Study On Tooth Surface Wear Performance Of The Coiled Tubing Injector Head Chain Drive

The chain drive system of the coiled tubing injector head makes the coiled tubing in or out the wellbore,which directly affects the coiled tubing operation capability in oil and gas wells.The downhole operation load of the coiled tubing,the elongation of the chain pitch,the shape of the sprocket tooth profile,etc.which have a significant impact on the stability of the chain drive system and the wear of the sprocket,resulting in a series of engineering problems such as roller breakage,scratch of the push plate,pipe slipping.Therefore,revealing the engage behavior and mechanical behavior of the injector head chain drive chain and sprocket,as well as the wear law and influencing factors of the sprocket tooth surface,which lays a theoretical foundation for the design and safe operation of the injector head.Based on the standard roller chain and sprocket,the engagement and contact mechanics model of the coiled tubing injector head is established to deduce calculation formulas of the contact position between the roller and the tooth surface,the angle of engages in,the angle of exits,the pressure angle,the tension of chain links,and the reaction force of the tooth surface.The parameter d is introduced to simulate the change of sprocket rotation angle when the injector head is working.Combined with the actual working conditions of the injector head,with the chain tight side force as the initial calculation condition and the chain loose side force as the convergence condition,the engagement track between the roller and the tooth surface and the tooth surface support reaction force are calculated by using Matlab software,and the accuracy of the calculation results is verified by the principle of mechanical balance.Based on Hertz contact theory,the change of the contact stress on the tooth surface is analyzed when the roller engages in the sprocket and exits the sprocket.Based on Archard wear model,the variation of tooth surface wear depth with roller engaging trajectory was analyzed,as well as the effects of injector head traction,chain pitch and chain entry angle on tooth surface wear.The research results show that: with the increase of the chain tightening force,the effect on the area of the wear area at the position where the roller engages has little influence,the area of the wear area at the position where the roller exit is significantly reduced,and the peak value of the wear depth of the tooth surface increases;With the increase of the chain pitch elongation,both the engage in position and the exit position of the roller will climb along the direction of the addendum circle,the wear area of the tooth surface will increase,but it will not exceed the working arc of the tooth profile,and the peak wear depth of the tooth surface will increases accordingly;Increasing the chain entry angle has an effect on the number of engagement rollers,which will from 9 teeth engaging at entry angle of 0° to 8 teeth engaging at entry angle of 30°,besides,the wear area of the tooth surface is reduced,but the tooth surface wear depth has little effect.According to the actual size of the injector head,establishing the 3D model of the injector head chain drive in SolidWorks software,and the finite element simulation analysis of the injector head chain drive is analyzed by ANSYS software.The calculation results show that: the calculation values by simulation and Matlab are basically consistent,including roller contact position,tooth surface support reaction,tooth surface contact stress and tooth surface wear volume,thus the accuracy of the theoretical wear model established in this paper is verified.