Attachment 2 Design details.pdf

Detailed Design of

Ma = 6 Ludwieg Tube Wind Tunnel for the

USAF Academy

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Abstract

This document gives an overall and detailed design description of Mach 6 Ludwieg tube for the USAFA.

The Ludwieg tube is divided into its main sections and each of these sections will be pre-sented in detail.

The report consists of three parts:

1. The detailed design description

2. Annex 1 with the main technical drawings

3. Annex 2 with technical documents of the main purchase parts and components

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Content

1 Introduction ___________________________________________________________ 5 2 Installation site _________________________________________________________ 5 3 Facility main components ________________________________________________ 6 4 High Pressure Components _______________________________________________ 7

4.1 Charge tube device_______________________________________________________ 7

4.1.1 Charge tube __________________________________________________________________ 7

4.1.2 Charge tube heating___________________________________________________________ 10

4.2 High pressure compressor and storage system _______________________________ 13

4.2.1 High pressure compressor ______________________________________________________ 13

4.2.2 High pressure dryer ___________________________________________________________ 14

4.2.3 Gas storage _________________________________________________________________ 14

4.2.4 Installation__________________________________________________________________ 14

4.2.5 Control board _______________________________________________________________ 15

4.3 Fast acting valve________________________________________________________ 16

4.3.1 Valve design ________________________________________________________________ 16

4.4 Nozzle ________________________________________________________________ 17

4.5 Test section and diffuser _________________________________________________ 18

4.5.1 Test section _________________________________________________________________ 18

4.5.2 Diffuser ____________________________________________________________________ 22

4.6 Vacuum components ____________________________________________________ 23

4.6.1 Vacuum dump tank ___________________________________________________________ 23

4.6.2 Vacuum pump _______________________________________________________________ 24

4.6.3 Overpressure ________________________________________________________________ 25

4.7 Mounting of flow elements _______________________________________________ 27

4.7.1 Charge tube _________________________________________________________________ 27

4.7.2 Valve block _________________________________________________________________ 30

4.7.3 Nozzle _____________________________________________________________________ 32

4.7.4 Test section and diffuser _______________________________________________________ 32

4.7.5 Diffuser movement and sealing__________________________________________________ 32

4.8 Material and finish______________________________________________________ 37 5 Operational equipment__________________________________________________ 37

5.1 Control and operation equipment _________________________________________ 37

5.2 Measurement instrumentation ____________________________________________ 40

5.2.1 Pitot rake ___________________________________________________________________ 40

5.2.2 Temperature ________________________________________________________________ 41

5.2.3 Pressure ____________________________________________________________________ 41

5.2.4 Linear motion _______________________________________________________________ 41

5.2.5 Controller __________________________________________________________________ 42

6 Alarm Plan ___________________________________________________________ 43 7 Power budget of the electrical equipment ___________________________________ 44 8 Mass budget __________________________________________________________ 45 9 Transport and Installation _______________________________________________ 46 10 Conclusions __________________________________________________________ 46

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1 Introduction

Within this document the detailed design of the USAFA Mach 6 Ludwieg tube tunnel will be explained.

We therefore divide the wind tunnel into its main sections and present their detailed design and the eligibility criteria for the different components and purchase parts.

For further information of purchase parts we referred on Annex 2.

Annex 1 of this report contains the technical drawings of the wind tunnel main parts.

Annex 2 inclose the technical documents of the purchase parts and components.

2 Installation site

The USAFA Ludwieg tube wind tunnel will be installed in a 21 x 13.5 m² laboratory room of the Department of Aerospace.

Due to the length of ~38 m the wind tunnel could not be installed completely inside the lab.

The main part of the charge tube has to be placed on the roof terrace beside the laboratory.

The first picture shows the proposed installation of the Ludwieg tube facility.

Fig. 1 Installation place of the Ludwieg tube wind tunnel

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3 Facility main components

The Ludwieg tube will be divided into the following main facility components:

• High pressure components

� Charge tube

� Fast acting valve

� High pressure compressor and storage system

• Heating and insulation

� Electrical heating

� Thermal insulation

• Nozzle and Test section

� Contoured nozzle

� Test section and diffuser

• Vacuum components

� Vacuum tank

� Vacuum pump

• Support elements

� Mounting and covering of the charge tube

� Mounting of nozzle and test section

� Vacuum tank support

• Electrical design

� Power supply and wiring diagram

� Control and operational equipment

� Measurement instrumentation

Between these components often multiple interfaces exist.

When dealing with such nondistinctive components, like the electrical heating of the charge tube, it may be necessary to mention it twice or even more often, e.g. by describing the charge tube as well as in the electrical design.

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4 High Pressure Components

4.1 Charge tube device

The charge tube provides the test gas for the shot under high pressure and temperature.

The inner diameter and the tube length together with gas pressure and temperature are essen-tial for the flow conditions and run time of the wind tunnel. The dimensioning of these pa-rameters was calculated and explained in detail in [1].

The charge tube can be divided into the actual tube, the heating and the thermal insulation.

4.1.1 Charge tube

Tube

The charge tube will be made of stainless steel 1.4571 (AISI 316Ti). This steel has the capa-bility to withstand the pressure (40 bar) and temperature (400 °C) and has certifications from the German Technical Control Board (TÜV).

The charge tube is divided into five sections. Four of these sections are 6 m long whereas the fifth is 3 m long. The 3 m long section is supposed to be installed inside the laboratory whereas the other four parts (total 24 m) are mounted outside the lab on the roof area.

The following table shows the data of the charge tube in which the dimensioning was done in

[1].

Quantity Length Outer diame-ter

Inner diame-ter

Wall thick-ness Material Mass

1 3 m 62 kg

4 6m

168.3 mm 158.3 mm 5 mm

1.4571 /

AISI 316 Ti 124 kg

Tab. 1 Charge tube data

Flanges

Each section is interconnected by welding neck flanges DIN 2636 (PN 64, ND 150). The flanges are also out of stainless steel 1.4571.

The following picture shows the connection of the flanges.

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Fig. 2 Flange connection

Between the flanges a so called measurement ring could be seen. This spacer block will have measurement orifices for pressure and temperature sensors. It can be adapted to different types of sensor ports very easily. When not in use the measurement ports can be closed by blind plugs.

This will ensure a large variety of measurement possibilities even those not considered during design phase.

The flanges will be fixed together by 8 M30 extension bolts. They will be used because they are qualified for higher temperatures than of normal screws.

The sealing between the flanges – measurement ring will be done by metal sealing rings shaped like normal O-rings. These rings which are made out of aluminium or copper can withstand the temperature of 400 °C.

The sealings will be fitted into O-ring grooves in the measurement ring. The measurement ring is centred to the flanges by a tongue and groove geometry like shown in the next figure

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Fig. 3 Flanges with measurement ring

The end of the charge tube will be closed by a blind flange DIN 2527 (PN 64, ND 150). This flange will contain the charge pressure port through which the tube will be filled up.

We set the pressure connection at the end of the tube so that the cold instreaming gas pushes the hot gas column towards the valve block region. The next figure shows the blind flange.

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Fig. 4 Blind flange connection

Beside the charge pressure port also measurement ports are inserted to the blind flange.

4.1.2 Charge tube heating

The test gas inside the tube has to be heated up to avoid condensation during a shot.

Therefore the charge tube will be heated and the heat will be transferred to the gas by conduc-tion.

4.1.2.1 Heating cables

The charge tube will be heated up by electrical heating cables wrapped upon the outside of the tube. The required electrical power was calculated in [1] to

P = 30.8 kW which is needed to heat up the tube to 400°C in one hour.

The permanent power consumption which is needed to equalize the heat losses is lower and was calculated to

Ploss = 8 kW

The charge tube will be divided into five heating sections; four six meter long parts and one three meter part. The six meter parts will be heated by three 24 m long heating cables, the three meter part with one 24 meter cable which will be wrapped around the tube as shown in the next figure.

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Fig. 5 Heating cables on the charge tube

The installed power is 9.6 kW for the six meter and 3.2 kW for the three meter parts. So the total installed heating power is 41.6 kW which is enough to heat the charge tube up to 400°C even with ambient temperatures of -30°C. The installed power at the 3m section could be less compared to the other sections because this part of the tube will be installed at the inside of the laboratory.

4.1.2.2 Thermo controller

Each tube section is controlled by a separate thermo controller which regulates the tempera-ture. The tube temperature will be registered at least at three different positions. Each control-ler checks thermocouple rupture and the heating circuit will be shut down if any failure ap-pears. Each temperature will be displayed on the control rack and could also be recorded by the measurement PC card.

4.1.2.3 Insulation

The insulation covers the tube with the flanges and the electrical heating cables to minimize the heat losses.

The charge tube will be insulated with rock wool pipe shells.

The inner pipe shells will have an inner diameter of 178 mm and a thickness of about 93 mm.

Around the inner shell will be an outer shell with 273 / 393 mm diameter and a thickness of

60 mm. So the total thickness of the insulation will be ~ 150 mm and therefore more than re-quired when compared with the heat loss calculation in [1].

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The following picture shows the insulation of the charge tube.

Fig. 6 Charge tube insulation

Not shown in this picture is the additional insulation around the flanges which could be re-moved easily to get access to the flanges and the measurement ring.

The outside of the insulation will be covered with thin stainless steel or aluminum foil to pro-tect the insulation against mechanical damaging. See also chap. 4.7.1.1.

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The high pressure compressor will be connected directly to the high pressure dryer to mini-mize the water content of the gas. Between the compressor and the dryer a pressure reducer will be installed. This reducer will be adjusted to 200 bars which ensures that the compressor works always against this high pressure which additional reduce the water.

4.2.2 High pressure dryer

To minimize the remaining water in the test gas a regenerative dryer will be installed between the compressor and the gas storage bottle. We will use a Bauer SECCANT dryer which is well adapted to the Bauer compressor. Both could be controlled by the compressor control unit. (Annex 2)

4.2.3 Gas storage

Then gas storage allows to store high pressure test gas for at least over 30 shots of the wind tunnel without using the compressor [1].

The storage consists of eight gas bottle with 50 liters each by a storage pressure of 200 bar.

Each bottle could be opened / closed manually.

Four bottles each will be linked to a unit with an additional pressure transducer for pressure monitoring at the control rack.

4.2.4 Installation

The compressor-dryer-storage unit could be mounted in the laboratory room close to the wind tunnel or even in another room or floor.

We need a pressure line between the storage and the control board which has to be close to the wind tunnel because the charge tube pressure will be adjusted at this board. This line shall be out of stainless steel tubes for example Ø 16 mm x 2 mm.

The electrical connection will be via our electrical cabinet while the controlling will be from the control rack. Therefore we will need additional power and signal lines between control rack /cabinet and the compressor station.

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4.2.5 Control board

The high pressure control board will be installed between the gas storage and the charge tube.

On this board the charge tube pressure could be regulated and the tube filled or released.

The following sketch shows the board with the valves and manometers.

Fig. 8 High pressure control board

The main part on the control board is the pressure reducer which guarantees that the charge tube pressure can’t exceed the safety limit. The max. adjustable back pressure will be about

50 bar. In addition to the electronic pressure transducers there are mechanical manometers for reservoir pressure, back pressure and charge tube pressure. The charge tube could be filled up and released by electric valves from the control rack but it is also possible to release the charge tube pressure by a manual valve at the control board. To avoid overpressure in the charge tube a safety valve has to be installed at the tube. The exact position of this safety valve has to be defined in accordance with the USAFA or national safety regulations.

The exact position of the board could be defined in arrangement with the laboratory staff and the USAFA responsible.

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4.3 Fast acting valve

The charge tube is connected to the valve block with the fast acting valve inside.

The fast acting valve closes the tube against the nozzle and the test section and starts the test run by opening and closing in milliseconds.

The working principle of the fast acting valve was explained in detail in [1].

The auxiliary valves are of electro-magnetic type and will be controlled by a timer module with millisecond precision. The test can be started by the operator direct at the timer with a

“Start”- button or by a trigger signal from the PC.

4.3.1 Valve design

The detailed design of the fast acting valve is nearly identical to the proposed design in [1].

Only minor modifications have been made.

Fig. 9 Design of the fast acting valve block

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The main body of the valve block, the flanges and the plunger track will be made out of stainless steel 1.4571/AISI 316 Ti. The plunger itself will be made out of aluminum alloy to reduce the mass which has to be accelerated.

The control pipe will be feed through the charge tube flange and the plunger track to the back-side of the plunger. The auxiliary valves will be positioned in a short distance to the valve block to reduce the venting times and therefore the opening and closing times of the fast act-ing valve.

The inner geometry of the valve and the plunger is almost identical with the valve geometry for the Ludwieg tube (HLB) of the TU Braunschweig. This Ludwieg tube was built in

2003/2004 by HST GmbH for the ISM - Institute of Fluid Mechanics in Braunschweig.

4.4 Nozzle

In the nozzle the test gas will be accelerated up to Ma = 6. It will be a Laval-type nozzle with a contoured geometry. The nozzle geometry and the principle design was shown in [1].

The nozzle will be parted into two sections. First is the nozzle throat with the subsonic part, the nozzle throat and most of the conical supersonic part. This nozzle insert will be made out of stainless steel 1.4571. Together with the valve plunger it represents the closure of the main valve.

The supersonic nozzle part will be made out of glass fiber laminate. The intersection to the first nozzle part will be made out of stainless steel, the intersection to the test chamber out of aluminum alloy. The nozzle body is shown in the next figure.

Fig. 10 Ma 6 nozzle, glass fiber body with metal intersections

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The nozzle body will be laminated on the same core than the HLB nozzle. This will guarantee that the contour is identical to the calculated and documented HLB nozzle.

The glass fiber will insure a very smooth inner surface of the nozzle. With a length of nearly

2.5 m the nozzle could not be machined out of steel with such surface precision as it will be with the glass fiber.

4.5 Test section and diffuser

4.5.1 Test section

The test section serves for installing the test models and the observation of the flow.

The inner diameter of the test section will be 496 mm and the length is about 980 mm.

For optical access the chamber will have three flanges DIN 2632 (PN 10, ND 250) for optical access and one rectangular flange for the probe chamber.

The following figure shows an overview of the test section.

Fig. 11 Test section, overview

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All parts of the test section will be made out of stainless steel. For the optical access the three

ND 250 flanges will be equipped with windows. The windows are sealed with o-rings and held by counter flanges.

The rectangular flange could be closed with a blind flange or equipped with the probe cham-ber.

4.5.1.1 Probe chamber

The probe chamber, made out of aluminum, could be installed under the test section instead of the blind flange.

It contains a linear motion unit which will be equipped with a six probe Pitot rake.

The linear motion unit and the probe chamber are shown in the next figures.

Fig.12 Probe chamber with linear motion unit

This motion unit will be controlled by a driver unit via PC software.

It allows a linear motion of 340 mm in x-axis (horizontal) and 240 mm in z-axis (vertical).

The chamber is equipped with all necessary vacuum feed throughs for the electrical supply and measuring lines. The motion unit is fixed to a second blind flange and could be removed very easily using the probe chamber for other measuring tasks.

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4.5.1.2 Model support

The test chamber could be equipped with two different model supports.

Both of these model supports are mounted in an intermediate flange which could be installed between test section and diffuser section.

The first model support is a stem bracket as shown in the next picture.

Fig. 13 Model support No. 1

The model will be installed on a steel tube which could be moved in the support flange in x-axis. This kind of model support could be very easily adapted to different models.

But movement is possible only in flow direction. Angle of attack simulation will be possible only with cranked adaptors.

The second model support is a manually angle of attack device as shown on the next picture.

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Fig. 14 Model support No. 2

The model will be mounted on a steel rod inserted in a sliding lead.

The pivot point of the adjustment lies in the axis of the side windows. The angle of attack could be adjusted by hand and angles of ± 15° will be possible.

The next figure shows the angle of attack device mounted in the tests section.

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Fig. 15 Model support No. 2 in the test section

Cables and pressure tubing from the model will be routed through the pivot to the probe chamber and vacuum tight connectors.

4.5.2 Diffuser

The test section is connected to the diffuser section. A diffuser is foreseen to increase the static pressure after the test section to avoid an early breakdown of the flow. The diffuser also helps to run against “higher” pressures in the vacuum tank. The diffuser will be built as a straight tube of 496 mm diameter with a length of ~ 1500 mm and act as so called shock dif-fuser.

The diffuser is made also of stainless steel 1.4571 / AISI 316 Ti.

To get access to the test section on the model the diffuser will slide into the vacuum tank.

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The sliding mechanism and the sealing of the diffuser section will be described in detail in chapter 4.7.5.

4.6 Vacuum components

The vacuum system consists of the vacuum tank, the vacuum pump, valves and other vacuum components. The vacuum system respectively the dump tank has the function to reduce the backpressure to avoid flow blockage and enable the start of the test run.

4.6.1 Vacuum dump tank

The vacuum dump tank for the USAFA Ludwieg tube will have a diameter of 1800 mm and a cylindrical length of 2300 mm. Together with dished bottoms and the flanges at both ends the overall length will be about 3300mm and a total volume of about 6 m³.

The tank will be out of stainless steel just like the other vacuum components.

The next picture shows the vacuum tank on the mounting frame which has to be fixed to the laboratory ground by steel bolts and dowels.

Fig. 16 Vacuum tank

To have accessibility to the tank inside and for optional measurements in the tank it will have two flanges NS 500 at the sides and one NS 500 flange at the end. The side flanges will be closed by aluminum plates held by flange rings as shown in the next picture.

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Fig. 17 Blind cover of vacuum tank flange

This blind covers could also be replaced by windows or other plates.

The end flange of the vacuum tank contains the supply pipe to the vacuum pump and the vac-uum pressure transducers.

This flange is equipped with one ISO-K 100 flange for the vacuum pump connection, one

ISO-K 100 flange for the safety valve port and four KF 25 flanges for sensor mounting.

The diffuser section will be connected via a NS 800 flange at the moving and sealing unit.

4.6.2 Vacuum pump

The vacuum pump reduce the pressure in the dump tank in the required time to the requested value. The dimensioning of the pump was done in [1].

The selected vacuum pump from Gardner Denver has the following data:

Type V-VC 500

Suction speed 660 m³/h

Ultimate vacuum 0.5 mbar

Motor power ~18 kW

Electrical supply TBD

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The electrical data of the vacuum pump are provisionally since the pump will be delivered from Garner Denver without motor. The motor will be selected after US regulations (NEMA-

MG1 UL certified).

The vacuum pump should be installed close to the vacuum tank so that the suction speed will not be reduced due to long tubing.

The next picture shows the proposed mounting position next to the tank.

Fig. 18 Vacuum tank and vacuum pump

The pump inlet will be connected via a flexible bellow and a pneumatic vacuum valve to the flange of the dump tank. The connections will be so called ISO-K flanges which are very common in the vacuum field.

4.6.3 Overpressure

In Technical Report of the Preliminary Design [1] the problem of overpressure in the vacuum system by fast acting valve malfunction was discussed.

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To avoid any overpressure in the vacuum tank or tubing a mechanical overpressure valve will be installed to the vacuum tank.

This valve opens when the pressure rise in the tank reach a adjustable value. The next draw-ing shows the safety valve.

Fig. 19 Vacuum tank overpressure safety valve

A stainless steel plate covers the exit of a ISO-K 100 flange. When the pressure in the dump tank is reduced the ambient pressure press the plate in the sealing and close the flange tightly.

If an overpressure of at least 20 mbar occurs in the tank the plate is lifted by the pressure and opens to the relieve tubing which will be installed between tank and laboratory wall outside.

The set pressure of the valve could be increased by a spring inside the valve.

The relieve tubing consists of a Ø100 mm stainless steel tube. This tubing will also takes the exhaust fumes of the vacuum pump. The tubing will be guided through the outside wall of the laboratory. The exact location has to be defined together with the USAFA responsible.

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4.7 Mounting of flow elements

All flow parts of the Ludwieg tube wind tunnel will have a centerline of 1250 mm.

The fast acting valve, the nozzle, the test section and the diffuser will be mounted on move-able carriages to enable access to these sections. The displacement is about 800 mm.

The charge tube will also be mounted on moveable carriages to allow thermal expansion of the heated tube. The displacement will be in the range of 200 mm for the total tube length.

4.7.1 Charge tube

The charge tube will be mounted and fixed on moveable carriages which roll on guide rails on a fixed frame. The next picture shows the end of the charge tube mounted on the carriages.

The tube is shown here without the electrical heating and insulation.

Fig. 20 Charge tube carriages and mounting frame

Each tube section of 6 m length will be mounted on two carriages. They will roll on stainless steel guiding rails as shown in the next detailed picture.

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Fig. 21 Moveable carriages and guiding rails

The mountings of the tube allow vertical adjustment to ensure exact alignment of all tube sec-tions.

The carriages are free to roll on the guiding rails to allow the elongation of the tube in conse-quence of the thermal expansion which will be in the range of 200 mm for the whole tube at

400°C.

The frame will be out of rectangular steel profiles protected with anti-rust paint.

The frame has to be fixed to the ground of the roof terrace of the laboratory building. The exact fixation has to be designed in close connection with the USAFA responsible.

Most of the 27 m long charge tube will be installed at the outside. The passage from outside to inside will be at the 3 m long tube section which is next to the fast acting valve block.

4.7.1.1 Covering

The outside sections of the charge tube need a covering for protection against the ambient conditions. Due to the elongation of the charge tube of 200 mm when heated up the covering could not be installed fix to the tube and insulation. The relative movement of the hot tube

USAFA Ludwieg Tube Detailed Design page 29 of 47 and the cold covering outside would be to large. That would end in permanent friction be-tween insulation and covering destroying the insulation little by little.

Due to this fact the whole tube with carriages and mounting frame has to be covered by sort of an all sides closed canopy.

This covering represents a significant architectural intervention which could not be taken

. The design, the manufacture and the assembly of the protective cover must be endorsed by the USAFA .

4.7.1.2 Wall opening

Due to the separation of the tube in an outer and inner section a wall opening in the laboratory outside wall is needed. This opening should have a diameter of about 550 – 600 mm. The de-tailed design has to be done by USAFA The exe-cution will be task of the USAFA.

The next figure shows a sketch of the proposed opening.

Fig. 22 Wall opening in the laboratory room

For the relieve tube a second hole (Ø 110 mm) is also needed. The position of this hole de-pends on the design of the outside coverage.

The sealing of the holes depends on the wall material and construction. The movement of the tube in the wall opening will be only about 15 – 20 mm.

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4.7.1.3 Inside charge tube

The passage between outside and inside tube section will be at the 3 m tube part. Therefore about 1.5 - 2 m charge tube will be mounted on the inside frame as shown in the next picture.

Fig. 23 Inside part of the charge tube

This will be the same frame and carriages than for the valve block, nozzle and so on.

4.7.2 Valve block

The valve block will be mounted on a moveable carriage which rolls on a welded steel frame with guiding rails. The carriages will be adjustable lateral and in height.

The valve block will be moveable to get better access to the charge tube in the case of a fail-ure or repair.

Normally the valve block carriage acts as fix point for the attached charge tube. Therefore a clamping mechanism will be fixed at the valve carriage as shown in the next pictures.

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Fig. 24 Valve block carriage

Fig. 25 Clamping mechanism of the valve block carriage

Two springs, with adjustable force, pull the crossbar with the friction plates on the main frame and keep the valve carriage in position. When the release lever is actuated the crossbar will be pressed down and opens the fixation; the carriage can be moved.

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4.7.3 Nozzle

The nozzle will be mounted on two moveable carriages as the valve block. This will assure access to the valve block inside and the plunger.

4.7.4 Test section and diffuser

The test section and the diffuser could be moved on carriages to get access to the test section.

Therefore the diffuser part will be moved inside the vacuum tank for about 800 mm.

The following figure shows the test section the diffuser on their carriages.

Fig. 26 Test section on carriage

4.7.5 Diffuser movement and sealing

To allow the movement of the test section and diffuser, the diffuser section can be moved inside the vacuum tank.

Therefore linear roller guides are mounted to the flange of the dump tank as shown in the next pictures.

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Fig. 27 Roller guide of the diffuser section

Fig. 28 Roller guide (without diffuser section)

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The diffuser will be guided by the rolls in the vacuum tank on one side and by the carriage on the other side. In total five roller guides will be installed, three at the bottom of the diffuser tube and two on top. This will prevent the diffuser to tip over.

The carriage could be adjusted in height to align the diffuser with the guiding exactly. The rolls are supported on springs and could be adjusted in contact pressure.

The next two pictures show the diffuser section pushed into the vacuum tank and open the section back of the test section giving access to the model support.

Fig. 29 Open diffuser section

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Fig. 30 Diffuser pushed into the vacuum tank

The sealing between diffuser and vacuum tank will be done by an inflatable sealing ring which is shown in the next picture.

Fig. 31 Inflatable sealing ring sealing ring air supply connector

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4.8 Material and finish

The main parts of the flow components will be made out of stainless steel, aluminum and glass fiber. These parts will not need additional finishing.

The mounting parts and the carriages will be made out of construction steel with anti-rust primer and top coat. The color of the coating could be chosen by the USAFA.

5 Operational equipment

5.1 Control and operation equipment

The control and operation equipment covers:

• temperature control of the charge tube (thermocouples type K) o 5 TC for the thermo controllers o 9 TC for temperature monitoring

• pressure control of the charge tube (pressure transducer, 0-50 bar abs.)

o 1 PT at the end of the tube o 1 PT at the valve section

• pressure control of gas reservoir and the supply line

(pressure transducer, 0-250 bar abs. / 0-50 bar abs.)

o 2 PT for the gas storage bottles (1 for each group of four bottles) o 1 PT for line pressure (at the entrance of the pressure reducer) o 1 PT test pressure (after the pressure transducer)

• timer for adjusting the opening time of the fast acting valve o red lion© preset timer, with internal or trigger start and four relay outputs

• pressure control of the vacuum tank (pressure transducer, 0 – 1 bar abs.)

o 1 PT for vacuum tank pressure

• vacuum sealing o 1 pressure switch for sealing pressure

• carriage fixation o 2 contact sensors (together in one signal line)

• linear motion controller mounted in two 19” racks with plug-in boxes for each measurement task.

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The scheme of the control and operation lines is shown in the next figure.

Fig. 33 Control and operation lines of the Ludwieg tube facility

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The boxes in the 19” racks will contain:

Boxes 1 and 2

Charge tube temperature controllers

The charge tube heating will be divided into five control circuits. The six meter long heating circuits consists out of three heating cables with one thermocouple per cable and the three meter long circuit out of one heating cable with two thermocouples will monitor 14 charge tube temperatures at the temperature rack.

Each heating circuit use one of the thermocouples as reference while the two (one) others will be controlled against damage. Thermocouple breakage will cause shut-off of the affected cir-cuit and optical signal at the control board.

Each of these temperatures could also be recorded by the PC data acquisition via analogue outputs of the temperature display.

Box 3

Charge tube pressure controllers

The charge tube pressure will be measured with one transducer at the valve block and one transducer at the end of the tube and monitored on the control rack and the PC data acquisi-tion.

Reservoir pressure

The pressure of the gas bottle reservoir will be monitored on the control rack with two pres-sure transducers (one for a group of four bottles).

Back line pressure

The pressure in the supply line, behind the pressure reducing valve will be monitored on the control rack.

Keyboard

The charge valve and the venting valve could be operated by switch keys.

Compressor

The high pressure compressor and the air dryer could be started and controlled also on this board. They will be stopped automatically by an adjustable pressure switch.

Box 4

Push-in box for the timer which activates the fast acting valve and a shot.

The timer module can be programmed in microsecond steps. With this timer the by-pass valve and the venting valve of the main valve will be activated. The timer module could be started

USAFA Ludwieg Tube Detailed Design page 40 of 47 by a button in the box or a trigger signal from the PC. By starting the time from the box the

PC will get a trigger signal from the timer module.

Box 5

In this box the monitoring of the vacuum tank pressure, controlling of the vacuum pump and the actuation of the vacuum valve will take place. The pressure will be recorded also by the

PC data acquisition.

Box 6

This push-in box contains the actuation unit of the X-Z traversing system. The controlling of this linear motion unit will be executed by special software on the PC.

Manual control and calibration board

Between the pressure reservoir and the charge tube the manual control and calibration board for high pressure will be installed. The schematic sketch and the function of this board was shown in Chap. Fig. 14.2.5.

5.2 Measurement instrumentation

5.2.1 Pitot rake

The USAFA Ludwieg tube will be equipped with a 6-point Pitot rake mounted on the linear motion in the test section. Each test port of the rake is connected to an absolute pressure trans-ducer for recording the pressure distribution in the test section.

The design of the Pitot rake will follow the design of the HLB Pitot rake which is shown in the next picture.

USAFA Ludwieg Tube Detailed Design page 41 of 47

Fig. 34 Pitot rake

The Pitot rake could be moved in the test section for 340 mm in flow direction (x-axis) and

240 mm normal to the flow direction (z-axis). In addition the rake head with the 6 Pitot tubes could be turned for ± 45° around the flow axis. So most of the test section could be measured.

5.2.2 Temperature

The thermocouples used for the thermo controllers will also be used for the test analyses.

Therefore the thermo controller analogue outputs will be relayed to the data acquisition.

5.2.3 Pressure

The pressure transducers used for the high pressure and vacuum controlling will be used also for test analyses by sending the analogue data to the data acquisition.

5.2.4 Linear motion

The linear motion unit will be installed in a special chamber which could be mounted under the test section instead of the rectangular blind flange.

USAFA Ludwieg Tube Detailed Design page 42 of 47

The travel distances of the linear motion are 340mm (x-axis) and 240 (z-axis). They have mo-tor modules with stepper motors connected to the drive control in the 19” rack. They will be controlled by a special software on the PC.

5.2.5 Controller

The measurement instrumentation will be controlled by PC, data acquisition card and special software. This equipment could be stored in an additional 19” rack or in a table housing as it is preferred by the USAFA.

The PC will be Windows based. The Data acquisition cards will be PCI-cards from National

Instruments with enough analogue inputs for all measurement channels and state of the art sampling rate. This could be for example a NI PCIe-6363 or NI PCIe-6259.

Controlling and displaying of the measurement data will be done with LabView from Na-tional Instruments.

This will contain the registration of all operational data like charge tube pressure and tempera-ture, reservoir pressure and vacuum tank pressure.

After a test the measured pressures in the tube and the Pitot pressures in the test section will be shown in a graphic display. This graph will show the traveling of the expansion wave in the tube as well as the flow development in the test section and the pressure rise in the vac-uum dump tank.

USAFA Ludwieg Tube Detailed Design page 43 of 47

6 Alarm Plan

In close co-operation with the USAFA the behavior of the Ludwieg tube facility or parts of it in a case of a failure or damage has to be defined. In the following listed the main, pos-sible, failures with the proposed alert signals and behavior.

Component Failure Alert signal Behavior

Heating Circuit

Breakage of TC Optical notice at the thermo controller

Shut down of the affected control circuit.

TC has to be changed.

Breakage of heating cable

Circuit fuse will open Cable has to be changed.

Overheating Optical notice at the thermo controller

Shut down of the affected control circuit.

Charge tube

Overpressure Optical notice at the pres-sure reading

Safety valve will open till pressure under limit

Leakage Charge tube pressure de-creases permanently

Fast acting valve closed completely?

Leak test at the flanges.

Leak test at supply line.

Fast acting valve

Does not close after run

Charge tube pressure de-creases permanently.

Tank pressure increases permanently.

Safety valve at the dump tank will open

Vacuum tank

Leakage Tank pressure increases permanently

Fast acting valve closed completely?

Safety valve closed completly?

Leak test at the tank and supply line.

Overpressure Optical notice at the pres-sure reading

Safety valve will open

Electrical failures

Crash of the temperature monitoring

No indication at the thermo controllers

Automatic shut down of all heating circuits.

Crash of the pressure moni-toring

No indication at the pressure readings.

Mechanical manometers still working.

Charge valve shut down.

Pressure release possible but not automatically done.

Tab. 2 Alarm plan

USAFA Ludwieg Tube Detailed Design page 44 of 47

7 Power budget of the electrical equipment

The following table shows a summary of all electrical equipment of the USAFA Ludwieg tube with the installation data as they are known so far.

Component Total number Voltage

Power

(each) Total power

Remarks

12 3.2 kW 38.4 kW Heating cables

277 V, 60 Hz, single ph. 3.2 kW 3.2 kW

Other volt-ages on re-quest

Compressor 1 400-480 V, 60Hz, 3-phase 11 kW

Other volt-ages on re-quest

Vacuum pump 1 380/660 V, 3-phase 18 kW

Other volt-ages on re-quest

Air dryer 1 24 VDC

Thermo controller

Pressure displays

TBD

~4

110 – 230 V, Single phase ~ 2.5 kW

Transformer for 24

VDC

100 – 240 V, Single phase

0.5 kW 1 kW

Motion Controller 1 110 – 230 V, Single phase 1 kW

PC, Controlling 110 – 230 V, Single phase ~2 kW

Total power ~ 78 kW

Tab. 3 Power budget

All electrical components will be controlled and supplied from the Control and Operation rack.

Therefore only one power supply line has to be provided by the USAFA. It was suggested that a 480 V AC, 3-phase, 60 Hz breaker with max. 400 Amps will be available.

The power cable will be dimensioned to allow all electrical equipment to run simultaneously even if this won’t happen very often.

The electrical wiring diagram is shown in Annex 1.

USAFA Ludwieg Tube Detailed Design page 45 of 47

8 Mass budget

The following table list the masses of the main components of the wind tunnel as far as they are known in this stage of the project.

Component Parts Material Mass Remarks

Charge tube (Outside)

24 m tubes Flanges

Heating cables Insulation

1.4571/AISI316Ti

Rockwool

2800 kg

Mounting frame (Outside)

Frame Guiding rails

Carriages

1.0037/AISI1005

1.4571/AISI316Ti

1.0037/AISI1005

1600 kg

Charge tube (Inside)

3 m tube Flanges

Heating cables Insulation

1.4571/AISI316Ti

Rockwool

120 kg

Mounting frame (Outside)

Frame Guiding rails

Carriages

1.0037/AISI1005

1.4571/AISI316Ti

1.0037/AISI1005

650 kg

Valve block Block

Plunger Nozzle throat

1.4571/AISI316Ti

160 kg

Nozzle Body

Intersection Flanges

Glass fiber

1.4571 / Aluminum 1.4571/AISI316Ti

100 kg

Test section Test section Windows Flanges

1.4571/AISI316Ti

PMMA

1.4571/AISI316Ti 290 kg

Probe chamber Chamber

Blind flange Aluminum 90 kg

Model support 1 Support Flange

1.4571/AISI316Ti 50 kg

Model support 2 Support Flange

1.4571/AISI316Ti 60 kg

Diffuser section 1.4571/AISI316Ti 170 kg

Vacuum tank Tank

Flanges 1.4571/AISI316Ti 2400 kg

Vacuum pump With tubing - 600 kg Exhaust Tubing 1.4571/AISI316Ti 75 kg

Roller guiding Guiding Flange

1.4571/AISI316Ti 200 kg

Compressor unit Compressor

Dryer Bottles

- 1200 kg

19" Rack Electric - 300 kg 1 rack

19" Rack Control and measurement equipment

- 500 kg 2 racks

Miscellaneous - 200 kg estimated

Total 11565 kg

Tab. 4 Mass budget

USAFA Ludwieg Tube Detailed Design page 46 of 47

USAFA Ludwieg Tube Detailed Design page 47 of 47

List of Figures

Fig. 1 Installation place of the Ludwieg tube wind tunnel Fig. 2 Flange connection Fig. 3 Flanges with measurement ring Fig. 4 Blind flange connection Fig. 5 Heating cables on the charge tube Fig. 6 Charge tube insulation Fig. 7 Flow chart of the high pressure system Fig. 8 High pressure control board Fig. 9 Design of the fast acting valve block Fig. 10 Ma 6 nozzle, glass fiber body with metal intersections Fig. 11 Test section, overview Fig.12 Probe chamber with linear motion unit Fig. 13 Model support No. 1 Fig. 14 Model support No. 2 Fig. 15 Model support No. 2 in the test section Fig. 16 Vacuum tank Fig. 17 Blind cover of vacuum tank flange Fig. 18 Vacuum tank and vacuum pump Fig. 19 Vacuum tank overpressure safety valve Fig. 20 Charge tube carriages and mounting frame Fig. 21 Moveable carriages and guiding rails Fig. 22 Wall opening in the laboratory room Fig. 23 Inside part of the charge tube Fig. 24 Valve block carriage Fig. 25 Clamping mechanism of the valve block carriage Fig. 26 Test section on carriage Fig. 27 Roller guide of the diffuser section Fig. 28 Open diffuser section Fig. 29 Diffuser pushed into the vacuum tank Fig. 30 Inflatable sealing ring Fig. 31 Flow chart of the sealing device Fig. 32 Control and operation lines of the Ludwieg tube facility Fig. 33 Pitot rake

List of Tables

Tab. 1 Charge tube data

Tab. 2 Alarm plan

Tab. 3 Power budget

Tab. 4 Mass budget