A viscometer is an instrument used to measure the viscosity of a fluid. For liquids with viscosities which vary with flow conditions, an instrument called a rheometer is used. Thus, a rheometer can be considered as a special type of viscometer. Viscometers can measure only constant viscosity, that is, viscosity that does not change with flow conditions.
A bearing is a machine element that constrains relative motion to only the desired motion, and reduces friction between moving parts. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Most bearings facilitate the desired motion by minimizing friction. Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads (forces) applied to the parts.
A magnetic bearing is a type of bearing that supports a load using magnetic levitation. Magnetic bearings support moving parts without physical contact. For instance, they are able to levitate a rotating shaft and permit relative motion with very low friction and no mechanical wear. Magnetic bearings support the highest speeds of any kind of bearing and have no maximum relative speed.
A brushless DC electric motor (BLDC), also known as an electronically commutated motor, is a synchronous motor using a direct current (DC) electric power supply. It uses an electronic controller to switch DC currents to the motor windings producing magnetic fields which effectively rotate in space and which the permanent magnet rotor follows. The controller adjusts the phase and amplitude of the DC current pulses to control the speed and torque of the motor. This control system is an alternative to the mechanical commutator (brushes) used in many conventional electric motors.
Balance shafts are used in piston engines to reduce vibration by cancelling out unbalanced dynamic forces. The counter balance shafts have eccentric weights and rotate in opposite direction to each other, which generates a net vertical force.
Engine balance refers to how the forces are balanced within an internal combustion engine or steam engine. The most commonly used terms are primary balance and secondary balance. First-order balance and second-order balance are also used. Unbalanced forces within the engine can lead to vibrations.
Condition monitoring is the process of monitoring a parameter of condition in machinery, in order to identify a significant change which is indicative of a developing fault. It is a major component of predictive maintenance. The use of condition monitoring allows maintenance to be scheduled, or other actions to be taken to prevent consequential damages and avoid its consequences. Condition monitoring has a unique benefit in that conditions that would shorten normal lifespan can be addressed before they develop into a major failure. Condition monitoring techniques are normally used on rotating equipment, auxiliary systems and other machinery like belt-driven equipment,, while periodic inspection using non-destructive testing (NDT) techniques and fit for service (FFS) evaluation are used for static plant equipment such as steam boilers, piping and heat exchangers.
A cycloidal drive or cycloidal speed reducer is a mechanism for reducing the speed of an input shaft by a certain ratio. Cycloidal speed reducers are capable of relatively high ratios in compact sizes with very low backlash.
On a helicopter, the main rotor or rotor system is the combination of several rotary wings with a control system, that generates the aerodynamic lift force that supports the weight of the helicopter, and the thrust that counteracts aerodynamic drag in forward flight. Each main rotor is mounted on a vertical mast over the top of the helicopter, as opposed to a helicopter tail rotor, which connects through a combination of drive shaft(s) and gearboxes along the tail boom. The blade pitch is typically controlled by the pilot using the helicopter flight controls. Helicopters are one example of rotary-wing aircraft (rotorcraft). The name is derived from the Greek words helix, helik-, meaning spiral; and pteron meaning wing.
In solid mechanics, in the field of rotordynamics, the critical speed is the theoretical angular velocity that excites the natural frequency of a rotating object, such as a shaft, propeller, leadscrew, or gear. As the speed of rotation approaches the object's natural frequency, the object begins to resonate, which dramatically increases system vibration. The resulting resonance occurs regardless of orientation. When the rotational speed is equal to the numerical value of the natural vibration, then that speed is referred to as critical speed.
Rotordynamics, also known as rotor dynamics, is a specialized branch of applied mechanics concerned with the behavior and diagnosis of rotating structures. It is commonly used to analyze the behavior of structures ranging from jet engines and steam turbines to auto engines and computer disk storage. At its most basic level, rotor dynamics is concerned with one or more mechanical structures (rotors) supported by bearings and influenced by internal phenomena that rotate around a single axis. The supporting structure is called a stator. As the speed of rotation increases the amplitude of vibration often passes through a maximum that is called a critical speed. This amplitude is commonly excited by imbalance of the rotating structure; everyday examples include engine balance and tire balance. If the amplitude of vibration at these critical speeds is excessive, then catastrophic failure occurs. In addition to this, turbomachinery often develop instabilities which are related to the internal makeup of turbomachinery, and which must be corrected. This is the chief concern of engineers who design large rotors.
Tire balance, also called tire unbalance or tire imbalance, describes the distribution of mass within an automobile tire or the entire wheel on which it is mounted.
A centrifugal fan is a mechanical device for moving air or other gases in a direction at an angle to the incoming fluid. Centrifugal fans often contain a ducted housing to direct outgoing air in a specific direction or across a heat sink; such a fan is also called a blower, blower fan, or squirrel-cage fan. Tiny ones used in computers are sometimes called biscuit blowers. These fans move air from the rotating inlet of the fan to an outlet. They are typically used in ducted applications to either draw air through ductwork/heat exchanger, or push air through similar. impellers. Compared to standard axial fans, they can provide similar air movement from a smaller fan package, and overcome higher resistance in air streams.
The Bölkow Bo 46 was a West German experimental helicopter built to test the Derschmidt rotor system that aimed to allow much higher speeds than traditional helicopter designs. Wind tunnel testing showed promise, but the Bo 46 demonstrated a number of problems and added complexity that led to the concept being abandoned. The Bo 46 was one of a number of new designs exploring high-speed helicopter flight that were built in the early 1960s.
The exoskeletal engine (ESE) is a concept in turbomachinery design. Current gas turbine engines have central rotating shafts and fan-discs and are constructed mostly from heavy metals. They require lubricated bearings and need extensive cooling for hot components. They are also subject to severe imbalance that could wipe out the whole rotor stage, are prone to high- and low-cycle fatigue, and subject to catastrophic failure due to disc bursts from high tensile loads, consequently requiring heavy containment devices. To address these limitations, the ESE concept turns the conventional configuration inside-out and utilizes a drum-type rotor design for the turbomachinery in which the rotor blades are attached to the inside of a rotating drum instead of radially outwards from a shaft and discs. Multiple drum rotors could be used in a multi-spool design.
The yaw system of wind turbines is the component responsible for the orientation of the wind turbine rotor towards the wind.
Industrial agitators are machines used to stir or mix fluids in industries that process products in the chemical, food, pharmaceutical and cosmetic industries. Their uses include:
The balancing of rotating bodies is important to avoid vibration. In heavy industrial machines such as gas turbines and electric generators, vibration can cause catastrophic failure, as well as noise and discomfort. In the case of a narrow wheel, balancing simply involves moving the center of gravity to the centre of rotation. For a system to be in complete balance both force and couple polygons should be close in order to prevent the effect of centrifugal force. It is important to design the machine parts wisely so that the unbalance is reduced up to the minimum possible level or eliminated completely.
Rotating unbalance is the uneven distribution of mass around an axis of rotation. A rotating mass, or rotor, is said to be out of balance when its center of mass is out of alignment with the center of rotation. Unbalance causes a moment which gives the rotor a wobbling movement characteristic of vibration of rotating structures.
Air bearings are bearings that use a thin film of pressurized gas to provide a low friction load-bearing interface between surfaces. The two surfaces do not touch, thus avoiding the traditional bearing-related problems of friction, wear, particulates, and lubricant handling, and offer distinct advantages in precision positioning, such as lacking backlash and static friction, as well as in high-speed applications. Space craft simulators now most often use air bearings and 3-D printers are now used to make air-bearing-based attitude simulators for CubeSat satellites.
