Download P16318 Poster

Summary:
Schuyler
Witschi (EE)
Lianna
Dicke (EE)
Luke
McKean (ME)
Selden
Porter (ME)
•As oil and gasoline prices continue to rise, along with their environmental
concerns, the discovery of natural gas sources in the United States creates the
opportunity to utilize natural gas as an alternative for transportation fuel
•This project relates to the means for delivering a portion of Compressed Natural
Gas (CNG) or any gaseous fuel for use in an internal combustion engine
through the use of a mass flow distribution device
•It is our goal to create a test fixture which involves the stepper motor provided
by CTS Corp. that can control mass flow in a repeatable and accurate manner
Gas Flow Theory:
Design:
Ball
Actuator
Seat
Regulated
Output
Natural Gas
Input
Natural Gas
Cam
• The flow was determined to be choked due to
its high pressure differential. The following
formula was used to determine the effective
valve throat area needed to meet the
engineering requirements:
• The final design integrates
a ball and seal valve
operated by a push rod that
rides a cam.
• The cam is driven by an
automotive actuator that
uses CAN protocol.
Where A0 is the effective throat area, m* is
the mass flow rate through the throat, T0 is
the total temperature at the throat, P0 is the
total pressure at the throat, R is the specific
gas constant, and γ is the adiabatic ratio of
the gas. This assumes the flow is isentropic
meaning it neglects viscosity and assumes
there is no heat transfer in or out of the flow.
• Lifting the ball a known
distance (a function of the
cam profile and actuator
position) results in a
solvable choke area and
mass flow rate.
• The cam profile can be tuned for different applications with
different flow control requirements.
Results:
• To prevent leak, the ball is pressed into the seat with a spring.
• By measuring flow out of the device under
certain conditions we could plot the position
to lift graph of the device which can be used
to tune it
• The spring, combined with the force from the pneumatic
pressure differential, makes a positive seal.
• O-rings are used in all mating surfaces to prevent leak and
provide adequate sealing.
By 25% throttle opening, the lower value of
target flow rate range for 60 psi was met. At
the upper limit of the available flow
measurement equipment, the flow was still in
the target range.
Eng. rqmt. #
ER1
ER2
ER3
ER4
ER5
ER6
ER7
Importance
9
9
9
9
9
3
3
Description
Accuracy of Position
Repeatability of Position
Leak Rate of Device
Operating Voltage
Dynamic Range of Position Steps
Flow @ 4 bar-g (58 psig)
Operating Inlet Pressure Range
Unit of Measure
% of commanded value
% of previous value
sccm
volts
# of motor steps
g/s
bar-g (psig)
Target Value
±5
±5
25
13.5
123
12-18
4 (58)
Measured Value
<2
<1
200
12
>100
16
1.7-4.1 (25-60)
sccm
ms
ms
0
N/A
NA
260
250
°C (°F)
-40-85 (-40-185)
bar-g (psig)
TBD
hrs
10,000
✓
✓
✓
liters
5.7
✓
Will be acknowledged in the design:
ER8
ER9
ER10
9
9
9
Total Leak
Open Response Time
Close Response Time
ER11
3
Operational Temperature Range
ER12
3
Burst Pressure
ER13
3
Operating life
ER14
1
Compatible Engine Size
✓