A modulating method based on the cyclic fuel quantity of a diesel engine was introduced for its retrofitted natural gas/diesel engine. According to the method

a strategy of controlling the quantities of pilot diesel and natural gas was determined. First

a pedal position was described as a total fuel demand. Then the cyclic quantities of desired pilot diesel and desired natural gas were calculated from a total fuel demand by means of equivalent heat value and a desired substitution ratio. Finally

a desired accelerograph position and a natural gas injection pulse were obtained according to calibration data. A reliable and fully functional control software was developed with the Matlab/Simulink

which contained such functions as signal input/output

calculation of control parameters

identification and switching of working mode

generation of executable files and download of them into the MotoTron hardware. The calibration of regulation MAPs was carried out on a dual fuel engine retrofitted from a WEICHAI mechanical pump diesel engine. The verification test shows that the dual fuel engine which employs cyclic fuel quantity regulation can work stably and reliably

and can achieve an accurate and fast control while retaining the power of the original engine. Though its brake efficiency is lower

a diesel/gas dual fuel engine is still attractive due to the lower price of natural gas.