Research On The Action Of Foreign Object Damage Of High Speed Rotating Blade

The blades of impeller machinery with high rotating speed are often damaged by foreign objects such as metal,sandstone,hailstone,which are ingested with airflow. It can lead to a degradation in the machine's performance and affect its normal working, even cause catastrophic accidents.According to the research findings of foreign objects damage(FOD) of blades on experiments and numerical analysis, analysis for the FOD of blades under various impact conditions is conducted by using the advanced computing techniques and analytical procedures. These impact conditions include various shapes and materials of foreign objects,motion and structural prestress of blades. The present dissertation aims at exploring a suit of integrated and systematic method for FOD of blades, and obtaining some useful conclusions, thus offering an important reference for the investigation of anti-impacting damage of blades under foreign object damage and structure optimization of blades.Firstly,the experiment for the steel sphere impacting on the leading edge of flat blade is simulated in the LS-DYNA.It provides reliable correlative parameters for the following analysis.Dynamic analysis for the leading edge of blades impacted with foreign objects with different shapes and static calculation for residual stress of the blades after impacting are done by combining Explicit and implicit analysis. An analysis based on energy method and the theory for plate and shell is conducted to explain the influence of blade's curvature on the impact damage characteristics. It emphasizes on the relationship between blade's deformation energy and its curvature.Cantilever panels with different curvature radii are used to simulate blades to investigate the foreign objects damage characteristics of impacting on the convex sides and concave sides of blades with different curvature radii. And some rules on the effects of blade curvature on the characteristics of foreign objects damage are obtained.The energy balance model, elastic stress wave propagation and the fundamental hydrodynamics are respectively used to analyse the impact load for hard body, hyperelastic soft body and plastic soft body impacting on the blades.Hyperelastic soft body(rubber) and plastic soft body(gelatine) impacting on the rigid walls are analysed by numerical simulation. The two kinds of soft bodys impacting on the leading edges of blades are also simulated.The results suggest the two kinds of soft bodys are sliced by blades during impacting.And the impact damage for blade caused by rubber impacting is greater than the one caused by gelatine impacting under the same impacting conditions. With the same initial impacting energy and impacting angle, sandstone, rubber and gelatine,which are respectively considered as hard body, hyperelastic soft body and plastic soft body, are used to analyze foreign objects damage of blades. And rules for impacting characteristics of blades under different material objects impacting are gained. Modal analysis for blades before and after different material foreign objects damage is conducted through the method for explicit algorithmic switch to implicit algorithmic. The results indicate that natural frequencies of the blade are more influenced by the foreign objects damage,but the mode shapes are less influenced.Variety and the producing sequence of stress wave in the blade during impacted by foreign objects are investigated by using stress wave theory for Lamb's problem.The possible damage to the blade caused by stress wave are also analyzed. Combined with numerical method, propagation and action characteristics of stress wave are researched.And the effects of impact load and strain rate on the propagation and action of stress wave are also analyzed.The results suggest that different impact load may lead to different crest values and wave lengths of incident wave in the blade. And the existing of strain rate increases the crest values of incident and reflected wave, decrease the attenuation velocity of stress wave.On the basis of theory of non-ideal impacting on the motion target in the terminal ballistics, an analysis model for foreign objects damage of blade with rotating motion is established to study the effects of blade's rotating motion on the foreign objects damage of blade.Nonlinear dynamics model for FOD of blade with structural prestress is founded to analyze the effects of centrifugal prestress on the FOD of blade. And the dynamic relaxation method is used to obtain the initial stress and displacement field of blades in the beginning of the analysis of impacting.Combined with the theory for stress wave, numerical analysis for foreign objects damage of real blade with different rotating speeds is carried out.Then, rules for FOD of blade under different centrifugal loads are acquired.Finally,M20 bolt and rubber debris,which are respectively considered as hard body and soft body,are used to investigate the foreign objects damage of multi-blades with rotating speed.Differences of impacting characteristics between the two kinds of foreign objects are compared.