US2500964A - Method of and apparatus for testing the inflammability of fluids - Google Patents

Description

March 21, 1950 M. v. SULLIVAN ETAL METHOD OF AND APPARATUS FOR TESTING THE INFLAMMABILITY OF FLUIDS 2 Sheets-Sheet 1 Filed May 8, 1945 .LE'LE Miles V Sullwah John K. WQH Q March 1950 M. v. SULLIVAN ETAL 2,500,964

METHOD OF AND APPARATUS FOR TESTING THE INFLAMMABILITY 0F FLUIDS Filed May 8, 1945 2 Sheets-Sheet 2 gjwuwvto'b MHes' V. Sullivan John K. WoH'e Patented Mar. 21, 1950 METHOD OF AND APPARATUS FOR TEST- ING THE INFLAMMABILITY OF FLUIDS Miles V. Sullivan, United States Navy, and John K. Wolfe, Bethesda, Md.

Application May 8, 1945, Serial No. 592,625

6 Claims. (01. 73-36) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This invention relates to a method of and apparatus for testing the inflammability of fluids.

An important consideration in the selection of a material for certain purposes may be the inflammability of the material. For example, one of the potential fire hazards frequently encountered in naval practice is the penetration or rupture of high pressure hydraulic lines by bullets or shell fragments and the production of an atomized spray of the liquid hydraulic oil by passage through the orifice caused by the bullet or fragment in the line. When this spray strikes a hot surface, spontaneous ignition may occur. The likelihood of ignition under these circumstances may be determined roughly by a measurement of the spontaneous ignition temperatures. The laboratory values obtained, however, must be considered as a minimum point at which ignition can occur, and fire will not necessarily result in actual practice, since the vapor concentrations in the vicinity of the open hot surface are not directly comparable to the conditions under which the measurement of spontaneous ignition temperature is made in a closed system, such as is the usual laboratory practice. This standard test therefore is of little help in predicting the ease of propagation of the flame throughout the spray and back into the line. It is this property of propagation of the flame throughout the spray and back into the line which presents the greatest fire hazard.

l-leretofore one method that has been used in determining therelative inflammability of liquid materials, and particularly of petroleum products, has been to determine the flash point. This test may consist of slowly heating the fluid in an open cup and passing a small flame over the cup at specified intervals. The flash point is taken as the temperature at which a flash of flame first appears on the surface of the liquid. Evaluation of the fire hazard of light petroleum fractions by means of the flash point technique has been found to be very useful, particularly on liquids in the gasoline, kerosene, and light fuel oil stages, but its usefulness in predicting the flre hazard of relatively non-volatile petroleum fractionation cuts is not well established. As is well known, many hydraulic fluids fall in the category of relatively non-volatile fluids. Accordingly, evaluation of the infiammability of such materials by a determination of the flash point may not produce informative results.

An object of this invention is to provide an eflicient and effective method of and apparatus for testing the inflammability of fluids.

In accordance with one embodiment of this invention, the fluid to be tested is combined with a controlled mixture of oxygen and nitrogen under pressure and is injected into one end of a chamber. An electric arc is located near the opposite end of the chamber and between the arc and the injection device is mounted a thermocouple whereby the degree of propagation of the flame of the ignited atomized mixture toward the injection device may be readily determined. The percentage of oxygen required to burn such a mixture and to produce a given propagation of the flame of the mixture toward the injection device is an accurate measure of the inflammability of the fluid being tested.

Other objects and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the drawings, wherein:

Fig. l is a side elevation of an inflammability testing apparatus constructed in accordance with one embodiment of this invention;

Fig. 2 is an enlarged, horizontal, sectional view of the propagation chamber, taken along the line 22 of Fig. 1;

Fig. 3 is a detailed, sectional view of a mixing chamber, constructed in accordance with this invention; and

Fig. 4 is a, detailed, sectional view of a metering device, constructed in accordance with this invention, whereby the flow of fluid to be tested may be accurately controlled.

Referring now to the drawings, and particularly to Figs. 1 and 2 thereof, it will be seen that the apparatus of this invention includes a propagation chamber 5, which may be formed by an elongated, double-walled cylinder, mounted on two spaced, vertically disposed brackets 6 of unequal height, the brackets being so located that the chamber 5 is tilted upwardly to the left, as

viewed in Fig. l, at an angle of approximately five degrees from the horizontal. The double walls of the propagation chamber are spaced to form therebetween an enclosed annular chamber 1 which serves as a water jacket and through which water is circulated to cool the chamber walls from an inlet pipe 8 and out an outlet pipe 9. The left end of the chamber 5, as shown in Fig. 2, is open, while the right end of the chamber is closed by a cover plate It, through which extends the nozzle and are injected into the chamber 5, they will be combined and atomized into a fine spray.

It will be noted that the nozzle H is off-centered, being mounted near the lower side of the plate iii which forms the right end wall of the chamber 5. In the operation of this apparatus, the spray enters the right end of the chamber 5 and passes through the chamber forming a cone of spray, the apex of which lies at the nozzle center. For optimum operation, it is desired that the center of the base of the cone, that is, the portion of the cone intersected by an igniting device is which is transversely mounted near the left end of the chamber and extends therei through, substantially coincide with the center of the igniting arc to provide uniform ignition of the spray. By tilting the chamber. 5 slightly upwardly along the path of the spray, and by so positioning the nozzle ii that the spray therefrom moves upwardly, at first, the trajectory of the spray may be made such as to locate the center of the cone in the center of the igniting arc. The length of the chamber 5 is selected so that the igniting device 53 may be so located therein that the flow of spraythrough the chamber will be sufficient to prevent appreciable diffusion of the spray with air tending to enter th chamber from the left end prior to its reaching the area of the ignition device, and at the same time the igniting device may be spaced from the nozzle Ii an adequate distance to provide a suitably long propagation path-for the flame. The necessity of this will become more apparent as the description of the operation of the apparatus proceeds.

By tilting the chamber 5' and cooling the walls thereof, the spray asit strikes the walls is quickly cooled and caused to liquify and at the same time the fluid will tend to flow to the right, towards a drain port l i formed adjacent the right end of the chamber, thus. avoiding the danger of the liquified spray being heated to itsflash point and itself igniting.

The atomizer I2 is connected througha line it to one end of a gas mixing'chamber. iii, a control valve I i being located in the line adjacentthe atomizer. Referring to Fig. 3, it will be seen that the mixing chamber is is athin-walled cylinder enclosed at either end by end. plates is and i9,

respectively. The line l5 connects to the chamber [6 through a port 28. formed in the end plate i8, adjacent the side wall of the cylinder, while a second port 2| is formed through the center of the opposite end-plate is to permit the left end of a tube 22, which is substantially smaller in diameter than the cylinder 15 and concentrically disposed therein, to extend therethrough. Thetube 22 is sealed to the end plate i9 and is connected at its outer end to a T type pipe junction fitting 23, one side of which is connected to an oxygen source 24, asshown in Fig. 1, and'the other side of which is connected to a nitrogen source 25, suitable metering control devices 26 and 2?, and indicators 55-5 being associated with the oxygen and nitrogen supplies respectively to provide a precisely controlled flow of gases from thesesupplies.

The construction of the mixing chamber l6 is such as to provide a circuitous path for the gases from the gas supplies so that complete mixing of the gases will occur prior to the gases reaching the atomizer 12. As shown in Fig. 3, the tube 22, which is connected'to the T pipe fitting 23, extends into the cylinder [6, substantially along the in the mixing chamber 16.

axis thereof, to a point slightly spaced from the right end wall 18. A disc 29 is mounted across the right end of the tube 22 and is provided with a small aperture 30 whereby the exit from the tube 22 is constricted to increase the turbulence of the gas. Gas passing through this aperture reverses direction and enters an annular chamber formed between the tube 22 and a larger diameter, concentrically disposed tube 3i, also mounted with- The right end of the tube 3| is mounted on the right end plate E8 of the chamber 16 and consequently is closed; however, the left end of the tube 31 extends to a point slightly spaced from the left end plate 19 of the chamber 15, and has mounted therein an annular disc 32 whereby the exit from this chamber is constricted similarly to the exit from the right end of the tube 22. A second annular chamber 33 is formed between the inner wall of the chamber l5 and the outer wall of the tube 3|.

Tracing the path of the gases as they enter the chamber 16 through the tube 22, it will be seen that the gases, being moved under pressure from the gas supplies 2 and 25, will move to the right down the tube 22, pass through the aperture 30 and thenmove to the left along the annular chamber formed between the tube 22, and the tube 3!, reverse direction at the left end of the chamber it and move to the right along the annular chamber 33 formed between the outer key 4i mountedon the plunger extends into and tube 3! and the chamber l6, and finally leave the mixing chamber through the port 29 and enter the pipe 15 which connects to the atomizer [2. The several reversals in the direction of movement and the turbulence occurring as the gases pass through the orifices in the discs 23 and 32 have been found to provide very satisfactory mixing of the gases supplied to the mixing chamber.

Between the point on the atomizer 12 at which the gas line 15 is connected and the nozzle H, as seen in Fig. 1, is also connected a pipe 3% which extends upwardly therefrom to the lower end of a Vertically disposed burette 35, having a metering valve 36 associated therewith. In the operation of this apparatus, a quantity of the fluid tobe tested is placed in the burette, the valve 35 being closed. When the valve is opened to permit the fluid to flow, the weight of the fluid in the burette causes the fluid to flow downwardly into the atomizer l2. If at the same time gases are supplied to the atomizer under pressure, the aspirator effect of the gases passing axially through the atomizer, causes the fluid 1 entering from the side to be carried into the nozzle H, where it is atomized and injected into the propagation chamber.

In some cases it may bedesirable to make the rate of flow of the fluid from the burette entirely independent of thev viscosity of the fluid, the aspirator effect of the gases passing through the atomizer, or the pressure effect of the Weight of the fluid in the burette. In order to accomplish this, in accordance with this invention; the metering device shown in Fig. 4 may be employed, being substituted .for the burette 35. This device comprises a syringe 31, the right end of which.

may be connected to the pipe 34 in the same manner as was the burette 35 and in place thereof. 7 A longitudinally movable plunger 33is mounted in the left portion thereof An externally threaded shaft 39, which may be rotated by a slow speed motor it, extends axially through and threadedly engages the left portion of the plunger 38 while a slidably engages the sides of a slot 42 formed in a block 43 which is mounted on the side of the syringe. In the operation of this device, it will be apparent that rotation of the shaft 39 in one direction will cause the plunger 38 to move to the right and thereby to force any fluid in the syringe into the atomizer through the pipe 34. Reversing the direction of the plunger and disconnecting the syringe from the pipe 34 permits inserting the end of the syringe in a suitable container holding the liquid to be tested and filling the syringe. With this device, the flow of fluid into the atomizer may be controlled to any desired value and a closely controlled fuel-air ratio maintained.

The igniting device l3 as shown in Figs. 1 and 2, comprises a pair of opposed, arc electrodes 44, transversely mounted through the left end portion of the chamber and spaced a sumcient distance from the left end thereof so that no appreciable diffusion of the spray with air will occur prior to the spray reaching the electrodes. The electrodes 44 are slidably mounted in insulators 45 which are fixed in opposed apertures 46 formed through the double walls of the propagation chamber 5, and the insulators are suitably sealed thereto to prevent leakage of water from the cooling jacket I. The electrodes are preferably so mounted that the space between their ends will be substantially bisected by the axis of the spray cone trajectory in order to provide uniform ignition and their ends are suitably spaced and squared to provide a relatively wide are. It is desirable that the electrodes be made of copper or other electrode metal of similar characteristics, rather than carbon, in order to keep burning of the ends of the electrodes at a minimum, since burning of the ends would increase the spacing therebetween and thereby change the characteristics of the arc.

In order to ignite the are between the elecg trodes, the electrodes may be connected through a switch 41 to a suitable current supply 49. It is desirable that rather than use a manual system of arcing wherein the arc would be struck by closing the switch ll and bringing the electrode ends together, that a high tension spark be initially supplied from the current supply 49 to strike the are which may thereafter be maintained by a much lower voltage current. In this way movement of the electrodes whereby the spacing between the electrodes might be disturbed may be avoided. Suitable time delay means 51% may be associated with the switch 41 to automatically hold the circuit closed for a predetermined period of time.

The propagation of the flame after ignition, for a given distance from the point of ignition at the are back toward the atomizer I2, is indicated by means of a thermocouple, the sensitive element 52 of which is located at such given distance within the propagation chamber between the igniting device I3 and the nozzle II. It is desirable that the sensitive element 52 be located approximately on the axis of the trajectory of the spray, and that the spacing between the sensitive element and the ignition device be sufficient to avoid any possibility of actuation of the thermocouple from the heat of the arc. Two leads 53 connect the sensitive element to an indicating device 56, conveniently located adjacent the chamber.

In the operation of this apparatus in testing a particular fluid for inflammability, a quantity of the fluid is placed in the burette 35, the valve 36 being closed, and the valves 26 and 21 are opened to the desired initial adjustment. Gas is allowed 'to flow through the atomizer for a period of approximately 45 seconds to permit the flow of gases to settle down to a constant rate and to obtain adequate mixing of the gases in the mixing chamber l6. Thereafter the valve 36 of the burette is opened or if the automatic feeding device shown in Fig. 4, is employed, this device is then actuated to start the flow of fluid from the syringe 37 into the atomizer. The spray of gas and fluid into the propagation chamber is permitted to continue for a sufiicient period to completely fill the propagation chamber with the atomized spray. Although the end of the propagation chamber is open, due to the length of the chamber, no appreciable diffusion or dilution with atmospheric air occurs, as hereinbefore explained, if the gas flow is made adequate. What willconstitute an adequate rate of flow for a particular case must be determined experimentally. After continuous spraying for a sufficient period, the switch 4'! is closed causing an arc to be struck between the electrodes i i. If sufiicient oxygen is being supplied, the mixture in the propagation chamber will be caused to burn, and a flame propagated toward the atomizer nozzle ll. When the flame reaches the thermocouple sensitive element 52, the thermocouple will indicate the presence of the flame. produce such an indication on the thermocouple indicator 56 is a direct indication of the inflammability of the fluid being tested. By starting with one hundred percent nitrogen and increasing the oxygen concentration, by aid of the metering control devices 26-21 and indicators 55-56, to vary the ratio of oxygen to nitrogen in a series of successive experiments, a minimum percentage of oxygen may be reached where the fluid under test will propagate a flame just enough to reach back to the thermosensitive element and give a positive test. By comparing this critical oxygen percentage with that required for other fluids, a relative inflammability evaluation of the fluid under test with respect to other fluids is obtained.

After each inflammability test, it is desirable that the propagation chamber be thoroughly cleaned. In order to facilitate this an air line 55 may be connected to the. atomizer l2 and air under pressure allowed to pass through the cham- 5 ber for a substantial period.

While but one embodiment of this invention has been shown and described it will be understood that many changes and modifications may be made therein without departing from the 55 spirit or scope of the present invention.

The invention shown and described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any 60 royalties thereon or therefor.

What is claimed is:

1. In an apparatus for testing the inflammability of a fluid, a propagation chamber, means for injecting a mixture of the fluid to be tested with 65 a non-combustion supporting gas and a combustion supporting gas into said chamber, means spaced from said injecting means and located within said chamber for igniting said mixture, and thermosensitive means located intermediate 70 said injecting means and said igniting means for indicating propagation of flame from the igniting means to a given distance toward the injecting means upon said mixture being ignited, and metering control means for providing determin- 76 able ratios of mixtures of said gases to said in- The oxygen concentration required to jecto'r means, whereby may be found a ratio resulting in a propagation of the flame to said given distance.

2. In an apparatus for testing the inflammability of a fluid, a propagation chamber, an injecting means, metering control means associated with said injecting means for providing determinable ratios of a non-combustible gas and a combustion supporting gas to said injecting means, means associated with said injecting means for supplying a controlled amount of a fiuid to be tested to said injecting means, ignition means spaced from said injecting means and located within said chamber, and a thermally sensitive element mounted in said propagation chamber between said i nition means and said injecting means for indicating the propagation of a flame in said mixture to a given distance from said ignition means.

3. In an apparatus for testing the infiammabiL- iity of a fluid, a propagation chamber, a source of non-combustible gas, a source of combustion supporting gas, means connected between said :sources and said propagation chamber for mixiing said gases, means associated with said propagation chamber for injecting said gases into :said chamber, means associated with said injecting means for combining a quantity of the fluid to be tested with said gases, ignition means spaced from said injecting means and located within said chamber, and means mounted within said chamber between said ignition means and said injecting means for indicating the propagation to a given distance toward said injecting means of a flame resulting from the ignition of said mixture, and metering control means connected between said sources and said mixing means for providing determinable ratios of said gases to said mixing means, whereby may be found a ratio resulting in a propagation of the flame to said given distance.

i. In an apparatus for testing the inflammability of a fluid, a propagation chamber, means for cooling the wall of said propagation chamber, a

nected between said sources and said mixing means for providing determinable ratios of said gases to said mixing means, whereby may be found a ratio resulting in a propagation of the flame to said given distance.

5. In an apparatus for testing the infiammability of a fluid, a propagation chamber, a source cinch-combustible gas, a source of combustion supporting gas, metering control means assowrciated with said sources for providing determinsource of non-combustible gas, a source of combustion supporting gas, means connected between said sources and said propagation chamber for mixing said gases, means associated with said propagation chamber for injecting said gases into said chamber, means associated with said injecting means for combining aquantity of the fluid to be tested with said gases prior to injection, ignition means spaced from said injecting means and located within said chamber, and means mounted within said chamber between said ignition means and said injecting means for indicating the propagation to a given distance toward said injecting means of a flame resulting from the ignition of said mixture, and metering control means conable'ratios of said gases, means connected between said metering control means and said propagation chamber for mixing said gases, means associated with said propagation chamber for inject- ;ing said gases into said chamber, means associated with said injecting means for combining a quantity of the fluid to be tested with said gases, ignition means spaced from said injecting means and located Within said chamber, and means mounted within said chamber between said ignition means and said injecting means for indicating the propagation to a given distance toward said injecting means of a flame resuiting from theignition of said mixture.

6. A method of testing the inflammability of a fluid which comprises in ecting a mlxture of measured quantities of the fluid to be tested, a non-combustion-supporting gas and a combustion-supporting gas into a propagating chamber, starting with an insufficient quantity of the combastion-supporting gas to support combustion, subjecting the mixture to an igniting temperature in the propagating chamber at a point spaced from the point of injection and repeating these steps with increased quantities of the combustion supporting gas to attain an ignitable mixture and working up to a determinable amount of the latter gas to a quantity suiiicient to propagate a flame from the point of ignition a given predetermined distance toward the point of injection.

MILES V. SULLIVAN.

JOHN K WOLFE.

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

UNITED STATES PATENTS Number Name Date 1,554,993 Ettele Sept. 29, 1925 1,625,277 Packard Apr. 19, 1927 1,627,204 Ruben May 3, 1927 1,779,569 Thompson Oct. 28, 1930 1,915,427 Kowalewski June 27, 1933 2,058,522 Smyly Oct. 27, 1936 2,311,868 Rhoads Feb. 23, 1943

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