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| Comparison Study of the Effects of Diesel/ Polyoxymethylene Dimethyl Ethers （PODE） on Pilot Ignition of Ethanol in An Optical Engine |
| DOI：10.13949/j.cnki.nrjgc.2023.04.004 |
| Key Words:reactivity controlled compression ignition（RCCI） polyoxymethylene dimethyl ethers（PODE） fuel injection strategy visualization |
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| Abstract:In order to improve the combustion and emissions of internal combustion engines， the combustion characteristics of reactivity controlled compression ignition（RCCI） were investigated on a light-duty optical engine. The combustion properties of direct-injected diesel fuel and polyoxymethylene dimethyl ethers（PODE） igniting ethanol which was injected into the intake manifold were compared. Visual experimental analysis of the combustion process was conducted by adjusting the timing and proportion of direct fuel injection into the cylinder. The results show that the combustion pressure and heat release rate increase first and then decrease as the injection timing is retarded. The best combustion performance was observed when the injection timing was 20° before the top dead center. When the proportion of direct-injected fuel in the cylinder is increased， both the peak combustion pressure and heat release rate per cycle increase continuously， and lead to an advance in the combustion phase and a more complete combustion. The images reveal that flames occur near the wall and then spread outward in both ignition modes. The highest flame brightness and largest flame area appears near the start of combustion. There is no exposure area in the flame field when PODE ignites ethanol， while there is more exposure when diesel ignites ethanol. Compared with diesel/ethanol， the PODE/ethanol has higher cylinder pressure and heat release rate peaks， shorter ignition delay and combustion duration， higher combustion efficiency， and lower soot formation. |
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