The work introduced an innovative pathway for converting biomass-derived carbonyls into long-chain ethers, examining their low-temperature oxidation in a modified Cooperative Fuel Research (CFR) engine. The conversion of 2-butanone achieved 100 % and the selectivity of sec -butyl isopropyl ether reached the maximum of 83.13 % under optimal reaction conditions. Conversion of biomass-derived carbonyls increased from 31.77 % at 1 h to 36.28 % at 12 h, with the mass yield of long-chain ethers rising from 53.94 % to 62.86 %. At the same compression ratio, the maximum in-cylinder pressure and temperature increased as the long-chain ethers blending ratio increased. At the critical compression ratio, the net heat release rates (NHR) for blended fuels with 10 vol%, 20 vol% and 30 vol% long-chain ethers at the low-temperature heat release peak were 9.6 J/deg, 10.1 J/deg, and 10.0 J/deg better than that of n -heptane (6.3 J/deg), respectively. CO emissions from blended fuels before compression ignition were higher than n -heptane, while the value for the blended fuel with 30 vol.% long-chain ethers was reduced by 44.97 % compared to n -heptane after autoignition.
Delin Lyu,Xuanjie Cui,Yuanqing Qu,Zhengyang Liu,Xiangning Liu,Zhen Huang,Dong Han
Increasing the compression ratio in spark-ignition (SI) engines improves thermal efficiency but raises knock risk. Knock resistance is measured by Research Octane Number (RON) in Cooperative Fuel Research (CFR) engines under standard conditions, which differ from modern SI engines. The CFR engine's knock sensor, fitted with a low-pass filter, fails to accurately detect high-frequency knock oscillations, making conventional RON inadequate for assessing knock resistance in modern engines. To address this, the CFR engine was modified by replacing the knock sensor with a cylinder pressure sensor for direct combustion pressure measurement and upgrading the carburetor to electronic fuel injection. Under stoichiometric conditions, the Maximum Amplitude of Pressure Oscillation (MAPO) and Integral of Modulus of the Pressure Oscillation (IMPO) methods were applied to evaluate PRF blends with RONs of 88–100. Strong correlations were observed between the fuels RON and both IMPO and MAPO measurements, with coefficients of determination of 0.98 and 0.99, respectively. This study also analyzed error sources and quantified measurement inaccuracies in both methods, with IMPO showing lower absolute error of RON and variability. To verify the reliability of the IMPO and MAPO methods in evaluating high-octane fuels, particularly those with RON >100, these methods were applied to test TRFs and oxygenated fuel blends with RONs of 94–108. Results showed deviations from conventional measurements; however, for fuels with RON >100, both methods effectively distinguished fuel knock resistance capacity. Additionally, IMPO and MAPO captured the knock resistance improvements for the addition of ethanol and 2-MF in gasoline blends.
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