M.K. Abbass

Diesel particulate emissions: The role of unburned fuel

The relationship between diesel fuel composition and that of the solvent organic fraction of diesel particulates was investigated for an old DI Petter engine and a modern DI Perkins engine. Polycyclic aromatic compounds (PAC) were identified using high-resolution capillary column chromatography with a parallel triple detector system for polycyclic aromatic hydrocarbons (PAH), nitrogen-containing PAH, and sulphur-containing PAH. Identification of the PAC using retention indexes was confirmed using an ion trap detector, which was also used to quantify the low-concentration ( < 1 ppm) benzo[a]pyrene. It was conclusively shown for both engines that the bulk of the particulate solvent organic fraction, including the PAH fraction, was unburned fuel. However, there was some evidence that high molecular weight five-ring PAH may have an in-cylinder formation contribution, and it is postulated that this could be due to pyrolysis of lower molecular weight unburned fuel PAH. The contribution of lubricating oil to the particulate PAC is discussed, and evidence is presented that shows the unburned fuel PAC accumulates in the lubricating oil and thus contributes to the particulate PAC via the large lubricating oil component of the particulate PAC.

Diesel particulate composition changes along an air cooled exhaust pipe and dilution tunnel

Exhaust particulate and gas composition samples were obtained at various distances along an externally air cooled exhaust from a Perkins 4-236 single cylinder engine. The change in the particulate composition was determined as a function of the exhaust distance and local temperature. Exhaust temperatures were in the range 200 - 260C at entry to the tunnel at all engine conditions. A constant filter paper and sample temperature of 50C was used for both exhaust and dilution tunnel samples and the filter paper was mounted in an oven for this purpose and the particulate sample was transported through heated lines to this oven. Associated with these particulate measurements were gas analysis measurements. UHC were measured at 180, 50 and 2C in the exhaust and the differences were taken as an indicator of the condensable hydrocarbons over that temperature difference. The results are described in this paper.

The Aging of Lubricating Oil, The Influence of Unburnt Fuel and Particulate SOF Contamination

The role of lubricating oil as a sink for polycyclic aromatic compounds (PAC) and alkanes derived from unburnt fuel is described for two different oils used in two different DI diesel engines. The diesel engines used were, an older technology Petter AV1 single cylinder mine pumping engine and a Perkins 4.236 current technology engine. Analysis of the oil was by gas chromatography using simultaneous parallel triple detection, allowing analysis of hydrocarbons and nitrogen and sulphur containing compounds. Analysis of unused lubricating oil showed negligible concentrations of PAC and low molecular weight alkanes (< C20). The oil from each engine was analysed periodically during use and showed a rapid and significant accumulation of hydrocarbons which reached significant concentrations after only 10 hours use. The older technology engine showed a much higher accumulation rate. The suggested origin of both the PAC and the alkanes is from a dual source, from unburnt fuel and from the solvent organic fraction of the particulate. Internal ratios of alkanes to C 16 and PAC to phenanthrene suggest the particulate derived SOF source of hydrocarbons is more significant for the Perkins engine than for the Petter engine.

The influence of PAH contamination of Lubricating Oil on Diesel Particulate PAH Emissions

The influence of contamination of lubricating oil on the emissions of total particulate, particulate polycyclic aromatic hydrocarbons (PAH) and unburnt fuel and gaseous emissions have been investigated for a modified Perkins 4,236 D.I. diesel engine. In this paper the emissions during fuel firing and motoring in the absence of fuel are compared. The results are discussed.

Factors influencing the composition of the organic fraction of diesel particulates

Abstract The major factors influencing the organic fraction, including the PAH emissions, of diesel particulates are shown to be: 1. 1. Unburned fuel and unburned fuel PAH. 2. 2. Lubricating oil and used lubricating oil PAH. 3. 3. Engine and exhaust deposits and their PAH content. It is concluded that the minimisation of the particulate organic fraction emissions through the minimisation of unburned fuel emissions and lubricating oil consumption will also minimise the PAH emissions.

A Comparison of Exhaust Pipe, Dilution Tunnel and Roadside Diesel Particulate SOF and Gaseous Hydrocarbon Emissions

The solvent organic fraction (SOF) of particulates from the exhaust pipe of a diesel engine, a dilution tunnel and a roadside sample are compared. Three different techniques of SOF analysis are also compared, vacuum oven, solvent extraction and pyroprobe/GC. Gaseous hydrocarbons and the methane contribution were measured in the exhaust pipe throughout the speed and load range of the engine at 185 C and 2 C. The unburnt hydrocarbons decreased with air/fuel ratio for all speeds and there was an overall decrease in emissions with increasing speed. The differential temperature technique showed the maximum mass of hydrocarbon which could condense from the gas phase onto the particulate as the SOF. The method compared well with the actual SOF of the tunnel particulate. Detailed examination of the SOF showed the exhaust pipe particulate SOF was composed of n-alkanes from C16 to C25, the dilution tunnel sample showed condensation of lower molecular weight hydrocarbons from the gas phase onto the particulate.

The determination of the lubricating oil fraction of dieselparticulates

Abstract Three new methods for the determination of the lubricating oil contribution to diesel particulate emissions are described. These are inherently simpler and less reliant on calibration procedures than current GC techniques.