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NOx REDUCTION BY FUEL WATER EMULSION INJECTION
Jithin Syam P.S
S7 Mechanical-A
Roll No:20


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Overview
History
Formation and harmful effects of NOx
Reduction Techniques of NOx
Water fuel emulsification technique
Method of injection
Advantages and Dis advantages.

History
The nitrogen oxide reduction technology based on fuel water emulsion injection (FWE), developed by MAN B&W Diesel.
Formation of NOx
Prompt NOx
Frequently observed in fuel-rich flames and at low temperatures.
Three possible sources:
Non-equilibrium nascent oxygen (O) and hydroxyl (OH) radical concentrations accelerate the rate of thermal NO mechanism.
Reactions of hydrocarbon radicals with molecular nitrogen
Reaction of nascent oxygen (O) with molecular nitrogen

Fuel NOx
Form nitrogen bearing fuels such as certain coals and oil.
Can contribute upto 50% of total emissions when combusting oil
As much as 80% when combusting coal.
Thermal NOx
Is highly temperature dependent.
Formed through high temperature oxidation of the diatomic nitrogen found in combustion air.
N2 + O NO + N
N+ O2 NO + O
N + OH NO + H

Harmful effects of NOx
Aggravate asthmatic conditions
React with the Oxygen in the air to produce ozone
Form nitric acid when dissolved in water.
Cause acid rain
Form clouds of smog in the summer

Principle
Add water to a fuel
The evaporation of water reduces the temperature maximum in the combustion zone.
The formation of nitrogen oxides is decreased by reduced reaction rates
The actually required water flow is calculated as a function of power
Method of injection
Will provide an emulsified diesel fuel to the engine s injector pump, with a water content from 0 to 40%.
Emulsification of the fuel is created mechanically in a fuel-mixing chamber.
Diesel pumped to the fuel-mixing chamber from the fuel tank where water is added to the fuel through a probe controlled by a microprocessor with controlling software.
Mechanical agitation technique results in the breakup of the water into small droplets that are dispersed throughout the diesel fuel, representing an emulsion.
Effect on Exhaust Emissions
%Reduction in NOx Vs Water
Diesel engine
Effect In the engine
This technique involves injecting water using the same injector as the fuel, eliminates the need for an additional fuel injector.
Electronic fuel injection is required to control the injection.
Altering the fuel then water injection process, is likely to come at a significant extra cost.
Combustion
When liquid is sprayed into a co-flowing air stream, the spray forms a jet inside the chamber.
The jet consists of evaporating liquid fuel droplets suspended in a hot environment.
Phase slip and temperature gradients exist between the droplets and the surrounding gas, leading to momentum, mass and energy transfer between the two phases.

Advantages
Reduction of nitrogen oxide emissions
Reduction of soot emissions
Controlling of the water quantity by the engine parameters
Usable in stationary as well as mobile application
Disadvantages
High initial cost
Severe corrosion problem
Separate pump for the fuel and water are needed along with the modification to the fuel delivery line and in the injectors.
Conclusion-Water Fuel Emulsion
Water content to 20%:
15-38% NOx reduction
1-3% efficiency reduction

Smaller particles:
Promotes higher NOx reduction
Little effect on efficiency reduction

NOx reduction is a function of chamber and flame temperature.
References
I.C.Engine By V.Ganeshan
I.C.Engine By Rajput
Emulsion and Emulsion Stability by Johan Siojblom
Dynamics of emulsification and de emulsification of water in crude oil emission by Bhardwaj
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