High Temperature Air Combustion has already been applied in various industrial furnaces. Steel producers use most of the revamped furnaces. These are: • Batch and continuous heating furnaces in which HRS burners with open flames were used, • Batch and continuous heat treatment furnaces in which HRS burners with radiant tubes were used. Apart from steel industry the HTAC systems were applied to melt aluminium or to incinerate odour, vapour gases for example in pulp and paper industry. In all these applications very high fuel savings (sometimes as high as 60%), reduction of NOx and production increase (by 20–50%) was achieved. Progress in applications of the HTAC increased also needs of more information and data required by furnace and process designers. For this reason study in larger scale where at least one set of regenerative burner systems is installed are very much needed. Aim of such studies is not only to verify furnace performance with respect to the known general advantages of HTAC but are focused on specific problems related to furnace and high-cycle regenerative burners operation, process and product properties or type of fuels used. Parallel to the semi-industrial tests numerical models of furnaces have to be developed and verified. In this work, mainly results of heat flux measurements as well as results of numerical modeling of heat transfer in the HTAC test furnace are presented. Results were obtained for propane combustion at firing rate equal to 200 kW. The general code, STAR-CD, was employed in this work to analyse the HTAC test furnace numerically. HTAC test furnace at Royal Institute of Technology (KTH) with capacity of 200 kW was used in this work. The furnace is equipped with two different high-cycle regenerative systems (HRS). In both systems the “honeycomb” regenerator is used. The two-burner system is made of two pairs (four burners) of high cycle-regenerative burners with switching time between 10 and 40 seconds. HTAC test furnace is equipped with four air-cooled tubes to take away heat from the furnace. The total radiative heat flux measured in the HTAC furnace shows very uniform distribution over the whole combustion chamber. For total radiative heat flux, the values are in the range of 110–130 kW/m 2 as measured by means of the total radiative heat flow meter at the furnace temperature 1100 C. Average total radiation flux on the top furnace wall is as high as 245.5 kW/m2 as well as total incident radiation flux. Total radiation heat flux on the air-cooled tube surface is very uniform along and around the tubes. Average radiant heat flux taken away by air cool tube is 35.46 kW/m2.

In this study, in order to obtain fundamental data for designing the practical gas turbine combustors in the chemical gas turbine (Ch/GT) combined cycle system and/or other gas turbine systems which utilize low heating value fuel such as coal and biomass gasification syngas, we have simulated low heating value fuel–air turbulent diffusion combustion. The simulated results for the profiles of temperature and species concentrations have been compared with the measured ones. As a reaction model, the flamelet model has been applied to predict the turbulent diffusion combustion characteristics. A flamelet library which indicates relationships for scalar dissipation rate, mixture fraction, and mass fraction of chemical species were given by the calculated results of counterflow diffusion flame using 16 chemical species and 25 elementary reactions. Clipped Gaussian and a log-normal distribution were employed as the PDFs of the mixture fraction and the scalar dissipation rate, respectively. In this model, the k -ε two equations turbulence model is used to describe the turbulent flow field and the radiative heat transfer is calculated by the six-flux model. The governing equations were solved iteratively by the SIMPLE algorithm. By the comparisons of the simulated and measured results, it was clarified that the simulated profiles conformed fairly well to the measured ones in the turbulent combustor, and that this combustion simulation model could predict the low heating value fuel turbulent diffusion combustion characteristics.

Nozzle-mix burners are widely used in heat treatment and non-ferrous melting furnaces, and other applications, where temperature uniformity is required. These burners are stable over a wide range of air-fuel ratios from very lean to rich (up to 50% of excess fuel), high turndown ratio and low NO X emissions at all air-fuel ratios. Here, the fuel is generally transported by a central jet and air through an annular jet. The separation between the fuel jet and the air annulus and confining wall are crucial for flame stabilization. The objective of the present work is to investigate the flow and flame characteristics of a nonpremixed nozzle-mix burner through a detailed parametric study. The inferences from this study will provide useful information for designers, regarding choice of parameters. The burner is modeled as an axisymmetric arrangement of fuel duct at the center, surrounded by a coaxial annular duct of air. The ducts discharge into a confined environment, formed by a chimney, placed coaxially with the ducts. The results of the numerical simulation show that for a given air-fuel ratio, as the fuel flow rate increased, the location of the flame base shifted from near the fuel nozzle towards the oxidizer nozzle. Similar shift in flame position was also observed for higher air velocities for a given fuel velocity. High fuel and air flow rates and small separation between fuel and air jets tend to destabilize the flame. For a given air-fuel ratio, flame height increased with increase in fuel flow rates, but the change became insignificant at higher flow rates. For a given fuel velocity, flame height decreased with increase in air flow rate for both buoyancy-controlled and momentum-controlled regimes. The air-to-fuel velocity ratio was found to be the most significant parameter in determining the flame height.

The objective of this study is to develop an evaluation tool for a design and performance of an extra heavy oil gasifier by a numerical simulation technique. The modelling and the numerical simulation for the extra heavy oil gasification on the 2.4 tons/day entrained flow gasifier of CRIEPI are described in this paper. The gas phase properties are calculated by three dimensional time-mean Eulerian conservation equations, in addition to the k-ε turbulence model. The fuel droplet behavior is modelled via a Lagrangian particle tracking approach. Four reaction processes are modelled in the present paper: atomization (micro-explosion), pyrolysis, coke gasification reaction, and gaseous phase reaction. As a result of the simulation, in a relationship between an oxygen ratio of the gasifier and the gasifier performance, such as heating value of the product gas, carbon conversion efficiency are presented. Distribution of gas temperature and gas composition in the gasifier, and the product gas composition are also presented. Comparison between the computational and the experimental results shows that the most features of the gasifier performance have been captured accurately by the computational procedure. The numerical simulation approach is very useful for the assessment of gasification performance, operation support and optimization of the gasifier design.

Reliability of turbines is very important for power plants, and the most common blade failure normally result from forced vibration which lead to fatigue failure of blades. In this study, a synthetical numerical model has been developed to obtain more precise evaluation of the reliability of blades. At first, the model used to analyze the dynamic stress of steam turbine blades is investigated, base on the results of dynamic stress analysis, a model to evaluate the fatigue life of turbine blade has been developed, many factors such as manufacturing technology of blades and erosion operating environment are considered to get more accurate results for the fatigue life prediction of blades. At last, a 323 mm blade in a 75MW steam turbine is analyzed by the model developed in this paper, it is shown clearly that the model can provide some significant data to evaluate the reliability of blade.

Sets of high-pressure ejection experiment were conducted to investigate the implementing of gases ejector with high-pressure condition. Numerical simulation was used to extend the study and overcome the limit of experiment facilities. Experiment shows that ejection coefficient of gases ejector was not sensitive to supply gas pressure changes. But which was affected greatly by backpressure in mixing cavity of ejector, as shown by simulation. The simulation result also implies that there are inherent relation between ejection coefficient, area ratio at inlet of mixing cavity and pressure different between supply gas pressure and the backpressure. And the relationship determines that in some range, the implementing of gas ejector was unstable.

The TVA Browns Ferry Nuclear Power Plant (BFNPP) withdraws its condenser cooling water from Wheeler Reservoir via an intake pumping station. Waste heat from the plant increases the condenser cooling water temperature. The heated water returns to the reservoir through three multiport diffusers containing a total of about 22,500 downstream facing ports. The ports are 2 inch diameter holes situated 6 inches apart both vertically and horizontally. The numerous small diffuser ports, the buoyancy of the heated effluent, and the large scale of the discharge area to be simulated present major challenges to developing a reliable three-dimensional computational fluid dynamics (CFD) method for predicting temperature distributions and flow patterns in Wheeler Reservoir. This paper presents an innovative CFD method and the results for numerically simulating under steady conditions the thermal discharge from the BFNPP. A finite-volume CFD package, FLUENT, was used to develop the required numerical models. The realizable k-ε turbulence model was selected for closure of the Reynolds-Averaged Navier-Stokes Equations. Second-order accurate schemes were used to discretize the governing equations. To simulate the discharge from thousands of diffuser ports, the CFD method features an innovative two-zone modeling approach, consisting of a multiple jet sectional model and an overall river model. The latter contains about 2 million computational cells for simulating the cooling water discharged from the thousands of multiport diffuser ports. The multiple jet sectional model, which simulates the flow from the individual discharge ports over a one foot slice of the diffuser pipe in great detail, provides the information for developing sectional boundary conditions for the diffuser effluent. These boundary conditions are then used in the overall river model for the whole study area. Validation and verification of the CFD models were performed using data from field measurements, hydraulic model tests, and other experiments. Comparisons between the CFD results and these data showed that the overall river model, based on the two-zone approach, can reproduce the major features of temperature and flow in the diffuser mixing zone. Model limitations exist, however, for low river flows, where requirements for steady behavior impede solution convergence.

A numerical approach-FAWS which is based on analytical Wilson point parameters and aims at simulating non-equilibrium wet steam flow in steam turbine for industrial application is developed successfully and described systematically in this paper. The 3D viscous condensation flow in an operating steam turbine stage is specially analyzed. The numerical accuracy of FAWS and some phenomena of condensation flow in 2D cascade are displayed and analyzed. Relevant results show that FAWS can be a useful tool to design the stage working in wet steam.

Flue gas recirculation is one of the most effective ways to reduce nitric oxides (NOx) emission in conventional industrial furnaces. To design an effective control scheme, one has to understand the dynamic relationships among different furnace inputs and outputs. This paper concentrates on the construction of such dynamic models for an industrial furnace using numerical simulations and frequency domain system identification techniques. The numerical simulations are based on the conservation equations of mass, momentum, and energy. The inputs to the furnace consist of the pressure head of the flue gas recirculation fan, the temperature of the combustion air, and the flow rate of the combustion air. The outputs considered herein are NOx and oxygen (O 2 ) concentrations. To obtain a dynamic model for this multi-input and multi-output system, low amplitude sinusoidal signals of different frequencies are administrated at the furnace input. The dynamic relationships among the inputs and outputs at these frequencies are established in terms of frequency responses (magnitude and phase) around a particular furnace operating point. These frequency responses are further processed by a least squares based system identification technique to convert them to a set of parametric models. The result of the system identification is a set of the transfer functions with the order ranging from 3 rd to 6 th . Studies have been carried out to verify the validity of these dynamic models by comparing the responses generated from these models with those obtained from the full-scale numerical solution. These dynamic models provide a starting point for the design of realtime optimal feedback control systems for minimizing NOx emission.

Air-cooled generators have been fulfilling a wide range of applications recently. Concurrent with a low cost target, the market demands high efficiency and high performance designs. Windage and friction losses, caused by rotor rotation and cooling gas flowing through the ventilation circuits, represents one of the largest loss components in air-cooled generators. Carefully managing the windage and friction loss is critical to ensure the success of air-cooled generators. This work is motivated by development of air-cooled high-speed generators. In such applications, the flow inside the annular gap between the rotor and stator is highly turbulent. The flow characteristics are not fully understood. Physics-based correlations, which calculate the windage and friction losses, don’t exist in the literature. The purpose of this work is to develop such transfer functions for machine design. Numerical simulations, using commercial CFD code FLUENT 6.0 and Design of Experiment (DOE) method, have been carried out to study the flow characteristics in the annular space between the cylindrical rotor and stator. All simulations were performed using an axial-symmetric model, along with RNG k-ε turbulence model and enhanced wall treatment. In the study, the generator rated speed ranged from 5000 to 20000 rpm; the Taylor number ranged from 1750 to 78000; and the Mach number ranged from 0.25 to 1.0. The effect of axial flow on windage loss was carefully studied. Axial flow exhibited a strong impact on windage loss. The CFD results are rationalized. Transfer functions for windage and axial friction losses are created. They provide a better basis to explore the design space at the early stage of the product development.

This work presents the main features, advantages and evaluation of applications of the novel “Ecotube” combustion improvement and emission reduction system by Ecomb AB of Sweden and Synterprise, LLC of Chattanooga, Tennessee. In the Ecotube system, the nozzles used for mixing are put on the suitable position inside the combustion chamber to control uniformity of temperature, mixing and reactants distribution in boilers and incinerators since the formation and reduction of pollutants (NO, CO and VOC) and in-furnace reduction processes (Air/Fuel staging, SNCR, flue gas recirculation and SOx reduction by dry sorbent injection) are related directly to mixing in a combustion chamber. The novel Ecotube combustion improvement system allows better control of mixing of the gases for example from a primary combustion zone with secondary combustion air or a recirculated flue gas. By means of the novel system it is possible to better control the residence time and to some degree gas phase temperature distribution as well as the heat release distribution in the furnace of the waste incinerators or boilers. This new combustion improvement system can be applied to supply different gas or liquid media — for example air, fuel, urea or even solid powder. Using the system a more efficient and environmentally clean combustion or incineration process can be performed. The Ecotube System may be used to meet increasingly stringent environmental emissions regulations, such as NOx SIP Call, while it delivers added benefits of reduced and stabilized CO and reduced fly ash and improved boiler efficiency. The study tool used in this work to present influence of the Ecotube system design on temperature as well as uniformity of reactants and flow field is numerical modeling. Using this tool, the influence of the position of the Ecotube system and the injection angle of the nozzles are studied. The studied boilers included the biomass waste incinerator, municipal solid waste incinerator and coal fired boiler. The concept of the Heat Release Distribution Ratio is proposed to classify the heat release inside the upper furnace of the boilers or incinerators. The results show that Ecotube spreads reaction zone over a larger furnace volume. The furnace flame occupation coefficient can be as high as 45% with the Ecotube system and it is around 40% higher comparing with the conventional multinozzle mixing system. Ecotube system allows keeping far more uniform heat release distribution, more uniform temperature distribution, and thus longer life of the heat transfer surfaces inside the furnace. Position of the Ecotube system and the injection angle of the nozzles are of primary importance and can be used as a technical parameter to control the boiler operation at different loads and varying operating conditions.

The high temperature and large pressure of inlet steam lead to large thermal stress and large thermal deformation in high pressure casing of turbine, it has an apparent effect on the reliability of casing and may lead to steamtight problem of the casing. Based on the temperature filed analysis and elastic contact theory, a three dimensional Finite Element model to analyze the deformation and stress of casing has been developed. And then the high pressure casing of a 100 MW steam turbine is analyzed, some numerical results such as temperature distribution, stress and deformation are obtained. It is shown that with higher temperature and larger pressure, larger prestressing of bolt is necessary to guarantee the steamtightness of casing, the operation experience of real casing shows the numerical analysis can provide usable data for casing design and improve its reliability.