Burn rate ratios

The combustion KDIE is determined from the burn rate ratios (ruhAbd) of the cylindrical HMX and HMX-dg pellets made from identically synthesized i HMX and HMX-dg powders. The HMX and HMX—dg pellet samples are pressed to 96—97 percent of the HMX single crystal density assuring any burn rate... 

C—H bond rupture is also present in the RDX static combustion event at 500 psig (3.55 MPa) and 1000 psig (6.99 MPa).28 Identically synthesized cylindricju pressed RDX and RDX- e pellets were burned in a window bomb and provide a 10 KDIE when their burn rates ratios are calculated (Table VIII). For the same reasons that solid state C—H bond rupture might be the rate-controlling step in the HMX combustion event, the rate-controlling C—H bond rupture in RDX... 

System (weight Mass extinction Yield factor, Yf Burn rate ratio,... 

N. E. Cohen, 13th Symp (Int) Combust (Proc) (1970), 1019—29 CA 76, 61471 (1972) To analyze and explain the mechanism of combustion of powdered metals in contact with a solid oxidizer (AP) with the powdered metal dispersed in solid AP (I), the combustion of various compressed I-Al and I-Mg mixts in N2 under various conditions in a high-pressure window bomb was studied. The regression-rate laws of the mixts at high and low pressures, the pressure limits for deflagration, and the structures of the combustion zone and of the surface were detd. The burning rate of various I-Al mixts, as a function of pressure, I particle size, and mixt ratio was determined by cinematography. The combustion was difficult to achieve... 

The ratio Vs At is the linear burn rate. We suppose it to be constant. Thus,... 

Turbulent mass burning rate versus the turbulent root-mean-square velocity by Karpov and Severin [18]. Here, nis the air excess coefficient that is the inverse of the equivalence ratio. (Reprinted from Abdel-Gayed, R., Bradley, D., and Lung, F.K.-K., Combustion regimes and the straining of turbulent premixed flames. Combust. Flame, 76, 213, 1989. With permission. Figure 2, p. 215, copyright Elsevier editions.)... 

The fact that the fuel/air ratio is spatially constant in HCSI engines, at least within a reasonably close approximation, allows substantial simplifications in combustion models. The burn rate or fuel consumption rate dm /dt is expressed as a function of flame surface area the density of the unburnt fuel/air mixture Pu, the laminar burning velocity Sl, and the fluctuations of velocities, i.e., E as a measure of turbulence, u. ... 

Zone II combustion proceeds with partial penetration of oxygen, resulting in simultaneous variations in particle density and diameter as the pores closest to the particle surface undergo oxidation, in addition to the external surface of the particle. The ratio of the actual burning rate to the maximum possible rate if the entire particle was subject to the oxygen partial pressure at the external particle surface is known as the effectiveness factor. 

The theory behind the method to measure the burning rate was not explicitly presented by Lamb et al. Obviously, the mathematical model must be based on the bed properties, such as packing ratio, loading density, bed height, as well as the trolley speed. No discussion is presented about the limitations and assumptions of the method. 

If the binder (BDR) concentration of AP-HTPB composite propellants is less than the stoichiometric ratio, the burning rate increases as (BDR) increases, as shown in Fig. 7.6. The burning rate of a propellant with the composition bdr(0-08) is... 

Fig. 7.13 shows the effect of the particle size of AP on burning rate.I l The propellants have the composition ap(0-80) and htpb(0-20). The AP particles are bimodal large-sized, with a 350 pm/200 pm mixture ratio of 4 3, and bimodal small-sized, with a 15 pm/3 pm mixture ratio of 4 3. The burning rate of the smaU-sized AP propellant is more than double that of the large-sized AP propellant. The pressure exponent of burning rate is 0.47 for the large-sized AP propellant and 0.59 for the small-sized AP propellant... 

Fig. 7.55 Effects of particle size and mixture ratio of AP and RDX on the burning rates of AP, RDX, and AP-RDX composite propellants.

The effects of the particle size of Mg and Tf on burning rate are shown in Fig. 11.5. The Mg-Tf pyrolants used to obtain the data shown in Fig. 11.5 all have a mixture ratio of = 0.60/0.40. The burning rate increases with decreasing Mg... 

Fig. 12.11 shows the structure of a rocket plume generated downstream of a rocket nozzle. The plume consists of a primary flame and a secondary flame.Fil The primary flame is generated by the exhaust combustion gas from the rocket motor without any effect of the ambient atmosphere. The primary flame is composed of oblique shock waves and expansion waves as a result of interaction with the ambient pressure. The structure is dependent on the expansion ratio of the nozzle, as described in Appendix C. Therefore, no diffusional mixing with ambient air occurs in the primary flame. The secondary flame is generated by mixing of the exhaust gas from the nozzle with the ambient air. The dimensions of the secondary flame are dependent not only on the combustion gas expelled from the exhaust nozzle, but also on the expansion ratio of the nozzle. A nitropolymer propellant composed of nc(0-466), ng(0-369), dep(0104), ec(0 029), and pbst(0.032) is used as a reference propellant to determine the effect of plume suppression. The burning rate characteristics of the propellants are shown in Fig. 6-31. Since the nitropolymer propellant is fuel-rich, the exhaust gas forms a combustible gaseous mixture with the ambient air. This gaseous mixture is ignited and afterburning occurs somewhat downstream of the nozzle exit. The major combustion products in the combustion chamber are CO, Hj, CO2, N2, and HjO. The fuel components are CO and H2, the mole fractions of which at the nozzle throat are co(0.47) and iH2(0.24).

The mass generation rate in the gas generator is controlled by the variable flow system and the mixture ratio of fuel-rich gas to air in the ramburner is optimized. The burning rate is represented by the relationship r = ap", where r is the linear burning rate, p is the pressure, n is the pressure exponent of burning rate, and o is a con-... 

The specific impulse of each pyrolant is computed as a function of air-to-fuel ratio, as shown in Fig. 15.7. In the computations, the pressure in the ramburner is assumed to be 0.6 MPa at Mach number 2.0for a sea-level flight When GAP pyrolant is used as a gas-generating pyrolant, the specific impulse is approximately 800 s at e = 10. It is evident that AP pyrolant and NP pyrolant are not favorable for use as gas-generating pyrolants in VFDR. However, the specific impulse and burning rate characteristics of these pyrolants are further improved by the addition of energetic materials and burning rate modifiers. 

Figure 3.2 Burning rate and area ratio data from black powder propellant.

In fact, an area ratio equation such as (3.4) can be compared with the burning rate equation (3.2) by taking note of the fact that [or 0.24 in equation (3.2)] becomes 1— (or 0.76) in the area ratio equation. Therefore, equation (3.4) may be written. 

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