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Propulsion and Energy

Studies yield hopeful results for saving fuel, meeting performance goals

By Jonathan S. Litt|December 2020

The Inlets, Nozzles and Propulsion Systems Integration Technical Committee focuses on the application of mechanical design, fluid mechanics and thermodynamics to the science and technology of air vehicle propulsion and power systems integration.

Between February and April, North Carolina-based Blue Force Technologies conducted a parametric study exploring shape characteristics appropriate for meeting common inlet design requirements. This study focused on inlets using serpentine (i.e., offset) diffuser shaping for low radar cross-section. Cost, complexity, size and radar cross-section are important constraints when designing relatively compact air intake systems with total pressure recovery and distortion characteristics suitable for existing commercial turbofan engines. Secondary flow features often migrate and coalesce within serpentine diffusers and are difficult to attenuate once they are established. The resulting flow defects persist to the engine face, impacting engine performance and operability. The methodical survey provided information about the secondary flow features within the diffuser and the design parameters that have the most influence on them, including diffuser length, centerline offset, aspect ratio distribution and area distribution. The study resulted in a database useful for the design of fixed-geometry, short-length, low-cost inlet systems capable of meeting a broader range of performance and operability requirements.

Clean Sky 2, the European program that promotes the development and testing of hybrid electric propulsion technology for 2035-era short- to medium-range airliners, announced multiple achievements by its research partners in the first half of the year.

In January, a research team from ONERA, the French national aerospace research center, announced results from a multidisciplinary design and performance analysis of a hybrid electric distributed propulsion concept known as DRAGON, or Distributed fans Research Aircraft with electric Generators by ONERA. DRAGON is an A320-like electrically powered aircraft concept using distributed fans along the wingspan on the pressure side in the rearward position. DRAGON is being used to mature transonic distributed electric propulsion. Results indicate 7% fuel burn reduction for a 2,750-nautical-mile (5,093-kilometer) design mission relative to a conventional configuration.

Also in January, NLR, the Netherlands Aerospace Center, announced results from an energy optimization study of a parallel hybrid electric propulsion system architecture retrofitted to a 150-passenger short-range Airbus A320neo, or new engine option, reference aircraft. Using a parametric system model and tool chain for HEP performance analysis and system optimization, NLR estimated reductions in fuel and total energy consumption of up to 7% and 5%, respectively, for short-range missions.

In June, DLR, the German Aerospace Center, shared results from two key studies. The first study involved an overall assessment of a hybrid electric A320 aircraft design concept. The assessment covered three variants, all powered by turbofan engines and electric motors, which aid the off-design engine operation in taxi and descent; the motors utilize electric power generated by solid-oxide fuel cells and a booster battery. The propulsion system architecture was designed to reduce fuel burn for off-design idle engine conditions, which accounts for about 10% of the total fuel consumption of the global A320 aircraft fleet. Off-design performance optimization resulted in estimated fuel savings of 4% to 9%. The second study involved an energy efficiency comparison between a partially turboelectric, boundary layer ingesting short-range aircraft concept and a conventional turbofan-engine-powered aircraft. The partially turboelectric concept utilizes a rear fuselage-mounted BLI inlet/fan driven by an electrical motor powered by two wing-mounted turbofan engines. DLR optimized the thrust fraction of the rear BLI fan for two powertrain technology levels (standard and advanced). Researchers observed block-fuel savings smaller than 2%.

Contributors: Tim Conners, Morgan Funderburk and Dyna Benchergui

2020 Year in Review

Aerospace Design and Structures

Image showing a solar panel array model with circular transparent discs and technical diagrams below. The setup appears to be part of an engineering or scientific experiment.

Morphing structures reach new heights, from tests on Earth to Mars

A sleek, black aircraft model inside a wind tunnel testing facility. The model is secured to the ground with cables and surrounded by metallic surfaces and equipment.

Structural dynamicists turn out important lab work despite another year of covid

A collage of two images. Left: A rocky, sandy landscape under a pale sky. Right: The shadow of a four-legged object with two protruding antennas cast on a similar sandy surface.

Space tourism flights show off distinctly different designs approaches

Aerospace Outreach

An airbus a330 aircraft, featuring a blue and white livery, takes off from an airport with a control tower in the background.

Industry sees increased profits, major acquisitions

A space station with solar panels orbits above Earth's atmosphere, with the vast blue planet and clouds visible in the background.

Celebrating 50 years since the launch of Skylab and other anniversaries

Airbus a330 in a hangar with flynas livery, undergoing maintenance with visible engine covers and detached wing components.

Programs encourage carbon-emission reductions

Aerospace Sciences

Close-up view of large metallic turbine blades inside an industrial facility. The blades are tightly grouped in a circular arrangement, reflecting light off their sleek surfaces.

Significant enhancements and improvements to test capability

Sequential grayscale images showing fluid flow at different angles (0° to 300°) for two cases: (a) φ = 0° and (b) φ = 120°. Orange, green, and yellow arrows indicate specific flow features.

Enhancing capabilities to measure, analyze and control fluid flows

A vertical stack of numerous identical satellite components arranged in a mirrored, symmetrical pattern inside a bright, high-ceilinged facility.

A year of exploration and commercialization of space

Aircraft Technology, Integration and Operations

A large airship is stationed inside a spacious hangar with a high, arched wooden ceiling. Several people in safety vests and helmets are gathered around it, and equipment is scattered throughout.

LTA Research building second, bigger zeppelin as first prepares for flight

An Airbus A321XLR aircraft flying above clouds with a clear blue sky in the background. The aircraft's markings and engines are visible.

Year of new designs, retirement of venerated models

Aircraft with tilt-rotor propellers in mid-flight against a clear blue sky.

Future vertical lift competition intensifies; eVTOL designs proliferate

Engineering and Technology Management

Blue Origin’s BE-4 engine for ULA’s Vulcan

Profits dip in aerospace, defense sectors

Virgin Galactic’s second SpaceShipTwo

Accelerating change on systems engineering tenets

Atmospheric picture of space

A century ago, aviation became an industry

Information Systems

A helicopter with the DARPA logo flies over a paved surface and adjacent sandy terrain.

Aerospace community continues to harness potential of human-machine teaming

A military man holding a tablet in a field.

UH-1 Huey flies autonomous resupply mission in test

Two airport ground staff in high-visibility vests walk beside a parked airplane at an airport. Other ground support equipment and vehicles are in the background.

Space and aviation sectors invest in community awareness, training and education to ward off increasing cyberattacks

Integration

Aerial view of a sleek, white jet with blue accents flying over rugged, mountainous terrain partially covered by clouds.

Bringing civil supersonic flight closer to fruition

Engineers and workers inside a large industrial facility assembling sections of a rocket or space vehicle with various equipment and machinery visible around.

Space exploration focuses on asteroids

An overhead view of a partially constructed aircraft surrounded by scaffolding and equipment in an industrial facility with workers in the background.

Low-boom technologies gain ground with improved measurement tools and more research

Program Committees

A large cylindrical object is positioned in the center of an industrial facility with yellow overhead cranes and metallic structures.

Space Launch System keeps pace

Tests at the Lockheed Martin Low Speed Wind Tunnel in Ohio

Going green moves to higher gear

NASA Electric Aircraft Testbed in Sandusky, Ohio

Electric efforts gaining power

Propulsion and Energy

A machine with glowing components and visible wires is housed in an industrial setting with concrete walls and pipes.

Taking off from Earth to space with pressure gain combustion research

A sleek prototype supersonic jet with the registration number N990XB is on a runway with rugged mountains in the background.

Accelerating toward hypersonic civilian flight

A man in a lab coat standing next to a machine.

Powering InSight, Parker Solar Probe on their missions

Space and Missiles

A spacecraft orbits above Earth, with the planet's blue surface and white clouds visible below. An open hatch is noted on the spacecraft's exterior.

Another record-setting year for spaceflight

A dark background with Earth visible as a small bright dot slightly off-center, part of a satellite or spacecraft structure is visible along the right edge of the image.

Small satellites capable of big science

A close-up image of a metallic object with a sharp edge, illuminated against a dark background.

U.S. military awards contracts for wide-ranging hypersonics projects

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Studies yield hopeful results for saving fuel, meeting performance goals