Numerical Investigation of Inlet Distortion for Different Rear Mounted Engine Installations at Taking-Off Conditions

2015 ◽  
Author(s):  
Hairun Xie ◽  
Yadong Wu ◽  
Anjenq Wang ◽  
Hua Ouyang
Keyword(s):  
Flow Field ◽  
Aircraft Engine ◽  
Operating Conditions ◽  
Operating Characteristics ◽  
Inlet Flow ◽  
Close Coupling ◽  
Inlet Distortion ◽  
Business Jet ◽  
Air Intake ◽  
A Minor

Rear mounted engines are widely used in business jet and regional jet applications. It is a “clean wing” design. The engine is mounted behind the wing, so that the inlet/exhaust of nacelle has a minor influence on the flow over the wing. The engine thrust line is close to the fuselage axis. As a result, the asymmetric yaw moment will be smaller when single engine stall occurs. Field experience and historical data have revealed that engine aerodynamic stability and fan aeromechanics are extremely sensitive to the uniformity and steadiness of inlet flow. Engine inlet flow could be distorted and separated at various operating conditions, such as, high ground crosswind, take off, and other high angle of attack (AOA) maneuvers. As a result, strict regulations and requirements were set by certification agencies to assess: i) aircraft maneuver capability, ii) engine operating characteristics, as well as iii) aerodynamics/aeromechanics behaviors and capability, with respect to flow field surrounding the entire propulsion system. Due to the nature of complexity of the flow field at air intake, the inlet compatibility of fuselage mounted engines becomes one of the most complicated & challenged item to meet the FAR33 as well as the FAR25 certification requirements. This research paper discusses the inlet compatibility of rear-mounted aircraft engine with respect to AOA and crosswind under various operating conditions. Models of two installed configurations, which set by relative position of engine to fuselage and wing, were created. At each case, the engine inlet flow field was calculated at various AOA and crosswind conditions. Comparisons of total pressure contours at air intake were made to assess the likelihood of flow separation. The radial and circumferential inlet distortion levels were calculated at the assumed inlet AIP location for each operating condition and installed configuration. Assessments are made based on intensive usage of CFD analysis, and substantiated by test results. The flow field information obtained by CFD calculation reveals a close coupling phenomenon exist among engine installation, AOA and inlet capability. Analytical results were also checked, and the results agreed well with that of the compliant flight tests.

Numerical Investigation of Crosswind Effect on Different Rear Mounted Engine Installations

2014 ◽  
Author(s):  
Hairun Xie ◽  
Yadong Wu ◽  
Anjenq Wang ◽  
Hua Ouyang
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Pressure Profile ◽  
Operating Conditions ◽  
Operating Characteristics ◽  
Close Coupling ◽  
Pressure Profiles ◽  
Air Intake ◽  
A Minor ◽  
Condition Assessments

The rear-mounted engine is widely used in business and regional jets. It is a “clean wing” design. The engine is mounted behind the wing, so that the inlet/outlet of the nacelle has a minor influence on the flow over the wing. The engine thrust line is close to the fuselage axis. As a result, the asymmetric yaw moment will be smaller when single engine stall occurs. Strict regulations and requirements were set by certification agencies to assess aircraft maneuver capability as well as engine operating characteristics. These regulations are mainly defined to evaluate structural strength, aerodynamics, & engine/aircraft performance. However, due to the nature of the complexity of the flow field at the air intake, the inlet compatibility of fuselage mounted engines becomes one of the most complicated & challenging items to meet FAR33 as well as FAR25 certification requirements, especially during cross wind operating conditions. This research paper discusses the inlet compatibility of rear-mounted aircraft engines with respect to the installed configuration and crosswind operating conditions. Models of two installed configurations, set by the relative position of engine to the fuselage and the wing were created. In each case, the engine inlet flow field was calculated at various ambient wind conditions. Comparisons of the total pressure profile at the air intake were made to assess the likelihood of flow separation at the inlet of engine. Inlet distortion levels of corresponding total pressure profiles were calculated for each operating and installed condition. Assessments are made based on intensive usage of CFD analysis of different engine installations and operating conditions. The flow field information obtained by CFD calculation reveals a close coupling phenomenon exists among engine installations, cross wind, and inlet capability.

Nacelle Aerodynamic Optimization and Inlet Compatibility

2015 ◽  
Author(s):  
Jingjing Chen ◽  
Yadong Wu ◽  
Zhonglin Wang ◽  
Anjenq Wang
Keyword(s):  
Pressure Loss ◽  
Operating Conditions ◽  
Maximum Pressure ◽  
Aerodynamic Optimization ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Induction System ◽  
Air Intake ◽  
Inlet Flow Distortion ◽  
The Impact

The design of air induction system is targeting to balance the internal and external flow characteristics as well as the structure and aerodynamic integrity. An optimized air intake design that providing velocity and pressure distributions with least drag and maximum pressure recovery could end up at the expense of higher inlet flow distortion and lower stability margin. Indeed, design requirements and considerations at different operating conditions, such as takeoff, and high AOA maneuvers, could be significantly different from that of cruise and level flight. One of the most challenged operating conditions to be certified for FAR33 & FAR25 requirements is ground crosswind condition, when “Engine” is operating statically on the ground with high crosswind presented. It could accommodate inlet separation or distortion resulted from crosswind, and triggers fan or core stall, as well as induces high fan and/or engine vibrations. Studies of engine inlet compatibility become one of the major tasks required during the engine developing phase. This research is a parametric study of using CFD to evaluate operational characteristics of the air induction system. Comparisons of various inlet designs are made and characterized into four categories, i.e., i) Inlet pressure loss, ii) Nacelle drag, iii) Inlet flow distortion, and iv) Inlet Mach distribution. The objective is to assess the impact of air induction design of turbofan upon inlet compatibility. The research introduces the Kriging model and weighting coefficients to optimize internal total pressure loss and external drag using the isolated nacelle model. Bezier equation was used to fit the optimized curves obtained by changing several control points of the baseline configuration of nacelle. To study the impact of asymmetric lip on flow separation in ground crosswind condition, the paper built crosswind model which introduce a inlet boundary as fan face. Comparisons are then made between the original and optimal nacelle, to show correlation between inlet compatibility and air intake profile.

Experimental Investigation of the Influence of Inlet Distortion on the Stall Inception in a Low Speed Axial Compressor

2009 ◽  
Author(s):  
Huabing Jiang ◽  
Yajun Lu ◽  
Wei Yuan ◽  
Qiushi Li
Keyword(s):  
Flow Field ◽  
Dynamic Response ◽  
Flow Separation ◽  
Flow Condition ◽  
Axial Compressor ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Stall Inception ◽  
Inlet Distortion ◽  
Compressor Performance

Inlet distortion is one of the major concerns for high maneuverability airplanes. An experiment is performed to investigate the influence of inlet distortion on the stall inception in a low speed axial compressor, where the distorted inlet flow field is simulated with a flat baffle placed upstream of the compressor. The flow field around a rotor blade is measured using 2D Digital Particle Image Velocimetry (DPIV) under both uniform and distorted inlet flow conditions. A comparison of flow fields reveals that the distorted inlet flow condition makes the compressor flow fields asymmetric. Flow separation and blockage within Distorted Sector A and Transition Sector B are more severe compared to Sector C. The distorted Sector A and Transition Sector B are the key regions that degrade compressor performance and stability. The large axial velocity makes the flow field within the Undistorted Sector C vigorous, which helps to suppress flow separation and blockage. Compressor rotor blades experience loading and unloading in a revolution period and the compressor exhibits strong dynamic response when it operates under distorted inlet flow conditions. Time-related pressure signals acquired at the rotor exit are utilized to analyze the development of the stall disturbance and the stall characteristic of the compressor. The development period of the stall disturbance is prolonged by the dynamic response of the compressor flow field under the distorted inlet flow condition. Dynamic development of the stall disturbance induced by inlet distortion reduces the compressor stall intensity. The frequency associated with the rotating stall cell is related to the rotating velocity of stall cells, which keeps the same value for uniform and distorted inlet flow conditions. Consequently, the stall inception of the compressor is influenced by the distorted inlet flow condition. The disturbance initiated in Distorted Sector A will experience development and damping when it propagates circumferentially, and might fail to survive the damping within Undistorted Sector C. Stall inception occurs only when the damping within Undistorted Sector C is insufficient to prevent its growth. The dynamic development of the disturbance can reasonably explain the influence of inlet distortion on compressor performance.

Nacelle: Air Intake Aerodynamic Design and Inlet Compatibility

2014 ◽  
Author(s):  
Jingjing Chen ◽  
Yadong Wu ◽  
Zhonglin Wang ◽  
Anjenq Wang
Keyword(s):  
Research Work ◽  
Operating Conditions ◽  
Pressure Recovery ◽  
Weighting Coefficient ◽  
Maximum Pressure ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Induction System ◽  
Air Intake ◽  
The Impact

One of the most challenging operating conditions to be certified for FAR33 & FAR25 requirements is ground crosswind condition. When “Engine” is operated using the designed inlet and nacelle, within the flight envelope, could accommodate inlet separation/distortion resulted from crosswind and high angle-of-attack operating conditions. Inlet flow separation and distortion could trigger fan or core stall, as well as induce high fan and/or engine vibrations. The air induction system or inlet of the engine is designed to provide velocity and pressure distributions with minimum distortion and maximum pressure recovery to the propulsion system. Engine-inlet-airframe compatibility is one of the major tasks required to be evaluated in detail during the engine developing phase. This research is a parametric study of using CFD to evaluate operational characteristics of the air induction system. Comparisons of various inlet designs are made and characterized into three categories, i.e., i) Inlet flow recovery, ii) Inlet flow distortion, iii) Inlet Mach distribution. The objective is to assess the impact of air induction design of turbofan upon inlet compatibility. The current research work includes four parts, i.e., i) A geometry modeling process of nacelle, inlet, wing and fuselage, ii) A meshes generator ICEM, iii) The ANSYS CFX CFD software which could achieves numerical simulation and post-processing, iv) The Matlab platform with the function of coupling all considerations listed above for inlet compatibility optimization, based on genetic algorithm and Kriging agent model. The research introduces the Kriging model and weighting coefficient to optimize total pressure loss coefficient and static pressure recovery coefficient, with the external nacelle flow ignored. Bezier equation was used to fit the optimized curves obtained by changing two control points at the inter surface of nacelle. The wing-mounted model coupled with the nacelles, fuselage and wings was then built to make the assessment of inlet compatibility of air intake system relative to the isolate model. Comparison of aerodynamic performance was then made between the original and optimal nacelle, to show correlation between inlet compatibility and air intake profile.

Efficient Modeling Strategy of an Axial Compressor Fan-Stage Under Inlet Distortion

2016 ◽  
Author(s):  
Bryan Lobo ◽  
Laith Zori ◽  
Paul Galpin ◽  
William Holmes
Keyword(s):  
Axial Compressor ◽  
Aircraft Engine ◽  
Potential Effect ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Flow Conditions ◽  
Geometry Model ◽  
Inlet Distortion ◽  
Modeling Strategy ◽  
Efficient Modeling

The front fan of a turbofan aircraft engine often operates under distorted inlet flow conditions. This distortion is caused by either flight operating conditions, such as a crosswind or boundary layer ingestion, or due to its nacelle installation. These flow conditions negatively impact the aerodynamic performance of the compression system. Moreover, the asymmetry of the flow causes non-uniform circumferential pressure distortions which can trigger a strong aeromechanical response in the fan blades. Numerical simulation can contribute to the design process if it can accurately predict the aerodynamic performance penalties and the loads experienced by the fan blades, thereby identifying potential problems early in the design phase. This requires accurate accounting of the pressure loads on the fan from the upstream inlet distortion and the potential effect of the downstream stator row. The loads are inherently transient in nature, requiring solutions on the full wheel geometry. However, full wheel modeling is expensive and not practical early in the design cycle. In this work, an efficient modeling strategy is proposed for an axial compressor fan with a downstream stator row (NASA Stage 67, rotor/stator) undergoing inlet distortion. A multi-frequency frozen gust analysis using the Fourier-Transformation (FT) pitch-change method is utilized to solve this flow problem on a reduced geometry (two rotor-passages only). A once-per-revolution inlet distortion modeled as a cosine variation in total pressure is imposed upstream of the rotor. The influence of the stator row on the fan is accounted for within a transient simulation by imposing a 360 degree profile at the exit of the rotor. The profile from the stator row is obtained previously from a steady-state simulation using a multiple mixing-plane approach. In this approach the stator potential flow and the pressure variation in the stator row due to inflow distortion are accounted for. The paper compares the reduced geometry model with full wheel transient predictions, thereby demonstrating the efficiency of the proposed method both in terms of accuracy and solution speedup. Important aerodynamic performance parameters as well as flow field solution monitors are compared to assess the viability of this modeling strategy.

Inlet Compatibility and Fan Aeromechanics of HBP Turbofan Engine

2017 ◽  
Author(s):  
Zhonglin Wang ◽  
Jingjing Chen ◽  
Yong Chen
Keyword(s):  
High Cycle Fatigue ◽  
Integrated System ◽  
Operating Conditions ◽  
Operating Characteristics ◽  
Preliminary Assessment ◽  
Turbofan Engine ◽  
Campbell Diagram ◽  
Inlet Distortion ◽  
Operation Conditions ◽  
Fan Blade

As an integrated system, turbofan engine airworthiness certification is a complex network because design, operating conditions and multi-disciplines are interlaced. Inlet compatibility specified in FAR regulations is to demonstrate satisfactory of engine operating characteristics throughout the flight envelope, which can be affected by engine installation and operation conditions. One limited operating condition is the high crosswind on the ground. Flow separated at engine inlet, unsteady and non-uniform, passing through the diffuser to the fan face, stimulated the fan blade at a broad frequency range, which could lead to high cycle fatigue. A ground crosswind test was conducted by an airplane company to demonstrate the engine inlet compatibility with engine mounted on the rear of the aircraft under various crosswind conditions [1] including 90-degree crosswind, quarterly headwind (315-degree) and quarterly tailwind (225-degree). Results showed that among all tested ambient wind conditions, the engine was the least stable under quarterly tailwind (225-degree). To predict the fan blade response driven by inlet separation, a process of evaluating inlet separation induced stimulus was illustrated in this paper. The stimuli were classified in two parts, i) synchronous stimulus induced by inlet distortion, and ii) non-synchronous stimulus induced by turbulence. Vibration of a wide-chord fan blade was evaluated by modal analysis and Campbell diagram. Test data of total pressure distortion at fan face were analyzed by Fast Fourier Transform (FFT), and the excitations in frequency domain were applied to fan blade for harmonic analysis. Results revealed that the synchronous excitation caused the blade resonating at an elevated stress level, as expected. This study provided a preliminary assessment and a better understanding of fan aeromechanics, when the engine is operating at the unsteady, unstable, and non-uniform flow environment. Discussions of how to control and how to decrease the vibration level were given in the study.

Numerical and Experimental Study on Bleed Impact on Intermediate Compressor Duct Performance

2018 ◽  
Author(s):  
Elias M. V. Siggeirsson ◽  
Niklas Andersson ◽  
Fredrik Wallin
Keyword(s):  
Flow Field ◽  
Pressure Coefficient ◽  
Aircraft Engine ◽  
Operating Conditions ◽  
Test Rig ◽  
Cfd Simulations ◽  
Local Effects ◽  
University Of Technology ◽  
The Difference ◽  
Operating Points

In this study, a comparison is done between an in-house experimental test rig at GKN Aerospace and simulations done using an in-house CFD solver at Chalmers University of Technology. The geometry represents an intermediate compressor duct of an aircraft engine. The main focus is on comparing the flow field at different operating conditions. Those conditions are controlled by extracted massflow through a bleed pipe, upstream of the intermediate compressor duct. The work presented in this paper is done using a RANS solver with the Spalart All-maras turbulence model. The CFD simulations compare well with measured data, for the lower bleed fraction, especially in terms of pressure coefficients in the intermediate compressor duct and at downstream locations. There are strong local effects due to instabilities in the bleed pipe for the higher bleed fraction, which caused the fluctuations in the pressure coefficient and resulted in degraded convergence. The difference in the flow field is also visible when comparing the operating points, where stronger total pressure wakes are noticed in the results for the lower bleed case.

scholarly journals Optimal Tuner Selection for Kalman Filter-Based Aircraft Engine Performance Estimation

2009 ◽  
Vol 132 (3) ◽  
Author(s):  
Donald L. Simon ◽  
Sanjay Garg
Keyword(s):  
Kalman Filter ◽  
Estimation Error ◽  
Engine Performance ◽  
Aircraft Engine ◽  
Operating Conditions ◽  
Performance Estimation ◽  
Experimental Simulation ◽  
Tuning Parameter ◽  
Estimation Accuracy ◽  
On Line

A linear point design methodology for minimizing the error in on-line Kalman filter-based aircraft engine performance estimation applications is presented. This technique specifically addresses the underdetermined estimation problem, where there are more unknown parameters than available sensor measurements. A systematic approach is applied to produce a model tuning parameter vector of appropriate dimension to enable estimation by a Kalman filter, while minimizing the estimation error in the parameters of interest. Tuning parameter selection is performed using a multivariable iterative search routine that seeks to minimize the theoretical mean-squared estimation error. This paper derives theoretical Kalman filter estimation error bias and variance values at steady-state operating conditions, and presents the tuner selection routine applied to minimize these values. Results from the application of the technique to an aircraft engine simulation are presented and compared with the conventional approach of tuner selection. Experimental simulation results are found to be in agreement with theoretical predictions. The new methodology is shown to yield a significant improvement in on-line engine performance estimation accuracy.

scholarly journals A New Method to Determine the Impact of Individual Field Quantities on Cycle-to-Cycle Variations in a Spark-Ignited Gas Engine

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4136
Author(s):  
Clemens Gößnitzer ◽  
Shawn Givler
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Turbulent Kinetic Energy ◽  
Negative Impact ◽  
Operating Conditions ◽  
Engine Operation ◽  
Gas Engine ◽  
Cycle Simulation ◽  
Simulation Results ◽  
The Impact

Cycle-to-cycle variations (CCV) in spark-ignited (SI) engines impose performance limitations and in the extreme limit can lead to very strong, potentially damaging cycles. Thus, CCV force sub-optimal engine operating conditions. A deeper understanding of CCV is key to enabling control strategies, improving engine design and reducing the negative impact of CCV on engine operation. This paper presents a new simulation strategy which allows investigation of the impact of individual physical quantities (e.g., flow field or turbulence quantities) on CCV separately. As a first step, multi-cycle unsteady Reynolds-averaged Navier–Stokes (uRANS) computational fluid dynamics (CFD) simulations of a spark-ignited natural gas engine are performed. For each cycle, simulation results just prior to each spark timing are taken. Next, simulation results from different cycles are combined: one quantity, e.g., the flow field, is extracted from a snapshot of one given cycle, and all other quantities are taken from a snapshot from a different cycle. Such a combination yields a new snapshot. With the combined snapshot, the simulation is continued until the end of combustion. The results obtained with combined snapshots show that the velocity field seems to have the highest impact on CCV. Turbulence intensity, quantified by the turbulent kinetic energy and turbulent kinetic energy dissipation rate, has a similar value for all snapshots. Thus, their impact on CCV is small compared to the flow field. This novel methodology is very flexible and allows investigation of the sources of CCV which have been difficult to investigate in the past.

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