Source Term Based Modeling of Rotating Cavitation in Turbopumps

2018 ◽  
Author(s):  
A. G. Vermes ◽  
C. Lettieri
Keyword(s):  
Price Competition ◽  
High Speed ◽  
Large Scale ◽  
Source Term ◽  
Experimental Testing ◽  
Rocket Engine ◽  
Computational Cost ◽  
Flow Coefficient ◽  
Rocket Engines ◽  
Launch Vehicles

The recent growth of private options in launch vehicles has substantially raised price competition in the space launch market. This has increased the need to deliver reliable launch vehicles at reduced engine development cost, and has led to increased industrial interest in reduced order models. Large-scale liquid rocket engines require high-speed turbopumps to inject cryogenic propellants into the combustion chamber. These pumps can experience cavitation instabilities even when operating near design conditions. Of particular concern is rotating cavitation, which is characterized by an asymmetric cavity rotating at the pump inlet, which can cause severe vibration, breaking of the pump and loss of the mission. Despite much work in the field, there are limited guidelines to avoid rotating cavitation during design and its occurrence is often assessed through costly experimental testing. This paper presents a source term based model for stability assessment of rocket engine turbopumps. The approach utilizes mass and momentum source terms to model cavities and hydrodynamic blockage in inviscid, single-phase numerical calculations, reducing the computational cost of the calculations by an order of magnitude compared to traditional numerical methods. Comparison of the results from the model with experiments and high-fidelity calculations indicates agreement of the head coefficient and cavity blockage within 0.26% and 5% respectively. The computations capture rotating cavitation in a 2D inducer at the expected flow coefficient and cavitation number. The mechanism of formation and propagation of the instability is correctly reproduced.

Source Term Based Modeling of Rotating Cavitation in Turbopumps

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
A. G. Vermes ◽  
C. Lettieri
Keyword(s):  
Price Competition ◽  
High Speed ◽  
Large Scale ◽  
Source Term ◽  
Experimental Testing ◽  
Rocket Engine ◽  
Computational Cost ◽  
Flow Coefficient ◽  
Rocket Engines ◽  
Launch Vehicles

The recent growth of private options in launch vehicles has substantially raised price competition in the space launch market. This has increased the need to deliver reliable launch vehicles at reduced engine development cost and has led to increased industrial interest in reduced order models. Large-scale liquid rocket engines require high-speed turbopumps to inject cryogenic propellants into the combustion chamber. These pumps can experience cavitation instabilities even when operating near design conditions. Of particular concern is rotating cavitation (RC), which is characterized by an asymmetric cavity rotating at the pump inlet, which can cause severe vibration, breaking of the pump, and loss of the mission. Despite much work in the field, there are limited guidelines to avoid RC during design and its occurrence is often assessed through costly experimental testing. This paper presents a source term based model for stability assessment of rocket engine turbopumps. The approach utilizes mass and momentum source terms to model cavities and hydrodynamic blockage in inviscid, single-phase numerical calculations, reducing the computational cost of the calculations by an order of magnitude compared to traditional numerical methods. Comparison of the results from the model with experiments and high-fidelity calculations indicates agreement of the head coefficient and cavity blockage within 0.26% and 5%, respectively. The computations capture RC in a two-dimensional (2D) inducer at the expected flow coefficient and cavitation number. The mechanism of formation and propagation of the instability is correctly reproduced.

scholarly journals Event-Driven Simulation Scheme for Spiking Neural Networks Using Lookup Tables to Characterize Neuronal Dynamics

2006 ◽  
Vol 18 (12) ◽  
pp. 2959-2993 ◽  
Author(s):  
Eduardo Ros ◽  
Richard Carrillo ◽  
Eva M. Ortigosa ◽  
Boris Barbour ◽  
Rodrigo Agís
Keyword(s):  
Synaptic Plasticity ◽  
High Speed ◽  
Large Scale ◽  
Computational Cost ◽  
Brain Structures ◽  
Spike Timing ◽  
Neuronal Dynamics ◽  
Event Driven ◽  
Synaptic Dynamics

Nearly all neuronal information processing and interneuronal communication in the brain involves action potentials, or spikes, which drive the short-term synaptic dynamics of neurons, but also their long-term dynamics, via synaptic plasticity. In many brain structures, action potential activity is considered to be sparse. This sparseness of activity has been exploited to reduce the computational cost of large-scale network simulations, through the development of event-driven simulation schemes. However, existing event-driven simulations schemes use extremely simplified neuronal models. Here, we implement and evaluate critically an event-driven algorithm (ED-LUT) that uses precalculated look-up tables to characterize synaptic and neuronal dynamics. This approach enables the use of more complex (and realistic) neuronal models or data in representing the neurons, while retaining the advantage of high-speed simulation. We demonstrate the method's application for neurons containing exponential synaptic conductances, thereby implementing shunting inhibition, a phenomenon that is critical to cellular computation. We also introduce an improved two-stage event-queue algorithm, which allows the simulations to scale efficiently to highly connected networks with arbitrary propagation delays. Finally, the scheme readily accommodates implementation of synaptic plasticity mechanisms that depend on spike timing, enabling future simulations to explore issues of long-term learning and adaptation in large-scale networks.

scholarly journals Flow instability effects related to purge through a gas turbine chute seal

2021 ◽  
Vol 5 ◽  
pp. 111-125
Author(s):  
Arijit Roy ◽  
Jens Fridh ◽  
James Scobie ◽  
Carl Sangan ◽  
Gary Lock
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Flow Instability ◽  
Flow Coefficient ◽  
Flow Instabilities ◽  
Pressure Measurements ◽  
Flow Conditions ◽  
Seal Design ◽  
Purge Flow ◽  
Unsteady Pressure Measurements

This paper investigates flow instabilities inside the cavity formed between the stator and rotor disks of a high-speed turbine rig. The cavity rim seal is of chute seal design. The influence of flow coefficient on the sealing effectiveness at constant purge flow rate through the wheel-space is determined. The effectiveness at different radial positions over a range of purge flow conditions and flow coefficients is also studied. Unsteady pressure measurements have identified the frequency of instabilities that form within the rim seal, phenomena which have been observed in other studies. Frequencies of these disturbances, and their correlation in the circumferential direction have determined the strength and speed of rotation of the instabilities within the cavity. Large scale unsteady rotational structures have been identified, which show similarity to previous studies. These disturbances have been found to be weakly dependent on the purge flow and flow coefficients, although an increased purge reduced both the intensity and speed of rotation of the instabilities. Additionally, certain uncorrelated disturbances have been found to be inconsistent (discontinuous) with pitchwise variation.

scholarly journals Mechanical Integrity of Thermal Barrier Coatings: Coating Development and Micromechanics

2020 ◽  
pp. 295-307
Author(s):  
Torben Fiedler ◽  
Joachim Rösler ◽  
Martin Bäker ◽  
Felix Hötte ◽  
Christoph von Sethe ◽  
...  
Keyword(s):  
Large Scale ◽  
Rocket Engine ◽  
Thermal Strain ◽  
Strain Differences ◽  
Thermal Barrier ◽  
Rocket Engines ◽  
Coating System ◽  
Barrier Coating ◽  
Coating Failure ◽  
Coating Delamination

Abstract To protect the copper liners of liquid-fuel rocket combustion chambers, a thermal barrier coating can be applied. Previously, a new metallic coating system was developed, consisting of a NiCuCrAl bond-coat and a Rene 80 top-coat, applied with high velocity oxyfuel spray (HVOF). The coatings are tested in laser cycling experiments to develop a detailed failure model, and critical loads for coating failure were defined. In this work, a coating system is designed for a generic engine to demonstrate the benefits of TBCs in rocket engines, and the mechanical loads and possible coating failure are analysed. Finally, the coatings are tested in a hypersonic wind tunnel with surface temperatures of 1350 K and above, where no coating failure was observed. Furthermore, cyclic experiments with a subscale combustion chamber were carried out. With a diffusion heat treatment, no large-scale coating delamination was observed, but the coating cracked vertically due to large cooling-induced stresses. These cracks are inevitable in rocket engines due to the very large thermal-strain differences between hot coating and cooled substrate. It is supposed that the cracks can be tolerated in rocket-engine application.

scholarly journals Effect of the MoSi2 coating on operational reliability of bipropellant rocket engine

2021 ◽  
Vol 260 ◽  
pp. 03003
Author(s):  
Kun Cai ◽  
Zhen Zhang ◽  
Na Wang ◽  
Yu Hu ◽  
Fengshan Wang
Keyword(s):  
High Temperature ◽  
Liquid Film ◽  
Film Cooling ◽  
Thermal Cycle ◽  
High Speed ◽  
Rocket Engine ◽  
Operational Reliability ◽  
Rocket Engines ◽  
Self Healing ◽  
Mosi2 Coating

This present study investigated the MoSi2 coating and its effect on reliability of bipropellant rocket engine. This coating is developed to protect the chamber substrate material form oxidization under hightemperature oxidative circumstance as bipropellant engine works. The multilayer structure of the MoSi2 coating shows excellent high-temperature and thermal-cycle resistance. Its characteristic of self-healing leads to the good performance under the long-time steady working condition for rocket engines. A 25000-seconds firing test was conducted to testify the performance of MoSi2 coating under high temperature above 1400℃. In addition, the influence of coating surface morphology on liquid film cooling was fully discussed in experiment and simulation. High-speed microscopy camera was used to study the effects of Weber number on the spreading and lasting of cooling liquid-film. the simulative comparison was conducted by OpenFOAM to present different transfer-heat modes, when a droplet impinges on the high-temperature surface of MoSi2 coating. All results show that higher smoothness of the coating is suitable for liquid-film cooling, strengthening liquid film spread and heat transfer. Moreover, scanning electron microscope (SEM) was used to study the effect of Mo layer residue on the coating thermal-cycle profermance. The test results indicates that Mo layer residue significantly cause penetrating cracks of the coating and then weaken the self-healing of the coating at downstream of throat. Therefore, it is important to strictly control the thickness of Mo layer by means of matching Mo target in ion plating. Thus after properly prolonging the infiltration time, Mo layer can be silicified completely without residue.

SIMULATION OF THE CURRENT-VOLTAGE CHARACTERISTICS OF SOLAR BATTERIES WITH CONSIDERING DECREASE OF LIGHTING DUE TO THE INFLUENCE OF JETS OF THE ELECTRIC PROPULSION

2019 ◽  
pp. 56-64
Author(s):  
Ya.N. MIGUNOV ◽  
V.V. ONUFRIEV
Keyword(s):  
Solar Cells ◽  
Temperature Gradient ◽  
Electric Propulsion ◽  
Protective Coatings ◽  
Rocket Engine ◽  
Solar Array ◽  
Rocket Engines ◽  
Lighting Conditions ◽  
Main Equation ◽  
Voltage Current Characteristic

A model for calculating the voltage-current characteristic of a solar array in the presence of a temperature gradient by its photovoltaic converters and their variable illumination due to possible pollution under the action of space factors, including operation of electric rocket engines, is described. The model is based on the main equation of a solar cell. In this case both a one-dimensional and a two-dimensional temperature gradients are taken into account. The principles of constructing a model are given, and the initial data selection is made. To simulate the lighting conditions of the solar array such a concept as effective illumination is used, i.e. the density of the radiation flux which falls on photovoltaic converters passing through the protective coatings. The features of simulation of the temperature distribution in the solar array and the effective illumination of its surface in cases of parallel, serial and mixed switching of solar cells are described. The calculation procedures and examples of solar cells are given. The construction of the model in universal mathematical package Mathcad is described. Some simulation results are discussed. Key words: solar array, mathematical simulation, illumination, temperature gradient, electric rocket engine, spacecraft, Mathcad.

Graphic method for assessing the margins of resistance to acoustic vibrations in the chambers of rocket engines by combustion noise

2020 ◽  
pp. 15-21
Author(s):  
R.A. Tsarapkin ◽  
V.N. Ivanov ◽  
V.I. Biryukov
Keyword(s):  
Rocket Engine ◽  
Spectral Characteristics ◽  
Combustion Process ◽  
Combustion Noise ◽  
Rocket Engines ◽  
Acoustic Vibrations ◽  
Statistical Regression ◽  
Unknown Parameters ◽  
Damping Decrement ◽  
Resonance Frequencies

An experimental method is proposed for estimating the damping decrements of pressure fluctuations in the combustion chambers of forced rocket engines. The method is based on the statistical processing of noise pressure pulsations in the vicinity of natural resonance frequencies for normal modes of acoustic vibrations of the reaction volume and the subsequent prediction of the instability of the combustion process relative to acoustic vibrations. Based on the theory of statistical regression for multidimensional experimental data, the problem of predicting unknown parameters of sample distributions is solved by asymptotic determination of the correlation coefficient of the damping decrement of pressure vibrations through optimal linear predictors and the Kolmogorov distribution. Keywords rocket engine, combustion chamber, acoustic vibrations, combustion noise, spectral characteristics, Kolmogorov criterion, damping decrement. [email protected]

Sign in / Sign up

Export Citation Format

Share Document