NPSS Volume Dynamic Capability for Real-Time Physics Based Engine Modeling

2011 ◽  
Author(s):  
Christopher Argote ◽  
Brian K. Kestner ◽  
Dimitri N. Mavris
Keyword(s):  
Boundary Conditions ◽  
Real Time ◽  
Fluid Dynamic ◽  
Critical Time ◽  
Momentum Conservation ◽  
Drop Out ◽  
Dynamic Equations ◽  
High Fidelity ◽  
Time Step ◽  
Engine Cycle

This paper introduces a new capability and method for solving transient engine cycles for the potential application of real-time simulation in the cycle analysis code Numerical Propulsion System Simulation (NPSS). This method utilizes a new element which models volume dynamics, a set of equations that characterize the unsteady behavior of fluid dynamic and thermodynamic properties with respect to a volume and boundary conditions. These equations are derived from the Euler equations for conservation of mass, momentum, and energy. Physics based real-time engine models often consider the effects of volume dynamics; however it is normal to see the momentum conservation drop out. This is largely due to the high frequency response of momentum which yields smaller time steps thus increasing the cost associated with computation time. The new high fidelity volume dynamics element is introduced with all three conservations laws working together. NPSS’s interpreted language provides the flexibility to allow the volume dynamics to be solved explicitly, however by rearranging the momentum equation, it can be solved implicitly therefore increasing the critical time step. In addition to improving transient modeling fidelity, the new volume dynamics element can be used to drive the cycle. Rather than balancing error terms in a Newton-Raphson solver, the volume dynamic equations provide the necessary communication between the engine cycle and boundary conditions. These equations alone can drive the engine model towards a steady state solution. Using a basic forward Euler numerical integration technique to solve the volume dynamic equations the engine cycle only requires a single pass per time step. This document illustrates the development of both the new element and the methodology in cycle modeling using the volume dynamics. Two example models are created and analyzed in this paper, first, a simple inlet, duct, nozzle system is analyzed. Second, a separate flow long duct turbojet is examined. These two models are used to demonstrate the real time capabilities of the high fidelity transient analysis, as well as highlight some of the challenges in the implementation of volume dynamics on a given cycle.

scholarly journals Multi-Fidelity Simulation of a Turbofan Engine With Results Zoomed Into Mini-Maps for a Zero-D Cycle Simulation

2004 ◽  
Author(s):  
Mark G. Turner ◽  
John A. Reed ◽  
Robert Ryder ◽  
Joseph P. Veres
Keyword(s):  
Boundary Conditions ◽  
Fluid Dynamic ◽  
Thermodynamic Cycle ◽  
High Fidelity ◽  
Operating Characteristics ◽  
Cycle Model ◽  
Turbofan Engine ◽  
Engine Model ◽  
Cycle Simulation ◽  
Component Models

A Zero-D cycle simulation of the GE90-94B high bypass turbofan engine has been achieved utilizing mini-maps generated from a high-fidelity simulation. The simulation utilizes the Numerical Propulsion System Simulation (NPSS) thermodynamic cycle modeling system coupled to a high-fidelity full-engine model represented by a set of coupled 3D computational fluid dynamic (CFD) component models. Boundary conditions from the balanced, steady-state cycle model are used to define component boundary conditions in the full-engine model. Operating characteristics of the 3D component models are integrated into the cycle model via partial performance maps generated from the CFD flow solutions using one-dimensional meanline turbomachinery programs. This paper high-lights the generation of the highpressure compressor, booster, and fan partial performance maps, as well as turbine maps for the high pressure and low pressure turbine. These are actually “mini-maps” in the sense that they are developed only for a narrow operating range of the component. Results are compared between actual cycle data at a take-off condition and the comparable condition utilizing these mini-maps. The mini-maps are also presented with comparison to actual component data where possible.

A Modular Code for Real Time Dynamic Simulation of Gas Turbines in Simulink

2002 ◽  
Vol 128 (3) ◽  
pp. 506-517 ◽  
Author(s):  
S. M. Camporeale ◽  
B. Fortunato ◽  
M. Mastrovito
Keyword(s):  
Mathematical Model ◽  
Real Time ◽  
Gas Turbine ◽  
Dynamic Behavior ◽  
Gas Turbines ◽  
Simulation Software ◽  
Computational Time ◽  
High Fidelity ◽  
Time Step ◽  
The Mathematical Model

A high-fidelity real-time simulation code based on a lumped, nonlinear representation of gas turbine components is presented. The code is a general-purpose simulation software environment useful for setting up and testing control equipments. The mathematical model and the numerical procedure are specially developed in order to efficiently solve the set of algebraic and ordinary differential equations that describe the dynamic behavior of gas turbine engines. For high-fidelity purposes, the mathematical model takes into account the actual composition of the working gases and the variation of the specific heats with the temperature, including a stage-by-stage model of the air-cooled expansion. The paper presents the model and the adopted solver procedure. The code, developed in Matlab-Simulink using an object-oriented approach, is flexible and can be easily adapted to any kind of plant configuration. Simulation tests of the transients after load rejection have been carried out for a single-shaft heavy-duty gas turbine and a double-shaft aero-derivative industrial engine. Time plots of the main variables that describe the gas turbine dynamic behavior are shown and the results regarding the computational time per time step are discussed.

Turbulence Radiation Interactions in a Statistically Homogeneous Turbulence With Approximated Coal Type Particulate

2012 ◽  
Author(s):  
Mathew Cleveland ◽  
Sourabh Apte ◽  
Todd Palmer
Keyword(s):  
Fluid Dynamic ◽  
Dynamic Equations ◽  
Step Size ◽  
Time Step ◽  
Time Step Size ◽  
Transfer Equations ◽  
Low Mass ◽  
Dynamic Time ◽  
Radiative Transfer Equations ◽  
Coal Type

Turbulent radiation interaction (TRI) effects are associated with the differences in the time scales of the fluid dynamic equations and the radiative transfer equations. Solving on the fluid dynamic time step size produces large changes in the radiation field over the time step. We have modified the statistically homogeneous, non-premixed flame problem of Deshmukh et al. [1] to include coal-type particulate. The addition of low mass loadings of particulate minimally impacts the TRI effects. Observed differences in the TRI effects from variations in the packing fractions and Stokes numbers are difficult to analyze because of the significant effect of variations in problem initialization. The TRI effects are very sensitive to the initialization of the turbulence in the system. The TRI parameters are somewhat sensitive to the treatment of particulate temperature and the particulate optical thickness, and this effect is amplified by increased particulate loading.

The Critical Time Step for Finite-Element Solutions to Two-Dimensional Heat-Conduction Transients

1978 ◽  
Vol 100 (1) ◽  
pp. 120-127 ◽  
Author(s):  
G. E. Myers
Keyword(s):  
Boundary Conditions ◽  
Nodal Point ◽  
Critical Time ◽  
Time Step ◽  
Various Boundary Conditions ◽  
Quadrilateral Elements ◽  
Triangular Elements ◽  
The Finite Difference Method ◽  
Critical Time Step ◽  
Element Shape

Computationally-useful methods of estimating the critical time step for linear triangular elements and for linear quadrilateral elements are given. Irregular nodal-point arrangements, position-dependent properties, and a variety of boundary conditions can be accommodated. The effects of boundary conditions and element shape on the critical time step are discussed. Numerical examples are presented to illustrate the effect of various boundary conditions and for comparison to the finite-difference method.

Thermo-Mechanical FEA/CFD Coupling of an Interstage Seal Cavity Using Torsional Spring Analogy

2010 ◽  
Author(s):  
Dario Amirante ◽  
Nicholas J. Hills ◽  
Christopher J. Barnes
Keyword(s):  
Heat Transfer ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Boundary Conditions ◽  
Direct Reduction ◽  
Time Step ◽  
Element Analysis ◽  
Local Conditions ◽  
Coupling Process ◽  
Engine Cycle

The optimisation of heat transfer between fluid and metal plays a crucial role in gas turbine design. An accurate prediction of temperature for each metal component can help to minimise the coolant flow requirement, with a direct reduction of the corresponding loss in the thermodynamic cycle. Traditionally, in industry fluid and solid simulations are conducted separately. The prediction of metal stresses and temperatures, generally based on finite element analysis, requires the definition of a thermal model whose reliability is largely dependent on the validity of the boundary conditions prescribed on the solid surface. These boundary conditions are obtained from empirical correlations expressing local conditions as a function of working parameters of the entire system, with validation being supplied by engine testing. However, recent studies have demonstrated the benefits of employing coupling techniques, whereby computational fluid dynamics (CFD) is used to predict the heat flux from the air to the metal, and this is coupled to the thermal analysis predicting metal temperatures. This paper describes an extension of this coupling process, accounting for the thermo-mechanical distortion of the metal through the engine cycle. Two distinct codes, a finite element analysis (FEA) solver for thermo-mechanical analysis and a finite volume solver for CFD, are iteratively coupled to produce temperatures and deformations of the solid part through an engine cycle. At each time step, the CFD mesh is automatically adapted to the FEA prediction of the metal position using efficient spring analogy methods, ensuring the continuity of the coupled process. As an example of this methodology, the cavity flow in a turbine stator well is investigated. In this test case, there is a strong link between the thermo-mechanical distortion, governing the labyrinth seal clearance, and the amount of flow through the stator well, which determines the resulting heat transfer in the stator well. This feedback loop can only be resolved by including the thermo-mechanical distortion within the coupling process.

High Fidelity Simulation of Fluid-Structure Interaction in a 1½ Stage Axial Turbine

2019 ◽  
Author(s):  
Joshua Zorn ◽  
Roger Davis ◽  
John Clark
Keyword(s):  
Control Volume ◽  
Numerical Technique ◽  
Fluid Structure Interaction ◽  
Momentum Conservation ◽  
Second Order ◽  
Constitutive Relationship ◽  
High Fidelity ◽  
Time Step ◽  
Fluid Structure ◽  
Structure Interaction

Abstract A high fidelity, fully coupled numerical technique for the simulation of airfoil and turbomachinery aeroelasticity configurations is presented. The unsteady structural and fluid dynamics equations are discretized by a control volume technique which is second order accurate in space along with a dual time-step scheme that is second order accurate in time. The momentum conservation equation for the solid is written in terms of the Piola-Kirchoff stresses and the displacement velocity components. The stress tensor is related to the Lagrangian strain and displacement tensors using the St. Venant-Kirchoff constitutive relationship. Source terms at the surface of the solid are included to account for surface pressure and body forces. Previous fluid-structure interaction studies of Turek’s cylinder flag and the AGARD 445.6 airfoil have provided confidence needed to accurately perform fluid structure interaction simulations in turbomachinery. In this study, a 1½ stage axial transonic turbine is simulated and results are validated with experimental data. Simulation results indicate that the inclusion of airfoil vibration leads to improved agreement with experimental unsteady surface pressures compared to simulations with fixed airfoils.

Thermo-Mechanical Finite Element Analysis/Computational Fluid Dynamics Coupling of an Interstage Seal Cavity Using Torsional Spring Analogy

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Dario Amirante ◽  
Nicholas J. Hills ◽  
Christopher J. Barnes
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Finite Element Analysis ◽  
Computational Fluid Dynamics ◽  
Finite Element ◽  
Boundary Conditions ◽  
Time Step ◽  
Element Analysis ◽  
Coupling Process ◽  
Engine Cycle

The optimization of heat transfer between fluid and metal plays a crucial role in gas turbine design. An accurate prediction of temperature for each metal component can help to minimize the coolant flow requirement, with a direct reduction of the corresponding loss in the thermodynamic cycle. Traditionally, in industry fluid and solid simulations are conducted separately. The prediction of metal stresses and temperatures, generally based on finite element analysis, requires the definition of a thermal model whose reliability is largely dependent on the validity of the boundary conditions prescribed on the solid surface. These boundary conditions are obtained from empirical correlations expressing local conditions as a function of working parameters of the entire system, with validation being supplied by engine testing. However, recent studies have demonstrated the benefits of employing coupling techniques, whereby computational fluid dynamics (CFD) is used to predict the heat flux from the air to the metal, and this is coupled to the thermal analysis predicting metal temperatures. This paper describes an extension of this coupling process, accounting for the thermo-mechanical distortion of the metal through the engine cycle. Two distinct codes, a finite element analysis (FEA) solver for thermo-mechanical analysis and a finite volume solver for CFD, are iteratively coupled to produce temperatures and deformations of the solid part through an engine cycle. At each time step, the CFD mesh is automatically adapted to the FEA prediction of the metal position using efficient spring analogy methods, ensuring the continuity of the coupled process. As an example of this methodology, the cavity flow in a turbine stator well is investigated. In this test case, there is a strong link between the thermo-mechanical distortion, governing the labyrinth seal clearance, and the amount of flow through the stator well, which determines the resulting heat transfer in the stator well. This feedback loop can only be resolved by including the thermo-mechanical distortion within the coupling process.

Towards guaranteed data-integrity: A method of preventing Questionable Research Practices

2018 ◽  
Author(s):  
Dick Bierman ◽  
Jacob Jolij
Keyword(s):  
Real Time ◽  
Open Data ◽  
Data Integrity ◽  
Drop Out ◽  
Research Practices ◽  
Major Aspect ◽  
Questionable Research Practices ◽  
Blockchain Technology ◽  
Integrity System ◽  
Secure Server

We have tested the feasibility of a method to prevent the occurrence of so-called Questionable Research Practices (QRP). A part from embedded pre-registration the major aspect of the system is real-time uploading of data on a secure server. We outline the method, discuss the drop-out treatment and compare it to the Born-open data method, and report on our preliminary experiences. We also discuss the extension of the data-integrity system from secure server to use of blockchain technology.

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