The Experts below are selected from a list of 42726 Experts worldwide ranked by ideXlab platform
Luis San Andrés - One of the best experts on this subject based on the ideXlab platform.
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Effect of Side Feed Pressurization on the Dynamic Performance of Gas Foil Bearings: A Model Anchored to Test Data
Journal of Engineering for Gas Turbines and Power, 2009Co-Authors: Tae-ho Kim, Luis San AndrésAbstract:Comprehensive modeling of gas foil bearings (GFBs) anchored to reliable test data will enable the widespread usage of these bearings into novel high speed turbomachinery applications. GFBs often need a forced cooling gas flow, axially fed through one end of the bearing, for adequate thermal management. This paper presents rotordynamic response measurements on a rigid rotor supported on GFBs during rotor speed run-up and coastdown tests with the GFBs supplied with increasing Feed gas Pressures to 2.8 bars. Rotor speed run-up tests to 35 krpm show that the bearing end side Feed gas pressurization delays the onset speed of rotor subsynchronous whirl motions. The test data validate closely the predictions of the threshold speed of instability and the whirl frequency ratio derived from a GFB model that implements the axial evolution of gas circumferential flow velocity as a function of the imposed side Feed Pressure. Rotor speed coastdown tests from 25 krpm with a low Feed Pressure of 0.35 bar evidence a nearly linear synchronous rotor response for small and moderately large imbalance mass distributions. A structural finite element rotordynamics model integrates linearized synchronous speed GFB force coefficients and predicts synchronous responses, amplitude, and phase angles, agreeing with the test data. The analysis and measurements demonstrate the profound effect of the end side Feed gas pressurization on the rotordynamic performance of GFBs.
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Rotordynamic Performance of Flexure Pivot Hydrostatic Gas Bearings for Oil-Free Turbomachinery
Journal of Engineering for Gas Turbines and Power, 2007Co-Authors: Xuehua Zhu, Luis San AndrésAbstract:Micro-turbomachinery demands gas bearings to ensure compactness, light weight, and extreme temperature operation. Gas bearings with large stiffness and damping, and preferably of low cost, will enable successful commercial applications. Presently, tests conducted on a small rotor supported on flexure pivot hydrostatic pad gas bearings (FPTPBs) demonstrate stable rotordynamic responses up to 100,000 rpm (limit of the drive motor). Test rotor responses show the Feed Pressure raises the system critical speed (increase in bearing direct stiffness) while the viscous damping ratio decreases. Predictions correlate favorably with experimentally identified (synchronous) direct stiffness bearing force coefficients. Identified experimental gas bearing synchronous damping coefficients are 50% or less of the predicted magnitudes, though remaining relatively constant as the rotor speed increases. Tests without Feed Pressure show the rotor becomes unstable at ~81 krpm with a whirl frequency ratio of 20%. FPTPBs are mechanically complex and more expensive than cylindrical plain bearings. However, their enhanced stability characteristics and predictable rotordynamic performance makes them desirable for the envisioned oil-free applications in high speed micro-turbomachinery.
Yanhong Wang - One of the best experts on this subject based on the ideXlab platform.
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clathrate hydrate capture of co2 from simulated flue gas with cyclopentane water emulsion
Chinese Journal of Chemical Engineering, 2010Co-Authors: Jinqu Wang, Xuemei Lang, L I Shifeng, Yanhong WangAbstract:Abstract Capture of CO 2 by hydrate is one of the attractive technologies for reducing greenhouse effect. The primary challenges are the large energy consumption, low hydrate formation rate and separation efficiency. This work presents a new method for capture of CO 2 from simulated flue gas [CO 2 (16.60%, by mole)/N 2 binary mixture] by formation of cyclopentane (CP) hydrates at initial temperature of 8.1 °C with the Feed Pressures from 2.49 to 3.95 MPa. The effect of cyclopentane and cyclopentane/water emulsion on the hydrate formation rate and CO 2 separation efficiency was studied in a 1000 ml stirred reactor. The results showed the hydrate formation rate could be increased remarkably with cyclopentane/water emulsion. CO 2 could be enriched to 43.97% (by mole) and 35.29% (by mole) from simulated flue gas with cyclopentane and cyclopentane/water (O/W) emulsion, respectively, by one stage hydrate separation under low Feed Pressure. CO 2 separation factor with cyclopentane was 6.18, higher than that with cyclopentane/water emulsion (4.01), in the range of the Feed Pressure. The results demonstrated that cyclopentane/water emulsion is a good additive for efficient hydrate capture of CO 2 .
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Clathrate Hydrate Capture of CO2 from Simulated Flue Gas with Cyclopentane/Water Emulsion
Chinese Journal of Chemical Engineering, 2010Co-Authors: Shuanshi Fan, Jinqu Wang, Xuemei Lang, Yanhong WangAbstract:Abstract Capture of CO 2 by hydrate is one of the attractive technologies for reducing greenhouse effect. The primary challenges are the large energy consumption, low hydrate formation rate and separation efficiency. This work presents a new method for capture of CO 2 from simulated flue gas [CO 2 (16.60%, by mole)/N 2 binary mixture] by formation of cyclopentane (CP) hydrates at initial temperature of 8.1 °C with the Feed Pressures from 2.49 to 3.95 MPa. The effect of cyclopentane and cyclopentane/water emulsion on the hydrate formation rate and CO 2 separation efficiency was studied in a 1000 ml stirred reactor. The results showed the hydrate formation rate could be increased remarkably with cyclopentane/water emulsion. CO 2 could be enriched to 43.97% (by mole) and 35.29% (by mole) from simulated flue gas with cyclopentane and cyclopentane/water (O/W) emulsion, respectively, by one stage hydrate separation under low Feed Pressure. CO 2 separation factor with cyclopentane was 6.18, higher than that with cyclopentane/water emulsion (4.01), in the range of the Feed Pressure. The results demonstrated that cyclopentane/water emulsion is a good additive for efficient hydrate capture of CO 2 .
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efficient capture of co2 from simulated flue gas by formation of tbab or tbaf semiclathrate hydrates
Energy & Fuels, 2009Co-Authors: Shifeng Li, Xuemei Lang, Jingqu Wang, Yanhong WangAbstract:Capturing CO2 by forming hydrate is an attractive technology for reducing the greenhouse effect. The most primary challenges are high energy consumption, low hydrate formation rate, and separation efficiency. This work presents efficient capture of CO2 from simulated flue gas (CO2 (16.60 mol %)/N2 binary mixtures) by formation of semiclathrate hydrates at 4.5 and 7.1 °C and Feed Pressures ranging from 2.19 to 7.31 MPa. The effect of 0.293 mol % tetra-n-butyl ammonium bromide (TBAB) and tetra-n-butyl ammonium fluoride (TBAF) on the hydrate formation rate, reactor space velocity, and CO2 separation efficiency was studied in a 1 L stirred reactor. The results showed the hydrate formation rate constant increased with increasing Feed Pressure and reached the maximum at 2.82 × 10−7 mol2/(s·J) with TBAB and 8.26 × 10−7 mol2/(s·J) with TBAF. The space velocity of the hydrate reactor increased with increasing Feed Pressure and reached a maximum of 13.46 h−1 with TBAB and 25.96 h−1 with TBAF. CO2 recovery was about...
Xuemei Lang - One of the best experts on this subject based on the ideXlab platform.
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clathrate hydrate capture of co2 from simulated flue gas with cyclopentane water emulsion
Chinese Journal of Chemical Engineering, 2010Co-Authors: Jinqu Wang, Xuemei Lang, L I Shifeng, Yanhong WangAbstract:Abstract Capture of CO 2 by hydrate is one of the attractive technologies for reducing greenhouse effect. The primary challenges are the large energy consumption, low hydrate formation rate and separation efficiency. This work presents a new method for capture of CO 2 from simulated flue gas [CO 2 (16.60%, by mole)/N 2 binary mixture] by formation of cyclopentane (CP) hydrates at initial temperature of 8.1 °C with the Feed Pressures from 2.49 to 3.95 MPa. The effect of cyclopentane and cyclopentane/water emulsion on the hydrate formation rate and CO 2 separation efficiency was studied in a 1000 ml stirred reactor. The results showed the hydrate formation rate could be increased remarkably with cyclopentane/water emulsion. CO 2 could be enriched to 43.97% (by mole) and 35.29% (by mole) from simulated flue gas with cyclopentane and cyclopentane/water (O/W) emulsion, respectively, by one stage hydrate separation under low Feed Pressure. CO 2 separation factor with cyclopentane was 6.18, higher than that with cyclopentane/water emulsion (4.01), in the range of the Feed Pressure. The results demonstrated that cyclopentane/water emulsion is a good additive for efficient hydrate capture of CO 2 .
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Clathrate Hydrate Capture of CO2 from Simulated Flue Gas with Cyclopentane/Water Emulsion
Chinese Journal of Chemical Engineering, 2010Co-Authors: Shuanshi Fan, Jinqu Wang, Xuemei Lang, Yanhong WangAbstract:Abstract Capture of CO 2 by hydrate is one of the attractive technologies for reducing greenhouse effect. The primary challenges are the large energy consumption, low hydrate formation rate and separation efficiency. This work presents a new method for capture of CO 2 from simulated flue gas [CO 2 (16.60%, by mole)/N 2 binary mixture] by formation of cyclopentane (CP) hydrates at initial temperature of 8.1 °C with the Feed Pressures from 2.49 to 3.95 MPa. The effect of cyclopentane and cyclopentane/water emulsion on the hydrate formation rate and CO 2 separation efficiency was studied in a 1000 ml stirred reactor. The results showed the hydrate formation rate could be increased remarkably with cyclopentane/water emulsion. CO 2 could be enriched to 43.97% (by mole) and 35.29% (by mole) from simulated flue gas with cyclopentane and cyclopentane/water (O/W) emulsion, respectively, by one stage hydrate separation under low Feed Pressure. CO 2 separation factor with cyclopentane was 6.18, higher than that with cyclopentane/water emulsion (4.01), in the range of the Feed Pressure. The results demonstrated that cyclopentane/water emulsion is a good additive for efficient hydrate capture of CO 2 .
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efficient capture of co2 from simulated flue gas by formation of tbab or tbaf semiclathrate hydrates
Energy & Fuels, 2009Co-Authors: Shifeng Li, Xuemei Lang, Jingqu Wang, Yanhong WangAbstract:Capturing CO2 by forming hydrate is an attractive technology for reducing the greenhouse effect. The most primary challenges are high energy consumption, low hydrate formation rate, and separation efficiency. This work presents efficient capture of CO2 from simulated flue gas (CO2 (16.60 mol %)/N2 binary mixtures) by formation of semiclathrate hydrates at 4.5 and 7.1 °C and Feed Pressures ranging from 2.19 to 7.31 MPa. The effect of 0.293 mol % tetra-n-butyl ammonium bromide (TBAB) and tetra-n-butyl ammonium fluoride (TBAF) on the hydrate formation rate, reactor space velocity, and CO2 separation efficiency was studied in a 1 L stirred reactor. The results showed the hydrate formation rate constant increased with increasing Feed Pressure and reached the maximum at 2.82 × 10−7 mol2/(s·J) with TBAB and 8.26 × 10−7 mol2/(s·J) with TBAF. The space velocity of the hydrate reactor increased with increasing Feed Pressure and reached a maximum of 13.46 h−1 with TBAB and 25.96 h−1 with TBAF. CO2 recovery was about...
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co2 capture from binary mixture via forming hydrate with the help of tetra n butyl ammonium bromide
Journal of Natural Gas Chemistry, 2009Co-Authors: Xuemei Lang, Shifeng Li, Jingqu Wang, Deqing LiangAbstract:Abstract Hydrate formation rate and separation effect on the capture of CO 2 from binary mixture via forming hydrate with 5 wt% tetra-n-butyl ammonium bromide (TBAB) solution were studied. The results showed that the induction time was 5 min, and the hydrate formation process finished in 1 h at 4.5 °C and 4.01 MPa. The hydrate formation rate constant reached the maximum of 1.84×10 −7 mol 2 /(s·J) with the Feed Pressure of 7.30 MPa. The CO 2 recovery was about 45% in the Feed Pressure range from 4.30 to 7.30 MPa. Under the Feed Pressure of 4.30 MPa, the maximum separation factor and CO 2 concentration in hydrate phase were 7.3 and 38.2 mol%, respectively. The results demonstrated that TBAB accelerated hydrate formation and enriched CO 2 in hydrate phase under the gentle condition.
Ahmad Fauzi Ismail - One of the best experts on this subject based on the ideXlab platform.
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performance of treated and untreated asymmetric polysulfone hollow fiber membrane in series and cascade module configurations for co2 ch4 gas separation system
Journal of Membrane Science, 2006Co-Authors: Ahmad Fauzi Ismail, N YaacobAbstract:This study investigates the effects of one-, two- and three-stage membrane system configurations in series arrangement for the CO2/CH4 separation for both untreated and treated membranes. Asymmetric polysulfone hollow fiber membranes were fabricated from 33 wt.% of polysulfone polymer using dry/wet phase inversion process. The produced membranes were characterized by pure gas permeation experiments, Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), density measurement and Thermogravimetric Analysis (TGA). For both untreated and treated membranes, the Pressure-normalized flux of CO2 decreased with increasing of the membrane stages. In addition, the selectivities of asymmetric hollow fiber membrane showed a more constant trend with Feed Pressure. Treated membrane exhibited lower Pressure-normalized flux than untreated membranes due to skin layer densification which increased the transport resistance, thus lead to the reduction in Pressure-normalized fluxes. Among all the three configurations studied, two-stage membrane configuration showed the most constant trend in term of selectivity. However, three-stage cascade configuration produced the highest CO2/CH4 selectivity especially when tested at low Feed Pressure range. Effect of stage cut on Feed Pressure showed an increasing trend with increasing of CO2 and CH4 Feed Pressure for all configurations. This is due to the increase of the permeation driving force, which caused the passage of larger amounts of more permeable gas through the membrane. This study showed that, three-stage cascade configuration exhibited the smallest stage cut values thus produced higher purity of CO2 in permeate stream.
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Effects of Feed Pressure and Retentate Flow Rate on the Performance of Locally Developed Polysulfone Membrane Oxygen Enrichment System
Jurnal Teknologi, 2001Co-Authors: Ahmad Fauzi Ismail, Chin Yin Tan, Fook Kiong ChanAbstract:Pengkayaan oksigen daripada udara persekitaran dengan menggunakan teknologi membran diterima secara meluas di seluruh dunia sebagai teknologi alternatif kepada kaedah konvensional seperti penjerapan ayunan tekanan dan sistem kriogenik. Pemisahan udara menggunakan membran adalah proses yang lebih anjal di mana ia memerlukan pelaburan modal yang rendah, kaedah operasi yang mudah dan murah jika dibandingkan dengan kaedah konvensional. Kajian dan pengujian telah dijalankan ke atas sistem membran gentian geronggang polisulfona, di mana kesan tekanan suapan dan kadar alir baki dikaji. Pada kadar alir malar, pengkayaan telapan meningkat dan kemudian menurun dengan peningkatan tekanan disebabkan oleh kesan perbezaan tekanan merentasi membran mempengaruhi kebolehtelapan lapisan kulit. Manakala pada tekanan suapan malar, nilai pengkayaan telapan maksimum dicapai pada kadar alir maksimum disebabkan oleh peningkatan rintangan penelapan. Nilai maksimum ketulenan telapan oksigen yang diperolehi dalam uji kaji ini ialah 27.2%. Kata kunci: Pemisahan udara; membran gentian geronggang; pengkayaan oksigen; kebolehtelapan; polisulfona Oxygen enrichment from surrounding air by using membrane is gaining wide acceptance through out the world today as an alternative to the conventional methods such as Pressure swing adsorption and cryogenic system. Air separation using membrane is a more flexible process that requires lower capital investment and simple operation. Studies and testing had been performed on a locally new developed polysulfone hollow fiber membrane system, where effects of Feed Pressure and retentate flow rate on the oxygen enrichment were observed. At constant retentate flow rate, permeate enrichment increased and then decreased with Pressure due to the effect of Pressure difference across the membrane, which affects the permeability of the skin layer. While at constant Pressure, the highest permeate enrichment value was obtained at highest retentate flow rate due to the increase of permeation resistance. The highest oxygen purity obtained in this experiment was 27.2% and the O2 permeate enrichment was 1.295. Key words: Air separation; hollow fiber membrane; oxygen enrichment; permeability; polysulfone
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Numerical solution of a mathematical model for hollow-fiber membrane gas separation system
1993Co-Authors: Ahmad Fauzi Ismail, Hamdani Saidi, Ali Abdul RahmanAbstract:A mathematical model has been developed for the separation of CO2 from natural gas (CH4) using hollow-fiber membrane module. Numerical solution technique using Runge-Kutta-Merson method, available from the NAG FORTRAN Library as the subroutine D02BBF, is used to solved the mathematical model. The model is used to predict the effects of the operating conditions, namely, Feed Pressure and Feed composition on the performance of the separation of CO2 from natural gas (CH4). The solution strategy employs initial value problem estimate and the establishment of Feed Pressure profile and gas composition profile . The model developed was used to predict the performance of a commercial size membrane permeator with a diameter and length of 5.08 cm and 304.8 cm respectively. The membrane area utilized was 232877.97 cm2 with 7200 active fibers. The volumetric Feed flow rate was 1.83 x 10 (6) cm3 (STP)/s. The ranges of Pressure and Feed composition used are 2068-5170 cm Hg and 5-50% respectively. The model predicted the carbon dioxide purity in the permeate stream 65.54% and retentate 0.146% respectively. The results obtained was based on Feed Pressure, Feed composition and temperature of 5170 cm Hg, 5% carbon dioxide and 25C respectively. The model also found that the Mechanical Energy Balance equation (Bernoulli equation) which was incorporated in the mathematical model satisfactorily predict the Feed Pressure drop along the fiber length. The predicted Feed Pressure drop was found to significantly affect the performance of a single-stage hollow-fiber membrane permeator.
S Sridhar - One of the best experts on this subject based on the ideXlab platform.
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air separation by facilitated transport of oxygen through a pebax membrane incorporated with a cobalt complex
RSC Advances, 2015Co-Authors: Harsha Nagar, Pavani Vadthya, Shiva N Prasad, S SridharAbstract:Separation of air to produce enriched oxygen (O2) and nitrogen (N2) has been of great importance in the chemical industry. In the present investigation, thin film composite (TFC) membranes were prepared by coating a thin layer of poly(ether-block-amide) (Pebax-1657) incorporated with a cobalt(II) phthalocyanine (CoPc) compound onto a polyethersulfone (PES) ultraporous substrate. The surface and cross-sectional morphologies, intermolecular interactions and crystalline nature of the membranes were investigated by SEM, FTIR and XRD spectroscopy, respectively. Effect of CoPc loading and Feed Pressure on the permeance of pure O2 and N2 gases was evaluated and ideal selectivity was determined using indigenously fabricated high-Pressure gas permeability equipment. O2/N2 ideal selectivity was enhanced from 2.9 to 8.5 with an increase in CoPc loading from 0 to 1 wt%, at a constant Feed Pressure of 2 kg cm−2. A molecular dynamics simulation based on a COMPASS force field was performed to understand the diffusion behavior of O2 and N2 through the CoPc loaded Pebax-1657 membrane. This study confirmed that the CoPc complex present in the Pebax-1657 membrane facilitates preferential O2 transport to produce enriched N2 and O2 from air for both inert gas and medical applications.
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reverse osmosis of edible vegetable oil industry effluent
Journal of Membrane Science, 2002Co-Authors: S Sridhar, Aniket Kale, A A KhanAbstract:Abstract Pilot-scale reverse osmosis (RO) studies were carried out to determine the feasibility of the process for treating the wastewater from a vegetable oil industry. The effect of varying Feed Pressure (0–69 bar) and Feed TDS concentration (0.54–5.2% w/v) on separation performance of the thin film composite (TFC) polyamide RO membrane was determined. At original effluent composition and Feed Pressure of 55.2 bar, high rejection of TDS (99.4%) and COD (98.2%) along with complete rejection of color and BOD was achieved with a reasonably high flux of 52.5 l/(m 2 h). The flux and percent rejection of pollutants improved significantly with increasing transmembrane Pressure at constant Feed concentration but decreased with increasing Feed TDS concentration. RO was found to be very suitable for treating oil effluents having TDS concentrations upto 52215 ppm.