Spray Combustion Characteristics of Single/Multi-Component Surrogate Fuel for Aviation Kerosene

2022 ◽  
Author(s):  
Wenjin Qin ◽  
Dengbiao Lu ◽  
Lihui Xu
Keyword(s):  
Soot Formation ◽  
Mean Field ◽  
Combustion Characteristics ◽  
Spray Combustion ◽  
Aviation Kerosene ◽  
Eddy Simulation ◽  
Air Mixing ◽  
Flow Field Characteristics ◽  
Lift Off ◽  
Surrogate Fuel

Abstract In this research, n-dodecane and JW are selected as single and multi-component surrogate fuel of aviation kerosene to study the Jet-A spray combustion characteristics. The spray combustion phenomena are simulated using large eddy simulation coupled with detailed chemical reaction mechanism. Proper orthogonal decomposition method is applied to analyze the flow field characteristics, and the instantaneous velocity field are decomposed into four parts, namely the mean field, coherent field, transition field and turbulent field, respectively. The four subfields have their own characteristics. In terms of different fuels, JW has a higher intensity of coherent structures and local vortices than n-dodecane, which promotes the fuel-air mixing and improves the combustion characteristics, and the soot formation is significantly reduced. In addition, with the increase of initial temperature, the combustion is more intense, the ignition delay time is advanced, the flame lift-off length is reduced, and soot formation is increased accordingly.

Simulating Flame Lift-Off Characteristics of Diesel and Biodiesel Fuels Using Detailed Chemical-Kinetic Mechanisms and Large Eddy Simulation Turbulence Model

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Sibendu Som ◽  
Douglas E. Longman ◽  
Zhaoyu Luo ◽  
Max Plomer ◽  
Tianfeng Lu ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Chemical Kinetic ◽  
Spray Combustion ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Kinetic Mechanisms ◽  
Lift Off ◽  
Biodiesel Fuels

Combustion in direct-injection diesel engines occurs in a lifted, turbulent diffusion flame mode. Numerous studies indicate that the combustion and emissions in such engines are strongly influenced by the lifted flame characteristics, which are in turn determined by fuel and air mixing in the upstream region of the lifted flame, and consequently by the liquid breakup and spray development processes. From a numerical standpoint, these spray combustion processes depend heavily on the choice of underlying spray, combustion, and turbulence models. The present numerical study investigates the influence of different chemical kinetic mechanisms for diesel and biodiesel fuels, as well as Reynolds-averaged Navier–Stokes (RANS) and large eddy simulation (LES) turbulence models on predicting flame lift-off lengths (LOLs) and ignition delays. Specifically, two chemical kinetic mechanisms for n-heptane (NHPT) and three for biodiesel surrogates are investigated. In addition, the renormalization group (RNG) k-ε (RANS) model is compared to the Smagorinsky based LES turbulence model. Using adaptive grid resolution, minimum grid sizes of 250 μm and 125 μm were obtained for the RANS and LES cases, respectively. Validations of these models were performed against experimental data from Sandia National Laboratories in a constant volume combustion chamber. Ignition delay and flame lift-off validations were performed at different ambient temperature conditions. The LES model predicts lower ignition delays and qualitatively better flame structures compared to the RNG k-ε model. The use of realistic chemistry and a ternary surrogate mixture, which consists of methyl decanoate, methyl nine-decenoate, and NHPT, results in better predicted LOLs and ignition delays. For diesel fuel though, only marginal improvements are observed by using larger size mechanisms. However, these improved predictions come at a significant increase in computational cost.

Large Eddy Simulation of High Reynolds Number Nonreacting and Reacting JP-8 Sprays in a Constant Pressure Flow Vessel With a Detailed Chemistry Approach

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Luis Bravo ◽  
Sameera Wijeyakulasuriya ◽  
Eric Pomraning ◽  
Peter K. Senecal ◽  
Chol-Bum Kweon
Keyword(s):  
Large Eddy Simulation ◽  
Internal Combustion Engines ◽  
Constant Pressure ◽  
Engine Performance ◽  
Spray Combustion ◽  
Pressure Flow ◽  
Detailed Chemistry ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Lift Off

In military propulsion applications, the characterization of internal combustion engines operating with jet fuel is vital to understand engine performance, combustion phasing, and emissions when JP-8 is fully substituted for diesel fuel. In this work, high-resolution large eddy simulation (LES) simulations have been performed in-order to provide a comprehensive analysis of the detailed mixture formation process in engine sprays for nozzle configurations of interest to the Army. The first phase examines the behavior of a nonreacting evaporating spray, and demonstrates the accuracy in predicting liquid and vapor transient penetration profiles using a multirealization statistical grid-converged approach. The study was conducted using a suite of single-orifice injectors ranging from 40 to 147 μm at a rail pressure of 1000 bar and chamber conditions at 900 K and 60 bar. The next phase models the nonpremixed combustion behavior of reacting sprays and investigates the submodel ability to predict auto-ignition and lift-off length (LOL) dynamics. The model is constructed using a Kelvin Helmholtz–Rayleigh Taylor (KH–RT) spray atomization framework coupled to an LES approach. The liquid physical properties are defined using a JP-8 mixture containing 80% n-decane and 20% trimethylbenzene (TMB), while the gas phase utilizes the Aachen kinetic mechanism (Hummer, et al., 2007, “Experimental and Kinetic Modeling Study of Combustion of JP-8, Its Surrogates, and Reference Components in Laminar Non Premixed Flows,” Proc. Combust. Inst., 31, pp. 393–400 and Honnet, et al., 2009, “A Surrogate Fuel for Kerosene,” Proc. Combust. Inst., 32, pp. 485–492) and a detailed chemistry combustion approach. The results are in good agreement with the spray combustion measurements from the Army Research Laboratory (ARL), constant pressure flow (CPF) facility, and provide a robust computational framework for further JP-8 studies of spray combustion.

Turbulence-Chemistry Interactions in Spray Combustion

2002 ◽  
Author(s):  
Vaidyanathan Sankaran ◽  
Suresh Menon
Keyword(s):  
Heat Release ◽  
Recirculation Zone ◽  
Vortex Breakdown ◽  
Separated Flow ◽  
Spray Combustion ◽  
Mixing Efficiency ◽  
Eddy Simulation ◽  
Swirl Intensity ◽  
Air Mixing ◽  
Combustion Processes

A prediction methodology based on Large-Eddy Simulation (LES) has been used to study turbulence-chemistry interactions in spray combustion. The unsteady interactions between spray dispersion and vaporization, fuel-air mixing and heat release has been investigated using a Stochastic Separated Flow model for spray within the LES formulation. The effects of swirl intensity and heat release are investigated here. Results show that the central toroidal recirculation zone (CTRZ), which is a manifestation of the vortex breakdown process, occurs only under high swirl conditions. Under non-reacting condition, droplets tend to concentrate in regions of low vorticity and increase in swirl increases the dispersion of the droplets. Mixing efficiency is enhanced and the size of the corner recirculation zone is decreased with increase in swirl. Increase in swirl also enhances the combustion processes for cases with heat release.

scholarly journals Experimental Study of the Effect of Hydrotreated Vegetable Oil and Oxymethylene Ethers on Main Spray and Combustion Characteristics under Engine Combustion Network Spray A Conditions

2020 ◽  
Vol 10 (16) ◽  
pp. 5460
Author(s):  
José V. Pastor ◽  
José M. García-Oliver ◽  
Carlos Micó ◽  
Alba A. García-Carrero ◽  
Arantzazu Gómez
Keyword(s):  
Vegetable Oil ◽  
Diesel Fuel ◽  
Ignition Delay ◽  
Soot Formation ◽  
Imaging Techniques ◽  
Detection Threshold ◽  
Combustion Characteristics ◽  
Engine Combustion ◽  
Lift Off ◽  
Oxygenated Fuels

The stringent emission regulations have motivated the development of cleaner fuels as diesel surrogates. However, their different physical-chemical properties make the study of their behavior in compression ignition engines essential. In this sense, optical techniques are a very effective tool for determining the spray evolution and combustion characteristics occurring in the combustion chamber. In this work, quantitative parameters describing the evolution of diesel-like sprays such as liquid length, spray penetration, ignition delay, lift-off length and flame penetration as well as the soot formation were tested in a constant high pressure and high temperature installation using schlieren, OH∗ chemiluminescence and diffused back-illumination extinction imaging techniques. Boundary conditions such as rail pressure, chamber density and temperature were defined using guidelines from the Engine Combustion Network (ECN). Two paraffinic fuels (dodecane and a renewable hydrotreated vegetable oil (HVO)) and two oxygenated fuels (methylal identified as OME1 and a blend of oxymethylene ethers, identified as OMEx) were tested and compared to a conventional diesel fuel used as reference. Results showed that paraffinic fuels and OMEx sprays have similar behavior in terms of global combustion metrics. In the case of OME1, a shorter liquid length, but longer ignition delay time and flame lift-off length were observed. However, in terms of soot formation, a big difference between paraffinic and oxygenated fuels could be appreciated. While paraffinic fuels did not show any significant decrease of soot formation when compared to diesel fuel, soot formed by OME1 and OMEx was below the detection threshold in all tested conditions.

Soot Formation in Diesel Fuel Jets Near the Lift-Off Length

2006 ◽  
Vol 7 (2) ◽  
pp. 103-130 ◽  
Author(s):  
L M Pickett ◽  
D L Siebers
Keyword(s):  
Heat Release ◽  
Diesel Fuel ◽  
Soot Formation ◽  
Air Entrainment ◽  
Operating Conditions ◽  
Entrainment Rate ◽  
Fuel Type ◽  
Fuel Jet ◽  
Air Mixing ◽  
Lift Off

Soot formation in the region downstream of the lift-off length of diesel fuel jets was investigated in an optically accessible constant-volume combustion vessel under quiescent-type diesel engine conditions. Planar laser-induced incandescence and line-of-sight laser extinction were used to determine the location of the first soot formation during mixing-controlled combustion. OH chemiluminescence imaging was used to determine the location of high-heat-release reactions relative to the soot-forming region. The primary parameters varied in the experiments were the sooting propensity of the fuel and the amount of fuel-air premixing that occurs upstream of the lift-off length. The fuels considered in order of increasing sooting propensity were: an oxygenated fuel blend (T70), a blend of diesel cetane-number reference fuels (CN80), and a #2 diesel fuel (D2). Fuel-air mixing upstream of the lift-off length was varied by changing ambient gas and injector conditions, which varied either the lift-off length or the air entrainment rate into the fuel jet relative to the fuel injection rate. Results show that soot formation starts at a finite distance downstream of the lift-off length and that the spatial location of soot formation depends on the fuel type and operating conditions. The distance from the lift-off length to the location of the first soot formation increases as the fuel sooting propensity decreases (i.e. in the order D2 < CN80 < T70). At the baseline operating conditions, the most upstream soot formation occurs at the edges of the jet for D2 and CN80, while for T70 the soot formation is confined to the jet central region. When conditions are varied to produce enhanced fuel-air mixing upstream of the lift-off length in D2 fuel jets, the initial soot formation shifts towards the fuel jet centre and eventually no soot is formed. For all experimental conditions, the observed location of soot formation relative to the heat-release location (lift-off) suggests that soot formation occurs in a mixture of combustion products originating from partially premixed reactions and a diffusion flame. The results also imply that soot precursor formation rates depend strongly on fuel type in the region between the lift-off length and the first soot formation.

A Numerical Study for the Effect of Liquid Film on Soot Formation of Impinged Spray Combustion

2021 ◽  
Author(s):  
Zhihao Zhao ◽  
Xiucheng Zhu ◽  
Le Zhao ◽  
Meng Tang ◽  
Seong-Young Lee
Keyword(s):  
Liquid Film ◽  
Soot Formation ◽  
Numerical Study ◽  
Spray Combustion
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