| Roadheader is the main equipment of mechanized coal excavation, but the existing machine relies solely on pick to cut coal rock. When cutting hard coal rock, roadheader cannot provide enough power, besides, the cutting process produces a lot of dust and spark, which is bad to safety production. In order to solve these problems, some scholars have proposed some ideas of high pressure water jet assisted cutting. This technology can help pick cut hard coal rock, reduce wear and extinguish sparks, which have good market prospects. But current research on the high pressure water jet assisted cutting focuses on the configuration of single tooth and jet without using the specific background of machinery, which limits the application and promotion of the technology. In order to use and develop this existing theoretical result, the high pressure water jet is applied to the roadheader. The roadheader cutting unit assisted with high pressure water jet is designed based on the applying working condition, and based on which the dynamics theory, simulation and experimental studies are carried on.The cutting unit structure form of roadheader with high pressure water jet is determined based on the design methodology and the idea of function and the key components of the cutting unit are designed in detail. The number and location of nozzles are studied in theory, generally 8~13 nozzles can be arranged preferential on the top of cutting head when the pressure reaches 40 MPa. In order to gain the minimum volume and maximum transmission efficiency, the value of parameters are optimized with multi-objective optimization method by the function of fgoalattain in Matlab.The load on the cutting unit is studied in theory, in which the high pressure water jet assisted coefficient sk is introduced to define the formula of single tooth load, and then to get the three-axis force and torques on the cutting head. Dynamic models about the lifting, rotating, drilling and torsion of the cutting unit action were established based on the second kind of Lagrange equation. The theoretical analyses of dynamic models obtain the response functions of equations in harmonic excitation and provide a theoretical basis for further research about random loading external incentives.The dynamics simulations in no-load and constant torque verify the correctness of the dynamic model. The variable-load dynamics simulation without water shows that the vibration of the cutting head mainly affected by the external load, reducer affected mainly by the internal drive, and connecting frame mainly affected by the rotation of the motor. The variable-load dynamics simulation with water assisted shows that it can be able to ameliorate the vibration of the cutting unit.The experiment about leakage and temperature rise of rotating seals show that the life of O-rings is 5.7 hours, the life of glyd ring and storage spring ring are more than eight hours, and the temperature stabilized at work were 24 ℃, 23 ℃ and 20 ℃. Cutting experiment of single pick with high pressure water jet shows the presence of the threshold pressure with water jet assisted cutting, which is about 2~3 times to the compressive strength of the rock. Front jet assisted is better than rear jet, but rear jet has a better effect on cross section groove. The combined jet breaking method is proposed, which is proved effectively in the experiments. The value of high pressure water jet assisted coefficient sk in different conditions is fitted in graphs according to the rate of force reduce based on the experiment. Experiment of cutting head with high pressure water jet shows the vibration signal’s maximum, mean and standard deviation is lower than the condition without water jet assistance, which proves that the high pressure water jet plays positive role in reducing vibration of cutting head. |
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