scholarly journals Study on the Spray Combustion of Liquid Fuel : Part 2, Flame Length and Combustion Process

1965 ◽  
Vol 31 (231) ◽  
pp. 1689-1701
Author(s):  
Masatake MAEZAWA
Keyword(s):  
Liquid Fuel ◽  
Combustion Process ◽  
Flame Length ◽  
Spray Combustion

Experimental Investigation of Low Emission Liquid Fuelled Reverse Cross Flow Combustor

2017 ◽  
Author(s):  
Preetam Sharma ◽  
Vaibhav Arghode
Keyword(s):  
Experimental Investigation ◽  
Reaction Zone ◽  
Liquid Fuel ◽  
Alternative Fuels ◽  
Reverse Flow ◽  
Hot Spot ◽  
Combustion Process ◽  
Cross Flow ◽  
Air Jet ◽  
Low Emission

This study deals with an experimental investigation of a low emission liquid fuelled (ethanol) reverse cross-flow combustor. This investigation is carried out to cater to the need of burning liquid fuels (including alternative fuels) with minimum emissions in gas turbine engines used for both aircraft and land based power generation applications using modern combustion technologies. In the present combustor design, the air inlet and the exhaust ports are located on the same side (and hence the name reverse-flow) whereas the liquid fuel is injected directly into the strong cross-flow of the air using a small diameter round tube to aid fuel atomization. Hence, a conventional atomization system is absent in the investigated combustor. The reverse-flow configuration allows effective internal product gas recirculation to facilitate the preheating and dilution of the oxidizer stream and stabilization of a distributed reaction zone. This apparently suppresses near stoichiometric reactions and hot spot regions resulting in low pollutant (NOx and CO) emissions. In the present case, the heat load is varied (keeping a constant air flow rate) from 3.125 kW to 6.25 kW which results in the thermal intensity variation from 19 MW/m3-atm to 39 MW/m3-atm. Two different tubes with internal diameters (dfuel) of 0.5 mm and 0.8 mm are used for injection of liquid fuel into the cross flow of air. The combustor was also tested in premixed-prevaporized (PP) mode with ethanol for benchmarking. The combustion process was found to be stable with NOx emissions of 1.6 ppm (premixed-prevaporized), 8 ppm (dfuel = 0.5 mm), 9 ppm (dfuel = 0.8 mm). The CO emissions were 5 ppm (premixed-prevaporized), ∼100 ppm (dfuel = 0.5, 0.8 mm), at atmospheric pressure operation (corrected to 15% O2) and ϕ = 0.7, Tadiabatic ∼1830 K. Reaction zone positioning inside the combustor was investigated using OH* chemiluminescence imaging and global flame pictures, and the same was found to be located in the vicinity of the air jet.

Humid Air NOx Reduction Effect on Liquid Fuel Combustion

2004 ◽  
Vol 126 (1) ◽  
pp. 69-74 ◽  
Author(s):  
A. G. Chen ◽  
Daniel J. Maloney ◽  
William H. Day
Keyword(s):  
Liquid Fuel ◽  
Nox Reduction ◽  
Flame Temperature ◽  
Substantial Reduction ◽  
Combustion Process ◽  
Pollutant Emissions ◽  
Humid Air ◽  
Wide Range ◽  
Reduction Of Nox ◽  
Reduction Effect

An experimental investigation was carried out at DOE NETL on the humid air combustion process using liquid fuel to determine the effects of humidity on pollutant emissions and flame stability. Tests were conducted at pressures of up to 100 psia (690 kPa), and a typical inlet air temperature of 860°F (733 K). The emissions and RMS pressures were documented for a relatively wide range of flame temperature from 2440-3090°F (1610–1970 K) with and without added humidity. The results show more than 90% reduction of NOx through 10% humidity addition to the compressed air compared with the dry case at the same flame temperature. The substantial reduction of NOx is due to a shift in the chemical mechanisms and cannot be explained by flame temperature reduction due to added moisture since the comparison was made for the same flame temperature.

Simultaneous Imaging of OH* Chemiluminescence and Flame Luminosity of Diesel and Biodiesel Spray Combustion

2011 ◽  
Author(s):  
Ji Zhang ◽  
Tiegang Fang
Keyword(s):  
Ambient Temperature ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Soot Formation ◽  
Combustion Process ◽  
Spray Combustion ◽  
Chemiluminescence Intensity ◽  
High Temperature Reaction ◽  
The Impact

The research on the spray combustion of diesel and biodiesel is vital to the understanding of emission formation and optimal utilization of fuel. This paper studies the biodiesel and diesel spray combustion in a constant volume chamber under different simulated diesel engine conditions. The ambient temperature at fuel injection varied from 800K to 1200K, while the ambient oxygen concentration was maintained at 21%. Simultaneous high speed imaging of OH* chemiluminescence and flame luminosity was employed to visualize the whole combustion process. Heat release rate was analyzed based on the measured combustion pressure. The apparent heat release rate analysis shows that biodiesel has a shorter ignition delay time than diesel, and biodiesel has a smaller cumulative heat release value due to its lower heating value. The overlaying image of OH* chemiluminescence and flame luminosity clearly identifies the high temperature reaction regions and soot formation regions. The line-of-sight images agree with the published observation that the hydroxyl radical is formed on the lean side of the flame edge. Decreasing ambient temperature greatly reduces the OH* chemiluminescence intensity of the diesel combustion, while the impact is smoother and milder for biodiesel combustion. Biodiesel shows a significantly lower level of flame luminosity than diesel under all conditions. These combined observations lead to a speculation that the soot oxidation process may serve as an important contributor to OH* chemiluminescence intensity for late stage combustion, and biodiesel shows a tendency to produce less soot than diesel under the investigated conditions.

Investigation of Swirling Air Flows Generated by Axial Swirlers in a Flame Tube

2006 ◽  
Author(s):  
Farhad Davoudzadeh ◽  
Nan-Suey Liu ◽  
Jeffrey P. Moder
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Liquid Fuel ◽  
Recirculation Zone ◽  
Combustion Process ◽  
Civil Aviation ◽  
Single Element ◽  
Fuel Injector ◽  
Flame Tube ◽  
Refined Grid

An unstructured and massively parallel Reynolds-Averaged Navier-Stokes (RANS) code is used to simulate 3-D, turbulent, non-reacting, and confined swirling flow field associated with a single-element and a nine-element Lean Direct Injection (LDI) combustor. In addition, the computed results are compared with the Large Eddy Simulation (LES) results and are also validated against the experimental data. The LDI combustors are a new generation of liquid fuel combustors developed to reduce aircraft NOx emission to 70% below the 1996 International Civil Aviation Organization (ICAO) standards and to maintain carbon monoxide and unburned hydrocarbons at their current low levels at low power conditions. The concern in the stratosphere is that NOx would react with the ozone and deplete the ozone layer. This paper investigates the non-reacting aerodynamics characteristics of the flow associated with these new combustors using a RANS computational method. For the single-element LDI combustor, the experimental model consists of a cylindrical air passage with air swirlers and a converging-diverging venturi section, extending to a confined 50.8-mm square flame tube. The air swirlers have helical, axial vanes with vane angles of 60 degree. The air is highly swirled as it passes through the 60 degree swirlers and enters the flame tube. The nine-element LDI combustor is comprised of 9 elements that are designed to fit within a 76 mm 76 mm flametube combustor. In the experimental work, the jet-A liquid fuel is supplied through a small diameter fuel injector tube and is atomized as it exits the tip and enters the flame tube. The swirling and mixing of the fuel and air induces recirculation zone that anchors the combustion process, which is maintained as long as a flammable mixture of fuel and air is supplied. It should be noted that in the numerical simulation reported in this paper, only the non-reacting flow is considered. The numerical model encompasses the whole experimental flow passage, including the flow development sections for the air swirlers, and the flame tube. A low Reynolds number K-e turbulence model is used to model turbulence. Several RANS calculations are performed to determine the effects of the grid resolution on the flow field. The grid is refined several times until no noticeable change in the computed flow field occurred; the final refined grid is used for the detailed computations. The results presented are for the final refined grid. The final grids are all hexahedron grids containing approximately 861,823 cells for the single-element and 1,567,296 cells for the nine-element configuration. Fine details of the complex flow structure such as helical-ring vortices, re-circulation zones and vortex cores are well captured by the simulation. Consistent with the non-reacting experimental results, the computation model predicts a major re-circulation zone in the central region, immediately downstream of the fuel nozzle, and a second, recirculation zone in the upstream corner of the combustion chamber. Further, the computed results predict the experimental data with reasonable accuracy.

Post-Combustion In-Cylinder Vaporization During Cranking and Startup in a Port-Fuel–Injected Spark Ignition Engine

2005 ◽  
Vol 128 (2) ◽  
pp. 397-402 ◽  
Author(s):  
Jim S. Cowart
Keyword(s):  
Combustion Chamber ◽  
Liquid Fuel ◽  
Combustion Process ◽  
Spark Ignition ◽  
Liquid Films ◽  
Spark Ignition Engine ◽  
Fuel Vapor ◽  
Intake Port ◽  
Warm Up ◽  
Flame Ionization

During port-fuel–injected (PFI) spark-ignition (SI) engine startup and warm-up fuel accounting continues to be a challenge. Excess fuel must be injected for a near stoichiometric combustion charge. The “extra” fuel that does not contribute to the combustion process may stay in the intake port or as liquid films on the combustion chamber walls. Some of this combustion chamber wall liquid fuel is transported to the engine’s oil sump and some of this liquid fuel escapes combustion and evolves during the expansion and exhaust strokes. Experiments were performed to investigate and quantify this emerging in-cylinder fuel vapor post-combustion cycle by cycle during engine startup. It is believed that this fuel vapor is evaporating from cylinder surfaces and emerging from cylinder crevices. A fast in-cylinder diagnostic, the fast flame ionization detector, was used to measure this behavior. Substantial post-combustion fuel vapor was measured during engine startup. The amount of post-combustion fuel vapor that develops relative to the in-cylinder precombustion fuel charge is on the order of one for cold starting (0 °C) and decreases to ∼13 for hot starting engine cycles. Fuel accounting suggests that the intake port puddle forms quickly, over the first few engine cranking cycles. Analysis suggests that sufficient charge temperature and crevice oxygen exists to at least partially oxidize the majority of this post-combustion fuel vapor such that engine out hydrocarbons are not excessive.

Modelling of Nitric Oxide Formation During Liquid Fuel Combustion

2016 ◽  
Vol 246 ◽  
pp. 279-283
Author(s):  
Stanisław Gil ◽  
Wojciech Bialik
Keyword(s):  
Nitric Oxide ◽  
Experimental Data ◽  
Carbon Monoxide ◽  
Liquid Fuel ◽  
Combustion Process ◽  
Fuel Combustion ◽  
Nitric Oxides ◽  
Oxide Formation ◽  
Nitric Oxide Formation ◽  
The Impact

A liquid fuel combustion process, being a source of many environmentally hazardous pollutants (e.g. nitric oxides, carbon monoxide, polycyclic aromatic hydrocarbons, soot and sulphur oxides), is a subject of extensive research aimed at reduction of their emissions. A high temperature of the combustion air tends to increase the content of NOX in exhaust gases. Based on the experimental data and literature as well as using the CFD tools, a model of light fuel oil combustion has been developed with an emphasis on nitric oxide formation. The model adequately reflects the impact of geometry changes in the flow of combustion substrates on concentrations of carbon monoxide and nitric oxides in the chamber. The quantitative results obtained are comparable to the experimental data.

Controlling Gravity Impact on Diffusion Flames by Magnetic Field

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Fouad Khaldi
Keyword(s):  
Magnetic Field ◽  
Scaling Laws ◽  
Diffusion Flames ◽  
Combustion Process ◽  
Flame Length ◽  
Dimensionless Number ◽  
Length Variation ◽  
Zero Gravity ◽  
Blue Color ◽  
Gravity Level

The ability to use a magnetic field as a means for controlling the role of gravity buoyancy on the combustion process is demonstrated by applying a strong vertical magnetic field gradient on a laminar gas jet diffusion flame. The confirmation is based on a comparison of flame appearance; in particular, length variation, to both elevated gravity (higher than earth’s gravity) and zero-gravity combustion experimental data. The comparison parameter is the dimensionless number G, defined as the ratio of gravity level generated by magneto-gravity buoyancy to earth’s gravity. The more important results are as follows. First, for G > 1, good agreement between magnetic and centrifuge length scaling laws reveals that the slight decrease of flame length according to L ∼ G−1/8 is the result of increasing artificial magnetically induced gravity strength. It ensues that flame thinning, bluing, lifting, and extinction are produced by similar mechanisms previously identified in centrifuge diffusion flames. Thereafter, at G ≅ 0, the flame assumes a nearly hemispheric shape and a blue color in perfect similarity to nonbuoyant flames under zero-gravity conditions generated in drop towers. Another important fact is that the magnetic field offers the ability to observe the flame behavior at low gravity levels 0 < G < 1. A primary interesting result is that flame length varies strongly, following the scaling law L ∼ G−1/2.

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