Method of operating an engine with a high heat of vaporization f

Internal-combustion engines – Precombustion and main combustion chambers in series – Having combustible mixture forming means

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Details

123262, 123299, 123 1A, F02F 326

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active

044468300

DESCRIPTION:

BRIEF SUMMARY
This invention relates to a method of operating a spark ignition type internal combustion engine with a fuel having a high latent heat of vaporization such as methanol and the like. More particularly, it relates to a method of operating an engine in which the fuel is introduced in a first stage to evaporate and atomize the major portion of the fuel and subsequently in a second stage to provide a rich air/fuel mixture in the vicinity of the spark plug for rapid ignition.
Fuels having a high latent heat of vaporization have been proposed for use in automotive type internal combustion engines. Methanol is a prime candidate for alternate piston engine fuel because it has a high octane rating and is readily producible from coal. The drawbacks associated with methanol, however, are its high latent heat of evaporation, its low heat energy heat content, and its tendency to dilute the lubricating oil and thereby cause increased piston ring and cylinder bore wear.
Methanol can be introduced into the engine in a variety of ways. With carbureted methanol introduction, the high latent heat of vaporization causes difficulties in getting the fuel evenly distributed in the intake air as it flows through the intake system to the cylinders. The usual remedy for this is to apply a large amount of heating to the intake system to assist evaporation. However, liquid methanol droplets still enter the cylinder where they can precipitate on the cylinder walls resulting in the dilution of the lubricating oil, which leads to accelerated cylinder wall and piston ring wear.
Injection of the methanol in the intake manifold with multi-point injections is another possibility for fuel introduction. This method eliminates the cylinder-to-cylinder fuel distribution problem, but it does not eliminate the probability of oil dilution on the cylinder wall. In fact, it may increase the oil dilution problem relative to a carbureted methanol introduction because of the reduced time available for evaporation and because no exhaust heat is transferred to the methanol.
This invention relates to a method of operating an engine that overcomes the above shortcomings by providing a two-stage introduction of methanol to the engine combustion chamber. A part of the combustion chamber in this case includes a central cavity in the face of the piston within which the major portion of the fuel is sprayed to be contained for evaporation and atomization to thereby minimize cylinder wall wetting.
It is an object of this invention, therefore, to provide a method of operating an engine with fuel having a high latent heat of vaporization to reduce the output of emissions while improving the volumetric efficiency of the engine by cooling the intake charge as well as associated parts of the engine.
It is a further object of the invention to operate an engine as described above in which the fuel is injected in a plurality of stages to first adequately evaporate and atomize the major portion of the fuel with a minimum of wall wetting, and secondly to subsequently provide a rich air/fuel mixture in the vicinity of the spark plug at the time of ignition to assure consistent and fast flame initiation.
The use of methanol or other fuels having a high latent heat of vaporization in automotive type vehicles is known. For example, Oswald et al, U.S. Pat. No. 4,123,997 and U.S. Pat. No. 4,216,744, both disclose the use of 100% methanol in an engine that has a bowl-in-piston type combustion chamber in FIG. 2, a compression ratio of around 12:1 to the engine, and a spark plug that is located essentially near the center or axis of the combustion chamber. However, all of the fuel is injected at once and there is no description how cylinder wall wetting and consequent dilution of the lubricating oil is avoided.
John, U.S. Pat. No. 4,117,810, describes a device for mixing both gasoline and methanol for use in an engine, and no description is given of the combustion chamber or the method of operating the engine in a manner to avoid the problems described above.
Eckert et al, U.S. Pat.

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patent: 4117810 (1978-10-01), John
patent: 4123997 (1978-11-01), Oswald et al.
patent: 4216744 (1980-08-01), Oswald et al.

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