Sharif Digital Repository

Electrostatic precipitators (ESPs) are widely recognized for their pivotal role in the collection of dust and particulate matter. ESPs are essential to ensure a particle- and dust-free atmosphere in industrial and non-industrial work environments. With the ever-increasing significance of maintaining air quality at the desired standards, the role of ESPs has gained paramount importance in mitigating airborne pollutants and protecting public health. Achieving higher collection efficiency for particulate matter and attaining cleaner air is of great importance in the design and selection of precipitators. On the other hand, particle collection efficiency is considered as a crucial factor for ESP... 

Numerical three-dimensional simulation of the entire regions of a gas turbine blade, including hot gas flow over the blade surface, conduction heat transfer within the blade metal, and coolant flow through the Internal cooling System, is highly time-consuming and expensive. Therefore, one-dimensional internal flow simulation is one of the main objectives of this research to address the limitations of commercial software in predicting the temperature distribution along the cooling path. In this study, a one-dimensional in-house simulation code is developed to simulate the coolant flow inside the cooling channels of the internal cooling system of the blade. Additionally, using artificial... 

Industrial centrifuge fans operate in various industries, specifically heavy industries such as pelletizing plants, steel mills, and cement plants. These fans transfer process gas in the production cycle. In some cases, due to their off-design working conditions, asymmetrical wear and failure happen on one side of the impeller's blades more than the other side. The most important reason is the heterogeneity of the entrance fluid's properties. One of the many critical parameters in this issue is the asymmetric distribution of particles between the two entrances of the fan. This research investigates the asymmetric erosion problem of a specific centrifugal fan with a double-suction side... 

One way to increase the power and efficiency of the gas turbines is to cool their incoming air. There are different methods to cool down the inlet air. One of the most widely used and suitable method is spraying or fogging the water droplets into the air at the gas turbine air inlet. In this research and for the first time, the effect of fogging system on the performance of a combined cycle incorporated with a J-class gas turbine (M-501J) is investigated using the computational fluid dynamics (CFD). There are so many parameters, which affect the amount of achieved efficiency. A few of them includes the average temperature and humidity at the outlet, the evaporation efficiency of the water... 

Using a Numerical simulation approach for modeling multiphase flows is a cost-effective and prevalent method in analyzing the physics of multiphase problems. One of the most applied needs of industry in using gas-particle simulation is the separation of particles using Air Classifiers which are industrial devices that can classify solid inlet particles based on their size using airflow patterns and other mechanisms. The present study focuses on a particular type of classifier using vortex to classify particles. Performance of these classifiers simulated using numerical Eulerian-Lagrangian DDPM model. The two critical studied performance parameters of the classifier are pressure drop and... 

Recent decades have seen a growing demand for high-power wind turbines resulting in turbines with larger blades and the advent of high-megawatt wind turbines. The blades of the megawatt-scale turbines experience more complicated flow phenomena compared to those of the smaller-scale wind turbines. Needless to say, the importance of an accurate solution and detailed analysis of all the parameters, including blades aerodynamic and aeroelastic performance as well as fluid-structure interaction, is more significant for the megawatt-scale turbines compared to smaller-scale turbines. The conventional methods of aerodynamic solutions for the blade, including analytical methods, such as BEMT78 and... 

Todays, heat recovery steam generator (HRSG) systems are used extensively in combined power plant cycles (consisting of Rankine cycles and Brighton gas cycle) to maximize their efficiencies. The role of HRSG is essential in providing additional energy needed in the steam cycle part. The HRSG has many pipes or harps. They recover the heat from the incoming gas from the gas turbine outlet, which may be boosted up by the duct burner unit. The main challenge in simulating heat recovery units such as tube bundles is to provide ultra-large and cost-efficient grids. In such situations, alternative models are used to simplify the simulation of the steam generator in full scale, including the... 

Nowadays, the study of flow and heat transfer in turbine engines has become critical due to their increasing use and importance in various engineering industries. The critical issue of blade burning in the first row of turbine’s blades illuminates the critical roles of numerical and experimental activities in reducing these undesirable effects. Since blade cooling is directly related to the secondary air system, one important issue in blade burning research is to utilize the conjugate heat transfer approach. As Known, an increase of about 1% in the mass flow of air entering into the secondary air system would cause an increase of about 0.5% in the engine specific fuel consumption (SFC),... 

The study of heat transfer using solid-liquid phase shifting has attracted much attention in applied engineering fields such as latent heat energy storage, building walls, waste energy recovery, battery thermal management, and more. Over the past few decades, the literature on phase shift has grown tremendously in terms of theory, laboratory, and numerical studies. Melting of phase change materials in rectangular chambers due to its wide range of engineering applications in fields such as casting, metallurgy, heat energy storage, and heat exchangers used in buildings, as well as aerospace issues including the use of These systems have been the subject of numerous studies on space missions to... 

One main problem in many numerical simulations is the lack of sufficient infrastructure data to precisely model and analyze the flow through complex geometries. Since experimental procedures are generally very expensive; and sometimes impossible, it becomes necessary to find alternative ways such as numerical approaches to predict the flow behavior through complex geometries. The heat exchangers can be categorized as geometries with complex configuration and apparently expensive to solve numerically. They are widely used in different industries including the aerospace. The restrictions in design and implementation of aviation’s heat exchangers have promoted the related companies to converge... 

Iran's experience shows that either single or combined power generation cycles, face heavy summer performance deficiencies. The most limitation of power generation in steam cycles is due to their poor condenser performance.The less condenser performance, the more turbine back pressure, and the more turbine back pressure, the less cycle power generation. The main objective of the present study is to reduce steam turbine back pressure in the combined cycle of an organic Rankine-vapor compression refrigeration by installing heat pipes in suitable locations inside the Air cooled condense (ACC). In order to do so, a commercial numerical simulation solver (FLUENT) is used to find the most suitable... 

There are some parameters, which can affect the performance of a combustor less and more, e.g., fuel-oxidant mixing process, turbulence generation, combustion process, and so on. A stoichiometric reaction as a unique reaction, in which all the reactants are consumed to form the stable products, can be categorized as the most economic reaction. The majority of industrial combustion apparatus consumes hydrocarbon fuels and departs from ideal combustion conditions, which expects products like CO2 and H2O. Combustion by-products reduce the combustion efficiency and cause environmental damages and human health problems. To resolve the human health problems and environmental hazardous issues, the... 

An important issue in aerospace propulsion systems is the reacting flow analyses, which involve many different concepts and physics including various chemical reactions mechanisms and radiation and convection heat transfer physics. As known, the computer simulation is a powerful tool to analyze the reacting flow physics in various combusting environments. It can suitably provide details of both chemical reaction occurrences and heat transfer physics. In combustion environments, the temperature gradient is noticeably affected by the density gradient. On the other hand, the accurate modeling of density gradients highly affects the computational results. In practice, the density-based methods... 

The co-existance of rarefied and near-continuum flow regimes is widelyencountered in analyzing the multiscale flow problems, e.g., micro-and nanoflows. Previous investigations have revealed that the continuum-based simulation methods would suffer from the lack of accuracy to predict the rarefied flow regimes. On the other hand, the molecular simulation methods are not computationally efficient in simulating the near-continuum flow regimes. Therefore, the use of hybrid simulation methods has been recommended as a serious alternative to simulate the multiscale flow problems. These methods apply the molecular methods in solving the rarefied flow regions and the continuum methods in solving the... 

Heavy fuel oil (HFO) is usually consumed in large scale furnaces, e.g., those of power plants. Experience shows that its combustion produces large amount of NOx emission. In present study, a large scale heavy fuel oil fired furnace is numerically simulated to investigate different possible solutions for NOx reduction. In this regard, a computational framework is firstly designed benefiting from the researches reported previously in literature. The results of this framework are then compared with available measurements to evaluate the accuracy of current designed computational framework. Second, the influences of a number of different controlling parameters are studied carefully to improve... 

The lubricating oil is commonly used to cool down the moving parts of turbine gas systems. In many applications, this oil is cooled down using a recirculating water circuit. The water is then cooled down using an air-cooled heat exchanger. Any deficiency in aerothermodynamic design of such heat exchanger would result in high temperature of gas turbine moving parts such as bearings. Obviously, this mal-performance has adverse effect on the lifetime of these parts and their maintanence aspects. Since the good performance of air-cooled heat exchanger has numerous advantages for the performance of related gas turbine unit, it is mandatory to design these heat exchangers in minimum sizes and... 

Nowadays, widespread needs for creating low pressure ambient in various industries make vacuum systems have different research and industrial applications. One of these applications is in cooling system of Rankine power cycle. In this case, the performance of the vacuum system has a direct and significant effect on the cooling performance of the condenser and consequently, power production of the steam turbine. Also, a considerable part of deration in thermal power plants industry is due to the thermal deration of the cooling systems. This is mostly because of malfunction of the condenser due to ambient temperature rise. Therefore, by providing suitable solutions to improve the efficiency... 

The steam turbines share a significant part of Iran's electricity production. Evidently improving the performance of these steam turbines will improve the performance of power plants and enhance the capability of power production in Iran. Since the behavior of steam turbines is highly nonlinear and that it is affected by various factors, it is difficult to determine the optimum operating conditions for each turbine in specific unit of a power plant. In addition, it is very difficult to model the turbine behavior based on the mathematical equations. Fortunately a large amount of information is collected and stored annually by the data-processing systems in each power plant. These collected... 

Air-cooled condenser is widely used in thermal power plants as its main cooling system. However, the thermal capacity of air-cooled condensers reduces considerably in environmental wind drafts. So, the purpose of this study is to find practicable solutions to minimize the mal-performance of air-cooled condensers in windy conditions in either design or off-design conditions and consequently prevent the related steam turbines power reduction. The target combined cycle power plant consists of 4*160 MW steam turbines and 4 air-cooled condensers in its steam cycle part. This research presents two general and practical remedies, which are also applicable to many different powerplants irrespective... 

Numerical simulations of participating media need careful solution of the radiation transfer equation (RTE) along the fluid flow governing equations. Evidently, the accuracy of achieved solutions highly depends on the accuracy of radiation transfer calculations. Despite numerous efforts performed in the previous researches, the RTE calculation still faces with several challenges from both accuracy and computational cost perspectives. The main objective of this research is to present new contributions in overcoming such challenges. So, a finite-volume (FV) solver is suitably developed to solve the RTE numerically. This extended solver is then coupled with an existing FV flow solver. The...