Mass discharge rate

As = burning surface area (sq inches), p = proplnt density (lb/cu inch). For stable operation, the mass flow rate must equal the mass discharge rate at the nozzle which is... 

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... 

Equation 4-18 is substituted into Equation 4-12 to obtain the mass discharge rate at any time t ... 

The first term on the right-hand side of Equation 4-19 is the initial mass discharge rate at hL = hi. 

A much simpler procedure is to calculate the mass discharge rate at the instant the leak occurs, assuming a fixed temperature and pressure within the tank equal to the initial temperature and pressure. The actual discharge rate at later times will always be less, and the downwind concentrations will always be less. In this fashion a conservative result is ensured. 

Since the burning rate of a propellant is dependent on the burning pressure, the mass balance between the mass generation rate in the chamber and the mass discharge rate from the nozzle is determined by the pressure. In addition, the propellant burning rate in a rocket motor is affected by various phenomena that influence the mass balance relationship. Fig. 14.4 shows typical combustion phenomena encountered in a rocket motor, from pressure build-up by ignition to pressure decay upon completion of the combustion. 

Mass Generation Rate and Mass Discharge Rate... 

The respective mass discharge rates of rh g for the booster stage and the sus-... 

An adaptation of Eq. (14.38) for a nozzleless rocket indicates that the port area increases as the burning surface of the propellant regresses, decreases and Aj increases, and so the choked condition is varied. Thus, the thrust generated by the nozzleless rocket is determined by the relationship of the mass generation rate in the port and the mass discharge rate at the rear-end of the port.I - l... 

Let us consider a gas flow in a port of an internal-burning propellant. The cross-sectional area of the port is assumed to be constant throughout the port from the head-end to the rear-end, i. e., the port is one-dimensional along the flow direc-tion.I l The mass discharge rate from the rear-end of the port, m, is given by... 

As for a rocket motor, the combustion pressure is determined by the mass balance between the mass generation rate and the mass discharge rate according to... 

Since the mass generation rate in the gas generator is dependent on the pressure therein and the mass discharge rate is dependent on the throat area of the nozzle attached to the end of the gas generator, the mass generation rate is altered by changing the throat area. Thus, a throttable valve is attached to the end of the gas generator. 

Fig.15.3 Fundamental concept of a variable-flow system as a function of mass generation rate and mass discharge rate.

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