Advances in Automobile Emission Control Techniques Essay Example

Advances in Automobile Emission Control Techniques Paper Contents: Abstract Introduction Types of emissions a) Tailpipe emissions b) Evaporative emissions 4. Emission standards 5. Need to control emissions 6. Emission Testing Procedures 7. Emission control techniques I. Tailpipe emission control techniques i) Increasing engine efficiency by Electronic Ignition, Fuel injection†¦ ii) Increasing vehicle efficiency ii) Increasing driving efficiency iv) Cleaning up the emissions by Air Injection, Exhaust Gas Recirculation, Catalytic Converter, Spark Optimizer II. Evaporative emission control techniques a) By capturing vented vapors b) Reducing refueling losses 8. Latest advances in control of emissions from automobiles I. Nasa’s laser technology II. Alcohols in diesel engines III. Fuel cell vehicles IV. Electric vehicles 9. Conclusion 10. Reference ABSTRACT In many urban areas, automobile transportation accounts for the majority of smog-forming emissions, and air pollution control legislation continues to spur the research and development of lower-emission automobiles. A study was conducted to explore the techniques for the control of exhaust emissions from automobiles. The study concludes by suggesting principles for making zero-emission vehicle policy by the development of technology for laser technology based vehicles, fuel cell vehicles, battery-powered electric vehicles, and the future effectiveness of policies to control emissions from gasoline vehicles. We will write a custom essay sample on Advances in Automobile Emission Control Techniques specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Advances in Automobile Emission Control Techniques specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Advances in Automobile Emission Control Techniques specifically for you FOR ONLY $16.38 $13.9/page Hire Writer INTRODUCTION Exhaust pollution originates inside an engine’s cylinder, where the mixture of air and gasoline is rapidly bounded. The head from combustion creates a high pressure, pushing the piston to produce the mechanical energy that moves the car . If the fuel is perfectly burned, the only by products would be water vapor and CO2. CO2 is non-toxic although it does cause global warming. Combustion is never perfect, and as a result, harmful pollutants such as unburned hydrocarbons (HC), nitrogen oxides (NOX), and carbon monoxide (CO) are created. Types of Emissions The Emissions produced by a vehicle fall into two basic categories: a) Tailpipe emissions b) Evaporative emissions Tailpipe Emissions: I. Hydro carbons (HC): These are emitted because of incomplete gasoline combustion, these combine with nitrogen oxides in the presence of sunlight to form ground-level oxygen, a major component of smog and has adverse health effects. II. NITROGEN OXIDES (NOx): Under the high pressure and temperature conditions in an engine, nitrogen and oxygen atoms in the air react to form various nitrogen oxides. Nitrogen oxides like HC are precursors to the formation of ozone. They also contribute to the formation of acid rain. III. CARBON MONOXIDE (CO): Carbon monoxide is a product of incomplete combustion and occurs when carbon in the fuel is partially oxidized rather than fully oxidized to carbon dioxide. It causes serious, possibly fatal, health problems. IV. LEAD (Pb): These emissions originate from the combustion of leaded gasoline. AÐ ´ lead compounds are used as fuel additives in large vehicles to control engine knocking. Enough lead in the atmosphere can cause lead poisoning and other health concerns. V. CARBON DIOXIDE (CO2): Although this is a product of complete combustion, it does not directly impair human health, but it is a â€Å"Green House Gas†, that traps the earth’s heat and contributes to the potential for global warming. VI. SULFUR DIOXIDE (SO2): This is a by-product formed by burning sulfur. Sulfur dioxide can combine with water to form sulfuric acid, a very corrosive chemical which can corrode metals. Control primarily consists of removing sulfur from fuel at the refinery. VII. EVAPORATIVE EMISSIONS: These are produced from the evaporation of fuel, and are large contributors to urban smog. I. GAS TANK VENTING (OR) DIURNAL: Gasoline evaporates as the temperature rises during the day, heating the fuel tank and venting the gasoline into the atmosphere. , II. RUNNING LOSSES: The escape of gasoline vapors from the engine and exhaust system when the car is running results in running losses. III. REFUELING LOSSES: These can cause a lot of HC vapor emission. The empty space inside a vehicle’s tank is filled with HC gases, and as the tank is filled, these gases are forced out into the atmosphere. IV. HOT SOAK: The engine remains hot for a period of time, after that car is turned off, and gasoline evaporation continues when the car is parked. In addition to these, automobile also generates several other sources of pollution which include: Water Pollution from fluids that leak from cooling systems, engines and transmissions. Hazardous waste from discarded fluids, tires, batteries and the like asbestos fibers from brake linings and clutches. EMISSION STANDARDS: To limit the amount of pollutants that can be released into the atmosphere certain standards are introduced â€Å"EMISSION STANDARDS†. Many emission standards focus on regulating the amount of material that can be released by he automobiles and the amount of smog forming material that can be released. Standards generally regulate the amount of carbon monoxide, oxides of nitrogen, the sulfur, HC and particulate matter (PM) that can be released. Evaporative emissions from the vehicle are limited by law and tested as part of the new vehicle type approval by a so-called SHED-TEST. The current limit is 2grams of HC per hour, which may amount to an evaporation of one liter (14 gallon) in a month. TRENDS IN ANNULAR VEHICULAR EMISSIONS IN DELHI (per thousands tonnes) Pollutants |1990-91 |1995-96 |2000-01 |2005-06 |2010-11 | |CO |139 |178 |202 |199 |206 | |HC |55 |71 |83 |82 |83 | |NOx |35 |44 |54 |60 |74 | |SO2 |04 |05 |07 |09 |11 | |TSP |07 |09 |12 |13 |14 | |Pb |0. 78 |0. 102 |0. 111 |0. 104 |0. 098 | (TSP – Total Suspended Particles) EMISSION STANDARDS FOR PETROL AND DIESEL VEHICLES: According to Bombay Motor Vehicle Act, the ideal emission limits are as follows: (a). Petrol Vehicles: 4. 5% by volume of carbon monoxide for 2 and 3 wheelers. 3. 0% by volume of carbon monoxide for 4 wheelers. (b). Diesel Vehicles: 65 hartidge smoke units (2. 45 m-1 of smoke density) measured by free acceleration method. NEED TO CONTROL EMISSIONS: The ever increasing technological demands of society impose needs for new, more accurate, less expensive and more efficient control solutions to existing emission problems (health, global warming, and acid rains). There are many adverse health effects caused by emissions, including cancer, premature death, and increased hospitalization. With increase in the number of vehicles the health effects will only be reduced with continual improvement in fuels and by adopting emission control techniques. EMISSION TESTING PROCEDURES: The first emission criteria was measuring tailpipe emissions in parts per million (PPM). The most common test used was the Idle Test usually a two-speed idle test, later to be succeeded with a Dynamometer (the latest variant is knows as the accelerated simulated mode ASM). ASM testing, tests for three gases instead of two; if one gas emission is higher, the vehicle fails the test. Usually, vehicle under 8500 GVW and gasoline powered vehicles are subjected ASM testing with the exemption of all wheel drive vehicles. Some cities are also using the technology that uses Laser to Detect Emissions. Research on establishing appropriate Chassis-Dynamometer Fuel Economy Test Methods and fuel consumption assessment methods for heavy-duty vehicles using simulation in order to promote the use of vehicles with good fuel efficiency and low carbon dioxide is being done. These results obtained have been used for preparing technical standards for automobile emissions. WHAT IS TESTED Tailpipe concentrations of carbon-monoxide and hydrocarbons ? Visual inspection of emission control system, includes the: Oxygen sensor †¢ Catalytic converter †¢ Leaded fuel inlet restrictor †¢ Air injector system Evaporative system ? Inspection for visible emissions (smoke) EMISSION CONTROL TECHNIQUES: As it is discussed previously there are two main types of emissions from automobiles. A) Tail pipe Emissions B) Evaporative Emissions So it is enough to control these emissions to avoid the adverse effects. Tail Pipe Emissions Control can be categorized into three parts. I. Increasing Engine Efficiency II. Increasing Vehicle Efficiency III. Increasing Driving Efficiency IV. Cleaning up the Emissions I. INCREASING ENGINE EFFICIENCY: Engine efficiency has been gradually improved by using following techniques. ELECTRONIC IGNTION: In an EI system, the Contact breaker points are replaced by an angular sensor of some kind either optical, where a vaned rotor breaks a light beam, or more commonly using a Hall Effect Sensor, which responds to a rotating magnet mounted on a suitable shaft. The sensor output is shaped and processed by suitable circuitry, then used to trigger a switching device such as a thyristor , which switches a large flow of current through the coil. EI systems were developed alongside other improvements such as fuel injection systems. After a while it became logical to combine the functions of fuel control and Ignition into one electronic system known as an engine management system (EMS). Modern EMS systems usually monitor other engine parameters such as temperature and the amount of pollution in the exhaust. This allows them to control the engine to minimize the unburnt fuel and other noxious gases, leading to much cleaner and more efficient engines. FUEL INJECTION SYSTEMS: The fuel droplet size and size distribution produced by fuel injection system is an important parameter in defining the efficiency and emissions output of an automotive engine. Fuel injection is a method to precisely meter fuel into an internal combustion engine, where the fuel is there burned in air to produce heat. The two features result in the following performance benefits. ? Emissions significantly reduced â€Å"engine ouT† or â€Å"feed gas† emissions (the chemical products of engine combustion). ? A reduction in final tail pipe emissions (=0. 99%) result. ELECTRONIC CONTROL UNIT: A vital component of any engine is the governor, which limits the speed of the engine by controlling the rate of fuel delivery. Modern electronically controlled engines achieve this through electronic control module or electronic control unit. The engine mounted computer. The ECM receives an engine speed signal from a sensor and then using algorithms and look up calibration tables stored in ECU. It controls the amount of fuel and its timing through electric or hydraulic actuators to maintain engine speed. Controlling the time of the start of injection of fuel into the pistons is the key to minimizing their emissions and maximizing the fuel economy. II. II. INCREASING VEHICLE EFFICIENCY: Contribution to the goal of reducing fuel consumption and related emissions come from, ? Light weight vehicle design ? Minimized air resistance ? Reduced rolling resistance ? Improved power train efficiency ? Increasing spark to the spark plug IIi. INCREASING DRIVING EFFICIENCY: Significant reduction of emissions comes from, ? Driving techniques (some 10 – 30% reduction) ? Unobstructed traffic conditions ? Cruising at an optimum speed for the vehicle ? Reducing the number of cold starts IV. CLEANING UP THE EMISSIONS: Advances in engine and vehicle technology continually reduce the amount of pollutants generated, but this is generally considered insufficient to meet emissions goals. Therefore, technologies to react with and clean up the remaining emissions have long been an essential part of emissions control. I. PCV VALVE: It was the first step leading to a complicated process to reduce auto emissions. The purpose of the positive crankcase ventilation (PCV) valve is to take the vapors produced in the crankcase during the normal combustion process, and redirecting them into the air/fuel intake system to be burned during combustion. These vapors dilute the air/fuel mixture, they have to be carefully controlled and metered so as not to affect the performance of the engine. This is the job of the positive crankcase ventilation (PCV) valve. At idle, when the air/fuel mixture is very critical, just a little of the vapors are allowed in to the intake system. At high speed when the mixture is less critical and the pressures in the engine are greater, more of the vapors are allowed in to the intake system. When the valve or the system is clogged, vapors will back up into the air filter housing or at worst, the excess pressure will push past seals and reate engine oil leaks. 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. II. AIR INJECTION: This is a very early emissions control system, the Air Injection Reactor (AIR) reduced the products of incomplete combustion by injecting fresh air into the exhaust manifolds of the engine in presence of this oxygen laden air, further combustion occurs in the manifold and exhaust pipe. Generally the air is delivered through an engine driven smog pump and air tubing to the manifolds. It is not generally in use any longer having been supplanted by cleaner burning engines and better catalytic converters. III. EXHAUST GAS RECIRCULATION (EGR): NOX emissions are generated differently than HC and CO emissions. HC and CO are the results of incomplete combustion of the fuel. NOx, on the other hand, is a byproduct, produced when nitrogen and oxygen in the air read at high temperatures. The higher the temperature the more NOx is formed, and so reducing peak combustion temperatures will reduce NOx formation. One way to accomplish this is by pulling some of the engine’s exhaust gas back into the cylinder. Because the exhaust gas has already been burned, it will not burn again and therefore shows down the rate at which the flame spreads from the spark plug through the cylinder chain. This slower burn reduces peak combustion temperature and NOx formation. The two problems with EGR a) They reduce the power capability of the engine b) At idle, there is very little air entering the engine. Any dilution of the fresh air charge with exhaust gas at idle will make the engine stumble and may e not run at idle. IV. CATALYTIC CONVERTERS: Automotive emissions are controlled in three ways, one is to promote 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 oxidation or combustion to occur. This additional area is called a catalytic converter. The catalytic converter looks like a muffler. A catalytic converter is a device, placed in the exhaust pipe, which converts various emissions into less harmful ones using platinum or palladium as a catalyst. They make for a significant, and easily applied, method for reducing tail pipe emissions. Their other significant effect on pollution was that they were incompatible with the use of Tetraethyl lead as an octane booster in gasoline, promoting the phasing-out of that additive as converter-fitted cars became more prevalent. The lead emissions were highly damaging to human health, and its virtual elimination has been one of the most successful reductions in air pollution. A secondary catalyst of Rhodium is used to break up nitrogen oxides back into nitrogen and oxygen PURPOSE AND FUNCTION OF CATALYTIC CONVERTER: A three way catalytic converter has three simultaneous tasks. (a) Oxidation of Carbon Monoxide to Carbon Dioxide 2 CO + O2 2 CO2 (b) Reduction of Nitrogen Oxides to Nitrogen NOX O2 + N2 (c) Oxidation of Hydrocarbons (un-burnt fuel) to Carbon Dioxide and water CXHy + NO2 X CO2 + MH2O The amount of oxygen to fuel in the engine is in a ratio for the most complete combustion. When there is more oxygen than required, then the system is sold to be running lean and the system is an oxidizing condition. The above two oxidizing reactions are favored. When there is more fuel than oxygen they the engine is running rich. The reduction of NOx is favored. For spark ignition engines the most commonly used catalytic converter is the three way converter which should only be used on engines that feature electronic fuel injection. A three-way catalyst reduces emission of CO, HC and NOx simultaneously but unwanted reactions can occur in the three-way such as the formation of H2S and NH3. Formation of each can be limited by modifications to the wash coat/precious metals used. For compression ignition engines the most commonly used catalytic converter is the diesel oxidation catalyst. The catalyst used excess O2 in the exhaust gas stream to oxidize CO to CO2 and HC to H2O and CO2. These converters often reach 90% effectiveness; however they are incapable of reducing NOX as chemical reactions always occur in the simplest possible way, and the existing O2 in the exhaust gas stream. To reduce NOX in a CI engine it is necessary to change the exhaust systems by SCR (Selective Catalytic Reduction) technology. For diesel engine we use particulate filter (PF) to reduce particulate or soot. Any sulfur in the fuel may be oxidized to oxides of sulfur in the combustion chamber. If sulfur passes over a catalyst it may be further oxidized in the catalyst. Sulfur oxides are precursors to sulfuric acid, a major component of acid rain. While it is possible to add substances the vanadium to the catalyst wash coat to combat sulfur oxide formation, this will typically reduce the effectiveness of the catalyst. The best solution is further refinement of fuel at the refinery to remove the sulfur however it is impractical. V. SPARK OPTIMISER: The spark is the fundamental means to ignite and allowing burning (combustion) to take place is the cylinder. Recent market invention has taken one step further to allow more efficient burning of fuel air mixture in petrol/gasoline vehicles. The electronic device helps to produce bugger, and more consistent spark to the spark plug. This reduces the amount of un-burnt fuel, and thus emitting less hydrocarbon and carbon monoxide to the environment. EVAPORATIVE EMISSIONS CONTROL: Efforts at the reduction of evaporative emissions include the capturing of vented vapors from within the vehicles and the reduction of refueling emissions. CAPTURING VENTED: Within the vehicle, vapors from the fuel tank are channeled through canisters containing activated carbon instead of being vented to the atmosphere. The vapors are absorbed within the canister, which feeds into the inlet manifold of the engine. When the vehicle is running, the vapor desorb from the carbon, are drawn into the engine and burned. REDUCING REFUELLING : All modern vehicles have tank filler necks that instead of just being a tube into the tank, as in earlier vehicles now have a small-diameter hinged and spring loaded door only large enough for the tip of the filler nozzle. This prevents vapor leakage when the filler cap is removed, and also prevents a catalytic converter-fitted vehicle being refueled with leaded fuel. This is accompanied by modifications to the filling station pumps. They are now equipped to suck the vapors back into the pump as they are displaced by fuel. Some have intakes around the head of the filler nozzle, while others have a rubber ‘boot’ that presses securely around the end of filler neck to prevent vapor escaping. LATEST ADVANCES IN CONTROL OF EMISSIONS FROM AUTOMOBILES: NASA’s Laser Technology ? Alcohols in Diesel Engines ? Fuel Cell Vehicles ? Electric Vehicles NASA’S LASER TECHNOLOGY: NASA’s Laser Technology was originally designed for satellites to measure the chemical makeup of earth’s atmosphere, low temperature oxidation catalysts (LTOC) this may be soon a part of future car’s exhaust system. LTOC technology is expected to reduce automotive pollution emissions by approximately 30% and the cost of aftermarket catalyst converters by 25%. Most modern automobiles are equipped with catalytic converters that treat engine exhaust before it leaves the car. Current technology requires the exhaust to reach a high temperature before the catalytic converter begins to work. LTOC begins to operate at a much lower temperature or as soon as the car is started. Because of its low temperature oxidation capabilities the NASA catalyst begins to work almost immediately enabling destruction of toxic gases even when catalytic converter is cold. The LTOC is a collection of technologies that enables the destruction of pollutant gases such carbon monoxide and hydrocarbons as well as NOx species. ALCOHOLS IN VEHICLES: Methanol and ethanol high octane liquid fuels are being used in cars. Cars designed to run on pure alcohol fuels have the potential to exit 80% to 90% less reactive hydrocarbons than advanced technology gasoline cars. Compressed Natural gas as fuel is used for fleet vehicles where long driving range is not important. Natural gas vehicles have the potential to emit 85% to 95% less reactive hydrocarbons than advanced technology gasoline engines. FUEL CELL VEHICLES: Fuel cells are like batteries in that they convert chemical energy directly into electricity. Fuel cell systems produce no polluting emissions and they contain no moving parts. Fuel cells are also 3 times more efficient than the IC engine. Unlike gasoline used by IC engine, most fuel cells utilize hydrogen, a renewable resource. The use of fuel cells will decrease our dependence on finite amount of fossil fuels. A major limitation of the cell is onboard hydrogen storage which requires a large tank to store hydrogen. To reduce this problem, methanol and gasoline reformations are used in prototype fuel cell cars. The methods of direct storage of hydrogen that appears to be most promising are those of glass micro spheres, carbon nano tubes, and graphite nano fibers. ELECTRIC CARS: Pure electric cars, relying only on stored battery power and plugging into recharge, do not have great prospects as general-purpose vehicles, but they could become increasingly handy in emerging market segments because of almost zero emissions. One future option might be electric mini cars, which are being explored in station car demonstration projects. Hybrid vehicles: These are powered by a combination of a combustion engine and an electric motor. Hybrids can double gas mileage while halving emissions. The heat generated during braking is stored as electricity in the cars battery pack and then is used to provide extra power for accelerating. Hybrid vehicles rely on gasoline stored in a conventional fuel tank, and do not need to be plugged into an external electricity source CONCLUSIONS: Automobiles equipped with emission control techniques are predicted of meeting emission standards that require reduction of up to 98+percent for Hc,96% for CO and 95% for NOX. ? Despite the fact that fuel use increased approximately 50% and vehicle miles traveled by 150% between 1970 and 2000,CO, VOC, NOX emissions are decreased by 44 million tons. ? The use of Catalytic converter helped bring about the elimination of gasoline containing lead, today lead from on-road vehicles accounts for less than 1%. The Society of Automotive Engineers selected the catalytic converter, fuel injection, and electronic engine controls to reduce automotive exhaust emissions. REFERENCES: http://en. wikipedia. org/wiki/Automobile_emissions_control http://www. greenercars. com/gbd5. html http://www. meca. org/galleries/default-file/ http://www. meca. org/galleries/default-file/advancedfact. pdf5thannivpr. pdf http://en. wikipedia. org/wiki/Automobile_emissions_control http://www. cleancarcampaign. org/emissions. shtml http://www. epa. gov/otaq/consumer/05-autos. pdf