Gas Turbine Research Articles

Laser surface alloying of Hastelloy X superalloy with Amdry 365 powder: Microstructural evolution and microhardness

Laser surface alloying is a surface modification technique that melts coat powder and substrate with high laser power density. This study aims to improve the properties of Hastelloy X, a Ni-based superalloy used for gas turbine components, by applying a NiCoCrAlY coating using laser surface alloying. The purpose of this study was to investigate the process parameters including laser scanning speed, laser power, and stand-off distance on the microstructure and microhardness of the alloying zones. The findings indicate that different microstructures were formed in different alloying zones such as cellular, columnar, and equiaxed. The results also revealed the presence of β and γ phases in the dendritic and interdendritic regions. The microhardness at the interface was higher than that of the other alloying areas due to the increased content of the Mo element. This study concluded that the properties of Hastelloy X can be improved by using NiCoCrAlY powder through a laser alloying process.

Analysis of the features of the operating conditions of modern gas turbine blades and review of methods for determining their high-temperature strength parameters

The subject of the study is modern methods and materials for the manufacture of gas turbine blades, as well as approaches and methods for assessing their dynamic and static strength under high-temperature loading. The first purpose of the article is to describe the main methods of manufacturing turbine blades, provide examples of the materials used and the features of their crystal structure. The second purpose of the article is to review approaches to ensuring the dynamic and static strength parameters of single-crystal turbine blades, in particular, to avoid dangerous resonance modes, to study the parameters of anisotropic creep, high-temperature fatigue life, and long-term strength. The goal of the article is to highlight the main advantages and disadvantages of existing methods, approaches and techniques for assessing and ensuring high-temperature strength parameters of turbine blades under static and dynamic loading, in order to select the objectives of further research. Methods used to create the publication: methods of analysis and comparison, which were used to search and compare open literature sources of information in accordance with the purpose of the article, as well as the method of deduction, which was used to identify the main shortcomings of existing methods for assessing the high-temperature strength of gas turbine blades under static and dynamic loading to outline the goals of further research. The following results have been obtained. Literature sources related to the methods of manufacturing turbine blades, namely, directional crystallization and single-crystal casting, were analyzed. The advantages of single-crystal alloys for the manufacture of turbine blades, namely increased heat strength, heat resistance, fatigue strength, durability and crack resistance, are emphasized. The main modern methods for assessing the high-temperature strength of gas turbine blades with regard to the anisotropic characteristics of single-crystal alloys are analyzed and described. Conclusions. This publication presents information about gas turbine blades, in particular, provides meaningful information about the methods of their manufacture, as well as the materials used to produce them. The study analyses and identifies the main damaging effects on gas turbine blades during their operation. The material describes the achievements of scientists who have developed numerical and experimental methods for assessing the impact of the anisotropic characteristics of single-crystal nickel heat-resistant alloys on the fatigue strength, durability and creep of turbine blades.

Introduction of Axisymmetric Grooves as a Tip Seal Treatment for Small-Core Turbines

Abstract The aerodynamic penalties associated with the tip gap flow in axial turbines remains a challenging problem for turbine manufacturers. As modern gas turbines with small-core architectures are brought online, the influence of the tip gap continues to grow. While technologies to reduce tip losses have been implemented into the blades, little attention has been paid to the casing around the rotor. In this study, an introduction of axisymmetric groove enhancements for the casing are examined computationally. These studies use the National Experimental Turbine (NExT) geometry, an engine-representative high-pressure turbine blade. Steady, RANS simulations are used to assess the basic characteristics of grooves, such as depth, location, and arrangement. The objective of this introductory study was to determine the feasibility of impacting the tip leakage vortex formation and the associated losses in rotor efficiency. Furthermore, analyses were done with different tip gap heights along with both flat- and squealer-tipped blades. Tip seals with a single groove are demonstrated to improve rotor aerodynamic efficiency relative to ungrooved seals by 0.4 points when applied to flat-tipped rotor blades and 0.15 points with squealer tips. Arrays of grooves show improvements for flat-tipped blade performance by 0.76 points, while having little additional aerodynamic effect on squealer tip over single-groove designs. Finally, grooved tip seals appear to exert greater influence on turbine aerodynamic performance at larger tip gaps, indicating that grooved tip seals alter the sensitivity of rotor performance to the tip clearance gap.

Scientific and technical business trips of scientists to Germany in the 1920s as one of the factors in the development of the Leningrad industrial complex

In the article, the author examines Leningrad scientists’ business trips to Germany in the 1920s as one of the directions of technology transfer mechanism implementation. The relevance of the study lies in the fact that the example of Leningrad shows the substance of this line of transfer, as well as a general assessment of its effectiveness. Thus, the historical memory of a unique experience is restored, which may be of interest at the present stage of Russia’s development. The study focuses on the problems of scientific and technical international cooperation with local scientific communities. This fills a gap in historical scholarship, as the specifics of such cooperation are considered mainly either at a community level or at the level of an individual organisation or individual. The main goal of the study is to determine the extent to which the contacts between Leningrad scientists and German specialists, established in the 1920s, influenced the modernisation of the Leningrad industrial complex. Research objectives are: to analyse the main cooperation directions between Leningrad scientists and German institutes, scientific centres, and laboratories in the period under consideration; to classify business trips, to identify general patterns, and to analyse the specific features of different types of business trips and their results. The article draws on a broad source base that includes previously unpublished archive documentation of the Russian State Academy of Economics, Central State Archive of St. Petersburg, and the Central State Academy of Technical Sciences of St. Petersburg. In the course of the study, drawing on specific cases, it was demonstrated that the active involvement of scientific personnel in Petrograd/Leningrad contributed to the accelerated development of a number of Soviet industries, such as diesel engineering, turbo and hydraulic turbine engineering, chemical processing of peat and shale, etc., made it possible to form the necessary technical base, as well as develop the human resources of scientific institutions and enterprises of the city.

Performance prediction of gasification-integrated solid oxide fuel cell and gas turbine cogeneration system based on PSO-BP neural network

By utilizing syngas produced from biomass gasification as fuel in a combined heat and power (CHP) system comprising solid oxide fuel cells (SOFC) and gas turbines (GT). This green technology uses syngas from biomass gasification in a CHP system with SOFC and GT. It integrates biomass gasification with new energy sources and has great potential for renewable energy. However, performance prediction remains challenging due to the complex multi-physics coupling between the bubbling fluidized bed gasifier (BFBG) and the SOFC-GT system. In addition, the system has various real-world applications and requires a universal method to comprehensively analyze its thermoelectric performance during operation. Thus, a robust theoretical model is essential for investigating the application of the BFBG-SOFC-GT system. In this study, a novel BFBG-SOFC-GT system utilizing 15 different types of biomass gas is constructed using Aspen Plus, and a particle swarm optimization-backpropagation (PSO-BP) neural network model is developed for performance prediction. Numerical simulations are also carried out to validate and analyze the integrated system. The effects of gasification temperature, steam-to-biomass mass (S/B) value, and anode temperature on SOFC voltage and current density, as well as the system's electrical efficiency and CHP efficiency, are analyzed. The results demonstrate that increasing gasification temperature decreases SOFC voltage, increases current density, and reduces both electrical and cogeneration efficiency. Conversely, increasing the S/B value and anode temperature leads to higher SOFC voltage, lower current density, and improved electrical and cogeneration efficiency. Additionally, the PSO-BP neural network model's effectiveness in predicting system performance is validated. The results show that, in error evaluations of voltage, current density, electrical efficiency, and cogeneration efficiency, R2 exceeds 0.98, MAPE is below 0.06, and RMSE is less than 0.33.

Development of Detailed and Reduced Chemical Kinetic Models for Ammonia Gas Turbines

Abstract The power generation sector has been recently moving toward decarbonization, and there is an increased interest in replacing conventional fossil fuels with fuels that produce reduced/zero carbon emissions. One such fuel is ammonia (NH3). However, ammonia is hard to ignite, has a low flame speed, and produces a significantly large amount of nitrogen oxide (NOx) emissions. Hence, using 100% ammonia as fuel in gas turbines requires significant modifications and the development of novel combustors. Blending hydrogen with ammonia, however, helps in having better control over the combustion properties. For example, a 70%/30% mixture of NH3/H2 mixture has a flame speed comparable to natural gas. Before utilizing hydrogen-blended ammonia in an actual gas turbine combustor, thorough simulation studies are required to evaluate its performance, possible hazards, and emissions. The literature lacks well-validated chemical kinetic models for the combustion of hydrogen-blended ammonia for undiluted mixtures at gas turbine-relevant conditions (∼20 bar). Most models available in the literature have been developed for ammonia extremely diluted in diluents such as argon or nitrogen. Hence, in this work, we develop a detailed chemical kinetic model for hydrogen-blended ammonia combustion and validate it with a wide range of experimental data for both dilute and undiluted mixtures relevant to gas turbine operating conditions. We outline the strengths and weaknesses of the current mechanism to aid future users of our chemical kinetic mechanism. The detailed chemical kinetic mechanism was reduced to a smaller version (32 species mechanism) without significant loss in accuracy using the directed relation graph with error propagation (DRGEP) and full species sensitivity analysis. The resultant mechanism can predict a wide range of experimental results with the least cumulative error and will be a valuable tool in computational fluid dynamics (CFD) simulations that will enable the development of gas turbines for zero-carbon power generation.

A mMSA-FOFPID controller for AGC of multi-area power system with multi-type generations

The exceptional growth in the penetration of renewable sources as well as complex and variable operating conditions of load demand in power system may jeopardize its operation without an appropriate automatic generation control (AGC) methodology. Hence, an intelligent resilient fractional order fuzzy PID (FOFPID) controlled AGC system is presented in this study. The parameters of controller are tuned utilizing a modified moth swarm algorithm (mMSA) inspired by the movement of moth towards moon light. At first, the effectiveness of the controller is verified on a nonlinear 5-area thermal power system. The simulation outcomes bring out that the suggested controller provides the best performance over the lately published strategies. In the subsequent step, the methodology is extended to a 5-area system having 10-units of power generations, namely thermal, hydro, wind, diesel, gas turbine with 2-units in each area. It is observed that mMSA based FOFPID is more effective related to other approaches. In order to establish the robustness of the controller, a sensitivity examination is executed. Then, experiments are conducted on OPAL-RT based real-time simulation to confirm the feasibility of the method. Finally, mMSA based FOFPID controller is observed superior than the recently published approaches for standard 2-area thermal and IEEE 10 generator 39 bus systems.

A Static/Dynamic Coupled Harmonic Balance Method for Dry Friction Systems Containing Rigid Body Modes

Abstract A harmonic balance method for underconstrained dry friction systems containing rigid body modes (HBM-RBM) is proposed. This method aims to overcome the encountered obstacle when applying the harmonic balance method to turbine blades damped by underplatform dampers (UPDs). The inspiration for HBM-RBM comes from the free interface modal synthesis method. The key innovation involves deriving the elastic inversion of the singular stiffness matrix through the elimination of rigid body modes. In this way, the general HBM framework can be adopted, and the frequency response of underconstrained dry friction systems can be solved in a static/dynamic coupled manner. The accuracy and efficiency are both verified on a lumped parameter model and a finite element model of turbines with UPDs from a real gas turbine. A comparative study between the HBM-RBM and the commonly adopted way of imposing artificial grounding springs (HBM-AGS) is conducted. Results demonstrate that the HBM-RBM holds a significant advantage over HBM-AGS, as it eliminates the need for artificial grounding springs (AGS) and avoids the necessity for numerous trial cases to determine AGS stiffness.

Probabilistic Modeling Geometric Tolerance and Low Cycle Fatigue Life of Gas Turbine Compressor Blade

Abstract This paper presents a probabilistic low cycle fatigue (LCF) assessment for geometric tolerances on high load contact surfaces of gas turbine compressor blades. The typical patterns of the geometric deviations for the root contact flank of the compressor blades are identified and characterized according to coordinate measurement machine (CMM) measurements of the blade root. These typical patterns are closely related to the root form manufacture tools and process. Finite element (FE) models for the typical geometric deviation patterns are created based on nodal coordinates transformation of the surface nodes on the blade root contact flanks and radius. An optimized blade root profile tolerance is established, which enables significant cost saving. The elastic-plastic FE analysis with nonlinear contact model, material strain-life test, response surface, and constrained Monte Carlo simulation are used to create a probabilistic LCF life model for the optimized tolerance. The model quantifies the effect of the geometric deviations, blade mass, and material property on the blade LCF life. The result shows that with the optimized tolerance, the probability of blade LCF failure is very low and acceptable. It is also shown that the strain life material property is the most critical factor for the LCF failure. The root profile tolerance and blade mass are seen to have a much weaker effect on the blade LCF life.

Multi Combustor Turbine Engine Acceleration Process Control Law Design

Abstract Focusing on the collaborative fuel supply and acceleration problem of multi combustor turbine engine, a variable geometry composite regulation acceleration control law design method based on the combination of compressor intermediate stage air bleed(CIB) and low-pressure turbine guide vanes(LTGV) is proposed. The multi combustor collaborative fuel supply law and variable geometry regulation law during acceleration process are obtained by Particle Swarm Optimization-Sequence Quadratic Program (PSO-SQP) optimization, and the composite regulation acceleration control strategy of dual/single combustion chamber idle acceleration process is explored. The multi combustor acceleration process simulation results indicate that the variable geometry composite regulation method can effectively alleviate the stability margin limitation of the compressor during the initial acceleration stage. Compared with conventional acceleration methods, the maximum relative reduction in acceleration time of our method reaches 26%; Enhancing the combustion exergy efficiency during the acceleration process can significantly improve the engine's acceleration performance.; For the acceleration process from single combustion chamber idle operation to normal operation of a dual combustion chamber, simultaneous fuel supply from both combustion chambers during acceleration has a shorter acceleration time. The research results of this paper can provide important references for the design of transition state control systems for multi combustor turbine engines.

Advanced hybrid neural network techniques for minimizing gas turbine emissions

Purpose Emissions have significant environmental impacts. Hence, minimizing emissions is essential. This study aims to use a hybrid neural network model to predict carbon monoxide (CO) and nitrogen oxide (NOx) emissions from gas turbines (GTs) to enhance emission prediction for GTs in predictive emissions monitoring systems (PEMS). Design/methodology/approach The hybrid model architecture combines convolutional neural networks (CNN) and bidirectional long-short-term memory (Bi-LSTM) networks called CNN-BiLSTM with modified extrinsic attention regression. Over five years, data from a GT power plant was uploaded to Google Colab, split into training and testing sets (80:20), and evaluated using test matrices. The model’s performance was benchmarked against state-of-the-art emissions prediction methodologies. Findings The model showed promising results for GT CO and NOx emissions. CO predictions had a slight underestimation bias of −0.01, with root mean-squared error (RMSE) of 0.064, mean absolute error (MAE) of 0.04 and R2 of 0.82. NOx predictions had an RMSE of 0.051, MAE of 0.036, R2 of 0.887 and a slight overestimation bias of +0.01. Research limitations/implications While the model demonstrates relative accuracy in CO emission predictions, there is potential for further improvement in future research. Practical implications Implementing the model in real-time PEMS and establishing a continuous feedback loop will ensure accuracy in real-world applications, enhance GT functioning and reduce emissions, fuel consumption and running costs. Social implications Accurate GT emissions predictions support stricter emission standards, promote sustainable development goals and ensure a healthier societal environment. Originality/value This paper presents a novel approach that integrates CNN and Bi-LSTM networks. It considers both spatial and temporal data to mitigate previous prediction shortcomings.

Математична модель камери згоряння газотурбінного двигуна, який працює на етанолі

Ethanol is one of the most promising alternative fuels for Ukraine. To convert existing projects of power and cogeneration plants based on gas turbine engines (GTEs) operating on petroleum products and natural gas to ethanol, as well as for their design and performance calculation, it is necessary to have a mathematical model of the working process of GTE combustor. The object of the study is the working process of the GTE combustor fueling on ethanol. The subject of the study is a mathematical model of the working process of GTE combustor fueling on ethanol. The work aims to improve a mathematical model of the working process of a GTE combustor fueling on ethanol by changing the algorithm for calculation of the fuel air ratio, considering thermal dissociation, and a correctly formulated equivalent chemical reaction path of the combustion process. To achieve the aim, the following tasks were solved: based on the use of experimental values of specific isobaric heat capacities of combustion products, which are a function of temperature and pressure, a mathematical model of the working process of the GTE combustor was improved ("simplified" mathematical model); based on the solution of the system of equations of chemical thermodynamics, a mathematical model of the working process of the GTE combustor was developed ("complex" mathematical model); the results of calculation by "simplified" mathematical model of the working process of the GTE combustor were compared with the "complex" one. The following results were obtained: the difference in the calculation of the combustion products' thermodynamic parameters between the developed mathematical models was less than 1.2% for the three modes of the General Electric CF6-80A engine. Conclusion: the "simplified" mathematical model of the working process of the GTE combustor fueling on ethanol was improved. A feature of the model is the implicit consideration of the effect of thermal dissociation and correctly formulated equivalent chemical reaction path of the combustion process by using experimental values of specific isobaric heat capacities of combustion products. This will improve the accuracy of fuel air ratio calculation and other thermodynamic parameters of GTE combustor mathematical models fueling on ethanol, without significantly complicating the model algorithm.

Оцінка можливості виявлення тріщин під час контролю ЛЮМ1-ОВ на лопатках турбін після нанесення комплексних жаростійких покриттів

Currently, gas turbine engines (GTD) are being improved and made more powerful by increasing the temperature of the gases in front of the turbine and increasing the air compression ratio in the compressor. In the aviation industry, nickel heat-resistant alloys such as ЖС6У-ВІ, ЖС26-ВІ, ЖС32-ВІ, etc. are used to manufacture GTD blades. Despite their high properties in terms of corrosion resistance and heat resistance, the service life of GTD blades and their protection against oxidation and corrosion damage is ensured by applying coatings using various technologies both to the flowing surface of the blade blades (heat-resistant and heat-protective) and to the inner surfaces of the cooled channels (diffusion coatings). Failure of turbine blades is one of the most severe types of damage to turbine blades, so at different stages of serial production, including after applying heat-resistant coatings, LUM1-OV inspection of blades is performed to detect cracks that can form during processing and lead to their failure during engine operation. The paper evaluates the possibility of detecting cracks on GTD turbine blades with complex heat-resistant coatings GCP+SDP-2. The study was carried out on samples of working blades in the form of an experiment. First, fatigue tests of the samples were carried out on a test bench until cracks appeared. Then, a complex heat-resistant coating of GCP (CrAl gas circulation coating) + SDP-2 (heat-resistant alloy of the Ni-Cr-Al-Y system) was applied to the blade profile in stages according to the serial technology. After each coating was applied, the blades were inspected by the LUM1-OV method to determine the possibility of crack detection. The results showed that immediately after the application of the complex heat-resistant coating, cracks on the blades were not detected, because they spread only in the GCP layer and partially pass into the SDP-2 layer without reaching the surface. The results obtained can be the basis for removing the luminescent inspection operation from the technological process, immediately after applying complex heat-resistant coatings. Since this does not allow detecting cracks in the blade material and can lead to unnecessary costs for additional technological operations.

Чисельно-експериментальне дослідження високотемпературної багатоциклової втомної міцності монокристалічних лопаток газових турбін

The subject of the research is anisotropic single-crystal turbine blades of aircraft gas turbine engines (AGTE), as well as their multi-cycle fatigue strength characteristics at high temperatures. The goal of this study was to determine the endurance limit of single-crystal high-pressure turbine blades of an AGTE at high temperatures of 820°C. The objective of the study is to develop a method for calculating and experimentally investigating the characteristics of high-temperature multi-cycle fatigue strength of gas turbine blades made of single-crystal nickel heat-resistant alloys. The research methods used are: method of computer modelling, which was used to create a 3D model of a cooled high-pressure turbine blade; finite element method, which was used to determine the stress-strain state of the blade according to the selected form of resonant vibrations; strain and resonance methods, which were used to determine the fatigue strength characteristics of single-crystal turbine blades under high-temperature loading. The following results were obtained. Literary sources describing theoretical and experimental methods for determining the strength characteristics of blades under combined dynamic and high-temperature loading were analyzed. The developed special installation for testing turbine blades under conditions of temperature and dynamic (resonant) loading was described. A combined method for assessing the multi-cycle fatigue strength at high temperatures is proposed, which includes studies on full-scale turbine blades and finite element calculations. The dynamic and temperature characterization of single-crystal turbine blades selected for the study was carried out and described. Fatigue tests were performed to determine the endurance limit of the blades at a high temperature equal to T = 820 °C. Conclusions. The scientific novelty of the obtained results is as follows. A specialized experimental setup was developed to study the endurance limit of single-crystal AGTE blades under high-temperature loading. A method for combining numerical (ANSYS) and experimental (field tests) study of high-temperature multi-cycle fatigue strength of turbine blades made of single-crystal heat-resistant alloys was developed. The direction of further research is presented.

Multi-criteria optimization next to a comparative analysis of a polygeneration layout based on a double-stage gas turbine cycle fueled by biomass and hydrogen

The significance and advantages of utilizing renewable energy sources are widely recognized. Upon examining past studies, it was revealed that there has been a lack of research on harnessing the waste energy from double-stage gas turbines powered by biomass-hydrogen hybrid fuel for polygeneration applications. Thus, a new configuration is proposed in the study for the multi-production of electricity, cooling, heating, and potable water. In the current research, a high-pressure turbine is driven by a combustion chamber fed by a biomass gasifier. Meanwhile, a low-pressure turbine is driven by a post-combustion chamber fed by hydrogen as fuel. The heat loss of the topping gas turbine cycle is recuperated by a supercritical Brayton cycle (SBC), a steam Rankine cycle (SRC), and a water heater. The waste heat of the supercritical Brayton cycle and steam Rankine cycle is recovered through an absorption refrigeration cycle and a thermoelectric generator, respectively. Thus, the heat loss of the topping system is completely recovered. The net power output of the gas turbine cycle is considered the electricity production of the system while the output power of the SBC and SRC is utilized in a reverse osmosis desalination system to produce potable water. The investigations conducted on the system are thermodynamic and exergy-economic assessments and three-objective optimization utilizing 5 gases (i.e., CO2, CO, Nitrogen, Air, and Helium) in the SBC. The final results reveal the superiority of Helium as the supercritical gas, bringing about an exergy efficiency (ηex) of 32.11 %, a total cost rate (C˙tot) of 103 $h−1, a payback period (PP) of 0.159 years, and a specific cost of polygeneration (cpoly) of 22.03 $GJ−1 for the system. Although the levelized cost of products of the configuration is high due to the freshwater production, ηex of the proposed system is higher than the previous systems based on a double-stage gas turbine cycle driven by biomass and hydrogen.

Numerical study on flow and heat transfer of combustion chamber and turbine under thermal shock test

In order to more accurately analyze the influence of the interaction between the aero-engine combustion chamber and the turbine, this paper establishes a combustion chamber-turbine cross-component model based on a high-pressure first-stage guide vane thermal shock test device for numerical research. The SST k-ω turbulence model, non-premixed combustion model and P1 radiation model are selected, and the test conditions are used as boundary conditions to carry out fluid-solid coupling unsteady calculation in ANSYS FLUENT. The numerical results are in good agreement with the experimental results. The complex flow field information between the combustion chamber and the turbine is obtained by analyzing the numerical results. It is found that there is an interaction between the combustion chamber and the turbine. The results show that the hot spot at the outlet of the combustion chamber will cause a stronger thermal shock to the downstream of the high-pressure first-stage guide vane during the migration process. The influence of the high-pressure first-stage guide vane on its upstream can be traced back to the position 0.3 times the chord length from the outlet of the combustion chamber.

Numerical research on the aerodynamic performance of inlet volute duct for a heavy-duty gas turbine

Numerical research on the aerodynamic performance of inlet volute duct for a heavy-duty gas turbine

Emissions and Flame Stability Assessment of Hydrogen Addition and Air Dilution in a Micro Gas Turbine Combustor Using 0D/1D Modeling by Chemical Reactor Network

Abstract Hydrogen emerges as a promising fuel for clean and sustain- able electricity production when utilized in micro gas turbines (mGTs). However, some challenges linked to hydrogen usage must be overcome as its high reactivity can lead to increased NOx emissions and flame instabilities. Literature suggests that combustion air humidification and/or exhaust gas recirculation (EGR) may be methods to reduce this reactivity. However, these measures are limited due to the small operating range of the mGT combustor. In this context, a 20 kWth mGT combustor is investigated un- der various inlet conditions to assess the effect of EGR towards increased flame stability and emission control when operating under hydrogen-enriched methane firing, using a Chemical Re- action Network (CRN) model. The CRN modeling is a fast and low computational complexity tool to model combustion perfor- mance and emissions by representing complex reactive flow fields through idealized reactor models, leading to reduced computa- tional costs. This study examines partial load conditions, fuel compositions, and the effect of combustion air dilution through EGR. The CRN model of the combustion process is designed based on combustion zones extracted from the main flow fields with similar thermo-chemical states from CFD, while emission predictions are experimentally validated for different operating points. Predicted NOx and CO emissions by the proposed CRN model show an acceptable agreement with the experimental data at high power loads. However, its accuracy diminishes for loads below 70% due to the variability in model tuning parameters across different loads, whereas the

Mixed Convection Flow of a Viscous Dissipative and Heat Generating/Absorbing Fluid Through a Slit Microchannel

This paper is aimed at investigating the consequences of viscous dissipation and super-hydrophobicity on a magnetized mixed convection flow of an electrically conducting fluid across an up facing microchannel influenced by a transverse magnetic field. The plates were alternatively heated and incorporated with heat source/sink effect. The modeled governing equations have been obtained using a semi-analytical (regular perturbation) method. Various line graphs have been plotted to demonstrate the behavior of key parameter dictating the flow. It was found out that the thermal gradient and fluid velocity are significantly enhanced for mounting values of mixed convection Gre, Brickman number Br, Darcy porous number K and heat source S parameters in the superhydrophobic microchannel for constant pressure gradient Г. On the other hand, the velocity deteriorates for increasing levels of magnetic field M and heat sink S factors. Further, the comparison of this present analysis with previously published literature for limiting cases when Г=S=0 and Gre=1 showcased an excellent concurrence, thereby confirming the accuracy and validity of this present investigation. The findings from this research will find relevance in engineering, technological and industrial processes such as for solar collectors, nuclear reactors cooled during emergency shutdown, nuclear power plants, gas turbines and the various propulsion devices for aircraft, missiles, satellites and space vehicles.

Methodical and algorithmic aspects of mathematical modeling of a screw aircraft power plant

The article describes the solution of a scientific problem that consists in expanding the functionality of the program “Calculation of the traction-economic and mass-specific characteristics of the power plant and aircraft motion parameters” through the introduction of additional algorithms and mathematical models for calculating the altitude-speed characteristics of screw aircraft power installations. At the same time, an internal calculation of the aircraft propeller thrust is used according to experimental aerodynamic coefficients, which makes it possible to increase the efficiency and reliability of complex theoretical studies of power plants of various types as part of aircraft at the stage of external design. A description is given of the developed algorithms: an algorithm for converting power on the output shaft of a gas turbine engine into thrust of an aircraft power plant; a mathematical model of a propeller that provides calculation of its thrust from experimental aerodynamic coefficients; an algorithm for determining the thrust of the power plant, taking into account the compressibility of the air and the interaction of the propeller and the elements of the airframe of the aircraft. Some features of the mathematical modeling of an aircraft propeller are revealed, in particular, the principle of propeller control by influencing the blade angle and rotational speed depending on the aircraft flight speed and a method for constructing the field of aerodynamic characteristics of an aircraft propeller in a wide range of blade angle and speed coefficient. In conclusion, the results of verification of the modified program are presented with an analysis of the obtained altitude-speed characteristics.