Effect of Closed Loop Fuel Control System Characteristics on Emissions from a Natural Gas-Fueled Engine

Achieving Low Emissions From a Biogas Fueled SI Engine Using a Catalytic Converter

“…Oxygen sensors suffer from multiple limitations some of which are related to the phenomenon of hysteresis. Hysteresis is when the sensor output does not change at the same equivalence ratio for increasing and decreasing A/F ratios, in other words, there is a longer response time from rich to lean than from lean to rich [2]. The controller must then compensate for this.…”

“…Two types of oxygen sensors are typically used: zirconia and titania [1], [2]. It has been seen that, when used in a natural gas engine, the zirconia oxygen sensor has a wider range of adjustability than the titania oxygen sensor [2]. The Titania oxygen sensor has a sharper transition to the lean side compared to that of the zirconia oxygen sensor.…”

“…The Titania oxygen sensor has a sharper transition to the lean side compared to that of the zirconia oxygen sensor. The oxygen sensor initially used for the gasoline fuel control system may be suitable for natural gas fuel control [2].…”

“…The implementation of exponential gain could possibly optimize the equivalence ratio average so that it can effectively work with the three-way catalyst. The application of exponential gain to the output of the oxygen sensor might also increase adjustability for specific installations of this system [2]. It is possible to change the typical oxygen sensor structure to allow for a more robust, breadth of sensing.…”

“…Closed loop control, applied to the use of natural gas, can be characterized by average A/F ratio, rich and lean excursion limits, and the skewness parameter of time variation in fuel to air (F/A) equivalence ratio [2]. The concentration of carbon monoxide in the exhaust is related to the rich excursion, whereas the oxygen concentration is related to the lean excursion.…”