Reduction of NOx Emission of Heavy Duty Gas Turbines by Improving Mixing Quality Using CFD Tools

Jets in cross flow are one of the fundamental issues for mixing studies. As a first step in this paper, a generic geometry of a jet in cross flow was simulated to validate the CFD (Computational Fluid Dynamics) tool. Instead of resolving the whole injection system, the effective cross-sectional area of the injection hole was modeled as an inlet surface directly. This significantly improved the agreement between the CFD and experimental results. In a second step, the calculated mixing in an ALSTOM EV burner is shown for varying injection hole patterns and momentum flux ratios of the jet. Evaluation of the mixing quality was facilitated by defining unmixedness as a global non-dimensional parameter. A comparison of ten cases was made at the burner exit and on the flame front. Measures increasing jet penetration improved the mixing. In the water tunnel the fuel mass fraction within the burner and in the combustor was measured across five axial planes using LIF (Laser Induced Fluorescence). The promising hole patterns chosen from the CFD computations also showed a better mixing in the water tunnel than the other. Distribution of fuel mass fraction and unmixedness were compared between the CFD and LIF results. A good agreement was achieved. In a final step the best configuration in terms of mixing was checked with combustion. In an atmospheric test rig measured NOx emissions confirmed the CFD prediction as well. The most promising case has about 40% less NOx emission than the base case.

Hourly Distribution of Diffuse Illuminance

It has been found that the values of ratio of hourly diffuse illuminance to daily diffuse illuminance, rvd, are very close to the corresponding values for diffuse solar radiation, rd, examined from the measured data of two locations. This has been further confirmed by examining the values for rvd and rd as calculated from TMY2 [1] data base for primary locations. Based on this, it has been proposed that the correlations available in literature to predict rd can be employed to predict rvd Adequacy of the correlation due to Satyamurty and Lahiri [2] available for rd has been examined to predict rvd as obtained from TMY2 data base for the 56 primary locations. It has been found that the values of rvd obtained from measured illuminance data of two locations have been predicted within a rms difference of 7.1% and within a rms difference of 4.3% for the 56 primary locations of TMY2 data when the correlation due to Satyamurty and Lahiri for rd has been employed after suitable modification.

Safety and Field Testing of a New Generation AC Module

Safety and quality requirements for a new type of AC module have been identified and its performance has been evaluated for two prototypes. The laboratory tests have to show whether the so-called PV2go inverter can comply with the expectations and where improvements are still necessary. Afterwards, the AC modules have been tested under typical European field conditions.

Design and Preliminary Testing of a Prototype Thermophotovoltaic System

Thermophotovoltaics (TPV) is technology similar to conventional solar photovoltaics, which have been in existence for over 50 years. The main difference between traditional solar photovoltaics and TPV is that, instead of the sun, an “emitter” is used to produce light, which is then converted into electricity by the TPV system. This emitter is heated via combustion or some other method until photons are ejected. Although the light utilized in the TPV system is not as energetic as that from the sun, the fact that the TPV cells can be placed in close proximity to the source (compared with the distance to the sun) increases the intensity of the light received by the cells. This results in a higher power production density than is possible with traditional solar photovoltaic systems. One estimate of maximum achievable output power density for TPV systems is 5W/cm2, approximately 500 times that of a traditional solar PV system. Researchers in this field have already demonstrated power densities of 1.5W/cm2. Other attractions of TPV systems include fuel versatility, compact size, silent sun-independent operation, and low maintenance costs. A TPV test station has been assembled at the Alberta Research Council in Canada. A general overview of the background technology and system components will be presented, as well as preliminary experimental results. Areas that require additional improvement in order to increase system efficiency will also be addressed.

Moving Boundary Model of Once Through Boiler Evaporators

Dynamic modeling and simulation of steam power plants is often adopted as a tool for control design, personnel training, efficiency improvement and on-line diagnostic. The boiler is possibly the most complex component of the thermal power plant. A usual boiler configuration is the so-called Once-Through arrangement. A common problem in 2-phase systems modeling is the correct calculation of the phase boundary. This is technically interesting in such boilers: the location of the phase transition changes rapidly depending on load conditions and temperature distribution along the walls. A lumped parameters, one-dimensional evaporator model implementing a moving boundary approach is presented and first validation results are discussed. The model takes into account the influence of radiation and convection on the gas side. The flow inside the pipes is divided into 3 regions (sub-cooled, 2-phase, superheated) and the model calculates the locations of the 2-phase transitions and the average steam quality along the pipes. The system is discretized using a staggered grid for higher numerical stability and is implemented in the computer program Aspen Custom Modeler (ACM). Results include the calculation of the system response to input signals simulating a load variation and a validation by comparison with a model implemented in a commercial software for power plant simulations (MMS). Input data, parameters and geometry are taken from an existing plant operating in Uppsala, Sweden.

Modeling of Waste-to-Energy Combustion With Continuous Variation of the Solid Waste Fuel

A mathematical model of a mass-burn, waste-to-energy combustion chamber has been developed that includes stochastic representation of the variability of the fuel (municipal solid waste, MSW). The drying, pyrolysis, gasification and combustion processes on the moving grate are governed by several factors such as proximate and ultimate analysis, particle size, moisture, heating value, and bulk density, all of which change continuously. This extreme variability has not been considered in past mathematical models of WTE combustion that used mean values of the MSW properties. The Monte Carlo stochastic method has been applied to provide a time series description of the continuous variation of solid wastes at the feed end of the traveling grate. The combustion of the solid particles on the grate is simulated using percolation theory. The feed variation and the percolation theory models are combined with the FLIC two-dimensional bed model developed by Sheffield University to project the transient phenomena in the bed, such as the break-up of waste particles and the channeling of combustion air throughout the bed, and their effects on the combustion process.

A Modeling Analysis of Non-Melting Solid Fuel Particle Heating

The heating of fuel particles is generally the first step in the process of gasification or combustion of solid fuels such as coal and biomass. The particle heating that is achieved via combined convection and radiation effects requires a rigorous analysis of heat transfer within as well as outside of the particle, which makes the lumped capacity approximation unsuitable. A more adequate representation of the heating-up process requires the inclusion of the internal convection within the solid particle, the blowing effects on the particle surface, the spatial and temporal variations of the solid thermal conductivity as well as the heat of pyrolysis reactions. The internal convection tends to equalize the temperature distribution within the solid, while the blowing effect contributes to the boundary layer thickening and eventually to a reduction in the convection heat transfer to the particle. To include the above-mentioned effects, a kinetic model for the total weight loss of the solid material was coupled with the heating model. A simple first-order reaction model for the total weight loss was utilized in this study. For materials with high moisture contents, the heat of pyrolysis reactions is an important factor in the heating rate and non-uniform heating of the solid particle. Thermal equilibrium between the solid and evolved gases was assumed within the particle and the equations for the conservation of mass and energy were solved numerically. Results show that surface blowing which is due to the devolatilization of the particle tends to reduce the convection heat transfer from the hot gases to the particle. Internal convection contributes to thermal uniformity in the particle. Heat of pyrolysis reactions plays an important role in the heating profile of the particle. It delays the temperature rise of the particle until most of the volatile materials is released.

Development of Systems Engineering Model for UREX Process

The mission of the Transmutation Research Program (TRP) at University of Nevada, Las Vegas (UNLV) is to establish a national nuclear technology research capability, a nuclear engineering test bed that can carry out effective transmutation and advanced reactor research and development effort. The main task of the Chemical Engineering Division, Argonne National Laboratories (ANL) is to design, model, and demonstrate countercurrent uranium solvent-extraction process. The division has developed MS Excel macros interface, called Argonne Model for Universal Solvent Extraction (AMUSE), to calculate flowsheets for treating high-level liquid waste. The AMUSE code forms all computational basis for flowsheet design and process development. The extraction process, including U, Tc, Pu/Np, Cs/Sr, and Am/Cm separations, is complicate and requires further system optimization for robust performance. A systems engineering model is proposed by the Nevada Center for Advanced Computational Methods (NCACM) at UNLV that provides process optimization through the adjustment on feed compositions, stages, number of sections and flow rates. The NCACM is designing and developing a MS Visual Basic graphical user interface (GUI) that provides multiple-run results and data reporting and presentation. All calculations are made by the interaction with the MS Excel macros, defined in ANL AMUSE codes. An optimization model, developed with the GUI, interconnects with MatLab’s optimization toolbox, commercial software from MathWorks. Due to the nature of the AMUSE code, all the computational results are generated from the existing AMUSE macros. The model also examines measure effects of process deviations, caused by operational upsets or product diversion.

Numerical Simulation of the Coupling Between Vortex Shedding and Acoustic Field in a Solid Propellant Engine

The paper investigates the numerical simulation of vortex shedding in the flow field of solid-propellant rocket motors. This phenomenon, resulting from the strong coupling between shear-layer instability and acoustic waves in the chamber, produces thrust and pressure oscillations. Numerical simulations are performed on the combustion chamber of the Ariane 5 MPS P230 (Solid Rocket Motor) with the commercial code Fluent CFD for conditions corresponding to 89 s of combustion time. The objective of the study is to reproduce the pressure oscillations frequencies and magnitudes, to compare the available experimental data and to capture the vortex shedding phenomena.

Investigation of Light Interaction With Transient Expanding Thick Flames

Optical behavior of spherical flames has been investigated using Shadowgraph method. A mathematical model has been developed to predict the intensity profile of refracted light beams interacting with a transient expanding thick flame. Experimental facilities have been built to visualize transient expanding spherical flames. Facilities include a cylindrical chamber with two end glasses for optical observation. Shadowgraph pictures of flame propagation have been taken using a high speed Charged Coupled Device camera. Flame edge has been located using the mathematical model and it has been compared to experimental measurements. Experimental results are in very good agreement with those predicted by the theoretical model.