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Effect of Film Cooling Hole Location on Flow Dynamics in a Rotating Detonation Combustor
No full textDetonative combustion can be employed to develop high-power-density combustors, such as the Rotating Detonation Combustor (RDC). The high combustor mass flow, combined with the significant heat release from detonation waves occurring near the walls of the narrow annulus, results in immense thermal loads on the walls. Managing these thermal loads is crucial for the successful application of RDCs in gas turbines. Previous studies have suggested that film cooling may offer a viable solution for mitigating the intense thermal loads. However, the impact of the coolant mass addition location on RDC performance remains unclear. Four film-cooled RDC architectures are investigated, where the holes covered different portions of the outer wall from near the reactant injection location to downstream in the oblique shock region. The high circumferential and axial pressure variations resulted in differing coolant flows, while the added coolant mass increased the chamber pressure. The increased chamber pressure significantly altered the fresh gas refill structure and the detonation height. Regarding cooling performance, the various cooling schemes had different impacts on how much the wall temperatures were reduced. Ultimately, having cooling further downstream was most effective at overall cooling of the outer wall. However, placing coolant jets in the detonation region modifies the initial mixture characteristics affecting the detonation combustion. In each cooling scheme, the injected coolant reacted with the unburnt fuel, leading to additional secondary deflagration heat release which reduced the amount of unburned hydrogen at the exit
Occulation Observations with Event-based Vision Sensors [ Poster ]
Get PDFEvent-based vision sensors (EVS) offer exceptional change detection capabilities due to their asynchronous and independent pixels which record binary events with changes in their photocurrent. The resulting address event representation data is a sparse timeseries list
Investigation of the Flow Field Morphology of Film Cooling in Supersonic Flow
No full textFilm cooling is widely implemented in highly thermally stressed gas turbine components. Its performance has been extensively investigated for several decades and many results are available in the literature. In conventional gas turbines, regions of supersonic flow are not prevalent and should generally be avoided. For this reason, results relative to film cooling in supersonic flow are limited. Nevertheless, a new interest related to Rotating Detonation Combustors (RDC) and supersonic turbines is growing. The implementation of those engine components in a gas turbine is likely to need film cooling for thermal protection. In this context, it becomes crucial to gain an understanding of how the film interacts with the freestream when operated in a supersonic flow. This paper investigates the effect caused by the injection of film cooling on the morphology of the supersonic flow field. Results obtained by means of schlieren imaging indicated that the coolant injection acts as a wedge inside the flow, determining the local formation of an oblique bow shock around each film cooling hole. The shape, inclination, and strength of the oblique shock showed a dependency on the fundamental dimensionless parameters considered for the characterization of the operating conditions of film cooling. Furthermore, as the amount of mass injected was increased, the inclination of the generated shocks increased and the impingement location of the reflected shock moved upstream along the injection plate. The fluid dynamics of this interaction affected the local pressure distribution on the injection plate, measured by means of Pressure Sensitive Paint (PSP). Different film cooling geometries and main flow conditions were tested at multiple operating conditions. The relative impact of the different parameters is presented, providing useful information for the design of a film cooled engine component exposed to a supersonic flow
Predictive Modeling and Sensitivity Analysis of Thermodynamic Irreversibilities in Peristaltic Transport of Bingham Plastic Fluid in Porous Media Using Artificial Neural Networks and Response Surface Methodology
No full textThis study focused on the optimal analysis of thermodynamic irreversibilities in the peristaltic transport of a Bingham plastic fluid in an asymmetric porous channel. The governing differential equations were solved numerically using MATLAB\u27s boundary value problem fourth-order method (bvp4c function) to estimate the pressure rise per wavelength ((Formula presented.)) and entropy generation ((Formula presented.)) under varying parameter conditions. Models for (Formula presented.) and (Formula presented.) were developed using Response Surface Methodology (RSM) and Artificial Neural Networks (ANNs) to provide comprehensive insights into the system. The coefficient of determination (R2) value for the RSM model of (Formula presented.) was 99.98%, whereas that for (Formula presented.) was 99.76%. The ANN models demonstrated high precision, with error margins ranging from 10−3 to zero for (Formula presented.) and 10−4 to zero for (Formula presented.). Sensitivity analysis revealed that (Formula presented.) was strongly influenced by the permeability parameter (Formula presented.), whereas (Formula presented.) was more sensitive to low values of (Formula presented.) and intermediate to maximum values of Brinkman number (Formula presented.). Model validation using residual plots, normal probability plots, and observation order comparisons confirmed the excellent agreement between the observed and predicted values. Both the RSM and ANN models achieved regression values near unity, demonstrating their robustness in modeling parameter interactions and system responses. This study establishes a reliable framework for analyzing peristaltic transport in complex fluid systems and provides valuable insights for optimization
Preliminary investigation of multi-body orbit architectures for Mars surface positioning, navigation, and timing
No full textAs space-faring countries advance from lunar exploration to Mars exploration, the requirement for persistent position, navigation, and timing (PNT) capabilities become crucial. This paper proposes several PNT architectures with near constant coverage of the entire Martian surface. Investigated in this research are orbits propagated in the Circular Restricted Three-Body Problem (CR3BP) and Bi-Circular Restricted Four-Body Problem (BCR4BP) in the Mars-Phobos system. Trajectories investigated include the Lyapunov, Short Period, Vertical, and Axial periodic orbit families defined with respect to the Mars-Phobos and Sun-Mars-Phobos multi-body systems. Further analysis such as position and geometric dilution of precision, stability, visibility coverage, and PNT system power considerations are conducted on these architectures to narrow options to best performer. For coverage of the equatorial region (±45 degrees), the Vertical family is chosen. For coverage of the entire Martian surface, a constellation consisting of 3 trajectories from the Axial family is the chosen architecture
Impacts of additive manufacturing on manufacturing supply chain design
No full textPurpose: This study investigates the critical enablers required for the successful integration of additive manufacturing (AM) into manufacturing supply chains (MSCs). It aims to identify the necessary conditions that must be present to unlock the full potential of additive manufacturing in enhancing supply chain resilience, responsiveness, and efficiency.
Design/methodology/approach: The research adopts a Necessary Condition Analysis (NCA) methodology to determine essential conditions for the effective adoption of AM. Data were collected through expert interviews across three strategically important industries (healthcare, aerospace/automotive and consumer goods). Eight key enablers were identified through analysis of the interview data.
Findings: The study identifies eight necessary conditions for integrating AM into MSCs, including business network development, technological advancement, information sharing, hybrid production models, capability redesign and process quality certification. It emphasizes that the absence of any one of these enablers can critically impede supply chain performance improvements, regardless of other strengths in the system.
Practical implications: The findings provide actionable guidance for firms and policymakers seeking to implement AM as a strategic supply chain tool. By understanding the industry-specific enablers that must be in place, decision-makers can better allocate resources and design implementation strategies that ensure the success of AM initiatives.
Originality/value: This research fills a notable gap in the existing literature by shifting the focus from sufficient to necessary conditions for AM integration. It introduces the NCA methodology into the AM and supply chain domain, offering a novel perspective on strategic implementation challenges
Event-Based Sensor Noise Modeling for Space Domain Awareness
No full textBuilding off the foundation of a physics-based end-to-end model for event-based vision sensors (EVS) observing resident space objects (RSOs), we apply new techniques to model realistic low-light sensor noise. While previous event-generation approaches simulate memorized current leakage and apply temporal noise models, our methods improve on these approaches and additionally account for current-following white noise as an event source. These model improvements are key components for accurate event-generating simulations which can advise requirements and concepts of operations for dedicated event-based Space Domain Awareness (SDA) architectures. An event-generation simulator which models the underlying physics is particularly important for space-based architectures where informative space-based truth data is limited. The EVS pixel’s independent and asynchronous recording of changes in photocurrent produces data with high temporal resolution and dynamic range making it an attractive technology for SDA. EVS are particularly appealing as a space-based payload because of their sparse data output reducing the need for downlink, computational, and power resources. To enable creation of a space-based EVS system, our physics-based end-to-end model now includes noise based on induced photocurrent to generate simulated events closer to known truth. We introduce a new Poisson-based method to model the noise generated by the temporal variation of the dark current and a method to tune high-frequency white noise on the induced photocurrent to model the noise on signals above the dark current. These techniques demonstrably improve EVS noise modeling by closely matching observed event rate and polarity behavior, moving EVS one step closer to operational space-based SDA usage
Exporting SysML Designs to Simulink
Get PDFVarious software systems have been developed to aid a systems engineer in evaluating system requirements, such as Dassault’s Magic System of Systems Architect (MSOSA) and MathWorks’ Simulink. Both software packages have different strengths; therefore, it is beneficial to export models from one software package to another. MSOSA provides a built-in tool that facilitates this transfer, built upon the Extension for Physical Interaction and Signal Flow Simulation (SysPhS) standard. However, the process is often unreliable and error prone and online documentation is largely lacking. This research used extensive trial and error to fill in the documentation gaps and create a method to reliably transfer constant values and state machines from MSOSA to Simulink. It was found that the most reliable and time-efficient method is to define constant values and state machines in MSOSA, export these to Simulink, then create and connect the remaining components of the system to complete the model. This process was applied to an example of a CubeSat electrical system. While this process is limited to only exporting constant values and state machines, it was found that this information is enough to generate a practical simulation in Simulink and evaluate system behaviors and designs for design requirements validation
Using Chia Blockchain Technology for Department of Defense Systems
No full textThe United States faces an escalating cybersecurity challenge, with national assets increasingly vulnerable to sophisticated attacks. The ever-reducing barriers to entry in the cyber realm, coupled with advanced persistent threats, underscore the critical imperative to fortify the defense of U.S. assets. Blockchain technology, pioneered by Satoshi Nakamoto over a decade ago, emerges as a resilient cryptographic solution capable of safeguarding data and assets from threats both within and outside a network. This paper delves into the potential of the Chia blockchain as a strategic ally for the Department of Defense (DoD) in bolstering its cybersecurity measures. Beyond a theoretical exploration, the paper provides tangible use cases that illustrate the practical application of Chia within the DoD framework. Notably, the examination extends to crucial areas such as financial auditing, identification management, and supply chain oversight, showcasing the versatility and efficacy of Chia in addressing multifaceted challenges faced by the DoD. © 2024 Curran Associates Inc.. All rights reserved
Cyber Game-Based Learning for DoD CEs
No full textCyber competition and conflict remain an enduring concern for the Department of Defense (DoD). Positive control of cyberspace is crucial across the vast diversity of military operations and supporting activities. People play an important role in cyber prevention, detection, and remediation, but they receive relatively little training outside of the annual Cyber Awareness Challenge. While this gamified training is a reasonable baseline, it primarily addresses cybersecurity from the office worker\u27s perspective. Other career fields within the DoD may benefit from specialized training in cybersecurity, in particular the civil engineering (CE) community supporting critical infrastructure protection. This paper surveys a range of contemporary cyber serious games and assesses each for potential inclusion into CE training. Furthermore, it suggests game elements and characteristics that are likely to benefit the CE community