ASSESSING THE IMPACT OF PRESSURE PULSES IN EXHAUST MANIFOLD DURING BLOWDOWN PROCESS ON IN-CYLINDER DISTRIBUTION USING T-RECS

摘要

In an internal combustion engine, both the two-stroke and the four-stroke variety, the ejection of exhaust gases from the cylinder is termed as blowdown. In a two stroke engine, during blowdown the in-cylinder gases which are at a pressure higher than the exhaust manifold pressure rush out of the exhaust port into the manifold, resulting in a high pressure wave propagating through the manifold. In a multi-cylinder engine where the exhaust ports of each cylinder are connected to the manifold, the high pressure pulses in the manifold will impact the in-cylinder performance of the cylinders downstream of the first cylinder. This impact was investigated using the Turbocharger Reciprocating Engine Computer Simulation (T-RECS), a zero-dimensional cycle simulation tool developed at the National Gas Machinery Laboratory (NGML). The manifold pressure distributions were generated using the NGML developed Virtual Pipeline Simulation Tool (VPST), which is a one-dimensional pipe flow simulation software package. The analysis assumed that at any given instant the exhaust port of only one cylinder is open while the exhaust ports of all other cylinders remain closed. The results showed that the in-cylinder pressure distributions could become significantly altered under the influence of the exhaust manifold pressure pulses. The knowledge gained would help in utilizing the pressure pulses more effectively in tuning the exhaust manifold.