High speed flow measurement devices for gasoline fuel injectors
Keywords: engines
flow measurement
coriolis
pressure measurement
instrumentation

Internal combustion engines (ICEs) are currently widely used in the transport sector, and there are increasingly stringent regulations on pollution from vehicles, such as carbon dioxide (CO2), nitrogen oxides (NOx) and particulate matter (PM). To meet these standards, efficiency improvements in ICEs are being made while limiting exhaust emissions by improving engine control, monitoring and management. Knowledge of mass injected in individual injections taken cycle-by-cycle and cylinder-by-cylinder in an engine can aid in delivering enhanced injector control for engine monitoring, performance and modelling to help achieve these efficiency improvements and limit emissions. Currently, there are no real-time and on-engine direct mass measurements of fuel flow in individual cylinders of an engine due to the lack of appropriate measurement techniques. To achieve this, in this thesis two potential solutions: pressure methods (One Pressure Transducer Method (OPTM) and Two Pressure Transducer Method (TPTM)) and direct measurement of mass flow rate using a Coriolis flowmeter (CFM) (Fast Next Generation Coriolis (FNGC)), were evaluated for future on-engine applications.
A spray rig was modified to run experiments for each of the solutions. First, the FNGC (CFM with Precise, Repeat Integral Signal Monitor (PRISM)) technique was implemented on the spray rig and used to measure injections of gasoline. Individual injections were detected, and a repeatability study was conducted on the injections. The work highlighted that the FNGC was capable of detecting features such as a negative mass flow rate at the start of injection (SOI) and partial injection detection. The tests showed the potential of FNGC for on-engine mass measurement in real-time.
The spray rig was then modified and used to conduct experiments to apply the OPTM and TPTM. Various pipeline setups were tested, and different injection detections methods were examined for finding the best technique to capture the injection in the pressure trace. Both the OPTM and TPTM can be used to calculate the mass injected of individual injections, and the experiments showed that the pressure methods were capable of on-engine real-time injection mass measurement. At simulated engine speeds above 3500 rpm for the pipeline design implemented reflected pressure waves from the preceding injection influenced the current injection pressure measurement, this causes to the mass calculated to be significantly different to gravimetric measurement; this effect seen is a function of the pipeline design. A cursory model based on the Transmission Line Model (TLM) technique was developed to further understand and examine the impact of pressure reflections on OPTM and TPTM. The first pressure reflection after an injection was matched; however, a suitable match was not found for the consequent pressure reflections, limiting the application of the model.
Finally, the fuel pipeline was designed and deployed on an engine using the outcomes from the spray rig experiments. The OPTM and TPTM were applied to the pressure measurement data taken on the engine, and the mass injected per injection values were calculated at various engine speeds. The data confirmed no adverse impacts on the pressure methods due to engine vibrations.