Rotor system

BE-2019 Model based diagnosis of rotor systems in power plants Dr, J, E.T. Penny Univ. Aston Birmingham... 

The prime vendor for the PRT shall perform lateral, torsional, and rotor response to unbalanee analyses of the eomplete rotor system and shall issue reports of these analyses to the Purehaser. 

Any torsional natural frequeney of the rotor system shall not be eloser than 10% to any operating speed (i.e., rated speed). 

In this automatic thrust balancing system, the pressure behind the compressor wheel is controlled to a value between the compressor suction pressure and the wheel peripheral pressure. As the expander inlet pressure increases above the compressor suction pressure level, the resulting thrust force pushes the compressor wheel, and hence the rotor system, towards the compressor suction. In the reverse situation, when the pressure behind the compressor wheel is reduced below the wheel peripheral pressure level, the rotor system moves toward the expander. 

Squeeze film dampers have long been used to combat rotor dynamic and stability problems that conventional bearings cannot solve on turbomachinery rotor systems. The use of squeeze film dampers in problem process machinery has tainted it as a treat-the-symptom solution, and many users shy away from using squeeze film dampers for this reason. Also, their limited use is explained by the difficulty in accurately predicting performance, particularly with o-ring supported dampers. 

Since these seals are an integral part of the rotor system, they affect the dynamic operating characteristics of the machine for instance, both the... 

When the suction pressure was raised by some 50psig (3.45 Bar) while maintaining the same discharge pressure, the unit regained its stability with the elimination of the subsynchronous component as shown in Figure 16-8. The subsynchronous instability in this machine was the result of aerodynamic excitation of the rotor systems occurring at a critical pressure rise across the machine of 770 psi differential (500-1270 psig). 

In a real rotor system the amount and location of unbalances cannot always be found. The only way to detect them is with the study of rotor vibration. Through careful operation, the amount and the phase angle of vibration amplitude can be precisely recorded by electronic equipment. The relation between vibration amplitude and its generating force for an uncoupled mass station is... 

The existence of unbalance in a rotor system may be in continuous form or discrete form, as shown in Figure 17-2. Ascertaining an exact distribution is an extremely difficult, if not impossible, task by today s techniques. 

One is the so-called A-plane approach. This approach states that only A-planes are necessary for a rotor system running over Ncritical speeds. The other technique, called the (N + 2)-plane approach, requires two additional planes. These two additional planes are for the two-bearing system and are necessary in this school of balancing. 

The locations of the critical speeds in the running-speed range for the entire rotor system. 

The overall vibration level on a machine is satisfactory for an initial or rough check. However, when a machine has a seemingly acceptable overall level of vibration, there may be hidden under this level some small levels of vibrations at discrete frequencies that are known to be dangerous. An example of this is subsynchronous instabilities in a rotor system. 

The inventory of these plants can run into over 20,000 items, including over 100 complete rotor systems. The field of spare parts is changing rapidly and is much more complex than in the past. A group of plants have gotten together in a given region and formed Part Banks. ... 

Figure 3-16. Wound-rotor systems (a) rotor power dissipated in resistance (b) rotor power retirement to supply iine [10],...

The MARS Microwave Synthesis System (Fig. 3.12 and Table 3.2) is based on the related MARS 5 digestion instrument and offers different sets of rotor systems with several vessel designs and sizes for various synthesis applications. 

Temperature measurement in the rotor systems is accomplished by means of an immersed fiber-optic probe in one reference vessel or by an IR sensor on the surface of the vessels positioned at the bottom of the cavity. Pressure measurement in HP-... 

Other microwave-assisted parallel processes, for example those involving solid-phase organic synthesis, are discussed in Section 7.1. In the majority of the cases described so far, domestic multimode microwave ovens were used as heating devices, without utilizing specialized reactor equipment. Since reactions in household multimode ovens are notoriously difficult to reproduce due to the lack of temperature and pressure control, pulsed irradiation, uneven electromagnetic field distribution, and the unpredictable formation of hotspots (Section 3.2), in most contemporary published methods dedicated commercially available multimode reactor systems for parallel processing are used. These multivessel rotor systems are described in detail in Section 3.4. 

Similar results were achieved when Biginelli reactions in acetic acid/ethanol (3 1) as solvent (120 °C, 20 min) were run in parallel in an eight-vessel rotor system (see Fig. 3.17) on an 8 x 80 mmol scale [87]. Here, the temperature in one reference vessel was monitored with the aid of a suitable probe, while the surface temperature of all eight quartz reaction vessels was also monitored (deviation less than 10 °C Fig. 4.4). The yield in all eight vessels was nearly identical and the same set-up was also used to perform a variety of different chemistries in parallel mode [87]. Various other parallel multivessel systems are commercially available for use in different multimode microwave reactors. These are presented in detail in Chapter 3. 

To ensure complete conversion for all examples of a 21-member library, irradiation times of 30-60 min were used (Scheme 7.39), employing a multi-vessel rotor system for parallel microwave-assisted synthesis (see Fig. 3.7). The results were confirmed by on-bead FTIR analysis, accurate weight-gain measurements of washed and dried resins, and post-cleavage analysis of the prepared enones. 

A vertically arranged rotor system consisting of protruding arms revolves within a cylindrical chamber fitted with stationary deflector protrusions. The combination of the movable rotor and static protrusions effectively mix the diced rubber feed and solvent by turbulent flow. It is usual to have at least three speed possibilities and thus lump-free preparation of the product is possible in relatively short mixing times. Mixing times for these machines is considerably less than for the Z-blade mixer. 

E.3.3.3 Rotor systems that have low inertia and are subject to accidental unloading should be equipped with a quick-acting brake to prevent damage from overspeed. 

Today s laboratory-scale batch microwave reactors generally offer a maximum batch size of 1 L reaction volume, in most cases divided into several smaller reaction vessels (multivessel rotor systems). According to the definition given at the beginning, this would not exactly match the one vessel ... 

In contrast to single-mode reactors, dedicated multimode instruments allow scale-up to be performed in multivessel rotor systems utilizing various types of sealed vessels. In these systems, reactions can be carried out in batch to synthesize multiple gram quantities (< 250 g) of material in typically up to 1 L processing volume. Most of the multimode instruments available for organic synthesis have been derived from closely related sample preparation equipment [39-41]. The MARS Microwave Synthesis System (Fig. 4) is based... 

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