论文标题
蒸汽膨胀器中进气歧管端口几何形状的影响的数值研究
Numerical Study on the effect of port geometry of intake manifold in a Steam Wankel Expander
论文作者
论文摘要
体积的Wankel Steam扩展器比其他正排量机具有许多优势，这是由于其高功率与重量比，紧凑度，较低的噪音，振动和潜在的特定成本较低，使其成为往复扩张器的优惠选择。通过旋转阀入院期间的蒸汽压降在入院持续时间内不可避免地在扩张器的进气歧管中。这些在摄入过程中的压力损失会改变整个实际扩展器的设计压力比，从而导致功率输出降低20％至30％。因此，将其减少以提高净功率输出至关重要。本研究的目标是双重的。在第一部分中，估计了现有的矩形端口几何形状估计扩展器的进气歧管的压力损失。在第二部分中，同一液压直径的梯形端口剖面是为进气歧管设计的，目的是减少进气损耗，从而提供更高的功率输出。使用Python 3.8对扩展器的理论压力体积循环进行热力学分析，并在ANSYS Fluent 19.2中的进气歧管上馈入已开发的CFD模型中的热力学分析。边界条件是从上述热力学模型中获得的，状态点值是从重建数据库获得的。据观察，梯形端口将压力损失显着降低了约50％，因此在从1200至3000 rpm的旋转速度范围内，净功率输出量增加了约7至21％。进行了进一步的研究，以研究不同流体流量和湍流参数对膨胀剂压力损失，功率输出和等性效率的影响。
A volumetric Wankel steam expander has numerous advantages over other positive displacement machines as an expansion device due to its high power to weight ratio, compactness, lower noise, vibration, and potentially lower specific cost making them a favourable choice over reciprocating expanders. Pressure drop of steam during admission through rotary valves, is inevitable across the intake manifold of the expander during admission duration. These pressure losses during intake, changes the design pressure ratio across the actual expander, which leads to a reduced power output by a reasonable margin of 20 to 30%. Therefore, it is crucial to reduce it to improve the net power output. The goal of the present research is twofold. In the first part, the pressure losses across the intake manifold of the expander is estimated for an existing rectangular port geometry. In the second part, a trapezoidal port profile of same hydraulic diameter is designed for the intake manifold with an aim to reduce the intake losses, thereby delivering a higher power output. The thermodynamic analysis is carried out for the theoretical pressure-volume cycle of the expander using Python 3.8 and the obtained data are fed into the developed CFD model on the intake manifold in ANSYS Fluent 19.2. The boundary conditions are obtained from the aforementioned thermodynamic model, and the state point values are obtained from the REFPROP database. It is observed that the trapezoidal port significantly reduces the pressure losses by a margin of around 50%, thereby delivering around 7 to 21% higher net power output and a increment of isentropic efficiency by a margin of 14% over a range of rotational speed varying from 1200 to 3000 RPM. Further investigations are conducted to study the effect of different fluid flow and turbulent parameters on the pressure loss, power output and isentropic efficiency of the expander.
