In previous article Emission Control Device and Measures-I, we have seen Catalytic Converter and Exhaust Gas Recirculation methods to control the emissions. Here I am going to present some other emission control measures which are quite uncommon.

1. Plasma Exhaust Treatment:

Non-thermal plasma technologies are being developed to reduce NOx emissions from gasoline and diesel exhaust. Since oxidation reactions dominate during plasma discharges in lean exhaust, the plasma alone is ineffective in reducing NOx. Combined plasma-catalyst systems, however, have been shown to enhance the catalyst selectivity and NOx removal efficiency. Non-thermal plasma reactors can be also designed as diesel particulate matter reducing devices. Plasma technologies still require a significant improvement in their consumption of electrical energy and in other areas.

2. Ammonia Injection:

As a fuel, ammonia does not hold much promise, but if used as an exhaust additives it can give excellent control for NOx emission . Ammonia and nitric oxide interact to form nitrogen and water. Ford motor co. has been doing investigation with injecting ammonia water in the exhaust manifold, downstream from the port. For an effective utilization of ammonia injection, the exhaust gas temperature has to be kept within strict limits and the injecting device has to be put sufficiently down to bring the gas temperature to 165ºc.This also demands a very close tolerance in air fuel ratio supplied by the carburettor . The present carburettors are incapable of this and it might be necessary to adopt electronic injection system to keep close control over fuel-air ratios.

3. Electronic Injection:

It is possible to develop an electronic injection system with sensors for air temperature,manifold pressure and speed which will precisely regulate the fuel supply giving only such air-fuel ratio as will give no HC or CO emissions. The emissions on deceleration can be completely removed by shutting off the fuel supply when the throttle is closed.But this system will still not be able to control the NOx emission .Combination of electronic injection and ammonia as an exhaust additives has an attractive future .

4. Using Alternative Fuels:

This is different and creative way of reducing emissions. If we have problem with petrol and diesel combustion, then why use them? Use something else which does not make that kinda pollution. This theme seems to be simple. But, finding out alternate fuel and designing machines according to them is quite unusual task. But, using alternate fuel is good idea.

Biodiesel is oxigenated fuel. So, it reduces the problem of Carbon Monoxide and Hydrocarbons and it boosts up the NOX. Similarly, different results are obtained by using CNG (Compressed Natural Gas) or LPG (Liquefied Petroleum Gas). Some properties are desirable and some are vice versa.

That’s All About Emissions.

For More Information check below

[1] Emission Control In Petrol Engine.

[2] Emission Control In Diesel Engine.

[3] Exhaust Gas Recirculation.

Related posts:

1. Emission Control Devices and Measures-I
2. Emission Control in C.I.Engine
3. Emission Control in S.I.Engine

In my article, Emissions we have studied about emissions, types, contents of emission gases and their major sources viz. C.I. Engines and S.I. Engines.

We have also discussed about emission control in Petrol Engines and Diesel Engines particularly. The reason behind discussing these both sources is that, they are the sources which contribute highest in total Worlds’ Emissions. Here We will see some more kind of Emission Control Devices.

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Emission Control Devices:

1. Catalytic Converter:

Catalytic converter is the device which is fitted on the way of outgoing gases from the engine to atmosphere. Catalytic converter compromises of some chemicals or active chemicals which reacts with content of outgoing gases like CO and NOX. Moreover, they take part in reaction as catalyst which causes their presence unchanged at the end of reaction. After reaction reactants like CO are converted into acceptable emissions like Carbon Di Oxide. Depending upon fuel quality, catalyst material, working temperature etc. life of catalytic converter varies. But generally they have good life and produce effective results.

Some of Major Kinds of Catalytic Converters are As Below:

a. Fast Light off Catalyst:

Allows the catalytic converter to work sooner by decreasing the exhaust temperature required for operation. Untreated exhaust emitted at the start of the legislated emissions test and on short journeys in the real world is curtailed. Changes to the thermal capacity of substrates and type and composition of the active precious metal catalyst have together affected big improvements.

b. Hydrocarbon Adsorber System:

They incorporate special materials, such as zeolites, into or ahead of the catalyst. Hydrocarbon emissions are collected when exhaust temperatures are too low for effective catalyst operation. The hydrocarbons are then desorbed at higher temperatures when the catalyst has reached its operating temperature and is ready to receive and destroy the hydrocarbons.

c. Electrically Heated Catalyst System:

As name suggest, it is provided with electrical heater for heating the catalyst material. At higher temperature, rate of reaction grows and hence electrical heating encourages the catalyst work better.

d. Lean Combustion:

Lean combustion is essential to limit carbon dioxide emissions and to reduce fuel consumption. New diesel technologies with greater use of electronic management and direct injection with unit injectors or common rail injection, can achieve further fuel consumption improvements. The conventional three-way catalyst technology used on petrol engines needs a richer environment with lower air:fuel ratios to reduce NOx, so a radical new approach is required.

e. DeNOx (or Lean NOx) Catalysts:

f. NOx adsorbers (NOx traps):

g. Thermally Durable Catalyst:

So, these are various methods of emission control by using Catalytic Converter. There is one more method for Controlling of NOX from engine.

Exhaust Gas Recirculation:

Exhaust gas recirculation is one of the popular methods now a days. This method mainly controls the NOX emissions. NOX is generated due to very high engine temperature which ranges from 1000 to 1100 degree Celsius. Engine runs at such high temperature due to rich mixtures provided for combustion. In EGR method on the part of outgoing (exhaust) gases is redirected to the input of engine. This suppresses the richness of mixtures. This causes to lower down the temperature of engine which in turn lowers the NOX percentage in exhaust.

More Emission Control Measures are provided in next article.

Related posts:

1. Emission Control in C.I.Engine
2. Emission Control in S.I.Engine
3. Emissions

C.I.Engine:

Compression Ignition Engine (Diesel Engine) are the one which fires up due to compression phenomena and they use diesel instead of Gasoline. In previous article, emission control in S.I.Engine we studied the various emissions from S.I.Engine and their control measures. Now, here we will see for emission control in Diesel engines.

As main energy source is getting replaced from original gasoline we here can get lot different results for power output of engine.

Various Emission Products of C.I.Engine:

1. Visible Products:

1. Smoke.
2. Metallic Particulates.

2. Invisible Products:

1. Carbon Monoxide. (CO).
2. Sulphur Di Oxide (SO2).
3. Unburnt Hydrocarbons (HC).
4. Oxides of Nitrogen (NOX).

Methods for Emission Control in C.I.Engine:

1. Water in Diesel Combustion:

This sound somewhat weird. But as we know that NOX formation increases as the temperature increases. So, to reduce the combustion temperature, water presence may become helpful.

2. Ceramic in Cylinder Coating:

Zirconia based ceramic combustion chamber coatings originally developed for adiabatic or low heat rejection engines have been shown to reduce diesel emissions. Reported results indicate that in-cylinder zirconia coatings are capable of reducing the carbonaceous fraction of diesel particulates without increasing NOx or other regulated emissions. Reductions in total PM emissions may be achieved by combining zirconia coatings with diesel oxidation catalysts. In-cylinder coatings are most effective in reducing emissions from older technology engines of relatively low thermal efficiency.

3. Low Emission Engine Designs:

Changes in diesel engine design contributed to some 10-fold decrease in emissions over the period from the late 1980’s to early 2000’s. The most important of these engine technologies are advanced fuel injection systems, air intake improvements, combustion chamber modifications, and electronic engine control. Additionally, exhaust gas recirculation (EGR) was introduced on both light- and heavy-duty diesel engines to control NO_x emissions. Low emission engine design—combined with increased exhaust gas after treatment—will continue to play important role in future diesel engines.

4. Advances in Technology:

Technology always finds answer to problems. New and developed Fuel Injection and Fuel Combustion techniques are very effective in the emission control activities.

5. Better Air Induction:

Emerging air induction technology options for meeting future emission standards include improved air charging strategies, through the use of electric superchargers, charge air cooling, optimized intake manifolds and intake ports, and variable valve actuation

So, these are the various ways to control the emissions from Diesel Engine.

Related posts:

1. Emission Control in S.I.Engine
2. Emissions
3. Green Engine

In previous article, emission, we discussed about various emissions and their sources. One of major sources is I.C.Engine. So, here we will discuss the emission control in I.C.Engines.

Emission Control in S.I. Engine:

Spark Ignition Engine emissions mainly contains, Carbon Monoxide, Oxides of Nitrogen and Hydrocarbons.

Methods of Emission Control:

As mentioned before, various ingredients of pollution are result of various processes in the engine and hence various types of emission control measures are used.

1. Controlling Emission of Unburnt Hydrocarbons and Carbon Monoxide:

1. Air Fuel Ratio Method:

Combustion needs both air and fuel in proper amount. Air fuel ratio must be so adjusted that it is neither a rich mixture nor the lean one. So, 17:1 is good air fuel ratio which is result of overall experiments.

When A/F ratio is rich HC remain unburnt or half burnt which releases the dangerous pollutants in the air. When A/F ratio moves towards the leaner side, emissions rises due to quenching of flame or it can be said that flame can not propagate in the engine cylinder.

2. Power Output:

This is factor which affects on HC concentration in the emission and not CO. As power output of engine increases the amount of HC increases in the exhaust. So, light and efficient cars or vehicles are better choice in the case.

3. Engine Speed:

Again, this factor matters only to HC. The amount of HC in exhaust decreases as the engine speed increases. The reason behind it is here. As the engine speed increases it increase the turbulence in cylinder and exhaust which is desirable for complete combustion of HC and hence desirable.

4. Spark Timing:

This is major factor of HC control. Whenever there is retard of 10 degree in spark timing the amount of HC decreases in the emission upto 100 ppm. But this reduction is achieved on the behalf of fuel economy. More retardation cause more decrease in HC but more fuel consumption.

5. Valve Overlap:

6. Intake Manifold Pressure:

7. Compression Ratio:

2. Emission Control of Oxides of Nitrogen (NOX):

1. Manifold Pressure:

An increase in manifold vaccum decreases load and temperature and increases the mass of residual gas. As a result the ignition delay is increased and the flame speed is reduced. Both these factors increase the time of combustion. This would reduce the maximum cycle temperature reducing the NO concentration in the exhaust.

2. Coolant Temperature:

As increase in the coolant temperature results in a reduction of heat losses to the cylinder walls and an increase in the maximum gas temperature. This results in an increase in NO concentration. An increase in deposit thickness causes an increase in CR, reduction in heat losses to the coolant and an increase in NO concentration.

3. Humidity:

The reduction in NO formation caused by an increase in mixture humidity is mainly due to the drop in maximum flame temperature. Test on hydrogen -air and ethylene -air mixtures indicated that 1% of water vapour reduced the flame temperature by 20ºc. This reduces the initial rate of NO production by about 25%.

So, these are the ways to control or reduce emissions from S.I.Engine. In next article we will see the emission control measures for C.I.Engine.

References:

[1] http://www.sae.org/technical/papers/2002-01-2147

[2] http://www.emissioncontrol.com/

[3]http://en.wikipedia.org/wiki/Automobile_emissions_control

Related posts:

1. Green Engine
2. Emissions