Method and system for predicting rocket nozzle deformation during engine start-up and shut-down transients

Inventors

Wang, Ten-See

Assignees

National Aeronautics and Space Administration NASA

Abstract

Computational fluid dynamics (CFD) computations are performed at time increments using structural properties of the nozzle and flow properties of combustion products flowing through the nozzle. Each CFD computation accounts for movement of the wall geometry of the rocket nozzle due to the flowfield. Structural dynamics computations are performed at each time increment using the CFD computations in order to describe the movement of the wall geometry. Mesh dynamics computations at each time increment redefine the flowfield to account for the movement of the wall geometry. The mesh dynamics computations are based on a spring analogy process. The computations are iterated to solution convergence at each time increment with results being output to an output device.

Core Innovation

This invention provides a method and system for predicting rocket nozzle deformation during the transient conditions associated with rocket engine start-up and shut-down. The method leverages computational fluid dynamics (CFD), structural dynamics, and mesh dynamics computations at time increments, integrating the interaction between the flowfield and the rocket nozzle's wall geometry during these short-duration transients. The CFD computations account for movement of the nozzle wall due to flow effects, structural dynamics computations describe the wall movement based on the CFD results, and mesh dynamics redefines the flowfield mesh to reflect wall motion using a spring analogy process.

The problem addressed is the inaccuracy and inefficiency in current nozzle side load prediction methods, which typically use loosely coupled models involving separate CFD and computational structural dynamics codes connected through an interface that requires interpolation. This interpolation causes inaccuracies, and the use of different codes with incompatible convergence criteria leads to computational inefficiency. Moreover, conventional rigid nozzle CFD methods fail to capture aeroelastic coupling—the fluid-structure interaction that causes oscillatory nozzle deformation and potentially damaging structural loads during start-up and shut-down transients.

The invention overcomes these challenges by integrating the nozzle's mechanical eigenmodes directly into the fluid-structure interaction process, thereby avoiding interpolation errors at the fluid-structure interface and enabling iterative convergence at each time step. The CFD computations solve time-varying transport equations including finite-rate chemistry and turbulence models that capture afterburning effects critical to accurate side load prediction. The mesh dynamics employ a spring analogy with a weighting function to preserve near-wall grid spacing when the nozzle wall deforms. Outputs include graphical and numerical data describing nozzle deformation and flowfield changes during engine transient operations.

Claims Coverage

The patent claims cover multiple inventive features spread across method and system claims addressing transient deformation prediction of rocket nozzles during engine start-up and shut-down.

The independent claims collectively disclose a computational method and system that tightly couple CFD, structural dynamics, and mesh dynamics with transient flow input parameters, finite-rate chemistry, turbulence modeling, and an advanced mesh deformation approach to predict rocket nozzle deformation during engine transient operations with improved accuracy and computational efficiency.

Stated Advantages

Documented Applications