contd...

• Mixture formation which depends on interactions between the injection spray, air motion and combustion chamber geometry.
• Air motion – swirl, squish etc,
• Injection spray formation -precise control of fuel injection process is necessary for formation of the desired spray and fuel atomization.
• Combustion chamber type- Indirect Injection or Direct Injection. The indirect injection engines are being phased out of production due to their poor fuel efficiency.
• Intake boost pressure

     Turbocharging especially with variable boost pressure coupled with EGR results in substantial reductions in both the NO_x and PM.
   Exhaust aftertreatment such as diesel particulate filter (DPF), diesel oxidation catalysts (DOC), selective catalytic reduction (SCR) of NO_x etc., are already in use.
      An overview of various technologies and direction of research and development which have been pursued to control NO_x and PM emissions from the CI engines are presented in Figs. 6.1 and 6.2 respectively.