Temperature dependency of the laminar burning velocity of fuel-rich methane oxygen measurements

First experiments to determine laminar burning velocities of methane-pure oxygen mixtures were carried out in 1932 by Jahn [1] for a wide range of equivalence ratios Φ (0.2 to 2.64) using a Bunsen burner. Since then, new and most important more accurate methods were developed to determine laminar burning velocities. One of these methods, namely the Heat Flux Method, which was introduced by de Goey et al. [2] in 1993, was used in the current work to validate the results for fuel-rich methane oxygen mixtures (Φ = 2.38 to 2.64) as published by Jahn. Regarding the current Heat Flux Bruner setup the range of velocities that can be determined are limited between 9 and 50 cm/s, which also limits the range of investigated equivalence ratios (Φ = 2.38 to 3.03), which is wider as the one investigated by Jahn [1]. Furthermore, the influence of the pre-heating temperature was also investigated by a variation of it from 263 up to 455 K. Based on these experimental data the temperature dependency of laminar burning velocities of fuel-rich methane oxygen mixtures was determined and as a result the coefficient α of the power law correlation SL = SL0 (T/T0)α was calculated. Due to the increase of the laminar burning velocity at higher pre-heating temperatures, the laminar burning velocities could also be determined at equivalence ratios up to a maximum value of Φ = 3.33 (TP = 455 K). The increase in accuracy of measurement methods to determine laminar burning velocities over the last decades [3] leads to an observed decrease in measured flame speeds. This tendency is confirmed in the current experiments, where the determined laminar burning velocities are lower than the ones measured by Jahn [1]. Regarding the temperature dependency of the laminar burning velocity, the results indicate that for the range of investigated equivalence ratios and temperatures (300 K to 455 K) the power law coefficient α was observed to be almost constant

Determination of a correlation for predicting lean blow off limits of gaseous fueled, premixed turbulent jet flame arrays enclosed in a hexagonal dump combustor

Combustion of natural gas with air in gas turbines is a key technology for efficient provision of electric energy and heat. More stringent regulations regarding the emission of pollutants, such as NOx emissions, are necessitating research on technologies to reduce NOx formation during the combustion process. One technical approach onto the reduction of NOx-formation during combustion is fuel-lean premixed combustion. Current lean combustion concepts applied in stationary gas turbine combustors rely on flame stabilization through recirculation of hot flue gas using swirling flows. Swirl stabilized flames may be prone to combustion instabilities especially in lean premixed arrangements. Therefore, another approach is followed in the present study. In this concept, a matrix of turbulent lean premixed jet flames in a dump combustor is applied. The matrix burner consists of a nozzle with an array of circular channels in a hexagonal arrangement and a combustion chamber with a hexagonal cross section. In order to develop an appropriate burner design based on this concept, the experimental determination and theoretical evaluation of the lean blow out limit using different nozzles and operating conditions were conducted in this work in order to quantify the influence of different parameters on the flame stability. The varied geometric parameters are the diameter of the circular channels in the burner matrix as well as the ratio of the free cross section area of the nozzle to the cross section are of the combustion chamber, the combustor area dump ratio. The lean blow limit was determined at different preheating temperatures and flow velocities. The results show that the velocity at the LBO limit increases with increasing channel diameter, area combustor dump ratio and preheating temperature. The experimental results of three matrix burner are correlated in terms of a critical Damkoehler number and it is shown through experimental validation, that the Damkoehler number correlation derived is capable of predicting the LBO of a scaled matrix burner

Large Eddy Simulation of the Two-Phase Reactive Flow Field in a Single Sector Laboratory Scale Rich-Quench-Lean Combustion Chamber

This work presents Large Eddy Simulation (LES) of a laboratory scale RQL combustion chamber. Simulations were carried out using an in-house LES-code for reactive, two-phase, adiabatic flow implemented in OpenFOAM. The twophase turbulent reactive flow is modeled following a coupled Euler-Lagrange approach in combination with a presumed Joint Probability Density Function (JPDF) combustion model and tabulated chemistry. The reaction progress of laminar premixed flames is tabulated using a kerosene-surrogate chemical reaction mechanism. Calculated and measured velocity fields of the gaseous and liquid phase are compared to each other for reacting and non-reacting conditions. The results show excellent agreement between the two-dimensional flow fields derived from PIV and LES for the non-reactive case. The results of the reactive case show very good agreement for the velocity field

Berechnung des instationaeren Stroemungsfeldes und der Flammenausbreitung im Zylinderraum eines Otto-Motors

SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

NO_x-Reduktion mittels der Fett-Mager- und der Magerverbrennung unter praxisnahen Betriebsbedingungen (Vorhaben 3.2.1.1)

The TURBOFLAM project carried out at MTU, was designed to investigate two combustion concepts for their reduction potential with respect to exhaust emissions and, in particular, NO_x emission: lean combustion by pre-vaporization and pre-mixing of liquid fuel, and rich-lean combustion. Both concepts are designed to reduce exhaust emissions by deliberate control of combustion itself rather than by exhaust-emission control, an alternative which proves to be by far more favorable both in terms of cost and environmental pollution aspects. The combustion chambers designed and manufactured for the project should be of structural designs which are capable of being taken over into practical applications without major difficulties. (orig.)In dem bei MTU durchgefuehrten TURBOFLAM-Vorhaben sollten zwei Verbrennungskonzepte auf deren Reduktionspotential bezueglich der Abgasemissionen und insbesondere der NO_x-Emission untersucht werden: die Magerverbrennung durch Vorverdampfung und Vorvermischung des fluessigen Brennstoffs und die Fett-Mager-Verbrennung. Bei beiden Konzepten wird nicht durch Abgasreinigung sondern durch gezielte Steuerung der Verbrennung die Reduktion der Schadstoffemission angestrebt, eine Alternative, die sich sowohl aus Kosten- wie auch aus Umweltbelastungsgesichtspunkten als die wesentlich guenstigere erweist. Die zur Durchfuehrung des Vorhabens ausgelegten und gefertigten Brennkammern sollten Bauformen aufweisen, die ohne groessere Schwierigkeiten in die Praxis uebernommen werden koennten. (orig.)SIGLEAvailable from TIB Hannover: D.Dt.F.QN1(6,44) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman