Since the use of diesel engines is still increasing, the contribution of their incomplete combustion products to air pollution is becoming ever more important. The presence of irritating and genotoxic substances in both the gas phase and the particulate phase constituents is considered to have significant health implications. The quantity of soot particles and the particle-associated organics emitted from the tail pipe of a diesel-powered vehicle depend primarily on the engine type and combustion conditions but also on fuel properties. The quantity of soot particles in the emissions is determined by the balance between the rate of formation and subsequent oxidation. Organics are adsorbed onto carbon cores in the cylinder, in the exhaust system, in the atmosphere and even on the filter during sample collection. Diesel fuel contains polycyclic aromatic hydrocarbons (PAHs) and some alkyl derivatives. Both groups of compounds may survive the combustion process. PAHs are formed by the combustion of crankcase oil or may be resuspended from engine and/or exhaust deposits. The conversion of parent PAHs to oxygenated and nitrated PAHs in the combustion chamber or in the exhaust system is related to the vast amount of excess combustion air that is supplied to the engine and the high combustion temperature. Whether the occurrence of these derivatives is characteristic for the composition of diesel engine exhaust remains to be ascertained. After the emission of the particles, their properties may change because of atmospheric processes such as aging and resuspension. The particle-associated organics may also be subject to (photo)chemical conversions or the components may change during sampling and analysis. Measurement of emissions of incomplete combustion products as determined on a chassis dynamometer provides knowledge of the chemical composition of the particle-associated organics. This knowledge is useful as a basis for a toxicological evaluation of the health hazards of diesel engine emissions.

Combustion of diesel fuel from a toxicological perspective. I. Origin of incomplete combustion products.

The regulated level of diesel particulate mass for 2008 light-duty diesel on-road engines will be 0005 g km−1 in Europe Measurements by weighing and analysis of this low level of particulate mass based on chemical extraction are costly, time consuming and hazardous because of the use of organic solvents, potentially carcinogenic An alternative to this analysis is proposed here: a thermal mass analyser that measures the volatile fraction (VOF) as well as the soot fraction of the particulate matter (PM) collected on a cleaned fibre glass filter This paper evaluates this new thermal mass measurement (TGA) as a possible alternative to the conventional chemical extraction method, and presents the results obtained with both methods when testing a diesel engine fuelled with a reference diesel fuel (REF), a pure biodiesel fuel (B100) and two blends with 30% and 70% v/v biodiesel (B30 and B70, respectively)

https://iopscience.iop.org/article/10.1088/0957-0233/18/3/015/pdf

Thermogravimetric analysis of diesel particulate matter

Significant amounts of particle-phase organic compounds are present in the exhaust of diesel vehicles. It is believed that some of these compounds have a greater impact on human health and the environment than other compounds. Therefore, it is of significant importance to speciate particle-phase organic compounds of diesel particulate matter (PM) to clarify the effects of PM on human health and the environment, and to understand the mechanisms of organic compounds formation in PM. A dilution source sampling system was incorporated into the exhaust measurement system of a single-cylinder heavy-duty direct-injection (D.I.) diesel engine. This system was designed specifically to collect fine organic aerosols from diesel exhaust. The detailed system is described in Kweon et al. [27]. Samples were collected on a series of quartz fiber filters and analyzed by gas chromatography/mass spectrometry (GC/MS) techniques to quantify particle-phase organic compounds for various engine-operating conditions. The Cummins N14-series single-cylinder research engine was run under the California Air Resources Board (CARB) 8-mode test cycle. Thirty nine particle-phase organic compounds were quantified with high resolution particularly for light and medium load conditions. At the high load conditions, most of the particle-phase organic compounds were below detection limit of the GC/MS. Results show that detailed organic chemical composition of PM is significantly affected by the change in the engine load and speed. Most of the organic compounds were observed at idling, light, and medium load conditions. The n-alkanes and PAHs comprised between 68 and 83% of the total identified particle-phase organic compounds with the n-alkanes between 39 and 44% and the PAHs between 28.5 and 39.3% for the conditions except the mode 2, in which the concentrations of the particle-phase organic compounds were above detection limits. The hydrocarbon distribution shows that the fractions of carbon numbers in PM varied significantly, particularly those with carbon numbers below 20 and between 25 and 30. Carbon numbers between 25 and 30 comprised a significant portion in the hydrocarbon distributions at light load and idling conditions. However, the fraction of the carbon number of less than 20 increased tremendously at higher loads. Carbon numbers of larger than 30 remained without significant change.

Effect of Engine Operating Conditions on Particle-Phase Organic Compounds in Engine Exhaust of a Heavy-Duty Direct-Injection (D.I.) Diesel Engine

The Impact of Oil Formulation on Emissions from Diesel Engines

Analysis of particulate organics in a forest atmosphere by thermodesorption GC/MS

Particulate-bound hydrocarbons emitted by diesel engines have been analysed using a rapid new technique. The method involves directly loading filter-borne particulate into a modified injection port of a gas chromatograph. Hydrocarbons are vaporized in this solid sample injection system and subsequently become adsorbed on to a chromatogaphy column. The merits of this procedure are demonstrated by comparing results with those obtained using conventional gas chromatography (with liquid injection) and thermogravimetry. The contribution of unburned engine oil to diesel particulate emissions has been investigated using the new method. For a DI truck diesel engine operated over the U.S. Federal Heavy Duty Transient Cycle it is shown that 40% of the particulate appears to be derived from unburned oil. For a comparable IDI truck diesel engine this value was 28%.

R. D. Cuthbertson

Papers

Direct analysis of diesel particulate-bound hydrocarbons by gas chromatography with solid sample injection