UNIVERSITY OF CINCINNATI Date: 14-Jan-2010 I, Bassam Abd El-Nabi , hereby submit this original work as part of the requirements for the degree of: Doctor of Philosophy in Aerospace Engineering It is entitled: Single Annular Combustor: Experimental investigations of Aerodynamics, Dynamics and Emissions Student Signature: Bassam Abd El-Nabi This work and its defense approved by: Committee Chair: San-Mou Jeng, PhD San-Mou Jeng, PhD Milind Jog, PhD Milind Jog, PhD Mustafa Furhan Andac, PhD Mustafa Furhan Andac, PhD Shaaban Abdallah, PhD Shaaban Abdallah, PhD 3/8/2010 447 Single Annular Combustor: Experimental investigations of Aerodynamics, Dynamics and Emissions A thesis submitted to the Division of Graduate Studies and Research of the University of Cincinnati in partial fulfillment of the requirements for the degree of DOCTORATE OF PHILOSOPHY (Ph.) in the Department of Aerospace Engineering and Engineering Mechanics of the College of Engineering March 2010 by Bassam Sabry Mohammad B., Mechanical Engineering, Cairo University, Egypt M., Mechanical Engineering, Cairo University, Egypt M., Nuclear Engineering, Missouri University of Science and Technology, USA Committee Chair: Dr. San-Mou Jeng i Abstract The present work investigates the aerodynamics, dynamics and emissions of a Single Cup Combustor Sector. The Combustor resembles a real Gas Turbine Combustor with primary, secondary and dilution zones (also known as fuel rich dome combustor). The research is initiated by studying the effect of the combustor front end geometry on the flow field.
Two different exit configurations (one causes a sudden expansion to the swirling flow while the other causes a gradual expansion), installed in a dump combustor, are tested using LDV. The results reveal that the expanding surface reduces the turbulence activities, eliminates the corner recirculation zone and increases the length of the CRZ appreciably. An asymmetry in the flow field is observed due to the asymmetry of the expanding surface. To study the effect of chamber geometry on the flow field, the dome configuration is tested in the combustor sector with the primary dilution jets blocked.
The size of the CRZ is reduced significantly (40 % reduction in the height). With active primary jets, the CRZ is reconstructed in 3D by conducting several PIV measurements off-center. The confinement appears to significantly influence the shape of the CRZ such that the area ratio is similar for both the confinement and the CRZ (approximately 85%). The primary jets considerably contribute to the heat release process at high power conditions.
Also, the primary jets drastically impact the flow field structure. Therefore, the parameters influencing the primary jets are studied using PIV (pressure drop, jets size, off- centering, interaction with convective cooling air, jet blockage and fuel injection). This study is referred to as a jet sensitivity study. The results indicate that the primary jets can be used effectively in controlling the flow field structure.
A pressure drop of 4.6% result in ii similar flows with no noticeable effect on the size of the CRZ and the four jets wake regions. On the other hand, the results show that the primary jets are very sensitive to perturbations. The cooling air interacts with the primary jet and influences the flow field although the momentum ratio has an order of magnitude of 100:1. The results also show that the big primary jets dictate the flow field in the primary zone as well as the secondary zone.
However, relatively smaller jets mainly impact the primary zone. Also, the results point to the presence of a critical jet diameter beyond which the dilution jets have minimum impact on the secondary region. The jet off-centering shows significant effect on the flow field though it is on the order of 1. The jet sensitivity study provides the combustion engineers with useful methods to control the flow field structure, an explanation for observed flow structure under different conditions and predictable flow field behavior with engine aging.
All results obtained from the jet sensitivity study could be explained in terms of jet opposition. Hence, similar results are expected under reacting conditions even though the results presented here are obtained under isothermal conditions. The fuel injection is also shown to influence the flow field. High fuel flow rate is shown to have very strong impact on the flow field and thus results in a strong distortion of both the primary and secondary zones.
The jets wake regions are shown to change in size with fuel injection. The left jet wake region continuously reduces in size with fuel injection while the right jet wake region does not. This offers a possible explanation for the observed combustion instabilities in the left primary jet region. The combustion instabilities are studied using a microphone, high speed camera and regular cameras.
The frequency spectrum for the sector is established at different pressure drops (2, 4 and 6%) as well as different pre-heat temperatures (200, 400 and 600F). The iii acoustic spectrum suggests that there are three frequencies of concern (280, 400 and 600 HZ). The high frequency appears to be related to the combustor ¼ longitudinal wave. The 280 Hz is due to a rotating instability while the 400 Hz is related to the primary jets.
The emissions emanating from the combustor are studied using FTIR at pressure drop of 4% and different power conditions. The sector emissions characteristics are determined. Water injection is also used to control the pollutant emissions. Water fuel ratio of 100% and 50% results in a corresponding reduction in the NOx concentration with 50% and 22% (at high power conditions).
No noticeable effects are observed on the NOx and CO at low power conditions. A high degree of homogeneity in the emissions contours is observed at the combustor exit at low power conditions (equivalence ratio of 0. However, this homogeneity is noticeably reduced at high power conditions (equivalence ratio of 0. iv v Acknowledgment All thanks are due to ALLAH (God) and may His peace and blessings be upon all His messengers and prophets including Moses, Jesus and Mohammad.
It was only through ALLAH's help and support that this work was accomplished. I can never thank Him enough for all the blessing He bestowed upon me throughout my life and I seek His forgiveness for all my shortcomings. I would like to especially recognize and express my gratitude to my advisor, Dr. It is certainly through his support, guidance and encouragement that this work is complete.
He trusted me and gave me a room to make my own decisions. Jeng was always ready to give advice anytime. Jeng is one of the best things that happened in my life. Jeng taught me the basics of research, how to interact with people, how to think differently and how to solve problems.
Also, my deepest appreciation to Dr. Abdallah Shabaan, Dr. Millind Jog and Dr. Gurhan Andac for their time and effort as my committee members.
I am also very thankful to the people at GE aviation. This work was not possible without their help and support. Special thanks to all my colleagues at the Combustion Research Lab. Jun Cai taught me how to use and setup the PIV, LDV and FTIR systems.
Curt Fox offered a great deal of help. He is the kind of person who would help you do anything, anytime in a timely manner! Also, I am very thankful to Samir, Fumi, and Kao. They helped me in experimental setup as well as running the experiments. I would especially like to thank my Mom and Dad.
I achieved this work because of their prayers. My father supported me financially since I arrived to the United States. He paid a vii huge amount of money to help me earn my degree. May ALLAH reward them for what they have done.
Finally, there is a single person who has had a greater effect on this work than anyone else, and that is my wife. She has been patient and she supported and encouraged me. She was taking care of the family duties to provide me with the environment and the time necessary to complete this effort. We have four kids and there was no chance for me to earn my degree if she didn’t sacrifice her time and effort.
viii “Read: In the name of thy Lord Who createth, Createth man from a clot, Read: And thy Lord is the Most Bounteous, Who teacheth by the pen, Teacheth man that which he knew not.” -Quran (20:114) “My Lord! Advance me in knowledge.” -Quran (96:1-5) vi Table of Contents Acknowledgment. vii Table of Contents. ix List of Figures .1 Flame stabilization and Generation of CRZ .4 Factors influencing the CRZ Size and strength .1 Swirl Number Effects .3 Reynolds Number Effects.4 Nozzle Insertion Effects .5 Realistic combustion chambers and effect of dilution jets .2 Effect of pressure on NOx generation .3 NOx reduction techniques .3 Dynamics and generation of Combustion Instabilities .1 Experimental setup, procedure and test conditions .1 Swirl Cup and test section.4 Test conditions, data acquisition and measurement Grid .2 Results and Discussions .1 Horizontal plane (X-Y) measurements for both configurations .2 Vertical plane (X-Z) measurements for both configurations .1 Axial velocity and turbulent fluctuating component .2 Radial velocity and turbulent fluctuating component.3 Vertical plane (Y-Z) measurements for both configurations .1 Axial velocity and turbulent fluctuating component .2 Tangential velocity and turbulent fluctuating component .4 Confinement effect on the flow field .1 Experimental setup, procedure and test conditions .1 Swirler and SAC Combustor .4 Test conditions, data acquisition and measurement grid .2 Results and Discussions .1 Mean flow measurements at the SAC mid plane using LDV .2 Reacting flow vs.1 Effect of pressure drop on the flow structure .2 Instantaneous PIV at SAC mid plane at pressure drop of 4.3 PIV off center measurements at pressure drop of 4.4 Effect of partially blocking the primary dilution jets strip .5 Effect of blocking the cooling holes underneath the primary dilution jets 97 3.6 Effect of primary jets off centering on the flow field .7 Effect of primary jet size on the flow field .1 Experimental setup, procedure and test conditions .1 Swirl cup and SAC Sector .3 Test conditions and data acquisition .2 Results and Discussions .1 Experimental setup, procedure and test conditions .1 Swirl cup and SAC Sector .3 Test conditions, data acquisition and measurement grid .2 Results and Discussions .1 Experimental setup, procedure and test conditions .1 Swirl cup and SAC Sector .3 Test conditions and data acquisition .2 Results and Discussions .1 Species Measurements at the center of the SAC sector exit .2 Species Contours at the SAC sector exit. 163 x List of Figures 1.1 Typical coaxial Axial and radial swirlers.2 Typical Swirl cup arrangement with counter rotating radial swirlers.3 Typical SAC Combustor with swirl cup.4 CFM56 swirl cup assembly.5 Illustration of Ideal and Real combustion emissions [61].6 Order of magnitude of Gas Turbine Combustion emissions [61].7 Typical pollutant formation trends as function of the equivalence ratio [12].8 Typical variation of the equilibrium and thermal NOx vs.9 Illustration of the effect of residence time on thermal NOx.10 DLN combustor concepts [61].11 Multiple point LDI combustor developed by NASA [114].12 Illustration of LP, RQL and LDI concepts [94].13 Severity of Carbon Monoxide intoxications [115].14 Illustration of generation and growth of pressure oscillations known as thermo-acoustic instabilities [126].1 Different configurations of the swirl cup under investigation .2 Rectangular Plexi-glass chamber (dump combustor) .3 Schematic of the Experimental facility to study the dump combustor Aerodynamics .4 Special flanges and adapters to allow installation of swirl cups to the vertical rig .5 Laser Doppler Velocimetry system provided by Artium Technologies .6 LDV setup on the vertical rig (plexi-glass chamber) .7 Measurements Coordinate system for both configurations .8 Axial velocity contours in the horizontal plane (configuration 1) .9 Axial velocity contours in the horizontal plane (base configuration) .10 Contours of the Root Mean Square of the axial velocity in the horizontal plane for configuration one .11 Contours of the Root Mean Square of the axial velocity in the horizontal plane for the base configuration.12 Axial velocity profiles in the X-Z plane (Config.