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More Electric Civil Aircraft : A Study on Boeing

Description:

The first "More Eletric Civil Aircraft" was Boeing 787, having its first flight on 19th december 2009. This aircraft type should be the basic for this paper. In detail, the following tasks have to be done:

1) Explaination why "more" electric can increase the overall system efficiency

2) General introduction of the Boeing 787 aircraft

3) Description of the differences in system architecture compared to former aircraft geneations focused on:

a) Engine systems

b) Bleed air systems

c) Hydraulic systems

d) Electrical systems

4) summary

Answer

Introduction

The design of the future aircrafts has been seen to evolve in accordance with the increase in reliability on the electrical systems. This excessive reliance on electrical systems has facilitated the birth of More-Electric Aircrafts (MEA), which has embraced itself with the emerging notions in terms of the number of critical electrical load. Furthermore, this significant alteration in terms of the governing system subsequently spread considerable impact on the rest of the design drivers that encourages for concise and robust civil aircraft design. The moot target, which contemporary aircraft designers cater, is to merge the reliability with the available options that might exhibit a significant enhancement of the overall efficiency of the civil aircraft while proposing alternative design architectures. Several apprehensions suggested that this emerging inclination of reliability could be further enhanced through the systematic use of back-up generation and redundancy. 


The current study suite is supposed to investigate the regulatory justifications of this embracement of more-electric aircrafts with the potential impacts on their absolute efficiencies coupled with a brief description of Boeing 787, which happens to be the first MEA in the history of civil aircrafts of electrical systems. Moreover, the study caters the systematic evaluation of the prevalent design drivers of a civil aircraft against the proposed MEA ones. Apart from all of that, this study desires to reflect certain fecund anticipation regarding the design architecture of the civil aircrafts of future.

Overview of the concept of MEA

Figure 1: Overview of the concept of MEA

Source: (Denning, 2013)


Explanation of “more” electric against the enhanced efficiency of the Aircraft

Before the advent of electrical systems, the civil aircrafts are designed based upon the conventional design architecture, which happens to assemble mechanical, hydraulic, electrical and pneumatic resources of power generation in order to propagate itself. In this architecture, the control fuel is supposed to be transformed into propulsive power that facilitates the mobility of the aircraft. The fuel leftover is fed into a intricate system of the corresponding components that are supposed to provide the non-propulsive power to the aircraft(Huber, 2014). The considerable intricacy of the ensemble has been discovered to impart adverse impact in the absolute efficiency of the aircraft since a nominal leak in the comprising components might pave the aircraft towards network outages and consequent flight delays coupled with the inconvenience to locate the fault at once.


Though we intend to talk about more-electric aircrafts in the current context, the proclivity of the contemporary design architecture is to develop all-electric aircraft, which is systematically devoid of the burden of the intricate ensemble of the non-electric components. This trend is destined to endow the prevailing aircraft design with the freedom from bleed air off-takes and on-engine hydraulic power generation, which altogether supplements the absolute efficiency of the aircraft while encouraging the development of high-voltage electrical networks for non-propulsive power generation. In order to respond to the respective for high-voltage electrical networks, bleed-less systems of air-conditioning, innovative fuel cells, variable frequency generators and intricate embedded digital distribution systems have been intended to integrate with the prevalent architecture in order to facilitate the birth of MEA’s.

Layout of MEA DC Power System

Figure 2: Layout of MEA DC Power System

Source: (Abdel-Fadil, 2013)

On a general note, the attempts that have been incorporated in the proposed architecture of MEA’s are supposed to enhance the prevalent absolute efficiency through;

  • Eliminating the prevalent hydraulic and air engines
  • Significantly enhancing the capability of power generation
  • Installing fecund electrical networking methods that might facilitate the ability of fault identification and protection
  • Proposing electromechanical actuators as a potent alternative of hydraulic actuators
  • Reduction in weight and space in order to decrease production and maintenance cost


The chief challenge that the architecture designers are supposed to cater is the rationalization of the available power sources and existing networks among the ensemble in order to device a bleedlessengine with a propulsive thrust of 40MW.  Furthermore, electrically operated generators are supposed to fuel the pumping engine auxiliaries while enabling the civil aircraft with landing gears with flight control actuation better known as Braking Doors(Huber, 2014). Apart from that, the proposed system is supposed to cater the power requisite regarding the cabin pressurization.

Conventional Power Distribution

Figure 3: Conventional Power Distribution

Source: (Huber, 2014)

  • Elimination of the hydraulic system consequently endow the architecture design with reduced system weight while providing a relative ease in the overall maintenance
  • The concept of bleedless engine is supposed to supplement the most to the cause of improved efficiency
  • Enhancement of controllability endowed the design with unimpeded access to power in the times of high demand
  • The ancillary characteristic of re-configurability is destined to retain the core functionality during major faults
  • The new design seem to incorporate considerable advancement in prognostics and diagnostics that consequently emancipates the availability of aircraft while promising intelligent maintenance

Power distribution layout in MEA

Figure 4: Power distribution layout in MEA

Source: (Gao, 2017)

The overall impact can be summarized as;

  • Considerable reduction in environmental impact
  • Considerable reduction in the amount of fuel burn 
  • Considerable impact in the operating costs


Brief Introduction of Boeing 787

As it was mentioned earlier in the introductory phase, the Boeing 787 happens to be the first civil aircraft, which contains nascent characteristics of a MEA aircraft. As per the empirical specifications provided by the Boeing Commercial Airplanes, it is an American jet airliner with twin-engines along with long haul and mid-size wide body(Gao, 2017). It is the first airliner with three-class seating arrangements with a composite airframe and conditioned to 20% efficient than the previous model of Boeing 767 in terms of fuel consumption(Wang, 2016). The distinct features of this airliner is mostly operated by electrical systems with raked wingtips and chevrons in the nacelles of two of the engines which are designed to reduce the noise considerably.

 Electrical system of Boeing 787

Figure 5: Overview of Electrical system of Boeing 787

Source: (Gao, 2017)

The electrical system flight operating system typically consists of;

  • 4 x 250killo Volt-Ampere primary channel starter generators with 500k-VA capacity per channel
  • 230VAC primary power generation (VF)
  • Electrical starter & generators with full-load rating of 250/225k-VA
  • Electric Environmental Control System with wing anti-Icing and pressurization
  • It happens to be the first twin-engine Jet liner which is literally bleedless

Despite several in-service disruptions regarding the incorporation of lithium-ion batteries that facilitates the setting of fire, it is one of the foremost exponents in the advent of MEA’s.


Brief Description of the new system architecture

Engine Systems

The engine systems of a civil aircraft are often described by the mechanical properties in the fecund discourses of the underlying context. In the prevalent architecture of designs, the mechanical properties are supposed to feed fuel to the governing engine from the local oil pumps. This has been accomplished by the means of mechanical gearboxes which is conditioned to propagate the fuel towards the central hydraulic pump and such other mechanically-driven subsystems along with the governing electrical generator. The emerging trends of the latest all-electric system is supposed to employ electro-mechanical actuators instead of the conventional ones that might facilitate the easy integration of the cardinal components of the actuation ensemble while reducing the amount of absolute fuel burn(Denning, 2013).

Direct Drive Architecture MEA

Figure 6: Direct Drive Architecture MEA

Source: (Huber, 2014)

Bleed air Systems

Bleeding might refer to the leakage of fuel, which is supposed to be governed by the pneumatic systems prevailing to the conventional design architecture. In general, this power for non-propulsive thrust is typically derived from the high-pressure compressors, which are conditioned to provide power to the Environmental Control System (ECS) and to provide hot air to serve the3 purposeof Wing Anti-Icing (WAI). This system is considered to be the element, which causes the massive reduction in terms of efficiency due to the sheer incapability to discern leaks. The notion that the contemporary design architects serve is to device a civil aircraft which is literally bleedless(Gao, 2017).

Regeneration Converters

Figure 7: Regeneration Converters

Source:(Baker, 2014)


Hydraulic Systems

These systems are conditioned to transmit the hydraulic power from the central hydraulic pump towards the embedded actuation systems that subsequently facilitates the seamless primary and secondary flight control. Moreover, this robust system with high power density is supposed to command the landing gear for employment, braking, retraction and engine actuation and several other auxiliary services. The flagrant drawbacks that it consists are the inflexible piping infrastructure, which facilitates the chances for leakage since the control fluids are corrosive in nature(Baker, 2014). The proposed architecture of the new MEA aircrafts are supposed to provide a potent substitute of the actuation system that can enable the aircraft to operate in a leakage-free atmosphere with increased access in the controllability while ensuring the feasible characteristics of the electrical systems.

Actuation system in MEA’s

Figure 8: Actuation system in MEA’s

Source: (Gao, 2017)

Electrical Systems

These systems are supposed to endow the entire aircraft with the power amenities serving the power requisites regarding the avionics, galleys, illumination and several other commercial loads that are supposed to feed the entertainment systems. The apprehensions regarding the flexibility consolidates the pursuit of “all-electric aircraft” since it is inherently devoid of a heavy infrastructure while having a considerable flexibility in the entire structure. The potential drawback of inherent low-power density needs to be mended by deploying high-voltage electrical networks that might feed the entire ensemble of embedded distribution.

Nascent trends of MEA

Figure 9: Nascent trends of MEA

Source: (Denning, 2013)

Summary Table

Design Architecture
Conventional Aircraft
MEA Aircraft
Electrical   Systems
These   systems are supposed to endow the entire aircraft with the power amenities   serving the power requisites regarding the avionics, galleys, illumination   and several other commercial loads that are supposed to feed the   entertainment systems.
The   apprehensions regarding the flexibility consolidates the pursuit of   “all-electric aircraft” since it is inherently devoid of a heavy   infrastructure while having a considerable flexibility in the entire   structure.
Hydraulic   Systems
These   systems are conditioned to transmit the hydraulic power from the central   hydraulic pump towards the embedded actuation systems that subsequently   facilitates the seamless primary and secondary flight control. Moreover, this   robust system with high power density is supposed to command the landing gear   for employment, braking, retraction and engine actuation and several other   auxiliary services.
The proposed architecture of the new MEA   aircrafts are supposed to provide a potent substitute of the actuation system   that can enable the aircraft to operate in a leakage-free atmosphere with   increased access in the controllability while ensuring the feasible   characteristics of the electrical systems.

Bleed   Air Systems
In   general, this power for non-propulsive thrust is typically derived from the   high-pressure compressors, which are conditioned to provide power to the   Environmental Control System (ECS) and to provide hot air to serve the3   purposeof Wing Anti-Icing (WAI). This system is considered to be the element,   which causes the massive reduction in terms of efficiency due to the sheer   incapability to discern leaks.
This   system is considered to be the element, which causes the massive reduction in   terms of efficiency due to the sheer incapability to discern leaks. The   notion that the contemporary design architects serve is to device a civil   aircraft which is literally bleedless
Engine   Systems
This has   been accomplished by the means of mechanical gearboxes that is conditioned to   propagate the fuel towards the central hydraulic pump and such other   mechanically-driven subsystems along with the governing electrical generator.
The   emerging trends of the latest all-electric system is supposed to employ   electro-mechanical actuators instead of the conventional ones that might   facilitate the easy integration of the cardinal components of the actuation   ensemble while reducing the amount of absolute fuel burn


Estimated outlook of the next generation Aircraft

As it was already mentioned in one of the prevailing segments of the entire study suite that the civil aircraft of the future intends to let itself operated through a system governed by electrical means. The infrastructural flexibility that the all-electrical system is supposed to endow the operating system with is due to the elimination of the governing design drivers of prevalent system, which, in return, is conditioned to affect the absolute efficiency adversely. Only advantage that the conventional system has to provide is the high power-density due to which all the non-propulsive power purposes and the commercial demands has been fed with the electrical systems(Abdel-Fadil, 2013). The discovery and subsequent development of solid-state power with enhanced reliability and high power density is considered to be the milestone which caters the underlying pursuit while mitigating the only drawback of the system entirely driven by electrical measures. The next generation civil aircraft celebrates the possibility of integrating high voltage embedded systems of power distribution that might enable the aircraft with a flexible yet robust power infrastructure while emancipating the absolute efficiency.  


Conclusion

The significant advent of technological expertise that led to the practice of solid state and reliable power electronics have ensured the leap in the architectural design of civil aircrafts. Though it has been extensively mentioned in some of the scholarly articles of the underlying disciplines that Boeing 787 happens to be the first civil aircraft to embrace the More-electrical approach is a sheer under specification since the military aircraft designers have pursued the dream of much-coveted “all-electric” aircraft in the verge of World War II. The reason of not being successful is the unavailability of the electrical systems with such infrastructural flexibility while having a high power density to ensure unimpeded distribution of propulsive and non-propulsive power. From the end of 1990’s when the researchers have been able to prove the fecundity of reliable solid-state power electronics to encourage a high-voltage embedded system, an “all-electric” civil aircraft has yet to be designed.

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