FR2474585A1 - COMBUSTION CONTROL METHOD APPLICABLE TO DIESEL ENGINES FOR THE USE OF ETHANOL OR METHANOL AS FUEL - Google Patents

Abstract

THE SUBJECT OF THE PRESENT INVENTION IS A COMBUSTION CONTROL PROCESS, APPLICABLE TO DIESEL ENGINES FOR THE USE OF ETHANOL OR METHANOL AS FUEL. IT IS CHARACTERIZED IN THAT EACH OF THE ENGINE'S COMBUSTION CHAMBERS IS PROVIDED WITH AN ELEMENT OF INCANDESCENCE, SUCH AS A RESISTOR. IT RELATES TO THE AUTOMOTIVE FIELD.

Description

COMBUSTION CONTROL METHOD APPLICABLE TO DIESEL ENGINES

  FOR THE USE OF ETHANOL OR METHANOL AS FUEL.

  The present invention relates to a combustion control method, applicable to diesel engines for the use of ethanol or methanol

as fuel.

  The current energy crisis, which is the result of the continuing rise in oil prices, has triggered a number of research projects for the use of alternative fuel sources. Alcohols play an important role in these studies because these fuels come from

  renewable sources, unlike the fossil deposits that are required

  limited and subject to impoverishment.

  The use of alcohols as fuel for diesel engines has been investigated by several institutions and the results obtained have been presented in recent symposia on other usable fuels held at Wolfsburg, Federal Republic of Germany. Germany, in November 1977, and in Asilomar, California, United States of America, in May

1979.

  Most of the solutions considered in these studies require

  major changes to the engines. In addition, only a few

  This allows the use of alcohol alone, without the addition of a certain amount of diesel oil. One of the few exceptions in the past has been to add amyl nitrate or a similar product to alcohol, which can be used virtually without making any changes to the current engines, but with a cost increase caused by additive. Vegetable oils can also be used as fuel for

  diesel engines, without having to make modifications.

  However, to date, the expenses incurred to produce such oils have been too high to be considered

usable spare.

  At present, ethanol and methanol are not produced in quan-

  sufficient for large-scale consumption in engines, but there are known processes for producing these fuels

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  from coal, gas such as ethane and methane, or wood.

  The difficulty encountered during the combustion of alcohols in diesel engines consists in the high resistance of these fuels or fuels

  knocking caused by high temperatures and pressures.

  This property is normally measured through the index

  octane, which is obtained by standardized methods, based on a comparison

  because of isooctane, corresponding to an index of 100, with nheptane, whose index is 0. The higher this octane number, the better the fuel

  suitable for use in spark ignition engines,

  feeling high compression rates. The octane numbers of ethanol and methanol are both greater than 100. In a diesel engine, the air is compressed and, at an appropriate time, the liquid fuel is injected through the injection system. . Due to the high pressures of the highly compressed air, the fuel is brought into a spontaneous combustion condition which initiates the combustion process. Habitually,

  the injection of alcohol does not cause inflammation in a sufficient time

  short to allow normal engine operation.

  In addition to the above-mentioned octane number, fuels have another property, namely their resistance to pre-ignition, which is defined by the ignition of a mixture of fuel vapor and air

  under the action of an incandescent body in the combustion chamber.

  It is known that this phenomenon has a disruptive effect on ignition engines.

  spark ignition, and may be caused by incandescence of deposits, by excessively hot spark plugs, etc.

  The resistance of fuels to pre-ignition is generally inde-

  pendent of their octane number. In the special cases of ethanol and

  methanol, for example, despite their resistance to

  During relatively long periods of time, at high pressures and high temperatures, these fuels ignite rapidly under the action of an incandescent element. Consequently, it suffices to have an incandescent element, such as a resistor, in the combustion chamber of diesel engines to enable them to operate with ethanol, methanol or other

  fuel having similar properties.

  Under conditions of operation higher than a given degree of power, the incandescent element can be replaced by a simple metal part

  which is heated by the temperatures prevailing in the combustion chamber.

  The starting operation can be carried out using a resistor or diesel oil. In the latter case, after warming up the engine, you can

  passing as fuel from diesel oil to methanol.

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  This simple modification to a conventional diesel engine allows it to run only with diesel oil, or with ethanol or pure methanol. In the case of ethanol and methanol, it is sufficient to add about 1% of castor oil or a similar substance for the lubrication of the injection system. Switching from one fuel to another only requires adjustment of the fuel injection pump with regard to the maximum fuel flow and, occasionally, injection timing. The amount of ethanol or methanol injected must be increased compared to the amount of diesel oil, since their minimum heating value is lower than the minimum calorific value of the diesel oil. Injection timing can be adjusted based on differences in fuels with respect to delay

between injection and combustion.

  More complex changes, which have now been developed

  by different specialists, for example concerning a double injection of

  fuel, an alcohol-air mixture, a fuel injection with simultaneous injection of diesel oil, etc., do not eliminate the use of diesel oil and allow it to be replaced by alcohols

  amounts of 90 to 50%. The claimed process makes it possible to use alternative

  ethanol, methanol or diesel oil without modifying the

  or without additional accessories such as injection pumps, fuel injection nozzles, metering devices, control systems, etc. It suffices to involve an incandescent element per cylinder, this element can be electric, or be constituted by a simple inactive part which is

  inflamed by the heat of combustion.

  Another advantage of the combustion process according to the invention is that it makes it possible to adjust the compression ratio of the engine in order to obtain

  optimal performance with minimal fuel consumption.

  To ensure the correct starting of the engine when cold, most common diesel engines operate with compression ratios that are higher than those required for optimum performance. The presence of incandescent elements in the combustion chambers makes it possible to start the engines more easily with diesel oil and ethanol or methanol, thereby allowing a reduction in the compression ratio

up to optimal values.

  Of course, the present invention is not limited to the embodiments

  described above which may be subject to many variations.

2474585.

Claims (1)

REVENDI CATION   Combustion process for the adaptation of diesel engines to the use   Fuels such as ethanol and methanol are characterized by providing each of the combustion chambers of the engine with an incandescent element, such as a resistor.