学位论文 > 优秀研究生学位论文题录展示

Studies of Submarine Engine Exhaust Silencers and Thermal Infrared Signature Reduction

作　者: Khurram Shehzad
导　师: Ji Zhenlin
学　校: 哈尔滨工程大学
专　业: Marine Engineering
关键词: exhaust silencer transmission loss pressure drop acoustic finite element method finite volume method cooling silencer thermal infrared signature marine engine exhaust
分类号: U674.76
类　型: 硕士论文
年　份: 2006年
下　载: 45次
引　用: 0次
阅　读: 论文下载

内容摘要

The 3-D numerical methods are used to predict the acoustic attenuation performance and flow resistance characteristics of submarine engine exhaust reactive silencers. In addition, simulations of temperature drop of exhaust gas by the use of dry type cooling silencer and water injection in tail pipe through spray nozzle are also performed. In this thesis, the fundamental theory of acoustic finite element method and brief introduction to the finite volume method, as well as the related software SYSNOISE and FLUENT are introduced. The transmission loss is predicted by finite element method using SYSNOISE, while pressure drop is calculated by finite volume method using FLUENT. Temperature drop simulations of both dry type cooling silencers and water injection in tail pipe are carried out by using heat transfer module and spray model in discrete phase modeling of FLUENT software.During surfacing and snorkeling, a submarine has to compromise its inherent stealth, as Exhaust Noise of diesel engines and the associated IR/Thermal Signatures of hot exhaust gases increases the vulnerability towards detection by sonars and IR detectors of hostile ASW aircrafts and vessels. Submarine diesel engine exhaust noise is controlled through the use of reactive silencers. The objective of the present work has been to simulate the acoustic and aerodynamic performance of selected submarine reactive silencers and to devise a method to minimize the IR/Thermal signatures of engine exhaust. Cooling of exhaust gases will result in a decrease of temperature of tail pipe or exhaust mast and a shift in the wavelength, thus masking the associated IR signatures.Numerical results of transmission loss of simple expansion chamber with offset extended inlet/outlet and expansion chamber with offset perforated extended inlet/outlet tubes showed that repeating dome behavior characteristics of one dimensional propagation do not extend beyond the first asymmetric (1,0) mode. Also predicted pressure drop of these two silencers are almost the same. Double chamber reactive silencers with double inter-connecting tubes have higher pressure drop and provide higher acoustic attenuation than the single chamber silencer at most frequencies after its first pass frequency. Using guiding annulus, the pressure drop may be decreased effectively, with negligible effect on acoustic attenuation performance. The influence of increasing the value of clearance ’L_C’ on the acoustic performance of reversing flow silencer is negligible at low frequencies and limited at higher frequencies. For reversing flow silencer, pressure drop varies inversely with the clearance space between the shell and guide plates.Temperature drop numerical simulation results of cooling silencers show that increasing the exhaust inlet velocity adversely affect the cooling process, resulting in a lower overall temperature drop. Temperature drop of exhaust gas passing through cooling silencer depends upon the cooling silencer dimensions i.e. larger the heat transfer surface area, greater will be reduction in the exhaust gas temperature. Water injection in the exhaust gas through spray nozzle has remarkable results and results in a greater reduction in exhaust gas temperature as compared to dry type cooling silencer.

全文目录

ABSTRACT  4-9
CHAPTER 1 INTRODUCTION  9-22
  1.1 Naval Stealth Technology  9-11
  1.2 Engine Exhaust Noise and Control  11-14
    1.2.1 Exhaust System Noise  11-12
    1.2.2 Exhaust Silencers  12-13
    1.2.3 Submarine Exhaust Silencing System  13-14
  1.3 Exhaust Thermal Infrared Signature Shielding  14-20
    1.3.1 Thermal Radiations  14-15
    1.3.2 Thermal and Selective Radiators  15-16
    1.3.3 Thermal Imaging  16
    1.3.4 IR Detectors/Sensors  16-18
    1.3.5 IR Detectors/Sensors Sensitivity Range  18-19
    1.3.6 Cooling of Exhaust Gas: Method for Shielding IR Signatures of Engine Exhaust  19-20
  1.4 Objectives of the Present Research  20-22
CHAPTER 2 ENGINE EXHAUST SYSTEM AND SILENCERS  22-34
  2.1 Exhaust System Representation  22-24
  2.2 Types of Exhaust Silencers  24-25
    2.2.1 Reactive Silencers  24
    2.2.2 Dissipative Silencers  24-25
    2.2.3 Combination Type  25
  2.3 Silencer Design Principles  25-33
    2.3.1 Acoustic Performance  25-29
    2.3.2 Aerodynamic Performance  29-32
    2.3.3 Mechanical Performance  32
    2.3.4 Structural Performance  32
    2.3.5 Economic Requirement  32-33
  2.4 Concluding Remarks  33-34
CHAPTER 3 ACOUSTIC SIMULATION AND ANALYSIS OF SILENCERS  34-55
  3.1 Introduction  34-39
    3.1.1 Transfer Matrix Method Based on Plane Wave Theory  34-37
    3.1.2 3-D Analytical Method  37-38
    3.1.3 Acoustic Finite Element Method (FEM)  38-39
    3.1.4 Acoustic Boundary Element Method (BEM)  39
    3.1.5 A Comparison of FEM and BEM  39
  3.2 Three Dimensional Waves  39-42
  3.3 Variational Formulation of Acoustic FEM  42-45
  3.4 Numerical Computation Using FEM  45-47
    3.4.1 ANSYS  45
    3.4.2 SYSNOISE  45-46
    3.4.3 Boundary Conditions  46
    3.4.4 Post Processing  46-47
  3.5 Acoustic Performance Calculations and Anaylysis of Silencers  47-53
    3.5.1 Expansion Chamber with Offset Extended inlet/Outlet  47-49
    3.5.2 Expansion Chamber with Offset Perforated Extended Inlet/Outlet Tubes  49-51
    3.5.3 Double Expansion Chamber Reactive Silencer with Double Inter-connecting Tubes  51-52
    3.5.4 Reversing Flow Silencer  52-53
  3.6 Concluding Remarks  53-55
CHAPTER 4 AERODYNAMIC SIMULATION AND ANALYSIS OF SILENCERS  55-72
  4.1 Introduction  55-57
    4.1.1 Pre-Processor  55-56
    4.1.2 Solver  56-57
    4.1.3 Post-Processor  57
  4.2 Governing Equations of Tubular Flow  57-60
    4.2.1 Standard k -ε Model  59-60
  4.3 Finite Volume Method (FVM)  60-62
  4.4 Numerical Computation Using FLUENT  62-63
    4.4.1 Boundary Conditions  62-63
    4.4.2 Solver Selection and Solution  63
  4.5 Aerodynamic Performance Calculations and Analysis of Silencers  63-71
    4.5.1 Expansion Chamber with Offset Extended inlet/outlet  63-65
    4.5.2 Expansion Chamber with Offset Perforated Extended Inlet/Outlet Tubes  65-67
    4.5.3 Double Expansion Chamber Reactive Silencer with Double Inter-connecting Tubes  67-69
    4.5.4 Reversing Flow Silencer  69-71
  4.6 Concluding Remarks  71-72
CHAPTER 5 COOLING SILENCERS  72-97
  5.1 Introduction  72-73
    5.1.1 Dry Type Cooling Silencer Design  72-73
  5.2 Governing Equations for Temperature Field  73-74
    5.2.1 Energy Equation in Solid Regions  74
  5.3 Numerical Computation Using FLUENT  74-77
    5.3.1 Material Physical Properties  74-76
    5.3.2 Boundary Conditions  76-77
    5.3.3 Turbulence Model  77
    5.3.4 Solution Process for Heat Transfer  77
  5.4 Temperature Drop Calculation and Analysis of Cooling Silencers  77-92
    5.4.1 Cooling Expansion Chamber with Offset Extended Inlet/Outlet  77-80
    5.4.2 Cooling Expansion Chamber with Offset Perforated Extended Inlet/Outlet Tubes  80-82
    5.4.3 Double Expansion Chamber Cooling Silencer with Double Inter-connecting Tubes  82-86
    5.4.4 Reversing Flow Cooling Silencer  86-92
  5.5 Cooling by Water Injection in Exhaust Gas: Numerical Simulation  92-95
  5.6 Concluding Remarks  95-97
COCLUSIONS  97-101
REFERENCES  101-107
ACKNOWLEDGEMENTS  107-108
Appendix A  108-109
Appendix B  109-110

Studies of Submarine Engine Exhaust Silencers and Thermal Infrared Signature Reduction

内容摘要

全文目录

相似论文