Turbocharger Rotor Research Articles

Vibration characteristics of a high-speed turbocharger rotor with mass unbalance based on simulation and experiment

Aiming at the problem of large-amplitude vibration appearing in turbochargers due to the effect of unbalance and nonlinear oil whirl/whip during operation, vibration characteristics with the variation of unbalance is studied by combining the simulation and the experimental test. Based on FE method and DOF reduction technique, a realistic turbocharging rotor is discretized into a series of master- and sub-elements by Timoshenko beam theory. The motion equations of turbocharger rotor-bearing system are derived by coupling rotor-floating ring equation and the oil-film Reynold equation. The research focuses on the unbalance effect on the sub-synchronous vibration and the total vibration level. The unbalance distribution, unbalance level, and the relative phase are the variables in the study. The result shows that 0.12× sub-synchronous from outer oil-film instability is responsible to the severe vibration at high-speed working conditions. Meaningfully, a suitable unbalance can significantly increase the onset speed for instability, and reduce overall vibration level. The mass unbalance of 1.5 g·mm on the compressor side shows good vibration characteristics, while the unbalance on the turbine side should be eliminated as much as possible. The proposed research provides a certain guidance for suppressing the total vibration level, and to control the unbalance in turbocharger rotor during operation.

Influence of External Clearance Variation on Vibration Characteristics of Ship Electrically Assisted Turbocharger Rotor Bearing System

Electrically assisted turbocharging (EAT) technology is an important technical means to effectively solve the problems of insufficient intake air and poor transient response of traditional turbocharged engines at low speed or acceleration, and to realize the electrification of marine internal combustion engine power system. In the EAT design stage, the original rotor model of a marine turbocharger was established and verified. Subsequently, the EAT rotor dynamics design and analysis were carried out, and the influence of the unbalanced phase and external clearance on rotor vibration was discussed. The results show that when the external clearance is small, extensive sub-synchronous vibration occurs and bifurcation occurs at high speed. When the external clearance is large, the sub-synchronous vibration component almost disappears but high synchronous vibration occurs at a high speed. At the same time, the shaft is significantly affected by the gravity load at low speeds, and the rotor makes a balanced motion on the critical limit cycle at high speed. In order to minimize the vibration and noise of the same type of EAT, it is recommended to control the outer clearance of the EAT bearing in the range of 0.30–0.36[Formula: see text]mm. The research content provides a reference for the dynamic design and analysis of the EAT, which effectively helps the development of the original engine of the ship electric auxiliary turbocharger and improves the operation stability of the EAT.

Dynamics and stability analysis of unbalance responses in mid‐positioned electrically assisted turbocharger rotor

AbstractElectrically assisted turbochargers (EAT) improve intake efficiency by motor‐assisted compressor impeller rotation, enhancing the system's transient response. However, the addition of motor rotor components has increased the number of unbalanced positions in the shaft system, leading to problems such as excessive compressor end vibration and complex changes in oil film stability. To evaluate the effects of unbalance in the motor rotor, along with the parameters of floating ring bearings (FRB), on the dynamic response of EAT, a finite element model of an EAT rotor supported by nonlinear FRB is developed, and the vibration response of the compressor end bearing is obtained by numerical integration. The results indicate: (1) In contrast to the effect of compressor and turbine unbalance, proper motor rotor unbalance is more effective in suppressing oil whirl instability in the high‐speed operating range. However, a new inner oil film whirl “instability interval” is also induced in the low‐speed operating range, leading to an increase in the Y1 compressor‐end amplitude at low and medium speeds, and this “instability interval” increases with the amount of unbalance. (2) When an oil whirl occurs in the oil film, the maximum eccentricity of the bearing surges and is greater than 0.3, which can be used as an effective threshold for determining whether the oil film is unstable in engineering applications. (3) A suitable outer oil‐film clearance range should be , otherwise, a wide range of outer oil‐film whirl instability occurs. Controlling the amount of unbalance and oil‐film clearance to suppress the sub‐synchronous vibration of the EAT, provides a theoretical basis for the design of the dynamics of the nonlinear rotor bearing system and improves the stability of the turbocharger's operation.

Nonlinear dynamics analysis of hydraulic turbochargers in reverse osmosis desalination plants

The hydraulic turbocharger plays a vital role in harnessing the energy stored in brine within reverse osmosis desalination plants. To optimize the efficiency and durability of this equipment, it is crucial to develop accurate dynamic models of the turbocharger rotor. An improved understanding of rotor dynamics enables the integration of innovative technologies such as Hydraulic Energy Management Integration, effectively enhancing efficiencies in systems characterized by small capacities and high rotational speeds. This study presents a dynamic modeling methodology for the hydraulic turbocharger. The analysis involves approximating the turbocharger rotor with an equivalent finite element shaft line model. Verification of the model’s natural frequency is conducted using three-dimensional finite element analysis, employing the ANSYS modal analysis module. Computational fluid dynamics is employed to evaluate the fluid forces, while the Reynolds equation is utilized to assess the journal bearing forces. The resulting model is employed to investigate the nonlinear dynamics of the rotor, examining the impact of various system parameters, including rotational speed, unbalance forces, and shaft geometrical parameters. The results highlight the significance of balancing the turbine and pump disks for optimal performance. Furthermore, the research demonstrates that increasing the shaft length reduces the rotor’s threshold speed, while increasing the shaft diameter initially raises the threshold speed until it reaches a critical value. Beyond this critical value, further increases in shaft diameter lead to a decrease in the threshold speed.

ВОССТАНОВЛЕНИЕ ВАЛА РОТОРА ТУРБОКОМПРЕССОРА ТКР-7С-6 ДВИГАТЕЛЯ ВНУТРЕННЕГО СГОРАНИЯ

The use of a turbocharger has a positive effect on the power of the internal combustion engine, reduces fuel consumption and positively affects the environmental friendliness of operation. Along with the positive effect on the operation of the internal combustion engine, turbochargers reduce the overall life of the engine. Small extreme wear and a small diameter of the rotor shaft limit the use of traditional recovery processes. (Research purpose). The research purpose is developing a method for restoring the rotor shaft of a turbocharger of internal combustion engines. (Materials and methods) A short-pulse laser surfacing of an antifriction ceramic coating with subsequent finishing treatment in the form of diamond smoothing was used to apply the restoration coating. The powder composition BN-B4C-LiO-MgO was used as a filler material. Preliminary studies have shown high adhesive strength of the coating and wear resistance in conditions of oil starvation. The surface was subjected to finishing treatment by diamond smoothing after the formation of the restoration coating. A laboratory installation has been developed to accelerate the rotor shaft in the turbocharger housing to 60,000 revolutions per minute, followed by an assessment of the acceleration time and the pressure increase in the compressor manifold. (Results and discussion) The presented method made it possible to restore the turbocharger rotor shaft with a surface roughness of Ra 0.32. Bench tests were conducted to evaluate the efficiency of a turbocharger with a restored shaft, the results of which showed that the intensity of unwinding of the turbocharger rotor shaft and the pressure increase in the compressor manifold are on average 10 percent higher than for a unit with a standard rotor shaft. (Conclusions) The presented technological process of restoring the worn surface of the rotor shaft of the 7C-6 turbocharger is of high practical importance and its application will improve the reliability and durability of turbochargers. The results can be used in the operating and repair enterprises.

Design of herringbone grooved thrust bearing for locomotive turbocharger rotor

The herringbone texture exhibited excellent tribological performance to minimize friction and wear. However, the application of this texture in the development of grooved thrust bearings is limited. Therefore, in this study, an attempt was made to design an oil-lubricated herringbone grooved thrust bearing for high-speed locomotive turbochargers. The designed bearing accommodates the axial load generated due to the pressure difference between the turbine and compressor wheel. The bearing design starts with applying Newton’s second law to predict the thrust load acting on the locomotive turbocharger rotor. The thrust load is calculated analytically and is found to be 4.54 kN for a design rotor speed of 1,00,000 rpm. Further, the herringbone grooved thrust bearing has been modeled numerically using non-linear Reynolds equation. The modified Reynolds equation is discretized using the finite volume method (FVM) and solved by successive over-relaxation (SOR) methodology to determine the static characteristics over the bearing surface. The developed HGTB is found to have a suitable load-carrying capacity of 4.6 kN, frictional torque of 0.25 N.m, and power loss of 2.98 kW. Further, a parametric analysis has been carried out to study the influence of design parameters such as the number of grooves, helix angle, angular groove width, groove depth, and speed on load-carrying capacity, frictional torque, and power loss.

Dynamic and stability comparison analysis of the high-speed turbocharger rotor system with and without thrust bearing via machine learning schemes

Dynamic and stability comparison analysis of the high-speed turbocharger rotor system with and without thrust bearing via machine learning schemes

Dynamic Characteristics of Electrically Assisted Turbocharger Rotor System Under Strong Impacts

Dynamic Characteristics of Electrically Assisted Turbocharger Rotor System Under Strong Impacts

A Design Method to Eliminate Sub Synchronous Response in Automotive Turbochargers utilizing Nonlinear Dynamics of Time Periodic Systems

The present work introduces a methodology for the dynamic design evaluation of high-speed rotors, applying nonlinear dynamics of time periodic systems. The paper focuses on the definition of design variables so as the system to avoid sub synchronous components in the response. The response of an unbalanced turbocharger rotor mounted on oil bearings with wire mesh dampers (WMDs) is evaluated with an efficient collocation method coupled to the pseudo arc length continuation to evaluate response limit cycles in the entire range of the rotating speed, which acts as bifurcation parameter. The specific system is used to demonstrate the method without loss of generality. The analytical model of the WMD component is implemented directly from the literature, while rigid rotor model and short bearing approximations are used for the rest components. Floquet theory is applied in the non-autonomous dynamic system and the stability characteristics of the response limit cycles are evaluated through Floquet multipliers, the magnitude of which act in the algorithm as stability index. A sensitivity analysis is performed at first to evaluate the correlation between WMD key design parameters and the time response of the system.A multi objective optimization method is embedded to set Floquet multipliers at specific values; in this way the response limit cycles retain stability and periodicity, avoiding any type of bifurcation which would render sub-synchronous component. Acceptable sets for design variables of journal bearings and WMDs are defined by multi-objective optimization and these are verified in efficiency by evaluating the response of the system by time integration, as a virtual experiment, for several operating conditions. The method requires severely lower computational time and capacity to render an acceptable design compared to the conventional design of experiment DoE procedure, and it is not limited on the analytical models of rotor, bearing, or other component.

Assessing the Sensitivity of the Rundown of a Turbocharger Rotor Shaft to Determine Its Technical Condition

Assessing the Sensitivity of the Rundown of a Turbocharger Rotor Shaft to Determine Its Technical Condition

A review on recent advancements in an automotive turbocharger rotor system supported on the ball bearings, oil film and oil-free bearings

A review on recent advancements in an automotive turbocharger rotor system supported on the ball bearings, oil film and oil-free bearings

Vibration characteristics of turbocharger rotor system considering internal thread texture parameters of semi-floating ring bearing

The internal thread texture causes changes in the dynamic characteristics of the oil film of the semi-floating ring bearing, which affects the amplitude of vibration and operating life of the turbocharger rotor system. Based on the fluid lubrication theory, the oil film governing equation of a semi-floating ring bearing with surface texture parameters is derived. The effects of the texture depth, position, and number of turns of the internal thread on the dynamic characteristics of the bearing oil film, such as the maximum pressure, load-carrying capacity and stiffness damping, are analyzed. Taking a type of turbocharger as an example, a hydrodynamic model is established to analyze the oil film lubrication in the semi-floating ring bearings, and the dynamic characteristic of the oil film is analyzed by computational fluid dynamics method. The results show that the maximum pressure, bearing capacity, and stiffness damping coefficient of oil film increase firstly and then decrease with the increase of texture depth and the number of thread turns in the range of journal rotation speed from 1000 to 20,0000 r/min. Compared with the non-texture bearings, the dynamic characteristics coefficients of the oil film such as bearing capacity and stiffness damping increase the most, when the depth of texture is 0.006 mm and the number of thread turns is 9. Secondly, the dynamic characteristic coefficient of oil film is improved when the texture is distributed in the middle than on both sides. The thread texture with appropriate parameters can suppress the rotor system vibration amplitude. The conclusion can provide a reference for the design of textual parameters of semi-floating ring bearings.

THERMAL ASSESSMENT ON TRIBOLOGICAL PROPERTIES OF TURBOCHARGER JOURNAL BEARING

High speed rotation of turbocharger rotor shaft could lead to significant frictional losses generated in journal bearing, which in turn affects the engine minimum speed. Therefore, this study is to mathematically predict the frictional behaviour for a turbocharger journal bearing, considering lubricant film formation and thermal effect. A mathematical model is initially derived from a 2-D Reynolds equation based on finite difference method and Modified Newton Raphson’s Method. Then, a reduced energy equation is integrated, to consider thermal effect. The mathematical model is validated with measured friction power of a typical automotive turbocharger obtained from literature. Through the analysis, it is shown that thermal analysis assumption correlates better with literature experimental data. The significant temperature rise in lubricant leads to the reduction of viscosity as well as the frictional power losses of the turbocharger. A parametric study using Taguchi methodis then conducted to optimize parameters, such as bearing width, type of engine oil used as lubricant and bearing radial clearance, for minimizing the friction power loss. The effect of bearing width is found to contribute the most to the frictional power loss, followed by the lubricant oil and lastly, the radial clearance of the bearing.

EVALUATION OF THE WEAR OF AN FE-AL ALLOYTURBOCHARGER ROTOR SEAL RING UNDER SELECTEDOPERATING CONDITIONS

This publication presents the possibility of extending the service life of the rotor shaft seal ring in an automotiveturbocharger by using an intermetallic Al-Fe alloy. Comprehensive results of tribological, metallographic andprofilometric tests of this alloy (vacuum cast) operating in a sliding association on a T-05 bench allowedthe representation of a real friction node. Based on empirical tests, it will be possible to determine whichalloy (Al-Fe alloy or the one currently used for sealing rings of a car turbocharger rotor shaft) has bettertribological properties. For this purpose, the research was based on an experiment that assumes three mainfactors determining the wear of the tested association. The result of the experimental plan was to obtain threedimensionaldiagrams showing the influence of the wear factors on the friction force and surface topography.

Microstructure and Mechanical Properties of Solid-State Rotary Friction Welded Inconel 713C and 32CrMo4 Steel Joints Used in a Turbocharger Rotor

The aim of this work was to determine the effect of selected parameters of friction welding, such as friction pressure and welding speed, on the mechanical properties and microstructure of friction-welded Inconel 713C-32CrMo4 joints. Tensile strength and hardness tests were carried out to determine the mechanical properties of the resulting welded joints. The results of the ultimate tensile strength, hardness, and microstructure were linked to the parameters of the welding process. It was found that the highest tensile strength was 1222 N/mm2. There was a significant increase in the hardness value in the thermo-mechanically affected zone for all samples. However, as the friction pressure increased, the zone with the higher hardness value migrated towards the 32CrMo4 material. In all weld tests, the fracture was found on the 32CrMo4 steel side. A distinct band of carbide formation was observed between the thermo-mechanically affected zone and the Inconel 713C base material.

Impact of Whirl and Axial Motion on Ball Bearing Turbocharger Dynamics

Ball bearing turbochargers (TCs) incorporate an angular contact ball bearing cartridge to reduce friction and oil consumption, improving the efficiency of internal combustion engines. In this investigation, axial and radial TC rotor motion was experimentally measured and used to develop a model of the TC rotor-bearing system, allowing for a detailed analysis of the TC bearing under varying operating conditions. In order to achieve the experimental objectives of this investigation, eddy-current proximity probes were used to measure the radial motion at the turbine and compressor sides of the TC. The measured radial motion shows whirl with subharmonics at low speed. The measured axial motion of the rotor was found to increase with TC speed. In order to analytically investigate the bearing dynamics, a complete TC model was developed that includes the mass distribution and flexibility of the TC compressor, shaft and turbine, and squeeze-film dampers (SFDs) that support the bearing cartridge. The model was used to replicate the whirl and axial motion of the test rig and then to determine which model parameters could be adjusted to minimize whirl without negatively affecting the bearing dynamics. Simulation results revealed that centrifugal effects cause a change in the bearing internal geometry, with a small clearance becoming a preload at higher speeds. When this effect is coupled with less compliant SFDs, the subharmonics are reduced and the overall sliding and number of large load cycles at the ball–race contacts are minimized, contributing to lower bearing friction and improved overall life.

Influence of a transient bubble dynamics cavitation model for squeeze film dampers on the run‐up behaviour of a turbocharger rotor

AbstractThe force response of squeeze film dampers and hydrodynamic bearings is significantly influenced by the occurence of cavitation inside the lubricant films. The viscosity of the occuring mixture of oil and air bubbles is vastly different than that of pure lubricant and therefore changes the pressure build‐up and thereby the stiffness and damping properties of the lubrication films. To accurately predict the force response of a squeeze film damper, the cavitation and its effect on the pressure build‐up therefore has to be taken into account. Well known cavitation algorithms for lubrication problems, like the Elrod algorithm or the two‐phase‐model, neglect the transient nature of outgassing and assume instantaneous bubble formation and collapse. In the presented paper, a transient bubble dynamics model based on the Rayleigh‐Plesset‐Scriven equation is utilised instead and its effect on the rotordynamic behaviour of a turbocharger rotor is examined based on fully transient multi body dynamics simulations.

Nonlinear vibration phenomena in hydrodynamically supported rotor systems

It is a well-known fact, that hydrodynamically supported systems are prone to nonlinear vibrations. Their exact simulative prediction with respect to frequency and amplitude is complicated by the fact that different system properties interact. The paper at hand outlines an approach that takes all relevant influences like rigid body motions, elastic deformations, nonlinear relation between fluid film pressure and bearing kinematics as well as temperature increase due to power loss or adjacent heat sources into account as detailed as necessary. Both journal and thrust bearings are considered as they contribute to the system's stiffness and damping capabilities. The approach is applied to self-excited pad vibrations of tilting pad thrust bearings as well as the run-up simulation of a turbocharger rotor under different axial loads. Both models are validated against measurements.

Typical Fault Modeling and Vibration Characteristics of the Turbocharger Rotor System

To study the typical failure mechanism (rotor unbalance, rotor friction, and rotor crack) and vibration characteristics of the turbocharger rotor system, a rotor system dynamics simulation model was established by an improved four-node aggregate parameter method. The geometric and physical characteristics of the rotor system under three failure states and its dynamics under operation were analyzed. Thus, a typical failure dynamics simulation model of the rotor system was established. On this basis, the output failure simulation signal was extracted using the Hu invariant moment feature extraction method to analyze the system vibration characteristics under each typical failure state of the rotor system. The results show that the model in this paper can effectively reduce the computational volume and computational time, and the errors of numerical simulation were less than 3%. When an unbalance fault occurred in the rotor system, the shaft trajectory was “0” shaped and the response spectrum was dominated by 1X. When the rotor system was frictional, the shaft trajectory was a slightly concave “8” shape, and the response spectrum was dominated by 0.5X. When the rotor system was cracked, the axial trajectory was a “vortex”, and the response spectrum was dominated by 0.5X. Thus, the study of typical failure mechanism and vibration characteristics of a turbocharger rotor system by simulation calculation is effective and has good research prospects, providing an important technical reference for dynamic analysis and fault diagnosis of the rotor system.

Research on fault diagnosis method of turbocharger rotor based on Hu-SVM-RFE

Abstract Several parameters need to be monitored for turbocharger rotor faults and the overlap between different fault parameters as well as the redundancy of data, which leads to increased calculation time and reduced classification accuracy. To improve the recognition rate of turbocharger rotor faults, a recursive elimination method based on the support vector machine-recursive feature elimination (SVM-RFE) combined with improved Hu invariant moments is developed for the axial orbit feature extraction of turbocharger rotor with rotor fault. Firstly, improved Hu-invariant moments are extracted for different rotor fault axis orbits, and then the feature ranking and selection are performed by the SVM-RFE method to filter out the feature combinations with higher classification recognition rates. Then, the feature matrix of the Hu-SVM-RFE algorithm screening combination was identified for classification using each of the three diagnostic algorithms. The results show that the optimal feature subset obtained by the Hu-SVM-RFE method can ensure the richness of the fault information of the turbocharger rotor with small number of features. And, a high classification rate can be obtained with low time consumption in combination with the probabilistic neural network (PNN) algorithm. Therefore, Hu-SVM-RFE feature screening method combined with PNN fault diagnosis technology has high accuracy and efficiency, which is of great significance for online fault identification of the supercharger rotor.