US2537526A

US2537526A - Nitroparaffin fuel

Info

Publication number: US2537526A
Application number: US687213A
Authority: US
Inventors: John A Hannum
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1946-07-30
Filing date: 1946-07-30
Publication date: 1951-01-09
Anticipated expiration: 1968-01-09

Description

Patented Jan. 9, 1951 NITROPARAFFIN FUEL John, A. Hannum, Detroit, Mich, assignor, by mesne assignments, to Borg-Warner CorporaF tion, Chicago, 111., a corporation of Illinois No Drawing. Application July 30; 1946, Serial No. 687,213

to such a vself-sufficientf'ue1 in which the fuelcomponent. is made up of one or more partially nitrated aliphatics of the nature of nitro and polynitroaliphatic hydrocarbons and in which an oxidizing agent selected. from the group of fully nitrated aliphatics; e. g., tetranitromethane, issemployed to supply. the fuel component with all or substantiallyall the. additional oxygen required for combustion of-the' mixture.

'Propellants containingboth fuel and oxygen in 'a1-com-bined1form; also called self-sufficient fuels, 'haveheretofore been proposed by Paul Winand in United States Patent" 914,624, issued March 9; 1909.. That; patent: teaches the 1186501 anitro benzol as. a. fuel and in particular the use in an engine ofv a: mixture =fa. nitro benzol' and tetranitromethane. One difficulty with such a fuel mixture is that it is high y explosive. Furthermore the Winand disclosure contemplates employing, such. nitrated carbon compounds as contain. a..,1arge proportion of carbon with-respect to the hydrogen present. The heat value derived from the combustion of carbon is substantially less-than results from the combustion ofhydrogen with the result that practice based on the Winand disclosure, even if otherwise operableand advantageous, is'subject to a lack of efficiency.

distinguished from the prior art disclosure of using with tetranitro'metha-ne' an aromatic hydrocarbon derivative, and particularly the nitrobenzols, -the=present invention contemplates the use therewith ofnitro and po ynitro aliphatic hydrocarbonsiandin particuIar mixtures that are nonrbrisant as hereafter defined. The. fuel components. are sufiiciently safe. to. be handled by ordinary methods. and; are not substantially more dangerous .to theuser tha-nwgasolineand similar substances. They possess a high. fuel value because, unlikearomatics, they generally have present more hydrogen than carbon. Furthermore ,they. arerelatively 10w in costless. for instance thanthe-nitrobenzola, w

These fuelrcomponentsvcontain a, portion of the oxygen. that is necessary for the. combustion of the carbon and hydrogen atoms that formthe basis. of the fuel the balance of the oxygen required for: combustion being. providedby a fully nitratedroxidizing agentthat with the fuel'com- .ponentcomprises.the; propellant or: selfesufiicient 11 Claims. (Cl. 521) While the. self-sufficientfuel of the present invention is described as, comprising a fuel component and an oxidizing agent, it isrecognized that each may possess properties of the other. For example tetranitromethane, as an oxidant, gives off considerable heat: when burned and nitromethane as a fuel contains a part. of the oxygen required for its combustion. Suchv selfsufficientfuels' are mono-fuels. in the sense that, if desired, both oxidant and fuel can be supplied with safety to the point: of combustion. mixed as distinguished from those fuels where the ingredients are stored separately either because they are spontaneously combustible when mixed or for some otherreason;

It is a general, object ofthe present invention to provide a self sumcient mono-fuel that is safe to handle, possesses a high fuel value and is of the proper viscosity and vapor pressure to provide a propellant. of improvedefficiency for the uses indicated herein'. Another object. is to provide a propellant. comprising a fuel component se ected from the group: of nitro and polynitro aliphatic hydrocarbons and an oxidizing agent from the group of fully nitratedialiphatics to supply to'the. propellant thebalance of oxygen required for combustion of the'fuel. Still. another object of the invention is. to provide a fuel comprising an oxidizing: agent and a non-brisant nitro or polynitro aliphatic hydrocarbon. A further object of the. invention is to provide a selfsufiicient fuel in. which the. fuel component may comprise afortuitous, mixture of mono-nitro aliphatics as derived from the reaction of. propane and nitric acid in the vaporphase and an oxidizing. a ent. Still another object is to provide a mono-fuel in which. both the oxidant and. fuel component may be mixed in advance without spontaneous combustion, or other harmful results. Other objectsof the. invention willbecome apparent as the description of the invention proceeds.

A propellant of the kind outlined above may be efficiently used for various purposes including a source of power for prime movers and more specifically such primemovers as gas turbines and reciprocating, internal combustion engines. Gas turbines heretofore have beensubject to a marked disadvantage-in that it has been-necessaryto provide a compressor as an integral part of the unit -in order that the requisite amount of oxygen might be made available for combustion of the 3 stallations. The fact that gas turbines in the past have derived their oxygen from the atmosphere imposed a marked ceiling limitation on aircraft driven by them because the atmosphere becomes more rarified as the altitude increases and has less available oxygen.

If a gas turbine could be provided with a suitable fuel which eliminated the foregoing disadvantages, its field of application would be considerably broadened. Fields in which it now has utility would be expanded and other fields in which its use is not now practical would be opened. At the present time gas turbines have found some use as stationary auxiliary equipment in power plants have been considered for use in driving railway locomotives. All of these uses would be expanded if the foregoing objections to the gas turbine as it now stands and to the fuel available for its use could be eliminated.

Although a prime use of the propellant described herein is for gas turbines it will be un-- derstood that it is susceptible to a wide variety of other uses. It may, for instance, be used in a reciprocating internal combustion engine and it may be used under a variety of circumstances as in aircraft, underwater craft, land vehicles and stationary installations. It can be used as a source of power for rockets. It is particularly useful at high altitudes where the rarified air offers little oxygen to support combustion. It can be used in many other situations where the burning of a self-sufiicient fuel or propellant is desired to make available heat energy or gas pressure due to combustion.

As indicated above the fuel that is the subject matter of this invention comprises an oxidizing agent in the form of a fully nitrated aliphatic hydrocarbon and a fuel component in the form of a nitro or polynitro aliphatic hydrocarbon. The fuel component embodied in the propellant will be one such as nitromethane CH3(NO2), that itself contains oxygen that may be used during combustion. It is contemplated that other fuel components from the class of nitro and polynitro aliphatic organic liquids may be used. Examples of such fuel components in addition to nitromethane are:

Nitroethane, CHI-I3.CHz.NO2.

l-nitropropane, CH3.CH2.CH2.NO2

2-nitropropane, (CH3)2CH.NO2 1,1-dinitropropane, C2H5.CH(NO2)2 2,2-dinitropropane, (CH3) 2C'(NO2) 2 1,2-dinitropropane, CH2NOz.CI-[NO2.CH3 1,3-dinitropropane, CH2NO2.CH2.CH2NO2 1,1-dinitroethane, CI-b.CH(NO2) 2 1,2,3-trinitropropane, CH2NO2.CHNO2.CH2NO2 1,1,l-trinitropropane, C(NOz)3.CI-I2CH3 Such nitro and polynitro aliphatics included as fuels, as distinguished from oxidants, within the scope of this invention include mononitromethane, dinitroethane and trinitropropane and those nitroethanes and nitropropanes below them in oxygen content but no nitroethanes or nitropropanes that are higher in oxygen content, as for instance dinitromethane. These are all to be distinguished from aromatic fuels such as the nitrobenzols that are dangerous to handle even -by skilled persons, to say nothing of persons who are not skilled in this art.

The fuel portion of the propellant mixture is limited to those nitro and polynitro aliphatics that contain not more than one nitro group; i. e., one molecule of oxygen, for each carbon atom "present. Under many conditions for most 6 .11-

' desired:

cient use the fuel and oxidant will be combined in substantially stoichiometric proportions; i. e., the combining proportions required for combustion. This is the most economical use of the materials because after combustion there remains no appreciable amount of either unconsumed fuel or oxidant. An advantage of using nitromethane or a similar oxygen-containing fuel as listed above resides in the fact that it contains a considerable amount of oxygen that is available during combustion to burn part of the carbon or hydrogen in the fuel. This in turn does not require the inclusion in the propellant of as much oxidizing agent as would otherwise be necessary. These fuel components are non-brisant nitro and polynitro aliphatic compounds. When a fuel is said to be non-brisant within the terms of this disclosure it is meant that it may be burned in contact with chilled iron.

A propellant prepared in accord with the present invention preferably Will contain a sufiicient amount of oxidizing agent to provide with the oxygen of the fuel the required total amount of oxygen for its complete combustion. As indicated above the proper oxygen content can be attained by providing the constituents in direct proportion to their molecular weights and the number of molecules called for in their respective reaction equations. 1

The oxidizing agent that is used in the present invention is an organic oxidant, as distinguished for instance from hydrogen peroxide, and is preferably selected from the group of fully nitrated aliphatic compounds and comprises tetranitromethane C(NOz) 4 and hexanitroethan'e C(NO2)3.C(NO2)3. A preferred combination to be selected comprises nitromethane as a fuel and tetranitromethane as an oxidant. These two ingredients are mixed in the following proportions by weight if a stoichiometric mixture is Per cent Nitromethane 55.5

Tetranitromethane 44.5

Considerable variation in the above percentages is permissible without departing from the scope of the invention. For example if a mixture of nitromethane CH3(NO2) and tetranitromethane C(N02)4 falls within the percentages by weight given below it is considered that the resultant propellant lies within the bounds of the present invention:

Per cent Nitromethane 25-75 Tetranitromethane -25 Thus it is contemplated that insofar as the proportions of fuel and oxidant are concerned a reasonable variation from the ideal calculated percentages is permissible and even desirable under certain conditions such as maintenance of desired combustion characteristics. The mixture of nitromethane and tetranitromethane emphasized above, while a preferred form of the invention, is intended to be illustrativeof the variations in composition permissible herein. The other fuels and oxidants listed also may be used either in stoichicmetric proportions or within the ranges hereafter set out.

Compositions in terms of percentage by weight are given below for other nitro and polynitro aliphatic fuels within the scope of the present invention, and for purposes of comparison the percentages of composition of the nitromethane .may be used for a particular. fuel.

fuels ararepeated- :It:shouldbezpointedout that whilev it: will generally be: the. case that the. fuel component will consist. of. only one of the folticular combination that is-contemplated. Since these calculations lie within the ability of one skilled. in this art they will not be given. here.

When tetranitromethane is the oxidant that is used the following table indicates the percentages by weight of fuel that are to be used. In the first column the fuel is listed. and inthe second column the percentage. by weight if a-v stoichiometric mixture of the fuel and tetranitro methane is desired. In the third column is listed the range of percentages by weight of fuel that will provide a satisfactory product when combined with tetranitromethane. In the case of both columns 2 and 3.the amount of tetranitromethane to be used may Ice-obtained by subtracting from 100%. the percentage of. the fuel indicated. This table is as follows:

If the oxidant to be used. is hexanitroethane the following table governs in which again the first column is the fuel, thesecond column the percent by weight of fuelarequired fora stoichiometric mixture with hexanitroethane and the third column indicates the-permissible range that Again the amount of hexanitroethane to be added is obtained by subtracting from 100% the indicated percentage by weight of the fuel:

Under certain conditions of use, mono nitro aliphatics are preferred. It is to be noted that mono nitro aliphatics are referred to herein simply as nitro aliphatics and that the prefix mono is not used-as for example mono nitromethane is referred to simply as nitromethane. On the other hand in the case of poly nitroaliphatics the prefixes, as di, tri and tetra are used. These mono. nitroaliphatic, compounds: include the following Nitromethane, CH3 (N02) Nitroethane, CH3.CH2NO2 l-nitropropane, CH3.CH2.CH2NO2 Z-nitropropane, (CH3) 2CH.NO2

This group of fuels may be used individually or they may be used in admixture with each other. An example of the latter is the fortuitous mixture of these compounds that results from the reaction of propane and nitric acid in the vapor or gas phase: seeU. S. Patent 1,967,657, granted July 24, 1934, to H. B. I-Iass et al. Such a mixture may be used with an oxidant in stoichiometric proportions, in which case the fuel of this fortuitous mixture is mixed with tetranitromethane in approximately the following proportions by weight:

Per cent by weight Tetranitromethane 65 Fortuitous, fuel mixture 35 Again if the oxidant is hexanitroethane the corresponding mixture will be approximately as follows: 1

Per cent by weight Hexanitroethane '70 Fortuitous fuel mixture 30 In each case, nitromethane, nitroethane, 1- nitropropane and 2-nitropropane are assumed to be present. Considerable latitude is permissible within the scope of the invention particularly when the fuel is such a fortuitous mixture as discussed above. Thus if the oxidant is tetranitromethane the propellants of this mixture that lie within the following percentages by weight are deemed to be within the present invention:

Per cent by weight Fortuitous fuel mixture 15-5'0 Tetranitromethane -50 Again propellants using hexanitroethane as the oxidant and a fortuitous fuel'mixture, if mixed in approximately the following ranges of percentage by weight, fall within the scope of this invention:

The combination of fuel and oxidant set out above may be used alone or in combination with still other ingredients and the addition of such other ingredients to a propellant mixture is contemplated as within the scope of this invention as defined in the claims. Such other ingredients may be in the form of a diluent or an inhibitor by which to control flame temperature, the rate of combustion and the like.

From the foregoing tables it will be seen that the invention broadly may comprise a nitro or polynitro aliphatic fuel and tetranitromethane in substantially the following range of percentages by weight:

I Per cent Tetranitromethane 5-90 Nitro or polynitro aliphatic fuel '9510 and in the same manner the fuel and hexanitroethane may be used within the following range of percentages by weight:

. Per cent Hexanitroethane 10-90 Nitro or polynitro aliphatic fuel -10 The fuel and the oxidizing agent may be supplied to the point of combustion as a mono-fuel that is already mixed and in liquid form. Point of combustion is a term not to be confined to the actual point of flame propagation but is construed to be the region to which the propellant is fed preparatory to the actual burning.

Although a preferred use of the present invention is in the form of a mono-fuel in which a single liquid entity is stored, transported and fed to the point of combustion, this is not necessary. .In certain cases it is desirable to maintain the constituents separate from each other until they :are brought together at the point of combustion. Such a procedure would be desirable if the combustion characteristics of the self-sufficient fuel were to be altered during use by altering the percentages in which the constituents are mixed at the point of combustion.

The propellant that is the subject of this invention may be used for various purposes and in various ways. Its use in a gas turbine or other prime mover has been emphasized here but it is not to be limitedto such use. It may be used in any apparatus and environment Where combustion of a fuel is employed as for instance a source of gas under pressure as by confined combustion of the propellant and retention of the products of combustion.

This application is a continuation in part of prior applications Serial No. 597,959, filed June 6, 1945, and Serial No. 640,386, filed January 10, 1946, both now abandoned.

I claim:

1. A self-sufficient liquid fuel comprising a compound selected from the group consisting of tetranitromethane and hexanitroethane as an oxidizing agent and a liquid nitroparafiin as a fuel, the latter characterized by containing not more than one nitro group for each atom of carbon.

2. A self-sufiicient liquid fuel comprising between five and ninety per cent by Weight of tetranitromethane as an oxidizing agent and the balance a liquid nitroparaffin as a fuel, the latter characterized by containing not more than one nitro group for each atom of carbon.

3. A self-sufficient liquid fuel comprising, in approximately stoichiometric proportions so as to give end products of carbon dioxide, water and nitrogen, tetranitromethane as an oxidizing agent and a liquid nitroparaffin as a fuel, the latter characterized by containing not more than one nitro group for each atom of carbon.

4. A prime mover propellant that comprises 25 to by weight of nitromethane and 75 to 25% by weight of tetranitromethane.

5. A propellant as in claim 4 consisting essentially of 25 to 75% of nitromethane and the balance tetranitromethane.

6. A propellant as in claim 4 consisting essentially of 55.5% nitromethane and 44.5% tetranitromethane.

7. A prime mover propellant comprising a plurality of homologous aliphatic nitro compounds, at least one of them consisting of a nitroparafiin of the nature of an oxidizing agent selected from the group consisting of tetranitromethane and hexanitroethane and at least one of them consisting of a nitroparafiin of the nature of a fuel having not more than one nitro group for each carbon atom appearing in the paraffin skeleton.

8. A propellant as in claim 7 including nitromethane as a fuel component.

9. A propellant as 'in claim 7 including a nitroethane fuel component.

10. A propellant as in claim 7 including a nitropropane fuel component.

11. A self-sufficient liquid-fuel comprising a compound selected from the group consisting of tetranitromethane and hexanitroethane as an oxidizing agent and, as as fuel, a fortuitous mixture of mono nitroparaflins obtained by interactin propane and nitric acid in the vapor phase.

JOHN A. HANNUM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 914,624 Winand Mar. 9, 1909 2,317,557 Senkus Apr. 27, 1943 FOREIGN PATENTS Number Country Date 26,261 Great Britain 1907 248,548 Germany June 25, 1912 24,839 Great Britain 1913

Claims

1. A SELF-SUFFICIENT LIQUID FUEL COMPRISING A COMPOUND SELECTED FROM THE GROUP CONSISTING OF TETRANITROMETHANE AND HEXANITROETHANE AS AN OXIDIZING AGENT AND A LIQUID NITROPARAFFIN AS A FUEL, THE LATTER CHARACTERIZED BY CONTAINING NOT MORE THAN ONE NITRO GROUP FOR EACH ATOM OF CARBON.