Pressure 780 INDEX

To compare with experimental results, the parameters corresponding to real conditions were used in our computation cases. The lubricant used in the experiment is polyglycol oil. The diameter of the steel ball is 25.4 mm, elastic modulus of the balls is 2.058 X 10 Pa, and the elastic modulus of the glass disk is 5.488 X 10 ° Pa. The circumstance temperature is 28 1 °C. The oil viscosity-pressure index is taken as 1.5 X10- Pa-. ... 

This is known as Vieille s Law. The exponent, n, is known as the pressure index of the propellant and is usually in the range 0-5 to 0-8. 

It can be shown that if the pressure index of the propellant exceeds 1 the rate of gas increase by factor 2 exceeds the rate of gas loss by factor 1, so that the pressure builds up in the motor, which finally explodes. Quite apart from such an extreme case, a low pressure index in the propellant is desirable so that irregularities in burning are quickly smoothed out with the least effect on rocket performance. It is for this reason that platonising agents mentioned on p. 181 are important, because they enable a very low pressure index to be achieved at ordinary operating pressures of the order of 14 MPa. 

Platonisation. In propellants, the addition of ingredients to produce a low pressure index over a working range of pressures. 

Pressure index. In propellants, the variation of burning speed following changes in pressure (seep. 180). 

Different classes of solid propellants DB, CMDB, and fuel rich (FR) have been developed in order to meet the requirements of various missions in terms of specific impulse (Lsp) and wide range of burn rates with low pressure index (n). High density, low temperature sensitivity and good mechanical properties constitute other essential requirements of these propellants. The salient features of such performance parameters are ... 

The burn rates of propellants are determined in a strand burner (Crawford bomb/ acoustic emission technique) at various pressures using an inert gas for pressurization. This data, when fitted in the empirical relation r = a.P" provides the pressure index n and the coefficient a. This technique is highly useful as a first approximation and is extensively used for propellant screening and quality control. The bum rates at different pressures are also determined by static testing in a ballistic evaluation motors (BEMs) and burn rates are typically scaled up from 1-5% for full scale motors. 

Bum rates of propellants are inversely proportional to the particle diameter of Al powder particles. This is corroborated by the increase in bum rate of propellants on incorporation of Alex in their formulations. The bum rate of solid propellant increases by about 100% on replacement of 9% Al by Alex powder (in a total of 18% Al) coupled with decrease in pressure index. 

In view of identical open frontal areas, filters with the 100/17 and 200/12 cell configurations will have identical open cross>sectional areas and gas velocity through their respective channels under conditions of constant flow rate. Thus, the pressure drop Apeh will now be proportional to /Z) according to Eq. (8). We call this ratio back pressure index, or BPI ... 

A lot of work has been done for the synthesis of azido nitroamino compounds, their properties and applications [32]. Reed and Dolah first started the study of this kind of compounds. Rosher, Morton, and Eimslic synthesized series of azido nitroamino compounds, and applied them as the composition of propellants. They notably rise the combustion/buming rate and specific impulse without influencing the pressure index. Their energy approximately equals that of HMX. Their detonation sensitivity is relatively low. They are widely applied in smoke-free propellants with low sensitivity to replace HMX. 

Newman AB, Sutton-Tyrell K, Voget MT, Kuller LH. Morbidity and mortality in hypertensive adults with a Low Ankel/Arm Blood Pressure Index. JAMA 1993 270 487-489. 

Ogten M, Hedblad B, Jungquist G, Isacsson SO, Lindell SE, Janzon L. Low ankle-brachial pressure index in 68-year old men prevalance, risk factors and prognosis. Results from prospective population study Men bom in 1914, Malmo, Sweden. EurJVasc Surg 1993 7 500-506. 

However, with the initial pressure growth the flame surface perturbations increase, which leads to discrepancies (see Fig. 2.15) between the calculated and the measured data on laminar flame velocities [26]. It can be said with confidence that the equations for the pressure index [26,41] do not characterize a laminar flame in a H2 + air mixture at elevated pressure. 

The temperature index a is given in Fig. 2.16c. for a wide range of H2 concentrations in H2+air mixtures. The temperature index of the laminar flame velocity has a minimum value in the range of H2 content approximately between 30% and 45% it grows in the lean and rich mixture ranges. The calculated temperature index data have been compared with the measured results of [19, 23]. For a complete description of the baric index values, SJP) ratios, similar to those illustrated in Fig. 2.14 by the solid curve, can be differentiated to find the pressure range where the transition to the negative pressure index occurs. 

Fig. 2.27 The relative decrease in the flame velocity with the growth of the initial pressure in mixtures diluted with water steam. Figures on the curves indicate the pressure index P...

Fig. 6.17 (a) Self-ignition delay time versus pressure for a 15% H2 + 85% air mixture with a nitrogen monoxide additive (7) and without this additive (2). (b) Self-ignition delay time pressure index versus pressure for a 15% H2 + 85% air mixture with a nitrogen monoxide additive (i) and without this additive (2)... 

Head pressure is a key extrusion variable. It is advantageous to know prior to extruding what the pressure will be because it affects safety, rupture disk rating, and vent flow. This paper describes development of a model to determine head pressure. The model is not intended to be highly accurate, but to provide a useful estimate. Therefore, the result is termed a head pressure index (HPI). Head pressure results from three process variables melt viscosity, flow rate, and flow restriction. With the HPI, an operator can make quick decisions about operating conditions, such as acceptable screw speed, melt temperature, and vent location. Experimental data is shown that correlates HPI with measured head pressure. 

It is evident from figures 9 and 10 that there is very good agreement between the measured pressure and the head pressure index. Most of the values have an error of less than 7% with the worst case having only about a 10%... 

A method has been developed to quickly obtain an estimate of the head pressure that can be expected during an extrusion run. Because the method employs simplifying assumptions, the resulting value is termed a head pressure index (HPI). The HPI is relatively easy to determine, yet still provides a very good estimate of actual pressure, as shown with experimental data. 

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