4.1 Airbus A320 ( PDFDrive ).pdf

In the framework of this thesis, a connection must be developed from CPACS to KTH's CEASIOM framework and in particular to its components AC Builder, AMB and SUMO. DLR's conceptual design tool VAMPzero will be linked via CPACS to KTH's CEASIOM components AMB, Propulsion and SDSA for a detailed analysis of aerodynamic and flight mechanical behaviour.

Greek formula symbols

Thesis breakdown

First the characteristics of the A320 are described followed by specifications of the VAMPzero input file. Therefore, the data from the Airbus A320 are of particular interest and the corresponding analyzes are performed in this thesis.

CPACS

Design environment

After the top level structure, the second level includes the header which means general information about the CPACS data set. Since the configuration of the A320 describes a single model, it is defined at level four by.

VAMPzero

Additional information about the application of computational methods is described in Böhnke's paper at the IEEE Aerospace Conference [2]. The presented convergence history is recorded during analysis with a minimal number of input values and demonstrates the numerical robustness of the code.

CEASIOM

AC Builder
SUMO
Propulsion
SDSA

At the next level of the tree, the structure of the control surfaces is described. The input file is provided by the interpretation and design of geometric descriptions of the aircraft in AC Builder.

Figure 2.7: Convergence history of parameters in VAMPzero

CPACS to AC Builder

Taper Ratio
Airfoils
Control surfaces
Unconventional aircraft configuration

At first, the wrapper generatesaircraft.mat, a Matlab file containing the aircraft definition in a TORNADO-readable structure. In this thesis a new wrapper script is developed to allow data transfer from VAMPzero to CEASIOM. For this reason, the sample Ranger 2000 XML file has been revised to identify the minimum number of parameters for data transfer.

The implementation of the data transfer assumes knowledge of the definition of the components and their associated coordinate systems. An example of the different definitions of taper ratio in CPACS and CEASIOM is presented in Section 3.1.1. The integration of airfoils in CEASIOM is indicated in the geometric description of the wings.

Previous wrapper applications automatically add control surfaces to the wing as sections. To improve aircraft shape accuracy, it is not feasible to integrate a rotated winglet as a further segment in the current version of AC Builder.

CPACS to AMB

CPACS to SUMO

One way to integrate parameters into the aircraft data structure is to add them manually to the XML file. After the unique integration of the parameters in afterWrapper.xml, future results will refer to these quantities, despite changes made to the aircraft in earlier steps in the design process. In this chapter the Airbus A320 is analyzed during the conceptual design process within CEA-SIOM.

First, the characteristics of the A320 are presented, followed by a description of the necessary input data of VAMPzero and their influence on estimated results. The differences between the models are specified by a comparison of the magnitudes of parameters that define the aircraft components. In addition to the geometric research of the A320, prediction methods of weights, moments of inertia and center of gravity are introduced and reviewed.

As a demonstration of the conceptual design process, a new aircraft generated by the VAMPzero design tool is implemented within CEASIOM. The AC Builder, AMB, Propulsion and SDSA components determine the aerodynamic and aeromechanical behavior of the aircraft.

Airbus A320

Additionally, the DATCOM, TORNADO and EDGE Euler aerodynamic methods are applied to quantify their impact on design sensitivity.

Input of VAMPzero

Comparison of different geometries

Fuselage
Vertical tail
Engine

The Cöllen model illustrates the A320 data after converting the VAMPzero output to CEASIOM with an envelope. The indicated sizes of the supplementary parameters are similar to the sizes in the Pester model. Since Pester model data and Cöllen model data are available in the same format, these data are considered.

The deviation of spanwise_kinkis caused by the user's manual input to add additional sections to the wing. The strong deviation of location between the size of the Cöllen model and the Pester model is mainly influenced by the z-translation generated by VAMPzero. The analysis of the deviation between the sizes of the Cöllen model and the Pester model is referred to the analysis of the wing in section 4.3.2.

The wingspan causes a small deviation of approximately 1.96% due to the wingspan deviation, as shown in Table 4.3. The thrust magnitude calculated in VAMPzero differs from the magnitude in the Pester model.

Figure 4.2: Computation of wingspan Pester (blue)

Weight breakdown

Structure Weight
System Weight
Powerplant Weight
Operating Items Weight
Maximum Zero-Fuel Weight
Maximum Takeoff Weight
Conclusion

The pie charts depict the weight distribution of the five weight estimation methods with respect to the Cöllen model. To compare the weight distribution of the medium range aircraft with the results in figure 4.5. The weight distribution is structured in the order of the weight definitions in the doctoral thesis of Isikveren [17].

Finally, the results are compared with the sizes provided by the manufacturer [11] and the weights of the Pester model. The estimated structure weight of the VAMPzero model agrees well with the result of the Pester model. The maximum zero fuel weight (MZFW) consists of the OEW and the maximum payload as described in.

As an example, the manufacturer's fuel weight given in Table 4.9 additionally includes a fuel reserve weight. With 9% deviation from manufacturer's size, MTOW is adequately predicted in VAMPzero.

Figure 4.5: Results of the stand-alone tool Weights and Balances

Moments of inertia

A comparison of the weight prediction tool AC Builder and the standalone tool Weights and Balances using the Torenbeek method shows that the Torenbeek method improves the weight estimation of AC Builder. The deviation between the calculated MTOW of the Cöllen model and the inherent size of the manufacturer is reduced from -20% to -13%. However, large weight fluctuations occur within the weight prediction process as in the OEW estimation, where the Torenbeek method even distorts the result.

In particular, structure weight in AC Builder and Weights and Balances is not predicted as well as in VAMPzero. The Pester model's MTOW coincides with the manufacturer's size due to a similar geometric input file from the A320, as opposed to a selected set of input parameters for VAMPzero. The data provided by the manufacturer is based on the documentation “A320 - Aircraft Characteristics for Airport Planning” [11].

The results from the center of gravity show that the predicted magnitude of the Cöllen model in AC Builder is distorted by applying the Torenbeek method from a deviation of -1% to -3% from the magnitude declared by the manufacturer. The stability and control analysis in sections 4.9 to 4.11 of the Cöllen model is based on the data set generated by Weights and Balances using the Torenbeek method.

Results of AC Builder

Results of SUMO

To demonstrate this, the surface pressure distribution at the trailing edge of the lifting surface is considered. Although the surface discretization is flat in this region, small elements are required that exhibit a high pressure gradient [27]. While the discrepancy could be resolved by using an adaptive mesh refinement solution for a single flight condition, this is not a necessary option for a large number of cases.

The algorithm implemented in SUMO generates a surface mesh that satisfies the first requirement regarding given tolerances [21]. Local geometric quantities such as maximum stretch ratio, normal angle tolerance, and number of iterations are used to define the discretization of the surface mesh. As long as the surface mesh is of sufficient quality, the volume mesh is useful for inviscid flow functions.

The volume grid contains the geometric representation for Navier-Stokes calculations in the EDGE CFD solver [27]. Geometric quantities such as far-field radius, far-field refinement and tet radius are specified while the remaining parameters are calculated in SUMO.

Figure 4.12: Skeleton of the fuselage, top view

Results of AMB

Conclusion

This section compares the results of the different methods to quantify the impact on design sensitivity. The following figures show the aerodynamic coefficients CL, CD and Cm of the DAT-COM, TORNADO and EGDE Euler methods. Caused by variations in the angle of attack between the body-fixed and the aerodynamic coordinate system, the coefficients CL and CD must be recalculated for each test case.

A reliable evaluation of the results of EDGE Euler is possible as long as the fluctuation of the mean value is known. Therefore, the convergence history of the aerodynamic coefficients must be verified for each test case. In particular, the results of the handbook method DATCOM are related to the results of TORNADO.

As long as the angle of attack is away from stall, TORNADO provides accurate results with the linear approximation of the lift coefficient. The deflection of the results between DATCOM and TORNADO is explained by the viscosity as in figure 4.18b.

Figure 4.15: Volume mesh, refinement 4 Table 4.13: Volume mesh data

Results of SDSA

The short-period mode is a strongly damped oscillation that results in a rapidly dying wavelike motion of the aircraft. We compare the manufacturer's reference data with data on a new aircraft that was designed using the aircraft conceptual design tool VAMPzero. Then, the aerodynamic and aeromechanical behavior of the new aircraft is analyzed within the CEA-SIOM AMB, Propulsion and SDSA components.

In the last step, the input and output correlations of the conceptual design tools are plotted on an N2 chart. In contrast to VAMPzero, the results of Cöllen (AC Builder) deviate more strongly from the manufacturer's reference data. Improved in part by the Torenbeek method of the standalone Weights and Balances tool, weight predictions approach reference sizes.

Using the aerodynamic methods DATCOM, TORNADO and EDGE Euler identifies the advantages and disadvantages of different methods. Stability and control analysis in SDSA shows that the dynamic flight behavior of the Cöllen (Torenbeek) model is rated as "acceptable". International Congress of Aeronautical Sciences, 2008 [6] Pester, Maria: Multidisciplinary conceptual aircraft design using CEASIOM.

25] Meador, William ; Smart, Michael: Reference enthalpy method developed from solutions of the boundary layer equations.