SYMPOSIA PAPER Published: 01 January 1976
STP32370S

A Calibration Procedural System and Facility for Gas Turbine Engine Exhaust Emission Analysis

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This paper is directed toward those individuals and organizations who, in the process of being regulated, are, or have been, required to develop their own standard reference materials, to establish the analytical procedures necessary to develop and maintain these materials, and to evolve a calibration methodology for using these standard materials in day-to-day operations, as well as for compliance testing.

In the Federal Register, (Vol. 38, No. 136, Part II, 17 July 1973) the Environmental Protection Agency (EPA) promulgated “Emissions Standards and Test Procedures for Aircraft.” Maximum allowable emission levels were established for smoke, carbon monoxide, hydrocarbons, and oxides of nitrogen; and, in addition, criteria were established for the measurement of these constituents. Requirements were also set for the measurement of carbon dioxide to be used in determining the representativeness of the sample. At that time, only a few selected standard reference materials, developed for the automotive industry, were available. These were three concentrations of carbon dioxide in nitrogen and five concentrations of propane in air, all certified to ±1 percent over a 95 percent confidence interval. The EPA required that all calibration gases would be known to ±2 percent without specification of the confidence interval. There was no suggestion as to a source of these relatively high accuracy gases, how to guarantee the accuracy of assay, or how they were to be maintained, monitored, and used. Generally poor experience with gas vendor's abilities to consistently supply gases within 2 percent of the certified analysis, and the demonstrated instability of some mixtures in the cylinder led, in part, to the decision to develop a standard reference materials laboratory in support of our emissions measurement technology programs. This standards laboratory was charged with :

1. Providing a bank of standard reference gases for use in all emissions measurement technology programs at Pratt and Whitney Aircraft.

2. Where analytical procedures for making high accuracy determinations of gas concentrations were lacking, to develop this capability.

3. Develop procedural systems necessary to make this reference bank of standards available for day-to-day instrumentation calibration, and 30-day detailed calibrations as required by the EPA.

4. Determine, insofar as practicable, our ability to perform analyses and assign concentration levels in comparison with the rest of the industry.

5. As National Bureau of Standards standard reference materials become available, to adopt these standards and phase them into our program.

These goals have been met in essentially all respects. In addition, it has been determined that the practically achievable precision and accuracy of measurement is significantly different from that implied by the EPA, and it is highly unlikely that their high accuracy requirements can be met.

Author Information

Elwood, JH
Pratt and Whitney Aircraft, East Hartford, Conn.
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Developed by Committee: D22
Pages: 255–272
DOI: 10.1520/STP32370S
ISBN-EB: 978-0-8031-4674-7
ISBN-13: 978-0-8031-0297-2