Numerical Simulation of Stirling Engines Using an Unsteady Quasi-One-Dimensional Approach

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Niklas Andersson ◽  
Lars-Erik Eriksson ◽  
Martin Nilsson
Keyword(s):  
Oscillatory Flow ◽  
Computer Code ◽  
Operating Conditions ◽  
Wall Friction ◽  
Smoothing Algorithm ◽  
Dimensional Approach ◽  
One Dimensional ◽  
Flow Equations ◽  
Engine Design ◽  
Stirling Engines

An existing computer code for solving the quasi-one-dimensional (Q1D) flow equations governing unsteady compressible flow in tubes with smoothly varying cross section areas has been adapted to the simulation of the oscillatory flow in Stirling engines for engine design purposes. By utilizing an efficient smoothing algorithm for the area function that preserves the total volume of the tube, it has been possible to achieve a highly accurate and fully conservative numerical scheme. Submodels for wall friction and heat transfer have been added, enabling the simulation of gas heaters, gas coolers, and regenerators. The code has been used for the modeling of an α-type Stirling engine and validated for a range of operating conditions with good results.

scholarly journals Radial turbine sound and noise characterisation with acoustic transfer matrices by means of fast one-dimensional models

2019 ◽  
pp. 146808741988942
Author(s):  
Antonio Torregrosa ◽  
Luis Miguel García-Cuevas ◽  
Lukas Benjamin Inhestern ◽  
Pablo Soler
Keyword(s):  
Mean Value ◽  
Operating Conditions ◽  
Design Stage ◽  
Transfer Matrices ◽  
Efficient Manner ◽  
One Dimensional ◽  
Engine Design ◽  
Lookup Tables ◽  
Single Entry ◽  
Radial Turbines

Estimating correctly the turbine acoustics can be valuable during the engine design stage; in fact, it can lead to a more optimised design of the silencer and aftertreatment, as well as to better prediction of the scavenging effects. However, obtaining the sound and noise emissions of radial turbocharger turbines with low computational costs can be challenging. To consider these effects in a time-efficient manner, the acoustic response of single-entry radial turbines can be characterised by means of acoustic transfer matrices that change with the operating conditions. Exploiting the different time-scales of the acoustic phenomena and the change in the operating point of the turbine, lookup tables of acoustic transfer matrices can be computed. Then, the obtained characterisation can be used in mean-value engine models. This article presents a method for generating these lookup tables by means of fast one-dimensional simulations of thoroughly validated fidelity, in terms of both acoustics and extrapolation capabilities. Due to the inherent behaviour of radial turbines, the number of computations needed to fill the lookup tables is relatively small, so the method can be used as a simple preprocessing phase before mean-value simulation campaigns.

scholarly journals Radiation phenomenon for large meteoroids

2020 ◽  
Vol 633 ◽  
pp. A25
Author(s):  
C. Park
Keyword(s):  
Mass Density ◽  
Computer Code ◽  
Inviscid Flow ◽  
Light Curves ◽  
Intrinsic Properties ◽  
Dimensional Approach ◽  
One Dimensional ◽  
Thermochemical Equilibrium ◽  
Transfer Problems ◽  
The Relationship

Aims. The relationship between the intrinsic properties of a large meteoroid, that is, mass, density, chemical composition, and flight velocity, and its spectrum are identified. Methods. Assuming thermochemical equilibrium and inviscid flow and using a quasi-one-dimensional approach, the flow-field and radiative transfer problems are solved from the ablating wall of a meteoroid to the observer on the ground. Results. The study discovers that the precursor region immediately ahead of the shock layer absorbs nitrogen and oxygen lines, and thereby modifies the spectrum received by the ground observer. The study leads to a computer code with which the observed spectra and light-curves for Benesov and Sumava meteoroids are numerically and approximately reproduced with the help of a meteoroid fragmentation theory. Luminous efficiency value is obtained as a byproduct.

On the rotational compressible Taylor flow in injection-driven porous chambers

2008 ◽  
Vol 603 ◽  
pp. 391-411 ◽  
Author(s):  
BRIAN A. MAICKE ◽  
JOSEPH MAJDALANI
Keyword(s):  
Two Dimensional ◽  
Dimensional Approach ◽  
Dimensional Theory ◽  
Rocket Motors ◽  
One Dimensional ◽  
Flow Equations ◽  
Isentropic Flow ◽  
Experimental Approaches ◽  
Turbulent Models ◽  
Explicit Criteria

This work considers the compressible flow field established in a rectangular porous channel. Our treatment is based on a Rayleigh–Janzen perturbation applied to the inviscid steady two-dimensional isentropic flow equations. Closed-form expressions are then derived for the main properties of interest. Our analytical results are verified via numerical simulation, with laminar and turbulent models, and with available experimental data. They are also compared to existing one-dimensional theory and to a previous numerical pseudo-one-dimensional approach. Our analysis captures the steepening of the velocity profiles that has been reported in several studies using either computational or experimental approaches. Finally, explicit criteria are presented to quantify the effects of compressibility in two-dimensional injection-driven chambers such as those used to model slab rocket motors.

scholarly journals Heat Transfer in Rotating Serpentine Passages With Trips Normal to the Flow

1992 ◽  
Vol 114 (4) ◽  
pp. 847-857 ◽  
Author(s):  
J. H. Wagner ◽  
B. V. Johnson ◽  
R. A. Graziani ◽  
F. C. Yeh
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Large Scale ◽  
Flow Direction ◽  
Operating Conditions ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large-scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips on the leading and trailing surfaces of the radial coolant passages were used to produce the rough walls. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges that are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from stationary and rotating similar models with trip strips. The heat transfer coefficients on surfaces, where the heat transfer increased with rotation and buoyancy, varied by as much as a factor of four. Maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels obtained with the smooth wall model. The heat transfer coefficients on surfaces where the heat transfer decreased with rotation, varied by as much as a factor of three due to rotation and buoyancy. It was concluded that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips and that the effects of rotation were markedly different depending upon the flow direction.

Conduction Cooling for an LSI Package: A One-Dimensional Approach

1982 ◽  
Vol 26 (1) ◽  
pp. 45-54 ◽  
Author(s):  
R. C. Chu ◽  
U. P. Hwang ◽  
R. E. Simons
Keyword(s):  
Dimensional Approach ◽  
One Dimensional ◽  
Conduction Cooling

scholarly journals Computation of Three-Dimensional, Rotational Flow Through Turbomachinery Blade Rows for Improved Aerodynamic Design Studies

1986 ◽  
Author(s):  
S. V. Subramanian ◽  
R. Bozzola ◽  
Louis A. Povinelli
Keyword(s):  
Three Dimensional ◽  
Maximum Flow ◽  
Cost Effective ◽  
Computer Code ◽  
Integration Scheme ◽  
Aerodynamic Design ◽  
Design Studies ◽  
Flow Equations ◽  
Transonic Compressor ◽  
Numerical Predictions

The performance of a three dimensional computer code developed for predicting the flowfield in stationary and rotating turbomachinery blade rows is described in this study. The four stage Runge-Kutta numerical integration scheme is used for solving the governing flow equations and yields solution to the full, three dimensional, unsteady Euler equations in cylindrical coordinates. This method is fully explicit and uses the finite volume, time marching procedure. In order to demonstrate the accuracy and efficiency of the code, steady solutions were obtained for several cascade geometries under widely varying flow conditions. Computed flowfield results are presented for a fully subsonic turbine stator and a low aspect ratio, transonic compressor rotor blade under maximum flow and peak efficiency design conditions. Comparisons with Laser Anemometer measurements and other numerical predictions are also provided to illustrate that the present method predicts important flow features with good accuracy and can be used for cost effective aerodynamic design studies.

A one-dimensional approach for iris identification

2004 ◽  
Author(s):  
Yingzi Du ◽  
Robert Ives ◽  
Delores Etter ◽  
Thad Welch ◽  
Chein-I Chang
Keyword(s):  
Dimensional Approach ◽  
One Dimensional ◽  
Iris Identification

Slow flow solutions and stability analysis of single machine to infinite bus power systems

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
M. G. Suresh Kumar ◽  
C. A. Babu
Keyword(s):  
Power Systems ◽  
Power System ◽  
Single Machine ◽  
Multiple Scales ◽  
Operating Conditions ◽  
Phase Portraits ◽  
Slow Flow ◽  
Approximate Analytical Expression ◽  
Flow Equations ◽  
Load Angle

Abstract Nonlinearity is a major constraint in analysing and controlling power systems. The behaviour of the nonlinear systems will vary drastically with changing operating conditions. Hence a detailed study of the response of the power system with nonlinearities is necessary especially at frequencies closer to natural resonant frequencies of machines where the system may jump into the chaos. This paper attempt such a study of a single machine to infinite bus power system by modelling it as a Duffing equation with softening spring. Using the method of multiple scales, an approximate analytical expression which describes the variation of load angle is derived. The phase portraits generated from the slow flow equations, closer to the jump, display two stable equilibria (centers) and an unstable fixed point (saddle). From the analysis, it is observed that even for a combination of parameters for which the system exhibits jump resonance, the system will remain stable if the variation of load angle is within a bounded region.

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