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Ceramic nozzle. The cracking in the convergent section, which was caused by thermal shock, can be seen. No appreciable erosion at the throat and no cracking in the divergent section occurred.
The same ceramic nozzle after run 2 sec additional operation, near stoichicmetric mixture ratio, estimated gas temperature. No further cracking occurred and the condition of the nozzle was little changed by the second run.
The nozzle apparently withstood the second thermal shock without further damage. The effect of further operation on erosion or cracking was not investigated. Results of a similar nature are presented in reference 1 where it was observed that a ceramic lining for a combustion chamber cracked but did not fall apart during operation. These results indicate that a ceramic rocket-nozzle liner can be successfully operated after it has cracked if it is properly supported.
The effect of cracking of the ceramic nozzle on the performance of the rocket was not accurately determined because the operating conditions of the engine and the composition of the propellants were not accurately controlled. The experiments do indicate, however, that no large effect on performance resulted from the cracking of the nozzle. The extent to which cracking of the rocket nozzle affects engine performance depends upon the location and the size of the cracks.
Cracks that result in an enlargement of the nozzle throat would obviously reduce engine perLormance. Properties of ceramic materials usually considered for high- temperature application are strength, melting point, thermal con- ductivity, heat capacity, resistance to fracture by thermal shock, and resistance to erosion and oxidation. In the application of ceramics for rocket-nozzle or combustion-chamber liners, strength of the material is unimportant when the material backing the ceramic is designed to withstand the operating pressures.
Resistance to thermal shock of ceramic materials is dependent upon strength, coefficient of thermal expansion, modulus of elasticity at fracture, thermal conductivity, and specific heat on a volume basis. Resist- ance to fracture by thermal shook is unnecessary for applications in which proper support of the ceramic nozzle or the liner prevents damage that would affect performance.
In such cases, the number of properties to be considered in the selection of a ceramic lining is greatly reduced. Show all pages in this report.Making a K class PVC rocket nozzle
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Kinney, George R. You Are Here: home unt libraries government documents department this report page: 4. These controls are experimental and have not yet been optimized for user experience. Reset Brightness 0.In that time, we have designed non-eroding metallic throat inserts made with pure tungsten, tungsten-rhenium alloys, and tungsten-rhenium alloys doped with hafnium carbide. These materials proved to be very successful through static motor firings which have been predicted through analytical results.
Figure 1 shows an example of the computed stress fields. This figure includes the radial, axial, hoop, and rz shear stresses. Typically, design decisions are based on the computed axial and hoop stresses because they tend to dominate the other stresses and failures are often a result of radial and axial cracks that resulting from these stresses.
Figure 2 shows the computed safety margins for all of the cases analyzed. This resulted in the selection of the braid architecture and part thickness recommended for a static motor firing. Figure 3 shows pictures of the successful static motor test firing. Example of computed stresses fields in CMC nozzle throat showing the computed radial aaxial bhoop cand rz shear stresses d. Calculated margins of safety for the computed axial a and hoop b stresses. We have been involved in this program throughout its duration of two years.
This program focuses on developing ultra-high temperature ceramic materials to survive in more severe thermal-structural and thermal-chemical rocket nozzle environments. To date we have designed the first four rocket nozzles that were successfully tested in the program. These motors employed a tantalum carbide throat material with an external rhenium or tantalum tungsten alloy metallic jacket. The fabrication processes included plasma spraying and hot isostatic processing HIP.
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Kinney and William G. The investigation was conducted on a pound-thrust acid - aniline rocket. The estimated combustion- Gas temperatures for the runs were from to F. Nozzles were mounted in a steel housing, which was attached to the com- bustion chamber. The convergent section of the nozzle cracked during an initial run, but it was operated a second time without further cracking or damage.Urgent driver jobs in bahrain
A thin chrome plating on the internal surface of graphite nozzles was effective in preventing oxidation and erosion that occurred during a run with unprotected graphite. Desirable properties of materials to be used are high strength, low thermal conductivity, high heat capacity, high melting point, and good resistance to thermal shock, oxidation, and erosion.
There are ceramics that satisfy most of these requirements but have a low resistance to thermal shock. Some grades of graphite have good resistance to thenral shock and other desired properties but have a low resistance to oxidation and erosion. Described herein is an investigation of 1 the thermal-shock resistance of a ceramic rocket nozzle containing a high percentage of sillimanite, 2 the usefulness of a ceramic nozzle cracked during previous operation, and 3 the effectiveness in preventing oxidation and erosion of graphite nozzles by chrome-plating the internal surface.
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Copy Citation. Univesal Viewer Copy.Nicholson, Niagara Falls, N. The highly corrosive and erosive conditions existing within devices of the above type required materials of high density and very refractory properties.
Consequently, such structures have been made almost entirely of dense, heavy, refractory substances especially designed to stand up under severe conditions of use with little or no regard or consideration apparently being given to the overall weight of the device although it is also highly desirable, particularly where such structures are used in aircraft, that the weight of the device be kept to a minimum. Other objects and advantages accruing from the present invention will become apparent as the description proceeds.
For example, a castable refractory cement of the type used to seat the dense refractory lining of the combustion chamber and nozzle can be used also to form the exit or tail cone body and, if desired, also a rear portion As a further modification, parof the nozzle body. According to a further feature or modification of the present invention the inner walls of the exit or tail cone can be optionally shielded by encasing the exit or tail cone body in a thin inner frusto-conical metal shell composed of stainless steel or other metal capable of resisting corrosion to the required extent.
Such a stainless steel or other metal shell however is thin enough that it will not add greatly to the weight of the overall device. The combustion chamber, nozzle, and exit or tail cone structures, regardless of their individual structural features, are confined within an external cylindrical metal shell in which the various parts are seated by means of a layer of refractory cement.
In order that the invention may be more fully understood, reference is made to the drawings which depict "ice specific and illustrative rocket motor structures, and parts thereof, embodying various features of the present invention and in which.
Solid Rocket Engines
Figure l is a rear elevational view of a rocket motor structure made in accordance with the teachings of the present invention. Figure 3 is a cross-sectional view similar to that of Figure 2 showing a modification of the present invention in which the exit or tail cone body is shielded by an inner metal shell. Figure 4 is a top plan view of a stainless steel tail cone lining or shell or the type used in constructing the IOCKEiZ motor structure of Figure 3; and.
Another novel reature or the lining structure shown in Figures 1 and 2 is the extension or the lining piece 11 which constitutes the inner cylindrical refractory wall of the combustion chamber a short distance forward so that it also forms a part of the inwardly tapering wall approaching the throat of the nozzle.
This feature of extending the length of the combustion chamber lining piece a short distance forward to form part of the entrance cone of the nozzle presents the fabricating advantage that the nozzle piece 12 is shortened so that its walls at one end are of thicker cross-section and consequently the nozzle can be more facilely formed by pressure molding than is the case when the walls of the nozzle lining piece taper to a relatively thin section at both ends. The nozzle lining 12 is also premolded and prefired and likewise is composed of a very dense and hard, highly refractory material which will satisfactorily resist the highly erosive conditions set up by the fiow of high velocity hot gases through the nozzle.Bay yanlis 2 english subtitles
As shown, the nozzle 12 does not extend the entire distance out to the confining metal shell 15 of the rocket motor but the outer face 14 of the nozzle is tapered inwardly in order to reduce the volume of the molded piece 12 and thereby cut down the weight of the nozzle. As stated before, the combustion chamber lining 11 and nozzle 12 are necessarily composed of a relatively dense, heavy material of high refractoriness. One such material which has been found highly satisfactory for such use is that described in my copending patent application Serial No.
Briefly that material can be described as being composed of granular silicon carbide held together by a bond of boron carbide and boron nitride. The lining 11 and nozzle 12 are seated in a confining cylindrical metal shell 15 by means of a layer 16 of castable refractory cement, such as a hydraulically setting calcium aluminate cement. The seating cement is also poured around the temporary form or core 10 to form the body of the exit or tail cone 17 which is also confined by the metal shell The confining shell 15 is provided with a mounting flange 18 for mounting to a fuel injector head through bolt holes Although a water solution of polyvinyl alcohol is specified as the temporary binder in the above mixture any of those materials commonly used for temporary binders in ceramic mixes, such as dextrin, concentrated waste cellulose sulfite liquors and powders, various resins, waxes and the like, can be used.
The molded nozzle is dried at F. An inlet tube made of graphite is used to pass nitrogen gas into the furnace chamber. A graphite plate, used to cover the top of the furnace, is provided with a hole in the center which serves as a vent for the gases created during the burning operation and also permits temperature readings to be taken of the furnace interior by means of an optical pyrometer.
The furnace is heated to an approximate temperature of C. A nitrogenous atmosphere is provided in the furnace chamber by introducing a stream of commercial grade dry nitrogen gas from a tank under pressure through the graphite inlet tube. Having established an atmosphere of nitrogen within the furnace the furnace is rapidly heated until a temperature of C.
The temperature is then held at O- C. A chemical analysis of a nozzle made in accordance with the above example shows the following composi tion for the fired nozzle:. Assuming that all the silicon is combined with carbon as silicon carbide and that all the nitrogen is present as boron nitride, BN, the following is the calculated composition of the fired nozzle:.
The combustion chamber lining 11 can be similarly made although it has usually been found desirable to form the combustion chamber lining by an edge tamping procedure because of the greater length and relatively thin wall thickness of the molded piece which renders the machine molding of such shapes rather difficult.View cart. How to Make Rocket Nozzle Mix If you look in the end of most black powder rockets, or at the end of a gerb fountainyou'll see a nozzle recessed into the end of the paper tube.
A Nozzle In Paper Tube A nozzle is a mechanical device with an orifice hole in it, which controls and directs the flow of a liquid or gas as it passes through it. Think of the nozzle you put on the end of your garden hose.
It controls the water flow, builds up higher pressure in the hose than would normally be there, and projects the water out in a nice stream. A rocket nozzle does essentially the same thing with the combustion gasses from the motor. This is what propels the rocket skyward.
Typically, the nozzle in a rocket, and the solid plug at the top of the rocket motor's fuel grain, is a rammed hand pounded with a mallet or pressed with a hydraulic or mechanical rocket press mixture of wax, clay, and grog.
Some folks use only clay in their nozzles. One time I pressed a bunch of wheel drivers with only bentonite clay nozzles, here in the Midwest hub of humidity.
Then, when I got out to Gillette, Wyoming, which was so dry my lips started cracking, my nozzles got so loose in the tubes that I could turn them with my finger. I quickly added a ring of Elmer's glue where the nozzle met the tube to secure them. Some folks expect their nozzle apertures to close a bit with the clay's expansion.
So, right before flight, they open the hole up to the correct diameter with a hand-twisted drill bit. Wax makes the clay much less prone to this problem.
Also, the clay alone, when pressed, forms a smooth, glossy surface; and nozzles and plugs have been known to get blown out of the tube by the pressure of the fuel burning.
The grog in this mix really helps the nozzle 'bite' into the side of the tube and resist blowout. The grog also helps the nozzle resist erosion of the hole during motor burn, whereas without the grog, the clay can wear away some and the nozzle aperture hole opens up some during the motor burn, which reduces pressure and thrust.
The technique I use to formulate these ingredients and mix them together is similar to the one David Sleeter recommends in his Amateur Rocket Motor Construction book. I get the wax that I like to use from the canning supplies department of my grocery store.
It reads "Household Paraffin Wax, for canning, candlemaking, and many other uses.Ecu immobilizer delete
They are both very fine, powdered, dry clay. When I first started making rockets, I imagined that 'clay' that should be like putty, or that I had to turn the dry clay powder into a 'play-dough' by adding water. We live and learn. No water is ever added to the clay. Grog is a man-made, sand-like product. It is made from fired pottery, crushed and screened.
Forums Engineering Mechanical Engineering. Right material for ceramic nozzle. Thread starter fahmi. Related Mechanical Engineering News on Phys.
It would help to describe the application and conditions you intend to use this nozzle for. I used to be involved in 'high power' model rocketry until a few years back when the hobby was blackballed by the ATF, the agency that tested and issued permits for handling the higher power stuff.
This was due to concerns that some terrorist would use the hobby motors for nefarious purposes.
Most of the 'reloadable' solid fuel motors I had been familiar with at the time, used machined carbon for the nozzles due to its relatively low cost, high heat resistance and ease of machining.
The single-use motors used some kind of impregnated black phenolic composite for their nozzles. The smallest motors Estes used fireclay, and to my knowledge, pyrotechnics people still use this type of nozzle on the rocket motors that lift their fireworks displays. In my experience I don't remember anyone using ceramics. While the heat resistance of some ceramics may be attractive, most ceramics I'm aware of have poor resistance to mechanical loads. They tend to shatter which could be very dangerous.Ultramet uses chemical vapor deposition to fabricate near-net-shape solid rocket combustion chambers and throats from refractory metals and ceramics.
Rhenium and tungsten offer flight-proven performance in the aggressive thermal and chemical environment of solid rocket chambers and throats. The only ductile material that provides zero erosion with highly aluminized solid rocket propellants is rhenium. These chambers are created by high-volume batch processing, which keeps production costs low.
Thin-wall rhenium chambers manufactured by chemical vapor deposition at Ultramet for tactical propulsion applications. Tungsten throat reinforced with tungsten foam. Tungsten is the material of choice when solid rocket propellant flame temperatures exceed the melting point of rhenium.
With its proficiency in chemical vapor deposition, Ultramet can manufacture tungsten throats as coated parts or freestanding inserts. Next-generation solid rocket propellants will have flame temperatures above the melting point of tungsten, so high temperature ceramics will be required. Ultramet ceramic composites and coatings can also be used to prevent erosion in the exhaust nozzle.
Solid Rocket Engines nellian Solid Rocket Engines Ultramet uses chemical vapor deposition to fabricate near-net-shape solid rocket combustion chambers and throats from refractory metals and ceramics. Refractory Metal Chambers and Throats. Contact an Expert. Refractory Metal Throats Tungsten throat reinforced with tungsten foam. Ceramic-lined Throats Ceramic-lined throat. Explore More Learn More about related products and services. Liquid Rocket Engines.
Solid Rocket Engines. Advanced Propulsion Concepts.
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