CHAPTER II
[Operating Principles of Two- and Four-Stroke Engines]—[Four-cycle Action]—[Two-cycle Action]—[Comparing Two- and Four-cycle Types]—[Theory of Gas and Gasoline Engine]—[Early Gas-Engine Forms]—[Isothermal Law]—[Adiabatic Law]—[Temperature Computations]—[Heat and Its Work]—[Conversion of Heat to Power]—[Requisites for Best Power Effect].
OPERATING PRINCIPLES OF TWO- AND FOUR-STROKE CYCLE ENGINES
Before discussing the construction of the various forms of internal combustion engines it may be well to describe the operating cycle of the types most generally used. The two-cycle engine is the simplest because there are no valves in connection with the cylinder, as the gas is introduced into that member and expelled from it through ports cored into the cylinder walls. These are covered by the piston at a certain portion of its travel and uncovered at other parts of its stroke. In the four-cycle engine the explosive gas is admitted to the cylinder through a port at the head end closed by a valve, while the exhaust gas is expelled through another port controlled in a similar manner. These valves are operated by mechanism distinct from the piston.
Fig. 5.—Outlining First Two Strokes of Piston in Four-Cycle Engine.