Table of Contents

Aerodynamics Series

2019년 4월 20일 토요일

Comparison of Airliner's Wing plan-form

 Comparison of Airliner's Wing plan-form

 As my personnel interest, I figured out wing plan-form of the modern airliners. Mainly, aircraft of Airbus and Boeing are compared in few ways to find design characteristics of the wing. 

You should know that performance of the aircraft is not only determined by the plan-form also by several factors like airfoil section, structure, position-of-wing, engine performance, and drag management. I hope you to see this article as 'fun-purpose' rather than serious 'performance comparison review'. 

1) AIRBUS family

 This shows direct comparison between Airbus-families including narrow and wide-bodies. As you could see that A330 and A340 is almost identical while the new two-engine-A35K has same size as A340. 

 Now the smallest A320's wing has smallest swept angle among the Airbus', and as aircraft goes heavy, wing has more swept angle. You could see A320 and 330 has almost similar AR except change of swept angle. In normalized view, even position of the engine is similar for A320 and 330 while more swept angle of the 330's wing is compensated by frontal-position of the engine. It is interesting to see that A320 and 330. 
 Relatively newer and heavier 350 and 380 has deeper swept angle and smaller AR than previous generation because span of the wing is limited by the practical structural and space reason. Portion of the leading edge device is also become smaller in recent generation.  

2) BOEING family

 Boeing having longer history than Airbus has more various line-up in their squad; their fancy version of classics like 777X or 747-8 will be considered in the 'Airbus-vs-Boeing'. Recent 787 and 777 show how airliner have developed in limited size for better performance.  

  You should know that trend of swept angle vs weight is kept in Boeing; heavies has deeper angle than narrow bodies or lighter ones. It showed 'engineering-convergence' strikingly strong for both of the two Airliner giants. 

3) Narrow-Bodies

 Now, we go to comparison of the two companies; both companies has their own best-seller in small-airliner class, 320 and 737. Both aircraft basically similar size however, in wing plan-form, layout is little bit different. 
 320 has more glider-like wing than 737, little bit smaller chord length with smaller swept angle. Also, 320 having longer landing gear and outer position of engine could adopt larger radius of the engine. While 320 has longer root section and outer aileron part. 
 If both aircraft have same airfoil section, 320 seems better efficiency at low speed region. We already know that low-speed region, take-off, climb, descent, and landing, takes relatively large portion of the flight-profile of narrow-bodies. 

 I have added 757 for this comparison, larger narrow-bodies, which will be replaced by Boeing's future NMA called 797. Basically, blue and green line has almost same profile except AR and engine position. In order to overcome the weight increase of 757, root-chord length is extended and engine is positioned at outer position. 

4) 330 vs Boeing's

 Tendency of 320 vs 737 is kept here; Airbus has smaller swept angle and root chord length. While 330 has longer span than 767, much frontal-position of the engine. 

 Newer 787 series has wider wing-span than 767 and become similar. Still, Boeing has deeper swept angle, and wider engine position for larger engine. 

 For three airliners, 330, 767, and 787, except engine position, Boeing family has similar layout than Airbus. Advanced wing-tip shape and longer root-section are noticeable for 787; it corresponds higher lift efficiency and heavier weight. 

 For two aircraft, difference of the swept angle is smaller than other two family comparison. Also, position of the engine is similar while 777 has longer span and root-chord length for its heavier weight. You could see that engine of the 777 is very large for its era. 
 Raked wing-tip makes noticeable difference at the tip. 

5) 350 vs 787 - Newest line-up

 Most striking feature of this comparison is here. Their newest aircraft from clean sheet is very similar for wing plan-form; only difference is probably its sizing scale. Generally, 350 is larger aircraft however, even layout of control surface is similar for each other. 
 We should watch Boeing's NMA that how they designed the wing plan-form from clean sheet; NMA is similar to 350 and 787 style or not. 

6) 350 vs 777 - Between Two-flag ships

 Actually, size of the 350 is positioned between 777 and 787, so comparison for the 350 is also done for 777. As the 350 is changed from glider-style to 787 style, now you could see Airbus has deeper swept angle than the Boeing's Classic. 777 has narrower engine position than 350 although they had larger radius engine. 
 777x extend its span and give smaller swept angle than previous aircraft to overcome increased weight. It is noticeable that making smaller swept angle is not recent trend.  

 7) 380 vs 747 - Four-engine symbols 

 Giants of two airliner giants, 380 and 747, are compared; 380 is 25% larger than 747 based on MTOW. Definitely, 380 has much larger wing than 747; it has smaller swept angle, wider span, and longer chord length. 
 Even, wings are normalized, 380's wing has bigger AR. 

 Now, we move on to add new generation of the 747-8, 

 748 has new wing with wider span, wing-tip and bigger engine. Its wing-tip is similar to 777 style. However, still, 380 is much larger aircraft than 747. Comparison of style is more convenient at normalized configuration. 
 In normalized configuration, position of the engine become very similar for 748. Modified 748 now has larger AR via added raked wing-tip. 

 8) Summary

* Mostly, Airbus has smaller swept angle than Boeing's similar class (320 and 330)

 * 330 and 340 is almost same configuration

 * Heavies has deeper swept angle and longer chord than narrow-bodies for both Airbus and Boeing

 * The newest clean-sheets, 350 and 787, has very similar design; Airbus now has highly swept one

 * New generation of Boeing, 777x and 748, has extended wing-tip

 * 777x has smaller swept angle than its predecessor; becoming Airbus style (?)

2019년 4월 2일 화요일

AIM-120C Study using Missile-SIM : Part 3 - CUDA / LREW / METEOR types. 2 : Sensitivity Analysis

Previous Work Status

Initial Version of Missile-SIM for Performance evaluation
Aerodynamic Validation of Missile-SIM for Trajectory 
AIM-120C Study using Missile-SIM : Part 1 - Sensitivity
AIM-120C Study using Missile-SIM : Part 2 - Launch Condition
AIM-120C Study using Missile-SIM : Part 2 - Launch Condition - revision
Patch note of Missile-SIM : Guidance Algorithm is added w/ Real-Time plot
W.I.P status of Missile-SIM : Addition of Air-propulsion part 1
W.I.P status of Missile-SIM : Addition of Air-propulsion part 2
AIM-120C Study using Missile-SIM : Part 3 - CUDA / LREW / METEOR types. 1 : Baseline Comparison

 6. Sensitivity of Generic CUDA / AIM-120C / CUDA+Booster / Ramjet(Meteor)

 After comparison of baseline generic model of the 4 missiles, I conducted sensitivity analysis for the hardware change of the missile, weight of the propulsion fuel, burn time of the fuel, ISP value, and drag. 
As described in the previous AIM-120C analysis (links in the upper part)

 ** Heat value % of the fuel is changed for Ramjet because ISP of the missile is not a fixed variable

 1) Weight of the fuel

   (1) CUDA
   (2) AIM-120C
   (3) CUDA+Booster
   (4) Ramjet

 2) Burn time of the motor

   (1) CUDA
   (2) AIM-120C
   (3) CUDA+Booster
   (4) Ramjet

 3) ISP value

   (1) CUDA
   (2) AIM-120C
   (3) CUDA+Booster
   (4) Ramjet

 4) Drag

   (1) CUDA
   (2) AIM-120C
   (3) CUDA+Booster
   (4) Ramjet

 5) Summary

   (1) Propulsion Weight

 Impact of propulsion weight for the 4 missiles are shown. 

 Smallest and draggy CUDA missile is sensitive among the three solid-fuel missiles. Definitely CUDA has the smallest launch weight and it means small change of the fuel could make huge impact. Meanwhile, CUDA+Booster has the smallest sensitivity because it has the largest portion of the fuel due to its additional stage. 

 Interestingly, Meteor is much more sensitive than the others because the ISP and range of the missile is great and its impact is also significant. 

  For their speed, CUDA and its booster version is sensitive because their peak speed is determined at CUDA stage. AIM-120C and Meteor has similar sensitive value for their peak speed. This is mainly caused by the weight of the CUDA is half of the AIM-120 Class. 

   (2) Burn Time

 Impact of burn-time for the 4 missiles are shown. 

 Sensitivity due to the burn time for the range is roughly similar to the four missiles. Basically longer burn time provides longer range at the same altitude because it avoid energy consumption at the much draggy higher Mach number. 

 However, it means that longer burn time scarifies its peak speed. 

 Interestingly, CUDA+Booster is three-times higher sensitivity for its peak speed because this type has much higher peak speed than the others. So, loss of peak speed seems larger. 

   (3) ISP

 Impact of ISP for the 4 missiles are shown. 

 Because ramjet has heat value for the fuel rather than ISP, it has different unit of sensitivity. Indeed, it is difficult to direct comparison. (1s of ISP is about less than 0.5% of 260s original value)

 Among the three solid-fuel missiles, impact of ISP change is significant for the CUDA+Booster. 

 ISP is the most honest parameter for the missile performance and longer missiles are naturally more affected by the ISP change. (for both range and speed)

   (4) Drag

 Impact of Drag for the 4 missiles are shown. 

 Most dreaded enemy of the aerodynamic men, drag only makes negative impact on the missile performance. 

 Impact of the drag is directly proportional to its range as shown in the range chart. However, for their speed, impact of the drag is little bit different. Peak speed of the CUDA and its boosted version is determined at the draggy CUDA status, indeed impact of the drag is larger than that of AIM-120C. 

 Meteor having longest range among candidate naturally degraded significantly due to the increase of the drag. Also, its peak speed is reached at the end of the long-burn-time and degradation of the peak speed is also larger than the solid-fuels. 

 ** Model of these missiles are 'generic'-ally made by myself, and precision of the simulation is speculation level; uncertainty of the model is caused by rough CFD mesh, CFD precision, imagined rocket model, atmospheric approximation and more. 

************** At Part 3
 After this Part 2, I will review some possibilities related to the enhancement of the booster and AIM-120C with trajectory optimization, sometimes called AIM-120D. 

 As you could see impact of trajectory and hardware through my contents, range of these candidates change significantly due to the slight change of hardware and trajectory optimization.