Fault Diagnosis Research Of Diesel Engine Moving Parts

As an improtant power plant,diesel engine plays a significant role in military affairs,transportation and industry.Due to running with superpower and high load,lots of faults are located on engine's moving parts.Researching the mechanisms of moving parts faults and getting their characteristic signals lead to realizing on-line condition monitoring and fault diagnosis of diesel engine.The crank-link mechanism made up of piston,link and crankshaft are principal moving parts of diesel,this paper has done mechanism analysis and experiment research on their typical faults,including scuffing,piston-slap,striking cylinder,bearings' abnormal clearance and bolt crack of connecting rod,the results can provide the basis for actual engineering problems.Having analyzed the mechanisms of scuffing,piston-slap and abnormal clearance of conrod bearing using muti-body dynamics simulation software,the characteristic signals of these faults were obtained.The piston will be impacted at TDCs and BDCs when scuffing fault occurs due to huge friction force reversing;the piston will slap the cylinder liner when its side thrust force reverses direction,then the cylinder block vibrates heavily;conrod force reversing and explosion pressure in cylinder will make conrod knock on the pins,generating impulse signals.Misfire,striking cylinder,conrod bolt crack,abnormal connecting rod bearing clearance as well as abnormal vavle clearance have been studyed on hypostatic diesel engine and the fault features in regard to cylinder head vibration with instantaneous speed have been captured.The impulse at firing phase disappears and intantaneous speed fluctuates in misfire conditon;Larger impulses appear at TDCs and intantaneous speed shakes in cylinder striking condition;Characteristic signal of connecting rod bolt crack is similar to striking's;Reversing impact signals appear when connecting rod bearing clearance gets abnormal;Hard vavle landing's amplitude and phase will vary when vavle's clearance becomes abnormal.All the characteristic signals are in accord with theoretical analysis.