Experimental Study on Noise Characteristic of Centrifugal Compressor Surge

The centrifugal air compressor test rig is was designed and established. The experimental study was carried out on the surge characteristics of centrifugal compressor including the pressure in the pipe and the noise characteristics under different rotation speed. The tested results showed that both the suction pressure and discharge pressure fluctuation increase under surge condition and the amplitude of discharge pressure fluctuation is significantly higher than that of suction pressure. In addition, the sound pressure level near the inlet pipe fluctuates under surge condition. The amplitude of sound pressure level fluctuation is increased with the rising of rotation speed. It is relative to the variation of discharge pressure of centrifugal compressor. The total sound pressure level under surge conditions is larger than that of steady working conditions. The change of sound pressure level reflects the changing of filed flow in centrifugal compressor. The signals of sound could be treated as a method to predict the occurring of surge. The experimental results will lay the foundation for the future research on the monitoring surge of centrifugal compressor and development of the surge control method

Dynamic Performance of Valve in Reciprocating Compressor Used Stepless Capacity Regulation System

Capacity regulation system by controlling suction valve is useful for large scale reciprocating compressor in petrochemical engineering field. The dynamic performance of adjustment device influences the stability and accurancy of this system. In this paper, a mathematical model of adjustment device coupled with the motion of suction valve is built, and the dynamic performances of valve plate are simulated. The results show that the displacement of actuator increases with the hydraulic oil pressure until the valve plate is keeped to be opened. The closing process of valve plate is delayed when the hold time of actuator is larger enough. Although the gas flow rate and power consumption of comressor decrease with the relax angle of actuator, the power is also consumed when the gas is not discharged through the discharge valve. The closing time decreases with the reset spring stiffness but increases with the diameter of hydraulic

Experimental Research on Surge and Stability Enhancement of Centrifugal Compressor

Centrifugal compressors are wildly used in many process industries. The stability of centrifugal compressor is one of the most important performances. When the compressor operates at the small volume flow rate, the working conditions of rotating stall and surge will occur, which lead to the unstable condition for centrifugal compressor. The signals of compressor are tested and analyzed when surge condition occurs in this paper. In addition, a new method to improve the compressor stability is proposed. It is called the active control casing treatment (ACCT) system. The flow in the compressor impeller is changed by the ACCT system and the stability of compressor is improved. The experimental researches have been done in this paper. The test results of ACCT system are also discussed in this paper

Performance Analysis of Centrifugal Compressor under Multiple Working Conditions Based on Time-weighted Average

A method of compressor performance analysis under multiple working conditions is present based on the Time-weighted average (TWA). The main operation parameters can be obtained based the estimate of the working conditions and times of compressors. Then the comprehensive analysis method can be used to get the overall performance of compressor. The performance of a basic centrifugal compressor was simulation by CFD method in this paper. The overall performance of the centrifugal compressor is calculated under different working conditions. The TWA analysis method can be used as a tool to evaluate the overall performance of compressor. And it can also be used during the design phase to improve the performance of compressor fundamentally

Ameliorative patterns of grey matter in patients with first-episode and treatment-naïve schizophrenia

Background Grey matter (GM) reduction is a consistent observation in established late stages of schizophrenia, but patients in the untreated early stages of illness display an increase as well as a decrease in GM distribution relative to healthy controls (HC). The relative excess of GM may indicate putative compensatory responses, though to date its relevance is unclear. Methods 343 first-episode treatment-naïve patients with schizophrenia (FES) and 342 HC were recruited. Multivariate source-based morphometry was performed to identify covarying \u27networks\u27 of grey matter concentration (GMC). Neurocognitive scores using the Cambridge Neuropsychological Test Automated Battery (CANTAB) and symptom burden using the Positive and Negative Symptoms Scale (PANSS) were obtained. Bivariate linear relationships between GMC and cognition/symptoms were studied. Results Compared to healthy subjects, FES had prominently lower GMC in two components; the first consists of the anterior insula, inferior frontal gyrus, anterior cingulate and the second component with the superior temporal gyrus, precuneus, inferior/superior parietal lobule, cuneus, and lingual gyrus. Higher GMC was seen in adjacent areas of the middle and superior temporal gyrus, middle frontal gyrus, inferior parietal cortex and putamen. Greater GMC of this component was associated with lower duration of untreated psychosis, less severe positive symptoms and better performance on cognitive tests. Conclusions In untreated stages of schizophrenia, both a distributed lower and higher GMC is observable. While the higher GMC is relatively modest, it occurs across frontoparietal, temporal and subcortical regions in association with reduced illness burden suggesting a compensatory role for higher GMC in the early stages of schizophrenia

Effects of Clostridium butyricum and sodium butyrate on growth performance, immunity, and gut microbiota of mirror carp Cyprinus carpio fed with soybean meal based diet

This study investigated the effects of Clostridium butyricum (CB) and sodium butyrate (SB) on the growth performance, intestinal immune, and gut microbiota of mirror carp (Cyprinus carpio) fed with a high level of soybean meal. Three hundred sixty healthy carp fingerlings (∼3.74 g) were divided into eight dietary treatments with four replicates and ten fish per replicate. Which include basal diet (Control group, C0); C0 supplemented with three levels of CB, 3 × 107 cfu/kg (C1), 3 × 108 cfu/kg (C2), 3 × 109 cfu/kg (C3); three levels of SB, 500 mg/kg (S1), 1000 mg/kg (S2), 2 000 mg/kg (S3); and 3 × 108 cfu/kg CB+ 1 000 mg/kg SB (CS), respectively. In 8-week trial, the survival rate of all groups was 100%. Compared with C0, the Weight Gain, Feed Conversion Ratio, Protein Efficiency Ratio were not significantly different in all groups (P > 0.05). Crude protein and ether extract contents were increased significantly (P < 0.05) when supplemented with different levels of CB and SB, and ash content increased significantly in the CB groups (P < 0.05). Serum globulin increased and glucose decreased significantly (P < 0.05) in the CB and SB groups. The intestinal T-SOD and glutathione activity in the foregut, midgut, and hindgut were increased (P < 0.05), and villus height of foregut and midgut were higher in the CB and SB (P < 0.05). Protease activities in the foregut and midgut were significantly increased (P < 0.05) in the C2, C3, S2, and S3. The lipase activity of the C2 and C3 in foregut, midgut, and hindgut; S2, S3, and CS in the foregut; S3 in midgut were significantly increased (P < 0.05). The gut microbiota was modulated at the phylum and genera level by CB and SB administration. In summary, our results indicated that CB and SB could promote the whole body CP and EE content, intestine immunity, digestive enzyme activity, and intestinal morphology, and modulated gut flora in carp

Natrium Benzoate Alleviates Neuronal Apoptosis via the DJ-1-Related Anti-oxidative Stress Pathway Involving Akt Phosphorylation in a Rat Model of Traumatic Spinal Cord Injury

This study aimed to explore the neuroprotective effects and mechanisms of natrium benzoate (NaB) and DJ-1 in attenuating reactive oxygen species (ROS)-induced neuronal apoptosis in traumatic spinal cord injury (t-SCI) in rats. T-SCI was induced by clip compression. The protein expression and neuronal apoptosis was evaluated by Western blotting, double immunofluorescence staining and transmission electron microscope (TEM). ROS level, spinal cord water content (SCWC) and Evans blue (EB) extravasation was also examined. Locomotor function was evaluated by Basso, Beattie, and Bresnahan (BBB) and inclined plane test (IPT) scores. We found that DJ-1 is expressed in spinal cord neurons and increased after t-SCI. At 24 h post-injury, the levels of DJ-1, p-Akt, SOD2, ROS, p-p38 MAPK/p38 MAPK ratio, and CC-3 increased, while the Bcl-2/Bax ratio decreased. NaB upregulated DJ-1, p-Akt, and SOD2, decreased ROS, p-p38 MAPK/p38 MAPK ratio, and CC-3, and increased the Bcl-2/Bax ratio, which were reversed by DJ-1 siRNA. The proportion of CC-3- and TUNEL-positive neurons also increased after t-SCI and was reduced by NaB. These effects were reversed by MK2206. Moreover, the level of oxDJ-1 increased after t-SCI, which was decreased by DJ-1 siRNA, NaB or the combination of them. NaB also reduced mitochondrial vacuolization, SCWC and EB extravasation, and improved locomotor function assessed by the BBB and IPT scores. In conclusion, NaB increased DJ-1, and thus reduced ROS and ROS-induced neuronal apoptosis by promoting Akt phosphorylation in t-SCI rats. NaB shows potential as a therapeutic agent for t-SCI, with DJ-1 as its main target