An internal combustion engine (ICE) is essentially an air pump. The more efficient the air flows through the air pump (ICE), the better power and fuel economy the ICE can deliver.
The ICE is a complex high-speed ballet of mechanical parts, designed to extract as much usable power from a spritz of gasoline in each cylinder. The theories on ICE operation go back at least a century, and ICE power and efficiency has seen a lot of improvement in the intervening decades.
In order to improve ICE fuel economy, engine makers have lightened the engine, optimized valve timing, moved to high-pressure direct fuel injection, and even tackled air flow optimization. Because the ICE must operate under a variety of speed and load conditions, keeping all these systems optimized is a complex computerized wonder of all its own.
Speaking of air control, there are a number of things that automakers have done, including variable (sort-of) intake runner length, and cylinder swirl-controlling features, among other methods, but some of these methods have yet to make it to the larger engines that power trucks, buses, trains, and ships, among others. Of course, there is always room for improvement, as demonstrated by researchers at Kansas State University (KSU).
The new system is called “Active Air Control” (AAC) and controls air flow to a much finer degree than on currently-available ICEs, which could improve emissions and fuel economy, especially in larger engines, such as those found in over-the-road tractor-trailers, marine engines, and diesel locomotives and backup generators.
Current ICEs operate on an average rich / lean principle, that is, in a large V8 engine, some cylinders may run leaner, while others may run richer, depending on speed and load. On average, the engine is running as efficiently has possible, but individual cylinders may be contributing to poor fuel economy and higher emissions.
KSU’s approach to AAC, US Patent 8622045, uses an air-flow meter to gauge, in real time, how much air is going into each cylinder. Using an electronic controller, a damper introduces enough turbulence to balance airflow so each cylinder gets the same charge. The result of this better balancing of airflow to each cylinder is less variance between cylinders and an overall improvement in emissions and fuel economy. The system has also been designs to retrofit and improve existing engines at a reasonable cost.
Image © Kansas State University