Aerodynamic Investigations of an Advanced VIGV Design of Adjustable Geometry for Very High Flow Turning

2015 ◽  
Author(s):  
David Händel ◽  
Reinhard Niehuis ◽  
Jan Klausmann
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
High Speed ◽  
Guide Vane ◽  
Operating Conditions ◽  
Total Pressure Loss ◽  
Inlet Guide Vane ◽  
Basic Design ◽  
Low Loss ◽  
Symmetric Profile

On the basis of experimental results the new design of a Variable Inlet Guide Vane (VIGV), as can be used for the control and regulation in multishaft compressors, is presented. Main goal of this investigation is a significant increase of the operating range and a reduction of the total pressure loss compared to a currently used basic design. For both designs 2D-cascades were build for detailed measurements in the High-Speed Cascade Wind Tunnel at the Institute of Jet Propulsion at the Universität der Bundeswehr München. The basic design exhibits a symmetric profile with only one segment. In contrast to that the new VIGV design consists of two symmetric vane segments which are arranged pivotable to each other. This provides the advantage of a symmetric profile for a fully opened VIGV associated with a low-loss level. For guidance of the flow, both vane segments can be rotated. Hence, the turning of the flow is split onto two segments. This avoids a huge flow separation on the suction side for high turning angles (Δβ > 30°) which is linked with a strong and abrupt loss increase. Due to the design, the new VIGV exhibits a gap between the two vane segments. Results with opened and sealed gap are presented and discussed. Using a sealing between the segments, a reduction of the profile loss could be detected for all investigated operating conditions. Even without a sealing in the gap, the “low-loss working range” is significantly increased. In addition, it is depicted that the presented results are valid for varying inflow velocities. This broadens the usability of the outcomes. Concluding, it is shown that all aims are achieved. Using the new VIGV design with sealing the low-loss working range can almost be doubled (Δβ > 55°) and the total pressure loss decreases in every working condition compared to the basic design.

scholarly journals Aerodynamic and Aeroelastic Effects of Design-Based Geometry Variations on a Low-Pressure Compressor

2020 ◽  
Vol 5 (4) ◽  
pp. 26
Author(s):  
Torben Eggers ◽  
Hye Rim Kim ◽  
Simon Bittner ◽  
Jens Friedrichs ◽  
Joerg R. Seume
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Vibration Amplitude ◽  
Guide Vane ◽  
Total Pressure Loss ◽  
Inlet Guide Vane ◽  
Gap Size ◽  
Operating Points ◽  
Bypass Ratio ◽  
Pressure Compressor

In modern aircraft engines, the low-pressure compressor (LPC) is subjected to a flow characterized by strong wakes and secondary flows from the upstream fan. This concerns ultra-high bypass ratio (UHBR) turbofan engines, in particular. This paper presents the aerodynamic and aeroelastic sensitivities of parametric variations on the LPC, driven by the design considerations in the upstream fan. The goal of this investigation was to determine the influence of design-based geometry parameter variations on the LPC performance under realistic inlet flow distributions and the presence of an s-duct. Aerodynamic simulations are conducted at the design and off-design operating points with the fan outflow as the inlet boundary conditions. Based on the aerodynamic results, time-linearized unsteady simulations are conducted to evaluate the vibration amplitude at the resonance operating points. First, the bypass ratio is varied by reducing the channel height of the LPC. The LPC efficiency decreases by up to 1.7% due to the increase in blockage of the core flow. The forced response amplitude of the rotor decreases with increasing bypass ratio due to increased aerodynamic damping. Secondly, the fan cavity leakage flow is considered as it directly affects the near hub fan flow and thus the inflow of the LPC. This results in an increased total-pressure loss for the s-duct due to mixing losses. The additional mixing redistributes the flow at the s-duct exit leading to a total-pressure loss reduction of 4.3% in the first rotor at design point. This effect is altered at off-design conditions. The vibration amplitude at low speed resonance points is increased by 19% for the first torsion and 26% for second bending. Thirdly, sweep and lean are applied to the inlet guide vane (IGV) upstream of the LPC. Despite the s-duct and the variable inlet guide vane (VIGV) affecting the flow, the three-dimensional blade design achieves aerodynamic and aeroelastic improvements of rotor 1 at off-design. The total-pressure loss reduces by up to 18% and the resonance amplitude more than 10%. Only negligible improvements for rotor 1 are present at the design point. In a fourth step, the influence of axial gap size between the stator and the rotor rows in the LPC is examined in the range of small variations which shows no distinct aerodynamic and aeroelastic sensitivities. This finding not only supports previous studies, but it also suggests a correlation between mode shapes and locally increased excitaion with increasing axial gap size. As a result, potential design improvements in future fan-compressor design are suggested.

scholarly journals Combustion Turbulence Flow in Trapped Vortex Combustor with Guide Vane and Blunt Body

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Zhuoxiong Zeng ◽  
Kaifang Guo ◽  
Xue Gong
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Blunt Body ◽  
Guide Vane ◽  
Total Pressure Loss ◽  
Structure Parameters ◽  
Optimum Structure ◽  
Turbulence Flow ◽  
Combustion Turbulence ◽  
Trapped Vortex

Numerical calculation was conducted to obtain the optimum structure parameters of the trapped vortex combustor (TVC) with the guide vane and blunt body. The results show that the optimum structure parameters of the guide vane are a/Hf=0.5, b/Li=0.2, and c/L=0.1, and the optimum structure parameters of blunt body are S/L=0.7, L2/L=0.1, and L1/Li=0.25. Then, the influence of different inlet conditions on the combustion turbulence flow was studied. The results show that high inlet temperature and low inlet velocity can effectively reduce total pressure loss; the equivalence ratio has little effect on total pressure loss. The study of unsteady flow shows that double vortices undergo the process of preliminarily forming-breaking down-forming again-being stable gradually.

Aerodynamic Investigations of a Variable Inlet Guide Vane With Symmetric Profile

2014 ◽  
Author(s):  
David Händel ◽  
Reinhard Niehuis ◽  
Uwe Rockstroh
Keyword(s):  
Boundary Layer ◽  
High Speed ◽  
Guide Vane ◽  
Reynolds Numbers ◽  
Boundary Layer Transition ◽  
Inlet Guide Vane ◽  
Experimental Investigations ◽  
Wide Range ◽  
Variable Inlet Guide Vane ◽  
Symmetric Profile

In order to determine the aerodynamic behavior of a Variable Inlet Guide Vane as used in multishaft compressors, extensive experimental investigations with a 2D linear cascade have been conducted. All the experiments were performed at the High-Speed Cascade Wind Tunnel at the Institute of Jet Propulsion. They covered a wide range of Reynolds numbers and stagger angles as they occur in realistic turbomachines. Within this work at first the observed basic flow phenomena (loss development, overturning) will be explained. For the present special case of a symmetric profile and a constant decreasing chord length along the vane height, statements about different spanwise position can be made by investigating different Reynolds numbers. The focus of this paper is on the outflow of the VIGV along the vane height. Results for an open flow separation on the suction side are presented, too. Stall condition can be delayed by boundary layer control. This is done using a wire to trigger an early boundary layer transition. The outcomes of the trip wire measurement are finally discussed. The objective of this work is to evaluate the influence of the stagger angle and Reynolds number on the total pressure losses and the deviation angle. The results of the work presented here, gives a better insight of the efficient use of a VIGV.

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.

Flow Investigation Through a 30° Turn Diffusing Duct in Subsonic Flow Regime

2009 ◽  
Author(s):  
Prasanta K. Sinha ◽  
Biswajit Haldar ◽  
Amar N. Mullick ◽  
Bireswar Majumdar
Keyword(s):  
Axial Velocity ◽  
Pressure Loss ◽  
Total Pressure ◽  
High Speed ◽  
Static Pressure ◽  
Transverse Velocity ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Pressure Probe ◽  
Mean Velocity

Curved diffusers are an integral component of the gas turbine engines of high-speed aircraft. These facilitate effective operation of the combustor by reducing the total pressure loss. The performance characteristics of these diffusers depend on their geometry and the inlet conditions. In the present investigation the distribution of axial velocity, transverse velocity, mean velocity, static and total pressures are experimentally studied on a curved diffuser of 30° angle of turn with an area ratio of 1.27. The centreline length was chosen as three times of inlet diameter. The experimental results then were numerically validated with the help of Fluent, the commercial CFD software. The measurements of axial velocity, transverse velocity, mean velocity, static pressure and total pressure distribution were taken at Reynolds number 1.9 × 105 based on inlet diameter and mass average inlet velocity. The mean velocity and all the three components of mean velocity were measured with the help of a pre-calibrated five-hole pressure probe. The velocity distribution shows that the flow is symmetrical and uniform at the inlet and exit sections and high velocity cores are accumulated at the top concave surface due to the combined effect of velocity diffusion and centrifugal action. It also indicates the possible development of secondary motions between the concave and convex walls of the test diffuser. The mass average static pressure recovery and total pressure loss within the curved diffuser increases continuously from inlet to exit and they attained maximum values of 35% and 14% respectively. A comparison between the experimental and predicated results shows a good qualitative agreement between the two. Standard k-ε model in Fluent solver was chosen for validation. It has been observed that coefficient of pressure recovery Cpr for the computational investigation was obtained as 38% compared to the experimental investigation which was 35% and the coefficient of pressure loss is obtained as 13% in computation investigation compared to the 14% in experimental study, which indicates a very good qualitative matching.

Experimental investigation of the role of struts in high speed mixing

2013 ◽  
Vol 117 (1188) ◽  
pp. 193-211 ◽  
Author(s):  
S. L. N. Desikan ◽  
J. Kurian
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
High Speed ◽  
Static Pressure ◽  
Mie Scattering ◽  
Total Pressure Loss ◽  
Pressure Losses ◽  
Mixing Performance ◽  
Supersonic Mixing

AbstractThis paper presents the experimental results of the role of struts in supersonic mixing. Experiments were carried out with novel strut configurations to show their capabilities on mixing with reasonable total pressure losses. The performances were compared with the Baseline Strut configurations (BSPI and BSNI). The analysis presented includes the mixing quantifications using Mie scattering signature, flow field visualisation, measurement of wall static pressure and the total pressure loss calculations. The results clearly demonstrated that the proposed strut configurations achieved increased mixing (7-8%) compared to BSPI with increase in total pressure loss (2%). On the other hand, when compared with BSNI, the mixing performance was found to be decreased by 6% with reduced total pressure loss (12%).

scholarly journals DEVELOPMENT OF AERODYNAMIC DIAGRAMS OF HIGH-LOADED REVERSE AXIAL FANS

2020 ◽  
Vol 2 ◽  
pp. 72-81
Author(s):  
Pavel V. Kosykh
Keyword(s):  
Flow Rate ◽  
Total Pressure ◽  
High Speed ◽  
Guide Vane ◽  
Pressure Coefficient ◽  
Aerodynamic Characteristics ◽  
Inlet Guide Vane ◽  
Ansys Software ◽  
Axial Fans ◽  
Limiting Values

Present-day achievements in the field of strength calculation and structural optimization allow creating main mine fans with higher tip speed than in currently used machines. The paper considers the features of calculating the aerodynamic diagrams of mine reverse axial fans with a tip speed over 200 m/s. It is shown that at such speed it is possible to obtain high-flow fans with significantly smaller dimensions than their existing counterparts. Aerodynamic diagrams with high reverse characteristics (flow rate of more than 0.7 from the direct mode for the network of the same aerodynamic characteristics as in direct mode) are developed. The aerodynamic characteristics of the developed diagrams are calculated in the ANSYS software package. It is shown that an increase in the tip speed contributes to an increase in reverse properties of fans compared to less high-speed machines designed for the same total pressure. The limiting values of axial velocity coefficient and pressure coefficient are determined, at which it is possible to obtain a fan without an inlet guide vane, with a monotonic dependence of total pressure on flow rate.

Flowfield Investigation of a Compressor Cascade at High Incidence—Part 1: Pneumatic Probe Measurements

2009 ◽  
Author(s):  
Pavlos K. Zachos ◽  
Vassilios Pachidis ◽  
Bernard Charnley ◽  
Pericles Pilidis
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Incidence Angle ◽  
Axial Flow ◽  
Quantitative Measure ◽  
Operating Conditions ◽  
Total Pressure Loss ◽  
Compressor Cascade ◽  
Engine Operation ◽  
Pressure Surface

The performance prediction of axial flow compressors and turbines still relies on the stationary testing of blade cascades. Most of the blade testing studies are done for operating conditions close to the design point or in off-design areas not too far from it. However, blade performance remains unexplored at very far off-design conditions, such as windmilling, characterised by operation under extremely low mass flows and rotational speeds which, in turn, imply highly negative incidence angle values. In this paper, the flow field generated by a 3-dimensional linear compressor cascade at a highly negative incidence angle and zero rotational speed is experimentally investigated using a pneumatic miniature cobra probe. The main objective of the study is to derive the total pressure loss through the blades at such a highly negative incidence angle. An overview of the blade geometry as well as of the experimental facility is given whereas the measurement strategy and the data acquisition technique are also presented. An uncertainty study taking into account the most significant factors affecting the quality of the results has been carried out. As shown by the measurements taken at specific positions downstream of the blades, the flowfield is dominated by highly separated flows on the pressure surface, which contribute to the increased values of the total pressure loss coefficient which seems to be weakly dependent on the inlet Mach number. The quantitative measure of the pressure losses at the extremely negative incidence angle examined can be considered to be a validation platform for correspondent numerical studies of similar flow conditions. Additionally, the experimental results obtained can be used to extend the applicability of the current pressure loss models, increasing the predictive capability of the through flow numerical approaches towards far off-design areas of component or whole engine operation.

The Effect of Tip Clearance and Hub Rotation on the Performance of an Axial Compressor Stator

2019 ◽  
Author(s):  
Chao Jiang ◽  
Jun Hu ◽  
Jiayu Wang ◽  
Jun Li ◽  
Rong Xu
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
High Speed ◽  
Pressure Ratio ◽  
Important Influence ◽  
Tip Clearance ◽  
Total Pressure Loss ◽  
Computation Method ◽  
Efficiency Curve ◽  
Total Pressure Ratio

Abstract In this paper, 1.5-stage high-speed compressor stator was studied using numerical computation method. Four gap cases were calculated under the condition of the hub being stationary or rotating, and the characteristic curves of the 1.5-stage compressor was obtained. Firstly, the influence of the change of the gap on the total pressure ratio and the efficiency curve was studied when the state of the hub is fixed. Then, the influence of the rotation of the hub on the total pressure ratio and the efficiency curve was discussed when the tip clearance is fixed. Finally, the total pressure loss of the stator channel would be analyzed. The above research would make people understand that the relative motion of the end wall has an important influence on the performance of the axial-flow compressor; when hub is stationary, the optimal gap is greater than 0, while when hub was rotating, the optimal gap was 0; and recognize that the variation of clearance and the motion state of the hub have an important influence on the distribution of total pressure loss along the span.

Active flow control by means of endwall synthetic jet on a high-speed compressor stator cascade

2017 ◽  
Vol 232 (6) ◽  
pp. 641-659
Author(s):  
Yong Qin ◽  
Yanping Song ◽  
Fu Chen ◽  
Ruoyu Wang ◽  
Huaping Liu
Keyword(s):  
Flow Control ◽  
Pressure Loss ◽  
Total Pressure ◽  
High Speed ◽  
Pressure Rise ◽  
Synthetic Jet ◽  
Total Pressure Loss ◽  
Momentum Exchange ◽  
Actuation Frequency ◽  
Flow Mixing

The underlying physics of the endwall synthetic jet in improving the aerodynamic performance of a high-speed compressor stator cascade is investigated in this paper. The effects of both injected momentum and actuation frequency are discussed in detail. In the investigations, the injected momentum is controlled by either changing the maximum jet velocity or modifying the tube diameter. Numerical results demonstrate that the streamwise momentum addition and flow mixing enhancement are the key factors of the endwall synthetic jet in improving the cascade performance. The high momentum fluid injected into the flow field can reenergize the passage flow, and the generated streamwise jet vortex contributes to the strengthening of flow mixing. Consequently, the momentum exchange between the low momentum fluid region and the main flow is enhanced and boundary layer separation on the blade suction surface is delayed. The loss characteristic in the corner region is improved as well. The intensified flow mixing will also increase the total pressure loss in the near-endwall region, which as a result will worsen the cascade performance, and hence the total effect of the endwall synthetic jet depends on the sum of its impacts. Moreover, the injected momentum and the actuation frequency have strong influences on the flow control effect. With the momentum coefficient and the reduced frequency being Cµ = 0.131% and F+ = 1.0, the reduction in total pressure loss coefficient and the increment in pressure rise coefficient are 7.3% and 3.3%, respectively.

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