Search sorting for titles with letters and numbers

[Kiran]

I have a large wiki with several files named things like "x 1", "x 2", "x 3" etc...

I've noticed that when I search for eg "x 5" the results are ordered: "x 15" then "x 5"

Is there any way to change this? 

I've tried nsort and nsortcs but both yield the same result