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Institute for Commercialization

Active Air Control

Reference Number: K 08-06

Inventors: Chapman, Kirby; Grauer, Diana K.

Owner: Kansas State University Research Foundation


Invention Summary

In an attempt to decrease pollutant emissions, the natural gas compression industry has refined the turbocharged engine to allow for increased air flow into the system. However, the physics of such systems, and the environments in which they operate, constrain further advancement in emission reduction. 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. Since NOx production is a highly nonlinear function of the corrected trapped equivalence ratio, the rich cylinders can produce disproportionately more NOx than the lean cylinders. The only way to lower the overall engine NOx production, and therefore engine emissions, is to ensure that each cylinder operates at the same target corrected trapped equivalence ratio.

This invention allows for active and real time measurement and control of the air flow rate into an engine cylinder. The system adjusts the air flow rate so that the air flow into multiple cylinders is the same. The effect of balancing the air in each cylinder allows for the production of an acceptably low quantity of NOx from each cylinder. One embodiment of this invention allows for the air controller to act as a damper. If the air flow sensor determines an unacceptable air flow rate in any cylinder, it will create an air flow disturbance. 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.


  • Low cost method to control and balance the NOx production from an engine system

  • Balances the trapped equivalence ratio between cylinders, thereby lowering NOx production

  • Allows legacy engines to meet compliance with EPA 2011 regulations requiring less than 0.5 gm/hp-hr NOx production

  • Flexible design allows the system to fit varying engine systems


Large bore, multi-cylinder legacy engines in the following fields

  • Pipeline

  • Rail

  • Marine

  • Back-up Generation