Oxides Of Nitrogen And Maintain A Clean Vehicle Engineering Essay

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ABSTRACT

The report reviews the most recent European regulations for automotive emissions. It also discusses various norms of vehicular emission norms including Euro 1 to Euro 6 (for petrol vehicles) and Euro I to Euro VI (for diesel vehicles .It also focuses on need to control emissions of vehicles which gave rise to the computerization of the automobile.

The ultimate goal of emission controlling system is to suppress the amount of toxic pollutants like hydrocarbons, carbon monoxide and oxides of nitrogen and maintain a clean vehicle.

The automotive emissions are measured using test cycle , which is a standard process.

One more concept includes systematic approach of management of vehicular emissions.

Emission control is the most important and vital task amongst all. Some of the popular devices installed in the vehicle are : catalytic converter, PCV valve, EGR valve, air pump and evaporative control systems. These are the devices which help the vehicle to meet the emission regulations .

CONTENTS

INTRODUCTION

European regulations for automotive emission are the norms prescribed

HC (hydrocarbons), CO (carbon monoxide), NOx (Nitrous oxide) levels set by the government which a vehicle would release when running .

These norms are called as Euro norms. In early 1970s, emission requirements for light road vehicles existed in the Europe , while emission requirements for heavy vehicles were introduced in the end of 1980s.

The new vehicles manufactured must meet the current or planned regulations for automotive emission . These regulations are implemented to have a control over air pollution .

The vehicle emission standards were termed as euro 1, euro 2, euro 3 , euro 4 , euro5 and euro 6 respectively, for both light vehicles and heavy vehicles.

The exhaust emission requiremen regulate four groups of compounds :

HC (hydrocarbons), NOx (Nitrous oxide) , CO (carbon monoxide) and particulate matter (PM). Of these four groups , carbon monoxide is less important from the point of view of health and the environment.

The emission regulations for light and heavy road vehicles in the Europe have been stiffened over the years and named as Euro (1,2,3.. and so on).

The government has made separate categories of vehicles and their emission regulations to maintain air quality in the environment. In response to tighter standards, manufacturers equipped new cars with

even more sophisticated emission control systems.

To meet these regulations , the auto manufacturers require the use of such systems which force the vehicle for reduced emission of gases like nitrogen oxides and other hydrocarbons. Some of the examples of these systems are catalytic converters in petrol vehicles ,EGR valve, air pump etc.

To achieve the standards of emission in the vehicle , a systematic approach is required which includes effective urban air quality and simultaneously address the 3 factors : fuel quality , vehicle technology and conditions of use.

Automotive emissions are measured using a standardized technique known as 'test cycle' . The emissions are measured in g/km for light vehicles and g/kwh for heavy vehicles. For heavy vehicles two there are two different test cycles -

ETC ( European Transient Cycle) , ESC ( European Stationary Cycle).

To satisfy the automotive regulations , there is a need to control the emissions from automobiles . This gave rise to the computerization of the automobile. There are also hydrocarbons released as a result of vaporization of gasoline and from the crankcase of vehicle. These lead the manufacturers to develop certain pollution control devices and the making of self adjusting engines. They were termed as feedback fuel control systems. An oxygen sensor was also used to measure fuel content of exhaust stream. This sends signal to microprocessor for analysis. This helps to monitor and diagnose the faults in emission systems.

Some popular emission control devices are EGR valve, catalytic converter, PCV valve, air pump , charcoal canister.

Engine efficiency improvements and exhaust after-treatment systems have driven massive cuts in carbon monoxide (CO),hydrocarbons (HC), nitrogen oxides (NOx)and particulate matter (PM) from cars and commercial vehicles.

The systematic approach to vehicle emission control system will allow for the development of sustainable air quality in the environment.

AUTOMOTIVE EMISSIONS

SOURCES OF VEHICULAR EMISSIONS- The burning of fuel in the engine gives power to move the car. Pollution from cars is produced from by-products of this combustion process (exhaust) and from the evaporation itself.

FIGURE1 : FIGURE SHOWING AUTOMOTIVE EMISSION

In a perfect engine , the air would convert all the carbon in the fuel to carbon dioxide and all the hydrogen into water. Nitrogen remains unaffected in the air. But, practically, combustion process cannot be perfect and the vehicle engine release several types of pollutants.

EXHAUST POLLUTANTS-

• HYDROCARBONS

Hydrocarbon emissions occurs when fuel molecules in the engine are unburned or burn partially.

Hydrocarbons react in the presence of nitrogen oxides and

sunlight to form a major component of smog that is ground-level ozone. Ozone is responsible for irritation of eyes,causes lung problems and causes respiratory problems. Many exhaust hydrocarbons are also toxic, with the potential to cause diseases like cancer.

• NITROGEN OXIDES (NOx)

Nitrogen and oxygen atoms in the air react to form various nitrogen oxides, Under the high pressure and temperature conditions in an engine, collectively

known as NOx. Nitrogen oxides, like hydrocarbons, are precursors to the

formation of ozone. It is also responsible for the formation of acid rain.

• CARBON MONOXIDE

Carbon monoxide is a product of incomplete combustion . This occurs when carbon monoxide is partially oxidized. Carbon monoxide causes heart problems as it reduces flow of oxygen in the bloodstream .

• CARBON DIOXIDE

Carbon dioxide does not directly harm human health, but it is a "greenhouse

gas" (GHG) that traps the earth's heat and contributes to the potential for global warming.

Apart from these emission there occurs fuel -evaporative emissions too . This occurs in several ways like

Diurnal (due to temperature rise in the day and heating of fuel tank)

Running losses (due to hot engine)

Hot soak (engine remains hot after car is turned off and evaporation of gasoline occurs)

Refuelling (gasoline vapours present in fuel tank come out while refuelling)

Road traffic share of emissions :

FIGURE 2 : Figure shows the content of gases on road traffic share of emissions.

SOURCE : Energy and transport figures, statistical pocket book .(europa,EU)

SYSTEMATIC APPROACH OF VEHICLE EMISSIONS

The systematic approach refers to a process of effective management of vehicle emissions control which is accomplished by simultaneously addressing vehicle technology, fuel quality and the vehicles' condition of use.

FIGURE 3 : systematic approach of vehicle emissions shows that these results from the interdependence among fuel quality, technology of vehicle and the vehicles' conditions of use.

The systematic approach is based on the scientific fact and evidence that shows the vehicular emissions are the result of interdependence and interaction among the properties of fuel used with a given stage of technology operating under specific service conditions like traffic.

EURO NORMS AND EMISSION STANDARDS

Euro 1

Euro 2

Euro 3

Euro 4

Euro 5

Euro 6

Passenger cars

July 1992 

Jan 1996

Jan 2000 

Jan 2005

Sept 2009

Sept 2014

Light commercial vehicles (N1-I)

Oct 1994 

Jan 1998

Jan 2000

Jan 2005

Sept 2010

Sept 2015 (diesel only)

Light commercial vehicles (N1-II & III) 

Oct 1994

Jan 1998

Jan 2001

Jan 2006

Sept 2010

Sept 2015 (diesel only)

Trucks and buses

1992

1995

 1999

2005

2008

 Motorcycles

2000

2004

2007

 Mopeds

2000

2004

TABLE1: The Dates from which the emission standards were applied

SOURCE: European emission standards(European commission)

The above listed vehicle emission norms were declared by the European union on respective dates. The Euro standards ensure that every 4 to 5 years , the new vehicle manufactured are cleaner.

Enhanced environmentally friendly vehicle or EEV is a term used for the definition of a 'clean vehicle' .

EUROPEAN EMISSION REGULATIONS FOR PASSENGER CARS

Tier

Date

CO

THC

NMHC

NOx

HC+NOx

PM

P***

Diesel

Euro 1†

July 1992

2.72 (3.16)

-

-

-

0.97 (1.13)

0.14 (0.18)

-

Euro 2

January 1996

1.0

-

-

-

0.7

0.08

-

Euro 3

January 2000

0.64

-

-

0.50

0.56

0.05

-

Euro 4

January 2005

0.50

-

-

0.25

0.30

0.025

-

Euro 5

September 2009

0.500

-

-

0.180

0.230

0.005

-

Euro 6 (future)

September 2014

0.500

-

-

0.080

0.170

0.005

-

Petrol (Gasoline)

Euro 1†

July 1992

2.72 (3.16)

-

-

-

0.97 (1.13)

-

-

Euro 2

January 1996

2.2

-

-

-

0.5

-

-

Euro 3

January 2000

2.3

0.20

-

0.15

-

-

-

Euro 4

January 2005

1.0

0.10

-

0.08

-

-

-

Euro 5

September 2009

1.000

0.100

0.068

0.060

-

0.005**

-

Euro 6 (future)

September 2014

1.000

0.100

0.068

0.060

-

0.005**

-

* Before Euro 5, passenger vehicles > 2500 kg were type approved as light commercial vehicles N1-I

** Applies only to vehicles with direct injection engines

*** A number standard is to be defined as soon as possible and at the latest upon entry into force of Euro 6

† Values in brackets are conformity of production (COP) limits

PM-Particulate matter , P-Particulate number

TABLE2 : European emission regulations for passenger cars ( category M*),g/km

SOURCE: WIKIPEDIA

European emission standards for light commercial vehicles (1305 kg - 1760 kg) (Category N1-II), g/km

Tier

Date

CO

THC

NMHC

NOx

HC+NOx

PM

P

Diesel

Euro 1

October 1994

5.17

-

-

-

1.4

0.19

-

Euro 2

January 1998

1.25

-

-

-

1.0

0.12

-

Euro 3

January 2001

0.80

-

-

0.65

0.72

0.07

-

Euro 4

January 2006

0.63

-

-

0.33

0.39

0.04

-

Euro 5 (future)

September 2010

0.630

-

-

0.235

0.295

0.005

-

Euro 6 (future)

September 2015

0.630

-

-

0.105

0.195

0.005

-

Petrol (Gasoline)

Euro 1

October 1994

5.17

-

-

-

1.4

-

-

Euro 2

January 1998

4.0

-

-

-

0.6

-

-

Euro 3

January 2001

4.17

0.25

-

0.18

-

-

-

Euro 4

January 2006

1.81

0.13

-

0.10

-

-

-

Euro 5 (future)

September 2010

1.810

0.130

0.090

0.075

-

0.005*

-

Euro 6 (future)

September 2015

1.810

0.130

0.090

0.075

-

0.005*

-

* Applies only to vehicles with direct injection engines

TABLE 3 : European emission regulations for light commercial vehicles(1305-1760kg)

SOURCE: WIKIPEDIA

European emission standards for light commercial vehicles >1760 kg max 3500 kg. (Category N1-III & N2), g/km

Tier

Date

CO

THC

NMHC

NOx

HC+NOx

PM

P

Diesel

Euro 1

October 1994

6.9

-

-

-

1.7

0.25

-

Euro 2

January 1998

1.5

-

-

-

1.2

0.17

-

Euro 3

January 2001

0.95

-

-

0.78

0.86

0.10

-

Euro 4

January 2006

0.74

-

-

0.39

0.46

0.06

-

Euro 5 (future)

September 2010

0.740

-

-

0.280

0.350

0.005

-

Euro 6 (future)

September 2015

0.740

-

-

0.125

0.215

0.005

-

Petrol (Gasoline)

Euro 1

October 1994

6.9

-

-

-

1.7

-

-

Euro 2

January 1998

5.0

-

-

-

0.7

-

-

Euro 3

January 2001

5.22

0.29

-

0.21

-

-

-

Euro 4

January 2006

2.27

0.16

-

0.11

-

-

-

Euro 5 (future)

September 2010

2.270

0.160

0.108

0.082

-

0.005*

-

Euro 6 (future)

September 2015

2.270

0.160

0.108

0.082

-

0.005*

-

* Applies only to vehicles with direct injection engines

TABLE 4 : European emission regulations for light commercial vehicles(>1760kg Max 3500kg)

SOURCE: WIKIPEDIA

EUROPEAN EMISSION STANDARDS IN DIFFERENT PARTS OF THE WORLD-

FIGURE4: Emission standards of automotive emission in different regions of the world.

SOURCE: European Commission's motor vehicle group

LIGHT AUTOMOTIVE VEHICLES -

The light automotive vehicles covers the vehicles under 3.5 tonnes, i.e. both passenger cars and light commercial vehicles. The first exhaust emission requirements and parameters for these were specified in Directive 70/220/EEC.

Three-way catalytic converters in petrol vehicles were introduced under Euro 1 emission standard (91/441/EEC), which came into force in 1992-93. Euro 2 came into action in 1996-97 (94/12/EC) and in 1998 the standards for Euro 3 and 4 (98/69/EC) were introduced, to take effect in 2000 and 2005 respectively. (see table 1). There are also standards for light commercial vehicles (table 3).

With the arrival of new control technology , the fuel quality standards were also stiffened which in many cases require a low sulphur content in order to work . The highest permitted amount of sulphur petrol was set at 150 ppm (parts per million) in the year 2000 and 50 ppm in 2005, and for diesel at 350 ppm in 2000 and 50 ppm in 2005. As the result of a new decision in 2003 (2003/17/EC) the limit for both fuels was reduced to 10 ppm in 2009.

For diesel and petrol vehicles Euro 2-4 norms are different. Under Euro 3 and Euro 4 norms, diesel vehicles are allowed to emit around three times more NOx than petrol vehicles. Emissions of particulates from petrol vehicles are not regulated since these are very low compared to emissions from diesel engines.

Along with the Euro 3 and 4 standards, new norms on durability were introduced, making manufacturers responsible for the emissions from light vehicles for a period of five years or 80,000 km (Euro 3) and five years or 100,000 km (Euro 4). This directive also included a decision to introduce on-board emission diagnostic systems (OBD) between 2000 and 2005 and a requirement for a low-temperature emission test (7°C) for petrol vehicle.

HEAVY AUTOMOTIVE VEHICLES-

The first European union regulation emissions from heavy vehicles, that is, vehicles heavier than 3.5 tonnes, came in 1988 (88/77/EEC).

The Euro I regulation for heavy vehicles came into action in 1992-93 (91/542/EC). It also laid down standards for Euro II, which was implemented in 1995-96. .

Euro V differs from Euro IV in its stricter emission requirement for NOx.

Many engine manufacturers are now able to meet Euro IV regulations without further exhaust gas treatment, but for some this is likely to require the use of both particulate filters and NOx reduction. Euro V is very likely to require special NOx reduction.

The 1999 directive also contains special voluntary standards for enhanced environmentally friendly vehicles (EEVs), as well as requirements for on-board diagnostic systems (OBD) .

GRAPH 1 : the progression of European emission standards for Diesel cars.

SOURCE: WIKIPEDIA

GRAPH 2 : progression of European emission standards for Petrol cars

SOURCE : WIKIPEDIA

EUROPEAN STANDARDS FOR PETROL CARS-

GRAPH3- Euro standards for petrol vehicle

SOURCE- European commission (Europa)

GRAPH4-Euro standards for diesel cars

SOURCE-European commission (Europa)

MEASUREMENT OF AUTOMOTIVE EMISSIONS

Test cycle- the automotive emissions are measured using test cycle , which is a standard process. For light vehicles ,emissions are measured in g/km. A process called bench-testing is performed for heavy vehicles and the results are expressed in relation to the engine power (g/kWh).

From the year 2000 the two different test cycles have been used in the EU. One transient (ETC, European Transient Cycle) and one stationary (ESC, European Stationary Cycle). The stationary cycle includes a sequence of constant engine speed and load modes. Smoke opacity is measured on the ELR (European Load Response) test.

EUROPEAN STATIONARY CYCLE (ESC)-

The ESC test cycle (also called as OICA/ACEA cycle) has been launched together with the ETC (European Transient Cycle) and the ELR (European Load Response) tests, for emission certification of heavy-duty diesel engines like trucks, in Europe starting in the year 2000 (source -Directive 1999/96/EC of December 13, 1999). The ESC test cycle consist of a 13-mode, steady-state procedure that replaces the R-49 test.

The engine is testing is done on an engine dynamometer over a sequence of steady-state modes . The engine must be operated for the prescribed time in each mode, completing engine speed and load changes in the first 20 seconds. The specified speed limit should be h within ±50 rpm and the specified torque should be within ±2% of the maximum torque at the test speed. Emissions are measured during each mode and averaged over the cycle using a set of weighting factors. Particulate matter emissions are sampled on one filter over the 13 modes. The final emission results are expressed in g/kWh.

EUROPEAN TRANSIENT CYCLE (ETC)

The ETC test cycle (also known as FIGE transient cycle) came into action, together with the ESC (European Stationary Cycle), for emission certification of heavy-duty diesel engines in Europe starting in the year 2000 (Directive 1999/96/EC of December 13, 1999). The ESC and ETC cycles replace the earlier R-49 test.

The ETC cycle has been developed by the FIGE Institute, Aachen, Germany, based on real road cycle measurements of heavy duty vehicles.

Different driving conditions are shown by three parts of this cycle, including urban, rural and motorway driving. The duration of the entire cycle is 1800 seconds. The duration of each part is 600 seconds.

First part represents city driving with a maximum speed of 50 km/h, frequent starts, stops, and idling. Second part is rural driving starting with a steep acceleration segment and slope. The average speed is about 72 km/h Third is motorway driving with average speed of about 88 km/h.

EVOLUTION OF EMISSION STANDARDS-

FIGURE 5- Evolution of emission standards and content of NOx and particulate matter in petrol and diesel.

SOURCE- ACEA

CONTROL SYSTEMS TO MEET VEHICLE EMISSION REGULATION

The need to have control systems in the emissions from automobiles gave rise to the computerization of the automobile. Hydrocarbons, carbon monoxide and oxides of nitrogen are produced during the combustion process and are emitted into the atmosphere from the exhaust pipe. There are also other sources of hydrocarbon emission such as crankcase of the automobile. The clean air act of 1977 set limits as to the amount of each of these pollutants that could be released from an automobile. The manufacturers decided to add a certain pollution control device and the creation of a self adjusting engine. In 1981, the first of self adjusting engine was made, called as feedback fuel control systems. An oxygen sensor was installed in the exhaust system and would measure the fuel content of the exhaust stream. It then would send a signal to a microprocessor, which would analyze the reading and operate a fuel mixture or air mixture device to create the proper air/fuel ratio. With the arrival of latest technologies p, they were able to adjust ignition spark timing and operate the other emission controls that were installed on the vehicle. The computer played an important role in sensing and diagnosing process. If a fault is seen, the computer will alert the vehicle operator by illuminating a malfunction indicator lamp. The computer will at the same time record the fault in it's memory, so that a proper repair could be done . Some of the more popular emission control devices installed on the automobile are: EGR VALVE, CATALYTIC CONVERTER, AIR PUMP, PCV VALVE, CHARCOAL CANISTER.

CATALYTIC CONVERTER -

There are three ways in which automotive emissions are controlled , first one is to enhance more complete combustion so that there are less by products. The second is to reintroduce excessive hydrocarbons back into the engine for combustion and the third is to provide an additional area for the occurrence of combustion . This additional area is called a catalytic converter. Inside the converter, there are pellets or a honeycomb made of platinum or palladium. The platinum or palladium are used as a catalyst ( a catalyst is a substance used to speed up a chemical process). When hydrocarbons or carbon monoxide in the exhaust are passed over the catalyst, it is converted to carbon dioxide and water, this is also called as oxidation process. As the converter works to clean the exhaust, it develops heat. The dirtier the exhaust, the harder the converter works and the more heat that is developed. If the converter works this hard to clean a dirty exhaust it will destroy itself ,so a limit is maintained. Also leaded fuel covers it with platinum or palladium and render the converter .

FIGURE 6- Schematic diagram of catalytic converter.

SOURCE- Chevrolet corvette exhaust catalytic converter c5 specifications

Catalytic oxidizers are used in most of the cars around the world. Because catalytic oxidizers cannot operate in the presence of lead, their introduction caused leaded gasoline to be ruled out. To reduce harmful emissions , Catalytic oxidizers are used in industrial processes, but their most common use is in automobiles.

Ideally the by-products of an automobile engine are only carbon dioxide, water, and some nitrogen. But in practice, the combustion process in an engine efficiency is never 100%, leaving unburned hydrocarbons. Now, catalytic oxidizers are assembled to a car's tailpipe rapidly oxidizes a large percentage of the remaining unburnt hydrocarbons, resulting in cleaner emissions.

FIGURE 7- Figure to describe the assembly position of catalytic converter

SOURCE- www.howstuffworks.com

The quality of catalytic oxidizers has improved over the years, resulting in cars which are more cleaner. But Still difficult is the lowering of CO2 (carbon dioxide) emissions. it is a known greenhouse gas, contributing to global warming.

PCV VALVE

The positive crankcase ventilation (PCV) system, is used to carry the vapours produced in the crankcase during the combustion stage , and redirecting them into the air/fuel intake system to be burned during combustion process. These vapours dilute the air/fuel mixture, they have to be carefully controlled and metered so as the performance of the engine is unaffected. This is the work of the positive crankcase ventilation (PCV) valve. At idle or steady position when the air/fuel mixture is very critical, just a small amount of the vapours are allowed in to the intake system. When the mixture is less critical, particularly at high speeds and the pressures in the engine are greater, more of the vapours are allowed in to the intake system. When the valve or the system is clogged, vapours will move back into the air filter housing or at worst, the excess pressure will push past seals and create engine oil leakage. If the wrong valve is used or the system has air leaks, the engine will idle rough, or at worst engine oil will be sucked out of the engine. So, proper selection of valve is to be done. Not all engines have PCV valves. Some (like Ford Escort, GM FWD cars with the Quad Four engine, etc.) ventilate the crankcase with a small breather hose and calibrated orifice. There is no spring-loaded PCV valve.

pcv_valve

FIGURE8- Schematic diagram of PCV valve

SOURCE-Wikipedia

EGR VALVE-

The aim of the exhaust gas recirculation valve (EGR) valve is to meter a small amount of exhaust gas into the intake system, (this dilutes the air/fuel mixture) so as to lower the combustion chamber temperature. The EGR valve helps the vehicle to efficiently completely burn fuel by re-circulating a portion of exhaust and running it through the combustion process again. This results in a cooler, complete combustion of the fuel which decreases the car's noxious emissions by prohibiting the formation of some harmful gases.

oxides of nitrogen are generated due to excessive combustion chamber temperature, which is a major pollutant. This is the most effective method of controlling oxides of nitrogen, in it's very design it negatively affects engine and its performance. The engine was not suitably designed to run on exhaust gas. Therefore , amount of exhaust entering the intake system should be carefully observed and controlled. This is done with a series of electrical and vacuum switches and the vehicle computer. Since EGR action suppresses performance by diluting the air /fuel mixture, it does not allow EGR action when the engine is cold .

EGR re-sends 5-10% of an engine's exhaust gas back to the engine cylinders. Internally mixing the incoming air with this exhaust gas dilutes the mixture with inert gas which slows the burning process , and suppresses the maximum temperatures. At high temperatures, NOx formation progresses much faster, EGR tends to limit the generation of NOx. EGR valves remain closed at engine idle because , the inert gas sent through the EGR is unable to provide necessary power to keep an engine running at low RPM.

Recirculation is usually achieved by piping a route from the exhaust manifold to the inlet manifold, which is called external EGR. Now a days , the EGR gas is cooled through a heat exchanger that allows the introduction of large amount of mass of recirculated gas.

EGR valves were a major cause of air pollution, mainly photochemical smog, the automotive engineers needed to do something to lower the maximum combustion temperatures which only occurred under certain high load driving conditions.

So they found a method to allow the very inert gas to get back into the combustion chamber only when needed. They needed a source of this gas which couldn't be air, because that contains oxygen and nitrogen which cause problems . So they selected carbon dioxide, which was supplied through the exhaust. That is mainly carbon dioxide and water (plus other noxious chemicals) . If we allow some of the exhaust gas to get back into the intake manifold under some limits when we need it , that would cool the combustion chamber and prevent the formation of the NOx . so it was called exhaust gas recirculation (EGR).

FIGURE 9: EGR valve and its schematic diagram

SOURCE: Delphi corporation

EVAPORATIVE CONTROL SYSTEM-

It is known that Gasoline evaporates very easily. It is also found that 20% of all hydrocarbon emissions from the automobile are from the gas tank. which is an evaporative source. The function of the evaporative control system is to capture and accumulate evaporative emissions from the gas tank and carburettor. A charcoal canister is used for the purpose of capturing. The fuel vapours adhere to the charcoal, until the engine is started, and engine vacuum can be used to draw the vapours into the engine, so that they can be burned along with the fuel/air mixture. Sealed gas tank filler cap is used for this system. Early 1970 cars used to release fuel vapours into the atmosphere through the a vented gas cap. Today with the use of sealed caps, modified gas tanks are used. The tank has to have the space for the vapours to collect so that they can then be vented to the charcoal canister. For vapour flow into the engine, a purge valve is used. It is operated by engine vacuum. One common problem with this system is that the purge valve goes bad and engine vacuum draws fuel directly into the intake system. This could foul the spark plugs. Most charcoal canisters have a special filter that should be replaced time to time. This system should be checked first when fuel mileage is reduced .

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FIGURE10-Evaporative emission system(charcoal canister)

SOURCE- DTC for EVAP system Toyota

AIR INJECTION SYSTEM-

It uses compressed air to inject the fuel into the cylinder of an internal combustion engine .Since no engine is 100% efficient, there will always be some unburned fuel in the exhaust, i.e. some fuel is remained after the complete combustion process. This increases hydrocarbon emissions. To remove this source of emissions an air injection system was developed . Combustion process includes fuel, oxygen and heat. Without any these components, combustion cannot take place. Inside the exhaust chamber there exists sufficient heat to enhance combustion, if we supply some oxygen than any unburned fuel will ignite. This combustion will not produce any power, but it will reduce excessive hydrocarbon emissions. This combustion is uncontrolled, so if the fuel content of the exhaust is excessive, explosions, that sound like popping, will occur. Diverter valve is used many times, when under normal conditions, such as deceleration, when the fuel content is excessive. It diverts the air away from the exhaust manifold. This is one emission control system that has no effect on engine performance. The only maintenance that is required is a careful inspection of the air pump drive belt.

Air Pump FIGURE11- Shows air injection system

Air injection technology was first introduced during the late 1960s and was used extensively throughout the 1970s. It was still widely used by some manufacturers through the 1980s. But due to recent strict norms of automotive emissions, cleaner-running engines are manufactured . The typical air injection system consists of a network of hoses and tubes, a belt-driven air pump and air-management valves. It also uses the onboard computer to control system operation. Some engines use pulse-air systems that doesn't have pump. Instead, alternating pressures in the exhaust stream are used to drive air into the exhaust system. Some late-model vehicles use a high-tech air injection system using an electric air pump controlled by the vehicle's Power train Control Module (PCM).

FIGURE12- diagram for air injection system

TURBOCHARGER-

Turbochargers are an integral part of the advanced clean diesel system. Turbochargers play an important role in increasing the efficiency and performance of a diesel engine . A turbo can significantly enhance an engine's horsepower without increasing its weight, which is the huge advantage that makes turbochargers so popular.

The turbocharger consists of a set of two turbines that recycle the energy from exhaust gases. In petrol engines, it takes 9,000 gallons of air to burn 1 gallon of fuel. For diesels, it takes 20,000 gallons of fuel.

The turbo, along with common fuel injection and direct injection, gives the diesel its highly extraordinary efficiency by extracting more power from the same engine.

The power output of any engine is determined by the fact : the more air and fuel, the greater the power.

FIGURE13-Figure showing the components and working of turbocharger.

Basically, all internal combustion engines are air pumps. Fuel is combined with air, then it is ignited, this provides power to the engine. Air is driven into the engine when the piston moves down in the cylinder and creates a vacuum.

FIGURE 14- Figure displaying location of turbocharger

SOURCE- www.howstuffworks.com

As air - fuel combination required is in very precise ratios, and fuel is pumped into cylinders at high pressures, the limiting factor for output power is how much air the engine can get.

Turbochargers contribute to the advanced clean diesel system of lower emissions by increasing the efficiency of the combustion process and burning fuel more efficiently. This process satisfactorily meet the regulations of emissions.

FIGURE 15-The twin-turbo system of a Nissan GT-R

FIGURE16-The Bugatti Veyron has 4 turbochargers that help the engine produce 1,001 horsepow

CONCLUSION-

Vehicle emission regulations are the norms specified by the government which sets up limits to different chemical compounds such as NOx, CO ,CO2,particulate matter and hydrocarbons. Automotive manufacturers develop their vehicle according the existing norm. The clean air act of 1977 was the vital directive which brought a sensation to enhanced environmentally friendly vehicle (EEV).

The norms were named as Euro (1 to 6 for petrol vehicles ) and Euro (I to VI for diesel vehicles).

vehicular emissions are the result of interdependence and interaction among the properties of fuel used with a given stage of technology operating under specific service conditions like traffic. This is the consequence of systematic approach and management of vehicle emissions.

Test cycles are conducted to check the emissions and exhaust system. It includes processes like ESC and ETC.

Control system of vehicle emission are the devices that help the vehicle to meet the vehicle norms of emission . It includes devices like , catalytic converter, air injection system, egr valve, pcv valve and evaporative control systems like charcoal canister.

Apart from the euro norms, one more challenge exists i.e. the emission of green house gas CO2 .It is still a major problem faced by the auto manufacturers, because a complete control over it has not been achieved despite of huge developments in technology.

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