How Does A High-Pressure Fluid Injection Pump Interact With A Laboratory Hydraulic Press In Htm Experiments?

In Hydro-Thermal-Mechanical (HTM) experiments, the high-pressure fluid injection pump acts as the precise controller of internal pore pressure, while the laboratory hydraulic press applies external mechanical stress. The injection pump maintains specific fluid boundary conditions—such as a constant 10 MPa—working in coordination with the press to simulate the migration of fluids through micro-cracks within a rock mass under load.

The core value of this interaction lies in the separation of variables: the hydraulic press simulates the weight of the earth (overburden stress), while the injection pump simulates groundwater behavior (pore pressure). This decoupling allows for the precise measurement of how temperature and stress independently or jointly affect fluid flow and rock permeability.

The Mechanics of the Interaction

Establishing Boundary Conditions

The primary function of the constant pressure injection pump is to establish and maintain fluid boundary conditions.

By setting a specific parameter, such as 10 MPa pore water pressure, the pump ensures a consistent internal environment regardless of external changes. This stability is essential for isolating fluid behavior from mechanical deformation data.

Coordinated Stress Application

While the injection pump handles the fluid, the laboratory hydraulic press manages the mechanical load.

Often equipped with a dual-acting pump, the press provides a rapid advance of the ram followed by a high-pressure, low-volume output. This allows the system to hold mechanical pressure on the sample for extended periods, creating a stable "container" for the fluid injection process.

Simulation of Micro-Crack Migration

The interaction between the two systems enables the realistic simulation of fluid migration.

As the press applies stress, it modifies the geometry of micro-cracks within the rock mass. The injection pump then forces fluid through these altering pathways, allowing researchers to observe how mechanical closure or opening of cracks affects flow rates.

Analyzing Multi-Field Coupling Effects

Thermal Impacts on Fluid Dynamics

The system allows for the quantitative analysis of temperature-dependent variables.

Researchers can track how temperature changes affect the dynamic viscosity of the fluid. Because the injection pump offers precise control over flow rate and pressure, these viscosity shifts can be measured accurately rather than estimated.

Pressure Gradient Distribution

The setup is critical for observing the temperature-carrying effect.

As heated fluid moves through the rock, it alters the pressure gradient distribution. The coordinated data from the pump (flow/pressure) and the press (stress/strain) reveals how thermal energy propagates through the rock matrix alongside the fluid.

Understanding the Operational Trade-offs

Complexity of Dual-System Control

Running two high-pressure systems simultaneously introduces significant control complexity.

Any fluctuation in the hydraulic press (mechanical load) can instantly alter the volume of the sample, causing immediate pressure spikes or drops in the injection pump system. Operators must ensure rigid synchronization to prevent data noise.

Long-Duration Stability

While laboratory presses are capable of holding pressure for extended periods, seal integrity becomes a challenge during long HTM experiments.

The combination of high temperature, high fluid pressure, and high mechanical stress places immense strain on seals. A minor leak in the injection circuit can be misinterpreted as fluid migration into the rock, skewing permeability results.

Making the Right Choice for Your Experiment

If your primary focus is Permeability Evolution: Ensure your injection pump has a highly sensitive flow meter to detect minute changes in viscosity and flow rate as the press alters the crack geometry.
If your primary focus is Mechanical Deformation: Prioritize a press with a high-precision dual-acting pump to ensure the mechanical confinement remains absolutely static, regardless of internal pore pressure buildup.

Success in HTM coupling experiments relies not just on the quality of individual components, but on the precise synchronization of mechanical confinement and fluid injection control.

Summary Table:

System Component	Primary Role in HTM Coupling	Key Control Parameter
Laboratory Hydraulic Press	Simulates overburden stress/mechanical load	Mechanical stress & axial strain
Injection Pump	Simulates pore pressure & groundwater behavior	Fluid boundary conditions & flow rate
Dual-Acting Pump	Ensures long-duration pressure stability	System confinement & volume output
Rock Sample	Acts as the porous medium for coupling	Permeability & micro-crack geometry

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References

Dianrui Mu, Junjie Wang. A coupled hydro-thermo-mechanical model based on TLF-SPH for simulating crack propagation in fractured rock mass. DOI: 10.1007/s40948-024-00756-y

This article is also based on technical information from Kintek Press Knowledge Base .