Halit Karabulut

Dynamic model of a two-cylinder four-stroke internal combustion engine and vibration treatment

Engine vibrations of large amplitude are caused by inertial effects of the piston–crankshaft mechanism and gas forces, and are transmitted to the chassis of a vehicle in the form of periodically varying forces through the engine mounts. Both the engine vibrations and mount forces may be minimized by designing proper engine components and mounts, which requires a dynamic simulation of the engine. In this study, a three degree of freedom dynamic model, enabling the simultaneous treatment of the piston–crankshaft mechanism and engine block, was devised for a two-cylinder four-stroke engine. Periodic and temporary variations of crankshaft speed, the variation of torque and power with speed, torsional and translational vibrations of the engine block, and the variation of mount forces with respect to the damping and stiffness coefficients of the mounts were studied. The torsional and translational vibrations of the engine block were found to be mainly affected by the combustion gas force and inertia force of the reciprocating masses, respectively. A simple relation has been obtained to determine the position and mass of counterweights used for eliminating the vertical vibration of the block.

Construction and testing of a dish/Stirling solar energy unit

AbstractThis study is concerned with the construction of a simple solar energy conversion system consisting of a parabolic dish concentrator and a Stirling engine. For this purpose, a parabolic dish concentrator consisting of planar mirror segments was built and coupled with a Stirling engine recently developed by the authors for solar energy conversion and domestic cogeneration. By mounting the engine to the bottom of the dish concentrator, the solar rays were directly reflected onto the hot end of the displacer cylinder. For the design of an appropriate parabolic dish concentrator reflecting solar rays onto the hot zone of a displacer cylinder and satisfying their uniform distribution, an equation was derived. The energy conversion unit constructed was tested under 820 W m−2 solar radiation. The engine started to run at 93°C hot end temperature. At steady running conditions, the hot end temperature of the displacer cylinder became stable at ∼156°C. The variation of shaft power with engine speed and char...

Numerical solution of boundary layer equations in compressible cross-flow to a cylinder

Abstract Two-dimensional, steady-state, compressible boundary layer and energy equations are solved numerically using finite difference method in cylindrical coordinates. The heat transfer from and to an isolated cylinder for cross-flow is calculated up to the separation point iteratively. The velocity and temperature profiles, and local Nusselt numbers around the cylinder are obtained for the constant wall temperature boundary condition at different oncoming velocities. The results are obtained for compressible and incompressible flow and given in diagrams.

Numerical analysis of laminar film-wise condensation

Abstract A numerical method is presented for the analysis of laminar film-wise condensation of vapour flowing downwards on a horizontal tube. The governing equations of condensate flow include the pressure gradient, inertia and convective terms in addition to gravity and viscous terms. The effect of vapour shear on condensation is determined by simultaneous computation of the condensate and vapour flow fields using compatible interfacial conditions. Results obtained from the analysis are given in diagrams and compared with the results given in literature.