Aerodynamic upgrade of
Surface Air Cooled Oil Cooler

Horizon 2020 / Clean Sky JU Call: H2020-CS2-CFP08-2018-01

The absolute necessity to reduce pollutant emissions as well as the future limited availability of fossil fuels will lead to a continuous increase of fuel costs in the coming years. As, today, the fuel costs contribute to about 40 % of the ownership cost of an aero-engine, the airline companies request drastic reductions of fuel burn (up to 30 %) for the next generation of engines, as an example, a decrease of 1 % in Specific Fuel Consumption (SFC) corresponds to a saving of about 50,000 € per engine. A main objective is therefore the reduction of the SFC to reduce fuel costs on one side and the ecological impact of its combustion on the other side.

This objectives are aligned with the high level objectives of Integrated Technology Demonstrators of new Engines defined in CleanSky2

Up to 23% of CO2 emission reduction vs. 2000 aircraft, i.e. at least ACARE 2020 target assigned to Engine. This goal is 9 % better than the assumed 2014 Reference status.
Noise levels making a significant step towards to ACARE 2035 targets (- 11 EPNdB per operation relative to 2000 situation: including engine, nacelle, aircraft technologies – airframe noise reduction, novel aircraft configurations – and ATM benefits).
Contribute to achieve NOX emission ACARE 2020 target (- 80% vs 2000 baseline).

The main improvements to apply on the current aero-engines to meet these objectives concern the global architecture of the turbomachine and the reduction of engine air extraction. Concerning the architecture, the solutions aiming at increasing the by-pass ratio and therefore decreasing the SFC (Open Rotor, Geared Turbofan, Contra-Rotating Turbofan) are characterized by complex mechanical transmissions allowing a more efficient cycle, but requesting a more important cooling capability by the oil of the lubrication circuit. In addition, the trend towards more electrical engines also results in more important cooling requirements. This heating increase has to cope with a decrease in the available coolant source almost exclusively used today, i.e. the fuel


As described in the call topic, the main aims of this project are:


Developing a predictive methodology on the SACOC (Surface Air Cooled Oil Cooler) air heat exchanger and its impact on the aerodynamics (including acoustics) of the secondary flow.

The work proposed in this proposal will contribute to this objectives by:

Characterize the aerodynamic performance of the SACOC as an User Defined Function, which can be included in standard simulation tools and which will consider the main parameters of its design.

Identify and model the temperature and heat transfer coefficient evolution on the complete surface of the SACOC and the coupling between the temperature and the aerodynamic fields.

Identify and model enthalpy drop (overall efficiency) from upstream to downstream of the ACO.

Perform a detailed numerical simulation (validated with experimental data) to identify the noise sources caused by the presence of the SACOC: i. identify the trailing edge noise of the splitter ii. estimate the impact of the vortices shed by the upstream fan wakes.


Evaluating new concepts without fins, paying special attention to the trade-off between thermal benefits and head losses in the secondary flow introduced by the new concepts.

The work proposed in this proposal will contribute to this objectives by:

Detailed simulation and parameter analysis of new SACOC concepts. Evaluation of aerodynamic, acoustic and thermal performances

3D Manufacturing and experimental testing of most promising SACOC concepts.

Sensitivy analysis and geometry optimization of selected SACOC concepts.

Relation to the CS2JU Work Plan

The proposal address the topic JTI-CS2-2018-CfP08-ENG-01-37: Aerodynamic upgrade of Surface Air Cooled Oil Cooler (SACOC). The topic leader is Safran.

This topic is located into the WP2 of the Engine ITD: Ultra High Propulsive Efficiency (UHPE) demonstrator addressing Short / Medium Range aircraft market, 2014-2021. Which aims to Design, development and ground test of a propulsion system demonstrator to validate the low pressure modules and nacelle technology bricks necessary to enable an Ultra High By-pass Ratio engine.

WP2 is aimed to procure TRL 5-6 maturation mid 2021 for a set of specific technologies dedicated to Ultra High Propulsive Efficiency concept. In particular efficient aerodynamic, themal and acoustic SACOC designs will affect the global aims:

Demonstrate aerodynamic efficiency and noise performance of the short air intake / low speed fan / exhaust ducts / variable area fan nozzle, considered as a whole, higher than those of today VHBR engines.

Demonstrate highly efficient and robust power gearbox integrated in an actual thermal and dynamic engine environment, and also integrated with the thermal management system (heat exchanger, etc).

Obtain acoustic data from engine ground test to consolidate noise benefits at aircraft level. For the methodologies that are used in the aerodynamic and aeroacoustic analysis, based on advanced CFD and CAA methods, they will also have undergone necessary development for robust analysis of engine noise generation and propagation. The involved aeroacoustic mechanisms will be better understood and the capacity to simulate these phenomena using CFD/CAA techniques will allow controling the noise-generation, with much better perspectives towards implementation in real-life aircraft.

Moreover, the Aerodynamic upgrade of Surface Air Cooled Oil Cooler (SACOC) is located inside WP2.5: Controls & Other Systems. In particular: Due to higher thermal fluxes to be managed and necessity to avoid prohibitive nacelle cross section increase, UHBR architecture needs specific and non conventional fuel, oil and electronic systems with most of their components installed around the HP core. In the demonstrator core and nacelle compartments must represent as close as possible the challenge of the final product. Accessory gear box, oil system and thermal management, including heat exchangers and their integration are the major challenges.