In this paper, an idea to make the flow uniform inside the manifolds of four and six cylinder engines without changing their main geometries is presented. In general the uniform distribution of air flow among the engine cylinders is very important. Non-uniform flow in the intake manifold outlets causes inadequate feeding of the cylinders, inappropriate combustion and reduces engine volumetric efficiency. So this matter is vital for improving engine performance. A flow guide blade is added into the manifold and uniformity of the air flow is studied in different regime using transient numerical simulations. The amount of air exited from each outlet and the effect of this blade on flow uniformity is investigated. The results showed that the blade has made the flow more uniform in the manifold outlets and it was also found that in the four-cylinder and six-cylinder engines the flow uniformity is increased by 67% and 75%, respectively. In other words, as the number of engine cylinders increase, the effect of using this blade increases.

Introduction. Figs of the variety ‘Roxo de Valinhos’ are currently cooled in a cold room at a temperature between (1 and 3) °C, and it is unknown how long it takes to cool the fruits to that temperature. The work was based on the need to determine the parameters of forced-air precooling of figs packed in a carton box used for exportation and commercialization in São Paulo State, Brazil. Materials and methods. The fruits were harvested at the harvest rami stage (3/4 of maturity) and at size “type 8”, corresponding to eight fruits per box, making up a total of 24 fruits per package. Forty-eight packages were utilized, 24 on each side to form a Californian tunnel. The airflow was 2.8 L·s–1 per kg of product, with an average velocity of the air of 2.0 m·s–1. The initial interior temperature of the fruits was 20 °C and the final temperature was 1 °C. The evolution of the fig interior temperature was registered. Results. The cooling curve was drawn and the exponential analytical model to predict the precooling parameters was made based on the experimental data. The cooling curve of fig showed a typical behavior; the average fruit temperature during precooling presented a rapid fall at the beginning of the cooling, and slowly declined when it was close to the final temperature. Conclusion. The cooling time was 110 min, the cooling coefficient was 0.0344 min–1, the Biot number was 1.3 and the convective heat transference coefficient was 23.8 °C·W–1·m–2.