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Robert E. Synovec - One of the best experts on this subject based on the ideXlab platform.
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Development of Ultrafast Separations Using Negative Pulse Partial Modulation To Enable New Directions in Gas Chromatography.
Analytical chemistry, 2019Co-Authors: Derrick V. Gough, Dong H Song, Sonia Schöneich, Sarah E. Prebihalo, Robert E. SynovecAbstract:Partial modulation via a pulse Flow Valve operated in the negative pulse mode is developed for high-speed one-dimensional gas chromatography (1D-GC), comprehensive two-dimensional (2D) gas chromatography (GC × GC), and comprehensive three-dimensional gas chromatography (GC3). The pulse Flow Valve readily provides very short modulation periods, PM, demonstrated herein at 100, 200, and 300 ms, and holds significant promise to increase the scope and applicability of GC instrumentation. The negative pulse mode creates an extremely narrow, local analyte concentration pulse. The reproducibility of the negative pulse mode is validated in a 1D-GC mode, where a pseudosteady-state analyte stream is modulated, and 8 analytes are baseline resolved (resolution, Rs ≥ 1.5) in a 200 ms window, providing a peak capacity, nc, of 14 at unit resolution (Rs = 1.0). Additionally, the pulse width, pw, of the pulse Flow Valve “injection” relationship to peak width-at-base, wb, resolution between peaks and detection sensitivity a...
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Ultrafast separations via pulse Flow Valve modulation to enable high peak capacity multidimensional gas chromatography
Journal of chromatography. A, 2018Co-Authors: H. Daniel Bahaghighat, Chris E. Freye, Derrick V. Gough, Paige E. Sudol, Robert E. SynovecAbstract:Ultrafast modulation with a modulation period PM ≥ 50ms via a pulse Flow Valve is demonstrated for comprehensive two-dimensional gas chromatography (GC×GC) and comprehensive three-dimensional (3D) gas chromatography (GC3). Significant increases in peak capacity and peak capacity production are achieved for GC×GC and GC3 relative to previous studies due to using pulse Flow Valve modulation. Due to the nature of the "partial" modulation process, the separation dimension following pulse Flow Valve modulation is not a traditional chromatogram, rather requires data processing to convert the data to expose the encoded chromatographic information, producing "apparent" chromatographic peaks. In the GC×GC mode, a 115-component test mixture was evaluated using a PM of 500ms, creating an apparent 2D peak width-at-base 2W with an average of 25ms, producing a 2nc of 20. Based on the average 1W of 1.0s for the 6min first dimension 1D separation, an ideal peak capacity nc,2D of 7200 is achieved (1,200/min peak production). For a high-speed GC×GC separation (30s run), a PM of 75ms produced apparent 2W of 8ms, ideal for the third dimension of a GC3 instrument. Using the knowledge gained from this high-speed GC×GC experiment, the pulse Flow Valve was implemented as the second modulator in GC3. Three samples were evaluated in the GC3 mode: a simple mixture containing 18 compounds (to illustrate basic concepts), the 115-component test mixture (to determine peak capacity figures-of-merit), and a diesel spiked with 8 polar compounds (to illustrate chemical selectivity benefits of GC3). For the 115-component test mixture with a 1PM of 1.2s and a 2PM of 60ms, average 1W of 3.2s, 2W of 130ms, and apparent 3W of 13ms were produced, resulting in a 1nc of 210, 2nc of 9.2, and 3nc of 5, respectively. Hence, an ideal peak capacity, nc,3D of ∼10,000 for GC3 was achieved for the 11min 1D separation window of the 115-component test mixture.
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Comprehensive two-dimensional gas chromatography using partial modulation via a pulsed Flow Valve with a short modulation period
Talanta, 2017Co-Authors: Chris E. Freye, H. Daniel Bahaghighat, Robert E. SynovecAbstract:Partial modulation via a pulsed Flow Valve for comprehensive two-dimensional (2D) gas chromatography (GC × GC) is demonstrated, producing narrow peak widths, 2Wb, on the secondary separation dimension, 2D, coupled with short modulation periods, PM, thus producing a high peak capacity on the 2D dimension, 2nc. The GC × GC modulator is a pulse Flow Valve that injects a pulse of carrier gas at the specified PM, at the connection between the primary, 1D, column and the 2D column. Using a commercially available pulse Flow Valve, this injection technique performs a combination of vacancy chromatography and frontal analysis, whereby each pulse disturbance in the analyte concentration profile as it exits the 1D column results in data that is readily converted into a 2D separation. A three-step process converts the raw data into a format analogous to a GC × GC separation, incorporating signal differentiation, baseline correction and conversion to a GC × GC chromatogram representation. A 115-component test mixture with a wide range of boiling points (36-372°C) of nine compound classes is demonstrated using modulation periods of PM = 50, 100, 250, and 500ms, respectively. For the test mixture with a PM of 250ms, peak shapes on 2D are symmetric with apparent 2Wb ranging from 12 to 45ms producing a 2nc of ~ 10. Based on the average peak width of 0.93s on the 1D separation for a time window of 400s, the 1D peak capacity is 1nc ∼ 430. Thus, the ideal 2D peak capacity nc,2D is 4300 or a peak capacity production of 650 peaks/min using the PM of 250ms. Additionally, for a PM of 50, 100 and 500ms, the 2nc are 4, 7, and 12, respectively. Retention times on 2D, 2tR, are reproducible having standard deviations less than 1ms. Finally, the processed data is shown to be quantitative, with an average RSD of 4.7% for test analytes.
Satish C Sharma - One of the best experts on this subject based on the ideXlab platform.
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Stability of a constant Flow Valve compensated multi-recess conical hybrid journal bearing operating with micropolar lubricant
Lubrication Science, 2014Co-Authors: Arvind K. Rajput, Satish C SharmaAbstract:The present paper investigates the influence of micropolar lubrication on the stability of a constant Flow Valve compensated multi-recess conical hybrid journal bearing system. Eringen's micropolar fluid theory has been used to model the micropolar lubrication in a fluid-film bearing system. The modified Reynolds equation of the micropolar lubricated bearing system has been solved using finite element method. Performance characteristics parameters of four pocket hybrid journal bearing system have been computed for the values of semi-cone angle 10°, 20° and for the judiciously selected micropolar parameters. Numerically simulated results indicate that the value of stability threshold speed margin gets increased substantially with the use of micropolar lubricant vis-a-vis Newtonian lubricant. Copyright © 2014 John Wiley & Sons, Ltd.
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performance of membrane compensated multirecess hydrostatic hybrid flexible journal bearing system considering various recess shapes
Tribology International, 2004Co-Authors: Narendra Singh, Satish C Sharma, S C Jain, Sanjeeva S ReddyAbstract:The paper describes a theoretical study concerning the performance of an externally pressurized multirecess hydrostatic/hybrid flexible journal bearing system by varying the geometric shape of recess and using the membrane Flow Valve restrictor as a compensating element. The four different recess geometries of the bearing studied in the present study are a square recessed bearing, a circular recessed bearing, an elliptical recessed bearing and a triangular recessed bearing. The equation governing the Flow of lubricant in a journal bearing together with 3D elasticity equation and restrictor Flow equation are solved by using the Finite Element Method. The study describes the effect of recess shape, bearing flexibility and a method of compensation on the performance characteristics of a hydrostatic/hybrid journal bearing system. A comparative performance of the membrane compensated hydrostatic/hybrid journal bearing system has also been studied vis-a-vis capillary, orifice and constant Flow Valve restrictors. The results presented in this study amply demonstrate that the shape of recess/pocket of a hydrostatic/hybrid flexible journal bearing system affects the performance of the bearing quite appreciably and a proper selection of recess shape along with a suitable compensating device is needed to get an improved performance from the bearing.
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a study of slot entry hydrostatic hybrid journal bearing using the finite element method
Tribology International, 1999Co-Authors: Satish C Sharma, S C Jain, R. Sinhasan, Vijay Kumar, Murugan SubramanianAbstract:Abstract A theoretical study concerning the static and dynamic performance of hydrostatic/hybrid journal bearing compensated by slot restrictor has been presented using the finite element method (FEM). Results have been presented for a double row symmetric as well as asymmetric configurations for different values of slot width ratios (SWR) and external load ( W 0 ). In order to have a better understanding of their performance vis-a-vis other non-recessed bearing configurations, the performance characteristics of slot-entry journal bearings have been compared with that of similar hole-entry compensated journal bearings using capillary, orifice and constant Flow Valve restrictors for the same bearing geometric and operating parameters. The comparative study indicates that asymmetric slot-entry journal bearings provide an improved stability threshold speed margin compared with asymmetric hole entry journal bearings compensated by capillary, orifice and constant Flow Valve restrictors.
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PERFORMANCE CHARACTERISTICS OF A CONSTANT Flow Valve COMPENSATED MULTIPLE HOLE-ENTRY HYBRID FLEXIBLE JOURNAL BEARINGS
Periodica Polytechnica Mechanical Engineering, 1992Co-Authors: Satish C Sharma, S C Jain, R. SinhasanAbstract:The multiple hole-entry flexible journal bearing configurations with constant Flow Valve compensation have been theoretically studied to determine the effects of bearing shell flexibility on the bearing performance characteristic. Finite element method has been used to obtain solutions of 3-dimensional elasticity equations and Reynolds equation. The non-dimensional parameter Cd is defined to account for the flexibility of bearing shell. Bearing performance characteristics have been presented for wide range of representative values of deformation coefficient (Cd) and non-dimensional external load (Wo). The results indicate that the bearing performance characteristic are significantly affected by bearing shell flexibility, both for hydrostatic (Ω=0.0) and hybrid (Ω≠0.0) modes of operations.
Vijay Kumar - One of the best experts on this subject based on the ideXlab platform.
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Thermohydrostatic rheological analysis of constant Flow Valve compensated multiple hole-entry hybrid journal bearings
Industrial Lubrication and Tribology, 2014Co-Authors: H.c. Garg, Vijay KumarAbstract:Purpose – The changing technological scenario necessitated hybrid journal bearings to operate under severe conditions of heavy load and high speed resulting into temperature rise of the lubricant fluid-film and bearing surface. To predict the performance of a bearing realistically, theoretical model must consider the combined influence of the rise of temperature and non-Newtonian behavior of the lubricant. The aim of the present paper is to study the effect of viscosity variation due to temperature rise and non-Newtonian behavior of the lubricant on performance of constant Flow Valve compensated multiple hole-entry hybrid journal bearings. Design/methodology/approach – Finite element method has been used to solve Reynolds equation along with restrictor Flow equation, 3D energy equation and 3D conduction equation using suitable iterative technique. The non-Newtonian lubricant has been assumed to follow cubic shear stress law. Findings – The thermohydrostatic rheological performances of symmetric and asymme...
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analysis of multirecess hydrostatic journal bearing operating with micropolar lubricant
Journal of Tribology-transactions of The Asme, 2009Co-Authors: Suresh Verma, Vijay Kumar, Kapil GuptaAbstract:This paper presents a theoretical study of the performance characteristics of a constant Flow Valve compensated multirecess hydrostatic journal bearings operating with micropolar lubricant. The finite element method and iterative procedure have been used to solve the modified Reynolds equation governing the micropolar lubricant Flow in the bearing. The performance characteristics are presented for a wide range of nondimensional load, lubricant Flow, and micropolar parameters. It has been observed that the micropolar parameters significantly influence the performance characteristics of the bearing.
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Non‐Newtonian and thermal effects in constant Flow Valve compensated symmetric hole‐entry hybrid journal bearing
Lubrication Science, 2007Co-Authors: H.c. Garg, Vijay Kumar, H.b. ShardaAbstract:Every high speed machine, demanding high level of perfection, can operate successfully through a precise design of bearings. Such a design can be formulated after carefully studying both static and dynamic characteristics of the journal bearing. The present paper described the study of static and dynamic performance of a hole-entry hybrid journal bearing system compensated with constant Flow Valve restrictor by considering the combined influence of thermal effects and non-Newtonian behaviour of the lubricant. The variation of the viscosity due to the non-Newtonian behaviour of the lubricant and temperature rise has been considered in the study. The numerical solution of the generalized Reynolds equation governing the Flow of the lubricant, having variable viscosity along with the energy and heat conduction equations, was obtained using finite element method. The non-Newtonian lubricant has been assumed to follow the cubic shear stress law. The study included the performance of a double row symmetric hole-entry hybrid journal bearing configuration containing 12 holes per row. The results presented in this paper indicate that change in viscosity of lubricant affects the performance of the hole-entry hybrid journal bearing system quite significantly. Copyright © 2007 John Wiley & Sons, Ltd.
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a study of slot entry hydrostatic hybrid journal bearing using the finite element method
Tribology International, 1999Co-Authors: Satish C Sharma, S C Jain, R. Sinhasan, Vijay Kumar, Murugan SubramanianAbstract:Abstract A theoretical study concerning the static and dynamic performance of hydrostatic/hybrid journal bearing compensated by slot restrictor has been presented using the finite element method (FEM). Results have been presented for a double row symmetric as well as asymmetric configurations for different values of slot width ratios (SWR) and external load ( W 0 ). In order to have a better understanding of their performance vis-a-vis other non-recessed bearing configurations, the performance characteristics of slot-entry journal bearings have been compared with that of similar hole-entry compensated journal bearings using capillary, orifice and constant Flow Valve restrictors for the same bearing geometric and operating parameters. The comparative study indicates that asymmetric slot-entry journal bearings provide an improved stability threshold speed margin compared with asymmetric hole entry journal bearings compensated by capillary, orifice and constant Flow Valve restrictors.
Suresh Verma - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear transient analysis of hole-entry journal bearing with constant Flow of micropolar fluids:
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2018Co-Authors: Kamal Budheeja, Suresh VermaAbstract:The present work deals with study and analysis of a symmetric hybrid journal bearing compensated with constant Flow Valve restrictor operating with micropolar fluid from stability point of view. Th...
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Effect of micropolar lubrication in non-circular hole-entry hybrid journal bearing with constant Flow Valve restrictor
Industrial Lubrication and Tribology, 2016Co-Authors: Rajneesh Kumar, Suresh VermaAbstract:Purpose In the present scenario of high-speed machines, the use of non-circular hole-entry bearing configuration, i.e. two-lobe, multi-lobe, lemon bore, etc., has becomes unavoidable, as the journal bearings with non-circular configurations provide better stability at high operating speed and heavy dynamic loading. Further, this research aims to show that the presence of micro particles in the lubricants greatly affects performance of the bearings, as their presence leads to non-Newtonian behaviors of the lubricant. Therefore, to consider the effect of these micro particles, the lubricant is modeled as a micropolar lubricant. The present work analyzes the effect of these micropolar lubricants on the performance of hole-entry circular and non-circular (two-lobe) hybrid journal bearings compensated with constant Flow Valve restrictor and compares with that of Newtonian lubricants. Design/methodology/approach The modified Reynolds equation governing the laminar Flow of iso-viscous, incompressible micropolar lubricant in the clearance space of a journal bearing system has been solved using finite element method and appropriate boundary conditions. Further, a comparative analysis between circular and non-circular (two-lobe) hybrid journal bearing compensated with constant Flow Valve restrictor operating with Newtonian and micropolar lubricant has been presented. Findings The numerically simulated results reveal that the non-circular bearing configuration provides better performance vis-a-vis the circular bearing configuration. Further, the increase in the micropolar effect of the lubricant enhances the performance of circular and the non-circular bearing configurations compared with the Newtonian lubricant. Also, in the case of the non-circular bearing configuration with an offset factor (δ = 1.5), the bearing performance improved compared with (δ = 1.25). Originality/value Many research studies have been done in the area of non-circular hybrid journal bearing with Newtonian lubricants with different types of restrictors, but the non-circular hole-entry constant Flow Valve-compensated hybrid journal bearing operating with the micropolar lubricant has not been analyzed. Therefore, in the present work, an effort has been made to fill this research gap.
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Performance characteristics of constant Flow Valve compensated conical multirecess hybrid journal bearing under micropolar lubrication
International Journal of Design Engineering, 2016Co-Authors: N.k. Rana, Satyam Shivam Gautam, Suresh VermaAbstract:This paper presents the theoretical study on the effect of micropolar parameters of the fluid and the semi-cone angle on the performance characteristics of a conical multirecess hybrid journal bearing under micropolar lubrication compensated with constant Flow Valve. The numerical solution of the modified Reynolds equation for micropolar fluid Flow on the conical surface has been done by using finite element method using Galerkin's technique along with the necessary boundary conditions and iterative scheme. The performance characteristics have been presented for a wide range of the semi-cone angle and the restrictor design parameter of the conical hybrid journal bearing system operating under Newtonian and micropolar lubrication. The study suggests that the semi-cone angle of the bearing, constant Flow Valve restrictor and micropolar parameters significantly influence the performance characteristics of conical bearing. With increase in semi-cone angle of bearing the direct stiffness, damping coefficients and the stability margin have been observed to increase significantly.
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on the stiffness and damping coefficients of constant Flow Valve compensated conical hydrostatic journal bearing with micropolar lubricant
Procedia Technology, 2016Co-Authors: N.k. Rana, Satyam Shivam Gautam, Suresh Verma, Faisal RahmaniAbstract:Abstract A theoretical analysis for performance characteristics of a conical multirecess hydrostatic journal bearing compensated with constant Flow Valve has been carried out considering micropolar lubricant. The numerical solution of the modified Reynolds equation for the conical bearing has been done using finite element method with necessary boundary conditions. The performance characteristics have been presented for various values of the restrictor design parameter, load, micropolar parameters, semi-cone angle and aspect ratio (L/D ratio) of the bearing at zero speed. It has been observed that the bearing develops large stiffness and damping coefficients with increase in restrictor design parameter, micropolar effect and semi-cone angle.
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Static Characteristics of Conical Hydrostatic Journal Bearing Under Micropolar Lubrication
Journal of The Institution of Engineers (India): Series C, 2014Co-Authors: N.k. Rana, Satyam Shivam Gautam, Suresh VermaAbstract:A theoretical analysis for static characteristics of a conical hydrostatic journal bearing for a multirecess constant Flow Valve compensated under micropolar lubrication has been carried out in this work. The numerical solution of the modified Reynolds equation for the conical bearing has been done using Finite Element Method (FEM) using necessary boundary conditions. The various static characteristics have been presented to analyze the performance of bearing at zero speed.
S C Jain - One of the best experts on this subject based on the ideXlab platform.
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performance of membrane compensated multirecess hydrostatic hybrid flexible journal bearing system considering various recess shapes
Tribology International, 2004Co-Authors: Narendra Singh, Satish C Sharma, S C Jain, Sanjeeva S ReddyAbstract:The paper describes a theoretical study concerning the performance of an externally pressurized multirecess hydrostatic/hybrid flexible journal bearing system by varying the geometric shape of recess and using the membrane Flow Valve restrictor as a compensating element. The four different recess geometries of the bearing studied in the present study are a square recessed bearing, a circular recessed bearing, an elliptical recessed bearing and a triangular recessed bearing. The equation governing the Flow of lubricant in a journal bearing together with 3D elasticity equation and restrictor Flow equation are solved by using the Finite Element Method. The study describes the effect of recess shape, bearing flexibility and a method of compensation on the performance characteristics of a hydrostatic/hybrid journal bearing system. A comparative performance of the membrane compensated hydrostatic/hybrid journal bearing system has also been studied vis-a-vis capillary, orifice and constant Flow Valve restrictors. The results presented in this study amply demonstrate that the shape of recess/pocket of a hydrostatic/hybrid flexible journal bearing system affects the performance of the bearing quite appreciably and a proper selection of recess shape along with a suitable compensating device is needed to get an improved performance from the bearing.
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a study of slot entry hydrostatic hybrid journal bearing using the finite element method
Tribology International, 1999Co-Authors: Satish C Sharma, S C Jain, R. Sinhasan, Vijay Kumar, Murugan SubramanianAbstract:Abstract A theoretical study concerning the static and dynamic performance of hydrostatic/hybrid journal bearing compensated by slot restrictor has been presented using the finite element method (FEM). Results have been presented for a double row symmetric as well as asymmetric configurations for different values of slot width ratios (SWR) and external load ( W 0 ). In order to have a better understanding of their performance vis-a-vis other non-recessed bearing configurations, the performance characteristics of slot-entry journal bearings have been compared with that of similar hole-entry compensated journal bearings using capillary, orifice and constant Flow Valve restrictors for the same bearing geometric and operating parameters. The comparative study indicates that asymmetric slot-entry journal bearings provide an improved stability threshold speed margin compared with asymmetric hole entry journal bearings compensated by capillary, orifice and constant Flow Valve restrictors.
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PERFORMANCE CHARACTERISTICS OF A CONSTANT Flow Valve COMPENSATED MULTIPLE HOLE-ENTRY HYBRID FLEXIBLE JOURNAL BEARINGS
Periodica Polytechnica Mechanical Engineering, 1992Co-Authors: Satish C Sharma, S C Jain, R. SinhasanAbstract:The multiple hole-entry flexible journal bearing configurations with constant Flow Valve compensation have been theoretically studied to determine the effects of bearing shell flexibility on the bearing performance characteristic. Finite element method has been used to obtain solutions of 3-dimensional elasticity equations and Reynolds equation. The non-dimensional parameter Cd is defined to account for the flexibility of bearing shell. Bearing performance characteristics have been presented for wide range of representative values of deformation coefficient (Cd) and non-dimensional external load (Wo). The results indicate that the bearing performance characteristic are significantly affected by bearing shell flexibility, both for hydrostatic (Ω=0.0) and hybrid (Ω≠0.0) modes of operations.