a De part ment of Aero nau ti cal En gi neer ing, Sathyabama Uni ver sity, Chennai, In dia b De part ment of Aero space En gi neer ing, B. S. Abdur Rahman Uni ver sity, Chennai, In dia Orig i nal sci en tific pa perIn rock etry ap pli ca tion, now-a-days in stead of monopropellants slowly com pos ite pro pel lants are in tro duced. Burn ing rate of a solid state com pos ite pro pel lant depends on many fac tors like ox i dizer-binder ra tio, ox i dizer par ti cle size and dis tri bution, par ti cle size and its dis tri bu tion, pres sure, tem per a ture, etc. Sev eral re searchers had taken the mass var ied com pos ite pro pel lant. In that, the am mo nium perchlorate mainly var ied from 85 to 90%. This pa per deals with the ox i dizer rich pro pel lant by al low ing small vari a tion of fuel cum binder rang ing from 2%, 4%, 6%, and 8% by mass. Since the per cent of the binder is very less com pared to the oxi dizer, the mix ture re mains in a pow der form. The pow der sam ples are used to make a pressed pel let. Experiments were con ducted in closed win dow bomb set-up at pres sures of 2, 3.5, and 7 MN/m 2 . The burn ing rates are cal cu lated from the combus tion pho tog ra phy (im ages) taken by a high-speed cam era. These im ages were pro cessed frame by frame in MATLAB, de tect ing the edges in the im ages of the frames. The burn ing rate is ob tained as the slope of the lin ear fit from MATLAB and ob served that the burn rate in creases with the mass vari a tion of con stit u ents present in solid state com pos ite pro pel lant. The re sult in di cates a re mark able in crease in burn rate of 26. 66%, 20%, 16.66%, and 3.33% for Mix 1, 2, 3, 4 com pared with Mix 5 at 7 MN/m 2 . The per cent age vari a tions in burn rate be tween Mix 1 and Mix 5 at 2, 3.5, and 7 MN/m 2 are 25. 833%, 32.322%, and 26.185%, re spec tively.

The effect of the different mixture in a high volumetric concentration of oxidizer-(AP), with least percentage of binder-(HTPB+TDI), for improving the propellant burn rate was investigated. The combustion experiment is performed using a window bomb setup and the high-speed camera is utilized to capture the flame images. An image processing approach is used to measure the burn rate and intrinsic instability of flame by discrete wavelet transform method. Region growing algorithm technique is used for image segmentation. The morphological operation is implemented with Euclidean distance measurement for the identification of flame height in configuring with dependent parameters (burning rate, diffusion flame height). The qualitative analysis (signal characterization) and quantitative analysis (mean, kurtosis, skewness, standard deviation, and frequency) were used to study the intrinsic instability characteristics of the flame diffusion. A result obtained from the analysis proves that the instability in fuel combustion occurs at higher mix and pressure level.

A pressurized window bomb arrangement for AP-HTPB combustion is studied using high speed images to analyze for unsteady combustion, resulting in combustion instability. The base combustion is unsteady and non-stationary. The base filtered heat release rate pattern displays intermittency, seldom observed in prior literature. The intermittency observed is of type 1, and subsequent analysis leads to questions on conventional amplitude spectra as a measure of instability. A novel indicator, the intermittency factor is defined to understand the role of intermittency. It is seen that intermittency is marked by fluctuating intermittency factor values, implying a large deviation in phase values.