Infrared Imaging of Black Liquor Dropletsweb.cecs.pdx.edu/~far/Past Capstone...

Maseeh College of Engineering and Computer Science

Mechanical Engineering Department

Sponsor: Anthony Ross Company

Infrared Imaging of Black Liquor Droplets

Group Members: Aaron Brandt

Will Carter Brent Illingworth

Matt Travis

Academic Advisor: Dr. David Sailor

Industry Advisor:

Dan Higgins, P.E.

March 9, 2005


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EXECUTIVE SUMMARY:

Black liquor is a byproduct of the kraft paper pulping process; it is made up of chemicals,

solids and water. A recovery boiler's main purpose is to provide heat in order to convert the chemicals

in the black liquor back to reusable form. This is accomplished by spraying the black liquor through

nozzles into the boiler. While the droplets are suspended in air, the water is evaporated, the solids are

combusted, and the reusable chemicals fall to the bottom of the boiler where they are recovered. The

excess heat from the process is used to create steam which can be used for other processes or to

produce power.

Mathematical models of the recovery boiler environment are utilized by the pulp and paper

industry to increase the life of equipment, increase chemical recovery, and reduce emissions to the

atmosphere. The most important factors in the model are airflow characteristics and black liquor

droplet size. Currently the method used to determine the droplet size is analytical. The model's

accuracy can be improved if the droplet size was based on empirical data.

The project sponsor, Anthony Ross Company, has expressed interest in a method of

determining black liquor droplet size though infrared imaging. Anthony Ross currently provides

infrared video cameras to kraft paper plants to image the inside of the boiler for maintenance purposes.

This same camera combined with a proper optical system could also be utilized to provide images for

dynamic droplet sizing.

The design team made a comparison between infrared imaging and other methods to measure

dynamic droplets. It was found that there are no other existing dynamic droplet sizing methods that

can handle the high temperatures and limited access issues of a recovery boiler. By designing an

adjustable optics assembly that can attach to Anthony Ross' infrared camera, clear images of the black

liquor droplets could be produced and accurate sizing can take place.

The design team has come up with a concept of an optical system that will incorporate flexible

fiber optics and standard lenses. The fiber optics will allow the optical system's viewing angle to be

adjusted so multiple regions of the spray can be analyzed. The focal length of the system will also be

adjustable and calibrated so that the user will know the distance to the droplet. This is necessary to

properly scale the image size to the actual size.

The assembly can be used at first as an R&D tool. Using the data, the current model could be

improved and accurately reveal the effect of droplet size on recovery efficiency. If significant


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improvements on efficiency can be made by using the system, the camera and optics assembly would

then become marketable to plants all over the world.

TABLE OF CONTENTS:

EXECUTIVE SUMMARY:................................................................................................................... 2

TABLE OF CONTENTS:...................................................................................................................... 3

INTRODUCTION & BACKGROUND INFORMATION:................................................................ 5

Figure 1: Schematic representation of pulping and chemical recovery process............................ 5

MISSION STATEMENT:...................................................................................................................... 6

PROJECT PLAN: .................................................................................................................................. 6

Table 1: Project plan visualization & target dates .......................................................................... 6

PRODUCT DESIGN SPECIFICATIONS:.......................................................................................... 7

Table 2: Product design specifications and metrics......................................................................... 8

EXTERNAL SEARCH – DROPLET SIZING .................................................................................... 8 LASER - DETECTOR SYSTEMS ................................................................................................................ 8

Figure 2: Generalized laser diffraction system [1] ......................................................................... 9 Figure 3: Schematic of a PDA system [2]...................................................................................... 10

IMAGING SYSTEMS .............................................................................................................................. 10 Figure 4: Laser sheet applied to paint spray for a LSD system [3]............................................... 11 Figure 5: a) Laser and camera setup, b) Images obtained from the VisiSizer™ system [3]......... 11

EXTERNAL SEARCH – COMPONENTS........................................................................................ 12 FIBER OPTICS....................................................................................................................................... 12

Figure 7: Left: Faceplate Right: Tapers [6] .................................................................................. 13 Figure 8: CCD coupled with a taper [6] ....................................................................................... 13 Figure 9: A type of mechanically compensated zoom lens ............................................................ 14 Figure 10: A type of optically compensated zoom lens.................................................................. 14

TIP ACTUATION ................................................................................................................................... 15 Figure 11: Piston & SMA actuators used in endoscopes [8] ........................................................ 15

INTERNAL SEARCH - LIGHT TRANSFER................................................................................... 15

Figure 12: Concept drawing for mirror based system.................................................................. 16 Figure 13: Concept drawing for fiber optic based system............................................................. 16

INTERNAL SEARCH – ACTUATION:............................................................................................ 17

TIP ACTUATION ................................................................................................................................... 17 Figure 14: Bracket type actuation unit .......................................................................................... 17 Figure 15: Planetary gear type actuator ....................................................................................... 18

LENS ACTUATION................................................................................................................................. 18 Figure: 16: Power screw linear actuator for lens position adjustment......................................... 18 Figure: 17: Planetary gear system actuated optics shown in the tip assembly ............................. 19


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INTERNAL SEARCH – COOLING/CLEANING: .......................................................................... 19

Figure 18: Airflow exits from the lens tube over the outermost window ...................................... 20

FINAL DESIGN EVALUATION & SELECTION: ......................................................................... 20

Table 3: Decision matrix ................................................................................................................ 21 Figure 19: 3-D model made up of winning concepts from decision matrix................................... 22

FUTURE CONSIDERATIONS: ......................................................................................................... 22

CONCLUSION & RECOMENDATIONS: ....................................................................................... 22

REFERENCES ..................................................................................................................................... 23

APPENDIX: .......................................................................................................................................... 25

APPENDIX A: SCHEMATICS OF TYPICAL RECOVERY BOILER SHOWING AIR PORT AND LIQUOR GUN LOCATIONS................................................................................................................ 25

APPENDIX B: ADDITIONAL EXTERNAL SEARCH DOCUMENTATION ................................. 26

APPENDIX C: INTERNAL SEARCH DOCUMENT ........................................................................ 27

APPENDIX D: TEST TO DETERMINE OBJECT SIZE AS A FUNCTION OF DISTANCE AWAY FROM THE OBJECT. ........................................................................................................... 34

APPENDIX E: PRODUCT DESIGN SPECIFICATIONS DOCUMENT......................................... 36


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INTRODUCTION & BACKGROUND INFORMATION:

The kraft paper pulping process uses an aqueous solution of sodium hydroxide (NaOH) and

sodium sulfide (Na2S) to break down the binding agents in wood pulp. During the pulping process,

most of the NaOH is consumed in the neutralization of wood acids, and some of the Na2S is oxidized

to sodium thiosulfate (Na2S2O3). The spent pulping chemicals in combination with dissolved wood

components and water make up what is referred to as the weak liquor byproduct of the pulping

process. The weak liquor is fed into evaporators where most of the water is removed. The liquid is

then referred to as black liquor.

Black liquor can be comprised of as much as 85 percent solids. Most of the solids are carbon

based and can be burned off. The recovery boiler is used for this process. Black liquor is sprayed

through nozzles into the boiler. The organic chemicals are combusted and the remaining water

evaporated. The generated heat is used to oxidize the inorganic sodium salts to reusable form and to

create steam, which can be used to produce power. Figure 1 is a schematic representation of the

pulping and chemical recovery process.

White Liquor

Steam

Smelt

Weak Liquor

concentratedBlack Liquor

E-1

E-2

E-3

E-4 E-5E-6

P-1 P-2 P-3 P-4

P-5P-6

Pulp Digester

Evaporator Evaporator Evaporator

Recovery Boiler

Causticizer

P-7

Air

Combustion consumessolids

Sodium returned to NaOH and NaS

Schematic of Pulping Process

E-7

P-8

P-9

Turbine

Figure 1: Schematic representation of pulping and chemical recovery process


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Anthony Ross Company produces mathematical models of the boiler environment. The models

predict boiler behavior, which can assist in improving chemical recovery and reducing wear on the

equipment. Two of the most important factors in the model are the airflow characteristics and droplet

size distribution. Anthony Ross would like to improve the model’s accuracy through experimental

determination of the droplet size distribution.

To obtain the droplet size distribution, high-speed infrared camera technology currently

employed as a boiler inspection tool, will be modified to capture images of the black liquor droplets.

The current camera and lens system has limitations. The camera lens is short and cannot extend into

the boiler to meet the necessary distance. The camera lens also does not have an adjustment for

viewing angle, making it difficult to view the liquor spray from the limited access points.

MISSION STATEMENT:

Design an optical assembly that will attach to the infrared camera currently being distributed by

Anthony Ross Company. The assembly will provide clear images of black liquor droplets to the

camera and allow Anthony Ross’ engineers to improve their mathematical model of the recovery

boiler.

PROJECT PLAN:

Table 1: Project plan visualization & target dates

ID Task Name Start Finish DurationJan 2005 Feb 2005 Mar 2005 Apr 2005 May 2005

1/2 1/9 1/16 1/23 1/30 2/6 2/13 2/20 2/27 3/6 3/13 3/20 3/27 4/3 4/10 4/17 4/24 5/1 5/8 5/15 5/22 5/29 6/5

1 4w1/28/20051/3/2005PROJECT DESIGN SPECS.

2 3.2w2/18/20051/28/2005INTERNAL / EXTERNALSEARCH

3 5w3/11/20052/7/2005CONCEPT GENERATION

4 7.2w3/28/20052/7/2005OPTICS DESIGN

5 2.8w2/24/20052/7/2005ACTUATION DESIGN

6 5w3/28/20052/22/2005HOUSING DESIGN

7 6.8w4/8/20052/22/2005SELECTION & EVALUATIONOF FINAL DESIGN

8 1.2w3/1/20052/22/2005WINTER QUARTER REVIEW

9 4.4w5/9/20054/8/2005PROTOTYPING

10 2.2w5/23/20055/9/2005TESTING & VERIFICATION

11 2.2w6/6/20055/23/2005FINAL REVIEW &OPTIMIZATION

12 2w6/10/20055/30/2005FINAL PROJECTPRESENTATION


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PRODUCT DESIGN SPECIFICATIONS:

Anthony Ross Company is the main customer for the optical assembly. The camera to be used

is distributed by Anthony Ross Co. through a license agreement with Enertechnix. The design team

has worked with Anthony Ross Co. to establish the following major design specifications:

1) The equipment will be safe to operate. It is possible that flame may escape the boiler through the

air injection ports where the assembly will most likely be inserted. The operator must be protected

from the escaping flame. The installation of the assembly onto the boiler must also be simple and not

require any actions that may pose a hazard to the operator.

2) The assembly must survive the boiler environment. The boiler can reach temperatures of

2,000°F and contains fast moving debris and harsh chemicals. The assembly must withstand the

environment for a minimum of 30 minutes without suffering damage or degradation to the image

quality.

3) The viewing angle must be adjustable. A viewing angle adjustment from 0º to -90º is required.

This is necessary to enable the user to locate and analyze different regions of the spray.

4) The camera must extend far enough into the boiler. Because of a recovery boiler’s internal

structure, the assembly must extend 1 meter into the boiler to allow for multiple views of the spray.

5) The focal length must be adjustable. In order to view different regions of the spray, the focal

length must be adjustable.

6) The focal length must be known and the depth of focus minimized. The focal length is

necessary to correctly scale the droplet image size to the actual size. By minimizing the depth of

focus, the focal length can accurately be used to determine the scaling factor. This is explained in

further detail in the external search.

Table 2 summarizes all of the product design specifications along with their metrics. The overall

ranking of the requirements is shown in the importance column as a portion of 100. The engineering

criteria columns indicate the importance of the criterion to meet the requirements on a scale of 1 - 5.


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Table 2: Product design specifications and metrics

EXTERNAL SEARCH – DROPLET SIZING

Although infrared imaging was the initially desired method for sizing the droplets, other

methods were explored in case there was a more suitable option. Measuring the size of dynamic

droplets is a common R&D practice in several different fields. Because of this, the group was able to

research several existing methods. These methods can be divided into two main categories: laser-

detector systems and imaging systems.

Laser - Detector Systems

Laser diffraction and phase Doppler anemometry (PDA) are two common methods that are

used mostly in a laboratory environment. The two systems combine lenses, lasers, and photo detectors

to generate dynamic droplet data.

Importance is scaled as a portion of 100 Rated on a scale of 1 - 5

REQUIREMENT IMPORTANCE

ENGINEERING

CRITERIA

Assembly

Temperature (F)

Clean Lens

(min)

Weight

(lbf)

Setup time

(min)

Transport

Volume

(in^2)

Image

Quality Length (in)

30 Minutes in boiler 14 5 5 5 2

Useable images 14 4 5 5 2

Transportable 6 5 5 3

Safe to use 15 5 4 3

Life in Service 6 4 5

Ease of installation 7 4 5 4 2

Short enough depth of focus 9 3 5 1

Large enough field of view 8 4

Adequate cooling 10 5 2 2

High Stability 4 5 3

Maintainability 7 4 3

Total 100

Importance of criteria 27 18 16 5 12 26 15

Method of Verification Test Test Measure Measure Measure Test Measure


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A laser diffraction system consists of a broadened laser beam that is passed through the spray

and scattered into a lens which focuses the light onto a detector array. An algorithm is then utilized to

determine the droplet size distribution. This method provides a line of sight measurement, thus

averaging the size distribution along the laser beam. Figure 2 is a schematic of a generalized laser

diffraction system.

Because of this averaging effect and known accuracy, the measurement would be an ideal solution

for this project. However other particles in the boiler would likely interfere and installation would be

difficult. The components would also require an infeasible amount of cooling to survive the boiler

environment.

Figure 2: Generalized laser diffraction system [1]

A PDA system works by focusing two or more laser beams at a point (measurement volume).

Photo detectors are placed at an off-axis location to gather scattered light from droplets that pass

through the measurement volume. The frequency and phase shift between the laser beams are

measured and provide both a velocity and size measurement. A schematic of a typical PDA system is

shown in figure 3.

The PDA system allows for very accurate measurements for both droplet size and velocity,

which would be a bonus to this project. The measurement only takes place within a relatively small

volume so it would have to be adjusted in order to obtain a size distribution. Similar to the laser

diffraction system, particle interference, installation and adequate cooling would also be a problem.


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Figure 3: Schematic of a PDA system [2] Imaging Systems

Imaging systems are commonly used in environments that do not allow for the installation of a

laser-detector system. They consist of a lens assembly, which focuses light onto a CCD (charged

coupled device), which converts the light into a digital image. The image can either be infrared or

visible if a light source is used. The digital images are analyzed by a software package which outputs a

size distribution based on the pixels that make up the droplets. The optical magnification and the

distance to the droplets must be known so the software can correctly scale the pixel dimensions to

actual droplet size.

A common problem with imaging systems is the optic’s depth of focus (also referred to as the

depth of field). A large depth of focus implies that a large section of the optical axis (axis normal to

lens) is in focus. Since the droplets closer to the camera appear larger than the ones further away,

errors will be present unless there is a way to determine the distance to the individual droplets.

By shortening the depth of focus to an appropriate level, the focal length of the optics system

can be accurately used as the distance to the droplets. The accuracy will increase as the depth of focus

decreases since only the droplets in focus are analyzed by the software. Increasing the aperture

diameter and decreasing the focal length of the lens assembly can shorten the depth of focus. Refer to

the ray diagrams in Appendix B for schematic representation.

In cases where the depth of focus cannot be narrow enough to provide desired accuracy, laser

imaging solutions have been used such as laser sheet droplet imaging (LSD) and laser induced

florescence imaging (LIF). Both of these systems involve exposing the spray to a laser sheet at a

known distance.


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As long as the laser sheet is in focus, accurate sizing can occur by only measuring the droplets that are

exposed to the light. The main difference between the two is the working wavelength of the laser and

CCD. The LSD works in the visible region while the LIF woks in the ultraviolet region of the

spectrum. Figure 4 shows an image from an LSD system.

Figure 4: Laser sheet applied to paint spray for a LSD system [3]

A unique example of a laser assisted imaging system is the VisiSizer™ system by Oxford

Lasers. The system is comprised of a visible light camera placed on one side of the spray and a

diffused laser on a screen on the other side of the spray. A clear image of the spray pattern is imaged

and software analyzes the size and velocity of the droplets. Figure 5 shows the system setup and an

example of the mages obtained.

Figure 5: a) Laser and camera setup, b) Images obtained from the VisiSizer™ system [3]


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Installing a laser imaging system would involve strategic placement of expensive components

that would not likely survive in the boiler without extensive cooling. Infrared imaging remains the

most appealing method. The cool temperature of the spray relative to its surroundings should allow for

high contrast. The portion that will be inside the boiler can be constructed of materials that are able to

withstand the high temperatures. The availability and possible marketability of Anthony Ross’

infrared camera for this purpose is an added benefit.

EXTERNAL SEARCH – COMPONENTS

Fiber Optics Since the viewing angle is to be adjustable, a fiber optic cable is an appealing option to transfer

the image. Fibers are able to transfer light around corners due the phenomenon of total internal

reflection (TIF). For a detailed description of TIF, refer to Appendix B. Fiber optic imaging is

accomplished using coherent fiber bundles which are cables consisting of multiple fibers who’s

relative position to one another is controlled. Each fiber can carry a certain signal flux that is

unaffected by the flux of neighboring strands. A bundle used for imaging divides the image into as

many separate light signals as there are fibers (thousands) and delivers it to a CCD. An example of a

device that uses a fiber bundle for imaging is an endoscope (shown in figure 6) which is used for

viewing the inside of a body.

Many components are available for the construction of a fiber-based imaging system. CCD

faceplates which provide 1:1 image transfer are available along with tapers which allow for image

magnification. Pictures of these components are shown in figures 7 and 8.

Figure 6: An endoscope [9]


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Figure 7: Left: Faceplate Right: Tapers [6]

Figure 8: CCD coupled with a taper [6]

Zoom Lenses In order to meet the optical requirements of the assembly, a lens system must be designed. The

design team researched zoom lenses as a possible option. As explained in the external search on

imaging systems, the properties of the focus are very important for accurate sizing. The advantage of

adding a zoom lens would be that the magnification could be varied which could allow more flexibility

for the user.

An image can be magnified by increasing the focal length of the lens (the distance between the

lens and the CCD). A zoom lens allows you to change the effective focal length which changes the

magnification. The resultant image must remain focused onto the CCD. This is done through what is

referred to as mechanical or optical compensation.

Mechanically compensated zoom lenses are the most common for infrared applications [10].

Typically one movable element provides the change in magnification while others eliminates any

resulting defocusing. The relationship between the movements in nonlinear so some form of a cam has

to be used. Figure 9 is a schematic of a mechanically compensated zoom lens that has three

independently movable elements.


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Figure 9: A type of mechanically compensated zoom lens [10]

An optically compensated zoom lens consists of two or more alternate lenses that are linked

and moved together with respect to the lenses between them. Defocusing does occur but because of

the arrangement it can be negligible depending on the application. Figure 10 shows an example of an

optically compensated zoom lens.

Figure 10: A type of optically compensated zoom lens [10]

When designing a lens system, the designer must take aberrations into consideration. An

aberration is a phenomenon that causes an inability for a lens system to form a perfect image. Because

zoom lenses involve more elements than simpler lens systems, aberrations become more of a problem

and must be compensated for. Complex zoom lenses such as the one shown in figure B-4 in the

appendix are necessary in order to correct for these aberrations.


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Tip Actuation The team researched several techniques currently used in endoscopes for tip actuation including

pistons and shape memory alloys (SMA). Pistons have a limited angle of actuation due to the ball joint

used. They are typically limited to 45º. Shape memory alloys can achieve 90º of actuation, but are

generally limited to low temperature applications which makes them perfectly adaptable to the medical

industry. The images of piston and SMA type actuators from are shown from left to right respectively

in figure 11.

Figure 11: Piston & SMA actuators used in endoscopes [8]

INTERNAL SEARCH - LIGHT TRANSFER

In order to transfer the light from the area to be viewed to the CCD of the infrared camera, the

light direction has to be able to change by 90º. Two main ideas were generated that would accomplish

this, a mirror based system and a fiber optic based system.

The mirror based system would reflect incoming light from the area of interest through a

movable lens for focus adjustment. This could be done by placing a mirror at 45º to the incoming

light. This would result in an inverted image, which would not affect the ability to measure droplets.

The assembly would fit over Anthony Ross' current short tube lens system. The concept drawing is

shown in figure 12.


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Figure 12: Concept drawing for mirror based system

The fiber optic based system would consist of a rotating lens system coupled to a fiber optic

bundle. The concept drawing is shown in figure 13. The lens system could either be a stand-alone

focusing system or a zoom lens combined with the focusing system. The focusing system would

consist of 2 lenses; the rear lens would be adjustable along the optical axis in order to change the

effective focal length.

Figure 13: Concept drawing for fiber optic based system


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INTERNAL SEARCH – ACTUATION:

It will be necessary to actuate the tip of either concept in order to obtain a direct line of sight to

the liquor spray. Actuation of a single lens or multiple lenses will also be needed to control the focal

length and magnification if a zoom lens is used.

Tip actuation Figures 14 and 15 indicate two techniques that could be used to actuate the tip of the assembly.

The unit shown in figure 14 is actuated by cables, which are tensioned by a handle near the camera

housing. The assembly will bend in the direction of the cable being placed under tension. The yellow

axes in the figure pass though pins which connect the brackets together and allow them to rotate. This

design would allow for the required 0º-90º of actuation.

By connecting the brackets to one another with springs, the force necessary for actuation is

reduced. A benefit of using this system is the large amount of space left in the center of the brackets

allowing maximum room for large diameter optics, which will increase the amount of light taken in

and decrease the depth of focus.

Figure 14: Bracket type actuation unit

Figure 15 shows a planetary gear type actuation technique. The figure shows the range of

motion of the tip in the 0° and -90° positions. The gear connector (shown in the -90° position)

connects the two sections of the assembly. The top arm of the gear connector is attached to a cable

that is tightened or loosened by the camera operator. The bottom arm of the bracket is connected to a

spring, which would be at its natural length when the tip is facing down as shown (-90° position). As


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the camera operator tightens the cable attached to the upper arm of the gear connecter, the tip would

move toward the 0° position. The disk at the end (facing left) would have a hole big enough to allow

the fiber bundle to pass through, and lens housing would be attached to the disk

Figure 15: Planetary gear type actuator

Lens actuation

To adjust focal length or adjust a zoom lens system, a precision actuation device is necessary to

move a lens. One possibility is to use a power screw to move a lens holder. Figure 16 shows one such

system with a series of power screws. This system can move a lens by approximately 1 to 2 inches. A

zoom system would require more linear actuation than a focal length adjustment system, so this system

would work well for a zoom lens.

Figure: 16: Power screw linear actuator for lens position adjustment

For focal length adjustment the linear movements are short, so the actuator could utilize a

planetary gear system that traverses a threaded insert. Figure 17 shows a design of the lens system tip


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which would work with the fiber optic based system. A torsionally stiff cable would be connected to

the brass colored gear (planet). The planet would rotate the lens holder (shown as gray with a circular

hole pattern near the back of the assembly) to move it though the threaded insert. This movement

through the threaded insert would maintain the alignment of the lens system while changing the focus

of the optics.

Figure: 17: Planetary gear system actuated optics shown in the tip assembly

INTERNAL SEARCH – COOLING/CLEANING:

There are limitations on the type of cooling methods that can be used in a recovery boiler. For

safety reasons, water is not allowed as a cooling liquid. If water comes in contact with the char bed

(see figure 1, Appendix A for char bed location) a steam explosion can take place. Compressed air is

the most practical solution for cooling because it is readily available on sight, doesn’t create safety

hazards and is the method of choice for cooling the infrared camera to which the lens system will be

attached.

To cool the lens system, a compressed air hose will be attached to a coupling outside the boiler.

The air will flow through the outer passageway of the tubes that make up the lens system housing.

Figure 17 shows the passage in which the air will travel (the transparent concentric cylinders). A

different view of the brass colored tip is shown in Figure 18. This figure shows the small holes in the

tip that will allow the air to escape the lens tube and pass over the window, keeping it clean.

Airflow can be increased if necessary by adding a second air port near the camera that will pass

air though small tubes that traverse the length of the small holes. Approximately half of these holes


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could contain tubes for airflow. The main purpose for the added airflow would be to increase the

airflow over the window for cleaning.

Figure 18: Airflow exits from the lens tube over the outermost window

FINAL DESIGN EVALUATION & SELECTION:

Table 3 is a decision matrix comparing the different proposals for light transfer, lens system

type, lens actuation, tip actuation, and cooling/cleaning system. The winners of each category are

summarized below:

Light transfer: The fiber optic system was chosen. The use of a fiber optic cable prevents the precise

alignment necessary with a mirror based system. The system also works well with other components

such as the cooling system and lens system.

Lens System Type: Due to the complexity of zoom lenses, the advantage of variable magnification is

not significant enough to incorporate one.

Lens Actuation: The threaded insert system was chosen since it is less complex and simpler to control

than the power screw system.

Tip Actuation: Actuation of the tip will be accomplished with the pin and bracket system due to its

durability and simplicity. The bracket design is also much easier to manufacture than the planetary

gear system.

Cooling/Cleaning System: Because of the cleaning advantage that the dual air port system has, it was

chosen.

A model of the assembly based on these decisions is shown in figure 19.


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Criteria scaled as on a range of 1-5, 5 being the best score possible

FIGURE

REF. CRITERIA TOTAL

LIGHT TRANSFER METHOD

Less Optical Precision Necessary

Component Availability

Workability with other

Components Design

Simplicity Mirror Based 12 1 4 2 3 10

Fiber Optic Based 13 5 3 4 4 16

LENS SYSTEM TYPE Ease of

Actuation Image QualityMagnification

Range Design

Simplicity

Zoom - Mechanically Compensated 10 1 4 5 2 12

Zoom - Optically Compensated 11 3 3 5 3 14

No Zoom N/A 5 5 1 5 16

LENS ACTUATION Linear Actuation

Distance

# of Mechanical

Control Components Durability

Accuracy of Actuation

Design Simplicity

Planetary Gear System with Threaded Insert 20 3 4 4 5 4.5 20.5

Planetary gear System with Power Screw 19 5 2 4 4 3.5 18.5

TIP ACTUATION Manufacture-

ability

# of Mechanical

Control Components Durability

Accuracy of Actuation

Design Simplicity

Pin and Bracket system 17 4 4 5 3.5 5 21.5 Planetary Gear System 18 3 3 4 4.5 3 17.5

COOLING/CLEANING METHOD Effective cooling

Effective tip cleaning

Design Simplicity

One Air Port 21 3 3.5 4.5 11

Dual Air Port 21 3.2 4.5 3.5 11.2 Table 3: Decision matrix


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Figure 19: 3-D model made up of winning concepts from decision matrix

FUTURE CONSIDERATIONS:

During the next term, optics manufacturers will be contacted to determine the components

necessary to have a working optics system. Optics calculations will be performed to determine the

actuation distance needed to provide the proper focus range. Once the optics system is designed and

more detailed dimensions known, the housing assembly parts can be designed in detail.

The cooling system will be analyzed and optimized with general heat transfer principles and

finite element models. It will be determined if a second air port is necessary or if one air port will be

sufficient in cooling the housing. If the second air port is not necessary for cooling purposes, it may

be needed to keep the window clean.

CONCLUSION & RECOMENDATIONS:

Through the combination of research and brainstorming the design team has came up with an

overall concept that will allow Anthony Ross to measure black liquor droplets with their current

infrared camera. The assembly will involve a lens system that will focus light into a fiber bundle,

which will deliver the light to the camera's CCD. The optics system will be housed within a double

walled tube that connects to the camera.

The focal length of the lens system will be adjusted by the actuation of a single lens with the

planetary gear system shown in figure 17. In order to rotate the optics system housing, the pin and

bracket system shown in figure 14 will be used. Both the focal length and rotation adjustments will be

controlled and indicated by dials near the camera attachment. Constant cooling and lens cleaning will

be accomplished by an air purge system that utilizes compressed air available in the plant.


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The biggest concern for the design group is the depth of focus requirement. In order to

minimize the depth of focus, the focal length needs to be as short as possible while the aperture is

maximized. The distance from the tertiary air port to the spray affects the focal length while the

diameter of the port determines the maximum aperture since the assembly has to fit through it. The

design team will ensure that the assembly will be optimized for theses considerations but cannot yet be

certain that it will be sufficient for providing accurate size measurements. The level of this concern

will be communicated to Anthony Ross Company as progress is made

REFERENCES

[1] Laser Diffraction Technology Focus. [Online] Malvern Instruments Ltd http://www.malps.com/ProcessEng/systems/laser_diffraction/technology/technology.htm, 3/3/05 [2] J Lacoste, D Kennaird, S Begg and M R Heikal, “Phase Doppler anemometry measurements of diesel spray” [Online] www.sussex.ac.uk/automotive/tvt2002/16_lacoste.pdf, 3/3/05 [3] Applications Note – Paint Sprays. [Online] Oxford Lasers www.oxfordlasers.com/hsi/uchi/apppaint.pdf, 3/3/05 [4] DA Greenhalgh, “Laser imaging of fuel injection systems and combustors”, Proceedings of the Institution of Mechanical Engineers, Vol 214 Part A [5] Fiber optic, total internal reflection. [Online] How It Works www.howitworks.com, 3/3/05 [6] Products associated with fiber optic systems incorporating CCD cameras, [Online] Schott North America. http://www.us.schott.com/fiberoptics/english/products, 3/3/05 [7] Terry Adams, Kraft Recovery Boilers, et. Al., 1997, Tappi Press. [8] J. Peirs, D. Reyaenrts, et. al., Design of Miniature Parallel manipulators for integration in a self propelling endoscope, Sensors & actuators A, Vol 85, Elsevier Science, 2000, pp. 409-417. [9] Veterinary Endoscope and Otoscope. [Online] Medit Endocopy http://endoscopy4vet.com, 3/4/05 [10] Allen Mann, Infrared Optics and Zoom Lenses, American Elsevier Publishing, 1973 [11] The Way a Zoom Lens Works/ [Online] Schneider http://www.schneider-kreuznach.com/knowhow/zoom_e.htm


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APPENDIX:

APPENDIX A: Schematics of typical recovery boiler showing air port and liquor gun locations.

Figure A-1: Tertiary air port and black liquor nozzle locations in a typical recovery boiler [7].

Figure A-2: Typical liquor gun configuration [7].


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APPENDIX B: Additional External Search Documentation

The following ray diagrams indicate the path that light takes through a generalized optics system. The diagrams illustrate how aperture diameter and focal length affect the depth of focus.

Figure B-1: Ray diagram indicating the effect of aperture on depth of focus

Figure B-2: Ray diagram indicating the effect of focal length on depth of focus


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Fiber Optics Technology: Fibers are able to transfer light around corners due the phenomenon of total internal reflection

(TIF). TIF occurs when the surrounding medium of the fiber is of a lower index of refraction and the angle of light incidence is greater than the angle at which it escapes (critical angle). This phenomenon is illustrated in figure 6.

Figure B-3: Total internal reflection [5].

Aberrations: An aberration is a phenomenon that causes an inability for a lens system to form a perfect image. Since zoom lenses are affected more by optical aberrations, complex design is necessary. A schematic of a commercially available Schneider zoom lens is shown in figure B-4.

Figure B-4: Schematic of a Schneider zoom lens [11]

APPENDIX C: Internal Search Document


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Figure C-1: Lens assembly and actuation housing The optical system and housing can be separated into several parts for evaluation concerning the internal search findings. Optics assembly, focus actuation, cooling, optics design, and housing design. These findings proceed on the assumption that fiber optic cables will be used to transmit the optical information to the infrared camera from the tip lens assembly. Tip actuation:

Tip actuation designs can be gear driven as in the design to the right. This design uses springs and a rolling set of planetary gears actuated by a cable to change the orientation of the tip assembly. The strong point of this design is the simple mechanical nature of the actuation. With few moving parts the assembly will have a small likelihood of failure.

Figure C-1: Planetary gear driven tip actuation The weakest point in this design is the sharp radius of the actuation. The fiber optic material is

exceptionally flexible but the short radius will force the optical cable to come into contact with the outer casing of the assembly. Contact in this manner will cause rapid temperature increase in the cable and possible damage.

Tip actuation can also be accomplished in a similar manner to a bore scope. Using this method several wires in flexible channels are channeled through the flexible portion of the assembly; by changing the tension in opposing cables the tip can be turned in a variety of ways giving the necessary movement as specified in the PDS. The major weakness of this system is the user interface for actuating the tip. Setting the tip in a given position may cause difficulty for the user.

Optics Lens Assembly: Optical design is a key component in this system. In order to change the focal length of the system the lens assembly must be located in the tip of the device to take advantage of certain optical advantages when using lenses over the fiber optics that are used to carry the information to the camera. Locating the lenses in the tip of the device requires a barrier to keep the optics clean. Using a sapphire barrier lens with a high velocity stream of air will keep all contaminates away from the lenses and provide moderate cooling of the system. Vents are located at every lens and support in the system to allow for the proper air flow.


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Figure C-3: Tip assembly example

Of note in the design in figure 3 are the sapphire crystal lens cover (green), stationary lens (Tan), adjustable lens assembly (grey) and interior support structure (blue). The outer housing made of Stainless steel with a possible thermal ceramic coating to minimize the corrosion and heat conduction effects on the system. The adjustable objective lens mechanism is operated using a combination of spur gears and 24 pitch threads to focus the image and maintain the proper alignment with the other parts of the optical system. The entire optical adjustment mechanism fits inside the outer sleeve of the device and can be positioned at any desirable point. Focal lens Adjustment: Optical quality of the highest order is paramount in this project. In order to deliver the edge definition for the droplets fine, measurable focal length adjustment is needed. Adjustment using a torsionally stiff wire and power screw in conjunction with a lens on a low friction track bar system is shown in Figure 4.


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Figure C-4: Power screw on track system

Strengths of system: • Easily adjustable with wide range and fine precision. • Prefabricated screw assemblies available. • Few moving parts.

Weaknesses: • System is only restricted from lateral movements at one point, creating stress concentration on

the power screw if subjected to abnormal loading conditions.

Figure C-5: Spur Gear Focus Focal length can be adjusted in a similar manner using a spur gear turning on a fixed axis with a movable lens assembly as shown in figure 5 above. In this design the inner assembly is attached to the outer base by fine threads on the outer surface and a spur gear. As the spur gear turns the gear on the lens assembly, the assembly rotates moving on the threads.


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Strengths of system:

• Easily adjustable with very fine precision. • Few moving parts. • Very solid and virtually impervious to breakage.

Weaknesses: • Narrow range of adjustment (~0.25 in). • Custom fabricated parts. • Precision too fine for large adjustments.

A solid mount non adjustable focal lens is also a design option for the system. Focusing the optics of the system at a preset mean depth of focus and using small lenses with large depth of focus is the simplest design available.

Strengths of system:

• Simple with no moving parts. • Very solid and virtually impervious to breakage.

Weaknesses:

• No Adjustment, does not fit original design criteria. • Does not give optimum optical clarity in most cases.

Figure C-6: Non adjustable Lens Main Tube Assembly: Two primary designs are available for the main tube assembly, solid core and bulkhead configuration. The bulkhead configuration uses periodically spaced supports across the length of the tube as can be seen in figure 7.

Figure C-7: Main tube assembly

These bulk heads maximize airflow for the entire system and provide channels for the mechanical cables that actuate the focus and the tip. The bulk heads also provide support for the fiber optic bundle that will transverse the center of the assembly.

Strengths of system: • Allow the use of thermally resistive materials in structural support roles. • Very solid and virtually impervious to breakage. • Allows good air flow. • Provides stiff paths for control cables as can be seen in figure 8.


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Weaknesses:

• Narrow range of adjustment (~0.25 in) • Custom fabricated parts • Precision too fine for large adjustments

Figure C-8: Main tube assembly profile

With four wires to control the ends and the wire to operate the adjustable objective portion of the optics system the other 7 ports will carry high speed air to the tip to maintain the cleanliness of the sapphire lens cover. In the tip section there will no longer be tubes to carry the air so the holes in the tip section will be open at the lenses. Free air travels through the main section of the housing maintaining a cooler temperature for the fiber optic core. The other bulkhead designs found in figure 8 at the right optimize the airflow characteristics and minimize the thermal conduction in the system but do not provide the optimum support for the five control cables necessary in this design.


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Figure C-9: Solid core 1 As an alternative to the bulk head design the solid core model keeps two completely separate air flows in the rigid length of the tube. This will lower the average temperature of the fiber optic bundle and give the opportunity for higher velocity air profiles to be developed in the out side channels. Figure 9 optimizes thermal resistance and will offer excellent airflow but lacks the structure to hold the control cables in a rigid manner.

Using the cables for the actuation of the tip requires that they are rigidly mounted for as much of their span as is possible. Figure 10 addresses this with the addition of channels for the control cables.

Figure 10 also has large outside air passages that allow high air velocities and good heat transfer to occur. The main detractor of this design is the large thermal conductance area to the center section through the side fins. This design is also restricts the available materials for use due to the unique geometry of the surfaces.

Figure C-10: Solid Core 2

Material Considerations: The exterior surface of this assembly will be subjected to a high temperature caustic environment and will be subjected to very corrosive conditions. To combat the corrosive effects, raise thermal resistance and lower absorption due to radiation inside the boiler a spray on ceramic should be used. Spray on ceramics can affect the characteristics of the outer shell in this case similarly to what


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galvanizing does for steel in wet environments. Although the effects of the boiler environment on the steel will not negate the effects of corrosion and thermal conductivity, the ramifications can be reduced and the lifespan of the assembly will be increased measurably. Conclusion: To ensure the best quality images through the IR camera assembly the best option is to use a wire tip actuation through a bulkhead main tube using a small power screw for focusing of the lens assembly. These design options in concert should render the most desirable results yielding good actuation and superior optical information.

APPENDIX D: Test to determine object size as a function of distance away from the object.

A test was performed using a Fuji Finepics 4800 zoom digital camera with 3x zoom. A ruler was placed at a particular location. A tape measure was then placed perpendicular to the ruler. Pictures were taken at varying distances from the ruler. The distance was recorded and image size was measured from each image on the computer screen. The test was performed using the 3x setting and 1x setting. The data is given below as well as a plot comparing both sets of data.

Actual length of ruler 12.875 1x zoom 3x zoom

Distance away (ft) Measured object size (in) Distance away (ft) Measured object size (in)2 6.5 4 8.2 3 4.4 9 3.8 4 3.3 15 2.3 6 2.1 24 1.45 9 1.4

1x & 3x zoom image sizes

0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30

diastance away from object (ft)

obje

ct im

age

size

(in)

The plot shows that the measured object size on the computer screen decreases rapidly as the distance away from the object increases. The relationship is similar for both the 1x and the 3x zoom


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settings. The plot shows that if a small object is imaged with a 3x zoom lens system, the image will not be much larger than if anon magnified lens system was used. Two of the images taken in the experiment are shown below. The first image was taken at a distance of 15 inches away from the ruler. The second image was taken at 24 feet from the ruler.

It is clear from the photos that the depth of focus is infinite. The infinite depth of focus will cause enormous error in the calculation of droplet size if a similar system were used. It is also apparent that an object that is 12.875 inches long is difficult to see at a distance of 24 ft with 3x zoom. This test was performed to illustrate the problem of having a depth of focus that is too large, and also that a zoom lens system may not be beneficial or helpful in imaging droplets.


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APPENDIX E: Product Design Specifications Document

DOCUMENT PURPOSE:

The purpose of this document is to:

Clearly outline customer requirements and define methods to verify them.

Provide a project plan.

MISSION STATEMENT:

Design an optical assembly that will attach to the infrared camera currently being distributed by

Anthony Ross Company. The assembly will provide clear images of black liquor droplets to the

camera and allow Anthony Ross’ engineers to improve their mathematical model of the recovery

boiler.

CUSTOMER IDENTIFICATION:

The following outline indicates our main customers along with their most important design criteria. Anthony Ross:

Performance Quality and reliability Testing Legal Product life

Boiler Personnel/Technicians:

Safety Maintainability Performance Size Weight Installation Ergonomics Quality and reliability Applicable codes

PROJECT PLAN:


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PRODUCT DESIGN SPECIFICATIONS:

Environment

Primary Customers: Recovery boiler personnel, Anthony Ross

Customer requirement:

Lens extension will be able to withstand environment up to 2000°F for 30 minutes.

Lens extension will be able to handle an environment that contains harsh chemicals, fast

moving debris.

Lens must fit through tertiary air port above the liquor guns (63 mm diameter).

Lens extension must extend at least 1 meter into the boiler.

Engineering Targets:

Lens extension will be capable of withstanding the recovery boiler environment for a period

of 30 minutes minimum.

The Lens extension must handle the boiler environment without loss of resolution or

equipment integrity.

Safety



The camera operator will be protected from flames that may escape from the boiler.


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The camera system will be safe to install.

Documentation on use and maintenance will be provided.


All components will conform to codes and standards governing recovery boiler operation.

Materials will be selected with properties that ensure compatibility with boiler environment.

Documentation explaining safe operation will be provided.

Maintenance



Tools and parts needed for maintenance will be defined.

Documentation describing the maintenance procedure and schedule.


Maintenance schedule will be determined to provide long life.

Documentation on maintenance will be provided.

Performance



Lens extension will have the ability to image black liquor droplets high resolution.

Lens extension must be able to provide clear images while in the boiler for 30-minute periods

and prevent damage to itself or the camera.

Lens extension must survive multiple trips into the boiler without image degradation or

damage.

A viewing angle adjustment from 0º to -90º is required. This is necessary to enable the user

to locate and analyze different regions of the spray.

Focal length must be adjustable and known.

Depth of focus must be narrow.


Camera and lens system will provide clear images. A clear image is defined as an image with

enough resolution that data may be obtained.

The camera system will withstand the recovery boiler environment for 30 minute periods.

Proper lens cleaning while extension is in the boiler such that view remains unobstructed.


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Focal length will be adjustable and indicated.

All customer performance criteria will be met.

Materials



Lens extension will withstand boiler properties.


Materials will tolerate boiler properties for periods of 30 minutes with no damage or

degradation of image resolution.

Materials will be selected to be economical and resistant to chemical wear.

Life in Service



Lens extension will have a long life with proper maintenance.


Lens extension will resist the boiler environments for periods of 30 minutes.

Lens extension system will perform up to current two-year warranty standard.

Quantity



Prototype is desired for verification of performance.

Future sales potential includes the pulp and paper industry.


One prototype will be produced to verify performance.

Manufacturing Facilities

Primary Customers: Anthony Ross


Customer would like to use onsite manufacturing facilities where ever possible.

External manufacturers may be utilized where necessary.



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Timely requests for needed parts will be given.

Testing

Primary Customers: Anthony Ross


Lens extension prototype will be tested in a recovery boiler environment to verify heat and

chemical resistance, image resolution and

Image resolution and clarity will be such that droplet size determination has a better accuracy

then current analysis.


Images will be taken from different access points.

Images will be taken at multiple angles and distances from the black liquor spray.

Images will be taken over 30 minute periods to check image resolution as function time.

Quality and Reliability


Good imaging.

Meets reliability standards in warranty.


Lens extension maintains quality image.

System will consistently produce clear droplet images.

Documentation



Drawings

o 2-D and 3-D drawings of all parts and assemblies

Instructions on camera lens extension use.

Maintenance instructions and timelines.


Provide all necessary documentation in a timely manner.

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