ATA employee working to establish international standards for turbine engine exhaust measurements

  • Published
  • By Patrick Ary
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  Dr. Robert Howard is an experienced traveler.

He's spent time away from his home in Manchester to visit Cologne, Germany; Interlaken, Switzerland; Wales and other places that he can't even remember off the top of his head.

One reason he may not be able to remember them is because he spends most of his time overseas in hotel conference rooms.

Howard, an engineering specialist in the Instrumentation and Diagnostics section of ATA's Technology and Analysis Branch, attends meetings affiliated with the Society of Automotive Engineers (SAE) twice a year. While those meetings sometimes take place in cities most people would love to visit for their culture and tourist attractions, Dr. Howard and other committee members spend most of their time working.

"These are true working meetings," he said. "Our agenda for this (most recent) meeting has us starting at 8 o'clock and adjourning at 6 p.m. every day. We take an hour for lunch. During lunch, depending on where we hold the meeting ... we'll grab sandwiches and bring them back in."

Howard is a member of the technical standards SAE E31 subcommittee, which deals with aircraft emissions. Committee members are developing a document that will establish an international standard for measuring particulate emissions from turbine engines.

Recently, Howard was recognized by SAE International "For outstanding contributions in furthering the goals of the Technical Standards Board and this Council, which are to serve the public, government and industry, through standardization, documentation and dissemination of information aimed at improving and advancing transportation safety and technology."

Particulate emissions are already regulated in industry and other areas. The difficulty in measuring emissions from turbine engines is the extreme conditions of the exhaust, according to Howard.

"(Inserting a probe) is very different from sticking it into an exhaust stack at an industrial plant or at the exhaust of a car or tractor-trailer truck," he said. "You have to be able to make the hardware survive, and then because of the really high gas velocities and the high temperatures at the high-power engine conditions, you have issues with getting the samples from that probe tip to the instrument without changing the sample."

The work Howard and other committee members are doing is specifying how to measure nonvolatile particles, which are carbonaceous particles - commonly referred to as soot.

(Volatile particles can form once the gases from the engine have left and mixed with the surrounding air. They are not measured because they don't exist near the exit plane of the engine, and the interior of a sample line cannot easily reproduce the conditions in the atmosphere.)

A standard for measuring particulate emissions is needed by everyone involved - the military, aircraft manufacturers and regulating bodies like the Environmental Protection Agency and the European Aviation Safety Agency. Many of those groups are represented on the SAE E31 committee.

"The EPA wants to have confidence that you're getting a comparable measurement, and the military wants to be sure they're using test standards for making aircraft engine exhaust measurements," Howard said. "They don't want to develop their own techniques independently and then have to argue with EPA that these are correct or acceptable."

A native of Grimsley, Tenn., Howard began his career at AEDC in 1987. As an engineering specialist in ATA's Instrumentation and Diagnostics Group, he helps develop and apply different types of diagnostics as needed by AEDC's test facilities and sometimes for off-base customers such as NASA.

Much of Howard's research has been with projects like the Aircraft Particulate Experiment (APEX), DOD's Interim Particulate Matter Test Method (IPMTM) Development and Alternate Aviation Fuel Experiment (AAFEX). NASA has been a major participant in most of the work, along with universities, private companies and the Air Force.

Starting with APEX 1 at a NASA Dryden facility, Howard and other project participants began developing a method to measure particles and then refining the process as they saw what worked and what didn't. The most recent work was an AAFEX 2 measurement test at a NASA facility near Edwards Air Force Base last year. Working with NASA to characterize engine exhaust products has funneled into his work with SAE E31.

"As we've marched forward through these campaigns there is less and less tinkering, because we become more confident in what we're doing and how we were doing it," Howard said. He also credits work from his ATA colleagues Katie Stephens, Roy Carroll, Gary Storey, Brad Besheres, Steve Lepley and Danny Catalano as being essential to accomplishments on those projects.

At the same time, other committee members in Europe have been involved in their own research on measuring particulate emissions. Everyone's work will go toward a final document that will define sampling methodology and the instrumentation needed to analyze those samples, which is what manufacturers are waiting for.

"The instruments are rather expensive, and altogether the engine companies will have to invest a few hundred thousand dollars for infrastructure changes to make this work," Howard said. "They want to know the committee has settled on the approach and how the measurements should be made before making the investment."

Howard and other committee members have been working on the procedure and document for the better part of a decade. He expects another two to three years before the document is finalized, but says committee members hope to have a good working draft complete by the summer. After that, it's a matter of tweaking the procedure based on manufacturers' testing.

"The major components are how to do the sampling, the instrumentation to measure mass, and the instrumentation to measure particle number density," Howard said. "So what the draft document will be lacking is applying this prescribed system to several different engine types, getting experience with the procedure and identifying shortcomings or practical issues engine manufacturers have in applying this technique, so then we can refine the document to better specify how these measurements should be made."

And while his wife, Martha, and other spouses see the sights and sounds of places around the world, Howard is OK with seeing most of it from a car window between an airport and a hotel.

"It feels gratifying," he said. "You get a gratification from working on something that you feel has a need and an urgency by lots of agencies and groups."