Extensive research into a variety of green technologies continues to pay dividends with breakthroughs in the battle to reduce vehicle emissions.
The latest success comes from a team of researchers at Purdue University and diesel engine manufacturer Cummings, who have found that with engine parameter modulation including lower air/fuel ratio, higher exhaust gas recirculation and earlier start of main injection it is possible to mitigate the biodiesel-NOx effect with blends of soy-based biodiesel.
Reductions in nitrogen oxides are accompanied by reductions in both PM and noise according to their study entitled Energy & Fuels, which was published on December 21.
Typically, biodiesel in diesel engines has a number of combustion advantages including reductions in CO, UHC and PM emissions as well as a net CO2 reduction. However, when energy density is 13 per cent lower than diesel, brake-specific fuel consumption increases to attain the same power – indeed under some operating conditions, biodiesel combustion will even emit more NOx than conventional diesel.
The Purdue/Cummings study looks at simultaneous modulation of the four parameters across their ranges on a modern six cylinder engine with common rail injection, a variable geometry turbocharger and exhaust gas recirculation at three different operating locations. It found that for each blend at each operating location, optimal air/fuel ratio shifted lower and optimal exhaust gas recirculation shifted higher. Optimal start of main injection was generally advanced while optimal rail pressure also generally increased. With each fuel at each location, the reduction of BSNOx was comparable to, or lower than, the corresponding nominal B0 levels.
The study was funded by Cummins, Inc., Office of Naval Research, and Energy Centre at Purdue Discovery Park with fuel donated by BP.
