Abstract
Keywords: Internal combustion engine, hydrogen, natural gas, flame speed, combustion model.
The use of hydrogen blended with natural gas is a viable alternative to pure fossil fuels because of increase of engine efficiency and expected reduction of total pollutant emissions. These blends offer a valid opportunity for tackling sustainable transportation, in view of the future stringent emission limits for road vehicles. Air pollution is particularly suffered in large urban areas, where cars and heavy duty vehicles greatly contribute to total emissions. Hydrogen is a very interesting energy vector for road transportation, however long time would be required to implement new refuelling infrastructures and new engines or power train systems capable to use hydrogen as fuel. Thus such blends could be employed since now without any important changes in both the distribution infrastructures and engine fuel systems of the current natural gas vehicles.
The aim of the paper is the investigation of the effects of hydrogen-natural gas blends on performance and efficiency of a spark ignition internal combustion engine. The activity evaluates the influence of hydrogen content in blends (ranging from 10% to 30% in volume) on flame propagation speed and heat release rates using an internal combustion engine model. Two different approaches have been used for ignition timing, either employing a Maximum Brake Torque (MBT) spark timing for each fuel or retaining the spark advance of the natural gas engine. Engine brake efficiency increments ranged between 2% and 4.5% for different blends and load conditions adopting MBT ignition timing. Actual running fuel costs were observed to increases 8% for HCNG 10 and 29% for HCNG 30 when compared to CNG using MBT ignition timing.