Shemot - The Secret of Success through the Three Alephs based on the Shvilei Pinchas 

The Chida, zy”a, writes in Avodat Kodesh (7), “concerning the appellation: ” אהיה אשר אהיה . Heexplains that this name employed in tefilah is capable of affecting salvation for everything in the world: I found in the manuscripts of the kabbalists that it is “ appropriate for a person to pray to the appellation אהיה אשר אהיה ” for any problem in this world — for sickness, for children, for wisdom, to be remembered, for monetary matters, to be saved from a storm at sea, for danger on the roads. It is essential, however, that he be pure, and that he utter sincerely: “Let it be the will of the esteemed name אהיה אשר אהיה ” “ that You have mercy on me and act on my behalf.” He should state his request clearly, and should repeat it three times.

יהי רצון מלפניך השם הגדול אהיה ,

אשר אהיה שתרחם עלי ותעשה, וישאל

בקשתו בלשון ברור, וכן יאמר ג’ פעמים

But how does this work?

Additionally, it is worth examining the statement in the Tikunei
Zohar (144b) that with the words: ” — “ אהיה אשר אהיה HKB”H alludes to tefillin shel yad and tefillin shel rosh. For, in the
four passages contained in the tefillin shel rosh, the name Havaya
appears twenty-one times — the numerical value of the
name אהי”ה ; this is alluded to by the first אהי”ה . Similarly, in
the four passages contained in the tefillin shel yad, the name
Havaya appears twenty-one times — accounting for the
second mention of the name אהי”ה . Thus, the two tefillin together are alluded to by the phrase: ” אהיה אשר אהיה “.