Study on the Influence of EGR on the Combustion Performance of Biofuel Diesel at Different Ambient Simulated Pressures

In order to explore the influence of EGR at different altitudes on the performance of biofuel diesel engines, a comparative experimental study is conducted with the biodiesel–ethanol–diesel B15E5 (biodiesel with 15% volume fraction, ethanol with 5% volume fraction and diesel with 80% volume fraction) mixed fuel at different EGR rate and different atmospheric pressure. The experimental results show that diesel engine power performance and economy goes up with the increase of atmospheric pressure, and it decreases with the increase of EGR rate. At 2200 rpm, the improvement range of medium and high diesel engine load is 1.5–6.8%, and that of 1800 rpm is 2.8–11.7%. At the same atmospheric pressure, with the increase of EGR rate, the power and economy turn worse. The peak combustion pressure and heat release rate both increased with the increase of the atmospheric pressure at full load. At the same atmospheric pressure, peak combustion pressure and peak heat release rate fall with the increase of EGR rate. At part load, firstly, smoke emissions fall with the increase of the load and then rise. As the atmospheric pressure goes up, the smoke emissions show a downward trend, with a decline of 6.6–40%, while the NOx emissions show a rising trend, with an increase of 1.2–8.5%. At the same atmospheric pressure, the smoke emission increase with the increase of EGR rate by 9–12.5%, and the NOx emissions increase with the decrease of EGR rate by 2.5–6.8%. The HC and CO Emissions decrease with the increase of atmospheric pressure. HC emission decreases by 9.3–19.1%, and CO emission decreases by 2.9–16.6%. At the same atmospheric pressure, the HC emission decreases with the increase of the EGR rate by 3.3–4.5% at medium and high loads, and the CO emission increases with the EGR rate by 3.1–4.5%.