Optical investigation of the fuel injector influence in a PFI spark ignition engine for two-wheel vehicles

Abstract

This paper describes the results obtained in a port fuel injection spark-ignition (PFI SI) engine by optical diagnostics during the fuel injection and the combustion process. A research optical engine was equipped with the fuel injection system, the head and the exhaust device of a commercial 250 cc engine for scooters and small motorcycles. Two injectors were tested: standard 3-hole injector that equipped the real reference engine and a 12-hole injector. The intake manifold was modified to allow the visualization of the fuel injection using an endoscopic system coupled with CCD camera. Size and number of the fuel droplets were evaluated through an image processing procedure. The cycle resolved visualization and chemiluminescence allowed to follow the combustion process from the spark ignition to the exhaust phase. All the optical data were correlated with engine parameters and exhaust emissions. The effect of the fuel injector type on deposits formed by fuel accumulation and dripping on the intake valves steams and seats was investigated. In particular, the evolution of diffusion-controlled flames due to the fuel deposits burning was analyzed. These flames were principally located near the intake valves, and they persisted well after the normal combustion event. The consequences were the formation and emission of soot and unburned hydrocarbons. The multi-hole injector helped reducing wall wetting and deposit formation so that the emission characteristic can be improved. The use of 12-hole injector allowed a more homogeneous distribution for a lower time of fuel droplets in the intake manifold than the 3-hole injector. This study also investigated the detailed physical/chemical phenomena to figure out reasons for the improvement using optical measurements.

Electric current as a source of information about control parameters of indirect injection fuel injector

“…with current pressure control downstream of the injector. A conclusion can be made that a radical change in the electric current at this point takes place following the change in the fuel pressure (7), which has been proved by the performed laboratory experiments.…”

“…Measuring the flow speed of individual injectors of the engine in real time was proved possible, which enables the accurate assessment of the injection process. Merola et al [7] presented a method of verifying fuel injection and the combustion process using optical diagnostics, using an endoscopic system coupled with a CCD camera mounted in the intake manifold.…”

New approach of model based detection of early stages of fuel injector failures

“…Using the photoelectric phenomenon, Bor et al [3], presented a diagnostic method that allows observation of injection growth, its assessment and determination of injection start and end. Merola et al [24] presented another optical method., which, using an endoscopic system coupled with a CCD camera, analyzes the structure and rate of change of the state of the expanding fuel after exiting the injector nozzle. In the last cited work, Alloca et al [1] thanks to the vision method, analyzes the quality of injection with the simultaneous use of a microphone for measuring acoustic emissions, Fourier analysis and wavelet analysis, assessing the phenomenon of atomization of the fuel mixture.…”

Fuel injector diagnostics based on observations of magnetic flux changes

“…The shorter the injection duration time, the greater the impact of the delay in opening and closing the injector relative to the preset time, therefore the flow diminished by certain value is obtained. The correct choice, of injection parameters and the design of the injector, allows you to limit irregularities the process of burning fuel in the engine combustion chamber and reduce the emission of soot and unburnt hydrocarbons [7]. Therefore, different types of injectors are compared.…”