The Effect of Gas and Surface Temperature on Cold-Side and Hot-Side Turbine Deposition

Deposition studies were conducted using two impingement jet facilities: a 60 m/s cold jet (830-950 K) impinging on a heated Hastelloy-X surface (1033-1255 K) and a 215 m/s hot jet (1450-1625 K) impinging on an uncooled ceramic target or a cooled thermal barrier coated (TBC) surface (1090-1400 K). These can be considered analogs for an internal impingement cooling jet flow and an external nozzle guide vane leading edge flow respectively. Airflows were seeded with 0-10 mu m Arizona road dust and deposition accumulated over a period of 5-10 min. Selected tests were completed with other size distributions. Studies were conducted by varying flow temperature at constant surface temperature and vice-versa. For both hot and cold impingement jets, the sensitivity of capture efficiency to fluid (and thus particle) temperature was found to be roughly double the sensitivity to surface temperature. Hot jet tests with three different size distributions of dust (0-5, 0-10, and 5-10 mu m) allowed particle size sensitivity to be evaluated. For both target types (ceramic and cooled TBC), the 0-10 mu m test dust produced the highest deposition rate of the three size distributions. Possible explanations for the observed behavior are proposed. Companion CFD studies modeling both impinging jets with particle deposition demonstrate that temperature induced variations in particle trajectories alone are not sufficient to explain observed deposition trends with temperature. Implications for the development of a universal sticking model relevant to gas turbine deposition are discussed.