Flame Tube Wall Research Articles

Burner Design Impact on the Flame Tube Walls Temperature State

Burner Design Impact on the Flame Tube Walls Temperature State

Study of Adiabatic Flame Temperature of a Jet Combustor using a Non-Circular Inlet

An experimental investigation on heat transfer at various zones of the combustion chamber has been carried out using a non-circular inlet at the flame tube. With an aim to improve the turbulent level in flow, the non-circular section used here is an elliptical one. In addition to this, two rectangular tabs are placed at major axis of the ellipse to achieve an efficient mixing of fuel and air. Fuel used for combustion is kerosene while LPG gas is used for pre ignition. Fuel is fed to the chamber by gravity system and it has been atomized by two fish tank pumps. Ignition of the fuel is done by spark plug with a separate setup. The setup comprises of growler and CDI coil which are powered electrically. During the experiment, combustion has been initiated by allowing the air from blower to the chamber. The fuel is sprayed into the flame tube through fuel injector placed at a specified distance. After the proper mixing of fuel and air, the mixture is ignited by spark plug setup. Initially LPG gas was used for preheating followed by kerosene for combustion. Fuel tank has been calibrated for mass flow rate. The experiment has been carried out for different intervals of time and the heat transferred from the flame tube wall and chamber wall is been measured using an infrared gun (ray gun) by pointing laser on the wall. The temperatures at different zones have been measured. It is seen that the overall heat transfer at secondary zone is minimum when compared with other zones for the same period of time. This indicates that if the fuel injector is placed before the secondary zone, then a maximum flame temperature can be obtained. This leads to an improvement in efficiency of the combustion chamber.

Experimental Studies of NOx Emissions in Sequential Fuel Combustion with a Diffusion Second Zone

This is the third paper on experimental research and optimization of combustion in the fuel-air mixture in the two-zone combustor at outlet gas temperatures of 1550–1700°C with meeting the requirements for harmful substances (NOx and CO) emissions. The experimental results on combustion of gaseous fuel in the combustor with two consecutive combustion zones are presented. Each zone has its own burner: the first burner is traditional and located at the end of the flame tube, while the second burner is sequential and located downstream on side walls of the flame tube. Fuel combustion in the second zone occurs at a low oxygen content and high temperature. Zones with maximal CO values ​​are shown to be formed near the flame tube walls, while maximal NOx concentrations are observed in the central zone of the flow recirculation. The penetration capacity of the fuel jets entering the second combustion zone was evaluated, and the jet trajectories in the blowing flow of hot gases in the first zone are shown. The results of optimization of the fuel distribution between two successive combustion zones, as well as the effect of the flow rate on the NOx and CO formation at the outlet gas temperature of 1550–1700°C, are presented. The results were obtained by testing the model low-emission combustor at the test facility of the All-Russia Thermal Engineering Institute.

Modeling of natural acoustic frequencies of a gas-turbine plant combustion chamber

The paper presents results of determination of natural acoustic frequencies of a gas-turbine plant annular combustion chamber model using 3D-simulation. At the beginning, a calculation procedure for determining natural acoustic frequencies of the gas-turbine plant combustion chamber was worked out. The effect of spatial inhomogeneity of the flow parameters (fluid composition, pressure, temperature) arising in combustion and some geometrical parameters (cooling holes of the flame tube walls) on the calculation results is studied. It is found that the change of the fluid composition in combustion affects the acoustic velocity not more than 5%; therefore, the air with a volume variable temperature can be taken as a working fluid in the calculation of natural acoustic frequencies. It is also shown that the cooling holes of the flame tube walls with diameter less than 2 mm can be neglected in the determination of the acoustic modes in the frequency range of up to 1000 Hz. This reduces the number of the grid-model elements by a factor of six in comparison with a model that considers all of the holes. Furthermore, a method of export of spatial inhomogeneity of the flow parameters from a CFD solver sector model to the annular combustion chamber model in a modal solver is presented. As a result of the obtained model calculation, acoustic modes of the combustion chamber in the frequency range of up to 1000 Hz are determined. For a standard engine condition, a potentially dangerous acoustic mode with a frequency close to the ripple frequency of the precessing vortex core, which is formed behind the burner device of this combustion chamber, is detected.

Development of a low-emission bifuel combustion chamber

The paper presents the experience gained by the “Saturn” science-and-production association in producing a bifuel combustion chamber for the E70/8RD engine. The data on the modernization of the combustion chamber based on the RQQL (rich /quick quench/poor combustion) technology that made it possible to reduce significantly the emissions of NOx while working on natural gas and to meet the requirements of the technical project of the engine are presented. The problem of providing the thermal state of the flame tube walls is also discussed.

Determination of thermal state and modification of the flame tube cooling system with the help of three-dimensional modeling methods

The results of calculating the thermal state of the flame tube walls are presented, a gas turbine engine annular combustor taken as an example. The three-dimensional Ansys Fluent simulation package is used. A finite element conjugate model is created. The conformal (node-to-node) interface gas-to-metal is a characteristic feature of the grid. The number of elements over the thickness of the wall is taken to be not less than 5. The total number of elements is 8.6 million. The HN50VMTYUB-VI heat-resistant alloy is used as the material of the flame tube. A thermal barrier coating (TBC) is deposited on the hot side of the flame tube. The thickness of the ceramic coating is assumed to be equal to 0.4 mm. The thermal barrier coating consists of an intermetallic bonding layer that contains elements of the wall material of the flame tube and ceramics, as well as a ceramic protective layer with low thermal conductivity. The shell surface of the flame tube walls is assigned to take into account the thermal barrier coating. The density of the ceramic coating is 6 t/m3, and the dependence of the isobaric heat capacity of the thermal barrier coating on the temperature in the range of 473 K to 1473 K is specified. The distribution of the heat flux in the thermal barrier coating is taken into account only in the direction perpendicular to the surface of the flame tube. The influence of the thermal barrier coating on the flame tube thermal condition is analyzed. Measures have been taken to improve the cooling system of the flame tube. Variations of the temperature of the flame tube along its length are analyzed.

Bioethanol Combustion in an Industrial Gas Turbine Combustor: Simulations and Experiments

Combustion tests with bioethanol and diesel as a reference have been performed in OPRA's 2 MWe class OP16 gas turbine combustor. The main purposes of this work are to investigate the combustion quality of ethanol with respect to diesel and to validate the developed CFD model for ethanol spray combustion. The experimental investigation has been conducted in a modified OP16 gas turbine combustor, which is a reverse-flow tubular combustor of the diffusion type. Bioethanol and diesel burning experiments have been performed at atmospheric pressure with a thermal input ranging from 29 to 59 kW. Exhaust gas temperature and emissions (CO, CO2, O2, NOx) were measured at various fuel flow rates while keeping the air flow rate and air temperature constant. In addition, the temperature profile of the combustor liner has been determined by applying thermochromic paint. CFD simulations have been performed with ethanol for five different operating conditions using ANSYS FLUENT. The simulations are based on a 3D RANS code. Fuel droplets representing the fuel spray are tracked throughout the domain while they interact with the gas phase. A liner temperature measurement has been used to account for heat transfer through the flame tube wall. Detailed combustion chemistry is included by using the steady laminar flamelet model. Comparison between diesel and bioethanol burning tests show similar CO emissions, but NOx concentrations are lower for bioethanol. The CFD results for CO2 and O2 are in good agreement, proving the overall integrity of the model. NOx concentrations were found to be in fair agreement, but the model failed to predict CO levels in the exhaust gas. Simulations of the fuel spray suggest that some liner wetting might have occurred. However, this finding could not be clearly confirmed by the test data.

3d calculation of a multiport low-emission combustor cooling system

The results of calculating coupled heat transfer for four versions of a multiport flame tube are presented. The walls of the tube of an experimental combustion chamber have a double segment structure with an impact-convective cooling system. The calculations were made taking into account the combustion and the influence of radiant fluxes. The thermal state of the flame tube walls determined by the results of a numerical experiment is compared with the data of full-level tests of the combustion chamber as a part of a gas generator of an engine. Recommendations are given concerning the modernization of the flame tube structure in order to improve the thermal state of its segments.

Numerical investigations of cooling holes system role in the protection of the walls of a gas turbine combustion chamber

Numerical simulations in a gas turbine Swirl stabilized combustor were conducted to investigate the effectiveness of a cooling system in the protection of combustor walls. The studied combustion chamber has a high degree of geometrical complexity related to the injection system as well as the cooling system based on a big distribution of small holes (about 3,390 holes) bored on the flame tube walls. Two cases were considered respectively the flame tube without and with its cooling system. The calculations were carried out using the industrial CFD code FLUENT 6.2. The various simulations made it possible to highlight the role of cooling holes in the protection of the flame tube walls against the high temperatures of the combustion products. In fact, the comparison between the results of the two studied cases demonstrated that the walls temperature can be reduced by about 800°C by the mean of cooling holes technique.

Numerical simulation of 3-D temperature distribution of the flame tube of the combustion chamber with air film cooling

The wall temperature distribution of the flame tube of the combustion chamber is strongly affected by the combustion, radiation and flow. The interaction of these influential factors forms a coupling system. In this paper, a new method, which is different from the previous methods, has been developed for calculating the temperature distribution of the flame tube wall together with the flow field inside and outside the flame tube. In the calculation, the combustion, heat radiation, cooling air film and injection stream mixing inside the flame tube as well as the secondary air flowing outside the flame tube have been simulated. The calculation, in this paper, uses the SIMPLE algorithm, thek - ɛ turbulence model and the auto-adjustable damping method. By using this method, the 3-D temperature distribution of the flame tube wall of the combustion chamber of an aeroengine has been simulated successfully. The calculation results are compared to the experimental data. The error of wall temperature is less than 10%.

The Influence of Fuel Composition on Smoke Emission from Gas-Turbine-Type Combustors : Effect of Combustor Design and Operating Conditions

Abstract The influence of fuel composition on smoke emission/combustor wall temperatures has been studied in a laboratory-scale gas-turbine-type combustor over the range of operating conditions of modern turbine combustors and as a function of combustor design. Fuel hydrogen content is shown to give the best prediction of smoke emission and of variations in flame tube wall temperature caused by changes in flame radiation. The major finding is that the influence of fuel composition on smoke emission/flame radiation falls virtually to zero at combustor pressures above about 10 bar. Significant reduction in sensitivity to fuel composition can also be obtained by varying combustor design and are tentatively correlated with increasing combustion intensity. The implication of these effects for aircraft operation is discussed and an explanation for the results is put forward based on changes in the chemical mechanisms leading to soot formation.

Temperature method of rating carbon deposition of scale from fuels

1. A temperature method has been developed for rating the carbon deposition properties of jet fuels, based on measuring the flame tube wall temperature, which changes as a function of carbon deposit formation on the walls during turbojet engine operation. 2. The evaluation is performed in a special small-size turbojet engine. The test period is five minutes. One kilogram of test fuel is required to determine the carbon number of a fuel. The-deviation among parallel test results does not exceed 10%.