MEC 3621 Internal Combustion
Engines
(IC Engines)

Prof. Dr. A.K.M. MOHIUDDIN

Introduction
• The purpose of internal combustion engines is the production of mechanical power from the chemical energy contained in the fuel.
• In internal combustion engines, as distinct from external combustion engines, this energy is released by burning or oxidizing the fuel inside the engine.
• The fuel-air mixture before combustion and the burned products after combustion are the actual working fluids.

• The work transfers which provide the desired power output occur directly between these working fluids and the mechanical components of the engine.
• The internal combustion engines which are the subject of this course are spark-ignition (SI) engines (sometimes called Otto engines, or gasoline or petrol engines, though other fuels can be used) and compression-ignition (CI) or diesel engines.

HISTORICAL PERSPECTIVE
• Otto, in the broader sense, was the inventor of the modern internal combustion engine as we know it today.
• Further developments followed fast once the full impact of what Otto had achieved became apparent. By the 1880s several engineers (e.g., Dugald Clerk, 1854-1913,; and James
Robson, 1833-1913, in England and Karl Benz, 1844 - 1929, in Germany) had successfully developed two-stroke internal combustion engines where the exhaust and intake processes occur during the end of the power stroke and the beginning of the compression stroke.
• James Atkinson (1846-1914) in England made an engine with a longer expansion than compression stroke, which had a high efficiency for the times but mechanical weaknesses • During the past four decades, new factors for change have become important and now significantly affect engine design and operation. These factors are, first, the need to control the automotive contribution to