Acceleration curve

The startup speed and temperature acceleration curves as shown in Figure 19-2 are one such safety measure. If the temperature or speed are not reached in a certain time span from ignition, the turbine will be shutdown. In the early days when these acceleration and temperature curves were not used, the fuel, which was not ignited, was carried from the combustor and then deposited at the first or second turbine nozzle, where the fuel combusted which resulted in the burnout of the turbine nozzles. After an aborted start the turbine must be fully purged of any fuel before the next start is attempted. To achieve the purge of any fuel residual from the turbine, there must be about seven times the turbine volume of air that must be exhausted before combustion is once again attempted. 

Fig 1 Typical Time-acceleration Curve for Projectile While in Gun... 

If we plot the velocity, F, of any process at different intervals of time, t, we get a curve whose slope indicates the rate at which the velocity is changing. This we call an acceleration curve. The area bounded by an acceleration curve and the coordinate axes represents the distance traversed or the amount of substance transformed in a chemical reaction as the case might be. 

Solve the amplitude of acceleration curves quadratic sum E between the top and the bottom interface of anchorage part. 

The source is brought to a. positive poteptial (I/) of several kilovolts and the ions are extracted by a plate at ground potential. They acquire kinetic energy and thus velocity according to their mass and charge. They enter a magnetic field whose direction is perpendicular to their trajectory. Under the effect of the field, Bg, the trajectory is curved by Lorentz forces that produce a centripetal acceleration perpendicular to both the field and the velocity. 

Water as an impurity accelerates the oxidation rate. Figure 4 compares growth curves for Si02 under dry and steam conditions. Halogens can also be introduced to the oxidation process, thereby reducing sodium ion contamination. This improves dielectric breakdown strength, and reduces interface trap density (15). 

A rotational viscometer connected to a recorder is used. After the sample is loaded and allowed to come to mechanical and thermal equiUbtium, the viscometer is turned on and the rotational speed is increased in steps, starting from the lowest speed. The resultant shear stress is recorded with time. On each speed change the shear stress reaches a maximum value and then decreases exponentially toward an equiUbrium level. The peak shear stress, which is obtained by extrapolating the curve to zero time, and the equiUbrium shear stress are indicative of the viscosity—shear behavior of unsheared and sheared material, respectively. The stress-decay curves are indicative of the time-dependent behavior. A rate constant for the relaxation process can be deterrnined at each shear rate. In addition, zero-time and equiUbrium shear stress values can be used to constmct a hysteresis loop that is similar to that shown in Figure 5, but unlike that plot, is independent of acceleration and time of shear. 

The crystalliza tion resistance of vulcaniza tes can be measured by following hardness or compression set at low temperature over a period of time. The stress in a compression set test accelerates crystallization. Often the curve of compression set with time has an S shape, exhibiting a period of nucleation followed by rapid crystallization (Fig. 3). The mercaptan modified homopolymer, Du Pont Type W, is the fastest crystallizing, a sulfur modified homopolymer, GN, somewhat slower, and a sulfur modified low 2,3-dichlorobutadiene copolymer, GRT, and a mercaptan modified high dichlorobutadiene copolymer, WRT, are the slowest. The test is often mn near the temperature of maximum crystallization rate of —12° C (99). Crystallization is accelerated by polyester plasticizers and delayed with hydrocarbon oil plasticizers. Blending with hydrocarbon diene mbbers may retard crystallization and improve low temperature britdeness (100). 

FIG. 17-73 Normal (perpendicular) rapping efficiency for various precipitated dust layers having about 0.03 g diist/cm (0.2 g diist/in ) as a function of maximum acceleration in multiples of g, Curve 1, fly ash, 200 or 300°F, power off. Curve 2, fly ash, 70°F, power off also 200 or 300°F, power on. Curve 3, fly ash, 70°F, power on. Curve 4, cement-ldln feed, 300°F, power off. Curve 5, cement dust, 300°F, power off. Curve 6, same as 5, except power on. Curve 7, cement-ldln feed, 300°F, power on. Curve 8, cement dust, 200°F, power off. Curve 9, same as 8, except power on. Curve 10, cement-ldln feed, 200°F, power off. Curve 11, same as 10, except at 70°F. Curve 12, cement-ldln feed, 200°F, power on. Curve L3, cement-ldln feed, 70°F, power on. °C = (°F — 32) x %. [Spioull, Air Polliit. Control Assoc. J., i.5, 50 (1965).]... 

Centripetal and Centrifugal Acceleration A centripetal body force is required to sustain a body of mass moving along a curve tra-jec tory. The force acts perpendicular to the direction of motion and is directed radially inward. The centripetal acceleration, which follows the same direction as the force, is given by the kinematic relationship ... 

In addition to secondarv resistance control, other devices such as reactors and thyristors (solid-state controllable rectifiers) are used to control wound-rotor motors. Fixed secondary reactors combined with resistors can provide veiy constant accelerating torque with a minimum number of accelerating steps. The change in slip frequency with speed continually changes the effective reac tance and hence the value of resistance associated with the reactor. The secondaiy reactors, resistors, and contacts can be varied in design to provide the proper accelerating speed-torque curve for the protection of belt conveyors and similar loads. 

The optimal conditions for accelerating of investigated reaction by ions Fe(III) and Ag(I) ai e the following pH 5,0 (acetic buffer), Cj. . =l,6T0 M, CpMSA=4T0 M, Cpp =2-10 M. Under these conditions, factors of sensitivity for kinetic determination of metals mentioned above were established as a slope s tangent of the calibration curves that is a plot of reaction velocity (change of optical density of ferroin s solution for 4 minutes) versus analyte s concentration. Factors of sensitivity for determination of Mn(II), Fe(III), Ag(I), Pd(II), Co(II) ai-e 5,5-10" 1,1-10" 2,5-10" 2,0-10" 8,0-10", respectively. 

The recommended practice would require that at each point on the motor speed-torque curve there should be a minimum 15-20% suiplus torque available, over and above the load torque, for a safe start (Figure 2.14). The torque thus available is known as the accelerating torque. 

To achieve the required performance, it is essential that at every point on the motor speed-torque curve the minimum available accelerating torque is 15-20% of its rated torque. In addition, the starting time must also be less than the thermal withstand time of the motor. For more details see Section 2.8. 

---