New technologies
Development of Measuring Technique for Compressor Vane Behavior Analysis
Katsumi Endo*
Makoto Kawamura**
Keisuke Nakazawa**
Abstract
Rotary compressors may emit noise caused by collision between vanes and the cylinder wall. To
minimize the noise, it is crucial to examine the details of the mechanism of such vane-operating noise
by tracing the behavior of the vanes in time series. This report describes a developed visualization
technique to monitor the motion of the vane under operating conditions. Also a method of measuring
pressure affecting the movement of the vanes is explained.
Key Words : Compressor, Vane, Noise, / Car Air Conditioning
1. Purpose
For understanding compressor vane noise mechanism,
relation among compressor rotation speed, ambient
temperature, discharge pressure and intake pressure
has been previously studied.(1)～(4) However, it has not
fully been clarified in detail what vane behavior causes
the noise. Since vane movement is influenced by the
balance between vane pressure at vane tip (pressure in
compression chamber) and vane back pressure (pressure in vane rear chamber space), we have developed a
Fig. 1 Compressor structure
new technique to measure the pressure in the compression chamber and in the vane rear chamber space, and
simultaneously to visualize the vane movement in order
to directly observe the mechanism.
2. Rotary compressor structure and
principle of operation
Fig. 1 and Fig. 2 show a typical rotary compressor
structure and compression process respectively. Cylinder
and rotor are sandwiched between front side block and
rear side block. Five vanes are placed at respective vane
slots in the rotor body. Each vane is pushed by vane
rear chamber pressure and rotates keeping in contact
with cylinder inner wall. Refrigerant is sucked from a
suction port into a compression chamber, compressed by
volume change in the chamber, and discharged into the
compressor rear chamber space. Lubricating oil mixed
in the refrigerant is separated in the rear space by the
oil separator to discharge only refrigerant. The oil is fed
to the vane rear chamber and the pressure is raised to
proper level, resulting in the vane collision force.
* Test Engineering Group, Global Technology Division
** Compressor Development Group, Compressor Business Unit
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Fig. 2 Compressing process
3. Consideration for vane behavior visualization
Since compressor vane operation noise varies with
thermal environment, measurements have to be conducted under a wide range of temperature. For example
high temperature durability and thermal shrinkage of
parts must be considered. Since the parts must endure
rather extreme conditions including high pressure and
high speed rotation, careful selection of material and
sensor setting method are needed. Also the sensors
must be embedded inside the small compressor parts.
In addition, acoustic resonance that prevents pressure
measurement in the closed space should be avoided.
Development of Measuring Technique for Compressor Vane Behavior Analysis
4. Method for visualizing vane behavior
4.1. Requirements for visualization
The following are needed for visualization equipment.
(1) Materials can endure high temperature and
pressure.
(2) View can be secured even in the operational
condition.
Considering the above, we selected materials for visibility and designed the measuring equipment structure.
4.2. Selection of part materials for visualization
To visualize the vane behavior, we studied whether
we can apply a transparent structure in the rear side
Fig. 3 Conventional structure
block. We compared the candidate material characteristics in terms of resistance to heat, pressure and shock,
and transparency considering refrigerant state in the
cylinder and the load by rotation parts. As a result of
the study in this perspective, we adopted the polycarbonate resin (Table 1).
Table 1 Candidate materials for visualization
○：Suitable　×：Inappropriate
Fig. 4 Visualized inside with the conventional structure
4.3. Compressor structure for visualization
To observe the vane behavior, all we have to do is to
use transparent materials for compressor rear side.
However, the refrigerant is liquid at the start time, thus
mist of the refrigerant and oil in the rear space occlude
the view and the vane behavior cannot be visualized
(Fig. 3, Fig. 4). We redesigned the rear side block with
the integrated transparent parts to eliminate empty
space in the rear part of the compressor (Fig. 5, Fig.
6). Instead, by an external oil separator, the refrigerant
and oil pass through the outside of the compressor
body.
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CALSONIC KANSEI TECHNICAL REVIEW vol.11 2014
5.2. Selection of pressure sensor
In order to measure pressure in compression chamber
and vane rear chamber, we selected a pressure sensor
to be mounted on the rotor perimeter portion and the
vane slot. Table 2 compares the characteristics of the
candidate sensors in consideration of body dimension,
lead wire dimension, weight, pressure measurement
range and heat resistance. We selected sensor-A in the
table that can endure high temperature and pressure.
Table 2 Pressure sensor comparison
Fig. 5 Modified structure for visualization
○：Suitable　×：Inappropriate
Fig. 6 Modified parts for visualization
5. Method for pressure measurement
5.1. Consideration for pressure measurement
The following should be considered for the pressure
measurement.
(1) Parts can endure a wide range of temperature
from low to high.
(2) Parts can endure high pressure.
(3) Parts can endure centrifugal force due to high
speed rotation.
(4) Sensor can be embedded in the internal parts.
(5) Weight balance in the compressor mechanism
should not be affected.
(6) Parts can endure thermal shrinkage.
(7)Acoustic resonance that interferes with the evaluation shall not occur.
On the basis of the above consideration, we selected
pressure sensor and designed the setting structure and
fixing method.
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5.3. Placement of pressure sensor
The sensor is provided at the rotor perimeter and the
vane slot respectively to measure pressure in the compression chamber and the rear chamber (Fig. 7). For
the rotor perimeter part, since it is considerably larger
than the size of the pressure receiving area of the
sensor, it is thus suitable for the sensor to be placed.
On the other hand, the vane slot width is narrower
than the sensor pressure receiving area, thus the sensor cannot be directly mounted on the slot. Instead, a
sensor storage room, connected with vane slot through
communicating tube, is separately provided (Fig. 8).
Resonance frequency of this communicating tube is
designed outside the audible zone (＜20kHz) to avoid
an influence on the evaluation. The following formula
shows resonance frequency f(Hz) and speed of sound c
(m/s).
Development of Measuring Technique for Compressor Vane Behavior Analysis
=
4
=
(1)
Table 3 Adhesives comparison
(2)
L : communicating tube length，k : specific heat ratio，
R : gas constant，T : gas temperature，M : molecular
weight
○：Suitable　×：Inappropriate
6. Results
Fig. 9 and Fig. 10 show an example of the visualized
vane and the results of the measured pressure respectively. The development of this measurement method
has enabled us to visualize the vane behavior and to
observe the pressure at each portion throughout the
operation process.
Fig. 7 Pressure sensor installation
Rotation speed = 800 rpm
Fig. 9 Visualized inside of the modified structure under
operating conditions
Fig. 8 Cross section of communicating tube
5.4. Fixing of pressure sensor
The selected pressure sensor is fixed to rotor with
adhesive. The adhesive must bear severe operation
state where thermal shrinkage, high centrifugal force
and vibration shock occur. We selected acrylic adhesiveC, considering tensile shear adhesive strength, peeling
adhesive strength, heat resistance and hardness (Table
3).
Fig. 10 Pressure measurement result
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CALSONIC KANSEI TECHNICAL REVIEW vol.11 2014
7. Conclusion
(1) A new visualization method for directly understanding the vane behavior has been developed.
(2) Measuring the pressure profile along the compression process has also been made possible to analyze
the pressure balance that controls the vane movement.
(3) Establishment of the method to simultaneously
observe the pressure and the vane behavior will
enable further detailed study on compressor noise
generation mechanism.
Reference
(1) Hiroshi Iijima, Mitsuhiro Fukuda：A model
to analyze the start characteristics of vane
compressor，CKTR，６，p.88-93(2009)
(2) Mitsuhiro Fukuda, Tadashi Yanagisawa, Makoto
Ijiri, Seichiro Yoda: Vane back pressure and its
calculation model in vane compressor. Transactions
of the JSRAE，20(3)，p.357(2003)
(3) Mitsuhiro Fukuda： Vane Behavior in Vane Compressors under Start-Up Operation (1st Report)，Transactions of the JSME B，59(567)，p.3487(1993)
(4) Mitsuhiro Fukuda: Vane Behavior in Vane Compressors under Start-Up Operation (2nd Repot) Transactions of the JSME B，60(571)，p.879(1994)
Katsumi Endo
Keisuke Nakazawa
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Makoto Kawamura