Integrated Propulsion System Research Articles

On Intake–Compressor Interactions Within an Integrated Propulsion System

Abstract The integration of a propulsion system into the airframe can contribute to the overall aircraft performance and is beneficial for military applications due to a reduction of the aircraft radar cross section. On the other hand, engine integration calls for serpentine engine intake systems in which generally combined pressure-swirl distortions are provoked, which affect the performance of the propulsion system. The military engine intake research duct was designed to provoke a large-scale flow separation as well as a combined pressure-swirl distortion. The serpentine research duct is tested in both a remote- and close-coupled setup with the Larzac 04 turbofan engine to assess the aerodynamic interactions between the flow within the intake duct and the compression system. The upstream effect of the compression system on the steady-state duct flow is within the range of expectations. Less is known from the open literature with regard to the unsteady character of the flow in such a setup. Three distinct unsteady flow phenomena caused by the serpentine shape of the duct are identified up- and downstream of the low pressure compressor in the remote-coupled setup. An additional distinct low frequency unsteadiness is provoked with a configuration which features vortex generators for flow control. All phenomena are largely attenuated by the upstream effect of the compressor in the close-coupled setup. Nonetheless, the surge margin is massively reduced due to the inflow distortion and stall cells within the first stage of the low pressure compressor are visualized at high thrust settings of both the remote- and close-coupled setup, which are expected to impact the durability of the compression system.

Electromagnetic Characteristics Analysis and Thrust Fluctuation Optimization in Integrated Propulsion, Levitation, and Guidance Systems

Electromagnetic Characteristics Analysis and Thrust Fluctuation Optimization in Integrated Propulsion, Levitation, and Guidance Systems

Trend Research on Maritime Autonomous Surface Ships (MASSs) Based on Shipboard Electronics: Focusing on Text Mining and Network Analysis

The growing adoption of electric propulsion systems in Maritime Autonomous Surface Ships (MASSs) necessitates advancements in shipboard electronics for safe, efficient, and reliable operation. These advancements are crucial for tasks such as real-time sensor data processing, control algorithms for autonomous navigation, and robust decision-making capabilities. This study investigates research trends in MASSs, using bibliographic analysis to identify policy and future research directions in this evolving field. We analyze 3363 MASS-related articles from the Web of Science database, employing co-occurrence word analysis and latent Dirichlet allocation (LDA) topic modeling. The findings reveal a rapidly growing field dominated by image recognition research. Keywords such as “datum”, “image”, and “detection” suggest a focus on collecting and analyzing marine data, particularly with deep learning for synthetic aperture radar imagery. LDA confirms this, with “image analysis and classification research” as the leading topic. The study also identifies national and organizational leaders in MASS research. However, research on Arctic routes lags behind that on other areas. This work provides valuable insights for policymakers and researchers, promoting a deeper understanding of MASSs and informing future policy and research agendas regarding the integration of electric propulsion systems within the maritime industry.

Abating CO2 and non-CO2 emissions with hydrogen propulsion

Abstract This contribution focuses on the abatement with hydrogen of CO2 and non-CO2 emissions. It is agenda-setting in two respects. Firstly, it challenges the globally accepted hydrocarbon sustainable aviation fuel (SAF) pathway to sustainability and recommends that our industry accelerates along the hydrogen pathway to ‘green’ aviation. Secondly, it reports a philosophical and analytical investigation of appropriate accuracy on abatement strategies for nitrogen oxides and contrails of large hydrogen airliners. For the second contribution, a comparison is made of nitrogen oxide emissions and contrail avoidance options of two hydrogen airliners and a conventional airliner of similar passenger capacity. The hydrogen aircraft are representative of the first and second innovation waves where the main difference is the weight of the hydrogen tanks. Flights of 1000, 2000, 4000 and 8000 nautical miles are explored. Cranfield’s state of the art simulators for propulsion system integration and gas turbine performance (Orion and Turbomatch) were used for this. There are two primary contributions to knowledge. The first is a new set of questions to be asked of SAF and hydrogen decarbonising features. The second is the quantification of the benefits from hydrogen on non-CO2 emissions. For the second generation of long-range hydrogen-fuelled aircraft having gas turbine propulsion, lighter tanks (needing less thrust and lower gas temperatures) are anticipated to reduce NOx emissions by over 20%; in the case of contrails, the preliminary findings indicate that regardless of the fuel, contrails could largely be avoided with fuel-burn penalties of a few per cent. Mitigating action is only needed for a small fraction of flights. For conventional aircraft this penalty results in more CO2, while for hydrogen aircraft the additional emission is water vapour. The conclusion is that our research community should continue to consider hydrogen as the key ‘greening’ option for aviation, notwithstanding the very significant costs of transition.

The design and development of an Integrated Propulsion System – Phase 1: the wheel architecture

The paper presents the design and development of an integrated powertrain system where the suspension system is also included in the wheel together with the electric machine. Based on a patent of one of the authors, the solution was virtually developed and tested. Different advancements were performed during the development phases for choosing the final architecture. Currently, the integrated propulsion system is manufactured and implemented on a L6E road vehicle to be tested and optimized.

The design and development of an Integrated Propulsion System – Phase 2: the functional electric behaviour strategy

The paper presents the integrated propulsion system implementation steps on a L6E road vehicle. The implementation followed several technical levels which are properly described within the paper. The functional behaviour in terms of electric propulsion was defined and developed. All the dedicated components were investigated, set and customized, to equip a L6E vehicle. Currently the electric machine, the battery pack, the user interface, the speedometer, the pedals, the power electronics etc. are implemented on a real existing L6E road vehicle, after they were defined and virtually tested.

The design and development of an Integrated Propulsion System – Phase 3: the testing bench

The paper presents the testing bench dedicated to the integrated propulsion system (IPS). The IPS consists of a wheel that carries the electric machine and the suspension inside. Its behaviour needs to be tested while being used independently on a test bench and then on road tests. Because no already existing testing bench was available for this kind of testing, a dedicated testing bench was designed and developed. Its main role is to investigate the functional behaviour of the wheel, together with the integrated suspension system behaviour. The tests were made following different scenarios, where different tire dimensions, different environment properties, different road profiles etc. were reproduced.

Overview of safety challenges associated with integration of hydrogen-based propulsion systems for climate neutral aviation

Electrification through hydrogen-based fuel cells as well as hydrogen combustion in gas turbines is a key strategy in aviation for achieving substantial reduction of emissions. However, this transition presents multifaceted challenges. Besides the development and improvement of technologies required for such hydrogen-fuelled aero engines, the safety of hydrogen storage and distribution systems on aircraft is paramount. Challenges associated with hydrogen in terms of its material properties, the design and selection of components for the conditioning and distribution, as well as the system design are being presented and discussed in this work. This includes the consideration of high diffusivity, flammability and reactivity of hydrogen and the consequences of these traits: hydrogen embrittlement, hydrogen-induced cracking and leakage, for instance. The challenges elaborated in this work are pertinent to both hydrogen fuel cell-based propulsion systems and hydrogen combusting gas turbines. Design considerations were derived and are being outlined in this work. These are transferable to applications in other industries such as automotive and stationary power plants. The need for novel rigorous safety protocols to enable a sustainable future in aviation is being highlighted.

H2Electra – a platform for comparative analysis of integration concepts for hydrogen-based electric propulsion in regional aircraft

Over the past decade numerous novel concepts for electric flight have been elaborated. Each unique in its own way and based on various assumptions and technological advances projected for the future. Within each concept design decisions have to be made on component level, propulsion system level and aircraft level. In order to be able to evaluate and analyse both, advanced components technologies and innovative propulsion system architectures, as well as to understand the effect of each design decision, a common baseline platform has been developed to allow for comparative analyses.This work presents such a platform with the hydrogen-based electrified regional aircraft concept called H2Electra. The iterative design process developed for this purpose is presented. It allows for a holistic approach to the development of an aircraft, its electrified propulsion system as well as the sizing of the components therein. Two propulsion system integration concepts are being considered in the evaluation: one partially fuselage-integrated and one nacelle-integrated. Challenges and trade-offs between the two concepts were analysed and evaluated, with safety and reliability being key design and decision-making metrics, alongside block-fuel efficiency and power density. In particular, the design decision on a suitable bus voltage and its effect on the powertrain sizing and integration were investigated.

Aerodynamic Instabilities in High-Speed Air Intakes and Their Role in Propulsion System Integration

High-speed air intakes often exhibit intricate flow patterns, with a specific type of flow instability known as ‘buzz’, characterized by unsteady shock oscillations at the inlet. This paper presents a comprehensive review of prior research, focused on unraveling the mechanisms that trigger buzz and its implications for engine stability and performance. The literature survey delves into studies concerning complex-shaped diffusers and isolators, offering a thorough examination of flow aerodynamics in unstable environments. Furthermore, this paper provides an overview of contemporary techniques for mitigating flow instability through both active and passive flow control methods. These techniques encompass boundary layer bleeding, the application of vortex generators, and strategies involving mass injection and energy deposition. The study concludes by discussing future prospects in the domain of engine-intake aerodynamic compatibility. This work serves as a valuable resource for researchers and engineers striving to address and understand the complexities of high-speed air induction systems.

Potential for Energy Recovery from Boundary-Layer Ingesting Actuator Disk Propulsion

The theoretical benefits of highly integrated propulsion systems are highlighted herein by assessing the potential for energy recovery utilization using actuator disk propulsion. Decomposing aerodynamic forces into thrust and drag for closely integrated bodies, particularly those employing boundary-layer ingestion, becomes challenging. In this work, a mechanical energy-based approach was taken using the power balance method. This allowed the performance to be analyzed through the mechanical flow power in the fluid domain, disregarding the need for any explicit definition of thrust and drag. Through this, the benefit of boundary-layer ingestion was observed from a wake energy perspective as a decrease in the downstream mechanical energy deposition and associated viscous dissipation. From a propulsion perspective, the reduction in power demand necessary to produce propulsive force indicated the possibility of power savings by utilizing the energy contained within the ingested boundary-layer flow.

Integrated Propulsion System Analysis Framework for Designing Advanced Air Mobility Aircraft

Integrated Propulsion System Analysis Framework for Designing Advanced Air Mobility Aircraft

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.

On the Method for Estimating the Integral Characteristics of a Generic Scramjet with an Integrated Propulsion System

On the Method for Estimating the Integral Characteristics of a Generic Scramjet with an Integrated Propulsion System

Multi-objective shape optimization of doubly offset serpentine diffuser using Adjoint method

Doubly offset serpentine diffusers are needed in the compact designs of modern stealth fighters with highly integrated propulsion systems. In addition, these doubly offset serpentine diffusers are also essential to provide reduced radar cross-section (RCS) due to the blockage of a complete line of sight. In this research, shape optimization of the doubly offset serpentine diffuser is achieved using a multi-objective approach to maximize the pressure recovery (PR) and minimize the flow swirl angle (α) and distortion coefficient (DC) at the aerodynamic interface plane (AIP). A computationally efficient Adjoint-based method was implemented for the optimization. For baseline geometry, an additional offset is added to NASA’s M2129 single serpentine duct to make it doubly offset serpentine diffusers. The freeform deformation technique was used to parametrize the baseline shape using 180 control points. A steady-state flow solution through the diffuser was achieved by solving Reynolds-Averaged Navier-Stokes (RANS) equations using a general-purpose computational analysis tool, i.e., ANSYS Fluent. The sensitivity of objective functions from the Adjoint solver was used to compute the required design change in the direction of minima or maxima of the objective functions using the steepest descent optimization technique. Subsequently, the calculated design changes were implemented through mesh Morpher. The Adjoint-based approach and freeform deformation resulted in a powerful and efficient optimization framework. The optimized shape showed a significant reduction in distortion coefficient and flow swirl angle, along with a slight increase in pressure recovery.

Dynamics performance of long combination vehicles with active control systems

A state-of-the-art review of the dynamics of long combination vehicles (LCVs) is provided. The performance-based standards (PBS) that are commonly used globally are reviewed, including those in Canada and Australia. The discussions include the low-speed and high-speed longitudinal, lateral, and yaw performance of LCVs, which in many respects are different than the conventional tractor-semitrailers. The low-speed discussions include the vehicle startability, gradeability, acceleration, and offtracking. The high-speed considerations include rollover dynamics, braking distance and time, overtaking, down-grade holding, and ride quality. Some of the latest development in actively controlled (intelligent) systems to improve LCVs’ dynamic performance is emphasised, such as hill-start assist (HAS), roll stability control (RSC), electronic stability control (ESC), electrified dolly (e-dolly), active trailer steering (ATS), active braking, slip control (SC), active trailer differential braking (ATDB), active and semi-active antiroll bars, and active and semi-active suspensions. The study concludes that although great progress has been made during the past two decades for integrating advanced, intelligent, electromechanical systems in LCVs, much more work remains to address some of the future environmental and performance demands, particularly considering the integration of electrical and alternative-fuel propulsion systems in heavy commercial vehicles.

CFD-Based Analysis of Installed Fuel Consumption and Aerodynamics of Transonic Transport Aircraft during Cruise Flight

Gas turbine fuel burn for an aircraft engine can be obtained analytically using thermodynamic cycle analysis. For large-diameter ultra-high bypass ratio turbofans, the impact of nacelle drag and propulsion system integration must be accounted for in order to obtain realistic estimates of the installed specific fuel consumption. However, simplified models cannot fully represent the complexity of installation effects. In this paper, we present a method that combines thermodynamic cycle analysis with detailed Computational Fluid Dynamics (CFD) modelling of the installation aerodynamics to obtain the fuel consumption at a given mission point. The flow field and propulsive forces arising in a transport aircraft powered by an ultra-high bypass ratio turbofan at cruise are first examined to characterise the operating conditions and measure the sensitivity to variations of the incidence at transonic flight. The proposed methodology, in which dynamic balance of the vehicle is achieved at each integration point, is then applied along a cruise segment to calculate the cumulative fuel burn and the change in the specific fuel consumption.

On the Method for Estimating the Integral Characteristics of a Generic Scramjet with an Integrated Propulsion System

On the Method for Estimating the Integral Characteristics of a Generic Scramjet with an Integrated Propulsion System

A kW-level integrated propulsion system for UAV powered by PEMFC with inclined cathode flow structure design

Open-cathode air-cooling polymer electrolyte membrane fuel cells (PEMFCs) with the lightweight and simple structure are widely used in state-of-the-art UAVs. In this work, a 1 kW-level PEMFC powered propulsion system with an inclined cathode flow structure is developed. The inclined cathode flow structure uses the airflow behind the blade root of the propeller to meet the reaction and cooling requirements of the PEMFC cathode. Such design discards the cathode axial fan in the current commercial PEMFC system and reduces the parasitic power, weight and volume caused by the axial fan. Compared with the current commercial PEMFC powered propulsion system, the specific power of the 1 kW PEMFC system, power-to-weight ratio and thrust-to-weight ratio of the 1 kW integrated propulsion system are increased by 33.0 %, 23.8 %, and 18.3 %, respectively. Besides, the space in the fuselage for the fuel cells and the weight of distribution wiring, as well as the wire loss, is also significantly saved by replacing the axial fan with proposed inclined cathode flow structure.

Dual-Solver Hybrid Computational Approach to Integrated Propulsion Aerodynamics

The demand for high-efficiency air vehicles and the development of distributed electric propulsion systems for aircraft are exposing the need for accurate aerodynamic prediction of multiple integrated propulsion systems. Conventional high-fidelity computational methods are too expensive, and low-cost low-fidelity methods make too many aerodynamic assumptions to be applied to these analyses. Dual-solver hybrid computational fluid dynamics (CFD) methods bridge the gap between these two categories of solvers, but many lack capabilities that are needed for complex vehicles. Recent improvements to the hybrid solver OVERFLOW-CHARM provide efficient and accurate analysis of integrated propulsion systems with hybrid CFD methods, as demonstrated on the wing–propeller system of the AIAA Workshop for Integrated Propeller Prediction. Predictions of propeller thrust are within 1% of conventional CFD data, and wing pressure coefficient distributions agree well with both experimental data and conventional CFD methods. The dual-solver results were obtained at half the computational cost of the full CFD simulation.