Internal Combustion Engines

Internal Combustion Engines

• Produce mechanical power from the chemical energy contained in fuel by burning or oxidizing the fuel inside the engine
• Fuel-air mixture before combustion and burned products after combustion are the working fluids
• Work transfers that provide the desired power output occur directly between these working fluids and the mechanical components of the engine

Types of Internal Combustion Engines

• Spark-ignition (SI) engines, also called Otto engines, or gasoline or petrol engines
• Compression-ignition (CI) or diesel engines

Characteristics and Applications

• Simplicity, ruggedness, high power to weight ratio, efficiency, and low cost
• Wide application in transportation (land, sea, and air) and power generation

History of Internal Combustion Engines

• Power-producing engines have served human beings for over two and a half centuries
• Initially, water, converted to steam, was interposed between the combustion gases and the work-producing piston-in-cylinder expander
• The internal combustion engine became a practical reality in the 1860s

Early Engines

• Early engines developed for commercial use burned coal-gas air mixtures at atmospheric pressure
• J.J.E.Lenoir developed the first marketable engine of this type in the 1860s
• Efficiency was at best about 5%

Development of Otto's Engine

• Nicolaus A. Otto and Eugen Langen introduced an atmospheric engine in 1867
• This engine used the pressure rise resulting from combustion to accelerate a free piston and rack assembly
• Thermal efficiencies of up to 11% were achieved
• Production engines, of which about 5000 were built, obtained thermal efficiencies of up to 11%

Otto's Four-Stroke Engine

• Proposed an engine cycle with four piston strokes: intake, compression, expansion, and exhaust
• First prototype four-stroke engine ran in 1876
• Comparison to Otto-Langen's engine shows enormous reduction in engine weight and volume
• Founded the internal combustion engine industry

Patents and Controversies

• Alphonse Beau de Rochas held an unpublished French patent issued in 1862 for the principles of the four-stroke cycle
• This discovery cast doubt on the validity of Otto's own patent for this concept