Effects of fuel-air mixing on flame structures and NOx emissions in swirling methane jet flames

1998 ◽  
Vol 27 (1) ◽  
pp. 1229-1237 ◽  
Author(s):  
T.S. Cheng ◽  
Y.-C. Chao ◽  
D.-C. Wu ◽  
T. Yuan ◽  
C.-C. Lu ◽  
...  
Keyword(s):  
Nox Emissions ◽  
Jet Flames ◽  
Air Mixing ◽  
Flame Structures

Model Analysis of Syngas Combustion and Emissions for a Micro Gas Turbine

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Chi-Rong Liu ◽  
Hsin-Yi Shih
Keyword(s):  
Gas Turbine ◽  
Flow Rate ◽  
Heat Input ◽  
Emission Characteristics ◽  
Nox Emissions ◽  
Fuel Flow Rate ◽  
Micro Gas Turbine ◽  
Fuel Flow ◽  
Temperature Distributions ◽  
Flame Structures

The purpose of this study is to investigate the combustion and emission characteristics of syngas fuels applied in a micro gas turbine, which is originally designed for a natural gas fired engine. The computation results were conducted by a numerical model, which consists of the three-dimension compressible k–ε model for turbulent flow and PPDF (presumed probability density function) model for combustion process. As the syngas is substituted for methane, the fuel flow rate and the total heat input to the combustor from the methane/syngas blended fuels are varied with syngas compositions and syngas substitution percentages. The computed results presented the syngas substitution effects on the combustion and emission characteristics at different syngas percentages (up to 90%) for three typical syngas compositions and the conditions where syngas applied at fixed fuel flow rate and at fixed heat input were examined. Results showed the flame structures varied with different syngas substitution percentages. The high temperature regions were dense and concentrated on the core of the primary zone for H2-rich syngas, and then shifted to the sides of the combustor when syngas percentages were high. The NOx emissions decreased with increasing syngas percentages, but NOx emissions are higher at higher hydrogen content at the same syngas percentage. The CO2 emissions decreased for 10% syngas substitution, but then increased as syngas percentage increased. Only using H2-rich syngas could produce less carbon dioxide. The detailed flame structures, temperature distributions, and gas emissions of the combustor were presented and compared. The exit temperature distributions and pattern factor (PF) were also discussed. Before syngas fuels are utilized as an alternative fuel for the micro gas turbine, further experimental testing is needed as the modeling results provide a guidance for the improved designs of the combustor.

scholarly journals Characterization of a Novel Porous Injector for Multi-Lean Direct Injection (M-LDI) Combustor

2017 ◽  
Author(s):  
Jianing Li ◽  
Umesh Bhayaraju ◽  
San-Mou Jeng
Keyword(s):  
Air Temperature ◽  
Mass Fraction ◽  
Direct Injection ◽  
Flame Temperature ◽  
Gaseous Fuel ◽  
Nox Emissions ◽  
Fuel Injector ◽  
Porous Tube ◽  
Lean Direct Injection ◽  
Air Mixing

A generic novel injector was designed for multi-Lean Direct Injection (M-LDI) combustors. One of the drawbacks of the conventional pressure swirl and prefilming type airblast atomizers is the difficulty of obtaining a uniform symmetric spray under all operating conditions. Micro-channels are needed inside the injector for uniformly distributing the fuel. The problem of non-uniformity is magnified in smaller sized injectors. The non-uniform liquid sheet causes local fuel rich/lean zones leading to higher NOx emissions. To overcome these problems, a novel fuel injector was designed to improve the fuel delivery to the injector by using a porous stainless steel material with 30 μm porosity. The porous tube also acts as a prefilming surface. Liquid and gaseous fuels can be injected through the injector. In the present study, gaseous fuel was injected to investigate injector fuel-air mixing performance. The gaseous fuel was injected through a porous tube between two radial-radial swirling air streams to facilitate fuel-air mixing. The advantage of this injector is that it increases the contact surface area between the fuel-air at the fuel injection point. The increased contact area enhances fuel-air mixing. Fuel-air mixing and combustion studies were carried out for both gaseous and liquid fuel. Flame visualization, and emissions measurements were carried out inside the exit of the combustor. The measurements were carried out at atmospheric conditions under fuel lean conditions. Natural gas was used as a fuel in these experiments. Fuel-air mixing studies were carried out at different equivalence ratios with and without confinement. The mass fraction distributions were measured at different downstream locations from the injector exit. Flame characterization was carried out by chemiluminescence at different equivalence ratios and inlet air temperatures. Symmetry of the flame, flame length and heat release distribution were analyzed from the flame images. The effects of inlet air temperature and combustion flame temperature on emissions was studied. Emissions were corrected to 15% O2 concentration. NOx emissions increase with inlet air temperature and flame temperature. Effect of flame temperature on NOx concentration is more significant than effect of inlet air temperature. Fuel-air mixing profile was used to obtain mass fraction Probability Density Function (pdf). The pdfs were used for simulations in Chemkin Pro. The measured emissions concentrations at the exit of the injector was compared with simulations. In Chemkin model, a network model with several PSRs (perfectly stirred reactor) were utilized, followed by a mixer and a PFR (plug flow reactor). The comparison between the simulations and the experimental results was investigated.

Investigation on NOx of a Low Emission Combustor Design With Multihole Premixer-Prevaporizer

2004 ◽  
Author(s):  
Yuzhen Lin ◽  
Yunhui Peng ◽  
Gaoen Liu
Keyword(s):  
Great Influence ◽  
Nox Emission ◽  
Emissions Reduction ◽  
Inlet Temperature ◽  
Main Stage ◽  
Nox Emissions ◽  
Baseline Design ◽  
Air Mixing ◽  
Reduction Of Nox ◽  
Two Stages

A low NOx emission combustor design was presented in this paper. The design features the premixer-prevaporizer tube with multihole and two stages arranged radially in line, with the outer stage being pilot stage and inner stage being main stage. The multihole premixer and prevaporizer is a part of main stage. The results of NOx emission were provided and also compared with the baseline design that the premixer and prevaporizer tube without multihole. The double swirler prefilming airblast atomizer was installed in the premixed prevaporized duct entrance. The mean drop size and radial fuel flux distribution were measured to determine proper configurations of the multihole premixer-prevaporizer. NOx emission investigations were carried out using a test combustor with one pilot stage and one main stage under the operating condition of high inlet temperature (800K) and inlet air pressure was atmospheric pressure. The experiment results demonstrated large NOx emissions reduction of the multihole premixer-prevaporizer compared with the baseline design. The more even fuel-air mixing, which was gained by the multiple jets, intensified the fuel and air mixing within the premixer-prevaporizer, resulted in the large reduction of NOx emission. The configurations of multihole premixer-prevaporizer had great influence on NOx emissions reduction.

Effect of Fuel/Air Mixing on NOx Emissions and Stability in a Gas Premixed Combustion System

2007 ◽  
Author(s):  
Arnaud Lacarelle ◽  
Jonas Moeck ◽  
Holger Konle ◽  
Stefan Vey ◽  
Christian Nayeri ◽  
...  
Keyword(s):  
Premixed Combustion ◽  
Nox Emissions ◽  
Combustion System ◽  
Air Mixing

Effects of Flame Structures on Direct Combustion Noise Produced by Lean-Premixed H2/Air Low-Swirl Jet Flames

2020 ◽  
Author(s):  
Takeshi Shoji ◽  
Yuki Iwasaki ◽  
Kodai Kato ◽  
Seiji Yoshida ◽  
Shigeru Tachibana ◽  
...  
Keyword(s):  
Combustion Noise ◽  
Jet Flames ◽  
Direct Combustion ◽  
Lean Premixed ◽  
Flame Structures

Influence of Swirl and Primary Zone Airflow Rate on the Emissions and Performance of a Liquid-Fueled Gas Turbine Combustor

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Parneeth Lokini ◽  
Dinesh Kumar Roshan ◽  
Abhijit Kushari
Keyword(s):  
Gas Turbine ◽  
Combustion Efficiency ◽  
Combustible Mixture ◽  
Airflow Rate ◽  
Nox Emissions ◽  
Swirl Number ◽  
Primary Zone ◽  
Air Mixing ◽  
Efficient Combustion ◽  
And Performance

This paper presents the results of an experimental study on the influence of swirl number (S) and primary zone airflow rate on the temperature, emission indices of the pollutants, and combustion efficiency in an atmospheric pressure liquid-fueled gas turbine (GT) combustor, equipped with a swirling jet air blast atomizer and operated with Jet A1 fuel. Experiments were conducted at three primary zone air flow rates and three swirl numbers (0.49, 0.86, and 1.32). For all the cases, it was found that the NOx emissions were very low (< 2 g/kg of fuel). At all the swirl numbers, an increase in primary zone airflow led to a nonmonotonous variation in CO while minimally affecting the NOx emissions. However, increase in the swirl number generated relatively higher NOx and lower CO owing to higher temperature resulting from efficient combustion caused by a superior fuel–air mixing. Also, the unburnt hydrocarbons (UHC) was quite high at S = 0.49 because of the unmixedness of fuel and air, and zero at S = 0.86 and 1.32. The combustion efficiency was very low (around 60%) at S = 0.49 while almost 100% at S = 0.86 and 1.32. The study conducted demonstrates a significant dependence of emissions and GT performance on the swirl number governed by the convective time scales and the residence time of the combustible mixture in the combustion zone.

A Review of the Concept of Fuel-Water Internally Rapid Mixing Injector in Burner System

2013 ◽  
Vol 465-466 ◽  
pp. 296-301 ◽  
Author(s):  
Mohamad Farid Sies ◽  
Norrizal Mustaffa ◽  
Hanis Zakaria ◽  
Hamidon bin Salleh ◽  
Bukhari Manshoor ◽  
...  
Keyword(s):  
Early Stage ◽  
Oxidation Stability ◽  
Biodiesel Fuel ◽  
Fuel Composition ◽  
Nox Emissions ◽  
Mixture Formation ◽  
Burning Process ◽  
System A ◽  
Air Mixing ◽  
External Combustion

This paper reviews the effects of premix fluids between biodiesel, air, and water for external combustion especially open burner. During burning process, biodiesel combustion involves the fuel-air mixing characteristic such as oxidation stability, stoichiometric point, bio-fuel composition, antioxidants and viscosity that influences more NOx emissions than diesel fuel. The strategies to reduce NOx emission are acquired with water additional in biodiesel fuel mixing during early stage of burning process. The method to mix biodiesel-water with injector was acquired in burner system. A vast majority of author reported that the variation in mixing of blending biodiesel ratio and water was found to enhance the burning process and mixture formation thus predominantly reducing the NOx emissions.

Prediction of the NOx-Emissions of a Swirl Burner in Partially and Fully Premixed Mode on the Basis of Water Channel LIF and PIV Measurements

2013 ◽  
Author(s):  
J. Sangl ◽  
C. Mayer ◽  
T. Sattelmayer
Keyword(s):  
Equivalence Ratio ◽  
Fuel Injection ◽  
Water Channel ◽  
Premixed Combustion ◽  
Nox Emissions ◽  
Swirl Burner ◽  
Engine Operation ◽  
Measured Velocity ◽  
Wide Range ◽  
Air Mixing

The paper describes the development and validation of an efficient and cost effective method for the prediction of the NOx emissions of turbulent gas turbine burners in the early burner design phases which are usually focused on the optimization of the swirler aerodynamics and the fuel air mixing. As the method solely relies on non-reacting tests of burner models in the water channel it can be applied before any test equipment for combustion experiments exists. In order to achieve optimum similarity of fuel air mixing in the water channel tests with engine operation the model is operated at the engine momentum ratio. During the LIF measurements the water flow representing the fuel is doped with fluorescent dye, a plane perpendicular to the length axis near the burner exit plane is illuminated with a 5W Ar-Ion Laser and the fluorescence is recorded with a video camera from downstream. From the video sequences the local probability density functions (PDF) of the dye concentration fluctuations are calculated from the data. Furthermore, the time mean velocity fields are measured with PIV. From the LIF data the PDFs of the local equivalence ratio are derived. Assuming flamelets, the NOx generation in the entire equivalence ratio range observed in the water channel tests is computed using the unstrained freely propagating one-dimensional flame model in Cantera and the GRI3.0 reaction scheme. Although neither flame stretch nor post flame NOx generation were considered the NOx values computed were in excellent agreement with the experimental data from perfectly premixed combustion experiments. The local time averaged NOx mole fraction is obtained by integrating the flamelet NOx over the mixture PDF. Finally the global NOx emission of the burner at the considered operating point is obtained by spatial integration considering the measured velocity field. The method was validated using a conical swirl burner with two fuel injection stages, allowing the degree of premixedness to be adjusted over a wide range depending on the specific fuel injection scenario. For the case with fuel injection along the air inlet slots NOx values slightly above the minimum NOx limit for perfectly premixed combustion were computed. This is consistent with the emission measurements and indicates finite mixing quality of this injection method. In the partially premixed regime the configurations with potential for low NOx emissions were reliably identified with the LIF and PIV based water channel method. The method also shows the steep increase of the NOx emissions with decreasing degree of premixing observed in the experiments but quantitative predictions would have required a postprocessing of the data from the LIF mixing study with a higher spacial resolution than available.

Study of Pulse Spray, Heat Release, Emissions and Efficiencies in a Compound Diesel HCCI Combustion Engine

2004 ◽  
Author(s):  
Wanhua Su ◽  
Xiaoyu Zhang ◽  
Tiejian Lin ◽  
Yiqiang Pei ◽  
Hua Zhao
Keyword(s):  
Heat Release ◽  
Combustion Engine ◽  
Combustion Efficiency ◽  
Diffusion Combustion ◽  
Injection Timing ◽  
Nox Emissions ◽  
Injection Process ◽  
Hcci Combustion ◽  
Air Mixing ◽  
Combustion Technology

A compound diesel HCCI combustion technology has been developed based on the combustion strategies of combination of controlled premixed charge compression ignition (CPCCI) through multi-injections and lean diffusion combustion (LDC) organized by a mixing enhanced combustion chamber. The purpose of this paper is to investigate the fuel spray evolution during multi-injections, heat release mode, thermo-efficiency and exhaust emissions from the compound combustion. In this work, the STAR-CD based, multidimensional modeling is employed to improve the understanding and assist the optimization of the multiple injection process. The parameters explored include the effects of injection timing, dwell time, and the pulse width. Insight generated from these studies provides guidelines on designing an injection profile for optimization of fuel-air mixing. By comparison of different heat release modes of conventional diesel combustion, the pure HCCI combustion and the compound HCCI combustion, the engine heat release can be summarized as forward concentrated mode (FC mode), post concentrated mode (PC mode) and dispersed mode (DS mode). The FC mode gives the highest thermo-efficiency but with highest NOx emissions. The PC mode gets lower NOx emissions but with the drawback of lower thermo-efficiency and higher soot emissions. The DS mode is a flexible heat release mode created by the compound HCCI combustion. A typical DS mode reveals two equivalent peaks of heat release. The first peak represents the CPCCI combustion and the later peak represents the lean diffusion combustion. The thermo-efficiency in a DS mode can reach approximately as high as that in FC mode, while NOx and soot emission can be reduced simultaneously and remarkably. The combustion efficiency and the heat loss in different combustion mode are also discussed.

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