Numerical Investigation of a Novel Approach for Mitigation of Forced Response of a Variable Geometry Turbine During Exhaust Braking Mode

2016 ◽  
Author(s):  
Ben Zhao ◽  
Leon Hu ◽  
Harold Sun ◽  
Ce Yang ◽  
Xin Shi ◽  
...  
Keyword(s):  
Shock Wave ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Forced Response ◽  
Aerodynamic Load ◽  
Variable Geometry ◽  
Original Design ◽  
Turbine Wheel ◽  
Nozzle Vane ◽  
Variable Geometry Turbine

One of critical concerns in a variable geometry turbine (VGT) design program is shock wave generated from nozzle exit at small open conditions with high inlet pressure condition, which may potentially lead to forced response of turbine wheel, even high-cycle fatigue issues and damage of inducer or exducer. Though modern turbine design programs have been well developed, it is difficult to eliminate the shock wave and all the resonant crossings that may occur within the wide operating range of a VGT turbine for automotive applications. This paper presents an option to mitigate intensity of the shock wave induced excitation using grooves on nozzle vane surface before the shock wave. Two kinds of turbines in which nozzle vanes with and without grooves were numerically simulated to obtain a three-dimensional flow field inside the turbine. The predicted performances from steady simulations were compared with test data to validate computational mesh and the unsteady simulation results were analyzed in detail to predict the responses of both shock wave and aerodynamic load acting on turbine blade surface. Compared with the original design, an introduction of grooves on nozzle vane surface mitigates the shock wave while also obviously reduces the amplitudes of alternating aerodynamic load on the turbine blades.

Behavior of a Variable Geometry Turbine Wheel to High Cycle Fatigue

2020 ◽  
Author(s):  
Calogero Avola ◽  
Alberto Racca ◽  
Angelo Montanino ◽  
Carnell E. Williams ◽  
Alfonso Renella ◽  
...  
Keyword(s):  
High Cycle Fatigue ◽  
Combustion Engine ◽  
Turbine Blades ◽  
Variable Geometry ◽  
Cycle Fatigue ◽  
Turbine Stage ◽  
Turbine Wheel ◽  
Variable Geometry Turbine ◽  
Turbine Design ◽  
Mechanical Optimization

Abstract Maximization of the turbocharger efficiency is fundamental to the reduction of the internal combustion engine back-pressure. Specifically, in turbochargers with a variable geometry turbine (VGT), energy losses can be induced by the aerodynamic profile of both the nozzle vanes and the turbine blades. Although appropriate considerations on material limits and structural performance of the turbine wheel are monitored in the design and aero-mechanical optimization phases, in these stages, fatigue phenomena might be ignored. Fatigue occurrence in VGT wheels can be categorized into low and high cycle behaviors. The former would be induced by the change in turbine rotational speed in time, while the latter would be caused by the interaction between the aerodynamic excitation and blades resonating modes. In this paper, an optimized turbine stage, including unique nozzle vanes design and turbine blades profile, has been assessed for high cycle fatigue (HCF) behavior. To estimate the robustness of the turbine wheel under several powertrain operations, a procedure to evaluate HCF behavior has been developed. Specifically, the HCF procedure tries to identify the possible resonances between the turbine blades frequency of vibrations and the excitation order induced by the number of variable vanes. Moreover, the method evaluates the turbine design robustness by checking the stress levels in the component against the limits imposed by the Goodman law of the material selected for the turbine wheel. In conclusion, both the VGT design and the HCF approach are experimentally assessed.

HCF Optimization of a High Speed Variable Geometry Turbine

2021 ◽  
Author(s):  
Alister Simpson ◽  
Sung in Kim ◽  
Jongyoon Park ◽  
Seong Kwon ◽  
Sejong Yoo
Keyword(s):  
High Speed ◽  
Forced Response ◽  
Variable Geometry ◽  
Blade Vibration ◽  
Operating Cycle ◽  
Turbine Wheel ◽  
Aerodynamic Loads ◽  
Radial Turbine ◽  
Wide Range ◽  
Variable Geometry Turbine

Abstract This paper describes the structural optimization of a high speed, 35mm tip diameter radial turbine wheel in a Variable Geometry Turbine (VGT) system, subjected to the wide range of aerodynamic loads experienced during the full operating cycle. VGTs exhibit a wide range of unsteady flow features, which vary as the nozzle vanes rotate through different positions during operation, as do the magnitudes and frequencies of the resulting pressure fluctuations experienced by the downstream turbine blades. The turbine wheel typically passes through a number of blade natural frequencies over their operating cycle, and there are a number of potential conditions where these unsteady aerodynamic loads can lead to resonant blade vibration. The focus of this work is on the development of a pragmatic design approach to improve the structural characteristics of a radial turbine blade with respect to High Cycle Fatigue (HCF), informed by detailed time-accurate Computational Fluid Dynamics (CFD) prediction of the unsteady pressure loads, coupled with FE vibration analysis to quantify the resulting blade vibration magnitudes. Unsteady CFD simulations are performed to determine the time-accurate pressure loads on the blades, and the results are used as input to forced response analysis to determine the peak alternating stress amplitudes. The detailed analysis results are then used to guide a subsequent parametric study in order to investigate the influence of key geometric parameters on the structural performance of the blade, with the optimum design identified through the use of a Goodman Diagram. The results quantify the influence of both blade thickness distribution and hub fillet details on the vibration characteristics of radial turbines.

Design of an Intermediate Turbine Duct Downstream of a High Pressure Turbine

2016 ◽  
Author(s):  
Chaoshan Hou ◽  
Hu Wu
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Low Pressure ◽  
Aerodynamic Load ◽  
Duct Flow ◽  
Original Design ◽  
High Pressure Turbine ◽  
Intermediate Turbine Duct ◽  
Low Pressure Turbine ◽  
Inlet Conditions

The flow leaving the high pressure turbine should be guided to the low pressure turbine by an annular diffuser, which is called as the intermediate turbine duct. Flow separation, which would result in secondary flow and cause great flow loss, is easily induced by the negative pressure gradient inside the duct. And such non-uniform flow field would also affect the inlet conditions of the low pressure turbine, resulting in efficiency reduction of low pressure turbine. Highly efficient intermediate turbine duct cannot be designed without considering the effects of the rotating row of the high pressure turbine. A typical turbine model is simulated by commercial computational fluid dynamics method. This model is used to validate the accuracy and reliability of the selected numerical method by comparing the numerical results with the experimental results. An intermediate turbine duct with eight struts has been designed initially downstream of an existing high pressure turbine. On the basis of the original design, the main purpose of this paper is to reduce the net aerodynamic load on the strut surface and thus minimize the overall duct loss. Full three-dimensional inverse method is applied to the redesign of the struts. It is revealed that the duct with new struts after inverse design has an improved performance as compared with the original one.

Finite Element Analysis for Turbine Blades with Contact Problems

2016 ◽  
Vol 33 (4) ◽  
Author(s):  
Yuan-Jian Yang ◽  
Liang Yang ◽  
Hai-Kun Wang ◽  
Shun-Peng Zhu ◽  
Hong-Zhong Huang
Keyword(s):  
Finite Element ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Contact Problems ◽  
Element Model ◽  
Von Mises Stress ◽  
Aerodynamic Load ◽  
Element Analysis ◽  
Von Mises ◽  
Three Dimensional Finite Element

AbstractTurbine blades are one of the key components in a typical turbofan engine, which plays an important role in flight safety. In this paper, we establish a establishes a three-dimensional finite element model of the turbine blades, then analyses the strength of the blade in complicated conditions under the joint function of temperature load, centrifugal load, and aerodynamic load. Furthermore, contact analysis of blade tenon and dovetail slot is also carried out to study the stress based on the contact elements. Finally, the Von Mises stress-strain distributions are obtained to acquire the several dangerous points and maximum Von Mises stress, which provide the basis for life prediction of turbine blade.

scholarly journals Investigation of Unsteady Aerodynamic Excitation on Rotor Blade of Variable Geometry Turbine

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Jian Liu ◽  
Wei-Yang Qiao ◽  
Wen-Hua Duan
Keyword(s):  
Pressure Fluctuation ◽  
Rotor Blade ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Variable Geometry ◽  
Blade Surface ◽  
Variable Geometry Turbine ◽  
Mach Numbers ◽  
Fluctuation Energy

To investigate the aerodynamic excitations in variable geometry turbines, the full three-dimensional viscous unsteady numerical simulations were performed by solving N-S equations based on SAS SST method. The aerodynamic excitations at varied expansion ratios with six different vane stagger angles that cause the unsteady pressure fluctuation on the rotor blade surface are phenomenologically identified and quantitatively analyzed. The blade pressure fluctuation levels for turbines with different vane stagger angles in the time and frequency domain are analyzed. As the results suggest, the blade excitation mechanisms are directly dependent on the operating conditions of the stage in terms of vane exit Mach numbers for all test cases. At subsonic vane exit Mach numbers the blade pressure fluctuations are simply related to the potential filed and wake propagation; at transonic conditions, the vane trailing edge shock causes additional disturbance and is the dominating excitation source on the rotor blade, and the pressure fluctuation level is three times of the subsonic conditions. The pressure fluctuation energy at subsonic condition concentrates on the first vane passing period; pressure fluctuation energy at higher harmonics is more prominent at transonic conditions. The variation of the aerodynamic excitations on the rotor blade at different vane stagger angles is caused by the varied expansion with stator and rotor passage. The aerodynamic excitation behaviors on the rotor blade surface for the VGT are significantly different at varied vane stagger angle. Spanwise variation of the pressure fluctuation patterns on is also observed, and the mechanism of the excitations at different spans is not uniform.

Advances in aerodynamic, structural design and test technology of variable geometry turbines

2021 ◽  
pp. 095765092110356
Author(s):  
Jie Gao ◽  
Yu Liu ◽  
Qun Zheng ◽  
Chen Liang
Keyword(s):  
Structural Design ◽  
Gas Turbines ◽  
Design Method ◽  
Turbine Blades ◽  
Load Condition ◽  
Aerodynamic Characteristics ◽  
Variable Geometry ◽  
Part Load ◽  
Test Technology ◽  
Variable Geometry Turbine

The variable geometry turbine is one of the technical means to effectively improve the part-load performance, part-load condition stability and manoeuvrability of gas turbines, aeroengines or even turbochargers. However, the design of the variable geometry turbine is very difficult, and the decrease in efficiency offsets some of the engine cycle benefits caused by turbine variable geometry. Therefore, it is very necessary to carry out research on variable geometry turbine technology so that the technology can be successfully applied to various types of gas turbine engines as soon as possible. This paper summarizes and analyzes the recent advances in the field of aerodynamic, structural design and test of variable geometry turbines. This review covers the following topics that are important for variable geometry turbine designs: (1) flow mechanisms and aerodynamic characteristics, (2) wide-condition aerodynamic design method for turbine blades, (3) variable vane turning design method, (4) structural design technology of variable vane system and (5) aerodynamic characteristics and reliability test technology for variable geometry turbines. The emphasis is placed on the variable vane turning design method. We also present our own insights regarding the current research trends and the prospects for future developments.

Effects of grooved vanes on shock wave and forced response in a turbocharger turbine

2019 ◽  
pp. 146808741987926
Author(s):  
Ben Zhao ◽  
Xin Shi ◽  
Harold Sun ◽  
Mingxu Qi ◽  
Panpan Song
Keyword(s):  
Shock Wave ◽  
Numerical Method ◽  
High Cycle Fatigue ◽  
High Efficiency ◽  
Forced Response ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Turbine Wheel ◽  
Trade Off ◽  
Grooved Surface

In radial inflow turbine design, the optimization of turbine geometry for aerodynamic performance improvement is often constrained by the requirement of reliability, thus facing a trade-off. One of the vital challenges for a better trade-off is how to mitigate the forced response of turbine wheel, while maintaining high efficiency, so as to avoid high cycle fatigue failure. In this article, using a grooved surface on nozzle vanes for the forced response reduction was investigated. In light of the fact that the investigation on the high cycle fatigue issue involves both aerodynamic interactions and structural analyses, a customized computer code was developed using MATLAB software to couple computational fluid dynamics simulations with finite element analysis calculations. Partial results were compared against experimental results, respectively, to validate the numerical method. The coupled numerical method reveals that using the grooved surface on the nozzle vane alters the shock wave structure, decreases the peak stress of turbine wheel by 8%, and deteriorates turbine efficiency by 0.05 percentage points.

Aerodynamic Design of Fixed and Variable Geometry Nozzleless Turbine Casings

1980 ◽  
Vol 102 (1) ◽  
pp. 141-147 ◽  
Author(s):  
P. M. Chappie ◽  
P. F. Flynn ◽  
J. M. Mulloy
Keyword(s):  
Design Method ◽  
Pressure Ratio ◽  
Wall Friction ◽  
Variable Geometry ◽  
Aerodynamic Design ◽  
Blade Vibration ◽  
Turbine Wheel ◽  
Design Constraints ◽  
Variable Geometry Turbine ◽  
Turbine Casing

A design method has been developed to produce nozzleless turbine casings which provide a centrifugal turbine wheel with a uniform inlet state. The analysis includes the effect of wall friction and has been found to accurately predict the mass flow versus pressure ratio characteristics of nozzleless casings. The uniform inlet state provided by this design approach provides turbine wheel/casing configurations with near optimum efficiency and a very low aerodynamic blade vibration excitation level. The model has been extended to produce variable area casings to simulate a simplified variable casing geometry. Testing has verified the accuracy of the approach both in the design point and variable geometry cases. Also depicted are new insights into turbine wheel design constraints discovered when using a variable geometry turbine casing.

scholarly journals Experimental and numerical investigations of tip clearance flow and loss in a variable geometry turbine cascade

2017 ◽  
Vol 232 (2) ◽  
pp. 157-169 ◽  
Author(s):  
Jie Gao ◽  
Weiliang Fu ◽  
Fukai Wang ◽  
Qun Zheng ◽  
Guoqiang Yue ◽  
...  
Keyword(s):  
Vortex Core ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Variable Geometry ◽  
Numerical Predictions ◽  
Rear Part ◽  
Clearance Flow ◽  
Variable Geometry Turbine ◽  
Vane Tip

Variable geometry turbines are widely employed to improve the off-design performance of gas turbine engines; however, there is a performance penalty associated with the vane-end partial gap required for the movement of variable vanes. This paper is a continuation of the previous work and aims to understand the leakage flow and loss mechanisms under the influence of the pivoting axis. Experimental investigations with a variable geometry turbine linear cascade have been conducted for tip gap heights of 1.1% and 2.2% blade spans as well as setting angles of −6°, 0°, and 6°, so as to reveal the three-dimensional clearance flow characteristics associated with partial gaps. Besides, numerical predictions are also carried out to better understand the experimental results. Pressure measurements were performed on the tip endwall as well as on the vane surface, and three-dimensional clearance flow fields downstream of the variable cascade were measured with a five-hole probe. The results show that as the vane setting angle is changed from design to closed, the vane loading increases and tends to be more aft-loaded, thus increasing the tip leakage loss, and vice versa. There are strong interactions between the flow around the pivoting axis and the leakage flow in the vane tip rear part, which leads to a low-pressure region on the tip endwall. The leakage vortex core is made up of the leakage flow in the vane tip rear part at both two tip gap heights, and the leakage vortex core formation process is different from the one in the rotor blade. The present results can provide useful references for the vane-end clearance design of variable geometry turbines.

A Radial Inflow Turbine Impeller for Improved Off-Design Performance

1982 ◽  
Author(s):  
J. M. Mulloy ◽  
H. G. Weber
Keyword(s):  
Operating Conditions ◽  
Shape Design ◽  
Variable Geometry ◽  
Turbine Wheel ◽  
Final Design ◽  
Variable Geometry Turbine ◽  
Turbine Casing ◽  
Radial Inflow Turbine ◽  
Inlet Conditions ◽  
Turbine Impeller

Given the instantaneous operating conditions of the radial inflow turbine on a diesel engine and the possible requirement of a variable geometry turbine casing, an alternate approach was used to design an impeller which could accommodate the large variations in inlet states. Several impeller designs were generated and tested. Each was found to give a performance advantage in some portion of the turbine map. A blunt inlet shape design was found to give the best performance at all suspected inlet conditions. A final design turbine wheel was generated to cover the operating range of a variable geometry turbine casing. It was found that this impeller gave improved efficiencies at all operating conditions.

Sign in / Sign up

Export Citation Format

Share Document