Simulation and characteristics of the coolant feeding tubes in tip clearance control system

Typical coolant feeding tubes of low pressure turbine tip clearance control system were numerically and experimentally investigated with three-dimensional calculations and full size experimental section, i.e. 90° curved round-section coolant feeding tubes. The outflow characteristic of impingement holes on coolant feeding tubes was studied, and the inlet parameters, arrangement of impingement holes were changed to examine the rules of inner flow and flow rate distribution of coolant feeding tubes. The effective inlet total pressure of impingement holes was defined, then one-dimensional flow net caculation model was established according to this new assumption. Finally the assemblies of coolant feeding tubes of low pressure turbine tip clearance control system were studied by this one-dimensional flow net model and experiments. It was found that with the increase of central angle, the outflow rate and the discharge coefficient increased. The outflow rate through the coolant feeding tube increased with the increasing of inlet Reynolds number，however the discharge coefficients of the impingement hole remained consistent. The comparison between numerical results and experimental data indicates that reasonable flow characteristics of the coolant feeding tubes can be obtained by the one-dimensional flow net model. The maximum relative error between calculation results and experiment data is 4.5%. All the results show that the one-dimensional flow net model has a reasonable accuracy and good application in the complex fluid nets like the tip clearance control system.