Couplings speed variation

Speed variation through variable-speed fluid couplings... 

Figures 8.7(a) and (b) illustrate variable-speed couplings which can provide a stepless speed variation over a wide range. The impeller and runner of the couplings are housed in a stationary housing with a built-in oil sump. Oil is...

Most turbines have relatively long bearing spans and highly flexible shafts. These factors, coupled with variations in process flow conditions, make turbine rotors highly susceptible to shaft deflection during normal operation. Typically, turbines operate in either the second or third mode and should have narrowbands at the second (2x) and third (3x) harmonics of shaft speed to monitor for mode shape. 

Note. Rigid couplings are not designed to absorb variations in torque and speed and should not be used in such applications. Maximum in-service coupling speed should be at least 15% below the maximum coupling speed rating. 

Speed variation Variation in speed equates to a corresponding variation in torque. Most variable-speed applications require some type of flexible coupling capable of absorbing these torsional variations. 

Hydraulic or electric couplings can be used to obtain speed variations. This is not a popular method because of severe coupling efficiency penalties throughout the range of operation. 

As the experiments were carried out on a single cylinder engine it was important to monitor the speed variation of the camshafts. A 720 pulse per revolution optical encoder was fitted via a bellows flexible coupling to the belt drive end of the crankshaft to measure crankshaft and thus the camshaft speed as the speed ratio is 2 1. The encoder index signal was used to synchronise the reading of camshaft torque with crank angle. 

Figure 6.52 An approximate iliustration of p and loss variation, with change in speed in a variable-speed fluid coupling...

Variations in required speed or speed increase or decrease from the driver may be handled by gear boxes, belt or chain drive, magnetic drive, magnetic or fluid couplings, or variable-speed motors. 

Gear couplings When properly installed and maintained, gear-type couplings do not generate a unique forcing function or vibration profile. However, excessive wear, variations in speed or torque, or over-lubrication results in a forcing function. 

Jackshafts Some machine-trains use an extended or spacer shaft, called a jackshaft, to connect the driver and a driven unit. This type of shaft may use any combination of flexible coupling, universal joint, or splined coupling to provide the flexibility required making the connection. Typically, this type of intermediate drive is used either to absorb torsional variations during speed changes or to accommodate misalignment between the two machine-train components. 

The model immunoassay is the enzyme-linked immunosorbent assay (ELISA) in which a non-specific capture antibody is bound to a surface, such as a multi-well plate or small tube [13]. In the basic form of ELISA, a second antibody tagged with an enzyme interacts specifically with the analyte. The enzyme assay produces a colored product that is read with a spectrophotometer. There are many variations on the basic immunoassay format that serve to increase sensitivity, specificity, linear range, and speed. Many commercial instruments have been developed to take advantage of various technologies for reporter molecules. The immunoassay may be coupled to an electronic sensor and transducer, such as a surface acoustical wave (SAW) sensor. Electrochemiluminescence (ECL) is a method in which the detector antibody is tagged with a ruthenium-containing chelate [13-15]. When the tag is... 

In addition to the high-pressure assembly, the modified system incorporates a new real-time data collection system coupled with a PC based computer. Experimental parameters, such as the valve firing sequence and the reactor temperature-control program, can be set from the computer. Reactants are introduced through two high-spe pulse valves or two continuous feed valves that are fed by mass flow controllers. In high-speed transient response experiments, the QMS is set at a particular mass value and the intensity variation as a function of time is obtained. In steady-flow experiments. 

For steady-state analysis (i.e., no time variation) the coupled system is essentially elliptic, with some hyperbolic characteristics. The continuity equation alone is clearly hyperbolic, having only first-order derivatives. That is, it carries information about velocity from an inlet boundary, across a domain, to an outlet boundary. By itself, the continuity equation has no way to communicate information at the at the outlet boundary back into the domain. Based on the second-derivative viscous terms, the momentum equation is elliptic in velocity. However, because it is first order in pressure, there is also a hyperbolic character to the momentum equation. Moreover the convective terms have a hyperbolic character. There are situations, for example in high-speed flow, where the viscous terms diminish or even vanish in importance. As this happens, and the second-derivative terms become insignificant relative to the first-derivative terms, the systems changes characteristics to hyperbolic. 

Similarly, when values of a, kija, and k(/i are known for the packed column, the variations in and k can be determined as functions of the respective flow rates and Mg, as discussed in Section IV,A. Various stirring speeds for each phase in the laboratory model can then be related to the phase flow rates (in the packed column) which have, respectively, identical ki and kc, as outlined in Fig. 34. Thus pairs of values ofi/ and Uq are simulated by each couple Nl and Nq. 

---