Low-Noise Design of Medium-Range Aircraft for Energy Efficient Aviation

Promising low-noise aircraft architectures have been identified over the last few years at DLR. A set of DLR aircraft concepts was selected for further assessment in the context of sustainable and energy-efficient aviation and was established at the TU Braunschweig in 2019, the Cluster of Excellence for Sustainable and Energy-Efficient Aviation (SE2A). Specific Top-Level aircraft requirements were defined by the cluster and the selected DLR aircraft designs were improved with focus on aircraft noise, emissions, and contrail generation. The presented paper specifically addresses the reduction of aviation noise with focus on noise shielding and modifications to the flight performance. This article presents the state of the art of the simulation process at DLR and demonstrates that the novel aircraft concepts can reduce the noise impact by up to 50% in terms of sound exposure level isocontour area while reducing the fuel burn by 6%, respective to a conventional aircraft for the same mission. The study shows that a tube-wing architecture with a top-mounted, forward-swept wing and low fan pressure ratio propulsors installed above the fuselage at the wing junction can yield significant noise shielding at improved low-speed performance and reduce critical fuel burn and emissions.

Performance-Based Navigation Flight Path Analysis Using Fast-Time Simulation

The growing demand for air transportation has led to an increase in worldwide air traffic inefficiency due to capacity constraints. The impacts associated with this situation can be reduced through operational changes. To better handle the problem, the Single European Sky ATM Research (SESAR) and the Next Generation Air Transportation System (NextGen) program suggest Performance-Based Navigation (PBN) as a solution. The Area Navigation (RNAV) and Required Navigation Performance (RNP) approaches belong to the group of PBN procedures. These procedures allow for a more efficient use of airspace by reducing route distances, fuel consumption and perceived aircraft noise. This article quantifies the benefits of PBN systems for two indicator parameters—fuel burn and flight time—and compares PBN systems to conventional instrument navigation procedures. The case studies use five airports in Brazil. The results of this analysis show that the benefits of the PBN approach vary with aircraft type and individual route characteristics.

Design Exploration and Performance Assessment of Advanced Recuperated Hybrid-Electric UAM Rotorcraft

The design of efficient, environmentally friendly and quiet powerplant for rotorcraft architectures constitutes a key enabler for Urban Air Mobility application. This work focuses on the development and application of a generic methodology for the design, performance and environmental impact assessment of a parallel hybrid-electric propulsion system, utilizing simple and advanced recuperated engine cycles. A simulation framework for rotorcraft analysis comprising models for rotor aerodynamics, flight dynamics and hybrid-electric powerplant performance is deployed for the design exploration and optimization of a hybrid-electric rotorcraft, modelled after the NASA XV-15, adapted for civil applications. Optimally designed powerplants for payload-range capacity, energy efficiency and environmental impact have been obtained. A comparative evaluation has been performed for the optimum designs. The respective trade-offs between engine, heat exchanger weight, thermal efficiency, as well as mission fuel burn and environmental impact have been quantified. It has been demonstrated that a recuperated gas turbine based hybrid-electric architecture may provide improvements of up to 6% in mission range capability without sacrificing useful load. At the same time, analyses performed for a representative 100 km mission suggest reductions in fuel burn and NOX emissions of up to 12.9% and 5.2% respectively. Analyses are carried at aircraft and mission level using realistic UAM mission scenarios.

Sustainable Technology on Aircraft Design: A Review

Next-generation air transportation is a key to influence the environment, safety, and the economy. Several programs strive to create emerging innovation towards sustainability, system integrity, and alternative fuels to guarantee a reduction of its environmental effect as greenhouse gas. Nowadays, the aerospace industry is looking forward to aviation sustainable developments across the globe. Few initiatives through a novel configuration of aircraft is established like Blended Wing Body, Flying V aircraft, Box wing Aircraft, and Double bubble Aircraft to enhance the cargo and passenger volume occupancy and cut-off the fuel burn percent. With the use of disruptive technologies, researchers are progressing the revolutionary airframe for transportation. A systematic overview and comprehensive survey of passenger-based aircraft are investigated. The objective study is to examine fuel burn and its impact on the environment by types of aircraft. In-depth literature review studies on four pillar strategies used to design an efficient airplane. In addition, this paper also serves on advancement in evolutionary technologies used in jet transport aircraft. Reflecting the benefits and challenges of different aircraft designs technologies were also highlighted. This paper highlights the future implications and managerial insights for future aircraft designers.

Fuel Performance Modelling At High Burn-Up by FEMAXI-6 Code

The scope of current research in the field of fuel performance is primary aimed to an improvement of the operating reliability, safety and cost effectiveness of the reactors in operation. The current requirement of nuclear industry is to have fuel suitable for load follow operation. Fission gas release, Pellet-Cladding Mechanical Interaction and stress corrosion cracking are the main phenomena that limit the variability of reactor operation from a safety perspective. To reasonable predict the fuel performance limits it is necessary to benchmark the computational tools against high quality experimental data. This work is devoted to the calculation of fuel performance using the code FEMAXI-6 based on the longest irradiation experiment in the Halden reactor. The fuel burn-up was approaching 90 MWd/kgUO2 in three selected rods which were equipped by the pressure sensors and were subjected to extensive post-irradiation examination. During the experiment, the rods were exposed to several periods of power cycling. The rods were manufactured with different fuel grain size and fuel-to-clad gap size.

A study on the core loading pattern of the VVER-1200/V491

The VVER-1200/V491 was a selected candidate for the Ninh Thuan I Nuclear Power Plant.However, in the Feasibility Study Safety Analysis Report (FS-SAR) of the VVER-1200/V491, the core loading pattern of this reactor was not provided. To assess the safety features of the VVER- 1200/V491, finding the core loading patterns and verifying their safety characteristics are necessary. In this study, two core loading patterns of the VVER-1200/V491 were suggested. The first loading pattern was applied from the VVER-1000/V446 and the second was searched by core loading optimization program LPO-V. The calculations for power distribution, the effective multiplication factor (k-eff), and fuel burn-up were then calculated by SRAC code. To verify several safety parameters of loading patterns of the VVER-1200/V491, the neutron delayed fraction (DNF), fuel andmoderator temperature feedbacks (FTC and MTC) were investigated and compared with the safety standards in the VVER-1200/V491 FS-SAR or the VVER-1000/V392 ISAR.

Experimental Investigation of Secondary Flows and Length Reduction for a Low-Pressure Compressor Transition Duct

The need to reduce fuel-burn and emissions, is pushing turbofan engines towards geared architectures with higher bypass ratios and small ultra-high-pressure ratio cores. However, this increases the radial offset between compressor spools leading to a more challenging design for compressor transition ducts. For the duct connecting the fan to the engine core this is further complicated by poor-quality flow generated at the fan hub which is characterised by low total pressure and large rotating secondary flow structures. This paper presents an experimental evaluation of a new rotor designed to produce these larger flow structures and examines their effect on the performance of an engine sector stators (ESS) and compressor transition duct. Aerodynamic data were collected via five-hole probes, for time-averaged pressures and velocities and phase-locked hot-wire anemometry to capture the rotating secondary flows. The data showed that larger structures promoted mixing through the ESS increasing momentum exchange between the core and boundary layer flows. Measurements within the duct showed a continued reduction in the hub boundary layer suggesting the duct had moved further from separation. Consequently, an aggressive duct with 12.5% length reduction was designed and tested and measurements confirmed the duct remained fully attached. Total pressure loss was slightly increased over the ESS, but this was offset by reduced loss in the duct due to improved flow quality. Overall, this length reduction represents a significant cumulative effect in reduced fuel-burn and emissions over the life of an engine.

Aircraft descent performance based on flight data

There are significant variations in the fuel consumption of aircraft during the descent phase of a flight. This paper uses aircraft flight data measurements to develop an improved understanding of these variations. A model of the aircraft engines is developed that is matched to flight data and shown to reproduce the time history of engine parameters. This model is used to determine the overall engine efficiency at each point during a descent. This enables an energy breakdown to be completed, in terms of mechanical energy from fuel, gravitational potential energy and kinetic energy. During descent, the aircraft engines operate at low overall pressure ratios corresponding to low fuel flow rates and low overall efficiencies. On average, the engine overall efficiency during descent is one-third of cruise efficiency. The airframe aerodynamic performance is deteriorated during descent with an average lift-to-drag ratio that is 87% of the average value at cruise. There are also large variations in air-track efficiency, and for the flights analysed the great circle descent distance was found to be 85% of the average descent air distance. To minimise fuel burn, flights should cruise as far as possible before starting descent and follow a trajectory with the shortest possible air distance. The descent air speed should be set to maximise the aircraft lift-to-drag ratio. Such descents could save up to 0.5% of the total aircraft mass in fuel.

A Simple Model for Wildland Fire Vortex–Sink Interactions

A model is developed to explore fire–atmosphere interactions due to the convective sink and vorticity sources in a highly simplified and idealized form, in order to examine their effect on spread and the stability of various fire front geometries. The model is constructed in a cellular automata framework, is linear, and represents a background flow, convective sink, and vortices induced by the fire plume at every burning cell. We use standard techniques to solve the resulting Poisson equations with careful attention to the boundary conditions. A modified Bresenham algorithm is developed to represent convection. The three basic flow types—large-scale background flow, sink flow, and vortex circulation—interact in a complex fashion as the geometry of the fire evolves. Fire-generated vortex–sink interactions produce a range of fire behavior, including unsteady spread rate, lateral spreading, and dynamic fingering. In this simplified framework, pulsation is found associated with evolving fire-line width, a fire-front acceleration in junction fires, and the breakup of longer initial fire lines into multiple head fires. Fuel is very simply represented by a single burn time parameter. The model fuel is uniform yet patchiness occurs due to a dynamic interaction of diffusive and convective effects. The interplay of fire-induced wind and the geometry of the fire front depends also on the fuel burn time.