Turbine speed, optimum

Beeause there is eonsiderable design flexibility in aeeommodating optimum turbine speed, standard meehanieal drive steam turbines are often ehosen. The offset aiTangement (Figure 4-41) provides additional freedom for the turboset eomponent layout. 

The control scheme shown in Fig. 17.4 is certainly quite common. But is it the best Figure 17.5 is a copy of the crude charge system in a now-defunct refinery in Port Arthur, Texas. I saw it in operation many years ago. It worked fine. The required flow of crude directly controls the governor. The turbine speed is then always at its optimum. The AP across the process-control valve is always zero, because there is no process-control valve. This design is a direct descendant of the original method of controlling the steam flow to pumps. The steam inlet valve was opened by the operator, so that the desired discharge flow was produced. 

The turbine speed is then always at its optimum. The AP across the process-control valve is always zero, because there is no process-control valve. This design is a direct descendant of the original method of controlling the steam flow to pumps. The steam inlet valve was opened by the operator, so that the desired discharge flow was produced. 

For the preliminary estimate of the expected efficiency of expansion turbines, in most cases it is sufficient to neglect Reynolds number effects (Rg > 10 ) and use the efficiency and specific speed correlations shown in Figure 2-12 for partial admission axial impulse, reaction radial inflow and full admission impulse and reaction axial turbines. Due to the economic advantage of the radial turbine, die radial inflow turbine is die best selection when operating in die specific speed range 20 < Nj < 140, whereby die optimum efficiency will be achieved at N, = 80. 

Figure 4-70 shows a four-body TPG train (string). As before, the expander supplies power to the generator. The steam turbine supplies power to the generator, provides startup power, and provides control for synchronization. The generator provides electricity, and the gear is used to allow the expander and steam turbine to operate at near optimum efficiency with the generator at its desired speed. 

The maximum turbine motor horsepower is at the optimum speed, N, which is one-half of the runaway speed. This is... 

Stall Torque. From Table 4-110 the stall torque for the turbine motor with 212 stages will be twice the torque value at optimum speed. Thus the stall torque for 10 Ib/gal mud weight flow is... 

The bit speed will be the optimum speed of the turbine motor, 685 rpm. The total flow area A., for the diamond bit is... 

Heat transfer can, of course, be increased by increasing the agitator speed. An increase in speed by 10 will increase the relative heat transfer by 10. The relative power input, however, will increase by 10In viscous systems, therefore, one rapidly reaches the speed of maximum net heat removal beyond which the power input into the batch increases faster than the rate of heat removal out of the batch. In polymerization systems, the practical optimum will be significantly below this speed. The relative decrease in heat transfer coefficient for anchor and turbine agitated systems is shown in Fig. 9 as a function of conversion in polystyrene this was calculated from the previous viscosity relationships. Note that the relative heat transfer coefficient falls off less rapidly with the anchor than with the turbine. The relative heat transfer coefficient falls off very little for the anchor at low Reynolds numbers however, this means a relatively small decrease in ah already low heat transfer coefficient in the laminar region. In the regions where a turbine is effective,... 

Kneule and Weinspach (1967) also measured the suspension characteristics of numerous stirrer types and agitated vessels. They found the optimum stirrer diameter d, and distance from the bottom H, to be given by dT/d, = 3.0-3.5 and Hj/d, = 0.3-0.5. The optimum shapes for the vessel bottom are hemispherical and elliptical a flat vessel bottom is unsuitable for particle suspension. For a vessel with an elliptical bottom, baffles, and a propeller stirrer installed at HJd = 0.2-0.8 pumping the liquid toward the floor, the constant b in Eq. (3.22) has the value b = 3.06. For a turbine stirrer with six paddles and Hj/d, = 0.3, the value is b = 1.21. In order to keep the particles in the same material system in suspension, the propeller stirrer must therefore operate at a rotational speed (3.06/1.21)1/2 = 1.59 times higher than a turbine stirrer of the same size. 

The optimum stirrer, from the point of view of energy efficiency, is the one that requires the least power at the critical speed of rotation. In terms of a dimensionless relation, this can be expressed as the condition where Ne Fr3/jj is minimum. For a propeller stirrer with Ne = 0.50 and a turbine stirrer with Ne = 10.0, and with the values of b already given for the two stirrers, the propeller stirrer requires only 20% of the power needed by the turbine stirrer. Mixing Equipment Co, CA, has recently introduced a new impeller design that consists of a pitched blade turbine (three blades). At the tips of the... 

A pilot-plant reactor, a scale model of a production unit, is of such size that 1 g charged to the pilot-plant reactor is equivalent to 500 g of the same material charged to the production unit The production unit is 2 m in diameter and 2 m deep and contains a six-blade turbine agitator 0,6 m in diameter. The optimum agitator speed in the pilot-plant reactor is found by experiment to be 330 r/min. a) What are the significant dimensions of the pilot-plant reactor (b) If the reaction mass has the properties of water at 70°C and the power input per unit volume is to be constant, at what speed should the impeller turn in the large reactor (c) At what speed should... 

Liquid turbines are large, slow-moving devices, and gas and steam turbines are small, fast-moving devices. This is easiest to see for an impulse turbine, for which we previously showed that the optimum velocity of the blade is one-half that o f the jet. So the speed of a single-stage impulse turbine rotor is set by the available jet speed. At Hoover Dam the fluid drops about 700 ft. Applying Bernou can solve for the... 

For a pure reaction turbine, prepare a plot of dW ldm)l dV/ l )opt. noz speed nozzle Speeds from zero to twice the optimum nozzle speed. Also show the torque as a function of nozzle speed on the same plot. 

Switzerland, with a net head of 5330 ft. The water from this plant drives an impulse turbine (Pelton wheel) with a diameter to the middle of the blades of 10.89 ft. The wheel turns at 500 rpm [1]. What is the ratio of blade speed to jet speed for this turbine How does this compare with the optimum discussed in Sec. 7.4 I... 

The mixer as a solid liquid reactor is generally most elTicient, i.e. Rq/cj is a maximum) at the just fully suspended condition for all impellers and for any particular solid-liquid pair, constant. Thus the overall optimum is obtained when (eT)ts lowest and an impeller-tank configuration that is eflicient for suspension is also efficient for reaction. In many cases, this corresponds to a large low-speed hydrofoil impeller, or pitched blade turbines of D/T 0.4. In this respect, the recent development of cheap and reliable gearboxes capable of handling the larger torques that low speeds imply is noteworthy. ... 

Vestas, the world s largest wind turbine manufacturer, markets a range of turbines from 660 kW-2.0 MW and have a model with 47 m diameter blades, generating a nominal output of 660 kW at 1650 rpm at an optimum wind speed of about 15 ms ... 

This technique was used daily on an alkylation unit that was refrigeration-compressor limited. During periods of cold weather, the compressor would change from horsepower-limited to speed-limited. Propane was then added to the refrigerant accumulator drum. The turbine governor control valve (i.e., the driver steam inlet valve) would open to maintain compressor speed. When the governor valve was fully open, the compressor was using maximum available horsepower. The optimum propane concentration had been reached. 

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