【作者】 张琨；

【导师】 沈胜强；

【作者基本信息】 大连理工大学 ， 热能工程， 2009， 博士

【摘要】 喷射器是一种应用广泛的流体机械,利用工作流体的射流来实现能量转化,并以显著的节能效果、低污染的工作性能、以及结构简单、造价低廉,操作和维修方便等优点,在工业领域中得到普遍的应用。喷射器依靠流体间的相互撞击来传递能量,其内部混合流动过程异常复杂。传统喷射器采用固定喷嘴结构,只有在设计条件下才能达到最佳工况,一旦工作参数偏离设计值,导致喷射器效率明显下降。喷射器工作范围狭窄制约了其在工业中的进一步应用,因此,开展对喷射器机理的研究对于工业节能环保有重要意义。本文提出了一种新型可调式喷射器,通过在喷嘴内部加入调节锥,依靠调节锥轴向进出喷嘴,达到改变喷嘴喉口面积的目的。同时采用实验和数值模拟相结合的研究方法,探寻了可调式喷射器的调节锥位置与工作参数及性能之间的关系。研究发现,该可调式喷射器可以改善固定结构喷射器偏离设计工况时效率下降明显的不足,扩大了喷射器的应用范围。本文主要研究工作如下:(1)提出了一种可调式喷射器结构设计方案,编写了喷射器性能与结构计算程序,计算分析了可调式喷射器各个工作参数对性能的影响,考察了压力、流量以及喷射系数之间的内在关系。研究发现,随着喷嘴喉口面积减少,喷射系数增加,工作流体流量下降。(2)建立了可调式喷射器二维轴对称数学模型,借助FLUNET软件对其内部流场进行了数值模拟。分析比较了可调式喷射器与传统的固定结构喷射器在相同工况下压力、温度和速度的分布及变化。结果发现,随着调节锥轴向移入喷嘴,喷嘴出口流体的轴线速度增加,流体混合扰动减少,工作效率提高。(3)自行设计研制了一套可调式喷射器实验系统,对可调式喷射器进行了一系列性能测试实验,测量了在调节锥在不同位置时工作流体、引射流体和出口流体的压力、温度、流量等参数及其变化。实验发现,可调式喷射器在非额定工况下喷射系数虽有下降,但仍具有较稳定的工作状态,拓宽了喷射器的工作范围,提高了经济性。更多还原

【Abstract】 Ejector is applied broadly in different kinds of fluid machinery, which uses working fluid to achieve heat and mass transfer. Ejector is energy-saving, less pollution, as well as simple construction and low cost and maintenance, so it is very popular in industrial fields.The complex of the flow inside ejector makes it difficult to have a better understanding. Conventional ejector must be designed to match the system operating conditions accurately, otherwise either the efficiency will be impaired or it will not work at all. The limited operating range of ejector restricts application on industries. Therefore, the research on ejectors is important to industry energy-saving and environment-protecting.In this paper, a novel adjustable ejector was brought out. A spindle moving into or out of nozzle axially changed nozzle throat area, which made the adjustable ejector different from conventional one. Experimental and numerical simulations were utilized to analysis connections between the positions of adjustable nozzle spindle and ejector performance parameters. The results indicated that the adjustable ejector, compared to conventional ejectors, could improve the efficiency caused by working parameters’ deviation from design point and widen the operating range.The main work and results of this paper are given as follows:(1) The blue print of the adjustable ejector was designed. Programs were compiled to analyze the effects of operating parameters, such as pressures, flow rates and entrainment ratio, on adjustable ejector performance. The results showed that the entrainment ratio rised and motive flow rate droped when nozzle throat area decreased.(2) 2-D axial symmetry model was set up to simulate adjustable ejector flow by Flunet. The static pressure, static temperature and velocity of adjustable ejector were displayed to compare that of conventional fixed-geometry ejector at the same working condition. The conclusion was that the nozzle exit velocity and ejector efficiency increased and mixed flow turbulence weakened with spindle moving into nozzle.(3) An adjustable ejector experiment apparatus was established with valves, pipes, fanges and metrical instruments. The working condition of adjustable ejector was recorded to measure pressures, temperatures and flow rates of motive fluid, suction fluid and discharge fluid. It revealed that the adjustable ejector owned relatively stable working condition on off-design point, although the entrainment ratio was not high. This makes adjustable ejector superior to conventional one and meets variational and economic demands of operating condition.更多还原