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1.
《Flow Measurement and Instrumentation》2006,17(2):81-86
Recently, critical nozzles have been extensively utilized to measure the mass flow rate in a variety of industrial applications. For the measurement of the mass flow rates in a wide range of operation conditions, the critical nozzle is required to be designed with different diameters. The objective of the present study is to investigate the effectiveness of a variable critical nozzle. A rod with a small diameter is inserted into the critical nozzle to change the effective cross-sectional area of the critical nozzle. Experimental work is performed to measure the mass flow rate of the critical nozzle with rod. Computational work is carried out using the two-dimensional, axisymmetric, compressible Navier–Stokes equations which are discretized using a fully implicit finite volume method. The diameter of the rod is varied to obtain different mass flow rates through the variable critical nozzle. Computational results predict well the measured mass flow rates. The boundary layer displacement and momentum thickness at the throat of the critical nozzle are given as a function of Reynolds number. The discharge coefficient of the critical nozzle is given as an empirical equation. 相似文献
2.
A chemically nonequilibrium supersonic flow of hydrogen and air has been investigated in a duct with conically divergent or
convergent walls. Elementary reaction schemes of radicals involved in reaction of hydrogen-air have been considered and solved
through the CHEMKIN code. The aim was to promote an understanding of characteristics of chemically nonequilibrium supersonic
flow by introducing a simple mathematical formulation. The temperature, pressure, and density all were found to decrease for
divergent ducts as the flow was accelerated, whereas they increased for a slightly convergent duct or a constant cross-sectional
area duct. For the divergent nozzle with a greater degree the flow became chemically frozen. But it was quite necessary to
take account of the effect of chemical nonequilibrium in a moderately expanded or all convergent conical ducts. As was expected,
it was found that the temperature, pressure and Mach number were reduced for a fuel-lean mixture. 相似文献
3.
下斜板可调的单膨胀斜面喷管型面设计和流场模拟 总被引:2,自引:0,他引:2
基于特征线法,并考虑变比热的影响,开展了高超声速飞行器用SERN设计.利用CFD数值模拟技术,计算得到了设计状态和沿飞行轨迹其它飞行状态下的SERN内外流场和特性.可以看到,在设计状态马赫数5时,基于特征线法得到的SERN内流场分布符合设计要求,而在其它较低的飞行马赫数下,SERN处于过膨胀状态,并且过膨胀的程度随飞行马赫数的降低而愈加严重.在马赫数25时,喷管膨胀面气流已发生明显分离,喷管性能急剧恶化.为了提高低马赫数条件下SERN的气动性能,分析了通过调节SERN下斜板角度从而实现其气动性能提高的方法.结果表明调节下斜板角度可以明显改善SERN非设计点的气动性能. 相似文献
4.
某型发动机非加力情况下收-扩尾喷管流动特性研究 总被引:1,自引:0,他引:1
《现代机械》2016,(3)
针对某型涡扇发动机的收-扩尾喷管模型在加力不接通试验工况下的流动特性,通过建立模型,进行相关的数值计算研究,获得了不同喉道面积、面积比和尾喷管落压比条件下的收-扩尾喷管模型的流量系数和推力系数数据及其变化规律,为发动机地面台架标定试验和飞行试验中发动机进口空气流量和标准净推力的确定提供了基础数据。 相似文献
5.
Influence of nozzle exit tip thickness on the performance and flow field of jet pump 总被引:2,自引:0,他引:2
The influence of exit tip thickness of nozzle δ
e
on the flow field and performance of a jet pump was studied numerically in this paper. It is found that δ
e
has influence on the distribution of turbulence kinetic energy k. If δ
e
is ignored, k takes the highest value but dissipates rapidly than that of nozzle with a certain tip thickness. δ
e
also affect apparently the development of tip vortex, which will occur near the exit tip of nozzle. The bigger the δ
e
is, the larger the vortex is. The tip vortex develops with the increase of flow rate ratio q. When q=1 and δ
e
=0.6∼0.8mm, a small vortex will be found downstream the tip vortex. And a concomitant vortex happens down the tip vortex in
the case of q=1 and δ
e
=0.8mm. As q increases to 2, the downstream small vortex disappears and the concomitant vortex becomes bigger. It is also found that the
tip vortex might interact with the possible backflow that formed in the throat tube and parts of suction chamber. The center
of backflow was affect evidently by δ
e
. With the increase of δ
e
, the center of backflow under the same q will go downstream. When δ
e
=0.4mm, the center of backflow goes farthest. Then, as the further increase of δ
e
, the center of backflow will go back some distance. Although, δ
e
has relatively great influence on the flow field within the jet pump, it exerts only a little impact on the performance of
jet pump. When δ
e
=0.2∼0.6mm, the jet pump possess better performance. In most case, it is reasonable to ignore the nozzle exit tip thickness
in performance prediction for the purpose of simplicity.
This paper was presented at the 9th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007. 相似文献
6.
The variable area cavitating venturi is an effective means to throttle the mass flow rate of liquid. The mass flow rate is a function of the upstream pressure, the pintle stroke, the density and saturation pressure of the liquid, independent of the downstream pressure. In this paper, a variable area cavitating venturi is designed and four different sets of experiments are conducted to investigate the performance of the variable area cavitating venturi. In these experiments, the mass flow rates are examined under different pintle positions, upstream pressures, downstream pressures and dynamic motions of the pintle. The experimental results indicate that the mass flow rate is independent of the downstream pressure when the ratio of the downstream pressure to upstream pressure is less than 0.8. The mass flow rate is almost linearly dependent on the pintle stroke for a constant upstream pressure. The discharge coefficient is a function of the pintle stroke, whereas the upstream and downstream pressures have rare influence on the discharge coefficient. The variable area cavitating venturi can control and measure the mass flow rate dynamically by determining the pintle stroke and the upstream pressure. 相似文献
7.
喷墨式水泥3D打印喷头泥浆流动规律分析 总被引:1,自引:0,他引:1
基于熔融沉积成型3D打印工艺,介绍了喷头直接挤出水泥浆的喷墨式水泥3D打印工艺,并通过进料口压力、喷口直径、螺杆转速和螺杆几何尺寸对喷头出料率影响的实验,研究了喷头内水泥浆的流动规律,指出了影响喷头出料的关键因素. 相似文献
8.
G. V. Kreinin A. A. Kosarev S. Yu. Misiurin A. A. Ovchinnikov V. V. Saiapin 《Journal of Machinery Manufacture and Reliability》2010,39(6):523-529
A drive consisting of a pneumatic high-speed jet engine, transfer mechanism, and a control device used for switching the gas
main ball valve is examined. A mathematical model is constructed, its dynamical criteria are determined, and a survey of the
gear dynamics is carried out. The usefulness of simple control algorithms of relay action is demonstrated, with a feedback
contour connected to speed, enabling the valve plug to be turned with a smooth and continuous approach to the final position. 相似文献
9.
10.
11.
某型发动机尾喷管特性确定方法 总被引:1,自引:0,他引:1
《现代机械》2017,(4)
获取发动机尾喷管特性是飞行推力确定的重要环节。通过对尾喷管特性物理意义的分析,提出了采用CFD数值仿真与地面全机校准试验相结合的尾喷管特性确定方法,以该方法获取的尾喷管特性为基础,在高空台试验中采用燃气发生器法计算发动机进口空气流量和出口总推力,并与高空台实测值进行对比,在所有功率状态下计算值与实测值的最大相对误差不超过5%,表明该方法确定的尾喷管特性满足飞行推力确定的精度要求,证明了该方法合理有效。 相似文献
12.
分析了内燃机气门头厚度对气门座磨损及其下陷量对燃烧性能的影响,气门和气门座接触面宽度与烧蚀、斑点形成的关系,气门落座拍击压强与耐磨性.对原配对互研工艺进行了改进,从保证气门落座压强及避免气门头弹性变形磨损等方面提出了改进意见. 相似文献
13.
An investigation of the flow inside the nozzle of a Cross-Flow turbine, which is a hydraulic turbine where the rectangular water jet issuing from the nozzle crosses the rotor blades twice, is presented here. Part of the investigation consisted in the experimental measurement of the static pressure distribution on the inside walls of two different nozzle configurations, both with the nozzle mounted alone and in the presence of a rotor. The tests performed in the presence of a rotor included the measurement of efficiency and covered a wide range of working conditions around the best efficiency point. The analysis of the results obtained in this way give us an indication of the influence of the turbine non-dimensional volume flow rate on the flow inside the nozzle and the way it affects the reaction degree of the machine and its efficiency level. Although most of the tests were carried out with a 25-blade rotor, one of the analysed nozzle configurations (that with an inside vane) was also tested with a 10-blade rotor, permitting the assessment of the effect the number of blades has on the flow in the nozzle.The flow inside the nozzle with no inside vane was numerically analysed using a method based on a Schwarz-Christoffel conformal transformation of variables. The numerical results show a fair agreement with the experimental data collected when the rotor was not present. A qualitative discussion of some of the losses occurring in the nozzle is advanced based on the computer results, and its conclusions are used for explaining the poor performance of the nozzle with no inside vane. 相似文献
14.
15.
喷雾锥角和雾化不均匀度是发动机喷嘴的两个重要指标.在多图平均法和对比度拉伸增强、LOG边缘检测、最大嫡法二值化、去除孤点、Deutsch细化后,用霍夫变换获取喷雾边界线,计算喷雾锥角.运用视频帧差提取粗略液位,互相关测度法得到准确液位,通过基于最小二乘法标定拟合的函数计算燃油体积和分布不均匀度. 相似文献
16.
Soon-Bum Kwon Sung-Jin Lee Seung-Young Shin Sung-Ha Kim 《Journal of Mechanical Science and Technology》2009,23(6):1736-1742
As recognized previously, a minimum-length nozzle has the smallest possible throat-to-exit length that is still capable of
maintaining uniform supersonic flow at the nozzle exit. In the present study, for the flow of moist air through a nearly minimum-length
nozzle designed by the method of characteristics, the effects of nonequilibrium condensation on the uniformity of flow properties,
the momentum efflux, and the flow distortion at the nozzle exit plane are discussed by experiment and numerical analysis of
a third-order Total Variation Diminishing (TVD) finite difference scheme. The onset and zone of nonequilibrium condensation
in a minimum-length nozzle are quite different from those of a general convergent-divergent supersonic nozzle. We know that
the uniformity of flow properties at the nozzle exit with regard to the flow with nonequilibrium condensation in a minimum-length
nozzle cannot be guaranteed. On the other hand, owing to the positions of the onset of condensation at the incident region
of expansion waves from the sharp corner just downstream of the nozzle throat, the deceleration gradient and magnitude of
heat released from the process of nonequilibrium condensation to the surrounding of ϕ0=60% are greater than those of ϕ0=70% in the case of T0=290K. Furthermore, it has been determined that the decrease in efflux of momentum from the nozzle exit for the stagnation
relative humidity of ϕ0=70%(T0=290K), which corresponds to the case with nonequilibrium condensation shock, is 6.8% smaller than that of isentropic expansion.
This paper was recommended for publication in revised form by Associate Editor Do Hyung Lee
Soon-Bum Kwon received his B.S. and M.S. degrees in Mechanical Engineering from Kyungpook National University in 1974 and 1980, respectively,
and his Ph.D. degree from Kyushu University in 1987. He is a Professor at the School of Mechanical Engineering at Kyungpook
National University. His research interests are compressible gas dynamics and nonequilibrium condensation. 相似文献
17.
A residence time of approximately 60 s for lubricant in the piston ring pack of a gasoline engine, running at 1500 rpm, 50% throttle, has been measured by adding a hydrocarbon marker to the oil in the sump and monitoring its build up in oil extracted from the top ring groove. Comparison of the rate of increase of oxidised products in the sump with the level of oxidation in the ring pack allows a rate of flow of oil entering the ring pack from the sump to be calculated as approximately 0.4 cm3 min−1 cylinder−1, with at least 88% returning to the sump and the remainder lost into the combustion chamber. The volume of oil in the ring pack was determined as approximately 0.4 cm3 cylinder−1, approximately one quarter of the free volume available between the top of the oil control ring and the top piston ring. 相似文献
18.
Hitoshi Soyama 《Wear》2013,297(1-2):895-902
In order to accurately and reliably evaluate the cavitation erosion resistance of materials using cavitating jet apparatus according to ASTM G134, the effect of various types of nozzle geometries on the erosion rate was investigated. As the erosion rate depends on the erosion time and the distance from the nozzle to the specimen, i.e., the standoff distance, the mass loss as a function of erosion time at the optimum standoff distance was measured. It was shown that the erosion rate depended on the nozzle geometry. In fact, the aggressive intensity of the cavitating jet IJ depends on the nozzle geometry. When a cavitating jet of low IJ was used in the erosion test, it took some time to reach the maximum cumulative erosion rate ERmax, which is recommended in ASTM G134 as a parameter for determining the cavitation erosion resistance of materials. In the present experiment, the difference in ERmax was more than 600%, and the time required to reach ERmax was also scattered over 600%, for the different nozzles used. It was also revealed that ERmax could be obtained from the product of IJ and the reciprocal of the relative cavitation erosion resistance of the material, RER. 相似文献
19.
SangYeop Han 《Journal of Mechanical Science and Technology》2001,15(5):646-655
This paper reports the effects of nozzle exit boundary layer swirl on the instability modes of underexpanded supersonic jets emerging from plane rectangular nozzles. The effects of boundary layer swirl at the nozzle exit on thrust and mixing of supersonic rectangular jets are also considered. The previous study was performed with a 30° boundary layer swirl (S=0.41) in a plane rectangular nozzle exit. At this study, a 45° boundary layer swirl (S=1.0) is applied in a plane rectangular nozzle exit. A three-dimensional unsteady compressible Reynolds-Averaged Navier-Stokes code with Baldwin-Lomax and Chien’sk-ε two-equation turbulence models was used for numerical simulation. A shock adaptive grid system was applied to enhance shock resolution. The nozzle aspect ratio used in this study was 5.0, and the fully-expanded jet Mach number was 1.526. The “flapping” and “pumping” oscillations were observed in the jet’s small dimension at frequencies of about 3,900Hz and 7,800Hz, respectively. In the jefs large dimension, “spanwise” oscillations at the same frequency as the small dimension’s “flapping“ oscillations were captured. As reported before with a 30° nozzle exit boundary layer swirl, the induction of 45° swirl to the nozzle exit boundary layer also strongly enhances jet mixing with the reduction of thrust by 10%. 相似文献
20.
A Critical Flow Venturi Nozzle (CFVN) is usually calibrated using dry air. Yet CFVNs in industrial and calibration service centers are often used to measure flow rates of humid air. Therefore, ISO 9300 provides the calculation method for the humidity effect on discharge coefficients of CFVN. However, since this method is only due to a theoretical analysis, it is important to confirm and check the ISO calculation method for the humidity effect on CFVN with its isentropic analysis by means of an experimental method.In this experiment, three CFVNs with diameters of 0.4, 0.8 and 1.6 mm were calibrated with dry air (with the dew point −40 °C), in a primary air flow standard system with a mercury sealed piston prover, installed at the Korea Research Institute of Standards and Science (KRISS). Another piston prover, a portable dry piston prover, was used as a reference meter and was also calibrated in the primary standard system using dry air. The repeatability of this dry piston prover was confirmed with the deviation being less than 0.05%. The CFVNs were tested with this dry piston prover, using humid air. For air types with high humidity, the humidity effect on flow rates through the CFVNs showed quite significant difference between the experimental results and those from the ISO method with isentropic analysis. But for air types with low humidity, its effect was relatively insignificant. 相似文献