Nozzle throat area

In an effort to determine the processes responsible for this type of behavior, Akiba and Tanno (A3), Sehgal and Strand (S2), and Beckstead (B6) have studied the coupling between the dynamics of the combustion process and the dynamic ballistics of the combustion chamber as described by Eq. (7). Each of these investigators has postulated admittedly simplified but slightly different combustion models to couple with the transient ballistic equations. Each has examined the combined equations for regions of instability. The results of these studies suggest a correlation between the L of the motor (the ratio of combustion-chamber volume to nozzle throat area) and the frequency of the oscillations. 

This maximum velocity depends on the molecular mass Mg, the specific heat y, and the stagnation temperature Tg. The velocity increases as y and Mg decrease, and as To increases. Based on Eq. (1.52), a simplified expression for mass flow rate in terms of the nozzle throat area Aj (= A ) and the chamber pressure (= pg) is given by... 

Equation (1.68) can be represented by a simplified expression for thrust in terms of nozzle throat area and chamber pressure ... 

Fig. 14.19 shows a typical set of pressure versus time curves obtained from tests on a rocket motor. When the I/D ratio defined in Fig. 14.19 is increased, the head-end chamber pressure is increased drastically immediately after the ignition stage. These grains are seven-pointed-star-shaped neutral-burning grains (diameter D = 114 mm), and are made of an AP-Al-CMDB propellant with the composition nc(0-25), ng(0-31), Ita(0-08), ap(0-27), and ai(0 09). The ratio of the initial burning surface area (Ayg) to the nozzle throat area (Aj), = AygjAp and the ratio of the... 

Fig. 15.4 A nozzle throat area controller based on insertion of a pintle into the throat.

Fig. 15.4 shows a schematic representation of a nozzle throat area controller used in a VFDR. The mass flow rate from the nozzle attached to the primary combustion chamber (gas generator) to the secondary combustion chamber (ramburner) is changed by inserting a pintle. The high-temperature gas produced in the gas generator flows into the ramburner through the pintled nozzle. The pintle inserted into the nozzle moves forward and backward in order to alter the nozzle throat area. As the nozzle throat area is made small, the mass flow rate increases according to the concept described above. The fuel-flow rate becomes throttable by the pintled nozzle. 

Expansion Ratio. In jet propulsion it is the ratio of die nozzle exit section area ro the nozzle throat area. In cartridge actuated device, it is the ratio of final to initial volume in a stroking type of CAD Ref Glossary of Ord (1959), 109-R... 

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