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.

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.

Probabilistic and Numerical Modelling of a Lobed Mixer at Windmilling Conditions

2013 ◽  
Author(s):  
Maxime Lecoq ◽  
Nicholas Grech ◽  
Pavlos K. Zachos ◽  
Vassilios Pachidis
Keyword(s):  
Flow Field ◽  
Response Surface ◽  
Gas Turbine ◽  
Pressure Loss ◽  
Total Pressure ◽  
Engine Performance ◽  
Operating Conditions ◽  
Total Pressure Loss ◽  
Operating Point ◽  
Mixing Losses

Aero-gas turbine engines with a mixed exhaust configuration offer significant benefits to the cycle efficiency relative to separate exhaust systems, such as increase in gross thrust and a reduction in fan pressure ratio required. A number of military and civil engines have a single mixed exhaust system designed to mix out the bypass and core streams. To reduce mixing losses, the two streams are designed to have similar total pressures. In design point whole engine performance solvers, a mixed exhaust is modelled using simple assumptions; momentum balance and a percentage total pressure loss. However at far off-design conditions such as windmilling and altitude relights, the bypass and core streams have very dissimilar total pressures and momentum, with the flow preferring to pass through the bypass duct, increasing drastically the bypass ratio. Mixing of highly dissimilar coaxial streams leads to complex turbulent flow fields for which the simple assumptions and models used in current performance solvers cease to be valid. The effect on simulation results is significant since the nozzle pressure affects critical aspects such as the fan operating point, and therefore the windmilling shaft speeds and air mass flow rates. This paper presents a numerical study on the performance of a lobed mixer under windmilling conditions. An analysis of the flow field is carried out at various total mixer pressure ratios, identifying the onset and nature of recirculation, the flow field characteristics, and the total pressure loss along the mixer as a function of the operating conditions. The data generated from the numerical simulations is used together with a probabilistic approach to generate a response surface in terms of the mass averaged percentage total pressure loss across the mixer, as a function of the engine operating point. This study offers an improved understanding on the complex flows that arise from mixing of highly dissimilar coaxial flows within an aero-gas turbine mixer environment. The total pressure response surface generated using this approach can be used as look-up data for the engine performance solver to include the effects of such turbulent mixing losses.

Unsteady Wet Steam Flow Field Measurements in the Last Stage of Low Pressure Steam Turbine

2015 ◽  
Author(s):  
Ilias Bosdas ◽  
Michel Mansour ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Shigeki Senoo
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Total Pressure ◽  
Low Pressure ◽  
Operating Conditions ◽  
Test Facility ◽  
Flow Structures ◽  
Wet Steam ◽  
Operating Condition ◽  
Last Stage

Modern steam turbines need to operate efficiently and safely over a wide range of operating conditions. This paper presents a unique unprecedented set of time-resolved steam flowfield measurements from the exit of the last two stages of a low pressure (LP) steam turbine under various volumetric massflow conditions. The measurements were performed in the steam turbine test facility in Hitachi city in Japan. A newly developed fast response probe equipped with a heated tip to operate in wet steam flows was used. The probe tip is heated through an active control system using a miniature high-power cartridge heater developed in-house. Three different operating points, including two reduced massflow conditions, are compared and a detailed analysis of the unsteady flow structures under various blade loads and wetness mass fractions is presented. The measurements show that at the exit of the second to last stage the flow field is highly three dimensional. The measurements also show that the secondary flow structures at the tip region (shroud leakage and tip passage vortices) are the predominant sources of unsteadiness at 85% span. The high massflow operating condition exhibits the highest level of periodical total pressure fluctuation compared to the reduced massflow conditions at the inlet of the last stage. In contrast at the exit of the last stage, the reduced massflow operating condition exhibits the largest aerodynamic losses near the tip. This is due to the onset of the ventilation process at the exit of the LP steam turbine. This phenomenon results in 3 times larger levels of relative total pressure unsteadiness at 93% span, compared to the high massflow condition. This implies that at low volumetric flow conditions the blades will be subjected to higher dynamic load fluctuations at the tip region.

scholarly journals Flow Distortion Into the Core Engine for an Installed Variable Pitch Fan in Reverse Thrust Mode

2020 ◽  
Author(s):  
David John Rajendran ◽  
Vassilios Pachidis
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Reverse Flow ◽  
Ground Plane ◽  
Operating Conditions ◽  
Flow Distortion ◽  
Engine Operation ◽  
Variable Pitch ◽  
The Core ◽  
Reverse Thrust

Abstract The flow distortion at core engine entry for a Variable Pitch Fan (VPF) in reverse thrust mode is described from a realistic flow field obtained using an integrated airframe-engine model. The model includes the VPF, core entry splitter, complete bypass nozzle flow path wrapped in a nacelle and installed to an airframe in landing configuration through a pylon. A moving ground plane to mimic the rolling runway is included. 3D RANS solutions are generated at two combinations of VPF stagger angle and rotational speed settings for the entire aircraft landing run from 140 to 20 knots. The internal reverse thrust flow field is characterized by bypass nozzle lip separation, pylon wake and recirculation of flow turned back from the VPF. A portion of the reverse stream flow turns 180° with separation at the splitter leading edge to feed the core engine. The core engine feed flow exhibits circumferential and radial non-uniformities that depend on the reverse flow development at different landing speeds. The temporal dependence of the distorted flow features is also explored by an URANS analysis. Total pressure and swirl angle distortion descriptors, as defined by the Society of Automotive Engineers (SAE) S-16 committee, and, total pressure loss into the core engine are described for the core feed flow at different operating conditions and landing speeds. It is observed that the radial intensity of total pressure distortion is critical to core engine operation, while the circumferential intensity is within acceptable limits. Therefore, the baseline sharp splitter edge is replaced by two larger rounded splitter edges of radii, ∼0.1x and ∼0.2x times the core duct height. This was found to reduce the radial intensity of total pressure distortion to acceptable levels. The description of the installed core feed flow distortion, as described in this study, is necessary to ascertain stable core engine operation, which powers the VPF in reverse thrust mode.

A Comparison between Measured and Computed Flow Fields in a Transonic Compressor Rotor

1980 ◽  
Vol 102 (4) ◽  
pp. 883-889 ◽  
Author(s):  
P. W. McDonald ◽  
C. R. Bolt ◽  
R. J. Dunker ◽  
H. B. Weyer
Keyword(s):  
Mach Number ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Computational Procedure ◽  
Operating Conditions ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Pressure Profiles

The flow field within the rotor of a transonic axial compressor has been computed and compared to measurements obtained with an advanced laser velocimeter. The compressor was designed for a total pressure ratio of 1.51 at a relative tip Mach number of 1.4. The comparisons are made at 100 percent design speed (20,260 RPM) with pressure ratios corresponding to peak efficiency, near surge, and wide open discharge operating conditions. The computational procedure iterates between a blade-to-blade calculation and an intrablade through flow calculation. Calculated Mach number contours, surface pressure distributions, and exit total pressure profiles are in agreement with the experimental data demonstrating the usefulness of quasi three-dimensional calculations in compressor design.

The Influence of the Total Pressure Profile on the Performance of Axial Gas Turbine Diffusers

2010 ◽  
Author(s):  
A. Hirschmann ◽  
S. Volkmer ◽  
M. Schatz ◽  
C. Finzel ◽  
M. Casey ◽  
...  
Keyword(s):  
Flow Separation ◽  
Gas Turbines ◽  
Total Pressure ◽  
Pressure Profile ◽  
Cfd Simulations ◽  
Pressure Profiles ◽  
Industrial Gas Turbines ◽  
Sst Turbulence Model ◽  
Highly Loaded ◽  
Good Agreement

Large industrial gas turbines for combined heat and power generation normally have axial diffusers leading to the heat recovery steam generator. The diffusers operate with high inlet axial Mach number (0.6) and with a non-uniform inlet total pressure profile from the turbine. Tests have been carried out on a generic highly loaded axial diffuser in a scaled axial diffuser test rig, with different inlet total pressure profiles including those that might be met in practice. The results show that the inlet total pressure profile has a strong effect on the position of flow separation, whereby a hub-strong profile tends to separate at the casing and the tip-strong profile on the hub. Steady CFD simulations using the SST turbulence model have been carried out based on extensive studies of the best way to model the inlet boundary conditions. These simulations provide good agreement with the prediction of separation in the diffuser but the separated regions often persist too long so that, in this highly loaded case with flow separation, the calculated diffuser pressure recovery can be in error by up to 30%.

Turning Mid Turbine Frame Behavior for Different HP Turbine Outflow Conditions

2011 ◽  
Author(s):  
Berardo Paradiso ◽  
Cornelia Santner ◽  
Josef Hubinka ◽  
Emil Go¨ttlich ◽  
Martin Hoeger
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Measurement Techniques ◽  
Operating Conditions ◽  
Time Resolved ◽  
Flow Angle ◽  
The Mean ◽  
Eu Project ◽  
The Eu

The design of turbine frames with turning vanes, known as turning mid-turbine frames (TMTF), becomes of great importance for high by-pass ratio engines with counter-rotating turbines. To achieve a more efficient low-pressure turbine the overall diffusion and radial offset should be increased. One goal of the EU project DREAM is to analyse the flow through a TMTF and a downstream arranged counter rotating LP rotor. The investigation of these complex interrelationships has been performed in the unique two-spool continuously operating transonic test turbine facility at Graz University of Technology. The test setup consists of an unshrouded HP stage, the TMTF and a shrouded LP rotor. The shafts of both turbines are mechanically independent, so the test rig allows a realistic two shaft turbine operation. The TMTF flow field is highly complex. It is a turbulent and unsteady flow dominated by strong secondary flows and vortex-interactions. The upstream transonic high pressure turbine stage produces a complex inflow with high levels of turbulence, stationary and rotating wakes and vortical structures. Therefore the application of advanced measurement techniques is necessary. To describe the HP-TMTF interaction time-resolved pressure measurements have applied within the project. The TMTF was instrumented with 10 fast response pressure transducers; static pressure tap recordings on the strut and on the TMTF end-walls have been also applied. Five hole probe, total pressure and total temperature rakes have been additionally acquired in the planes just in front of the struts and downstream to evaluate the performance of the TMTF. The results of these conventional techniques are presented in this work and they represent the necessary starting point for the evaluation and the description of the flow field. The idea is to start the study analysing the mean quantities and the overall performance of the two stages for different conditions and to leave the analysis of the time-resolved results for further investigation. Detailed investigations will start from the data presented in this paper; indeed, the use of unsteady measurement techniques is time consuming and cannot be performed for such a large amount of flow conditions, radial planes and HP vane - TMTF relative positions. Three operating conditions for different clocking positions have been considered. The variation of the operating conditions has been achieved by varying the HP shaft velocity and pressure ratio, with a consequence change of pressure ratio in the LP rotor. For this analysis the LP shaft velocity was kept constant. The TMTF performance variations will be analysed in terms of total pressure loss coefficient and exit flow angle; the mean interaction between the structures coming from the HP stage and the struts will represent the interpretation key to explain these variations. This work is part of the EU project DREAM (ValiDation of Radical Engine Architecture SysteMs, contract No. ACP7-GA-2008-211861).

scholarly journals Reconstructing Compressor Non-Uniform Circumferential Flow Field From Spatially Undersampled Data: Part 2 — Practical Application for Experiments

2020 ◽  
Author(s):  
Fangyuan Lou ◽  
Douglas R. Matthews ◽  
Nicholas J. Kormanik ◽  
Nicole L. Key
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Field ◽  
Leading Edge ◽  
Pressure Profile ◽  
Sampled Data ◽  
Mean Values ◽  
Novel Method

Abstract In the previous part of the paper, a novel method to reconstruct the compressor non-uniform circumferential flow field using spatially under-sampled data points is developed. In this part of the paper, the method is applied to two compressor research articles to further demonstrate the potential of the novel method in resolving the important flow features associated with these circumferential non-uniformities. In the first experiment, the static pressure field at the leading edge of a vaned diffuser in a high-speed centrifugal compressor is reconstructed using pressure readings from nine static pressure taps placed on the hub of the diffuser. The magnitude and phase information for the first three dominant wavelets are characterized. Additionally, the method shows significant advantages over the traditional averaging methods for calculating repeatable mean values of the static pressure. While using the multi-wavelet approximation method, the errors in the mean static pressure with one dropout measurement are 70% less than the pitchwise-averaging method. In the second experiment, the full-annulus total pressure field downstream of Stator 2 in a three-stage axial compressor is reconstructed from a small segment of data representing 20% coverage of the annulus. Results show very good agreement between the reconstructed total pressure profile and the experiment at a variety of spanwise locations from near hub to near shroud. The features associated with blade-row interactions accounting for passage-to-passage variations are resolved in the reconstructed total pressure profile.

Accounting for Circumferential Flow Nonuniformity in a Multi-Stage Axial Compressor

2021 ◽  
Author(s):  
Fangyuan Lou ◽  
Douglas R. Matthews ◽  
Nicholas J. Kormanik ◽  
Nicole L. Key
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Pressure Field ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Pressure Profile ◽  
Mean Flow ◽  
Forcing Functions ◽  
Wake Interactions ◽  
Flow Nonuniformity

Abstract The flow field in a compressor is circumferentially non-uniform due to geometric imperfections, inlet flow nonuniformities, and blade row interactions. Therefore, the flow field, as represented by measurements from discrete stationary instrumentation, can be skewed and contribute to uncertainties in both calculated one-dimensional performance parameters and aerodynamic forcing functions needed for aeromechanics analyses. Considering this challenge, this paper documents a continued effort to account for compressor circumferential flow nonuniformities based on discrete, under-sampled measurements. First, the total pressure field downstream of the first two stators in a three-stage axial compressor was measured across half of the annulus. The circumferential nonuniformities in the stator exit flow, including vane wake variability, were characterized. In addition, the influence of wake variation on stage performance calculations and aerodynamic forcing functions were investigated. In the present study for the compressor with an approximate pressure ratio of 1.3 at design point, the circumferential nonuniformity in total pressure yields an approximate 2.4-point variation in isentropic efficiency and 54% variation in spectral magnitudes of the fundamental forcing frequency for the embedded stage. Furthermore, the stator exit circumferential flow nonuniformity is accounted for by reconstructing the full-annulus flow using a novel multi-wavelet approximation method. Strong agreement was achieved between experiment and the reconstructed total pressure field from a small segment of measurements representing 20% coverage of the annulus. Analysis shows the wake-wake interactions from the upstream vane rows dominate the circumferentially nonuniform distributions in the total pressure field downstream of stators. The features associated with wake-wake interactions accounting for passage-to-passage variations are resolved in the reconstructed total pressure profile, yielding representative mean flow properties and aerodynamic forcing functions.

Investigation of the Flow Field and the Pressure Recovery in a Gas Turbine Exhaust Diffuser at Design, Part-Load and Over-Load Condition

2020 ◽  
Author(s):  
Maximilian Bauer ◽  
Simon Hummel ◽  
Markus Schatz ◽  
Martin Kegalj ◽  
Damian M. Vogt
Keyword(s):  
Mach Number ◽  
Flow Field ◽  
Pressure Distribution ◽  
Gas Turbine ◽  
Total Pressure ◽  
Operating Conditions ◽  
Pressure Recovery ◽  
Heavy Duty ◽  
Part Load ◽  
Design Load

Abstract The performance of axial diffusers installed downstream of heavy duty gas turbines is mainly affected by the turbine load. Thereby the outflow varies in Mach number, total pressure distribution, swirl and its tip leakage flow in particular. To investigate the performance of a diffuser at different load conditions, a generic diffuser geometry has been designed at ITSM which is representative for current heavy duty gas turbine diffusers. Results are presented for three different operating conditions, each with and without tip flow respectively. Part-load, design-load and over-load operating conditions are defined and varied at the diffuser inlet in terms of Mach number, total pressure distribution and swirl. Each operating point is investigated experimentally and numerically and assessed based on its flow field as well as the pressure recovery. The diffuser performance shows a strong dependency on the inlet swirl and total pressure profile. A superimposed tip flow only influences the flow field significantly when the casing flow is weakened due to casing separation. In those cases pressure recovery increases with additional tip flow. There is a reliable prediction of the CFD simulations at design-load. At part-load, CFD overpredicts the strut separation, resulting in an underpredicted overall pressure recovery. At over-load, CFD underpredicts the separation extension in the annular diffuser but overpredicts the hub wake. This leads to a better flow control in CFD with the result of an overpredicted overall pressure recovery.

Sign in / Sign up

Export Citation Format

Share Document