Reciprocating-Engine-fundamentals

POWERPLANT PISTON INDIANA ENGINE FUNDAMENTALS

• Presenter: Engr. Vindell Nino Singco

• Institution: Indiana, IAU 1992

FUNDAMENTAL RECIPROCATING ENGINE OPERATING PRINCIPLES

• A fundamental overview of how reciprocating engines operate.

PISTON ENGINE FUNDAMENTALS

Basic Principles of Engine Operation

• The relationship between Pressure, Volume, and Temperature.

Internal Combustion Engines

• Convert heat energy into mechanical energy.

• Process:

  • Gasoline vaporized and mixed with air.

  • Mixture forced/drawn into a cylinder.

  • Compressed by a piston.

  • Ignited by an electric spark.

• Terms:

  • Bore: Inside diameter of a cylinder.

  • Stroke: Distance piston moves from Top Dead Center (TDC) to Bottom Dead Center (BDC).

TYPES OF ENGINES

Classification Methods

• By Operating Cycles:

• By Cylinder Arrangement:

• By Method of Thrust Production:

• All engines are heat engines converting fuel into heat then to mechanical energy to produce thrust.

Internal Combustion Type

• Most current aircraft engines are internal combustion due to combustion occurring inside the engine.

RECIPROCATING ENGINES

Common Designs

• Conventional designs recognized due to popularity and usage.

Classification by:

• Cylinder Arrangement:

  • In-line, V-type, radial, opposed.

• Method of Cooling:

  • Liquid cooled, air cooled.

AIR-COOLED ENGINES

• Most aviation piston engines are air-cooled.

• Historically used water-cooled engines, but air-cooled became dominant post-World War II.

• Used in general aviation aircraft where drag is not a major consideration.

• Manufacturers like Lycoming and Continental produce these engines for light aircraft (e.g., Cirrus, Cessna).

Cooling Mechanism

• Cool air circulates directly over heat dissipation fins.

• Heat escape:

  • Exhaust: ~44%

  • Fins: ~12%

  • Oil: ~8%

• Fins increase surface area for improved cooling.

LIQUID-COOLED ENGINES

• Heat is transferred from cylinders to coolant.

• Coolant circulates through a radiator in the airstream.

• Advantages:

• High power safely.

• Disadvantages:

  • Weight from coolant, heat exchanger, tubing.

INLINE ENGINES

• Typically have an even number of cylinders (some three-cylinder variants).

• Can be liquid or air cooled.

• Has one crankshaft.

• Benefits:

  • Small frontal area for better aerodynamics.

  • Inverted engines offer lower landing gear and more pilot visibility.

OPPOSED OR O-TYPE ENGINES

• Two banks of cylinders opposite each other with a shared crankshaft.

• Predominantly air-cooled.

• Advantages:

  • Low weight-to-horsepower ratio.

  • Low vibrations ideal for aircraft wings.

V-TYPE ENGINES

• Cylinders in two banks set 60° apart.

• Often have 12 cylinders, are liquid or air cooled.

• Historical significance from World War II, common in older aircraft.

RADIAL ENGINES

• Cylinders arranged radially around a central crankcase.

• Rugged and dependable.

• Varieties: single-row (3, 5, 7, 9) and double-row radial designs.

• Applications: Older cargo planes, warbirds, and crop spray planes.

OPERATING CYCLES

Types

1. Four-stroke

2. Two-stroke

3. Rotary

4. Diesel

FOUR-STROKE CYCLE

• Most aircraft reciprocating engines use the four-stroke cycle (Otto cycle).

• Advantages in high performance and supercharging adaptability.

• Requires two crankshaft revolutions (720°) for one power cycle.

• Timing of ignition and valve events varies per engine specification.

CYCLE STROKES

1. Intake Stroke:

   • Piston moves down, reducing cylinder pressure, allowing air-fuel mixture intake through valves.

2. Compression Stroke:

   • Piston compresses the mixture; ignition occurs near TDC (20°-35° before TDC).

3. Power Stroke:

   • Piston pushed down by expanding gases, turning the crankshaft and producing propeller power.

4. Exhaust Stroke:

   • Piston moves up, expelling exhaust gases, creating low pressure that aids fresh charge intake.

VALVE TIMING AND OVERLAP

• Timing specified in degrees of crankshaft travel.

• Valve opening sequence necessary to prevent cyclical operational problems.

TWO-STROKE CYCLE

• Utilized in ultra-light, light sport, and experimental aircraft.

• Completes cycles in one up-and-down piston movement per crankshaft revolution.

• Functions of intake and exhaust occur simultaneously.

ROTARY CYCLE

• Features a three-sided rotor in an elliptical housing.

• Unique cycle with low vibration, predominantly in experimental and light aircraft.

DIESEL CYCLE

• Relies on high compression for ignition.

• Air intake compressed, with fuel introduced at max pressure, leading to combustion and piston movement.

END OF DOCUMENT

• Authoritative source for piston engine fundamentals, Indiana IAU 1992.