Susumu Kotake

On the Deposit-Induced Surface Ignition of Internal Combustion Engines

The problem of deposit-induced surface ignition in internal combustion engines is studied analytically with perturbative method with respect to reaction term, to predict the quantitative criterion of ignition of the mixture. As the fuel has a higher concentration, a larger heat of reaction, a larger coefficient of reaction rate, or a smaller activation energy, the ignition resistance becomes greater. The large heat capacity of the mixture, the low temperature of inlet air, the low temperature at the surface of burning deposit and the high engine speed decreas the tendency towards the surface ignition. The combustion temperature of deposit is proportional to the square root of the ratio of the concentration diffusivity of oxygen to the thermal diffusivity of the material of deposit. In the case of turbulent motions of the mixture, the use of turbulent diffusivities could lead to a similar conclusion. As for the effect of engine speed, the heat associated with viscous motion of the mixture must be taken into consideration.

Flow and Heat Transfer of Non-Newtonian Fluids on a Flat Plate

An experimental study is presented of the flow and heat transfer of non-Newtonian fluids (CMC-, PVA-solution in water) past a flat plate, in order to obtain fundamental information about the behavior of non-Newtonian fluids in motion, especially in turbulent flow, and their characteristics of heat transfer. Velocity and temperature distributions of the fluids past a plate are measured in the range of the main velocities of 10∼70cm/sec and of the heat fluxes of 0.9∼1.8×104kcal/hr·m2. As the main velocity of the fluid is increased the velocity and temperature distributions and the heat transfer characteristics approach those of Newtonian fluids. The behavior of momentum and heat transfer of non-Newtonian fluids becomes the same as that of Newtonian fluids at the main velocity larger than the value at which the shape factor of velocity boundary layer is nearly equal to that of the fully turbulent flow of Newtonian fluids (a1.3). These characteristics of flow and heat transfer can not be accounted for by the Reynolds number based on the power-law model.