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Controlled Auto-Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), can improve the fuel economy of gasoline engines and simultaneously achieve ultra-low NOx emissions. However, the difficulty in combustion phasing control and violent combustion at high loads limit the commercial application of CAI combustion. To overcome these problems, stratified mixture, which is rich around the central spark plug and lean around the cylinder wall, is formed through port fuel injection and direct injection of gasoline. In this condition, rich mixture is consumed by flame propagation after spark ignition, while the unburned lean mixture auto-ignites due to the increased in-cylinder temperature during flame propagation, i.e., stratified flame ignited (SFI) hybrid combustion.

SCHC (SI-CAI hybrid combustion), also known as spark-assisted HCCI, has been proved to be an effective method to stabilize combustion and extend the operation range of high efficiency, low temperature combustion. The combustion is initiated by the spark discharge followed by a propagation of flame front until the auto-ignition of end-gas. Spark ignition and the spark timing can be used to control the combustion event. The goal of this research is to study the effect of flame propagation on the auto-ignition timing in SCHC by means of chemiluminescence imaging and heat release analysis based on an optical engine. With higher EGR (exhaust gas recirculation) rate, more fuel is consumed by the flame propagation and stronger correlation between the flame propagation and auto-ignition is observed.

In order to investigate feasibility of DME (Di-methyl ether) assisted gasoline CAI (controlled-auto ignition) combustion, direct DME injection is employed to act as the ignition source to trigger the auto-ignition combustion of premixed gasoline/air mixture with high temperature exhaust gas. Intake re-breathing valve strategy is adopted to obtain internal exhaust recirculation (EGR) that regulates heat release rate and ignitability of the premixed gasoline and air mixture. The effects of intake re-breathing valve timing and 2nd DME injection timing of different split injection ratios were investigated and discussed in terms of combustion characteristics, emission and efficiencies. The analyses showed that re-breathing intake valve timing had a large effect on the operation range of CAI combustion due to EGR and intake temperature variation.

Controlled Auto Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), is one of the most promising combustion technologies to reduce the fuel consumption and NOx emissions. In order to take advantage of the inherent ability to retain a large and varied amount of residual at part-load condition and its potential to achieve extreme engine downsizing of a poppet valve engine running in the 2-stroke cycle, a single cylinder 4-valves camless direct injection gasoline engine has been developed and employed to investigate the CAI combustion process in the 2-stroke cycle mode. The CAI combustion is initiated by trapped residual gases from the adjustable scavenging process enabled by the variable intake and exhaust valve timings. In addition, the boosted intake air is used to provide the in-cylinder air/fuel mixture for maximum combustion efficiency.

In recent years, in order to develop more efficient and cleaner gasoline engines, a number of new engine operating strategies have been proposed and many have been studied on different engines but there is a lack of comparison between various operating strategies and alternative fuels at different SI modes. In this research, a single cylinder direct injection gasoline engine equipped with an electro-hydraulic valve train system has been commissioned and used to study and compare different engine operation modes. In this work, the fuel consumption, gaseous and particulate emissions of gasoline and its mixture with ethanol (E15 and E85) were measured and analysed when the engine was operated at the same load but with different load control methods by an intake throttle, reduced intake valve duration, and positive overlap.

Internal combustion engines are subjected to part-load operation more than in full load during a typical vehicle driving cycle. The problem with the Spark Ignition (SI) engine is its inherent low part-load efficiency. This problem arises due to the pumping loses that occur when the throttle closes or partially opens. One way of decreasing the pumping losses is to operate the engine lean or by adding residual gases. It is not possible to operate the engine unthrottled at very low loads due to misfire. However, the load can also be controlled by changing the intake valve closing timing - either early or late intake valve closing. Both strategies reduce the pumping loses and hence increase the efficiency. However the early intake valve closure (EIVC) can be used as mode transition from SI to CAI combustion.

Some of the challenges of optimising the gasoline direct-injection engines are achieving high rates of atomisation and evaporation of fuel sprays for effective fuel-air mixture formation. This is especially important for the stratified charge when operating under cold-start and part-load conditions. Poorly mixed charge results in the increased production of total Hydrocarbons and Nitrogen Oxides. Many studies have previously focused on improving the spray characteristics of a single fuel injection strategy from direct-injection gasoline injectors, with fuel rail pressures of up to 20MPa. The current study focuses on a split injections strategy and its influence on the spray's structure, fuel-air mixing and atomisation rates. Short pulse widths in the range of 0.3ms to 0.8ms are employed. In particular, the effects of dwell times between the two injections on the second injection's spray characteristics are evaluated.

Engine downsizing is an effective technology to lower automotive CO2 emissions. However, the high load low speed regions are plagued with knocking combustion that are usually overcome by retarding the ignition. This interferes with the efficiency gains due to very late combustion. This paper reports the use of Exhaust Gas Recirculation (EGR) on a Ford Ecoboost 1l downsized gasoline turbocharged direct injection (GTDI) engine to improve efficiency by optimising combustion phasing unlocked by the improved knock resistance with EGR dilution. Further ignition system upgrades are tested for impact towards further efficiency improvements. 75mJ (standard) and 120mJ (high energy) ignition systems were compared. The experimental results showed that the brake specific fuel consumption (BSFC) can be improved by 5.6% with EGR dilution at 25%. When considering combined effects of EGR and high energy ignition upon engine fuel economy, the BSFC gain improves to 7.9%.

Turbulent Jet Ignition (TJI) is a pre-chamber ignition system for an otherwise standard gasoline spark ignition engine. TJI works by injecting chemically active turbulent jets to initiate combustion in a premixed fuel/air mixture. The main advantage of TJI is its ability to ignite and burn, completely, very lean fuel/air mixtures in the main chamber charge. This occurs with a very fast burn rate due to the widely distributed ignition sites that consume the main charge rapidly. Rapid combustion of lean mixtures leads to lower exhaust emissions due to more complete combustion at a lower temperature. For this research, the effectiveness of the Mahle TJI system on combustion stability, lean limit and emissions in a single cylinder spark engine fueled with gasoline at different speeds was investigated. The combustion and heat release process was analyzed and the exhaust emissions were measured.

Biobutanol, i.e. n-butanol, as a second generation bio-derived alternative fuel of internal combustion engines, can facilitate the energy diversification in transportation and reduce carbon dioxide (CO2) emissions from engines and vehicles. However, the majority of research was conducted on spark-ignition engines fuelled with n-butanol and its blend with gasoline. A few investigations were focused on the combustion and exhaust emission characteristics of homogeneous charge compression ignition (HCCI) engines fuelled with n-butanol-gasoline blends. In this study, experiments were conducted in a single cylinder four stroke port fuel injection HCCI engine with fully variable valve lift and timing mechanisms on both the intake and exhaust valves. HCCI combustion was achieved by employing the negative valve overlap (NVO) strategy while being fueled with gasoline (Bu0), n-butanol (Bu100) and their blends containing 30% n-butanol by volume (Bu30).

Controlled Auto Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), is one of the most promising combustion technologies to reduce the fuel consumption and NOx emissions. Most research on CAI/HCCI combustion operations have been carried out in 4-stroke gasoline engines, despite it was originally employed to improve the part-load combustion and emission in the two-stroke gasoline engine. However, conventional ported two-stroke engines suffer from durability and high emissions. In order to take advantage of the high power density of the two-stroke cycle operation and avoid the difficulties of the ported engine, systematic research and development works have been carried out on the two-stroke cycle operation in a 4-valves gasoline engine. CAI combustion was achieved over a large range of operating conditions when the relative air/fuel ratio (lambda) was kept at one as measured by an exhaust lambda sensor.

An experimental study has been carried out with the end goal of minimizing engine-out methane emissions with Premixed Micro Pilot Combustion (PMPC) in a natural gas-diesel Dual-Fuel™ engine. The test engine used is a heavy-duty single cylinder engine with high pressure common rail diesel injection as well as port fuel injection of natural gas. Multiple variables were examined, including injection timings, exhaust gas recirculation (EGR) percentages, and rail pressure for diesel, conventional Dual-Fuel, and PMPC Dual-Fuel combustion modes. The responses investigated were pressure rise rate, engine-out emissions, heat release and indicated specific fuel consumption. PMPC reduces methane slip when compared to conventional Dual-Fuel and improves emissions and fuel efficiency at the expense of higher cylinder pressure.

Climate change mitigation is the main challenge for the automotive industry, as the government issues legislation to combat CO2 emissions. In addition to electrification and battery electric vehicles, using low-carbon and zero-carbon fuels in Internal Combustion (IC) engines can also be an effective way to reach net zero-carbon transport. This study investigated and compared the combustion characteristics, performance and emissions of a highly boosted spark ignition (SI) engine fuelled with EU VI 95 RON E10 gasoline and blends of second-generation bio-gasoline with different ethanol contents of 5% (E5), 10% (E10), and 20% (E20). The single-cylinder SI engine was equipped with a centrally mounted high-pressure injector and supplied externally boosted air. Engine experiments were conducted at 2000 RPM and 3000 RPM with low and high load operations.

The environmental and sustainable energy concerns in transport are being addressed through the decarbonisation path and the potential of hydrogen as a zero-carbon alternative fuel. Using hydrogen to replace fossil fuels in various internal combustion engines shows promise in enhancing efficiency and achieving carbon-neutral outcomes. This study presents an experimental investigation of hydrogen (H2) combustion and engine performance in a boosted spark ignition (SI) engine. The H2 engine incorporates both port fuel injection (PFI) and direct injection (DI) hydrogen fuel systems, capable of injecting hydrogen at pressures of up to 4000 kPa in the DI system and 1000 kPa in the PFI operations. This setup enables a direct comparison of the performance and emissions of the PFI and DI operations. The study involves varying the relative air-to-hydrogen ratio (λ) at different speeds to explore combustion and engine limits for categorising and optimising operational regions.