Controlling air flow decreases pollutants in piston engines

The Kansas State University Research Foundation, a non-profit corporation, has received a patent for a system that controls the air flow to pistons in reciprocating internal combustion engines. The patent ‘Active Air Control’ credits former faculty member Kirby Chapman and doctoral graduate Diana Grauer as the system’s inventors.

The patent summary states that the natural gas compression industry is refining the turbocharged engine to allow for increased air flow into the system. However, it notes that, “Within a specific engine frame, the fuel flow rate, air flow rate and scavenging efficiency of the system must be the same for each cylinder to achieve identical corrected trapped equivalence ratios. If this is not accomplished, some cylinders will operate leaner than average and some richer than average.”

Developed at the university, the new system uses an air flow sensor to measure and control the air flow rate into each piston in real time. Algorithms adjust the air flow rate accordingly and equalise the rate in multiple cylinders at the same time.

Figure of the air control system from the patent paperwork.

“If the air flow sensor determines an unacceptable air flow rate in any cylinder, it will create an air flow disturbance,” states the summary. “Based on the measurements in the engine cylinders, logic algorithms will trigger the actuators to adjust the air flow rate so that it is again the same in all cylinders.”

The effect of balancing the air in each cylinder reduces the levels of nitrogen oxides produced during combustion in the engine. The system therefore offers a low-cost method to control and lower the production of nitrogen oxides and helps legacy engines meet compliance with EPA 2011 regulations.

Designed to fit various engine systems, the system enables large-bore, multi-cylinder engines used in rail, marine, pipeline, back-up generation and other fields to run efficiently while producing low levels of emissions.