http://orcid.org/0000-0003-1925-6447
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ABSTRACT
The present study deals with the turbine casing radiation effect on the impinging cooling encountered in the blade tip active clearance control (ACC) system of aero-engine turbine. To this end, numerical simulations are carried out for a simplified model, that is, a pipe with a single row of impinging jets. The effects of the nozzle-to-plate distance to the diameter of the impinging hole (H/d = 2–8), the number of the holes (n = 17–68), the impinging wall temperature (Tp = 400–800 K), and the inlet Reynolds number (Re = 5,000–20,000) on the flow and heat transfer are investigated. Analysis is performed on the radiation heat transfer effects on the corresponding flow fields and surface heat flux distributions. The results indicate that, with the radiation included in the simulations, the mass flow rate of the cooling jet near the end of the pipe decreases significantly under the conditions of high wall temperature and small nozzle-to-plate distance. Radiation heat transfer should be accounted for in the numerical study for the casing cooling as it affects the flow and heat transfer remarkably. When the nozzle-to-plate distance is relatively large, such as H/d is larger than 8, the radiative heating leads to uniform heat flux and the radiative heating can suppress the uneven distributions of the heat flux.
Nomenclature
| A | = | area (m2) |
| AR | = | outlet area ratio |
| D | = | inner diameter of the pipe (m) |
| d | = | diameter of the impinging hole (m) |
| e | = | emissivity |
| H | = | nozzle-to-plate distance (m) |
| h | = | convection heat transfer coefficient (w/m2 K) |
| = | mass flow rate (kg/s) | |
| n | = | number of the holes |
| pnt | = | total pressure at the first hole near the pipe inlet (Pa) |
| ps | = | static pressure (Pa) |
| = | dimensionless pressure ratio | |
| q | = | heat flux (w/m2) |
| qR | = | radiation heat flux (w/m2) |
| Re | = | inlet Reynolds number |
| Sx | = | distance between the holes (m) |
| Tj | = | upstream temperature of the impinging jet (K) |
| Tp | = | target plate temperature (K) |
| t | = | piped wall thickness (m) |
| ΔT | = | temperature difference (K) |
| u | = | velocity (m/s) |
| μ | = | dynamic viscosity (kg/(m · s)) |
| ρ | = | density (kg/m3) |
| Subscripts | = | |
| 0 | = | result without considering radiation |
| in | = | inlet |
| j | = | jet hole |
| MC | = | considering radiation with Monte Carlo method |
| p | = | plate |
| tube | = | tube surface |
| tot | = | total |
Nomenclature
| A | = | area (m2) |
| AR | = | outlet area ratio |
| D | = | inner diameter of the pipe (m) |
| d | = | diameter of the impinging hole (m) |
| e | = | emissivity |
| H | = | nozzle-to-plate distance (m) |
| h | = | convection heat transfer coefficient (w/m2 K) |
| = | mass flow rate (kg/s) | |
| n | = | number of the holes |
| pnt | = | total pressure at the first hole near the pipe inlet (Pa) |
| ps | = | static pressure (Pa) |
| = | dimensionless pressure ratio | |
| q | = | heat flux (w/m2) |
| qR | = | radiation heat flux (w/m2) |
| Re | = | inlet Reynolds number |
| Sx | = | distance between the holes (m) |
| Tj | = | upstream temperature of the impinging jet (K) |
| Tp | = | target plate temperature (K) |
| t | = | piped wall thickness (m) |
| ΔT | = | temperature difference (K) |
| u | = | velocity (m/s) |
| μ | = | dynamic viscosity (kg/(m · s)) |
| ρ | = | density (kg/m3) |
| Subscripts | = | |
| 0 | = | result without considering radiation |
| in | = | inlet |
| j | = | jet hole |
| MC | = | considering radiation with Monte Carlo method |
| p | = | plate |
| tube | = | tube surface |
| tot | = | total |