Combustion Phasing Controllability with Dual Fuel Injection Timings

Reactivity controlled compression ignition through in-cylinder blending gasoline and diesel to a desired reactivity has previously been shown to give low emission levels and a clear simultaneous efficiency advantage. To determine the possible viability of the concept for on-road application, the control space of injection parameters with respect to combustion phasing is presented. Four injection strategies have been investigated, and for each the respective combustion phasing response is presented. Combustion efficiency is shown to be greatly affected by both the injection-timing and injection-strategy. All injection strategies are shown to break with the common soot-NOx trade-off, with both smoke and NOx emissions being near or even below upcoming legislated levels. Lastly, pressure rise rates are comparable with conventional combustion regimes with the same phasing. The pressure rise rates are effectively suppressed by the high dilution rates used

Experimental investigation of low octane fuel composition effects on load range capacity in Partially Premixed Combustion (PPC)

Abstract Manente and coworkers [1] discovered that a fuel in the gasoline boiling range with 70 Octane Number (ON70) is applicable for Partially Premixed Combustion (PPC) over the complete load range without additional engine adaptations. Using such a fuel in combination with an appropriate dilution strategy was shown to simultaneously achieve low emissions and high efficiency without any drawback in combustion control. In the present paper the load range applicability of ON70 fuels in PPC is further investigated. To do so, four fuels in the ON70 range are selected, with different chemical and physical properties. The goal of testing these fuels is to achieve low emissions and high efficiency over the complete load range of PPC

Experimental study on the impact of operating conditions on PCCI combustion

In a short–term scenario, using near–standard components and conventional fuels, PCCI combustion relies on a smart choice of operating conditions. Here, the effects of operating conditions on ignition delay, available mixing time, combustion phasing and emissions are investigated. In the PCCI regime, NOX and smoke have been shown to be efficiently reduced with elongated mixing time. For viable PCCI combustion, one would require a Combustion Delay (CD) which is long enough to bring both NOX and smoke levels down to acceptable values. For the completeness of combustion, the resulting unburned hydrocarbon and carbon monoxide emissions, as well as the associated fuel consumption; mixing time should, however, be as short as possible. Most parameters strongly correlate with combustion delay, independent of how this is achieved. Lastly, the best points experienced for a number of cases are given

In-cylinder soot precursor growth in a low-temperature combustion diesel engine : laser-induced fluorescence of polycyclic aromatic hydrocarbons

The growth of poly-cyclic aromatic hydrocarbon (PAH) soot precursors are observed using a two-laser technique combining laser-induced fluorescence (LIF) of PAH with laser-induced incandescence (LII) of soot in a diesel engine under low-temperature combustion (LTC) conditions. The broad mixture distributions and slowed chemical kinetics of LTC "stretch out" soot-formation processes in both space and time, thereby facilitating their study. Imaging PAH–LIF from pulsed-laser excitation at three discrete wavelengths (266, 532, and 633 nm) reveals the temporal growth of PAH molecules, while soot-LII from a 1064-nm pulsed laser indicates inception to soot. The distribution of PAH–LIF also grows spatially within the combustion chamber before soot-LII is first detected. The PAH–LIF signals have broad spectra, much like LII, but typically with spectral profile that is inconsistent with laser-heated soot. Quantitative natural-emission spectroscopy also shows a broad emission spectrum, presumably from PAH chemiluminescence, temporally coinciding with of the PAH–LIF

Combustion phasing controllability with dual fuel injection timings

Reactivity controlled compression ignition through in-cylinder blending gasoline and diesel to a desired reactivity has previously been shown to give low emission levels and a clear simultaneous efficiency advantage. To determine the possible viability of the concept for on-road application, the control space of injection parameters with respect to combustion phasing is presented. Four injection strategies have been investigated, and for each the respective combustion phasing response is presented. Combustion efficiency is shown to be greatly affected by both the injection-timing and injection-strategy. All injection strategies are shown to break with the common soot-NOx trade-off, with both smoke and NOx emissions being near or even below upcoming legislated levels. Lastly, pressure rise rates are comparable with conventional combustion regimes with the same phasing. The pressure rise rates are effectively suppressed by the high dilution rates used

Euro VI without fuel penalty? Experimental study on the impact of operating conditions and fuel composition on PCCI combustion

Poster presentati

Premixed charge compression ignition combustion modeling with a multi-zone approach including inter-zonal mixing

Premixed charge compression ignition (PCCI) is a clean and efficient alternative for classical diesel combustion. The concept of PCCI combustion is associated with early injection of the fuel whilst applying high exhaust gas recirculation (EGR) levels and operation with a highly lean mixture such that ignition takes place (well) after the injection event. Thus, it is possible to reduce soot and oxides of nitrogen (NOx) emissions simultaneously. PCCI combustion is analyzed using a multi-zone model. In the multi-zone model, chemical mechanisms which are much more detailed compared to those used in computational fluid dynamics (CFD) approaches can be introduced directly. The CFD model is still used to predict the initial fuel stratification in the cylinder which is important to improve the quality of the model. For the analysis, dedicated experiments with n-heptane are used to evaluate the results of the model. In such a multi-zone model, 10 zones prove to be sufficient to describe the stratification with adequate resolution. It is observed that different fuel distributions have a large influence on the emissions when there is no mixing between the zones. To overcome this dependence, a basic inter-zonal diffusive mixing is applied. The level of mixing is estimated with a sensitivity study. When the inter-zonal mixing is included, emission results become much less sensitive to the crank angle (CA) at which the charge stratification is sampled and the simulation is initialized

Preliminary analysis of soot and UHC emissions under PCCI conditions

The concept of premixed charge compression ignition (PCCI) is associated with early injection of the fuel whilst applying high exhaust gas recirculation (EGR) levels and operation with a highly lean mixture such that ignition takes place after the injection event. Thus, it is possible to reduce soot and nitric oxides (NOx) emissions to very low values. PCCI combustion is analyzed using a multi-zone model. It is confirmed that no soot is formed in both numerical and experimental analysis. However, the trend of unburned hydrocarbon (UHC) emissions is not predicted accurately. The cooling model has a considerable impact on the ignition behaviour