Forces in Aerodynamics: Blended Wing Body - Research Paper Example

?Running Head: Blended wing Body Blended Wing Body Advanced Aerodynamics 3530, summer Man always wished to fly, after he made automobiles and ships. Several efforts were made since the early 1400’s to watch the skies closely. Ornithopters, Hot air balloons and Gliders have seen light in this process. In 1903 the Wright brothers came up with a flight model and since then the aircrafts have been undergoing many changes. The evolution took place from gliders to today’s supersonic aircrafts. The desire to optimize the efficiencies and performance of the aircrafts, have lead to many innovative designs and one such design made is the “Blended Wing Body”. This concept though initially failed to impress and had results that forced scientists to stick to the conventional methods, experiments have been conducted to correct these errors and now efforts are being made to realize this concept and the results are fruitful. We shall now take a close look at the concept of BWB and how the research of Dr. Joseph R Chambers helps us to understand this theory. This paper explains all the concepts of BWB and how when put to use can cause great results and finally the application of this concept. Blended Wing Body The efforts made to increase the efficiencies of both the commercial aircrafts and the military aircrafts have been successful through the Blended wing Body concept that has recently had a successful prototype built by NASA and other industrial partners. The concept of the “Blended Wing Body” as the name suggests is to have a body or a flying wing with which the outer wings are blended. This concept has displayed several advantages over the conventional aircrafts in the overall aerodynamic efficiencies. Due to the contour of the aircraft, it has maximum lift and can take off with a minimum drag. This is possible as the whole aircraft is integrated into a single lifting surface with the body, engines, and wings all in one single blended surface. Figures 1 and 2 represent the Blended wing body aircraft and the conventional 747-400 Boeing model aircraft repectively. Figures 1 and 2 clearly show the difference between a BWB aircraft with the outer wings integrated with the fuselage and the convetinal Boeing 747-400 with its wings attached with the body and not integrated with it. Figure 3 compares the sizes of an Airbus and a BWB aircaft The above figure gives an excellent comparision between the conventional aircraft and the BWB aircraft. We can observe several variations like the integrated body and wings, the mounted engines on the rear of the fuselage, the other parameters like the span, weight, passenger capacity and seating arrangement are shown and the overall design of the BWB is also clear. This design of the BWB aircraft highly influences the factors like reducing noise in the take off and landing operations, increasing fuel efficiency, reducing unwanted emissions, and inturn making travelling more economical. “The unique layout of the BWB configuration places the noise generating engines above and rear of the wing-centerbody upper surfaces, suggesting that a significant reduction in projected noise might not be obtained from a structural shielding as compared with conventional configurations” (Joseph R. Chambers) This BWB designed aircraft with a double deckered interior cabin can carry as many as 800 passengers, which is approximately double the number (416) in the Boeing 747-400. Figure 4 shows double deckered seating arrangement in a BWB aircraft The BWB aircraft have been designed to withstand internal pressure loads which induce high bending stresses and the additional bending and compression loads, that arise as a result of aerodynamic and gravitational forces. These structures have high strengths and can take both cabin and high bending loads. The experiments conducted by NASA have proved that the design of BWB has drastically changed some features that proved to be higly advantageous over the conventional design. The fuel consumption, the weight, and the direct cost of operation have been lowered with BWB aircrafts. The BWB aircrafts are made of composite materials unlike the convetional aircrafts and thus have less weight but great strength when compared to the conventional models. Since the entire body of the BWB aircrafts can be considered to be a flying wing during its take off and flight, there would be less drag and high lift force that enables less fuel consumption and thus cuts down the direct cost of operation. Figure 5 Gives some advantages of BWB aircraft over conventional models. BWB aircrafts do not have a vertical tail and aft fuselage tail and yet they have great stability. In the place of the vertical tail the BWB aircrafts have the engines and the engine pylons mounted on the upper aft surface of the blended fuselage centerbody. Experiments are in process to have hydrogen as fuel for the BWB aircrafts instead of the fuel used by conventional aircrafts. Though carrying hydrogen fuel is dangerous, the BWB aircrafts are facilitated with special fuel tanks that can assure high level of safety. Figure 6 shows the interior cross sectional view of the BWB aircraft with engines mounted on the rear of the fuselage. Though the BWB aircraft have advantages over conventional aircrafts, they are not being used commercially. Though they have huge passenger carrying capacity, safety parameters are yet to be scrutinised completely. Prototypes are still being tested for safety factors such as control and stability problems. NASA in colloboration with Boeing Phantom works developed the first BWB aircraft. The newly built BWB aircraft was designated as X-48B. It has 20.4-feet wing span and vertical fins and rudders at the end of the wingtips and elevons along the trailing edges of the wings. It has a gross weight of 523-lbs and has three turbojet engines to provide a combined thrust of 160-lbs. It has a top speed of 138 mph and can cruise at an altitude of 10,000 feet with a flight duration of 40 minutes ("X-48B Blended Wing Body," 2009). It took off for the first time on the July 20, 2007 at NASA’s Dryden Flight Research Center, Edwards Airforce Base in California. Figure 7 shows the X-48B BWB aircraft designed by NASA and Boeing Phantom works The actual time X-48B was in the air before landing was approximately 31 minutes and travelled at an altitude of 7,500 feet. This increased confidence in the BWB design aircrafts. The BWB aircrafts can also be operated with a remote pilot with pilot view camera in place. (see figur 6). Some important aerodynamic design aspects of BWB aircrafts are: Inboard Wind Design: The inner portion of the wing contains the passenger and cargo cabis with thickness to chord ratios of 18% approximately. Other consideratins include Deck angle limits and shock strength of the centerboby Kink: This is the region in which the thin supercritical outboard wing blends with the thick inboard airfoil. The design issues with this aspect are the surface smoothness, shock strength, sweep and buffet tailoring. Trim: Another crucial design aspect that needs attention is the cruise trim which is a multi disciplinary problem, highly influenced by the Center of Gravity and stability parameters of the aircraft. It requires the trimming of the mid cruise configuration with required CG and minimal control deflections. (Mark A Potsdam, Mark A. Page, Robert H. Liebeck 1-2) But even this BWB design has its own limitations and pitfalls. Though this design has been proved to be efficient and economic,there are certain drawbacks that need to be addressed. As the research of Dr. Joseph R. Chambers at NASA Langely Research center suggests, there have been three areas of challenges for the BWB design. They are disciplinary, operational and economic challenges. The disciplinary challenges include aerodynamic design challenges like take off and landing and other parameters such as stability and control. BWB aircrafts do not have the aft fuselage tail and the vertical tail. This greatly affects the aerodynamic parameters like stability and control. Absence of a aft tail increases the angle of attack. This creates stability and control problems anfd “tumbling” may take place. But the Digital flight controls proved successful with B-2 and eliminates these stability issues. The upper aft fuselage centerbody mounted engines and engine pylons can be a problem as shock inducing inflows can damage the turbo engines and at high speeds the BWB flights should also be able to provide enough drag for the entire centerbody.The noncircular pressurised cabin design solves these problems. Figure 8 shows an overall view of a BWB aircraft with the fuel tanks in outer wings and turbo engines that are likely to get damaged by the inducing shocks The operational challenges include the safety and accomodation of large number of passengers, as many as 800, and the payload. But the centerbody fuselage provides huge room for passengers with a great seating capacity. The BWB does not have windows to see the skies and relax, so some system has to be in place to keep away passenger anxieties. Finally the economic challenges are obvious. Producing unconventional aircraft designs require a huge investment and come with consideral risk to an airline. Companies can and have gone bankrupt when a new aircraft design did not work out. Research at NASA Langely Research Center is in progress to find solutions to these various issues of the BWB. We may still see Blended Wing Body aircrafts flying commercially someday. References 1. Boeing Image, Initials. (2006, October 27). Boeing to begin ground testing of x- 48B blended wing body concept. (Figure 1) Retrieved from http://www.boeing.com/news/releases/2006/photorelease/q4/061027a_lg.jpg 2. Boeing photo, Initials. (n.d.). Boeing to begin ground testing of x-48b blended wing body concept. (Figure 2) Retrieved from http://www.boeing.com/companyoffices/gallery/images/commercial/747400-14.html 3. Size comparison of 747 vs. bwb. (n.d.)(Figure 3). Retrieved from http://www.twitt.org/Slide5a.jpg 4. Joseph R. Chambers. Aeronautics, NASA. (n.d.). Innovation in flight: Research of the NASA Langley Research Center on revolutionary advaced concepts for Aeronautics. USA 5. Joe, Mizrahi. (1999, April). Double-deckered bwb interior. (Figure 4) Retrieved from http://www.twitt.org/bwb8.jpg 6. The blended wing body. (n.d.). (Figure 5) Retrieved from http://www.twitt.org/Slide3a.jpg 7. X-48b interior. (n.d.). (Figure 6) Retrieved from http://i.treehugger.com/images/2007/10/24/x-48b%20interior-jj-001.jpg 8. X-48B Blended Wing Body. (2009, April). Retrieved from http://www.nasa.gov/centers/dryden/news/FactSheets/FS-090-DFRC.html 9. X-48b front. (n.d.). (Figure 7) Retrieved from http://www.granitegrok.com/pix/x-48B_front.jpg 10. Mark A Potsdam, Mark A. Page, Robert H. Liebeck , . "Blended Wing Body Analysis and Design." 1-2. Web. 10 Jun 2011. . 11. Overview of BWB schematic. (n.d.). (Figure 8) Retrieved from http://1.bp.blogspot.com/_Zw1NzznL1us/TVJelQya4hI/AAAAAAAAAAg/UAPLfHxHZJg/s1600/http___www.aoe.vt.bmp Read More