Delta and Epsilon angles

Training
Procedures
Delta and Epsilon angles

For many years Garrett defined the angular positions of turbine and compressor housings relative to the centre housings vertical centre lines in terms of alpha and beta angles. Garrett currently defines more accurately the orientation in terms of delta and epsilon angles.

The diagram below shows how the delta (δ) and epsilon (ε) angles are defined:

Angles Orientation Tool

Check out how to set the turbine and compressor housing orientations using the Garrett Angles Tool by modifying the ε and δ angles.

Conversion

For the mathematically minded, it is interesting note that we can convert alpha (α) and beta (β) angles to epsilon and delta angles by using the following formulae:

epsilon = 360º – beta

delta = alpha – beta + 90º

Note: If after using these formulae, the resulting angle is a negative value, it is necesary to add 360 degrees (one revolution) to the negative value.

Example

Problem	Solution
if alpha = 0º and beta = 180º epsilon = 360º – beta = 360º – 180º = 180º delta = alpha – beta + 90º = 0º – 180º + 90º = -90º to obtain the correct delta angle we merely add 360º ( one revolution ) delta = – 90º + 360º = 270º	So it means that if alpha = 0º and beta = 180º are equivalent to epsilon = 180º and delta = 270º

Problem

Solution

if alpha = 0º and beta = 180º

epsilon = 360º – beta = 360º – 180º = 180º

delta = alpha – beta + 90º = 0º – 180º + 90º = -90º

to obtain the correct delta angle we merely add 360º ( one revolution )

delta = – 90º + 360º = 270º

So it means that if alpha = 0º and beta = 180º

are equivalent to

epsilon = 180º and delta = 270º