2015 IR&D Annual Report

Sampling System Investigation for the Determination of Semi-Volatile Organic Compounds (SVOC) Emissions from Engine Exhaust, 03-R8442

Principal Investigators
E. Robert Fanick
Svitlana Kroll
Chris A. Sharp
Shraddha Quarderer
John E. Gomez

Inclusive Dates: 01/01/14 – 12/31/15

Background — Semi-volatile organic compounds (SVOC) are a group of compounds that may form during combustion and/or are present in the unburned portion of the fuel and lubricating oil that ultimately becomes part of the exhaust. Many of these compounds are considered toxic or carcinogenic. Since these compounds are present in very low concentrations in diesel engine exhaust, the methods for sampling, handling, and analyzing these compounds are critical to obtaining representative and repeatable results. Engine testing is typically performed using a dilution tunnel method. With a dilution tunnel, the collection of a representative sample is important to ensure that the sample is representative of the actual exhaust. Experiments were performed to determine the equilibration time and other sampling parameters required for the measurement of SVOC. The results show that representative results can be obtained with this method.

Approach — The main objective of this project was to validate and qualify the SwRI dilute sampling procedures for use as a dilute exhaust sampling method. Some of the individual tasks included:

  • Identifying and implementing possible refinements and improvements in SwRI's dilute-based sampling method
  • Evaluating the constant volume system (CVS) tunnel soot equilibration variables (tunnel wall effects)
  • Establishing the test to test repeatability for measuring SVOC
  • Determining SVOC trap breakthrough
  • Comparing collection efficiency of various sample media
  • Validating procedures for sample media handling and media blanks
  • Comparing solvents for removal of particulate- and volatile-phase compounds
  • Optimizing the sampling system design

A 2012 Ford 6.7L engine was used to produce the engine exhaust throughout the entire experiment. The testing started with a "clean" dilution tunnel, and engine-out exhaust ("dirty" exhaust) was sampled to determine the equilibration time for the dilution tunnel. Tests using different filter media and trap breakthrough experiments were also performed. The exhaust was then changed to aftertreatment-out ("clean" exhaust), and the equilibration time was determined from a "dirty" tunnel to a "clean" tunnel. Figure 1 shows a schematic of the dilute exhaust SVOC sampling system. Samples were collected periodically throughout the tunnel equilibration period, and these samples were extracted and analyzed by gas chromatography/mass spectroscopy (GC/MS).

Figure 1: New sample system schematic for dilute exhaust SVOC measurements.
Figure 1: New sample system schematic for dilute exhaust SVOC measurements.

Accomplishments — As a result of this study, several accomplishments and improvements were made to the dilute exhaust sampling system. These improvements included:

  • Implementation of a background air SVOC sampling system, in addition to the traditional tunnel blank
  • Implementation of closed-loop control to maintain constant flow rate on the dilute exhaust SVOC sampling system
  • Implementation of 8-x10 inch Zefluor™ filter instead of the traditional 20x20 inch Pallflex filter
  • Elimination of polyurethane foam (PUF) in the SVOC sample train (use XAD porous polymer resin only)
  • Installation of a heated blanket around the secondary dilution tunnel for the dilute exhaust SVOC sampling system
  • Implementation of a field blank procedure for each day of testing to account for ambient air contributions
  • Implementation of sampling surrogates and an internal, clean-up, and recovery standard to improve quantitation
  • Improvement of solvent extraction techniques for extraction of XAD and filters
  • Optimization of the solvent system to reduce losses in surrogate compounds
  • Validation of sample media handling for both extraction and collection
  • Evaluation of different filter media
  • Determination of test-to-test repeatability
  • Determination of the tunnel equilibration period
  • Determination of trap breakthrough

In addition to the accomplishments listed above, the Environmental Protection Agency (EPA) agreed to allow this method to be introduced for a review and comment period in the Code of Federal Regulations. This accomplishment will allow the SwRI method to be used as an alternative for sampling and analysis of SVOC in dilute engine exhaust. Several papers were presented on this topic at Coordinating Research Council (CRC), Society of Automotive Engineers (SAE), and Emissions 2015 conferences; and the method will be sent for the EPA review period in October 2015.

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