Insights into the hydrocarbon and carbon monoxide emissions in moderately and highly dilute Low Temperature Combustion

Abstract

Low-temperature combustion in diesel engines offers attractive benefits through simultaneous reduction in the nitrogen oxide emissions and the soot emissions. However, it is known that the in-cylinder conditions typical of low-temperature combustion operation tend to produce high emissions of unburned hydrocarbons and carbon monoxide, reducing the combustion efficiency. The present study develops from the hypothesis that this characteristic poor combustion efficiency is due to the in-cylinder mixture preparation strategies which are non-optimally matched to the requirements of the low-temperature combustion mode. In this work, the effects of three key fuel path parameters, namely the injection fuel quantity ratio, the dwell and the injection timing, on the carbon monoxide and hydrocarbon emissions were examined using a central-composite-design design-of-experiments method. The experiments were performed on a single-cylinder diesel research engine operating in a mixing-controlled low-temperature combustion mode at high and moderate exhaust gas recirculation rates with a split fuel injection for all conditions. The experiments identified the potential of fuel metering control for optimising the hydrocarbon emissions in low-temperature combustion by showing the effects of the fuel control parameters on the fuel mixing quality and the emission formation mechanisms. The response surfaces created from the detailed statistical analysis give a potent visualisation of the constraints on low-temperature combustion operation. This in turn allowed improved prescription of combustion modifications with the potential to moderate the negative effects observed.

The effects of increasing FAME biodiesel content on combustion characteristics and HC emissions in high-EGR low temperature combustion

“…Experiments were performed in a single-cylinder diesel engine research facility that is described in detail in a number of previous studies from the authors' research group [20,21,22,23,24]. The facility features an AVL 5402 single-cylinder research engine-a single cylinder version of typical 2.0 litre four-cylinder automotive high-speed direct injection (HSDI) diesel enginemounted on a compact 38 kW dynamometer test bed.…”

A Study on Kinetic Mechanisms of Diesel Fuel Surrogate n-Dodecane for the Simulation of Combustion Recession

“…However, to meet future requirements of increased efficiency and reduced emissions, various modifications to the basic diesel cycle, such as the use of homogeneous charge compression ignition (HCCI) [13], exhaust gas recirculation (EGR) [25], or some other form of low temperature combustion (LTC) strategy [17], are likely required. LTC, in general, has shown great promise in mitigating emissions of nitrogen oxides (NO x ) and particulate matter (PM) [30]. While different LTC operating strategies and injection processes greatly influence the final emissions outcomes, end of injection (EOI) processes, in particular, have been found to play a critical role with respect to hydrocarbon emissions.…”

Effects of intake-port throttling on combustion behaviour in diesel low-temperature combustion

“…The research engine facility, which has been fully described and illustrated schematically in a number of previous works from the authors' research group, [7][8][9][10][11] was instrumented with the provision to measure boosted intake air temperature and pressure, fuel and air flow rates, and in-cylinder pressure. Intake pressure was measured using Kistler 4045A5 piezo-resistive pressure transducer while the in-cylinder pressure was measured with a piezoelectric AVL QC34C flushmounted water-cooled transducer.…”

“…It was anticipated that there will be significant changes in the quantity and in-cylinder location of HC species which may help to supplement the current knowledge on CO formation and overall combustion efficiency trends. In addition, the potential of increased in-cylinder mixing to extend the rather narrow boundaries 7,8 of acceptable LTC combustion (particularly with respect to soot emissions) is investigated.…”