Jianping Yin

Low- Speed Aerodynamics and Aeroacoustics of CROR Propulsion Systems

Contra Rotating Open Rotor (CROR) propulsion systems have come back into focus as a possible economic and environmentally friendly powerplant for future transport aircraft. nHaving been widely applied to the simulations of single rotation propellers, the DLR CFD code TAU and the aeroacoustic analysis tool APSIM have been employed for the analysis of the complex aerodynamics and aeroacoustics of this type of aircraft propulsion system. nIn order to demonstrate the codes applicability to these types of simulations as well as to develop an understanding of the impact of configuration variations, a generic 8x8 and 10x8 pusher CROR powerplant are studied here at typical sea-level take-o conditions of M=0.2. The results allow for a detailed analysis of the aerodynamic interactions between the two rotors as well as the noise generation mechanisms, allowing for an improved understanding of interaction tone sources. In addition, the impact of the numerical approach to the aeroacoustic simulations on the results is studied with a focus on determining the importance of the quadrupole contributions.

Aerodynamic and Aeroacoustic Installation Effects for Pusher-Configuration CROR Propulsion Systems

Contra Rotating Open Rotor (CROR) propulsion systems have come back into focus as a possible economic and environmentally friendly powerplant for future transport aircraft. nHaving been widely applied to the simulations of single rotation propellers, the DLR CFD code TAU and the aeroacoustic analysis tool APSIM have been employed for the analysis of the complex aerodynamics and aeroacoustics of this type of aircraft propulsion system. nInstallation effects, i.e. the mutual interactions between airframe components and the rotors, have a pronounced impact on the aerodynamic and aeroacoustic performance for this type of engine. In this paper, the impact of the presence of the pylon is studied for a representative 10x8-bladed pusher-configuration CROR powerplant at typical cruise and ntake-off conditions. The numerical results allow for a detailed analysis of the aerodynamic interactions between the pylon and the rotors enabling for an improved understanding of the installation impact on blade loads and noise emissions.

Coupled uRANS and FW- H Analysis of Installed Pusher Propeller Aircraft Configurations

In this paper the aeroacoustic phenomena characteristic of a pusher-propeller cofiguration and their aerodynamic causes are discussed and analyzed. The work was done in the frame of the European-funded project CESAR (Cost Effective Small AiRcraft). The configuration under study is an industrially relevant design with a wing-mounted pusher npropeller, which features a close coupling of the turboshaft engines exhaust nozzles and a five bladed propeller. An established numerical analysis approach is applied in this study, which couples a high-fidelity unsteady aerodynamic simulation using the DLR TAU-Code with the DLR APSIM Code for a subsequent aeroacoustic evaluation. APSIM computes nthe sound propagation into the far eld based on the Ffowcs-Williams/Hawkings (FW-H) equations. A detailed analysis of the contributions of various components of the installation as well as nflight condition specific parameters toward the overall noise generation by the propeller is presented. Furthermore, the possible scattering effect of the wing and nacelle is discussed. A detailed analysis of specific aspects of the numerical approach for the aeroacoustic analysis is made through a comparison between the results achieved using both a FW-H impermeable and permeable formulation. The numerical error due to both njet exhaust and propeller wake impingement on the FW-H permeable surface as well as the impact of cutting a hole in this permeable surface to avoid possible issues of these effects are discussed.

Pylon Trailing Edge Blowing for the Control of CROR Unsteady Blade Loads

Contra Rotating Open Rotor (CROR) propulsion systems show promise as a highly economic and environmentally friendly powerplant for future transport aircraft. Installation effects, i.e. the mutual interactions between airframe components and the rotors, have a pronounced impact on the aerodynamic and aeroacoustic performance for this type of engine. In the present study, a coupled aerodynamic and aeroacoustic analysis using the DLR numerical methods TAU and APSIM is performed to assess the potential of pylon blowing to achieve a reduction of unsteady blade and rotor loadings and corresponding noise emissions caused by the installation of the powerplant on the aircraft.

Progress in Aerodynamic and Aeroacoustic Integration of CROR Propulsion Systems

Contra-Rotating Open Rotor (CROR) propulsion systems have seen renewed interest as an economic and environmentally friendly powerplant for future transport aircraft. Installation effects, i.e. the mutual interactions between airframe components and the rotors, have a pronounced impact on the aerodynamic and aeroacoustic performance for this type of engine. In the past five years, DLR’s Institute of Aerodynamics and Flow Technology has performed a number of numerical studies investigating important aspects relating to engine-airframe integration of CROR engines. In this article an overview of coupled aerodynamic and aeroacoustic simulations investigating representative pusher-configuration CROR engines will be given, focusing on the impact on aerodynamic performance and aeroacoustics caused by the presence of a pylon, nthe potential for noise reduction by employing trailing-edge blowing at the pylon trailing edge as well as the performance and noise variations caused by different senses of rotation of the rotors. It is shown that the interaction with the pylon strongly impacts blade performance and front rotor noise emissions but that the use of active flow control in the form of pylon trailing-edge blowing can alleviate these adverse installation effects to a notable extent.

Aerodynamic and Aeroacoustic Analysis of Contra-Rotating Open Rotor Propulsion Systems at Low-Speed Flight Conditions

Contra Rotating Open Rotor (CROR) propulsion systems have come back into focus as a possible economic and environmentally friendly powerplant for future transport aircraft. Having been widely applied to the simulations of single rotation propellers, the DLR CFD code TAU and the aeroacoustic analysis tool APSIM have been employed for the analysis of the complex aerodynamics and aeroacoustics of this type of propulsion system. In order to demonstrate the codes applicability to these simulations a generic 8x8 pusher CROR powerplant was designed and uRANS computations at typical sealevel take-off conditions of M = 0.2 were performed for two angles of attack. The results allow for a detailed analysis of the aerodynamic interactions between the two rotors as well as the noise generation mechanisms.

The Case for Counter-Rotation of Installed Contra-Rotating Open Rotor Propulsion Systems

Contra Rotating Open Rotor (CROR) propulsion systems have seen renewed interest as a possible economic and environmentally friendly powerplant for future transport aircraft. Installation effects, i.e. the mutual interactions between airframe components and the rotors, have a pronounced impact on the aerodynamic and aeroacoustic performance for nthis type of engine. In this paper, the impact on aerodynamic performance and noise emissions caused by the presence of a pylon as well as a variation in the sense of rotation of the rotors is numerically studied for a representative 10x8-bladed pusher-configuration CROR engine at typical take-off conditions. In particular, the sense of rotation influence on blade and rotor performance and loadings as well as on the handling quality relevant in-plane rotor forces is analyzed, as is the resulting impact on the noise emissions in the near- and farfield and the flyover noise results. Having been widely applied to the simulations of single as well as contra-rotation propellers, the DLR CFD code TAU and the aeroacoustic analysis tool APSIM allow for a detailed analysis and an improved understanding of the complex aerodynamics and aeroacoustics of this type of propulsion system.

Aerodynamic and Aeroacoustic Analysis of Installed Pusher-Propeller Aircraft Configurations

In this paper, the aeroacoustic phenomena characteristic of a pusher-propeller configuration and their aerodynamic causes are discussed and analyzed. The work was done in the framework of the European-funded project CESAR(for ‘cost effective small aircraft’). The configuration under study is based on an industrially relevant business aircraft design with a wing-mounted pusher propeller, which features a close coupling of the turboshaft engine exhaust nozzles and a five bladed propeller. An established numerical analysis approach is applied in this study, which couples a high-fidelity unsteady aerodynamic simulation using theDLRunstructured finite volume flow solver (TAU) code with the DLR Ffowcs-Williams–Hawkings code APSIM for a subsequent aeroacoustic evaluation. A detailed analysis of the contributions of various components of the installation as well as flight-condition specific parameters toward the overall noise generation by the propeller is presented, which highlights the dominant role the engine-jet impingement on the propeller plays for the aeroacoustic characteristics of this type of aircraft configuration. A detailed analysis of specific aspects of the input surface used for the aeroacoustic analysis is made through a comparison between the results achieved using both impermeable and permeable Ffowcs-Williams–Hawkings formulations. The numerical error due to both jet exhaust and propeller wake impingement on the Ffowcs-Williams–Hawkings permeable surface as well as the impact of cutting a hole in this permeable surface to avoid possible issues of these effects are discussed.

Simulation of noise radiation from installed pusher propeller aircraft configurations (Section 8.3)

The influence of the elastic rotor blade deformation and the aerodynamic interference from the fuselage on the rotor aerodynamics as well as rotor noise characteristics was studied. A BO105 Main Rotor /Tail Rotor/Fuselage (FUS) configuration is chosen for the numerical simulations. A coupling of unsteady free wake 3-D panel method (UPM) and Airbus Helicopters’ (formerly: Eurocopter) rotor code HOST was conducted to account for the effect of elastic blade deformation as well as compressibility correction. The effect of fuselage is simulated by using two fuselage models in UPM, (1) potential theory in form of a panelized fuselage and (2) an analytic fuselage influence formulation derived from isolated fuselage simulation based on (1).Measurement techniques based on microphone-arrays are well-known and common practice on scaled models in wind tunnels with closed test section. Usually, full-scale Reynolds numbers are not achieved. To increase the Reynolds number measurements are performed in cryogenic and/or pressurized wind tunnels. nAt the DLR Institute of Aerodynamics and Flow Technology the microphone array measurement technique was further developed to perform measurements in a cryogenic wind tunnel at temperatures down to 100 K. In order to use a microphone array in a cryogenic environment, coming to grips with cold hardiness and ensuring long term stability of the array fairing and the electronic devices, especially the microphones, are the primary challenge. nIn a first step measurements of the radiated noise from a single rod configuration have been conducted in the cryogenic wind tunnel DNW-KKK using a prototype microphone array designed for cryogenic environment. Measurements were carried out with a wide range of operational flow parameters. The measured sound radiation results showed a very good agreement with theory and a Reynolds number dependency of the measured and predicted sound power was shown.The aeroacoustic phenomena characteristic of a pusher-propeller configuration and their aerodynamic causes are discussed and analyzed. The work was done in the frame of the European-funded project CESAR (Cost Effective Small AiRcraft). The configuration under study is an industrially relevant design with a wing-mounted pusher propeller, which features a close coupling of the turboshaft engines exhaust nozzles and a five bladed propeller. The coupling of an Actuator Disc (TAU AD) model and unsteady free wake panel method (UPM) is employed for the computation of the propeller unsteady aerodynamic force in pusher installations. The Ffowcs-Williams/Hawkings (FW-H) equations based code APSIM is used to compute the sound propagation into the far field. A detailed comparison of the current fast coupling method with high-fidelity uRANS (TAU) simulation results and the differences between the two approaches are discussed. The noise reduction through a redesigned engine exhaust nozzle is presented.

Pylon blowing for the reduction of installation-associated noise of CROR engines (Section 8.2)

The influence of the elastic rotor blade deformation and the aerodynamic interference from the fuselage on the rotor aerodynamics as well as rotor noise characteristics was studied. A BO105 Main Rotor /Tail Rotor/Fuselage (FUS) configuration is chosen for the numerical simulations. A coupling of unsteady free wake 3-D panel method (UPM) and Airbus Helicopters’ (formerly: Eurocopter) rotor code HOST was conducted to account for the effect of elastic blade deformation as well as compressibility correction. The effect of fuselage is simulated by using two fuselage models in UPM, (1) potential theory in form of a panelized fuselage and (2) an analytic fuselage influence formulation derived from isolated fuselage simulation based on (1).Measurement techniques based on microphone-arrays are well-known and common practice on scaled models in wind tunnels with closed test section. Usually, full-scale Reynolds numbers are not achieved. To increase the Reynolds number measurements are performed in cryogenic and/or pressurized wind tunnels. nAt the DLR Institute of Aerodynamics and Flow Technology the microphone array measurement technique was further developed to perform measurements in a cryogenic wind tunnel at temperatures down to 100 K. In order to use a microphone array in a cryogenic environment, coming to grips with cold hardiness and ensuring long term stability of the array fairing and the electronic devices, especially the microphones, are the primary challenge. nIn a first step measurements of the radiated noise from a single rod configuration have been conducted in the cryogenic wind tunnel DNW-KKK using a prototype microphone array designed for cryogenic environment. Measurements were carried out with a wide range of operational flow parameters. The measured sound radiation results showed a very good agreement with theory and a Reynolds number dependency of the measured and predicted sound power was shown.The aeroacoustic phenomena characteristic of a pusher-propeller configuration and their aerodynamic causes are discussed and analyzed. The work was done in the frame of the European-funded project CESAR (Cost Effective Small AiRcraft). The configuration under study is an industrially relevant design with a wing-mounted pusher propeller, which features a close coupling of the turboshaft engines exhaust nozzles and a five bladed propeller. The coupling of an Actuator Disc (TAU AD) model and unsteady free wake panel method (UPM) is employed for the computation of the propeller unsteady aerodynamic force in pusher installations. The Ffowcs-Williams/Hawkings (FW-H) equations based code APSIM is used to compute the sound propagation into the far field. A detailed comparison of the current fast coupling method with high-fidelity uRANS (TAU) simulation results and the differences between the two approaches are discussed. The noise reduction through a redesigned engine exhaust nozzle is presented.