Pallabazzer 



2,0 



1.2 



Cs 



o.a 



OA 



Fig. 20 - Variation of c, 

 with Xj , for a hydrojec- 

 tor (if/ = 0.9, a. p.) 



W 

 0.B 

 0,6 



0.2 

 OJO 



3 i. 6 $ I 



3 i. 6 a to 



Fig. 21 - Variation of -n^ 

 with X., for a hydrojec- 

 tor (v)/ = 0.9, a. p.) 



(a) In a range of k^ of practical interest (this corresponds to a range 

 of 10"'* < e < 10"2, which is both a valid solution of the equations and of prac- 

 tical interest), the hydrojector can provide higher specific thrust than the 

 water jet at the same speed. While the increase of /3p becomes less and less 

 efficient at higher values (Fig. 16), the effect of increasing K^ is more and 

 more efficient (Fig. 19); values of a higher than 1 can be obtained at k^ > 2. 



From the equation of state and from Eq. (9) it can be seen that at 

 given pressure and given e, k^ is proportional to the gas temperature. This 

 means, for example, that the substitution of cold air at T = 288°K with hot gas 



1132 



