Research On The Experimental Recognition Technology Of Exciting Force Extraction From Body Vibration Of Internal Combustion Engine

Control of vibration in internal combustion engine is a hot issue among internal combustion engine design and application. Dynamic analysis and vibration force verification on internal combustion engine both are key segments and bases for vibration control and vibration isolation design in internal combustion engine field. Though, two methods, theoretical computation and experimental strategy, for vibration source acquisition about internal combustion engine are applicable, deviations between them always emerges, however, experimental method is thought to be closer to practical situations and possess direct engineering application value.This subject aims at the recognition of exciting force from the body vibration of an internal combustion engine. With the domestic first use of dual-layer vibration isolation system, the main researches done are as the following:(1) The main vibration sources are verified through theoretical analyses to be3order and6order overturn torque. Reciprocating inertia force (torque) and rotational inertia force (torque) are zero theoretically.(2) A program for vibration force source recognition has been designed according to the theory for exciting force extraction from the body vibration of an internal combustion engine.(3) The deviation of each systematic parameter has been verified through measurements and references. The influence of systematic parameters’(inertia parameters, stiffness, damping, coordinates of center of mass) errors on the accuracy of recognition has been assessed.(4) At last, exciting forcesrecognizing test of has been done over multi-working conditions and multi-test points on a diesel gen set, and the data has been analysed on both time-domain and frequency-domain.Moreover, computations on the recognition of vibration forces from the body vibration test has been accomplished and the investigation of the computation method about vibration force source recognition over multi-working conditions and multi-test points has been investigated, in addition, the verification of the recognizing accuracy has been conducted.(5) Through this research on the experimental recognition technology of the exciting force extraction from the body vibration of an internal combustion engine, the following suggestions have been proposed:multiple test points are applicable in body vibration test given the lack of acknowledge about the vibration isolation system of the diesel gen set and sufficient equipment provision, and the statistical method proposed in this article can be adopted on vibration force recognition, otherwise, the principle of test points arrangement introduced by this article, i.e. arrange3-4points selectively. In addition, it is suggested that the internal combustion engine should be mounted on a solid test rig with huge mass to fulfill rigid body assumption as more as possible, also, test points are suggest to be mounted on the position with greater rigidity so as to avoid interferences such as local vibration and resonance which is responsible for abnormal signals.In conclusion, different combinations would yield different recognition outcomes owing to measurement error, coordinate errors of test points and the complicity of the gen set. To improve the accuracy of recognition when encountering massive test points condition, histogram statistical method has been introduced and this is an extraordinary innovation. The author believed that this method could be adopted and improved in the future practices.