US2185157A - Improved diesel fuel - Google Patents

Description

Patented Dec. 26, 1939 UNITED STATES 2,195,157 nurnovan DIESEL rum.

Edwin M. Nygaard and George S. C'randall, Woodbury, N. J., assignors to Socony-Vacnum Oil Company, Incorporated, New York, N. Y., a corporation of New York No Drawing.

2 Claims.

This invention "relates to fuels for internal combustion engines of the compression ignition or Diesel type and is more particularly concerned with the modification or control of the combusll tion characteristics of liquid hydrocarbon fuels, which are normally used in Diesel engines, by the addition to such fuels of a novel characterizing ingredient.

As is well known to those'familiar with the art, the requirements of a Diesel cycle engine call for a fuel whose ignition and combustion characteristics are opposite to those normally required by a fuel for an engine operating on the Otto cycle, the latter engines being typified by the ordinary spark ignition gasoline engine.

The combustion desired in a spark ignition engine is characterized by controlled or controllable slowness of fuel ignition, too rapid ignition giving rise to the phenomenon known as "knocking. In an engine operating on the Diesel cycle, on the other hand, enhanced speed of ignition is desired, since the fuel is injected into the combustion space and may exert maximum efficiency only when the delay period between injection and ignition is short.

In 9. Diesel engine, therefore, improperly delayed ignition causes knocking, the reason for such knocking being the reverse for that in an Otto cycle engine. It will be seen, therefore,

90 that a fuel having combustion characteristics which are most desirable for an Otto cycle engine is for this reason not desirable for use in a Diesel engine. Likewise, an addition agent which is normally considered to improve the 88 combustion characteristics of a fuel for an Otto cycle engine is not considered desirable for use 2. Diesel cycle.

' This invention has to do specifically with fuels for Diesel engines and has for its primary object 40 the development of a method for accelerating the spontaneous ignition of liquid hydrocarbon fuels in compression ignition engines, which method is characterized by the admixture .of tetranitro methane with the fuel prior to its ignition.

4g Tetranitro methane is a compound having the probable empirical formula C(NOzM. which is well known to the art,.and may be prepared by various published methods illustrative of which are the following:

60 (a) By the'action of fuming nitric acid in concentrated sulfuric acid on nitrofo'rm (see Schischkofi', Ann. 119, 248, (1861)).

(b) By the action of silver nitrite'on iodonitromethane (see Hantzch, Ber. 39, 2479 (1906)).

(c) By extensive nitration of aromatic hydro- Application November 30, 1938, Serial No. 243.117

carbons or their nitro derivatives with nitrosyi sulfuric acid (see Claessen, D. R. P. 184, 229, Centralblatt .1907, II, 366).

((1) By the action of diacetyl orthonitric acid or fuming nitric acid on acetic anhydride 6 (Pictet, Genequand Ber. 36, 2225, (1903), Pictet, Khotinsky, Compt. rend. 144, 211, (1907); Ber. 40, 1164 (1907)).

(e) By the action of nitrogen 'pentoxide on acetic anhydride (Schenk, D. R. P. 211, 198 and 10 211, 199, Centralblatt, 1909, II, 81).

(I) By the action of nitric acid (D=1.53) on acetic anhydride, (Chattaway, J. Chem. Soc. 97, 2099 (1910)).

In demonstrating the value of tetranitro methane as an improver of the ignition quality of 9. Diesel fuel, we have prepared this compound by the method of Chattaway referred to under Example (j) above and have prepared a blend of 0.5 per cent tetranitro methane inya base stock of the type commonly known as No. 2 fuel oil, which had a flash point of 156 F., specific gravity of 0.86 and a Lovibond color of 0.25. The

ignition quality of the base stock and the fuel blend was determinedby comparison with a standard reference fuel in a converted C. F. R. engine, using the ignition delay method. The value obtained in this test is expressed as the cetane number, which is the per cent by volume of cetane in a blend of,cetane and alpha methyl naphthalene having the same combustion characteristics as the sample under test, (see Proc. Am. Soc. Testing Materials, volume 36, I, 418 (1936)).

The cetane number of the base stock used in this test was 42 and that of the 0.5 per cent blend of tetranitro methane in the same base stock was '49. Thus, the ignition quality of the fuel was increased seven cetane numbers by the admixture with the fuel of only 0.5 per cent tetranitro methane prior to its ignition.

Tetranitro methane may be used in the method contemplated by this invention in amounts varying from about 0.1'per cent to about 5.0 per cent, and it is to be understood that when the term "Diesel fuel, Diesel type fuel, or liquid hydrocarbon fuel, etc, are used herein, we have reference to any liquid hydrocarbon adapted for use in any compression ignition engine.

We claim:

1. The method of accelerating the ignition of liquid fuels in an internal combustion engine of the type wherein ignition of the fuel is spontaneously eflected by injection into the compressed air in the engine cylinder which comprises ad- 66 mixing with the fuel .prior to ignition a minor proportion of tetranitro methane. v

2. The method of accelerating the ignition of liquid fuels in an internal combustion engine of 5 the type wherein ignition of the fuel is spontaneously effected by inJection into the compressed air in the engine cylinder which comprises admixing with the fuel prior to ignition about 0.5 per cent of tetranitro methane.

EDW'DI M. NY GAARD. I GEORGE S. CRANDALI