Numerical Investigation on Performance of Axisymmetric Variable Geometry Scramjet Combustor Equipped with Strut Flame Holder

ABSTRACT

This manuscript designed an axisymmetric variable geometry scramjet combustor equipped with a strut flame holder to help the combustor work in a wide flight Mach numbers and conducted a series of numerical calculations and experiments to study the performance of the axisymmetric combustor. The characteristics of the combustor under the different flight Mach numbers (2, 4, 6) are discussed by the numerical calculations, and the results testify that the designed combustor can operate in a large range of the flight Mach number. Then the performances of the combustor in high Ma (4 and 6) are studied. The maximum pressure ratio of the combustor under Ma = 6 is about 6.5. With the divergence ratio increasing, the thermal chock of the combustor decreases under the flight Ma = 4. When the flight Ma is 2, and the divergence ratio is 3.2, the combustor can work well with the fuel injected by the center cone and the wall₁. However part of the oxygen near the bottom wall can not be ignited, and the flame distribution is uneven. To solve this problem, the multi-wall fuel injected method is taken. With the wall₂ fuel added, the mixing efficiency of the fuel increases, and the flame near the bottom wall is established. The results in this study are valuable for the future axisymmetric variable geometry scramjet combustor design and the optimization of combustion distribution uniformity.

KEYWORDS:

• Supersonic combustion
• variable geometry
• axisymmetric combustor
• strut flame holder

Highlights

1. An axisymmetric combustor with variable area was designed in this manuscript.

2. The combustion performances in different numerical conditions were discussed.

3. The relationship between equivalence ratios and combustor performance was studied.

4. Strut/wall combined injection scheme was researched to improve combustion uniformity.

Acknowledgments

This research work is supported by the China Postdoctoral Science Foundation (Grants No. 2020M681102).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Nomenclature

A=Cross-sectional area (m²)

x_m=Moving distance of the bottom wall of the section III

θ=The deflection angle of the combustor

d=Circle diameter

h=The length of the rectangle in the runway-circle

ER=Equivalence ratio

ER_center=Equivalence ratio of the fuel injected by the center cone

ER_strut=Equivalence ratio of the fuel injected by the struts

ER_wall1=Equivalence ratio of the fuel injected by the wall₁

ER_wall2=Equivalence ratio of the fuel injected by the wall₂

ER_s-w=Equivalence ratio of the fuel injected by the single-wall fuel injection method

ER_m-w=Equivalence ratio of the fuel injected by the multi-wall fuel injection method

Ma=Mach number

k=Divergence ratio

p_w=Wall static pressure (MPa)

p₀=Pressure of combustor entrance (MPa)

P=Static Pressure

P_t=Total pressure (MPa)

T_t=Total temperature (K)

η=Combustion efficiency

Additional information

Funding

This work was supported by the China Postdoctoral Science Foundation [2020M681102].