PARAMETRIC STUDY OF SUPERSONIC NOZZLE FOR BASE PRESSURE CONTROL USING EXPERIMENTAL AND OPTIMIZATION METHOD
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Abstract
In high-speed fluid dynamics, base pressure controls find many engineering
applications such as automobile industry and defense applications, and sudden
expansion is a common problem for numerous fields. Several studies have been reported
on the control of the flow field with sudden expansion. The passive control method
controls the high-speed supersonic flows with geometrical change in a sudden
expansion duct-like with cavities, ribs, cylinders, aerospikes, step bodies, etc. Based on
the passive control method, it is found that the passive control does not need energy and
resulting cost-effectively. Hence, the researchers introduce the active control method
using a microjet controller. Therefore, the present study focuses on dynamic control
with the microjets in an orifice of a 1 mm diameter to inject the air in the base
recirculation region. The microjets with a sonic Mach number of 1 mm diameter were
in the base area as a control mechanism at 900
intervals. Since the air is drawn from the
main settling chamber, the NPR will be the same as the respective NPR’s used for tests.
Experiments were conducted in the presence and absence of the microjets for area ratio
3.24 and L/D ratio from 10 to 1. Mach numbers of the study were 1.87, 2.2, and 2.58.
The parameters were optimized using the design of experiments (DOE) approach. Three
parameters have been selected for the flow and the DOE. In this study, an L27 orthogonal
array of Taguchi design is used. The variance analysis is used to examine the
contribution in terms of percentage. A multiple linear regression equation is used to find
the correlations between the numerous factors that affect the base pressure. It is found
that the developed models are statistically suitable and capable of producing accurate
predictions for both the cases in the presence and absence of control. According to the
present findings, it is evident that the L/D ratio is the most critical parameter that affects
the maximum increase or decrease of the base pressure for a given parameter.