**6. Conclusions**

Combustion simulations are performed on the four-stroke single-cylinder direct injection compression ignition engine running at a constant speed of 1500 rpm, injection timing of 25° BTDC with diesel and 20% blend of Jatropha biodiesel. Standard FVM (finite volume method) of CFD (computational fluid dynamics) is considered while simulating the two-phase engine flow. 3-Dimensional N-S (Navier–Stokes) equations are solved with k-ε turbulence model.

• Results of combustion simulations are presented for half-cycle by considering the two strokes compression and expansion at zero load condition. *The physiochemical properties of B-20 blend differ significantly with those of diesel. The processes like fuel injection, mixture propagation, and combustion differ significantly. For* 570° to 830° CA, swirl ratio varies from 1.3 to 0.89 for diesel, whereas it varies from 1.3 to 0.92 for B-20 JOME. For 720°-800° CA, tumble ratio decreases from 0.03 to 0.42 and increases to zero during the combustion stroke. For B-20 JOME, tumble ratio decreases from 0.03 to 0.44 and increases to 0.03 for the same CA. Some fluctuations are observed in the biodiesel tumble ratio from 700° to 720°CA.

