Final Report-High Velocity Gas Gun - Welcome to CUNY - The City

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Final Report-High Velocity Gas Gun ME 474 1 Abstract The second part of senior design involves the building of the prototype conceptualized in the first semester. The prototype is a material testing apparatus, made to test composite materials that will be used in turbine blades. Projectiles are fired unto the test specimen thereby simulating three- point bending. The projectiles of diameters ¼” – 1” will achieve the velocity of 1000 m/s or greater. The device consists of a pressure system, release system and a data acquisition sub-system. The working fluid is compressed helium. The working fluid is stored in a reservoir to achieve working pressure of 2000 psi then it is released by the solenoid onto the diaphragm. The diaphragm will rupture on a predetermined pressure and launch the projectile to the environmental chamber at the desired velocity. The test specimens will be held by two vertical clamps. Analysis of the particle or test specimen is not part of the scope for this project.

Transcript of Final Report-High Velocity Gas Gun - Welcome to CUNY - The City

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Abstract The second part of senior design involves the building of the prototype conceptualized in the first semester. The prototype is a material testing apparatus, made to test composite materials that will be used in turbine blades. Projectiles are fired unto the test specimen thereby simulating three- point bending. The projectiles of diameters ¼” – 1” will achieve the velocity of 1000 m/s or greater. The device consists of a pressure system, release system and a data acquisition sub-system. The working fluid is compressed helium. The working fluid is stored in a reservoir to achieve working pressure of 2000 psi then it is released by the solenoid onto the diaphragm. The diaphragm will rupture on a predetermined pressure and launch the projectile to the environmental chamber at the desired velocity. The test specimens will be held by two vertical clamps. Analysis of the particle or test specimen is not part of the scope for this project.

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Nomenclature Symbol Name PA Atmospheric Pressure

P Reservoir pressure (working pressure)

VC Control Volume

V Volume of Reservoir

VR Volume of gas at Rupture disk

PR Rupture disk pressure

A Cross-sectional area of fittings between rupture disk and reservoir

L Distance between rupture disk and reservoir

M Mass of projectile

ν Velocity of projectile

UK Kinetic Energy of projectile

UG Energy released by gas

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Introduction For research, granted by National Aeronautics and Space Administration (NASA) and the United States Army, Professor B. Liaw requires an apparatus for high velocity impact testing. The apparatus is going to be used to test composite materials to be used in turbine blades; the simulation is three-point bending on the blade. The system must project steel spheres of ¼” - 1” diameters with the velocity of at least 1000 m/s to a stationary test specimen. A complete system has to be designed: the pressure system, release mechanism, barrel and data acquisition. The final length of the entire system must not exceed 16ft. because of laboratory space. The system was designed employing a process of problem definition, team assemble, budget and schedule layout, research, concept development, final concept review, prototype development and testing, then a final presentation. Both physical prototype and computer models were made a part of the process. The final design called for the use of helium discharged at 2000 psi from a reservoir. For the release mechanism a solenoid and diaphragm. Optoelectronics interfaced will LabView for the data acquisition. Stainless steel flanged piping and smooth bored barrel will be utilized. The system will mostly involve ready-made parts that are compatible to the product design specification.

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Problem Statement We need to optimize the energy held by a fluid to launch projectiles.

Objective The objective in this project is to build a high velocity impact testing research apparatus resembling the schematic shown above in Fig.1. The apparatus that NASA built achieved velocities between 220 to 440 m/s. We need a velocity of 1000 m/s or greater. The project must be approached by using the mechanical design process.

Fig.1-Schematic of a high velocity impact testing apparatus (NASA)

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Product Design Specification

1. Project steel spheres of ¼”-1”diameters with velocity > 1,000 m/s 2. Be < 16ft due to laboratory space. 3. Contain a release device with rapid response time. 4. Involve a pressured gas subsystem for the working fluid. 5. Included data acquisition for velocity measurement of the projectile.

Our PDS is govern by the 1000m/s or greater velocity. The projectile itself may even change as part of experimentation but the velocity is crucial.

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Design Concepts Pressure System The two design concepts available to us are the two stage pressure system, and the single stage pressure system. Fig.-Two stage pressure system Hot burning gas from gunpowder drives a piston which in turn compresses hydrogen gas in the second stage. High pressure is developed, valve is ruptured and the projectile is accelerated down the barrel. For the single stage pressure system, the pressure from a high pressure tank is used to drive the projectile. Helium gas was chosen because it is safe to handle, non-flammable and because of its properties such as:

Compressibility: Helium gas is very compressible; as a result, it produces high energy when it undergoes adiabatic expansion.

Low boiling point: Has a boiling point of –195oC, as it evaporates as soon as it is released to the atmosphere.

Inert Gas: It does not react with the material it is contained in. This is critical because at very low temperature most material becomes brittle, and any reaction with the gas will result to failure.

Easy to detect when leaked. Release Mechanism The basic function of the trigger mechanism is to restrain the reservoir pressure while there is no testing and also and also to release the working pressure so that the projectile is launched with maximum efficiency and safety. In order to accomplish this task two basic

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components needed are (1) a test switch and (2) a release mechanism. Both tasks could be performed with one single component, however, in order to increase the level of safety and control over the test, separate components will be used for each role. The main differences between the test switch and the release mechanism are that the test switch needs to be remotely operated while the release mechanism doesn’t and that the release mechanism needs to “release” the working pressure almost instantaneously while the switch doesn’t need to be as fast operating. Components that could perform the task as release mechanism are (1) rupture disks (2) mechanical systems and (3) solenoid valves. Solenoid valve Solenoid valves are electrically operated devices used to control the on / off or directional control flow of air, inert gas, water, light oils and other clean flowing media. They do not regulate flow. Solenoid valves consist of two main elements, an electrical coil in the solenoid, and a valve body or pressure vessel. When the solenoid is energized by an electrical signal, the plunger / diaphragm opens or closes a valve orifice, which gives the valve on / off or directional control of the media. When selecting a solenoid valve, it is important to consider safety, reliability, media compatibility and suitability for the operating environment when selecting the best product for a given application. Rupture Disk Rupture disks are thin metallic devices shaped in the form of a disk that is designed to burst predictably when pressure within a certain range is applied. To achieve this level of predictability on side of the disk is often scored so that it ruptures in the middle. These devices are good for pressure safety systems and other such industrial and laboratory uses. Test Switch (Solenoid Valve) Release Mechanism (Rupture Disk)

Solenoid Valve

Rupture Disk Quick change Rupture disk holder

Moderately fast operating for both opening and closing.

Should be easily changed

Normally closed Non-fragmenting 110/220 volt electrical source Reliable at operating temperature Maintains reliability over a Long life cycle Reliable at operating pressure Diaphragm should be compatible with Helium gas

Low performance tolerance (for burst pressure)

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Data Acquisition Data acquisition purpose is to measure a projectile speed at the gun nozzle exit. Various methods are utilized for data acquisition; however, these were narrowed down to Photography, Infrared Ballistic Screens, and Optoelectronic devices. The customer design specifications for the data acquisition device are: 1. 2-3 emitter-detector pairs mounted at the exit of the nozzle 2. Using sensors along with the LabVIEW software, projectile velocity will be calculated 3. A sensor with a rapid response time is required Initially our customer, Professor Liaw wanted to utilize optoelectronic devices for data acquisition, so his design specifications were based on this method. Optoelectronics is the term for the combined technologies of optics and electronics. Optoelectronic devices are electronic components that emit or detect optical radiation. An emitter is a light-emitting diode (LED) or an infrared emitting diode (IRED), and a photodiode sensor is a detector that detects the optical radiation. This concept won because of a response time of 1 nanosecond. A higher response time will give a more accurate projectile velocity. Measuring the projectile velocity using this concept involves a basic technique. Velocity is calculated using the equation

v = d/t where, v = velocity of projectile d = distance between point a and point b t = time it takes for projectile to travel between point a and point b Infrared light from the lasers or emitters, spaced at measured intervals, passes across the path the projectile must travel when it exits the gun. Each laser shines onto a photodiode sensor or detector. The detector will emit a voltage proportional to the amount of light hitting the detector. As the projectile intercepts the laser beam it shadows the detector causing a jump in voltage, which is recorded on the LabView software along with the time it takes the projectile to reach that detector. By checking the front panel of the LabView software, the time it takes the projectile to travel between any two lasers or sensors can be determined easily. Since the distance between any two lasers is known, the projectile velocity can be calculated by using the equation (v = d/t) Ballistic Screens Ballistic screens are sheet of lights positioned at precise interval. As projectile breaks each ballistic screen, the computer records time from firing to determine projectile speed. Ballistic screens detect projectiles as small as 0.17 calibers at low velocity, and sensitivity increases with larger projectiles. Photography Photography involves a digital high speed camera taking snapshot of the flying projectile at speeds up to 5,000 frames per second. The snapshots taken have very high resolution.

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Barrel The barrel is final length of piping that the projectile will encounter. The barrel ensures that the projectile impacts on the test specimen accurately. The barrel also mandates the correct acceleration of the projectile before it becomes airborne. A barrel with a length no more than 5 ft. long with an inner diameter of no more than ½”, ¼” and ⅛” will fulfill the targeted requirements. Barrel should not deform due to high pressure, friction by the projectile and temperature changes; it is non-expendable and should last through out numerous tests. There were three different types of barrel configurations to choose from, sabot, screw and smooth bore. Screw bore Screw bore barrel configurations are similar to those used in long range rifles. They are very accurate because it makes projectile (bullet) spin prior to impact, thus reducing the chance of the bullet moving from “side to side” before impact. The types of barrels are costly because they are difficult to manufacture for the apparatus. There is also high friction (heat transfer) on the projectile. Sabot The sabot is a “shoe” that cradles the projectile down the barrel. The bullet is adhered to the sabot and there is a stopping mechanism at the end of the gun for the sabot. The bullet looses adhesion once the sabot is stopped and it is then propelled forward. This system is also accurate but more complex. There is also more mechanical design involved and therefore more room for mechanical failure and deformation on the sabot when it is stopped. There is a lower friction than the screw bore but complexity could be avoided. Smooth Bore Smooth bore barrel are similarly used in hand gun and air pistol design. They are not as accurate as the screw bore but this can be over come by placing the barrel closer to the target or using a longer barrel. It is less costly and complex than the fore mentioned configurations. The tolerances (parallelism) on this barrel must be high to assure optimization of the working pressure, accuracy and reduced friction. Decision Tree for Gas Gun Design

Gas Gun

Energy Source Trigger Mechanism Barrel Data Acquisition

Mechanical System

Rupture Disk

Solenoid Valve

Single Stage

Gas Pressure System

Helium

Smooth Bore

Screw Bore

SabotTwo Stage

Photographic

Nitrogen

Infrared Ballistic Screen

Optoelectronic

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Analysis and Testing Working Pressure Calculations The pressure analysis was done using the laws of thermodynamics and physics. This enabled us estimate the maximum velocities corresponding to different pressure that can be obtained in the system. This relationship was obtained by relating the maximum theoretical velocities to the input parameters, such as the mass of the projectile, input pressure and the input volume. This is expressed mathematically below.

Vmax = f (m, p, v) In order to obtain the above relationship, using thermodynamics and physics, certain assumptions were made. These assumptions are:

Negligible barrel friction No air resistance inside the barrel( vacuum) Energy is conserved. All the energy released by the gas is transmitted into the projectile Isothermal, and Adiabatic condition in the system

From thermodynamics, a gas contained in a tank undergoes adiabatic expansion and releases energy. This energy is given by the equation below:

G

KK

A UPp

KPV

=⎥⎥

⎢⎢

⎡⎟⎠⎞

⎜⎝⎛−

−1

11

where, P = Gas pressure PA = Atmospheric pressure V = Volume of gas in test cylinder K = Ratio of specific heat = 1.6667 UG = Energy released by the gas From physics, the kinetic energy of a moving body is given by:

2

2mvUk =

where, m = mass of projectile UK = kinetic energy of the projectile ν = maximum velocity of the projectile

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As previously assumed, if all the gas energy released is transmitted onto the projectile, then; UK = UG and the velocity is calculated. CASE 1 (L ≈ 0; VC = V : PR = P ) The sample calculation was done, using ¼" , ½", & 1" diameter spherical steel ball.

m = ρ * VP

ρ = Density of steel 7860 (kg/m3)

VP = 34 π*R3 = volume of projectile : R = radius of spherical projectile

Results are tabulated below. Pressures producing different velocities

pressure v1/2 v1/4 v1 (psi) m/sec m/sec m/sec 100 256.2765 726.1526 90.60742200 398.6629 1129.601 140.9486300 507.7217 1438.616 179.5067400 599.719 1699.288 212.0327500 680.8393 1929.14 240.713600 754.2371 2137.111 266.6631700 821.7824 2328.499 290.544800 884.6924 2506.752 312.786900 943.8123 2674.267 333.68811000 999.7578 2832.787 353.46771100 1052.993 2983.629 372.28941200 1103.88 3127.815 390.28061300 1152.706 3266.161 407.54311400 1199.703 3399.326 424.15911500 1245.064 3527.855 440.19651600 1288.949 3652.202 455.71231700 1331.494 3772.753 470.75431800 1372.816 3889.837 485.36371900 1413.014 4003.738 499.5762000 1452.176 4114.703 513.4219

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Estimated velocities for different diameter projectile Vs pressure

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 500 1000 1500 2000 2500

pressure( psi)

velo

city

(m/s

ec)

Series1

Series2

Series3

1/4

1

1/2

The above graph gives the velocities when ¼" , ½", & 1" diameter steel spherical balls are subjected to different pressures. Tracing the pressure up to the desired cure, the maximum theoretical velocity is found. CASE 2 (VC = VR) The pressure at the rupture disk has to reach the rated pressure of the disk for it to burst. If this rated pressure is not reached, gas energy will not be released to the projectile. The pressure at this position was, therefore analyzed, to enable us feed the system with the right amount of pressure. At the rupture disk, we have a new control volume and the volume is given as:

VR = V + A*L where, V = Volume of test cylinder A = Area of cross section(s) of fittings between cylinder and rupture disk L = Distance between cylinder and rupture disk From thermodynamics:

KRRVP = PVK

PR = K

RVVP ⎟⎟

⎞⎜⎜⎝

⎛ = Pressure at rupture disk

For our design VR = 1000cc & V = 500cc. Using a 1/2-inch diameter spherical steel ball, PR was calculated at different input pressure P. Result obtained are tabulated below, and a graph also plotted

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Rupture disk pressure Vs Cylinder pressure

y = 0.315x - 9E-13

0

100

200

300

400

500

600

700

800

900

1000

0 500 1000 1500 2000 2500 3000 3500

Cylinder pressure(psi)

Rup

ture

dis

k pr

essu

re(p

si)

Series1Linear (Series1)

Slope = 0.315 (If desired, adjustment can be made for higher pressures using the slope) The above graph relates the rupture disk pressure to the input pressure. For example, a rupture disk that is rated 700 psi, will require about 2200 psi of input pressure to rupture. Having determined the right input pressure, the graph below can be used to approximate the maximum velocity of the projectile.

P PR (psi) (psi) 100 31.49714200 62.99427300 94.49141400 125.9885500 157.4857600 188.9828700 220.48 800 251.9771900 283.47421000 314.97141100 346.46851200 377.96561300 409.46281400 440.95991500 472.45711600 503.95421700 535.45131800 566.94851900 598.44562000 629.94272100 661.43992200 692.9372300 724.43412400 755.93132500 787.42842600 818.92562700 850.42273000 944.9141

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Velocity Vs Rupture disk pressure

0

500

1000

1500

2000

2500

0 500 1000 1500 2000 2500

Pressure(Psi)

Velo

city

(m/s

)

Series1Series2

1000cc

500cc

This is done by tracing the 700psi of pressure to 1000cc (VR) curve, and reading-off the corresponding maximum velocity, which equals 1200m/sec. Finite Element Analysis on Barrel The Barrel was the only component of the apparatus that was design entirely. In order to ensure that it could withstand the pressure of the working fluid finite element analysis was utilized. The material (416 SS) and its properties were applied in Pro/Mechanica 2001. One end was constraint to simulate attachment to the rest of the system. Then, a pressure of 3000 psi was applied to the inside of the barrel

Fig.- Internal Pressure of 3000psi

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As seen in the figure below the maximum Von Mises Stress is 8000 psi at the exit end of the barrel The maximum tensile yield of 416 SS is 140,000 psi. Even with a safety factor of ten the maximum stress computed would not cause the barrel to yield. Fig.-Enlarged view of the exit end of the barrel

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Computational Fluid Dynamics Analysis of Working Fluid Preprocessing is the first step in building and analyzing a flow model. It includes building the model (or importing from a CAD package), applying a mesh, and entering the data.

Gambit software was used for preprocessing. The computational fluid dynamic solver, FLUENT, does the calculation and produces the results. In modeling the gas gun problem, the drag force was taken in consideration, but friction forces exerted on the projectile sides and blow-by effect were all ignored. For every position the projectile moves, the FLUENT software calculated the projectile velocity, pressure force exerted on the projectile, and time elapse from rest. The magnitude of the projectile displacement from rest was interpreted as the length of the barrel. The only parameters allowed to change are the diameter of the projectile, the type and pressure of the gas present in the reservoir. In this analysis helium gas at 1000 psi was exerted on a half inch diameter steel projectile. From the appendix, the velocity vs. projectile displacement (barrel length) graph shows a maximum velocity of approximately 800 m/s. Comparing the theoretical velocity,1000 m/s, calculated under the same physical conditions, a difference was examined due to the frictional force.

The diaphragm separates the high pressure region (Helium gas @1000psi) from the low pressure region (helium gas @ ambient pressure). As soon as the high pressure is exposed a shock wave will propagate upstream as shown in Figure 2.

As the shock wave gets closer to the projectile a higher pressure force will be exerted on the surface on the projectile causing it to increase its velocity, thence expanding the mesh (dynamic mesh). The projectile’s motion is assigned by a user-define function (UDF). A user-defined function, or UDF, is a function that you program that can be dynamically loaded with the FLUENT solver to enhance the standard features of the code. UDFs are written in the C programming language. UDFs are executed as either interpreted or compiled functions in FLUENT. Values that are passed to the solver by a UDF or returned by the solver to a UDF must be specified in SI units.

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Product Architecture The gas gun is designed to release certain amount of gas. Upon release, the gas undergoes adiabatic expansion, which produces energy. This energy is used to drive a projectile inserted inside the barrel. The data acquisition is triggered to measures the time it takes the projectile to pass two holes drilled on the barrel, which is then converted to velocity. The schematic and functions of the system (pressure and release) and of the DAQ subsystems are as follows:

Main Pressure Cylinder

PressureGages

Relief Valve

Reservoir

Safety Valve

ManualValve

Pressure Transducer

Pressure Gage

ExpanderSolenoid

Valve

Electrical Relay

Shoot Switch

Rupture Disk & HolderInsertion

Point

ProjectileIN

Barrel

DAQ

Line Voltage

Pressure Regulator

Line VoltagePressure System Release System

Fig.-Product Architecture (systems and subsystems)

Pressure System Pressure Transducer and Gage For accurate digital pressure reading, and enables us to read the pressure away from the gun. Pressure Vessels and Regulator The Pressure Vessel is the main storage cylinder, and the Regulator enables us drain the gas in a controlled manner, in terms of flow rate and pressure.

Reservoir The pressure reservoir enables us to measure the volume of gas used per text.

Release System

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Solenoid Valve Allows remote triggering for testing. Rupture Disk The pressure-containing element designed to burst open and relieve an overpressure condition at a predetermined differential pressure, and specific temperature. Rupture Disk Holder Allows proper seating of the rupture disk and ensure proper alignment with fluid flow.

Data Acquisition Subsystem

Fig-DAQ Schematic

The S2011 laser kit is a complete laser diode system, which includes a visible laser

module, DC power supply, and mounting hardware. To set up the laser kit, simply plug the laser supply and turn the power switch on to begin laser operation. The S2011 laser kit is powered by 4.5 mW and emits pulse wave with ranging wavelength 635 nm – 640 nm unto high speed silicon detector. Thorlabs DET high speed detectors are ideal for measuring both pulsed wave and continuous wave light sources. A photocurrent output signal is transmitted through the BNC coaxial cable connected to the high speed detector. This photocurrent is converted to voltage by adding a terminating resistor at the end of the coaxial cable for viewing on the LabVIEW software. There are several internal triggering methods available such as edge, hystersis, window, and digital for the data acquisition board installed in the computer system. Edge triggering method was used to acquire data from the data acquisition board.

Power Supply

E

Relay

DAQ Board LABVIEW

Software

Computer System

Laser module (E) Photo detector(S)

Trigger

E S

S

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Other Components Barrel Launch tube that facilitates the acceleration of the projectile. Other Features: 2 holes 2” apart to accommodate laser beam to pass through. Connections Hose & Fittings enables changes in diameter of fittings along gun. Support Supports the gun and serves as a spacer between the gun and the table. Fasteners ¼”-20 hex. Head Bolts (316S) Flange Bolts: Grade 8, 1”-8 Other features

Pressure detection supply side of rupture disk Safety Relief Valve on upstream of solenoid valve. Manual depressurization valve.

Configuration and Parametric Design

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Pressure gages & Transducers

Soleniod Valve

Rupture Disk & Holder

Photo detector Kit

Hose and Fittings

Shaft Holder

Data Acquisition

Pressure vessels

Final Design Modular Design The architecture and operational principle behind the gas gun dictated that a modular design approach be used. The modular design gives the gas gun the advantage of allowing easy repair, replacement, trouble -shooting or change of components without affecting other parts of the product. The approach is also good for use of standardized components and interfaces. Given the design parameters particularly the working space in which the gun will be constructed and the size of the table on which it is bolted the sizing of the components was a primary selection criterion along with pressure specifications. Pressure Vessels and Regulator From the pressure analysis it was determined that a maximum operating pressure of 2000 psig could achieve the desires speed of 1000 m/s for the size projectiles being considered. Pressure Reservoir The size of the pressure reservoir was determined by the burst pressure of the rupture disk compensated for losses caused by pressure drop due to expansion of the gas between the solenoid valve and the rupture disk. Consideration had to be made also for leaks in the system. The pressure reservoir selected was a sample cylinder made by HOKE® that has a capacity of 500 cc and a maximum operating pressure of 5000 psig @ 70˚ F. This cylinder was made by special order because no pressure sample cylinders above 1800 psig were available as off the shelf items. Other features include a Teflon lining and the pressure vessel material Monel.

Reservoir size: Length 19”, Outside Diameter 1.9”

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Main Pressure Cylinder The capacity of the main pressure cylinder was determined from the capacity of the pressure reservoir and the number of test required per cylinder. The cylinder was rented from TW Smith and refilled as needed. The picture to the right shows the main pressure cylinder with the pressure regulator and steel braided hose connected.

Size: T (Diameter 9.25”, Height 55”) Pressure: 2640 psig @ 70˚ F Safety valve type: diaphragm Material: 316 SS

The operating pressure of the reservoir controlled using a helium pressure regulator with a range 200 – 2500 psi. Both pressure vessels are connected by a 5 ft length of steel braided hose rated at maximum pressure of 3000 psi. By replacing the pressure regulator adjustments gas gum has the capabilities of operating up 2800 psi. To prevent overpressure above this limit a diaphragm safety valve is connected between the main pressure cylinder and the reservoir. Also connected in this location is a safety relief valve to depressurize the system of any residual pressure once testing is complete, both component are important safety features. Solenoid Valve A pilot operated solenoid valve is used to perform the task as a shoot switch. This solenoid valve is a normally closed valve operated by a double wound coil and allows full flow. The valve used was ordered and built to specifications. The detail of the operation of the solenoid this valve is prone to overheat if left on for more than a couple of minutes, as a result of this a momentary switch is used to control its operation. Please see appendix A. for other relevant information on the solenoid valve and its operation.

Maker: Atkomatic Max. Pres.: 3000 psi Position: NC Weight: 21.0 lb Voltage: 115v 60 Hz Relay: Model R-300 Material : 316 SS Nominal pipe size: 1 ½”

Fig.-ATKOMATIC Solenoid Valve Rupture Disk Assembly

The rupture disk is a pressure-containing element designed to burst open and relieve an overpressure or vacuum condition at a predetermined differential pressure, and specific temperature. For this design the rupture disk is used to maximize the effect of the shock wave in accelerating the projectile when it is exposed to the high pressure gas.

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Specifications Maker: Continental Corp. Model: MICRO X Material: 316 SS Pres. Range: 270 – 2800 psi. Tolerance: ± 5% of Burst Pres. Made to specification

The rupture disk used is a tension type disk, its principle of operation is shown by the diagram above.

Rupture Disk Holder The rupture disk is held in place by a holder which allows the proper seating of the rupture disk and ensures that it is properly aligned with the direct flow of the gas once it is released by the solenoid valve. A flat seated rupture disk holder was selected because it offers to potential of producing the disks “in house”. The J-Hook on the rupture disk holder ensures that the disk sub-assembly is always in the correct position.

Maker: Continental Nom. Size:1 1/2 “ф Type: J - Hook Material: 316 SS Seating: Flat

To complete the rupture disk assembly are two ANSI 1500# flanges which holds the rupture disk holder in place with 4 bolts torqued to the desired specifications based on the pressure at which a test will be performed. To accommodate the J-Hook a ¾ “diameter hole (depth ½”) is drilled on top of the inlet flange. The interface between the rupture disk holder and the flanges are each sealed with a 1/8" thick, 1 ½" inner diameter Teflon gasket. A pressure transducer is also place on the inlet flange by drilling a ¼" diameter hole through the side of the flange. The purpose of this transducer is to record the pressure at the inlet to the rupture disk before testing to ensure that it is not being exposed to greater than 80% of the rated burst pressure, and also to ensure that a differential pressure of > 5 psi is achieved across the solenoid valve.

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The picture to the right shows the final assembly of the of the rupture disk holder with the pressure transducer in place.

Flange Class: ANSI 1500# Maximum Torque: 183 lb-ft Flange material: 316 SS Flange Bolts: Grade 8, 1”-8; Length 7”

Data Acquisition High speed silicon detectors are off-shelf items manufactured by Thorlabs Inc. The unit comes with a photodiode and internal 12 V battery enclosed in a black anodized aluminum housing. The head includes a removable 1” optical coupler providing easy mounting of ND filters and other stackable lens mount accessories# 8-32 tapped hole is provided on the base of the housing to mount Thorlabs’ positioning device such as post, post holder, and mounting plates. Specifications include rise/fall time lesser than one nanosecond and spectral response of 200- 1100 nm.

Fig.-DET 210-High Speed Silicon Detector

The adjustable laser diode kit is an off-shelf item manufactured by Thorlabs Inc. The kit includes a visible laser module, DC power supply, and mounting hardware. The laser is mounted in a KM1-T mount which provides convenient mounting and alignment of the laser pointing and is classified as an N-type laser. Laser housing is made from anodized aluminum housing with glass lens. Specifications include operating voltage -4.5 – 5.5 V, wavelength 635 nm, and focusable output

beam. Fig.-Adjustable Laser Diode Kit National Instrument manufactured this data acquisition board. Its

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physical dimension is 10 cm by 16 cm. The NI 5112 digitizer feature deep onboard acquisition memory, 100 Ms/s real-time and 2.5Gs/s random interleaved sampling, 100 MHz bandwidth with 20 MHz limit option, ± 25mV to ± 25V, 10 or 32 mB memory buffer with multirecord capture mode, and 8 bits resolution. Fig. - Data Acquisition Board Barrel The gun barrel serves as the launch tube that facilitates the acceleration of the projectile. The barrel also serves as a possible insertion point for the projectile (the projectile could also be loaded at the discharge flange of the rupture disk assembly. This item was designed and outsourced for manufacture. It was designed to withstand a pressure of 3000 psi when the inner diameter is 1” (i.e. for launching a 1” projectile). It surface of the bore is highly polished to reduce frictional losses. The barrel is connected to the discharge side flange of the rupture disk assembly by a (1 ½ “ – 1” ) reducing nipple since the flange has a bore of 1 ½ “ and the barrel is designed to a 1” schedule 80 pipe (OD 1.315”) based on the design specification of firing projectiles close to 1” diameter. Two holes (2” apart, the second being ½” from the end of the barrel) are drilled through the barrel. The photo detector kits are aligned with these holes serve as pathways for the laser beams to sense the projectile as it passes. The picture to the right shows the barrel assembled to the discharge flange and an exploded view of the detection holes mentioned.

Maker: W.E.Rayl Finish: (ID) 32 Tolerance: ±0.002” Overall length: 20” Outer Diameter: 1.315”

All these major components are held together with a series of schedule 80, 316 SS, NPT pipe connections. The entire assembly is clamped between 6 aluminum holders (off the shelf items) and bolted to the special pre-tapped piezoelectric table.

Aluminum Holder

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Conclusions and Recommendations Despite the fact that all the above mentioned design specifications were met and in some cases exceeded, there is still room for some improvements. In terms of safety the design is quite safe with the operator located behind the vertical breadboard, however the main pressure cylinder too close to the operator and the data acquisition system in its present position. Since the pressure transducers allows us to be able to sense pressures at the main pressure points, and can be read 12 ft away it is recommended that the operator and the data acquisition apparatus be relocated to the adjacent room. The rupture disk assembly satisfies all the functions for which it was intended (1. to serve as an insertion point for the projectile 2. to allow easy replacement of the rupture disk with two to three tests per day in mind). This assembly however, is bulky and offers the possibility of being simplified. In its present form the assembly sometimes turns whenever the bolts are tightened. This causes the transducer and the hole for the alignment of the rupture disk to move to undesirable positions. This problem could be rectified by using brackets to bolt the inlet flange to the table to ensure that it stays in one position at all times. It was noticed during testing and by calculations that the pressure drop after the solenoid valve is opened caused by the increased volume (between the solenoid valve and the rupture disk) is quite significant. This pressure drop could be minimized in two ways:

1. The capacity of the pressure reservoir could be increased from 500cc to 1000cc. 2. Using the existing 500cc capacity reservoir the operational procedure could be changed

to allow a pre-loading of the rupture disk to 50% to 70% of the rated burst pressure prior to setting the final operating pressure in the reservoir.

Both of these measures serve to minimize the pressure drop mentioned.

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Acknowledgements We would like to Respectfully Thank,

B. Liaw, Professor, Advisor, Mentor and Friend C. Watkins, Herbert G. Kayser Professor R. Raj, Professor P. Ganatos, Professor Y. Andreopoulos, Professor A.Walser, Dean of Undergraduate Studies National Aeronautics and Space Administration United States Army L. Hernandez, Chief Laboratory Technician J. Chen, Senior Laboratory Technician R. Kallfa, Senior Laboratory Technician M. Askanazy, Senior Laboratory Technician Y. Liu Z. Yang S. Xanthos Our ME 474 Classmates for their support: Idesta Adams; Brenton Balfour; Rodrigo Cajiao; Kenneth Crossman; Nathan Hosannah; Ansab Khan; Denise Lue Lueong; Naresh Mahangu; Kabemba Nyembo; Roopchand Samaroo; Ashley Soljour; Jiyun Song; Godwin Uwechue; Ricardo Villela; Paula Washington.

Our suppliers: WE Rayl Inc., Thorlabs, TW Smith, McMaster-Carr, Setra. All the Professors who illustrated the path to becoming good engineers.

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References Books

Van Wylen, Borgnakke. Fundamentals of Thermodynamics. USA: John Wiley and Sons;1998.

Machinery’s Handbook #26;2000 Howard E. Boyer and Timothy L. Gall, Eds., Metals Handbook, American Society for Metals, Materials Park, OH, 1985. Journals

Choi, S., Pereira, J., Janosik, Bhatt, T., Foreigh Oject Damage Behavior of Two Gas-Turbine Grade Silicon Nitrides by Steel Ball Projectiles at Ambient Temperatures. National Aeronautics and Space Administration, Glenn Research Center: 2002 Websites

www.iceweb.com.au/Technical/Technical.htm www.shopfnc.com/asco/ascotech.htm www.thurometal.com www.fibreglast.com www.standa.lt www.mcmaster.com www.newport.com

www.thorlabs.com www.matweb.com

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Appendix Gantt Charts Spring 2003

Fall 2003

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Barrel Calculations

hoop stress yields,

= 3828 psi. where: p = internal pressure= 3000 psi. r = outside radius of the barrel = 0.6575in. t = normal wall thickness = 0.6575 - 0.1285 = 0.529 in.

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CFD Analysis Velocity vs Barrel length

0

100

200

300

400

500

600

700

800

900

0.0 1.4 6.1 13.127.6

48.061.2

Barrel length (in.)

Velo

city

(m/s

)

Force vs Projectile displacement

0

5000

10000

15000

20000

25000

0.0 0.4 3.9 10.821.0

41.458.0

Projectile displacement (in.)

Forc

e (N

)

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Shop Drawings

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SOURCE: http://www.circle-seal.com/Atkomatic/manuals/8000.doc Valves with double wound coils are ordered with an Atkomatic time delay relay. The following diagram shows how these relays are wired:

Double Wound Coils The double wound coils consist if two coil windings within the same encapsulation. The windings are the primary, which consists of a heavy wire coil with relatively few turns and a low resistance and a secondary coil winding of many turns of fine wire with a high resistance. To open the valve, power is initially applied across the primary winding (red to yellow) and the combination of primary and secondary circuits in series (red to black) as shown schematically:

V

V BLACKYELLOW

RED

SECONDARYPRIMARY The high current through the primary circuit generates a strong magnetic field that actuates the valve. This current is sufficiently high that the coil would overheat if the current were allows to continue for more than a couple of minutes. After a fraction of a second, (the delay is caused by the dropout time of the relay) the yellow lead is disconnected and the voltage remains applied only across the combination of the primary and secondary windings in series. The low current through both windings produces a lower strength magnetic field that is sufficient to hold the valve open. The low current produces only modest heating of the coil allowing the valve to remain actuated open continuously. This steady state condition is shown schematically:

V

BLACKYELLOWRED

SECONDARYPRIMARY

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Operation Opening When voltage is applied across the coil leads a current is produced in the coil windings which generates a magnetic field. The magnetic field attracts the plunger and causes it to move toward the center of the coil or magnetic stop. Initially the plunger slides freely on the stem until it impacts the nut or shoulder at the end of the stem. The plunger’s momentum is then transferred to the stem and the stem is lifted off the seat screw pilot orifice. Fluid from the cavity above the piston flows through the pilot orifice in the seat screw and through the drilled hole in the center of the piston to the downstream side of the valve. Pressure above the piston decreases since the pilot orifice is larger in diameter that the bleed orifice. Inlet pressure acting around the annular area outside of the main valve seat at the bottom of the piston then pushes the piston up, thus initiating flow through the valve. Note that flow through the valve creating a pressure drop across the valve is required to hold the piston open. If flow is diminished the piston will move toward the closed position. To maintain the valve fully open a pressure drop of 3 to 5 psid across the valve is required. Closing When voltage is removed from the coil leads, the magnetic field collapses. Gravity pulls both the plunger and stem down until the stem point seals off the pilot orifice. Fluid flow from the valve’s inlet side through the bleed orifice in the piston charges the cavity above the piston to a pressure equal to the valve’s inlet pressure. Since downstream pressure is acting against the center portion of the bottom of the piston, the pressure forces acting on the piston are unbalanced and act to push the piston to the closed position ( gravity and, with some valves, a piston spring assists in the closing ).