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Homogeneous Charge Compression Ignition (HCCI) has emerged as a promising technology for reduction of exhaust emissions and improvement of fuel economy of internal combustion engines. There are generally two proposed methods of realizing the HCCI operation. The first is through the control of gas temperature in the cylinder and the second is through the control of chemical reactivity of the fuel and air mixture. EGR trapping, i.e., recycling a large quantity of hot burned gases by using special valve-train events (e.g. negative valve overlap), seems to be practical for many engine configurations and can be combined with any of the other HCCI enabling technologies. While this method has been widely researched, it is understood that the operating window of the HCCI engine with negative valve overlap is constrained, and the upper and lower load boundaries are greatly affected by the in-cylinder temperature.

In the automotive industry, engine downsizing has been widely accepted as an enabler to improving the fuel economy and reducing the CO₂ emissions. The Atkinson cycle is one of the key technologies. In this paper, the Atkinson cycle with different expansion ratios are compared and analyzed. The investigation is compared with the benchmark whose expansion and compression ratio are identical. The aim is to understand the inherent characteristics of the over-expansion and its effect on the engine performance and emissions. The simulation results show that, the Atkinson cycle produces higher efficiency due to over-expansion. The Atkinson cycle has higher internal EGR compared with the benchmark at equivalent conditions, which contributes to lower the NOx and CO emissions.

Particulate Emissions from Homogeneous Charge Compression Ignition (HCCI) combustion are routinely assumed to be negligible. It is shown here that this is not the case when HCCI combustion is implemented in a direct injection gasoline engine. The conditions needed to sustain HCCI operation were realized using the negative valve overlap method for trapping high levels of residual exhaust gases in the cylinder. Measurements of emitted particle number concentration and electrical mobility diameter were made with a Cambustion DMS500 over the HCCI operating range possible with this hardware. Emissions of oxides of nitrogen, carbon monoxide and unburned hydrocarbons were also measured. These data are presented and compared with similar measurements made under conventional spark ignition (SI) operation in the same engine. Under both SI and HCCI operation, a significant accumulation mode was detected with particle equivalent diameters between 80 and 100 nm.

Diesel engines are the versatile power source and is widely used in passenger car and commercial vehicle applications. Environmental temperature conditions, fuel quality, fuel injection strategies and lubricant have influence on cold start performance of the diesel engines. Strategies to overcome the cold start problem at very low ambient temperature include preheating of intake air, coolant, cylinder block. The present research work investigates the effect of coolant temperatures on passenger car diesel engine’s performance and exhaust emission characteristics during the cold start at cold ambient temperature conditions. The engine is soaked in the -7°C environment for 6 hours. The engine coolant is preheated to the desired coolant temperatures of 10 and 20°C by an external heater and the start ability tests were performed.

In this work, a detailed process for manufacturing 3D alumina composite microengine pistons is presented. A novel moulding process is developed for shaping alumina composites into accurate micrometer-sized parts with a combination of softlithography micromoulding techniques and colloidal ceramic powder process. Ultrathick SU-8 UV-lithography is used for making master moulds followed by mirror duplication of PDMS softmoulds. A preceramic coating resin (PCR) was used as the binder instead of the traditionally organic binders and the PCR turns into an additive to the composite after the sintering process. The sedimentation of Al2O3/acetone suspensions has been characterized with varying poly vinyl pyrrolidone (PVP) as a dispersant. Optimized PCR and curing conditions have been investigated in the soft moulding process, and prove successful in achieving dense and uniform microcomponents.

A study of Multiple Premixed Compression Ignition (MPCI) with heavy naphtha is performed on a light-duty single cylinder diesel engine. The engine is operated at a speed of 1600rpm with the net indicated mean effective pressure (IMEP) from 0.5MPa to 0.9MPa. Commercial diesel is also tested with the single injection for reference. The combustion and emissions characteristics of the heavy naphtha are investigated by sweeping the first (−200 ∼ −20 deg ATDC) and the second injection timing (−5 ∼ 15 deg ATDC) with an injection split ratio of 50/50. The results show that compared with diesel combustion, the naphtha MPCI can reduce NOx, soot emissions and particle number simultaneously while maintaining or achieving even higher indicated thermal efficiency. A low pressure rise rate can be achieved due to the two-stage combustion character of the MPCI mode but with the penalty of high HC and CO emissions, especially at 0.5MPa IMEP.

This paper presents the findings of theoretical and practical studies of an exhaust-gas reforming process, as applied to hydrocarbon fuels. It is shown that hydrogen-containing gaseous reformed fuels can be produced by the interaction of hot combustion products and an n-heptane feedstock in a small-scale catalytic reforming reactor. Predicted and observed reformed fuel chemical compositions were found to correlate well at the lower reactor space velocities tested, where chemical equilibrium conditions can be closely approached. Under these conditions, respective hydrogen and carbon monoxide yields of around 32 and 20 volume per cent were obtained. Under certain conditions, it was found that carbon solids were deposited on the reforming catalyst. Measures taken to avoid this problem included changes in the reforming oxidant to fuel ratio, and the addition of excess steam to the oxidant composition.

Biofuels development and specification are currently driven by the engine (mainly gasoline- and diesel-type) technology, existing fossil fuel specification and availability of feedstock. The ability to use biofuels with conventional fuels without jeopardising the standard fuel specifications is a very effective means for the implementation of these fuels. In this work the effect of dual fuelling with in-cylinder injected ULSD fuel or synthetic second generation biofuels (a Gas-To-Liquid GTL fuel as a surrogate of these biofuels as its composition, specifications and production process are very similar to second generation biofuels) and with inlet port injected bioethanol on the engine performance and emissions were investigated. The introduction of anhydrous bioethanol improved the NOx and smoke emissions, but increased total hydrocarbons and carbon monoxide.

This paper presents a computational investigation of the in-cylinder charge characteristics within a motored 4-valve direct injection HCCI engine cylinder with applied negative valve overlapping. Non-typical intake valve strategy was investigated; whereby the pair of intake valves was assumed to follow the same low-lift short-duration valve-lift profile but actuated at different timings. The phase of intake-valve-opening relative to that of exhaust-valve-closing was optimized in terms of pumping losses. The flow fields generated with such an intake valve strategy were compared to those produced in the same engine cylinder but with typical early and late intake-valve-timing. The computational results of such an approach showed modifications in the in-cylinder swirl and tumble motions during the intake and compression strokes.

Limits on the total future potential of biodiesel fuel due to the availability of raw materials mean that ambitious 20% fuel replacement targets will need to be met by the use of both first and next generation biodiesel fuels. The use of higher percentage biodiesel blends requires engine recalibration, as it affects engine performance, combustion patterns and emissions. Previous work has shown that the combustion of 50:50 blends of biodiesel fuels (first generation RME and next generation synthetic fuel) can give diesel fuel-like performance (i.e. in-cylinder pressure, fuel injection and heat release patterns). This means engine recalibration can be avoided, plus a reduction in all the regulated emissions. Using a 30% biodiesel blend (with different first and next generation proportions) mixed with Diesel may be a more realistic future fuel.

In this paper blends of diesel and gasoline (dieseline) fuelled Partially Premixed Compression Ignition (PPCI) combustion and the comparison to conventional diesel combustion is investigated. The tests are carried out using a light duty four cylinder Euro IV diesel engine. The engine condition is maintained at 1800 rpm, 52 Nm (equivalent IMEP around 4.3 bar). Different injection timings and different amounts of EGR are used to achieve the PPCI combustion. The results show that compared to the conventional diesel combustion, the smoke and NOx emissions can be reduced by more than 95% simultaneously with dieseline fuelled PPCI combustion. The particle number total concentration can be reduced by 90% as well as the mean diameter (from 54 nm for conventional diesel to 16 nm for G50 fuelled PPCI). The penalty is a slightly increased noise level and lower indicated efficiency, which is decreased from 40% to 38.5%.

The purpose of this study is to improve the carbon monoxide (CO) and total hydrocarbons (THC) conversion efficiency of a diesel oxidation catalyst (DOC) by enhancing the monolith thermal behaviour through modification of the substrate cell density and wall thickness. The optimisation is based on catalyst properties (light off performance, conversion efficiency, pressure drop and mechanical durability). These properties were first estimated using theoretical equations derived from literature in order to select commercially available substrates for further modelling studies. The thermal behaviour and conversion efficiency of the selected catalysts under diesel exhaust gas conditions were numerically studied using data from an EU5 diesel engine operating a New European Driving Cycle (NEDC). This simulation was carried out on a commercial exhaust aftertreatment modelling program, AXISUITE. The predictions were compared to a reference coated 400/4 catalyst.