**3.2 Variation of the back pressures**

In the present analysis, the effect of back pressure (i.e., 80, 90 and 100 kPa) on the performance of the domain with uniform cross-sectional area (i.e., divergent angle of 1.5°) are studied. The back pressure of 80 and 100 kPa are identified based on the experimental results by Sun et al. **Figures 8**–**11** represent the contour lines of static pressure, density, Mach number and temperature along the Mid-plane with

**Figure 7.**

*Static pressure distribution at constant back pressure with variable divergence angles.*

different back pressure at a uniform cross-sectional area. From the results, it is noted that with an increase in the adverse pressure due to the rapid mixing of the fluid particles, the shock wave train developed lead to intense combustion, the Mach train developed should expand along the length and also moves towards the leading edge of the isolator leading to rapid rise in the pressure along the axis of the isolator so that the pressure at the inlet of the isolator can match the enhanced negative pressure. Additionally, as the shock wave train approaches the supersonic inlet, the unstart conditions are observed at the entrance of the isolator. A strong separation region occurs because of the interaction between shock wave and boundary layer. Due to the increase in the pressure gradient four Mach disks are observed in the domain. With different back pressure of 80, 90 and 100 kPa, symmetric planes of the scramjet isolator the contours of the static temperature,

*Static temperature distribution with uniform cross-sectional area with different back pressure.*

*Mach number distribution with uniform cross-sectional area with different back pressure.*

*Numerical Investigation of the Shock Train in a Scramjet with the Effects of Back-Pressure…*

*DOI: http://dx.doi.org/10.5772/intechopen.92555*

*Static pressure distribution with uniform cross-sectional area with different back pressure.*

**Figure 9.**

**Figure 10.**

**Figure 11.**

**11**

#### **Figure 8.**

*Density distribution with uniform cross-sectional area with different back pressure.*

*Numerical Investigation of the Shock Train in a Scramjet with the Effects of Back-Pressure… DOI: http://dx.doi.org/10.5772/intechopen.92555*

#### **Figure 9.**

impact of the divergent angle on the scramjet combustor has greater significance on

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

In the present analysis, the effect of back pressure (i.e., 80, 90 and 100 kPa) on the performance of the domain with uniform cross-sectional area (i.e., divergent angle of 1.5°) are studied. The back pressure of 80 and 100 kPa are identified based on the experimental results by Sun et al. **Figures 8**–**11** represent the contour lines of static pressure, density, Mach number and temperature along the Mid-plane with

the flow field.

**Figure 7.**

**Figure 8.**

**10**

*Static pressure distribution at constant back pressure with variable divergence angles.*

*Density distribution with uniform cross-sectional area with different back pressure.*

**3.2 Variation of the back pressures**

*Mach number distribution with uniform cross-sectional area with different back pressure.*

#### **Figure 10.**

*Static pressure distribution with uniform cross-sectional area with different back pressure.*

#### **Figure 11.**

*Static temperature distribution with uniform cross-sectional area with different back pressure.*

different back pressure at a uniform cross-sectional area. From the results, it is noted that with an increase in the adverse pressure due to the rapid mixing of the fluid particles, the shock wave train developed lead to intense combustion, the Mach train developed should expand along the length and also moves towards the leading edge of the isolator leading to rapid rise in the pressure along the axis of the isolator so that the pressure at the inlet of the isolator can match the enhanced negative pressure. Additionally, as the shock wave train approaches the supersonic inlet, the unstart conditions are observed at the entrance of the isolator. A strong separation region occurs because of the interaction between shock wave and boundary layer. Due to the increase in the pressure gradient four Mach disks are observed in the domain. With different back pressure of 80, 90 and 100 kPa, symmetric planes of the scramjet isolator the contours of the static temperature,

**Figure 12.**

*Mach number and pressure variation along the mid-plane with different back pressure at a uniform crosssectional area.*

pressure, Mach number and density are shown in the figure. From the results it is observed that at a back pressure of 80 kPa in the scramjet isolator, enhancement in pressure is affected due to the presence of the normal or oblique shock waves. Whereas in the case of 90 kPa back pressure, pressure rise is noted far away from the shock wave train due to the intermixing of the disorganized streamlines developed by the shock wave train. Additionally, when compared to downstream mixing region additional enhancement in the static pressure is observed due to the development of upstream shock wave train. For an adverse pressure of 100 kPa, the pressure drops in a given length due to fanno flow is much higher when compared to the increase in pressure due to intermixing and also the peak pressure is observed followed by the sequential reduction in pressure.

From **Figure 12**, it is observed that the static pressure along the axis of the isolator is observed to increase substantially. Also, with different back pressure investigated it is observed that the static pressure distribution does not get influenced significantly because of the Mach wave train in the shock wave region of the isolators.

**Author details**

Santhosh Kumar Gugulothu<sup>1</sup>

Andhra Pradesh, India

Hyderabad, India

Hyderabad, India

**13**

\*, B. Bhaskar<sup>2</sup> and V.V. Phani Babu<sup>3</sup>

1 Department of Mechanical Engineering, National Institute of Technology,

*Numerical Investigation of the Shock Train in a Scramjet with the Effects of Back-Pressure…*

*DOI: http://dx.doi.org/10.5772/intechopen.92555*

2 Department of Mechanical Engineering, GITAM School of Technology,

3 Department of Mechanical Engineering, MLR Institute of Technology,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: santoshgk1988@gmail.com

provided the original work is properly cited.

#### **4. Discussions**

The present analysis is focused on the significance of diverging angles and the effect of adverse pressure gradient on the behavior of the shock wave train is analyzed using the simulation. An identical flow inlet is considered at the inception point of the scramjet isolator for different diverging angles, i.e., 0, 0.5, 1 and 1.5° followed by different back pressure, i.e., 80, 90 and 100 kPa have been investigated. The following has been observed. It is observed that the shock wave train has moved near to the leading edge of the isolator with an increase in the divergent angle. At a divergent angle of 1.5°, as the flow gets separated the strong expansion wave is generated leading to the negative pressure drop at the inception of the shock wave train. When compared to the divergent angles of 1 and 1.5° in the scramjet isolator, the divergent angle of 0° with constant isolator area supports better back pressure. With an increase in adverse pressure gradient, because of the intense turbulent combustion, the shock wave train developed should expand along the length and also moves towards the leading edge of the isolator leading to rapid rise in the pressure so that the pressure at the inlet of the domain can match the enhanced negative pressure. A strong separation region occurs because of the interaction between shock wave and boundary layer.

*Numerical Investigation of the Shock Train in a Scramjet with the Effects of Back-Pressure… DOI: http://dx.doi.org/10.5772/intechopen.92555*
