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.

scholarly journals Calculation for the Opening Delay of a Discharge Reed Valve in Compressors (Opening Mechanism Based on the Valve Deformation-Gas Flow-Oil Film Flow Behavior)

2013 ◽  
Vol 79 (806) ◽  
pp. 2003-2018 ◽  
Author(s):  
Fumitaka YOSHIZUMI ◽  
Yasuhiro KONDOH ◽  
Takahiro MOROI ◽  
Shinji TAMANO ◽  
Yohei MORINISHI
Keyword(s):  
Gas Flow ◽  
Film Flow ◽  
Flow Behavior ◽  
Oil Film ◽  
Reed Valve

scholarly journals Opening Delay of a Reed Valve for Refrigerant Gas Discharges in Compressors (Visualization of Oil Film Behaviors and Measurement of Valve Deformations in the Opening Process)

2012 ◽  
Vol 78 (795) ◽  
pp. 3787-3802 ◽  
Author(s):  
Fumitaka YOSHIZUMI ◽  
Yasuhiro KONDOH ◽  
Kazunori YOSHIDA ◽  
Takahiro MOROI ◽  
Shinji TAMANO ◽  
...  
Keyword(s):  
Gas Discharges ◽  
Oil Film ◽  
Reed Valve ◽  
Opening Process

Effect of Oil on the Dynamics of Compressor Suction Valve

1997 ◽  
Author(s):  
H. Ezzat Khalifa ◽  
Xin Liu
Keyword(s):  
Relative Effect ◽  
Viscous Force ◽  
Reciprocating Compressor ◽  
Cylinder Pressure ◽  
Oil Viscosity ◽  
Valve Seat ◽  
Rapid Release ◽  
Valve Stiction ◽  
Valve Opening ◽  
Reed Valve

Abstract The presence of oil on the suction valve of a reciprocating compressor has long been known to be responsible for the so-called valve stiction phenomenon. With stiction, the opening of the valve is delayed until later in the suction stroke, which results in a reduction in volumetric efficiency and increases the probability of valve failure. In this paper, a model is presented for analyzing the dynamic behavior of a round reed valve in the presence of oil. It is shown that the primary reason for stiction is the viscous force arising from dilating the oil film between the valve and its seat. This dilation takes place as the cylinder pressure on one side of the valve reed falls below the suction pressure in the intake plenum upstream of the valve. The viscous force delays the valve opening until later in the suction stroke. Because the film dilation resistance is directly proportional to the oil viscosity and decreases rapidly as the film thickens, the film eventually breaks and the valve begins to accelerate rapidly until it impacts the valve stop. The delayed rapid release of the valve and the associated impact are shown to subject the valve to much higher forces than would be experienced without the effect of stiction. The relative effect of oil viscosity and valve/seat contact area on valve force is presented for a representative reciprocating compressor equipped with suction valves.

BIOFLUID FLOW THROUGH A THROTTLE VALVE: A COMPUTATIONAL FLUID DYNAMICS STUDY OF CAVITATION

2016 ◽  
Vol 16 (03) ◽  
pp. 1650034 ◽  
Author(s):  
XIUMEI LIU ◽  
JIE HE ◽  
JIYUN ZHAO ◽  
ZHENG LONG ◽  
WENHUA LI ◽  
...  
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
High Viscosity ◽  
Initial Position ◽  
Operating Conditions ◽  
Valve Seat ◽  
Cavitation Phenomenon ◽  
Throttle Valve ◽  
Valve Opening ◽  
Flow Through

Biofluid flow through a throttle valve is investigated numerically and experimentally in our paper. Numerical studies are performed in order to obtain the mass flow rate through the valve under different operating conditions. Pressure drop behind the throttle valve and formation of the vortex flow downstream has been evaluated. The vortices were mainly distributed on top of the valve rod, the corner of the channel and the corner of the valve seat. When valve opening increases, the vortices grow and cause higher pressure drop. In other words, more energy is lost due to these growing vortices and high viscosity of biofluid. Furthermore, experimental flow visualization is conducted to capture cavitation images near the orifice using high-speed camera. The initial position of cavitation occurred near throttle orifice while cavitation zone downstream is caused by circulating bubbles clusters. As the opening of the valve is decreased, the area and strength of vortices in the corner of the channel grow and cause higher pressure drop firstly, then decrease. In addition, there are a lot of bubble clusters on top of the valve rod and the corner of the valve seat, which flowed downstream and collapsed, then filled the entire channel. In general, the valve opening plays very important role in the performance of a throttle valve. The results would help to observe, understand and manage the cavitation phenomenon in a throttle valve, and improve the performance of throttle valves.

Implementing variable valve actuation on a diesel engine at high-speed idle operation for improved aftertreatment warm-up

2019 ◽  
Vol 21 (7) ◽  
pp. 1134-1146
Author(s):  
Kalen R Vos ◽  
Gregory M Shaver ◽  
Mrunal C Joshi ◽  
James McCarthy
Keyword(s):  
Particulate Matter ◽  
High Speed ◽  
Exhaust Valve ◽  
Exhaust Gas ◽  
Warm Up ◽  
Aftertreatment System ◽  
Idle Speed ◽  
Variable Valve Actuation ◽  
Brake Mean Effective Pressure ◽  
Valve Opening

Aftertreatment thermal management is critical for regulating emissions in modern diesel engines. Elevated engine-out temperatures and mass flows are effective at increasing the temperature of an aftertreatment system to enable efficient emission reduction. In this effort, experiments and analysis demonstrated that increasing the idle speed, while maintaining the same idle load, enables improved aftertreatment “warm-up” performance with engine-out NOx and particulate matter levels no higher than a state-of-the-art thermal calibration at conventional idle operation (800 rpm and 1.3 bar brake mean effective pressure). Elevated idle speeds of 1000 and 1200 rpm, compared to conventional idle at 800 rpm, realized 31%–51% increase in exhaust flow and 25 °C–40 °C increase in engine-out temperature, respectively. This study also demonstrated additional engine-out temperature benefits at all three idle speeds considered (800, 1000, and 1200 rpm, without compromising the exhaust flow rates or emissions, by modulating the exhaust valve opening timing. Early exhaust valve opening realizes up to ~51% increase in exhaust flow and 50 °C increase in engine-out temperature relative to conventional idle operation by forcing the engine to work harder via an early blowdown of the exhaust gas. This early blowdown of exhaust gas also reduces the time available for particulate matter oxidization, effectively limiting the ability to elevate engine-out temperatures for the early exhaust valve opening strategy. Alternatively, late exhaust valve opening realizes up to ~51% increase in exhaust flow and 91 °C increase in engine-out temperature relative to conventional idle operation by forcing the engine to work harder to pump in-cylinder gases across a smaller exhaust valve opening. In short, this study demonstrates how increased idle speeds, and exhaust valve opening modulation, individually or combined, can be used to significantly increase the “warm-up” rate of an aftertreatment system.

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