Ultra High Bypass Ratio Research Articles

Potential of Hydrogen Fuel Cell Aircraft for Commercial Applications with Advanced Airframe and Propulsion Technologies

The present work demonstrates a comparative study of hydrogen fuel cells and combustion aircraft to investigate the potential of fuel cells as a visionary propulsion system for radically more sustainable medium- to long-range commercial aircraft. The study, which considered future airframe and propulsion technologies under the Se2A project, was conducted to quantify potential emissions and costs associated with such aircraft and to determine the benefits and drawbacks of each energy system option for different market segments. Future technologies considered in the present work include laminar flow control, active load alleviation, new materials and structures, ultra-high bypass ratio turbofan engines, more efficient thermal management systems, and superconducting electric motors. A multi-fidelity initial sizing framework with coupled constraint and mission analysis blocks was used for parametric airplane sizing and calculations of all necessary characteristics. Analyses performed for three reference aircraft of different sizes and ranges concluded that fuel-cell aircraft could have operating cost increases in the order of 30% compared to hydrogen combustion configurations and were caused by substantial weight and fuel burn increases. In-flight changes in emissions of fuel cell configurations at high altitudes were progressively reduced from medium-range to long-range segments from being similar to hydrogen combustion for medium-range to 24% for large long-range aircraft, although fuel cell aircraft consume 22–30% more fuel than combustion aircraft. Results demonstrate a positive environmental impact of fuel cell propulsion for long-range applications, the possibilities of being a more emission-universal solution, if desired optimistic technology performance metrics are satisfied. The study also demonstrates progressively increasing technology requirements for larger aircraft, making the long-range application’s feasibility more challenging. Therefore, substantial development of fuel cell technologies for long-range aircraft is imperative. The article also emphasizes the importance of airframe and propulsion technologies and the necessity of green hydrogen production to achieve desired emissions.

Electroacoustic Liner for tonal and broadband noise attenuation of turbofans

The new generation of Ultra-High-By-Pass-Ratio (UHBR) turbofan engine while considerably reducing fuel consumption, threatens higher noise levels at low frequencies because of its larger diameter, lower number of blades and rotational speed. This is accompanied by a shorter nacelle, leaving less available space for acoustic treatments. Therefore, alternative solutions to classic liners are required. The SALUTE H2020 project has taken up this challenge, proposing electro-active acoustic liners, made up of loudspeakers (actuators) and microphones (sensors). The electro-active means allow to program the surface impedance on the electroacoustic liner, but also to conceive alternative boundary laws. Test-rigs of gradually increasing complexities have allowed to raise the Technology Readiness Level (TRL) up to 3-4. In this paper, we illustrate the control strategies and the experimental results achieved on the Phare2 test-bench. Phare2 is a reproduction of a real turbofan (scale 1:3), available in the Laboratory of Fluid Mechanics and Acoustics in the Ecole Centrale of Lyon. The noise attenuation accomplished by the electroacoustic liner is assessed by an antenna of microphones surrounding the turbofan inlet, and two rings of microphones placed upstream and downstream the liner in the nacelle. Both broadband and tonal noise are targeted with very promising results.

A numerical analysis of isolated propeller noise using a lattice Boltzmann method approach

Current environmental needs to achieve carbon neutral commercial aviation by 2050 require the development of new technologies and aircraft configurations. Among the different technological developments proposed, the use of open fan or Ultra-High Bypass Ratio configurations is of interest due to their higher propulsive efficiency and performance. To support the development of such technologies, accurate and efficient tools early in the design stages are needed to predict aerodynamic performances and noise levels. One such tool is the lattice Boltzmann method, which can perform high-fidelity aeroacoustic simulations of flows around propellers and engines. The lattice Boltzmann approach can be advantageous over other numerical methods due to its easy integration with complex geometries, its low numerical dissipation properties, and its high level of computational efficiency. This paper presents the aerodynamic and aeroacoustic numerical study of an isolated propeller using the commercial lattice Boltzmann solver ProLB. Large Eddy Simulations were carried out using a compressible hybrid thermal version of the solver. An aeroacoustic analysis using a Ffowcs-Williams and Hawkings acoustic analogy for far-field noise was carried out. The objective is to assess the capabilities of the solver to predict acoustic emissions of an isolated propeller towards the future study of an installed case.

Numerical and experimental investigations of diffusion-induced boundary layer separation on aero-engine nacelles

Aero-engine nacelles have to fulfill design requirements at both cruise and off-design conditions. Under engine windmilling conditions the ingested streamtube massflow is relatively low. A key off-design condition is take-off, which, in conjunction with an engine windmilling scenario, results in the stagnation point of the ingested streamtube being located significantly inside the intake. The combination of high angle of attack and low engine massflow rates leads to a strong flow acceleration and subsequent diffusion of the boundary layer on the upper quadrants of the external nacelle cowl, which can terminate with subsonic separation from the leading-edge. Under this condition, Reynolds number effects can play a dominant role on the separation onset and characteristics and 3D-annular wind tunnel tests cannot always achieve Reynolds’ number equivalent to full scale. A novel quasi-2D rig configuration representative of the aerodynamics of a full-size aero-engine nacelle under windmilling end of runway conditions examined in detail the characteristics of the boundary layer on the external cowl of a nacelle prior to diffusion-induced separation. Separation of the boundary layer was independently promoted through changes to represent different engine massflow rates and freestream Mach number on the rig to determine the limits of steady Reynolds Averaged Navier Stokes (RANS) methods to discern the onset of boundary layer separation. For the conditions and geometry investigated, the combined experimental and computational results showed that there was laminar to turbulent transition of the boundary layer ahead of the subsonic diffusion. The work showed that steady RANS can predict the onset of boundary layer separation with an uncertainty of approximately 10% on notional engine massflow rate and 0.05 on freestream Mach number relative to a nominal operating freestream Mach number of 0.25. This provides guidance for the industrial design and optimization of future windmilling-tolerant nacelles for large ultra-high bypass ratio turbofan engines.

Installed nacelle aerodynamics at cruise and windmilling conditions

PurposeThe decrease in specific thrust achieved by Ultra-High Bypass Ratio (UHBPR) aero-engines allows for a reduction in specific fuel consumption. However, the typical associated larger fan size might increase the nacelle drag, weight and the detrimental interference effects with the airframe. Consequently, the benefits from the new UHBPR aero-engine cycle may be eroded. This paper aims to evaluate the potential improvement in the aerodynamic performance of compact nacelles for installed aero-engine configuration.Design/methodology/approachDrooped and scarfed non-axisymmetric compact and conventional nacelle designs were down selected from a multi-point CFD-based optimisation. These were computationally assessed at a set of installation positions on a contemporary wide-body, twin-engine transonic aircraft. Both cruise and off-design conditions were evaluated. A thrust and drag accounting method was applied to evaluate different aircraft, powerplant and nacelle performance metrics.FindingsThe aircraft with the compact nacelle configuration installed at a typical installation position provided a reduction in aircraft cruise fuel consumption of 0.44% relative to the conventional architecture. However, at the same installation position, the compact design exhibits a large flow separation at windmilling conditions that is translated into an overall aircraft drag penalty of approximately 5.6% of the standard cruise net thrust. Additionally, the interference effects of a compact nacelle are more sensitive to deviations in mass flow capture ratio (MFCR) from the nominal windmilling diversion condition.Originality/valueThis work provides a comprehensive analysis of not only the performance but also the aerodynamics at an aircraft level of compact nacelles compared to conventional configurations for a range of installations positions at cruise. Additionally, the engine-airframe integration aerodynamics is assessed at an off-design windmilling condition which constitutes a key novelty of this paper.

A Rapid RI-TP Model for Predicting Turbine Wake Interaction Broadband Noise

Future UHBR (Ultra-High Bypass-Ratio) engines might cause serious ‘turbine noise storms’ but, at present, turbine noise prediction capability is lacking. The large turning angle of the turbine blade is the first major factor deserving special attention. The RANS (Reynold Averaged Navier–Stokes equation)-informed (here called RI) method and LINSUB (the bound vorticity 2D model LINearized SUBsonic flow in cascade), developed to predict fan broadband noise, coupled with a two-flat-plates (here called TP) assumption for the turbine blade, is applied here, and one autonomous rapid RI-TP model for predicting turbine wake interaction broadband noise has been developed. Firstly, taking the single axial turbine test rig NPU-Turb as the object, both the experimental data and the DDES/AA (delayed Detached Eddy Simulation/Acoustic Analogy) hybrid model have been used to validate the RI-TP model. High consistency in the medium and high frequencies among the three designed and off-designed rotation speeds indicates that the RI-TP model has the ability to predict turbine broadband noise rapidly. And compared with the original RANS-informed method, with one thin-flat-plate assumption on the blade, the RI-TP model can enhance the PWL (sound power level) in almost the whole spectral range below 10 KHz, which, in turn, is closer to the experimental data and the DDES/AA prediction results. The PWL trend with a ‘dividing point’ position is also studied. The spectrum would move up or down if the location is away from true value. In addition, the extraction location for turbulence as an input for the RI-TP model is negligible. In the future, multi-stage characteristics and the blade thickness effect should be further considered when predicting turbine noise.

Quantification of Blade Vibration Amplitude in Turbomachinery

Experimental monitoring of blade vibration in turbomachinery is typically based on blade-mounted strain gauges. Their signals are used to derive vibration amplitudes which are compared to modal scope limits, including a safety factor. According to industrial guidelines, this factor is chosen conservatively to ensure safe operation of the machine. Within the experimental campaign with the open-test-case composite fan ECL5/CATANA, which is representative for modern lightweight Ultra High Bypass Ratio (UHBR) architectures, measurements close to the stability limit have been conducted. Investigation of phenomena like non-synchronous vibrations (NSV) and rotating stall require a close approach to the stability limit and hence demand for accurate (real-time) quantification of vibration amplitudes to ensure secure operation without exhaustive safety margins. Historically, short-time Fourier transforms of vibration sensors are used, but the complex nature of the mentioned coupled phenomena has an influence on amplitude accuracy, depending on evaluation parameters, as presented in a previous study using fast-response wall-pressure transducers. The present study investigates the sensitivity of blade vibration data to evaluation parameters for different spectral analysis methods and provides guidelines for fast and robust surveillance of critical vibration modes.

A Review of Novel and Non-Conventional Propulsion Integrations for Next-Generation Aircraft

The aim of this review paper is to collect and discuss the most relevant and updated contributions in the literature regarding studies on new or non-conventional technologies for propulsion–airframe integration. Specifically, the focus is given to both evolutionary technologies, such as ultra-high bypass ratio turbofan engines, and breakthrough propulsive concepts, represented in this frame by boundary layer ingestion engines and distributed propulsion architectures. The discussion focuses mainly on the integration effects of these propulsion technologies, with the aim of defining performance interactions with the overall aircraft, in terms of aerodynamic, propulsive, operating and mission performance. Hence, this work aims to analyse these technologies from a general perspective, related to the effects they have on overall aircraft design and performance, primarily considering the fuel consumption as a main metric. Potential advantages but also possible drawbacks or detected showstoppers are proposed and discussed with the aim of providing as broad a framework as possible for the aircraft design development roadmap for these emerging propulsive technologies.

Windage Torque Reduction in Low-Pressure Turbine Cavities Part II: Experimental and Numerical Results

Abstract Minimizing the losses within a low-pressure turbine (LPT) system is critical for the design of next-generation ultra-high bypass ratio aero-engines. The stator-well cavity windage torque can be a significant source of loss within the system, influenced by the ingestion of mainstream annulus air with a tangential velocity opposite to that of the rotor. This paper presents experimental and numerical results of three carefully designed Flow Control Concepts (FCCs)—additional geometric features on the stator surfaces, which were optimized to minimize the windage torque within a scaled, engine-representative stator-well cavity. FCC1 and FCC2 featured rows of guide vanes at the inlet to the downstream and upstream wheel-spaces, respectively. FCC3 combined FCC1 and FCC2. Superposed flows were introduced to the upstream section of the cavity, which modelled the low-radius coolant and higher radius leakage between the rotor blades. In addition to torque measurements, total and static pressures were collected, from which the cavity swirl ratio was derived. Additional swirl measurements were collected using a five-hole aerodynamic probe, which traversed radially at the entrance and exit of the cavity. A cavity windage torque reduction of 55% on the baseline (which has no flow control) was measured for FCC3, at the design condition with superposed flow. For this concept, an increase in the cavity swirl in both the upstream and downstream wheel-spaces was demonstrated experimentally and numerically. With increasing superposed flow, the contribution of FCC1 surpassed FCC2, due to more mass flow entering the downstream wheel-space across the rotor fins (passing FCC1), and less ingestion from the annulus into the upstream wheel-space (passing FCC2). The torque changes from the concepts are explained using the fluid dynamic evidence from experimental swirl measurements and computational simulations. The simulations allow translation to engine-operating conditions and practical information to the engine designer.

Impact of 2D engine nacelle flow on buffet

Numerical studies on the interaction of nacelle and airfoil shock dynamics are performed. To keep the computational cost at an acceptable level, first 2D investigations on the interaction of nacelle and airfoil are performed that cover basic dynamic phenomena of this configuration. The transonic flow around the OAT15A airfoil is computed at buffet conditions, i.e., freestream Mach number Ma∞=0.73\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Ma{_\\infty } = 0.73$$\\end{document}, chord-based freestream Reynolds number Rec=2·106\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Re_c = 2\\cdot 10^6$$\\end{document}, and angle of attack α=3.5∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha = 3.5^\\circ $$\\end{document} using wall-modeled LES. Two configurations are considered, one which includes a generic 2D ultra-high bypass ratio (UHBR) engine nacelle geometry and one without an engine, which is denoted the baseline case. In addition to the airfoil shock, the flow field of the nacelle configuration is characterized by a shock wave on the upper part of the nacelle. Furthermore, the introduction of the UHBR-engine nacelle leads to a reduced effective angle of attack and Mach number in the flow to the airfoil. The changes in the topology of the flow to the airfoil caused by the nacelle lead to a reduced strength of the airfoil shock and a less developed buffet, which resembles the behavior close to the stability limit. The reduced shock dynamics yields lower pressure fluctuations at the airfoil trailing edge. A frequency analysis of time series data from the airfoil shock location shows a reduction of the buffet frequency for the nacelle configuration. Further investigations of the flow field dynamics using sparsity-promoting dynamic mode decomposition reveal a mutual mode between the airfoil shock and the nacelle shock. The existence of this mode has consequences for future investigations of nacelle airfoil interaction in transonic flow.

Powered turbofan effects on aircraft aerodynamics at high-lift: A study on the NASA CRM-HL

High-lift operating conditions of aircraft are known to comprise a series of complex physical features, making the three-dimensional flow difficult to discern and analyse. In such scenario, the effect of underwing engine installation, especially in the case of large-diameter ultra-high bypass ratio turbofans, has been little investigated. In this paper, we present a numerical study on the NASA High-Lift Common Research Model aircraft with powered turbofan engines, focused on the effect of propulsion system integration. A validated Computational Fluid Dynamics model is first employed to analyse the aerodynamics along the wing polar, at an angle of attack up to 18∘, close to near stall. The flow field on the suction side of aerodynamic surfaces is qualitatively similar to previous results obtained at lower Reynolds number for a throughflow nacelle, whereas on the pressure side a relevant distortion is present near the stall. The same case is simulated again by using a fully coupled Body Force Model fan stage representation, further inspecting the flow past the nacelle, the distribution of the propulsive forces, and the sensitivity of the fan working point to the operating incidence. The analysis reveals the complexity of the three-dimensional flow and the large azimuthal redistribution occurring on the nacelle, relative to an isolated configuration.

Acoustic absorption of the over-the-rotor liner applied to a ducted fan

The shortened intake length of the ultra-high bypass ratio engine leaves limited space for acoustic liner installation. The conventional intake liner has to extend to the proximity of the fan rotor to reach the same acoustic level, forming a so-called over-the-rotor (OTR) liner. Large eddy simulation method is used in this paper to analyze the acoustic absorption of the OTR liner. The results show that the dissipated energy of OTR liner orifices varies along the duct axial direction. The orifices close to the blade leading edge have the highest velocity and thereby dissipate the most energy. The magnitude and pattern of orifice velocity are different distinctly at the upstream and downstream of the rotor affected by the pressure distribution inside the duct as well as the blade surface. The time delay of orifice flow along the circumferential direction indicates that the motion of fluid inside of the orifice is primarily driven by the hydrodynamic pressure perturbance of the passing rotor. The OTR liner exhibits more complicated acoustic absorption characteristics than conventional intake liner so further investigation is necessary to understand the underlying mechanisms.

Effect of Unsteady Fan-Intake Interaction on Short Intake Design

Abstract The next generation of ultrahigh bypass ratio civil aero-engines promises notable engine cycle benefits. However, these benefits can be significantly eroded by a possible increase in nacelle weight and drag due to the typical larger fan diameters. More compact nacelles, with shorter intakes, may be required to enable a net reduction in aero-engine fuel burn. The aim of this paper is to assess the influence of the design style of short intakes on the unsteady interaction under crosswind conditions between fan and intake, with a focus on the separation onset and characteristics of the boundary layer within the intake. Three intake designs were assessed, and a hierarchical computational fluid dynamics (CFD) approach was used to determine and quantify primary aerodynamic interactions between the fan and the intake design. Similar to previous findings for a specific intake configuration, both intake flow unsteadiness and the unsteady upstream perturbations from the fan have a detrimental effect on the separation onset for the range of intake designs. The separation of the boundary layer within the intake was shock driven for the three different design styles. The simulations also quantified the unsteady intake flows with an emphasis on the spectral characteristics and engine-order signatures of the flow distortion. Overall, this work showed that is beneficial for the intake boundary layer to delay the diffusion closer to the fan and reduce the preshock Mach number to mitigate the adverse unsteady interaction between the fan and the shock.

Reduced Order Model of Nonlinear Structures for Turbomachinery Aeroelasticity

AbstractThis work concerns the numerical modeling of geometric nonlinear vibrations of slender structures in rotation using an original reduced order model based on the use of dual modes along with the implicit condensation method. This approach is an improvement of the classical ICE method in the sense that the membrane stretching effect is taken into account in the dynamic resolution. The dynamics equations are first presented and the construction of the reduced order model (ROM) is then proposed. The second part of the paper deals with numerical applications using the finite element method, first for a three-dimensional cantilever beam, then for an Ultra-High Bypass Ratio (UHBR) fan blade subject to aerodynamic loads. In the applications considered, the proposed method predicts more accurately the geometrically nonlinear behavior than the ICE method.

Influence of swirl and ingress on windage losses in a low-pressure turbine stator-well cavity

As part of the drive towards achieving net-zero flight by 2050, the development of ultra-high bypass ratio engines will place greater importance on the efficiency of the low-pressure turbine. Stator-well cavities can be a significant source of loss within this system, primarily due to the ingestion of annulus air, which can rotate at a speed less than that of the disc. This paper presents the results of a joint experimental/numerical campaign to relate windage torque to the flow physics in a scaled, engine-realistic stator-well geometry with superposed flows. The primary variables were the pressure ratio across the stator row and the swirl ratio at inlet to the cavity. This is the first paper to relate simultaneous torque and swirl measurements in a stator-well cavity. The numerical simulations have also provided insight into the fluid dynamic behaviour. A reduction in cavity windage torque with superposed flow rate was shown, consistent with the increase in swirl measured by experiments and predicted by computations. The pre-swirled superposed flows reduce the ingestion of negatively swirling fluid from the annulus, effectively increasing the swirl ratio of the flow in the cavity towards that of the rotor. This reduces windage losses; at the design condition with superposed flow, the cavity windage torque reduced by 60% of that of the reference case. Sealing effectiveness increased with superposed flow rate. This was demonstrated through gas concentration measurement/simulations, a reduced radial flow velocity into the cavity and a reduced mass flow rate across the interstage seal. The application of a turbulent transport model showed that ingestion could be explained by shear-driven diffusion. Ingestion increased as inlet swirl ratio reduced, while the pressure ratio was found to have a negligible influence on windage moment coefficient, swirl ratio and sealing effectiveness. In addition to providing fluid dynamic insight, the gas concentration results can be used for validating thermomechanical models. The results in this paper will be of practical interest to the engine designer who wishes to scale information to engine-operating conditions.

Investigation of the orifice flow of over-the-rotor liner and its interaction with the rotor flow field

The emergence of ultra-high bypass ratio engines calls for advanced noise control technology. A promising technology is installing the acoustic liner at the casing over the rotor (OTR), forming the so-called OTR liner. Experiments have shown that this treatment could compensate for the reduced noise absorption due to the shortened intake length. Compared with the conventional liner receiving a pure acoustic pressure excitation, the OTR liner is exposed to the combined aerodynamic pressure perturbance and high acoustic pressure excitation, leading to complex flow mechanisms in the liner orifices. In this work, the large-eddy simulation method is used to investigate the flow phenomenon of OTR liner where each liner orifice is explicitly modeled to capture the flow behaviors at the blade tip proximity. Interesting findings are as follows: first, OTR liner orifices have an asynchronous dynamic response with a phase lag corresponding to the blade traversing speed; second, oscillating flow, resembling that in a classical Helmholtz resonator, is formed in the upstream liner orifices, while a bias flow appears in the downstream liner orifices. The dramatically different flow behaviors lead to non-uniform energy dissipation among orifices, implying the uniform impedance assumption in conventional acoustic liner definition fails when installing the liner near the rotor blade. Results also show that the orifice flow interacts with the blade tip leakage flow, affecting the development of the tip leakage vortex that may impact the rotor–stator interaction noise.

On the reduction of the noise in a low-pressure turbine cascade associated with the wavy leading edge

The low-pressure turbine (LPT) has become a potential noise source for future ultra-high by-pass ratio engines. In this paper, the feasibility and mechanism of wavy leading edge (WLE) noise control in the LPT cascade model are analyzed. The flow field and acoustic data are obtained with the large eddy simulation and Ffowcs Williams–Hawkings methods, which are validated using experimental data. The acoustic results are compared for different models; the maximum noise reduction can achieve 8.6 and 3.7 dBA in the frequency bands of FR#2 (315–4000 Hz) and FR#4 (6300–16 000 Hz), respectively; the noise reduction does not vary proportionally to the WLE parameter. The noise source is identified in the baseline model, and then the effect of WLE amplitude and wavelength on the noise source and its control on pressure fluctuations are evaluated. The pressure statistics demonstrate that WLE with a smaller wavelength and a larger amplitude can reduce the impingement of stator wakes on the leading edge of the rotor and stabilize the pressure fluctuation. To analyze the mechanism of WLEs on noise control, the pressure spectrum in terms of amplitude and coherence coefficient is utilized to explain the excellent noise performance of the WLE model in FR#2. The proposed similarity coefficient of coherence can quantify the destructive interference level and thus the coherence characteristics of the sound source. Generally, the noise reduction level can be predicted by the combination of the similarity coefficient and the amplitude spectrum of the pressure fluctuations for the WLE models.

Аналіз впливу похибок вимірювання на абсолютні похибки експериментального визначення ККД вентилятора

The subject of research in this article is the experimental determination of the characteristics of fans of turbofan engines with a high and ultra-high bypass ratio. Increasing the efficiency of fans of engines of the specified class requires solving many complex interrelated problems, one of which is the determination of characteristics based on test results. The goal is to substantiate the need to use a method based on the determination of torque and the formation of requirements for the accuracy of its measurement. Tasks: clarification of previously obtained relationships between measurement errors and accuracy of determination of efficiency and air flow, formation of universal dependencies that allow analysis of absolute errors of determination of efficiency of any fan or compressor based on known measurement errors, analysis of the accuracy of alternative methods of organization of measurements and calculations the specified parameters, a comparative study of the specified methods and the formation of recommendations for their practical use on the example of the characteristics of a real fan. The following results have been obtained: the formulas that relate the absolute errors of calculating the efficiency and air flow with the absolute errors of the measured parameters (mathematical models of errors) have been clarified, as well as the requirements for the accuracy of the torque measurement necessary to determine the efficiency with the specified accuracy have been specified. The scientific and practical novelty of the results obtained is as follows: the mathematical models of errors in determining the efficiency and air flow in the fan have been clarified, which connect the errors of the calculation results with the errors of the measured parameters, because of the use of these models, experimental methods of determining the characteristics of compressors and fans have been developed; for the first time, the distribution of errors in the entire area of determining the characteristics of a specific fan was analyzed in detail. It is shown that the errors in determining the efficiency of the fan depend significantly on the degree of pressure increase and air flow. At small values of these parameters, the errors increase significantly. In the area of low engine operating modes (close to the area of the low air consumption), the errors in determining the efficiency based on the processing of the measurement results are so large that a reliable determination of the efficiency becomes practically impossible without the involvement of additional information, which can be used as the calculated characteristics of the fan, and as well as the mathematical model of the engine and the results of measuring parameters of the work process in other nodes, except for the fan itself.

Design Investigation of Potential Long-Range Hydrogen Combustion Blended Wing Body Aircraft with Future Technologies

Present work investigates the potential of a long-range commercial blended wing body configuration powered by hydrogen combustion engines with future airframe and propulsion technologies. Future technologies include advanced materials, load alleviation techniques, boundary layer ingestion, and ultra-high bypass ratio engines. The hydrogen combustion configuration was compared to the configuration powered by kerosene with respect to geometric properties, performance characteristics, energy demand, equivalent CO2 emissions, and Direct Operating Costs. In addition, technology sensitivity studies were performed to assess the potential influence of each technology on the configuration. A multi-fidelity sizing methodology using low- and mid-fidelity methods for rapid configuration sizing was created to assess the configuration and perform robust analyses and multi-disciplinary optimizations. To assess potential uncertainties of the fidelity of aerodynamic analysis tools, high-fidelity aerodynamic analysis and optimization framework MACH-Aero was used for additional verification. Comparison of hydrogen and kerosene blended wing body aircraft showed a potential reduction of equivalent CO2 emission by 15% and 81% for blue and green hydrogen compared to the kerosene blended wing body and by 44% and 88% with respect to a conventional B777-300ER aircraft. Advancements in future technologies also significantly affect the geometric layout of aircraft. Boundary layer ingestion and ultra-high bypass ratio engines demonstrated the highest potential for fuel reduction, although both technologies conflict with each other. However, operating costs of hydrogen aircraft could establish a significant problem if pessimistic and base hydrogen price scenarios are achieved for blue and green hydrogen respectively. Finally, configurational problems featured by classical blended wing body aircraft are magnified for the hydrogen case due to the significant volume requirements to store hydrogen fuel.

Air Ejector Analysis in Extended Operational Perimeter for Control Oriented Simulation of Bleed-Air Aircraft Systems

The integration of large size Ultra High Bypass Ratio (UHBR) engines introduces new restrictions of space for their integration with the aircraft wing. Under this scenario, a reduction of the size of the bleed air system and particularly of the pre-coolers is requested. The current research aims to introduce air-air ejectors as a potential solution. A combined methodology based on experimental and CFD analyses is proposed to obtain physical insights and validation material for the development of a robust and accurate lumped model, capable of simulating the static and dynamic ejector behaviour in normal and abnormal conditions. In this paper, an overview on the performed initial activities on the dynamic aspects is provided.