Showing papers on "Liquid-propellant rocket published in 2019"

Dynamical systems approach to study thermoacoustic transitions in a liquid rocket combustor

Abstract: Liquid rockets are prone to large amplitude oscillations, commonly referred to as thermoacoustic instability. This phenomenon causes unavoidable developmental setbacks and poses a stern challenge to accomplish the mission objectives. Thermoacoustic instability arises due to the nonlinear interaction between the acoustic and the reactive flow subsystems in the combustion chamber. In this paper, we adopt tools from dynamical systems and complex systems theory to understand the dynamical transitions from a state of stable operation to thermoacoustic instability in a self-excited model multielement liquid rocket combustor based on an oxidizer rich staged combustion cycle. We observe that this transition to thermoacoustic instability occurs through a sequence of bursts of large amplitude periodic oscillations. Furthermore, we show that the acoustic pressure oscillations in the combustor pertain to different dynamical states. In contrast to a simple limit cycle oscillation, we show that the system dynamics switches between period-3 and period-4 oscillations during the state of thermoacoustic instability. We show several measures based on recurrence quantification analysis and multifractal theory, which can diagnose the dynamical transitions occurring in the system. We find that these measures are more robust than the existing measures in distinguishing the dynamical state of a rocket engine. Furthermore, these measures can be used to validate models and computational fluid dynamics simulations, aiming to characterize the performance and stability of rockets.

Application of QGA-BP for Fault Detection of Liquid Rocket Engines

Abstract: In order to overcome the shortcomings of traditional back propagation (BP) and single genetic algorithm (GA), a method based on quantum GA (QGA) is proposed to optimize the BP neural network for fault detection of liquid rocket engines. In this QGA-BP method, a dynamic improvement strategy is adopted to adjust the rotation angle according to the evolution situation, and a quantum catastrophe strategy is used as an operation criterion during evolution. Then, the improved QGA is used to optimize the weight and threshold of the BP neural network from multiple spots. This method is applied to a typical fault detection process of a liquid rocket engine. Representative history test data of engine state is used to verify this method, and the results show that the convergence speed, the evolution generation, and the accuracy of fault detection of the QGA-BP model are all improved compared with the traditional BP neural network and the single GA.

An experimental study into the effect of injector pressure loss on self-sustained combustion instabilities in a swirled spray burner

Abstract: Combustion instabilities depend on a variety of parameters and operating conditions. It is known, especially in the field of liquid rocket propulsion, that the pressure loss of an injector has an effect on its dynamics and on the coupling between the combustion chamber and the fuel manifold. However, its influence is not well documented in the technical literature dealing with gas turbine combustion dynamics. Effects of changes in this key design parameter are investigated in the present article by testing different swirlers at constant thermal power on a broad range of injection velocities in a well controlled laboratory scale single injector swirled combustor using liquid fuel. The objective is to study the impact of injection pressure losses on the occurrence and level of combustion instabilities by making use of a set of injectors having nearly the same outlet velocity profiles, the same swirl number and that establish flames that are essentially identical in shape. It is found that combustion oscillations appear on a wider range of operating conditions for injectors with the highest pressure loss, but that the pressure fluctuations caused by thermoacoustic oscillations are greatest when the injector head loss is low. Four types of instabilities coupled by two modes may be distinguished: the first group features a lower frequency, arises when the injector pressure loss is low and corresponds to a weakly coupled chamber-plenum mode. The second group appears in the form of a constant amplitude limit cycle, or as bursts at a slightly higher frequency and is coupled by a chamber mode. Spontaneous switching between these two types of instabilities is also observed in a narrow domain.

Single-Phase Instability in Non-Premixed Flames Under Liquid Rocket Engine Relevant Conditions

Abstract: Under rocket-relevant conditions, real-gas effects and thermodynamic nonidealities are prominent features of the flow field. Experimental investigations indicate that phase separation can occur, de...

Numerical Investigation of the Clocking Effect Between Inducer and Impeller on Pressure Pulsations in a Liquid Rocket Engine Oxygen Turbopump

Abstract: The clocking positions between the inducer and the impeller have a certain impact on the performance of the high-speed centrifugal pump, which however, is often ignored by designers. In the present study, three-dimensional numerical simulation based on detached eddy simulation method is adopted to evaluate the influence of this clocking effect on unsteady pressure pulsations in a full-scale liquid rocket engine oxygen turbopump. A new omega vortex identification method is introduced to clarify the internal correlation between unsteady flow structures and pressure pulsations and to shed comprehensive light on the formation mechanism of this clocking effect. Results show that the clocking effect has little influence on the unsteady pressure field in inducer passages while it significantly affects the rotor–stator interaction (RSI) effect leading to the alteration of the pressure spectra in RSI region, diffuser and volute diffuser pipe. The components at the inducer blade passing frequency in the pressure spectra are remarkably suppressed and the total pressure pulsation energy in these regions is decreased by an average of 13.94%, 12.94%, and 34.65%, respectively, when the inducer blade trailing edges are located in the middle of two adjacent impeller blades. The vortex analysis in the specific region reveals that the pressure pulsations in RSI region and the downstream regions are closely associated with the unsteady vortex shedding from the diffuser blades and the formation of the clocking effect is precisely due to different processes of the periodic vortex shedding from the diffuser blade pressure surfaces.

Numerical Investigation on Radiative Heat Loads in Liquid Rocket Thrust Chambers

Abstract: In liquid rocket engines, wall heat transfer analyses are of primary importance for the thrust chamber design. Numerical investigations usually derive the convective heat flux from computational fl...

Spontaneous and Triggered Longitudinal Combustion Instability in a Single-Injector Liquid-Rocket Combustor

Abstract: Spontaneous and triggered longitudinal combustion instability is simulated numerically in a single-injector liquid-rocket engine using a recently developed axisymmetric compressible flow solver. Tu...

Consequences of modeling demands on numerical rocket thrust chamber flow simulation tools

Abstract: Numerical simulation of liquid rocket thrust chamber flows is a challenging task which requires a comprehensive tool validation strategy encompassing laboratory- to full-scale test cases. While the former are widely used as the first step to verify advanced numerical schemes and thermochemical models, the latter can often no more be simulated in a reasonable time frame due to the extreme computational effort necessitated by the enlarged dimensions and configurational changes. Conclusions drawn from tools with such limitations are only of little help for a thrust chamber designer and, hence, ill-posed to adequately tackle the simulation challenges of such a device. This paper discusses the modeling demands for numerical thrust chamber flow simulation tools and outlines the indispensable validation approach from laboratory- via subto full-scale configurations using consistent model features throughout the test cases. Consequences of this obligation are exposed to drive the tool setup. Exemplarily, the Airbus DS thrust chamber flow simulation philosophy is presented.

Progress in Additively Manufactured Copper-Alloy GRCop-84, GRCop-42, and Bimetallic Combustion Chambers for Liquid Rocket Engines

Abstract: Additive Manufacturing (AM) has significantly evolved over the last decade for use in the aerospace industry, particularly for liquid rocket engines. AM offers a considerable departure from traditional manufacturing to rapidly fabricate components with complex internal features. High performance liquid rocket engine combustion chambers that operate in a high heat flux environment are fabricated using a copper-alloy liner with a series of integral coolant channels. Copper-alloys provide the necessary conductivity and material strength for adequate design margins offering high performance without the need for film coolant. Copper-alloys present unique challenges to properly melt the powder in laser-based AM processes due to their high reflectivity and conductivity. Starting in 2014, NASA’s Marshall Space Flight Center (MSFC) and Glenn Research Center (GRC) have developed a process for AM of GRCop (Copper- Chrome-Niobium) alloys using Selective Laser Melting (SLM). GRCop, originally developed at GRC, is a high conductivity, high-strength, dispersion strengthened copper-alloy for use in high-temperature, high heat flux applications. NASA has completed significant material characterization and testing, along with hot-fire testing, to demonstrate that GRCop-42 and GRCop-84 alloys are suitable for use in combustion chambers. Additional development and testing has been completed on AM bimetallic chambers using GRCop-84 liners and superalloy jackets, fabricated using two Directed Energy Deposition (DED) processes: Electron Beam Freeform Fabrication (EBF³) and Blown Powder DED. NASA completed hot-fire testing on various AM chambers using GRCop-84, GRCop-42, and bimetallic chambers in Liquid Oxygen (LOX)/Hydrogen, LOX/Methane, and LOX/Kerosene propellants.

Analysis of Wall–flame Interaction in Laminar Non-premixed Combustion

Abstract: The study is aimed at demonstrating a methodology for the time-scale characterization of the chemistry-wall-heat-transfer interaction. The driving chemical time-scale is estimated by means of the t...

PHM by Using Multi-Physics System-Level Modeling and Simulation for EMAs of Liquid Rocket Engine

Abstract: The need for condition-based maintenance to improve reusable launch vehicle readiness, reliability and safety, with affordable maintenance cost and quick turnaround time is recognized. But the problem of detecting faults and predicting failure in the components of reusable rocket engine systems is difficult and complex to solve. Since the number of data samples on the fault or failure status during the actual operation of the rocket engine is very small, it is difficult to adapt a data-drive approach of health management. Furthermore, the failure modes for these systems might transcend electrical, mechanical, and fluid systems. Therefore, one of the key concepts of the approach proposed in this study for fault detection and diagnosis is model-based quantitative assessment that considers system-level interactions in the target system. In this approach, multi-physics system-level modeling and simulation for a target system are conducted by using Modelica, an equation-based, object-oriented modeling language that allows acausal modeling for complex cyber-physical systems. Modelica has an important modeling capability for system-level interactions that involve multi-physics phenomena. One advantage of the model-based health-monitoring approach is that faults and failure modes are traced back to physically meaningful information, which is invaluable for the maintainer. Thus, this model-based approach for condition-based maintenance has the potential to provide reliable early fault detection and diagnosis during post-flight investigation for maintenance decision-making. In this study, multi-physics system-level modeling and simulation for a target system under both normal and abnormal conditions have been conducted based on an understanding of the failure mechanism to obtain prior data sets for fault detection and diagnosis. In this proposed approach, the Dynamic Time Warping (DTW)algorithm was utilized to evaluate dissimilarity between the prior data sets and sensor measurement data obtained during the flight, and hierarchical clustering technique was applied for categorization in failure mode based on dissimilarity of these data. In addition, a trial case study has been conducted on electromechanical actuators (EMAs), an important component of a rocket engine, towards the construction of model-based prognostics and health management (PHM)technologies for reusable liquid rocket engines. Based on the trial results of the model-based approach constructed in this study, the possibility of fault detection and diagnosis was demonstrated for virtual EMAs of a liquid rocket engine.

Non-Rocket, Non-Reactive Quantum Engine: Idea, Technology, Results, Prospects

Abstract: The control tests of the two prototypes of non-jet propulsion of quantum engine KvD-1-2009 (model of 2009) with horizontal thrust and antigravitator KvD-1 with vertical thrust, were conducted on March 3rd, 2018 by a public commission of specialists chaired and initiated by the former Minister of General Machine-Building Industry of the USSR (space branch) Oleg D. Baklanov. KvD-1-2009 developed a specific thrust of more than 100 N/kW, which is more than 100 times more efficient than the liquid rocket engine (LRE).

Liquid rocket engine combustion stabilization devices

Abstract: Combustion instability, which results from a coupling of the combustion process and the fluid dynamics of the engine system, was investigated. The design of devices which reduce coupling (combustion chamber baffles) and devices which increase damping (acoustic absorbers) are described. Included in the discussion are design criteria and recommended practices, structural and mechanical design, thermal control, baffle geometry, baffle/engine interactions, acoustic damping analysis, and absorber configurations.

Mathematical simulation of dynamic processes in hydraulic and gas paths at the start of a liquid-propellant rocket engine with generator gas after-burning

Abstract: One of the key problems in the design of liquid-propellant rocket engines (LPREs) is the assurance of a trouble-free LPRE start. LPRE bench tryout is highly expensive, and emergency situations may have grave consequences (including engine and bench equipment destruction), Because of this, one of the main tools that allow one to predict the LPRE dynamic characteristics and start-up operation features at the design and tryout stages is mathematical simulation. One of the most important and complex problems in LPRE start simulation is the description of LPRE gas–liquid volume filling, processes caused by pump cavitation, and the kinetics of propellant ignition and burn-out in the gas generator and the combustion chamber. This paper presents a modified mathematical model of cavitating pipe dynamics, which keeps its structure and operability over a wide cavitation number range and in mutual transitions between the cavitation and the cavitation-free pump operation, which is required for the numerical study of working processes in an LPRE at its start. An approach to the construction of a nonlinear mathematical model of LPRE hydraulic path filling is presented. The approach allows one, if necessary, to automatically change the scheme of partitioning the hydraulic path into finite hydraulic elements in the process of its filling at engine start. A scheme of approximate substitution of delay equations in the mathematical model of LPRE gas path dynamics is proposed. The scheme is constructed with account for the features of calculation of LPRE start transients, and it allows the simulation accuracy to be improved with the minimum of model complication. The operability of the mathematical models developed is demonstrated by the example of simulating the start of a sustainer LPRE with oxidizing generator gas after-burning. The results of this study may be used in the mathematical simulation of the start of modern LPREs.

Perspective circuit solutions of liquid rocket engine by expanded cycle

Abstract: Актуальность работы обусловлена перспективой применения кислородно-водородных ЖРД безгазогенераторной схемы для решения различных космических задач. Работа может быть полезна инженерам и студентам, специализирующимся в области систем охлаждения ракетного двигателестроения, тепломассобмена и теплозащиты реактивных двигателей. Безгенераторные схемы используются в качестве маршевых двигателей разгонных блоков и трех ступеней ракет. Среди разработчиков следует выделить КБХА (РН Ангара ЖРД 0146), Pratt & Whitney (РН AtlasCentaur-SaturnRL 10), SEP (РН Ариан 5 (Vulcain, Vulcain2, Vinci)). Существуют три типа безгенераторных схем: открытая (сброс парогаза в закритическую часть сопла), закрытая (сброс парогаза в КС) и смешанная, из чего вытекает ряд схем с разными особенностями подачи компонентов. Безгенераторные схемы особенно эффективны при применении криогенных компонентов топлива (кислород, водород, метан и др.). Крайне актуальной задачей в безгенераторных схемах является существенный подогрев горючего компонента для увеличения энергетических параметров двигателя. На данный момент весьма перспективной задачей для безгенераторных двигателей является использование данных двигателей в качестве межорбитальных буксиров. Межорбитальный буксир предназначен для доставки полезного груза на геосинхронную орбиту с последующим возвращением на низкую околоземную орбиту, а также для выведения космических кораблей на межпланетные орбиты. Несмотря на относительную простоту, надежность, низкую стоимость межорбитальных буксиров с РДТТ, более перспективным считается корабль с ЖРД благодаря высоким энергетическим характеристикам и возможности осуществления многократного запуска, останова и регулирования уровня тяги в процессе работы двигателей. Ключевые слова: регенеративное проточное охлаждение, безгазогенераторные схемы, ТНА, тепломассообмен, теплозащита корпуса двигателя, ЖРД, рубашка охлаждения, криогенные компоненты топлива, математическая модель ЖРД, ПГС, хладагент.

Particle swarm algorithm-based damage-mitigating control law analysis and synthesis for liquid-propellant rocket engine:

Abstract: The damage-mitigating control is a novel technique to ameliorate the reliability and safety of liquid-propellant rocket engines by achieving an optimized trade-off level between overall dynamic per...

An MPC Approach to Transient Control of Liquid-Propellant Rocket Engines

Abstract: The current context of launchers reusability requires the improvement of control algorithms for their liquid-propellant rocket engines. Their transient phases are generally still performed in open loop. In this paper, it is aimed at enhancing the control performance and robustness during the fully continuous phase of the start-up transient of a generic gas-generator cycle. The main control goals concern end-state tracking in terms of combustion-chamber pressure and chambers mixture ratios, as well as the verification of a set of hard operational constraints. A controller based on a nonlinear preprocessor and on linear MPC (Model-Predictive Control) has been synthesised, making use of nonlinear state-space models of the engine. The former generates the full-state reference to be tracked while the latter achieves the aforementioned goals with sufficient accuracy and verifying constraints for the required pressure levels. Robustness considerations are included in the MPC algorithm via an epigraph formulation of the minimax robust optimisation problem, where a finite set of perturbation scenarios is considered.

Hardware-in-the-loop Simulation Platform for Fault Diagnosis of Rocket Engines

Abstract: In this paper, a hardware-in-the-loop platform for real-time simulation of rocket engine fault diagnosis is constructed using rapid prototype method. The platform mainly includes a main workstation, a rocket engine model terminal, and a fault diagnosis terminal. The main workstation designs an interface to observe the required parameters. The rocket engine model terminal uses automatic code generation technology to embed the model into an industrial computer with a real-time system. The fault diagnosis terminal uses the dual-system architecture of FPGA+DSP to design the prototype of the fault diagnosis principle and combines the automatically generated code with the handwritten code. The algorithm performs real-time verification. Based on ARMA model, a fault diagnosis algorithm for liquid rocket engine is proposed, which has been tested repeatedly under digital conditions and hardware conditions. The results show that the running time of the ARMA model-based diagnostic algorithm in the hardware platform is 3.5ms. The built-in hardware-in-the-loop simulation platform can simulate the common typical faults of the rocket engine and can verify the diagnostic algorithm in real-time.