Increasing efficiency and reducing emissions on gasoline engines using synthetic fuels

Pleasing results come from work package C2. Under the leadership of the Institute for Combustion Engines (VKA) at RWTH Aachen University, ten fuel mixes with methanol, ethanol, iso-butanol and 2-butanol as well as methanol as a pure component were examined with regard to their suitability for use in car gasoline engines.

An oxygen-free gasoline with a research octane number (RON) of 94 served as the basic fuel for the thermodynamic investigations on a single-cylinder research engine with direct injection. The pure alcohol components were added to this basic fuel in proportions between 3% and 40% (v / v). A total of ten fuel mixtures with different properties were determined. The individual characteristics can be seen in Figure 1.

The defined mixtures as well as pure methanol and the reference fuel should then be considered in terms of efficiency and emissions. The basic investigations included stoichiometric partial and full load operation, charge dilution by means of exhaust gas recirculation (EGR) and excess air as well as catalyst heating and oil dilution.

Overall, the results are very promising: For example, pure methanol has been shown to have great potential for increasing efficiency and reducing NOx emissions. With the same compression ratio, methanol was 23.5% more efficient than the reference fuel RON98. The efficiency increase for fuel blends was 12.6%. By combining a high enthalpy of vaporization with a high laminar flame speed, methanol enables knock resistance and high combustion stability under high loads and cold start conditions.

In comparison, the blends with butanol and ethanol had a higher calorific value, but were less knock-resistant. The higher boiling temperature also triggered an increase in HC emissions under cold start conditions. With regard to EGR compatibility and lean-burn combustion, further efficiency advantages and an emission reduction with the fuel mixtures and pure components can be expected.

Cover Picture: FEV Europe GmbH, remaining pictures: vka


More Information

Christian Wouters
Research Associate
Gasoline engines Thermodynamics
Institute for Combustion Engines VKA
RWTH Aachen University