Propellant nozzle

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). 

Volume of vessel (free volume V) Shape of vessel (area and aspect ratio) Type of dust cloud distribution (ISO method/pneumatic-loading method) Dust explosihility characteristics Maximum explosion overpressure P ax Maximum explosion constant K ax Minimum ignition temperature MIT Type of explosion suppressant and its suppression efficiency Type of HRD suppressors number and free volume of HRD suppressors and the outlet diameter and valve opening time Suppressant charge and propelling agent pressure Fittings elbow and/or stub pipe and type of nozzle Type of explosion detector(s) dynamic or threshold pressure, UV or IR radiation, effective system activation overpressure Hardware deployment location of HRD suppressor(s) on vessel... 

Special propulsion also requires relevant calculations and distribution of the anodes. For Kort nozzles, the total surface area of the mdder is determined and a basic protection current density of 25 mAm" imposed. The anodes are attached on the external surface at a spacing of 0.1 r to 0.25 r at the region of greatest diameter. Internally the anodes are fixed to the strengthening stmts. With Voith-Schneider propellers, the anodes are arranged around the edge of the base of the propeller. 

Fig. 17-4 Distribution of galvanic anodes for different shapes of stem, (a) Steamer stern one propeller, one balance rudder, (b) Steamer stern one propeller, a suspension rudder, (c) Tugboat stem two propellers, a Kort nozzle mdder. (d) Transom stem two propellers, a suspension mdder. (e) Transom stem two propellers, two suspension mdders.

The turboprop engine has a power turbine instead of the nozzle as seen in Figure 4-2. The power turbine drives the propeller. The unit shown schematically is a two-shaft unit, this enables the speed of the propeller to be better controlled, as the gasifier turbine can then operate at a nearly constant speed. Similar engines are used in helicopter drive applications and many have axial flow compressors with a last stage as a centrifugal compressor as shown in Figure 1-14. 

Figure 9.43 shows the schematic diagram of an axial fan system. The air flows through a nozzle toward the impeller, where static pressure rises. The impeller is attached to a hub. The impeller is also called the propeller. The propeller is followed by a diffuser. 

In the 1930s ducts or nozzles surrounding highly loaded propellers were introduced. Experiments had shown that propeller efficiency was improved, and many of these devices (often referred to as Kort nozzles) have been used in tugs and fishing boats. Theoretical analysis of ducted propellers has shown that the efficiency can be improved compared to conventional propellers when some of the thrust is produced by the fluid flow around the nozzle. 

The combustion process is carried out in a thrust chamber or a motor case, and the reaction products are momentarily contained therein. The newly formed species are heterogeneous in composition and involve a wide variety of low molecular weight products. The temperature of these products is generally high, and it ranges from about 2,000°F (1,100°C) in gas generators to well over 8,000°F in advanced liquid propellant engines. The combustion products leave the chamber and are directed and expanded in a nozzle to obtain velocities from about 5,000 to 14,000 ft/sec. 

D.P. Laverty, Carbides For Solid Propellant Nozzle Systems , Rept No AFRPL-TR-68-164, Contract F04611-67-C-0094, TRW Equipt Labs, Cleveland (1968) 25) M.L. Williams, The... 

MinyAvn, London (1967) H) Anon, Research and Development Programs , Rept No APL-U-RQR/67-3, JHU/APL, Contract NOW-62-0604 (1967) I) A.C. Parmee S.F.W. Woodhouse, Assessment of Materials for Use as Nozzle Inserts in Solid Propellant Rocket Motors Part V, Tungsten , Rept No RPE-TR-67/17, Rocket Propn Estbmt, Westcott (Engl)... 

In a solid-propellant rocket motor, the propellant is contained within the wall of the combustion chamber, as shown in Fig. 1. This contrasts with liquid systems, where both the fuel and oxidizing components are stored in tanks external to the combustion chamber and are pumped or pressure-fed to the combustor. In hybrid systems, one component, usually the fuel, is contained in the combustion chamber, while the other component is fed to the chamber from a separate storage tank, as in liquid systems. The solid-propellant motor also has an ignition system located at one end to initiate operation of the rocket. The supersonic nozzle affects the conversion of... 

In addition to the energy requirements of solid propellants, Eq. (3) shows that consideration must be given to the mass-flow rate of the combustion products through the nozzle. Because all solids burn on the exposed surface, the mass flow of propellant combustion products is given by the equation... 

During this period, the mass discharge rate through the motor nozzle increases as the flame spreads over the propellant, causing an increase in the chamber pressure (as shown in Fig. 2) which is described by... 

There are a variety of igniter designs which are currently employed in solid-propellant rockets. These types include rocket-exhaust (pyrogen), pyrotechnic, and hypergolic igniters, each of which can be located in the head-end closure of the motor or in the exhaust nozzle at the aft-end of the motor. The heat-transfer information appropriate to each of these possible combinations is discussed in the following sections. 

Ciepluch (C3) was the first to demonstrate that solid propellants could be extinguished by the rapid venting of gases from the combustion chamber. This was accomplished by suddenly opening a secondary nozzle to achieve the needed venting rate. If the depressurization rate was above a critical value, extinguishment could be achieved if below it, the pressure would seek a new steady state determined by the new chamber ballistics. 

Iridium Coating for Spacecraft Rocket Nozzles. The coating of rocket nozzles with iridium is a good example of the ability of CVD to provide a complete composite material, in this case a structural refractory shell substrate coated with a corrosion- and oxidation-resistant component. The device is a thruster rocket nozzle for a satellite. The rocket uses a liquid propellant which is a mixture of nitrogen tetroxide and monomethyl hydrazine. 

A speedboat is propelled by a water jet motor that takes water in at the bow through a 10 cm diameter duct and discharges it through an 50 mm diameter nozzle at a rate of 80 kg/s. Neglecting friction in the motor and internal ducts, and assuming that the drag coefficient for the boat hull is the same as for aim... 

Main uses. Caesium metal is used in the production of vacuum tubes as a scavenger to reduce residual gaseous impurities after the tubes have been sealed. Cs may be generated in situ by heating a pellet of caesium chromate mixed with a metal powder (Zr, Ca, Ba). Cs metal is used as the propellant in ion thrusters (employed in satellites for orientation control) it is ionized in a vacuum chamber, the Cs+ are then accelerated through a nozzle (high specific impulse because of high atomic mass). 

---