The Engine executable is the main powerhouse for Qlik Sense. All delivery of content to the user(s) and reloads occur within that .EXE. So it's going to take up lots of RAM, but that's the point of in memory software.
So in addition to gwassenaar who asked whether you're experiencing performance problems, is this unusual? How many apps do you have? How big are those apps on disc? How many concurrent users? How many reloads? etc.
In general, the only reason to be concerned with memory usage is when it's unexpected or if you're exhausting the system's memory allocation.
Define "too much".
Did you tell it to stop at a set amount of memory?
Qlik software caches calculations done so the next time you request the same calculation the results will be available faster.
On a default install, Qlik will take memory for caching till up to 70%. This is complete healthy and normal and he way it is designed. If Qlik is not installed on a dedicated server (not advised) you can reduce this 70% limit.