Combustion Cycle-by-Cycle Variations in a Common Rail Direct Injection Engine Fueled with Dimethyl Carbonate–Diesel Blend

In consideration of the multiple split injection, heavy exhaust gas recirculation (EGR) atmosphere, high latent heat of vaporization of dimethyl carbonate (DMC), and low cetane number, the combustion variations of both diesel and D10 (a fuel blend of 10% of DMC in diesel) have been investigated with characteristic parameters of indicated mean effective pressure $p_{mi}$, peak pressure $p_{\text{max}}$, and initial 10% combustion duration ${\theta }_d$. Results show that the cyclical coefficients of variation (COVs) of three characteristic parameters are lower than 2%. This means good combustion quality thanks to the precise control of fuel injection. The COVs for diesel are much smaller than those for D10 fuel. The COVs of $p_{mi}$, $p_{\text{max}}$, and ${\theta }_d$ rise with a declining center of heat release (COHR), while the COVs show visible growth with the increase in EGR rate. The anticipation of possible combustion instability due to pilot injections did not happen. Both $p_{\text{max}}$ and ${\theta }_d$ have good corresponding relations with $p_{mi}$. The $p_{mi}$ positively rises with the increase in $p_{\text{max}}$, while the higher $p_{mi}$ adversely corresponds to the shorter ${\theta }_d$. As a whole, the correlations between $p_{mi}$ and $p_{\text{max}}$ are higher than that between $p_{mi}$ and ${\theta }_d$, which means that $p_{\text{max}}$ is more dependent on $p_{mi}$ than ${\theta }_d$ The fact that the correlations between $p_{mi}$, $p_{\text{max}}$, and ${\theta }_d$ are higher than 0.67 further points to the choice of $p_{\text{max}}$ and ${\theta }_d$ as evaluating subjects for cyclic variations in cylinder complex process.