History - EngineKnowHow

The modern internal combustion engine is the combination of centuries of development in ideas and technology convalescing into the engines we know and use today. For example, the earliest known example of a conrod and crankshaft being employed to convert rotational motion into linear motion was found at a 3rd century AD Roman Sawmill in Turkey. The Romans are also known to have employed valves throughout their water supply systems and pistons within a cylinder as part of their pumping systems.

 

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Roman Water Pump, or Siphona

Tullia Ritti, Klaus Grewe, Paul Kessener: "A Relief of a Water-powered Stone Saw Mill on a Sarcophagus at Hierapolis and its Implications", Journal of Roman Archaeology, Vol. 20 (2007), pp. 138–163 (148, fig. 10)

4th Century AD Roman Sawmill in Hierapolis, Turkey

 

 

 

 

 

 

 

 

 

The development of the internal combustion engine is attributed to have begun with the Gunpowder Engine developed by Christian Huygens in 1680. Contrary to internal combustion engines today which combust a fuel / air mixture to exert a positive pressure on the piston the Gunpowder Engine generated a partial vacuum to force the movement of a piston. A quantity of gunpowder was exploded within a cylinder, the first example a cannon with the expansion of gases forcing a piston to the top of the cylinder. As the piston neared the top of the cylinder it would uncover holes in the cylinder wall allowing the gases to escape. As the pressure reduced within the cylinder due to the exhausting and cooling of the gases a vacuum formed underneath the piston. This partial vacuum, in addition to the weight of the piston, forced the piston to travel back down the cylinder to below its original starting point. This concept is known as the “Atmospheric Principle” and attachment of a rope to the top of the piston allowed this forced movement to be utilised.

Denis Papin, who worked underneath Christian Huygens, improved upon the concept by replacing the gunpowder with steam to condense within the cylinder. This concept was utilised by Thomas Newcomen in 1712 to produce the Atmospheric Steam Engine which laid the groundwork for nearly two centuries of steam engine development providing technology necessary for the internal combustion engine.

The first commercially viable internal combustion engine was the Lenoir Gas Engine of 1860 which operated on a mixture of coal gas and air. The Lenoir Gas Engine was a single cylinder engine however combustion occurred both above and below the piston. For each side of the piston, as the piston moved to increase the volume in the cylinder slide valves would admit the fuel / air mixture into the chamber until approximately half stroke where the valves would close and the fuel / air mixture was ignited via electrical spark. Following the transfer of power from the combustion gases to the piston the piston then travelled back down the cylinder and slider valves would allow the expulsion of the exhaust gases. Unlike the Gunpowder Engine which operated on the Atmospheric Principle the Lenoir Gas Engine combusted the fuel / air mixture so that a positive pressure would force the movement of the piston. Importantly though this fuel / air mixture wasn’t compressed prior to combustion and efficiency was below 5%.

The next commercially successful engine was the Free Piston Engine, a type of atmospheric engine developed by Nikolaus Otto and Eugen Langen and released in 1867. The Free Piston Engine was composed of a long vertical cylinder which housed a heavy piston which was forced vertically upwards following the combustion of a gas fuel and air mixture which generated a vacuum in the cylinder. This vacuum would then force the piston, along with the weight of the piston, back down the cylinder capturing the transfer of energy from the combustion. Slide valves controlled the admittance of the fuel / air mixture, a gas flame for ignition and the exhausting of the combustion products. Attached to the top of the piston was a rack that extended vertically from the cylinder. This rack drove a pinion gear to convert the linear motion into rotary motion and only engaged on the downward stroke. Owing to the long length of the cylinder a greater expansion of the gases could occur which raised the efficiency of the Free Piston Engine to approximately 11%.

 

The Free Piston Engine of 1867

illustration, 1896. Library of Congress, Washington, D.C. (Digital File Number: cph 3c10411 )

The Lenior Engine

 

 

 

 

 

 

 

 

 

 

 

In 1876 Otto improved upon the design of the Free Piston Engine by releasing the Otto Silent Engine where the engine cycle was completed in four strokes of the piston. <link>.  The four piston strokes comprised an intake stroke where the fuel / air mixture was admitted into the cylinder, a compression stroke where the fuel / air mixture was compressed and ignited, an expansion or power stroke where work is delivered to the piston and an exhaust stroke where the combustion products are expelled from the cylinder.  This engine also replaced the rack and pinion of the Free Piston Engine with a connecting rod and crankshaft with the crankshaft connected to a flywheel.  The engine was commercially successful following its reduced size relative to the Free Piston Engine and its overall efficiency of 14%.  Following the release of the four stroke engine patents for the two stroke engine, which combined the intake / compression strokes and the expansion / exhaust strokes were awarded from 1877.

In 1884 the patent which Otto had received for his Otto Silent Engine was considered invalid in his native Germany following the discovery of an unpublished patent by Alphonse Beau de Rochas awarded in France in 1862. In addition to proposing the four stroke cycle he also proposed that ignition could occur through compression of the fuel / air mixture.

In 1892 Rudolf Diesel patented a new form of the Otto Silent Engine where combustion of the fuel / air mixture was achieved via injection of the fuel following compression of the air as opposed to ignition of the fuel / air mixture via a flame or spark.

 

The first Diesel Engine

The Otto Engine