Deposition With Hot Streaks in an Uncooled Turbine Vane Passage

Abstract

The effect of hot streaks on deposition in a high pressure turbine vane passage was studied both experimentally and computationally. Modifications to Ohio State’s Turbine Reaction Flow Rig allowed for the creation of simulated hot streaks in a four-vane annular cascade operating at temperatures up to 1093°C. Total temperature surveys were made at the inlet plane of the vane passage, showing the variation caused by cold dilution jets. Deposition was generated by introducing sub-bituminous ash particles with a median diameter of 11.6 μm far upstream of the vane passage. Results indicate a strong correlation between surface deposits and the hot streak trajectory. A computational model was developed in Fluent to simulate both the flow and deposition. The flow solution was first obtained without particulates, and individual ash particles were subsequently introduced and tracked using a Lagrangian tracking model. The critical viscosity model was used to determine particle sticking upon impact with vane surfaces. Computational simulations confirm the migration of the hot streak and locations susceptible to enhanced deposition. Results show that the deposition model is overly sensitive to temperature and can severely overpredict deposition. Model constants can be tuned to better match experimental results, but must be calibrated for each application.

A review of multiphase flow and deposition effects in film-cooled gas turbines

“…For investigation of the particle deposition on NGV, RANS equations are mostly used to predict velocity, temperature fields, and film cooling effectiveness. A similar application has been reported by Casaday et al [38], Casaday et al [39], Barker et al [59] and Casaday et al [60]. In addition, the effect of particle deposition in a compressor stage was also investigated by using RANS [61].…”

“…For comparison of the capture efficiencies on the NGV, some results were obtained by considering various influence factors, such as particle material [24], particle size [25,29,34], gas temperature [25,34], blowing ratio [33], inlet turbulence level [37], deposition time [34], and hot streak [35,38,39]. Effects of the gas temperature and particle size are analyzed in fig.…”

Numerical Study of Deposition in a Full Turbine Stage Using Steady and Unsteady Methods

“…Compared to experimental results in Webb et al [15], Barker et al [14] determined that their deposition model predicts initial deposition relatively well, but is not valid after large-scale deposits begin to form causing geometry changes. Casaday et al [16] used the deposition model to investigate the effects of a non-uniform inlet temperature profile on external deposition, and found by comparing to experiments that the model could be tuned to produce more representative results. Suman et al [17] performed a computational study of deposition in a full stage axial compressor using a multiple reference frame, frozen-rotor approach focused on small particulate that could evade an inlet filter.…”

“…Because the experiment by Haldeman et al was performed at temperatures much lower than those typically found in gas turbines, a tuning process was performed in order to produce a fictitious particle type with constants, A, B, and C, that would deposit in the simulations. The critical viscosity model used was tuned using typical vane capture efficiencies from experiment for coal ash particles at an inlet temperature of approximately 1400 K [16]. By tuning the model parameters to the vane capture efficiencies from high temperature experiments, realistic vane capture efficiencies were achieved in the simulation at an inlet temperature of 443 K. This tuning was assumed to be appropriate for the blade surface as well due to the lack of experimental, rotating blade deposition data available.…”

“…By tuning the model parameters to the vane capture efficiencies from high temperature experiments, realistic vane capture efficiencies were achieved in the simulation at an inlet temperature of 443 K. This tuning was assumed to be appropriate for the blade surface as well due to the lack of experimental, rotating blade deposition data available. The main ash properties are summarized in Table 2.5 and described in further detail in [16].…”