Tech Briefs Magazine - February 2022 - MD-3

tualized, optimized, and validated using
multiphysics simulation software.
Design Challenges for Gas
Flowmeters
All gas meters currently available in
India have their own limitations. For
example, in diaphragm meters, leakage
from moving parts and the diaphragm
can cause measurement errors. Rotary
displacement meters and turbine meters,
on the other hand, have close to
35 components, increasing the probability
of mechanical failure and fatigue.
Further, the enclosure size for any gas
meter is fixed, so any new meter design
must fit within the given enclosure size.
Therefore, the size of the device is another
important criterion for any new
gas meter design. All these different
criteria make it a challenge for these
devices to be approved during the final
quality testing stages. In fact, rejection
rates can be very high.
The Raychem team set out to minimize
the number of components in gas
flowmeters and reduce their rejection
rate during the quality testing phase,
thereby reducing the total cost of manufacturing
for these devices. To do so, the
Raychem team performed simulation
analyses in the COMSOL Multiphysics®
software.
Validating Designs with
Simulation
The team developed four gas meters
based on design optimization using
TRIZ, a problem-solving methodology,
and customer requirements. They
started by validating a finite element
model of a conventional gas meter design.
The team then extended their findings
to evaluate the proposed designs.
The first of the new gas meter designs
is a modification of the existing diaphragm
system, where the pantograph
assembly is replaced with a Scotch-Yoke
mechanism to reduce the number of
components.
After arriving at their optimized design
(Figure 1), the team was able to
eliminate several mechanical components
from the original design, in addition
to improving the accuracy and
sensitivity of the measurement. The
number of components in the meter
system was significantly reduced, from
35 components of the earlier diaphragm
design to 5 or 6 components, thus asMotion
Design, February 2022
MD Motion Control Feature 0222_1.indd 3
TH(721)=720 deg
Surface: Total Displacement (m)
×10-18
7
6
5
4
3
2
1
Z
y
X
Figure 1. Geometry of the Scotch-Yoke design.
Time=10 s
Surface: Velocity Magnitude (m/s) Streamline: Velocity Field (spatial frame)
1
0.8
0.6
0.4
0.2
y
Z
X
Figure 2. Velocity profiles of the flowing gas in the Möbius band flowmeter.
suring the mechanical ruggedness and
integrity of the system.
The next design consists of a Möbius
band turbine, where the rotation of the
turbine is used to measure the gas flow
rate. These gas meters measure the gas
volume by determining the velocity of
the gas moving through the Möbius
strip. The Möbius-band-shaped rotor is
placed in the way of the gas flow passing
over it, which rotates the shaft. The
output of the shaft is transferred to a
bevel gear system. The turbine infers the
velocity of the gas, which is transmitted
mechanically to an electronic or mechanical
counter.
3
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1/17/22 5:05 PM
http://info.hotims.com/82318-800
Tech Briefs Magazine - February 2022

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