Study On Noise Control Of Pulse-jet Engine

Especially when the crisis of energy consumption, pollutions and the following greenhouse effect is deteriorating, with the advantages of high combustion efficiency with low excess air coefficient; high combustion intensity with high heating efficiency; low content of polluting exhaust gas, especially NOx, the pulse-jet engines become important more and more. However, with the disadvantage of noise, it is harmful for human health, it is necessary to control the noise of the pulse-jet engines.In the paper, the air intake noise controlling technique and the influence of noise controlling to the pulse-jet engine performance were studied. The acoustic performance of resisting muffler was analysed with the ANSYS software and the transfer losing curve was concluded. It is important for further research.The noise controlling and engine performance testing experiment was designed. The experiment platform was established. According to that the engine construction dimension and the check valve are critical to the pulsation combustion, 3 of the resisting mufflers were chosen and studied. As shown in experiments, the noise was depressed by all 3 resisting mufflers, especially at the position of 30cm away from the air intake with the most of 9 db. The resisting muffler m11 of expanding ratio 11 was effective to the noise depression. However, with the higher expanding ratio, the noise depression was weaken and disabled with high frequency. According to the noise depressing frequency, the 3 mufflers were effective in the working frequency range, the ending frequency muffler m11 was appropriate. It is shown that the expanding ratio should be chosen within allowable range instead of the maximum.In the preconditions of well starting-up and the steady performance, 3 resisting mufflers with different thickness fiberglass were designed and studied. As shown in experiments, the acoustic pressure were depressed, especially at the position of 30cm away from the air intake, mostly 5 db. The acoustic pressure value of each testing position were declined as the fiberglass thickness getting thicker and thicker. In the aspect of noise depressing frequency, the effect were excellent in the high frequency range and poor in the low frequency range. It is coincident to the noise controlling theory.The working frequency was tested both in pressure wave analyzing theory and noise frequency analyzing theory. The working frequency of pulse-jet engine with the same conditions were absolutely same, however, 13.3% to 20.9% departure with the calculating value. According to the analysis, the difference was the result of coupling of the noise conditions and the heating conditions. Is was shown that the influence of mufflers to the engine working frequency was tiny. As a result of tiny velocity of sound difference.The gasoline consumption was tested. As shown in the experiments: as the result of that the resisting mufflers'resistance to the air intake was small, the gasoline consumption ratio and the excess air coefficient were influenced little by resisting mufflers and the gasoline consumption ratio was influenced by preventing mufflers.The emission was tested. As shown that: before and after the installment of the resisting mufflers, the contents of NOx,HC,CO were rather low. The NOx value was smaller than 2.67ppm and mostly 0, the HC value was smaller than 17.7ppm, the CO value was smaller than 8.71×10-2%. It was shown that the resisting mufflers is suitable for the noise controlling.