Studies of Submarine Engine Exhaust Silencers and Thermal Infrared Signature Reduction.pdf

1、The 3-D numerical methods are used to predict the acoustic attenuationperformance and flow resistance. characteristics of submarine engine exhaustreactive silencers. In addition, simulations of temperature drop of exhaus

2、t gas bythe use of dry type cooling silencer and water injection in tail pipe through spray}:ozzle are also performed. In this thesis, the fundamental theory of acoustic finiteelement method and brief introduction to the

3、 finite volume method, as well as therelated software SYSNOISE and FLUENT are introduced. The transmission loss ispredicted by finite element method using SYSNOISE, while pressure drop iscalculated by finite volume metho

4、d using FLUENT. Temperature drop simulationsof both dry type cooling silencers and water injection in tail pipe are carried out byusing heat txansfer module and spray model in discrete phase modeling of FLUENTsoftware.

5、 During surfacing and snorkeling,a submarine has to compromise its inherentstealth,as Exhaust Noise of diesel engines and the associated IR/ThermalSignatures of hot exhaust gases increases the vulnerability towards det

6、ection bysonars and IR detectors of hostile ASW aircrafls and vessels. Submarine dieselengine exhaust noise is controlled through the use of reactive silencers. Theobjective of the present work has been to simulate the a

7、coustic and aerodynamicperformance of selected submarine reactive silencers and to devise a method tominimize the IR/Thermal signatures of engine exhaust. Cooling of exhaust gaseswill result in a decrease of temperature

8、of tail pipe or exhaust mast and a shift inthe wavelength, thus masking the associated IR signatures. Numerical results of transmission loss of simple expansion chamber with offsetextended inletloutlet and expansion

9、chamber with offset perforated extendedinletloutlet tubes showed that repeating dome behavior characteristics of onedimensional propagation do not extend beyond the first asymmetric (l, 0) mode.Also predicted pressure dr

10、op of these two silencers are almost the same. Doublechamber reactive silencers with double inter-connecting tubes have higherpressure drop and provide higher acoustic attenuation than the single chambersilencer at most

11、frequencies after its first pass frequency. Using guiding annulus,the pressure drop may be decreased effectively, with Negligible effect on acousticattenuation performance. The influence of inereasing the value of cleara

12、nce "Lc"on the acoustic performance of reversing flow silencer is negligible at lowfrequencies and limited at higher frequencies. For reversing flow silencer,pressure drop varies inversely with the clearance space betwee

13、n the shell andguide plates. Temperature drop rn}merical simulation results of cooling silencers show thatincreasing the exhaust inlet velocity adversely affect the cooling process, resultingin a lower overall temper

14、ature drop. Temperature drop of exhaust gas passingthrough cooling silencer depends upon the cooling silencer dimensions i.e. largerthe heat transfer surface area, greater will be reduction in the exhaust gastemperarirre