If you're in Dubai, they'll detain you at the airport. However, when you go to the airline desk to check in for your flight, they won't let you check in, they'll turn you away and you'll lose the flight and your money.
It is your responsibility to ensure that you are in possession of a valid passport. By the way, you're also in UAE illegally, the cops will arrest you and lock you up if they catch you.
Get yourself to your embassy and see if they can give you an emergency passport.