Comparison between lean burn and Rich Burn engines:-
After certain emission calibration levels Lean‐burn gas engines are more economical and these can even operate at higher loads,
But in rich‐burn engines have lower emission levels with a single after treatment these are more tolerant of broad fuel ranges and ambient conditions, and generally have better transient load capability.
Principle of operation of Rich Burn engines:-
Rich‐burn engines operate at principle of stoichiometric air/fuel ratio (AFR) according to this principle air in exact quantity is supplied to burn all of the fuel. This will leads to reduction in nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), and HAPS (Hazardous Air Pollutants) after certain treatment for all in one i.e. by using catalytic converter used in cars.
Lean burn engines working principle:-
In these engines Lean‐burn engines use a lot of excess air. These engines take up to twice the amount needed in rich burn engines for complete fuel combustion. Excess air used in lean burn effectively cools down the peak combustion temperatures in the cylinder, this will reduces the NOx production and allows low engine‐out emissions without the need for an after treatment system in many applications.
In these engines there are advantages of reducing the detonation probability thus it will leads to higher Brake Mean Effective Pressure loads and an optimized combustion phasing. This results in higher power density and usually produces better fuel efficiency.
Emissions in Rich-burn engines:-
Rich‐burn engines have emissions of 12‐16 g/bhph‐hr NOx i.e. “5,000 ‐ 6,500 mg/Nm3@ 5 percent 02 in the exhaust gas “, in most stoichiometric/AFR exhaust gas composition and the increased exhaust gas temperatures allow the use of a three‐way catalyst.
These engines have high NOx conversation rates i.e. above 99 percent that significantly reduce all three major types of engine‐out emissions ‐ NOx, CO and HC , Since there are low emissions that will destroy inferior but hazardous pollutants like formaldehyde (CH20).
Rich-burn engines emission are below 50 mg/Nm3 NOx and ultra‐low total hydrocarbon emissions, which will leads to decreased overall greenhouse gas footprint.