Background
Starting with engine model year 2016, exhaust particle sensors are required for on-highway diesel engines in the United States for onboard diagnostics to detect component failure or exceedance in particle emissions relative to a regulatory threshold limit. This trend is expected to continue for gasoline direct injection engines as well as for non-road engines in the near future. Particle sensors will also be required in countries like Japan, China, and the European Union in the 2018–2020 timeframe. The use of all kind of sensors onboard vehicles will flourish during this decade including sensors for emissions monitoring. Currently, all utilized onboard particle-sensing technologies suffer from issues related to time-delays, accuracy, sensitivity, and durability. With the continuous global tightening of the emissions threshold, there is a critical need for robust and economic particle-sensing technology that mitigates existing problems and pushes the sensitivity to detect low particle concentration in engine exhaust. The goal of this investigation is to validate a proof-of-concept and develop a novel sensor prototype that is fundamentally different from marketplace sensor technologies.
Figure 1: This simplified drawing represents the voltage breakdown (VB) and/or voltage-versus-current (VI) relationship between two electrodes as a function of particle concentration presence.
Approach
The novelty element of the new design relies on exploiting the relationship between voltage breakdown (VB) and/or voltage-versus-current (VI) relationship between two electrodes as a function of particle concentration presence, as simplified in Figure 1. The flowing gas and aerosol mixture would alter the properties of the dielectric medium between the two electrodes resulting in unique signatures of the VB and the VI relationships. Gap distance between the electrodes, applied voltage, electric current, gas type, and particle concentrations are all variable parameters that were examined extensively.
Accomplishments
This work serves as an example of collaboration combining the skillsets of two SwRI groups. It directly contributes to SwRI’s existing Particle Sensor Performance & Durability (PSPD) consortium by advancing the state of knowledge in the field of particle sensing. The work opens a potential venue of collaboration with the Department of Defense, Department of Energy, and the U.S. Environmental Protection Agency. Finally, this project leverages the space-flight remote and in situ instrumentation capabilities and the particle-sensing heritage to further develop novel ground-based detectors.
This proof of concept was a success and we obtained differentiable VI properties as a function of particle concentration. The sensor is extremely sensitive to soot concentrations and the gas flow rate. A patent disclosure has been submitted. Results pave the way to a potentially new SwRI-led sensor development that is based on robust and non-expensive technology.