Mixture ratio

Fig. 25. Drift ia monomer composition (—) and copolymer composition (-) with conversion for three initial monomer mixtures. Ratios are based on...

The mass flow ratio p, sometimes also called mixture ratio, is defined as... 

Let us then consider an arbitrarily selected point in a pipe in winch gas and solid particles are flowing. The flow of the mixture of gas and solid parti cles need not be homogeneous, i.e., the concentration of particles may vary across the cross-section of the pipe. This means that the mixture ratio p. should generally be regarded as a function of position in the pipe, and therefore the definition, Eq. (14.1), should be replaced by... 

Figure 14.1 shows that the void fraction approaches zero, and, the smaller the mixture ratio /a, the greater the void fraction 4>. In some cases, the void fraction characteristic number for classification of the type of flow in pneumatic conveying. But generally speaking, the void fraction is not the only criterion that determines the behavior of the flow. 

Both of these functions f and g are specific for the solid material in question and to some extent also for the diameter of the tube and the mixture ratio p. The great advantage of Eq. (14.113) is that no material or particle friction factors are needed. 

In principle, the velocities c and ti can be determined by taking a series of pictures at a very high frequency of the flow through a transparent plastic tube. Because of the particle size distribution, each particle moves at a different velocity, and this makes this method difficult to apply in practice. We have therefore used an indirect method, where we have measured the pressure losses of pneumatic conveying for two mixture ratios and then fit the parameters so that Eq, (14.126) coincides as accurately as possible with measured pressure losses. 

We measured the pressure losses for two different mixture ratios in a horizontal pipeline with a length of 89.6 m ... 

The first step in the dimensioning process is to choose the mixture ratio jx. For the compressor type, which is not considered here, we choose fx = 3.0, i.e., fii, = 9.1 kg/s. Next we have to decide D, the diameter of the tube, i.e., we need a criterion for the choice of velocity of air. A crucial aspect which affects the choice of velocity is the wearing of the tube the higher the velocity is the greater is the wear. On the other hand, the velocity cannot be too low because of the risk of pluming (the velocity difference v - c has to be positive in all parts of the piping). Here we choose = 50 m/s with =1.2 kg/m. This gives D = 0.44 m. 

For conventional gasoline, the stoichiometric ratio is approximately 14.7. Its precise value varies slightly with the composition of the gasoline. Maximum power is achieved with a slightly rich air/fuel ratio— say, 12.5. Maximum efficiency is achieved with a slightly lean mixture—say, 16—although this best-economy mixture ratio is somewhat dependent on combustion quality. 

Sato, M. 1965. The mixture ratio of the lichen genus Thamnolia in New Zealand. The Bryologist 68 320-324. 

Figure 2.4 Relationship of viscosity to water and organic modifier mixture ratio...

From the theoretical viewpoint, acetonitrile is the most suitable solvent to study the correlation of retention times and log P values of analytes, since the dipole moment (2.44) is nearly equal to that of water (2.55) (Figure 4.4). The electron donor effect can therefore be eliminated, and the elution order is not changed on modification of the acetonitrile-water mixture ratio. The first choice of an eluent should therefore be an acetonitrile-water mixture for non-ionic compounds in reversed-phase liquid chromatography. Methanol, acetone, THF, or DMF can then be added to improve the resolution. 

Since the mixture ratio is not specified explicitly for this general expression, no effort is made to eliminate products and n = 11. Thus the new mass balance equations (a = 4) are... 

Figure 3.2 depicts the explosion limits of a stoichiometric mixture of hydrogen and oxygen. Explosion limits can be found for many different mixture ratios. The point X on Fig. 3.2 marks the conditions (773 K latm) described at the very beginning of this chapter in Fig. 3.1. It now becomes obvious that either increasing or decreasing the pressure at constant temperature can cause an explosion.

Reported flame speed results for most fuels vary somewhat with the measurement technique used. Most results, however, are internally consistent. Plotted in Fig. 4.21 are some typical flame speed results as a function of the stoichiometric mixture ratio. Detailed data, which were given in recent combustion symposia, are available in the extensive tabulations of Refs. [24-26], The flame speeds for many fuels in air have been summarized from these references and are listed in Appendix F. Since most paraffins, except methane, have approximately the same flame temperature in air, it is not surprising that their flame speeds are about the same (—45 cm/s). Methane has a somewhat lower speed (<40 cm/s). Attempts [24] have been made to correlate flame speed with hydrocarbon fuel structure and chain length, but these correlations... 

If one examines the gp and gB on the graph shown in Fig. 4.40, one can make some interesting observations. The burner port diameter is fixed such that a rich mixture ratio is obtained at a value represented by the dashed line on Fig. 4.40. When the mixture ratio is set at this value, the flame can never flash back into the stove and bum without the operator s noticing the situation. If the fuel is changed, difficulties may arise. Such difficulties arose many decades ago when the gas industry switched from manufacturer s gas to natural gas, and could arise again if the industry is ever compelled to... 

It is assumed here that the fuel-air (F/A) mixture is essentially air that is, the density of the mixture does not change as the amount of fuel changes. From the momentum equation, this fuel-air mixture ratio becomes... 

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