2. Fluid Dynamics of Combustion System for Diesel Engines P M V Subbarao Professor Mechanical Engineering Department Use of Fluid Dynamics to Design Matured Combustion System….

3. Schematic of Combustion in diesel Engine

4. The Design Algorithm to Facilitate Fluid Dynamics The basic concept of the design model is as follows. The fuel injected into a combustion chamber is divided into many zones. Events in each zone, such as droplet break-up, evaporation, air–fuel mixing, ignition, heatrelease, heat transfer and formation of exhaust emis are traced and calculated in order to obtain zonal temperature and compositions. The mass, internal energy and mole quantity of NOx of every zone are calculated to obtain cylinder-averaged temperature, air–fuel ratio and NOx concentration.

5. Fluid Dynamics Factors Geometric Features

6. Spray development After fuel is injected into the cylinder, spray break-up takes place in few crankshaft angles followed by wall impingement. In these stages, the movement of the fuel jet follows different laws. Before break-up, the jet follows the energy conservation law and the intial velocity of jet is as follows:

7. Diesel fuel injection nozzles Sac type VCO-type The holes in a modern injection system are very small, typically 50 – 250 μm, and they are manufactured using a complicated EDM (Electro Discharge Machining) process.

8. Actuation of Injector Nozzle

9. Mass flow rate through Nozzle

10. Flow of Fuel through Finite Length Circular Pipe

11. Coefficient of Discharge Nurick’s Number, K p v is the vapor pressure of the fuel.

12. Optimal Design of Nozzle Hole

14. Why Is It Happening?

15. Component of Design Model The Global design model contains the following submodels: spray development, Air entrainment and mixing, Droplet evaporation, Heat transfer of a zone, Combustion and thermodynamic calculation, NOx formation, Calculation of gas properties Chemical equilibrium compositions.

16. Spray Formation Spray formation is explained as Breakup Mechanism, described as: Stretching of fuel ligament into sheets or streams. Appearance of ripples and protuberances. Formation of small ligaments or holes in sheets. Collapse of ligaments or holes in sheets. Further breakup due to vibration of droplets. Agglomeration or shedding from large drops. The flow parameters of a jet: Jet Reynolds number Jet weber number Ohnesorge number