High-pressure direct injection (HPDI) of natural gas coupled with diesel pilot injection is a
promising method by which emissions of particulate matter (PM) and nitrogen oxides (NOx) can
be reduced. In light of increasingly stringent U.S. EPA emissions regulations on heavy-duty
diesel engines, there is great need to develop combustion strategies that reduce targeted
pollutants; for heavy-duty engines these are namely PM and NOx. A gravimetric technique has
been used in this investigation to measure the PM emissions from a Cummins ISX 400 engine
converted to HPDI of natural gas with diesel pilot. The engine experiments have been run using
the AVL 8-mode steady-state test protocol, which simulates the U.S. EPA heavy-duty transient
test procedure. The repeatability of particulate matter emissions measurements from HPDI
fuelling has been established, as well as the effect of varying injection pressure, timing and pilot
diesel fuel quantity on PM emissions. In addition, the composition of the HPDI exhaust PM was
analysed for fuel-like and oil-like volatile organic fraction (VOF) components using a direct
capillary injection of filter-borne PM into a gas chromatograph/flame ionization detector
(GC/FID) technique.
The effect of retarding injection timing on PM emissions was not consistent across the range of
engine operating conditions characterized by modes 1,4,5, and 8 of the AVL test. It was
suspected that high cylinder pressures resulting from advanced fuel injection timing or unwanted
fuel interaction with cylinder wall and piston surfaces was impeding good mixing between
injected natural gas and air for the current engine geometry.
Results also showed that increased injection pressure was a potential strategy for reducing PM
emissions, but for high load test points and the current engine geometry, a suspected air/fuel
mixing problem may have produced higher PM emissions than expected.
The difference in the PM emissions for these three injected pilot fuel quantities was not
statistically significant, so no conclusions were drawn regarding the effect of increasing the pilot
fuel quantity on PM emissions.
Finally, the VOF of total PM mass emissions from HPDI combustion was between 34-58% based
on analyses using modes 1,4,5,8 of the AVL 8-mode test.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/11626 |
| Date | 11 1900 |
| Creators | Baribeau, Anne-Marie |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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