柴油机燃烧室不同结构对缸内流场的影响分析

运用三维建模软件Pro/E、有限元分析软件ANSYS Workbench和流体分析软件CFX三种软件进行联合仿真,研究燃烧室结构对柴油机缸内的速度场及压力场影响。先运用Pro/E进行三维建模,再通过ANSYS Workbench对其划分网格,最后通过ANSYS Workbench中的CFX模块对其不同燃烧室形状进行速度场及压力场分析,所得结果对分析提高燃油利用率和燃烧效率,为燃烧室的形状优化提供了依据。     

转子发动机径向密封片动态特性模拟

本文把转子发动机主要结构参数，转速和工作室内压力等作为输入数据来模拟径向密封片在密封槽中的移动和它与转子室内壁的贴合情况，预测显示，在各种负荷，较高转上确实存在径向密封片与转子室内壁贴合不严或脱开及在槽中移动的现象，预测结果与实验结果基本一致，该模型可作为整体式径向密封片设计时的分析工具。     

Investigation of self-excited combustion instabilities in two different combustion systems

The objective of this paper is to characterize dynamic pressure traces measured at self-excited combustion instabilities occurring in two combustion systems of different hardware. One system is a model lean premixed gas turbine combustor and the other a fullscale bipropellant liquid rocket thrust chamber. It is commonly observed in both systems that low frequency waves at around 300Hz are first excited at the onset of combustion instabilities and after a short duration, the instability mode becomes coupled to the resonant acoustic modes of the combustion chamber, the first longitudinal mode for the lean premixed combustor and the first tangential mode for the rocket thrust chamber. Low frequency waves seem to get excited at first since flame shows the higher heat release response on the lower frequency perturbations with the smaller phase differences between heat release and pressure fluctuations. Nonlinear time series analysis of pressure traces reveals that even stable combustion might have chaotic behavior with the positive maximum Lyapunov exponent. Also, pressure fluctuations under combustion instabilities reach a limit cycle or quasi-periodic oscillations at the very similar run conditions, which manifest that a self-excited high frequency instability has strong nonlinear characteristics.     

Parametric simulation and performance analysis of a solar gas turbine power plant from thermodynamic and exergy perspectives

Using solar energy in gas turbine cycles is a new method that can improves the efficiency of gas turbines. Placing a solar receiver before a combustion chamber can raise the temperature of the air coming into the chamber and reduce the consumption of fuel in the chamber. The system that combines a solar energy receiver with a gas turbine cycle is technically called a “solar gas turbine”. The goal of this paper is the parametric simulation and performance analysis of a gas turbine cycle equipped with a solar receiver from thermodynamic and exergy aspects of view. The selected parameters in this study, include the pressure ratio of compressor, the temperature of gases at the turbine inlet and the direct normal irradiance. The obtained results indicate that the fuel consumption of this combined system is reduced by using a solar receiver and the temperature of gases entering the combustion chamber increased. The reduction of consumed fuel, in turn, reduces the rate of exergy destruction in the combustion chamber. Another important point is that the solar receiver itself has the least amount of exergy destruction. The net power generated by a solar gas turbine cycle is 10 % higher than that produced by a simple gas turbine cycle. Also, the studies show that the electrical efficiency of a solar gas turbine cycle is about 41 % higher than the simple gas turbine cycle.

     

提取内燃机燃烧压力高频成分进行压力高频振荡研究

研究内燃机缸内压力高频振荡的机理以及压力高频振荡对燃烧噪声的影响。利用小波分析技术确定缸内压力高频振荡出现的范围,从而确定了燃烧室空腔声模态模型的对应曲轴转角范围。用声响应法和有限元法分别测量和计算不同曲轴转角下燃烧室空腔声模态,并对测量值和计算值对应曲轴转角进行了温度修正,模态试验结果与有限元计算结果较吻合。并对测量的缸内燃烧压力信号和噪声信号进行了分析。研究结果表明：缸内燃烧压力高频振荡是燃烧室的多阶共振频率受到激励引起共振的结果,燃烧压力高频振荡是影响燃烧噪声的重要因素。     

On the method for hot-fire modeling of high-frequency combustion instability in liquid rocket engines

This study presents the methodological aspects of combustion instability modeling and pro-vides the numerical results of the model (sub-scale) combustion chamber, regarding geometrical dimensions and operating conditions, which are for determining the combustion stability boundaries using the model chamber. An approach to determine the stability limits and acoustic characteristics of injectors is described intensively. Procedures for extrapolation of the model operating parameters to the actual conditions are presented, which allow the hot-fire test data to be presented by parameters of the combustion chamber pressure and mixture (oxidizer/fuel) ratio, which are customary for designers. Tests with the model chamber, based on the suggested scaling method, are far more cost-effective than with the actual (full-scale) chamber and useful for injector screening at the initial stage of the combustor development in a viewpoint of combustion instabilities.     

Two-Dimensional Piston Ring Lubrication—Part II: Elastic Ring Consideration

A two-dimensional analysis for piston ring lubrication is presented by considering elastic deflection, EHL and cavitation effects. A numerical procedure is developed for solving hydrodynamic pressure and oil film, thickness shape due to ring deflection and elastic deformation. An elliptic cylinder liner and elastic ring are considered to investigate the circumferential flow effect which has been ignored in previous studies. Results for a typical automotive engine demonstrates that the elastic deflection and deformation of the piston ring have a tendency to reduce the gap caused by the noncircular cylinder. Under the high combustion chamber pressure, the minimum film thickness tends to have a uniform value in the circumferential direction. In turn, this provides a level of control of circumferential flow when the combustion chamber pressure is low. However, the elastic deflection of the piston ring always creates a potential for large blow-by around the piston ring gap area when the cylinder is non-circular. The two-dimensional analysis presented also reveals a reduction of piston ring oil film thickness due to the circumferential flow compared to one-dimensional analysis.     

Adaptation of a zero-dimensional cylinder pressure model for diesel engines using the crankshaft rotational speed

Tighter emission regulations are driving the development of advanced engine control strategies relying on feedback information from the combustion chamber. In this context, it is especially seeked for alternatives to expensive in-cylinder pressure sensors. The present study addresses these issues by pursuing a simulation-based approach. It focuses on the extension of an empirical, zero-dimensional cylinder pressure model using the engine speed signal in order to detect cylinder-wise variations in combustion. As a special feature, only information available from the standard sensor configuration are utilized. Within the study, different methods for the model-based reconstruction of the combustion pressure including nonlinear Kalman filtering are compared. As a result, the accuracy of the cylinder pressure model can be enhanced. At the same time, the inevitable limitations of the proposed methods are outlined.     

Cycle resolved no emissions and its relation with combustion chamber pressure in an s.i. engine with fast response no analyzer

A fast response NO analyzer was applied to investigate the relation between cycle-by-cycle NO emissions and combustion chamber pressure. NO emissions were sampled at an isolated exhaust manifold of 4-stroke spark ignition engine to avoid the interference of exhaust gas from other cylinders. The linear correlation analysis was performed with collected data of NO emissions and combustion chamber pressure with respect to the various air-fuel mixture ratios and engine loads. The sampled data sets were obtained during 200 cycles at each operating condition. The results showed that there was a typical pattern in NO emissions from an exhaust port through a cycle. It was possible to set a block of crank angle in which the linear correlation coefficient between NO emissions and combustion chamber pressure was high. As the engine load increased, NO emissions were more dependent on combustion chamber pressure after TDC. It was also analyzed that the correlation between two parameters with respect to air-fuel mixture ratio tended to increase as mixture went leaner. Furthermore, this correlation coefficient for the mixture near the lean limit seemed to be kept high even though combustion was unstable.     

喷油器的匹配计算

利用发动机工作过程模拟软件AVLBOOST对12缸柴油机的工作过程进行了模拟分析，在原型机的仿真计算结果与试验值符合较好的前提下，提出了综合考虑燃烧室形状、涡流比及喷孔配置等多因素的最优配置方法。试验结果表明，所提出的优化方案是可行的。     

Combustion characteristics of a swirl chamber type diesel engine

A numerical model that utilizes Computational Fluid Dynamics (CFD) techniques is simulated for the analysis of a swirl chamber type diesel engine. This research also reveals the effects of swirl chamber passage hole geometry on the combustion characteristics of a swirl chamber type diesel engine depending on the shape, angle, and area of the jet passage. Turbulence kinetic energy is generated by compound effects of the pressure, heat release, NOx concentrations, and soot concentrations. Results show that combustion characteristics are affected by the passage hole areas and the passage hole inclination angles.     

旋转燃烧室冷却结构设计研究

针对新型旋转燃烧室的传热与冷却问题进行了深入研究。根据燃烧室的热传导特点,列出其热传导微分方程,讨论了传热问题的边界条件,使用有限元方法对燃烧室壁进行了温度场和应力场计算,结合实验修正取得了各个冷却通道之间的换热量及换热系数。在此基础上提出了双层螺旋通道的冷却方案。分析计算结果与实验结果相吻合。     

Hot-fire injector test for determination of combustion stability boundaries using model chamber

This study realizes the conceptual method to predict combustion instability in actual full-scale combustion chamber of rocket engines by experimental tests with model (sub-scale) chamber. The model chamber was designed based on the methodologies proposed in the previous work regarding geometrical dimensions and operating conditions, and hot-fire test procedures were followed to obtain stability boundaries. From the experimental tests, two instability regions are presented by the parameters of combustion-chamber pressure and mixture (oxidizer/fuel) ratio, which are customary for combustor designers. It is found that instability characteristics in the chamber with the adopted jet injectors can be explained by the correlation between the characteristic burning or mixing time and the characteristic acoustic time. In each instability region, dynamic behaviors of flames are investigated to verify the hydrodynamically-derived characteristic lengths of the jet injectors. Large-amplitude pressure oscillation observed in upper instability region is found to be generated by lifted-off flames.     

Calculation on cylinder pressure fluctuation by using the wave equation in KIVA program

Cylinder pressure fluctuation during combustion process of internal combustion engine is closely related to combustion noise and knock.The current studies are based on cylinder pressure test to obtain ...     

Combustion stability characteristics of the model chamber with various configurations of triplet impinging-jet injectors

Combustion stability characteristics in actual full-scale combustion chamber of a rocket engine are investigated by experimental tests with the model (sub-scale) chamber. The present hot-fire tests adopt the combustion chamber with three configurations of triplet impinging-jet injectors such as F-O-O-F, F-O-F, and O-F-O configurations. Combustion stability boundaries are obtained and presented by the parameters of combustion-chamber pressure and mixture (oxidizer/fuel) ratio. From the experimental tests, two instability regions are observed and the pressure oscillations have the similar patterns irrespective of injector configuration. But, the O-F-O injector configuration shows broader upper-instability region than the other configurations. To verify the instability mechanism for the lower and upper instability regions, air-purge acoustic test is conducted and the photograph of the flames is taken. As a result, it is found that the pressure oscillations in the two regions can be characterized by the first impinging point of hydraulic jets and pre-blowout combustion, respectively.     

直喷式柴油机燃烧系统的均匀试验设计研究

在SD195柴油机涡流室改直喷过程中,采用了均匀设计试验法优化柴油机性能,用均匀设计表安排了采用浅W燃烧系统柴油机的燃烧室尺寸、油嘴喷孔直径和油嘴伸出量对性能影响的试验,经回归分析得到了最佳的试验结果。用单因素试验法分析了诸因素对性能的影响规律,发现燃烧室尺寸对性能有重大影响,在考虑交互作用情况下,油嘴孔径、伸出量的参数选择时要综合考虑燃烧室尺寸,试验最终获得良好效果。同时证明了均匀设计法的有效性,表明均匀设计试验法是安排多水平试验的良好方法。     

Investigation of nonlinear numerical mathematical model of a multiple shaft gas turbine unit

The development of numerical mathematical model to calculate both the static and dynamic characteristics of a multi-shaft gas turbine consisting of a single combustion chamber, including advanced cycle components such as intercooler and regenerator is presented in this paper. The numerical mathematical model is based on the simplified assumptions that quasi-static characteristic of turbo-machine and injector is used, total pressure loss and heat transfer relation for static calculation neglecting fuel transport time delay can be employed. The supercharger power has a cubical relation to its rotating velocity. The accuracy of each calculation is confirmed by monitoring mass and energy balances with comparative calculations for different time steps of integration. The features of the studied gas turbine scheme are the starting device with compressed air volumes and injector’s supercharging the air directly ahead of the combustion chamber.     

燃气热力性质的计算和分析

本文讨论了C－H－O－N'系燃料的燃气热力性质：提出了四种具有不同准确度的简捷计算方法;分析了现有各种近似计算方法（包括本文提出的）的准确度;总结了计算的规律。     

Analysis of combustion and flame propagation characteristics of LPG and Gasoline fuels by laser deflection method

This work is to investigate the combustion characteristics and flame propagation of the LPG (liquified petroleum gas) and gasoline fuel. In order to characterize the combustion processes of the fuels, the flame propagation and combustion characteristics were investigated by using a constant volume combustion chamber. The flame propagation of both LPG and gasoline fuels was investigated by the laser deflection method and the high-speed Schlieren photography. The result of laser deflection method show that the error of measured flame propagation speed by laser method is less than5% compared with the result of high-speed camera. The flame propagation speed of the fuel is increased with the decrease of initial pressure and the increase of initial temperature in the constant volume chamber. The results also show that the equivalence ratio has a great effect on the flame speed, combustion pressure and the combustion duration of the fuel-air mixture.     

基于CFD的氢气／空气当量比对微尺度燃烧室燃烧特性影响的分析

以美国麻省理工学院（MIT）研制的硅基六晶片微燃烧室为研究对象,提出利用二维CFD（计算流体动力学）数值模拟的方法,研究在保持微尺度燃烧室进口氢气／空气流量不变的情况下,改变氢气／空气当量比对燃烧室燃烧特性的影响。整个模拟计算主要包括氢气／空气的流动路径、微燃烧室的内部区域以及整个燃烧室的墙壁面;同时在计算过程中我们考虑了氢气／空气的流体动力学特性、传热学特性和详细的基元反应机理。结果表明,利用二维CFD数值模拟的方法研究微尺度燃烧室燃烧特性可行,与国外实际测量结果较为相似,为今后微型燃气轮机燃烧室的研制及改进提供了一定的参考依据。