There would be no royalties for internal use of the engine. If you use the engine for internal data analysis or visualization, and those results are later used in a commercial venue, there is still no royalty.
Want to know if I can use Unreal Engine as part of an internal tool for data analysis through VR or for commercial research for free.
The difference between the two would be research in company whose primary business isn’t research but uses the results of analyses to help make business decisions, and the other is related to businesses that get paid for the information that they produce.