I know little about internal combustion engines and I feel a little confused about brake and shaft powers. I read a book that only talks about shaft power, and other that only talks about brake power, without making a proper definition of the physical meaning of these quantities. I'm now thinking that they both mean the same thing: useful power on the crankshaft (the power produced by the engine cylinders less the losses and the power that is used in accessory components).
For example, in Mechanics and thermodynamics of propulsion (1992) (Hill Peterson), pag. 155, the the brake specific fuel consumption uses shaft power in its definition, and not the brake power (as the name suggests it).
I would really appreciate some clarification, or some book suggestions, since the ones that I read are too vague.