Summer Vocational Training Report

on

Estimation of Air Leakage Rate and Static Pressure for the Selection of Air Blower for Ellipsoidal Fabric Structure

Submitted By

Aayush SinghalB. Tech (III Year)

Mechanical EngineeringG.L.A. University

Mathura

Training Period

(01 to 30 June 2016)

Under the Guidance of

Devendra KumarScientist ‘D’

Aerial Delivery Research & Development Establishment Defense Research & Development Organization

Ministry of Defense, Government of India Agra Cantt – 282 001

AERIAL DELIVERY RESEARCH & DEVELOPEMENT ESTABLISHMENTInflatable System Group (ISG)

CERTIFICATE

This is to certify that the project report compiled by Mr. Aayush Singhal which is entitled ''Estimation of static pressure and air leakage rate for the selection of air blower for ellipsoidal fabric structure" is an authentic record of the effort carried out by him during the period of his summer training from 30 May to 30 June 2016. The report is aimed towards the partial fulfillment of the requirement of the training certificate duly accredited by Aerial Delivery Research & Delivery Establishment (ADRDE), Agra under the guidance of Mr. Devendra Kumar, Scientist 'D', ISG.

Devendra Kumar, Scientist 'D' Project Guide

ACKNOWLEDGEMENT

Aerial Delivery Research & Development Establishment (ADRDE) is one of the premier establishments of Defense Research and Development organization (DRDO). This establishment is committed to provide the users state-of-the-art product & services to its customers in areas of the aerodynamic decelerators, pneumatic structures, aircraft arrester barriers and allied systems through research and development, innovation, team work and following up the same by continual improvement based on user's perception.

I am highly obliged to Mr. Debasish Chakrabarti, Director ADRDE, Agra for allowing me to associate with this esteemed establishment as a summer trainee in 'Inflatable System Group’ for one month period from 30 May to 30 June 2016.

Further, I extend my heartfelt gratitude to the Group Director, Mr. Amitabh Pal, Scientist 'F' for entrusting me with such a substantial project on "Air Supported Structure". Working in this project has certainly been a good learning experience and has reinforced my knowledge of Pneumatic Structures to a great deal.

Most importantly, I express my sincere thanks to Mr. Devendra Kumar, Scientist 'D' for his unflagging guidance throughout the progress of this project as well as valuable contribution in the preparation and compilation of the text.

I am thankful to all those who have helped me for the successful completion of my training at ADRDE. Agra.

(Aayush Singhal)B. Tech (III Year)

Mechanical EngineeringG.L.A. University

Mathura

1.0 Introduction 12.0 Types of Air Structures 1

2.1 Air Supported Structures 22.2 Air Inflated Structures 33.0 Subsystems Used in Air Structures 44.0 Materials Used for the Manufacturing of Envelopes 55.0 Coating Methods 65.1 Direct Coating 65.2 Transfer Coating 65.3 Melt Coating 75.4 Calendaring (Rolling) 76.0 Sealing Methods 76.1 Radio Frequency Sealing Method 76.2 Adhesive/Gluing 87.0 Air Blowers for Air Supported Structures 87.1 Types of Blowers 8

7.1.1 Centrifugal Blowers 87.1.2 Positive Displacement Blowers 98.0 Anchoring Systems for Air Supported Structures 98.1 Types of Anchors Used 108.2 Materials Used to Make Anchors 129.0 Advantages and Disadvantages of Pneumatic Structures 1210.0 Applications of Pneumatic Structures 1211.0 Future of Inflatable Space Structures 1311.1 Inflatable Power Antennae 1311.2 Solar Sail Booms 1311.3 Inflatable Radiator 1312.0 Top 5 Notable Air Structures 1412.1 Alaska Dome 1412.2 Bennett Indoor Athletic Complex 1412.3 Carrier Dome 1512.4 Harry Jerome Sports Centre 1512.5 Tokyo Dome 1613.0 Objective 1714.0 Conclusion 19

INDEX

References

ABOUT ADRDE

Aerial Delivery Research & Development Establishment (ADRDE) is one of the premier

establishments of Defense Research and Development organization (DRDO).

ADRDE deals with high-level research in defense related technologies. Various projects are under progress like parachutes for different application, aerostats for surveillance, platforms for heavy drop, floatation for Space Recovery Experiment (SRE), aircraft arrester barrier system for air force, etc.

Defense Research and Development organization (DRDO) is a premier organization of the Government of India, responsible for development of technology for use by the three services of defense in India. It was formed in 1958 by the merger of Technical Development Establishment and the directorate of Technical Development and Production with the Defense Science Organization.

My training area for one month was in Inflatable System Group where development of inflatable system for both defense application and to some extent for high end research oriented organization like ISRO are being carried out.

1.0 Introduction:Who first thought of the idea for inflatable buildings? We’ve written about the first person to actually design and build an air structure, David Geiger, but he wasn’t actually the first

person to think of the idea - only the first to put it into practice. So who did come up with the idea, then? Well, as with any invention, it’s hard to say who first came up with an idea, but it’s easy to figure out who first submitted patents for it. In the case of inflatable structures, the first U.S. patent was submitted by a gentleman named Woldemar A. Bary, way back on April 28th, 1955. The patent itself was accepted (presumably) on June 3rd, 1958 - a full 12 years before the unveiling of Geiger’s air structure at the 70’s World Fair. After David Geiger created the first air supported structure, the 70’s saw other domes go up around the world - including the first North American domes of Ralph Farley. [1]

An air-supported (or air-inflated) structure is any building that derives its structural integrity from the use of internal pressurized air to inflate a pliable material (i.e. structural fabric) envelope, so that air is the main support of the structure, and where access is via airlocks. It is usually dome-shaped, since this shape creates the greatest volume for the least amount of material. To maintain structural integrity, the structure must be pressurized such that the internal pressure equals or exceeds any external pressure being applied to the structure (i.e. wind pressure). The structure does not have to be airtight to retain structural integrity - as long as the pressurization system that supplies internal pressure replaces any air leakage, the structure will remain stable. All access to the structure interior must be equipped with some form of airlock - typically either two sets of parallel doors or a revolving door or both. Air-supported structures are secured by heavy weights on the ground, ground anchors attached to a foundation, or a combination of these. Among its many uses are sports and recreation facilities, warehousing and temporary shelters etc. The structure can be either wholly, partial, or roof-only air supported. A fully air-supported structure can be intended to be a temporary or semi-temporary facility or permanent, whereas a structure with only an air-supported roof can be built as a permanent building. The largest air-supported dome in the world is "The Dome" in Anchorage, Alaska at 180,000 square feet (17,000 m2). [1]

Fig. 1: “The Dome” in Anchorage

2.0 Types of Air Structures:Air structures are also known as pneumatic structures. The word “pneumatic” is derived from the Greek word “pneuma” (meaning breath of air), thus these are the structures which are supported by air. A pneumatic structure is a constructed form that derives its rigidity from captured pressurized gas. The term “Pneumatic Structures” encompasses constructions such as inflatable play areas for children (“bouncy castles”), as well as covered tennis courts or swimming pools in winter months. When deflated, pneumatic structures have little rigidity and become loose piles of fabric. When inflated, they attain a

preconceived form and respond dynamically to outside forces, such as wind, rain, and snow, to keep their form. The inflation, usually by means of a blower or fan, pushes air into the closed fabric forms to create a pressure differential across the material membrane, with a higher dynamic pressure inside the form. This creates a tensile force across the membrane. This tensile force unfolds the fabric until the form is found. To restate, a pneumatic structure is an inflated membrane experiencing purely tensile forces. Due to scale and costs, air is usually the choice of inflating gas. There are two major types: single-membrane and double-membrane. Much of the physics of the two cases boils down to the same principles, but the two types drive dramatically different architectural forms.

Single-membrane structures use the interior of the bubble as the active, usable space. To enter a single-membrane pneumatic structure, a person must cross through a threshold, across which there is the pressure differential. This often requires some kind of an airlock. Double-membrane structures use pressurized cells as walls, ceilings, and supports. A person inside a double-membrane is not enclosed within a pressurized space, but is enclosed by pressurized spaces. [2] Pneumatic structures can be classified in two categories as mentioned below.

(i) Air Supported Structures(ii) Air Inflated Structures

2.1 Air Supported Structures:The shape of an air-supported structure is limited by the need to have the whole envelope surface evenly pressurized. If this is not the case, the structure will be unevenly supported, creating wrinkles and stress points in the pliable envelope which in turn may cause it to fail. In practice, any air supported surface involves a double curvature. Therefore, the most common shapes for air-supported structures are hemispheres, ovals, and half cylinders. The main loads acting against the air-supported envelope are internal air pressure, wind, or weight from snow build-up. To compensate against wind force and snow load, inflation of the structure is adjusted accordingly. Modern structures have computer controlled mechanical systems that monitor dynamic loads and automatically compensate the inflation for it. The better the quality of the structure, the higher forces and weight it can endure. The best quality structures can withstand winds up to 120 mph (190 km/h), and snow weight to 40 pounds per square yard (21.7 kilograms per square metre).

The interior air pressure required for air-supported structures is not as much as most people expect and certainly not discernible when inside. The amount of pressure required is a function of the weight of the material - and the building systems suspended on it (lighting, ventilation, etc.) - and wind pressure. Yet it only amounts to a small fraction of atmospheric pressure. Internal pressure is commonly measured in inches of water, inAq, and varies fractionally from 0.3 inAq for minimal inflation to 3 inAq for maximum, with 1 inAq being a standard pressurization level for normal operating conditions. In terms of the more common pounds per square inch, 1 inAq equates to a mere 0.037 psi (2.54 mbar). [1]

Fig. 2: Air supported structure for sport activities

2.2 Air Inflated Structures:An inflatable is an object that can be inflated with a gas, usually with air, but hydrogen, helium and nitrogen are also used. One of several advantages of an inflatable is that it can be stored in a small space when not inflated, since inflatables depend on the presence of a gas to maintain their size and shape. Function fulfilment per mass used compared with non-inflatable strategies is a key advantage. Stadium cushions, impact guards, vehicle wheel inner tubes, emergency air bags, and inflatable space structures employ the inflatable principle. Inflation occurs through several strategies: pumps, ram-air, billowing, and suction.

There are two types of air inflatable structures: high-pressure and low-pressure. In a high-pressure inflatable, structural limbs like pillars and arches are built out of a tough, flexible material and then inflated at a relatively high pressure. These limbs hold up passive membranes. The space where the visitors or inhabitants stay is at normal atmospheric pressure. For example, airplane emergency rafts are high-pressure inflatable structures. Low-pressure inflatables, on the other hand, are slightly pressurized environments completely held up by internal pressure. In other words, the visitors or inhabitants experience a slightly higher than normal pressure. Low-pressure inflatables are usually built of lighter materials. Both types of inflatables (the low-pressure type more so) are somewhat susceptible to high winds.

Inflatable castles and similar structures are temporary inflatable buildings and structures that are rented for functions, school and church festivals and village fetes and used for recreational purposes, mainly used by children. The growth in popularity of moonwalks has led to an inflatable rental industry which includes inflatable slides, obstacle courses, games, and more. Inflatables are ideal for portable amusements because they are easy to transport and store.

These are made of a synthetic fabric, of which different colors have been sewn together in various patterns. An electric blower constantly forces air into the figure, replacing air lost through its fabric and seams. They are internally lit by small incandescent light bulbs (also used in nightlights), which are covered by translucent plastic snap-on globes that protect the fabric from the heat if they should rest against it. [3]

Fig. 3: Air inflated structure for recreational activities

3.0 Subsystems Used in Air Structures: (i) Envelope:

They can be made of different materials. These are not made of continuous materials. Materials are seamed together using adhesive sealing, heat bonding or

mechanical jointing.(ii) Cable System:

They act as the supporting system. They experience tension force due to upward force of the air. Can be placed in one or two directions for better network and stability.

(iii) Pumping Equipment: It is used to supply and maintain the internal pressure of the structure. Fans, blowers, and compressors are generally used for the pumping system. The amount of the air required depends on the weight of the material and

the wind speed.(iv) Entrance Doors:

Doors can be ordinary doors or airlocks. Airlocks minimize the chances of having an unevenly pressurized

environment.

Fig. 4: Entrance doors(v) Foundation:

Pneumatic structures are secured to ground using heavy weights, ground anchors or attached to a foundation.

Weights of the materials and the wind loads are used to determine the most appropriate anchoring system.

When anchoring is done to the soil, the cable is attached directly inserted and the frictional forces of the soil hold it downwards.

Soil anchoring systems include screws, disks, expanding duckbill and arrowhead anchors.

Pneumatic structures are designed to uphold or withstand the wind speed of 120 mph and snow load of 40 pounds/yard2. [2]

Fig. 5: Air supported structure with subsystems

4.0 Materials Used for the Manufacturing of Envelopes:For envelopes, the material used should exhibit following properties:

They should be of light weight. They should have high tensile strength and tear resistance.

Materials given below are generally used for the fabrication of the structures.(i) Fibreglass:

They have high tensile strength, elasticity and durability. They are generally coated with Teflon or silicon to increase resistance to

extreme temperatures and UV radiations.(ii) Polyester:

Most common envelope material for small structures. PVC is applied to the polyester using a bonding or adhesive agent. PVC coated polyester is used for envelopes with small size.

(iii) ETFE: It is very energy efficient because of transparency, insulation and UV

resistance. It is also light weight and has a life span of 20 years and is recyclable.

(iv) Nylon: Vinyl coated nylon has more strength, durability and stretch than polyester. They have a higher cost. [1]

Fig. 6: Different types of coated fabrics

Fig. 7: Layers of coated fabric

5.0 Coating Methods: Coating is the process of covering a substrate (nylon, polypropylene, polyester, polyamide, cotton, wool, woven or non-woven fabrics or sheets), with a product (PVC, PU, silicone or other) to alter and enhance its physical properties and appearance. Various coating methods are mentioned below:5.1 Direct Coating:The PVC coating paste is directly applied to the fabric in four layers. Applications are side curtains, tilts and tarpaulins for trucks, railway wagons & containers, sports mats, swimming pool covers, and textile architecture.

Fig. 8: Direct coating

5.2 Transfer Coating:The coating paste (PU, silicone, etc.) is applied to the fabric via a paper carrier. Applications are protective clothing, outdoor sports clothing, shoe protectors, mattress protectors, airbags and tents.

Fig. 9: Transfer coating

5.3 Melt Coating: Through melt coating we produce a film out of different polymers which is then laminated onto a carrier. This carrier can be a textile, a felt, knitted fabric, another film or paper. Applications are technical textiles for sewer renovation.

Fig. 10: Melt coating

5.4 Calendaring (Rolling):We manufacture TPO (thermoplastic polyolefin) and PVC films which are embossed to give the film a textured aspect. Applications are car dashboards, door panels, sun visors, wall coverings and pond liners. [4]

Fig. 11: Rolling

6.0 Sealing Methods:Sealing methods used in fabrication of air structures are mentioned below.6.1 Radio Frequency Sealing Method:Also known as high frequency welding and dielectric sealing, this manufacturing process uses electromagnetic energy and pressure to weld and permanently bond thermoplastic, vinyl and coated fabrics to create a dimensional product. The RF sealing process is most often referred to as radio frequency welding because of the way the electrostatic energy and pressure are used to realign the molecules to form a new, strong bond of the materials being fused together. Using this RF seal service, a new, one-piece permanent bond is created that is impenetrable and resistant to tearing. [5]

The radio frequency welding process scrambles the molecules in flexible polymeric materials to be joined for the dimensional requirements and product functionality. RF welding is a three-step process involving the preparation and positioning of the components, adding of electromagnetic energy and pressure to molecularly combine the materials, and finally, the cooling of the materials. When cooled, the newly formed seam is as strong or even potentially stronger than the original material. The RF welding process can only be used with materials of a polar molecular construction, the most common being

PVC and Polyurethane, although many other coated materials such as nylon are feasible. RF sealing works much better with stretchable unsupported film type materials such as TPU and TPE type materials. [6]

Fig. 12: Radio frequency sealing machine [4]

6.2 Adhesive/Gluing: Gluing can provide an air tight solution, but gluing takes much longer than RF welding and often uses hazardous solvents that are harmful to the environment. Glued seams are also subject to failure once the adhesive has worn out. [6]

7.0 Air Blowers for Air Supported Structures:Blowers are mechanical or electro-mechanical devices used to induce gas flow through ducting, electronics chassis, process stacks, etc.- wherever flow is needed for exhausting, aspirating, cooling, ventilating, conveying, and so on. Blowers cool electronic enclosures, induce drafts in boilers, increase airflow on engines, and are configured in a variety of designs such as centrifugal flow or rotary lobe styles. Motors usually drive blowers, though they can be powered by other means such as engines. Often used interchangeably with “Fans,” blowers are defined by the ASME as having a ratio of discharge pressure over suction pressure between 1.11 and 1.2, while fans are defined as anything below this ratio and compressors are defined as anything above it. Some makers of portable fans refer to their units as blowers even if they do not necessarily conform to the ASME distinction, which applies to permanently installed industrial process equipment. Another kind of blower is the mobile or hand held device used for moving fallen leaves. [1]

7.1 Types of Blowers:7.1.1 Centrifugal Blowers: Centrifugal blowers use high speed impellers or blades to impart velocity to air or other gases. They can be single or multi-stage units. Like fans, centrifugal blowers offer a number of blade orientations, including backward curved, forward curved, and radial.

Blowers can be multi- or variable speed units. They are usually driven by electric motors, often through a belt and sheave arrangement, but some centrifugal blowers are directly coupled to drive motors. Fan speed can be changed to vary flow rates by resizing sheaves, using variable speed drives, etc., but dampers are even more common as a means of adjusting flow. Fan affinity laws dictate that a percent reduction in speed will produce a like reduction in flow. [1]

Fig. 13: Centrifugal blower 7.1.2 Positive Displacement Blowers: Positive Displacement blowers are similar in principle to positive displacement pumps in that they use mechanical means to squeeze fluid and thereby increase pressure and/or velocity. Centrifugal designs, on the other hand, impart velocity and pressure to media by flinging them outward with impellers. Among positive displacement blowers, the Roots, or rotary lobe, type is common, which uses two counter-rotating lobed rotors to move fluid through the blower, much the way a gear pump moves oil or other viscous liquids. A cutaway blower (below) shows one of the two rotors. Positive displacement lowers are often driven by direct-coupled electric motors but they can be driven by gas engines. [1]

Fig. 14: Positive displacement blower

8.0 Anchoring Systems for Air Supported Structures: An anchor is used to prevent the structure from drifting from its location due to wind. There are numerous types of anchors and the heavy ones are normally produced through casting or drop-forged from carbon steel.

8.1 Types of Anchors Used: (i) Wedge Anchor:Application: Steel structure, railings, cantilever bracket, escalator, curtain wall, doors and windows, mechanical equipment, cable tray, wooden structure.

Fig. 15: Wedge anchor

(ii) Sleeve Anchor:Application: Steel structure, ceiling, railing, handrails, bracket, floor, staircase, mechanical equipment and door.

Fig. 16: Sleeve anchor

(iii) Metal Frame Anchor:Application: Windows and doors.

Fig. 17: Metal frame anchor

(iv) Bolt Anchor:Application: Elevator installation, heavy objects installation, steel structure, glass curtain wall, bridge etc.

Fig. 18: Bolt anchor

(v) Drop In Anchor:Application: Drop in anchor is suitable to concrete and natural hard stone. It can be used for the installation of fire equipment, air conditioner, exhaust duct, upside-down tube, curtain wall and ceiling etc.

Fig. 19: Drop in anchor (vi) Tie Wire Anchor:Application: Tie wire anchor is suitable to concrete and natural hard stone. It can be used for ceiling and light weight suspension.

Fig. 20: Tie wire anchor

(vii) 4Pcs Heavy Duty Anchor:Application: Steel structure, bracket, escalator, curtain wall, doors & windows, chairs, trash can, railings, and deceleration strips etc. [7]

Fig. 21: 4Pcs heavy duty anchor

8.2 Materials Used to Make Anchors: (i) Steel Cables: Steel wires are twisted into strands which are then twisted around a core to form the cable.

(ii) Ballasts: Materials for ballasts of smaller structures include sand bags, concrete blocks or bricks. The ballasts must be placed around the perimeter of the structure to evenly distribute the load. [7]

9.0 Advantages and Disadvantages of Pneumatic Structures: (i) Advantages:

Considerably lower initial cost than conventional buildings. Lower operating costs due to simplicity of design (wholly air-supported structures

only). Easy and quick to set up, dismantle, and relocate (wholly air-supported structures

only). Unobstructed open interior space, since there is no need for columns. Able to cover almost any project. Custom fabric colours and sizes, including translucent fabric, allowing natural

sunlight in.

(ii) Disadvantages: Continuous operation of fans to maintain pressure, often requiring redundancy or

emergency power supply. Dome collapses when pressure lost or fabric compromised. Cannot reach the insulation values of hard-walled structures, increasing

heating/cooling costs. Limited load-carrying capacity. Continuous operation of fans and blowers to maintain pressure. [1]

10.0 Applications of Pneumatic Structures (i) Sports and Recreation: It has the ability to span greater distances without beams and columns. For example, American football and baseball grounds.

Fig. 22: Air supported sports dome

(ii) Military Structures: For storage and emergency medical operations. To protect radar stations from adverse weather conditions. [2]

11.0 Future of Inflatable Space Structures:11.1 Inflatable Power Antennae:

The Power Antennae utilizes an inflatable parabolic reflector. Parabolic reflector acts as a solar concentrator and focuses energy concentrator and

focuses energy onto a solar array. A beam splitter is mounted in front of the array to deflect RF onto a feed. The feed is used to separate optical from RF energy. Can be used for deep space power generation and high gain power generation and

high gain RF communications concurrently. [8]

11.2 Solar Sail Booms: Solar sails are devices that reflect photons from the reflect photons from the sun

and convert some sun and convert some energy into thrust. Inflatable rigidizable booms can be used for booms can be used for support. Inflation gas is introduced at the base. Utilizes the concept of glass transition glass transition rigidization. Since tube is rigidized, it can withstand substantial loads after deployment. [9]

11.3 Inflatable Radiator: High power generation on Space-based defence systems require large amounts of

heat rejection. Inflatable radiator can capture heat during power generation periods and radiate

into space power generation periods. During power generation phase, radiator is extended out spacecraft while filled

with waste heat. Steam is condensed gradually as heat is radiated into space. Radiator is retracted during this period to maintain constant saturation pressure.

This also keeps radiator constant saturation pressure. This also keeps radiator protected from space debris. [10]

12.0 Top 5 Notable Air Structures: 12.1 Alaska Dome:At 180,000 square feet, The Dome is officially the largest sports complex of its kind on the planet. Held down with pipes and cables plunging 40 feet into the ground, supported by pressurized air, The Dome houses a 400-meter USA Track & Field certified track, full-size soccer field, full-size football field, weight equipment, batting cages and much more. Snow and wind sensors automatically increase or decrease pressure and temperature of The Dome, keeping it at 15 to 17 lbs of air pressure per square inch, creating an hyperbaric chamber.

Fig. 23: Alaska dome

12.2 Bennett Indoor Athletic Complex:The Bennett Indoor Athletic Complex is an air-supported structure that provides an indoor venue for athletics to the Toms River Regional Schools. It is part of the Bennett Complex, which also features outdoor facilities. The Bennett Complex is located between Hooper Elementary and Toms River Intermediate East at 1519 Hooper Avenue in Toms River. It is named after long time Superintendent John Bennett, who served the district from 1960-1977. Amongst other events, the Bennett Complex has hosted the track meet component of the NJSIAA Tournament of Champions in 2007, 2008, 2009, 2010, 2011, 2012 (for indoor athletics only), 2013, and 2014. The Indoor Athletic Complex is also known as The Bubble, and is home to many New Jersey State indoor athletic meets (including state championships). The Indoor Complex features a 200 meter six-lane track with and eight-lane straightaway, a Finish Lynx electronic timing system, and accommodates field events such as shot put, high jump, pole vault, long jump, and triple jump. The Indoor Complex was first installed for the 2006-2007 school year. The Indoor Complex was damaged by Hurricane Sandy, but was repaired and reopened in January 2013.

Fig. 24: Bennett indoor athletic complex

12.3 Carrier Dome:Carrier Dome is a 49,250-seat domed sports stadium located on the campus of Syracuse University in the University Hill neighbourhood of Syracuse, New York. It is home to the Syracuse Orange football, basketball, and lacrosse teams. In 2006–07, the women's basketball team began playing home games in the Dome. New York high school football state championships as well as the annual New York State Field Band Conference championships are held in the stadium, as are occasional concerts. The Carrier Dome is the largest domed stadium of any college campus, and the largest domed stadium in the North-eastern United States. Also, it is the largest on-campus basketball arena in the nation, with a listed capacity of 33,000; however, this limit has been exceeded several times.

Fig. 25: Carrier Dome

12.4 Harry Jerome Sports Centre:The Harry Jerome Sports Centre is a 53,000 of sports facility located in Burnaby, BC. It is the primary programming location for many volleyball & other sporting events as well as the home of the Volleyball BC offices. The Harry Jerome Sports Centre is the large white dome located at 7564 Barnet Highway in North Burnaby, approximately 1.5km east of the Hastings St. turn off to Simon Fraser University.

Fig. 26: Harry Jerome sports centre for volleyball

12.5 Tokyo Dome:Tokyo Dome is a stadium located in Bunkyo, Tokyo, Japan. Construction on the stadium began on May 16, 1985, and it opened on March 17, 1988. It was built on the site of the Velodrome, adjacent to the predecessor ballpark, Korakuen Stadium. It has a maximum total capacity of 55,000 depending on configuration, with an all-seating configuration of 42,000.Tokyo Dome's original nickname was "The Big Egg", with some calling it the "Tokyo Big Egg". Its dome-shaped roof is an air-supported structure, a flexible membrane held up by slightly pressurizing the inside of the stadium. It is the home field of the Yomiuri Giants baseball team, and has also hosted music concerts, basketball, American football and association football games, as well as puroresu (pro-wrestling) matches, mixed martial arts events, kickboxing events, and monster truck races. It is also the location of the Japanese Baseball Hall of Fame which chronicles the history of baseball in Japan. [11]

Fig. 27: Tokyo dome

13.0 Objective:Estimation of air leakage rate and static pressure for the selection of air blower for ellipsoidal fabric structure

Fig. 28: Sketch of the structure in CATIA V5

Input Parameters:Dimensions of ellipsoidal fabric structure:Semi-axis, a = 15 mSemi-axis, b = 10 mSemi-axis, c = 10 mLeakage gap at the base of the structure = 0.001 mHeight of the centre of air blower, = 1 mDiameter of blower duct, d = 0.5 mLength of blower duct, l = 4 mDensity of coated fabric = 2 kg/m2

Thickness of coated fabric, t = 0.001 mStrength of coated fabric, = 100 MPa

Velocity of air at CoG of the structure, = 10 m/s

Velocity of air at the centre of the blower, = 0 m/s

Wind velocity, = 160 km/h = 44.44 m/s

Density of air, = 1.225 kg/ (at sea level and at 15°C)

Kinematic viscosity of air, = 15

Height of CoG of the structure, = = 3.75 m

Ellipsoidal Parameters:

Volume of semi-ellipsoid, V = = 3141.59

Surface area of semi-ellipsoid, A =

Projected area of ellipse, =

Perimeter of ellipse,

Calculations:Calculation of Internal Pressure:Applying Bernoulli’s equation at points on the surface and at a distance from it outside with the same datum,

where = Stagnation pressure

= Atmospheric pressure

= Stagnation velocity = 0 m/s

= Gravitational acceleration = 9.81 m/s2

=

= 1209.63 Pa

Internal pressure, 12 mbar

Calculation of Stress:Equating the total pressure force inside the structure to the total resisting force in the coated fabric,

Internal pressure Projected area Stress Perimeter Thickness of fabric (t)

471.24 =

MPaFactor of Safety:

FoS = = = 14.03

Calculation of Volumetric Flow Rate:

Velocity of leaking air, 44.26 m/s

Volumetric flow rate, Leakage gap at the base

79.33

Calculation of static pressure considering friction losses:

Velocity at blower duct outlet, = = = 17.55 m/s

Reynolds’s No.,

Flow is turbulent.

Coefficient of friction, = 0.0029

Friction head loss in the blower duct using Darcy-Weisbach equation,

= 1.46 m

Pressure head loss due to , 17.54 Pa

Assuming the bend of the curved duct to be at an angle of 90 , K (local loss coefficient) is taken as 0.45.

= 7.06 m

Pressure head loss due to 84.84 Pa

Total friction loss = = 102.38 Pa

Now, applying Bernoulli’s equation at the centre of blower and the CoG considering the friction losses,

where Static pressure

= 1400.65 Pa = 14 mbar

14.0 Conclusion:Air supported and inflated structures are very useful in various ways and these are having a very deep impact on market too. Markets using inflatables are found to be in profit as customers can be easily attracted to these. The scope and future of these inflatables can be seen in various aspects.

Air supported structures are becoming more common and providing shelter for a number of different activities. Such structures are limited, however, in their ability to provide a controlled environment under the climatic conditions that exist in some areas of Canada. Their cost and limited life may also be a deterrent where the portability and speed of erection and dismantling cannot be fully exploited.

References:[1] https://en.wikipedia.org/wiki/Air-supported_structure_and-airblowers[2] https://www.slideshare.net/Krishnagnr/pneumatic-structures-55250260[3] https://en.wikipedia.org/wiki/Inflatable_building[4] www.sioen.com/technical-textiles/5-coating-techniques[5] Espalin, D., Medina, F., Arcaute, K., Zinniel, B., Hoppe, T., Wicker, R., (2009).

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[6] Rashilla, R.J., (1993). All-composite pressure vessels for natural gas vehicle (NGV) fuel tank. Proceedings of the Conference for Advanced Composites Technologies, Dearborn, MI, pp. 8–11

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