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Multidisciplinary Senior Design Conference
Kate Gleason College of Engineering
Rochester Institute of Technology
Rochester, New York 14623
Project Number: P16452
ACTIVE RECIPROCATING COMPRESSOR VALVE ASSEMBLY
Mechanical Engineering
Ian Nanney
Negar Salehi
Robert Osborn
IMAGE
Electrical Engineering
Keith Leung
Christopher Reynolds
Abstract
Compressors have valves that are passive devices which work with a spring. The purpose of this project is to
develop and build an active reciprocating compressor valve assembly that controls when to release air from a
compressor. Our assembly consists of a designed test pressure vessel that enables the testing of the active pressure
valve. The active valve uses a solenoid, powered with DC current to actuate four poppets as to when to release
compressed air inside of the pressure vessel. LabVIEW software was utilized to generate a signal to the solenoids as
to when to motion the poppets fore and aft in their cylindrical valve chambers.
This exhibit will display an actively controlled compressor valve assembly that was developed in Multidisciplinary
Senior Design (MSD). It is very important that the actively controlled valve be able to achieve the same pressure
profile as a passive compressor valve. This will be the first step towards proving that this technology can replace the
traditional passive valves. This task is one of the main challenges for the team and the goal is to achieve this
requirement through theory and simulation. Also, it is necessary to investigate different technologies that can be
used to actuate the valve under the appropriate conditions (speed, temperature, pressure, etc.). After benchmarking
and multiple concept selection processes, the team concluded that solenoids will provide the most efficient and
appropriate actuation for our design. Due to safety issues, the designed active valve cannot be directly tested on the
existing compressor. Therefore, a small vessel with inlet and suction valves will need to be designed to model the
compressor and facilitate testing for compression cycle behavior.
Background--Negar
Dresser-Rand is an American global supplier of custom engineered rotating equipment for many
applications such as oil, gas, power and other industries worldwide. The company has been striving to provide the
most efficient and reliable rotating products and lead in safety, quality, and cycle time[1].
In February 2011, a new Dresser-Rand single stage, dual acting reciprocating compressor was installed and
commissioned on Rochester Institute of Technology’s (RIT) campus by a team of undergraduate engineers for their
senior capstone design experience (Figure 1). This donation was a major part of an initiative to develop a strong
collaboration between Dresser-Rand and RIT that began more than eight years ago. The intent of the compressor test
cell at RIT is for both educational and research purposes.
Standard compressors operate with passive mechanical valves that utilize springs to direct airflow based on the
pressure difference. Significant gains on efficiency and wear are possible if these valves are actively controlled
(limiting impact velocities, chattering, etc.). The design, build, and test an active compressor valve assembly is
necessary to investigate different technologies that can be used to actuate the valve under the appropriate conditions
Copyright © 2012 Rochester Institute of Technology
Proceedings of the Multidisciplinary Senior Design Conference
Page 2
(speed, temperature, pressure,
etc.
Figure 1: Passive pressure control valve
The goal of this project is to design and build an active reciprocating compressor valve assembly that controls
when to release air from the compressor. The demonstration will require instrumentation to prove the design is
meeting reciprocating compressor like specifications. Similar technology has been developed such as in 2007 by the
Southwest Research Institute (SWI) by Dr. Klaus Brun (http://www.swri.org/9what/releases/2007/plateval.htm)
where the individual valves were attached to a plate that was driven by an electromagnetic actuator. However,
similar ideas have not yet been fully studied and are very costly.
Design Process
Customer Req. and Specifications/Eng. Requirements
The project was governed based upon the customer requirements that were implemented.
These stipulations and request were utilized in the progress of the project so that the end product
would suffice the customers needs. Below in Table 2, illustrates the needs of the customer.
Customer Rqmt.
Importance
Description
Comments/Status
#
CR1
1
Valves open and close simultaneously.
Valve opening and closing are actively
CR2
1*
controlled
Very important!!!
Pressure vessel simulates compressor
CR3
3
cylinder
CR4
1
Logs data in an easy to read format
Demonstration system behaves similarly
CR5
2
to the ESH-1 compressor.
Active valve system conclusively
CR6
3
performs better than passive spring
Active
valves
assembly
is
interchangeable with passive valve
CR7
2
assembly.
CR8
1
Compatible with Labview
Able to see components in use during a
CR9
3
demonstration.
Valves seat firmly against housing when
CR10
1
closed
Test bench is constructed to avoid user
CR11
1
injury
Valve opens and at a rate of 6Hz per
CR12
2
second
Table 2: Active Reciprocating Compressor Valve Assembly Customer Requirements
The most critical customer requirement and goal of this project was to ensure that the valve will
actuate open and closed all while being actively controlled. If this need was not meet the entire
project would not be met and the creation of an active reciprocating valve would have failed.
Other notable requirements are that the valve must open and close, otherwise the functionality of a
the valve would cease to operate resulting in the failure of the assembly. In order to enable the
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Proceedings of the Multi-Disciplinary Senior Design Conference
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universal installation and functionality of the valve, the end product must be able to demonstrate
the same system behavior and result as the passive valve and the valve must be able to fit in all
locations that the current passive valve exists. in order for the functionality to operate equal to or
better than the current model, the active valve needed to seat firmly against the housing and
possibly minimize the amount of ‘chatter’ that the passive valve displays. No injury must also be
witnessed during the running of the valve or test bench.
In order for the engineers to be able to produce a valuable product for the customer, the
engineers must generate guidelines and values that they must meet all while meeting the customer
requirements. The values and requirements created can be seen in Table 3 below.
Engr.
Unit of Marginal
Ideal
Requirement
Comments/Status
Measure
Value
Value
(metric)
Measures Vacuum Valve
S1
Flow Rate Flow Rate
ft3/h
175.3
185.45
Need modeling results
Reasonable
S2
Safe
Weight
lb
75
50
S3
Reasonable Size
ft3
3x3x4
2x2x3
Cylinder
S4
Pressure
psi
7
5
periodic wave
Cylinder
S5
Frequency
Hz
2
6
S6
Cylinder Size
in3
123.34
141.4
Number
of
S7
discharge valves
-1
4
Number of data
points
taken
(sample
S8
frequency)
Hz
12
100
S9
Sensor
V
TBD
0 to 10
Sensor
S10
resolution
%
TBD
<5
Vacuum
Inlet
S11
Valve Flow Rate
ft3/h
1844
1854
Table 3: Active Reciprocating Compressor Valve Assembly Engineering Requirements
rqmt. #
Function
From the table, the ideal values can be seen which are the expected numerical values to be delivered as well
as the values that are satisfactory for the continuation and running of the project and is within the
theoretical simulation. The ideal values, are the values that the original simulation and system were
designed with. The marginal values were then determined while varying the ideal values until the
simulation results were not desired.
Copyright © 2016 Rochester Institute of Technology
Proceedings of the Multidisciplinary Senior Design Conference
Page 4
Figure 2: Active Reciprocating Compressor Valve Assembly Functional Decomposition
System Level Concept Selection
Through research of multiple forms of pressurized vessel system, a number of ideas were formulated to
develop the system design. Concept differences involved a vacuum tank, vacuum valve, vessel pressure of 3psi and
18psi, inlet regulator, and a dynamic valve. Below in Figure 3, is the system pugh chart the Active Reciprocating
Compressor Valve Assembly.
Figure 3: Active Reciprocating Compressor Valve Assembly System Pugh Chart
From this figure, a comparison was made between all the different types of concepts generated in the brainstorming
process. Critical criteria was selected and placed on the farthest left side of the table where the concepts were
weighted against. Pluses, minuses, and zeros were used to rank how well the the concepts were when compared to
Concept 3. When the ranking process was completed, the total minuses, pluses, and zeros, were tallied up to the
respective column. With all the results gathered, the most positive concepts and ideas can be picked from the chart
and concepts. Below in Figure 4, we can see Concept 2, which is the selected concept to create.
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Proceedings of the Multi-Disciplinary Senior Design Conference
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Figure 4: Active Reciprocating Compressor Valve Assembly System selected concept
Concept 2 illustrates the selected system with a regulator valve that introduces the pressurized air into the assembly,
an actuator that releases the air to atmosphere and a vacuum valve that sets the pressure back to 0 psi in the tank.
Within the tank is a pressure sensor to monitor the pressure within the vessel which intern returns a voltage reading
to the external control system. The external control system then sends a signal out and controls the vacuum valve,
regulator and actuator so that the vessel maintains a sinusoidal like curve.
Simulation and Analysis
One of the important customer requirements is pressurizing the vessel in a way that it follows a
compression cycle. Simscape simulation was done to understand the flow of air through the system and determine
what combinations of valves and tanks can result in a compression cycle pattern.
The system is consisted of an inlet, suction, and outlet valve (which is the active valve designed by the
team). The vessel size is 0.1ft^3. The pressure enters at 50 psig and pressurizes the vessel to 5 psig. Once the vessel
reaches 5 psig, the outlet valve opens and reliefs the compressed air to atmosphere. After the outlet valve closes, the
suction valve opens until the pressure inside the vessel is back to 0 psig. The graph below shows that the system has
an overshoot value of about 1 psi, thus meaning that the pressure inside the vessel will reach 6 psig instead of 5.
However the results are close to ideal and the overshoot can be neglected. The compression cycle repeats at a
frequency of 4HZ, which is the customer's requirement.
The orifice area and mass flow rate values of inlet and suction valve that are obtained from this simulation
model assisted the team in purchasing the suitable valves. Most importantly, the orifice area value of the outlet valve
obtained from this simulation played a significant role in designing and dimensioning the active valve.
Copyright © 2016 Rochester Institute of Technology
Proceedings of the Multidisciplinary Senior Design Conference
Page 6
Figure 5: Model and Simulation of the Active Reciprocating Compressor Valve Assembly System
Detailed Design
Figure 6: Solenoid Cover
The entire system is composed of two main portions: the valve assembly, which is what the project is based upon,
and the vessel, the container used to contain air for testing the valves.
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Figure 7: Poppet
The Poppet is what is being actuated to open and close the valves. It has a gap in the center to hold neodymium,
N52, magnets. The magnets are held in the poppet because of interference; the magnets are force-fit into the poppet.
The material of the poppet, acetal, is a plastic, and when used in the brass solenoid covers, has a low coefficient of
friction. The chamfer at the top of the poppet is there to allow the poppet to center itself to the hole. The chamfer
also allows for the poppet to wedge itself into the hole easier, allowing for easier deformation of the plastic for
sealing to occur.
Copyright © 2016 Rochester Institute of Technology
Proceedings of the Multidisciplinary Senior Design Conference
Page 8
Figure 8: Solenoid Cover
The Solenoid Cover is a housing for the poppet, as well as a means to protect the solenoid from any elements
coming from the compressor. The locating pin exists as a means to prevent the cover from rotating and twisting the
wires connected to the solenoid. The flange locates the solenoid cover within the bottom piece of the valve
assembly to allow the poppets to have the same base location to measure displacement. The part is made from brass
because of the low coefficient of friction with plastic and due to it being non-magnetic, so it won’t interfere with the
solenoid. Around the outside of the cover is a solenoid, which is being used to actuate a poppet on the inside of the
cover.
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Proceedings of the Multi-Disciplinary Senior Design Conference
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Figure 9: Valve Assembly Bottom
The Valve Assembly Bottom is the housing unit for all of the solenoids and poppets. There are four locations to
place solenoid covers, four holes to allow the compressed air to exit the assembly, and four more holes to align this
piece, the valve assembly top, and the cover plate together via bolts. Within the largest holes, there is a ledge to
locate the solenoid covers vertically, to small through holes to allow for wires for the solenoids, and one more hole
to locate the solenoid covers. In the center of the part is a hole for a threaded insert, due to being unable to create
threads in the plastic piece. The piece is made from HDPE for two reasons: it reduces the weight of the overall
system, and it allows for better sealing with the top portion of the part by having a softer material mating with a
harder material. The material on the outside diameter is removed in order to reduce the weight. The ledge in the
center of the part, with a diameter of 6”, is to give the poppets room to move and to give air pathways to exit the
system.
Copyright © 2016 Rochester Institute of Technology
Proceedings of the Multidisciplinary Senior Design Conference
Page 10
Figure 10: Cover Plate
The Cover Plate is a meant to go between the two valve assembly halves. Its purpose is to secure the solenoid
covers, preventing any translating motion. It is fastened down by a rim on the valve assembly top, as well as a
screw/bolt in the center. In the center of the plate, there is a countersink to allow for the screw with a countersink to
center the plate within the bottom valve assembly. While the holes for the air and for the screws are as large as the
counterparts in the bottom valve assembly, the holes for the poppets are slightly larger to prevent obstruction of the
poppets by the plate, due to the screws causing some clearance when positioning the parts.
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Proceedings of the Multi-Disciplinary Senior Design Conference
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Page
Figure 11: Valve Assembly Top
The Valve Assembly Top is the top half of the valve assembly. The four holes on the square area is for securing the
valve assembly to the pressure vessel, while the ridge in the circular section is meant to house an o-ring, creating a
seal to prevent the air from escaping within the vessel.
Copyright © 2016 Rochester Institute of Technology
Proceedings of the Multidisciplinary Senior Design Conference
Page 12
Figure 12: Vessel
The Vessel is where the air will be compressed. It is modeled so the volume is as close as possible to the volume of
the compressor in possession by RIT.
Electrical Design
The solenoids driving the actuation in the active valve assembly must be designed to produce a sufficient
force to overcome the pressure in the vessel. This required force can be expressed as shown in Equation 1.
(1)
The cross-sectional area of the solenoid is calculated in equation 2:
(2)
Substituting Equation 2 into Equation 1 and using
,
This is the total force that must be overcome by the solenoids. Therefore, divided across four solenoids, each must
provide a force of 1.7059 Newtons.
Equation 3 models the force of a solenoid:
(3)
The parameters of equation 3 are: N, the number of coils in the solenoid;
, the cross-sectional area of the
solenoid; g, the gap between the solenoid and the moving poppet; and I, the current through the solenoid.
Electromagnetic permeability is a constant of
.
Equations 4 through 7 show necessary substitutions that must be made to design the solenoid.
(4)
(5)
(6)
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Proceedings of the Multi-Disciplinary Senior Design Conference
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(7)
Making these substitutions into equation 3:
Simplifying:
(8)
The resistivity of copper is
. The cross-sectional area of 32 AWG wire
. The gap
between the solenoid and the magnets in the poppet is
. Using a voltage of
, the force
provided by a solenoid of these dimensions is
, which is more than adequate for the calculated
requirements.
Actuation: Solenoids+Displacement Measurement System
The Hall Effect sensor consist of a thin piece of semiconductor material such as gallium arsenide (GaAs),
indium antimonide (InSb) or indium arsenide (InAs) passing a continuous current through itself. When the device is
placed in a magnetic field, the flux lines exert a force on the semiconductor material which deflects the electrons to
the ends of the semiconductor slab. As these electrons and holes move a voltage is produced between the two ends
of the semiconductor material. The movement of electrons through the semiconductor material is affected by the
presence of an external magnetic field. Below in Figure……….. We can see an image of a simple hall effect
sensor.
Figure 13: Hall Effect sensor
The application of the hall effect sensor is endless and used in multiple applications. The auto industry has used this
technology for shifting the vehicle into different gears, sensors that detect if doors are open or closed, and for
determining vehicle handling monitoring the position of the steering column.. The cell phone industry has also used
this technology in a similar manner in their flip phones. As the flip phones closed the screen is shut off when the
hall effect sensor senses the magnetic field of the magnet in the ear piece and further shuts the screen off.
The application of the hall effect sensor for our project will be used to measure the magnetic field
movement of the poppets inside the solenoid. The magnetic field will then induce a voltage that will then be
measured and converted into a displacement.
The solenoid actuation will be driven with a magnetic force that is created through a solenoid, with the
solenoid driven by a motor driver which is fed 36 volts from a power supply. The motor driver outputs a PWM
which is controlled by a DAQ interfacing between a motor driver and a computer with LABVIEW. The actuation
will be monitored with the use of a Hall Effect sensor which is a transducer that varies output voltage as it responds
to a magnetic field.
Copyright © 2016 Rochester Institute of Technology
Proceedings of the Multidisciplinary Senior Design Conference
Page 14
Power & Controls
Two power supplies were used in the integrated system in order for it to function properly and effectively.
A high voltage 200W power supply unit which outputs 5.9A power supply was used to power the motor driver. The
second power supply with a low voltage output was used to power the four Hall Effect Sensors.
■ LABVIEW/DAQ
■ PWM
■ Relays
● Build and Integration process
Problem Tracking
Problems were tracked and monitored through a matrix where a solution to the problem was the end result.
Below in Figure14 is a sample page from the problem tracking matrix file utilized.
Figure 14: Problem Tracking
Such problems that occurred was the Solenoid cannot produce the expected amount of force, the solenoid cannot
produce the expected amount of force that was calculated, Hall Effect sensor orders didn’t go through, the heat
produced by the solenoid is affecting current draw and response time, among many other problems. The steps taken
to determine a solution to the problems were consistent by analyzing the problem, generating potential solutions,
selecting and planning a solution, implementing a solution and evaluating the solution. This method allowed the
team to be consistent and through while analyzing problems and approaching efficient and working solutions.
Results and Discussions
● Conclusion & Recommendations
● Reference
○ [1] Dresser-Rand
○ http://www.electronics-tutorials.ws/electromagnetism/hall-effect.html
● Acknowledgements
○ Dr. Slack
○ Dr. Day
○ Dr. Whellin
Project P16452