The Research Of Reducing The Nitrogen Oxide Emission From Marine Diesel Engine By Wet Inlet Air With Spraying Water

The limit to the engine emission has been accepted by all the world nations. The international community already established some laws to restrict the emissions from engines. A lot of countries in the world also put forward to research to treat with and restrict the emissions at concentrate on the development economic at the same time. It is one of most important objects to reduce the harmful emissions from diesel engine as the main power of the marine transportation. This paper aim to reduce the nitrogen oxide (NO,) emission from marine 4 stroke diesel engine by spraying water in scavenge box. Spraying water in the scavenge box is increasing the air into diesel cylinder. The burning in the cylinder with water, the burning velocity can be controlled , will induce to decrease the NO, quantity formed in burning process. But there are some problems with the method of burning add water in cylinder. For one thing, it is to insure that lubricant film shouldn't be broken when the water into the cylinder, and there is no abnormal wear. Another, the water quantity into the cylinders must be controlled. It is to make sure the engine works well, and the other emission characteristics are uninfluenced. A water spray system has been designed in this paper. It is proved By the experiment that when the fog is enough thin the saturated air in the scavenge box could form in a short time even the condition in lower temperature. And also the spray system can avoid the water the direct entering the air cylinder. There are some characteristics of lower power consumption, good fog effect, operation and maintenance simple etc. It attains to expect the result in experiments. Due to the simulation calculating add water in diesel spirit process is substantially to make use of that the water in humidity could imbibe a lot of heat in the fuel burning process in the cylinders. It makes the temperature lowering in the fuel burning period in the cylinder, then the speed of forming NO, decreases. In imitate born process in NO,, multi-area burn model with combination radiates to transmit heat the model were applied in the program of calculation. It avoids the calculation error because of excessive simplify and suppose boundary temperature conditions in the cylinder wall. The imitation is more near to the reality. Due to some research reports, the high temperature space (over 1200K) is the mainly forming NO, region, therefore the computation of the lower temperature processes of after expand and exhaust is neglected, so that the compute program is simplified and the constringency of the calculating speed up. The calculation result is basic to match the actual condition. We used the program to calculate the NO produced from the MAN- B&W 4 stroke marine diesel. When the diesel engine run under the MaximumContinuance Rate (MCR), the NO conduct quantity from the diesel engine can reduce roughly 12% increasing the humidity inlet air to the cylinders from 30% to 100%.In order to further make sure the possibility of the method of reducing NOx emission by spray water in scavenge box 4 stroke marine diesel, we first time made experiments in the laboratory in which there is a perfect marine power unit. Experiment results prove that the NOx emission can be controlled effectively by means of spray water in scavenge and under the MCR the diesel engine NOx emission and can reduce 13%. In the experiment, the engine run very well and the emission characteristics had no any bad change. Otherwise at the same power/rpm, the exhaust temperature and maximum pressure of each cylinder of the engine lowered a little after spray water in scavenge box. Reason out from here, the decrease NOx emission method of the spraying in scavenge box is not effect the engine power, dependability and life. -It is able to be use in current marine turbo-charge diesel .engines as long as the fog state and the water flow can be controlled appropriately.