I hate to say this, but Spaldings have given you bad advice. It is not usual to have to apply potash for fruiting pears, what's usual is to apply a balanced fertiliser such as Growmore in Spring.
The likely explanation for your tree not producing fruit is hard to be definite about without more information (how long have you had the tree, are there are other pear trees nearby, did it flower but not produce fruit, what, precisely, have you been feeding it, is it in the ground or a pot, etc.) but given the cold spring we had this year, if it flowered, its likely the flowers were caught in frost or fell off before they were pollinated, assuming the tree itself is healthy.
More info would enable a clearer answer.

I would imagine the advice for potash comes from the old adage of "potash for petals" - you won't get fruit if you don't have flowers and you won't get flowers if the plant doesn't feel the need to sow its wild oats, as it were!

So if you have been giving it lots of nitrogen-rich food the plant will have lovely green leaves and all that chlorophyll will mean that it is feeling well-fed and it won't be thinking about babies (ie setting seed)

Bamboo is right in that you need a balanced feed, but if you have been (over)feeding it with something rich in nitrogen you may need to redress the balance a little first with a high potash feed at the right time of year, which probably isn't as we go into October.

Did you still get lots of blossoms but less fruit? Most apple and pear trees need to be pollinated by another variety. Even the small amount of varieties described as self-pollinating will yield a heavier fruit crop through cross-pollination.

As a follow-on from Myron's post, whose tree is cross-pollinating yours? If it's one of your neighbour's trees, check it's still there!