Numerical Assessment of Four-Port Through-Flow Wave Rotor Cycles with Passage Height Variation

The potential for improved performance of wave rotor cycles through the use of passage height variation is examined. A Quasi-one-dimensional CFD code with experimentally validated loss models is used to determine the flowfield in the wave rotor passages. Results indicate that a carefully chosen passage height profile can produce substantial performance gains. Numerical performance data are presented for a specific profile, in a four-port, through-flow cycle design which yielded a computed 4.6% increase in design point pressure ratio over a comparably sized rotor with constant passage height. In a small gas turbine topping cycle application, this increased pressure ratio would reduce specific fuel consumption to 22% below the un-topped engine; a significant improvement over the already impressive 18% reductions predicted for the constant passage height rotor. The simulation code is briefly described. The method used to obtain rotor passage height profiles with enhanced performance is presented. Design and off-design results are shown using two different computational techniques. The paper concludes with some recommendations for further work

Application of Preconditioned, Multiple-Species, Navier-Stokes Models to Cavitating Flows

A preconditioned, homogenous, multiphase, Reynolds Averaged Navier-Stokes model with mass transfer is presented. Liquid, vapor, and noncondensable gas phases are included. The model is preconditioned in order to obtain good convergence and accuracy regardless of phasic density ratio or flow velocity. Both incompressible and finite-acoustic-speed models are presented. Engineering relevant validative and demonstrative unsteady and transient two and three-dimensional results are given. Transients due to unsteady cavitating flow including shock waves are captured. In modeling axisymmetric cavitators at zero angle-of-attack with 3-D unsteady RANS, significant asymmetric flow features are obtained. In comparison with axisymmetric unsteady RANS, capture of these features leads to improved agreement with experimental data. Conditions when such modeling is not necessary are also demonstrated and identified

AIAA 2001-0279 Preconditioning Algorithms for the Computation of Multi-Phase Mixture Flows Preconditioning Algorithms for the Computation of Multi-Phase Mixture Flows

presence of shocks, although the bulk of the flow may remain incompressible. This situation presents a unique challenge to the design of CFD algorithms. The development of appropriate numerical schemes for such multi-phase problems is the subject of the present paper. There are many levels of modeling that may be utilized in multi-phase computations The crucial requirement of multiphase algorithms is the ability to accurately and efficiently span both incompressible and compressible flow regimes. For singlephase applications, time-marching techniques have long been established as the method of choice for high-speed compressible flows, while artificial compressibility or preconditioning techniques have enabled the extension of these methods to the incompressible and low-speed compressible regimes ABSTRACT Preconditioned time-marching algorithms are developed for a class of isothermal compressible multi-phase mixture flows, relevant to the modeling of sheet-and super-cavitating flows in hydrodynamic applications. Using the volume fraction and mass fraction forms of the multi-phase governing equations, three closely related but distinct preconditioning forms are derived. The resulting algorithm is incorporated within an existing multi-phase code and several representative solutions are obtained to demonstrate the capabilities of the method. Comparisons with measurement data suggest that the compressible formulation provides an improved description of the cavitation dynamics compared with previous incompressible computations