Special characters in csv writing

I am opening the file using 'utl_file.fopen()' and writing
text data into that.There is no issues as far as writing data into file.
We have some data that contains special chars(other than english).Forexample we have data like this
Brandgefördernd

When i am writing this data into text file,It is getting printed as
Brandf ö rdernd
Here the character ó is getting printed as ö.
After analysing I found that if I can open text file in 'UTF-8' format,The issue will be solved.But how to open a file in 'UTF-8' format instead of 'ASCII' format.Is there any way to specify encoding scheme while opening the file?
The defaut character set of database I am using is 'UTF-8'
Any help will be much appreciated.