Expansion

—1. The act or proce of increasing in bulk; dilatation of any substance through its particles becoming more widely separated from one another by the influence of heat. With gases, the property of expansion is characteristic, that is, any gas admitted into a closed chamber will immediately dilate until it has completely filled the chamber, sometimes becoming extremely rarefied in the proce . With open ports the expansive energy of steam acts from the water in the boiler as its fixed oint of fulerum, but after it is “cut off” it acts rom the fixed ends of the cylinder. 2. That portion of the cycle of a heat engine in which the fluid gives off the initial energy stored in it, while being gradually expanded down to the point at which it is rejected from the engine.