Is it permissible to fast in Ramadan with the intention of fulfilling a specific vow?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and messenger.

If the intended meaning of the question is that he fasts in Ramadan with two intentions or with the intention of fulfilling a vow in case it is permissible for him not to fast, then this is impermissible. The time of Ramadan is specific for its sake. Nothing may be associated with it and it may not be replaced with anything else.

An-Nawawi said: Ash-Shaafi’i and his companions said: "The month of Ramadan should be  exclusively for fasting Ramadan only, so nothing else should be associated with it. If a presiding resident, traveler or one who is sick intends to fast for expiation, fulfill a vow, make up (a missed fast), voluntary fasting or intends to fast absolutely without specification, then his intention and fasting are both invalid for what he intended and for Ramadan. This is what was stated and confirmed by his companions.

Allaah Knows best.