Sounds interesting. A first question (please bear in mind that I am not an engineer, I am an educational scientist specialized in adult education):

When you say that you are "going to superimpose virtual description .. to a real physical machine", what do you exactly mean? Do you have an image (e.g., photograph) of a real compressor and you superimpose virtual elements?

Then, what is it you want to measure? The extent to which transfer of knowledge is improved, compared to traditional methods of teaching?

Dear Mr Hamminger

It is an honour  someone of you caliber interested in my research

Augmented reality allow us to superimpose virtual image to a REAL physical object by seeing it thought  electronic screen (eq smartphone, AR goggle)   equipped with digital camera.

1) I am going to create an animation, for example  the rotation of the internal A/C compressor pump, which is hidden from view at the real thing, and using a Augmented reality software installed on smartphone, student will be able to view the running of the A/C compressor pump on the smartphone screen, complete with sound. 

I have an example of the animation but i am not planning to superimposed it to a real engine at this moment, but will do it with much simpler machine :-) Please visit 

https://www.youtube.com/watch?v=DZhIc2Hmuaw

2) Yes, I have 3 parameters in mind (i) understanding (ii) attention (iii) enjoyment but it may not be appropriate  because it is based on my thinking and not based on theories.

3) For research conceptual framework,  I have been looking at :

(i) Cognitive Load Theory and the  Format of Instruction Paul Chandler & John Sweller   ( read abstract only, not buying the literature ,expensive for me ) 

(ii) Experiential Learning (Alice Y. Kolb dan David A. Kolb ,2011)

(iii) (Cognitive Theory Of Multimedia Learning (Meyer,2014)