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How Do Rocket Engines Work?
Published in Travis S. Taylor, Introduction to Rocket Science and Engineering, 2017
Figure 4.4 shows a converging–diverging nozzle illustrating the different regimes of flow and how the velocity increases as the area changes, which was described by Equation 2.24. The convergent–divergent nozzle design is also known as the de Laval nozzle after the Swedish inventor Gustaf de Laval who developed it in the 19th century. As mentioned earlier in this section, the subsonic flow on the converging side breaks the sound barrier at the throat if the engine is designed properly. If M# = 1 at the throat, then the mass flow through the nozzle is said to be a choked flow or sometimes just choked.
D
Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[fluid dynamics] A nozzle introduced based on the fluid-dynamic analysis by Gustaf de Laval (1845–1913) used in rocket engines. The specific design of the De Laval nozzle guides pressurized gas from subsonic to supersonic flow velocity resulting in optimal energy conversion from the heated entry gas to kinetic flow velocity using a choked flow condition. The De Laval nozzle was initially designed for steam turbines and later found perfect applications in super-sonic jet engines (see Figure D.17).
A perspective review on the bonding mechanisms in cold gas dynamic spray
Published in Surface Engineering, 2019
Antonio Viscusi, Antonello Astarita, Roberta Della Gatta, Felice Rubino
The Cold Gas Dynamic Spray, or generally referred Cold Spray (CS), is a relatively new spray technology which falls under the larger family of thermal spray processes [1–4]. In conventional thermal spraying processes, such as wire arc and flame spray, the sprayed particles are partially or fully molten when they deposit on the substrate [5,6]; moreover, the impacting velocity onto a target surface is usually below 200 m s−1 [7,8]. By the advent of high-velocity oxyfuel process, the particles velocity was increased and the processable materials selection was amplified [9]. On the other hand, the cold spray uses less thermal and more kinetic energy, so the powder particles remain in a solid state upon impact onto substrate [10]. Therefore, it can cope with the production of different kind of coatings, pure metals, alloys, composites, nanostructure materials as well as amorphous materials [11–13], on a wide variety of substrate. The cold spray technique can be usefully used in many critical applications, such as biomaterials field, polymer and polycarbonates surfaces and marine environment [14–17]; functional coatings can also be manufactured by CS to improve the performances of the components to the operating conditions, in particular, fatigue [18,19], wear [20,21] and corrosion [22–26]. It was also proved to be an effective method to produce free shape precursors for metal foams structures [27,28]. The process can be schematised as follows: the particles, ranging from 1 to 50 µm in diameter [29], are delivered from a powder feeder through a powder injection tube into a nozzle by a separated stream of powder carrier gas, typically air, nitrogen or helium, and then accelerated by the propellant gas (see Figure 1) [30]. The propellant gas (also called carrier gas) is heated at high temperature by an electric heater and injected at high pressure into a converging–diverging de-Laval nozzle (Figure 1), where the mixing with the powders occurs. The gas/powders mixture is accelerated through the de-Laval nozzle to supersonic conditions [31]. The achieved impact velocities usually range between 300 and 1200 m s−1 [32].