FIGURE 3-^4. Area and velocity ratios as function of pressure ratio for the diverging section of a supersonic nozzle.
Example 3-3. Design a nozzle for an ideal rocket that has to operate at 25 km altitude and give 5000 N thrust at a chamber pressure of 2.068 MPa and a chamber temperature of 2800 K. Assuming that k = 1.30 and R = 355.4 J/kg-K, determine the throat area, exit area, throat velocity, and exit temperature.
SOLUTION. At 25 km the atmospheric pressure equals 0.002549 MPa (in Appendix 2 the ratio is 0.025158 which must be multiplied by the pressure at sea level or 0.1013 MPa). The pressure ratio is
Pi/P\ = Pi/Pi = 0.002549/2.068 = 0.001232 = 1/811.3
The critical pressure, from Eq. 3-20, is p, = 0.546 x 2.068 = 1.129 MPa
The throat velocity, from Eq. 3-23, is v, = —-RT\ =J2* L3,° 355.4 x 2800 = 1060 m/sec ' y k+ 1 1 V 1.3 + 1
Was this article helpful?
What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.