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Technical Paper

A Method of Shared Regenerative Power Management

The characteristics of large electrical loads encountered in the modern More Electric Aircraft (MEA) require regenerative power processing in order to preserve the power quality within acceptable transient and steady state limits. In an MEA with large active loads and pulsed power demands, it is necessary to employ an architecture that safely and effectively processes regenerative energy resulting from the dynamic loads. For instance, the electrical flight control actuation presents one of the largest regenerative power sources encountered by the generation system. Typical approach is to dissipate this energy through resistors of the power electronics which increases the size and penalizes the aircraft.
Technical Paper

Potential Technology to Unclog Hot Day Operational Limit

Fuel has been a popular choice for thermal system designers to use for absorbing aircraft accessory heat load due to its consumable nature. However, the shortcoming of using fuel as a heat sink is the dependency of environmental conditions. This deficiency has plagued the current United States Air Force fleet operation especially performing ground hold and low altitude attack mission during hot days. A Northrop Grumman led industrial team, commissioned by AFRL Power directorate through the INVENT program, has vigorously explored potential technologies to assist air force to enhance the mission capability. The results show various promising technologies not only can extend the hot day operational limit but also can potentially have an unrestricted capability. This paper describes the results from the study performed by Northrop Grumman for an advanced unmanned air vehicle (AUAV) for potential technologies and discusses the modeling approach in support of the analytical process.
Journal Article

A Hybrid Economy Bleed, Electric Drive Adaptive Power and Thermal Management System for More Electric Aircraft

Minimizing energy use on more electric aircraft (MEA) requires examining in detail the important decision of whether and when to use engine bleed air, ram air, electric, hydraulic, or other sources of power. Further, due to the large variance in mission segments, it is unlikely that a single energy source is the most efficient over an entire mission. Thus, hybrid combinations of sources must be considered. An important system in an advanced MEA is the adaptive power and thermal management system (APTMS), which is designed to provide main engine start, auxiliary and emergency power, and vehicle thermal management including environmental cooling. Additionally, peak and regenerative power management capabilities can be achieved with appropriate control. The APTMS is intended to be adaptive, adjusting its operation in order to serve its function in the most efficient and least costly way to the aircraft as a whole.
Technical Paper

Electric Thermal Management Architectures

The escalation of vehicle operating costs due to continuously rising fuel prices has prompted aircraft designers to focus on more energy efficient designs. Among the heavy energy consumers in aircraft operations, the thermal management system is one of the largest. This is especially true of the refrigeration system powered by engine bleed air power. With the push towards more electric vehicles, an entirely new trade space has been opened up with regards to electric thermal management and the cost of bleed air versus electrical power. Despite favorable energy savings, the electric approach has increased the burden on the propulsion engine shaft power extraction systems (gearbox and drive train), electrical generators, power conditioning units, and electrical distribution systems. This paper presents potential architectures which utilize energy recovery and integration principles to address the challenges on the power generating system.
Journal Article

Power & Thermal Systems Integration Techniques for High Performance Jet Aircraft

The high electrical power demand and heat rejection characteristics of a high energy laser pose new challenges to airframe power and thermal system designers. Typically, the power demand requires additional power storage devices and electrical generator upsizing which will adversely impact the engine performance and installation envelope. The thermal system is complicated by an already limited onboard heat sink, resulting in a bulkier system. Utilizing conventional approaches, the aircraft will suffer from additional weight, less available installation volume, and lower overall performance. This paper presents a potential integrated power and thermal system with attributes to minimize aircraft penalty. The system is a collection of various integration techniques that will be discussed individually for potential standalone application.
Technical Paper

Recirculating Regenerative Environmental Control System

The rapid increase of liquid cooling demand from high-power and high-density avionics in military aircraft has been a challenge for aircraft cooling system designers. A number of state-of-the-art approaches were presented in SAE 2003-01-2399. This paper is a continuation of that discussion on the advancement of environmental-control-system design to meet the higher demands for liquid cooling. In this paper, another advanced environmental control system will be presented. The advanced system is one of a new generation of “bootstrap” air-cycle cooling systems. Similar to a traditional bootstrap air-cycle system, the advanced system is powered by high-pressure engine bleed air and uses ambient ram air and/or on-board fuel as a heat sink. However, unlike a typical air-cycle system, the advanced system maximizes usage of engine bleed pressure to form a recirculation flow path.
Technical Paper

Dual Expansion Energy Recovery (DEER) Environmental Control System

A balance of mission capability, agility, survivability, affordability and mission range is a key to the advanced fighter aircraft design. The advanced fighter aircraft is equipped with high power and density electronic equipment to achieve a superior level of mission capability. Electrical power supplied to this equipment is generated by engine powered generator. The heat generated by this equipment typically is cooled by an onboard environmental control system (ECS) operated by high-pressure pneumatic air from the engine compressor. Both the supplied power and power generating the cooling source are a power extraction from the engine. As fuel is the sole energy resource in the aircraft, this power presents a penalty of the use of fuel and results in reduction in the mission range. The challenge to ECS designer is to maximize the cooling capacity with the minimum energy consumption.
Technical Paper

Aircraft Thermal Management -Heat Sink Challenge

Complex, high-powered electronics used on modern aircraft generate large amounts of heat, and the complexity and energy demands only grow with each new generation of electronics. Commensurate heat sinks capable of absorbing this load are the crucial element in an aircraft's thermal management system, and so the capacities of heat sinks must evolve with this electronics growth. This paper presents an industry survey of conventional heat sinks in current use and then introduces and discusses potential advances in heat sink technologies. These technologies show significant promise to increase the capacity of thermal management systems on future aircraft and thereby unlock the full performance of next generation electronics.