scholarly journals Numerical simulations of an intake-compressor system

2018 ◽  
Vol 2 ◽  
pp. VQB6CK
Author(s):  
Thomas Kächele ◽  
Rudolf P. M. Rademakers ◽  
Tim Schneider ◽  
Reinhard Niehuis
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Pressure Field ◽  
Negative Impact ◽  
Measurement Data ◽  
Safety Margin ◽  
Aircraft Design ◽  
Interface Plane ◽  
Intake Flow ◽  
The Impact

Integrated propulsion plays a major role in future civil and military aircraft design. A key component of these systems are highly bent intake geometries. As the flow passes through such ducts, combined total pressure and swirl distortions are generated which have a negative impact on compressor performance, safety margin, and durability. Due to weight and space limitations, a close coupling of intake and compressor is necessary. An experimental test case including a highly bent intake geometry and a state of the art turbofan engine was established and extensive measurement data was acquired. This publication compares results of three different numerical approaches to this test data: Isolated intake simulations, isolated compressor simulations with distorted inflow conditions, and a coupled simulation of intake and three stage compressor. The isolated intake simulation is able to reproduce the static wall pressure field of the intake as well as the occurring flow separation. Towards the interface plane to the compressor however, significant deviations are observed. The upstream effect of the compressor working under the combined pressure swirl distortion is assessed via the second simulation approach. The influence of the swirl and total pressure distortion on the compressor is first simulated separately and then compared to the impact of the combined distortion. The coupled intake-compressor simulation reveals the manipulation of the intake flow field by an upstream static pressure field. In contrast to experiments a slightly unsteady operation point and an asymmetric intake flow field were observed.

Flow field behind a complex total pressure distortion screen

2019 ◽  
Vol 233 (14) ◽  
pp. 5075-5092
Author(s):  
M Sivapragasam
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Design Methodology ◽  
Pressure Field ◽  
Alternative Interpretation ◽  
Interface Plane ◽  
Screen Design ◽  
Pressure Distributions ◽  
Water Jet Cutting ◽  
Distortion Index

The flow field behind a complex total pressure distortion screen is investigated experimentally and numerically. The distortion screen is designed using an established design methodology and fabricated by water-jet cutting technique. The distorted total pressure field behind the screen is quantified by a distortion index parameter, which is evaluated from computations and experiments for several values of inlet Mach number. The root-mean-square error between the target total pressure values and that achieved by the screen design at the aerodynamic interface plane is 4.75%. The evolution of the distorted total pressure field downstream of the screen is presented in detail in terms of radial and circumferential total pressure distributions and their gradients. An alternative interpretation of the distorted total pressure field is made by means of defining a total pressure flux existing behind the screen and expanding it using derivative-moment transformation technique. It is seen that the circumferential vorticity is a major contributing factor to the total pressure flux.

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.

scholarly journals Experimental and numerical investigation on total pressure distortion generated by a rectangular movable flat baffle

2021 ◽  
Vol 13 (2) ◽  
pp. 168781402199439
Author(s):  
Baofeng Tu ◽  
Bin Xuan ◽  
Chuanpeng Li ◽  
Xinyu Zhang ◽  
Jun Hu
Keyword(s):  
Flow Field ◽  
Mass Flow ◽  
Total Pressure ◽  
Quantitative Relationship ◽  
Interface Plane ◽  
Detached Eddy Simulation ◽  
Insertion Depth ◽  
Distortion Coefficient ◽  
Pressure Region ◽  
Blocking Coefficient

A distortion generator equipped with a motor-activated movable flat baffle was installed just upstream of a rectangular plenum entrance to investigate the effects of inlet total pressure distortion on the stability and performance of an auxiliary power unit (APU). Experiments and numerical simulations on a direct connect scale inlet model of the APU were carried out to obtain a quantitative relationship between the insertion depth of the flat baffle in the flow stream and the total pressure distortion intensity and region. In the experiments, the blocking coefficient and total pressure distortion coefficient were controlled by adjusting the insertion depth of the flat baffle and the mass flow. In the simulations, detailed flow field was analyzed based on the detached-eddy simulation (DES) method. The results show that the pressure distribution of the distorted flow on the aerodynamic interface plane (AIP) can be divided into a high-pressure region, a transition region, and a low-pressure region. The area affected by the distorted flow was larger than the inserting area of the flat baffle. That area was more related to the relative blocking coefficient, and less affected by the mass flow. The total pressure distortion coefficient had a linear relationship with the mass flow rate and is positively correlated with the relative blocking coefficient. As the relative blocking coefficient increased to a certain value, an exponential growth in the total pressure distortion coefficient occurred, and consequently, the flow field distortion was intensified. In the flow field, a pair of corner vortices were formed at the corner between the flat baffle and the bottom wall of the inlet pipe, and a large separation zone was formed behind the flat baffle and exhibits certain unsteady characteristics.

Experimental Study on the Effect of Clocking on the Propagation of Inflow Pressure Distortions in a Low Pressure Turbine Stage

2020 ◽  
Author(s):  
L. Simonassi ◽  
M. Zenz ◽  
P. Bruckner ◽  
S. Pramstrahler ◽  
F. Heitmeir ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Total Pressure ◽  
Low Pressure ◽  
Vibration Characteristics ◽  
Test Facility ◽  
Turbine Stage ◽  
Rotor Vibration ◽  
Low Pressure Turbine ◽  
The Impact

Abstract The design of modern aero engines enhances the interaction between components and facilitates the propagation of circumferential distortions of total pressure and temperature. As a consequence, the inlet conditions of a real turbine have significant spatial non-uniformities, which have direct consequences on both its aerodynamic and vibration characteristics. This work presents the results of an experimental study on the effects of different inlet total pressure distortion-stator clocking positions on the propagation of total pressure inflow disturbances through a low pressure turbine stage, with a particular focus on both the aerodynamic and aeroelastic performance. Measurements at a stable engine relevant operating condition and during transient operation were carried out in a one and a half stage subsonic turbine test facility at the Institute of Thermal Turbomachinery and Machine Dynamics at Graz University of Technology. A localised total pressure distortion was generated upstream of the stage in three different azimuthal positions relative to the stator vanes. The locations were chosen in order to align the distortion directly with a vane leading edge, suction side and pressure side. Additionally, a setup with clean inflow was used as reference. Steady and unsteady aerodynamic measurements were taken downstream of the investigated stage by means of a five-hole-probe (5HP) and a fast response aerodynamic pressure probe (FRAPP) respectively. Strain gauges applied on different blades were used in combination with a telemetry system to acquire the rotor vibration data. The aerodynamic interactions between the stator and rotor rows and the circumferential perturbation were studied through the identification of the main structures constituting the flow field. This showed that the steady and unsteady alterations created by the distortion in the flow field lead to modifications of the rotor vibration characteristics. Moreover, the importance of the impact that the pressure distortion azimuthal position has on the LPT stage aerodynamics and vibrations was highlighted.

scholarly journals Reconstructing Compressor Non-uniform Circumferential Flow Field from Spatially Undersampled Data - Part 1: Methodology and Sensitivity Analysis

2021 ◽  
pp. 1-12
Author(s):  
Fangyuan Lou ◽  
Nicole L. Key
Keyword(s):  
Sensitivity Analysis ◽  
Flow Field ◽  
Total Pressure ◽  
Pressure Field ◽  
Sampled Data ◽  
Wavelet Approximation ◽  
Multi Stage ◽  
Reconstructed Signal ◽  
Data Points ◽  
Aero Engines

Abstract The flow field in a compressor is circumferentially non-uniform due to the wakes from upstream stators, the potential field from both upstream and downstream stators, and blade row interactions. This non-uniform flow impacts stage performance as well as blade forced vibrations. Historically, experimental characterization of the circumferential flow variation is achieved by circumferentially traversing either a probe or the stator rows. This involves the design of complex traverse mechanisms and can be costly. To address this challenge, a novel method is proposed to reconstruct compressor nonuniform circumferential flow field using spatially under-sampled data points from a few probes at fixed circumferential locations. The paper is organized into two parts. In the present part of the paper, details of the multi-wavelet approximation for the reconstruction of circumferential flow and use of the Particle Swarm Optimization algorithm for selection of probe positions are presented. Validation of the method is performed using the total pressure field in a multi-stage compressor representative of small core compressors in aero engines. The circumferential total pressure field is reconstructed from 8 spatially distributed data points using a triple-wavelet approximation method. Results show good agreement between the reconstructed and the true total pressure fields. Also, a sensitivity analysis of the method is conducted to investigate the influence of probe spacing on the errors in the reconstructed signal.

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.

Performance of a Subsonic Compressor Airfoil With Upstream, End-Wall Injection Flow

2021 ◽  
Author(s):  
Aaron J. Pope ◽  
Andrew Oliva ◽  
Aleksandar Jemcov ◽  
Scott C. Morris ◽  
Mark Stephens ◽  
...  
Keyword(s):  
Total Pressure ◽  
High Speed ◽  
Pressure Field ◽  
Incidence Angle ◽  
Suction Side ◽  
Secondary Flows ◽  
Injection Flow ◽  
Wall Injection ◽  
End Wall ◽  
The Impact

Abstract The performance of a compressor stator airfoil with end-wall injection was studied experimentally and computationally. The geometry was a high-speed, subsonic, linear cascade. The independent variables studied were airfoil incidence angle and mass flow rate of end-wall injection upstream of the stator. The end-wall injection was intended to simulate upstream “leakage” through hardware gaps in the end-walls of gas-turbine engines. The exit of the cascade was interrogated experimentally by a five-hole-probe and a total pressure Kiel probe to provide total pressure measurements, which were used to calculate total pressure loss coefficients at the exit of the test section. Computational studies were completed to examine the end-wall flow physics and entropy generating mechanisms through the stator section. The experimental results showed a distinct decrease in the downstream total pressure field with end-wall injection flow, and the impact of the upstream injection on the stator loss coefficient was not a function of the incidence angle. The computational investigation found that the majority of the end-wall injection’s effect on the downstream total pressure field was observed as an increase in the size of the secondary flows on the suction-side of the stator near the upper end-wall.

scholarly journals Reconstructing Compressor Non-Uniform Circumferential Flow Field From Spatially Undersampled Data: Part 1 — Methodology and Sensitivity Analysis

2020 ◽  
Author(s):  
Fangyuan Lou ◽  
Nicole L. Key
Keyword(s):  
Sensitivity Analysis ◽  
Flow Field ◽  
Total Pressure ◽  
Pressure Field ◽  
Sampled Data ◽  
Wavelet Approximation ◽  
Multi Stage ◽  
Reconstructed Signal ◽  
Data Points ◽  
Aero Engines

Abstract The flow field in a compressor is circumferentially non-uniform due to the wakes from upstream stators, the potential field from both upstream and downstream stators, and blade row interactions. This non-uniform flow impacts stage performance as well as blade forced vibrations. Historically, experimental characterization of the circumferential flow variation is achieved by circumferentially traversing either a probe or the stator rows. This involves the design of complex traverse mechanisms and can be costly. To address this challenge, a novel method is proposed to reconstruct compressor nonuniform circumferential flow field using spatially under-sampled data points from a few probes at fixed circumferential locations. The paper is organized into two parts. In the present part of the paper, details of the multi-wavelet approximation for the reconstruction of circumferential flow and use of the Particle Swarm Optimization algorithm for selection of probe positions are presented. Validation of the method is performed using the total pressure field in a multi-stage compressor representative of small core compressors in aero engines. The circumferential total pressure field is reconstructed from 8 spatially distributed data points using a triple-wavelet approximation method. Results show good agreement between the reconstructed and the true total pressure fields. Also, a sensitivity analysis of the method is conducted to investigate the influence of probe spacing on the errors in the reconstructed signal.

scholarly journals Analysis of the Impact of Auxiliary Ventilation Equipment on the Distribution and Concentration of Methane in the Tailgate

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3076 ◽  
Author(s):  
Magdalena Tutak ◽  
Jarosław Brodny
Keyword(s):  
Methane Concentration ◽  
Negative Impact ◽  
Measurement Data ◽  
Hard Coal ◽  
Auxiliary Equipment ◽  
Mining Operations ◽  
Air Stream ◽  
Intersection Area ◽  
Cfd Method ◽  
The Impact

Methane, which is commonly found in hard coal deposits, represents a considerable threat to the safety of mining operations in these deposits. The paper presents the results of tests, aiming to limit the negative impact of methane on hard coal exploitation and improve work safety. The tests encompassed an analysis of methane concentration distributions in the tailgate (in the intersection area with the longwall), with account being taken of auxiliary ventilation equipment. This equipment is responsible for reducing methane concentration levels in the intersection area between the longwall and the tailgate. The analyses presented in the article were conducted for a spatial model of a longwall area, using the Computational Fluid Dynamics (CFD) method. Account was taken of the real-world measurements of the headings as well as the measurement data concerning methane concentration and ventilation parameters. The tests took into account methane emissions from the mined coal and from the goaf with caving. The analyses were performed for the system with and without auxiliary equipment, for different velocities of the additional air stream. This made it possible to compare both systems and determine the impact of auxiliary equipment on the distribution and concentration of methane in the most vulnerable area of exploitation. The distributions of the air and gas mixture were also determined in the analysed headings and goaf with caving. The results obtained clearly demonstrate that using auxiliary equipment has a significant effect on the ventilation parameters of the air stream and leads to reduction in methane concentrations in the most vulnerable section of the longwall. These results also confirmed the advantages of auxiliary ventilation equipment, which should contribute to their wider application in underground hard coal exploitation.

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