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Design and validation of a single-jack variable Mach number nozzle in a cryogenic transonic wind tunnel

Yu Chengguo, Zhang Zhili, Wang Ning, Nie Xutao, Peng Qiang, Chen Zhenhua

Journal of Theoretical and Applied Mechanics

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2022

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Vol. 60 nr 4

719--732

EN

The wind tunnel with variable Mach numbers controlled by a single jack is highly desired in the aerospace, automobile and building industry due to its superior controllability and working range. Decreasing the temperature of a test gas is an efficient and economical approach to achieving higher Reynolds numbers that accommodate all working statuses of test subjects, which however, brings new challenges to the wind tunnel design nowadays. This paper proposes a new design concept of a single-jack variable Mach number nozzle based on its particular cryogenic characteristics, as the nozzle is the core structure to achieve variable Mach numbers. The contours of the nozzle under different Reynolds numbers and Mach numbers are modeled and solved by an incomplete elliptic integral, followed by modification with cryogenic characteristics. A 0.3-m cryogenic wind tunnel is utilized as a validation platform for the nozzle design, resulting in designed contours being in line with the measured contours. Moreover, the root means square (RMS) deviations of Mach number 1.3 at the core position are controlled within 0.011 in low and high temperatures, which surpasses the other existing wind tunnels.

2

CFD analysis of the effect of the exhaust manifold design on the close-coupled catalytic converter performance

Martinez-Martinez S., Leal-Garza R. D., Sanchez-Cruz F. A., Villarreal E. B., Amado-Covarrubias M.

Journal of KONES

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2010

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Vol. 17, No. 4

303-311

EN

It is a common practice to mount a catalytic converter directly at the outlet of the exhaust manifold in order to reduce the cold start emissions from the automotive engines by improving the light-off time. The so called Close-Coupled Converter, because of its nearness to the engine, is more exposed to non-uniform fluid flows comingfrom the individual manifold runners, what frequently yields a stream of gases flowing mainly through a section of the monolith causing the aging of the catalyst and low conversion efficiency, among other negative effects. Computational Fluid Dynamics (CFD) has became a very useful and widely used tool to analyze and optimize this kind of exhaust after-treatment systems in a relatively fast and accurate way for design purposes. There are several designs of exhaust manifolds whose shape and dimensions are mainly restricted not only by the engine characteristics but by the space constraints of the particular vehicles they are designedfor. In this work the commercial CFD code ANSYS FLUENT was used to evaluate and compare the effect of three shapes of exhaust manifolds on the fluid flow uniformity at the entrance of the Close-Coupled Converter. Pressure drop in the entire Manifold-Converter device is also an important parameter considered for the design evaluation. The manifolds investigated are of type cast, 4-2-1 and L-shaped, which are commonly used in the automotive industry.

3

Nierównomierność rozpływu mieszaniny dwufazowej gaz - ciecz w układzie minikanałów współpracujących równolegle

Miłaszewicz B., Ulbrich R.

Inżynieria i Aparatura Chemiczna

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2010

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Nr 3

69-70

PL

Nierównomierna dystrybucja faz do poszczególnych kanałów jest powszechnym zjawiskiem i powoduje istotne obniżenie sprawności aparatów wykorzystujących przepływ w kanałach równoległych. Jest to zjawisko skomplikowane, słabo poznane w zakresie badań w minikanałach. W artykule przedstawiono badania przepływu opadającego mieszaniny dwufazowej do układu ośmiu minikanałów. Zastosowano dwa typy głowicy różniące się geometrią. Wykazano istotne znaczenie zarówno geometrii głowicy jak i strumieni doprowadzanych faz.

EN

Phase maldistribution to particular channels is common phenomena and causes significant efficiency reduction of devices using parallel flow. It is very complicated and poorly examined phenomena in minichannels. Research results of two-phase downward flow of mixture to the system of eight parallel minichannels are presented in the paper. Two kinds of header of various geometry was employed. It was proved that both geometry and volumetric flow rate of gas and liquid had a substantial significance on flow uniformity.

4

Badania eksperymentalne wpływu zmian sposobu zasilania powietrznego gruntowego wymiennika ciepła typu rurowego na jego charakterystykę przepływową. Część 1. Równomierność rozpływów

Amanowicz Ł., Wojtkowiak J.

Ciepłownictwo, Ogrzewnictwo, Wentylacja

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2010

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T. 41, nr 6

208-212

PL

Przeprowadzono badania modelowe powietrznych gruntowych wymienników ciepła w układzie Tichelmanna w skali 1:4 oraz układów o zmodyfikowanym sposobie podłączenia czerpni i wyrzutni. Zbadano układy składające się z 3, 5 i 7 równoległych gałęzi odchodzących od kolektora pod kątem 450 i 900. Zaobserwowano znaczący wpływ sposobu podłączenia czerpni i wyrzutni na równomierność rozpływu powietrza w poszczególnych gałęziach. Zaproponowano prostą zmianę sposobu podłączenia powodującą istotną poprawę równomierności rozpływu.

EN

Several experiments using models of ground earth-to-air pipe-type heat exchangers in Tichelmann 1/4 scale structure and structures with modified air handling system were carried out. Structures with 3, 5 and 7 parallel pipes connected to main pipe with angles of 450 and 900 were investigated. Significant influence of air inflow and outflow locations on uniformity of the airflow in particular pipes was observed. Simple method improving flow rate uniformity in parallel pipes is suggested.