Based on detonation-driven shock tunnels, key issues that play important roles in extending the test time are introduced in this chapter, and the corresponding solutions are proposed, evaluated, and discussed in detail, including the tailored-interface condition, the shock–boundary-layer interaction at the end of the driven section, and the precursor shock damping in the vacuum tank. The research work on these issues was carried out to find out the flow physics and application methods to improve the high-enthalpy shock tunnel for meeting the test time requirement for supersonic combustion and scramjet engine experiments. With application of the aforementioned theories and methods to the high-enthalpy shock tunnel, a large-scale detonation-driven hypersonic flight-duplicated shock tunnel (the JF-12 shock tunnel) was successfully developed, which can provide test times of more than 100 microseconds and is capable of duplicating hypersonic flight conditions for Mach numbers of 5–9 at altitudes of 25–50 km.

The detonation-driven shock tunnel is one of three important classes of hypersonic and high-enthalpy ground testing facilities that are based on the shock-heated principle. The theory and methods for developing the detonation-driven shock tunnels aiming at hypervelocity flow generation are summarized in this chapter. At first, the primary concepts for detonation drivers are presented to demonstrate their unique advantages for aerodynamic ground-based testing. The difficult problems arising from the development of hypervelocity shock tunnels for simulating flight conditions are identified and discussed in detail to address critical issues underlying the high-enthalpy shock tunnel design. Then, three kinds of detonation-driven shock tunnels are introduced, and their key techniques and performances are reviewed and discussed in detail. Finally, some experiments are summarized to demonstrate the capability of the detonation-driven hypersonic shock tunnel and the importance of the measurement techniques for hypersonic and high-temperature flow experiments. Both are the frontiers of high-enthalpy flow research for developing hypersonic vehicles.

In order to introduce hypersonic ground testing facilities, background information in hypersonics is presented to show to readers what we want to do, where we have been, and where we are going to go. These will provide with a good indication of the research needs that are called as hypersonic vehicle ground testing. It is of fundamental importance that a vehicle design must be carefully evaluated in ground test facilities before flight testing can proceed. Indeed, the development of hypersonic vehicles is related to the capability development of hypersonic ground testing facilities.

This chapter also elucidates the issue of particle-particle contact in a multiphase system. The focus is, however, different than in the previous chapters. Those chapters considered the modelling of collision processes where the objective was to explore the collision dynamics (e.g., deformation and velocity). In this chapter, however, we study heat conduction between particles. This indicates that the particles have different temperatures as they collide. First, we examine a mathematical model for heat conduction if the collision is elastic. Later, it is shown how the same strategy can be used if there is a permanent (plastic) deformation during a collision. Finally, consider dissipative forces.

A gas turbine engine is a device that is designed to convert the thermal energy of a fuel into some form of useful power, such as mechanical (or shaft) power or a high-speed thrust of a jet. The engine consists, basically, of a gas generator and a power conversion section, as shown in Figures 1.1 and 1.2.

In this chapter, we will get familiar with a unique performance gauge, which is not process dependent, but is rather state dependent, by definition. In other words, the newly defined, so-called “polytropic” efficiency is independent of the size of a turbomachine (in terms of the total-to-total pressure ratio). In addition, we will have a means of computing the overall efficiency of several stages, sharing the same total-to-total magnitudes of pressure ratio and efficiency, without having to resort to the thermodynamics of each individual stage. The point is made that adding more stages to a multistage turbomachine will have drastic, but totally opposite, effects on turbines as contrasted to compressors. We will prove through this exercise that adding more turbine stages enhances the performance of the final turbine configuration. The effect in compressors, on the other hand, is that of performance deterioration.

Consider the simplest nonafterburning, single-spool turbojet engine, which is schematically shown in Figure 12.1. Assuming a viable (i.e., stable compressor) operation mode, there are obvious constrains relating the gas-generator components to one another. These generally enforce the uniformity of shaft speed, as well as ensure the mass and energy conservation principles (Figure 12.2).

Utilization of axial-flow compressor stages (Figure 9.1) in gas turbine engines is a relatively recent development. The history of this compressor type began after an era when centrifugal compressors were dominant (Figure 9.2). It was later confirmed, on an experimental basis, that axial-flow compressors can run much more efficiently. Earlier attempts to build multistage axial-flow compressors entailed running multistage axial-flow turbines in the reverse direction. As presented in Chapter 4, a compressor-stage reaction, in this case, will be negative, a situation that has its own performance degradation effect. Today, carefully designed axial-flow compressor stages can very well have efficiencies in excess of 80%. A good part of this advancement is owing to the standardization of thoughtfully devised compressor-cascade blading rules.

In this chapter, a turbomachinery-related nondimensional groupings of geometric dimensions and thermodynamic properties will be derived.

In this chapter, the flow-governing equations (conservation laws) are reviewed, with applications that are purposely turbomachinery related. Particular emphasis is placed on the total (or stagnation) flow properties. A turbomachinery-adapted Mach number definition is also introduced as a compressibility measure of the flow field. A considerable part of the chapter is devoted to the total-relative properties, which, together with the relative velocity, define a legitimate thermophysical state. Different means of gauging the performance of a turbomachine, and the wisdom behind each of them, are discussed. Also explored is the entropy-production principle, as a way of assessing the performance of turbomachinery components. The point is stressed that the calculation of entropy production may indeed be desirable, for it is the only meaningful performance measure that is accumulative (or addable) by its mere definition.

This chapter introduces the reader to the modelling of particle-particle collisions. We assume that two spherical particles collide along the normal axis to plane of contact – that is, we only examine a head-on impact. In the beginning, attention is paid to the contact mechanics. The objective is therefore to prepare the reader for fundamental analysis. First, we investigate a simple case of a single force acting on a surface. This problem gradually extends to a similar contact between two spherical bodies (Hertz theory). Next, these bodies are allowed to move towards each other, and we observe their deformation – i.e., a head-on collision. The collision is also elastic, so there is no mechanical energy loss upon impact. Later, this issue is expanded upon by introducing dissipative forces during the contact in addition to the elastic forces discussed above. These dissipative forces are of different types: both linear and non-linear. Finally, another topic is introduced, which is plastic deformation. Here, the colliding bodies are allowed to deform permanently.

From a historical viewpoint, the centrifugal compressor configuration was developed and used, even in the propulsion field, well before axial-flow compressors were. Due to their large envelope and weight (Figure 11.1), the common belief that such a “bulky” compressor type has no place except in aerospace applications is not exactly accurate. For example, with a typical total-to-total pressure ratio of, for example, 5:1, it would take up to three axial-compressor stages to absorb similar amounts of shaft work that a single centrifugal compressor stage would. In fact, the added engine length, with so many axial stages, would increase the skin friction drag on the engine exterior, almost as much as the profile drag, which is a function of the frontal area.

Interactions between particles in multiphase flow may also involve adhesion – i.e., an attraction between the particles. This issue is the main topic of this chapter. The first sections of the chapter, however, focus on a primary case: forces acting between two solid surfaces close to each other. A typical example is an interaction between two spherical bodies, which mimic two particles in a multiphase flow. This situation is later extended to a more complex case: the bodies change their shape due to these adhesive interactions. For this, two theories were developed in the literature (JKR and DMT), and they are fully described in the chapter. Later, it is shown how these theories can be adopted to investigate particle-particle collisions in a multiphase flow. In other words, this topic constitutes an extension of the previous chapter, where the focus was on purely “mechanical” interactions without considering any adhesive forces. Finally, the last section of the chapter describes rough surfaces. There is a brief description of how this real-life issue influences the adhesion between two bodies in contact.