型线结构对涡旋膨胀机性能影响的研究

发布时间：2018-07-20 16:24

【摘要】：利用有机朗肯循环回收发动机废气余热,是实现节能减排和环境保护的有效技术途径之一。本文对有机朗肯循环发动机废气余热回收系统的关键部件涡旋膨胀机进行了相关模拟和研究,研究内容如下。首先,对涡旋型线啮合理论进行了介绍,明确了涡旋型线啮合的基本条件。构造出线段渐开线、正四边形渐开线和圆渐开线三种等壁厚渐开线类涡旋型线并对其结构参数进行了计算,分析了三种型线对涡旋膨胀机结构参数和工作性能的影响,得出如下结论:在小型轻量化的前提下,圆渐开线优于另外两种型线。其次,针对本课题组有机朗肯循环系统中的涡旋膨胀机,在保证其占用空间不变的前提下,建立了高次曲线组合型线、圆弧组合型线及变径基圆渐开线涡旋型线三种变壁厚涡旋膨胀机的几何模型,为之后的膨胀机流场仿真及性能的分析奠定了基础。再次,以R123为工质,采用RNG k??湍流模型、PISO流场求解算法及动网格技术对涡旋膨胀机内部流场进行了三维非定常数值模拟,得到了各曲轴转角下涡旋膨胀机内部压力、速度及温度的分布情况及变化规律,并对膨胀机排气过程进行了分析。由于涡旋膨胀机的工作过程是非稳态过程,其质量流量、输出扭矩、功率等参数随运行时间不断变化。文章最后针对建立的三种变壁厚涡旋齿膨胀机模型,利用Fluent进行膨胀机工作过程的非稳态数值模拟,得出型线类型及运行工况对涡旋膨胀机性能的影响规律:(1)针对本课题组所用圆渐开线涡旋膨胀机,当占用空间及运行工况相同时,变径基圆渐开线与圆渐开线涡旋膨胀机相比,扭矩增大0.03Nm,功率提高5.33W,效率提升3.3%。组合型线与圆渐开线涡旋膨胀机相比,扭矩、功率及效率均有所下降。(2)对于高次曲线组合型线涡旋膨胀机,当进出口边界条件相同时,输出扭矩随转速的增大而降低,输出功率及效率随转速的增大先升高随后降低;当膨胀机进口过热度、转速及出口压力一定时,输出扭矩、功率及效率随进口压力的增加而增加。
[Abstract]:The recovery of engine exhaust heat by organic Rankine cycle is one of the effective technical ways to realize energy saving and environmental protection. In this paper, the vortex expander, a key component of the exhaust gas waste heat recovery system of organic Rankine cycle engine, is simulated and studied. The research contents are as follows. Firstly, the theory of vortex line meshing is introduced, and the basic conditions of vortex line meshing are defined. The involute, quadrilateral involute and circular involute are constructed, and the structure parameters of involute are calculated. The influence of the three kinds of involute on the structure parameters and working performance of the scroll expander is analyzed. The conclusion is as follows: the circular involute is superior to the other two shapes on the premise of small weight. Secondly, in view of the vortex expander in the organic Rankine circulatory system of our group, on the premise of keeping its occupied space unchanged, the combination curve of high order curve is established. The geometric models of three kinds of variable wall thickness vortex expander with combined arc profile and variable diameter base circle involute vortex line have laid a foundation for the simulation of flow field and the analysis of the performance of the expander. Thirdly, using R123 as working medium, using RNG KG? The turbulent model PISO flow field solution algorithm and dynamic grid technique are used to simulate the internal flow field of the vortex expander. The distribution and variation of the internal pressure, velocity and temperature of the vortex expander under the crankshaft rotation angle are obtained. The exhaust process of the expander is analyzed. Since the working process of the vortex expander is unsteady, the mass flow, output torque and power of the vortex expander vary with the running time. In the end of this paper, the unsteady numerical simulation of the expander's working process is carried out by using fluent, aiming at the three kinds of models of variable wall thickness vortex tooth expander. The effects of profile type and operating conditions on the performance of scroll expander are obtained. (1) for the circular involute scroll expander used in our group, when the space is occupied and the operating conditions are the same, the involute of variable diameter base circle is compared with the circular involute vortex expander. Torque increased by 0.03Nm, power increased by 5.33W, efficiency increased by 3.3Nm. Compared with the circular involute vortex expander, the torque, power and efficiency of the combined involute vortex expander are decreased. (2) for the high order curve combined type vortex expander, when the inlet and outlet boundary conditions are the same, the output torque decreases with the increase of the rotational speed. The output power and efficiency first increase and then decrease with the increase of rotational speed, and when the inlet superheat, speed and outlet pressure of the expander are fixed, the output torque, power and efficiency increase with the increase of inlet pressure.
【学位授予单位】：北京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X734.2;U464

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