Multi-Intensity-Layer PIV application to a Gas Turbine Combustor

The new technique ‘Multi-Intensity-Layer PIV’ was applied to a gas turbine combustor to detect the instantaneous droplet distribution and its behavior. Mie scattering theory is applied to the conventional Particle Image Velocimetry and the technique enables us to detect the instantaneous planar droplet velocity and size information. This M-PIV technique was evaluated with a generally used industrial burner under atmospheric pressure and had a good agreement with PDA results. So now on this study the M-PIV was used to a highly pressurized gas turbine combustor for evaluation comparing with PDA results. The difference from the previous evaluation with an industrial burner is that the flow field is pressurized to 0.25 MPa so that many optical error sources exist. We are concentrated into the flow structure formed by a pilot burner installed in the combustor and as a first step the evaluation is undertaken in cold flow condition. The purpose of this study is the evaluation of M-PIV within the application into a gas turbine combustor. Evaluation was done under comparison with size-classified PDA since this new technique tries to describe droplet behavior and flow structure for each droplet size classes. The combustion chamber is specially designed for the laser diagnostics in order to undertake the measurement under realistic operating conditions. The technique is evaluated with the PDA results. The results indicates that Velocity component comparison indicates the technique has basically good agreement with PDA results and some discrepancy observed due to dense spray region. In the downstream region there is the perfect agreement with PDA results because the spray is much more diluted than the nozzle exit. Additionally, the technique can describe the different flow structure that depends upon the intensity information. By comparing with PDA results the flow structure of each layer is able to represent size discriminated flow information. We conclude that the technique is applicable to a pressurized flow field. Multi-Intensity-Layer PIV application to a Gas Turbine Combustor Naoki YAMADA, Yuji IKEDA and Tsuyoshi NAKAJIMA Department of Mechanical Engineering Kobe University Rokkodai, Nada, Kobe 657-8501 JAPAN ABSTRACT The new technique ‘Multi-Intensity-Layer PIV’ was applied to a gas turbine combustor to detect the instantaneous droplet distribution and its behavior. Mie scattering theory is applied to the conventional Particle Image Velocimetry and the technique enables us to detect the instantaneous planar droplet velocity and size information. This M-PIV technique was evaluated with a generally used industrial burner under atmospheric pressure and had a good agreement with PDA results. So now on this study the M-PIV was used to a highly pressurized gas turbine combustor for evaluation comparing with PDA results. The difference from the previous evaluation with an industrial burner is that the flow field is pressurized to 0.25 MPa so that many optical error sources exist. We are concentrated into the flow structure formed by a pilot burner installed in the combustor and as a first step the evaluation is undertaken in cold flow condition. The purpose of this study is the evaluation of M-PIV within the application into a gas turbine combustor. Evaluation was done under comparison with size-classified PDA since this new technique tries to describe droplet behavior and flow structure for each droplet size classes. The combustion chamber is specially designed for the laser diagnostics in order to undertake the measurement under realistic operating conditions. The technique is evaluated with the PDA results. The results indicates that Velocity component comparison indicates the technique has basically good agreement with PDA results and some discrepancy observed due to dense spray region. In the downstream region there is the perfect agreement with PDA results because the spray is much more diluted than the nozzle exit. Additionally, the technique can describe the different flow structure that depends upon the intensity information. By comparing with PDA results the flow structure of each layer is able to represent size discriminated flow information. We conclude that the technique is applicable to a pressurized flow field.The new technique ‘Multi-Intensity-Layer PIV’ was applied to a gas turbine combustor to detect the instantaneous droplet distribution and its behavior. Mie scattering theory is applied to the conventional Particle Image Velocimetry and the technique enables us to detect the instantaneous planar droplet velocity and size information. This M-PIV technique was evaluated with a generally used industrial burner under atmospheric pressure and had a good agreement with PDA results. So now on this study the M-PIV was used to a highly pressurized gas turbine combustor for evaluation comparing with PDA results. The difference from the previous evaluation with an industrial burner is that the flow field is pressurized to 0.25 MPa so that many optical error sources exist. We are concentrated into the flow structure formed by a pilot burner installed in the combustor and as a first step the evaluation is undertaken in cold flow condition. The purpose of this study is the evaluation of M-PIV within the application into a gas turbine combustor. Evaluation was done under comparison with size-classified PDA since this new technique tries to describe droplet behavior and flow structure for each droplet size classes. The combustion chamber is specially designed for the laser diagnostics in order to undertake the measurement under realistic operating conditions. The technique is evaluated with the PDA results. The results indicates that Velocity component comparison indicates the technique has basically good agreement with PDA results and some discrepancy observed due to dense spray region. In the downstream region there is the perfect agreement with PDA results because the spray is much more diluted than the nozzle exit. Additionally, the technique can describe the different flow structure that depends upon the intensity information. By comparing with PDA results the flow structure of each layer is able to represent size discriminated flow information. We conclude that the technique is applicable to a pressurized flow field. INTRODUCTION Droplet dynamics and its interaction to surrounding swirl air flow was investigated using phase Doppler anemometry (PDA) and particle image velocimetry (PIV). In our previous research we went through the 4 steps, laser diagnostics error estimations considering with optimizations of optical settings, combustion chamber optimum designing for optical diagnostics, PDA applications and laser sheet visualization. In the error estimation process various possible error sources were considered, such as droplet sticking on the optical windows, alternation of diffractive index due to the ambient pressure changing, location of the probe volume and slit location changing due to unfixed optical pathways, etc. Combustion chamber was carefully designed on the next step with considering the area of interest and its location, required optical pathways, size and location of the optical windows for PDA and PIV measurements, required thickness of the combustion chamber itself and optical windows that fits for the ambient pressure up to 5.0 MPa. After these steps PDA was applied to the combustion chamber under realistic operating conditions. With PDA results time averaged size classified droplet behavior, slip velocity, scalar distributions such as Reynolds number, drag coefficient, Reynolds stress, vorticity and dilatation were discussed. Utilizing the high data acquisition feasibility of PDA time scale of the turbulent and coherent structures was also discussed. And now here in this study the target is focused on the droplet dynamics under high pressure, For understanding of the droplet behavior phase Doppler anemometry (PDA/PDPA), with which temporary averaged droplet size and velocity information is available, was widely used . The technique is good for understanding the time domain information and suitable for acquiring time series data for statistical analysis at each measurement point so that we are able to know the detailed time history of velocity and the time scale of the turbulence and coherent structures. For recent years Particle image velocimetry (2) (3) (4) (PIV) is used to investigate the instantaneous spatial structure since the technique is based on spatial domain. In recent years spatial resolution is well improved (5) (6) and spatially detailed information is available. But the problem on PIV for the application to spray field there are no droplet size information acquired so that we cannot know of which droplet size the acquired velocity is. For a solution for this problem we proposed “Multi-Intensity-Layer PIV” (7) (8) (9) technique that utilize Mie scattering theory (10) (11) for PIV and enable us to get droplet size discriminated PIV. This M-PIV technique was evaluated with a generally used industrial burner under atmospheric pressure and had a good agreement with PDA results (7) (8) . So now on this study the M-PIV was used to a highly pressurized gas turbine combustor for evaluation comparing with PDA results. The difference from the previous evaluation with an industrial burner is that the flow field is pressurized to 0.25 MPa so that many optical error sources (12) (13) are exist (i. e., Thick optical windows on the light pathways, diffractive index is in vary, etc) We are concentrated into the flow structure formed by a pilot burner installed in the combustor and as a first step the evaluation is undertaken in cold flow condition. The purpose of this study is the evaluation of M-PIV within the application into a gas turbine combustor. Evaluation was done under comparison with size-classified PDA (14) since this new technique tries to describe droplet behavior and flow structure for each droplet size classes. EXPERIMENTAL DESCRIPTION Figure 1 shows a schematic drawing of the test nozzle assembly. High-pressure air passed through axial swirler vanes surrounding the nozzle, and was then ejected at the swirler exit, which had an inner diameter of 81 mm. At the tip of the nozzle body, which had an outer diameter of 54 mm, a pressure-swirl atomizer (DELAVAN Inc.) was mounted on the central axis of the nozzle. The flow rate of the atomizer was 35 GPH (gallons per hour), and a spray angle of 80° was chosen to create a hollowcone spray. The test nozzle assembly, which had a vertical traverse system, was mounted in a pressure vessel of 230 mm in inner diameter and 1,300 mm in vertical length. It could operate at pressures up to 5.0 MPa. The combustion chamber was designed with purged quartz windows, through which laser diagnostics and chemiluminescence measurements of combusting spray could be made from outside the combustion chamber. This study was done under non-combustion condition so that water was injected instead of fuel (light oil). Water was pressurized by a fuel pump and sprayed into the vessel. The pressure vessel was carefully designed, and much attention was paid to the size and location of the optical windows used to measure phase Doppler anemometry (PDA) and laser simultaneously. The area of interest extended about 80 mm downstream from the nozzle exit. To measure droplet size and velocity, an Ar-ion laser and a fiber PDA system (DANTEC) were used. The focal lengths of the transmitting and receiving optics were both 600mm, both the transmitting and receiving optics were mounted on a one-dimension horizontal traverse table. The light source for PIV is Nd:YAG laser (400mJ/pulse) and images are captured by a cross-correlation camera (Kodak ES1.0, 1008H x 1018W pixels). The experiments were conducted under a fixed air temperature of 20°C, an airflow rate of 0.172 m/s. and fuel (water) flow rate was 104 kg/h. The ambient air pressure was 0.25 MPa. Fig.1 Experimental apparatus Nozzle Swirler Optical window