|Title of Invention||
A DISCHARGE MUFFLER FOR A HERMETICALLY SEALED RECIPROCATING COMPRESSOR
|Abstract||A discharge muffler for a hermetically sealed reciprocating compressonconsisting of a hollow body having an inlet tube and an outlet tube, characterized in that the said body is internally divided by baffle plates having one or more baffle holes forming chambers having one or more perforations to lead the discharge gas through the chambers of the discharge muffler from the inlet tube to the outlet tube.|
|Full Text||FORM - 2
THE PATENTS ACT, 1970
TITLE : A DISCHARGE MUFFLER FOR A HERMETICALLY SEALED
APPLICANT (S): KIRLOSKAR COPELAND LIMITED
OF 1202/1. GHOLE ROAD, PUNE - 411 005, MAHARASHTRA, INDIA. AN INDIAN COMPANY.
The following Specification particularly describes the nature of this invention and the
manner in which it is to be performed :-
This invention relates to a discharge muffler for a hermetically sealed reciprocating compressor.
This invention particularly relates to the discharge mufflers for hermetically sealed compressors.
Hermetic Sealed compressors are used to compress low pressure vapor from evaporator & deliver high pressure & high temperature vapor to condenser.
In a typical hermetic compressor working suction gas enters in the shell cavity through suction tube. This gas is sucked in a suction muffler due to suction stroke of a piston. The gas flows to a cylinder bore via a suction plenum in a cylinder head through a passage in a crankcase or connecting tubes between suction muffler & cylinder head & suction port in a valve plate. This low pressure gas is compressed to high pressure & delivered to a discharge muffler via a discharge port in the valve plate to cylinder head plenum. In the discharge plenum gas is attenuated and delivered to condenser of appliance through a discharge tube connected to a discharge muffler by a discharge shock loop.
The hermetic compressor generally comprises a lower and upper shell, inside which three or more resilient members hold the pump assembly (coil springs). The whole assembly body is supported by legs, which are attached to a shell. The compressor pump assembly consists of motor component stator and rotor and gas compressor mechanism. The rotor is fitted directly on the crankshaft. The stator is mounted on the crankcase through fasteners. The crankshaft is housed in the main bearing provided in the crankcase. The
power required for rotation of the crankshaft is given by a motor. The hermetic compressor generally comprises a 2-pole Induction motor as the prime mover.
In the hermetically sealed refrigeration compressor, gas enters through the suction tube and travels into the shell, which surrounds the pump assembly.
The gas is further picked up by the suction pick up tube and led into the crankcase, which then goes into the suction plenum in the cylinder head through suction mufflers, which are in built in the crank case. Inside, the motor and pump assembly are cooled by refrigerant available inside the shell cavity. In this process the refrigerant picks-up heat from these (motor and pump assembly) hotter components before it reaches in to the crankcase by heat convection. It is well known from basics of thermodynamics that suction gas super heating will result in reduced compressor performance as density of gas reduces with increased temperature which means less mass flow rate in to the cylinder bore.
The suction and discharge of gas in a hermetic compressor is achieved by means of opening and closing of the pressure driven suction and discharge reed valves respectively. Each rotation of the crankshaft results in the motion of the piston from TDC to BDC (suction) and subsequently from BDC to TDC (discharge).
The discharge muffler in accordance with this invention is designed in the view that the discharge pulse is reduced by more than 70 % in a hermetic reciprocating compressor.
For this, in accordance with this invention the discharge muffler design is optimized for the attenuation characteristics (I.e. transmission loss through the muffler ) and the pressure drop due to pulsating gas flow through the muffler. The attenuation curves ( from 0 Hz to 4000 Hz ) and pressure drop values are presented herewith to illustrate the effect of varying the design parameters like, baffle hole diameter, insertion tube diameter, insertion tube length and the chamber length on the performance of the muffler. The parameters are varied such that they cover a wide range, however the overall dimensions ( or size ) of the muffler remain the same.
According to this invention there is provided a discharge muffler for a hermetically sealed reciprocating compressor, consisting of a hollow body having an inlet tube and an outlet tube, characterized in that the said body is internally divided by baffle plates having one or more baffle holes forming chambers having one or more perforations to lead the discharge gas through the chambers of the discharge muffler from the inlet tube to the outlet tube.
The invention will now be described with reference to the accompanying drawings, in which
Figure 1 is a schematic diagram of a discharge muffler in accordance with this invention. The discharge muffler for a hermetically sealed compressor includes multiple muffling chambers (in this case, three ) incorporating baffles in between the chambers and an insertion tube and outlet tube.
Fig 2 shows the effect of varying the baffle hole diameter from 7 mm to 12
(The curve 1 shows the attenuation characteristics for the claimed muffler)
It is seen that the attenuation is better for minimum diameter, but the
pressure drop is higher.
Fig 3 shows the curves with varying chamber length. The pressure loss values do not vary much, however from manufacturing point of view, the chamber lengths are kept same.
Fig 4 shows the effect of varying the insertion tube diameter. The attenuation is higher with minimum tube diameter, but this gives a higher pressure drop which affects the compressor performance adversely.
Fig 5 shows the effect of varying the insertion tube length. It can be observed that there is a frequency shift of the first higher peak. It is aimed that the peak should remain in the frequency of around 1250 Hz.
Figure 6 shows the experimental sound testing results which show the pulse spectrum with old muffler and the new optimized muffler in the time and frequency domain. The results clearly show the reduction in discharge pulsation by almost 71 %.
Figure 7 shows the graph of real pressure versus frequency for an inlet tube inlet diameter of 4.927 mm. The delta P = 38.731 kPa.
Figure 8 shows the graph of real pressure versus frequency for an inlet tube inlet diameter of 10.16 mm. The delta P = 11.158 kPa.
Figure 9 shows the graph of real pressure versus frequency for an inlet tube insertion length of 12.7 mm. The delta P = 14.503 kPa.
Figure 10 shows the graph of real pressure versus frequency for an inlet tube insertion length of 32.105 mm. The delta P = 15.358 kPa.
Figure 11 shows the graph of real pressure versus frequency for a baffle hole diameter of 7.137 mm. The delta P = 28.689 kPa.
Figure 12 shows the graph of real pressure versus frequency for a baffle hole diameter of 11.125 mm. The delta P = 13.31 kPa.
Figure 13 shows the graph of real pressure versus frequency for an optimized configuration in which inlet diameter is 8.102 mm, insertion length 22.86mm and baffle hole diameter of 10.0 mm. The delta P = 14.8 kPa. In this configuration the muffler gives the best attenuation of noise of the total compressor in the 1 to 2.5 kHz sound frequency range which is the most irritating to the human ear perception.
As can be seen in this graph there are varied and numerous pulsations in the 1 to 2.5 kHz range which cause much irritation to the human ear.
Thus the length of each muffling chamber as claimed above can be varied or kept same depending on the effect on pulsation reduction and from the view of manufacturability.
Also the cross-section of the muffling chambers could be elliptical, circular or any other arbitrary shape depending on the availability of the space in the hermetic shell.
In accordance with a preferred embodiment of this invention, the baffle could have one or multiple holes for the passage of the compressed gas across the muffling chambers, for optimizing the pressure loss through the muffler. As seen in Figure 1, the muffler generally indicated by the reference numeral 10 in accordance with this invention has a hollow body MC having a shell S internally divided by baffle plates BP into chambers. Fluid is led into the discharge muffler by inlet tube IT and is discharged after muffling through the outlet tube OT. Each of the baffle plates BP has a hole H at the center of diameter 10.076mm, however it may vary from 4.97mm to 20mm.
Thus in accordance with this invention there is provided a discharge muffler in which the baffle and the muffler chambers excluding bottom and top chambers are made integral as a separate part. In particular, the insertion length of the inlet tube is 22.86, however it may vary from 12 mm to 32 mm inch and the insertion tube inside diameter is 8 mm, however it may vary from 5 mm to 10. 5 mm.
While the present invention has been described herein with reference to a specific embodiment thereof, it is contemplated that the invention is not limited thereby and various changes and modifications may be made therein for those skilled in the art without departing from the scope of the invention.
1. A discharge muffler for a hermetically sealed reciprocating compressonconsisting of a hollow body having an inlet tube and an outlet tube, characterized in that the said body is internally divided by baffle plates having one or more baffle holes forming chambers having one or more perforations to lead the discharge gas through the chambers of the discharge muffler from the inlet tube to the outlet tube.
2. A discharge muffler as claimed in claim 1, in which the diameter of the inlet tube is 8.102 mm, the insertion length 22.86mm the muffler body is divided into three chambers by baffle plates having baffle holes and the baffle hole diameter is 10.0 mm.
3. A discharge muffler as described herein with reference to the accompanying drawings.
Dated this 15th day of January, 2002.
OfR. K. Dewan&Co., Applicants' Patent Attorney.
|Indian Patent Application Number||1048/MUM/2001|
|PG Journal Number||41/2007|
|Date of Filing||30-Oct-2001|
|Name of Patentee||KIRLOSKAR COPELAND LIMITED|
|Applicant Address||1202/1 GHOLE ROAD, PUNE,|
|PCT International Classification Number||N/A|
|PCT International Application Number||N/A|
|PCT International Filing date|