Improvement of energy efficiency and ecological cleanliness of internal combustion engines with spark ignition is a task of vital importance and alternative fuels are one of the ways to solve it. Many researches and tests conducted by various institutes all over the world revealed advantages of different alternative fuels, unfortunately, alongside with disadvantages. Mixing fuels was proposed to eradicate known downsides, starting new wave of IC engine process researches running on alternative fuel mixtures.
Author consider propane widely spread in many countries for low cost and reducing emissions of harmful substances in exhaust gases. To deal with its main limitations: reduction in engine power and torque when used in gas phase, it is proposed to add portions of gasoline to propane. As parameters of this mixture differs from gasoline or propane alone, it is necessary to develop new methods for IC engine control taking into account peculiarities of this mixture to improve energetic, ecological and economical figures.
To achieve this goal, author developed: IC engine process model, algorithms to set control parameters (ignition and fuel systems) and approach to decrease knock occurrence probability. Mathematical model is based on Vibe function and extended for 2-component fuel mixture processing. It allows calculation of work, efficiency, mechanical and thermal load, state of working substance and engine performance figures. Author propose algorithm for ignition timing calculation in real time using in-cylinder pressure peak position as a criterion of optimality and algorithm of propane/gasoline ratio variation to allow using optimal spark advance angles and prevent knock. Knock prevention approach includes forecasting part and 2-stage reacting part for keeping optimal ignition as long as possible.
The control method proposed is confirmed by experiments. Car model “Lada 21108M” with 1.8 liter 16 valve engine was equipped by propane/petroleum mixture supply system. Test runs on MAHA LPS 3000 dyno stand under control or developed method showed increase of engine power and torque. Knock, emissions and fuel cost were decreased.