Double Scroll Turbine for Automotive Applications: Engine Operating Point Versus Dynamic Blade Stress From Forced Response Vibration

2018 ◽  
Author(s):  
David Hemberger ◽  
Roberto De Santis ◽  
Dietmar Filsinger
Keyword(s):  
Pulse Energy ◽  
Internal Combustion Engines ◽  
Forced Response ◽  
Operating Conditions ◽  
Blade Vibration ◽  
Structural Dynamic ◽  
Vibration Excitation ◽  
Engine Combustion ◽  
Operating Points ◽  
Combustion Cycle

As a means of meeting ever increasing emissions and fuel economy demands car manufacturers are using aggressive engine downsizing. To maintain the power output of the engine turbocharging is typically used. Compared to Mono scroll turbines, with a multi-entry system the individual volute sizing can be better matched to the single mass flow pulse from the engine cylinders. The exhaust pulse energy can be better utilised by the turbocharger turbine improving turbocharger response. Additionally the interaction of the engine exhaust pulses can be better avoided, improving the scavenging of the engine. Besides the thermodynamic advantages, the multi-entry turbine represents a challenge to the structural dynamic design of the turbine. A higher number of turbine wheel resonance points can be expected during operation. In addition, the increased use of exhaust pulse energy leads to a distinct accentuation of the blade vibration excitation. Using validated engine models, the interaction of the multi-entry turbine with the engine has been analyzed and various operating points, which may be critical for the blade vibration excitation, have been classified. These operating points deliver the input variables for unsteady computational flow dynamics (CFD) analyses. From these calculations unsteady blade forces were derived providing the necessary boundary conditions for the structural dynamic analyses by spatially and temporally high-resolved absolute pressures on the turbine surface. Goal of the investigation is to identify critical operating conditions. Important is also to investigate the effect of a scroll connection valve on blade excitation. The investigations utilize validated tools that were introduced and successfully applied to several turbine types in a series of publications over recent years. It can be stated that the engine operating condition and the admission type significantly influence the forced response reaction of the blade to the different excitation orders (EO). In case of equal admission even (or multiples of two) EOs generate the largest dynamic blade stress as can be expected due to the two turbine inlet segments. This reaction also increases with the engine speed. In the case of unequal admission, the odd EOs produce the largest forced response reaction. The maximum dynamic blade stress occurs in the region where the scroll connection is just closed. Above all, the scroll connection valve influences the Beta value and thus the basic behavior — unequal or equal admission. It has been possible to reconstruct the forced response behavior of the turbine blade within an engine combustion cycle. For the first time it could be shown for a double scroll application that there is a significant dynamic blade stress change dependent on the engine crankshaft angle. Certainly, due to the inertia of the mass and damping (mass, structure, flow), the blade will not exactly follow the predicted course. However, it is clear that the transient processes within an engine combustion cycle will affect the dynamic blade stress. This applies to the turbine wheels investigated in the work at hand with low damping, high eigenfrequencies and the considered internal combustion engines — as they are typically used in the passenger car sector.

On the Effect of Axial Spacing Between Rotor and Stator Onto the Blade Vibrations of a Low Pressure Turbine Stage at Engine Relevant Operating Conditions

2016 ◽  
Author(s):  
Andreas Marn ◽  
Florian Schönleitner ◽  
Mathias Mayr ◽  
Thorsten Selic ◽  
Franz Heitmeir
Keyword(s):  
Rotor Blade ◽  
Low Pressure ◽  
Forced Response ◽  
Operating Conditions ◽  
Turbine Stage ◽  
Blade Vibration ◽  
Structural Dynamic ◽  
Flow Measurements ◽  
Vibration Measurements ◽  
Excitation Mechanisms

In order to achieve the ACARE targets regarding reduction of emissions, it is essential to reduce fuel consumption drastically. Reducing engine weight is supporting this target and one option to reduce weight is to reduce the overall engine length (shorter shafts, nacelle). However, to achieve a reduction in engine length, the spacing between stator and rotor can be minimised, thus changing the rotor blade excitation. Related to the axial spacing, a number of excitation mechanisms with respect to the rotor blading must already be considered during the design process. Based on these facts several setups have been investigated at different engine relevant operating points and axial spacing between the stator and rotor in the subsonic test turbine facility (STTF-AAAI) at the Institute for Thermal Turbomachinery and Machine Dynamics at Graz University of Technology. In order to avoid upstream effects of supporting struts, these struts are located far downstream of the stage which is under investigation. For rotor blade vibration measurements, a novel telemetry system in combination with strain gauges is applied. To the best of the author’s knowledge, the present paper is the first report of blade vibration measurements within a rotating system in the area of low pressure turbines under engine relevant operating conditions. In addition, aerodynamic measurements including unsteady flow measurements have been conducted, but will not be presented in this paper. By analysing the flow field, aerodynamic excitation mechanisms can be identified and assigned to the blade vibration. However, this is not presented in this paper. Within this paper, the flow fields are analysed in both upstream and downstream of the turbine stage, visualised for two axial gaps and then compared to the forced response of the blading. Detailed structural dynamic investigations show critical modes during the operation which are identified by the telemetry measurements as well. Finally the influence of the axial spacing regarding the rotor blade excitation and vibration can be elaborated and is prepared to get a better understanding of basic mechanisms. The paper shows that reducing axial spacing is a promising option for reducing engine weight, but aeroelasticity must be carefully taken into account.

Compressor Design for Multi-Point Operating Conditions of Turbocharged Gasoline Engines

2010 ◽  
Author(s):  
Tao Chen ◽  
Yangjun Zhang ◽  
Xinqian Zheng ◽  
Weilin Zhuge
Keyword(s):  
Internal Combustion Engines ◽  
Gasoline Engine ◽  
Design Method ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Combustion Engines ◽  
Gasoline Engines ◽  
Compressor Design ◽  
Operating Points ◽  
Load Conditions

Turbocharger compressor design is a major challenge for performance improvement of turbocharged internal combustion engines. This paper presents a multi-point design methodology for turbocharger centrifugal compressors. In this approach, several design operating condition points of turbocharger compressor are considered according to total engine system requirements, instead of one single operating point for traditional design method. Different compressor geometric parameters are selected and investigated at multi-point operating conditions for the flow-solutions of different design objectives. The method has been applied with success to a small centrifugal compressor design of a turbocharged gasoline engine. The results show that the consideration of several operating points is essential to improve the aerodynamic behavior for the whole working range. The isentropic efficiency has been increased by more than 5% at part-load conditions while maintaining the pressure ratio and flow range at full-load conditions of the gasoline engine.

Characterization of Contact Kinematics and Application to the Design of Wedge Dampers in Turbomachinery Blading: Part 1—Stick-Slip Contact Kinematics

1998 ◽  
Vol 120 (2) ◽  
pp. 410-417 ◽  
Author(s):  
B. D. Yang ◽  
C. H. Menq
Keyword(s):  
Friction Force ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Operating Conditions ◽  
Force Model ◽  
Blade Vibration ◽  
Stick Slip ◽  
Friction Forces ◽  
Contact Kinematics ◽  
Stiffness And Damping

Friction dampers are often used in turbine design to attenuate blade vibration to acceptable levels so as to prolong blades’ service life. A wedge damper, also called a self-centering, blade-to-blade damper, can provide more design flexibility to meet various needs in different operating conditions when compared with conventional platform dampers. However, direct coupling of the two inclined friction interfaces of the wedge damper often leads to very complex contact kinematics. In Part I of this two-part paper, a dual-interface friction force model is proposed to investigate the coupling contact kinematics. The key issue of the model formulation is to derive analytical criteria for the stick-slip transitions that can be used to precisely simulate the complex stick-slip motion and, thus, the induced friction force as well. When considering cyclic loading, the induced periodic friction forces can be obtained to determine the effective stiffness and damping of the interfaces over a cycle of motion. In Part II of this paper, the estimated stiffness and damping are then incorporated with the harmonic balance method to predict the forced response of a blade constrained by wedge dampers.

Effects of S-Shaped Intake on Aeromechanical Characteristics of a Transonic Fan

2020 ◽  
Author(s):  
Yun Zheng ◽  
Kang Xu ◽  
Hui Yang ◽  
Qingzhe Gao ◽  
Xiubo Jin
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Forced Response ◽  
Mode Shapes ◽  
Flow Distortion ◽  
Plane Model ◽  
Response Level ◽  
Blade Vibration ◽  
Structural Dynamic ◽  
Transonic Fan

Abstract S-shaped intakes are widely used in aero-engines of modern fighters because of the demand for reducing radar cross-section. Besides, boundary layer ingestion (BLI) configurations are proposed in civil engines recently due to the high propulsion efficiency and low fuel consumption. And S-shaped ducts are usually used as transition sections of diffusers in BLI intakes. Compared with normal straight intakes, it is inevitable to bring in the influence of inlet distortion and acoustic reflection for S-shaped intakes. Meanwhile, composite fan blades, shorter intakes and integrated blisks are common in engine designs. So, fan blades are prone to serious vibrations such as flutter and forced response, which may lead to high-cycle fatigue, and further cause structural failure. The aeromechanical characteristics of a transonic fan (NASA rotor67) in presence of a s-shaped intake are predicted by an in-house integrated time-domain aeroelasticity code. The three dimensional, time-accurate, unsteady Reynolds-Averaged Navier-Stokes equations are solved in fluid domain, and the structural dynamic equations of blade vibration are solved with a modal superimposition method. Mode shapes and natural frequencies of rotor blade are obtained with a commercial Finite Element code, and the Campbell diagram is presented. Full-annulus aeroelastic calculations are conducted to obtain the transient response and the aerodynamic damping of fan blades. Different techniques for interface between the intake and the rotor are used for comparison to demonstrate the influence of upstream interaction. A mixing-plane model is used at the interface to model the blade vibration without interactions with the distortion, while a sliding-plane model is used at the same condition to include the flow distortion and acoustic effects on the fan blade motion. S-shaped intakes with two different axial length are investigated for the forced response and flutter stability. This study indicates that the forced response level is attenuated due to the decrease of distortion level as the length increases, while the flutter stability is determined by the phase difference between the upstream and the reflective acoustic wave.

Development of a Multipoint Matching Method for Turbocompound Systems

2016 ◽  
Author(s):  
Zhanming Ding ◽  
Weilin Zhuge ◽  
Yangjun Zhang ◽  
Yong Yin ◽  
Shuyong Zhang
Keyword(s):  
Internal Combustion Engines ◽  
Waste Heat ◽  
Single Point ◽  
Poor Performance ◽  
Driving Cycle ◽  
Operating Conditions ◽  
Matching Method ◽  
Matching Process ◽  
Power Turbine ◽  
Operating Points

Turbocompounding is a promising waste heat recovery technology to improve fuel economy of internal combustion engines and comply with increasingly stringent emission regulations. The performance of a turbocompound engine is significantly influenced by the matching of the turbocharger turbine and the power turbine. Conventionally, the matching of the turbocharger turbine and power turbine is carried out at a single operating point. Single-point matched turbocompound systems tends to have poor performance at off-design operating conditions, which restrained the fuel-saving potential of turbocompound engines under driving cycle conditions. In the present study, a multipoint matching method for turbocompound systems was developed, which was essentially an optimization process of the swallowing capacities of the turbocharger turbine and the power turbine to achieve best performance at multiple matching points. In order to improve the performance of turbocompound engines under driving cycle conditions, common operating points of a driving cycle were used as matching points in the matching process. Common operating points under a driving cycle were determined by clustering the dynamic profiles of the driving cycle. A simulation study was carried out to examine the effectiveness of the multipoint matching method. The performance of the multipoint matched turbocompound system was compared against two single-point matched turbocompound systems under stationary operating points and driving cycle conditions respectively. According to the simulation results, the multipoint matched turbocompound system could attain satisfactory BSFC benefit under a wider operating range when compared with the two single-point matched turbocompound systems. The multipoint matched turbocompound engine showed the largest reduction in fuel consumption under driving cycle conditions.

scholarly journals Characterization of Contact Kinematics and Application to the Design of Wedge Dampers in Turbomachinery Blading: Part I — Stick-Slip Contact Kinematics

1997 ◽  
Author(s):  
B. D. Yang ◽  
C. H. Menq
Keyword(s):  
Friction Force ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Operating Conditions ◽  
Force Model ◽  
Blade Vibration ◽  
Stick Slip ◽  
Friction Forces ◽  
Contact Kinematics ◽  
Stiffness And Damping

Friction dampers are often used in turbine design to attenuate blade vibration to acceptable levels so as to prolong blades’ service life. A wedge damper, also called a self-centering blade-to-blade damper, can provide more design flexibility to meet various needs in different operating conditions when compared with conventional platform dampers. However, direct coupling of the two inclined friction interfaces of the wedge damper often leads to very complex contact kinematics. In Part I of this two-part paper, a dual-interface friction force model is proposed to investigate the coupling contact kinematics. The key issue of the model formulation is to derive analytical criteria for the stick-slip transitions that can be used to precisely simulate the complex stick-slip motion and, thus, the induced friction force as well. When considering cyclic loading, the induced periodic friction forces can be obtained to determine the effective stiffness and damping of the interfaces over a cycle of motion. In Part II of this paper, the estimated stiffness and damping are then incorporated with the harmonic balance method to predict the forced response of a blade constrained by wedge dampers.

Effects of Stator Flow Distortion on Rotating Blade Endurance: Part 1—Aerodynamic Excitation Aspects

2012 ◽  
Author(s):  
Vishwas Iyengar ◽  
Harold Simmons
Keyword(s):  
Operating Conditions ◽  
Flow Distortion ◽  
Blade Vibration ◽  
Structural Dynamic ◽  
Rotating Blade ◽  
Flow Disturbances ◽  
Structural Dynamic Model ◽  
Flow Interactions ◽  
Computational Fluid Dynamics Cfd ◽  
Major Factors

Blade vibrations, with the possibility of a failure, are one of the major factors controlling the reliability of all compressors and turbines. Flow disturbances upstream and downstream of rotor/ stator will produce wake pulses that excite the blades. This requires a structural dynamic model of the blade stress response for a given excitation and a method to estimate the pulsating forces acting on the rotating blades by the stationary components and, vice versa, for rotor pulsations acting on the stator. This paper discusses the efforts made to understand the aerodynamic instabilities caused by the vane and its role in generation of blade vibration. Here, comprehensive computational fluid dynamics (CFD) are used to get a better understanding of the stator-rotor flow interactions at different operating conditions and their effect on overall pulsation and vibration levels. This model is based on blade dynamic response measurements and on careful CFD simulations of basic flow altering scenarios. It is found that a surprisingly low misalignment angle (relative) could result in fatigue damage stress levels in most cases. This paper presents several example cases to demonstrate typical flow profiles for axial and radial compressors/ turbines with varying stator flow distortions. It is Part 1 of a two-part high cycle fatigue (HCF) failure analysis procedure, dealing with aerodynamic excitation aspects.

scholarly journals Optimizing the Shape of a Compression-Ignition Engine Combustion Chamber by Using Simulation Tests

2019 ◽  
Vol 26 (3) ◽  
pp. 138-146
Author(s):  
Ireneusz Pielecha ◽  
Jerzy Merkisz
Keyword(s):  
Combustion Chamber ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Combustion Process ◽  
Operating Conditions ◽  
Multidimensional Data ◽  
Compression Ignition ◽  
System Quality ◽  
Compression Ignition Engine ◽  
Engine Combustion

Abstract Modern solutions used in compression-ignition internal combustion engines are quite similar to each other. The use of high-pressure, direct fuel injection results in high combustion rates with controlled exhaust emissions. One of the combustion system quality criteria is to obtain adequately high thermodynamic indicators of the combustion process, which are obtained through, among others, the right combustion chamber geometry. Its shape influences the fuel atomization process, turbulence of fuel dose, evaporation and the combustion process. Optimizing the combustion chamber shape is one of the decisive factors proving the correct execution of the combustion process. This article presents the methodology of choosing the combustion chamber shape (changes of three selected combustion chamber dimensions) by using the optimization methods. Generating multidimensional data while maintaining the correlation structure was performed by using the Latin hypercube method. Chamber optimization was carried out by using the Nelder-Mead method. The combustion chamber shape was optimized for three engine load values (determined by the average indicated pressure) at selected engine operating conditions. The presented method of engine combustion chamber optimization can be used in low and high speed diesel propulsion engines (especially in maritime transport applications).

Impact of Mistuning on the Vibration Behaviour of the Last Stage in a Model Three Stage Low Pressure Steam Turbine

2011 ◽  
Author(s):  
Christoph Heinz ◽  
Markus Schatz ◽  
Michael V. Casey ◽  
Heinrich Stu¨er
Keyword(s):  
Steam Turbine ◽  
Amplitude Distribution ◽  
Low Pressure ◽  
Forced Response ◽  
Operating Conditions ◽  
Scale Model ◽  
Resonance Frequencies ◽  
Pressure Steam ◽  
Last Stage ◽  
Operating Points

The last stages of a low-pressure steam turbine, with long freestanding blades, may experience forced response excitation during resonance crossing at start-up and shut-down and this can be responsible for blade failure. This paper presents an experimental investigation of the circumferential blade amplitude distribution at different operating conditions and for different mistuning configurations in a scale model of a state-of-the-art low pressure steam turbine. Five configurations are investigated; two with different intentionally mistuned frequency arrangements, where the blades are placed alternately in different high-low configurations and three randomly mistuned systems. For the randomly mistuned systems the standard deviation of the resonance frequencies of the last stage blades is varied. The maximum blade amplitude and the circumferential blade amplitude distribution of each mistuning configuration are compared at different operating points and at a repeatable rotational speed gradient. The behaviour of the blade amplitude distribution at different operating conditions shows that the vibration levels depend on both the mistuning configuration and the operating points.

An equilibrium phase spray model for high-pressure fuel injection and engine combustion simulations

2017 ◽  
Vol 20 (2) ◽  
pp. 203-215 ◽  
Author(s):  
Zongyu Yue ◽  
Rolf D Reitz
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Phase Equilibrium ◽  
Diesel Engine ◽  
Internal Combustion Engines ◽  
Fuel Injection ◽  
Equilibrium Phase ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Engine Combustion

High-pressure fuel injection impacts mixture preparation, ignition and combustion in engines and other applications. Experimental studies have revealed the mixing-controlled and local phase equilibrium characteristics of liquid vaporization in high injection pressure diesel engine sprays. However, most computational fluid dynamics models for engine simulations spend much effort in solving for non-equilibrium spray processes. In this study, an equilibrium phase spray model is explored. The model is developed based on jet theory and a phase equilibrium assumption, without modeling drop breakup, collision and finite-rate interfacial vaporization processes. The proposed equilibrium phase spray model is validated extensively against experimental data in simulations of the engine combustion network Spray A and in an optical diesel engine. Predictions of liquid/vapor penetration, fuel mass fraction distribution, heat release rate and emission formation are all in good agreement with experimental data. In addition, good computational efficiency and grid-independency are also seen with the present equilibrium phase model. The examined operating conditions cover wide ranges that are relevant to internal combustion engines, which include ambient temperatures from 700 to 1400 K, ambient densities from 7.6 to 22.8 kg/m3 and injection pressures from 1200 to 1500 bar for diesel sprays.

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