Gas Flow Duct Research Articles

Analysis of systems for cooling liquid injection in turbine engine gas flow duct

The subject of this article is a system for cooling liquid injection in gas flow duct of aviation gas-turbine engine (GTE). The goal is to soften the acuteness of contradictions between economic and ecological requirements; ecological requirements and technological limitations; marketing and service life requirements, due to the application of a system for cooling liquid injection in gas flow duct of GTE. The tasks to be solved are: development of a classification, revealing the advantages and drawbacks of various technologies of systems for cooling liquid injection in the gas flow duct of GTE, analysis of the investigation methods used for cooling liquid injection systems, and analysis of the system application experience in various aircraft (A/C) and A/C projects. The methods used are: search of corresponding information sources on the Internet and analysis based on operational experience in the aviation branch. The following results were obtained: in terms of found information sources, classification of systems for cooling liquid injection in the gas flow duct of GTE has been developed; advantages and drawbacks of various cooling liquid injection technologies have been formulated; it was revealed that, three types of methods (experimental, computational fluid dynamic, and analytical) are used for cooling liquid injection system investigation; results of available research are briefly presented; application of cooling liquid injection systems in A/C with the purpose of extending the airplane flight envelop, increasing of aviation GTE thrust/power, and decreasing emissions of nitrogen oxides during takeoff have been analyzed. Conclusions. The scientific novelty of the results obtained is as follows: 1) information from numerous sources of literature that clarifies classification, advantages and drawbacks of various technologies of cooling liquid injection in the gas flow duct, development of these system investigations by various methods, and experience of these systems application both in real A/C, and in A/C projects were collected in the review article; 2) necessity in development of transport category A/C design methodology taking into account installation of the system for cooling liquid injection in the gas flow duct of GTE has been revealed. The goal and challenges of the following research in this field are outlined.

Формування динамічних моделей газотурбінних двигунів для використання в системах автоматичного керування та контролю

The subject of the study is the process of forming a mathematical model (MM) of an aviation gas turbine engine, which provides the calculation of parameters of the work process in stable and transient operating modes for use in the evaluation of dynamic characteristics, in the analysis and synthesis of automatic engine and aircraft control systems, as part of aviation simulators, and in on-board control and diagnostics algorithms. The goal is to substantiate the structure and methodology of MM formation, intended for use in real and accelerated time scale systems. Task: formulation of requirements for MM, substantiation of the interaction between static and dynamic submodels, substantiation of the composition of arguments and the way of considering the influence of external conditions, as well as the position of the elements of the mechanization of the gas flow duct. For this, the methods of the theory of airjet engines are used. The following results were obtained: the requirements for MM of aircraft gas turbine engines designed to solve the problems of engine and aircraft control were formulated, and the structural forms of MM were substantiated, which ensure high accuracy of modeling with minimal complexity and the possibility of real-time implementation. The scientific and practical novelty of the obtained results is as follows: the requirements for dynamic MM of aircraft engines have been summarized, the problems of structural implementation and combination of static and dynamic submodels, the rational selection of their input parameters and considering the influence of external conditions on static and dynamic characteristics have been analyzed, the software implementation of MM in in the Matlab Simulink environment of a two-shaft turbofan engine and compared the simulation results obtained using the developed simplified MM and the original nonlinear thermo-gas-dynamic model based on the solution of the joint operation equations of components. It is shown that in the working range of modes, the MM error does not exceed 5%, the dynamic errors of the rotor rotation frequencies are less than 4%, the compressor pressure and gas temperature are less than 7%, or the thrust is less than 10%. Errors in estimating the duration of acceleration and deceleration of the engine are within 0.2...0.6 s.

Investigating the effects of reactant gas flow geometrical shape on the performance of solid oxide fuel cell

ABSTRACT Solid oxide fuel cells powered by renewable fuels will be a panacea for our current challenges to meet the global energy demand and mitigate climate changes stemming from the widespread use of carbon-rich fuels. Accordingly, this numerical investigation has examined the geometrical shape effects of reactant gas ducts, and the thickness of electrodes on solid oxide fuel cell performance. The model was also validated using the experimental result of a rectangular shape gas flow duct conducted at Dr. T. Nejat Veziroğlu Clean Energy Research Center of Niğde Ömer Halisdemir University in Türkiye. Thus, the finding of this work disclosed that the semicircular gas flow duct has outstanding performance following rectangular, trapezoidal and triangular geometrical shapes. The additional remarkable results of this work are that the shape of the reactant gas flow channel and the thickness of the cathode have more substantial effects on airflow than fuel flow under identical electrolyte thickness. The finding also revealed that a peak power density has been achieved when the thickness of an anode gets thicker up to a certain limit then it is sharply decreasing. On the contrary, the performance of the model is increasing as the thickness of the air electrode is increasing. 9 Solid oxide fuel cells powered by renewable fuels panacea for our current challenges to meet the global energy demand and mitigate climate changes stemming from the widespread use of carbon-rich fuels rectangular shape gas flow duct conducted at Dr. T. Nejat VeziroğluNiğdeHalisdemir peak power density has been achieved when the thickness of an anode gets thicker up to a certain limitis decreasingincreasing.

Fine particle removal by a two-stage electrostatic precipitator with multiple ion-injection-type prechargers

A novel two-stage electrostatic precipitator (ESP) with multiple ion injection type chargers and parallel collection plates was developed and shown to efficiently collect particles from the corrosive waste gas discharged from semiconductor and optoelectronic processes. Multiple carbon brush electrodes for the generation of ions were located outside of the main gas flow, but the injection of clean air and induced voltage between the outer and inner plates of the charging stage carried ions into the main gas flow; thus, gases and particles in the main flow did not corrode or contaminate the charger. The particle collection performance of the ESP was evaluated experimentally for 0.3 μm particles, PM (Particular matter) 10, and PM 2.5 by varying the application voltages to the charging stage, main gas flow rate, and distance of the carbon brush discharge electrode from the main gas flow duct. The novel ESP achieved particle collection efficiency of 89.5% and 99.5% at the best condition when the voltage was applied to only the charging stage and to both the charging and collection stages, respectively. The particle collection efficiency of the charging stage only and the two-stage ESP was characterized according to the corona discharge power and main flow rate based on Deutsch's collection theory. Also, a simplified 2D simulation results show that the electric field is very high not only near outer carbon fibers but also near the outer metallic electrode edge.

Heat Transfer Enhancement by Vortex Generators for Compact Heat Exchanger of Automobiles

The paper describes the effects of heat transfer enhancement and gas-flow characteristics by wing-type-vortex-generators inside a rectangular gas-flow duct of a plate-fin structure exhaust gas recirculation (EGR) cooler used in a cooled-EGR system. The analyses are conducted using computational fluid dynamics (CFD). The numerical modelling is designed as a gas-flow rectangular duct of an EGR cooler using two fluids with high temperature gas and coolant water whose flow directions are opposite. The gas-flow duct used to separate two fluids is assembled with a stainless steel material. The inlet temperature and velocity of gas flowed inside gas-flow duct are 400°C and 30 m/s, respectively. Coolant water is flowed into two ducts on both a top and a bottom surface of the gas-flow duct, and the inlet temperature and velocity is 80°C and 0.6 m/s, respectively. Wing-type-vortex-generators are designed to achieve good cooling performance and low pressure drop and positioned at the center of the gas-flow duct with angle of inclination from 30 to 150 degrees at every 15 degrees. The temperature distributions and velocity vectors gained from numerical results were compared, and discussed. As a result, it is found that the vortices guided in the proximity of heat transfer surfaces play an important role in the heat transfer enhancement and low pressure drop. The collapse of the vortices is caused by complicated flow induced in the corner constituted by two surfaces inside gas-flow duct.

Performance of Ultrafine Particle Collection of a Two-Stage ESP Using a Novel Mixing Type Carbon Brush Charger and Parallel Collection Plates

A novel two-stage electrostatic precipitator (ESP) for information technology manufacturing industries was developed. It uses a mixing type carbon brush charger located outside of the main gas flow duct to completely prevent contact of the polluted gases with the chargers, and applies an additional electric field between the upper and bottom plates of the charging stage to enhance collisions between ions and particles, thereby increasing the particle charges. The performance of the ESP was evaluated experimentally for ultrafine particles with a mean diameter of 100 nm based on number, and of 200 nm based on surface area by varying the voltages of the chargers and for generating the additional electric field, and by varying the number of the chargers. Finally, the collection efficiencies of the ESP were compared to those obtained from Deutch's collection theory using the average experimental particle charges. The total air flow rate used in the tests was approximately 110 L/min with a 10:1 ratio of the main and mixing flows in the ESP, and the applied voltages of the charger and additional electric field were –10 to –22 kV, and –5 to –10 kV, respectively. Collection efficiencies in the ESP were linearly proportional to the increase in the number of chargers and the increase in the applied voltage to the chargers, which in turn were inversely proportional to the increase in the applied voltage used to generate the additional electric field. A collection efficiency of the ESP of > 90% was obtained at a flow rate of 110 L/min, corresponding to flow speeds of approximately 0.19 m/s through the charging stage and 0.23 m/s through the collection cell based on the total particle number at an applied voltage to the triple chargers of –15 kV and an additional electric field between the upper and bottom plates in the charging stage of –6 kV/100 mm.

On reaction coupled transport phenomenon in reformer ducts

In compact steam reformer the probability of component degradation and failure depends strongly on the local temperature gradients coupled by various transport processes and chemical reactions in multi-functional materials. In this paper, the modeling and analysis of coupled mass transport and heat transfer processes are conducted for compact design steam reformer duct, which consists of a porous layer for the reforming reactions of methane, the fuel gas flow duct and solid plate. A fully three-dimensional computational fluid dynamics (CFD) approach is applied to calculate transport processes and effects of thermal conductivities of the involved multi-functional materials on reforming reaction rates and heat transfer/temperature distributions, in terms of surface temperatures/heat fluxes and Nusselt numbers. The steam reformer conditions such as mass balances associated with the chemical reactions and gas permeation to/from the porous layer are implemented in the calculation. The results reveal that a small thermal conductivity of the porous layer and solid plates promote high reforming reaction rates, and the convective heat transfer at the top interface varies more significantly along the main flow reformer duct.

Analysis of Heat Transfer and Transport Processes in SOFCS Involving Internal Reforming Reactions

The heat transfer rates in solid oxide fuel cells (SOFCs) are controlled by various operating and design parameters and have significant effects on chemical reactions and coupled transport processes. In this article, the considered composite duct consists of a porous anode layer for the internal reforming reactions of methane, the fuel gas flow duct, and the solid plate. A fully three-dimensional calculation code is employed to analyze heat transfer and combined effects of internal reforming/electrochemical reactions on the coupled transport processes, with the purpose to reveal the importance of various parameters. The results show that the internal reforming reactions are mostly confined within 200–300 μm into the anode porous layer and almost no methane reaches the triple phase boundary (TPB) after the first 10% of the duct length. The operating temperatures have significant effects on the chemical reactions, fuel gas distribution, and overall performance. This study also evaluated the convective heat transfer in the fuel flow duct, in terms of interface thermal boundary/temperature gradients and convective heat transfer coefficients.

The CFD approach to analyse transport phenomena-coupled chemical reactions relevant for methane reformers

Various transport phenomena in conjunction with chemical reactions are strongly affected by reformer configurations and the properties of the involved porous catalyst layers. The considered composite duct is relevant for a methane steam reformer and consists of a porous layer for the catalytic chemical reactions, the fuel gas flow duct and the solid plate. In this paper, a fully three-dimensional calculation method is developed to simulate and analyse the reforming reactions of methane, with the purpose of revealing the importance of design and operating parameters. The reformer conditions, such as mass balances associated with the reforming reactions and gas permeation to/from the porous catalyst reforming layer, are applied in the analysis. The results show that the characteristic parameters have significant effects on the transport phenomena and the overall reforming reaction performance.

The Performance Analysis of a Multi-Duct Proton Exchange Membrane Fuel Cell Cathode

A 3-D numerical study was carried out first to analyze flow, heat and mass transfer as well as current distribution in a single half-cell cathode duct of a Proton Exchange Membrane (PEM) fuel cell. From practical point of view, it is necessary to put the appropriate number of cells in a stack. Hence, the above study on a single half-cell is extended to a multiple ducts. Due to multi-duct configuration the assumption of uniform flow distribution would no longer hold true. Therefore, the duct flow maldistribution is considered in the simulation of the multiple ducts. The flow arrangement of the PEM fuel cell resembles that of the plate heat exchangers. Hence, the various types of flow distributions pertinent to the plate heat exchangers are applied to the PEM fuel cell ducts and their effects on heat and mass transfer as well as current distribution are studied in detail. The water formed at the active surface due to the electrochemical reaction diffuses through the porous layer and eventually enters the gas flow duct. A high gas velocity removes the product water at a faster rate from the duct. In nominal-linear and hyperbolic flow distribution cases, the mass fraction of water in the duct is more than that in severe-linear and hyperbolic flow distribution cases. This means that the membrane retains higher water content in nominal distribution cases. This in turn results in higher membrane conductivity and lower ohmic loss. This is the reason for better performance for nominal maldistribution cases over the severe maldistribution cases.

Analysis of parameter effects on transport phenomena in conjunction with chemical reactions in ducts relevant for methane reformers

Various transport phenomena in conjunction with chemical reactions are strongly affected by reformer configurations and properties of involved porous catalyst layers. The considered composite duct is relevant for a methane steam reformer and consists of a porous layer for the catalytic chemical reactions, the fuel gas flow duct and solid plate. In this paper, a fully three-dimensional calculation method is developed to simulate and analyze reforming reactions of methane, with purpose to reveal the importance of design and operating parameters grouped as three characteristic ratios. The reformer conditions such as mass balances associated with the reforming reactions and gas permeation to/from the porous catalyst reforming layer are applied in the analysis. The results show that the characteristic ratios have significant effects on the transport phenomena and overall reforming reaction performance.

Parameter Effects on Transport Phenomena in Conjunction with Internal Reforming Reactions in Intermediate Temperature SOFCs

Various transport phenomena in conjunction with chemical reactions are strongly affected by solid oxide fuel cells (SOFCs) configurations and properties of involved porous anode. The considered composite duct is relevant for an intermediate temperature (600-800oC) SOFC and consists of a porous anode layer for the internal reforming reactions of methane, the fuel gas flow duct and solid plate. In this paper, a fully three-dimensional calculation method is developed to simulate and analyze internal reforming reactions, with purpose to reveal the importance of design and operating parameters outlined as three characteristic ratios. The SOFC conditions such as mass balances associated with the internal reforming reactions and gas permeation to/from the porous anode are applied in the analysis. The results show that the characteristic ratios have significant effects on the transport phenomena and overall reforming reaction performance.

Numerical simulation of effects of flow maldistribution on heat and mass transfer in a PEM fuel cell stack

A 3D numerical study was carried out to analyze flow, heat and mass transfer first in a single half-cell cathode channel of proton exchange membrane (PEM) fuel cell. From practical point of view, it is necessary to put the appropriate number of cells in a stack. Hence, the above study on a single half-cell is extended to a stack of channels. Due to stacking, the assumption of uniform flow distribution would no longer hold true. Therefore, the channel flow-maldistribution is considered. The water formed at the active surface due to the electrochemical reaction diffuses through the porous layer and eventually enters the gas flow duct. The higher gas velocities in the duct result in faster water vapour removal which leads to a lower value of water vapour into the duct and hence a lower Nusselt number.

Analysis of chemical-reaction-coupled mass and heat transport phenomena in a methane reformer duct for PEMFCs

Mass, heat and momentum transport processes are coupled with catalytic chemical reactions in a methane steam reforming duct. It is often found that endothermic and exothermic reactions in the ducts are strongly integrated by heat transfer from adjacent catalytic combustion ducts. In this paper, a three-dimensional calculation method is developed to simulate and analyze reforming reactions of methane, and the effects on various transport processes in a steam reforming duct. The reformer conditions such as mass balances associated with the reforming reactions and gas permeation to/from the porous catalyst reforming layer are applied in the analysis. The predicted results are presented and discussed for a composite duct consisting of a porous catalyst reaction layer, the fuel gas flow duct and solid layers. Parametric studies are conducted to reveal the importance of reformer designs and operating conditions. The results show that the variables, such as porous layer configuration, temperature and catalyst loading, have significant effects on the transport processes and reformer performance.

A NUMERICAL INVESTIGATION OF GAS FLOW AND HEAT TRANSFER IN PROTON EXCHANGE MEMBRANE FUEL CELLS

Gas flow and heat transfer in both cathode and anode channels have been modeled and analyzed for proton exchange membrane fuel cells. The simulated channel consists of a porous electrode layer (anode or cathode), gas flow duct, and solid current collector. The characteristics of gas flow and heat transfer in terms of friction factor and Nusselt number were investigated by a three-dimensional computational fluid dynamics code (CFD). A combined thermal boundary condition, which is unique for fuel cells and interfacial conditions between the porous layer, the gas flow duct, and the solid current collector, were clarified and applied in the calculation. The heat generation and mass transport processes have been modeled and implemented into the code by proper source terms. Furthermore, the effects of various parameters on the generation of heat, mass transport process, gas flow, and heat transfer are assessed also. These parameters include current density and permeability, effective thermal conductivity, and thickness of porous diffusion layer.

Three-dimensional computational analysis of gas and heat transport phenomena in ducts relevant for anode-supported solid oxide fuel cells

Various transport phenomena occurring in an anode duct of medium temperature solid oxide fuel cell (SOFC) have been simulated and analyzed by a fully three-dimensional calculation method. The considered composite duct consists of a thick porous layer, the gas flow duct and solid current interconnector. Unique fuel cell boundary and interfacial conditions, such as the combined thermal boundary conditions on solid walls, mass transfer associated with the electrochemical reaction and gas permeation across the interface, were applied in the analysis. Based on three characteristic ratios proposed in this study, gas flow and heat transfer were investigated and presented in terms of friction factors and Nusselt numbers. It was revealed that, among various parameters, the duct configuration and properties of the porous anode layer have significant effects on both gas flow and heat transfer of anode-supported SOFC ducts. The results from this study can be applied in fuel cell overall modeling methods, such as those considering unit/stack level modeling.