Real Time Soot Concentration, Smoke Number, Size, and Number Measurement for Diesel Engines and Gas Turbines

Siris™ measures real-time diesel and gas turbine engine soot emissions. This new instrument, invented and developed by Process Metrix, measures total soot particle (agglomerate) mass, Smoke Number, mean size, and primary/agglomerate particle number...all at 10 Hz data rates..


Siris™ is a new instrument that measures real-time diesel engine and gas turbine soot emissions. Measurements can be obtained directly from raw exhaust, or following a dilution system. Invented and developed by Process Metrix under contract to the U.S. Government, this commercial-ready system has the capability to provide "equivalent gravimetric" measurements using optical diagnostics in real time. Our goal is not to entirely replace conventional filter-based measurement technology, but to provide time-resolved measurements of soot emissions. This time resolution provides greater insight into soot formation mechanisms as a function of engine operating parameters; critical information necessary to optimize performance for minimum emission.

Siris™ provides the following output data at 10 Hz data rates:

  • Total mass,
  • Soot agglomerate mean size,
  • Smoke Number,
  • Primary/Agglomerate particle number,
  • Surface area.

Siris™ uses laser light scattering collected at two angles to measure and calculate the total particle (agglomerate) mass, Smoke Number, and size using a fundamental scattering theory (patent # 7,782,459) based on the well-defined soot properties of the spherical primary soot particles that comprise the agglomerates. Once the mass and size are known, the Smoke Number, primary/agglomerate particle number and surface area are computed from these parameters over a wide dynamic range, given as follows:

  • Measurable particle mass concentration: 0.001–1000 mg/m3,
  • Measurable Smoke Number Range: 0.02 - 100,
  • Measurable particle sizes range: 50–500 nm
  • Measurable Number and Surface area based on parameters above,

Most importantly, Siris™ has been carefully evaluated against gravimetic sampling in a real diesel engine and gas turbine test configuration. Results (at left) incorporate standard values of carbon refractive index and density, which are independent of engine operating conditions, to calculate mass emissions from the measured scattering signals. The graph clearly shows quantitative correlation between the real-time Siris™ measurements, and the filter-based gravimetric data.

The time-resolution capability of the Siris system is illustrated in the data shown below. These data represent optical measurements of soot particulate over an engine driving cycle. Measurements were made on a 1-second update interval. Cumulative mass is illustrated as well – the ending value correlating with the gravimetic filter analysis as shown above.

Siris™ is available in three different configurations:

  • Stand-alone –The optical head alone, with configuration and readout software.
  • Valve Control – The stand alone system packaged in an enclosure with appropriate valving for calibration and process gas flow control,
  • Process Ready – Process Metrix has partnered with Sierra Instruments to integrate Siris™ into Soot-Trak™, Sierra's real time engine soot mass emisisons system. Soot-Trak is completely integrated with Sierra's world renowned Model BG-3 Partial Flow Sampling System (PFSS). The combination yields real-time measurements of soot mass, particle size, primary particle surface area and number in parellel with standard EPA gravimetric filter sampling also provided by the BG-3.

For more information on the Siris™ system contact:

Donald Holve, Ph.D
voice:(925) 460-0385 x116

For information on Soot-Trak (Siris™ integrated with Sierra Instruments BG-3 Particulate Sampling system) contact:

Del Pier
voice: (517) 575-7485