代写MENG 4019 - Practical 5 – 2022调试数据库编程

MENG 4019 - Practical 5 – 2022

Task: design and simulate the operation of  a hydraulic curcuit. Activate the thermal option, monitor and control the thermal regime

First, we build the conceptual circuit, introducing a few hydraulic resistances and different paths for the oil to flow:

1.    Open Automation studio, select and insert the following components from the Hydraulic set of components.

2.    Connect all elements as shown below and check all is connected correctly it works. We are interested in studying the thermal effects, so the circuit will not be set for other tasks:

3.   To determine the thermal regime, we can use thermometers. An alternative is using the node Dynamic Measuring Instruments:

4.   The usual linking of the thermometers does not work well:

5.    From Simulation Options in the Simulation menu, Activate the Thermal Evolution in the Fluid Simulation tab

6.    Set the thermometers to directly connect with the measuring points

7.    Run the simulation

We see that the thermal option works, the temperature increases. The max power for the default values (120 l/min = 0.002 m3/s, at 80 bar) means a heating power of 16 kW.

8.    We can change the reservoir with a multi-port reservoir, to have a better control of the ports:

9.    Running the simulation, we realise that something is not quite right. The temperature increases, then reaches a plateau. Examining the results, we can see that the oil enters the circuit at 25 deg C, which means that the thermal inertia of the reservoir is unrealistic. On the other hand, we see that the two major resistances – the orifice and the variable relief valve – have a temperature increase, as expected. Settings below: relief valve: 250 bar (to protect the pump and circuit), the variable relief valve 80 bar and 3.5 mm orifice opening

10.  If we check the reservoir properties, we see that the infinite volume option is true. This is not realistic, so we set the option to false and the volume of the reservoir at 150 l

11. We see that the temperature starts rising in the whole circuit

12. The temperature increases fast if we change the settings of the variable relief valve to 200 bar, displacement to 200 cm3/rev:

13.   If we leave it too long, we see that the system evolves towards destruction:

14. We need to provide a means to cool the circuit. We insert a cooler and a valve, plus a couple of thermometers:

The oil returns to the reservoir until it reaches the desired temperature, when, by switching the valve, we can direct the oil through the cooler

15. We run the circuit to check all is correct. Because the cooler is off-line (oil diverted directly to the reservoir), the temperature in and out of the cooler is 25 deg C, which is the default temperature for simulation

16.  Running the oil through the cooler seems to work, but it is not much help

17. We need to set the parameters of the cooler. With the last settings, we have a flow of 240 l/min at 200 bar, with the return of the oil at atmospheric pressure. This means that the circuit needs to dissipate 80 kW

The cooler has a switching temperature of 50 deg C and a deactivation temperature of 40 deg C We set the maximum dissipation from 2 to 100 kW

18.  Even with the max dissipation set, the results are not much better. We can adjust the valve details to indicate correct flow:

19.  We need to set the folowing characteristics of the dissipation curves:

20. We check if it works. Below 50 deg C - the switching temperature – the cooler is not active. This is normal:

21.

22. Running for a long time, we see that the temperature reaches a plateau and stops increasing

23. To note – real systems

- are generally less thermally stressed – this circuit was set to produce and dissipate 80 kW of thermal power. This is highly unusual in practice, as sytems are designed (and optimised) for the task they need to fulfill

- dissipate extra heat to the atmosphere – the piping, various components, pump, etc. we did not set this, but it is possible

Save the circuit. Explore alternatives. Add functionality and test. Document your work.