Dimensional Optimization of Key Parameters Using DoE Technique to Achieve Better NO _X Emission Values in Mass Production of Single Cylinder Small Diesel Engines for 3 Wheeler Applications

Oxides of Nitrogen (NOx) emissions are considered as among the most harmful emissions globally having a direct influence on human beings and the environment. This work deals with a strategy to arrive at achieving lower NOx values consistently in mass production of single cylinder automotive diesel engines meeting BS IV Emission standards using the DoE technique for dimensional optimization of critical parameters. Catalytic converters and particulate filters are mostly used as after - treatment devices for compression Ignition (CI) engines for bringing down the limits (Values) of the pollutants from the tail pipes. But the real ingenuity lies in achieving the same effect through optimization of in - cylinder combustion. Optimization of the critical factors like Nozzle Tip Protrusion (NTP), Static Injection Timing (SIT), Bumping Clearance (BC) and Swirl Number (SN) are considered as the most important engine design parameters for ensuring the optimum combustion which help release of minimal harmful pollutants. In this work, a standard L9 Orthogonal Array (OA) table was used in designing experiments for a study of the interactive model between the said factors and their levels to achieve consistently lower NOx emission values. The design specification of NTP considering the tolerance limit was set between 3.0 mm to 3.30 mm and similarly SIT, BC and Swirl value were set between 0.19 mm to 0.27mm, 0.65mm to 0.75 mm and 2700 rpm to 2800 rpm respectively. Tests were conducted on the basis of standard OA table and the corresponding NOx emissions were measured. It is found that, NTP of 3.2 mm, SIT of 0.19 mm, BC of 0.70 mm and Swirl Rate of 2775 rpm were seen yielding the least NOx emissions. Statistical observations showed the above mentioned combination exhibiting a reduction of NO_X achieved with respect to the design specification as 22% and the variation of NOx between engines as 1.1%.