Military Engine Response to Compressor Inlet Stratified Pressure Distortion by an Integrated CFD Analysis

2006 ◽  
Author(s):  
Leonardo Melloni ◽  
Petros Kotsiopoulos ◽  
Anthony Jackson ◽  
Vassilios Pachidis ◽  
Pericles Pilidis
Keyword(s):  
Engine Performance ◽  
Low Pressure ◽  
Operating Conditions ◽  
High Fidelity ◽  
Inlet Flow ◽  
Performance Simulation ◽  
Simulation Strategy ◽  
Compressor Inlet ◽  
And Performance ◽  
Pressure Compressor

Especially in aircraft applications, the inlet flow is quite often non uniform resulting in severe changes in compressor performance and hence, engine performance. The magnitude of this phenomenon can be amplified in military engines due to the complex shape of intake ducts and the extreme flight conditions. The usual approach to engine performance simulation is based on non-dimensional maps for compressors and turbines and assumes uniform flow characteristics throughout the engine. In the context of the whole engine performance, component-level, complex physical processes, such as compressor inlet flow distortion, can not be captured and analyzed. This work adopts a simulation strategy that allows the performance characteristics of an engine component, resolved from a detailed, high-fidelity analysis, to be transferred to an engine system analysis carried out at a lower level of fidelity. The methodology described in this paper utilizes an object-oriented, zero-dimensional gas turbine modeling and performance simulation system and a high-fidelity, three-dimensional, computational fluid dynamics (CFD), low-pressure compressor model. The CFD model is based on the overall geometry and performance of the low-pressure compressor of a modern, two-spool, low by-pass ratio (LBR) military turbofan engine and is subjected to both clean and distorted inlet flows. The analysis involves the generation of two characteristic maps for the first stage of the LP compressor from CFD simulations that account for a range of operating conditions and power settings with a uniform and a distorted inlet flow. The same simulation strategy could be adopted for other engine components such as the intake or the high-pressure compressor and for different magnitudes and types of distortion (i.e. radial, circumferential). By integrating the CFD-generated maps, into the 0-D engine analysis system, this paper presents a relative comparison between the ‘uniform-inlet’ engine performance (baseline compressor stage map) and the engine performance obtained after using the map accounting for a typical extent of stratified inlet distortion. The analysis carried out by this study, demonstrates relative changes in the simulated engine performance larger than 1%.

A Fully Integrated Approach to Component Zooming Using Computational Fluid Dynamics

2004 ◽  
Vol 128 (3) ◽  
pp. 579-584 ◽  
Author(s):  
Vassilios Pachidis ◽  
Pericles Pilidis ◽  
Fabien Talhouarn ◽  
Anestis Kalfas ◽  
Ioannis Templalexis
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Turbine ◽  
Engine Performance ◽  
Integrated Approach ◽  
High Fidelity ◽  
Performance Simulation ◽  
Fully Integrated ◽  
Engine Component ◽  
Simulation Strategy

Background . This study focuses on a simulation strategy that will allow the performance characteristics of an isolated gas turbine engine component, resolved from a detailed, high-fidelity analysis, to be transferred to an engine system analysis carried out at a lower level of resolution. This work will enable component-level, complex physical processes to be captured and analyzed in the context of the whole engine performance, at an affordable computing resource and time. Approach. The technique described in this paper utilizes an object-oriented, zero-dimensional (0D) gas turbine modeling and performance simulation system and a high-fidelity, three-dimensional (3D) computational fluid dynamics (CFD) component model. The work investigates relative changes in the simulated engine performance after coupling the 3D CFD component to the 0D engine analysis system. For the purposes of this preliminary investigation, the high-fidelity component communicates with the lower fidelity cycle via an iterative, semi-manual process for the determination of the correct operating point. This technique has the potential to become fully automated, can be applied to all engine components, and does not involve the generation of a component characteristic map. Results. This paper demonstrates the potentials of the “fully integrated” approach to component zooming by using a 3D CFD intake model of a high bypass ratio turbofan as a case study. The CFD model is based on the geometry of the intake of the CFM56-5B2 engine. The high-fidelity model can fully define the characteristic of the intake at several operating condition and is subsequently used in the 0D cycle analysis to provide a more accurate, physics-based estimate of intake performance (i.e., pressure recovery) and hence, engine performance, replacing the default, empirical values. A detailed comparison between the baseline engine performance (empirical pressure recovery) and the engine performance obtained after using the coupled, high-fidelity component is presented in this paper. The analysis carried out by this study demonstrates relative changes in the simulated engine performance larger than 1%. Conclusions. This investigation proves the value of the simulation strategy followed in this paper and completely justifies (i) the extra computational effort required for a more automatic link between the high-fidelity component and the 0D cycle, and (ii) the extra time and effort that is usually required to create and run a 3D CFD engine component, especially in those cases where more accurate, high-fidelity engine performance simulation is required.

scholarly journals Blade Roughness Effects on Compressor and Engine Performance—A CFD and Thermodynamic Study

Aerospace ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 330
Author(s):  
Jasem Alqallaf ◽  
Joao A. Teixeira
Keyword(s):  
Surface Roughness ◽  
Gas Turbine ◽  
Pressure Ratio ◽  
Engine Performance ◽  
Low Pressure ◽  
Performance Degradation ◽  
Simulation Software ◽  
Operating Conditions ◽  
Blade Surface ◽  
Pressure Compressor

Degradation of compressors is a common concern for operators of gas turbine engines (GTEs). Surface roughness, due to erosion or fouling, is considered one of the major factors of the degradation phenomenon in compressors that can negatively affect the designed pressure rise, efficiency, and, therefore, the engine aero/thermodynamic performance. The understanding of the aerodynamic implications of varying the blade surface roughness plays a significant role in establishing the magnitude of performance degradation. The present work investigates the implications due to the degradation of the compressor caused by the operation in eroding environments on the gas turbine cycle performance linking, thereby, the compressor aerodynamics with a thermodynamic cycle. At the core of the present study is the numerical assessment of the effect of surface roughness on compressor performance employing the Computational Fluid Dynamics (CFD) tools. The research engine test case employed in the study comprised a fan, bypass, and two stages of the low pressure compressor (booster). Three operating conditions on the 100% speed-line, including the design point, were investigated. Five roughness cases, in addition to the smooth case, with equivalent sand-grain roughness (Ks) of 15, 30, 45, 60, and 150 µm were simulated. Turbomatch the Cranfield in-house gas turbine performance simulation software, was employed to model the degraded engine performance. The study showed that the increase in the uniform roughness is associated with sizable drops in efficiency, booster pressure ratio (PR), non-dimensional mass flow (NDMF), and overall engine pressure ratio (EPR) together with rises in turbine entry temperature (TET) and specific fuel consumption (SFC). The performance degradation evaluation employed variables such as isentropic efficiency (ηis), low pressure compressor (LPC) PR, NDMF, TET, SFC, andEPR. The variation in these quantities showed, for the maximum blade surface degradation case, drops of 7.68%, 2.62% and 3.53%, rises of 1.14% and 0.69%, and a drop of 0.86%, respectively.

scholarly journals CFD Study of Nozzle Configurations for Ultra High Bypass Engines

1993 ◽  
Author(s):  
H. Zimmermann ◽  
R. Gumucio ◽  
K. Katheder ◽  
A. Jula
Keyword(s):  
Engine Performance ◽  
Operating Conditions ◽  
Aerodynamic Design ◽  
Thrust Coefficient ◽  
Optimum Range ◽  
Installation Effects ◽  
Wide Range ◽  
And Performance ◽  
Aircraft Aerodynamics ◽  
Bypass Ratio

Performance and aerodynamic aspects of ultra-high bypass ratio ducted engines have been investigated with an emphasis on nozzle aerodynamics. The interference with aircraft aerodynamics could not be covered. Numerical methods were used for aerodynamic investigations of geometrically different aft end configurations for bypass ratios between 12 and 18, this is the optimum range for long missions which will be important for future civil engine applications. Results are presented for a wide range of operating conditions and effects on engine performance are discussed. The limitations for higher bypass ratios than 12 to 18 do not come from nozzle aerodynamics but from installation effects. It is shown that using CFD and performance calculations an improved aerodynamic design can be achieved. Based on existing correlations, for thrust and mass-flow, or using aerodynamic tailoring by CFD and including performance investigations, it is possible to increase the thrust coefficient up to 1%.

Design and Performance of a Controlled Turbocharging System on Marine Diesel Engines

2006 ◽  
Author(s):  
Ioannis Vlaskos ◽  
Ennio Codan ◽  
Nikolaos Alexandrakis ◽  
George Papalambrou ◽  
Marios Ioannou ◽  
...  
Keyword(s):  
Steady State ◽  
Engine Performance ◽  
Operating Conditions ◽  
Electric Actuator ◽  
Engine Simulation ◽  
Engine Control System ◽  
Turbocharging System ◽  
Compressor Impeller ◽  
Marine Diesel ◽  
And Performance

The paper describes the design process for a controlled pulse turbocharging system (CPT) on a 5 cylinder 4-stroke marine engine and highlights the potential for improved engine performance as well as reduced smoke emissions under steady state and transient operating conditions, as offered by the following technologies: • controlled pulse turbocharging, • high pressure air injection onto the compressor impeller as well as into the air receiver, and • an electronic engine control system, including a hydraulic powered electric actuator. Calibrated engine simulation computer models based on the results of tests performed on the engine in its baseline configuration were used to design the CPT components. Various engine tests with CPT under steady state and transient operating conditions show the engine optimization process and how the above-mentioned technologies benefit engine behavior in both generator and propeller law operation.

Direct Coupling of a Two-Dimensional Fan Model in a Turbofan Engine Performance Simulation

2016 ◽  
Author(s):  
Ioannis Templalexis ◽  
Alexios Alexiou ◽  
Vassilios Pachidis ◽  
Ioannis Roumeliotis ◽  
Nikolaos Aretakis
Keyword(s):  
Three Dimensional ◽  
Engine Performance ◽  
System Level ◽  
Design Parameters ◽  
High Fidelity ◽  
Two Dimensional ◽  
Performance Simulation ◽  
Cfd Models ◽  
Component Design ◽  
Complex Phenomena

Coupling of high fidelity component calculations with overall engine performance simulations (zooming) can provide more accurate physics and geometry based estimates of component performance. Such a simulation strategy offers the ability to study complex phenomena and their effects on engine performance and enables component design changes to be studied at engine system level. Additionally, component interaction effects can be better captured. Overall, this approach can reduce the need for testing and the engine development time and cost. Different coupling methods and tools have been proposed and developed over the years ranging from integrating the results of the high fidelity code through conventional performance component maps to fully-integrated three-dimensional CFD models. The present paper deals with the direct integration of an in-house two-dimensional (through flow) streamline curvature code (SOCRATES) in a commercial engine performance simulation environment (PROOSIS) with the aim to establish the necessary coupling methodology that will allow future advanced studies to be performed (e.g. engine condition diagnosis, design optimization, mission analysis, distorted flow). A notional two-shaft turbofan model typical for light business jets and trainer aircraft is initially created using components with conventional map-defined performance. Next, a derivative model is produced where the fan component is replaced with one that integrates the high fidelity code. For both cases, an operating line is simulated at sea-level static take-off conditions and their performances are compared. Finally, the versatility of the approach is further demonstrated through a parametric study of various fan design parameters for a better thermodynamic matching with the driving turbine at design point operation.

Effects of Inlet Flow Distortion on the Performance of Aircraft Gas Turbines

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Joachim Kurzke
Keyword(s):  
Control System ◽  
Gas Turbines ◽  
System Simulation ◽  
Engine Performance ◽  
Thermodynamic Cycle ◽  
Operating Conditions ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Inlet Flow Distortion ◽  
The Impact

This paper describes how the fundamental effects of inlet flow distortion on the performance of gas turbines can be evaluated with any engine performance program that employs an integrated parallel compressor model. In this simulation method, both pressure and temperature distortions are quantified with coefficients, which relate the pressure (respectively temperature) in the spoiled sector to the value in the clean sector. In single spool compressor engines, the static pressure at the exit of the clean sector equals that of the distorted sector. This hypothesis does not hold true with multispool compressor engines because the short intercompressor ducts, which often contain struts or vanes, do not allow the mass flow transfer over the sector borders, which would be required for balancing the static pressures. The degree of aerodynamic coupling of compressors in series can be described in the performance simulation program by the simple coupling factor introduced in this paper. There are two fundamentally different reasons for the change in engine performance: First, there is the impact of the flow distortion on the component efficiencies and thus the thermodynamic cycle and second there are performance changes due to the actions of the control system. From the engine system simulation results, it becomes clear why inlet flow distortion has only a minor impact on the thermodynamic cycle if the comparison of the two operating conditions (with clean and distorted inlet flow) is made at the properly averaged engine inlet conditions. For each compressor, the parallel compressor theory yields two operating points in the map, one for the clean sector and one for the spoiled sector. The performance loss due to the distortion is small since the efficiency values in the two sectors are only a bit lower than the efficiency at a comparable operating point with clean inlet flow. However, the control system of the engine can react to the inlet flow distortion in such a way that the thrust delivered changes significantly. This is particularly true if a compressor bleed valve or a variable area nozzle is opened to counteract compressor stability problems. Especially, using recirculating bleed air for increasing the surge margin of a compressor affects the performance of the engine negatively. Two examples show clearly that the pros and cons of recirculating bleed can only be judged with a full system simulation; looking at the surge line improvement alone can be misleading.

Simulation-Aided PEM Fuel Cell Design and Performance Evaluation

2004 ◽  
Vol 2 (1) ◽  
pp. 20-28 ◽  
Author(s):  
Junxiao Wu ◽  
Qingyun Liu
Keyword(s):  
Fuel Cell ◽  
Catalyst Layer ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Operating Conditions ◽  
Half Cell ◽  
Flow Channels ◽  
Simulation Strategy ◽  
Cell Simulation ◽  
And Performance

A multi-resolution fuel cell simulation strategy has been employed to simulate and evaluate the design and performance of hydrogen PEM fuel cells with different flow channels. A full 3D model is employed for the gas diffusion layer and a 1D+2D model is applied to the catalyst layer. Further, a quasi-1D method is used to model the flow channels. The cathode half-cell simulation was performed for three types of flow channels: serpentine, parallel, and interdigitated. Simulations utilized the same overall operating conditions. Comparisons of results indicate that the interdigitated flow channel is the optimal design under the specified operating conditions.

Modelling and Assessment of Compressor Faults on Marine Gas Turbines

2012 ◽  
Author(s):  
I. Roumeliotis ◽  
N. Aretakis ◽  
K. Mathioudakis ◽  
E. A. Yfantis
Keyword(s):  
Gas Turbines ◽  
Engine Performance ◽  
Performance Model ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Maximum Speed ◽  
Performance Modelling ◽  
Engine Operation ◽  
Marine Propulsion ◽  
And Performance

Any prime mover exhibits the effects of wear and tear over time, especially when operating in a hostile environment. Marine gas turbines operation in the hostile marine environment results in the degradation of their performance characteristics. A method for predicting the effects of common compressor degradation mechanisms on the engine operation and performance by exploiting the “zooming” feature of current performance modelling techniques is presented. Specifically a 0D engine performance model is coupled with a higher fidelity compressor model which is based on the “stage stacking” method. In this way the compressor faults can be simulated in a physical meaningful way and the overall engine performance and off design operation of a faulty engine can be predicted. The method is applied to the case of a twin shaft engine, a configuration that is commonly used for marine propulsion. In the case of marine propulsion the operating profile includes a large portion of off-design operation, thus in order to assess the engine’s faults effects, the engine operation should be examined with respect to the marine vessel’s operation. For this reason, the engine performance model is coupled to a marine vessel’s mission model that evaluates the prime mover’s operating conditions. In this way the effect of a faulty engine on vessels’ mission parameters like overall fuel consumption, maximum speed, pollutant emissions and mission duration can be quantified.

Strategies for Simulating Flow Through Low-Pressure Turbine Cascade

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
Andreas Gross ◽  
Hermann F. Fasel
Keyword(s):  
Coherent Structures ◽  
Turbine Blades ◽  
Engine Performance ◽  
Flow Simulation ◽  
Flow Region ◽  
Suction Side ◽  
Low Pressure ◽  
Operating Conditions ◽  
Laminar Separation ◽  
Low Pressure Turbine

Laminar separation on the suction side of low-pressure turbine blades at low Reynolds number operating conditions deteriorates overall engine performance and has to be avoided. This requirement affects the blade design and poses a limitation on the maximum permissible blade spacing. Better understanding of the flow physics associated with laminar separation will aid in the development of flow control techniques for delaying or preventing flow separation. Simulations of low-pressure turbine flows are challenging as both unsteady separation and transition are present and interacting. Available simulation strategies have to be evaluated before a well-founded decision for the choice of a particular simulation strategy can be made. With this in mind, this paper provides a comparison of different flow simulation strategies: In particular, “coarse grid” direct numerical simulations, implicit large-eddy simulations, and simulations based on a hybrid turbulence modeling approach are evaluated with particular emphasis on investigating the dynamics of the coherent structures that are generated in the separated flow region and that appear to dominate the entire flow. It is shown that in some instances, the effect of the dominant coherent structures can also be predicted by unsteady Reynolds-averaged Navier–Stokes calculations.

Modeling of Start-Up From Engine-Off Conditions Using High Fidelity Turbofan Engine Simulations

2015 ◽  
Vol 138 (5) ◽  
Author(s):  
Stefan Bretschneider ◽  
John Reed
Keyword(s):  
Development Process ◽  
Model Development ◽  
Engine Performance ◽  
Static Friction ◽  
Operating Conditions ◽  
High Fidelity ◽  
Turbofan Engine ◽  
Control Laws ◽  
Component Design ◽  
Start Up

Engine models are widely used to simulate the engine behavior at steady state and transient operating conditions over the full flight envelope. Within the engine development process such simulations are used to support component design, evaluate engine performance, operability and test data, as well as to develop and optimize the engine controls. Recent developments have raised interest in the modeling of start-up processes of turbofan engines in order to support the definition of sufficient engine control laws. This implies that simulations are started at a condition where the engine shafts are static and temperatures and pressures are equal to ambient. During start-up the engine can only be operated transiently through the sub-sub-idle region (near zero speed) using a starter torque. The activity presented here was targeted to support the development of industrial-standard high-fidelity turbofan engine models capable of simulating start-up, shutdown or windmilling operation. Within the three previously mentioned cases starting from an engine-off condition, ground start from zero-speed is the most challenging in terms of physical and numerical modeling. For this reason, this paper concentrates on that case only. Zero mass flow and speed at the beginning of the simulation impose a set of special problems that do not exist in standard simulations: the modeling of a static engine-off condition, the modeling of static friction, and the modeling of reverse flows. The requirement to support an existing industrial model development process also made it necessary to apply the same quality of physical modeling to start-up simulations as would be the case for above-idle engine simulations. The physical effects present during engine start are discussed and modeling solutions are presented. Finally, results of a dry crank simulation are presented and discussed, illustrating that the expected effects are present and that the simulation is capable of predicting the correct trends.

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