Diesel exhaust particulates are the subject of increasingly
severe legislation controlling mass emissions throughout
the world. Other emissions, which are currently
unregulated, are also receiving closer scrutiny. In
particular, polycyclic aromatic compounds (PAC), some of
which are known carcinogens, are being studied.
A total exhaust solvent scrubbing apparatus (TESSA) has
been constructed to sample diesel exhaust hydrocarbons,
using a solvent mixture to strip organic compounds from
exhaust gases. This avoided adsorption of hydrocarbons
onto particulates, when fitted close to the exhaust port,
and minimised the formation of sampling artifacts. TESSA
yielded new information, enabling lighter more volatile
organics such as 2- and 3-ringed PAC to be characterised,
these could not be collected by a dilution tunnel filter,
which trapped particulates effectively but did not sample
the hydrocarbons which had remained in the gas-phase.
TESSA has proved itself to be uniquely suitable for the
sampling of gaseous hydrocarbons with which there is
currently an increased interest.
Experiments using TESSA have confirmed that there is a
contribution to the exhaust from small amounts of fuel
passing through the combustion chamber substantially
unchanged, as well as from partially burnt or pyrolysed
products of combustion. New techniques have been
developed to aid the interpretation of data obtained from
high resolution gas chromatography and gas
chromatography/mass spectrometry, in order to assess the
origin of specific groups of compounds within the highly
complex samples obtained from diesel exhaust. Naphthalene
and phenanthrene were shown to increase their concentration
relative to their alkylated derivatives in an exhaust
sample when compared to the relative concentrations found
in the fuel. These parent compounds were being formed
within the combustion chamber, as well as surviving in
unburnt fuel. Nitro-PAC were detected only at
considerably lower concentrations than had previously been
found on dilution tunnel filter samples.
Two new methods for assessing the contribution of
lubricating oil to diesel exhaust emissions have been
developed, and involved matching common peaks in a sample
and a lubricating oil standard. The results demonstrated
that lubricating oil makes a significant contribution to
the total particulates. Increased control of lubricating
oil leakage to the exhaust would help to reduce particulate
emissions to below the new stringent limits.
Date of Award | 1988 |
---|
Original language | English |
---|
Awarding Institution | |
---|
THE ORIGINS OF THE ORGANIC FRACTION IN DIESEL EXHAUST EMISSIONS
TRIER, C. J. (Author). 1988
Student thesis: PhD