Performance Investigation Into Supersonic Diffuser for a High Pressure Centrifugal Compressor

Author(s):  
Takao Sugimoto ◽  
Tsukinami Kawanishi ◽  
Hiroshige Kumamaru ◽  
Yasumasa Tohbe

In high pressure centrifugal compressors, the overall stage performance is greatly influenced by its diffuser performance. Extremely complicated non-uniform and unsteady flow exists in the region between the impeller exit and the diffuser inlet. Furthermore, in the case of supersonic diffuser, shock waves can be observed near the diffuser inlet. These can cause aerodynamic losses. Therefore, it is essential to recognize such complicated flow to realize an appropriate diffuser design. An investigation into the performance of supersonic diffuser was carried out using a high pressure compressor test rig for a small industrial gas turbine with a high back swept impeller and a quasi pipe-shaped channel diffuser. In addition, 3D quasi-unsteady flow analyses of the entire compressor by a RANS code with Non Linear Harmonic method at several operating conditions between surge and choke were conducted to investigate the details of unsteady flow between the impeller exit and the diffuser exit. The results of the performance test and that of the 3D unsteady flow analyses have shown good agreement in the pressure rise and the isentropic efficiency at several operating conditions. These support high accuracy of the flow analyses and the performance measurements.

Author(s):  
Alexander Lange ◽  
Matthias Voigt ◽  
Konrad Vogeler ◽  
Henner Schrapp ◽  
Erik Johann ◽  
...  

The present paper introduces a novel approach for considering manufacturing variability in the numerical simulation of a multistage high-pressure compressor (HPC). The manufacturing process is investigated by analyzing three of a total of ten rotor rows. Therefore, 150 blades of each of the three rows were 3D scanned to obtain surface meshes of real blades. The deviation of a scanned blade to the design intent is quantified by a vector of 14 geometric parameters. Interpolating the statistical properties of these parameters provides the manufacturing scatter for all ten rotor rows expressed by 140 probability density functions. The probabilistic simulation utilizes the parametric scatter information for generating 200 virtual compressors. The CFD analysis provides the performance of these compressors by calculating speed lines. Postprocessing methods are applied to statistically analyze the obtained results. It was found that the global performance parameters show a significantly wider scatter range for higher back pressure levels. The correlation coefficient and the coefficient of importance are utilized to identify the sensitivity of the results to the geometric parameters. It turned out that the sensitivities strongly shift for different operating points. While the leading edge geometry of all rotor rows dominantly influences the overall performance at maximum efficiency, the camber line parameters of the front stages become more important for higher back pressure levels. The analysis of the individual stage performance confirms the determining importance of the front stages—especially for highly throttled operating conditions. This leads to conclusions regarding the robustness of the overall HPC, which is principally determined by the efficiency and pressure rise of the front stages.


Author(s):  
Alexander Lange ◽  
Matthias Voigt ◽  
Konrad Vogeler ◽  
Henner Schrapp ◽  
Erik Johann ◽  
...  

The present paper introduces a novel approach for considering manufacturing variability in the numerical simulation of a multi–stage high–pressure compressor (HPC). The manufacturing process is investigated by analyzing three of totally ten rotor rows. Therefore, 150 blades of each of the three rows were 3D scanned to obtain surface meshes of real blades. The deviation of a scanned blade to the design intent is quantified by a vector of 14 geometric parameters. Interpolating the statistical properties of these parameters provides the manufacturing scatter for all ten rotor rows expressed by 140 probability density functions. The probabilistic simulation utilizes the parametric scatter information for generating 200 virtual compressors. The CFD analysis provides the performance of these compressors by calculating speed lines. Post–processing methods are applied to statistically analyze the obtained results. It was found that the global performance parameters show a significantly wider scatter range for higher back pressure levels. The correlation coefficient and the coefficient of importance are utilized to identify the sensitivity of the results to the geometric parameters. It turned out that the sensitivities strongly shift for different operating points. While the leading edge geometry of all rotor rows dominantly influences the overall performance at maximum efficiency, the camber line parameters of the front stages become more important for higher back pressure levels. The analysis of the individual stage performance confirms the determining importance of the front stages — especially for highly throttled operating conditions. This leads to conclusions regarding the robustness of the overall HPC, which is principally determined by the efficiency and pressure rise of the front stages.


2020 ◽  
pp. 12-19
Author(s):  
Nikolay Shuvaev ◽  
◽  
Aleksandr Siner ◽  
Ruslan Kolegov ◽  
◽  
...  

Ensuring safety of flights is the most important task that is being solved in the process of designing an aircraft engine and aircraft. The most complex are the physical processes occurring inside the aircraft engine, especially in its gas generator: combustion chamber, high-pressure compressor and high-pressure turbine. The unsteady flow of gas in the flow duct of the aircraft engine is very complex, it is difficult to model, because the flow is characterized by a wide range of time and space scales. Unsteady flow in a high-pressure compressor can cause surge and breakdown of the compressor and the entire engine as a whole. Along with the detachment flows causing the surge, in the flow duct there can be resonant phenomena associated with the propagation of powerful sound waves along the flow duct of the engine, which, when a direct and reflected wave is imposed, create a very powerful standing wave that affects the structure. With a certain combination of conditions, the coincidence of the natural frequencies of the oscillations of the air volume and the solid body, such resonant processes in the flow duct of the gas turbine engine can lead to serious breakdowns, such as breakage of rotor blades and guide vanes, destruction of the aeroengine framework and other. The main difficulty is that it is problematic to identify such processes at the design and debugging stage, since there are no suitable mathematical models, and for experimental verification it is required to withstand the specific operating conditions of the node that are not known in advance. This work is devoted to the creation of a calculation technique that will allow in the future to diagnose resonance phenomena at the design stage and thereby significantly reduce the costs for the design, testing and manufacture of an aircraft engine. The proposed technique is based on the nonstationary Navier-Stokes equations for a compressible gas.


Author(s):  
Gary M. Colby ◽  
Timothy R. Griffin ◽  
Manoj K. Gupta ◽  
Harry F. Miller ◽  
Steven E. Nove ◽  
...  

This paper describes the mechanical and aerodynamic testing of the high-pressure CO2 compressors for the Tupi I, Tupi II, and Tupi III projects. This includes the results of the API 617 mechanical test and a special magnetic bearing exciter test to demonstrate rotordynamic stability at design operating conditions, as well as the results of the ASME PTC-10 Type 2 inert gas performance test and the ASME PTC-10 Type 1 full load–full pressure test on a CO2–hydrocarbon gas mixture equivalent to the actual process gas. A brief description of the compressor design and manufacture is also presented.


Author(s):  
Philip Magin ◽  
Florian Danner ◽  
Matthias Voigt ◽  
Ronald Mailach

Abstract The intended operating point of turbomachinery is subject to numerous kinds of uncertainty. These range from varying ambient conditions, across geometric deviations in a component, to system related loading variability resulting in engine-to-engine variation in component matching. In order to guarantee safe operation at all conditions, it is essential to consider the above uncertainties when designing turbomachinery. In the present work, a probabilistic assessment is performed of the influence of possible operational uncertainties on the aerodynamic performance metrics of an aero-engine multistage high pressure compressor (HPC). To propagate uncertainties, Monte Carlo simulations (MCS) with Latin Hypercube Sampling (LHS) were performed, with both correlated and uncorrelated inputs. Each sample consisted of a steady state computational fluid dynamics (CFD) evaluation of the compressor. The statistical input for the boundary conditions was acquired from a MCS of the engine cycle performance at cruise, accounting for flight-to-flight variations in ambient conditions and engine-to-engine variations in component properties. With the chosen approach, it is possible to quantify the variability in aerodynamic performance of an HPC that is subject to uncertain operating conditions and thus shows the importance of input correlations. Results highlight that deterministically determined performance metrics can differ considerably from the statistical mean, revealing the benefits of a probabilistic assessment. In contrast to performing MCS on the cycle only, a CFD based assessment can also be used to draw conclusions on the aerodynamic mechanisms responsible for changes in efficiency or surge margin.


Author(s):  
Eunhwan Jeong ◽  
Pyun Goo Park ◽  
Sang Hun Kang ◽  
Jinhan Kim

This paper presents the results of performance test and numerical analysis of a supersonic impulse turbine. The test has been conducted using high pressure cold air. The overall turbine performance and turbine nozzle behavior for various operating conditions have been investigated. Experiment and numerical analysis also have been conducted to investigate the nozzle-rotor clearance effect on the turbine performance. It has been found that turbine performance degrades with increasing the axial clearance and this phenomenon is mainly due to the increased stagnation pressure loss in the axial clearance region.


Author(s):  
Sascha Po¨nick ◽  
Dragan Kozˇulovic´ ◽  
Rolf Radespiel ◽  
Bernd Becker ◽  
Volker Gu¨mmer

The paper presents numerical and experimental results for a low speed compressor cascade with bleed air removal at the endwall. The aerofoil design is representative for a stator blade in a modern high pressure compressor near the casing wall. Secondary air is commonly supplied by simple bleed geometries downstream of stator rows. The focus of the present investigation was the systematic development of a passage integrated bleed configuration which, with the constraint of an invariable bleed mass flow rate, provides advantageous effect on the main flow and furthermore a high pressure recovery in the bleed flow. Steady 3D RANS simulations were performed using the Spalart-Allmaras turbulence model. In both, numerical simulations and experiments, an improved performance was found. Beside reduced losses and increased pressure rise the wake flow downstream of the customized bleed geometry was found to be more homogeneous with decreased deviations due to a favorable influence on the secondary flow.


Author(s):  
Ozgur Balli

AbstractA conventional and advanced exergy analysis of a turbofan engine is presented in this paper. In this framework, the main exergy parameters of the engine components are introduced while the exergy destruction rates within the engine components are split into endogenous/exogenous and avoidable/unavoidable parts. Also, the mutual interdependencies among the components of the engine and realistic improvement potentials depending on operating conditions are acquired through the analysis. As a result of the study, the exergy efficiency values of the engine are determined to be 25.7 % for actual condition, 27.55 % for unavoidable condition and 30.54 % for theoretical contion, repectively. The system has low improvement potential because the unavoidable exergy destruction rate is 90 %. The relationships between the components are relatively weak since the endogenous exergy destruction is 73 %. Finally, it may be concluded that the low pressure compressor, the high pressure compressor, the fan, the low pressure compressor, the high pressure compressor and the combustion chamber of the engine should be focused on according to the results obtained.


Author(s):  
Atsushi Tateishi ◽  
Toshinori Watanabe ◽  
Takehiro Himeno

This paper focuses on the buoyancy-induced unsteady flow phenomenon inside high-pressure compressor disk cavities. In order to understand the flow structure in a realistic configuration, a 10-stage core compressor of the NASA/GE Energy Efficient Engine is adopted as a computational target. The numerical flow simulation is conducted on a full annulus model, where the temperature distribution on the wall is modeled based on the core test results. The time-averaged flow fields are obtained by detached eddy simulation (DES) and two-dimensional axisymmetric Reynolds-averaged Navier-Stokes (RANS) simulation, and the difference is discussed in detail. The DES result showed large-scale, vortical structures with significant radial velocity fluctuations especially in the rear part of the compressor. These fluctuations create radial arm-like structure in the temperature distribution in the cavity, and greatly enhance the mixing between the bore coolant and hot air near the cavity wall. In addition, it is observed that the hot air discharged from the cavities creates a large cell at bore region, which extends across several rear stages. Although the present study successfully illustrates the entire structure of unsteady flow in heated compressor disk cavities including full stages, a more detailed validation will be needed to further confirm the applicability of DES for the targeted flow.


Author(s):  
Philipp Gilge ◽  
Andreas Kellersmann ◽  
Jens Friedrichs ◽  
Jörg R Seume

Deterioration of axial compressors is in general a major concern in aircraft engine maintenance. Among other effects, roughness in high-pressure compressor reduces the pressure rise and thus efficiency, thereby increasing the specific fuel consumption of an engine. Therefore, it is important to improve the understanding of roughness on compressor blading and their impact on compressor performance. To investigate the surface roughness of rotor blades of a compressors, different stages of an axial high-pressure compressor and a first-stage blisk (BLade–Integrated–dISK) of a regional aircraft engine is measured by a three-dimensional laser scanning microscope. Fundamental types of roughness structures can be identified: impacts in different sizes, depositions as isotropically distributed single elements with steep flanks and anisotropic roughness structures direct approximately normal to the flow direction. To characterise and quantify the roughness structures in more detail, roughness parameters were determined from the measured surfaces. The quantification showed that the roughness height varies through the compressor depending on the stage, position and the blade side. Overall complex roughness structures of different shape, height and size are detected regardless of the type of the blades.


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