Development of NOx Sensors for Heavy Vehicle Applications

Armstrong, T.R. ; Soltis, R.E.

Oak Ridge National Laboratory

关键词: Steady-State Conditions;    Pumping;    Flow Rate;    Transients;    Valves;   

DOI  :  10.2172/940393
RP-ID  :  ORNL99-0566
RP-ID  :  DE-AC05-00OR22725
RP-ID  :  940393

美国|英语

来源: UNT Digital Library

【 摘 要 】

A DOE CRADA was initiated in February 2000 between Ford Motor Company and the US Department of Energy's Oak Ridge National Laboratory (ORNL). The overall objective of the research agreement was to characterize the performance of emission sensors and identify potential areas of improvement and to develop improved insulating materials with a lower capacitance to minimize radio frequency (RF) interference. A bench-scale device was developed at ORNL to evaluate sensor performance. The test stand was designed to enable control of the gas composition, flow rate, and temperature. An air-actuated three-way valve was used to control the injection of the test gas in order to elucidate the transient behavior of the sensor. The major finding from the studies was that transient test results showed that response time of the sensor to NO was highly dependent on the temperature. The time constant decreased with increasing gas temperature and achieved a constant valve of 610 ms for temperatures greater than or equal to 350 C. The steady-state valves O{sub 2} and NO{sub x} pumping currents were measured under steady-state conditions using a picoammeter. The measured pumping currents were extremely low and required an electrically quiet environment for accurate readings. ORNL developed also modified the existing insulator material to decrease its dielectric constant in order to reduce radio frequency interference from the internal heater. This was accomplished by adding low dielectric constant sintering aids to alumina.