This paper presents a linear acoustic model of a multi-cylinder intake manifold that can be used as part of a hybrid time/frequency domain method to calculate the intake wave dynamics of practical naturally aspirated engines.
A four-cylinder, intake boosted, port fuel injection (PFI), spark-ignition (SI) engine is modified to a three-cylinder engine with the outer two cylinders working in the conventional four stroke cycle and with the inner cylinder working only with the expansion and exhausting strokes.
The target application is an engine valve train which traditionally uses cam-based lifter driven rocker arms to regulate the cylinders' intake and exhaust valve motion.
The main sensor signals used by the controller are the cylinder pressure, intake exhaust pressure, and intake temperature.
The intended purpose of physical model building for the cylinder air intake is prediction of the air intake rate and computation of optimal valve control action before a lot of effort is put into a real experiment at the engine test bench.
For the flow into the cylinder through intake valve, the upstream stagnation pressure and temperature are the intake manifold pressure and temperature (pim, Tim), respectively, and the downstream static pressure is the cylinder pressure (p).
In spite of the design effort that is usually made to keep the cylinder air intake independent of each other in this kind of engines, results showed a considerable acoustic coupling between the intake primary manifolds and the upstream components.
In the structure-gesture video, the explanation was accompanied by an identical number of gestures that portrayed the structure of each part of the system, for example, the crankshaft, the cylinder, the intake valve, the piston, the spark plug and the exhaust valve.
Timed injection, in which a small quantity of gasoline is squirted into each cylinder or intake-valve port during the intake stroke of the piston, is employed on a number of cars.
