Quasi-2D Unsteady Flow Solver Module for Rocket Engine and Propulsion System Simulations

A grid adaptation procedure suitable for use during unsteady flow computations is described. Transfinite interpolation is used to generate structured grids for the computation of steady and unsteady Euler flows past aerofoils. This technique is well suited to unsteady flows, since instantaneous grid positions and speeds required by the flow solver are available directly from the algebraic mapping. A different approach to grid adaptation is described, wherein adaptation is performed by redistributing the interpolation parameters, instead of the physical grid positions. This results in the adapted grid positions, and hence speeds, still being available algebraically. Grid adaptation during an unsteady computation is performed continuously by imposing an ‘adaptation velocity’ on grid points, thereby applying the adaptation over several time steps and avoiding the interpolation of the solution from one grid to another, which is associated with instantaneous adaptation. For both steady and unsteady flows the adapted grid technique is shown to produce sharper shock resolution for a very small increase in CPU (central processing unit) requirements.

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A two-level computational graph method for the adjoint of a finite volume based compressible unsteady flow solver

Parallel Computing ◽

10.1016/j.parco.2018.12.001 ◽

2019 ◽

Vol 81 ◽

pp. 68-84 ◽

Cited By ~ 1

Author(s):

Chaitanya Talnikar ◽

Qiqi Wang

Keyword(s):

Unsteady Flow ◽

Finite Volume ◽

Flow Solver ◽

Graph Method

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Predicting Bladerow Interactions Using a Multistage Time-Linearized Navier-Stokes Solver

Journal of Turbomachinery ◽

10.1115/1.1516570 ◽

2003 ◽

Vol 125 (1) ◽

pp. 25-32 ◽

Cited By ~ 5

Author(s):

W. Ning ◽

Y. S. Li ◽

R. G. Wells

Keyword(s):

Unsteady Flow ◽

Frequency Domain ◽

Test Data ◽

Computational Efficiency ◽

Unsteady Flows ◽

Navier Stokes ◽

Test Cases ◽

Numerical Accuracy ◽

Flow Solver ◽

Time Marching

A multistage frequency domain (time-linearized/nonlinear harmonic) Navier-Stokes unsteady flow solver has been developed for predicting unsteady flows induced by bladerow interactions. In this paper, the time-linearized option of the solver has been used to analyze unsteady flows in a subsonic turbine test stage and the DLR transonic counter-rotating shrouded propfan. The numerical accuracy and computational efficiency of the time-linearized viscous methods have been demonstrated by comparing predictions with test data and nonlinear time-marching solutions for these two test cases. It is concluded that the development of efficient frequency domain approaches enables unsteady flow predictions to be used in the design cycles to tackle aeromechanics problems.

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Effects of the Clocking on the Internal Flow in a 1.5 Stage Axial Turbine

Volume 6: Turbomachinery, Parts A and B ◽

10.1115/gt2006-90472 ◽

2006 ◽

Cited By ~ 1

Author(s):

Jongil Park ◽

Minsuk Choi ◽

Jehyun Baek

Keyword(s):

Unsteady Flow ◽

Relative Efficiency ◽

Message Passing Interface ◽

Flow Simulation ◽

Internal Flow ◽

Leading Edge ◽

Maximum Efficiency ◽

Axial Turbine ◽

Flow Solver ◽

Local Efficiency

A three-dimensional unsteady flow simulation is conducted to investigate clocking effects of a row of stators on the performance and internal flow in a 1.5 stage axial turbine. Although the original turbine has 22 blades of the first stator, 28 blades of the rotor and 28 blades of the second stator, the first stator is reduced by a factor of 22/28 to fit the blade ratio 1:1:1. The unsteady flow solver is implemented using the second order time marching and sliding mesh scheme between blade rows. And then, this flow solver is parallelized using MPI (Message Passing Interface) libraries to overcome the limitation of memories and to save the calculation time. Six relative positions of two rows of stators are investigated by positioning the second stator being clocked in a step of 1/6 pitch. The relative efficiency benefit of about 1% is obtained depending on clocking positions. At mid-span, the first stator wake is mixed up with the rotor wake before arriving at the leading edge of the second stator. The time-averaged local efficiency along the span at the maximum efficiency shows more uniform distribution than that at the minimum efficiency. Moreover, the variation of local efficiency at the mid-span does not coincide with that of overall efficiency. Therefore, it is found in this case that the only wake trajectory of the first stator is not a proper means of predicting the best and worst efficiency positions. This is why the relative efficiency benefit depending on the clocking position is obtained near the hub and casing in this study. So, it is necessary to find a general cause of the clocking effect which is applicable to every test case. The difference between maximum and minimum instantaneous efficiencies during one period is found to be smaller at the maximum efficiency than at the minimum efficiency.

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Analysis of the Unsteady Flow in an Aspirated Counter-Rotating Compressor Using the Nonlinear Harmonic Method

Volume 7: Turbomachinery, Parts A and B ◽

10.1115/gt2009-60285 ◽

2009 ◽

Cited By ~ 1

Author(s):

Emanuele Guidotti ◽

Mark G. Turner

Keyword(s):

Flow Field ◽

Unsteady Flow ◽

Frequency Domain ◽

Navier Stokes ◽

Test Case ◽

Numerical Accuracy ◽

Flow Solver ◽

Harmonic Method ◽

Flow Change ◽

Inlet Boundary Condition

A multistage frequency domain (Nonlinear Harmonic) Navier-Stokes unsteady flow solver has been used to analyze the flow field in the MIT (rotor/rotor) aspirated counter-rotating compressor. The numerical accuracy and computational efficiency of the Nonlinear Harmonic method implemented in Numeca’s Fine/Turbo CFD code has been demonstrated by comparing predictions with experimental data and nonlinear time-accurate solutions for the test case. The comparison is good, especially considering the big savings in time with respect to a time accurate simulation. An imposed inlet boundary condition takes into account the flow change due to the IGV (not simulated in the computational model). Details of the flow field are presented and physical explanations are provided. Also, suggestions and recommendations on the use of the Nonlinear Harmonic method are provided. From this work it can be concluded that the development of efficient frequency domain approaches enables routine unsteady flow predictions to be used in the design of modern turbomachinery.

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Hybrid Rocket Engine Design Optimization at Politecnico di Torino: A Review

Aerospace ◽

10.3390/aerospace8080226 ◽

2021 ◽

Vol 8 (8) ◽

pp. 226

Author(s):

Lorenzo Casalino ◽

Filippo Masseni ◽

Dario Pastrone

Keyword(s):

Design Optimization ◽

Rocket Engine ◽

Propulsion System ◽

Future Perspective ◽

Rocket Engines ◽

Hybrid Rocket ◽

Feed System ◽

Research Activities ◽

Multi Stage ◽

System Design Optimization

Optimization of Hybrid Rocket Engines at Politecnico di Torino began in the 1990s. A comprehensive review of the related research activities carried out in the last three decades is here presented. After a brief introduction that retraces driving motivations and the most significant steps of the research path, the more relevant aspects of analysis, modeling and achieved results are illustrated. First, criteria for the propulsion system preliminary design choices (namely the propellant combination, the feed system and the grain design) are summarized and the engine modeling is presented. Then, the authors describe the in-house tools that have been developed and used for coupled trajectory and propulsion system design optimization. Both deterministic and robust-based approaches are presented. The applications that the authors analyzed over the years, starting from simpler hybrid powered sounding rocket to more complex multi-stage launchers, are then presented. Finally, authors’ conclusive remarks on the work done and their future perspective in the context of the optimization of hybrid rocket propulsion systems are reported.

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Predicting Bladerow Interactions Using a Multistage Time-Linearized Navier-Stokes Solver

Volume 5: Turbo Expo 2002, Parts A and B ◽

10.1115/gt2002-30309 ◽

2002 ◽

Author(s):

W. Ning ◽

Y. S. Li ◽

R. G. Wells

Keyword(s):

Unsteady Flow ◽

Frequency Domain ◽

Test Data ◽

Computational Efficiency ◽

Unsteady Flows ◽

Navier Stokes ◽

Test Cases ◽

Numerical Accuracy ◽

Flow Solver ◽

Time Marching

A multistage frequency domain (time-linearized/nonlinear harmonic) Navier-Stokes unsteady flow solver has been developed for predicting unsteady flows induced by bladerow interactions. In this paper, the time-linearized option of the solver has been used to analyze unsteady flows in a subsonic turbine test stage and the DLR transonic counter-rotating shrouded propfan. The numerical accuracy and computational efficiency of the time-linearized viscous methods have been demonstrated by comparing predictions with test data and nonlinear time-marching solutions for these two test cases. It is concluded that the development of efficient frequency domain approaches enables unsteady flow predictions to be used in the design cycles to tackle aeromechanics problems.

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