Design and performance of liquid hydrogen fueled aircraft for year 2050 EIS

The present paper reports on the investigation of long-range LH2 aircraft concepts for year 2050 entry into service. The paper attempts to identify the limitations set by the LH2 storage technology when targeting typical design payload-range missions. In particular, the paper aims at providing a reasonable estimate of the upper efficiency levels set by low-weight rigid cell foam insulated tank technology, when integrated in a conventionallyshaped airframe. Additionally, a sensitivity study on the gravimetric efficiency of the tanks will be carried out, to identify the required roadmap for LH2 storage technology that is compliant with the typical long range mission requirements. Results for the different LH2 aircraft are compared with a year 2020 and year 2050 reference aircraft fueled with conventional jet-A

Numerical Analysis of Design Parameters With Strong Influence on the Aerodynamic Efficiency of a Small-Scale Self-Pitch VAWT

In the paper, four key design parameters with a strong influence on the performance of a small-scale high solidity variable pitch VAWT (Vertical Axis Wind Turbine), operating at low tip-speed-ratio (TSR) are addressed. To this aim a numerical approach, based on a finite-volume discretization of two-dimensional Unsteady RANS equations on a multiple sliding mesh, is proposed and validated against experimental data. The self-pitch VAWT design is based on a straight blade Darrieus wind turbine with blades that are allowed to pitch around a feathering axis, which is also parallel to the axis of rotation. The pitch angle amplitude and periodic variation are dynamically controlled by a four-bar-linkage system. We only consider the efficiency at low and intermediate TSR, therefore the pitch amplitude is chosen to be a sinusoidal function with a considerable amplitude. The results of this parametric analysis will contribute to define the guidelines for building a full size prototype of a small scale turbine of increased efficiency

Design of an innovative off road hybrid vehicle by energy efficiency criteria

The environmental impact of road transport is significant because it is a major user of energy and the major user of the world's petroleum that is extracted every year. This creates air pollution, including nitrous oxides and particulates, and is a significant contributor to global warming through emission of carbon dioxide, for which transport is the fastest-growing emission sector. These impacts assume a particular importance if considered the place where they are emitted such as the cities and highways that develop near the human settlements. By subsector, road transport can globally be considered the largest contributor to global warming. This paper takes into account an effective design methodology, which is based on an effective energy optimization of the vehicle and its main components. This method takes inspiration from constructal law, even if it could not be limited to this. The inspiration is limited to considering the fluxes of different physical magnitudes inside a complex system, such as a vehicle is, and analyzing how they develop and how they develop and mix. This analysis leads to a general analysis to the vehicle and to an effective optimization based on energy principle by a step by step optimization that allows identifying the critical elements that limit the flow of the different magnitudes inside the system, with particular attention to the factor that limits energy efficiency at different scale levels. The components have been considered only if they are industrial grade and inside a modular design, which allows merging design, finalized to energy efficiency, minimization of exergy disruption and of LCA impacts. The emotion that has been caused by the end of the production of the most successful British vehicle that is Land Rover Defender has stimulated to produce a sample design of a vehicle in this class producing different alternatives for different uses. The case of a vehicle that can compete with Discovery in terms of use and specifications has been considered, Results have been surprising demonstrating that the use of industrial grade components and their accurate choice will allow defining new vehicle platforms that can radically improve energy efficiency of vehicles

Temperature oscillations in the wall of a cooled multi pulsejet propeller for aeronautic propulsion

Environmental and economic issues related to the aeronautic transport, with particular reference to the high-speed one are opening new perspectives to pulsejets and derived pulse detonation engines. Their importance relates to high thrust to weight ratio and low cost of manufacturing with very low energy efficiency. This papers presents a preliminary evaluation in the direction of a new family of pulsejets which can be coupled with both an air compression system which is currently in pre-patenting study and a more efficient and enduring valve systems with respect to today ones. This new pulsejet has bee specifically studied to reach three objectives: a better thermodynamic efficiency, a substantial reduction of vibrations by a multi-chamber cooled architecture, a much longer operative life by more affordable valves. Another objective of this research connects directly to the possibility of feeding the pulsejet with hydrogen. This paper after a preliminary analysis of the pulsejet takes into account two necessary stages of this activity with the initial definition of the starting point of this activity, which aim to define an initial thermodynamic balance of a Lenoir cycle and a preliminary but effective estimation of the thermal problem. It analyses the heat transfer process through the wall of the combustion chamber of a pulsejet for aeronautic propulsion. The inside wall is exposed to burning gases with an average temperature of 1500 K, which oscillates with an amplitude 500 k and a frequency of 50 Hz. It has been considered the possibility of using Hydrogen injection to reduce the environmental impacts at the price of introducing a cooling water envelope at an average temperature of 80 °c. The water mass flow to ensure this condition has been evaluated and it has been evaluated both the average temperature profile within the wall and the effects of the oscillations of gas temperature inside the combustion chamber. Obtained results have allowed starting an effective activity through a radically new pulsejet architecture, which is expected to outclass any former pulsejet in term of operative life and of compression ratio with a consequent step increase in terms of thermodynamic efficiency

Study on the Manipulation of Plasma Density around a Cubesat Using Magnetohydrodynamics

During hypersonic flight regime or re-entry flights, a phenomenon known as radio blackout occurs, in which the high velocities attained lead to a significant increase in temperature surrounding the vehicle. This raise is so substantial that the molecules around the vehicle start to ionize, surrounding the vehicle in electrons. These electrons will prevent electromagnetic waves from leaving or reaching the aircraft, preventing all communications. Several blackout mitigation schemes have been proposed, among which is the magnetic window.  In this scheme, a magnetic field is imposed near the nose of the aircraft, which will then prevent electron movement, generating a spectral window through which the electromagnetic waves can pass. In this work, the effectiveness of this method in affecting the plasma density is tested. The mesh is tested for grid independency, ensuring an accurate solution in a sensible ammount of time. The effect of different magnetic field intensities is then tested for a CubeSat flying in hypersonic flight regime, in order to determine the effect of the magnetic field in the electron number density. Keywords: Magnetohydrodynamics, Radio blackout, Magnetic window, CubeSa

Development of an aerodynamic analysis tool for boundary layer ingestion concept design

The methods incorporated in an aerodynamic analysis tool are introduced to support aircraft conceptual designs, where a boundary layer ingestion (BLI) propulsion system is deployed. In order to integrate the BLI model to a generic tool for aircraft designs, two methods of approximating boundary layer profiles along the airframe/fuselage have been examined. For an airfoil-shaped wing/body configuration, the airfoil analysis program XFOIL is used and, alternatively, the flat plate boundary layer theory may be adopted. With the boundary layer characteristics approximated from these methods, the fan performance in terms of pressure ratio and efficiency is corrected considering the inflow distortion incurred by the boundary layer ingested, based on a simplified parallel compressor method. Given the corrected fan pressure ratio and efficiency, an equivalent velocity bookkeeping method is used for predicting the BLI fan performance in terms of power requirement and thrust generation. A validation against the boundary layer approximation is also presented in comparison with the RANS-based CFD simulations for a blended wing body (BWB) aircraft

Conceptual Design of a Compressor Vane- HEX for LH2 Aircraft Engine Applications

In order to meet the ambitious environmental targets set by the Paris Agreement, new sustainable carbon neutral aviation fuels need to be introduced. The high gravimetry energy density of hydrogen, makes it a prime candidate for a future aviation fuel. However, the associated poor volumetric energy density, requires an increased aircraft volume and associated penalty in aerodynamic performance. The required volume occupied by the hydrogen fuel can be decreased in half, if stored in its liquid form. This however requires that the liquid hydrogen (LH2) is kept at cryogenic temperatures, requiring adequate tank insulation. Moreover, to increase the effective heating value of hydrogen, the fuel distribution system will include heat exchanger technology to increase the fuel temperature before injection in the combustion chamber. The present work provides an outlook of different heat exchanger technology for application in hydrogen fueled gas turbine aero engines. The heat exchangers can be placed in the vicinity of the engine to reject the heat generated by the gas core to the hydrogen fuel. Ideally, they are strategically located to use heat management to maximize the engine efficiency and ensuring sufficient component durability. Moreover, the combination of liquid hydrogen’s high specific heat with cryogenic storage temperatures results in a formidable cooling capacity that can be explored by more compact heat exchanger solutions

An outlook for radical aero engine intercooler concepts

A state of the art turbofan engine has an overall efficiency of about 40%, typically composed of a 50% thermal and an 80% propulsive efficiency. Previous studies have estimated that intercooling may improve fuel burn on such an engine with a 3-5% reduction depending on mission length. The intercooled engine benefits stem firstly from a higher Overall Pressure Ratio (OPR) and secondly from a reduced cooling flow need. Both aspects relate to the reduced compressor exit temperature achieved by the intercooler action. A critical aspect of making the intercooler work efficiently is the use of a variable intercooler exhaust nozzle. This allows reducing the heat extracted from the core in cruise operation as well as reducing the irreversibility generated on the intercooler external surface which arises from bypass flow pressure losses. In this respect the improvements, higher OPR and lower cooling flow need, are achieved indirectly and not by directly improving the underlying thermal efficiency. This paper discusses direct methods to further improve the efficiency of intercooled turbofan engines, either by reducing irreversibility generated in the heat exchanger or by using the rejected heat from the intercooler to generate useful power to the aircraft. The performance improvements by using the nacelle wetted surface to replace the conventional intercooler surface is first estimated. The net fuel burn benefit is estimated at 1.6%. As a second option a fuel cooled intercooler configuration, operated during the climb phase, is evaluated providing a net fuel burn reduction of 1.3%. A novel concept that uses the rejected heat to generate additional useful power is then proposed. A secondary cycle able to convert rejected intercooler heat to useful thrust is used to evaluate three possible scenarios. The two first cases investigate the impact of the heat transfer rate on the SFC reduction. As a final consideration the geared intercooled engine cycle is re-optimized to maximize the benefits of the proposed heat recovery system. The maximum SFC improvement for the three cycles is established to 2%, 3.7% and 3%

Métodos numéricos para a dinâmica de gases e escoamentos magnetohidrodinâmicos a números de Mach arbitrários : aplicações em tubeiras magnetoplasmadinâmicas

A magnetohidrodinâmica (MHD) é a área cientí ca que se dedica ao estudo da interação de um uido condutor em movimento com um ou vários campos magnéticos. Fenómenos desta natureza são extremamente comuns no campo da astrofísica, sabendo-se que grande parte dos efeitos observados na dinâmica dos plasmas resulta da interação do escoamento com campos elétricos e/ou magnéticos. Outro campo de aplicação da ciência da MHD diz respeito à análise de sistemas de propulsão elétrica, mais concretamente na modelação de tubeiras magnetoplasmadin âmicas (MPD). Os sistemas MPD utilizam a força de Lorentz como principal mecanismo de aceleração, o que lhes permite obter velocidades de escape extremamente elevadas para uma pequena massa de gás propelente. Uma forma de analisar este tipo de escoamentos é através de ferramentas numéricas baseadas nas equações que governam o escoamento MHD. O trabalho que aqui vai ser exposto pode dividir-se em duas partes. Na primeira é elaborado um método numérico e caz para resolver as equações de Euler, que apresenta algumas novidades relativamente aos métodos existentes sendo capaz de calcular escoamentos a número de Mach arbitrário. Este método é baseado no algoritmo PISO e utiliza o esquema AUSM+ up para o cálculo dos uxos convectivos. É apresentada uma explicação pormenorizada sobre as bases deste método, onde vai ser demonstrado que é possível adaptar o esquema AUSM de forma a este ser integrado num algoritmo baseado na equação da pressão. Vai também ser acrescentado e testado no código em uso o esquema de interpolação de alta resolução CUBISTA. Para validar o código proposto são apresentados resultados para uma tubeira axissimétrica a operar em vários regimes de número de Mach. O caso de teste seguinte compreende um túnel com um obstáculo de secção circular cujo escoamento será abordado nos três regimes de esc. subsónico, transónico e supersónico. Esta primeira parte do trabalho é encerrada com o cálculo de um escoamento supersónico e hipersónico mais complexo, no qual o uido vai de encontro a um objeto de geometria circular gerando ondas de choque a montante do obstáculo. A segunda parte do trabalho compreende a extensão do método, anteriormente proposto para análise das equações de Euler, agora aplicado ao cálculo de escoamento MHD compressível. Este novo método é igualmente baseado no algoritmo PISO mas utiliza uma versão modi cada do esquema AUSM, devidamente adaptada para escoamento MHD. O método aqui proposto vai ser exposto de forma pormenorizada e as várias técnicas de correção do campo magnético são aqui apresentadas. No que concerne à sua validação, são utilizados vários casos de teste padrão do tipo uni-dimensional e bidimensional. Inicialmente vão ser abordados dois problemas de escoamento MHD resistivo em canais de secção quadrada. Seguidamente a ordem de precisão do método vai ser analisada através do cálculo de ondas de Alfvén num espaço bidimensional. A precisão no cálculo de descontinuidades vai ser posteriormente analisada com recurso ao problema de Riemann uni-dimensional e a vários problemas bidimensionais de escoamento MHD ideal. O método de simulação MHD aqui desenvolvido vai nalmente ser aplicado na análise paramétrica dos efeitos da geometria dos elétrodos sobre o desempenho de uma tubeira MPD de campo induzido