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Otto Cycle Engine Development and Mechanics

May 18, 2025

Otto Cycle Engine - Key Concepts and Historical Development

Introduction

  • The Otto Cycle engine is a fundamental model for internal combustion engines, developed by Nikolaus August Otto in 1876.
  • Incorporates the basic processes: intake, compression, combustion, expansion (power), and exhaust in a single piston-cylinder apparatus.

Historical Context

  • Stirling and Ericsson cycles were developed to address high-pressure boiler dangers of early steam engines.
  • Lenoir's internal combustion engine was simpler but less efficient.
  • Brayton improved efficiency by introducing a compression process before combustion.

Otto Cycle Mechanics

  • Comprises two isochoric (constant volume) and two isentropic (constant entropy) processes.
  • Requires four piston strokes and two crankshaft revolutions to complete a cycle.

Transition to Liquid Fuels

  • Originally used illuminating gas (methane).
  • Transition to liquid hydrocarbons (gasoline) began in 1885.

Technological Advancements

  • Development of the float-feed carburetor by Wilhelm Maybach in 1892, pivotal for the automobile era.
  • Karl Benz built the first practical automobile using Otto cycle engine.

Patent and Development Timeline

  • Alphonse Eugene Beau de Rochas patented the four-stroke cycle IC engine in the 1860s.
  • Otto was the first to build and operate a successful engine.
  • Dugald Clerk developed a two-stroke version in 1878, introducing the concept of supercharging.

Efficiency and Calculations

  • Thermal efficiency measured by specific internal energies and compression ratios.
  • Example problems illustrate thermal efficiency calculations for Otto cycle engines.

Practical Applications

  • Otto cycle engines became competitors to steam engines in small- and medium-sized markets.
  • Used in various applications: boats, lawn mowers, saws, etc.

Alternate Cycles

Six-Stroke Engines

  • Aim to increase efficiency by adding two additional strokes using steam or water.
  • Variants include pair of cylinders sharing an extra cylinder.

Atkinson Cycle

  • Allows higher expansion ratio than compression ratio for higher efficiency.
  • Modern Atkinson cycle uses variable valve timing (VVT) technologies for efficiency.
  • Widely used in hybrid electric vehicles (HEVs).

Dual-Combustion Cycle

  • Combines constant volume and constant pressure combustion.
  • More representative of real engine cycles.

Modern Applications and Innovations

  • Atkinson engines used in HEVs for better fuel economy and emission reduction.
  • Cox Tee Dee .010 model recognized as the smallest internal combustion engine.

Conclusion

  • Otto cycle engines laid the foundation for modern internal combustion engines.
  • Ongoing developments explore efficiency improvements and alternative cycles for various applications.