[L1] 1 Overview [L2] 1) Definition [L4] - An energy conversion device that generates mechanical energy by burning fuel supplied inside the engine and moving a piston up and down with the power of thermal energy. [L4] - External Combustion Engine: A device where fuel is supplied to a combustion unit installed outside the engine to heat a working fluid, and the phase-changed fluid flows into the cylinder to operate the engine. [L5] * Steam engine, Steam turbine [L2] 2) Features [L4] - Compact, lightweight, and high thermal efficiency. [L4] - Requires separate supply systems for lubrication and cooling. [L4] - The type depends on the engine classification and quality level. [L4] - Self-starting is impossible, so a starting device (starter) is required. [L4] - Reciprocating types generate significant shock, vibration, and noise. [L1] 2 Operation of Internal Combustion Engine [L2] 1) Operation Method [L3] ① 2-Stroke Engine [L4] - Expansion/Exhaust Stroke → Scavenging Stroke [L4] - Simple structure, but fuel consumption is high because the intake and exhaust strokes are unclear. [L3] ② 4-Stroke Engine [L4] - Intake → Compression → Power (Explosion) → Exhaust [L4] - Firing Order by Cylinder Count [L5] * 4-Cylinder Right-Hand : 1-3-4-2 [L5] * 4-Cylinder Left-Hand : 1-2-4-3 [L5] * 6-Cylinder Right-Hand : 1-5-3-6-2-4 [L5] * 6-Cylinder Left-Hand : 1-4-2-6-3-5 [L2] 2) Number of Cylinders and Phase Angle [L4] - 2-Stroke Cycle Explosion Angle : 360 / Number of Cylinders [L4] - 4-Stroke Cycle Explosion Angle : (360 x 2) / Number of Cylinders [L2] 3) Key Terms [L4] - Stroke Volume : Piston Cross-sectional Area x Stroke Length [L4] - Total Stroke Volume (Displacement) : Stroke Volume x Number of Cylinders [L4] - Combustion Chamber Volume : Volume when the piston is at Top Dead Center (TDC) [L4] - Compression Ratio : Ratio of volume after compression [L4] - Overlap : Time when both intake and exhaust valves are open simultaneously [L4] - Backfire : Phenomenon where explosion occurs immediately after the intake stroke because the ignition timing is too early [L4] - Blowdown : Period when exhaust begins through the scavenging port due to the piston's own pressure [L1] 3 Types of Internal Combustion Engine [L2] 1) Classification by Form [L3] ① Reciprocating Internal Combustion Engine [L3] ② Gas Turbine [L2] 2) Classification by Fuel [L3] ① Gas Engine [L3] ② Gasoline Engine [L3] ③ Diesel Engine (including Heavy Oil) [L2] 3) Classification by Ignition Method [L3] ① Hot-bulb Engine (2-Stroke Cycle) [L3] ② Spark Ignition Engine (SI) [L3] ③ Compression Ignition Engine (CI) [L2] 4) Classification by Cycle [L3] ① Otto Cycle [L3] ② Diesel Cycle [L3] ③ Sabathe (Dual) Cycle [L2] 5) Classification by Operation Method [L3] ① 2-Stroke Cycle : An engine that completes 1 cycle while the crankshaft rotates once (2 strokes). [L3] ② 4-Stroke Cycle : An engine that completes 1 cycle while the crankshaft rotates twice (4 strokes).