Time-dependent Vibration Frequency Reliability Analysis of Blade Vibration of Compressor Wheel of Turbocharger for Vehicle Application

Blade vibration failure is one of the main failure modes of compressor wheel of turbocharger for vehicle application. The existing models for evaluating the reliability of blade vibration of compressor wheel are static, and can not reflect the relationship between the reliability of compressor wheel with blade vibration failure mode and the life parameter. For the blade vibration failure mode of compressor wheel of turbocharger, the reliability evaluation method is studied. Taking a compressor wheel of turbocharger for vehicle application as an example, the blade vibration characteristics and how they change with the operating parameters of turbocharger are analyzed. The failure criterion for blade vibration mode of compressor wheel is built with the Campbell diagram, and taking the effect of the dispersity of blade natural vibration frequency and randomness of turbocharger operating speed into account, time-dependent reliability models of compressor wheel with blade vibration failure mode are derived, which embody the parameters of blade natural vibration frequency, turbocharger operating speed, the blade number of compressor wheel, life index and minimum number of resonance, etc. Finally, the rule governing the reliability and failure rate of compressor wheel and the method for determining the reliable life of compressor with blade vibration is presented. A method is proposed to evaluate the reliability of compressor wheel with blade vibration failure mode time-dependently.

Method for Evaluating the Reliability of Compressor Impeller of Turbocharger for Vehicle Application in Plateau Area

As turbocharging diesel engines for vehicle application are applied in plateau area, the environmental adaptability of engines has drawn more attention. For the environmental adaptability problem of turbocharging diesel engines for vehicle application, the present studies almost focus on the optimization of performance match between turbocharger and engine, and the reliability problem of turbocharger is almost ignored. The reliability problem of compressor impeller of turhocharger for vehicle application when diesel engines operate in plateau area is studied. Firstly, the rule that the rotational speed of turbocharger changes with the altitude height is presented, and the potential failure modes of compressor impeller are analyzed. Then, the failure behavior models of compressor impeller are built, and the reliability models of compressor impeller operating in plateau area are developed. Finally, the rule that the reliability of compressor impeller changes with the altitude height is studied, the measurements for improving the reliability of the compressor impellers of turbocharger operating in plateau area are given. The results indicate that when the operating speed of diesel engine is certain, the rotational speed of turbocharger increases with the increase of altitude height, and the failure risk of compressor impeller with the failure modes of hub fatigue and blade resonance increases. The reliability of compressor impeller decreases with the increase of altitude height, and it also decreases as the increase of number of the mission profile cycle of engine. The method proposed can not only be used to evaluating the reliability of compressor impeller when diesel engines operate in plateau area but also be applied to direct the structural optimization of compressor impeller.

Reverse Engineering of Turbocharger Compressor Designs Based on Non-Parametric CAD Data

The improvement of turbocharger components-such as compressor-by means of virtual methods can be done most efficiently if those component’s geometries are given in a parameterized format. It is shown here how the geometric description of turbocharger compressors that have a neutral format (ASCII or STEP/IGES) can be transformed in a parameterized description. This description is then used to perform parameter variations which are validated via simulation methods like CFD. The parameterization of the geometry is therefore a very important step within the workflow of the virtual design of turbocharger components as without it the investigation of different geometries are very time-consuming and expensive.

Research and development on transonic compressor of high pressure ratio turbocharger for vehicle internal combustion engines

The pressure ratio required for a turbocharger centrifugal compressor increases with internal combustion engine power density. High pressure ratio causes a transonic flow field at the impeller inducer. Transonic flow narrows the stable flow range and de-teriorates stage efficiency. In this work, an advanced high pressure ratio transonic compressor was designed. The experimental results show that the maximum pressure ratio of this turbocharger is about 4.2, the maximum efficiency is above 80% and the stable flow range at the designed rotating speed is up to 34%. A turbocharger with this transonic compressor has been applied to some vehicle research actually, and improved power density by 40%.

Influence of volute distortion on the performance of turbocharger centrifugal compressor with vane diffuser

As the geometry of the volute of turbocharger compressor is non-axisymmetric,it causes a distortion at the outlet of the diffuser and influences the upstream components.A distortion model in which a pressure distortion was applied as outlet boundary condition was established to simulate the distortion induced by the volute.It turned out to be sufficient to impose a circumferentially asymmetric pressure distribution at the outlet of the diffuser to replace the volute.Based on the distortion model which was verified,the influence of the amplitude of the distortion on the performance of centrifugal compressor was studied in detail.The results show that the distortion severely harms aerodynamic stability of the investigated compressor.The larger the amplitude of the distortion,the worse the performance of the compressor.The distortion induced by asymmetric volute propagates to upstream components and causes local flow separation at part of diffuser and impeller,and then causes the compressor surge.When the amplitude of the volute distortion is 10%,the stable flow range of the centrifugal compressor decreases to near zero.To authors’knowledge,the relationship between the compressor performance and distortion amplitude is first obtained quantitatively,which provides evidence to improve the performance of turbocharger compressor by decreasing the distortion induced by asymmetric volute.

A novel experimental method to evaluate the impact of volute's asymmetry on the performance of a high pressure ratio turbocharger compressor

All components of a turbocharger compressor are axisymmetric except for the spiral-shaped,gas-collecting overhung volute.In this paper,a novel experimental method to evaluate the impact of the volute's asymmetry on centrifugal compressor performance is proposed and applied to a high pressure-ratio turbocharger compressor.This method can isolate the impact of the volute's asymmetry on the compressor performance for the first time.Experiments prove the considerable impact of the volute's asymmetry on the compressor performance,especially the stability and efficiency.The impact of the volute's asymmetry on compressor stability correlates with rotational speed and thus with the pressure ratio,constricting the stable flow range by up to 47 percent and decreasing the maximum efficiency by 4.8 percent at the design speed.The results provide evidence to exploit the potential of intrinsic non-axisymmetric flow induced by asymmetric volute to improve the performance of turbocharger compressor with a high pressure ratio.

Effects of blade bowing on the performance of a high pressure-ratio turbocharger centrifugal compressor with self-recirculation casing treatment

The effects of blade bowing on the performance of a high pressure-ratio turbocharger centrifugal compressor were studied by experiments and numerical simulation.The results showed that the negative bowing was capable of increasing the choke mass rate and the efficiency but decreased the surge mass flow rate,while the positive bowing had the opposite effects.When coupling with the self-recirculation casing treatment,the surge mass flow rate of the compressor with negative bowing blade was almost identical with that of the prototype,while the choke mass flow rate was still larger,and the total effect contributed to an increase of the stable flow range by 5.85%at design speed.Besides,the flow mechanism of the coupling effects of blade bowing and self-recirculation casing treatment was discussed.

Effects of Reynolds number on the performance of a high pressure-ratio turbocharger compressor

The effects of Reynolds number on the performance of a high pressure-ratio turbocharger compressor were investigated by both experiments and numerical simulation. The experimental results show that the pressure ratio and the efficiency of the compressor respectively decrease by 7.9% and 6.9% when Reynolds number drops from 9.86×10 5 to 2.96×10 5 . The numerical simulation predicts a similar trend as the experimental results although it underestimates the deterioration of the performance under low Reynolds number conditions. According to simulation results, the boundary layer thickness increases at the inducer, which decreases the throat area and leads to smaller choke mass flow rate. The increments of the boundary thickness are relatively small at the rear part of the impeller. The boundary layer separation flow is severe. The interaction between boundary layer separation flows and leakage flows causes the high loss region at the rear part of the impeller passage under low Reynolds number condition.

车用柴油机高压比宽流量增压器研制

目的 对于单级高压比宽流量增压器,为适应发动机强化指标,进行一系列的改进设计。方法 利用仿真设计与试验相结合的方法,对高海拔环境应用增压器进行改进设计。通过理论推导,确定压气机及涡轮的气动性能优化设计方法,开展高稳定裕度转子轴承系统设计方法研究与验证。结果 匹配高压比宽流量增压器的发动机与原机相比,高原功率恢复了17%,发动机排气温度降低了7%,增压器转速降低了13%。结论 在原机的基础上设计了压比为4.6的宽流量高性能涡轮增压器,成功实现了高压比宽流量增压器的设计,满足了发动机平原、高原不同环境的运行需求。

废气涡轮增压器压气机流场特性分析

为提高某废气涡轮增压器工作性能,文中对压气机流场特性进行理论与试验研究,通过Fluent软件对不同工况下压气机的性能参数进行仿真,得到流体的压强、流速和温度云图,通过增压器性能试验测试压气机流量、效率及压比,并对压气机进行结构优化。结果表明:仿真结果与试验结果相对误差小于5%,结构优化后的压气机叶轮对流力的利用率提高32.8%,流场压力极值增大5.83%,蜗壳割舌部位压力集中减弱,蜗壳背部最大流速降低2.89%,最高温度提高20.06%,为增压器压气机结构的进一步优化提供依据。

基于联合运行规律的增压器压气机非定常流动模拟

为了提高压气机在非定常流动状态下与增压器的匹配精度,基于增压器运行工况提出了内部联合运行规律,并开展不同结构压气机的非定常流动特性和性能修正研究。结果表明,在3种结构压气机中,除了高速大流量联合工况外,采用进口直径减小1 mm的等长叶片压气机的非定常流动性能有明显优势,且喘振性能更好。基于非定常系数对压气机性能修正后,压气机性能更接近实际工作状态。

小排量国Ⅵ柴油机涡轮增压器喘振优化设计

匹配某小排量国Ⅵ柴油机时,增压器压气机出现了喘振现象,导致发动机扭矩明显降低,需要设计一款新型压气机。通过加大压气机叶片θ角、叶片出口β角、叶片弦长、叶轮进口尺寸、叶轮出口宽度,减小扩压器出口与叶轮出口直径的比值,设计了优化方案。进行了优化方案和原方案的压气机性能仿真计算、增压器台架压气机性能试验、发动机台架增压器性能匹配试验,结果表明:优化方案改善了压气机小流量区域的稳定性,提高了堵塞流量;在发动机全转速范围内,流量减小时压比特性曲线斜率始终为负,压气机运行稳定,未发生喘振;发动机可以加载到最大设计扭矩,提升了发动机的动力性能。

Measurement and Numerical Simulation of a Small Centrifugal Compressor Characteristics at Small or Negative Flow Rate

For centrifugal compressors used in automotive turbochargers, the extension of the surge margin is demanded because of lower engine speed. In order to estimate the surge line exactly, it is required to acquire the compressor characteristics at small or negative flow rate. In this paper, measurement and numerical simulation of the characteristics at small or negative flow rate are carried out. In the measurement, an experimental facility with a valve immediately downstream of the compressor is used to suppress the surge. In the numerical work, a new boundary condition that specifies mass flow rate at the outlet boundary is used to simulate the characteristics around the zero flow rate region. Furthermore, flow field analyses at small or negative flow rate are performed with the numerical results. The separated and re-circulated flow fields are investigated by visualization to identify the origin of losses.

Multi-point Optimization of Recirculation Flow Type Casing Treatment in Centrifugal Compressors

High-pressure ratio and wide operating range are highly required for a turbocharger in diesel engines. A recirculation flow type casing treatment is effective for flow range enhancement of centrifugal compressors. Two ring grooves on a suction pipe and a shroud casing wall are connected by means of an annular passage and stable recirculation flow is formed at small flow rates from the downstream groove toward the upstream groove through the annular bypass. The shape of baseline recirculation flow type casing is modified and optimized by using a multi-point optimization code with a metamodel assisted evolutionary algorithm embedding a commercial CFD code CFX from ANSYS. The numerical optimization results give the optimized design of casing with improving adiabatic efficiency in wide operating flow rate range. Sensitivity analysis of design parameters as a function of efficiency has been performed. R is found that the optimized casing design provides optimized recirculation flow rate, in which an increment of entropy rise is minimized at grooves and passages of the rotating impeller.

CFD Simulation of Pulsation Noise in a Small Centrifugal Compressor with Volute and Resonance Tube

The rotational frequency tone noise emitted from the automobile turbocharger is called the pulsation noise. The cause of the pulsation noise is not fully understood, but is considered to be due to some manufacturing errors, which is called the mistuning. The effects of the mistuning of the impeller blade on the noise field inside the flow passage of the compressor are numerically investigated. Here, the flow passage includes the volute and duct located downstream of the compressor impeller. Our numerical approach is found to successfully capture the wavelength of the pulsation noise at given rotational speeds by the comparison with the experiments. One of the significant findings is that the noise field of the pulsation noise in the duct is highly one-dimensional although the flow fields are highly three-dimensional.

发动机涡轮增压器压气机出口漏油故障的诊断与维修

增压器压气机漏油故障是发动机的常见故障,这不仅影响了发动机的性能,还可能引发安全问题。阐述了增压器压气机的润滑油密封和泄漏原理,分析了压气机漏油的原因,列出了各种压气机假性漏油情况,详细描写了压气机漏油的诊断流程和检查方法,可有效减少误判和避免故障复发。

涡轮增压器离心压气机内部流场周向非均匀特性研究

涡轮增压器离心压气机蜗舌对气流的滞止效应会导致蜗壳周向静压分布不均匀。为了进一步挖掘压气机气动性能提升潜力,利用全环三维数值模拟对其内部非对称流场进行了分析。结果表明,不同工作状态下扩压器内部静压分布规律随流量变化,流量减小,静压最大值从周向90°位置逐渐迁移至蜗舌附近。沿流向,蜗舌诱导的非均匀静压会逆流反向传播到扩压器进口。此外,扩压器进口非均匀静压分布对单个叶轮通道性能具有一定影响,即存在一个“临界流量点”,在近堵塞点至流量临界点之间,从蜗舌对应的叶片通道开始,单个叶片通道流量和通道损失沿叶轮旋转方向先减小后增大,效率先增大后减小;在临界点至近堵塞点之间,单个叶片通道流量和通道损失沿叶轮旋转方向先增大后减小,效率先减小后增大。

某轮系泊试验主机增压器喘振原因分析

现代船用柴油机广泛采用废气涡轮增压器。新造船舶在进行主机系泊试验时,有可能发生主机增压器压气机喘振的现象。本文基于某船在系泊试验过程中出现的增压器喘振现象,通过实船螺旋桨轴扭矩的测量数据及推进特性曲线分析,找出引起增压器喘振的主要因素,并提出在系泊试验时的具体规避方法。

国六涡轮增压柴油机喘振机理与喘振控制研究

涡轮增压柴油机在瞬态过程中存在喘振问题,影响可靠性和驾驶体验,尤其对于利用进气节流阀提高热管理性能的国六涡轮增压柴油机,其喘振问题亟待解决。试验对象为排量10.5 L的重卡发动机,进行不同发动机转速下突降油门试验,通过对比发现发动机在中低转速突降油门过程更容易发生喘振;另外,进行热管理模式下不同进气节流阀关闭速度和最小关闭开度的突降油门试验,通过对比喘振规律发现,热管理模式下进气节流阀关闭速度越快,进气阻塞作用越强,而进气节流阀最小开度越小,最小折合流量越小,喘振风险越大。在空气系统模型基础上搭建喘振控制策略,经过验证可知,热管理模式下喘振控制策略能有效防止突降油门过程超出喘振线,一定程度上解决了国六涡轮增压柴油机喘振问题。

涡轮增压器压气机规格化设计研究

离心压气机因其单级压比高、工作范围宽、结构简单可靠等特点被广泛用于船用涡轮增压器中。为了满足增压器对柴油机的匹配需求,增压器压气机需要进行规格化设计,形成具有不同的通流能力的压气机。本文基于某国产增压器,分别开展了改变叶轮子午线高度、改变扩压器喉口面积和几何模化三种规格化方式对增压器流量和效率的影响研究。结果表明:改变扩压器喉口面积可实现较小流量范围的压气机规格化设计,7.8%的流量变化对效率的影响在0.3%以内;改变子午型线可实现稍大流量范围的压气机规格化设计,12.1%的流量变化对效率的影响在1.1%以内;几何模化可实现较大流量范围的压气机规格化设计,且对效率影响较小,1.90倍流量变化仅导致0.34%的效率变化,通过多种规格化组合使用可实现压气机较大范围内流量的连续变化。本文研究结果为国产增压器系列化规格化设计提供了有效支撑。