Rich-burn, Quick-quench, Lean-burn Research Articles

A phenomenological model for predicting the size of soot primary particles emitted from an aero-engine combustor

Soot particles emitted from aero-engines are harmful to airport local air quality, and the adverse impact from soot particles is closely related to particle morphology, microstructure and chemical properties. To understand those properties of aviation soot particles, combustion experiments using conventional aviation fuel RP-3 were conducted on a Rich-Burn/Quick-Quench/Lean-Burn (RQL) aero-engine combustor. The soot emissions from the RQL combustor were analyzed via a high resolution transmission electron microscope (HRTEM), and the size distributions of primary particles at different power levels were determined based on the HRTEM images. Since the primary particle size is strongly related to the power level and follows an S-shaped curve, a phenomenological model with low-computational complexity and general applicability was established. Furthermore, the model was validated by using previously published experimental data of a CFM56–2C1 aero-engine burning four different fuels, including sustainable aviation fuels (SAF), demonstrating the influence of fuel properties on primary particle sizes at different power levels.Novelty and Significance Statement: In this paper, combustion experiments were conducted on an RQL combustor burning RP-3 fuel. Based on the HRTEM observation, the log-normal size distributions of primary particles at different power levels were determined. Furthermore, based on the fact that the relationship between primary particle size and power level followed an S-shaped curve, a phenomenological model linking primary particle size and combustor power was proposed and validated.

The design and performance of a RP-3 fueled high temperature rise combustor based on RQL staged combustion

Employing rich-burn/quick-quench/lean-burn (RQL) staged combustion, a RP-3 fueled high temperature rise combustor was designed and tested. The outlet temperatures and the corresponding temperature rises were measured, which indicated that the high temperature rise combustor was realized. Using particle image velocimetry (PIV), high-speed photography and chemiluminescence imaging diagnostics, the flow and CH∗/OH∗ chemiluminescence characteristics of the high temperature rise combustor were investigated. Comparison between non-reacting flow and reacting flow shows the thermal expansion and baroclinic effects caused by combustion could eliminate inner local recirculation region. Reaction happens intensively in the shear mixing region between the inner flow and the outer flow, as the droplet atomization and mix with air were enhanced by shearing effect. The momentum of jet is the dominating factor that affects flame structure. High momentum cold jet could enter the reaction zone and quench the flame.

Flow and flame characteristics of a RP-3 fuelled high temperature rise combustor based on RQL

Based on RQL (rich-burn/quick-quench/lean-burn) low emission combustion technology, a RP-3 fuelled high temperature rise combustor was proposed. The flow and radicals (OH∗, CH∗, and NO∗) distribution of combustor were investigated by Particle Image Velocimetry (PIV) and chemiluminescence imaging. Although the change of primary holes structure has great influence on the characteristics of flow and reaction zone, the airflow has same effect on the reaction zone. High-brightness values of CH∗ mainly occurred in the shear layer under the parallel airflow, and the reaction zone exhibited a smooth boundary. When swirling and vertical airflows acted on the boundary of the reaction zone, the luminance in the reaction zone was reduced and the boundary became wrinkled. The starting boundaries of NO∗ and OH∗ were basically coincident, although the end boundary of NO∗ lagged. When the axial position of the primary holes was located at H/2, compared with the symmetric structure, the mean residence time and area of the NO-producing region in the quenching zone with the staggered structure could be reduced by about 20% and 47%, respectively.

Multiple Injector Model for Primary Breakup of a Liquid Jet in Crossflow

R ADIAL injection of liquid jets into a high-velocity and hightemperature cross stream at elevated pressures has various applications in fuel injection systems and advanced aircraft engines, such as gas turbines, afterburners, augmenters, and various combustors. Since this type of fuel injection can improve the fuel atomization and vaporization characteristics, it is commonly used in turbojet augmenter sections and rich burn-quick quench-lean burn, lean premixed prevaporized, and ramjet and scramjet combustion systems. To date, several analytical, experimental, and numerical studies have investigated various characteristics of the jet-incrossflow (JICF) atomization. Experimental studies have developed several correlations that predict various features of the JICF atomization. Because of the nature of the experimental studies, the results and correlations proposed by each study aremainly applicable within the specific parameter ranges of that study. The JICF atomization problem involves very complex physics, such as strong vortical structures, small-scale wave formation, stripping of small droplets from the jet surface, and formation of ligaments and droplets with a wide range of sizes. The JICF atomization process can be divided into three main phases: 1) injection of a liquid jet perpendicular to a gaseous crossflow, 2) deflection and deformation of the jet, and 3) disintegration of the jet into ligaments and droplets. The atomization mechanism is believed to start by the growth of waves that form on the surface of the jet after injection from the nozzle. The relative velocity between the gas and the liquid phase amplifies the surface waves up to the point where the jet breaks up into smaller droplets. Apart from the three phases mentioned above, more complex small-scale physical processes are involved in the problem, such as particle stripping from the jet. From the computational point of view, the complete numerical simulation of such a problem, resolving most important flow scales on the Eulerian frame, is still expensive, especially for industrial applications. These issues signal the demand for some simpler yet reliable models that can be used for industrial design purposes and, at the same time, take into account the flow conditions and the physical properties of the liquid and gas phases. In this paper, we review some of the challenges involved in modeling of the JICF atomization and propose a model that provides realistic predictions of the jet atomization in crossflows. Our focus will be turbulent jets. To validate the model, we perform several experiments. We first validate our experiments by showing that their resulting correlations are in good agreement with the available literature. Then, we use our experimental results to validate our model results. We decided to perform our own experiments rather than making comparisons to previous studies for twomain reasons. First, we needed spatial droplet size and velocity distributions downstream of the nozzle. Although there are studies available that provide that information (such asWu et al. [1]), they mostly consider laminar jets, whereas we are focused on turbulent jets. Second, performing our own experiments provides us with all the information we need to set up our simulations from initial flow parameters to geometrical specifications. A review of some of the experimental studies devoted to studying various characteristics of the JICF problem can be found in Mashayek andAshgriz [2].Wewill present a brief review on some of the experimental and theoretical literature more relevant to the purposes of this paper. One of the first models for atomization of a liquid phase injected normal to a gas stream was that of Reitz [3]. He modeled the atomization by estimating the wavelength and growth rate of the surface waves and relating the breakup droplet sizes to the wavelengths. Liu et al. [4] also modeled a liquid jet injected normal to a gas stream by successive injection of droplets into the gas phase. They did not consider the stripping of droplets from the surface of the jet and Received 24 April 2010; revision received 6 April 2011; accepted for publication 8 April 2011. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0001-1452/11 and $10.00 in correspondence with the CCC. ∗Department of Physics, 60 St. George Street. Department of Civil Engineering, 35 St. George Street. ; Department of Mechanical and Industrial Engineering, King’s College Road (Corresponding Author). AIAA JOURNAL Vol. 49, No. 11, November 2011

Characterization of Ceramic Matrix Composite Fasteners Exposed in a Combustor Linear Rig Test

Combustion tests on SiC/SiC CMC components were performed in an aircraft combustion environment using the rich-burn, quick-quench, lean-burn (RQL) sector rig. SiC/SiC fasteners were used to attach several of these components to the metallic rig structure. The effect of combustion exposure on the fastener material was characterized via microstructural examination. Fasteners were also destructively tested, after combustion exposure, and the failure loads of fasteners exposed in the sector rig were compared to those of as-manufactured fasteners. Combustion exposure reduced the average fastener failure load by 50% relative to the as-manufactured fasteners for exposure times ranging from 50 to 260 hours. The fasteners exposed in the combustion environment demonstrated failure loads that varied with failure mode. Fasteners that had the highest average failure load, failed in the same manner as the unexposed fasteners.