Juliana Early

Aircraft Cost Modelling using the Genetic Causal Technique within a Systems Engineering Approach

The paper is primarily concerned with the modelling of aircraft manufacturing cost. The aim is to establish an integrated life cycle balanced design process through a systems engineering approach to interdisciplinary analysis and control. The cost modelling is achieved using the genetic causal approach that enforces product family categorisation and the subsequent generation of causal relationships between deterministic cost components and their design source. This utilises causal parametric cost drivers and the definition of the physical architecture from the Work Breakdown Structure (WBS) to identify product families. The paper presents applications to the overall aircraft design with a particular focus on the fuselage as a subsystem of the aircraft, including fuselage panels and localised detail, as well as engine nacelles. The higher level application to aircraft requirements and functional analysis is investigated and verified relative to life cycle design issues for the relationship between acquisition cost and Direct Operational Cost (DOC), for a range of both metal and composite subsystems. Maintenance is considered in some detail as an important contributor to DOC and life cycle cost. The lower level application to aircraft physical architecture is investigated and verified for the WBS of an engine nacelle, including a sequential build stage investigation of the materials, fabrication and assembly costs. The studies are then extended by investigating the acquisition cost of aircraft fuselages, including the recurring unit cost and the non-recurring design cost of the airframe sub-system. The systems costing methodology is facilitated by the genetic causal cost modeling technique as the latter is highly generic, interdisciplinary, flexible, multilevel and recursive in nature, and can be applied at the various analysis levels required of systems engineering. Therefore, the main contribution of paper is a methodology for applying systems engineering costing, supported by the genetic causal cost modeling approach, whether at a requirements, functional or physical level.

Design and Analysis Integration using Systems Engineering for Aircraft Structural Design

Systems Engineering provides a set of methods and approaches that can be used to handle the interactions between different components and disciplines involved in a design process. This work demonstrates a framework that uses automation and analysis integration methods and allows for the automatic generation simulation models and results, which are used to perform some of the tasks within a systems engineering process. For example, the Verification of the different components and disciplines with the design, and the Validation of the design using Technical Performance Measures (TPM) compared against the initial requirements and specification of the design. An example of a Multi-disciplinary analysis and trade-study, for which all the data was automatically generated, is shown allowing the best concept to be selected from a range concepts with two high-level parameters varied.

Implementation of Menter's Transition Model on an Isolated Natural Laminar Flow Nacelle

This study evaluates the implementation of Menters γ-Re θ Transition Model within the CFX12 solver for turbulent transition prediction on a natural laminar flow nacelle. Some challenges associated with this type of modeling have been identified. The computational fluid dynamics transitional flow simulation results are presented for a series of cruise cases with freestream Mach numbers ranging from 0.8 to 0.88, angles of attack from-2 to 0°, and mass flow ratios from 0.60 to 0.75. These were validated with a series of wind-tunnel tests on the nacelle by comparing the predicted and experimental surface pressure distributions and transition locations. A selection of the validation cases are presented in this paper. In all cases, computational fluid dynamics simulations agreed reasonably well with the experiments. The results indicate that Menters γ-Re θ Transition Model is capable of predicting laminar boundary-layer transition to turbulence on a nacelle. Nonetheless, some limitations exist in both the Menters γ-Re θ Transition Model and in the implementation of the computational fluid dynamics model. The implementation of a more comprehensive experimental correlation in Menters γ-Re θ Transition Model, preferably the ones from nacelle experiments, including the effects of compressibility and streamline curvature, is necessary for an accurate transitional flow simulation on a nacelle. In addition, improvements to the computational fluid dynamics model are also suggested, including the consideration of varying distributed surface roughness and an appropriate empirical correction derived from nacelle experimental transition location data.

Experimental and numerical analysis of a classical bleed slot system for a turbocharger compressor

This paper presents an insight into the performance and inducer flow field of a turbocharger centrifugal compressor incorporating a classical bleed slot system with various slot positions. The bleed slot is popular widely used map width enhancement method in the turbocharger industry. Even though the technique has been used for a long time, further study is still required to gain a better understanding of the flow structures inside the compressor stage due to the bleed slot. Therefore, this detailed study of the bleed slot system has been performed through a careful CFD analysis validated against experimental data. Three different positions of the bleed slot opening on the impeller shroud have been analysed and discussed in terms of their impact on the map width of the compressor. Discussion focuses on the slot flow variation throughout the speedline, the inducer inlet swirl near the surge flow condition and its impact on map width enhancement. The paper also demonstrates the capability of CFD analyses to predict the surge point.

Reynolds Number Effects on Fully-Developed Pulsed Jets Impinging on Flat Surfaces

A systematic study of the effect of the Reynolds number on the fluid dynamics and turbulence statistics of pulsed jets impinging on a flat surface is presented. It has been suggested that the influence of the Reynolds number may be somewhat different for a jet subjected to pulsation when compared to an equivalent steady jet. A comparative study of both steady and pulsating jets is presented for a Reynolds number range from Re=4,730 to Re=10,000. All the other factors that affect the flowfield are kept constant, which are H/d=3, St=0.25, and d=30.5  mm. It was found that for the range of the Reynolds numbers tested, pulsation results in a shortening of the jet core, the centerline axial velocity component declines more rapidly, and higher values of the radial velocity component for r/d>0.75 are observed. As the Reynolds number increases, the jet spreads more rapidly, the turbulent kinetic energy and nondimensional turbulent fluctuations decrease, and the flowfield near the impinging surface changes drastic...

Periodic transonic flow and control

The current understanding of periodic transonic flow is reviewed briefly. The effects of boundary-layer transition, non-adiabatic wall conditions and modifications to the aerofoil surface geometry at the shock interactions on periodic transonic flow are discussed. Through the methods presented, it is proposed that the frequency of periodic motion can be predicted with reasonable accuracy, but there are limitations on the prediction of buffet boundaries associated with periodic transonic flows. Several methods have been proposed by which the periodic motion may be virtually eliminated, most relevantly by altering the position of transition fix, contouring the aerofoils surface or adding a porous surface and a cavity in the region of shock interaction. In addition, it has been shown that heat transfer can have a significant effect on buffet.

Tanker Mission Implication on a Civil Aerial Refuelling Transport System’s Benefit Evaluation

As the emphasis on initiatives that can improve environmental efficiency while simultaneously maintaining economic viability has escalated in recent years, attention has turned to more radical concepts of operation. In particular, the cruiser–feeder concept has shown potential for a new generation, environmentally friendly, air-transport system to alleviate the growing pressure on the passenger air-transportation network. However, a full evaluation of realizable benefits is needed to determine how the design and operation of potential feeder-aircraft configurations impact on the feasibility of the overall concept. This paper presents an analysis of a cruiser–feeder concept, in which fuel is transferred between the feeder and the cruiser in an aerial-refueling configuration to extend range while reducing cruiser weight, compared against the effects of escalating existing technology levels while retaining the existing passenger levels. Up to 14% fuel-burn and 12% operating-cost savings can be achieved when ...

Experimental and Numerical Benchmarking of an Improved Meanline Modelling Method for Automotive Turbocharger Centrifugal Compressors

After the development of a new single-zone meanline modelling technique, benchmarking of the technique and the modelling methods used during its development are presented. The new meanline model had been developed using the results of three automotive turbocharger centrifugal compressors, and single passage CFD models based on their geometry.The target of the current study was to test the new meanline modelling method on two new centrifugal compressor stages, again from the automotive turbocharger variety. Furthermore the single passage CFD modelling method used in the previous study would be again employed here and also benchmarked.The benchmarking was twofold; firstly test the overall performance prediction accuracy of the single-zone meanline model. Secondly, test the detailed performance estimation of the CFD model using detailed interstage static pressure tappings.The final component of this study exposed the weaknesses in the current modelling methods used (explicitly during this study). The non-axisymmetric flow field at the leading and trailing edges for the two compressors was measured and is presented here for the complete compressor map, highlighting the distortion relative to the tongue.Copyright

Assessing 1D Loss Models for the Off-Design Performance Prediction of Automotive Turbocharger Compressors

Single-Zone modelling is used to assess three 1D impeller loss model collections. An automotive turbocharger centrifugal compressor is used for evaluation. The individual 1D losses are presented relative to each other at three tip speeds to provide a visual description of each author’s perception of the relative importance of each loss. The losses are compared with their resulting prediction of pressure ratio and efficiency, which is further compared with test data; upon comparison, a combination of the 1D loss collections is identified as providing the best performance prediction. 3D CFD simulations have also been carried out for the same geometry using a single passage model. A method of extracting 1D losses from CFD is described and utilised to draw further comparisons with the 1D losses. A 1D scroll volute model has been added to the single passage CFD results; good agreement with the test data is achieved. Short-comings in the existing 1D loss models are identified as a result of the comparisons with 3D CFD losses. Further comparisons are drawn between the predicted 1D data, 3D CFD simulation results, and the test data using a nondimensional method to highlight where the current errors exist in the 1D prediction.Copyright

Economics Modelling for Systems Engineering in Aircraft

The paper is primarily concerned with the modeling of aircraft manufacturing cost. The aim is to establish an integrated life cycle balanced design process through a Systems Enginee ring approach to interdisciplinary analysis and control. The cost modeling is achieved using the Genetic Causal approach that enforces product family categorization and the subsequent generation of causal relationships between deterministic cost components and their design source. This utilizes causal parametric cost drivers and the definition of the physical architecture from the Work Breakdown Structure (WBS) to identify product families. The higher level application to aircraft requirements and functiona l analysis is investigated and verified relative to life cycle design issues for the relationship between acquisition cost and Direct Operational Cost (DOC), for a range of both metal and composite nacelles. The lower level application to aircraft physical architecture is investigated and verified for the Work Breakdown Structure (WBS) of an engine nacelle, including a sequential build stage investigation of the materials, fabrication and assembly costs. That is extended to consider acquisition cost, includ ing the recurring unit cost and the non -recurring design cost of larger airframe assemblies. The systems costing methodology is greatly facilitated by the Genetic Causal cost modeling technique as the latter is highly generic, interdisciplinary, flexible, multilevel and recursive in nature, and can be applied at the various analysis levels required of Systems Engineering. Therefore, the main contribution of paper is the application of the Genetic Causal cost model within the Systems Engineering context, whe ther at a requirements, functional or physical level.