Fuel injection characteristic measurements under a transient injector driving condition using an injector driving algorithm

Abstract

A new experimental system was developed to measure the cumulative injected fuel mass (CIFM) according to the driving time during the operation of a gasoline injector in an actual vehicle driving condition. An algorithm was developed to calculate the fuel injection timing and injection duration based on engine speed, crank position, and intake air mass data. The intake air mass and engine speed under the vehicle driving conditions were simulated using a computer. In this study, phase I of the FTP-75 mode was used as the vehicle driving mode. GT-Suite® was used as the computer simulation software. The engine part load data, an automatic transmission shift map, torque converter data and various vehicle specifications were used as input data for the GT-Suite® simulation. The computer simulation time interval is 0.05 seconds. An injector drive signal corresponding to the fuel injection amount and timing calculated by the developed algorithm was generated in a FPGA DAQ system. The drive signal from the FPGA DAQ is supplied to the base terminal of the transistor to switch the injector drive voltage source to control the fuel injection. The real-time measurement of the CIFM was done using load cells, dynamic strain amplifiers, and the FPGA DAQ system. The CIFM was measured at intervals of 0.05 seconds using an experimental apparatus developed when the vehicle was driven in the FTP-75 mode. A low-pass filter was used to remove the noise due to the impact force of the fuel jet on the load cell when measuring the CIFM. Twenty-eight repetitive measurements were conducted for an uncertainty analysis of the measurement data. A normal distribution was used as the error function. The deviation % distribution from the average CIFM value was evaluated at the 95 % confidence level. The deviation % from the average CIFM value was 3 % at 50 seconds after the start of phase I of the FTP-75 mode and converged to 0.2 % at 512 seconds.