**2. Waveriders**

In the waverider design, it is the first step to define the generation field and then the streamlines constituting the compression surface of the waverider. In the current study, the design conditions of the vehicle are chosen as follows: height of 25 km and free stream with the inflow Mach number to be 5.0. Thereafter, the shape together with the pressure distribution is determined. Typically, a waverider design process can be divided into: selection and design of the basic flow field in the flow direction, solving of the basic flow field, streamline tracing, and application of the osculating theory in the spanwise direction. After that, points representing streamlines are obtained. Streamlines and compression surface can be generated using CAD tools. For example, in this study, an automatic 3D configuration generation program based on the UG API is developed. Meanwhile, an aerodynamic force estimation program is built. Usually, remodel design of the waverider is needed for a specific purpose.

The basic flow field is usually a steady inviscid supersonic flow one, which is the core of the design of a waverider. Basic flow fields used for waverider design can be

#### **Figure 1.**

*Cone-derived waverider. (upper) Configuration with surface mesh for rapid estimation. (bottom) CFD simulation under design conditions.*

**33**

**Figure 2.**

*Flow chart of conceptual scramjet design.*

**3. Scramjet**

*Airframe-Propulsion Integration Design and Optimization*

classified into two types: steady two-dimensional (2D) planar or asymmetrical supersonic flow fields and three-dimensional (3D) supersonic flow fields. Since 2D planar or asymmetrical flow fields can be calculated easily by fast calculation methods such as the method of characteristics (MOC), most of the basic flow fields used for rapid design and optimization of waveriders are of the 2D planar or asymmetrical type. The supersonic flow around a cone at a zero angle of attack, which is known as a conical flow field, is a typical 2D asymmetrical basic flow field. In 1968, Jones et al. [15] first used this kind of flow field to design a waverider known as the conederived waverider. The conical flow field is by far the most widely used basic flow field for waveriders, and the cone-derived waverider has become the most widely used waverider owing to the ease of its calculation and better volumetric efficiency than wedge-derived waverider on account of the concave streamlines being closer to the shock wave. **Figure 1** shows our designed cone-derived waverider configuration and numerical simulation results. The surrogate modes for aerodynamic shape optimization were carried out based on the values of lift-to-drag ratio and volumetric efficiency response [8]. In the present study, the commercial software Fluent and Insight are chosen for the numerical simulation and optimization, respectively.

Regarding the conceptual design of scramjet, the stream thrust analysis [9] was superior to that of the thermodynamic cycle or first law analyses as it managed to account for several phenomena such as the geometry of the combustor, the velocity, mass of the fuel, and the exhaust outlet pressure not matching the ambient. **Figure 2**

A scramjet was first designed by using stream thrust analysis, to obtain the overall parameters and flow state parameters at the in-/outlet of each components. When the stream thrust was analyzed, a group of state parameters were determined such as pressure, density, and temperature together with velocity and areas in each component's inlet and outlet. These parameters were delivered to the following two-dimensional components' design of the inlet, isolator, combustor, and nozzle. When the overall dimension of the scramjet internal flow passage was determined, the performance of a scramjet that allowed a supersonic flow to pass through the engine without choking in the inlet throat, combustor, and nozzle were analyzed by

Using the above conceptual design method and performance evaluation, the initial design and analysis of a scramjet were performed. The optimization was conducted to generate more practical results based on the specific objectives. The flow chart describing the conceptual design method and optimization process is shown in **Figure 3**. As the design and evaluation of scramjet are highly nonlinear problems,

briefly introduces the design procedure and method of scramjet.

the quasi-one-dimensional evaluation program.

*DOI: http://dx.doi.org/10.5772/intechopen.85187*

### *Airframe-Propulsion Integration Design and Optimization DOI: http://dx.doi.org/10.5772/intechopen.85187*

classified into two types: steady two-dimensional (2D) planar or asymmetrical supersonic flow fields and three-dimensional (3D) supersonic flow fields. Since 2D planar or asymmetrical flow fields can be calculated easily by fast calculation methods such as the method of characteristics (MOC), most of the basic flow fields used for rapid design and optimization of waveriders are of the 2D planar or asymmetrical type.

The supersonic flow around a cone at a zero angle of attack, which is known as a conical flow field, is a typical 2D asymmetrical basic flow field. In 1968, Jones et al. [15] first used this kind of flow field to design a waverider known as the conederived waverider. The conical flow field is by far the most widely used basic flow field for waveriders, and the cone-derived waverider has become the most widely used waverider owing to the ease of its calculation and better volumetric efficiency than wedge-derived waverider on account of the concave streamlines being closer to the shock wave. **Figure 1** shows our designed cone-derived waverider configuration and numerical simulation results. The surrogate modes for aerodynamic shape optimization were carried out based on the values of lift-to-drag ratio and volumetric efficiency response [8]. In the present study, the commercial software Fluent and Insight are chosen for the numerical simulation and optimization, respectively.
