ENGINE WASH OPTIMISATION

1 . A method of optimising engine wash event scheduling comprising:

a) determining an underlying deterioration gradient;

b) determining a total deterioration gradient;

c) setting a number of engine wash events, x;

d) calculating engine deterioration for x engine wash events;

e) calculating the washed engine cost of engine deterioration for x engine wash events; and

f) iterating steps c) and d) for different x to optimise the number of engine wash events with respect to the cost of engine deterioration.

2 . A method as claimed in claim 1 wherein step 1a) comprises steps of:

a) in a fuel flow data series, identifying engine wash events;

b) for each data subset between consecutive engine wash events, identifying: a minimum point being a post-engine wash event fuel flow; a maximum point being a pre-engine wash event fuel flow; and a gradient-therebetween; and

c) calculating the underlying deterioration gradient by averaging the gradients between each adjacent pair of minimum points in the data series.

3 . A method as claimed in claim 1 wherein step 1b) comprises steps of:

a) in a fuel flow data series, identifying engine wash events;

b) for each data subset between consecutive engine wash events, identifying: a minimum point being a post-engine wash event fuel flow; a maximum point being a pre-engine wash event fuel flow; and a gradient therebetween; and

c) calculating a total deterioration gradient by averaging the gradients of all the data subsets.

4 . A method as claimed in claim 2 wherein identifying engine wash events comprises identifying discontinuities in the data.

5 . A method as claimed in claim 2 wherein identifying engine wash events comprises comparing the data to known engine wash event times.

6 . A method as claimed in claim 1 wherein step 1d) comprises steps of:

a) setting x engine wash events and sub-dividing the time by x to give x time segments;

b) for each time segment:

i. calculating a segment underlying deterioration by integrating the underlying deterioration gradient by the time segment length;

ii. calculating a segment total deterioration by integrating the total deterioration gradient by the time segment length;

iii. subtracting the segment underlying deterioration from the segment total deterioration to give the segment deterioration; and

c) summing the segment deteriorations to give the engine deterioration.

7 . A method as claimed in claim 6 wherein step 6a) comprises multiplying the segment time length by an utilisation factor.

8 . A method as claimed in claim 1 wherein step 1e) comprises steps of:

a) multiplying the engine deterioration by a pre-determined cost multiplier to give the cost of engine deterioration for x engine wash events; and

b) adding the cost of x engine washes to the cost of engine deterioration for x engine wash events to give a washed engine cost.

9 . A method as claimed in claim 1 wherein a further step between steps 1e) and 1f) comprises:

subtracting the washed engine deterioration cost from an engine deterioration cost where x=0 to give a washed cost saving.

10 . A method as claimed in claim 9 wherein step 1f) comprises optimising the number of engine wash events with respect to the washed cost saving.

11 . A computer program having instructions adapted to carry out the method according to claim 1 .

12 . A computer readable medium, having a computer program recorded thereon, wherein the computer program is adapted to make the computer execute the method according to claim 1 .

13 . A computer program comprising the computer readable medium as claimed in claim 1 .