Characterizations of Cyclic Combustion Variations in RCCI Engine Using Multifractal Detrended Fluctuations Analysis

This study experimentally investigated the cyclic variations and partial burn in reactivity-controlled compression ignition (RCCI) engines. Multifractal Detrended Fluctuations Analysis (MFDFA) is employed for the purpose of describing cyclic variations and partial burn. The experiments are carried out on a modified diesel engine. Diesel is injected directly into the cylinder, whereas petrol is introduced into the inlet manifold via the port-injection system to facilitate RCCI combustion. This study explores the influence of the gasoline/diesel premixing ratio \(\left( {r_{p} } \right)\) on combustion stability and partial burn. It was found that the cyclic variations in CA₁₀, CA₅₀, and COV_IMEP increased with \(r_{p}\). Results indicate that the percentage of misfiring cycles increased from 36.4% to 83.1% when \(r_{p}\) increased from 40 to 50%. MFDFA analysis shows that total heat release (THR) time series becomes anti-persistent and its degree of multifractality decreases with \(r_{p}\). The multifractal analysis also shows that THR, CA_10, and CA₅₀ have large fluctuations at smaller scales, and these fluctuations are persistent in nature, while smaller fluctuations at large scales are anti-persistent in nature.