Investigation of Fixed-Rake Sampling System for the Assessment of Emission Characteristics of Gas Turbine Engines

The regulations proposed by the US Environmental Protection Agency to limit the quantity of pollutant gases emitted by aircraft engines allow the exhaust of engines submitted for compliance testing to be sampled by a fixed-multipoint rake. However, the onus is placed on the manufacturer to prove the representativeness of the samples taken in this relatively cheap fashion. To illustrate best possible accuracies, the exhaust of an M45H civil turbofan engine has hen extensively sampled and a computer program has been used to select the optimum configuration of a cruciform rake. The program demanded excellent agreement between the sampling methods and this proved to be the case in actual tests. However, the program also indicates that the errors of a simply designed rake giving area-weighted samples would also be less than 10%. Sampling in the FAA diamond pattern would give rise to a 20% error in CO emissions.Copyright © 1983 by ASME