No abstract

No abstract

An improved physical model to predict flyash deposition is developed and discussed in this paper. This model differs from its predecessor [1, 2] by accounting for deposition of syngas ash particles below the ash softening temperature. The modified deposition model is based on the critical viscosity approach. To test this model, deposition of ash particles impacted on a flat, 45° wedge shape geometry is computed and the results obtained from the numerical model are compared to Crosby et al. [3]. Large Eddy Simulation (LES) is used to model the flow field and flyash particles are modeled using a discrete Lagrangian framework. Results quantify deposition for 4 pm particles of various ash composition samples. Most of the deposition occurs at the stagnation region of the target plate. At 1456K, out of all the ash samples considered in this study, ND ash sample shows the highest capture efficiency (8.84%) and HNP01 ash sample exhibits the lowest capture efficiency (3.61%). In general, capture efficiencies for all ash samples followed an exponential trend with temperature. Additionally, this model is also compared to results obtained from the flat plate deposition experiments conducted here at Virginia Tech using PVC particles [4]. In the case of PVC particles, the sticking probability in the deposition model assumed an exponential increase in deposition rate with temperature and was calibrated with one experimental data point. The results obtained from this model for PVC particles showed excellent agreement with the experimental measurements over a range of temperatures.

No abstract

The paper investigates the deposition and erosion caused by Syngas ash particles in a film cooled leading edge region of a representative turbine vane. The carrier phase is predicted using large eddy simulation for three blowing ratios of 0.4, 0.8, and 1.2. Ash particle sizes of 1 μm, 3 μm, 5 μm, 7 μm, and 10 μm are investigated using Lagrangian dynamics. The 1 μm particles with momentum Stokes number, Stp=0.03 (based on approach velocity and leading edge diameter), follow the flow streamlines around the leading edge and few particles reach the blade surface. The 10 μm particles, on the other hand with a high momentum Stokes number, Stp=0.03, directly impinge on the surface, with blowing ratio having a minimal effect. The 3 μm, 5 μm, and 7 μm particles with Stp=0.03, 0.8 and 1.4, respectively, show some receptivity to coolant flow and blowing ratio. On a number basis, 85–90% of the 10 μm particles, 70–65% of 7 μm particles, 40–50% of 5 μm particles, 15% of 3 μm particles, and less than 1% of 1 μm particles deposit on the surface. Overall there is a slight decrease in percentage of particles deposited with increase in blowing ratio. On the other hand, the potential for erosive wear is highest in the coolant hole and is mostly attributed to 5 μm and 7 μm particles. It is only at BR=1.2 that 10 μm particles contribute to erosive wear in the coolant hole.