Data from a Variable Rate Shape High Pressure Injection System Operating in an Engine Fed Constant Volume Combustion Chamber

In current systems, for a given nozzle and injection pressure (pump speed), the shape of the injection rate is fixed and the injection timing is the only variable the engine designer can vary. For this non-interactive injection system, changing the injector nozzle (number and diameter of holes) will proportionately change the injection shape. New injection systems in which the rate of injection is a controlled variable are being developed. Results from one such injector, called the UCORS (Universal Combustion Optimization and Rate Shaping), are reported in this paper. The system can dynamically control its injection rate shape by controlling the position and size of a pilot injection relative to the main injection.

Data and analysis from an out-of-engine and combustion chamber study of the UCORS injection system are presented. Experimental techniques include rate tracing using a Bosch type rate of injection meter, injector pressure tracing, high speed photography, two-color pyrometry, and combustion pressure tracing. Results indicate that rate shaping does change the combustion chamber heat release rate. Combustion temperatures were insensitive and soot concentrations (KL) were tremendously sensitive to the injection rate shape. For our experiments, greater soot oxidation occurred as the pilot was positioned closer to the main injection. The lowest end state concentration occurred when the pilot and main injection were equally sized and positioned 0.83 ms apart.