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This paper summarizes the Heavy-Duty In-Use Testing (HDUIT) measurement allowance program for Particulate Matter Portable Emissions Measurement Systems (PM-PEMS). The measurement allowance program was designed to determine the incremental error between PM measurements using the laboratory constant volume sampler (CVS) filter method and in-use testing with a PEMS. Two independent PM-PEMS that included the Sensors Portable Particulate Measuring Device (PPMD) and the Horiba Transient Particulate Matter (TRPM) were used in this program. An additional instrument that included the AVL Micro Soot Sensor (MSS) was used in conjunction with the Sensors PPMD to be considered a PM-PEMS. A series of steady state and transient tests were performed in a 40 CFR Part 1065 compliant engine dynamometer test cell using a 2007 on-highway heavy-duty diesel engine to quantify the accuracy and precision of the PEMS in comparison with the CVS filter-based method.

Nanoparticle formation during exhaust sampling and dilution has been examined using a two-stage micro-dilution system to sample the exhaust from a modern, medium-duty diesel engine. Growth rates of nanoparticles at different exhaust dilution ratios and temperatures have been determined by monitoring the evolution of particle size distributions in the first stage of the dilution system. Two methods, graphical and analytical, are described to determine particle growth rate. Extrapolation of size distribution down to 1 nm in diameter has been demonstrated using the graphical method. The average growth rate of nanoparticles is calculated using the analytical method. The growth rate ranges from 6 nm/sec to 24 nm/sec, except at a dilution ratio of 40 and primary dilution temperature of 48 °C where the growth rate drops to 2 nm /sec. This condition seems to represent a threshold for growth. Observed nucleation and growth patterns are consistent with predictions of a simple physical model.