Hydrodynamic-Pressure-Induced Elastic Deformation of Thrust Slide-Bearings in Scroll Compressors and Oil Film Pressure Increase Due to Oil Envelopment

This paper presents the concept of the Elasto-Hydrodynamic Lubrication?EHL?of thrust slide-bearings in scroll compressors, resulting in the superior lubrication characteristics of these bearings. The thrust plate undergoes elastic deformation due to axial loading, resulting in the formation of a uniform fluid wedge between the orbiting and fixed thrust plates. This wedge region has very high induced oil film pressure, which explains the remarkably good lubrication characteristics of the thrust slide-bearing. Furthermore, the high oil film pressure induces further local elastic deformation of the thrust plate, forming an EHL oil pocket with the thrust plate and a further increase in the oil film pressure between the sliding surfaces due to this oil envelopment. The formation of the EHL pocket was confirmed using FEM analysis and lubrication tests on the elastic deformation of the thrust plate. Subsequently, the additional increase in oil film pressure, due to the EHL pocket effect, was examined in computer simulations applying the average Reynolds equation for the boundary of elastic deformation of the thrust plate. In these studies, a 6.7% increase in oil film pressure was ascertained for a small cooling capacity scroll compressor driven at 3600 rpm with 0.1 kW motor. The oil envelopment contributes to the superior lubrication performance of the thrust slide bearings scroll compressors

Optimization of EHL Lubrication Performance in Thrust Slide-Bearings of Scroll Compressors

Previous studies [Refs. 1, 2] revealed the formation of a uniform oil wedge at the periphery of the thrust plate, caused by the elastic deformation of the orbiting thrust plate due to the pressure difference across the orbiting thrust plate, is a significant factor in the high lubrication performance in thrust slide-bearings. In addition to the uniform wedge formation, the high oil film pressure also induces a local elastic deformation of the fixed thrust plate normal to its surface. The normal thrust plate deformation and the oil wedge effectively form an elasto-hydrodynamic-lubrication (EHL) pocket, even more effectively increasing the oil film pressure between the sliding surfaces, due to the envelopment of the oil, as confirmed in our companion paper [3], and an earlier, less-detailed contribution [4]. The present study focuses on aspects of EHL that have both positive and negative effects on the lubrication performance of the thrust slide-bearings in scroll compressors. Theoretical calculations using the average Reynolds equation and Patier-Chen solid contact theory, for the boundary of the local elastic deformation of the thrust slide-bearing, were conducted for a small cooling capacity scroll compressor driven at 3600 rpm with 0.1 kW. An approximate method was developed using characteristic curves to determine the oil film axial force, the average oil film thickness, the frictional force and the frictional coefficient. The calculations considered a variety of pressure differences due to the operation pressure and the thickness of thrust plate. Also cases with a fixed uniform wedge angle at the periphery were calculated. The calculated results suggest a possible maximum reduction in frictional coefficient of about 55% compared to that with a fixed uniform wedge angle. The reduction rate increases with decreasing thrust plate thickness, which, however, restricts the operation pressures to a lower pressure range. Design guidelines for optimizing EHL will be suggested. References: [1] Oku, T., Ishii, N., Anami, K., Knisely, C.W., Sawai, K., Morimoto, T., Hiwata, A. : Theoretical Model of Lubrication Mechanism in the Thrust Slide-Bearing of Scroll Compressors, HVAC&R Research Journal ASHRAE Vol.14, No.2, pp.239-358, 2008-3. [2] Ishii, N., Oku, T., Anami, K., Knisely, C.W., Sawai, K., Morimoto, T., Iida, N. : Experimental Study of the Lubrication Mechanism for Thrust Slide Bearings in Scroll Compressors, HVAC&R Research Journal ASHRAE Vol.14, No.2, 2008-4. [3] Ishii, N., Tsuji, T., Anami, K., Nokiyama, K., Morimoto, T., Sakuda, A., Oku, T., Sawai, K., Knisely, C.W., : “Hydrodynamic-Pressure-Induced Elastic Deformation of Thrust Slide-Bearings in Scroll Compressors and Oil Film Pressure Increase Due to Oil Envelopment,” abstract submitted to 2014 Purdue Herrick Conferences. [4] Ishii, N., Tsuji, T., Oku, T., Anami, K., Knisely, C.W., Nokiyama, K., Morimoto, T., Sakuda, A., Sawai, K. 2012 “Elasto-Hydrodynamic Lubrication Effect in Thrust-Slide Bearings of Scroll Compressors,” 2012 Purdue Conference Paper on (Paper 1438)

Elasto-Hydrodynamic Lubrication Effect in Thrust-Slide Bearings of Scroll Compressors

This paper presents the concept of the Elasto-Hydrodynamic Lubrication (EHL) effect for the thrust slide-bearings in scroll compressors, which accounts for the superior lubrication characteristics of these bearings. The thrust plate undergoes elastic deformation due to axial loading, resulting in the formation of a fluid wedge between the orbiting and fixed thrust plates, a region with very high induced oil film pressure which, in turn, accounts for the remarkably good lubrication characteristics of the thrust slide-bearing. Furthermore, the high oil film pressure induces further elastic deformation of the thrust plate, which forms a lubrication pocket with the thrust plate, more effectively increasing the oil film pressure between the sliding surfaces. The formation of the lubrication pocket was confirmed using FEM analysis and lubrication tests on the elastic deformation of the thrust plate. Subsequently a computer simulation flow chart to analyze the elasto-hydrodynamic lubrication of thrust slide-bearing is presented

An Experimental Study of Lubrication in Thrust Slide-Bearings of Scroll Compressors - Effect of Thickness and Inside Form of Thrust Plate -

The present study focuses on the effect of the thickness and inner form of the thrust plate in a scroll compressor upon the lubrication features. A simplified model of a annular thrust slide-bearing with thinner thrust plate submerged in a refrigerant oil VG-56 was operated under pressure using R-22 as the pressurizing gas, where the pressure difference was adjusted from 0 to 1.0 MPa. The friction force and coefficient of friction were measured over a wide range of orbiting speeds. The wedge angle due to elastic deformation is naturally increased with decreasing thrust plate thickness, resulting in a clear improvement in lubrication characteristics of the thrust slide-bearing. Subsequently, similar lubrication tests were conducted for the thrust plate model with a realistic inner form, one as complicated as that in actual scroll compressors, while maintaining the thickness of the thrust plate as in the previous test. No significant change in lubrication features relative to those from the simplified annular model were identified, confirming the validity of using simplified annular model tests to assess the basic lubrication characteristics of the thrust slide-bearing in scroll compressors

Calculated Optimal Mechanical Efficiency of a Large Capacity Reciprocating Compressor

In this study, calculations of the mechanical efficiency of a large reciprocating compressor, developed by Mayekawa MFG. Co., Ltd., with a per cylinder suction volume of 1300 cm3 were carried out. These calculations were used to confirm whether the empirical combination of major design parameters in the Mayekawa compressor delivers optimal mechanical efficiency. Initially, the theoretical equation of motion of the rotating crankshaft is developed. Subsequently, computer calculations are carried out to determine the mechanical efficiency for various combinations of the major design parameters for operating speeds of 800, 1000 and 1200 rpm. From these calculations, the optimal combination parameters yielding the maximum mechanical efficiency could be determined, and then compared with the empirical combination used in the Mayekawa compressor

Metabolomic approach to the exploration of biomarkers associated with disease activity in rheumatoid arthritis

We aimed to investigate metabolites associated with the 28-joint disease activity score based on erythrocyte sedimentation rate (DAS28-ESR) in patients with rheumatoid arthritis (RA) using capillary electrophoresis quadrupole time-of-flight mass spectrometry. Plasma and urine samples were collected from 32 patients with active RA (DAS28-ESR≥3.2) and 17 with inactive RA (DAS28-ESR<3.2). We found 15 metabolites in plasma and 20 metabolites in urine which showed a significant but weak positive or negative correlation with DAS28-ESR. When metabolites between active and inactive patients were compared, 9 metabolites in plasma and 15 in urine were found to be significantly different. Consequently, we selected 11 metabolites in plasma and urine as biomarker candidates which significantly correlated positively or negatively with DAS28-ESR, and significantly differed between active and inactive patients. When a multiple logistic regression model was built to discriminate active and inactive cohorts, three variables—histidine and guanidoacetic acid from plasma and hypotaurine from urine—generated a high area under the receiver operating characteristic (ROC) curve value (AUC = 0.8934). Thus, this metabolomics approach appeared to be useful for investigating biomarkers of RA. Combination of plasma and urine analysis may lead to more precise and reliable understanding of the disease condition. We also considered the pathophysiological significance of the found biomarker candidates

女性における全人工股関節置換術後の静的立位中の足底振動刺激の即時効果

Purpose: Proprioceptive function of the lower limbs deteriorates in patients following total hip arthroplasty. Patients show poor balance and rely more on visual information than proprioceptive information. Plantar vibration stimuli can mechanically enhance somatosensory input from the plantar cutaneous mechanoreceptors, thereby improving static balance. Plantar vibration stimuli may improve static balance in patients after total hip arthroplasty. This is the first study to investigate whether plantar vibration stimuli affects static balance during the early phase following total hip arthroplasty. Materials and methods: In this cross-over design study, 16 female patients (aged 65.1 ± 11.0 years) received plantar vibration stimuli for 2 minutes or the sham interventions after total hip arthroplasty in a randomized order on different days. The foot centre of pressure was measured for the total path length, mediolateral path length, and anteroposterior path length directions before and immediately after the interventions in the static standing position both with eyes open and closed. Patients were instructed to minimize body sway when standing. Results: A significant increase was observed in the centre of pressure parameters in the eyes closed condition than in the eyes open condition. The centre of pressure parameters for the eyes closed condition was significantly decreased after vibration interventions than that before intervention. Conclusions: This study supports the view that plantar vibration stimuli can change static balance in patients in the early phase after total hip arthroplasty temporarily by up-weighting sensory information. These stimuli may serve as a treatment option for influencing balance following total hip arthroplasty.博士（医学）・甲第760号・令和2年12月24日This is a post-peer-review, pre-copyedit version of an article published in Somatosensory and motor research. The final authenticated version is available online at: http://dx.doi.org/10.1080/08990220.2020.1784129

Coupled fluid-solid modelling of the valve dynamics in reciprocating compressors

A novel method coupling computational fluid dynamics (CFD) and finite element method (FEM) was developed to account for the complex physics of the reciprocating compressor. The developed method is based on data exchange between the two solvers at each time step. We address the challenges related to valve dynamics, where the motion of solid components is not prescribed as for pistons, but result from the combined interactions between pressure, velocity, spring forces and impact forces during each revolution. The coupling method enables accurate computation of the solid-fluid interaction, where at each time step the pressure acting on the valve computed by CFD is transferred to the FEM simulation, and the three-dimensional valve motion computed by FEM is transferred to the CFD simulation. It is demonstrated on the dynamics of a ring plate discharge valve in a reciprocating ammonia compressor to quantify the effect of impact damping which arises from the gas dynamics, leading to reduced forces on the valve. The results from the coupling simulations are compared against novel experimental measurements obtained by instrumenting a real compressor. The coupled CFD-FEM simulation gives detailed insights into the valve behaviour and was used also to investigate pressure inhomogeneities, which can lead to tumbling motion of the valve ring.Coupled fluid-solid modelling of the valve dynamics in reciprocating compressorsacceptedVersio

Coupled fluid-solid modelling of the valve dynamics in reciprocating compressors

A novel method coupling computational fluid dynamics (CFD) and finite element method (FEM) was developed to account for the complex physics of the reciprocating compressor. The developed method is based on data exchange between the two solvers at each time step. We address the challenges related to valve dynamics, where the motion of solid components is not prescribed as for pistons, but result from the combined interactions between pressure, velocity, spring forces and impact forces during each revolution. The coupling method enables accurate computation of the solid-fluid interaction, where at each time step the pressure acting on the valve computed by CFD is transferred to the FEM simulation, and the three-dimensional valve motion computed by FEM is transferred to the CFD simulation. It is demonstrated on the dynamics of a ring plate discharge valve in a reciprocating ammonia compressor to quantify the effect of impact damping which arises from the gas dynamics, leading to reduced forces on the valve. The results from the coupling simulations are compared against novel experimental measurements obtained by instrumenting a real compressor. The coupled CFD-FEM simulation gives detailed insights into the valve behaviour and was used also to investigate pressure inhomogeneities, which can lead to tumbling motion of the valve ring