The Experts below are selected from a list of 64773 Experts worldwide ranked by ideXlab platform
Wolfgang Schroder - One of the best experts on this subject based on the ideXlab platform.
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hydrodynamic instability and shear layer effects in turbulent premixed combustion
Physics of Fluids, 2016Co-Authors: Stephan Schlimpert, Matthias Meinke, Wolfgang Schroder, Antje Feldhusen, Jerry H Grimmen, Benedikt RoidlAbstract:A turbulent premixed plane jet flame is analyzed by large-eddy simulations. The analysis shows that the flame front wrinkling is strongly influenced by the shear layer effect when the Gas Expansion effects are small leading to larger flame front amplitudes at the flame base than at high Gas Expansion ratios. However, the hydrodynamicinstabilityeffect induces a continuously increasing flame front amplitude which yields an enhanced flame pocket generation at the flame tip. Both phenomena influence the magnitude of the turbulent burning area and burning area rate response through the flame front deflections which are determined by the contribution coefficient. This coefficient represents the mutual interaction between the flame and the flow. At low Gas Expansion ratios, the total heat release rate spectra of the turbulentflame are wider in terms of dominant modes at Strouhal numbers which are linked to the mean flame height oscillations. Thus, at low Gas Expansion ratios, the vortex-flame interaction is less damped by the flame in the sense that vortices can perturb the flame front stronger. The total heat release rate trend of St−2.2 previously found for a round jet flame is also determined for the current slot jet at realistic Gas Expansion ratios indicating a general tendency to transfer energy from large to small flame structures. At high Gas Expansion ratios, an increasing Markstein length leads to an energy transfer between neighboring dominant modes in the low frequency range 1 < St < 10 and the burning area rate response becomes more important for the total heat release rate spectra of the turbulent slot flames which agrees with recent findings for a laminar premixed plane flame.
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hydrodynamic instability and shear layer effect on the response of an acoustically excited laminar premixed flame
Combustion and Flame, 2015Co-Authors: Stephan Schlimpert, Santosh Hemchandra, Matthias Meinke, Wolfgang SchroderAbstract:Combustion instabilities can cause serious problems which limit the operating envelope of low-emission lean premixed combustion systems. Predicting the onset of combustion instability requires a description of the unsteady heat release driving the instability, i.e., the heat release response transfer function of the system. This study focuses on the analysis of fully coupled two-way interactions between a disturbance field and a laminar premixed flame that incorporates Gas Expansion effects by solving the conservation equations of a compressible fluid. Results of the minimum and maximum flame front deflections are presented to underline the impact of the hydrodynamic instability on the flame and the shear layer effect on the initial flame front wrinkling which is increased at decreasing Gas Expansion. These phenomena influence the magnitude of the burning area and burning area rate response of the flame at lower frequency excitation more drastically than reduced-order model (ROM) predictions even for low temperature ratios. It is shown that the general trend of the flame response magnitudes can be well captured at higher frequency excitation, where stretch effects are dominant. The phase response is influenced by the DL mechanism, which cannot be captured by the ROM, and by the resulting discrepancy in the flame pocket formation and annihilation process at the flame tip. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved,
Sergio Uson - One of the best experts on this subject based on the ideXlab platform.
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thermoeconomic assessment of a natural Gas Expansion system integrated with a co generation unit
Applied Energy, 2013Co-Authors: Wojciech Kostowski, Sergio UsonAbstract:The paper presents a thermoeconomic assessment of an Expansion system applied in the natural Gas transportation process. The system consists of two turboexpander stages reducing the natural Gas pressure and providing mechanical energy to drive electric generators. Gas pre-heating, required to prevent hydrate formation, is performed upstream of each Expansion stage using waste heat recovered from a Gas engine, which contributes to the total system electricity production. The system constitutes a hybrid energy generation unit as the generated electricity derives partially from the physical exergy of pressurized natural Gas, and partially from the primary energy of fuel. The presented thermoeconomic description of the system comprises definitions of system quality indicators, as well as an identification of irreversibility bound to the operation of the system’s components.
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Comparative evaluation of a natural Gas Expansion plant integrated with an IC engine and an organic Rankine cycle
Energy Conversion and Management, 2013Co-Authors: Wojciech Kostowski, Sergio UsonAbstract:Abstract The aim of the paper is to propose and evaluate an innovative exergy recovery system for natural Gas Expansion, based on the integration of an internal combustion engine (ICE) and an organic Rankine cycle (ORC), and to compare it with other alternatives. Natural Gas Expansion plants are a substantial improvement to the conventional Gas pressure reduction stations, based on the throttling process, since the available physical exergy of pressurized Gas is converted into mechanical energy by means of an Expansion machine (turbine or piston expander) instead of being lost in the throttling process. However, due to the hydrate formation problem the Gas has to be pre-heated prior to the Expansion, which diminishes the system performance. An efficient method for performing this pre-heating is by the proposed system that comprises an ICE and an ORC: Pre-heating of natural Gas is carried out partially directly by the co-generation module, via the engine cooling cycle, and partially indirectly, by means of the engine exhaust Gases, which supply heat for the ORC, while the ORC condenser is connected with the lowest stage of natural Gas pre-heating. Other alternatives are the use of an ICE without ORC, the use of a boiler, and even Expansion in a throttling valve. The paper evaluates the performance of the aforementioned four configurations by means of both energy and exergy analysis. Several alternative performance indicators have been defined, calculated and discussed. Sources of irreversibilities have been identified by means of exergy analysis methodology. The fuel-product approach was used to define the exergy efficiency. Except for the reference system with a throttling valve, the analyzed systems achieve favourable values of exergy efficiency (up to 52.6%), and outstanding performance ratios (0.69–0.77), relating the energy fluxes of generated work to the fuel locally combusted in the system.
Hao Chen - One of the best experts on this subject based on the ideXlab platform.
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a hydroxyl radical detection system using Gas Expansion and fast gating laser induced fluorescence techniques
Journal of Environmental Sciences-china, 2017Co-Authors: Hao Chen, Pinhua Xie, Xingbiao Xing, Liuyi Ling, Fengyang Wang, Yihui Wang, Jianguo Liu, Wenqing LiuAbstract:An OH radical measurement instrument based on Fluorescence Assay by Gas Expansion (FAGE) has been developed in our laboratory. Ambient air is introduced into a low-pressure fluorescence cell through a pinhole aperture and irradiated by a dye laser at a high repetition rate of 8.5kHz. The OH radical is both excited and detected at 308nm using A-X(0,0) band. To satisfy the high efficiency needs of fluorescence collection and detection, a 4-lens optical system and a self-designed gated photomultiplier (PMT) is used, and gating is actualized by switching the voltage applied on the PMT dynodes. A micro channel photomultiplier (MCP) is also prepared for fluorescence detection. Then the weak signal is accumulated by a photon counter in a specific timing. The OH radical excitation spectrum range in the wavelength of 307.82-308.2nm is detected and the excited line for OH detection is determined to be Q1(2) line. The calibration of the FAGE system is researched by using simultaneous photolysis of H2O and O2. The minimum detection limit of the instrument using gated PMT is determined to be 9.4×105molecules/cm3, and the sensitivity is 9.5×10-7cps/(OH·cm-3), with a signal-to-noise ratio of 2 and an integration time of 60sec, while OH detection limit and the detection sensitivity using MCP is calculated to be 1.6×105molecules/cm3 and 2.3×10-6cps/(OH·cm-3). The laboratory OH radical measurement is carried out and results show that the proposed system can be used for atmospheric OH radical measurement.
G B Andresen - One of the best experts on this subject based on the ideXlab platform.
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a smart combination of a solar assisted absorption chiller and a power productive Gas Expansion unit for cogeneration of power and cooling
Renewable Energy, 2018Co-Authors: G B AndresenAbstract:Solar assisted absorption chiller is one of efficient cooling production systems for large cooling capacities. The main drawback of this system is that in addition to the electricity consumption, it demands for a lot of heat in relatively high temperature range of 90–120 °C, though the solar system may provide a significant portion of this heating demand. On the other hand, in Gas transmission systems, there are some Expansion stations in which Gas pressure is reduced considerably and this pressure drop causes temperature collapse in Gas stream. Power productive Gas Expansion station (PPGES) is the most recent design proponed for these stations in which the unit is equipped with power generation systems. In this work, taking advantage of this temperature fall for cooling production is proposed by coupling the station with an absorption chiller. In this case, the chiller could also provide the heating demand of the Expansion station. In order to evaluate the effectiveness of the proposed configuration, it is simulated for a case study in Denmark, i.e. Aarhus University (AU) hospital absorption chiller and Viborg Gas station. The results show that the Expansion station could provide an annual cooling production contribution of 27%. In addition, the paper presents an extensive economic assessment to prove the impact of the proposed system economically. The results show a great enhancement in the levelized cost of energy (LCOE) of the case study in case of employing the hybrid system instead of the conventional chiller.
Wojciech Kostowski - One of the best experts on this subject based on the ideXlab platform.
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thermoeconomic assessment of a natural Gas Expansion system integrated with a co generation unit
Applied Energy, 2013Co-Authors: Wojciech Kostowski, Sergio UsonAbstract:The paper presents a thermoeconomic assessment of an Expansion system applied in the natural Gas transportation process. The system consists of two turboexpander stages reducing the natural Gas pressure and providing mechanical energy to drive electric generators. Gas pre-heating, required to prevent hydrate formation, is performed upstream of each Expansion stage using waste heat recovered from a Gas engine, which contributes to the total system electricity production. The system constitutes a hybrid energy generation unit as the generated electricity derives partially from the physical exergy of pressurized natural Gas, and partially from the primary energy of fuel. The presented thermoeconomic description of the system comprises definitions of system quality indicators, as well as an identification of irreversibility bound to the operation of the system’s components.
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Comparative evaluation of a natural Gas Expansion plant integrated with an IC engine and an organic Rankine cycle
Energy Conversion and Management, 2013Co-Authors: Wojciech Kostowski, Sergio UsonAbstract:Abstract The aim of the paper is to propose and evaluate an innovative exergy recovery system for natural Gas Expansion, based on the integration of an internal combustion engine (ICE) and an organic Rankine cycle (ORC), and to compare it with other alternatives. Natural Gas Expansion plants are a substantial improvement to the conventional Gas pressure reduction stations, based on the throttling process, since the available physical exergy of pressurized Gas is converted into mechanical energy by means of an Expansion machine (turbine or piston expander) instead of being lost in the throttling process. However, due to the hydrate formation problem the Gas has to be pre-heated prior to the Expansion, which diminishes the system performance. An efficient method for performing this pre-heating is by the proposed system that comprises an ICE and an ORC: Pre-heating of natural Gas is carried out partially directly by the co-generation module, via the engine cooling cycle, and partially indirectly, by means of the engine exhaust Gases, which supply heat for the ORC, while the ORC condenser is connected with the lowest stage of natural Gas pre-heating. Other alternatives are the use of an ICE without ORC, the use of a boiler, and even Expansion in a throttling valve. The paper evaluates the performance of the aforementioned four configurations by means of both energy and exergy analysis. Several alternative performance indicators have been defined, calculated and discussed. Sources of irreversibilities have been identified by means of exergy analysis methodology. The fuel-product approach was used to define the exergy efficiency. Except for the reference system with a throttling valve, the analyzed systems achieve favourable values of exergy efficiency (up to 52.6%), and outstanding performance ratios (0.69–0.77), relating the energy fluxes of generated work to the fuel locally combusted in the system.
