Large Range Of Operating Conditions Research Articles

The Analysis of Particular Specifications of A 26650-Type Cell

Abstract The scientifical data of the batteries LiFePO4- based is short. The present paper talks about the data sheet of the usage of this kind of battery, provided by the Mather company production, data sheet which has insufficient information about the performance of this kind of battery. This paper presents the performance of a numerous experimental investigations. It entitles prescribing definite conditions to operate, for instance implemented electricity and the background heat, parameters requested to certify a future pattern precisely. In consequence, it can be searched a large range of operation conditions which can involve extreme cases regarding the fact that the battery normally is not used. Even more, the results of the experiments provide the base platform for analogy with simulations under various conditions. The on- going agreements or disparity between them are a good provider to perfect a future model and to upgrade and enhance the understanding of a battery.

Refrigeration machine modeling for exergy-based performance and optimization potential evaluation of chillers in real field plants

Abstract To investigate and optimize a refrigeration system, the behavior at various operating conditions must be known or determined. The performance and improvement possibilities may then be inferred from measurement data and compared with corresponding performance key figures. These values are typically referred to normal conditions and it is usually unknown which ones represent an adequate operation. However, it is relevant for refrigeration plant operators to have reference values for a large range of operation conditions as a baseline for determining the obtainable improvements. The present work proposes the application of steady-state models of refrigeration machines for increasing the range of applicability of the exergy-based optimization potential index method. Four different modeling approaches are evaluated and discussed: equation-fit, physical lumped parameter, refrigeration cycle and artificial neural network based models. The practical usage of the improved evaluation method is shown for the subsystem refrigeration machine on a real field installation as a case study. With the introduced additional limits for the optimization potential index, the interpretability of the results is increased. The distinction between adequate (technical requirements exceeded), acceptable (technical requirements fulfilled) and inadequate (potential for improvement) operation according to the state of the art in technology is straightforward, which is important in practice.

Numerical and Experimental Study of a Jet-and-Recirculation Stabilized Low Calorific Combustor for a Hybrid Power Plant

An atmospheric prototype burner is studied with numerical and experimental tools. The burner system is designed for operation in a hybrid power plant for decentralized energy conversion. In order to realize such a coupled system, a reliable combustion system has to be established. Numerical and experimental findings in the presented study demonstrate the capabilities of the novel burner system in suitable operation conditions. In this system, a solid oxide fuel cell (SOFC) is mounted upstream of the burner in the gas turbine system. The combination of both realizes a large operational flexibility with comparably high overall efficiency. Since the combustor is operated with SOFC off-gas, several challenges arise. Low calorific combustion needs careful burner design and numerical modeling, since the heat-loss mechanisms occur to be in the order of magnitude of thermal power output. Thus, different modeling strategies are discussed in the paper. The numerical studies are compared with experimental results and high-quality simulation results complement limited measured findings with easy-to-use low fidelity RANS models. A priori measurements are employed for the selection of investigation points. It is shown that the presented combustor system is able to cover low-calorific combustion over a large range of operation conditions, despite major heat-loss effects, which are characterized by means of numerical CFD (Computational Fluid Dynamics) modeling.

Optimisation of the Rectisol TM Design with Packing: the Rectisol TM Demonstration Unit

The RectisolTM process is used for more than 80% of the gasification projects for acid gas removal. The RectisolTM process is an efficient way to remove sulfur compounds, CO2 and other traces from syngas with chilled methanol as solvent. In order to respond to the customer need for continuous CapEx (Capital Expenditure) and OpEx (Operational Expenditure) improvement, the use of packing to replace trays in the absorber and reabsorber columns seems promising. Nevertheless, as RectisolTM is a process with a large range of operating conditions (Liquid to gas ratio (L/G), temperature, pressure, liquid loads…), the correlations from literature, mostly established for low pressure distillation, should be out of their domain of validity for some sections. This uncertainty leads to increased design margins to ensure the quality of the product gases. In order to have a better understanding of the performance of packings for RectisolTM applications, a demonstration unit has been built and connected to a commercial size RectisolTM unit in order to perform tests with packings. Gas and liquid flows circulating in the RectisolTM Demonstration Unit (RDU) are directly extracted from and returned to the main plant. The RDU generates performance data on the use of packing in the RectisolTM columns of an industrial scale application and significantly improves the understanding of the operating limits.Based on the results of the tests performed on the RDU, optimized design rules for the RectisolTM process with packing have been defined. This new design allows to significantly reduce the CapEx and OpEx compared to the unoptimized design with packing or tray design and has already been applied in industrial scale RectisolTM.

On the Combination of Large Eddy Simulation and Phenomenological Soot Modeling to Calculate the Smoke Index From Aero-Engines Over a Large Range of Operating Conditions

Nowadays, models predicting soot emissions are neither able to describe correctly fine effects of technological changes on sooting trends nor sufficiently validated at relevant operating conditions to match design office quantification needs. Yet, phenomenological descriptions of soot formation, containing key ingredients for soot modeling exist in the literature, such as the well-known Leung et al. model (Combust Flame 1991). However, when blindly applied to aeronautical combustors for different operating conditions, this model fails to hierarchize operating points compared to experimental measurements. The objective of this work is to propose an extension of the Leung model over a wide range of condition relevant of gas turbines operation. Today, the identification process can hardly be based on laboratory flames since few detailed experimental data are available for heavy-fuels at high pressure. Thus, it is decided to directly target smoke number values measured at the engine exhaust for a variety of combustors and operating conditions from idling to take-off. A large eddy simulation approach is retained for its intrinsic ability to reproduce finely unsteady behavior, mixing, and intermittency. In this framework, The Leung model for soot is coupled to the thickened flame model (TFLES) for combustion. It is shown that pressure-sensitive laws for the modeling constant of the soot surface chemistry are sufficient to reproduce engine emissions. Grid convergence is carried out to verify the robustness of the proposed approach. Several cases are then computed blindly to assess the prediction capabilities of the extended model.

Scramjet Isolator Shock-Train Leading-Edge Position Modeling Based on Equilibrium Manifold

AbstractA dynamic model showing the relationship between backpressure and shock-train leading edge (STLE) is necessary in the development of a STLE automatic control algorithm. In this research, a nonlinear dynamic model based on equilibrium manifold expansion is presented to locate the STLE position in a large range of operation conditions. The initially started flow field of a hypersonic inlet at different throttling ratios was experimentally studied at freestream Mach numbers 4.5–6.0. The nominal STLE position was defined by the pressure ratio method. The variation of STLE position with backpressure and freestream Mach number was then discussed. Testing with the experimental data, past models could only be used locally, whereas for large range of operation conditions they lose effectiveness. Therefore, the nonlinear dynamic modeling method based on equilibrium manifold is introduced to solve this problem, the simulation results, and comparisons at large range of operation conditions show its validity.

Effects of the slots on the performance of swirl-vane separator

Swirl-vane separator is responsible for the separation of more than 80% of water liquid from steam in steam generator. It is vital to understand and predict the separation performance for the design purpose. To facilitate the understanding of separation process and provide data for the verification of CFD simulation, experiments on small-scale swirl-vane separators are carried out to study the effect of the slots on the separation performance. Tests were performed with the water superficial velocity ranging from 3.3×10−4m/s to 1.4×10−2m/s and the air superficial velocity in the range of 5.7–12.4m/s. The separation efficiency in the studied cases is in the range of 77.3–99.9%. It depends mainly on the superficial velocity of water. For the pressure drop, the influence of air superficial velocity is dominant. Moreover, it is found that the distribution of the separated water is sensitive to both the water superficial velocity and the air superficial velocity. The fraction of water separated from the down-comer increases with the decrease in the air superficial velocity, while the opposite trend is observed for the fraction of water separated from the assistant barrel. Increasing the height of the slot, upper riser and orifice ring results in a larger fraction of water collected in the down-comer. By adding the tangential slots, separation efficiency is improved at a high water superficial velocity. To assure good separation performance in a large range of operation conditions, usage of the slot is recommended.

A model to predict R134a refrigerant leakage through the radial clearance of rolling piston compressors

In this paper a non-isothermal two-phase model for oil–R134a refrigerant mixture flow is presented to predict the R134a leakage through the radial clearance of rolling piston compressors. The flow is divided in a liquid single-phase region and in a two-phase region, in which the homogeneous model is used to simulate the flow. The refrigerant leakage is determined using the mixture mass flow rate and the refrigerant mass fraction variation along the flow. The results are obtained for inlet pressures varying from 200 to 700 kPa, inlet temperatures ranging from 40 to 60 °C, and minimal clearances between 10 and 60 μm. The results are firstly compared to existing isothermal model data, showing that there is a significant difference between the leakage flow rates predicted by isothermal and non-isothermal models. Finally, a useful general equation for compressor designers is proposed to calculate the refrigerant leakage for a large range of operation conditions.

Water‐gas shift reaction kinetics over μ‐structured Pt/CeO2/Al2O3 catalysts

AbstractPlatinum/ceria/alumina catalysts have been prepared in the microchannels of stainless steel platelets. These catalysts are very active for the water‐gas shift reaction between 250–400°C. The use of microreactors as kinetic devices has a clear advantage that the thin catalyst film allows the determination of the intrinsic kinetics even in the case of fast reactions. However, the channel design should be such that plug flow conditions are favored. The kinetics of the water‐gas shift reaction, free from internal diffusion limitations, have been studied over thin catalyst layers over a large range of operation conditions. The reaction rate is almost zero‐order in carbon monoxide and strongly inhibited by the partial pressure of hydrogen and to a lesser extent to that of carbon dioxide. An overall activation energy of 76.8 ± 2 kJ/mol has been measured. The data are best described by a dual‐site mechanism, where platinum provides an adsorption site for carbon monoxide and ceria an adsorption site for water. The rate‐determining step involves the formation of a complex between a carboxyl species and a hydroxyl group that decomposes over a free platinum site into carbon dioxide and hydrogen. © 2006 American Institute of Chemical Engineers AIChE J, 2006

Experimental Study on the Transition in the Velocity of Individual Taylor Bubbles in Vertical Upward Co-Current Liquid Flow

An experimental study is presented concerning the transition in the velocity of individual Taylor bubbles in vertical co-current liquid flow. Velocities of individual Taylor bubbles rising in co-current liquids (kinematic viscosities from 10 −6 to 5.7 × 10 −6 m 2 s −1 ) in acrylic columns of 22 mm, 32 mm and 52 mm internal diameter were measured for a wide range of Reynolds number of the flowing liquid using two non-intrusive experimental techniques. The measuring section was located at 6.0 m from the gas injection. The operating conditions used correspond to inertial controlled regime. The data showed an unexpected feature of the bubble motion: the velocity coefficient C changes even when the flow regime in the liquid ahead the bubble is still laminar, i.e., the transition in the bubble velocity starts at liquid Reynolds numbers much lower than 2100. Additional experiments, employing PIV measurements, showed a developed laminar liquid flow ahead the bubble nose. Based on a dimensional analysis, the most important dimensionless numbers for the phenomena were identified and, after processing all data, an empirical correlation was established to predict the velocity coefficient C for a large range of operation conditions. This information is very important for vertical two-phase slug flow modelling.