Numerical Simulation and Analysis of the Effect of Spray Cooling on Muffler Performance in the Engine Exhaust System

摘要

In the engine exhaust system, exhaust muffler is usually installed to reduce exhaust noise. However, there are at least two factors restricting the performance of a muffler. One is the bandwidth in low frequencies while another is pressure drop. For the former, the bandwidth of a muffler depends on the ratio of its size to the wave length. Nevertheless, the wavelength always is related to the wave speed, which climbs with the increase of the temperature. For the latter, the pressure loss will fall if the temperature is lower. Water spray cooling in the exhaust system, as an approach to lowering the temperature, has the potential to improve the low-frequency acoustic performance and reduce its hydrodynamic resistance. In the paper, a numeric model is built to simulate the above cooling mechanism. Based on the theory of two-phase flow, the numeric analysis method of Euler-Lagrange is employed to analyze the water spray cooling mechanism of high-temperature gas in exhaust muffler system. The variation of the pressure drop of a muffler, with the amount and pattern of water injected, is studied in this paper. Some qualitative rules of the effect of spray cooling on muffler performance are also provided.