US2914910A

US2914910A - Propyl nitrate monofuel and method of use with nickel salts

Info

Publication number: US2914910A
Application number: US461645A
Authority: US
Inventors: Jr Charles H King
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1954-10-11
Filing date: 1954-10-11
Publication date: 1959-12-01
Anticipated expiration: 1976-12-01

Description

United States Patent PROPYL NITRATE MONOFUEL AND. METHOD OF USE WITH NICKEL SALTS Charles H. King, Jr., Manchester, Conn., assignor to United Aircraft Corporation, East Hartford, Conn, a corporation of Delaware No Drawing. Application October :11, 1954 Serial No. 461,645 1 14 Claims. (Cl. 60-3544) The present invention relates to an improved monofuel or mono-propellant for reaction motors, rockets, jetpropulsion motors, as well as other jet-propelled devices.

The term jet-propulsion devices, as used herein, relates to devices which derive their driving power from the escape through a jet or nozzle at relatively high velocy of the mass comprisingth p oduct .v esult n from a combustion or exothermic decomposition of a fuel. The jet may be exhausted into the open air as in the rocket type of device, or it may be directed on a movable object as in the turbine type of device.

Propyl nitrate is known to be a useful monofuel or mono-propellant for jet-propulsion devices as evidenped by the prior patent to Doumani-et .al,. 2,- 6 4 s07'9. The term propyl nitrate as used herein relates .to both normal propyl nitrate and isopropyl nitrate which are chemical isomers. 1 n using .propylnitrate as 'a monofuel," as for example, in a jet-propulsion motor, it is charged into a feed tank and pressured with an inert gas, such as nitrogen. The fuel ispre'ssured'lbythe inert gas contained in a second tank under high pressure, as for example, 1500 2,914,910 Patented Dec. 1, 1959 f ce as a slurry would also be disadvantageous as the presence of the catalytic metal surface would tend to make e affected during storage and in the feed lines to the combustion chamber.

Examples of suitable nickel salts which may be used in accordance with the present invention are nickel: car,- bonyl, nickel acetyl acetonate, nickel diisopropyldithiocarbarnate and nickel dinormalpropyldithiocarbamate.

Generally, the salt, calculated as metallic nickel, is in an amount from 0.02 to 1.0 percent by weight of the propyl nitrate and preferably from 0.1 to 0.25 percent by Weigh Compa t ve. een condu w ich ow he 1LlPIiQ result obtained by the addition of a soluble p.s.i., through suitable lines and a pressure reducing control valve. The pressured propyl nitrate is then released from the fuel tank and fed through suitable lines andcontrol valves through an ejector or atomizer into a combustion chamber. In the combustion chamber, the propyl nitrate is ignited by suitable means and-allowed to decompose or burn.

The paramount disadvantage'of gpropyl nitrate as a monofuel is that a large combustioncharriber isrequred to decompose it. This is undesirable, particularly in .air-

craft, where'lightnessflin weight 'is so essential and avjail- 1 able Space is often at a premium. I I,

An obj ct of my invention is to provide c aly c means whereby'a smaller combustion chamber may be employed for decomposing-prqpyl nitrate than fhashereinvention to provide catalytic means to improve the .starting characteristics and combustion efficiency of propyl nitrate as a mono-propellant,

"I have discovered that the foregoing objects may. be

accomplished by the additiontopropyl nitrate of a soluv.tof ore been possible. .It is also a ,further object ,of my ticles in the combustion chamber bymerely.feeding nickel particles from an outside ,line to the combustion chamber sincethis would require a .mechanism to inject anddis- :perse a streamof metal particles .inthe combustion cham- =b.er against .the .high combustion :pressure. -Merely intro'duci'ng' 'the' metal particles v a,nd .the propyl ,riitrate' f uel :nickel salt compared to pure propyl nitrate'or for propyl nitrate with salts of other metals as shown in Table 1. For example, there is an increase of specific impulse .(lsp) to 167 sec. when normal propyl nitrate, containing 0.725 percent nickel carbonyl by weight (0.25 percent Ni) is decomposed in a chamber with ac'haracteristic length (11*) or 430 inches compared to marginal operation at a specific impulse at 145 sec. for the same chamber using pure normal propyl nitrate. Since 51 67 see. is the theoretical specific impulse for the test conditions-a chamber pressure of 300 p.s .i. and normal atmospheric pressure exhaust, this corresponds to an increase in combustion efliciency from 87 to Since this concentration of nickel carbonyl in normal-p opyl n rat else Produced e ent a ly 109% combustion efliciency when the characteristic length i (L*) of the combustionchamber was'reduced to 315 inches, further. reduction in characteristic .length'is obtainable using this catalyst-fuel mixture. The characteristic length L* is the ratio of the combustion chamber volume to the exhaust nozzle throat area in consistent throat area in consistent units and is a measure of the volume required for combustion which is essentially unaffected by the scale of the rocket or combustion chamber. The particular tests related were accomplished using cylindrical combustion chambers of approximately 401135; thrust requiring a fuel flow of about 0.25 lb. of propyl nitrate per sec. The combustion chamber with a characteristic length of 430 inches was 3 inches in diameter and 5 /2 inches long and exhaust-nozzle throat area was approximately 0.09 sq..in. Additional tests in Table I were accomplished in a chamber identical in cross section and throat area but only 4 inches long (L*=3l5 inches).

The results obtained by using the soluble nickel salts are not only advantageous but are surprising. For example, chromium acetyl acetonate,which is an effective catalyst for the decomposition of a similar mono-propellant, namely, ni'tromethane, did not increase the rate of decomposition of normal propyl nitrate as shown in Table I. i

In order to describe my invention even further, data on the decomposition of normal propyl nitrate' containing four different nickel salts ,are presented in Table I. As can be seen, specific impulse and combustion efficiency were increased from 4.2 to 20.2% by the addition of .varying amounts of these salts. v i '7 In addition, to show that all metal salts do not "have the same desirable catalytic effect on the decomposition of normal propyl nitrate, further data are presented in Table I. These data show that salts of iron, lead, cobalt On the other hand, with the nickel salt Table I Chamber Com- Metal in lap lap with C with Percent L in. pound in Solution Without Without Oom- Com Increase Solution pound pound l 315 0.21 0. 048 144 3, 310 153 3. 520 6. 2 Nwkel Amyl Acemnate 315 0. 44 0. 141 3,240 153 a. 520 7. s Nickel dlisopropyldlthlooarbamate g: g: 32 g: fig g 2: Nickel dlnormalpropyldithiocarbamate- 315 1. 05 0. 152 140 3, 220 149 3. 430 6. 4 315 0. 145 0.05 143 3, 290 154 3, 5 7. 7 it? 3335 it 151% ill it;

. 0.25 4 Nickel wrbmyl 430 0. 29 0. 10 144 3, 310 161 a, 700 12. 5 430 0.725 0. 145 3, 340 167 3. 850 15. 2 as 13% it? 12st 2-? 0 methyl lead l I 430 2.0 t 1.28 145 a. 340 139 3, 200 -4. 1 430 0. 57 0. 06 148 3, 400 149 3, 430 0. 7 750 1. 91 0. 20 118 2, 720 117 2, 690 -0. 8 Cobalt naptheuate (N ate 1) (Note 2) 430 1. 91 O. 20 144 3. 310 145 3, 340 0. 7 430 4. 76 0. 50 145 3. 340 138 3. 170 -4. 8 430 4. 75 1. 35 145 3, 340 No data (nozzle 0 ogging) Iron pentacarbonyl 430 2. o 0. 57 145 3, 340 121 2. 780' --16. 5 430 0. 5 0. 14 145 3, 340 146 3, 360 0. 7 Carbon Disulphide 430 2.0 145 3, 340 145 3, 340 0 Ferrocene 315 0.2 No Data-wonld not run 430 0. 17 No Do. a-would not run Chromium acetyl acetonate 315 139 I 35% h 533 I 6 Water 430 0.25 145 3,340 145 3,340 I 0 Norm 1.Nuodex cobalt napthenate with solvent, 10.5% cobalt by welght. No'rn 2.150 lb. thrust chamber. All other chambers produced approximately 4011). thrust.

and chromium, when dissolved in normal propyl nitrate, do not promote the decomposition of the fuel. From the data of Table I, the decomposition actually appears to be inhibited as shown by decreases in specific impulse when salts of these metals are added to the normal propyl nitrate.

Standard parameters used to measure rocket perform: ance and mentioned in the text and Table 1 are defined as follows in Table 11 below:

7 Table II (1) Specific impulse as determined by thrust- Specific impulse=thrust/fuel flow (2) Specific impulse as determined from chamber pressure where P =chamber pressure f =exhaust nozzle throat area W=fuel flow Cp=thf1l$t coefi'icient expressed by t=nozzle divergence coeflicient C =nozzle discharge coefiicient =velocity coefficient P =ambient atmospheric pressure P =combustion chamber pressure =ratio of specific heats (3) Characteristic velocity, C*, as determined from chamber pressure and fuel flow-- where P =chamber pressure f =exhaust nozzle throat area g=gravitational constant W=fuel fiow rate The theoretical C* may be expressed by the equation where v=ratio of specific heats g=gravitational constant R=universal gas constant T=combustion chamber temperature M =average molecular weight By .utilizing my invention, smaller combustion chambers are required due to the improvement in the decomposition of propyl nitrate. Hence, lighter combustion chambers may be used, which is particularly advantageous for aircraft.

The invention in its broader aspects is not limited to the specific processes and stepsdescribed but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

I claim:

1. An improved monopropellant composition for use in jet propulsion devices consisting essentially of propyl nitrate and a nickel salt soluble in said monopropellant and in an amount from about 0.02% to about 1% by weight calculated as metallic nickel of said propyl nitrate, said nickel salt on decomposition yielding finely divided nickel particles.

2. An improved monopropellant composition as defined in claim 1 wherein the soluble nickel salt is an amount from 0.1 to 0.25% by weight of the propyl nitrate, calculated as metallic nickel.

3. An improved monopropellant composition as define-d in claim 1 wherein the soluble nickel salt is selected from the group consisting of nickel carbonyl, nickel acetyl acetonate, nickel diisopropyldithiocarbamate and nickel dinormalpropyldithiocarbamate.

4. An improved monopropellant composition as defined in claim 3, wherein the soluble nickel salt is nickel carbonyl.

5. An improved monopropellant composition as defined in claim 3, wherein the soluble nickel salt is nickel acetyl acetonate.

6. An improved monopropellant composition as defined in claim 3, wherein the soluble nickel salt is nickel diisopropyldithiocarbamate.

7. An improved monopropellant composition as defined in claim 3, wherein the soluble nickel salt is nickel dinormalpropyldithiocarbamate.

8. A novel method for decomposing propyl nitrate monopropellant in a combustion chamber of a jet propulsion device comprising adding to said propyl nitrate outside of the combustion chamber a nickel salt soluble in said propyl nitrate and in an amount from about 0.02% to about 1% by weight calculated as metallic nickel of propyl nitrate, passing the propyl nitrate and soluble nickel salt to the combustion chamber, converting said nickel salt into finely divided nickel particles and decomposing the propyl nitrate in the presence of said nickel particles dispersed throughout.

9. The method as defined in claim 8, wherein the soluble nickel salt is added in an amount from 0.1 to 0.25% by weight of the propyl nitrate calculated as metallic nickel.

10. The method as defined in claim 8, wherein the soluble nickel salt is selected from the group consisting of nickel carbonyl, nickel acetyl acetonate, nickel diisopropyldithiocarbamate and nickel dinormalpropyldithiocarbamate.

11. The method as defined in claim 10, wherein the soluble nickel salt is nickel carbonyl.

12.-The method as defined in claim 10, wherein the soluble nickel salt is nickel acetyl acetonate.

13. The method as defined in claim 10, wherein the soluble nickel salt is nickel diisopropyldithiocarbamate.

14. The method as defined in claim 10, wherein the soluble nickel salt is nickel dinormalpropyldithiocarbamate.

References Cited in the file of this patent UNITED STATES PATENTS Bartleson et al. July 17, 1951 Doumani et al. July 14, 1953 Maisner Oct. 5, 1954 OTHER REFERENCES Chemical & Engineering News, vol. 26, No. 39, Sept.

27, 1948, pages 2892, 2893.