Calculating distortion metrics¶
Main file that calculates various distortion metrics given data.
- class distorted.distortion.Distortion(dataframe)[source]¶
This class defines a Distortion object.
- Parameters:
dataframe (string) – CSV filename.
- PrattAndWhitneyKD2()[source]¶
Calculates Pratt and Whitney KD2.
\(KD_{2} = \frac{\sum_{r=1}^{n}[\theta _{r}^{-}(\frac{\Delta P}{P})_{r}\frac{OD}{D_{r}}]}{\sum_{r=1}^{n}[\frac{OD}{D_{r}}]}\)
where
\(r\) = particular ring of total pressure probes
\(\theta _{r}^{-}\) = circumferential extent in degrees of largest single pressure depression below \(P_{avg}\) for a given ring
\((\frac{\Delta P}{P})_{r}\) = \((P_{avg} - P_{min})/P_{avg}\) in percent, for a particular ring
\(P_{avg}\) = average pressure per ring
\(P_{min}\) = minimum pressure per ring
\(OD\) = outer diamter of duct
\(D_{r}\) diameter of particular ring
\(n\) = number of measurement rings
- Return type:
float
- RollsRoyceDC60()[source]¶
Returns the Rolls-Royce DC60 index
\(DC(\Theta \;critical)/\bar{P} = \frac{P_{avg}-P_{min},\Theta^{-}_{c},avg}{q_{avg}}\)
where
\(P_{avg}\) = The area-weighted mean total pressure over the engine inlet
\(P_{min},\Theta^{-}_{c},avg\) = The minimum area-weighted mean total pressure for a sector whose circumferential extent is ‘Theta’ critical
\(q_{avg}\) = The area-weighted average velocity head over the engine inlet
- Returns:
Calculated Distortion Index
- Return type:
float
- RollsRoyceDeltaPDeltaPAvg()[source]¶
Returns the Rolls-Royce Pavg-Pmin(Theta Critical)/Pavg index
\(\Delta P(\Theta critical)/\bar{P} = \frac{P_{avg}-P_{min},\Theta^{-}_{c},avg}{P_{avg}}\)
where
\(P_{avg}\) = The area-weighted mean total pressure over the engine inlet
\(P_{min},\Theta^{-}_{c},avg\) = The minimum area-weighted mean total pressure for a sector whose circumferential extent is ‘Theta’ critical
- Returns:
Calculated Distortion Index
- Return type:
float
- pDeltaPavg1()[source]¶
Returns a simple distortion index
\(\frac{\Delta P_{max-min}}{\bar{P}}=\frac{P_{max}-P_{min}}{P_{avg}}\)
where
\(P_{max}\) = Maximum inlet total pressure
\(P_{min}\) = Minimum inlet total pressure
\(P_{avg}\) = Average inlet total pressure
- Returns:
Calculated Distortion Index
- Return type:
float
- pDeltaPavg2()[source]¶
Returns a simple distortion index
\(\frac{\Delta P_{avg-min}}{\bar{P}}=\frac{P_{avg}-P_{min}}{P_{avg}}\)
where
\(P_{min}\) = Minimum inlet total pressure
\(P_{avg}\) = Average inlet total pressure
- Returns:
Calculated Distortion Index
- Return type:
float
- NAPCKTheta()[source]¶
Returns the Naval Air Propulsion Center KTheta index WORK IN PROGRESS
\(K\Theta = \frac{\frac{\Theta^{-}}{2\pi}\left [\sqrt{q/P}\right]_{ref}}{\sqrt{\frac{q}{P}/\frac{\bar{q}}{\bar{P}}}}\)
where
\(\Theta^{-}\) = Circumferential extent of the total pressure region less than the plane average total pressure
\(P\) = Average inlet total pressure within the low pressure region
\(\bar{P}\) = Average inlet total pressure
\(q\) = Average dynamic pressure in low pressure region
\(\bar{q}\) = Average inlet dynamic pressure
- Returns:
Calculated Distortion Index
- Return type:
float
- AVCOLycomingDI()[source]¶
Returns the AVCO Lycoming DI index WORK IN PROGRESS
\(DI = (\frac{P_{avg}-P_{low\:avg}}{P_{avg}})\sqrt{\overline{M*E*R}}\)
where
\(P_{avg}\) = Area-weighted average total pressure
\(P_{low\:avg}\) = Area-weighted total pressure in regions where P is less than \(P_{avg}\)
\(M\) = Magnitude or shape factor = \(6.0(P_{avg}-P_{low\:avg})/(P_{avg}-P_{low\:min})\)
\(P_{low\:min}\) = minimum total pressure level
\(E\) = Extent of distorted region = \(2.0(A_{L})/A_{tot}\)
\(A_{L}\) = Area over which the total pressure is less than \(P_{avg}\)
\(A_{tot}\) = total annulus area
\(R\) = Radial distortion sensitivity = maximum of \(2.0(A_{L,hub}/A_{L})\) or \(2.0(A_{L,tip}/A_{L})\)
\(A_{L,hub}\) = Area extent of low pressure regions which fall in the inner 50% annulus area
\(A_{L,tip}\) = Area extent of low pressure regions which fall in the outer 50% annulus area
- Returns:
Calculated Distortion Index
- Return type:
float