Design And Validation Of An Adjustable Dynamic Vibration Absorber For Piping Vibration Suppression In Skid Mounted Compressor Unit

The vibration control for a reciprocating compressor as well as piping has always been a challenge. Because of compact installation and limited space for the skid mounted compressor unit, it is difficult to arrange a piping support freely or change the piping layout. A new type of adjustable dynamic vibration absorber (DVA), consisting of an annular clamp and several discrete spring-mass systems (DVA subsystem), was proposed to solve this problem. The spring-mass system of this new DVA used the electromagnet and leaf spring equipped with linear slideway, which permitted continuous adjustment of the DVA’s natural frequency by means of variation of the mass and change of the electromagnet’s position. The finite element models of the piping with DVA was established to analyze the harmonic responses in the case of pre- and post- installation of DVA so as to validate the DVA performance of vibration suppression. The results showed that this DVA could suppress vibration effectively at original resonance frequency. Compared with the traditional DVA, multiple distributed units of DVA subsystems in an annular clamp could obtain a much wider frequency band, which overcame the defect that two resonance peaks appeared after installing the traditional DVA. The results also showed that this DVA, equipped with multiple sets of DVA subsystems with different natural frequencies, had an effective vibration suppression for the piping vibration simultaneously excited by multiple resonant frequencies. The study indicates that this novel adjustable DVA can effectively damp the piping vibration of the skid mounted compressor unit

Experimental Investigation Of A Horizontal Hermetic Scroll Compressor With Novel Oil Circuit Design

Owing to its reliable operation and low maintenance requirement, the scroll compressor has a potential application for oil and gas industry, e.g. the natural gas production for gas wells with low production and boil-off-gas recovery for gasoline filling stations. Though millions of scroll compressors are put into the refrigeration and air conditioning market each year, a much smaller number of such equipments have been used in the field of oil and gas production. This should be attributed to much larger quantity of compression heat for the natural gas compressor due to higher pressure ratio and larger isentropic exponent, which can not be taken way from oil circulation with traditional oil circuit design typical of refrigeration application. This paper presents an experimental investigation of a horizontal hermetic scorll compressor with novel oil circuit design. The oil was not injected but carried into the compression chamber by the suction gas to remove the compression heat. The oil circuit was so designed that the high pressure oil from the oil-gas separator was cooled, throttled into low pressure, and then stored in the horizontal motor casing, where the oil together with the suction gas entered the compression chamber. Owing to self-balancing, the oil level in the casing was kept constant whatever the operating conditions could be. Based on the novel oil circuit design, a vertical scroll compressor for commercial refrigeration was modified into a horizontal prototype compressor for natural gas compression. The prototype compressor was validated under a wide range of operating conditions in the closed loop test system. Its thermodynamic performances including flow rate and power consumption were tested under various working conditions. The results showed that the compressor could work reliably as the suction pressure ranged from 0 MPa(Gauge) to 0.25 MPa, and with one stage compression the maximal discharge pressure reached 3 MPa as the suction pressure was kept at 0 MPa

Two nonmonotone multiobjective memory gradient algorithms

In this paper, two types of nonmonotone memory gradient algorithm for solving unconstrained multiobjective optimization problems are introduced. Under some suitable conditions, we show the convergence of the full sequence generated by the proposed algorithms to a weak Pareto optimal poin

Application of Poly (vinylbutyral) Nanocomposites in Environment Design

This text passed an adoption to totally mix a method to lead to make even PVB/SiO2 compound material into the nano SiO2 grain son in gather the PVB material.. With the UV-VIS, FT-IR, XRD, SEM etc. modern tested means token tiny view facial look, structure and optics function of material. Result enunciation:because the lead of the nano SiO2 grain son go into and make the compound material of the PVB/SiO2 have good ultraviolet rays to shield function; Meanwhile, the tenacity of material gets an obvious exaltation, it splits an elongation rate is 8 times than the for pure PVB material. Key words: nanocomposite; mixing process; nanometer silica; environment desig

Statistical delay distribution analysis on high-speed railway trains

Published by SpringerOpen, Heidelber

The ultra-low-frequency shear modes of 2-4 layer graphenes observed in their scroll structures at edges

The in-plane shear modes between neighbor-layers of 2-4 layer graphenes (LGs) and the corresponding graphene scrolls rolled up by 2-4LGs were investigated by Raman scattering. In contrast to that just one shear mode was observed in 3-4LGs, all the shear modes of 3-4LGs were observed in 3-4 layer scrolls (LSs), whose frequencies agree well with the theoretical predication by both a force-constant model and a linear chain model. In comparison to the broad width (about 12cm$^{-1}$) for the G band in graphite, all the shear modes exhibit an intrinsic line width of about 1.0 cm$^{-1}$. The local electronic structures dependent on the local staking configurations enhance the intensity of the shear modes in corresponding 2-4LSs zones, which makes it possible to observe all the shear modes. It provides a direct evidence that how the band structures of FLGs can be sensitive to local staking configurations. This result can be extended to n layer graphene (n > 4) for the understanding of the basic phonon properties of multi-layer graphenes. This observation of all-scale shear modes can be foreseen in other 2D materials with similar scroll structures.Comment: 14 pages, 5 figure

Key criterion for achieving giant recovery strains in polycrystalline Fe-Mn-Si based shape memory alloys

In this study, it is proposed that coarsening austenitic grains is a key criterion for achieving giant recovery strains in polycrystalline Fe-Mn-Si based shape memory alloys. In order to verify the hypothesis, the relationship between recovery strains and austenitic grain-sizes in cast and processed Fe-Mn-Si based shape memory alloys was investigated. The recovery strain of cast Fe-19Mn-5.5Si-9Cr-4.5Ni alloy with the coarse austenitic grains of 652 µm reached 7.7% while the recovery strain of one with the relatively small austenitic grains of 382 µm was only 5.4%. Moreover, a recovery strain of 5.9%, which is the highest previously published value for solution-treated processed Fe-Mn-Si based shape memory alloys, was obtained by coarsening the austenitic grains through only solution treatment at 1483 K for 360 min in a processed Fe-17Mn-5.5Si-9Cr-5.5Ni-0.12C alloy. However, its recovery strain was still 5.9% after thermo-mechanical treatment consisting of 10% tensile strain at room temperature and annealing at 1073 K for 30 min. This happens because annealing twins play a negative role, refining the austenitic grains, limiting the recovery strains to below 6%. In summary, coarse austenitic grains enable the achievement large recovery strains by two mechanisms. Firstly, the grains are bigger, and consequently there are fewer grain boundaries, and thus their suppressive effects of grain boundaries on stress-induced ε martensitic transformation is reduced. Secondly, coarse austenitic grains are advantageous to introduce ε martensite with single orientation and reduce the collisions of different martensite colonies, especially when the deformation strain is large. As such, the ceiling of recovery strains is dependent on the austenitic grain-sizes

The causal relationship between air pollution, obesity, and COVID-19 risk: a large-scale genetic correlation study

ObjectiveObservational evidence reported that air pollution is a significant risk element for numerous health problems, such as obesity and coronavirus disease 2019 (COVID-19), but their causal relationship is currently unknown. Our objective was to probe the causal relationship between air pollution, obesity, and COVID-19 and to explore whether obesity mediates this association.MethodsWe obtained instrumental variables strongly correlated to air pollutants [PM2.5, nitrogen dioxide (NO2) and nitrogen oxides (NOx)], 9 obesity-related traits (abdominal subcutaneous adipose tissue volume, waist-to-hip ratio, body mass index, hip circumference, waist circumference, obesity class 1-3, visceral adipose tissue volume), and COVID-19 phenotypes (susceptibility, hospitalization, severity) from public genome-wide association studies. We used clinical and genetic data from different public biological databases and performed analysis by two-sample and two-step Mendelian randomization.ResultsPM2.5 genetically correlated with 5 obesity-related traits, which obesity class 1 was most affected (beta = 0.38, 95% CI = 0.11 - 0.65, p = 6.31E-3). NO2 genetically correlated with 3 obesity-related traits, which obesity class 1 was also most affected (beta = 0.33, 95% CI = 0.055 - 0.61, p = 1.90E-2). NOx genetically correlated with 7 obesity-related traits, which obesity class 3 was most affected (beta = 1.16, 95% CI = 0.42-1.90, p = 2.10E-3). Almost all the obesity-related traits genetically increased the risks for COVID-19 phenotypes. Among them, body mass index, waist circumference, hip circumference, waist-to-hip ratio, and obesity class 1 and 2 mediated the effects of air pollutants on COVID-19 risks (p < 0.05). However, no direct causal relationship was observed between air pollution and COVID-19.ConclusionOur study suggested that exposure to heavy air pollutants causally increased risks for obesity. Besides, obesity causally increased the risks for COVID-19 phenotypes. Attention needs to be paid to weight status for the population who suffer from heavy air pollution, as they are more likely to be susceptible and vulnerable to COVID-19

The Intoxication Effects of Methanol and Formic Acid on Rat Retina Function

Objective. To explore the potential effects of methanol and its metabolite, formic acid, on rat retina function. Methods. Sprague-Dawley rats were divided into 3- and 7-day groups and a control. Experimental groups were given methanol and the control group were provided saline by gavage. Retinal function of each group was assessed by electroretinogram. Concentrations of methanol and formic acid were detected by GC/HS and HPLC, respectively. Results. The a and b amplitudes of methanol treated groups decreased and latent periods delayed in scotopic and photopic ERG recordings. The summed amplitudes of oscillatory potentials (OPs) of groups B and C decreased and the elapsed time delayed. The amplitudes of OS1, OS3, OS4, and OS5 of group B and OS3, OS4, and OS5 of group C decreased compared with the control group. The IPI1 of group B and IPI1-4 of group C were broader compared with the control group and the IPI1-4 and ET of group B were broader than group C. Conclusions. Both of scotopic and photopic retinal functions were impaired by methanol poisoning, and impairment was more serious in the 7-day than in the 3-day group. OPs, especially later OPs and IPI2, were more sensitive to methanol intoxication than other eletroretinogram subcomponents