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In order to improve the impactor performance, the dynamic performance of gas-liquid united hydraulic hammer should be optimized. Based on the analysis of the operating principle for the hydraulic impactor, one simulation model of gas-liquid united hydraulic impactor was built with AMESim software. By setting different simulation parameters, curves of displacement, velocity, acceleration and cavity pressure were obtained under different working conditions. The key component can be obtained by the analysis of activity index. The whole simulation results provide a reliable basis for component selection and parameter optimization of hydraulic impactor.

Hydraulic impactor is the key operating equipment of impact mechanism including hydraulic hammer [

As can be seen in

Based on the assumption of linear model, hydraulic impactor should be firstly linearized and then be studied ideally. According to the linear theory, the system pressure is constant, hydraulic oil is incompressible, viscosity is constant, nitrogen chamber is adiabatics. According to the kinetic balance equation, fluid continuity principle and equation of state of gas, mathematical equation of hydraulic impact mechanism [

1) Piston Dynamics

2) Dynamics Equation of Directional Control Valve

3) Gas State Equation of Nitrogen in The Condition of Adiabatic State [

where, m_{p}, m_{v} are respectively the mass of piston and directional control valve;_{N} is the pressure of nitrogeon chamber; P_{0} is the initial pressure of nitrogeon cavity;_{1}, p_{2}, p_{3} are pressures of front cavity of piston, rear cavity and differential control valve; A_{p}_{1}, A_{p}_{2}, A_{p}_{3} are effective volumes of front piston, rear cavity and nitrogeon chamber; A_{v}_{1}, A_{v}_{2} are effective volumes of front directional control valve, rear cavity; V_{N}, V_{0} are instant volumes when nitrogeon chamber works and initial volumes of nitrogeon chamber.

Based on the working principle of hydyaulic impactor. According to the theory, the system pressure is constant, the model use hydraulic component design (HCD), pneumatic component design (PCD), mechanical library of AMESim software (LMS Imagine. Lab AMESim Rev 13 SL2) to build control model. As showed in

The modeling simulation is followed by the working principle of hydraulic hammer. However, due to the restricton of model library, some parts cannot be applied with the pratical system components. So parts can be replaced and simplified with simple component. The response of the system can be studied via modifying the working parameters in different working conditions. Besides, the model can be applied in the simulation of similar system.

When piston mass is 42 kg, frequency is 35/3 HZ, velocity and displacement curve can be showed in

As showed in

Obviously, input flow of the back cavity is 270 L/min, the output flow of the front cavity is 250 L/min, their flow difference is provided by oil supply system.

1) Mathematical definition of activity index

a) Activity: integration of power that is the component of number i from the submodel, expression is described as follow:

where, the unit of activity is J which describe the energy of assigned component. Because what we consider is the absolute value of power, so it is different from the definition of energy.

b) Activity index: the ratio between activity of submodel and total activity.

2) Analysis of model activity index

The analysis results is showed in

Piston mass | 20 | 30 | 35 | 42 | 50 | 55 | 60 | 65 | 68 | 70 | 75 | 80 |
---|---|---|---|---|---|---|---|---|---|---|---|---|

Impact energy | 320.8 | 379.3 | 392.9 | 395.5 | 430.5 | 443 | 455.7 | 467.7 | 424.7 | 503.7 | 443.9 | 420.2 |

The paper explains the application of AMESim software in the modeling of gas-liquid united hydraulic hammer. Based on the working principle of hydraulic impactor, mathematical model can be built. The data, necessary for constructing models, were obtained from theoretical calculation. The output of the model is a variety of curves considered as main performance indicator. The activity index research provide a theory for simplying model and find out the research priorities, which we can find the fast way to improve the impact energy of the impactor. The reasonable hydraulic impactor model provides a good platform for the impacor character research, and research with respect to compensation flow of impactor, impact rebound, oil return, the holes and so on will be discussed in another paper.

ZishanXu,GuopingYang,HanghangWei,ShutaoNi, (2015) Dynamic Performance Analysis of Gas-Liquid United Hydraulic Hammer. Engineering,07,499-505. doi: 10.4236/eng.2015.78046