Is there a game engine that does not use a graphics API such as OpenGL or DX? I want a simple 2D game engine for use in my simple game console.
Allegro 4.x is probably the closest you're going to get to this. It has pure software blitting for 2D sprites. Granted, it will still need to use DirectX to draw to the screen, but that would be more or less true for anything.
That being said, you said this:
This statement suggests that you equate software rendering to "simple". This is not the case.
There's nothing inherently complex about using OpenGL or D3D to do 2D rendering. Indeed, the whole purpose of using a game engine is to abstract the details away, so that you don't directly have to do any of that stuff. You don't have to care about OpenGL or D3D code to use Allegro 5 or SFML; they handle all of that transparently.
So really, just use a good engine; don't bother yourself about the minor details.
Running without a graphics API is not necessarily simpler. In fact what you're talking about here is a software rasterizer, which is going to be orders of magnitude more complex than using a graphics API. It will also be custom code so if you hit any problems with it you won't be able to get help as easily.