Corn and soybean biodiesel blends as alternative fuels for diesel engine at different injection pressures

• Pre-heat up to 80 °C for biodiesel blends should compensate the high viscosity.
• The increase of injection pressure (IP) improves engine performance parameters.
• At high IP (200 bar), peak pressure for diesel fuel exceeds that for fuel blends.
• The difference in the position of Pmax for all fuels are in range of 1–2 °C.A.

Experimental study has been carried out using corn and soybean fuel blends at the most recommended blending ratio of 20% biodiesel (C20 and S20) with conventional diesel fuel as alternative fuel for diesel engines. The effect of fuel injection pressure (IP) on diesel engine performance using C20 and S20 blends in comparison with that using neat diesel fuel is studied. Preliminary experiments regarding the analysis of fuel properties indicate that a preheat temperature up to 60–80 °C for these biodiesel fuel blends is necessary to compensate their high viscosity as compared with that of neat diesel fuel. A series of tests are conducted on four-stroke single cylinder air cooled direct injection (DI) diesel engine at different engine speeds, loads and IP of 180, 190 and 200 bar. The investigating parameters include the engine performance parameters (brake thermal efficiency – ηB and brake specific fuel consumption – BSFC) and other necessary parameters (air-to-fuel ratio – A/F ratio, mass of injected fuel – mf, exhaust gas temperature – Texh, cylinder wall temperature – Twall, in-cylinder dynamic pressure – Pcyl, and both value and position of maximum pressure – Pmax and θ@Pmax, respectively). The properties of corn and soybean blended fuels affect the fuel injection system and cause an increase in the duration of fuel injection to cover more time according to the increase in the amount of injected fuel necessary to overcome the power loss accompanied with the biodiesel low energy content. The major conclusion is that, the increased injection pressure gives better results regarding the engine performance parameters (both BSFC and ηB) in comparison with case of the original injection pressure for all tested fuels, thus the best results are obtained at high injection pressure of 200 bar. At this conditions it is concluded that, the increase of engine ηB and the decrease of BSFC approach 15% (from the original pressure of 180 bar), while the values of Pmax for diesel fuel are slightly higher than those for blended fuels no matter the engine operating conditions.