摘要
压气机作为燃气轮机的核心部件,对燃气轮机及其热力循环的性能影响显著,准确预测压气机性能至关重要。该文基于通用级特性曲线,采用改进的逐级叠加法构建了一个变几何多级轴流式压气机性能预测模型。该模型针对现代重型燃气轮机压气机的变几何特点,提出了考虑入口导叶(IGV)和可变静叶(VSV)的压气机级特性计算方法。通过在引气级所对应的连续性方程中扣除引气量的方式,该模型还预测了级间引气对压气机性能的影响。与实验结果的对比验证表明:该模型不仅可准确地预测压气机整机性能及变几何结构、级间引气对压气机性能的影响,结果的相对误差最低可达0.450%,而且可得到压气机各级的几何参数和热力学参数,为后续开发压气机部件稳态和动态模型提供了基础。
[Objective]The stage-stacking method,which is based on stage characteristic curves and uses a sequential calculation scheme,is a valuable tool for predicting the performance of multistage axial-flow compressors.A slight variation in mass flow can cause considerable changes in the pressure ratio because the compressor operates at high speed,and constant speed lines exhibit near-vertical orientation.To avoid this issue,a traditional approach is to convert the mass flow rate boundary into pressure ratio boundary conditions.This undoubtedly increases the complexity of calculations.Furthermore,practical monitoring parameters and boundary conditions linked with other components in an entire gas turbine system are state variables,namely,pressure and temperature,rather than the mass flow rate.Consequently,if we adopt the mass flow rate boundary condition,an initial value must be assumed,and the result may be obtained through an intricate iterative process.Thus,the calculation frequently becomes highly inefficient.Targeting the complexities and inefficiencies inherent in the traditional approach,a modified stage-stacking method is developed.The modified stage-stacking method,similar to the traditional approach,is based on two generalized stage performance curves,namely,pressure coefficient and efficiency curves.Each stage is considered as an independent control volume,delineated by its physical boundary.This method uses thermodynamic parameters—static temperature,static pressure,and axial velocity—along meridional streamline at a mean radius of all stage inlets and outlets as unknown variables.When conservation of mass,momentum,and energy is applied to each stage,a nonlinear system with 3n governing equations is obtained for a compressor of n stages.These equations involve 3n variables with the inlet total pressure,the total temperature,and the outlet total pressure as boundary conditions.Thus,the group of equations can be simultaneously solved.The Newton-Raphson method is used as the iterative numerical solver for the nonlinear algebraic equation set.The thermodynamic properties are determined by functions from the Multiflash library.Furthermore,while assuming a linear mathematical correlation between the variable stator vane and the inlet guide vane(IGV),the impact of the variable geometry of a modern heavy-duty gas turbine compressor on the performance is investigated.In addition,to analyze the effect of air bleeding on compressor performance,the bleeding quantity is deducted from the pertinent continuity equation.According to this approach,a model is developed to predict the performance of a multistage axial-flow compressor featuring variable geometry.To validate the accuracy of the model,four representative compressors for fixed geometry,variable geometry,and interstage bleeding with distinct parameters are selected as research subjects.Compared with field data,the results are in good agreement with an average relative error of only 1.593%for fixed geometry compressors.For variable geometry compressors,excellent agreement is observed between the predicted results and field data,with a maximum relative error of 3.856%at high constant speed lines.For low constant speed lines,despite the largest relative error of 10.834%,the absolute error remains small and within an acceptable range.Of great importance is the strong conformity between the trends of compressor performance with speed variation and IGV adjustments obtained from this model and field data,providing a substantial indication of the result accuracy.If a suitable IGV schedule is chosen,the relative error can be as low as 0.450%.In addition,the model can accurately estimate the geometric and thermodynamic parameters with limited design parameters,with root mean square errors of 0.022 and 0.918,respectively.These results show that the modified stage-stacking method can not only precisely calculate the overall performance of axial-flow compressors and assess the impact of the variable geometry on compressor performance but also obtain the geometric and thermodynamic parameters of each stage of such compressors.This method serves as a valuable framework for developing steady-state and dynamic compressor models.
作者
刘欢
张士杰
LIU Huan;ZHANG Shijie(School of Engineering Science,University of Chinese Academy of Sciences,Beijing 100190,China;Key Laboratory of Advanced Energy and Power,Institute of Engineering Thermophysics,Chinese Academy of Sciences,Beijing 100190,China)
出处
《清华大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2024年第5期869-878,共10页
Journal of Tsinghua University(Science and Technology)
基金
国家科技重大专项(2017-I-0002-0002)。
关键词
轴流式压气机
变几何
多级
性能预测
级间引气
axial-flow compressor
variable geometry
multistage
performance prediction
interstage bleeding
