Experimental Study on Injector Spray Pattern Optimization for a Turbocharged GDI Engine Combustion System

Changan Automobile Company recently develops a new 1.0L turbocharged GDI engine for its future vehicle as an affordable fuel-saving option. Fuel direct injection and turbo-charging are integrated to significantly improve fuel economy and power. Injection spray pattern plays an important role on GDI engine combustion system because of its critical influences on combustion and oil dilution. In this paper, four injector patterns were tested in an optical engine with Planar, double sided Laser Induced Fluorescence (LIF) with fuel & tracer and flame imaging methods to evaluate spray, mixture formation and combustion process in cylinder. Spray pattern and mixture formation are studied using LIF, while flame and combustion characteristics are studied by flame natural luminosity. The pictures of piston crown and glass liner are also evaluated for fuel spray impingement. Four types of multi-hole injectors are prepared. The Initial spray pattern layouts are studied before the test by CAD for matching sprays with piston bowl for catalyst heating operation in split injection mode and avoiding spray impingement on inlet valves. These four injectors are evaluated at three engine conditions: catalyst heating, 1500 rpm/WOT, and 2000 rpm/2 bar. According to the test result, the most suitable injector pattern is chosen as the final one for the turbocharged GDI engine. Additional minimum calibration is also carried out for the selected injector pattern at the three engine conditions. Special attention on fuel-air mixing, cylinder liner impingement and piston wetting by fuel spray are paid to maximize air utilization, and minimize possible oil dilution and soot emissions.