Flow in the coolant passages of an internal combustion engine cylinder head

Detailed measurements of the coolant flow field have been made in the water passages of the cylinder head of an internal combustion engine. They were obtained by casting a transparent acrylic model of the cylinder head and using a mixture of hydrocarbon fluids at a predetermined temperature and concentration which ensured that the refractive index of the fluid was identical to that of the acrylic. This arrangement allowed the use of laser Doppler velocimetry to measure local velocities throughout the cooling passages. The results show that the flow was unevenly distributed with around three quarters of the total passing through the exhaust-portside passages and larger coolant velocities close to the top of the head than close to the gas face. The results of this study aimed to assist the improvement of the specific cylinder head design.