1. Determination of initial and boundary conditions for numerical simulation of turbine rear exhaust nozzle casting
The results show that the pouring temperature of lost foam casting is 20 ~ 80 ℃ higher than that of sand casting. Negative pressure degree is a very important parameter in lost foam casting production. For iron castings, the negative pressure is generally controlled at 0.04 ~ 0.06 MPa. According to the actual production process, the gate cup is empty, and the casting material should be given; The cavity filled with foam gives FOAM material. The mold material gives dry sand material.
In addition to the heat boundary conditions and inner gate temperature in the same city, the numerical simulation of lost foam casting also needs to set the pressure boundary conditions. One is located at the gate cup on the top of the sprue, and the other is located outside the mold. Its size is set to 1.04 ATM and 1 atm respectively. Casting conditions of lost foam casting for exhaust pipe after turbine.
2. Determination of operation parameters of lost foam casting for turbine rear exhaust pipe
Lost foam casting simulation mainly simulates the mold filling process, solidification process and Shrinkage Cavity Prediction of the exhaust pipe after the turbine. Set the thermal parameter, flow parameter and general operating parameter in the run parameter of ProCAST software. The total simulation time step is set to 10000; The initial time step DT is 0.0001 s, and the maximum time step dtmax is 5S; The feeding length is set as 5 mm in the operating parameters of temperature field. At this time, macro shrinkage and looseness will occur outside the macro isosurface; Set the poros value to 1 for the most advanced shrinkage calculation; Select 1 from the specified thermal options for heat transfer analysis. Lost foam casting simulation needs to set the pressure driven internal flow, and set pinlet to 1, indicating that all pressure boundary conditions are also internal flow boundary conditions.