1 Purpose; Principle; Advantages; Discussion of Pre-Ignition, "Ping and Detonation"; After-Burning Fuel;
The Importance of Turbulence
The subject of "turbulence, an aid to fuel distribution," is briefly discussed on page 115. The subject of "flame propagation" is briefly given on pages 290 and 301, and on pages 1054, 116 "compression ratio" is discussed. On page SO6 the purpose, principle and advantage of the Ricardo head is briefly discussed. All of these subjects are closely allied with carburetion.
The subjects of turbulence and combustion chamber design are considered of great importance iii engine design and the story of the development of the Ricardo L-head engine design is reprinted below.'
"Ever since the first lazy flame was persuaded to work, man has persistently endeavored to speed it up and by so doing, increase its usefulness.
"While recognizing the importance of flame-speed, engineers have only recently recognized the necessity of precisely controlling the speed of the flame with reference to the speed of their engines.
"Generally the public wants acceleration, so-called "get away," power and economy.
"The usual procedure has been to go to large valves giving heavier charge, increase in compression, and improvements in carburetor design.
"With each step along this line while greater power and acceleration were available, greater economy was not apparent, the knocking tendency of fuels limiting the possible compression.
"After studying the problem we were convinced that the limitation of modern engines was in the combustion chamber, where the real job of converting the energy of the fuel into useful power was accomplished.
"We reviewed the art and reconsidered this well-known fact, that ii, 190(1, Sir Dugald Clerk discovered that when the explosive mixture was in the state of agitation or turbulence the charge burned with great promptness, resulting in higher power and efficiency.
"He proved that the only reason why high speeds were possible with any engine was due to turbulence of the mixture.

Pre-Ignition and "Ping"
There are other features of combustion chambers which limit the useful return from fuels and the pleasure of performance.
"Our engineers began an investigation as to the causes of pre-ignition and ping in an engine burning the present-day gasoline.
`During this research, which extended over a period of years, they evolved the detonation theory now accepted (see footnote 2).
"They discovered the influence of hotspots in the combustion chamber.
"They noted the influence of spark-plug location and the value of multiple-spark plugs.
"They found the influence of firing in a compact combustion chamber.
"They first noted the facts which led to the bouncing-pin and methods of measuring detonation.
"They noted the effects of long flame travel.
"They noted the effect of the combustion chamber in producing greater acceleration of combustion, and they noted the improved carburetion effect of turbulence due to the cylinder walls and mixture temperatures being the donnnating factors in carburetion.
"Then flintily come to the conclusion that the charge must be as compact as possible cued the hate of the flame to the farthest end of the effective combustion chamber as short as is possible.

After-Burning Fuel
"Among the more important phenomena observed in their research on combustion chambers was the effect known as after-burning.
"With the usual forms of combustion chambers there is always an intensely bright flame of great heat passing the exhaust valve and filling the exhaust manifold. Investigators have long known that where the flame from the exhaust reaches out into the air there was combustion continuing too late to contribute power to the piston.
"To be fully effective the flame must contribute its heat to the mixture during the period known as the tinge of explosion; namely, from the moment the spark juleps until the moment of maximum pressure.
"Lying over the wall surfaces and covered with flame, there is a stagnant layer of gas known by engineers and scientists to exist, in which combustion is never effective.
Fig. 1. (A) Indicates a (lark stagnant layer in a lazy moving ntiytti're approximately 11„ Melt thick, constituting in a combustion chamber between 8 and 12 per cent of the total volume of useful fuel. This layer burns too slowly to contribute its power to the piston before the exhaust valve is open.
Fig. 2. (B) Indicates the practical elimination of this dark, stagnant layer, due to turbulence in a Ricardo head by driving this gas layer out into the body of the flame. Thus the 8 to 12 per cent of otherwise wasted fuel is made to burn in time to contribute power to the piston rather than heat to the exhaust.
Reprinted by permission from booklet, The Ricardo Mead, copyrighted by Waukesha Motor Co., Waukesha, Wis. Ricardo heads have been used since 11123 on all Waukesha engines and are manufactured under U.S. patent No. 1,474,003, owned by above company. Ricardo replacement heads can be obtained from this company for Ford cars, Ford trucks, Fordson tractors, Dodge cars, and Dodge-Uraltam trucks and many other cars.
2 The now accepted theory of detonation is that the knock is due to a secondary explosion caused by an extraordinarily high pressure or compression, due to too long a flame run front the point of ignition to the combustion chamber wall. Detonation is not a spark knock. About one one-thousandth of a second after the mixture has been ignited, the detonation takes place. Then the pressure in the combustion chamber jumps front a low pressure to a very high pressure. It is this sudden secondary explosion which makes the ping. Elimination of this ping was the initial purpose of the Ricardo head which creates turbulence.

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Carburetor Manuals: Ricardo Cylinder Head