Advantages of a supersonic split line nozzle over a submerged movable nozzle

Advantages of a supersonic split line nozzle over a submerged movable nozzle

Ravnan, Sigurd (TU Delft Aerospace Engineering; TU Delft Space Engineering)

Zandbergen, B.T.C. (mentor)
Gill, E.K.A. (graduation committee)
van Zuijlen, A.H. (graduation committee)
Faenza, Martina (graduation committee)

Delft University of Technology

Aerospace Engineering

2021-03-11

The supersonic split line (SSSL) nozzle has been considered for years in the use of solid rocket motors. The SSSL nozzle is an attractive alternative to the more conventional submerged movable (SM) nozzle. The SSSL nozzle can save up to 43% on nozzle mass and 25% on the thrust vector control (TVC) system mass. The SSSL nozzle also has the benefit of the amplification factor, which is a result of the SSSL nozzle turning the flow in the supersonic region. The shock waves formed deflect the flow more than the mechanical deflection. Only limited research is available on the SSSL nozzle. This thesis aims to expand on the knowledge of the SSSL nozzle in cooperation with Nammo Raufoss. The aspects that are researched in detail are as following: The effect on the amplification factor when moving the split and changing the expansion ratio of the nozzle. Furthermore, to determine how well the SSSL nozzle compares to a more traditional SM nozzle, a comparison between the SSSL and the SM nozzle is performed at equal performance. This comparison has a focus on the mass differences. The performances of the SM nozzle and the SSSL nozzle are determined by simulations with computational fluid dynamics (CFD). From the CFD simulations, the amplification factor of the SSSL nozzle was determined. In order to compare the SSSL nozzle and the SM nozzle a mass model is developed. The model uses the calculated performance from the CFD simulations to calculate the mass difference between the two nozzle and TVC systems. The results show that the amplification factor increases when moving the split further down stream. Furthermore, when increasing the expansion ratio the amplification factor decreases. For the SSSL nozzle with a total expansion ratio of 12 and the split location at an expansion ratio of 1.75, the maximum amplification factor is 1.57. Additionally, a linear relationship between the amplification factor and the ratio of the expansion ratio at the split to the total expansion ratio of the nozzle is observed. The SSSL nozzle experiences increasing thrust and Isp losses while vectoring when the split is located further downstream, while receiving only a slight increase in the amplification factor. The results from the mass model show that the SSSL nozzle is on average 37% lighter than the SM nozzle for a vectoring duty cycle of 0.25. To conclude, for an increasing ratio between the expansion ratio at the split to the total expansion ratio of the nozzle, the amplification factor increases. Additionally, the SSSL nozzle is the lighter option when only the aerodynamic effects are considered. It was also seen that the temperature and heat flux around the split area was high, to overcome this the SSSL nozzle might need additional thermal protection which could potentially lead to a higher mass. It was observed that the largest mass difference between the SSSL and SM nozzle system was found when the split of the SSSL nozzle is located at an expansion ratio that gives the highest possible Isp.

Supersonic split line nozzle
Submerged movable nozzle
amplification factor
Thrust vector control

http://resolver.tudelft.nl/uuid:6605a556-1a5f-4db1-bc7c-d1824feba24f

Student theses

master thesis

© 2021 Sigurd Ravnan