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In a previous paper [ 1 ], the authors have proposed a cost effective air hybrid concept based on a proprietary intake system and cam profile switching (CPS) system [ 2 ]. It was shown through engine simulations that the pneumatic hybrid operation could be achieved with about 15% regenerative efficiency. The proposed air hybrid operation can be achieved with proven technologies and engine components and hence it represents a cost-effective, reliable and quick deployable solution for low carbon vehicles. In this work, a four-cylinder 2 litre diesel engine has been modelled to operate on refined air hybrid engine configurations and the braking and motoring performance of each configuration have been studied. Both air hybrid systems can be constructed with production technologies and incur minimum changes to the existing engine design.

Low combustion efficiency and high hydrocarbon emissions at low loads are key issues of natural gas and diesel (NG-diesel) dual fuel engines. For better engine performance, two diesel-spray-orientated (DSO) bowls were developed based on the existing diesel injector of a heavy-duty diesel engine with the purpose of placing more combustible natural gas/air mixture around the diesel spray jets. A protrusion-ring was designed at the rim of the piston bowl to enhance the in-cylinder flame propagation. Numerical simulations were conducted for a whole engine cycle at engine speed of 1200 r/min and indicated mean effective pressure (IMEP) of 0.6 MPa. Extended coherent flame model 3 zones (ECFM-3Z) combustion model with built-in soot emissions model was employed. Simulation results of the original piston bowl agreed well with the experimental data, including in-cylinder pressure and heat released rate (HRR), as well as soot and methane emissions.

In this paper, a novel cost-effective air hybrid powertrain concept for buses and commercial vehicles, Brunel Regenerative Engine Braking Device (RegenEBD) technology, is presented and its performance during the braking process is analysed using the Ricardo WAVE engine simulation programme. RegenEBD is designed to convert kinetic energy into pneumatic energy in the compressed air saved in an air tank. Its operation is achieved by using a production engine braking device and a proprietary intake system design. During the braking operation, the engine switches from the firing mode to the compressor mode by keeping the intake valves from fully closed throughout the four-strokes by installing the Variable Valve Exhaust Brake (VVEB) device on the intake valves. As a result, the induced air could be compressed through the opening gap of intake valves into the air tank through the modified intake system.

A base diesel fuel with 37% 1-3 ring aromatics and 12.9% PAH was passed through a dearomatising process that removed the two and three ring aromatics and reduced the single ring aromatics to 14%. These two fuels plus a combination of 60% of the original fuel with 40% of the low aromatic fuel were tested on a Perkins Phaser TCIC diesel engine of US 1991 emissions standards over the EC 13 mode cycle. The fuels and particulate SOF were analysed for all the n-alkanes and all of the PAH of significant concentration. The high speed maximum power particulate SOF were analysed in detail for all three fuels and mass emissions of 15 n-alkanes and 15 PAH determined and 15 other non-fuel PAH searched for. Most of the results showed that the composition of the SOF in terms of n-alkane and PAH was predominantly unburnt fuel compounds, the fuel with negligible PAH had very low PAH emissions compared with the parent fuel with a high PAH content.

The relationship between a diesel engine lubricating oil consumption and the particulate volatile unburnt lube oil emissions depends on the combustion efficiency of the lube oil in the engine. Very little data exists on this topic and this is reviewed. An experimental procedure for the determination of lubricating oil consumption from a calcium mass balance between the lubricating oil and particulate was used combined with a thermogravimetric analysis of the particulate to obtain the unburnt lube oil emissions, together these techniques enabled the lube oil combustion efficiency to be determined This technique only requires the particulate filter paper as an experimental measurement in the engine test. Initial results for a Perkins 4-236 NA DI diesel engine are presented for a range of loads and speeds.

The results of an experimental study in a DI Diesel engine are presented which shows that partial premixing, using direct diesel fumigation of the inlet air, achieved a reduction in the ignition delay, the magnitude of high frequency rapid pressure fluctuations, the maximum rate of pressure rise and the amplitude of the rate of the high frequency pressure oscillations. Two methods of diesel fumigation were investigated. The difference between these two methods was the degree of premixing of diesel fuel with the inlet air. The first technique used a fine (5 micron) diesel spray onto a glow plug and the second technique used prevaporised diesel. A Perkins 4-236 engine was run both with and without fumigation at two different steady state speeds roughly covering both city and highway running conditions.

Pure sunflower oil was used in a Perkins 4-236 DI diesel engine at 2200 rpm and maximum power, particulate samples at 50°C were obtained from the exhaust 7m from the exhaust port in an air cooled exhaust pipe. The engine lubricating oil was fresh and contained no fuel contamination. The sunflower oil had higher particulate, UHC, CO and NOx emissions than for diesel. This was attributed to the shorter ignition delay and higher diffusive burning. The higher UHC emissions also resulted in a higher particulate SOF. Sunflower oil contained no fuel PAH above 1 ppm and there was no source of PAH from the lubricating oil. However, significant PAH emissions were found in the particulate SOF, but at a level well below that for diesel. It was shown that the bulk of this PAH could be attributed to the thermal desorption of PAH from the exhaust pipe walls. Hence, there was little PAH generated by pyrosynthesis as part of the combustion process.

A numerical study has been performed to investigate the soot emission from a high-speed single-cylinder direct injection diesel engine. It was shown that the current KIVA CFD code with the standard evaporation model could predict the experimental trend, where at a low speed running condition a higher smoke reading is reached when increasing the injector protrusion into the piston chamber and conversely a lower smoke reading was recorded for the same change in injector protrusion at a high running speed condition. Evidence of inappropriate air/fuel mixing was seen via rates of heat release analyses, especially in the high-speed conditions. Efforts to reduce this discrepancy by way of improvements to the KIVA breakup and evaporation models were made. Results of the modified models showed improvements in the vapor dispersion of the atomizing liquid jet, thus affecting the mixing rates and predicted smoke emissions.

Over the last decade, the high speed direct injection (HSDI) diesel engine has made dramatic progress in both its performance and market share in the light duty vehicle market. However, with ever more stringent emission legislation to be introduced over coming years, the simultaneous reduction of NOx and Particulate Matter (PM) from the HSDI diesel engine is being intensively researched. As part of a European Union (EU) NICE integrated project, research has been carried out to investigate the fuel injection and combustion from a narrow cone fuel injector in a high speed direct injection single cylinder engine with optical access utilising a multiple injection strategy and various alternate fuels. The fuel injection process was visualised using a high speed imaging system comprising a copper vapour laser and a high speed video camera. The auto-ignition and combustion process was analysed through the chemiluminescence images of CHO and OH using an intensified CCD camera.

Over the last decade, the diesel engine has made dramatic progress in its performance and market penetration. However, in order to meet future emissions legislations, Nitrogen Oxides (NOx) and particulate matters' (PM) emissions will need to be reduced simultaneously. Nowadays researchers are focused on different combustion modes which can have a great potential for both low soot and low NOx. In order to achieve this, different injection strategies have been investigated. This study investigates the effects of split injection strategies with high levels of Exhaust Gas Recirculation (EGR) on combustion performance and emissions in a single-cylinder direct injection optical diesel engine. The investigation is focused on the effects of injection timing of split injection strategies. A Ricardo Hydra single-cylinder optical engine was used in which conventional experimental methods like cylinder pressure data, heat release analysis and exhaust emissions analysis were applied.

The piston bowl design is one of the most important factors that affect the air/fuel mixing and the subsequent combustion and pollutant formation processes in a direct injection diesel engine. The bowl geometry and dimensions, such as pip region, bowl lip area, and torus radius are all known to have an effect on the in-cylinder mixing and combustion process. In order to understand better the effect of torus radius, three piston bowls with different torus radius and lip shapes designs but with the same lip area and pip inclination were investigated using Computational Fluid Dynamics (CFD) engine modelling. KIVA3V with improved sub-models was used to model the in-cylinder flows and combustion process, and it was validated on a High-Speed Direct Injection (HSDI) engine with a 2nd generation common rail fuel injection system.

This work is part of a larger programme to investigate the storage at low power conditions and release at high power conditions in real diesel engine exhaust systems. The initial particle storage in the oxidation catalyst, followed by a release of particles a few minutes later, is explored, and the associated particle size distribution changes determined. A Ford 1.8L IDI Diesel Engine, Turbocharged and Intercooled (TCIC), and equipped with Exhaust Gas Recirculation (EGR), was used under high speed and high power conditions, both during cold start. The commercial close-coupled diesel oxidation catalyst had an associated hydrocarbon adsorber for cold start hydrocarbon control. The tests were carried out using a step cold start to a fixed low power output, typical of city driving. The ELPI particle size analyser was used together with constant temperature gravimetric filter based mass samples upstream and downstream of the catalyst.

The purpose of the European « SPACE LIGHT » (Whole SPACE combustion for LIGHT duty diesel vehicles) 3-year project launched in 2001 is to research and develop an innovative Homogeneous internal mixture Charged Compression Ignition (HCCI) for passenger cars diesel engine where the combustion process can take place simultaneously in the whole SPACE of the combustion chamber while providing almost no NOx and particulates emissions. This paper presents the whole project with the main R&D tasks necessary to comply with the industrial and technical objectives of the project. The research approach adopted is briefly described. It is then followed by a detailed description of the most recent progress achieved during the tasks recently undertaken. The methodology adopted starts from the research study of the in-cylinder combustion specifications necessary to achieve HCCI combustion from experimental single cylinder engines testing in premixed charged conditions.

An oxidation catalyst was fitted on a DI diesel engine for an experimental study involving an oxidation catalyst and the use of superheated steam for fumigating the intake air. Results are compared with that of the influence of low level of fumigation of the intake air with superheated diesel fuel. Exhaust emissions of NOx, CO, UHC, TPM, SOF and Carbon were measured and quantified on upstream and downstream of a low light off temperature (250 °C) oxidation catalyst. The technique used an electric vaporizer for producing superheated steam and prevaporised superheated diesel fumes at 350 °C, respectively. A low emissions version of Perkins 4-236 engine with squish lip piston was run both with and without fumigation at two speeds 1200 rpm and 2200 rpm. Roughly covering both city and highway running conditions.

Results showed the influence of the oxidation catalyst on exhaust emissions from a DI diesel engine due to the partial premixing, fumigation of the intake air with diesel fuel. Exhaust emissions of NOx, CO, UHC, TPM, SOF and Carbon were measured and quantified on upstream and downstream of a low light off temperature (250 °C) oxidation catalyst. Two methods of diesel fumigation of the intake air with fuel were used. The difference between these two methods was the degree of premixing of diesel fuel with the intake air. The first technique used a high-pressure fine diesel spray onto a glow plug and the second technique used an electric vaporizer for prevaporised superheated diesel fumes at 350 °C. A low emissions version of Perkins 4-236 engine with squish lip piston was run both with and without fumigation at two speeds 1200 rpm and 2200 rpm. Roughly covering both city and highway running conditions.

Results of an experimental study of a DI Diesel engine are presented, which show the influence of partial premixing fumigation of the intake air with diesel fuel on the exhaust emissions and the engine performance parameters. Exhaust emissions of NOx, CO, UHC, TPM, SOF and Carbon were measured and quantified. Engine performance parameters include the event of the start of combustion and fuel consumption besides other parameters, which were published elsewhere. The study also showed that during a “normal operation” of a DI diesel engine, no emissions trade-off exists between NOx and TPM. Rather these emissions need separate technological measures for their specific control. Two methods of diesel fumigation were used. The difference between these two methods was the degree of premixing of diesel fuel with the intake air.

Reduction of NOx was achieved in an experimental study in a DI Diesel engine. Results are presented, which show the comparison of the influence of partial fumigation of the intake air with superheated diesel fuel vapour and that of steam on the exhaust emissions and the engine performance parameters. Exhaust emissions of NOx, CO, UHC, TPM, SOF and Carbon were measured and quantified. The technique used for fumigating the intake air with fuel and steam consisted of an electric vaporizer for producing perfectly prevaporised superheated diesel fumes and steam at 350°C. A low emissions version of Perkins 4-236 engine with squish lip piston was run with the fumigation of the intake air with superheated fuel vapour and that of steam at two speeds 1200 rpm and 2200 rpm, roughly covering both city and highway running conditions.

The effects of Air/Fuel (A/F) ratios and Exhaust Gas Re-Circulation (EGR) rates on Homogeneous Charge Compression Ignition (HCCI) combustion of n-heptane have been experimentally investigated. The experiments were carried out in a single-cylinder, 4-stroke and variable compression-ratio engine equipped with a port fuel injector. Investigations concentrate on the HCCI combustion of n-heptane at different A/F ratios, EGR rates and their effects on knock limit, engine load, combustion variability, and engine-out emissions such as NOx, CO, and unburned HC. Variations of auto-ignition timings and combustion durations in the two-stage combustion process are analyzed in detail. Results show that HCCI combustion with a diesel type fuel can be implemented at room temperature with a conventional diesel engine compression-ratio. However, its knock limit occurs at very high A/F ratios, although high EGR rates can be tolerated.

Modern heavy duty diesel engines can well extend the goal of 50% brake thermal efficiency by utilizing waste heat recovery (WHR) technologies. The effect of an ORC WHR system on engine brake specific fuel consumption (bsfc) is a compromise between the fuel penalty due to the higher exhaust backpressure and the additional power from the WHR system that is not attributed to fuel consumption. This work focuses on the fuel efficiency benefits of installing an ORC WHR system on a heavy duty diesel engine. A six cylinder, 7.25ℓ heavy duty diesel engine is employed to experimentally explore the effect of backpressure on fuel consumption. A zero-dimensional, detailed physical ORC model is utilized to predict ORC performance under design and off-design conditions.

In order to meet increasingly stringent emissions standards and lower the fuel consumption of heavy-duty (HD) vehicles, significant efforts have been made to develop high efficiency and clean diesel engines and aftertreatment systems. However, a trade-off between the actual engine efficiency and nitrogen oxides (NOx) emission remains to minimize the operational costs. In addition, the conversion efficiency of the diesel aftertreatment system decreases rapidly with lower exhaust gas temperatures (EGT), which occurs at low load operations. Thus, it is necessary to investigate the optimum combustion and engine control strategies that can lower the vehicle’s running costs by maintaining low engine-out NOx emissions while increasing the conversion efficiency of the NOx aftertreament system through higher EGTs.