Patent Application
20080021661
Reference is now made to the accompanying figures depicting aspects of the present invention, in which:
According to one embodiment, the performance mathematical representation is provided as equations for each of the measured engine parameters. These equations are adjusted using field engine performance data. The initial performance mathematical representation 12 is provided using a flight test and is registered in an equation file 14. In step 16, real field engine performance data is acquired on multiple engine samples. Based on the equation file 14 and on the field engine performance data, the expected engine performance is calculated in step 18 and provides a baseline to which the field data is to be compared. The field engine performance data 16 is normalized in step 20 using standard methods to remove the effect of ambient temperature and pressure variation and reduce the data to a single standard operating condition. The deviation between the expected and the field engine performance data is calculated in step 22 and field performance data is cleaned from diverging data by discarding data outside a deviation tolerance band is discarded in step 24. In step 26, the average deviation between the expected engine performance data and the cleaned field performance data is calculated for each engine sample and, in step 28, the data is corrected for each engine sample according to the calculated average deviation such that the adjusted average performance of each engine sample is the same. The average deviation of each field engine parameter from the expected performance parameter is added to the corresponding measured field engine parameter to align all the data to the same reference. In step 30, the sets of field performance data from all the engine samples are combined into a single data set and a performance mathematical representation is constructed by fitting the equations on the single data set such that the performance mathematical representation represents the average performance of all the engine samples.
Using the newly constructed performance mathematical representation, the expected engine performance and the deviation between the expected and the field performance data are recalculated in step 32. If there remain trends in the data that cannot be well represented by the mathematical representation, an additional correction factor is calculated in step 34 to remove the trend. Typically this will be a correction factor to remove trends with altitude that cannot be captured by a simple mathematical representation of the engine performance. It may also include the impact of changes in customer installation effects like the level of bleed extraction if it is measured. Then, in step 36, the data scatter over the constructed performance mathematical representation is calculated and if an improved scatter is required, the process is carried out again using the equation file updated in step 40 using the constructed performance mathematical representation. When the data scatter is appropriate in step 36, the new improved equation file is implemented in step 38.
Calculation of the improved performance mathematical representation can be done at one single time, when sufficient data is available to provide a sufficient statistical sample or alternatively, the performance mathematical representation can be constantly updated using new available field engine performance data.
It should be appreciated that the process can be carried out based on a small sample of data, but the statistical significance of the result is then decreased.
In one embodiment, the improved ETCM® only consider field performance data acquired during the early life of an engine in order to eliminate the impact of the engine performance deterioration on the improved performance mathematical representation. A drawback of this procedure is the reduction of the data sample available for improving the performance mathematical representation.
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without department from the scope of the invention disclosed. Modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.
