Peter Jozsa

Reduction of NOx stored at low temperatures on a NOx adsorbing catalyst

Isothermal storage and reduction of NO2 with CO, C3H6 and H2 as reducing agents on a lean NOx adsorber was investigated by temperature programmed desorption (TPD) and temperature programmed reduction (TPR) studies. The reduction of NOx was clearly favoured with H2 as reducing agent. Carbon monoxide and C3H6 showed fairly low reduction of NOx. The NOx reduction at low temperatures with H2 as reducing agent was found to be effective, clearly much more effective than for CO.

A Potential Soot Mass Determination Method from Resistivity Measurement of Thermophoretically Deposited Soot

Miniaturized detection systems for nanometer-sized airborne particles are in demand, for example in applications for onboard diagnostics downstream particulate filters in modern diesel engines. A soot sensor based on resistivity measurements was developed and characterized. This involved generation of soot particles using a quenched co-flow diffusion flame; depositing the particles onto a sensor substrate using thermophoresis and particle detection using a finger electrode structure, patterned on thermally oxidized silicon substrate. The generated soot particles were characterized using techniques including Scanning Mobility Particle Sizer for mobility size distributions, Differential Mobility Analyzer—Aerosol Particle Mass analyzer for the mass–mobility relationship, and Transmission Electron Microscopy for morphology. The generated particles were similar to particles from diesel engines in concentration, mobility size distribution, and mass fractal dimension. The primary particle size, effective density and organic mass fraction were slightly lower than values reported for diesel engines. The response measured with the sensors was largely dependent on particle mass concentration, but increased with increasing soot aggregate mobility size. Detection down to cumulative mass as small as 20–30 μg has been demonstrated. The detection limit can be improved by using a more sensitive resistance meter, modified deposition cell, larger flow rates of soot aerosol and modifying the sensor surface.

Thermal Management System for Particle Sensors Design, Performance and Verification

This paper presents the thermal performance of a proposed thermal management device (patented in 2009) intended for a thermophoresis-based soot sensor. The performance was studied for temperatures ranging from 50 to 400°C and for exhaust speeds up to 10 m/s. It also presents the design and basic concepts. The performance study and design development were performed with finite element analysis (FEA). The FEA results were then verified with experiments in a heated wind tunnel. The relative performance of the device was found to increase for higher temperatures and lower wind speeds. The main conclusion drawn from this paper was that it is feasible to cool a sensor surface enough for a thermophoresis-based soot sensor in a diesel exhaust system.

Performance of a thermal management system for thermophoresis based soot sensors — Design, performance and verification

This paper presents the thermal performance of a proposed thermal management device (patented in 2009) intended for a thermophoretic based soot sensor. The performance was studied for temperatures ranging from 50°C to 400°C and for exhaust speeds up to 10m/s. It also presents the design and basic concepts. The performance study and design development was performed with finite element analysis (FEA). The FEA results were then verified with experiments in a heated wind tunnel. The relative performance of the device was found to increase for higher temperatures and lower wind speeds. The main conclusion drawn from this study was that it is feasible to cool a sensor surface enough for a thermophoretic based soot sensor in a diesel exhaust system.