发动机机体缸盖冷却水CFD模拟计算与分析

应用ANSYS CFX软件对某高强化重型发动机的机体、缸盖冷却水道进行了CFD模拟计算,分析了缸盖冷却水流量分布均衡性,考查了缸盖冷却水流动情况。并对网格数量和网格品质度等对模拟计算精度的影响进行了分析。研究表明,网格精度和网格数量对计算精度影响明显。     

分隔室压燃式天然气发动机燃烧室结构参数对燃烧特性的影响

利用详细的化学动力学机理与CFD多维数值模拟计算软件研究了燃烧室结构参数对分隔室压燃式天然气发动机燃烧特性的影响。为验证模型的正确性,将实验值与计算值进行了对比。通过模拟计算,讨论了燃烧室通道截面积、通道倾角、通道形状、通道布置对着火时刻、缸内平均温度和压力以及NO排放的影响。结果表明:通道截面积在132.66 mm2时综合性能最佳;通道倾角为50°时能取得较好的燃烧性能;圆形通道在着火性能、NO排放性能均优于圆角方形通道;通道布置方式对燃烧性能的影响较小。     

适用于HCCI发动机的基础燃料化学动力学模型Ⅰ:比较现有模型

随着HCCI燃烧技术的不断发展,燃料化学动力学机理在燃烧计算中发挥着越来越重要的作用.纵览了近年来基础燃料各种不同类型反应机理与试验研究情况,为评价现有反应机理对HCCI发动机燃烧过程的适用性,将机理模型的计算结果与HCCI燃烧相关试验进行了综合比较验证.通过4种典型基础燃料机理的计算与激波管、速压机和HCCI发动机等...     

阳极焙烧炉内煤气流动和燃烧的数值模拟

采用计算燃烧学的原理和模型以及CFD软件对燃烧煤气的阳极焙烧炉炉内的流动和燃烧过程进行了数值模拟计算,讨论了炉内温度场、流场、O2浓度场的分布规律,分析了这些因素对阳极炭块焙烧质量的影响。研究表明,在设计阳极焙烧炉时应考虑对气流分布有影响的各种因素。     

HCCI发动机燃烧多维数值模拟(Ⅰ)——模型的建立和比较

使用多维骨架动力学模型模拟了以异辛烷为燃料的均质压燃(HCCI)发动机的燃烧过程。通过结合多维CFD程序KIVA和反应动力学程序CHEMKIN实现了化学反应与流动的耦合运算。结果表明网格密度和时间步长对HCCI的燃烧过程影响不大,而初始温度对着火点影响显著。通过修改多维模型比较了RNG k-ε湍流模型和标准k-ε湍流模型、Han和Reitz传热模型和传统传热模型、Kong的混合模型和无混合模型,以及不同的缝隙区模型,发现使用RNG k-ε湍流模型、Han和Reitz传热模型和缝隙流动模型计算结果与实验值更为接近。修改后的多维模型在不同当量比下计算得到的压力、放热率和排放值与实验完全一致。     

CA6DL1—30柴油机燃烧室改进的模拟与实验研究

为研究燃烧室形状对柴油机燃烧和排放性能的影响,应用大型通用CFD软件STAR—CD程序对3种不同形状的燃烧室内燃烧过程进行了多维数值模拟计算,研究了不同的燃烧室形状对缸内气流运动以及缸内燃烧温度和排放的影响,并通过实验验证了计算模型的正确性。     

复合供气压燃式天然气发动机的燃烧特性

根据分层燃烧理论,设计了分隔室复合供气压燃式天然气发动机燃烧系统.采用化学动力学简化机理模型与CFD耦合对发动机的着火和燃烧过程进行了模拟计算,并验证了模拟计算结果的有效性.结果表明,进气温度、电热塞温度、喷气时刻、供气量对发动机的燃烧特性有较大影响.进气温度过高时,燃烧趋向单级燃烧,将导致爆燃,而且产生较高的NO排放.电热塞温度过高同样导致高的燃烧速率,增大爆燃趋势;高压供气时刻提前使燃烧压力、温度和压力升高率上升,NO排放随之增加;在现有的较低喷气速率下,当缸内喷气持续期控制在40～50 °CA时,燃烧时刻最佳;当进气道供气量比例较高时,会发生敲缸现象.     

双燃料内燃机引燃油混合气形成与燃烧过程模型研究

对于双燃料发动机，引燃油蒸发、混合与燃烧是在天然气与空气混合物为介质的情况下，通过采用离散液滴模型，模拟了引燃油的蒸发与混合过程；采用经过修正的Shell模型，对引燃油的着火过程进行了数值模拟；以阿伦纽斯公式为基础，综合湍流对化学动力学的影响，提出了一个新的燃烧模型．经过模拟计算与实验对比，验证了该数值模型的模拟效果．     

汽油机燃烧过程模拟计算及爆震预测

将计算焰前反应的化学反应动力学模型与燃烧模型及湍流火焰传播模型相结合,建立了含有碳氢燃料焰前反应的简易化学动力学模型的汽油机双区燃烧模型。用该模型能较好地模拟汽油机燃烧过程,并能实现爆震预测,研究影响爆震发生的诸多因素。采用此模型对４９２ Ｑ Ａ 汽油机进行模拟计算的结果与试验结果能较好地吻合,证明了该模型的可行性。     

采用并行计算和简化机理的HCCI发动机多维模拟

HCCI燃烧过程多维数值模拟十分耗时.采用并行计算和简化机理对HCCI燃烧过程多维CFD模拟计算进行了加速对比.研究基于16-CPU计算机集群系统,采用消息传递的并行算法(Message-Passing Interface,MPI)方式计算.结果表明,内燃机HCCI燃烧多维燃烧模拟,采用8个CPU能获得最大收益:纯流动计算加速5倍,耦合化学反应流动计算加速4倍,简化反应机理又可加速9倍.通过优化选择并行计算CPU数量和反应机理,使得HCCI发动机单个循环模拟时间由一个月缩短到一天,大大提高了汽车发动机燃烧模拟计算的效率.而且采用三维CFD耦合化学反应的模拟计算,可以解析HCCI发动机着火燃烧过程,提供详细的流动、燃烧和排放物生成的瞬态信息.     

Accelerating multi-dimensional combustion simulations using GPU and hybrid explicit/implicit ODE integration

Simulating multi-dimensional combustion with detailed kinetics often requires solving a large number of ordinary differential equation (ODE) problems at each global time step. In many cases, the ODE integrations account for the bulk of the total wall-clock time for the simulation. This paper introduces CHEMEQ2-GPU – a new explicit stiff ODE solver (based on the existing CHEMEQ2 solver) that exploits the parallel architecture of the modern graphics processing unit (GPU) to accelerate ODE integration in multi-dimensional combustion simulations. We also demonstrate efficient application of the CPU and GPU as co-processors, for further speedup. We describe a hybrid explicit/implicit ODE solver approach that combines the strengths of both solver types running simultaneously on the GPU and CPU, respectively. A dynamic load balancing scheme was used to assign the kinetics ODE integrations over all grid points to either the CPU-based implicit solver DVODE (which is the more efficient solver for highly stiff grid points) or CHEMEQ2-GPU (more efficient for moderately stiff or non-stiff grid points). We demonstrate CHEMEQ2-GPU and the hybrid approach in 3-D simulations of homogeneous charge compression ignition (HCCI) engines. The test cases applied two different n-heptane reaction mechanisms (a large detailed model and a small skeletal model) and three different mesh sizes. Engine simulations were performed using KIVA-CHEMKIN. CHEMEQ2 was about 2–3 times faster than DVODE, with similar prediction accuracy. The CHEMEQ2-GPU speedup relative to CHEMEQ2 increased linearly with the number of grid points for the range of meshes tested in this work. Assuming ideal linear scaling of simulation time with number of processors, the speed of CHEMEQ2-GPU on the Tesla C2050 GPU was equivalent to CHEMEQ2 running on approximately 13 parallel 2.8 GHz CPU processors for the finest mesh; and the hybrid solver approach was equivalent to CHEMEQ2 on ～15 such CPU processors. In summary, CHEMEQ2-GPU provided the additional computing power of 14 parallel CPU processors (for the finest mesh tested) and the hybrid solver approach demonstrated a method to efficiently apply these additional co-processors with existing CPU cores for combustion simulations. CHEMEQ2-GPU scales favorably with the number of grid points and is available by request to the authors. This work presents opportunities for further development, particularly in CPU/GPU load balancing algorithms.     

燃烧室结构对微型摆式发动机燃烧过程影响的数值模拟

基于Fluent-CFD软件建立了摆臂自由运动条件下的微型摆式发动机内燃烧过程三维动态网格数值模型，采用正丁烷氧化一步反应机理模拟了三种内径的燃烧室内流动与燃烧过程，考察了燃烧室内径对系统性能的影响。结果表明：增大内径可以减小燃烧室底部区域燃料残留，促进燃烧更快完成，提高燃烧室内的峰值压力和缩短峰值出现时间，有利于提高发动机的输出功、功率密度和效率。     

非下交曲线坐标系数值模拟加力燃烧室湍流两相流燃烧

采用双流体模型对航空发动机加力燃烧室的湍流两相流燃烧过程进行了数值模拟,数值计算方法为非正交曲线坐标下非交错网络的SIMPLE方法,差分网络分区方法生成,计算时对整个流场进行分区迭代直至得到收敛结果。气相化学反应速率用涡旋破碎模型（EBU）,充分考虑两相之间的质量、动量和能量的相互作用,数值模拟结果合理。     

弱电网下考虑装置死区效应时的逆变器并网电能质量分析

弱电网接入下,逆变器-电网级联系统的阻抗不匹配易导致逆变器并网系统的稳定性能降低。为建立更准确的逆变器输出阻抗模型,以LCL型并网逆变器为例,将装置死区效应考虑到并网逆变器建模中。同时,考虑长线路对地分布电容的影响,建立弱电网下长线路分布参数模型并分析其输入阻抗幅频特性。基于此,采用基于奈奎斯特稳定判据的阻抗分析法分析并网系统稳定性并计算其稳定裕度,研究随着死区时间和长送出线线路长度的增加并网系统稳定裕度值的变化规律,并利用PSIM 9.0平台建立相关仿真模型,证明了理论分析的准确性和可行性。     

混煤燃烧反应动力学参数的热重研究

采用热天平,对两种标准煤的混煤燃烧反应动力学参数进行了实验研究。首先对热天平实验的重复性进行了验证,确保获得的实验参数准确、可靠。采取不同的燃烧方式分析动力学参数的变化。非等温燃烧的研究表明,以特征温度区间计算,表观活化能和频率因子均随混煤中烟煤比例的增加而降低。升温速率增加,混煤燃烧的表观活化能有所下降。等温燃烧的研究表明,模型的选择对动力学参数的研究影响很大,通过计算,认为球对称收缩核模型适合于混煤等温燃烧动力学参数的研究。表观活化能的计算结果表明高活性煤种的存在可以很好的改善混煤的着火性能,并且存在最佳掺混比例。图6表5参3     

内燃机歧管多分支动量守恒边界模型研究

为了实现歧管分支模型对于不同分支数的适用性,推导建立了多分支动量守恒边界模型.首先,在连续性方程和能量方程基础上,考虑到分支结构和流动参数影响造成工质流经多分支接头时动量变化,建立了适用于任意分支数的多分支动量守恒边界模型;而后建立激波管测试算例,对比分析传统的等压模型、压力损失模型及动量守恒模型等不同多分支模型的计算...     

Experimental Validation of the Multiple Absorption Coefficient Zonal Method (MACZM) in a Dynamic Modeling of a Steel Reheating Furnace

In this work, the multiple absorption coefficient zonal method (MACZM) is being implemented and validated numerically. The method is demonstrated to be highly suitable for the analysis of radiative heat transfer in multidimensional inhomogeneous non-grey media. A uniform rectangular fine grid is considered and small CPU time is achieved. This makes the method of great interest for transient applications. The validity of the method is demonstrated in two steps. First, cases with simple geometry are considered and results are compared to results generated by direct numerical integration. Results are also generated by MODRAY, which is a source project based on an original method called the flux-planes approximation, and are shown to be equally accurate. Second, the case of a steel reheating furnace is considered. In a previous work, the furnace heat balance and temperature profiles were simulated using a finite difference computation approach and radiative exchange factors generated by MODRAY. Experiments were performed and results generated by the model were found to be in good agreement with experimental data. The radiative exchange factors are now recalculated with MACZM. They are shown to be very close to those generated by MODRAY. The comparison of the two methods clearly shows that MACZM is much faster for the calculation of the volume-volume radiative exchange factors on a uniform rectangular grid.     

基于床层下降的链条炉数值模型与计算

建立了考虑床层下降的链条锅炉二维稳态层燃数值模型,通过求解床层高度控制方程得到床层高度沿炉排前进方向变化的分布,利用动网格技术实现床层高度的下降。对比层燃模型和单元体炉实验结果,实验测得燃烧后床层高度为30 mm,改进后模型预测值为26.9 mm,表明改进后的模型可以更准确地预测床层高度、床层燃烧温度、气体产物分布,提高了层燃数值模型的计算精度。     

A time-averaged model for production of syngas from fuel-rich partial oxidation in the reversal flow reactor

Based on the analogy with steady counter flow reactor, a 1D time-averaged model with detailed kinetics is developed, which is applicable to modeling of production of syngas from fuel-rich partial combustion in reversal flow burner (RFB). The model is evaluated by comparing its predictions of temperature distributions and major syngas components in RFB with experimental data, good agreement between experimental results and predictions is observed. The model is then used to study the influence of mixture velocity, equivalence ratio and heat loss on the combustion characteristics in RFB. It is demonstrated that huge computational time can be saved by a factor of 140 using the developed model compared to the complete transient model. The developed model can be used for quick optimal design of syngas production in RFB with greatly reduced computational time and high accuracy.     

Detailed numerical simulation of thermal radiation influence in Sandia flame D

In order to investigate the influence of thermal radiation in turbulent combustion processes, Sandia flame D is numerically simulated, with multiple-time scale (MTS) k–ε turbulence model for turbulence, the combination of probability density function (PDF) transportation method, Lagrangian flamelet model (LFM) and the detailed chemical reaction mechanism GRI 3.0 (consisting of 53 species and 325 elemental reactions) for combustion and finite volume/correlated-k (FV/CK) method for radiation heat transfer. To account for turbulence’s influence on radiation, the effects of turbulence–radiation interactions (TRI) are investigated in radiation calculations and it is recommended that for detailed numerical simulation TRI should be considered. Numerical results with and without radiation influence being taken into accounted are compared with experimental data. Different from reports by other researchers, our simulation results show that although the magnitude of thermal radiation is relatively small, its influence on combustion process is significant. It is suggested that turbulence and chemical reactions may magnify the influence of thermal radiation.