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Pinku Debnath,K.M. Pandey Techno-Press 2023 Advances in aircraft and spacecraft science Vol.10 No.3
The detonation combustion is a supersonic combustion process follows on shock wave oscillations in detonation tube. In this paper numerical studies are carried out combined effect of blockage ratio and spacing of obstacle on detonation wave propagation of hydrogen-air mixture in pulse detonation combustor. The deflagration to detonation transition of stoichiometric (ϕ=1)fuel-air mixture in channel has been analyzed for effect of blockage ratio (BR)=0.39, 0.51, 0.59, 0.71 with spacing of 2D and 3D. The reactive Navier-Stokes equation is used to solve the detonation wave propagation mechanism in Ansys Fluent platform. The result shows that fully developed detonation wave initiation regime is observed near smaller vortex generator ratio of BR=0.39 inside the combustor. The turbulent rate of reaction has also a great significance role for shock wave structure. However, vortices of rapid detonation wave are appears near thin boundary layer of each obstacle. Finally, detonation combustor demonstrates the superiority of pressure gain combustor with turbulent rate of reaction of 0.6 kg mol/m3 -s inside the detonation tube with obstacle spacing of 12 cm, this blockage enhanced the turbulence intensity and propulsive thrust. The successful detonation wave propagation speed is achieved in shortest possible time of 0.031s with a significance magnitude of 2349 m/s, which is higher than Chapman-Jouguet (C-J) velocity of 1848 m/s. Furthermore, stronger propulsive thrust force of 36.82 N is generated in pulse time of 0.031s.
Obula Reddy Kummitha,K.M. Pandey 한국CDE학회 2021 Journal of computational design and engineering Vol.8 No.1
The shear mixing and streamline vortices are the notable parameters to influence the air–fuel mixing in hypersonic flows. The shock wave development and Mach number significantly influence the shear mixing phenomenon. Hence, this research introduced an unconventional strut and tested its performance for the generation of shock waves at different flow conditions (M = 2,4,6). The Reynolds-averaged Navier–Stokes equations are solved to evaluate the performance of the new strut. Both the DLR scramjet strut injector and wavy wall strut injector are assessed for the shear mixing development. Turbulence for the association of shock waves, mixing layer, and the boundary layer has been modeled with the SST k-ω model. The variation in shock development and its interactions are investigated further with an increase in Mach number. The scramjet flow structure differentiation found the increased number of oblique shock waves with the wavy wall strut fuel injector. It increases the turbulence level with increased streamline vortices, turbulent intensity, and turbulent kinetic energy. The shock wave generation analysis at different Mach numbers (M = 2,4,6) found fewer interactions between the shock wave and shear layer with increased Mach number. From the examination of shock wave generation and its interaction with the shear layer and analysis of turbulent parameters, it is found that the wavy wall strut has an appreciable effect on shock-induced blend augmentation of fuel and air.
Debnath, Pinku,Pandey, K.M. Techno-Press 2020 Advances in aircraft and spacecraft science Vol.7 No.3
The exhaust nozzle serves back pressure of Pulse detonation combustor, so combustion chamber gets sufficient pressure for propulsion. In this context recent researches are focused on influence of nozzle effect on single cycle detonation wave propagation and propulsion performance of PDE. The effects of various nozzles like convergent-divergent nozzle, convergent nozzle, divergent nozzle and without nozzle at exit section of detonation tubes were computationally investigated to seek the desired propulsion performance. Further the effect of divergent nozzle length and half angle on detonation wave structure was analyzed. The simulations have been done using Ansys 14 Fluent platform. The LES turbulence model was used to simulate the combustion wave reacting flows in combustor with standard wall function. From these numerical simulations among four acquaint nozzles the highest thrust augmentation could be attained in divergent nozzle geometry and detonation wave propagation velocity eventually reaches to 1830 m/s, which is near about C-J velocity. Smaller the divergent nozzle half angle has a significant effect on faster detonation wave propagation.
Microsatellite Analysis of Three Poultry Breeds of India
Pandey, A.K.,Tantia, M.S.,Kumar, Dinesh,Mishra, Bina,Chaudhary, Preeti,Vijh, R.K. Asian Australasian Association of Animal Productio 2002 Animal Bioscience Vol.15 No.11
The genetic variability of three poultry breeds namely Aseel, Miri and Nicobari taken from different geographical locations of India were evaluated using 15 microsatellite loci. No. of alleles varied from 3 to 9 in Aseel, 3 to 8 in Miri and 2 to 7 in Nicobari. Mean PIC values in Aseel, Miri and Nicobari breeds were 0.64, 0.66 and 0.63, respectively. Average unbiased heterozygosity and direct count heterozygosity were 0.65 and 0.59, 0.68 and 0.61, and 0.64 and 0.57 in Aseel, Miri and Nicobari breeds, respectively. High heterozygosity values revealed in this study are indicative of low level of inbreeding, large population size and no or low selection pressure for commercial trait in all three populations. The estimate of genetic distances using Nei's standard, Nei's minimum and Reynold's distance revealed Aseel and Nicobari to be more closely related than Miri breed of poultry.
PREDICTORS OF VARIATION IN STOCK RETURNS: EVIDENCE FROM MALAYSIAN COMPANY PANEL DATA
I M Pandey,H K Chee People&Global Business Association 2002 Global Business and Finance Review Vol.7 No.1
We use Malaysian company panel data (1,729 firms/years observations) to examine the effects of beta, size, book-to-market value (BM) ratio, earnings-price (E/P) ratio, dividend yield, payout and leverage on the expected stock returns. Our results are based on the fixed effects regression models as these perform statistically better than the random effects and pooled OLS models. Results of the one-way fixed effects univariate regressions indicate that beta, size, book-to-market value (BM) ratio, earnings-price (E/P) ratio and dividend yield individually play a significant role in explaining variation in stock returns, and payout and leverage do not have statistically significant effect. The explanatory power of size (natural log of market capitalization) is the highest. The one-way fixed firm effects multivariate regression results show that size is persistently a significant dominant variable together with other variables in explaining stock returns. Beta has consistently a positive relation with stock returns by itself and together with other variables. But its explanatory power is less than size and other variables. Contrary to results of previous research, BM ratio is not persistently a significant variable; its significance disappears when we incorporate size and E/P ratio or dividend yield in regressions. The explanatory power of regressions increases considerably when we use the two-way fixed firm and time effects models for estimation. Further, size remains a dominant predictor of stock returns variation, leverage loses its significance and B/M ratio becomes statistically significant when we control for both the firm and time effects.