Design and Analysis of a Second-Throat Exhaust Diffuser for Altitude Simulation

Park, Byung Hoon; Lim, Jihwan; Park, Sunghyun; Lee, Ji Hyung; Yoon, Woong-Sup

doi:10.2514/1.b34342

Cited by 24 publications

(3 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…n order to experimentally evaluate the highaltitude performance of the said nozzles, a high altitude test (HAT) facility system consisting of a supersonic exhaust diffuser is generally employed [1,2,3,4]. The main purpose is to reduce the nozzle back pressure sufficiently to have full flow at the design pressure [5].…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigations At High Altitudes For Nozzles Performance Monitoring

Qureshi¹,

Ozair²,

Ahmad³

et al. 2023

JISR-C

View full text Add to dashboard Cite

Large area ratio nozzles that are employed for space propulsion applications are not meant to be tested at the ground-level conditions because of the flow conditions that occurs in their divergent section due to their low exhaust pressures. Therefore, it is desired to perform the experimental evaluation at high-altitude to evaluate the performance of the said nozzles. Generally, a high-altitude test facility, consisting of a supersonic exhaust diffuser, is generally employed. In thispaper, a second-throat exhaust diffuser has been numerically investigated to predict its minimum starting pressure, and to understand the flow physics in the diffuser using Computational Fluid Dynamics (CFD). Numerical computation of the flow field in the diffuser system is done for the two cases: 1) when the nozzle and the diffuser system are initially evacuated to a low pressure, and 2) when the nozzle and the diffuser system are initially at ambient pressure (1 bar). Simulations have been carried out for cold flow situation (Ȗ=1.4) over a range of nozzle inlet stagnation pressures. Numerical results compare favorably with the theoretical and experimental results and provide adequate insight to the flow physics and internal shock structures formed in thediffuser in addition to minimum starting pressure, diffuser wall pressure and vacuum thrust.

show abstract

Section: Introductionmentioning

confidence: 99%

Numerical Investigations At High Altitudes For Nozzles Performance Monitoring

Qureshi¹,

Ozair²,

Ahmad³

et al. 2023

JISR-C

View full text Add to dashboard Cite

show abstract

“…Among the types of supersonic diffusers, the second throat exhaust diffuser (STED) is generally known to be more suitable for testing engines with higher operating pressures than the constant area exhaust diffuser (CAED) because the STED can be operated at a wider range of pressures than the CAED can. Park et al investigated the effects of the essential geometric factors of the STED (such as second throat area ratio, nozzle expansion ratio, and nozzle contour) on starting and evacuation performance [4]. Annamalai et al studied the basic design variables and flow characteristics of the CAED, which can be used as basic data for the STED through the use of one-dimensional normal shock theory [5].…”

Section: Introductionmentioning

confidence: 99%

Numerical Study on the Flow and Heat Transfer Characteristics of a Second Throat Exhaust Diffuser According to Variations in Operating Pressure and Geometric Shape

Han

Kim

et al. 2021

Energies

View full text Add to dashboard Cite

A numerical study was conducted to investigate the flow and heat transfer characteristics of a supersonic second throat exhaust diffuser for high-altitude simulations. The numerical results were satisfactorily validated by the experimental results. A subscale diffuser using nitrogen was utilized to investigate starting pressure and pressure variation in the diffuser wall. Based on the validated numerical method, the flow and heat transfer characteristics of the diffuser using burnt gas were evaluated by changing operating pressure and geometric shape. During normal diffuser operation without cooling, high-temperature regions of over 3000 K appeared, particularly near the wall and in the diffuser diverging section. After cooling, the flow and pressure distribution characteristics did not differ significantly from those of the adiabatic condition, but the temperature in the subsonic flow section decreased by more than 1000 K. Furthermore, the tendency of the heat flux from the diffuser internal flow to the wall was similar to that of the pressure variations, and it increased with operating pressure. It was confirmed that the heat fluxes of the supersonic and subsonic flows in the diffuser were proportional to the operating pressure to the 0.8 and −1.7 power, respectively. In addition, in the second throat region after separation, the heat flux could be scaled to the Mach number ratio before and after the largest oblique shock wave because the largest shock train affected the heat flux of the diffuser wall.

show abstract

“…As reported in the open literature, various methodologies are adopted to simulate altitude conditions in the ground testing facilities [1][2][3]. In small thruster facilities where output varies from a sub-Newton to a few Newton level, a vacuum pump is usually employed to evacuate the vacuum cell during its operations.…”

Section: Introductionmentioning

confidence: 99%

Analytical and experimental investigation of satellite thruster vacuum performance employing supersonic ejectors

Sultan

Khan

Omer

2018

J Braz. Soc. Mech. Sci. Eng.

View full text Add to dashboard Cite

The present study is carried out to investigate the performance of a cold gas thruster operating under the vacuum with a high expansion ratio. A pressure recovery system employing diffuser and multistage ejectors is employed to evacuate a vacuum cell whose pressure is an indicating parameter of an operating altitude (i.e. nozzle exit condition). The cold gas thruster has an expansion area ratio of 60. For ejector design, the parameters like the length to diameter ratio (L/D e) and ejector nozzle stagnation pressure (P tot) seem to have significant importance, and their effects on vacuum cell pressure are studied by using both analytical and experimental techniques. Role of second throat type diffuser in the overall pressure recovery is also investigated. The required exit pressure is achieved by a two-stage ejector system having constant area mixing chambers. The ejectors' stagnation pressures are considered from 12 to 20 bars, while (L/D e) is considered from 4.5 to 15 and 2.5 to 16.5 for Ejector-1 and Ejector-2, respectively. Minimum vacuum cell pressure is achieved with the (L/D e) of 7 and 9 and stagnation pressure (P tot) of 18 and 20 bars for Ejector-1 and Ejector-2, respectively. The thrust coefficient (CF) and the specific impulse (Isp) were found in good agreement with the theoretical results.

show abstract

Design and Analysis of a Second-Throat Exhaust Diffuser for Altitude Simulation

Cited by 24 publications

References 16 publications

Numerical Investigations At High Altitudes For Nozzles Performance Monitoring

Numerical Investigations At High Altitudes For Nozzles Performance Monitoring

Numerical Study on the Flow and Heat Transfer Characteristics of a Second Throat Exhaust Diffuser According to Variations in Operating Pressure and Geometric Shape

Analytical and experimental investigation of satellite thruster vacuum performance employing supersonic ejectors

Contact Info

Product

Resources

About