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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

A blue and white Boeing airplane flying with mountains and clouds in the background.

Structures tested; modeling developed

A spherical structure with beams and a central device is set against a backdrop of a planet and a bright light source, suggestive of space exploration equipment.

On-orbit demonstrations and ground tests push technology forward

A satellite with a large mesh antenna orbits above Earth, with blue oceans and white clouds visible in the background.

Deployable structures expand the capabilities of small satellites

Aerospace Outreach

A black and dark green World War II-era bomber aircraft with Canadian flags on it is parked on a tarmac, surrounded by trees and patches of grass under a clear sky.

Recognizing NASA’s 60th anniversary, World War I centennial

A formal gathering inside a hangar with a space shuttle and a large american flag in the background, attended by an audience in business attire.

Space commerce, drones draw legal interest

A vintage biplane with a radial engine and military roundel markings is parked on a grassy field, with another biplane in the background.

Olympics pay tribute to first hot air balloon flight, industry events call for preserving space artifacts

Aerospace Sciences

A photograph of a large, empty, rectangular steel chamber with a dark opening at the far end and two small windows on each side.

Facility improvements make progress amid heavy year of ground testing

Image showing two graphs: (a) Density and (b) Velocity, each with labeled coflow and jet dimensions, and color scales indicating density (0-1.8) and velocity (0-600 m/s), respectively.

Enabling diagnostics for opaque flows, complex surfaces and nonintrusive flow measurements

Visual simulation of fluid dynamics, showing four stages of airflow patterns and temperature gradients, represented by various colors and a scale ranging from 0 to 2.5e+00 on the right.

From micro-vortex generators to supersonic parachute dynamics, researchers glean deeper insights

Aircraft Technology, Integration and Operations

A large vehicle, covered in a bright blue tarp, is situated on a trailer in a spacious industrial workshop area. Various machinery and equipment are visible in the background.

Aircraft operators rebound but continue to struggle with delays

A parachute system is descending from the sky, carrying a cargo load suspended by strings against a clear blue sky.

Developing parachute systems and simulating fluid-structure interactions

A fleet of United-branded electric vertical takeoff and landing (eVTOL) aircraft hover near an airport runway at sunset.

Aircraft operations welcomes new Concept of Operations and focus on sustainability

Engineering and Technology Management

Solar Impulse 2

A year that caught public’s notice

Atmospheric picture of space

A century ago, aviation became an industry

Virgin Galactic’s second SpaceShipTwo

Accelerating change on systems engineering tenets

Information Systems

A person looking at a computer monitor displaying data charts and graphs. A bottle and some snacks are on the desk.

Advancing technologies for safety-critical applications

Atmospheric picture of space

Machine learning, quantum computing speed ahead

An unmanned aerial vehicle (UAV) flying over a vast desert landscape under a clear blue sky.

Pairing AI with human-machine teaming for the next step forward

Integration

Visualization of airflow simulation over an aircraft wing, showing turbulent flow patterns in shades of purple and pink, with a color scale indicating high to low velocity regions.

Continued progress toward the CFD Vision 2030 goals

Military personnel gather around and observe a large drone-like vehicle on a field. One individual in uniform is seated inside the vehicle, while another person stands nearby explaining.

Aerospace traffic management faces new challenges

A rocket engine is ignited, expelling colorful exhaust flames and smoke. The engine is partially enclosed in a structure with platforms and scaffolding visible in the background.

Pieces are coming together for CFD Vision 2030

Program Committees

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

rotating detonating engine

New and existing systems show progress

Propulsion and Energy

A close-up view of an aircraft engine undergoing testing while mounted on a test stand, showcasing intricate wiring and components against a clear sky background.

Gas turbine engines focus on decarbonization of commercial air travel

Robotic metallic device with a sharp, pointed front and windows, mounted inside an industrial facility.

Simulation and ground testing mark progress

Modern building with a multi-story, glass-front facade illuminated at night, displaying interior activity on both floors. Upper structure appears cantilevered, with office spaces visible through large windows.

Exploring high-speed propulsion for weapons, passenger aircraft

Space and Missiles

A series of four images showing a bird holding a long, rectangular object while flying against a cloudy sky background.

Small-satellite launches and opportunities increase

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 nighttime sky with a rocket launch, featuring a bright trail ascending diagonally, with the moon and stars visible through scattered clouds.

Missile defense tests show progress

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Studies yield hopeful results for saving fuel, meeting performance goals