Runaway speed

Figure 8-11 shows the effleieney variation with the tip speed ratio. This eurve also shows the runaway speed. Runaway speed is aehieved when turbine torque falls to zero at blade speeds higher than the design speed. If failure oeeurs above the tip speed, the rotor ean be defined as a fail-safe rotor design. 

For this example, the stall torque of the motor is 2,824 ft-lb. The runaway speed is 1,614 rpm and coincides with zero torque. The motor produces its maximum horsepower of 217 at a speed of 807 rpm. The torque at the peak horsepower is 1,412 ft-lb, or one-half of the stall torque. 

If the turbine motor is lifted off the bottom of the borehole and circulation continues, the motor will speed up to the runaway speed of 1,614 rpm. In this situation the motor produces no drilling torque or horsepower. 

The runaway speed N. (rpm) for any turbine motor can be determined from... 

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

Maximum Horsepower. From Table 4-110 the maximum horsepower for the turbine motor with 212 stages is 217. From Equation 4-143 it can be seen that the maximum power is proportional to the stall torque and the runaway speed. Since the circulation flowrate is the same, the runaway speed is the same for this case. Thus, the maximum horsepower will be proportional to the stall torque. The maximum power will be (for the circulation flowrate of 400 gal/ min and mud weight of 10 Ib/gal)... 

E.3.3.1 An overspeed trip should be considered when the HPRT and other equipment in the train cannot tolerate the calculated overspeed (runaway speed). It is important to realize that overspeed with inlet liquids rich in absorbed gas or with liquids that partially flash as they flow through the HPRT can be several times higher than overspeed with water. With such liquids, the overspeed cannot be accurately determined. 

E.4.4 It may be useful to verify the overspeed trip setting for the HPRT at the manufactnrer s test facility. Determining the runaway speed during a water test may be considered, but this speed can be accurately calculated once performance with water is known. Rnnaway speed for gas rich-steams cannot be determined by water tests. 

O Turbine Construction Safe For Runaway Speed (2.11.1) Thruot Collar (2.9.B) Raolacaabla 0 Innaral 0 Nona... 

In contrast to steam turbines, in which runaway overspeediug is always a problem, pump-turbines operating at design head go to zero torque at about 130 to 140 percent of design speed. Thus, overspeed protection may not be necessary if the pump-turbine can withstand 140 to 150 percent of design speed and it is the sole driver. When a steam-turbine helper is used, it should be provided with the usual overspeed trip-out mechanism. 

The basic phenomenon was observed in modeling studies by Bjoreskov and Slinko (1965) that sudden increase in inlet temperature caused a transient drop of the peak temperature. The wrong-way response name was given by Mechta et al (1981) after they experienced the opposite a sudden of inlet temperature resulted in an increase of the peak temperature (which may eventually cause a runaway.) The work used a pseudo-homogeneous reaction model and explained the phenomenon by the different speeds of transient response in gas and solid. The example in the last part of Chapter 7.4 explained the speed difference by the large difference in heat capacity of gas and solid phases. For this a two-phase model is needed and spatial and time changes must be followed. 

Combinations of weather conditions, wind speed and wind direction along witli boiling point, vapor density, diffusivity, and heat of vaporization of tlie chemical released vary the healtli impact of tlie released chemical on the nearby population. To model a runaway reaction, the release of 10,000 gallons was assumed to occur over a 15-minute period. Tlie concentration of the chemical released was estimated, using procedures described in Part III (Chapter 12) for each combination of weather condition, wind speed, and wind direction. The results, combined with population data for tlie area adjacent to tlie plant, led to probability estimates of the number of people affected. Table 21.5.3 sunimarizes tlie findings. 

The objective of the present work was to determine the influence of the light intensity on the polymerization kinetics and on the temperature profile of acrylate and vinyl ether monomers exposed to UV radiation as thin films, as well as the effect of the sample initial temperature on the polymerization rate and final degree of cure. For this purpose, a new method has been developed, based on real-time infrared (RTIR) spectroscopy 14, which permits to monitor in-situ the temperature of thin films undergoing high-speed photopolymerization, without introducing any additive in the UV-curable formulation 15. This technique proved particularly well suited to addressing the issue of thermal runaway which was recently considered to occur in laser-induced polymerization of divinyl ethers 13>16. 

The usual precautions regarding temperature and vibration control also apply to the ultracentrifuge. To overcome air resistance and the attendant frictional heating, the compartment in which the rotor spins is evacuated and may be thermostated over a wide range of temperatures. The rotor is mounted on a flexible drive shaft that minimizes the need for precise balancing as a requirement for vibration-free operation. Finally, the rotor assembly is enclosed in an armored steel chamber for safety. At these speeds, a runaway rotor is deadly ... 

Autocatalysis is a distinctive phenomenon while in ordinary catalysis the catalyst re-appears from the reaction apparently untouched, additional amounts of catalyst are actively produced in an autocatalytic cycle. As atoms are not interconverted during chemical reactions, this requires (all) the (elementary or otherwise essential) components of autocatalysts to be extracted from some external reservoir. After all this matter was extracted, some share of it is not introduced in and released as a product but rather retained, thereafter supporting and speeding up the reaction(s) steadily as amounts and possibly also concentrations of autocatalysts increase. At first glance, such a system may appear doomed to undergo runaway dynamics ( explosion ), but, apart from the limited speeds and rates of autocatalyst resupply from the environment there are also other mechanisms which usually limit kinetics even though non-linear behavior (bistability, oscillations) may not be precluded ... 

Prior knowledge of the local sound speeds is not required when beginning a simulation. If compression occurs at state A, then > c. If compression stops at state B, then , +c, > v. Note that as a consequence of the instability at point A of Eq. (12), runaway expansion on the tensile strain side of state A is also a valid solution of the steady state Euler equations. Such an expansion solution may have physical significance if there exists a larger volume where... 

N stirrer revolution speed also runaway number, 2UjR,pCpk (Sec. 11.5.c) hr- s ... 

---