I'm uncertain of Quirrel's motivations here. It's possible that up-till-now has been Just According To Plan, and the plan is to blame Harry for attempting to break Bellatrix out of Azkaban, and hence utterly discredit him as a possible later rival. However, this seems a little much like a Xanatos Roulette; Quirrel could not necessarily have planned for the Auror he fought to be there and to react in the precise way he did, and he certainly could not have planned for Harry's Patronus v2.0 being able to block AK (and Harry wanting to do so), nor for Harry losing his Patronus afterward. Thus, it seems likely that either Quirrel was indeed planning to be caught, but in a less flamboyant way, or that he meant to carry off the breakout and was messed up himself by Harry's actions.