We present planforms of line plumes formed on horizontal surfaces in turbulent convection, along with the length of line plumes measured from these planforms, in a six decade range of Rayleigh numbers (10 5 < Ra < 10 11 ) and at three Prandtl numbers (Pr = 0.7, 5.2, 602). Using geometric constraints on the relations for the mean plume spacings, we obtain expressions for the total length of near-wall plumes on horizontal surfaces in turbulent convection. The plume length per unit area (L p /A), made dimensionless by the near-wall length scale in turbulent convection (Z w ), remains constant for a given fluid. The Nusselt number is shown to be directly proportional to L p H/A for a given fluid layer of height H. The increase in Pr has a weak influence in decreasing L p /A. These expressions match the measurements, thereby showing that the assumption of laminar natural convection boundary layers in turbulent convection is consistent with the observed total length of line plumes. We then show that similar relationships are obtained based on the assumption that the line plumes are the outcome of the instability of laminar natural convection boundary layers on the horizontal surfaces.

We study the dynamics of line plumes on the bottom plate in turbulent convection over six decades of Rayleigh number $(10^5

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Su per charg ing is a pro cess which is used to im prove the per for mance of an en gine by in creas ing the spe cific power out put whereas ex haust gas recirculation re duces the NO x pro duced by en gine be cause of su per charg ing. In a con ven tional en gine, su per charger func tions as a com pres sor for the forced in duc tion of the charge taking me chan i cal power from the en gine crank shaft. In this study, su per charg ing is achieved us ing a jet com pres sor. In the jet com pres sor, the ex haust gas is used as the mo tive stream and the at mo spheric air as the pro pelled stream. When high pressure mo tive stream from the en gine ex haust is ex panded in the noz zle, a low pressure is cre ated at the noz zle exit. Due to this low pres sure, at mo spheric air is sucked into the ex pan sion cham ber of the com pres sor, where it is mixed and pres sur ized with the mo tive stream. The pres sure of the mixed stream is fur ther in creased in the di verg ing sec tion of the jet com pres sor. A per cent age vol ume of the pres sur ized air mix ture is then in ducted back into the en gine as su per charged air and the bal ance is let out as ex haust. This pro cess not only saves the me chan i cal power re quired for su per charg ing but also di lutes the con stit u ents of the en gine ex haust gas thereby reduc ing the emis sion and the noise level gen er ated from the en gine ex haust. The geomet ri cal de sign pa ram e ters of the jet com pres sor were ob tained by solv ing the govern ing equa tions us ing the method of con stant rate of mo men tum change. Us ing the the o ret i cal de sign pa ram e ters of the jet com pres sor, a computational fluid dinamics anal y sis us ing FLUENT soft ware was made to eval u ate the per for mance of the jet com pres sor for the ap pli ca tion of su per charg ing an IC en gine. This eval ua tion turned out to be an ef fi cient di ag nos tic tool for de ter min ing per for mance op timi za tion and de sign of the jet com pres sor. A jet com pres sor was also fab ri cated for the ap pli ca tion of su per charg ing and its per for mance was stud ied.

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