Multi-objective CFD-based design method for axial compressors
Doctoral thesis, 2014
Economic aspects such as reducing specific fuel consumption and ever growing environmental requirements on emissions and perceived noise levels are the major incentives in the pursuit to improve aircraft engines.
The overall efficiency of the engine is a combination of propulsive efficiency and thermal efficiency. A new, promising engine concept with very high propulsive efficiency is the so-called Open Rotor. In order to facilitate high thermal efficiency, the core of the engine must be designed with a high turbine inlet temperature as well as a high overall pressure ratio in combination with being light and compact. For the low-pressure compression system, the desire to reduce weight leads to a reduction of the number of stages. This must be realized by a combination of high transonic rotor speeds and high stage loadings in order to maintain the required pressure ratio. However, this becomes a tough design challenge aerodynamically as it will be more difficult to design the compressor with respect to high efficiency and sufficient stability along the entire operating line. This thesis presents a new design methodology, accounting for both efficiency and stability. The optimal set of solutions in the multi-objective space is explored with help of CFD computations integrated with an optimization framework that consists of a meta-model assisted genetic algorithm. In order to utilize the design process for industrial applications, the reductions in total design time and computational resources are also addressed. The validity of the analysis method developed is assessed by means of experimental data obtained from three transonic, highly loaded compressor cases including a rotor in isolation, a rotor-stator configuration and a three stage compressor.
Q3D
Turbomachinery
Design
Meta-modeling
Optimization
CFD
Validation
Compressor
Transonic
Virtual Development Laboratory, VDL, Hörsalsvägen 7a
Opponent: Professor Tom Verstraete
Author
Lars R Ellbrant
Chalmers, Applied Mechanics, Fluid Dynamics
Design of compressor blades considering efficiency and stability using CFD based optimization
ASME Turbo-expo 2012,;Vol. 8(2012)p. 371-382
Paper in proceeding
CFD optimization of a transonic compressor using multiobjective GA and metamodels
28th Congress of the International Council of the Aeronautical Sciences 2012, ICAS 2012; Brisbane; Australia; 23 September 2012 through 28 September 2012,;Vol. 4(2012)p. 2698-2712
Paper in proceeding
Balancing efficiency and stability in the design of transonic compressor stages
Proceedings of the ASME Turbo Expo 2013,;Vol. 6 B(2013)p. (Article number) GT2013-94838
Paper in proceeding
CFD validation of a high speed transonic 3.5 stage axial compressor
ISABE-2011,;(2011)
Other conference contribution
Tillväxten av den globala flygtrafiken ställer höga krav på flygmotor prestanda med avsikt att minska flygets klimatpåverkan.
Ett av det mest lovande flygmotorkoncept som visar stor potential att sänka bränsleförbrukningen är den så kallade Open rotor-motorn. För att realisera den låga bränsleförbrukningen måste dock dess kärnmotor vara lätt och kompakt samtidigt som dess verkningsgrad är hög, vilket också ställer höga krav på varje ingående komponent. Ett specifikt mål gällande kompressorn är att hitta en konstruktion som kan upprätthålla ett högt tryckförhållande samtidigt som den är lätt, har en hög verkningsgrad samt att marginalen mot pumpning är hög. En lätt kompressor med högt tryckförhållande leder till att varje kompressorsteg har en hög aerodynamisk last. En svårighet i det är att det blir desto svårare att uppnå en hög verkningsgrad samtidigt som stabiliteten är tillfredställande. För att lyckas med den här utmaningen måste nya konstruktionsmetoder utvecklas där man kan balansera flera krav samtidigt.
I avhandlingen presenteras en ny konstruktionsmetod som kan användas för att hitta en balanserad kompressorkonstruktion med avseende på verkningsgrad och stabilitet. Metoden kopplar samman avancerade optimeringsalgoritmer med ett strömningsmekaniskt beräkningsverktyg. För att uppnå tidseffektivisering har en förenklad beräkningsmodell tagits fram. Modellen har även validerats med hjälp av prestandamätningar från tre experimentellt utvärderade kompressorer.
Economic aspects such as reducing the fuel consumption and ever growing environmental requirements on emissions are the major incentives in the pursuit to improve aircraft engines.
A new, promising engine concept that has the potential of significantly reduce the fuel consumption of the air transportation is the so-called Open Rotor. In order to facilitate its potential, the core of the engine must be light, compact and have high efficiency. For the low-pressure compressor, the desire to reduce weight in combination of the required pressure ratio leads to a high aerodynamic load on each stage. However, this becomes a tough design challenge as it will be more difficult to achieve a high efficiency while having sufficient stability. In order to design such a compressor new design methods must be developed in which one can consider several requirements simultaneously.
This thesis presents a new design methodology that can be used to find balanced compressor stages with respect to efficiency and stability. The method is based on advanced optimization algorithms coupled to a computational tool that predicts the aerodynamic performance. Furthermore, a simplified computational model has been developed in order to reduce the design time, making it suitable for industrial applications. The validity of the computational method is assessed by means of experimental data obtained from three highly loaded compressor cases.
Driving Forces
Sustainable development
Areas of Advance
Transport
Subject Categories
Fluid Mechanics and Acoustics
ISBN
978-91-7597-069-1
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie
Virtual Development Laboratory, VDL, Hörsalsvägen 7a
Opponent: Professor Tom Verstraete