Reduction of CO2 emissions is one of the key tasks for automotive industries worldwide. Therefore, energy resources offering advantages with respect to CO2 savings are of high interest. Compressed Natural Gas (CNG) is offering this benefit by emitting approx. 25% less CO2 compared to liquid fuels due its chemical properties. But additionally, CNG has huge potential for improving the thermal efficiency of spark ignited (SI) engines due to other combustion-specific properties such as high knock resistance and extreme stratification capabilities for lean air-/fuel ratio.
For current passenger car standard applications a power drop of approx. 10% is noticed by use of CNG, which occurs from reduced volumetric efficiency of intake manifold fuel injection. But, this drawback can be compensated by direct injection of CNG straight into the combustion chamber, and therefore giving way to utilize all the benefits from using CNG as automotive fuel.
Besides of extreme low CO2 emission and favorable engine out emissions, the engine concept operates without power loss and with absolute low fuel consumption. The “Direct CNG Injection” may be a highly attractive solution for sustainable CO2 reduction with automotive propulsion systems.
The given results have been gained in joint development program “NICE” initiated by the European Community together with DaimlerChrysler, Siemens AG and University of Technology Graz.