Experimental Investigation on Ignition Performance of LESS Combustor

2011 ◽  
Author(s):  
Zhenbo Fu ◽  
Yuzhen Lin ◽  
Jibao Li ◽  
Chih-Jen Sung
Keyword(s):  
Pressure Drop ◽  
Flow Field ◽  
Civil Aviation ◽  
Inlet Temperature ◽  
Reacting Flow ◽  
Main Stage ◽  
Minor Effect ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

In the design of next-generation civil aviation gas turbine combustors, there is high demand to improve the efficiency of combustion technology to decrease the amount of fuel consumed and to reduce the emissions in an effort to lessen the environmental impacts. This paper introduces a novel, ultra-low emissions combustor, namely Low Emission Stirred Swirl (LESS) combustor, employing the lean premixed prevaporized (LPP) approach. The LESS combustor is a single annular layout. Its dome is comprised of two stages — the pilot stage and the main stage. The pilot stage is a typical swirl cup design which uses a pressure swirl atomizer with dual counter-rotating radial swirlers to atomize the fuel and form a diffusion flame, and is located in the centerline of the combustion chamber. The main stage surrounding coaxially the pilot stage includes one annulus as premixer and 14 plain orifice atomizers with 14 small dual counter-rotating radial swirlers arranged uniformly on the dome of the annulus, which lead to the main premixed flame. Five different igniter locations are chosen according to the CFX-simulated non-reacting flow field of a simplified mainstage combustor. Only the pilot pressure swirl atomizer is operated in the present ignition performance tests. The model combustor is a single module rectangular combustor with normal inlet temperature and normal inlet pressure. Under the test conditions of air pressure drop of 0.5%–9%, the ignition performance of the model LESS combustor is analyzed. The lean lightoff fuel/air ratio (LLO FAR), characterizing the ignition performance of a combustor, is investigated herein. In addition, the effects of igniter locations and pilot fuel nozzles on LLO FAR are studied. Specific to the LESS combustor, the igniter location has minor effect on the LLO FAR values. However, as expected, the combustor dome pressure drop and attendant reference velocity along with spray SMD impact LLO FAR. Furthermore, CFX-simulated results of the flow field, spray characteristics, and gas-liquid interactions under the typical condition of combustor operation are presented and discussed to provide insight into the ignition processes and performance.

Nonlinear Breakup Model for a Liquid Sheet Emanating From a Pressure-Swirl Atomizer

2007 ◽  
Vol 129 (4) ◽  
pp. 945-953 ◽  
Author(s):  
Ashraf A. Ibrahim ◽  
Milind A. Jog
Keyword(s):  
Flow Field ◽  
Ambient Pressure ◽  
Internal Flow ◽  
Liquid Sheet ◽  
Nonlinear Instability ◽  
Breakup Length ◽  
Sheet Breakup ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

Predictions of breakup length of a liquid sheet emanating from a pressure-swirl (simplex) fuel atomizer have been carried out by computationally modeling the two-phase flow in the atomizer coupled with a nonlinear analysis of instability of the liquid sheet. The volume-of-fluid (VOF) method has been employed to study the flow field inside the pressure-swirl atomizer. A nonlinear instability model has been developed using a perturbation expansion technique with the initial amplitude of the disturbance as the perturbation parameter to determine the sheet instability and breakup. The results for sheet thickness and velocities from the internal flow solutions are used as input in the nonlinear instability model. Computational results for internal flow are validated by comparing film thickness at exit, spray angle, and discharge coefficient with available experimental data. The predictions of breakup length show a good agreement with semiempirical correlations and available experimental measurements. The effect of elevated ambient pressure on the atomizer internal flow field and sheet breakup is investigated. A decrease in air core diameter is obtained at higher ambient pressure due to increased liquid-air momentum transport. Shorter breakup lengths are obtained at elevated air pressure. The coupled internal flow simulation and sheet instability analysis provides a comprehensive approach to modeling sheet breakup from a pressure-swirl atomizer.

Pressure-Scaling of Pressure-Swirl Atomizer Cone Angles

2006 ◽  
Author(s):  
D. R. Guildenbecher ◽  
R. R. Rachedi ◽  
P. E. Sojka
Keyword(s):  
Pressure Drop ◽  
Ambient Pressure ◽  
Cone Angle ◽  
Subsequent Increase ◽  
Gas Entrainment ◽  
A Value ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer ◽  
Measure Cone

An experimental investigation was conducted to study the effects of increased ambient pressure (up to 6.89 MPa) and increased nozzle pressure drop (up to 2.8 MPa) on the cone angles for sprays produced by pressure-swirl atomizers having varying amounts of initial swirl. This study extends the classical results of DeCorso and Kemeny [1]. Shadow photography was used to measure cone angles at x/D0=10, 20, 40, and 60. Our lower pressure results for atomizer swirl numbers of 0.50 and 0.25 are consistent with those of DeCorso and Kemeny [1], who observed a decrease in cone angle with an increase in a pressure drop-ambient density product until a minimum cone angle was reached at ΔPρair1.6~200. Results for atomizers having higher swirl numbers do not match the DeCorso and Kemeny [1] results as well, suggesting that their correlation be used with caution. Another key finding is that an increase in ΔPρair1.6 to a value of 1000 leads to continued decreases in cone angle, but that a subsequent increase to 4000 has little effect on cone angle. Finally, there was little influence of atomizer pressure drop on cone angle, in contrast to findings of previous workers. These effects are hypothesized to be due to gas entrainment.

Hybrid Pressure-Swirl/Twin-Fluid Atomizer for Emission Controls

2006 ◽  
Author(s):  
Andrew C. S. Lee ◽  
Paul E. Sojka
Keyword(s):  
Flow Field ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Drop Size ◽  
Air Flow ◽  
Exit Plane ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

An experimental study was conducted to characterize the performance of a hybrid atomizer used in emission control devices. Characterization included drop size distribution, measured using a forward light-scattering instrument, the air flow field (axial and radial velocities), measured using 2-D PIV, and turbulence characteristics of the air flow field, measured using LDA. The air flow field showed characteristics common to turbulent free round jets beyond approximately 8 exit orifice diameters from the atomizer exit plane. The centerline velocity increased with an increase in mass flow rate, while radial velocities were two orders of magnitude smaller than centerline values. The jet spreading factor initially increased with an increase in axial distance from the exit; however, it stabilized at a value of 0.09 at z/Do=11.8. Turbulence intensity along the jet centerline stabilized at 25% at z/Do=7.9. Drop size data showed complex dependencies on liquid and air mass flow rates, and on internal geometry. The influence of liquid mass flow rate on drop size was significantly smaller for the hybrid atomizer than for the pressure swirl atomizer component housed inside the hybrid unit, thus indicating a higher turndown ratio for the hybrid device. Drop size distributions produced by the hybrid atomizer showed multiple peaks, indicating there is more than one important atomizing mechanism. Finally, reducing the gap between the pressure-swirl atomizer and the exit plane of the outer casing resulted in a reduction in drop size.

Pressure-Scaling of Pressure-Swirl Atomizer Cone Angles

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
D. R. Guildenbecher ◽  
R. R. Rachedi ◽  
P. E. Sojka
Keyword(s):  
Pressure Drop ◽  
Ambient Pressure ◽  
Cone Angle ◽  
Spray Angle ◽  
Subsequent Increase ◽  
A Value ◽  
Nozzle Pressure ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

An experimental investigation was conducted to study the effects of increased ambient pressure (up to 6.89MPa) and increased nozzle pressure drop (up to 2.8MPa) on the cone angles for sprays produced by pressure-swirl atomizers having varying amounts of initial swirl. This study extends the classical results of DeCorso and Kemeny, (1957, “Effect of Ambient and Fuel Pressure on Nozzle Spray Angle,” ASME Transactions, 79(3), pp. 607–615). Shadow photography was used to measure cone angles at x∕D0=10, 20, 40, and 60. Our lower pressure results for atomizer swirl numbers of 0.50 and 0.25 are consistent with those of DeCorso and Kemeny, who observed a decrease in cone angle with an increase in nozzle pressure drop, ΔP, and ambient density, ρair, until a minimum cone angle was reached when ΔPρair1.6∼100MPa(kg∕m3)1.6 (equivalent to 200psi(lbm∕ft3)1.6). Results for atomizers having higher initial swirl do not match the DeCorso and Kemeny results as well, suggesting that their correlation be used with caution. Another key finding is that an increase in ΔPρair1.6 to a value of 600MPa(kg∕m3)1.6 leads to continued decrease in cone angle, but that a subsequent increase to 2000MPa(kg∕m3)1.6 has little effect on cone angle. Finally, there was little effect of nozzle pressure drop on cone angle, in contrast to findings of previous workers. These effects are hypothesized to be due to gas entrainment.

INTERNAL AND NEAR-NOZZLE FLOW OF A PRESSURE-SWIRL ATOMIZER UNDER VARIED FUEL TEMPERATURE

2007 ◽  
Vol 17 (6) ◽  
pp. 529-550 ◽  
Author(s):  
Seoksu Moon ◽  
Choongsik Bae ◽  
Essam F. Abo-Serie ◽  
Jaejoon Choi
Keyword(s):  
Nozzle Flow ◽  
Fuel Temperature ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

Study of pressure swirl atomizer with tangential input at design point and outside of design point

2020 ◽  
Vol 32 (12) ◽  
pp. 127113
Author(s):  
Kiumars Khani Aminjan ◽  
Balaram Kundu ◽  
D. D. Ganji
Keyword(s):  
Design Point ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

Studies on air core size in a simplex pressure-swirl atomizer

2017 ◽  
Vol 42 (29) ◽  
pp. 18649-18657 ◽  
Author(s):  
Zhilin Liu ◽  
Yong Huang ◽  
Lei Sun
Keyword(s):  
Core Size ◽  
Air Core ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

A Numerical Approach for the Simulation of Internal Nozzle Flow in a Pressure Swirl Atomizer Using Different Turbulent Models and Towards an Effective Inlet Weber Number

2013 ◽  
Author(s):  
Ahmadreza Abbasi Baharanchi ◽  
Seckin Gokaltun ◽  
Shahla Eshraghi
Keyword(s):  
Weber Number ◽  
Computational Cost ◽  
Internal Flow ◽  
Numerical Approach ◽  
Reynolds Stress Model ◽  
Multiphase Model ◽  
Vof Model ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

VOF Multiphase model is used to simulate the flow inside a pressure-swirl-atomizer. The capability of the Reynolds Stress Model and variants of the K-ε and K-ω models in modeling of turbulence has been investigated in the commercial computational fluid dynamics (CFD) software FLUENT 6.3. The Implicit scheme available in the volume-of-fluid (VOF) model is used to calculate the interface representation between phases. The atomization characteristics have been investigated as well as the influence of the inlet swirl strength of the internal flow. The numerical results have been successfully validated against experimental data available for the computed parameters. The performance of the RNG K-ε model was found to be satisfactory in reducing the computational cost and introducing an effective Weber number for the flow simulated in this study.

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