Nozzle during expansion

The instrument in my laboratory uses laser desorption ionization with a Nd YAG laser and a TOF-MS. The particles are drawn into the instrument on a continuous basis and undergo a supersonic expansion when they pass through the inlet nozzle. During the expansion, the particles pick up different speeds that are a function of their size. They then pass through two scattering lasers. The time it takes the particle to travel between the two lasers can be correlated with particle size, allowing the particle size to be determined precisely. Knowing the particle speed and position, it is possible to time its arrival at the center of the spectrometer with a Nd YAG laser pulse (266 nm). The pulse is able to desorb ionized species from the particle, which can then be analyzed by the spectrometer. 

This discussion has been concerned primarily with the chemistry of the polymer in filled crosslinked elastomer formulations. Since the purpose of these formulations is to produce a gas with high enthalpy, thermochemistry is important. The heat of combustion of the components and the effect of the nature and molecular weight of the gaseous products are included in several literature references. The increase in enthalpy that can be obtained by adding finely divided metals to the formulations makes the use of these materials desirable in many applications. Their presence has catalyzed many excellent studies on two-phase gas flow particularly during expansion in a nozzle. 

The metals also present an additional problem in that the product oxide, fluoride, or nitride species may be a solid phase at the combustion temperature or condense during expansion through the rocket nozzle. Figure 2 presents a graphical comparison of the phase properties of the... 

The nozzle (5) during expansion is shown in Figure 3. After expansion, recirculation occurs where the droplets collide and depending on the melt temperature, (TmeitX droplet velocity and the vapour pressure of CO2 different particle morphologies occur. 

The gas flow (nitrogen N2) through conventional straight bore holes or apertures during expansion of gas from an atomizer nozzle is that of under-expanded jets if the atomization pressure is above the critical value 0.189 MPa. In this case the gas exits the nozzle at a Mach number Ma = UJc = 1. The state of gas at the nozzle exit, that is at the Inlet in Figs. 18.15 and 18.16, can be determined by the stagnation conditions in the atomizer as follows ... 

The gas temperature at the atomizer exit calculated under the hypothesis of an isentropic expansion of the gas (7 expanded,isentropic(7 o = 400 °C)= 183 °C) is much lower than the measured values further away from the nozzle. That shows the strongly dissipative effects of the gas flow during expansion and the effective mixing with the (warm) recirculating gas. In [1, 39], these effects have been investigated experimentally and numerically. This viscous heating effect may be beneficial since more thermal energy is introduced into the breakup zone. 

Aluminum-containing propellants deflver less than the calculated impulse because of two-phase flow losses in the nozzle caused by aluminum oxide particles. Combustion of the aluminum must occur in the residence time in the chamber to meet impulse expectations. As the residence time increases, the unbumed metal decreases, and the specific impulse increases. The soHd reaction products also show a velocity lag during nozzle expansion, and may fail to attain thermal equiUbrium with the gas exhaust. An overall efficiency loss of 5 to 8% from theoretical may result from these phenomena. However, these losses are more than offset by the increase in energy produced by metal oxidation (85—87). 

Bedload was sampled during competent flows at the same vertical than suspended sediment. Bedload analysis has been based upon 215 samples, 145 during 2002-2003 and 70 during 2003-2004. At SMS we used a 29-kg cable-suspended Helley-Smith sampler with a 76-mm intake and an expansion ratio (i.e. ratio of nozzle exit area to entrance area) of 3.22 (Fig. 2c). Bedload was measured at... 

A Study of Combustion and Recombination Reactions During the Nozzle Expansion Process of a Liquid Propellent Rocket Engine , Ibid, pp 366-74 F2) W.E. Johnson W. 

The strong influence exerted by many. of these factors, especially degree of confinement and charge diameter, shows that the energy release which is initiated in the deton front does not occur instantaneously. Hence, any theory (such as "curved-front or "nozzle ) must take into consideration the lateral expansion (See Ref 61, pp 188-201). This expansion (if at all appreciable during time t, where reaction zone thickness is a-Dt) will modify the deton process because a) part of the energy released is used in the expansion (See Ref 61, p 201), hence does not contribute to propaga tion of rhe wave front, and b) peak temp and pressure are lower than when lateral expansion... 

Sh. Tsuchiya, Chemical Equilibrium Lag During Rapid Expansion Through Rocket Nozzle , BullChemSocJapan 34, 854-59 (1961) CA 56,11871 (1962)... 

Poor nozzle access during coating Requires tallest expansion chamber... 

The second vessel (7) is then filled with CO2 until reaching the second operating pressure. This is the expansion pressure at which the mixture is placed downstream of the nozzle. This pressure is fixed during all the experiment with a back-pressure regulator (10). 

During the experiments the valve between the two vessels is open. The saturated mixture sprayed into the expansion vessel via the nozzle, is subjected to a sudden drop in pressure, resulting in supersaturated conditions and the crystallisation of the cocoa butter. This powder is collected in the bag inside the second vessel. This process is known... 

If the reaction times taking place in the reacting mixture are extremely fast compared to the expansion time, then chemical equilibrium will be maintained at all instances during the expansion process this flow process is referred to as eauili- brium flow. However, expansion in the nozzle may occur so rapidly that the reactions may not be fast enough to maintain equilibrium. In fact the expansion can be... 

An additional advantageous possibility in heat transfer rockets is the use of a diabatic nozzle in which propellant heating continues during the expansion process. While difficult to achieve in practice, such heating extends the potential propellant performance beyond the limitation associated with a maximum, pre-expansion temperature. 

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