Characterization of Oil Droplets in the Lower Cavity of a Rotary Compressor

2020 ◽  
Author(s):  
Puyuan Wu ◽  
Jun Chen ◽  
Paul E. Sojka ◽  
Yang Li ◽  
Hongjun Cao
Keyword(s):  
High Speed ◽  
Discharge Rate ◽  
Current Phase ◽  
Rotary Compressor ◽  
Oil Droplets ◽  
Air Conditioners ◽  
Lower Cavity ◽  
Lubricant Oil ◽  
Flow Velocimetry ◽  
Size And Morphology

Abstract The rotary compressor is widely used in small air conditioners, and is the most important element in the system. It relies on eccentric rolling pistons that rotate at high speed to compress refrigerant in the cylinder. The lubricant oil in the rotary compressor is used for lubricating the bearing and sealing the clearance of sliding parts. However, the oil can experience complex and highly-coupled atomization processes when discharged from the cylinder, and part of oil droplets can exhaust from the rotary compressor by the refrigerant flow and reduce the efficiency and reliability of the compressor as a result. Thus, characterizing the behavior of oil droplets in the lower cavity of a rotary compressor where the atomization occurs is a major challenge for manufacturers who rely on CFD tools to predict the multiphase flow. By modifying a rotary compressor, the oil behavior in the lower cavity of a rotary compressor is observed and recorded by shadowgraphy. In the current phase, the number, size, and morphology of oil droplets are analyzed statistically with image processing method, which provides better understanding to the atomization mode in the lower cavity, the velocity of the mist of oil droplets is calculated with Optical Flow Velocimetry. The results can assist designers in improving the CFD analysis of compressors and ultimately reducing the Oil Discharge Rate (ODR).

Visualization of Oil Droplets Distribution in a Rotary Compressor

2019 ◽  
Author(s):  
Puyuan Wu ◽  
Jun Chen ◽  
Paul E. Sojka
Keyword(s):  
Multiphase Flow ◽  
High Speed ◽  
Imaging System ◽  
Discharge Rate ◽  
Current Phase ◽  
Rotary Compressor ◽  
Cfd Analysis ◽  
High Speed Imaging ◽  
Oil Droplets ◽  
Rolling Piston

Abstract A rotary compressor relies on an eccentric rolling piston, which rotates at high speed, to compress gas in the compression chamber. The oil in the rotary compressor is used for lubricating the bearing and sealing the clearance of sliding parts. However, the oil can exhaust from the rotary compressor by the refrigerant flow and reduce the reliability of the compressor as a result. Thus, studying the behavior of oil droplets distribution in a rotary compressor is a major challenge for manufacturers who rely on CFD tools to predict the multiphase flow. By modifying a rotary compressor, the oil behavior inside the cylinder is observed and recorded by a high-speed imaging system. In the current phase, multiple targeted locations, including the space between the bearing housing and the stator, and the space above the stator are measured in different conditions. The number, size, velocity, and morphology of oil droplets are analyzed based on multiple snapshots. The result can assist designers in improving the CFD analysis of compressors and ultimately reducing the oil discharge rate (ODR).

Experimental Measurement of Oil Droplets Size and Velocity Above the Rotor/Stator in a Rotary Compressor

2021 ◽  
Author(s):  
Puyuan Wu ◽  
Jun Chen ◽  
Paul E. Sojka ◽  
Yang Li ◽  
Hongjun Cao
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Outer Region ◽  
Droplet Size Distribution ◽  
Rotary Compressor ◽  
Discharge Process ◽  
Oil Droplets ◽  
Lower Cavity ◽  
Lubricant Oil ◽  
Rolling Piston

Abstract Hundreds of millions of Air conditioning (AC) systems are produced each year. Many of them, especially small AC appliances, use rotary compressors as the system’s heat pump due to their simple structure and high efficiency in a small system. Lubricant oil is used in the rotary compressor to lubricate the moving parts, such as the crankshaft and the rolling piston, and to seal the clearance between the sliding parts, e.g., the clearance between the rolling piston and the cylinder, and the vane and the cylinder. As the compressed refrigerant vapor is discharged from the cylinder through the discharge port, part of lubricant oil in the cylinder would be carried by the vapor and atomize into small droplets in the lower cavity during the discharge process, which is complicated and highly-coupled. Some of these oil droplets would ultimately be exhausted from the compressor and enter other parts in the system, reducing the compressor reliability and deteriorating the heat transfer of the condenser and the evaporator in the system. Our previous research studied the atomization of the lubricant oil during the discharge process in the compressor’s lower cavity. However, the oil droplets’ behavior downstream of the lower cavity is unknown. Thus, studying the oil droplets’ behavior after passing through the rotor/stator can help understand how the rotor/stator would affect the droplet size distribution and movement, thus controlling the flow rate of escaped oil droplets. In this study, a hot gas bypass test rig is built to run a modified rotary compressor with sapphire windows right above the rotor/stator. The oil droplets’ size distribution and movement along the radial direction are obtained at the shaft’s rotating frequency of 30 and 60 Hz by shadowgraph. It is found that droplet size at 30 and 60 Hz varies little in the inner region of the rotor/stator clearance and would increase sharply above the clearance and keep increasing in the outer region of the clearance. More importantly, droplet velocity has a downward velocity component at the inner region and an upward velocity component at the outer region of the rotor/stator clearance. With the result of droplet size distribution and droplet velocity above the rotor/stator, we propose the model of the oil droplet’s path above the rotor/stator, which can be understood as the coupling of a swirling jet and a rotating disk.

Flow Characterization in the Upper Cavity of a Rotary Compressor

2021 ◽  
Author(s):  
Puyuan Wu ◽  
Ang Li ◽  
Jun Chen ◽  
Paul E. Sojka ◽  
Yang Li ◽  
...  
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Ambient Pressure ◽  
Internal Flow ◽  
Rotating Disk ◽  
Rotary Compressor ◽  
Oil Droplets ◽  
Lubricant Oil ◽  
Swirling Jet

Abstract As hundreds of millions of Air conditioning (AC) systems are produced each year, and many of them use rotary compressors as the heat pump, optimizing the flow inside the rotary compressor to improve its reliability and efficiency becomes a key issue of the manufactures. Since the invention of the rotary compressor, its internal flow has been studied numerically with real models. However, a rotary compressor’s internal flow can be extremely complicated due to the complex internal structures’ geometry and high-speed moving parts, making it difficult to interpret the result by CFD simulation and repeat the simulation in different models. In our experiments for observing lubricant oil droplets above the rotor/stator in a rotary compressor, droplets’ movement reveals that two major effects control the gas flow in the compressor’s upper cavity. One is the swirling jet produced by the high-speed rotating rotor with no-slip condition on its sidewall. The other one is the rotating disk effect induced by the top of the high-speed rotating rotor. Either of them has been studied individually in different areas. For example, the swirling jet is often used in combustors while the rotating disk is applied in the viscous pump. However, the coupling of these two effects in the rotary compressor with different velocity ranges, size scales, and fluid properties has not been studied according to our best knowledge. In our simulation, a model that only consists of a simplified rotor, simplified stator, sidewall, and discharge tube (outlet) is built. Thus, the effect by small parts, such as the balance block and coils, is excluded. The rotor is set to rotate at 30, 60, and 90 Hz. Uniform velocity calculated with the theoretical flow rate and ambient pressure conditions are given at the inlet (rotor/stator clearance) and outlet, respectively. No-slip conditions are defined at other walls. Steady-state K-ω SST turbulence models are applied, and the cases are computed with OpenFoam. The CFD results show an inner recirculation zone above the rotor that creates a downward velocity component above the rotor and an outer circulation zone above the stator. The CFD result meets the observation of the droplets’ movement above the rotor/stator. With the CFD results and the experiment’s observations, we propose the model of the oil droplet’s path in the rotary compressor’s upper cavity, which can help reduce the exhausted lubricant oil droplets from the compressor.

Characterization of Oil Droplets in the Lower Cavity of a Rotary Compressor

2021 ◽  
Author(s):  
Puyuan Wu ◽  
Jun Chen ◽  
Paul Sojka ◽  
Yang Li ◽  
Hongjun Cao
Keyword(s):  
Rotary Compressor ◽  
Oil Droplets ◽  
Lower Cavity

Commercializing an Automatically Deployable Rollover Protective Structure (AutoROPS) for a Zero-Turn Riding Mower: Initial Product Safety Assessment Criteria

2004 ◽  
Author(s):  
J. R. Etherton ◽  
E. A. McKenzie ◽  
J. R. Powers
Keyword(s):  
Electromagnetic Interference ◽  
High Speed ◽  
Safety Assessment ◽  
Human Error ◽  
Product Safety ◽  
Current Phase ◽  
Protective Structure ◽  
Private Industry ◽  
Cooperative Effort ◽  
Safety Research

Fatal injuries have occurred to operators of zero-turn riding mowers when these machines rolled over during high speed sharp turns or on uneven terrain. These mowers are frequently operated in low clearance conditions such as around trees and when loaded onto low-roofed trailers. The automatically deployable rollover protective structure (AutoROPS) can provide both protection during rollover events and the capability to operate a mower in low clearance conditions. Until recently, AutoROPS technology development has occurred only in a government laboratory. In the current phase of development, private industry has taken an interest in the AutoROPS technology and is pursuing, with NIOSH, the product testing and development needed to commercialize the AutoROPS on a zero-turn riding mower. The government’s role, as a partner with private industry in bringing new safety technology into practical application, is discussed. Importantly, for the AutoROPS product to be as effective as possible, it should not introduce additional, unacceptable risks. Previous product safety assessments led by government laboratories are reviewed. These assessments were made to minimize hazards in products developed in government labs. A product safety assessment was performed on the AutoROPS during its design phase. In addition to minimizing the severity and frequency of operator injury resulting from an accidental rollover, the assessment considered 1) environmental factors such as corrosion, electromagnetic interference, and vibration; 2) human error avoidance; and 3) safeguard reliability analysis. This assessment was a cooperative effort between the safety engineering design team at the Division of Safety Research of the National Institute for Occupational Safety and Health; a ROPS manufacturer; and a zero-turn riding mower manufacturer. Design features are being incorporated into the prototype AutoROPS to address hazards encountered in normal use of these machines.

scholarly journals A partial compensation scheme for MMC-based railway cophase power supply

2020 ◽  
Vol 2 (4) ◽  
pp. 305-317
Author(s):  
Peiliang Sun ◽  
Kang Li ◽  
Chen Xing
Keyword(s):  
Power Factor ◽  
Power Supply ◽  
High Speed ◽  
Current Phase ◽  
Compensation Scheme ◽  
Railway Systems ◽  
Grid Side ◽  
Phase Angles ◽  
Traction Load ◽  
Partial Compensation

Abstract This paper presents a partial compensation scheme for V/v transformer cophase traction power supply in high-speed railway systems. The scheme compensates variable traction load current, and controls the current phase at the secondary side of the V/v transformer for power factor correction and negative sequence current reduction. To achieve this, the grid side current phase angles are optimized while satisfying the grid code on the power factor and voltage unbalance limits. The optimized phase angles are then used to design control references under varying load conditions. The compensation control action is updated regularly based on real-time measurements of the traction load, and the required currents are controlled by a 25-level single-phase back-to-back MMC power conditioner to achieve the compensation target. Static and dynamic load compensation performances are verified based on the simulation studies.

818 Visualization Study on Lubricant Oil Film Behavior around Piston Skirt with High Speed Camera

2008 ◽  
Vol 2008.46 (0) ◽  
pp. 313-314
Author(s):  
Yohei NAKAMURA ◽  
Keita TAMAOKI ◽  
Katsuyuki OHSAWA ◽  
Yoshitaka OCHIAI
Keyword(s):  
High Speed ◽  
High Speed Camera ◽  
Oil Film ◽  
Piston Skirt ◽  
Lubricant Oil

An Experimental Study on Opening Delay of a Reed Valve for Reciprocating Compressors

2011 ◽  
Author(s):  
Fumitaka Yoshizumi ◽  
Yasuhiro Kondoh ◽  
Kazunori Yoshida ◽  
Takahiro Moroi ◽  
Masakazu Obayashi ◽  
...  
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Valve Seat ◽  
Film Rupture ◽  
Air Conditioners ◽  
Oil Film ◽  
Gas Compression ◽  
Valve Opening ◽  
Reed Valve ◽  
Opening Process

Automatic reed valves are widely used to control refrigerant gas flow in reciprocating compressors for automotive air conditioners. The oil film in the clearance between the reed and the valve seat causes a delay in opening of the valve. This opening delay of the discharge valve leads to over compression, which increases losses such as friction in sliding components and gas overheating. Therefore it is important to understand the behavior both of the oil film and the elastic reed deformation in order to reduce losses due to the delay. This study aims to develop an experimental setup that enables simultaneous visualization of the oil film rupture and measurement of the reed deformation, and to observe this behavior during the valve opening process. The gas-compression stroke is simulated by controlling compressed air with an electromagnetic valve. The oil film rupture is visually observed using a high speed camera through a special valve seat made of glass. The total deformation of the cantilever reed is identified by multipoint strain measurement with 12 strain gauges. The experiment finds that the opening process is divided into four stages. In the first stage, the reed remains stuck to the seat and deforms while the bore pressure increases. In the second stage, cavitation occurs in the oil film and the film starts to rupture. In the third stage, the oil film ruptures and the bore pressure starts to decrease. Finally, in the fourth stage, the reed is separated from the seat and the gas flows through the valve. Reducing the reed/seat contact area changes the reed deformation in the first stage, thereby increasing the reed/seat distance and realizing an earlier oil film rupture and a shorter delay.

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