2021 Volume 52 Issue 4 Pages 826-832
In-cylinder inhomogeneity in a port-fuel-injected (PFI) spark-ignition (SI) engine at cold start is investigated experimentally. The equivalence ratio distribution in cylinder is described assuming a normal distribution. The standard deviation, the degree of inhomogeneity, is determined based on the exhaust gas analysis. Before experiments, all the experimental setup including fuel is soaked for ten hours at defined soak temperatures. The test engine is driven by using a starter motor at a constant speed of 350 rpm and the fuel is injected once at a certain cycle. Just after the injection, the engine is stopped and the exhaust gas is rapidly confined using a solenoid valve installed downstream the exhaust valve. By using an FID, the exhaust mass of fuel is calculated. Without spark, the amount of fuel trapped in cylinder is measured. With the spark (with combustion), the amount of fuel trapped but not involved in combustion is measured. The standard deviation of equivalence ratio in cylinder is determined so that the exhaust mass of fuel estimated by model consistently reproduce the experimental results. The standard deviation of mixture is shown to be on the order of unity for a conventional configuration of PFI SI engine.
