The utilization and loss of available energy in aerospace systems

“Theoretical principles and analytical methodology for the control volume-based energy availability methodology for aerospace vehicles are developed; applications are made to jet-propelled and rocket-propelled vehicles as well as to stand-alone engine systems. Energy availability utilization characteristics of a modeled turbojet engine are studied across a wide range of operating conditions of throttle setting, flight altitude, and flight Mach number. The method is also extended to consider jet-powered vehicles. Fundamental principles regarding entropy generation and energy availability are developed, including directly linking entropy generation and maximum range and endurance of a powered aircraft. Theory and application of the energy utilization methodology with allocation of losses and productive usage are also developed and shown for atmospheric accelerating and climbing (access-to-space) rockets both at specific flight points as well as across missions. Flight conditions required for optimal performance in terms of energy utilization and entropy generation are theoretically derived and verified with applications. Performance impact of entropy generation both in the engine and in the wake on vehicle performance are studied; studies are made for representative rocket systems. In addition, mission-integrated form of the theoretical availability balance formulation has been derived and generalized for an N-stage rocket and cast in both dimensional and non-dimensional forms; theory for special cases and optimization criteria are defined and tested. The primary objective of this work has been to formulate, characterize, and investigate performance of airbreathing and rocket-powered aerospace systems, specifically from the standpoint of energy availability utilization”--Abstract, page iv

Air Launched Vehicle Exergy Analysis During Aircraft Boost Phase

The analysis of air launched vehicles carrying payloads to low earth orbit is complex. The integration of the aircraft flight phase and the launch vehicle flight phase requires the integration of systems functioning from different energy relationships. System exergy balance provides a relationship to integrate the efficiency of the aircraft launcher and the efficiency of the launch vehicle in a single, integrated system assessment. The exergy balance of the aircraft flight phase can be calculated with the launch vehicle included as part of the vehicle mass. As exergy balance allows for separate of the masses, different velocities, and different propulsion systems to continue the mission analysis after separation through payload orbital insertion and aircraft landing. This paper presents the initial assessment of the aircraft launch phase up to separation of the launch vehicle. Showing the method of integration afforded by the system exergy balance relationship

Proceedings of 3rd International Energy, Exergy and Environment Symposium

Proceedings of the 3rd International Energy, Exergy and Environment Symposium IEEES3, 1-5 July 2007, Évora, Portuga

Recent Advances in Technology, Strategy and Application of Sustainable Energy Systems

The global COVID-19 pandemic has had strong impacts on national and international freight, construction and tourism industry, supply chains, and has resulted in a rapid decline in the demand for traditional energy sources. In fact, research has outlined that urban areas depend on global supply chains for their day-to-day basic functions, including energy supplies, food and safe access to potable water. The disruption of global supply chains can leave many urban areas in a very vulnerable position, in which their citizens may struggle to obtain their basic supplies, as the COVID-19 crisis has recently shown. Therefore, solutions aiming to enhance local food, water and energy production systems, even in urban environments, have to be pursued. The COVID-19 crisis has also highlighted in the scientific community the problem of people’s exposure to outdoor and indoor pollution, confirmed as a key element for the increase both in the transmission and severity of the contagion, on top of involving health risks on their own. In this context, most nations are going to adopt new preferential policies to stimulate the development of relevant sustainable energy industries, based on the electrification of the systems supplied by renewable energy sources as confirmed by the International Energy Agency (IEA). Thus, while there is ongoing research focusing on a COVID 19 vaccine, there is also a need for researchers to work cooperatively on novel strategies for world economic recovery incorporating renewable energy policy, technology and management. In this framework, the Sustainable Development of Energy, Water and Environment Systems (SDEWES) conference provides a good platform for researchers and other experts to exchange their academic thoughts, promoting the development and improvements on the renewable energy technologies as well as their role in systems and in the transition towards sustainable energy systems. The 14th SDEWES Conference was held in Dubrovnik, Croatia. It brought together around 570 researchers from 55 countries in the field of sustainable development. The present Special Issue of Energies, specifically dedicated to the 14th SDEWES Conference, focuses on four main fields: energy policy for sustainable development, biomass energy application, building energy saving, and power plant and electric systems

Comparative analysis of alternative fuels in detonation combustion

Detonation combustion prominently exhibits high thermodynamic efficiency which leads to better performance. As compared to the conventionally used isobaric heat addition in a Brayton cycle combustor, detonation uses a novel isochoric Humphrey cycle which utilises shocks and detonation waves to provide pressure-rise combustion. Such unsteady combustion has already been explored in wave rotor, pulse detonation engine and rotating detonation engine configurations as alternative technologies for the next generation of the aerospace propulsion systems. However, in addition to the better performance that the detonation mode of combustion offers, it is crucial to observe the environmental concerns as well. Therefore, this paper presents a one-dimensional numerical analysis for alternative fuels: Jet-A, Acetylene, Jatropha Bio-synthetic Paraffinic Kerosene, Camelina Bio-synthetic Paraffinic Kerosene, Algae Biofuel, and Microalgae Biofuel under detonation combustion conditions. For simplicity, the analysis is modelled using an open tube geometry. The analysis employs the Rankine-Hugoniot Equation, Rayleigh Line Equation, and Zel’dovich–von Neumann–Doering model and takes into account species mole, mass fraction, and enthalpies-of-formation of the reactants. Initially, minimum conditions for the detonation of each fuel are determined. Pressure, temperature, and density ratios at each stage of the combustion tube for different types of fuel are then explored systematically. Finally, the influence of different initial conditions is numerically examined to make a comparison for these fuels

Entropy-based performance analysis of jet engines; Methodology and application to a generic single-spool turbojet

Recently developed methodology that provides the direct assessment of traditional thrust-based performance of aerospace vehicles in terms of entropy generation (i.e., exergy destruction) is modified for stand-alone jet engines. This methodology is applied to a specific single-spool turbojet engine configuration. A generic compressor performance map along with modeled engine component performance characterizations are utilized in order to provide comprehensive traditional engine performance results (engine thrust, mass capture, and RPM), for on and off-design engine operation. Details of exergy losses in engine components, across the entire engine, and in the engine wake are provided and the engine performance losses associated with their losses are discussed. Results are provided across the engine operating envelope as defined by operational ranges of flight Mach number, altitude, and fuel throttle setting. The exergy destruction that occurs in the engine wake is shown to be dominant with respect to other losses, including all exergy losses that occur inside the engine. Specifically, the ratio of the exergy destruction rate in the wake to the exergy destruction rate inside the engine itself ranges from 1 to 2.5 across the operational envelope of the modeled engine --Abstract, page iii

Heat Transfer in Energy Conversion Systems

In recent years, the scientific community’s interest towards efficient energy conversion systems has significantly increased. One of the reasons is certainly related to the change in the temperature of the planet, which appears to have increased by 0.76 °C with respect to pre-industrial levels, according to the Intergovernmental Panel on Climate Change (IPCC), and this trend has not yet been stopped. The European Union considers it vital to prevent global warming from exceeding 2 °C with respect to pre-industrial levels, since this phenomenon has been proven to result in irreversible and potentially catastrophic changes. These climate changes are mainly caused by the emissions of greenhouse gasses related to human activities, and can be drastically reduced by employing energy systems, for both heating and cooling of buildings and for power production, characterized by high efficiency levels and/or based on renewable energy sources. This Special Issue, published in the journal Energies, includes 12 contributions from across the world, including a wide range of applications, such as HT-PEMFC, district heating systems, a thermoelectric generator for industrial waste, artificial ground freezing, nanofluids, and others

Large Steel Tank Fails and Rockets to Height of 30 meters - Rupture Disc Installed Incorrectly

AbstractAt a brewery, the base plate-to-shell weld seam of a 90-m3 vertical cylindrical steel tank failed catastrophically. The 4 ton tank “took off” like a rocket leaving its contents behind, and landed on a van, crushing it. The top of the tank reached a height of 30 m. The internal overpressure responsible for the failure was an estimated 60 kPa. A rupture disc rated at < 50 kPa provided overpressure protection and thus prevented the tank from being covered by the European Pressure Equipment Directive. This safeguard failed and it was later discovered that the rupture disc had been installed upside down. The organizational root cause of this incident may be a fundamental lack of appreciation of the hazards of large volumes of low-pressure compressed air or gas. A contributing factor may be that the standard piping and instrumentation diagram (P&ID) symbol for a rupture disc may confuse and lead to incorrect installation. Compressed air systems are ubiquitous. The medium is not toxic or flammable. Such systems however, when operated at “slight overpressure” can store a great deal of energy and thus constitute a hazard that ought to be addressed by safety managers

Development of Improved CFD Tools for the Optimization of a Scramjet Engine

In the present work, a plugin has been developed for use with the DoD HPCMP CREATE-AV Kestrel multi-physics solver that adds volumetric source terms to the energy equation. These source terms model the heat released due to combustion, but are much more computationally efficient than a full chemistry model. A thrust-based optimization study was then carried out under the control of Sandia National Laboratories\u27 Dakota toolkit. Dakota was allowed to control the amount of heat added to three regions of the scramjet combustor. The plugin was then extended to consider ignition delay time. By comparing ignition delay time to dwell time, it is possible to determine whether the fuel in a cell should be combusted. Results from this analysis are compared to results gathered using a 22-species chemistry model. The ignition delay source term is shown to capture relevant flow physics at a reduced computational cost. Additionally, the expression for second-law (exergetic) efficiency for a scramjet engine is derived and optimized using Dakota. Finally, Dakota was extended to control the geometry of the scramjet engine, allowing for the numerical optimization of the scramjet expansion system. The results from these computationally-efficient optimizations can then be used to inform researchers of potentially optimal solutions before higher-fidelity models are used

Exergy analysis and optimization of the power mode operation of a bimodal nuclear thermal rocket

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