单环形燃烧室：空气动力学，动力学和排放的实验研究

    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, offcentering, 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 4.3% and 7.6% result in

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 1.0 mm. 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

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.