Reservoir (G)

Boundary conditions for gas network at constant or time-varying pressure and temperature

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Libraries:
Simscape / Foundation Library / Gas / Elements

Description

The Reservoir (G) block sets boundary conditions in a gas network. The volume of gas inside the reservoir is assumed infinite. Therefore, the flow is assumed quasi-steady. Port A, a gas conserving port, represents the reservoir inlet.

Gas enters and leaves the reservoir at the reservoir pressure, but its temperature is determined by the direction of gas flow. If gas flows into the reservoir, its temperature is determined by the gas network upstream. The reservoir acts as a heat sink. If gas flows out of the reservoir, its temperature equals that of the reservoir. The reservoir acts as a heat source. You specify the reservoir pressure and temperature with block parameter values or physical signals.

This block also functions as a reference point for pressure and temperature measurements in a gas network. These measurements are relative to the reservoir pressure and temperature, respectively. Connect the reservoir inlet to port B of a Pressure and Temperature Sensor (G) block to measure relative pressure and temperature of a node connected to the A port of the sensor.

Assumptions and Limitations

• Gas in the reservoir is quasi-steady.

Examples

Pneumatic Actuation Circuit

How the Foundation Library gas components can be used to model a controlled pneumatic actuator. The Directional Valve is a masked subsystem created from Variable Local Restriction (G) blocks to model the opening and closing of the flow paths. The Double-Acting Actuator is a masked subsystem created from Translational Mechanical Converter (G) blocks to model the interface between the gas network and the mechanical translational network.

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Pneumatic Motor Circuit

How a pneumatic vane motor can be modeled using the Simscape™ language. The Pneumatic Motor component is built using the Simscape Foundation gas domain. It inherits from the foundation.gas.two_port_steady base class, which contains common equations that implement the upwind energy flow rate and the gas properties at the ports. The Pneumatic Motor subclass implements equations that describe behaviors specific to the component, such as the motor torque and flow rate characteristics and the mass and energy balance. The Pneumatic Motor block is inserted into the model using the Simscape Component block without the need to generate a separate library.

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Choked Flow in Gas Orifice

The choking behavior of a gas orifice modeled by the Local Restriction (G) block. The Controlled Reservoir (G) blocks are used to set up controlled pressure and temperature boundary conditions from the Reservoir Inputs subsystem to test the gas orifice.

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Ports

Input

P — Pressure control signal, Pa

physical signal

Physical signal port that provides the reservoir pressure control signal.

Dependencies

To enable this port, select Provide input signal for pressure.

T — Temperature control signal, K

physical signal

Physical signal port that provides the reservoir temperature control signal.

Dependencies

To enable this port, select Provide input signal for temperature.

Conserving

A — Reservoir inlet

gas

Gas conserving port associated with the reservoir inlet.

Parameters

Provide input signal for pressure — Method to specify pressure

off (default) | on

Method to use to specify the pressure in the reservoir. If you clear this check box, the block models pressure based on the value of the Reservoir pressure parameter or atmospheric pressure. If you select this check box, the block models pressure based on the value of the signal at port P.

Reservoir pressure specification — Select specification method for reservoir pressure

Atmospheric pressure (default) | Specified pressure

Select a specification method for the reservoir pressure:

• Atmospheric pressure — Use the atmospheric pressure, specified by the Gas Properties (G) block connected to the circuit.

• Specified pressure — Specify a value by using the Reservoir pressure parameter.

Dependencies

To enable this parameter, clear the Provide input signal for pressure check box.

Reservoir pressure — Pressure in the reservoir

0.101325 MPa (default)

Enter the desired pressure in the reservoir. This pressure remains constant during simulation.

Dependencies

To enable this parameter, clear the Provide input signal for pressure check box and set Reservoir pressure specification to Specified pressure.

Provide input signal for temperature — Method to specify reservoir temperature

off (default) | on

Method to use to specify the temperature in the reservoir. If you clear this check box, the block models temperature based on the value of the Reservoir temperature parameter. If you select this check box, the block models temperature based on the value of the signal at port T.

Reservoir temperature — Temperature in the reservoir

293.15 K (default)

Enter the desired temperature in the reservoir. This temperature remains constant during simulation.

Dependencies

To enable this parameter, clear the Provide input signal for temperature check box.

Cross-sectional area at port A — Area normal to flow path at the reservoir inlet

0.01 m^2 (default)

The cross-sectional area of the reservoir inlet, in the direction normal to gas flow path.

Inputs outside valid range — Action to take when signal values are outside of valid range

Warn and limit to valid values (default) | Limit to valid values | Error

Action for the block to take when the input signal values are outside of valid range:

• Limit to valid values ― The block limits the input signal to the minimum or maximum valid values, but does not issue a warning.

• Warn and limit to valid values ― The block issues a warning and limits the input signal to the minimum or maximum valid values.

• Error ― Simulation stops with an error.

Dependencies

To enable this parameter, select at least one of these check boxes:

• Provide input signal for pressure

• Provide input signal for temperature

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2016b

R2026a: Model a controlled reservoir

The Controlled Reservoir (G) and Reservoir (G) blocks have been combined into the Reservoir (G) block. Select the Provide input signal for pressure and Provide input signal for temperature check boxes to control the reservoir conditions by using input signals. Otherwise, you can control the reservoir conditions by using the block parameters.

If you use a Controlled Reservoir (G) block in your custom composite components, you must update the composite component code:

• Old syntax: source = foundation.gas.elements.controlled_reservoir;

• New syntax: source = foundation.gas.elements.reservoir;