Research And Design On Oil Mist Detector Of Marine Diesel Engine Crankcase

Due to high thermal efficiency, excellent economy and easy start, diesel engine is adaptive to various kinds of ships and was used as propulsion power since the end of19th century. To1950s, steam engine has almost replaced by diesel engine in newly built ships. Marine diesel engine has become the main power of civilian ships, medium-sized ships and conventional submarine.Diesel engine is the most important apparatus in the ship. The evaporation of lubricating oil will produce oil gas with high temperature due to mechanical friction and local heating in long-time work. If this lasts for too long, the concentration of the oil mist in crankcase will then rise and the excessive concentration could become a hidden danger of explosion. Such explosion may cause financial loss and casualties. Therefore, much attention has been drawn to the method of detecting the concentration of oil mist in crankcase all over world.The detector of the concentration of oil mist in crankcase is a important guarantee for the safe work of diesel engine. There are currently some kinds of detectors, but they have similar working principle. Detection precision and level of automation are higher and higher since the first detector come out. Though there are some mature products in foreign countries, rare research was conducted in China.This thesis first analyses basic principles of several oil mist detection methods and then their advantages, disadvantages and feasibilities. An oil mist detection apparatus with waning function was designed (including hardware and software) in consideration of various aspects.The main work which has been finished in this thesis is as follows:1) Analyzed the reason that caused the concentration higher of the crankcase oil mist density, and then researched some OMDs used in marine diesel engine;2) Analyzed the methods of oil mist density detection, and compared their advantages, disadvantages, and presented a more feasible and more project based on these methods;3) Completed the hardware designs,including signal acquisition circuit, date processing circuit, power supply circuit, communication design,alarming and displaying section, etc; Completed the human-machine interface, the function of communication between man and machine was accomplished;4) Finally made some analysis based on the experiment, the results basically meets the requirements.