads.

32 Ford Mustang

33 All wheel drive

34 AWD Power is delivered to any 2 of the four wheels at any time. The biggest advantage of an AWD vehicle is that it provides the best traction in all kinds of conditions. The cons of an AWD vehicle are that it is heavier which hurts acceleration and uses more fuel. AWD is also the most expensive drivetrain option but will provide the most traction resulting in a safer ride.

35 4WD 4WD means the power from the engine is delivered to all 4 wheels all of the time 4X4 is engaged and has an option to operate in a RWD format to conserve fuel. The biggest advantage of a 4WD vehicle is that it provides the versatility and power to take on any terrain or weather condition. The con of a 4WD vehicle is that it operates in RWD format most of the time and has less traction then a AWD vehicle.

36 Why high performance cars are RWD? High performance cars have a higher torque at the wheels. If a high torque is at the wheels of a FWD, the car tends to pull hard to the right or the left and the driver could lose control.

37 One basic thing! Practically, torque is a better measurement of how quickly your car will accelerate, while horsepower (relative to weight) is a better measure of your car's top speed

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39 Fun question! What do you think? Which one does Batman use as batmobile? 4WD AWD

40 Fun question! What do you think? Which one does Batman use as batmobile? 4WD AWD

41 Thank you