Automobile Engineering

  • Automobile Engineering

Automobile Engineering is a branch study of engineering which teaches manufacturing, designing, mechanical mechanisms as well operations of automobiles. It is an introduction to vehicle engineering which deals with motorcycles, cars, buses, trucks, etc. It includes branch study of mechanical, electronic, software and safety elements. Some of the engineering attributes and disciplines that are of importance to the automotive engineer and many of the other aspects are included in it:


Safety engineering: Safety engineering is the assessment of various crash scenarios and their impact on the vehicle occupants. These are tested against very stringent governmental regulations. Some of these requirements include: seat belt and air bag functionality testing, front and side impact testing, and tests of rollover resistance. Assessments are done with various methods and tools, including Computer crash simulation (typically finite element analysis), crash test dummy, and partial system sled and full vehicle crashes.
Visualization of how a car deforms in an asymmetrical crash using finite element analysis.



Fuel economy/emissions: Fuel economy is the measured fuel efficiency of the vehicle in miles per gallon or kilometers per liter. Emissions testing includes the measurement of vehicle emissions, including hydrocarbons, nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), and evaporative emissions.



NVH engineering (noise, vibration, and harshness): NVH is the customer's feedback (both tactile [felt] and audible [heard]) from the vehicle. While sound can be interpreted as a rattle, squeal, or hot, a tactile response can be seat vibration or a buzz in the steering wheel. This feedback is generated by components either rubbing, vibrating, or rotating. NVH response can be classified in various ways: powertrain NVH, road noise, wind noise, component noise, and squeak and rattle. Note, there are both good and bad NVH qualities. The NVH engineer works to either eliminate bad NVH or change the “bad NVH” to good (i.e., exhaust tones).



Vehicle Electronics: Automotive electronics is an increasingly important aspect of automotive engineering. Modern vehicles employ dozens of electronic systems.[1] These systems are responsible for operational controls such as the throttle, brake and steering controls; as well as many comfort and convenience systems such as the HVAC, infotainment, and lighting systems. It would not be possible for automobiles to meet modern safety and fuel economy requirements without electronic controls.



Performance: Performance is a measurable and testable value of a vehicle's ability to perform in various conditions. Performance can be considered in a wide variety of tasks, but it's generally associated with how quickly a car can accelerate (e.g. standing start 1/4 mile elapsed time, 0–60 mph, etc.), its top speed, how short and quickly a car can come to a complete stop from a set speed (e.g. 70-0 mph), how much g-force a car can generate without losing grip, recorded lap times, cornering speed, brake fade, etc. Performance can also reflect the amount of control in inclement weather (snow, ice, rain).

Shift quality: Shift quality is the driver's perception of the vehicle to an automatic transmission shift event. This is influenced by the powertrain (engine, transmission), and the vehicle (driveline, suspension, engine and powertrain mounts, etc.) Shift feel is both a tactile (felt) and audible (heard) response of the vehicle. Shift quality is experienced as various events: Transmission shifts are felt as an upshift at acceleration (1–2), or a downshift maneuver in passing (4–2). Shift engagements of the vehicle are also evaluated, as in Park to Reverse, etc.

Durability / corrosion engineering: Durability and corrosion engineering is the evaluation testing of a vehicle for its useful life. Tests include mileage accumulation, severe driving conditions, and corrosive salt baths.

Drivability: Drivability is the vehicle's response to general driving conditions. Cold starts and stalls, RPM dips, idle response, launch hesitations and stumbles, and performance levels.

Cost: The cost of a vehicle program is typically split into the effect on the variable cost of the vehicle, and the up-front tooling and fixed costs associated with developing the vehicle. There are also costs associated with warranty reductions and marketing.

Program timing: To some extent programs are timed with respect to the market, and also to the production schedules of the assembly plants. Any new part in the design must support the development and manufacturing schedule of the model.



Assembly feasibility: It is easy to design a module that is hard to assemble, either resulting in damaged units or poor tolerances. The skilled product development engineer works with the assembly/manufacturing engineers so that the resulting design is easy and cheap to make and assemble, as well as delivering appropriate functionality and appearance.

Quality management: Quality control is an important factor within the production process, as high quality is needed to meet customer requirements and to avoid expensive recall campaigns. The complexity of components involved in the production process requires a combination of different tools and techniques for quality control. Therefore, the International Automotive Task Force (IATF), a group of the world's leading manufacturers and trade organizations, developed the standard ISO/TS 16949. This standard defines the design, development, production, and when relevant, installation and service requirements. Furthermore, it combines the principles of ISO 9001 with aspects of various regional and national automotive standards such as AVSQ (Italy), EAQF (France), VDA6 (Germany) and QS-9000 (USA). In order to further minimize risks related to product failures and liability claims of automotive electric and electronic systems, the quality discipline functional safety according to ISO/IEC 17025 is applied.


 Chassis layout of car


 

Concept of aerodynamics shape in vehicle





 


Automotive aerodynamics differs from aircraft aerodynamics in several ways. First, the characteristic shape of a road vehicle is much less streamlined compared to an aircraft. ... Third, the operating speeds are lower (and aerodynamic drag varies as the square of speed).

Automotive aerodynamics is the study of the aerodynamics of road vehicles. Its main goals are reducing drag and wind noise, minimizing noise emission, and preventing undesired lift forces and other causes of aerodynamic instability at high speeds. Air is also considered a fluid in this case. For some classes of racing vehicles, it may also be important to produce downforce to improve traction and thus cornering abilities.




  • Classification of automobile vehicle

  •  Two wheeler chassis layout


  • Four wheeler chassis layout




  •  Transmission system


Requirement of transmission system




Components transmission system are:-


Clutch:-
                Function of transmitting the torque from the engine to the drivetrain. Smoothly deliver the power from the engine to enable smooth vehicle movement. Perform quietly and to reduce drive-related vibration.

Types of clutch:-

Single plate clutch:-
                      Single plate clutch is a type of friction clutch in which power is transmitted by means of friction between the contact surface usually called clutch plates. As name suggest a this clutch consists of only one clutch plate with both side friction lining (frictional surface).


Multiple plate clutch:-A multi-plate clutch is a type of clutch in which the multiple clutch plates are used to make frictional contact with the flywheel of the engine in order to transmit power between the engine shaft and the transmission shaft of an automobile vehicle.

Coil spring clutch:-
A multi-coil spring clutch unit mainly uses a flywheel, a cover-pressing, a pressure-plate, a driven-plate, thrust springs, and a release-lever mechanism. ... This cover takes the reaction of the thrust coil springs and also provides a pivot point for the release-levers.


Diaphragm spring clutch:-
Diaphragm spring as one of the main parts of the clutch creates pressure force of the clutch it besides creates pressure force of the clutch it enables engagement and disengagement of clutch. Diaphragm spring when performing her function is dynamically loaded.




Gear Box:-
                    Most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft (e.g. a motor crankshaft). This means that the output shaft of a gearbox rotates at a slower rate than the input shaft, and this reduction in speed produces a mechanical advantage, increasing torque.


Constant gear mesh gearbox -

Constant gear mesh gearbox employed helical gears for power transmission. The gears are rigidly fixed in the lay shaft. The gears in output shaft rotates freely without engaging with shaft, thus not transmitting power. The gears in both shafts are always meshed together.
To engage the gears with output shaft dog clutch is used. the dog clutch is shifted by the seletor fork moved by gear lever.To provide reverse gearing a idler gear is used.


When the gear lever is pushed, the gear selector fork pushes the dog clutch. The dog clutch engages the gear and the output shaft, thus power from lay shaft now transmitted to output shaft.

Synchromesh gearbox:-
 



Synchromesh gearbox is the latest version of Constant mesh type. It is a manually operated transmission in which, change of gears takes place between gears that are already revolving at the same speed. In this type of gearbox,  gears can rotate freely or it are locked on layout shaft. Synchromesh is really an improvement on dog clutch. The synchronizer is the main part of this gearbox that stabilizes the speed. A synchronizer is a kind of clutch which lets components turning at different speeds. To synchronize the speeds cone friction is used. This synchronizer consists two parts, Synchro cone and Baulk ring. Cone is the part of a gear and ring is the part of the synchronizer. The baulk ring prevents the gears engaging before they are rotating at correct speeds. While engaging, the ring will gradually slide into the cone and the friction will slow or speeds up the gear wheel. Finally, it stabilizes the speed of synchronizer and gear and thus revolves at the same speed. The gears on the layshaft are fixed to it while those on the main shaft are free to rotate on the same.


Epicyclic gearbox:-

Components of Epicyclic Gearbox

1. Ring gear- It is a type of gear which looks like a ring and have angular cut teethes at its inner surface ,and is placed in outermost position in en epicyclic gearbox, the inner teethes of ring gear is in constant mesh at outer point with the set of planetary gears ,it is also known as annular ring.

2. Sun gear- It is the gear with angular cut teethes and is placed in the middle of the epicyclic gearbox; the sun gear is in constant mesh at inner point with the planetary gears and is connected with the input shaft of the epicyclic gear box.

One or more sun gears can be used for achieving different output.

3. Planet gears- These are small gears used in between ring and sun gear , the teethes of the planet gears are in constant mesh with the sun and the ring gear  at both the inner and outer points respectively.

The working principle of the epicyclic gearbox is based on the fact the fixing any of the gears i.e. sun gear, planetary gears and annular gear is done to obtain the required torque or speed output. As fixing any of the above causes the variation in gear ratios from high torque to high speed. So let’s see how these ratios are obtained.

  Overdrive:-
                       Generally speaking, overdrive is the highest gear in the transmission. Overdrive allows the engine to operate at a lower RPM for a given road speed. This allows the vehicle to achieve better fuel efficiency, and often quieter operation on the highway.



Propeller Shaft:-The propeller shaft is what makes any vehicle move by connecting the rear differential to the engine's and transmission system. It is a mechanical component shaped like a tube which allows the transmission to power the differential.


Universal joints:-Universal joints fitted at each end of the propeller shaft allow it to move through an angle while maintaining free rotation. A universal joint is a joint between two rotating shafts that allows them to move at any angle and in all directions.




Final Drive:- A final drive is that part of a power transmission system between the drive shaft and the differential. Its function is to change the direction of the power transmitted by the drive shaft through 90 degrees to the driving axles.


Differential:-The differential is a device that splits the engine torque two ways, allowing each output to spin at a different speed. The differential is found on all modern cars and trucks, and also in many all-wheel-drive (full-time four-wheel-drive) vehicles.


Torque Tube:-The "torque tube" transmits this force by directly coupling the axle differential to the transmission and therefore propels the car forward by pushing on the engine/transmission and then through the engine mounts to the car frame.


Road Wheel:-A drive wheel is a wheel of a motor vehicle that transmits force, transforming torque into tractive force from the tires to the road, causing the vehicle to move. The powertrain delivers enough torque to the wheel to overcome stationary forces, resulting in the vehicle moving forwards or backwards.

Axle :- Axles are rods or shafts that connect to the drive wheels. The main purpose of axles is to transfer power from the transmission to the wheels. As the axle turns, the wheels go around, and without a functioning axle, wheels do not move. Axles also serve to bear the weight of the vehicle and its passengers and cargo.


Hotchkiss drive:-

The Hotchkiss drive is a system of power transmission. It was the dominant form of power transmission for front-engine, rear-wheel drive layout cars in the 20th century. The name comes from the French automobile firm of Hotchkiss, although it is clear that other makers (such as Peerless) used similar systems before Hotchkiss.



During the early part of the 20th century the two major competing systems of power transmission were the shaft-drive and chain-drive configurations. The Hotchkiss drive is a shaft-drive system (another type of direct-drive transmission system is the torque tube, which was also popular until the 1950s).




All shaft-drive   systems consist   of   a driveshaft (also called a "propeller   shaft" or Cardan shaft) extending  from the transmission in  front to  the differential in the  rear.  The differentiating characteristic   of the Hotchkiss   drive   is the fact that it uses universal joints at both ends of the driveshaft, which is not enclosed. The use of two universal joints, properly phased and with parallel alignment of the drive and driven shafts, allows the use of simple cross-type universals. (In a torque-tube arrangement only a single universal is used at the end of the transmission tail shaft, and this universal should be a constant velocity joint.)



In the Hotchkiss drive, slip-splines or a plunge-type (ball and trunnion u-joint) eliminate thrust transmitted back up the driveshaft from the axle, allowing simple rear-axle positioning using parallel leaf springs. (In the torque-tube type this thrust is taken by the torque tube to the transmission and thence to the transmission and motor mounts to the frame. While the torque-tube type requires additional locating elements, such as a Panhard rod, this allows the use of coil springs.)



Some Hotchkiss drive shafts are made in two pieces with another universal joint in the center for greater flexibility, typically in trucks and specialty vehicles built on truck frames. Some installations use rubber mounts to isolate noise and vibration. The 1984–1987 RWD Toyota Corolla (i.e., Corolla SR5 and GT-S) coupe is another example of a car that uses a 2-part Hotchkiss driveshaft with a rubber-mounted center bearing.



This design was the main form of power transmission for most cars from the 1920s through the 1970s. Presently (circa 2012), it remains common in pick-up trucks, and sport utility vehicles.

Control systems

Steering systems :-
                The steering system converts the rotation of the steering wheel into a swivelling movement of the road wheels in such a way that the steering-wheel rim turns a long way to move the road wheels a short way. ... The steering effort passes to the wheels through a system of pivoted joints.




The function of a steering system is to convert the rotary movement of the steering wheel in driver's hand into the angular turn of the front wheels on road.

Rack and Pinion steering systems :-
                                    Rack-and-pinion steering is quickly becoming the most common type of steering on cars, small trucks and SUVs. It is actually a pretty simple mechanism. A rack-and-pinion gearset is enclosed in a metal tube, with each end of the rack protruding from the tube. A rod, called a tie rod, connects to each end of the rack.



The pinion gear is attached to the steering shaft. When you turn the steering wheel, the gear spins, moving the rack. The tie rod at each end of the rack connects to the steering arm on the spindle.


Wheel geometry

Caster:-




Camber:-
 


King pin inclinations :-





 

Toe in &Toe out ;-




Braking systems:-

Need of braking systems:-

Hydraulic braking system:-

Hydraulic braking system is a type of braking system in which unlike the mechanical braking system, hydraulic fluid is used to transmit the brake pedal or brake lever force from the brake pedal or brake lever to the final drum shoes or disc caliper in order to achieve braking.





Drum brake system:-



A drum brake system consists of hydraulic wheel cylinders, brake shoes and a brake drum. When the brake pedal is applied the two curved brake shoes, which have a friction material lining, are forced by hydraulic wheel cylinders against the inner surface of a rotating brake drum.



 Air brake systems:-

An air brake or, more formally, a compressed air brake system, is a type of friction brake for vehicles in which compressed air pressing on a piston is used to apply the pressure to the brake pad needed to stop the vehicle. ... George Westinghouse first developed air brakes for use in railway service.

How does an air brake work?


The brakes are applied by pushing down the brake pedal (also called the foot valve or treadle valve). The harder you push down on the pedal, the more air pressure is applied from the storage tanks into the brake chambers. ... The air pressure used to apply the brakes must be built up in the reservoirs by the compressor.


Master cylinder:-
What is a brake master cylinder?
The master cylinder is the heart of the brake's hydraulic system. It converts the force exerted on the brake pedal into hydraulic pressure to apply the brakes. ... The fluid inside acts like a liquid linkage between the master cylinder's pistons and the calipers and wheel cylinders.


  • Suspension Systems,Wheels & Tyres :- 
Purpose of suspension system:-







 Wishbone type suspension system:-

Working :-


   The wishbone type is the most popular independent suspension system.It consists of two (occasionally parallel) wishbone-shaped arms to locate the wheel.Each wishbone or arm has two mounting points to the chassis and one joint at the knuckle. The shock absorber and coil spring mount to the wishbones to control vertical movement.The vehicle weight is transmitted from the body and the cross member to the coil spring through which it goes to the lower wishbone member.The wishbones not only position the wheels and transmit the vehicle load but also rest acceleration, braking and cornering forces.The upper arms are shorter in length then the lower ones. This helps to keep the wheel track constant thereby avoiding the tyre scrub thus minimizing wear.





MacPherson suspension system:-

MacPherson suspension work:-


The MacPherson strut combines a shock absorber and a coil spring into a single unit. ... Each wishbone, which has two mounting positions to the frame and one at the wheel, bears a shock absorber and a coil spring to absorb vibrations.


 Trailing link type suspension system:-

A trailing-arm suspension, sometimes referred as trailing-link is a vehicle suspension design in which one or more arms (or "links") are connected between (and perpendicular to and forward of) the axle and a pivot point (located on the chassis of a motor vehicle). ... It is used on the front axle.


Coil spring suspension system:-





Leaf spring type suspension system:-

Leaf spring is a suspension system for vehicles that has been used as far back as medieval times. They were originally called carriage or laminated springs. Its system has been tried and true, primarily used on almost all vehicles up to the 1970's and still today on trucks and vans that haul heavy loads.

How does a leaf spring suspension work?


The ends of the leaf spring bundle are attached to the chassis of the car or truck, and the axle is then attached to the center of the leaves. When the axle moves on various road conditions, the leaves compress and absorb the motion rather than transferring all the energy directly to the chassis.

Shock absorber suspension system,:-

Shock absorbers are a necessary part of car suspension. Most vehicles have one shock absorber for each of the four tires. They play a very important role in a vehicle's suspension system. The main purpose of shock absorbers is to limit overall vehicle body movement, or sway.


Air suspension suspension system:-

 


Air suspension is a type of vehicle suspension powered by an electric or engine-driven air pump or compressor. This compressor pumps the air into a flexible bellows, usually made from textile-reinforced rubber. ... The air pressure inflates the bellows, and raises the chassis from the axle.



Working mechanism of the air suspension

The air suspension system starts with the onboard air compressor which gets power from the electrical system of the car and enables inflammation of each bag. The Compressor feeds high-pressure air to each spring by using either polyurethane pipes or stainless steel tubes.
Many of the times, people get a separate tank which helps in maintaining the instant pressure within the system. This can allow smoother transitions during large pressure changes. This component can be inbuilt or one can even customize it as per the requirements.






In the air suspension, the compressor operates like any other pumps. It draws external air in the storage tank, compresses it to high pressure and delivers it to the other end. With the integration of controller, it guides the system about when to pump the air and what quantity of air is necessary. Such controllers can be manual or electrical in nature.

  •  Electrical Systems

Battery:-

Automotive lead acid battery construction and operation:-






A Lead Acid Battery consists of Plates, Separator, and Electrolyte, Hard Plastic with a hard rubber case. ... These two plates are separated using a separator which is an insulating material. This total construction is kept in a hard plastic case with an electrolyte. The electrolyte is water and sulfuric acid.

 Starting  System :-

Layout of starting system:-








Construction of starting motor:- 


The starting system includes the battery, starter motor, solenoid, ignition switch, and in some cases, a starter relay. An inhibitor (neutral safety) switch is included in the starting system circuit to prevent the vehicle from being started while in gear.

Bendex drive :-


Bendex drive:-



    A Bendex drive is a type of engagement mechanism used in starter motors of internal combustion engines.
    The device allows the pinion gear of the starter motor to engage or disengage the flywheel of the engine automatically, when the starter is powered or when the engine fires, respectively.
    The Bendix system places the starter drive pinion on a helical drive spring.
    When the starter motor begins turning, the inertia of the drive pinion assembly causes it to wind the spring, forcing the length of the spring to change and engage with the ring gear.
    When the engine starts, back drive from the ring gear causes the drive pinion to exceed the rotation speed of the starter, at which point the drive pinion is forced back and out of mesh with the ring gear.


 Ignation systems and their components:-

Battery Ignition System:-

 
Battery Ignition System is used in automobiles to produce spark in the spark plug for the combustion of fuel in the I.C. engine. Here the main source for the spark generation is the battery. It is mostly used in light commercial vehicles. Almost in every petrol engine, the need of spark is required to burn the fuel in the Engine. And thus an ignition system is always there in petrol or gasoline engine for the spark generation. There are different ignition system such as a magneto ignition system, distributorless ignition system and electronic ignition system. Here we will discuss one of the ignition system them. So let’s get started.

Magneto ignition system:-


The working principle of this ignition system is similar to the working principle of coil or battery ignition system except that in it magneto is used to produce energy but not the battery. Here are the following scenarios that occur in it.

    When engine in the system starts it help magneto to rotate and thereby producing the energy in the form of high voltage.
    The one end of the magneto is grounded through contact breaker and the ignition capacitor is connected to it parallel.
    The contact breaker is regulated by the cam and when the breaker is open, current flows through the condenser and charges it.
    As the condenser is acting like a charger now, the primary current flow is reduced thereby reducing the overall magnetic field generated in the system. This increases the voltage in the condenser.
    This increased high voltage in the condenser will act as an  EMF thereby producing the spark at the right spark plug through the distributor.
    At the initial stage, the speed of the engine is low and hence the voltage generated by the magneto is low but as the rotating speed of the engine increases, it also increases the voltage generated by the magneto and flow of the current is also increased. To kick start the engine, we can use an external source such as the battery to avoid the slow start of the engine.




Electronic ignitions system:-


    To understand the working of the electronic ignition system let’s consider above figure in which all the components mentioned above are connected in their working order.
    When the driver switch ON the ignition switch in order to start a vehicle the current starts flowing from the battery through the ignition switch to the coil primary winding, which in turn starts the armature pickup coil to receives and send the voltage signals from the armature to the ignition module.
    When the tooth of the rotating reluctor comes in front of the pickup coil as shown in the fig the voltage signal from pickup coil is sent to the electronic module which in turn senses the signal and stops the current to flow from primary coil.
    When the tooth of the rotating reluctor goes away from the pickup coil, the change in voltage signal is sent by pickup coil to the ignition module and a timing circuit inside ignition module turns ON the current flow.
    A magnetic field is generated in the ignition coil due to this continuous make and break of the circuit which induced an EMF in secondary winding which increases the voltage upto 50000 Volts.
    This high voltage is then sent to distributor ,which has the rotating rotor and distributor points which is set according to the ignition timing.
    When the rotor comes in front of any of those distributor points the jumping of voltage through the air gap from the rotor to the distributor point takes place which is then sent to the adjacent spark plug terminal through the high tension cable and a voltage difference is generated between the central electrode and ground electrode which is responsible for generating a spark at the tip of the spark plug and finally the combustion takes place.



    To understand the working of the electronic ignition system let’s consider above figure in which all the components mentioned above are connected in their working order.
    When the driver switch ON the ignition switch in order to start a vehicle the current starts flowing from the battery through the ignition switch to the coil primary winding, which in turn starts the armature pickup coil to receives and send the voltage signals from the armature to the ignition module.
    When the tooth of the rotating reluctor comes in front of the pickup coil as shown in the fig the voltage signal from pickup coil is sent to the electronic module which in turn senses the signal and stops the current to flow from primary coil.
    When the tooth of the rotating reluctor goes away from the pickup coil, the change in voltage signal is sent by pickup coil to the ignition module and a timing circuit inside ignition module turns ON the current flow.
    A magnetic field is generated in the ignition coil due to this continuous make and break of the circuit which induced an EMF in secondary winding which increases the voltage upto 50000 Volts.
    This high voltage is then sent to distributor ,which has the rotating rotor and distributor points which is set according to the ignition timing.
    When the rotor comes in front of any of those distributor points the jumping of voltage through the air gap from the rotor to the distributor point takes place which is then sent to the adjacent spark plug terminal through the high tension cable and a voltage difference is generated between the central electrode and ground electrode which is responsible for generating a spark at the tip of the spark plug and finally the combustion takes place.

    To understand the working of the electronic ignition system let’s consider above figure in which all the components mentioned above are connected in their working order.
    When the driver switch ON the ignition switch in order to start a vehicle the current starts flowing from the battery through the ignition switch to the coil primary winding, which in turn starts the armature pickup coil to receives and send the voltage signals from the armature to the ignition module.
    When the tooth of the rotating reluctor comes in front of the pickup coil as shown in the fig the voltage signal from pickup coil is sent to the electronic module which in turn senses the signal and stops the current to flow from primary coil.
    When the tooth of the rotating reluctor goes away from the pickup coil, the change in voltage signal is sent by pickup coil to the ignition module and a timing circuit inside ignition module turns ON the current flow.
    A magnetic field is generated in the ignition coil due to this continuous make and break of the circuit which induced an EMF in secondary winding which increases the voltage upto 50000 Volts.
    This high voltage is then sent to distributor ,which has the rotating rotor and distributor points which is set according to the ignition timing.
    When the rotor comes in front of any of those distributor points the jumping of voltage through the air gap from the rotor to the distributor point takes place which is then sent to the adjacent spark plug terminal through the high tension cable and a voltage difference is generated between the central electrode and ground electrode which is responsible for generating a spark at the tip of the spark plug and finally the combustion takes place.



Automobile Air conditioning System


Layout of car air conditioning system:



Working of car air conditioning system:-

Working of car air conditioning system.The layout of car air conditioning system is shown in figure.The  main  components  of  the  system    are    compressor,    condenser,    receiver/dryer, Expansion valve and evaporator. In this system the heat is absorbed and transferred in the following stepsi.Refrigerant leaves the compressor as high pressure vapour.ii.By  removing  heat  via  condenser,  the  vapour  becomes  low  temperature liquid.iii.Moisture  and  contaminants  are  removed  by  the  receiver  dryer,  where  the clean refrigerant is stored until it is needediv.The expansion valve controls the flow of refrigerant into the evaporator.v.Heat  is  absorbed  from  the  air  inside  the  passenger  compartment  by  the  low pressure refrigerant, causing the liquid to vaporize and greatly decreased passenger compartment temperature.The refrigerant returns to the compressor as a low pressure, low temperature vapours and a cycle completed. 


Important  precautions  to  be  taken  while  using  air  conditioning  system    of vehicle:-
 

i.Operate  the  air  conditioner  periodically  or  at  least  once  a  week  to  keep  the internalparts lubricated as well as prevent the hoses from hardening.
ii.Do not switch ON the A.C. at high speeds which may result in the ceasing of compressor.
iii.Do not stick anything into the air outlet or the air inlet. As it dangerous and it can cause injury or damage.
iv.Avoid  exposing  a  body  directly  to  a  continuous  cool  air  flow  for  long periods-It is not good for health.
v.Avoid  placing  any  obstacles  near  the  inlet  or  outlet-if  inlet  or  outlet  is blocked it may causes damage to the unit.
vi.Do not run or stop the unit frequently. If run or stop the unit more than 4-5 times an hour, it may cause damage to the unit.
vii.The air filter should be cleared at least once every two weeks
viii.When theunit is cleaned, set the selector switch at off position
ix.Never operate A.C. with heater on.
x.Do not charge the refrigerant in the A.C. system before flushing


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