Friday, 13 September 2013

WINDSHIELD WASHER


          A windshield washer system for an automotive vehicle includes a fluid reservoir, a pump mounted within the fluid reservoir and a heater mounted in proximity to the pump so as to provide heat to fluid contained within the reservoir. The system further includes a nozzle operatively associated with the pump for applying fluid from the reservoir to an outside surface of an automotive vehicle. The heater may comprise an electric resistance element, such as a positive temperature coefficient element mounted about a pumping chamber of the pump. In any event, the heater provides sufficient heat to the fluid contained within the reservoir to prevent water in the fluid from freezing at ambient temperatures normally encountered by automobiles.
          According to another aspect of the present invention, a nozzle incorporated in the present system may be of the telescoping variety such that it has a first position for spraying and a second, or retracted, position when it is not spraying. In this fashion, a neat, uncluttered appearance may be achieved, while protecting the nozzle from damage. In any event, the nozzle is close-coupled to the pump, so as to minimize the fluid volume between the pump and nozzle. This promotes drain back of fluid from the nozzle to the pump, while allowing heat to flow from the pump to the nozzle, thereby further inhibiting freezing of water within the nozzle.




WINDSHIELD WASER FLUID
          Windshield washer fluid is sold in many formulations, and some may require dilution before being applied, although most solutions available in North America come premixed with no diluting required. The most common washer fluid solutions are given labels such as "All-Season", "Bug Remover", or "De-icer", and usually are a combination of solvents with a detergent. Dilution factors will vary depending on season, for example in winter the dilution factor may be 1:1, whereas during summer the dilution factor may be 1:10. It is sometimes sold as sachet of crystals, which is also diluted with water. Distilled water is the preferred diluent, since it will not leave trace mineral deposits on the glass. Anti-freeze, or methylated spirits, may be added to a mixture to give the product a lower freezing temperature. But methanol vapor is harmful when breathed in, so more popular now is an ethanol winter mix, e.g. PAV, water, ethanol (or isopropanol), and ethylene glycol.
          Concerns have been raised about the overall environmental aspects of washer fluid. Widespread, ground-level use of wiper fluid (amounting to billions of liters each year) can lead to cumulative air pollution and water pollution. Consumer advocacy groups and auto enthusiasts believe that the alcohols and solvents present in some, but not all, windshield washer fluid can damage the vehicle. These critics point to the corrosive effects of ethanol, methanol, and other components on paint, rubber, car wax, and plastics, and groups propose various alternatives and homemade recipes so as to protect the finish and mechanics of the motor vehicle.

WINDSHIELD WASHER NOZZLE(S)
          This model is equipped with two hood mounted washer nozzles. Each nozzle emits two streams into the wiper pattern. If the nozzle performance is unsatisfactory they can be adjusted. To adjust insert a pin into the nozzle ball and move to proper pattern. The right and left nozzles are identical. It is an advantage of the present system that separated fluid lines and nozzles are eliminated, with the entire system being contained in a single assembly, so as to allow the protection of the fluid and the entire system from freezing with a single heat source.




WINDSHIELD WASHER SYSTEM

All models are equipped with electrically operated windshield washer pumps. The wash function can be accessed in the OFF position of the wiper control switch. Holding the wash button depressed when the switch is in the OFF position will operate the wipers and washer motor pump continuously until the washer button is released. Releasing the button will stop the washer pump but the wipers will complete the current wipe cycle. Followed by an average of two more wipe cycles before the wipers park and the module turns off.

The electric pump assembly is mounted directly to the reservoir. A permanently lubricated motor is coupled to a rotor type pump. Fluid, gravity fed from the reservoir, is forced by the pump through rubber hoses to the hood mounted nozzles which direct the fluid streams to the windshield. The pump and reservoir are serviced as separate assemblies.





ADVANTAGES
o   It is an advantage of the present system that the use of hydrocarbon-based freezing point depressants may be eliminated with the present system.
o   It is another advantage of the present system that the nozzle included with the system is self-draining so as to allow the nozzle to purge itself of fluid when the system is not being energized and therefore to further protect the system against freezing.

DISADVANTAGES
o   Windshield washer fluid can damage the vehicle. These critics point to the corrosive effects of ethanol, methanol, and other components.



          In conclusion, it can be said that windshield washer is one of the most important parts of a vehicle’s equipment and that, despite the fact that most people do not pay much attention to this, they are really helpful when it comes to keeping the windshield clean and ensuring that visibility levels are as high as possible.

Tuesday, 10 September 2013

Anti-Lock Braking System (ABS)


It is a safety system in automobiles. It prevents the wheels from locking while braking. The purpose of this is to allow the driver to maintain steering control under heavy braking and, in some situations, to shorten braking distances (by allowing the driver to hit the brake fully without skidding or loss of control).


How Do Wheels Lock?

During braking, wheels lock if the brake force applied is more than the friction between the road and tyre. This often happens in a panic braking situation, especially on a slippery road. When the front wheels lock, the vehicle slides in direction of motion. When the rear wheels locks, the vehicle swings around. It is impossible to steer around an obstacle with wheels locked. Locked wheels can thus result in accident. Skidding also reduce tyre life.


What Does ABS Do?

The system detects when the wheel are about to lock and momentarily release the pressure on locking wheel. The brakes are reapplied as soon as the wheels have recovered.
A toothed wheel (pole wheel) is fitted to the rotating wheel hub. A magnetic sensor mounted on each wheel in close in close proximity to the teeth, generates electrical pulses when the pole wheel rotates. The rate at which the pulses are generated (frequency) is a measure of wheel speed. This signal is read by electronic control unit (ECU). When a wheel is lock, the ECU sends an electrical signal to the modulator valve solenoid, which release pressure from the brake chamber. When the wheel recovers sufficiently, the brake pressure is reapplied again by the switch off signal to the modulator valve.
The modulator valve has an addition ‘hold’ state which maintains pressure. In break in the chamber, thus optimizing the braking process. The cycling of modulator valve (5 to 6 times per second) is continued till the vehicle comes to a controlled stop.
With ABS, the vehicle remains completely stable even when the driver continues to press the brake pedal during braking, thus avoiding accidents.




Components:

The anti-lock braking system consists of following components.


Wheel Speed Sensor
    The wheel speed sensor consists of a permanent magnet and coil assembly. It generates electrical pulses when the pole wheel rotates. The rate at which the pulses are generated is a measure of wheel speed. The voltage induced increases with the speed of rotation of the wheel and reduces with increasing gap between the pole wheel and the sensor.

Pole Wheel
    Pole Wheel is a toothed wheel made of ferrous material. It normally has teeth on the face. In some cases where it is not possible to install the sensor parallel to the axle, the pole wheels are designed with teeth on periphery. The pole wheel fitted on standard 9-20, 10-20 tires has normally 100 evenly spaced teeth. 80 evenly spaced teeth pole wheels are used for the vehicles having the tyre diameter less than 9mm.

Sensor Extension Cable
    The sensor extension cable is a two core cable which connects the wheel speed sensor to the Electronic Control Unit. The inner core sheathing is of EPDM rubber and the outer sheathing is polyurethane which provide abrasion resistance to the cable. The cable has a module plug with two pins is connected to the control assembly. The cable has two cores-brown and black in colour.

Electronic Control Unit

    The ECU is the core component of the ABS system. Wheel speed sensor signal are the input to the Electronic Control Unit. The ECU computers wheel speeds, wheel deceleration and acceleration. If any wheel tends to lock, the ECU actuates the corresponding Modulator valve to prevent wheel lock. The ECU is normally mounted in driver's cabin.

    The ECU consists of 7 major circuits,
> Input circuit
> Master circuit
> Slave circuit
> Driver circuit
> Feedback circuit
> Power supply circuit
> Fail safe circuit

The functions of ECU,
> It receives wheel speed signal from the sensor. The wheel speed signals are processed and appropriate output signals are sent to the modular valves in the event of a wheel lock.
> It continuously monitors the status and operation of ABS components and wiring.
> It alerts the driver in the event of occurrence of any electrical fault in the ABS system by actuating a warning lamp.
> It disconnects the exhaust brakes during ABS operations.
> It enables the service technician to read the faults in the system either through a diagnostic controller or a blink code lamp.

Modulator Valve Cable
    The Modulator valve cable has thee cores. There are two solenoid interface lines and a common ground line. The inner core sheathing is of EPDM type and the outer sheathing is polyurethane which provide abrasion resistance to the cable.
    The cable has a three pin moulded socket is connected to the modulator valve solenoid at one and an interlock connector with locking feature at the other end. The cores are brown, blue and green.

Modulator Valve

    ABS Modulator valve regulate the air pressure to the brake chamber during ABS action. During normal braking it allows air to flow directly from inlet to delivery. Modulator valve cannot automatically apply the brakes, or increase the brake application pressure above the level applied by the driver through the dual brake valve.

    There is an inlet port, Delivery port and Exhaust passage.
> The inlet port is connected to the delivery of quick release valve or relay valve.
> The delivery port is connected to the brake chamber.
> The exhaust passage vents air from the brake chambers.

    The modulator valve has two solenoids. By energizing the solenoids, the modular valve can be switched to any of the following modes.
> Pressure
> Pressure hold
> Pressure release

Quick Release Valve

    Quick release valve are fitted in air braking system to release the air from the brake chamber quickly after release of brake pedal. This prevents delay in brake release due to long piping runs or multiples of brake chamber being exhausted through the brake valve.

Relay Valve
    Relay valve provides a means of admitting and releasing air to and from brake chamber quickly, in accordance with the signal pressure from the delivery of the dual brake valve.
    Air from the reservoir passes through the valve into the brake chamber. The pressure applied to the brake is equal to the signal pressure from the dual brake valve. When the brake pedal is released the signal pressure is released. The pressure in the brake chamber is released directly through the exhaust port of the relay valve.

Warning Lamp

     Vehicle are fitted with an ABS warning lamp. It is a LED indicator lamp amber in colour and lights up when the system has detected any electrical fault. ABS warning lamp is located on the instrument panel in form of a driver.

Blink Code Lamp

    This lamp is green in colour and is used to indicate the stored faults in the system to the service technician on operating a blink code switch. The nature of fault in the system can be diagnosed by the number of flashes.

Off Highway Switch
    This is an optional switch in front of the driver which can be switched ON when the vehicle is operating off highway. In this mode, ABS control will; allow higher wheel slip to achieve shorter stopping distance than with normal ABS control.

Blink Code Switch
    A momentary switch that grounds the ABS Indicator Lamp output is used to place the ECU into the diagnostic blink code mode and is typically located on the vehicle's dash panel.

TURBOCHARGER


          A turbocharger or turbo is a forced induction device used to allow more power to be produced for an engine of a given size. A turbocharged engine can be more powerful and efficient than a naturally aspirated engine because the turbine forces more intake air, proportionately more fuel, into the combustion chamber than if atmospheric pressure alone is used. Turbo are commonly used on truck, car, train, and construction equipment engines. Turbo are popularly used with Otto cycle and Diesel cycle internal combustion engines.

          There are two ways of increasing the power of an engine. One of them would be to make the fuel-air mixture richer by adding more fuel. This will increase the power but at the cost of fuel efficiency and increase in pollution levels… prohibitive! The other would be to somehow increase the volume of air entering into the cylinder and increasing the fuel intake proportionately, increasing power and fuel efficiency without hurting the environment or efficiency. This is exactly what Turbochargers do, increasing the volumetric efficiency of an engine.

          In a naturally aspirated engine, the downward stroke of the piston creates an area of low pressure in order to draw more air into the cylinder through the intake valves.  Now because of the pressure in the cylinder cannot go below 0 (zero) psi (vacuum) and relatively constant atmospheric pressure (about 15 psi) there will be a limit to the pressure difference across the intake valves and hence the amount of air entering the combustion chamber or the cylinder. The ability to fill the cylinder with air is its volumetric efficiency. Now if we can increase the pressure difference across the intake valves by some way we can make more air enter into the cylinder and hence increasing the volumetric efficiency of the engine. It increases the pressure at the point where air is entering the cylinder, thereby increasing the pressure difference across the intake valves and thus more air enters into the combustion chamber. The additional air makes it possible to add more fuel, increasing the power and torque output of the engine, particularly at higher engine speeds.
          Turbochargers were originally known as Turbo superchargers when all forced induction devices were classified as superchargers; nowadays the term "supercharger" is usually applied to only mechanically-driven forced induction devices. The key difference between a turbocharger and a conventional supercharger is that the latter is mechanically driven from the engine, often from a belt connected to the crankshaft, whereas a turbocharger is driven by the engine's exhaust gas turbine. Compared to a mechanically-driven supercharger, turbochargers tend to be more efficient but less responsive.

HISTORICAL PERSPECTIVE

The turbocharger was invented by Swiss engineer Alfred B├╝chi. His patent for a turbocharger was applied for use in 1905. Diesel ships and locomotives with turbochargers began appearing in the 1920s.

AVIATION:

During the First World War French engineer Auguste Rateau fitted turbochargers to Renault engines powering various French fighters with some success. In1918, General Electric engineer Sanford Moss attached a turbo to a V12 Liberty aircraft engine. The engine was tested at Pikes Peak in Colorado at 4,300 m to demonstrate that it could eliminate the power losses usually experienced in internal combustion engines as a result of reduced air pressure and density at high altitude.


Turbochargers were first used in production aircraft engines in the 1920s, although they were less common than engine-driven centrifugal superchargers. The primary purpose behind most aircraft-based applications was to increase the altitude at which the airplane could fly, by compensating for the lower atmospheric pressure present at high altitude.


PRODUCTION AUTOMOBILES:

The first turbocharged diesel truck was produced by Schweizer Maschinenfabrik Saurer (Swiss Machine Works Saurer) in 1938 .The first production turbocharged automobile engines came from General Motors in 1962. At the Paris auto show in1974, during the height of the oil crisis, Porsche introduced the 911 Turbo – the world’s first production sports car with an exhaust turbocharger and pressure regulator. This was made possible by the introduction of a waste gate to direct excess exhaust gasses away from the exhaust turbine. The world's first production turbo diesel automobiles were the Garrett-turbocharged Mercedes 300SD and the Peugeot 604, both introduced in 1978. Today, most automotive diesels are turbocharged.

1962 Oldsmobile Cutlass Jet fire
1962 Chevrolet Corvair Monza Spyder
1973 BMW 2002 Turbo
1974 Porsche 911 Turbo
1978 Saab 99
1978 Peugeot 604 turbo diesel
1978 Mercedes-Benz 300SD turbo diesel (United States/Canada)
1979 Alfa Romeo Alfetta GTV 2000 Turbo delta
1980 Mitsubishi Lancer GT Turbo
1980 Pontiac Firebird
1980 Renault 5 Turbo
1981 Volvo 240-series Turbo


OPERATING PRINCIPLE

A turbocharger is a small radial fan pump driven by the energy of the exhaust gases of an engine. A turbocharger consists of a turbine and a compressor on a shared shaft. The turbine converts exhaust heat to rotational force, which is in turn used to drive the compressor. The compressor draws in ambient air and pumps it in to the intake manifold at increased pressure resulting in a greater mass of air entering the cylinders on each intake stroke. The objective of a turbocharger is the same as a supercharger; to improve the engine's volumetric efficiency by solving one of its cardinal limitations. A naturally aspirated automobile engine uses only the downward stroke of a piston to create an area of low pressure in order to draw air into the cylinder through the intake valves. Because the pressure in the atmosphere is no more than 1 atm (approximately 14.7 psi), there ultimately will be a limit to the pressure difference across the intake valves and thus the amount of airflow entering the combustion chamber. Because the turbocharger increases the pressure at the point where air is entering the cylinder, a greater mass of air (oxygen) will be forced in as the inlet manifold pressure increases. The additional air flow makes it possible to maintain the combustion chamber pressure and fuel/air load even at high engine revolution speeds, increasing the power and torque output of the engine. Because the pressure in the cylinder must not go too high to avoid detonation and physical damage, the intake pressure must be controlled by venting excess gas. The control function is performed by a waste gate, which routes some of the exhaust flow away from the turbine. This regulates air pressure in the intake manifold.



COMPONENTS OF A TURBOCHARGER
The turbocharger has four main components. The turbine (almost always a radial turbine) and impeller/compressor wheels are each contained within their own folded conical housing on opposite sides of the third component, the center housing/hub rotating assembly. The housings fitted around the compressor impeller and turbine collect and direct the gas flow through the wheels as they spin. The size and shape can dictate some performance characteristics of the overall turbocharger. The turbine and impeller wheel sizes dictate the amount of air or exhaust that can be flowed through the system, and the relative efficiency at which they operate. Generally, the larger the turbine wheel and compressor wheel, the larger the flow capacity. The center hub rotating assembly houses the shaft which connects the compressor impeller and turbine. It also must contain a bearing system to suspend the shaft, allowing it to rotate at very high speed with minimal friction. Waste gates for the exhaust flow.



TURBINE WHEEL:
           The Turbine Wheel is housed in the turbine casing and is connected to a shaft that in turn rotates the compressor wheel.



COMPRESSOR WHEEL (IMPELLER)
         Compressor impellers are produced using a variant of the aluminum investment casting process. A rubber former is made to replicate the impeller around which a casting mould is created. The rubber former can then be extracted from the mould into which the metal is poured. Accurate blade sections and profiles are important in achieving compressor performance. Back face profile machining optimizes impeller stress conditions. Boring to tight tolerance and burnishing assist balancing and fatigue resistance. The impeller is located on the shaft assembly using a threaded nut.
WASTE GATES:
          On the exhaust side, a Waste gate provides us a means to control the boost pressure of the engine. Some commercial diesel applications do not use a Waste gate at all. This type of system is called a free-floating turbocharger. However, the vast majority of gasoline performance applications require Waste gates. Waste gates provide a means to bypass exhaust flow from the turbine wheel. Bypassing this energy (e.g. exhaust flow) reduces the power driving the turbine wheel to match the power required for a given boost level.



ADVANTAGES
1. More specific power over naturally aspirated engine. This means a turbocharged engine can achieve more power from same engine volume.
2. Better thermal efficiency over both naturally aspirated and supercharged engine when under full load (i.e. on boost). This is because the excess exhaust heat and pressure, which would normally be wasted, contributes some of the work required to compress the air.
3. Weight/Packaging. Smaller and lighter than alternative forced induction systems and may be more easily fitted in an engine bay.
4. Fuel Economy. Although adding a turbocharger itself does not save fuel, it will allow a vehicle to use a smaller engine while achieving power levels of a much larger engine, while attaining near normal fuel economy while off boost/cruising. This is because without boost, less fuel is used to create a proper air/fuel ratio.

DISADVANTAGES
1. Lack of responsiveness if an incorrectly sized turbocharger is used. If a turbocharger that is too large is used it reduces throttle response as it builds up boost slowly otherwise known as "lag". However, doing this may result in more peak power.
2. Boost threshold- A turbocharger starts producing boost only above a certain rpm due to a lack of exhaust gas volume to overcome inertia of rest of the turbo propeller. This results in a rapid and nonlinear rise in torque, and will reduce the usable power band of the engine. The sudden surge of power could overwhelm the tires and result in loss of grip, which could lead to under steer/over steer, depending on the drive train and suspension setup of the vehicle. Lag can be disadvantageous in racing, if throttle is applied in a turn, power may unexpectedly increase when the turbo spools up, which can cause excessive wheel spin.
3. Cost- Turbocharger parts are costly to add to naturally aspirated engines. Heavily modifying OEM turbocharger systems also require extensive upgrades that in most cases requires most (if not all) of the original components to be replaced.
4. Complexity- Further to cost, turbochargers require numerous additional systems if they are not to damage an engine. Even an engine under only light boost requires a system for properly routing (and sometimes cooling) the lubricating oil, turbo-specific exhaust manifold, application specific downpipe, boosts regulation. In addition inter -cooled turbo engines require additional plumbing, while highly tuned turbocharged engines will require extensive upgrades to their lubrication, cooling, and breathing systems; while reinforcing internal engine and transmission parts.
TURBO LAG AND BOOST
           The time required to bring the turbo up to a speed where it can function effectively is called turbo lag. This is noticed as a hesitation in throttle response when coming off idle. This is symptomatic of the time taken for the exhaust system driving the turbine to come to high pressure and for the turbine rotor to overcome its rotational inertia and reach the speed necessary to supply boost pressure. The directly-driven compressor in a supercharger does not suffer from this problem. Conversely on light loads or at low RPM a turbocharger supplies less boost and the engine acts like a naturally aspirated engine. Turbochargers start producing boost only above a certain exhaust mass flow rate (depending on the size of the turbo). Without an appropriate exhaust gas flow, they logically cannot force air into the engine. The point at full throttle in which the mass flow in the exhaust is strong enough to force air into the engine is known as the boost threshold rpm. Engineers have, in some cases, been able to reduce the boost threshold rpm to idle speed to allow for instant response. Both Lag and Threshold characteristics can be acquired through the use of a compressor map and a mathematical equation.



APPLICATIONS
·        Gasoline-powered cars
Today, turbo charging is commonly used by many manufacturers of both diesel and gasoline-powered cars. Turbo charging can be used to increase power output for a given capacity or to increase fuel efficiency by allowing a smaller displacement engine to be used. Low pressure turbo charging is the optimum when driving in the city, whereas high pressure turbo charging is more for racing and driving on highways/motorways/freeways.
·        Diesel-powered cars
Today, many automotive diesels are turbocharged, since the use of turbocharging improved efficiency, driveability and performance of diesel engines, greatly increasing their popularity.
·        Motorcycles
The first example of a turbocharged bike is the 1978 Kawasaki Z1R TC. Several Japanese companies produced turbocharged high performance motorcycles in the early 1980s. Since then, few turbocharged motorcycles have been produced.
·        Trucks
The first turbocharged diesel truck was produced by Schweizer Maschinenfabrik Saurer (Swiss Machine Works Saurer) in 1938.
·        Aircraft
A natural use of the turbocharger is with aircraft engines. As an aircraft climbs to higher altitudes the pressure of the surrounding air quickly falls off. At 5,486 m (18,000 ft), the air is at half the pressure of sea level and the airframe experiences only half the aerodynamic drag. However, since the charge in the cylinders is being pushed in by this air pressure, it means that the engine will normally produce only half-power at full throttle at this altitude. Pilots would like to take advantage of the low drag at high altitudes in order to go faster, but a naturally aspirated engine will not produce enough power at the same altitude to do so.




          Here the main aim is to effectively utilize the non renewable energy such as petrol and diesel. Complete combustion of the fuels can be achieved. Power output can be increased. Wind energy can be used for air compression. We conclude that the power as well as the efficiency is increasing 10 to 15 % and pollution can also decrease. From the observation we can conclude that when the full throttle valve is open at that time the engine speed is 4000 rpm and by this the turbocharger generate 1.60 bar pressurized air. Generally the naturally aspirated engine takes atmospheric pressurized air to the carburetor for air fuel mixture but we can add the high density air for the combustion so as the result the power and the complete combustion take place so efficiency is increasing.

Monday, 9 September 2013

DTSI (Digital Twin Spark Ignition System)


It is very interesting to know about complete combustion in automobile engineering, because in actual practice, perfect combustion is not at all possible due to various losses in the combustion chamber as well as design of the internal combustion engine. Moreover the process of burning of the fuel is also not instantaneous. However an alternate solution to it is by making the combustion of fuel as fast as possible. This can be done by using two spark plugs which spark alternatively at a certain time interval so as increase the diameter of the flame & burn the fuel instantaneously. This system is called DTSI (Digital Twin Spark Ignition system). In this system, due to twin sparks, combustion will be complete.

This paper represents the working of digital twin spark ignition system, how twin sparks are produced at 20,000 Volts, their timings, efficiency, advantages & disadvantages, diameter of the flame, how complete combustion is possible & how to decrease smoke & exhausts from the exhaust pipe of the bike using Twin Spark System.


How Does It Works?


Digital Twin Spark ignition engine has two Spark plugs located at opposite ends of the combustion chamber and hence fast and efficient combustion is obtained. The benefits of this efficient combustion process can be felt in terms of better fuel efficiency and lower emissions. The ignition system on the Twin spark is a digital system with static spark advance and no moving parts subject to wear. It is mapped by the integrated digital electronic control box which also handles fuel injection and valve timing. It features two plugs per cylinder.


This innovative solution, also entailing a special configuration of the hemispherical combustion chambers and piston heads, ensures a fast, wide flame front when the air-fuel mixture is ignited, and therefore less ignition advance, enabling, moreover, relatively lean mixtures to be used. This technology provides a combination of the light weight and twice the power offered by two-stroke engines with a significant power boost, i.e. a considerable "power-to-weight ratio" compared to quite a few four-stroke engines.

Moreover, such a system can adjust idling speed & even cuts off fuel feed when the accelerator pedal is released, and meters the enrichment of the air-fuel mixture for cold starting and accelerating purposes; if necessary, it also prevents the upper rev limit from being exceeded. At low revs, the over boost is mostly used when overtaking, and this is why it cuts out automatically. At higher speeds the over boost will enhance full power delivery and will stay on as long as the driver exercises maximum pressure on the accelerator.

Main characteristics

• Digital electronic ignition with two plugs per cylinder and two ignition distributors.
• Twin overhead cams with camshaft timing variation.
• Injection fuel feed with integrated electronic twin spark ignition.
• A high specific power.
• Compact design and Superior balance.


Construction


Digital spark technology is currently used in Bajaj motor cycles in India, because they have the patent right. Digital twin spark ignition technology powered engine has two spark plugs. It is located at opposite sides of combustion chamber. This DTS-I technology will have greater combustion rate because of twin spark plug located around it. The engine combust fuel at double rate than normal. This enhances both engine life and fuel efficiency. It is mapped by the digital electronic control box which also handles fuel ignition and valve timing.

A microprocessor continuously senses speed and load of the engine and respond by altering the ignition timing there by optimizing power and fuel economy.


Advantages & Disadvantages


Advantages

• Less vibrations and noise

• Long life of the engine parts such as piston rings and valve stem.

• Decrease in the specific fuel consumption

• No over heating

• Increase the Thermal Efficiency of the Engine & even bear high loads on it.

• Better starting of engine even in winter season & cold climatic conditions or at very low temperatures because of increased Compression ratio.

• Because of twin Sparks the diameter of the flame increases rapidly that would result in instantaneous burning of fuels. Thus force exerted on the piston would increase leading to better work output.

Disadvantages

• There is high NOx emission

• If one spark plug get damaged then we have to replace both

• The cost is relatively more


Applications


It uses in automotive engines. In India Bajaj has patented for dts-i technology. At present platina, xcd125, 135, discover150, pulsar135, 150, 180, 200, 220 etc. are using the dts-i(digital twin spark ignition system). Which means the petrol enters into the cylinder burns more efficiently.

Hence the application of these technologies in the present day automobiles will give the present generation what they want i.e. power bikes with fuel efficiency. Since these technologies also minimize the fuel consumption and harmful emission levels, they can also be considered as one of the solutions for increasing fuel costs and increasing effect of global warming.

The perfect Combustion in Internal Combustion engine is not possible. So for the instantaneous burning of fuels in I.C. engine twin spark system can be used which producing twin sparks at regular interval can help to complete the combustion.

Wednesday, 4 September 2013

ADAPTIVE CRUISE CONTROL


           Adaptive Cruise Control (ACC) is an automotive feature that allows a vehicle’s cruise control system to adapt the vehicle speed to the environment. A radar system attached to the front of the vehicle is used to detect whether slower moving vehicles are in the ACC vehicle path. If a slower moving vehicle is detected, the ACC system will slow the vehicle down and control the clearance, or time gap, between the ACC vehicle and the forward vehicle. If the system detects that the forward vehicle is no longer in the ACC vehicle path, the ACC system will accelerate the back to its set cruise control speed. This operation allows the ACC vehicle to autonomously slow down and speed up is controlled is via engine throttle control and limited brake operation.


HOW DOES IT WORK?
           The radar headway sensor sends information to a digital signal processor, which in turn translates the speed and distance information for a longitudinal controller. The result? If the lead vehicle slows down, or if another object is detected, the system sends a signal to the engine or braking system to decelerate. Then, when the road is clear, the system will re-accelerate the vehicle back to the set speed.
           The adaptive cruise control (ACC) system depends on two infrared sensors to detect cars up ahead. Each sensor has an emitter, which sends out a beam of infrared light energy, and a receiver, which captures light reflected back from the vehicle ahead.
           The first sensor, called the sweep long-range sensor, uses a narrow infrared beam to detect objects six to 50 yards away. At its widest point, the beam covers no more than the width of one highway lane, so this sensor detects only vehicles directly ahead and doesn't detect cars in other lanes. Even so, it has to deal with some tricky situations, like keeping track of the right target when the car goes around a curve. To deal with that problem, the system has a solid-state gyro that instantaneously transmits curve-radius information to the sweep sensor, which steers its beam accordingly.
           Another challenge arises when a car suddenly cuts in front of an ACC-equipped car. Because the sweep sensor's beam is so narrow, it doesn't "see" the other car until it's smack in the middle of the lane. That's where the other sensor, called the cut-in sensor, comes in. It has two wide beams that "look" into adjacent lanes, up to a distance of 30 yards ahead. And because it ignores anything that isn't moving at least 30 percent as fast as the car in which it is mounted, highway signs and parked cars on the side of the road don't confuse it.
Information from the sensors goes to the Vehicle Application Controller (VAC), the system's computing and communication center. The VAC reads the settings the driver has selected and figures out such things as how fast the car should go to maintain the proper distance from cars ahead and when the car should release the throttle or downshift to slow down. Then it communicates that information to devices that control the engine and the transmission.
There are several inputs:
System on/off: If on, denotes that the cruise-control system should maintain the car speed.
Engine on/off: If on, denotes that the car engine is turned on; the cruise-control system is only active if the engine is on.
Pulses from wheel: A pulse is sent for every revolution of the wheel.
Accelerator: Indication of how far the accelerator has been pressed.
Brake: On when the brake is pressed; the cruise-control system temporarily reverts to manual control if the brake is pressed.
Increase/Decrease Speed: Increase or decrease the maintained speed; only applicable if the cruise-control system is on.
Resume: Resume the last maintained speed; only applicable if the cruise-control system is on.
Clock: Timing pulse every millisecond.
There is one output from the system:
Throttle: Digital value for the engineer throttle setting.
ADAPTIVE CRUISE CONTROL FEATURES
o Maintains a safe, comfortable distance between vehicles without driver interventions
o Maintains a consistent performance in poor visibility conditions.
o Maintains a continuous performance during road turns and elevation changes
o Alerts drivers by way of automatic braking.

PHYSICAL LAYOUT
         The ACC system consists of a series of interconnecting components and systems. The method of communication between the different modules is via a serial communication network known as the Controller Area Network (CAN).
o ACC Module  – The primary function of the ACC module is to process the radar information and  determine if a forward vehicle is present. When the ACC system is in 'time gap control', it sends information to the Engine Control and Brake Control modules to control the clearance between the ACC Vehicle and the Target Vehicle.
o Engine Control Module  – The primary function of the Engine Control Module is to receive  information from the ACC module and Instrument Cluster and control the vehicle's speed based  on this information. The Engine Control Module controls vehicle speed by controlling the engine's throttle.
o Brake Control Module  – The primary function of the Brake Control Module is to determine  vehicle speed via each wheel and to decelerate the vehicle by applying the brakes when  requested by the ACC Module. The braking system is hydraulic with electronic enhancement, such as an ABS brake system, and is not full authority brake by wire.
o Instrument Cluster  – The primary function of the Instrument Cluster is to process the Cruise Switches and send their information to the ACC and Engine Control Modules. The Instrument Cluster also displays text messages and telltales for the driver so that the driver has information regarding the state of the ACC system.
o CAN – The Controller Area Network (CAN) is an automotive standard network that utilizes a 2 wire bus to transmit and receive data. Each node on the network has the capability to transmit 0 to 8 bytes of data in a message frame. A message frame consists of a message header, followed by 0 to 8 data bytes, and then a checksum. The message header is a unique identifier that determines the message priority. Any node on the network can transmit data if the bus is free. If multiple nodes attempt to transmit at the same time, an arbitration scheme is used to determine which node will control the bus. The message with the highest priority, as defined in its header, will win the arbitration and its message will be transmitted. The losing message will retry to send its message as soon as it detects a bus free state.
o Cruise Switches  – The Cruise Switches are mounted on the steering wheel and have several buttons which allow the driver to command operation of the ACC system. The switches include:
'On': place system in the 'ACC standby' state
'Off'': cancel ACC operation and place system in the 'ACC off' state
'Set +': activate ACC and establish set speed or accelerate
'Coast': decelerate
'Resume': resume to set speed
'Time Gap +': increase gap
'Time gap –': decrease gap

ADVANTAGES & DISADVANTAGES


ADVANTAGES
1. The driver is relieved from the task of careful acceleration, deceleration and braking in congested traffics.
2. A highly responsive traffic system that adjusts itself to avoid accidents can be developed.
3.  Since the breaking and acceleration are done in a systematic way, the fuel efficiency of the vehicle is increased.
DISADVANTAGES
1. A cheap version is not yet realized.
2. A high market penetration is required if a society of intelligent vehicles is to be formed.
3. Encourages the driver to become careless. It can lead to severe accidents if the system is malfunctioning.
4. The ACC systems yet evolved enable vehicles to cooperate with the other vehicles and hence do not respond directly to the traffic signals.



          The present work itself is a result of very advance technology used in the automobile industries. There is continuous change in technology and we also accept new technology by replacing the old concepts. Since now a days, vehicle owner are cruises about the speed of the vehicle but as speed increase the same result in decrease in safety. But we have the advance technology like Adaptive Cruise Control then it controls the every section of the car and provides safety and comfort. As the automatic technology provide great advancement in human comfort, safety and other drive condition it become more popular in foreign countries as well as in India.

Tuesday, 7 May 2013

Electromagnetic Brake



          Electromagnetic brakes are the brakes working on the electric power & magnetic power. They works on the principle of electromagnetism. These are totally friction less. Due to this they are more durable & have longer life span. Less maintenance is there. These brakes are an excellent replacement on the convectional brakes  due to their many advantages. The reason for implementing this brake in automobiles is to reduce wear in brakes as it friction less. Therefore there will also be no heat loss. It can be used in heavy vehicles as well as in light vehicles. The electromagnetic brakes are much effective than conventional brakes & the time taken for application of brakes are also smaller. There is very few need of lubrication. Electromagnetic brakes gives such better performance with less cost which is today’s need. There are also many more advantages of Electromagnetic brakes. That’s why electromagnetic brakes are en excellent replacement on conventional brakes.
          Electromagnetic brakes are of today’s automobiles. A electromagnetic braking system for automobiles like cars, an effective braking system. And, by using this electromagnetic brakes, we can increase the life of the braking unit. The working principle of this system is that when the magnetic flux passes through and perpendicular to the rotating wheel the eddy current flows opposite to the rotating wheel/rotor direction. This eddy current trying to stop the rotating wheel or rotor. This results in the rotating wheel or rotor comes to rest/ neutral.

HISTORY

          It is found that electromagnetic brakes can develop a negative power which represents nearly twice the maximum power output of a typical engine, and at least three times the braking power of an exhaust brake. (Reverdin 1994). These performance of electromagnetic brakes make them much more competitive candidate for alternative retardation equipments compared with other retarders. By using by using the electromagnetic brakes are supplementary retardation equipment, the friction brakes can be used less frequently, and therefore practically never reach high temperatures. The brake linings would last considerably longer before requiring maintenance and the potentially “brake fade” problem could be avoided. In research conducted by a truck manufacturer, it was proved that the electromagnetic brake assumed 80% of the duty which would otherwise have been demanded of the regular service brake (Reverdin 1974). Further more the electromagnetic brakes prevents the danger that can arise from the prolonged use of brake beyond  their capability to dissipate heat. This is most likely to occur  while a vehicle  descending a long gradient at high speed. Ina study with a vehicle with 5 axles and weighting 40 tones powered by a powered by an engine of 310 b.h.p travelling down a gradient of 6% at a steady speed between 35 and 40 m.h.p, it can be calculated that the braking power necessary to maintain this speed ot the order of 450 hp. The brakes, therefore, would have to absorb 300 hp, meaning that each brake in the 5 axels must absorb 30 hp, that a friction brake can normally absorb with selfdestruction. The magnetic brake is wall suited to such conditions since it will independently absorb more than 300 hp (Reverdin 1974). It therefore can exceed the requirements of continuous uninterrupted braking, leaving the friction brakes cool and ready for emergency braking in total safety. The installation of an electromagnetic brake is not very difficulty if there is enough space between the gearbox and the rear axle. If did not need a subsidiary cooling system. It relay on the efficiency of engine components for its use, so do exhaust and hydrokinetic brakes. The exhaust brake is an on/off device and hydrokinetic brakes have very complex control system. The electromagnetic brake control system is an electric switching system which gives it superior controllability.

CONSTRUCTION

          The construction of the electromagnetic braking system is very simple. The parts needed for the construction are electromagnetic, rheostat, sensors and magnetic insulator. A cylindrical ring shaped electromagnet with winding is placed parallel to rotating wheel disc/ rotor. The electro magnet is fixed, like as stator and coils are wounded along the electromagnet. These coils are connected with electrical circuit containing one rheostat which is connected with brake pedal. And the rheostat is used to control the current flowing is used to control the magnetic flux. And also it is used to prevent the magnetization of other parts like axle and it act as asupport frame for the electromagnet. The sensor used to indicate the disconnection in the whole circuit. If there is any error it gives an alert, so we can avoid accident.


WORKING PRINCIPLE

          The working principle of the electric retarder is based on the electric retarder is based on the creation of eddy currents with in a metal discs rotating rotating between two electro magnets, which set up a force opposing the rotation of the discs. If the electromagnet is not energized, the rotation of the disc free and accelerates uniformly under the action of the weight to which its shaft is connected. When the electromagnet is energized, the rotation of the disc is retarded and the energy absorbed appears as heating of the discs. If the current exciting the electromagnet is varied by a rheostat, the raking force varies  indirect proportion of the value of the current. The development of this invention began when the French company Telma, associated with Raoul Sarazin, developed and marketed several generations of electric brake based on the functioning principle described above. A typical retarder consists of stator and rotor. The stator hold 16 induction coils, energized separately in group of four. The coils are made up of varnished aluminium wire mounted in epoxy resin. The stator assembly is supported resiliently through anti-vibration mountings on the chasis frame of the vehicle. The rotor is made up of two discs, which provide the braking force when subjected to the electromagnetic influence when the coil are excited. Care fully design of the fins, which are integral to the disc, permit independent cooling of the arrangement.

ADVANTAGES

1. Electromagnetic brakes can develop a negative power which represents nearly twice the maximum power output of a typical engine.

 2. Electromagnetic brakes work in a relatively cool condition and satisfy all
the energy requirements of braking at high speeds, completely without the use of friction. Due to its specific installation location (transmission line of rigid vehicles), electromagnetic brakes have better heat dissipation capability to avoid problems that friction brakes face times the braking power of an exhaust brake.

 3. Electromagnetic brakes have been used as supplementary retardation equipment in addition to the regular friction brakes on heavy vehicles.

 4. Electromagnetic brakes has great braking efficiency and has the potential to regain energy lost in braking.

 5. It’s component cost is less.

DISADVANTAGES

1. The installation of an electromagnetic brake is very difficult if there is
Not enough space between the gearbox and the rear axle.

2. Need a separate compressor. 
3. Maintenance of the equipment components such as hoses, valves has to done periodically. 

4. It cannot use grease or oil.

APPLICATIONS

1. Used in crane control system.

2. Used in winch controlling.

3. Used in lift controlling.

4. Used in automatic purpose.



          The lot’s of new technologies are arriving in world. They create a lot of effect. Most industries got their new faces due to this arrival of technologies. Automobile industry is also one of them. There is a boom in World’s automobile industry. So lot’s of research is also going here. As an important part of automobile, there are also innovations in brakes. Electromagnetic brake is one of them.
          A electromagnetic braking for automobiles like cars, an effective braking system. And, by using this electromagnetic brakes, we can increase the life of the braking unit. The working principle of this system is that when the electromagnetic flux passes through and perpendicular to the rotating wheel the eddy current is induced in the rotating wheel or rotor. This eddy current flows opposite to the rotating wheel. This eddy current tries to stop the rotating wheel or rotor. This results in the rotating wheel or rotor comes to rest.

CRDI (Common Rail Direct Injection)


     CRDi stands for Common Rail Direct Injection meaning, direct injection of the fuel into the cylinders of a diesel engine via a single, common line, called the common rail which is connected to all the fuel injectors.

     Whereas ordinary diesel direct fuel-injection systems have to build up pressure anew for each and every injection cycle, the new common rail (line) engines maintain constant pressure regardless of the injection sequence. This pressure then remains permanently available throughout the fuel line. The engine's electronic timing regulates injection pressure according to engine speed and load. The electronic control unit (ECU) modifies injection pressure precisely and as needed, based on data obtained from sensors on the cam and crankshafts. In other words, compression and injection occur independently of each other. This technique allows fuel to be injected as needed, saving fuel and lowering emissions.

     More accurately measured and timed mixture spray in the combustion chamber significantly reducing unburned fuel gives CRDi the potential to meet future emission guidelines such as Euro V. CRDi engines are now being used in almost all Mercedes-Benz, Toyota, Hyundai, Ford and many other diesel automobiles.


History


     The common rail system prototype was developed in the late 1960s by Robert Huber of Switzerland and the technology further developed by Dr. Marco Ganser at the Swiss Federal Institute of Technology in Zurich, later of Ganser-Hydromag AG (est.1995) in Ober├Ągeri. The first successful usage in a production vehicle began in Japan by the mid-1990s. Modern common rail systems, whilst working on the same principle, are governed by an engine control unit (ECU) which opens each injector electronically rather than mechanically. This was extensively prototyped in the 1990s with collaboration between Magneti Marelli, Centro Ricerche Fiat and Elasis. The first passenger car that used the common rail system was the 1997 model Alfa Romeo 156 2.4 JTD, and later on that same year Mercedes-Benz C 220 CDI.

     Common rail engines have been used in marine and locomotive applications for some time. The Cooper-Bessemer GN-8 (circa 1942) is an example of a hydraulically operated common rail diesel engine, also known as a modified common rail. Vickers used common rail systems in submarine engines circa 1916. Early engines had a pair of timing cams, one for ahead running and one for astern. Later engines had two injectors per cylinder, and the final series of constant-pressure turbocharged engines were fitted with four injectors per cylinder. This system was used for the injection of both diesel oil and heavy fuel oil (600cSt heated to a temperature of approximately 130 °C). The common rail system is suitable for all types of road cars with diesel engines, ranging from city cars such as the Fiat Nuova Panda to executive cars such as the Audi A6.

Operating Principle


     Solenoid or piezoelectric valves make possible fine electronic control over the fuel injection time and quantity, and the higher pressure that the common rail technology makes available provides better fuel atomisation. In order to lower engine noise, the engine's electronic control unit can inject a small amount of diesel just before the main injection event ("pilot" injection), thus reducing its explosiveness and vibration, as well as optimizing injection timing and quantity for variations in fuel quality, cold starting and so on. Some advanced common rail fuel systems perform as many as five injections per stroke.

     Common rail engines require very short (< 10 second) or no heating-up time at all , dependent on ambient temperature, and produce lower engine noise and emissions than older systems. Diesel engines have historically used various forms of fuel injection. Two common types include the unit injection system and the distributor/inline pump systems (See diesel engine and unit injector for more information). While these older systems provided accurate fuel quantity and injection timing control, they were limited by several factors:

• They were cam driven, and injection pressure was proportional to engine speed. This typically meant that the highest injection pressure could only be achieved at the highest engine speed and the maximum achievable injection pressure decreased as engine speed decreased. This relationship is true with all pumps, even those used on common rail systems; with the unit or distributor systems, however, the injection pressure is tied to the instantaneous pressure of a single pumping event with no accumulator, and thus the relationship is more prominent and troublesome.


• They were limited in the number and timing of injection events that could be commanded during a single combustion event. While multiple injection events are possible with these older systems, it is much more difficult and costly to achieve.


• For the typical distributor/inline system, the start of injection occurred at a pre-determined pressure (often referred to as: pop pressure) and ended at a pre-determined pressure. This characteristic resulted from "dummy" injectors in the cylinder head which opened and closed at pressures determined by the spring preload applied to the plunger in the injector. Once the pressure in the injector reached a pre-determined level, the plunger would lift and injection would start.




     In common rail systems, a high-pressure pump stores a reservoir of fuel at high pressure — up to and above 2,000 bars (psi). The term "common rail" refers to the fact that all of the fuel injectors are supplied by a common fuel rail which is nothing more than a pressure accumulator where the fuel is stored at high pressure. This accumulator supplies multiple fuel injectors with high-pressure fuel. This simplifies the purpose of the high-pressure pump in that it only has to maintain a commanded pressure at a target (either mechanically or electronically controlled). The fuel injectors are typically ECU-controlled. When the fuel injectors are electrically activated, a hydraulic valve (consisting of a nozzle and plunger) is mechanically or hydraulically opened and fuel is sprayed into the cylinders at the desired pressure. Since the fuel pressure energy is stored remotely and the injectors are electrically actuated, the injection pressure at the start and end of injection is very near the pressure in the accumulator (rail), thus producing a square injection rate. If the accumulator, pump and plumbing are sized properly, the injection pressure and rate will be the same for each of the multiple injection events.

Advantages & Disadvantages


Advantages

     CRDi engines are advantageous in many ways. Cars fitted with this new engine technology are believed to deliver 25% more power and torque than the normal direct injection engine. It also offers superior pick up, lower levels of noise and vibration, higher mileage, lower emissions, lower fuel consumption, and improved performance.

     In India, diesel is cheaper than petrol and this fact adds to the credibility of the common rail direct injection system.

Disadvantages

     Like all good things have a negative side, this engine also have few disadvantages. The key disadvantage of the CRDi engine is that it is costly than the conventional engine. The list also includes high degree of engine maintenance and costly spare parts. Also this technology can’t be employed to ordinary engines.

Applications


     The most common applications of common rail engines are marine and locomotive applications. Also, in the present day they are widely used in a variety of car models ranging from city cars to premium executive cars.

     Some of the Indian car manufacturers who have widely accepted the use of common rail diesel engine in their respective car models are the Hyundai Motors, Maruti Suzuki, Fiat, General Motors, Honda Motors, and the Skoda. In the list of luxury car manufacturers, the Mercedes-Benz and BMW have also adopted this advanced engine technology. All the car manufacturers have given their own unique names to the common CRDi engine system.

     However, most of the car manufacturers have started using the new engine concept and are appreciating the long term benefits of the same. The technology that has revolutionized the diesel engine market is now gaining prominence in the global car industry.

     CRDi technology revolutionized diesel engines and also petrol engines (by introduction of GDI technology).
     By introduction of CRDi a lot of advantages are obtained, some of them are, more power is developed, increased fuel efficiency, reduced noise, more stability, pollutants are reduced, particulates of exhaust are reduced, exhaust gas recirculation is enhanced, precise injection timing is obtained, pilot and post injection increase the combustion quality, more pulverization of fuel is obtained, very high injection pressure can be achieved, the powerful microcomputer make the whole system more perfect, it doubles the torque at lower engine speeds. The main disadvantage is that this technology increase the cost of the engine. Also this technology can’t be employed to ordinary engines.


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