Patent Application
20050058572
The present invention provides a hypergolic fuel analytical device. More specifically, a testing device to test the reactive characteristics of hypergolic substances is provided, wherein an oxidizer and reactive fuel/substance are atomized and mixed under pressured gas force, and the reaction characteristics thereof measured for analysis.
Hypergolic fuels are substances which, when exposed to an oxidizer, ignite relatively spontaneously without the need of an ignition source. Traditionally, hypergolic fuels have been used in rocket engines, boosters, missiles, etc. In order to determine which substances are useful as a hypergolic fuel, various characteristics thereof must first be determined. In particular, the ignition delay characteristics of certain hypergolic substances, and combinations of hypergolic substances with oxidizers, must be tested so as to determine the suitability of the substance for use as a hypergolic fuel in a rocket engine.
Conventionally, drop test devices have been used to test hypergolic fuels. With such drop test devices, the oxidizer is usually loaded in a drop generator type device (such as a 100 micro-liter syringe, or a very small burette) while a few drops of fuel are placed in a container placed on a support plate. The oxidizer is then dropped into the fuel, and ignition delay measured.
Ignition delay can then be measured in different ways. One common way to measure ignition delay is through the use of a motion sensor and a photodiode connected to an oscilloscope. For example, as an oxidizer drop hits the crucible and ignites the fuel, the oscilloscope successively picks up the vibration of the crucible from the oxidizer drop hitting the crucible and the light emission from the ignition event. These two signals can be sent to two distinct oscilloscope channels and ignition delay is read directly on the oscilloscope screen.
Prior to running another test, the fuel crucible needs to be replaced. The oxidizer micro-liter syringe also needs to be refilled every two to three tests depending upon its internal volume. The fuel crucible and the oxidizer syringe are usually refilled manually.
Due to the frequency of the reloads, and in order to avoid any accidental contact between the oxidizer and the fuel, two experimenters are needed to perform ignition delay measurements with a drop test device. Furthermore, drop tests devices cannot be remotely triggered. Both experimenters, therefore, have to extra precautions when testing a fuel for which the ignition event “strength” is unknown.
As experienced by users of drop test devices, the cleanliness of the photodiode plays an important role in a test series, as combustion gases deposit on the photodiode and tend to block out the light from the ignition event. It is therefore important to frequently clean the photodiode. The previously mentioned operations usually take a few minutes to perform leading to a relatively slow test rate, e.g., 30 to 50 tests an hour may be performed by two experimenters working together using such a drop test device. The slow test rate inherent to drop devices is of particular importance when performing many tests, as the test repeatability tends to degrade significantly as the test conditions change (room temperature or humidity) and the photodiode gets dirtier.
Issues related to the cleanliness of the photodiode can be avoided by using a high speed video camera to record the ignition event and later derive the ignition delay. However, while high speed video cameras provide a convenient means of measuring ignition delay, their inherent characteristics (internal memory mainly) facilitate the recording of a continuous chain of events rather than a discrete chain of events.
Finally, when using a drop test device, propellants are not atomized, as they would be in a rocket engine injector. In most cases, this leads to ignition delay values much higher those recorded during actual test firings. As an example, when recorded with a drop test device, ignition delay values of a hypergolic fuel developed by the US Navy (Block 0) average around 9 milliseconds, while ignition delay of the same fuel in a rocket engine has been shown to be around 3 milliseconds. The discrepancy between these two values strongly depends on the type of fuel tested, and cannot be theoretically derived.
A two-jet apparatus has been proposed for measurement of ignition delays of hypergolic rocket propellants was previously proposed by Spengler, et al. in a paper entitled “Measurements of Ignition Delays Of Hypergolic Liquid Rocket Propellants”. In the apparatus disclosed therein, unlike the present invention, a liquid is pressurized within an injector unit and released via capillary tubes as a liquid jet into a combustion chamber by opening an oxidizer-side valve and a fuel-side valve in a precise sequence. The droplets of oxidizer and fuel are created by the transformation of the jets kinetic energy into a shear force that breaks the atomic bonds of the liquid jets. Further, each of the above mentioned valves, unlike the present invention, is magnetic, and the duration of the injection must be controlled by precisely opening and closing the valves.
The two-jet apparatus has certain drawbacks. Namely, measurement of combustion events with such apparatus becomes inaccurate as the speed of measurement increases, i.e., timing problems occur with the operation of the valves, no variation in injection angle is possible, relatively high pressure must be maintained in order to get good droplet distribution, and a precise alignment of the two injectors is necessary in order for the streams of oxidizer and fuel emanating from the apparatus to impinge on each other. Most of the breakup occurs when the jets impinge on each other thus reducing their kinetic energy to zero.
Further, if the user wishes to measure a series of combustions in relative succession, fast response valves are needed to attain any sort of accuracy whatsoever, which increases the complexity and cost, and decreases the reliability of the device. In addition, the two-jet apparatus ejects the propellant in relatively large droplet form. In such form, complete combustion is unlikely, leading to a high measuring error (standard deviation).
It is an object of the present invention to provide a hypergolic fuel analytical device which overcomes the problems of the conventional devices, such as described above. Specifically, it is an object of the present invention to provide a device for testing hypergolic fuels and oxidizers, wherein the fuel and atomizer are atomized (as in the true applications thereof). In atomizing the propellants, it is an object of the present invention to provide an apparatus which can measure ignition delay values much closer to the test fire conditions ignition delay values.
Further, it is an object of the present invention to provide a device which may provide a more continuous chain of events (ignitions) than the conventional test devices, so as to efficiently utilize a high speed camera in measuring a chain of hypergolic ignitions.
In order to achieve the object of the present invention described above, in a first embodiment of the present invention, a hypergolic fuel analytical device is provided comprising:
In a second embodiment of the present invention, the hypergolic fuel analytical device of the first embodiment above is provided, further comprising:
In a third embodiment of the present invention, the hypergolic fuel analytical device of the first embodiment above is provided, further comprising an ignition detection means.
In a fourth embodiment of the present invention, the hypergolic fuel analytical device of the first embodiment above is provided, further comprising a programmable computer control means electrically connected to the switching means, wherein testing operation of the device may be controlled thereby.
In a fifth embodiment of the present invention, the hypergolic fuel analytical device of the first embodiment above is provided, further comprising a containment means adjacent the fuel atomization means and oxidizer atomization means, for containment of hypergolic reactions.
In a sixth embodiment of the present invention, the hypergolic fuel analytical device of the first embodiment above is provided, further comprising:
In a seventh embodiment of the present invention, the hypergolic fuel analytical device of the fourth embodiment above is provided, further comprising:
In an eighth embodiment of the present invention, the hypergolic fuel analytical device of the first embodiment above is provided, further comprising a third valve flowably connected to said second valve, and said gas conduction means connected to said third valve opposite said second valve.
In a ninth embodiment of the present invention, a hypergolic fuel analytical device is provided comprising:
a-11d are high speed photographs of the hypergolic reaction of Block 0 (22% manganese acetate tetrahydrate in methanol solution (w/w)) and 97% hydrogen peroxide, as described in Test Example 1.
a-12f are high speed photographs of the hypergolic reaction of Block 0 and 97% hydrogen peroxide, as described in Comparative Test Example 1.
The hypergolic fuel analytical device of the present invention comprises atomizing nozzles to disperse separate liquid streams of oxidizer and hypergolic fuel into droplets. These droplets form two sprays that cross each other and react. The Two-Jets Apparatus uses capillary tubes to inject liquid jets into a combustion chamber. The droplets are created by the transformation of the jets kinetic energy into a shear force that breaks the atomic bonds of the liquid jets.
The sprays generated with the device of the present invention can be defined as aerosols; mixtures of air and dispersed liquid (whereas jets, such as are created with conventional devices, are purely liquid). Aerosols are more beneficial than jets in measuring ignition delay because they enhance mass transfer and mass distribution. Mass transfer is improved, thanks to the transformation of a liquid into a vapor. Mass distribution is enhanced because the liquid/vapor is spatially spread throughout the region of interest.
In the case of hypergolic propellants, the improved mass transfer and mass distribution provided by the aerosols (sprays) allow for the liquids of interest to react with each other immediately after contact. All of the kinetic energy imparted to the liquids is used to get droplets to hit (impinge upon) each other with the highest efficiency possible. In contrast, when jets impinge on each other, part of the kinetic energy imparted to the liquids is used to break up the jets into droplets. The droplets then “use” the remaining kinetic energy to travel and impinge on each other.
Thus, the pressure required to get a good droplet distribution (large number of small droplets) is much lower with the hypergolic fuel analytical device of the present invention than it would be with any apparatus using the impingement of two-jets to created droplets. For example, the present device has been shown to provide repeatable results with pressures as low as 15 psig, whereas a conventional two-jets device may require as much as 50 psig of pressure to achieve reasonable jet breakup.
Further, the pressures required by a two-jets device are more dependent on mass flow rate and orifice diameter than with the present invention. In addition, the improved mass transfer and mass distribution provided by aerosols lead to faster mixing in turn leading to faster ignition and better test reproducibility.
In the first embodiment of the present invention, as illustrated in
An oxidizer atomization means 35 is flowably connected to the first gas lead 31, and a fuel atomization means 36 is flowably connected to the second gas lead 32. An oxidizer supply means 61 is flowably connected to the oxidizer atomization means 35, and a fuel supply means 63 is flowably connected to the fuel atomization means 36.
In the structure described above, when desiring to test the performance characteristics of a hypergolic fuel, fuel is fed from the fuel supply means 63 into the fuel atomization means 36, and oxidizer is fed from the oxidizer supply means 61 into the oxidizer atomization means 35. The switching means 45 then, or simultaneously, activates the first valve 13, so as to open the first valve 13 and fill the reservoir 25 with compressed inert gas. The switching means 45 may then activate the second valve 15, so as to open same. This action acts to release the compressed inert gas from the second valve 15 into the oxidizer atomization means 35 and the fuel atomization means 36, via the first gas lead 31 and the second gas lead 32.
The simultaneous rush of the compressed inert gas through the fuel atomization means 36 and the oxidizer atomization means 35 acts to spray the hypergolic fuel and the oxidizer into a predetermined intersecting spray pattern 79, as shown in
The oxidizer atomization means 35 likewise may be provided with an oxidizer atomization adjustment apparatus, wherein the oxidizer atomization means 35 is adjustably connected with the oxidizer atomization means adjustment apparatus 57. For example, as shown in
In testing the ignition characteristics of a fuel or oxidizer, adjustment of the angle of intersection of the two components may produce varying ignition test results. The fuel atomization means adjustment apparatus 59 and the oxidizer atomization means adjustment apparatus 57 allows a user of the device to control the flow pattern of the fuel and oxidizer, i.e., the intersection angle of the fuel and oxidizer. Thus, various flow patterns may be tested, so as to determine the most desirable flow pattern.
Hypergolic fuel ignition processes occur in sub-second intervals. As such, to accurately record the ignition characteristics of a hypergolic fuel, the ignition thereof with an oxidizer must be electronically observed using recording equipment. The present invention provides an ignition detection means 40, as illustrated in
The ignition detection means 40 may optionally include detection means such as heat, energy and light detection means. The data produced by the ignition detection means 40 may be used to compute, for example, the ignition delay inherent in a particular hypergolic fuel/oxidizer mixture. Such data is very important in the determination of the usefulness of such a component combination in highly specific applications, such as rocketry.
In a further embodiment, the hypergolic fuel analytical device of the present invention may comprise a programmable computer control means for controlling the operation of the device. Such a computer control means (not illustrated in the Figures herein) is electrically connected to the switching means 45, so as to be capable of controlling the input and output of compressed gas into the device system via the control of the first valve 13 and the second valve 15. Such automation of the device may enable repeated, extremely quick testing of a hypergolic fuel, much faster than is humanly possible.
In a sixth embodiment of the present invention, as shown in
Likewise, an oxidizer supply control means 71 may be provided in flowable connection with the oxidizer supply means 61 and the oxidizer atomization means 35, so as to control the supply of oxidizer fed to the oxidizer atomization means. As with the fuel supply control means 72, the oxidizer supply control means 71 may be in flowable connection with one or more oxidizer supplies 82, so as provide the user of the device of the present invention with the capability of testing one or more different types of oxidizers as desired.
To further automate the process, as well as providing higher repeatability, the programmable computer control means mentioned above may be electrically connected with the fuel supply control means 72 and the oxidizer supply control means 71, so as to control the supply of fuel and oxidizer fed to the fuel atomization means 36 and the oxidizer atomization means 35 from the fuel supply means 63 and oxidizer supply means 61, as well as allowing the user to preselect which type of fuel and/or oxidizer to test, in which order to test the combinations, the speed of testing, etc.
Thus, a user of the device of the present invention can control the switching means 45, the fuel supply control means 72, the oxidizer supply control means 71 and the ignition detection means 40 via the programmable computer control means, thereby automating the entire testing process of a hypergolic fuel. Such control is achieved by electrically connecting the computer control means, such as a personal computer, with the switching means 45 (such as an electrical switch), the fuel supply control means 72 (such as an electric pump), the oxidizer supply control means 71 (such as an electric pump), and an ignition detection means 40 (such as a video camera).
The programmable computer control means is then, for example, programmed to, in a first step, feed a specified amount of fuel and oxidizer to the fuel atomization means 36 and oxidizer atomization means 35, in a second step, to pressurize the reservoir 25 via the first valve 13 and switching means 45, in a third step, to open the second valve 15 via the switching means 45, thus spraying the fuel and oxidizer into contact with each other and, in a fourth step, to simultaneously activate the ignition detection means 40 (such as a video camera) to record the ignition process.
Unlike conventional techniques and devices, the device of the present invention can provide for repeated testing in an extremely fast manner, as the device needs no cleaning between tests. Further, if desired, in a further embodiment of the present invention, as shown in
As described in the fifth embodiment of the present invention, and as illustrated in
Thus, the present invention provides a device capable of quickly and repeatedly testing the ignition of a hypergolic fuel and oxidizer. In contrast, whereas the conventional two-jet apparatus utilizes two magnetic valves to inject two ignition components, the present invention utilizes a simpler, more precise and more reliable system having at least one electronically controlled valve to inject pressurized gas into the fuel and oxidizer so as to atomize same, repeat such test repeatedly in a short period of time, and record and analyze the results of such tests, thus achieving the unexpected results found herewith.
However, the present invention may, as shown in
In a further ninth embodiment of the present invention, as shown in
The processes leading to ignition of a hypergolic fuel and an oxidizer are, generally, the injection of propellants (hypergolic fuel and an oxidizer) from the device, the impingement of the propellants (contact with each other), the visible reaction of the propellants, and the ignition of the propellants, as graphically illustrated in
Specifically, as shown in
1. Define as time=0, the first step corresponds to the time at which the propellants are ejected from their container. In the case of the drop-test, only one propellant is set in motion at that time. In the case of a two-sprays or two-jets device, all propellants are set in motion at that time (i.e., time=0).
2. The second step corresponds to the first contact between the propellants.
3. The third step corresponds to the first visible sign of reaction between the propellants, typically a “cloud” of reaction vapors.
4. The fourth and final step corresponds to the first visible sign of ignition.
As shown in
With the conventional two-jets apparatus, the mixing of the propellants is improved, but ignition is still delayed by the time required to transform the jets into droplets and the time for those droplets to impinge on each and react. However, as illustrated in
Further, as illustrated in
The present device also allows for better test repeatability than the conventional two-jets devices and conventional drop test devices. As shown in
Typically, the test results obtained with a conventional drop test device follow a relatively wide Gaussian distribution. The smallest ignition delay value is typically much lower than the distribution peak value. In contrast, ignition delay tests with a spray device, such as the present invention, and conventional two-jets devices, are typically more repeatable than those performed with drop test devices. The Gaussian distributions are usually centered around a value very close to the smallest measured ignition delay value. However, it was unexpectedly discovered that the superior mixing of the propellants due to the spraying of same from atomizing/spray nozzles on the device of the present invention substantially outperformed the conventional two-jets apparatus.
Approximately 0.75 ml of Block 0 (22% Manganese Acetate Tetrahydrate in Methanol solution (w/w)), a hypergolic fuel, was poured into the fuel supply means of the present device, and approximately 0.75 ml of 97% hydrogen peroxide, an oxidizer, was poured into the oxidizer supply means (the hypergolic fuel and oxidizer being collectively referred to as the “propellants”) of the hypergolic fuel analytical device of the first, second and fifth embodiment of the present invention. A compressed gas source containing argon was attached to the device. The inert gas (argon) pressure was set at 15 psig.
Thereafter, the device was activated so as to spray the propellants into the containment means and, simultaneously, record the ignition process with an ignition detection means (a high speed video camera).
As shown in
Note: The 0.75 ml of oxidizer and 0.75 ml of fuel allowed performance of approximately 10 ignition delay tests. Thus, each test required approximately 0.075 ml of fuel and oxidizer per ignition delay test.
Approximately 0.02 ml of 97% hydrogen peroxide, an oxidizer, was placed in the dropper portion of a conventional drop test device. Then, approximately 0.02 ml of BLOCK 0 (22% Manganese Acetate Tetrahydrate in Methanol solution (w/w)), a hypergolic fuel, was placed in the crucible of said drop test device. Thereafter, the BLOCK 0 was dropped into the oxidizer and, simultaneously, the ignition process was recorded with an ignition detection means (a high speed video camera).
As shown in
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