TeamPAC
Phase 3
3/6/2016
The Design and Testing of Pulse-Jet Cleaning Systems
Prepared For:
Date: December 15, 2004
Precision AirConvey Corp.
Pencader Corporate Center
210 Executive Drive #6
Newark, DE 19702
Senior Design Advisor
Dr. Michael Keefe
University of Delaware
Newark, DE 19716
Team PAC® is pleased to report our design, testing, and conclusions to a semester long
research project on the Pulse-Jet cleaning system of an Industrial Filtration System
________________________________________________________________________
Precision AirConvey Sponsors:
Tom Embley
Precision AirConvey, CEO
Kevin Byrne
Product Development Manager
Erik Adams
Manager of Sales Operations
Senior Design Team:
Cliff Cieslak -----------clifford.cieslak@us.army.mil
Anthony Davis --------antsurf@udel.edu
Danté Gabrielli --------dante@udel.edu
Michael Kutzer --------mkutzer@udel.edu
The attached information describes the process used in completing the proposition
presented in response to PAC®’s desire for a dust collector to add to their line of
products.
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Table of Contents
I.
Title Page ...........................................................................................................1
II.
Table of Contents ...............................................................................................2
III.
Executive Summary ...........................................................................................3
IV. Introduction ........................................................................................................3
V.
Prelude ...............................................................................................................4
VI. Benchmarking ....................................................................................................5
VII. Concept Development ........................................................................................6
VIII. Test Box Design .................................................................................................9
IX. Venturi Design .................................................................................................11
X.
Venturi Validation ...........................................................................................13
XI. Sensor Selection ...............................................................................................14
XII. Data Acquisition Box Selection .......................................................................15
XIII. Test Plan...........................................................................................................15
XIV. Test Expectations .............................................................................................16
XV. Test Results ......................................................................................................17
XVI. Conclusions from Testing ................................................................................23
XVII. Future Testing & Path Forward ....................................................................24
XVIII. Appendixes ...................................................................................................26
XIX. Equation Index .................................................................................................41
XX. Figure Index .....................................................................................................42
XXI. Special Thanks .................................................................................................43
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Executive Summary
The proposed project is to design an Industrial Filtration System that steadily competes
with companies in the market. PAC® (Precision AirConvey Corporation) is currently
having trouble finding a reliable supplier for their specific needs in the paper and plastic
trimming industry. Upon the completion of this project we have a working prototype,
implementation of proven ideas and designs, and a positive path forward for the
company. The overall intent was to aid PAC® in steps leading to a final product that they
can sell to various customers. The success of this project has allowed PAC® to no longer
depend on outside suppliers for products and product troubleshooting and allowing PAC®
to deal with dust filtration problems directly.
To achieve this goal, we broke down the full filtration system into a set of subsystems
including a hopper, air inlet and outlet, access doors, filter alignments, and the cleaning
cycle. This allowed
us to improve the
quality
of
the
filtration system in
small
manageable
steps.
After some
detailed
benchmarking,
we
noted that the most
discerning subsystem
was the methods used
in the cleaning cycle.
According to our
premise,
slight
modifications to the
cleaning system may
drastically impact its
overall performance.
To quantify this, we
compared many tests performed on different aspects of our cleaning system design and of
the competition’s system including source length1, Venturis, and source pipe diameter2.
With accurate numeric measurements, PAC® will be able to easily convince customers of
their superiority in the market.
Figure 1: PAC’s line of equipment, circled is the required
filtration system
Introduction
PAC® presented us with their problem of finding reliable dust-collectors from outside
distributors for their industry’s specific needs. Our mission was to begin the process of
designing a dust-collector that PAC® fully understands, manufactures, and distributes
directly to their customers.
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Our approach is centered on a scaled down version of a competitor’s model. With this
model we performed tests to optimize important variables that will set PAC® apart from
their competition. To test the cleaning system, we scaled down a MAC® dust-collector
(See Appendix A, Figure 18). We used this vendor because they used the same filter
configuration we are using. The scaled version consisted of a single filter in the
horizontal position. Our goal in Using this “Test Box” was to find pressure vs. time,
peak pressures inside the filter, velocity of the air, a final source length and diameter, and
prove our Venturi is superior. We tested the Torit® Venturi, no Venturi and the Venturi
that we have designed, and compared the results to optimize the cleaning cycle for our
dust-collector prototype.
Prelude:
From the start, we were given two fundamental sets of customer wants, one business and
one academic. On the business end, we were given the task of designing a filtration
system with several constraints and the goal of a working prototype. The academic side
asked that we document all work, going into extensive detail on one aspect of the design,
with the intent of proving all variables and staying true to the methods, and curriculum of
the University of Delaware senior design course. Our goal was to satisfy both sets of
wants, keeping an honest and accurate log of all work throughout the project, while
maintaining a pace suitable for our lofty goal.
Knowing what was ahead of us, we fsfsfsf
decided to break down the project into
weekly meetings, acceptable goals, and
subsystems. In order to reach our goal
we chose to separate the aspects of this
project into parts that either Precision
AirConvey or we could work on
separately or as a group. This intent in
mind, the overall model was broken into
individual parts (Figure 2).
Each individual part, or subsystem, was
then assessed by our team and further
labeled as either an independent or
dependent subsystem. The explosion
Figure 2: Overall Subsystem Layout
vent (Figure 2, Label 1) represents the
main safety precaution of the project. Because this system does not directly effect, and is
not directly affected by, any of its mechanical surroundings it can be considered an
independent subsystem. When dealing with flammable dust particles, like flour or paper,
the combination of low humidity and a spark can cause a flash ignition, resulting in a
short, but powerful burst or explosion.
Like the explosion vent, the dust collection barrel (Figure 2, Label 3) can be considered
an independent subsystem. Since it is a stand-alone part and the only requirements are
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that the barrel opening matches the size of the seal. Unlike the explosion vent, the dust
collection system requires little design, as the seal and barrel are used universally by
competitors and can be ordered commercially. The major concern with this subsystem
was introduced in our visit to Avery Dennison in North Carolina. Ken Perdue, our
contact in industry, brought up the important point that his employees have no way of
knowing when their particular dust collection barrel is full. Further, checking the dust
level requires them to shut off the entire scrap and dust collection system for several
hours requiring them to cease production completely or dump all paper scraps during the
down time. Regardless of the alternative, both result in losses for the customer that could
be solved with an effective system to measure the level of dust in the collection barrel.
Upon further research we found that a barrel capacity meter can be bought commercially
and field installed.
As a team, our main concern with the project as a whole lies in the cleaning system
(Figure 2, Label 2). This feature includes aspects of the system that will set us apart from
the competition. If we can introduce a similar product that cleaned quieter, faster, or
more efficiently than the competitors, it would easily put Precision AirConvey in a
position to contend with far more established filtration companies. After consulting with
Precision AirConvey and our sources in the University, we concluded that, building a
scaled test container mimicking the cleaning cycle of a full sized system, would allow us
to validate our ideas through testing on a more cost-effective scale.
Benchmarking:
Through our research we have found many useful benchmarks. Most of these
came from engineering brochures from companies who already produce dust
collectors. The first of these companies is MAC® Equipment, Inc. From their
engineering brochure we were able to obtain several very useful drawings of their dust
collection system, and its subsystems.
In our supply of product catalogues, a copy of the Torit® Company’s products proved to
be very useful. In the catalogue a picture of their Venturi (See Appendix M, Figure 34)
design and a graph of, the pressure in inches of H2O of the shockwave created by the
Venturi versus time of the shockwave in seconds (See Appendix M, Figure 35) was gave
us numbers to shoot for when designing our Venturi. Another major contribution of the
Torit® catalogue was their illustration of their “filter yoke,” (See Appendix M, Figure 36)
or method of securing the filters inside the unit. This aspect greatly helped to visualize
the interior of a standard dust collection system.
Appendix O, Figure 39 was initially one of our more useful discoveries; it simply
illustrates how the Torit® filtration system operates in both normal operation and filter
cleaning. This gave us a better understanding of what we needed to design and how we
could improve upon the current technology in an attempt to create new solutions to the
problem.
Although less useful than the others, the DUST-HOG® brochure gave us a look at the
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innovative ideas being produced by the younger competitors in the market. Appendix N,
Figure 37 shows the one of a kind cleaning system they use which, although useful in
some applications, is likely too weak for uses with paper dust and those sharing a similar
particle nature. Also shown is the closure system for the filter change hatch (Appendix N,
Figure 38). This is a very simple and easy configuration which, according to our sales
input at Precision AirConvey, is the main selling point of DUST-HOG®’s industrial
filtration systems.
Concept Development
In Phase 1, we focused on creating concepts for a test system that could accurately
represent and measure aspects of the overall cleaning process. We defined critical
measurements as those pertaining to pressure, pulse velocity, source length1, and source
diameter2. The main constraints in designing this “Test Box”3 included:










Low Total Cost
Ease of Manufacturing
Laminar air inlet under standard operating conditions
The ability to integrate our design into the final prototype
A fan connection capable of fitting existing PAC® hardware
The ability to test multiple source diameters (1” and 1 ½”)
An air to cloth ratio 1.5 to 1
A Can Velocity of 382.7 FPM (feet per minute)
The ability to test multiple Venturis
The ability to test multiple source lengths
For our final concept, we chose an inexpensive design capable of producing effective
adverse conditions, allowing the filter to easily clog. Before reaching this final concept,
we considered many designs including angled filters, multiple filters, a hopper, and a
tilting “Test Box” design.
While most of these concepts were disregarded due to cost, several were immediately
removed because the ideas in general were not applicable to the final prototype. In our
concept consideration, we theorized that through data acquisition, adding extra filters
would become trivial; as a correlation could be estimated between pressure drop and
filter length. Once this data is collected, a trend line can be produced that represents the
drop in pressure as it is applied to the change in length. From this trend line, we initially
thought we would be able to estimate the pressure drop as additional filters are added
(assuming the trend applies as the pressure approaches zero). This assumption eliminated
the need for excess materials to accommodate for extra filters. We also found that using
1
Source length is defined as the distance between the opening of the Venturi and the opening of the
compressed air source pipe (see Fig. 2).
2
Source diameter is defined as the diameter of the pipe used to release compressed air into the clean air
plenum of the “Test Box”
3
The scaled version of the Mac® dust collector
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angled filters or a tilt design would not be applicable in our final design due to the
increase in cost4.
After combining all knowledge and designs, we decided to make a single horizontal filter
test system with a separate clean airside and a separate dirty airside. Both the
competition’s clean airside and ours can house a Venturi in addition to inserting a pipe
that can inject the burst of high-pressure air used in the cleaning process. The dirty
airside holds both the clean and dirty filters. With the approval of PAC® on our overall
“Test Box design, we were able to move forward and build our “Test Box”.
Figure 3: Final “Test Box” Specifications
4
Based on research of the competition, it became obvious that the benefit to cost ratio was too low to merit
extensive research on the angled filter design.
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Our overall design setup for testing is shown below (Figure 4).
Figure 4: Final Concept Layout
The labeled aspects of Figure 4 are as follows:
1. The test box, used to house the filter and overall system.
2. The Venturi (not specifically shown). This is one of if not the most important part
of the cleaning cycle. The compressed air will be forced into the diverging
portion of the nozzle, then into the converging area. According to the basic
principles of fluid dynamics, this flow, upon exit and given the correct
backpressure, will create a shock wave within the filter, knocking dust off as it
propagates. In this exit, we are hoping to achieve compressed flow at speeds
nearing three times the speed of sound.
3. Pneumatic Actuator. Compressed air release valve controller.
4. Goyen Valve. Air release valve, capable of releasing air in intervals as short as
1/10 of a second.
5. 1 ¼ inch tubing to connect the compressor to the valve, and valve to clean airside.
6. Compressed Air Tank
7. Pressure gauge. Reports to us the maximum pressure achieved during the
cleaning cycle
8. Pump inlet to compress air
9. Pressure gauge for Tank
10. Differential pressure reading from clean air and dirty air.
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Test Box Design:
After choosing the single horizontal filter configuration by breaking down each concept
of the “Test Box” and deciding which concept was best according to the needs and
constraints of PAC® we determined dimensions of the “Test Box”. The “Test Box” is a
scaled down version of a full size MAC® dust-collector, which uses the same filter
configuration we use. The two variables that dictate the dimensions of the “Test Box”
are the Air to Cloth Ratio and the Can Velocity. The Air to Cloth Ratio is defined as the
amount of airflow into the dust-collector in CFM (cubic feet per minute) divided by the
square footage of filter media5 in the dust collector. The Can Velocity is defined as the
upward air stream speed calculated at the horizontal cross-sectional plane of the collector
housing that passes through the bottom surface of the filters. To calculate Can Velocity
the following equation was used (Eq. 1):
Can _ Velocity 
ACFM
( Area _ of _ Tube _ Sheet )  ( No. _ of _ Bags)( Area _ bag _ bottom)
In this equation, the ACFM (actual cubic feet per minute) is the volume of the air flowing
per minute at the operating temperature, pressure, and composition.
The dust-collector we scaled down is a standard 12-filter system6 rated for 4000 CFM.
Each filter is 13.8” OD (outer diameter), each with a filter media square footage of 254
ft2. At the request of our sponsor, we were asked to keep the A/C (Air to Cloth) ratio at
approximately 1.5 to 1.
The first step in designing the “Test Box” was using the A/C ratio to scale the CFM down
to our single filter design. The scaled CFM was calculated to be 381 CFM. Because fans
are not rated to be this exact CFM, we rounded up to 400 CFM for all remaining
calculations. This additional 29 CFM was found to be negligible & only increased the
A/C ratio by 0.07.
When this was complete we calculated the Can Velocity for the full size dust-collector to
be 382.7 FPM. The width of the “Test Box” was taken directly from the MAC® dustcollector and is 20.125”. Using the calculated CFM, Can Velocity, the known width of
the “Test Box”, and the dimensions of the filter, the height of the “Test Box” was
calculated to be 15”.
The next logical step was to calculate the dirty air inlet and clean air outlet dimensions.
According to ASHRAE7, air flow in a main branch duct (in an industrial application)
should remain between 1300 FPM and 2200 FPM to keep noise at a moderate level. We
chose 1300 FPM because it fit this constraint and gave round numbers for the inlet and
outlet dimensions. Using 400 CFM at 1300 FPM, the inlet and outlet dimensions were
5
Filter media refers to the material actively being used in the filtration process.
A standard 12 filter system is one containing two columns, and three rows of double stacked filters.
7
American Society of Heating, Refrigeration & Air Conditioning Engineers
6
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determined to be 7.5”Φ or 6”x8” rectangular equivalent8. To help evenly distribute
airflow, the inlet to the dirty air side and outlet from the clean air side, were placed
centered on top of the box. Calculations are listed in Appendix B, Figure19.
The “Test Box” was constructed using plexi-glass. Constructing the box using plexi-glass
allows us to view the cleaning of the filter and get a visual of how the cleaning system
actually functions. The plexi-glass has flexure strength of 1200 PSI and the “Test Box”
must only withstand 120 PSI, therefore the plexi-glass is more than sufficient for this
given application.
Additional dimensions and specifications including the length of the dirty air side, length
of the clean air side, thickness of the plexi-glass and number, location, and distribution of
screws required to hold the box together were provided by PAC®.
The filter brace was added with the intent of restraining the filter without effecting flow.
We suspended the filter brace on the open side of the filter using four threaded rods; one
in each corner, which were tightened using hex bolts until the filter was air tight on both
ends. The other ends of the threaded rods were tightened on the clean air side of the tube
sheet, securing the Venturi in place. The only governing variable controlling the
dimensions of the
brace was that it
had to fit in the
box. Based on this
variable,
the
dimensions were
determined to be
Clean Air Outlet
12.38”x12.26”.
With the “Test
Box” dimensions
complete,
the
dimensions for the
compressed
air
source inlet were
determined. This
inlet was asked to
accommodate two
different source
pipe diameters (1”
and 1.5”).
Torit® Venturi
1.5” Flange
Pressure Transducers
Figure 5: Fabricated “Test Box”.
The connection between the source and “Test Box” was also required to be a slip fit,
accommodating for the variation of source length. This was accomplished by making the
8
The inlet and outlet dimensions were determined using an ASHRAE approved ductulator.
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source inlet 1.5” and placing a slip fit flange capable of being bolted to the “Test Box” on
each source pipe.
For detailed drawings of the “Test Box” refer to Appendix D, Figure 21.
Venturi Design
The problem of designing a Venturi for the pulse jet cleaning system needed to be
redefined in terms of fluid dynamics. From the customer’s perspective, we were asked to
define a successful Venturi that is capable of cleaning the filters while using minimal
amounts of the in-house compressed air9. In Laymen’s terms, the customer wanted the
“biggest bang for their buck.” To put this into fluid terms, we needed to define the most
effective cleaning cycle. In order to do this, we made use of our industry veteran, Bob
Betances, who gave us one highly applicable paper10 published on the topic of Venturis
that described their uses in Pulse Jet Cleaning Systems.
From this paper, we were able to define an effective pulse jet cleaning cycle with the
highest possible exit velocity11. This effectively gave us adequate grounds to redefine a
successful Venturi as one
that is capable of
achieving the highest exit
velocity possible; given
specific flow conditions.
The problem was further
simplified after speaking
with a University of
Delaware
professor,
Andras
Szeri,
who
specializes in areas of
fluid dynamics.
After
several
conversations, we were
reminded that we could
calculate the ideal ratio of
throat diameter to exit
diameter using the input
and output pressures of the
Venturi. Furthermore, by
Figure 6: Theoretical pressure ratio relationships of
converging diverging nozzles. (White, 628; figure 9.11)
9
Minimizing compressed air usage lowers cost which was found to be the top concern of customers.
Filtration & Separation, K Morris, C. J. Cursley & R. W. Allen; Presented June 1990 at the 5th World
Filtration Congress, Nice. France
11
Exit Velocity is defined as the speed at which a fluid leaves an opening (in this case the Venturi). More
commonly, a volumetric flow rate or mass flow rate is used to better describe a flow.
10
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designing a Venturi that has a slightly higher exit pressure than expected, we could create
flow expansion within the filter, by increasing the cleaning efficiency through potential
vibration of the filter medium.
To accurately estimate the input and output pressures, the operating conditions of the
filter were defined before cleaning. We noted that a pressure difference of 4” of water
between the clean and dirty airsides initiated the cleaning cycle on most of the
competitor’s systems. The assigned electronically controlled industrial filtration systems
have an expected output pressure of 4” of water below atmospheric12 or 100.33 kPa
(absolute)13. The input pressure was approximately equal to the back pressure within the
compressed air tank, 90 PSI (gauge) or 721.88 kPa (absolute)14. This assumption was
made using the theory that the total energy of the air exiting the source pipe should equal
that of the air entering the Venturi (zero losses). Furthermore, the use of a substantially
large compressed air reservoir allowed a near constant 90 PSI source exit pressure to be
accurately assumed.
Knowing these pressures, a mach number was calculated using an exit pressure 2.9 PSI or
20 kPa above the expected ideal exit pressure (mentioned earlier as 14.55 PSI or 100.33
kPa), which compensated for a small exit flow expansion. According to Compressible
Flow Theory15, the result will produce a series of complex super-sonic waves, releasing
excess energy until the Venturi exit pressure matches the back pressure16 within the filter.
Ideally, the energy of these waves will produce additional movement of the filter
medium, aiding in the dust removal process.
With the pressure ratio (Po/P) determined as approximately 6 to 1, we found that an
estimated exit mach number of 1.83 was associated with our given design using the
following formula17 (Eq. 2):
 Po 2 / 7 
2
Ma  5    1
 P 

With the Mach number calculated, the ratio between the throat area (At) and the exit area
(A) was estimated using the following, solved for A/At18 (Eq. 3):
Ma  1  1.2
12
A
1
At
This assumes the pressure within the clean air plenum to be approximately equal to 1 atmosphere
This calculation assumes a standard conversion factor of 2.490E2 kPa per 1” Water, and 1 atmosphere
equal to 101.33 kPa (http://www.members.optusnet.com.au/ncrick/converters/pressure.html).
14
This calculation assumes a standard conversion factor of 6.895 kPa per 1 PSI, and 1 atmosphere equal to
101.33 kPa (http//www.vikingpump.com/documents/Metrics_and_US_Conversion_Formulas.pdf).
15
Compressible Flow Theory specifically referring to frictionless, isothermal, compressible flow through
converging-diverging nozzle.
16
Fluid Mechanics, Fifth Edition. Frank M. White, page 630.
17
White, 610; formula 9.35
18
White, 616; formula 9.48c (Assuming a ratio between 1.0 and 2.9)
13
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This resulted in a ratio of approximately 1.47, which then gave us the throat diameter
equal to approximately 7.492 inches assuming that the exit diameter was equal to one
half-inch below the inner diameter of the filter, or 9 inches 19. Once the throat and exit
diameters were chosen, the inlet diameter was chosen to be a half-inch larger than the exit
diameter, or 9.5 inches20.
With the one-dimensional analysis complete and knowledge of effective Venturi shapes
from our previous research21, we proceeded to design the overall Venturi shape. We
chose lengths based on general input from our industry expert regarding angles of
convergence and divergence.
The theoretical design, shown
in Figure 7, shows the ideal
Venturi shape.
The actual
prototype, shown in Appendix
H Figure 22 was produced
using five pieces of rolled sheet
metal welded into the basic
shape of the Venturi. This
basic shape was then machined
to better fit the ideal design of
the Venturi.
Figure 7: Theoretical Venturi Design
Venturi Validation
Considering the design specifications of the Venturi prototype, the major design
validation test must included one, which proves that the Venturi promotes aspiration of
near stagnant air within the clean air plenum, and proof that the exit velocity of the actual
pulse matches the estimated exit velocity. To accomplish this task the theoretical exit
velocity of the pulse was estimated using the Mach number associated with the Venturi,
and the speed of sound in air; assuming a fixed temperature and pressure22. To calculate
the speed of sound in air, given these conditions, and a known specific-heat ratio (k) and
density (given as 1.40 and 1.20 kg/m3 respectively, we can use the formula below to
calculate the speed of sound (a) assuming air to be a perfect gas (Eq. 4):
19
This one half inch allows for small errors to be made in the alignment of the filter while still creating
desirable flow conditions.
20
The inlet diameter was chosen noting that a larger inlet diameter creates more potential for aspirated air
during the pulsing process, leading to a larger cleaning burst.
21
Filtration & Separation, K Morris, C. J. Cursley & R. W. Allen
22
Temperature and Pressure shall be defined as 20oC and 101.33 kPa (68oF and 1 atm)
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a
kp

From this formula, the speed of sound at the given conditions was approximated to be
343.83 m/s or about 1128.05 ft/s. With that said, and a distance between sensors of less
than a foot (approximately 10 inches), a duration between samples of approximately 0.7
milliseconds, or approximately 1500 samples per second were required to accurately
estimate velocity based on a correlation between pressures in the given sensors. Given
our estimated exit Mach of 1.83, we expected an exit velocity equal to approximately
2064.33 ft/s. At this speed, the required sample rate increased to approximately 2500
samples per second to calculate an average velocity based on pressure readings.
It should further be noted that the above sample rates assumed minimal data acquisition.
This means that each sensor was expected to acquire one to two points of data as the
pressure wave passed. With the specified data application requiring the estimation of
accurate peak pressures, an absolute minimum of three to four data points per sensor was
required. This increased the sample rate to approximately 10,000 samples per second.
Sensor Selection
Sensor specifications were implicitly defined to include the ability to sample an estimated
peak pulse differential of approximately 2.90 PSI (20 kPa) with a response time of 0.1
milliseconds. Upon browsing various catalogues and categories of sensors, it became
clear that pressure accuracy was not possible with a low response time sensor. Higher
response time came in relation to higher peak pressures. Fundamentally, this should not
have posed a problem; however the minimum error associated with these pressure
transducers was  1%. With 10,000 Hz (0.1 millisecond response time) sensors, the
minimum available peak pressure was 250 PSI. This gave the sensor an error of less than
or equal to  2.5 PSI.
For our purposes, the 10,000 Hz sensors would give us accurate velocity reading if we
compared the time difference associated with the initial pressure change readings23.
While this would give us potentially accurate average pulse speed-readings, the error
associated with the pressure reading would be as high as  86% of the expected peak
pulse reading. We found this result to be an inexcusable error.
A more plausible solution was introduced by our partners at Precision Air Convey based
on the assumption that lower response time sensors could still record single peak
pressures. For this reason, it was decided that the sensor selection should be based on the
overall maximum pressure rating. With this assumption, sensors with a maximum
pressure reading of 5 PSI were chosen. The resultant error when compared to our
expected peak pressure reduced to  1.72% (noting that these sensors also demonstrate a
1% error of their maximum pressure rating). For the 5-PSI sensors, 200 Hz (5
millisecond response-time) was the highest frequency response available.
23
Initial pressure change readings are defined as the first above zero pressure reading as recorded by the
data acquisition card.
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With the lower frequency response sensors, an accurate multiple point pressure versus
time curve became impossible; however, according to supplier input, the sensors were
capable of producing a single data point at the peak pulse pressure. With high-speed data
acquisition software, the peak pulse pressure was assigned to a set system time24. By
calculating the difference between system times for each transducer reading and
measuring the lengths between transducers, an average velocity can be calculated using
the fundamental definition of average velocity (Eq. 5):
V
L
t
Data Acquisition Box Selection
We were required to accurately sample data with a minimum input duration of 0.1
milliseconds, and a data acquisition card capable of a minimum of 10,000 samples per
second. Due to the generosity of a university professor, J. Q. Sun, our group was given
access to an E-series PCI Data Acquisition Board25. This board was specifically designed
for high speed data acquisition of both digital and analogue signals. The board is capable
of acquiring signals as fast as 250,000 samples per second26 on each of the multi-channel
inputs.
With this data acquisition setup, professor Sun also made an up-to-date version of
LabView software available to the team. With this software, we could effectively
interface with the National Instruments DAQ Board, in addition to collecting and
analyzing data.
Test Plan
To accomplish our goals, we have
implemented three sensors into the “Test
Box.”
Our hope, through extensive
testing, was to gain a detailed
understanding of the correlation between
pressure and time, both at one single point
in the filter, and over the entire filter
length. Our testing will include variations
in source length, source diameter, and
pulse duration. The goal was to find an
ideal source length, source diameter, and
pulse duration for our Venturi prototype,
and compare our competitor’s prototype.
Figure 8: Static Pressure sensor layout
24
Note that standard set system time is fundamentally a millisecond timer assigning January 1 st, 1922 as
time 0.
25
Specifically labeled PCI-MIO-16E-4 DAQ board, now known as the NI PCI-6040E DAQ board
26
National Instruments product specifications; http://sine.ni.com/apps/we/nioc.vp?cid=10795&lang=US
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We then compared these ideals with the hope of showing the overall superiority of our
design. Further, as a control in our experimentation, we then tested the system with no
Venturi implemented. With this test, we proved that a Venturi is a necessary part of the
Pulse Jet Cleaning System. Through multiple iterations, we showed that our data is valid
through an overall repeatability of the various pressure readings.
Test Expectations
We were able to define an angle of propagation for the compressed air pulse using
several methods made viable through research27 (Figure 9).
.
Figure 9: Linear propagation diagram with variable definitions
Defining the angle of propagation gave us the ability to define  algebraically. This was
done using basic trigonometry associating the exit diameter of the source (d), the entrance
diameter of the venturi (D), and the source length (L) (Eq. 6):
 Dd 

 2L 
  tan 1 
With this equation, (and various measurements from a Torit® dust collector28), we were
able to calculate the angle of propagation that is associated with the standard operation29
to be equal to approximately 13.4o. Using this angle, the entrance diameter of the PAC®
prototype, and solving equation XX for L, we estimated the ideal source length of the
PAC® venturi to be approximately 17.84”. (Eq. 7)
27
Major assumptions include linear fluid expansion, and negligible boundary conditions associated with the
clean air plenum.
28
Measurements from Torit® dust collector include a source length (L) equal to 14”, source diameter (d)
equal to 1”, and a venturi diameter equal to 7.67”.
29
Standard operation is defined as operation under industrial conditions, including both constant air flow,
and material clogging.
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L
Dd
2 tan( )
Test Results
For testing, we programmed in LabView with the idea of acquiring data from the three
pressure sensors simultaneously30 using an inlaid sub-VI in the LabView code. When the
VI was unable to collect the desired data, we attempted writing our own sequential
acquisition code, which slowed down the sampling rate.
In order to assign a time to each data point, we used a ‘start/stop’ system and logged the
system time at the beginning and end of each test. By doing this, we assumed that the
time between samples would be equal. This meant  t could be calculated with a time
assigned to each data point. While early tests proved promising, further work showed
large discrepancies in average speed calculations. In a second iteration, we used the
method of system times assigned to each data point to compensate for the inaccuracy.
This method proved to be too complex for the processor to handle at high speeds and
yielded fewer than 200 samples per second.
Multiple sensor data collection, high speed, and single sensor acquisition became our
only viable option. Although, this option proved to be effective in peak pulse pressure
and pulse duration measurements, it made calculating average speed impossible (Due to
variations in each location and peak pressures in each individual pulse).
In preliminary single sensor testing, peak pressures occurred at the third pressure
transducer, rather than the first. The single sensor testing contradicted our initial
assumption associated with a pressure drop over the length of the filter. By speaking
with an expert in the field of industrial filtration, we learned that a pressure rise over the
first several feet of a filter wall is a common outcome, and can be attributed to both the
exit angle and diameter of the venturi. We began further testing to further validate this
phenomenon, which we labeled shadowing.
Shadowing is a restriction of the expansion of a flow caused by the exit angle and
diameter of the venturi. This then creates a low-pressure area (with respect to the static
pulse pressure) in the shadowed area (Figure 10).
30
Note that simultaneous data acquisition is impossible with a single processor, however for our purposes
high speed sequential (1, 2, 3, 1, 2, 3…) data acquisition can be considered simultaneous.
17
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Low pressure ‘shadow’
Figure 10: Shadowing diagram
The effects of shadowing along with finding a correlation between the pressure drop and
the filter length became impossible to do with our single filter “Test Box.”
Peak pressures at each source length were found to be both measurable and repeatable
using a constant source pressure. A rise in pressure was found as the source pipe reached
the back wall of the clean air plenum when we tested the Torit® venturi however, no
specific peak was found. A simple sleeve, when proposed and constructed increased the
length and volume of the clean air plenum (note length and volume change). In doing so
a uniform increase in pressure was noted at the two overlapping source lengths 31. This
showed initial signs of a positive correlation between the volume of the clean air plenum
and the peak static wall pressure. The new sleeve also produced enough additional
source length to find a peak when plotting the static pressure versus the source length.
31
Overlapping source lengths are defined as pressure readings taken at the same measured source length
with and without the sleeve implemented.
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Static Wall Pressure (PSI)
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
30.5
Source Length (inches)
Extended Plenum
Original Plenum
Figure 11: Torit® venturi Pressure versus Source Length
Static Wall Pressure (PSI)
For comparison, we took the difference in the static pressure readings of the two
overlapping source lengths, and by averaging them we were able to define a scaling
factor. When subtracted from all data taken with the extension sleeve, the scaling factor
created a uniform data set from the two setups.
0.3
0.25
0.2
0.15
0.1
0.05
0
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29 30.5
Source Length (inches from venturi opening)
Torit® Venturi
Figure 12: Scaled Torit® venturi Pressure versus Source Length
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After scaling the data collected from the Torit® venturi, we found a visible peak at 29”.
This, when applied to equation 6, gave us an angle of expansion of only 6.56o, less than
half our expected angle of 13.4o. To explain this low angle of expansion, we considered
the differences between our tests and realistic operational conditions32. Of those
discussed, the most plausible, and only realistic difference causing the disparity was that
we were testing on a dead box33. Further research on theoretical fluid flows proved
promising as the decrease in expansion occurred with a decrease in counter flow.
With the new theoretical angle of expansion defined as 6.56o, a simple calculation was
made using this angle in equation 7 to calculate the theoretical source length for the
PAC® venturi, which we found to equal 36.96”. Immediately we realized that this source
length, even with a larger expansion sleeve would be impossible to reach given the
special restrictions of our testing area. Realizing this limitation, we continued testing
with the hope of seeing a rise in the peak pressures as we neared our maximum possible
source length with the PAC® prototype.
Immediately, we began testing the PAC® prototype with the hopes of finding a rise in the
peak pressure as the source length neared our new theoretical value. As testing
progressed, we saw no such increase in peak static wall pressures, which lead us to no
reasonable conclusions about the PAC® prototype, except that at low source lengths, it
was grossly outperformed by the Torit® venturi. (Figure 13)
Static Wall Pressure (PSI)
0.3
0.25
0.2
0.15
0.1
0.05
0
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
30.5
Source Length (inches from venturi opening)
PAC® Venturi Prototype
Figure 13: Scaled PAC® venturi Pressure versus Source Length
Realistically, this result is understandable as the maximum source length that we were
capable of testing was only 27”, which is nearly 10” away from our theoretical optimized
length.
32
33
Assuming Torit®’s optimization testing was done under standard operating conditions
Dead Box is defined as the “Test Box” with zero flow when the cleaning cycle is not initiated.
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Static Wall Pressure (PSI)
Our final filter testing included optimizing the pulse-jet system using no venturi. While
our theoretical equation can be applied to the no-venturi-case, a much larger margin of
error is associated between the theoretical and the actual value. The main argument
behind this is that with no venturi, the filter entrance is a far more abrupt transition
leading to complex flow conditions. The theoretical value was calculated to be 34.78”
which, like the Torit® venturi, proved to be impossible to measure with our testing
apparatus. The small difference between the maximum source length tested and the
theoretical source length is small enough to see a general rising trend. The major
discrepancy is that no general rising trend is seen. This leads us to conclude that with no
venturi, no predictable peak will occur.
0.3
0.25
0.2
0.15
0.1
0.05
0
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29 30.5
Source Length (inches from venturi opening)
Source Pipe Only
Figure 14: Scaled No venturi Pressure versus Source Length
When comparing the optimum source length plots, an apparent difference is seen
between the peak of the Torit® venturi and the peaks from the other two test conditions
(Figure 15).
21
Static Wall Pressure (PSI)
TeamPAC
Phase 3
3/6/2016
0.3
0.25
0.2
0.15
0.1
0.05
0
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29 30.5
Source Length (inches from venturi opening)
Torit® Venturi
PAC® Venturi Prototype
Source Pipe Only
Figure 15: Scaled Comparison of Pressure versus Source Length
The difference between the two highest peaks, when calculated, only shows a 3%
difference. This seemingly minute difference leads to a 278 lbs increase in cleaning
force34 when applied to the entire filter area35. This 278 lbs increase comes at no
apparent expense, as it is achieved solely be implementing the venturi and without any
increase in the use of compressed air.
To find where this additional cleaning force came from, we tested the pressure drop
within the clean air plenum during the cleaning process. Our intent was to find a
negative correlation between the increase in static wall pressure, and a decrease in the
pressure between the clean air plenum. The thought process behind these tests was
centered on the idea that, the more negative the pressure within the clean air plenum, the
more air is aspirated into the filter during cleaning (increasing the volume of the cleaning
pulse). Due to time constraints, it became impossible to test all three systems with and
without the extension sleeve. To minimize potential error associated with leaking due to
the additional seems of the extension sleeve, we tested only with the original “Test Box.”
Immediately, an inverted bell curve was noted while plotting the raw pressure data versus
time. Further testing showed a good correlation between data points, allowing us to
accurately compare the pressure drops at different source lengths. After collecting data
for each cleaning system36, setup a comparison plot similar to figure 15 above (Fig 16).
34
Cleaning force is defined as the force perpendicular to the filter median which is thought to be
responsible for much of the cleaning process.
35
Filter area is set at (FILTER SPECS!)
36
Cleaning Systems are simply defined as specific venturi’s (i.e. PAC® venturi prototype or the Torit®
venturi) or the use of a source pipe alone.
22
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0
-0.05
1
3
5
7
9
11
13
15
17
19
21
23
25
27
Static Pressure (PSI)
-0.1
-0.15
-0.2
-0.25
-0.3
-0.35
-0.4
-0.45
-0.5
Source Length (inches from venturi opening)
Torit® Venturi
PAC® Venturi Prototype
Source Pipe Only
Figure 16: Comparison of Pressure versus Source Length in Clean Air Plenum
From this data, we see some correlation between the rising static wall pressures in and the
decreasing pressure within the clean air plenum, but even more so, we see a distinct rise
in the level of aspirated air37 as we increased the source length. This increase, with
further testing, and an increased clean air plenum may further explain and validate the
use of a venturi in the process of pulse-jet cleaning.
One major discrepancy between this data (Figure 16) and the static wall pressure data
(Figure 15) is the lower clean air pressure readings produced when testing the PAC®
prototype in comparison to the source pipe alone. This difference does not correlate to
the higher static wall pressures measured with the source pipe alone (when compared to
the PAC® prototype). This discrepancy, which contradicts the negative correlation
between static wall pressures within the filter and static pressures within the clean air
plenum, cannot be confidently explained without further testing. This being said, when
looking at the pressure data collected from the clean air plenum, it appears that both
venturis out perform a source pipe alone38.
Conclusions from Test Results
Based on the static pressure data collected in the extensive testing of the various cleaning
systems, we found that the Torit® venturi outperformed both the PAC® venturi prototype,
and the source pipe alone. It must be noted that these test results are based on testing
done on a range of source lengths from 0.0” to 30.5”. The Torit® venturi showed a
37
We assume a more negative pressure reading within the clean air plenum to directly correspond to a
larger volume of aspirated air (this assumption is based on idea gas behavior).
38
This assumes the idea that a larger volume pulse will clean more effectively than a pulse with less
volume.
23
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notable advantage of approximately 3% when compared to the maximum reading from
the competition, which subsequently corresponds to a 278 lbs increase in cleaning force.
Future Testing & Path Forward
Due to our initial success in designing and testing aspects of the pulse-jet cleaning
system, our sponsor has offered to support our team for the duration of the spring
semester. The goals for the spring have been defined as, but are not limited to:
1. Repeating testing under standard operating conditions.
2. Determining the relationship between the volume of the clean air plenum and the
magnitude of static wall pressure.
3. Further defining the parameters required to achieve maximum static wall
pressures.
4. Determining the cleaning effects of various pulse durations over the length of to
filters in series.
5. Defining the effects of different filter media areas on the cleaning process.
6. Correlating the pressure loss in the compressed air tank to the pulse duration.
7. Repeating testing on dirty filters to verify assumptions on increased cleaning
efficiency.
Repeating testing under standard operating conditions will be done using the full sized
prototype produced by PAC® (Figure 17). With this prototype, we will be able to test the
pulse-jet cleaning system during live operation. These tests will allow us to verify our
linear propagation assumptions, and further increase our understanding of the process of
pulse-jet cleaning.
Figure 17: Front and back views of the PAC® full prototype
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Determining the relationship between the volume of the clean air plenum and the
magnitude of static wall pressure will allow PAC® to decide on an efficient size of the
clean air plenum. This will potentially allow PAC® to produce dust collectors using
minimal material, while achieving maximum cleaning potential. To do this, we will need
to design an adjustable sleeve for the existing “Test Box” that will allow us to test
multiple volumes of the clean air plenum.
Further defining the parameters required to achieve maximum static wall pressures was
defined as a want based on our finding during senior design. Through testing, we
actually discovered that changing aspects of the “Test Box” gave us more desirable
cleaning results. If this holds true next semester, future testing should increase our
familiarity with the system, increasing our understanding, and thereby increasing our
ability to define parameters that achieve higher static wall pressures.
Determining the cleaning effects of various pulse durations over the length of to filters in
series will hopefully give us the pressure drop over filter length correlation we hoped to
achieve during senior design. By adding an additional filter, we will hopefully be able to
find exactly where the effect of shadowing ends and the pressure drop begins. This will
allow us to define the overall cleaning efficiency over the entire filter, rather than
focusing on one portion.
Defining the effects of different filter media areas on the cleaning process is something
that we initially ignored based on our sponsors cost restraints, and initial assumptions on
filter performance. Further research has shown that changing the type of filter material
may increase the performance of the cleaning system as different dust particles cling to
different surfaces in previously unforeseen ways. The idea behind this testing is that by
choosing a filter media specifically for paper dust, PAC® will easily increase their overall
cleaning performance.
Correlating the pressure loss in the compressed air tank to the pulse duration is a
calculation that can be calculated in almost any introductory thermodynamics course
making many assumptions on the behavior of the gas being used. We hope to correlate
this calculation to actual data so that PAC® can more accurately choose a compressed air
holding tank for the pulse-jet cleaning process.
Repeating testing on dirty filters to verify assumptions on increased cleaning efficiency is
by far the most important of our future goals. While initially, dirty filter testing was
postponed based on problems with repeatability of filter clogging, and the messy overall
process, we hope to finally validate the assumptions made correlating ideal cleaning
conditions39 to actual filter cleaning. By proving our assumptions correct, the project will
finally come full circle, demonstrating its obvious application to industrial filtration.
39
Ideal cleaning conditions as defined during senior design include: High exit mach, high static wall
pressure, and high volume of aspirated air.
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Appendix A
Figure 18: MAC® dust collector and highlighted “Test Box” dimensioning
26
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Appendix B
Figure 19: “Text Box” calculations
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Appendix C
Figure 20: “Text Box” calculations
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Appendix D
Figure 21: Test Box Dimensions
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Appendix E
Figure 22: Test Box Sleeve Dimensions
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AppendixF
Figure 23: Test Box Set-UP
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Appendix G
Figure 24: Sensor Wiring Layout
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Appendix H
Figure 25: Venturi Prototype
Figure 26: DAQ Box
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Appendix I
Figure 27: Compressed air tank and Goyen valve setup
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Appendix J
Figure 28: UDesign customer wants
Figure 29: UDesign ordered wants
Figure 30: UDesign top 10 wants and descriptions
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Appendix K
Figure 31: UDesign comparing, scaling and scoring benchmarks and metrics
Figure 32: UDesign
ordered metrics
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Appendix L
Figure 33: UDesign ranking of initial concepts
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Appendix M
Figure 34: This is an example of
Torit®’s model venturi attached to one
of their cartridge filters.
Figure 35: The above graph illustrates
the pressure versus time tests
conducted by Torit® with their venturi
implemented in the pulse-jet cleaning
system.
Figure 36: The above illustrates a basic
overview of our main competitor’s
industrial dust collector. Shown in the
cutaway is an illustration of their filter
support system. This is an aspect of our
system that we are yet to fully design.
38
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Appendix N
Figure 37: The cleaning system on the DUST-HOG® SUPRA-BLAST.
Figure 38: The DUST-HOG®
quick change filter door.
39
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Appendix O
Figure 39: The above illustration shows both normal, and cleaning cycle operation as
shown in the Torit® product catalogue.
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Equation Index
Equation 1 ..........................................................................................................9
Equation 2 ........................................................................................................12
Equation 3 ........................................................................................................12
Equation 4 ........................................................................................................14
Equation 5 ........................................................................................................15
Equation 6 ........................................................................................................16
Equation 7 ........................................................................................................17
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Figure Index
Figure 1 ..............................................................................................................3
Figure 2 ..............................................................................................................4
Figure 3 ..............................................................................................................7
Figure 4 ..............................................................................................................8
Figure 5 ............................................................................................................10
Figure 6 ............................................................................................................11
Figure 7 ............................................................................................................13
Figure 8 ............................................................................................................15
Figure 9 ............................................................................................................16
Figure 10 ..........................................................................................................18
Figure 11 ..........................................................................................................19
Figure 12 ..........................................................................................................19
Figure 13 ..........................................................................................................20
Figure 14 ..........................................................................................................21
Figure 15 ..........................................................................................................22
Figure 16 ..........................................................................................................23
Figure 17 ..........................................................................................................24
Figure 18 ..........................................................................................................26
Figure 19 ..........................................................................................................27
Figure 20 ..........................................................................................................28
Figure 21 ..........................................................................................................29
Figure 22 ..........................................................................................................30
Figure 23 ..........................................................................................................31
Figure 24 ..........................................................................................................32
Figure 25 ..........................................................................................................33
Figure 26 ..........................................................................................................33
Figure 27 ..........................................................................................................34
Figure 28 ..........................................................................................................35
Figure 29 ..........................................................................................................35
Figure 30 ..........................................................................................................35
Figure 31 ..........................................................................................................36
Figure 32 ..........................................................................................................36
Figure 33 ..........................................................................................................37
Figure 34 ..........................................................................................................38
Figure 35 ..........................................................................................................38
Figure 36 ..........................................................................................................38
Figure 37 ..........................................................................................................39
Figure 38 ..........................................................................................................39
Figure 39 ..........................................................................................................40
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Special Thanks
The Precision Air Convey Corporation Senior Design team would like to especially thank
Professors Cloud, Glancey, Keefe, Schwartz, Sun, Szeri, and Wilkins for their help
during senior design, and their never-ending patience with our team. In addition, we
would like to thank Bob, Dennis, Kevin, Tom, Eric, Andy, and everyone else we may
have forgotten at PAC® for their help, guidance, and input over the course of this project.
43