Numerical Optimization of a Trapezoidal Labyrinth Seal for Pulsed Compression Reactor (PCR)

A sealing system using labyrinth seal is proposed to minimize gas leaks in a Pulsed Compression Reactor, for which the geometric parameters of trapezoidal shape are evaluated. The set of parameters was optimized by minimizing gas leaks, using the Multiobjective Genetic Algorithm with the Genetic Aggregation method, which performs a regression model with the data generated by the correlation of parameters. The CFD simulation evaluates gas leakage for the given geometry and constant boundary conditions, inlet pressure 10 MPa, piston velocity 25 m/s, 35° cavity angle and 150 mm piston length. The values in the input set have been reduced to manufacturable quantities. The analysis of the velocity behavior shows a sudden increase in velocity in the final part of the cavity, and consequently, the turbulence kinetic energy presents peaks in that area. The most sensitive parameters are the gap between the piston and cylinder, and the width of the cavity. The minimum flow leakage is 0.001024 kg/s with a gap of 30 µm. When comparing between the smooth and grooved piston, there are regions where having a smooth surface is better than grooving it. In general, over a threshold gap-value of 150 µm is better to use a piston with labyrinth seals. For a gap of 250 µm the leakage flow was 0.301391 kg/s this represents a decrease of 34% compared to a smooth piston.