Mud mixers are widely used in ground mud tanks for drilling fluids. The mud agitator consists of a drive motor (motor), a gear reducer (also called a gearbox), a reducer output shaft, and an impeller. A properly designed mud agitator can suspend all solid particles uniformly, and the shearing effect is appropriate, which is consistent with the drilling fluid mud performance of the entire solid control system and saves power.
Most mud agitators are driven by electric motors. These motors have explosion-proof functions and can be installed horizontally or vertically. The motor may be connected to or mounted directly to a gear reducer, which in turn drives the impeller shaft. The impeller is mounted on a shaft a certain distance from the bottom of the container.
An impeller (also called a turbine) on a mud agitator converts mechanical energy into the motion of a fluid. A lot of research has been done on the impellers of mud agitators and it has been found that each impeller transfers energy to the fluid in two ways: (1) pumping capacity. (2) Shearing ability.
The impeller design of the mud agitator can only improve one of the two capabilities, but not both. The amount of fluid passing through the impeller is his pump displacement, or conveying capacity; Aiyi Machinery has carried out a large number of tests to determine the flow characteristics and capabilities of a specific model and size of impeller, and the shear rate is rarely predicted. The shear rate is considered to be a speed gradient related to distance. The shear rate can be measured at a point from the tip of the mud agitator blade, and the maximum and average values can be calculated. The shear stress is the shear rate. And the viscosity of the fluid. For mud, the shear stress and shear rate are almost the same. However, most drilling fluids are non-Newtonian fluids, so the predictions of experimental and theoretical models are different from the actual situation. The shear rate required by the mud agitator depends on many variables, including the design of the impeller, the distance of the blade end from the tank wall, the baffle, especially the mud concentration, the solid particle size distribution of the mud, the drilling fluid density, plastic viscosity, and static cutting Force, yield value, etc. Aiyi Machinery suggested that the reasonable mixing of drilling fluid components is achieved by the vortex of the fluid in the turbulent zone, which is related to the boundary of the fluid in the mud tank. Therefore, the manufacturing of the mud agitator impeller must be based on a known movement curve.
The construction of the mud agitator impeller depends on the function of the impeller and the geometry of the mud tank. The flow direction of the mud impeller design can be roughly divided into radial flow and axial flow. This can be used to describe the flow pattern of mud in the mud tank. The impeller may burn up to two, but the impellers of mud agitators used in oil fields usually have four or more blades. To meet economic requirements and drilling fluid mud characteristics, mud agitator impellers are usually made of stainless steel or carbon steel. The blades of the mud agitator impeller can be flat (Figure 3), angled (Figure 4), or wavefront (Figure 5). The blades of the mud agitator can be welded to a center disk (Figure 6) or bolted to a patterned plate that is fixed to the disk or connector (Figure 7).
1.Radial flow impeller of mud agitator impeller classification
Radial flow occurs when the mud agitator impeller blade is installed vertically, that is, the impeller blade and the solid axis of the mud agitator are in a straight line (Figure 8). In radial flow, the impeller in the tank is mainly horizontal, The circulation way stirs the mud. Ideally, the mark will move upwards as soon as it touches the wall of the tank and it will always remain evenly suspended in the mud tank. When used alone, the radial flow impeller of the mud agitator should be installed near the bottom of the tank, preferably less than 12 inches (about 30 cm) from the bottom of the irrigation tank. In order to use the top and bottom of the mud tank to mix evenly, the depth of the mud tank must be limited to about 6ft (1.83m). The radial flow liquid flow is installed slightly higher, resulting in two mud movement zones, one on the mud agitator impeller. Above, one below the impeller of the mud agitator, the upper and lower layers share a boundary, thus showing different mixing efficiency. This situation should be avoided and emphasis should be placed on the proper position of the impeller on the solid shaft.
2.Axial flow impeller of mud impeller classification
The blades of the mud agitator have a certain inclination angle towards the bottom of the mud tank. The most typical is 45 to 60 degrees from the vertical direction (see Figure 4). The mud agitator impeller mainly moves in axial flow. Rotating motion of the mud agitator blades also promotes axial flow of the fluid. The axial flow of the slurry agitator impeller is from the tank side of the mud tank, and the tank wall can drive the fluid to move upward and reach the surface of the mud tank slurry. Once here, a cycle is completed, and after it is contained, it restarts. When used alone, the mud agitator impeller is installed 2/3 to 3/4 of the impeller diameter from the bottom of the mud tank. Due to the rotation of the impeller, the mud is still moving in a radial flow in the mud tank. In most cases, the combination of radial and axial movements results in a more complete mixing of the mud. When the depth of the mud tank exceeds 6ft (1.83m), other types of axial flow impellers are required, and two or more impellers are required on each solid shaft.
Most axial-flow slurry agitator impellers have a fixed blade inclination angle (see Figure 4), which makes the blade tip flow more and more toward the center. The power output of this type of slurry agitator is smaller, but Shear force is greater.
3, wave impeller classification of mud agitator impeller
Equipped with a variable pitch mud agitator impeller (see Figure 5), known as contour line or wave surface impeller, it promotes both radial and axial flow types to a higher or lower degree. Compared with the traditional single-sided impeller, the inclination and inclination of the mud agitator impeller determines the smaller shear stress of the mud agitator impeller. The most typical feature of this agitator impeller is that it transmits less shear to the mud Therefore, in order to understand the exact magnitude of the shear force, it is necessary to understand the use of mud tanks . This impeller design approached the aeroplane propeller.