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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Limit Cycle Oscillating Detonation Wave Behavior Analysis Within a Rotating Detonation Engine

Limit cycle oscillation (LCO) detonation wave behaviors are presented and analyzed for test times exceeding 20 s in a water-cooled rotating detonation engine (RDE). LCO detonation waves exhibit cyclic acceleration and deceleration, resulting in oscillating wave spacing at unique process conditions. In previous RDE studies, similar behaviors have been studied as microsecond-scale instabilities leading to ascending or descending modal transitions. In the current work, however, LCO waves are considered a persistent wave mode, occupying unique portions of the operational envelope adjacent to those of their equally spaced counterparts. These occurrences of LCO waves are repeatable, enduring behaviors. A method to generate shifted contour surfaces specifically intended to extract and analyze wave spacing variation through time, termed limit cycle oscillation visualization (LCOV) surfaces, is presented. LCOV surfaces transform data into the reference frame of a primary traveling wave and are used to analyze quasi-steady, short-timescale, and transitional LCO modes. Results are leveraged to understand the relationship between fill height, wave strength, local wave acceleration, and subsequent LCO wave spacing for individual wave sets. In conclusion, quasi-steady LCO waves display wave spacing oscillations between equal spacing values associated with ±1 wave across runs exceeding 18 s.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2023

Consideration of Nonideal Detonation Regimes Influenced by Wave Modes in a Water-Cooled Rotating Detonation Engine Using OH* Chemiluminescence

Although inherently unstable, existing research in rotating detonation combustion supports its application in notionally steady processes resulting in greater availability compared to conventional, constant pressure combustion. Further improvements rely on a more in-depth understanding of system losses and identifying conditions which optimize device performance. Within this study, the presence and proportion of ideal and nonideal combustion regimes are compared across a variety of process conditions and wave modes. Here, large-scale data analysis seeks to summarize proportional heat release associated with commensal, parasitic, and detonative combustion averaged across individual traces of OH* chemiluminescent data acquired at the detonation plane. Means of regime partitioning based on the anatomy of the time-resolved OH* signal are proposed to ensure consistent analysis throughout the current and future studies concerning combustion regimes. Of particular interest is the possible influence of wave on the nonideal combustion in relative proportion to the desired detonation. Results showed improved percent detonation with increasing significance for the following trends: decreasing equivalence ratio, increasing wave count, decreasing wave velocity, and increasing detonation time. Increased wave number, brought on by decreased equivalence ratios and wave velocities, is thought to decrease fill region surface area, and therefore, decrease nonideal contact burning. Additional analysis is performed to consider possible trend variation due to the presence of stable galloping waves, which were found to have minimal influence on relative percent detonation values. The outcome of this study suggests operational states, which correspond to increased wave quantities for increased proportions of reactants consumed by the targeted detonative combustion regime.

42 ENGINEERING↗
DOE OSTI2020

Demonstrated Low Pressure Loss Inlet and Low Equivalence Ratio Operation of a Rotating Detonation Engine (RDE) for Power Generation

Presentation. An Aerojet Rocketdyne (AR) program was funded by the National Energy Technology Laboratory (NETL), part of the U.S. Department of Energy, to evaluate the benefits of an RDE in a turbine power plant system. Aerojet Rocketdyne subcontracted a variety of support for the program with efforts in modeling, diagnostic techniques, and test campaigns. Over the span of the program more than 700 hot fire tests were conducted at 4 facilities with 7 RDE assemblies. This presentation will cover results from the final test campaign conducted by Aerojet Rocketdyne.

03 NATURAL GAS↗
DOE OSTI2020

High Fidelity Simulations of a Methane-Oxygen Rotating Detonation Rocket Engine

The rotating detonation combustor (RDC) is an important realization of pressure gain combustion for practical applications. The RDC system is characterized by a highly unsteady flow field, with multiple reflected pressure waves following the strong detonations and the existence of partially-burnt gases entrained within the detonation annulus during the injector recovery process. While experimental efforts have provided macroscopic properties of an RDC with a given fuel-oxidizer mixture and geometry, limited optical access and reduced lifespan of flow-field diagnostic equipment constrain understanding of the mechanisms that lend to wave stability, controllability, and sustainability. To this end, high-fidelity numerical simulations of the Air Force Research Laboratory (AFRL) methane-oxygen rotating detonation rocket engine (RDRE) are performed to provide detailed insight into the detonation physics and anomalous behavior within the combustor. The results highlight the merit of high-fidelity numerical studies in analyzing the combustion processes and injector dynamics of a complex combustion system. The simulations capture the general wave behavior observed within the experimental studies. Three different operating conditions, with varying global equivalence ratio and system mass flow rate, are considered: (1) baseline configuration, (2) high equivalence ratio, and (3) high mass flow rate. The high mass flow rate case results in increased detonation wave strength whereas the high equivalence ratio results in increased deflagrative heat release. The high equivalence ratio case results in chaotic behavior with two pairs of counter-rotating detonation waves, whereas a single pair of co-rotating waves is observed in the baseline and high mass flow rate cases. Further, parasitic combustion of the reactant mixture ahead of the detonation wave diminishes its strength and reduces propagation speed to approximately 50-60\% of the Chapman-Jouguet (CJ) condition. In this work, a detailed analysis of the detonation wave behavior, injector dynamics, and the statistics of combustion parameters are presented.

Prakash, Supraj↗
DOE OSTI2023

Survey of Machine Learning-Based Rotating Detonation Engine Diagnostics: Evaluation for Broad Application in Experimental Facilities

This work evaluates and compares various convolutional neural networks (CNNs) trained in previous NETL studies according to metrics effecting diagnostic feasibility, external applicability, and performance. Each CNN surveyed, including image classification, object detection, and time series classification, is used to develop total RDE diagnostics and evaluated alongside conventional techniques with respect to real-time capabilities. Real-time capable diagnostics are deployed and evaluated in the laboratory environment using an altered experimental setup, which is outlined herein for possible adaptations in external experimental facilities.

Johnson, Kristyn↗
DOE OSTI2023

Survey of Machine Learning-Based Rotating Detonation Engine Diagnostics: Evaluation for Broad Application in Experimental Facilities

This work evaluates and compares various convolutional neural networks (CNNs) trained in previous NETL studies according to metrics effecting diagnostic feasibility, external applicability, and performance. Each CNN surveyed, including image classification, object detection, and time series classification, is used to develop total RDE diagnostics and evaluated alongside conventional techniques with respect to real-time capabilities. Real-time capable diagnostics are deployed and evaluated in the laboratory environment using an altered experimental setup, which is outlined herein for possible adaptations in external experimental facilities.

Johnson, Kristyn↗
DOE OSTI2023

Consideration of Non-Ideal Detonation Regimes Influenced by Wave Modes in a Water-Cooled Rotating Detonation Engine Using OH Chemiluminescence

Within this study, the presence and proportion of ideal and non-ideal combustion regimes is compared across a variety of process conditions and wave modes. Large-scale data analysis seeks to summarize proportional heat release associated with commensal, parasitic, and detonative combustion averaged across individual traces of OH* chemiluminescent data acquired at the detonation plane. Means of regime partitioning based on the anatomy of the time-resolved OH* signal are proposed to ensure consistent analysis throughout the current and future studies concerning combustion regimes.

Johnson, Kristyn↗