Showing papers on "Liquid-propellant rocket published in 2021"

Pseudo-boiling and heat transfer deterioration while heating supercritical liquid rocket engine propellants

Abstract: Heating of liquid propellants used as the coolant in rocket engines may lead to undesired phenomena such as pseudo-boiling or heat transfer deterioration under specific conditions. This can be an issue for propellants characterized at the same time by relatively low critical pressure and temperature. Light hydrocarbons, as for instance methane, belong to this family. In the present paper, a critical review is made of the main results obtained by Authors and their coworkers for the present application. Focus is on the correlations and trends inferred by their numerical simulations mainly carried out considering methane as the coolant, perhaps the most challenging one.

On melting heat transport and nanofluid in a nozzle of liquid rocket engine with entropy generation

Abstract: Because of increased heat production or reduction in effective surface area for heat exclusion, modern electronic equipment typically confronts thermal critical difficulties. This most interesting difficulty may be overcome by either developing an optimal shape for refrigeration systems or increasing heat transfer characteristics. In this situation, nanofluid works well in resolving all of these challenges. The goal of this work is to investigate a 2D flow of nanofluid across a rocket engine with entropy generation and Bejan number. The first equations are converted to non-dimensional forms by utilizing similarity transformations and then solved by using the variational iterative method. Tables and graphs have been used to convey the idea of the relevant aspects affecting hydrothermal performance. The graphs of velocity and temperature profiles, entropy generation and skin friction, and the Nusselt number for the related parameters, are provided, and the logical and physical explanations behind them are underlined. To the best of the authors' knowledge, nobody has recently tried to investigate a 2D flow of a nanofluid across a rocket engine with entropy generation and Bejan number. Furthermore, the accomplishments of this study are unique, and the numerical findings have never been published by any scholar. The velocity profile increases with increasing estimations of melting parameter. The thermal profile is enhanced for growing magnitudes of the Eckert number. The entropy generation profile increases for the increasing values of the volume fraction of nanoparticles.

Performance Analysis and Mass Estimation of a Small-Sized Liquid Rocket Engine with Electric-Pump Cycle

Abstract: The propellant supply system of a liquid rocket engine using an electric pump has high reliability because of the relatively small number of components. The system also has the merit of a quick response and ease of control owing to its simple configuration. Recently, the rocket lab developed the Rutherford engine, which has an electric pump cycle, because of the improved technology in the electric motor and battery. This paper examined the development of the electric-pump cycle and compared the performance with other cycles for a small-sized low-thrust rocket engine. Performance analysis and mass estimation were conducted using the developed analysis program, in which reliability in mass estimation was improved based on the designed configuration or real performance data from commercial products. In addition, the modeling method and analysis procedure were described in detail. The results showed that it is possible to develop a small-sized engine with an electric-pump cycle when the present technologies are applied. The electric-pump cycle had a smaller dry mass than the gas-generator cycle, even at a low thrust level of 500 N, and showed higher performance in specific impulse and speed increments.

A Method for Real-Time Fault Detection of Liquid Rocket Engine Based on Adaptive Genetic Algorithm Optimizing Back Propagation Neural Network

Abstract: A real-time fault diagnosis method utilizing an adaptive genetic algorithm to optimize a back propagation (BP) neural network is intended to achieve real-time fault detection of a liquid rocket engine (LRE). In this paper, the authors employ an adaptive genetic algorithm to optimize a BP neural network, produce real-time predictions regarding sensor data, compare the projected value to the actual data collected, and determine whether the engine is malfunctioning using a threshold judgment mechanism. The proposed fault detection method is simulated and verified using data from a certain type of liquid hydrogen and liquid oxygen rocket engine. The experiment results show that this method can effectively diagnose this liquid hydrogen and liquid oxygen rocket engine in real-time. The proposed method has higher system sensitivity and robustness compared with the results obtained from a single BP neural network model and a BP neural network model optimized by a traditional genetic algorithm (GA), and the method has engineering application value.

Model-Based Robust Transient Control of Reusable Liquid-Propellant Rocket Engines

Abstract: Reusable liquid-propellant rocket engines (LPREs) imply more demanding robustness requirements than expendable ones due to their extended capabilities. Therefore, the goal of this article was to develop a control loop adapted to all the operating phases of LPRE, including transients, and robust to internal parametric variations. First, thermo-fluid-dynamic simulators representative of the gas-generator-cycle engines were built. These simulators were subsequently translated into nonlinear state-space models. Based on these models, the continuous subphase of the start-up transient is controlled to track precomputed reference trajectories. Beyond the start-up, throttling scenarios are managed with end-state-tracking algorithm. Model predictive control has been applied in a linearised manner with robustness considerations to both scenarios, in which a set of hard state and control constraints must be respected. Tracking of pressure (thrust) and mixture-ratio operating points within the design envelope is achieved in simulation while respecting constraints. Robustness to variations in the predominant parameters, to external state perturbations, and to the possible impact of an observer on the loop, is demonstrated.

Spray patterns of multi-element swirl coaxial injector of interacting spray under different injection conditions

Abstract: Multi-element injectors have been used in liquid rocket engines to obtain high thrust, and the gas-centered swirl coaxial injector is a representative injection system because it provides high mixing performance. Investigations of the spray characteristics of injection systems have focused on the characteristics of single-element injectors, including the spray angle, breakup, and atomization mechanism of the liquid sheet formation. However, the spray characteristics of multi-element injectors need to be studied because of their usage in real rocket engine systems. In this paper, spray patterns and interacting spray under different injection conditions are analyzed using the backlight imaging technique, and the dominant flow fields are observed using the dynamic mode decomposition method. The spray angle in the case of the gaseous nitrogen with a high Reynolds number is calculated to be lower than the case with a low Reynolds number. From the averaged images, it is found that there are two dominant flow fields: one is located in the vicinity of the injector head and the other is in the interacting spray zone, which is related to a secondary breakup via an adjacent injector. As a result of the dynamic mode decomposition analysis, however, the spray zone near the injector is confirmed to be a more dominant flow field than the interacting spray zone.

Numerical Investigation on the Thermal Behaviour of a LOx/LCH4 Demonstrator Cooling System

Abstract: Reliability of liquid rocket engines is strictly connected with the successful operation of cooling jackets, able to sustain the impressive operative conditions in terms of huge thermal and mechanical loads, generated in thrust chambers. Cryogenic fuels, like methane or hydrogen, are often used as coolants and they may behave as transcritical fluids flowing in the jackets: after injection in a liquid state, a phase pseudo-change occurs along the chamber because of the heat released by combustion gases and coolants exiting as a vapour. Thus, in the development of such subsystems, important issues are focused on numerical methodologies adopted to simulate the fluid thermal behaviour inside the jackets, design procedures as well as manufacturing and technological process topics. The present paper includes the numerical thermal analyses regarding the cooling jacket belonging to the liquid oxygen/liquid methane demonstrator, realized in the framework of the HYPROB (HYdrocarbon PROpulsion test Bench) program. Numerical results considering the nominal operating conditions of cooling jackets in the methane-fuelled mode and the water-fed one are included in the case of the application of electrodeposition process for manufacturing. A comparison with a similar cooling jacket, realized through the conventional brazing process, is addressed to underline the benefits of the application of electrodeposition technology.

Innovative methods for obtaining artificial roughness on the surfaces of heat-loaded parts of the liquid rocket engines combustion chamber

Abstract: The article shows the scope of combined processing in the manufacture of parts and assembly units of liquid rocket engines in the aerospace industry. The most effective methods for obtaining artificial roughness on the surfaces of products of special equipment are considered. Empirical studies of changes in the physicomechanical properties of the material using various methods of combined processing have been performed. Qualitative and quantitative relationships between the hydraulic characteristics of the rocket engine combustion chamber manufactured using the combined method and the quality of the surface layer of the product are described and formalized. The analysis of modern processing methods is carried out, as well as the latest methods for producing artificial roughness on the surfaces of rocket engine parts are presented. The relevance and need for the use of high technology in obtaining surface layers of products included in the composition of the combustion chamber of liquid rocket engines are substantiated. The results obtained can significantly expand the technological capabilities of production, as well as significantly improve the technical characteristics of special equipment in the aerospace industry.

Upper Stage Liquid Propellant Rocket Engine: A Case Analysis

Abstract: This paper provides an overview of the design and development process for the L75 liquid propellant rocket engine (LPRE) foreseen as upper stage of a satellite launch vehicle application. Emphasis is put on the choice of available technologies, an adequate operational cycle, and the most suitable propellant combination. Problems encountered during the development and resulting solution approaches are described. Furthermore, a survey of upper stages including their main performance data currently in operation worldwide is presented. Since economical constraints are more important today compared to previous developments schedule and cost figures and their drawbacks are investigated as well. Finally, a summary regarding the development status of the Brazilian L75 engine is reported.

Thermal Analysis on Regenerative Cooled Liquid Propellant Rocket Thrust Chamber Using ANSYS

Abstract: In this research work, thermal analysis has done on a rocket engine’s thrust chamber with four different shapes like, circular, rectangular with greater breath (b>d), rectangular with greater depth (d>b) and rectangular with greater depth with edges filleted coolant channel models to establish perfect suitable shape for the coolant channels in order to maintain the entire thrust chamber within the melting point of its materials. Finite Element Method (FEM) has adopted to establish the thermal behaviour of the coolant channel’s materials such as Nickel, Copper and Zirconium under the specific boundary conditions. Temperature distribution with respect to the nodal distances at thrust chamber’s inlet, throat and outlet portions with four different shapes of coolant channel models under Nickel, Copper and Zirconium materials were attained and compared with each other. Finite element results reveals that the successful configuration for generatively cooled rocket thrust chamber must have the coolant passage shape of rectangular cross section with greater depth (b>d).

Physics-Aware Neural Network Flame Closure for Combustion Instability Modeling in a Single-Injector Engine.

Abstract: Neural networks (NN) are implemented as sub-grid flame models in a large-eddy simulation of a single-injector liquid-propellant rocket engine. The NN training process presents an extraordinary challenge. The multi-dimensional combustion instability problem involves multi-scale lengths and characteristic times in an unsteady flow problem with nonlinear acoustics, addressing both transient and dynamic-equilibrium behaviors, superimposed on a turbulent reacting flow with very narrow, moving flame regions. Accurate interpolation between the points of the training data becomes vital. The NNs proposed here are trained based on data processed from a few CFD simulations of a single-injector liquid-propellant rocket engine with different dynamical configurations to reproduce the information stored in a flamelet table. The training set is also enriched by data from the physical characteristics and considerations of the combustion model. Flame temperature is used as an extra input for other flame variables to improve the NN-based model accuracy and physical consistency. The trained NNs are first tested offline on the flamelet table. These physics-aware NN-based closure models are successfully implemented into CFD simulations and verified by being tested on various dynamical configurations. The results from those tests compare favorably with counterpart table-based CFD simulations.

Method for Predicting the Stability Limit to Acoustic Oscillations in Liquid-Propellant Rocket Engine Combustion Chambers Based on Combustion Noise

Abstract: An experimental method for determining the critical pressure perturbations leading to acoustic instability in combustion chambers of liquid-propellant rocket engines has been developed and used to estimate the stability of the working process. The method involves statistical processing of recorded noise pressure pulsations near the natural resonant frequency range for all normal modes of acoustic oscillations in cylindrical combustion chambers and gas generators. The oscillation damping coefficient (decrement), characterizing the difference between the generated and dissipated energy, is used as a diagnostic criterion for predicting the stable or unstable states of a dynamic system. The method is based on the theory of self-oscillating dynamic systems and one-dimensional Markov random processes using the Fokker–Planck–Kolmogorov equation. Analysis of a nonlinear differential equation with a symmetrized stochastic right-hand side describing white noise for experimentally determined amplitudes of pressure pulsations and their statistical processing using Mera software allows the state of self-oscillating systems to be identified as stable or unstable. The method is “passive;" it is applicable without using standard external impulse disturbing devices.

Hybrid Rocket Engine Performance Assessment Using Plume Luminosity Oscillations

Abstract: Spectral analyses were performed on high-speed video of three nitrous-oxide/paraffin-based hybrid rocket launches and one static test fire of a nitrous/paraffin-based hybrid rocket motor. The image...

A Reinforcement Learning Approach for Transient Control of Liquid Rocket Engines

Abstract: Nowadays, liquid rocket engines use closed-loop control at most near-steady operating conditions. The control of the transient phases is traditionally performed in open loop due to highly nonlinear system dynamics. This situation is unsatisfactory, in particular for reusable engines. The open-loop control system cannot provide optimal engine performance due to external disturbances or the degeneration of engine components over time. In this article, we study a deep reinforcement learning approach for optimal control of a generic gas-generator engine's continuous startup phase. It is shown that the learned policy can reach different steady-state operating points and convincingly adapt to changing system parameters. Compared to carefully tuned open-loop sequences and proportional-integral-derivative (PID) controllers, the deep reinforcement learning controller achieves the highest performance. In addition, it requires only minimal computational effort to calculate the control action, which is a big advantage over approaches that require online optimization, such as model predictive control.

Detailed Measurement of Oxidizer-Rich Staged Combustion Injector Dynamics in Model Rocket Combustors

Abstract: This paper presents experimental results from a model rocket combustor that uses a gas-centered swirl-coaxial injector element injecting warm oxygen and ambient temperature RP-2 fuel with 900 psia ...

Theoretical and Experimental Investigations on the Acoustic Absorptions of Baffled Injectors

Abstract: Baffled injectors are widely used to restrain transverse combustion instabilities in liquid rocket engines. However, there is still a lack of theoretical research on the attenuation mechanisms. In ...

Numerical Investigation of Injection, Mixing and Combustion in Rocket Engines Under High-Pressure Conditions

Abstract: The design and development of future rocket engines severely relies on accurate, efficient and robust numerical tools. Large-Eddy Simulation in combination with high-fidelity thermodynamics and combustion models is a promising candidate for the accurate prediction of the flow field and the investigation and understanding of the on-going processes during mixing and combustion. In the present work, a numerical framework is presented capable of predicting real-gas behavior and nonadiabatic combustion under conditions typically encountered in liquid rocket engines. Results of Large-Eddy Simulations are compared to experimental investigations. Overall, a good agreement is found making the introduced numerical tool suitable for the high-fidelity investigation of high-pressure mixing and combustion.