Investigations of the Gas Injection System on a HD-CNG-Engine 2003-01-0625
In the present work investigations of a 7.8 liter-TC-IC-IVECO-CNG engine were performed with single point (SPI) *) and with multipoint (MPI) gas injection systems.
Three types of MPI injectors available on the market were compared for stationary and transient engine operation.
There are several advantages of MPI e.g. better possibility to equalize the air-fuel-ratio of the cylinders, optimization of the gas injection timing and of the gas pressure for different operating conditions.
With different injector types there are different optimum injection timings, due to different injection durations, but at the optimum conditions there is little difference in the combustion quality.
The injectors with higher flow rate can cause more λ-excursions in the dynamic response and with sudden changes of the gas pressure.
The gas pressure in the CNG-rail can be used to improve some operating conditions: lower pressure for low load, higher pressure for better dynamic response and for the full load operation.