Mass generation rate

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. 

Let us consider a propellant burning in a rocket motor as shown in Fig. 14.8. The mass generation rate in the chamber, ntg, is given by... 

Mass Generation Rate and Mass Discharge Rate... 

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... 

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. 

The mass generation rate in the gas generator is controlled by the variable flow system and the mixture ratio of fuel-rich gas to air in the ramburner is optimized. The burning rate is represented by the relationship r = ap", where r is the linear burning rate, p is the pressure, n is the pressure exponent of burning rate, and o is a con-... 

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

The mass generation rates are expressed by htgi = piAiti = pjAikip" for propellant 1 thg2 = P2A2T2 = for propellant 2... 

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