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| Effects of Lean Burn on Performance of A Methanol Direct Injection（MDI） Spark Ignition Engine |
| DOI：10.13949/j.cnki.nrjgc.2023.04.003 |
| Key Words:methanol direct injection（MDI） spark ignition engine combustion thermal efficiency emission |
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| Abstract:A turbocharged Miller cycle gasoline direction injection（GDI） engine was modified to a methanol direct injection（MDI） engine with high compression ratio （13.8）， and experimental study was conducted to investigate the effects of lean burn on engine performance and emissions at speed of 2 750 r/min and brake mean effective pressure（BMEP） of 1.1 MPa and 1.5 MPa. Results show that ignition delay and combustion duration of MDI extends as combustion excess ratio （λ） increases， and MDI shows much shorter ignition delay and combustion duration than that of original GDI engine at high dilution rate. The stable combustion limit extends from λ=1.5 of original GDI engine to above 1.7 of MDI engine. As to gas emissions， lean burn leads to higher HC emission， while the CO emissions show a trend of first decreasing and then increasing and reach the minimum value at λ of about 1.1. CO， HC and NOx emissions of MDI engine are always lower than that of original GDI engine. As to thermal efficiency， the maximum brake thermal efficiency（BTE） of original GDI and modified MDI engine at load of 1.1 MPa reaches 39.8% and 44.1% respectively， which increases by 2.5% and 3.2% when compared with that of stoichiometric combustion. As load increases from 1.1 MPa to 1.5 MPa， the maximum BTE reaches 44.5% with λ equals 1.4. |
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