Acoustic Analysis Of Side Exhaust System With Water Spray

The side exhaust system is a new type of cabin exhaust system proposed in recent years.The principle of the side exhaust system is to use a lateral duct system instead of the traditional ductwork to guide the exhaust port to the side of the ship for discharge.For the purpose of infrared suppression and noise control,a spray cooling device and an exhaust muffler are usually installed in the side exhaust system.On the other hand,the opening of the water-cooling device often turns the exhaust medium from a single high-temperature gas into a gas-liquid mixed medium with a temperature gradient.These conditions greatly affect the sound transmission characteristics of the medium.Therefore,studying the acoustic characteristics of muffler under the condition of high temperature,high speed and gas-liquid blending has become an important issue of exhaust gas noise control.In this paper,the influence of different media conditions on the acoustic characteristics of water spray mufflers is discussed by analyzing the change of physical parameters before and after the water discharge of the side exhaust system.Including the temperature,flow rate and gas-liquid two-phase flow on the muffler transmission losses.Set up a water spray test bench,and to determine the pipeline gas-liquid two-phase flow for the mist flow.The mathematic model of the mist flow is established,and the formula of sound velocity and density is deduced.Finally,the change law of the muffler transmission loss when the gas content is different is obtained.It is found that the decrease of temperature causes the muffler's transmission loss curve to move to low frequency.The gas-liquid two-phase medium also makes the muffler transmission loss move to low frequency.Based on the derivation of the sound velocity and density formula of the mist-flow media,this paper gives the numerical simulation of the muffler considering the temperature gradient and the liquid phase in the real working condition by taking the secondary muffler as an example.The method was used to calculate the muffler transmission loss after the secondary muffler rated working condition.In addition,according to the different design schemes of the primary muffler,the effect of the arrangement of the sound absorbing material on the noise reduction characteristics of the muffler is discussed through numerical simulation.Finally,numerical simulation of the entire side exhaust muffler is performed.The acoustic characteristics of a spray-side side exhaust system with different water spray volumes were analyzed.