Flow separation in rocket nozzles under high altitude condition

Abstract

The knowledge of flow separation in rocket nozzles is crucial for rocket engine design and optimum performance. Typically, flow separation is studied under sealevel conditions. However, this disregards the change of the ambient density during ascent of a launcher. The ambient flow properties are an important factor concerning the design of altitude-adaptive rocket nozzles like the dual bell nozzle. For this reason an experimental study was carried out to study the influence of the ambient density on flow separation within conventional nozzles.

Wall Pressure and External Velocity Field Relation in Overexpanded Supersonic Jets

“…The criteria used in figure 4 were also derived for higher Mach number and/or turbulent incoming boundary layer. Since the Mach numbers of the present study remain relatively moderate, the use a laminar separation criterion might also lead to more precise prediction [39]. Nevertheless, it is worth precising that these criterion are also obtained using data coming from different flow fields, and various experiments with different boundary conditions.…”

Parametrical Investigation of Transverse Injection in a Dual-Bell Nozzle During Altitude-Varying Conditions

“…Extreme caution should be taken during DBN wind tunnel testing, as many studies demonstrated that DBNs behaved differently depending on whether the tests were performed in altitude chambers or at ambient conditions. Varying the feeding total pressure during experiments also greatly influences the behaviour of DBNs as it changes the Reynolds number and modifies the effective wall shape of the sensitive inflection region [11,15,[19][20][21]. Though many of the previous studies provided significant information on DBN behaviour during the ascent and descent phases, only a few of them have focused on the control of transition and retransition, as well as side-loads generation in DBNs.…”

Numerical Investigations At High Altitudes For Nozzles Performance Monitoring

“…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].…”

“…In this paper, a second-throat supersonic exhaust diffuser (STED) is numerically investigated using CFD [6]. Accurately predicting the starting pressure helps in constructing the test facility equipment appropriately and economically [2,3]. In the present study, the flow field in the STED is computed for cold flow of nitrogen gas (Ȗ=1.4) for simulating the highaltitude test configuration of a small-scale conical nozzle.…”