Comparison of an On-Board, Real-Time Electronic PM Sensor with Laboratory Instruments Using a 2009 Heavy-Duty Diesel Vehicle
EmiSense Technologies, LLC (www.emisense.com) is commercializing its electronic particulate matter (PM) sensor that is based on technology developed at the University of Texas at Austin (UT). To demonstrate the capability of this sensor for real-time PM measurements and on board diagnostics (OBD) for failure detection of diesel particle filters (DPF), independent measurements were performed to characterize the engine PM emissions and to compare with the PM sensor response. Computational fluid dynamics (CFD) modeling was performed to characterize the hydrodynamics of the sensor's housing and to develop an improved PM sensor housing with reproducible hydrodynamics and an internal baffle to minimize orientation effects. PM sensors with the improved housing were evaluated in the truck exhaust of a heavy duty (HD) diesel engine tested on-road and on a chassis dynamometer at the University of California, Riverside (UCR) using their Mobile Emissions Laboratory (MEL).
The mass ratio of air to fuel (air-fuel ratio) of an operating internal combustion engine is a very important metric for pollution control. Typically the air-fuel ratio is not directly measured, but instead the excess air factor Lambda (λ) is used. Lambda is the ratio of actual air-fuel ratio to the stoichiometric air-fuel ratio. Commonly switching type sensors are used. Those can detect 3 states: λ =1, λ >1 and λ < 1, and are used under low and medium load conditions to keep λ in the optimum operating range for a catalytic converter. Wideband O2 sensors are exhaust analysis devices that are used to measure air-fuel mixtures over a very large range up to air. These sensors are used in more and more engines today for closed loop fueling control under all operation conditions. They are especially important for new lean-burn technologies, clean diesel applications and for alternative fuel engines.