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A new ignition method named Flame Accelerated Ignition (FAI) is proposed in this paper. The FAI system composes of a spark plug and a flame acceleration tunnel with annular obstacles inside. The FAI was experimentally investigated on a rapid compression machine (RCM) with optical accessibility and a single-cylinder heavy duty research engine. In RCM, the flame is significantly accelerated and the combustion process is evidently enhanced by FAI. The ignition delay and the combustion duration are both sharply decreased compared with conventional spark ignition (CSI) case. According to the optical diagnostics, the flame rushes out of the exit of the flame acceleration tunnel at maximum axial speed over 40 m/s, which exceeds 10 times that of CSI flame propagation. In radial direction, the flame curls outwards near the tunnel exit and keeps growing afterwards.

This research focuses on the potential of Homogeneous Charge Induced Ignition (HCII) combustion meeting the Euro V emission standard on a heavy-duty multi-cylinder engine using a simple after-treatment system. However, in our previous studies, it was found that the gasoline ratio was limited in HCII by the over-high compression ratio (CR). In this paper, the effects of reducing CR on the performances of HCII at medium and high loads were explored by experimental methods. It was found that by reducing CR from 18:1 to 16:1 the peak in-cylinder pressure and the peak pressure rise rate were effectively reduced and the gasoline ratio range could be obviously extended. Thus, the combustion and emission characteristics of HCII at medium and high loads were noticeably improved. Soot emissions can be significantly reduced because of the increase of premixed combustion ratio. The reduction could be over 50% especially at high load and high speed conditions.

Homogeneous Charge Induced Ignition (HCII) combustion utilizes a port injection of high-volatile fuel to form a homogeneous charge and a direct injection of high ignitable fuel near the Top Dead Center (TDC) to trigger combustion. Compared to Conventional Diesel Combustion (CDC) with high injection pressures, HCII has the potential to achieve diesel-like thermal efficiency with significant reductions in NOx and PM emissions with relatively low-pressure injections, which would benefit the engine cost saving remarkably. In the first part of current investigation, experiments were conducted at medium load with single diesel injection strategy. HCII exhibited great potential of using low injection pressures to achieve low soot emissions. But the engine load for HCII was limited by high heat release rate. Thus, in the second and third part, experiments were performed at high and low load with double diesel injection strategy.

Gasoline engines suffer low thermal efficiency and diesel engines have the emission problem of the trade-off between NOx and soot emissions. Homogeneous Charge Induced Ignition (HCII) is introduced using a port injection of gasoline to form a homogeneous charge and using a direct injection of diesel fuel to ignite. HCII has the potential to achieve high thermal efficiency and low emission combustion. However, HCII combustion mode still has problems of high THC emissions at low load and high pressure rise rate at high load. In order to improve the gasoline reactivity and reduce THC emissions, double injection of diesel was applied in HCII mode. In order to reduce peak pressure rise rate (PPRR), a two-staged high-temperature heat release is achieved at suitable engine condition. The effects of HCII mode on combustion and emission characteristics are studied in a light-duty engine.

A Homogeneous charge induced ignition (HCII) combustion, realized by in-cylinder fuel blending of gasoline and diesel fuel, was developed and carefully optimized, both on a single cylinder and a multi-cylinder light-duty diesel engines, for high thermal efficiency and near zero emissions in a wide engine-operation range up to IMEP of 1 MPa. The effects of mixing and chemical parameters of HCII combustion, which can be controlled by production-viable hard-ware using conventional gasoline and diesel fuel, include injection timing of diesel fuel, injection rate pattern of diesel fuel (such as split injection), the gasoline/diesel ratio, boost pressure and exhaust gas recirculation (EGR). Based on a single cylinder engine, the experimental result shows that the interaction of the mentioned control parameters plays decisive role in determination of exhaust emissions and thermal efficiency.

Knocking is the main obstacle of increasing compression ratio to improve the thermal efficiency of gasoline engines. In this paper, the concept of stratified stoichiometric mixture (SSM) was proposed to suppress knocking in gasoline engines. The rich mixture near the spark plug increases the speed of the flame propagation and the lean mixture in the end gas suppresses the auto ignition. The overall air/fuel ratio keeps stoichiometric to solve the emission problem using three way catalysts (TWC). Moreover, both the rich zone and lean zone lead to soot free combustion due to homogeneous mixture. The effect on the knocking of homogeneous and stratified mixture was studied in a direct injection spark ignition (DISI) engine using numerical simulation and experimental investigation respectively.

According to China's “oil-poor, gas-litte, coal-rich” structure of energy resources, to promote the development of coal-based methanol fuel as a clean alternative to gasoline and diesel fuel is one of the most realistic options. So the adaptability of methanol gasoline blend fuel used in the gasoline engine and vehilce should be investigated. Engine load performance, engine out emission, air fuel ratio variation and combustion characteristics were tested in a PFI Euro III gasoline engine using gasoline, M10, M15, M20, M30 as fuel without any modification of the engine. Air fuel ratio, light-off temperature and load characteristics of catalystic conversion coefficient were also investigated. And effects of methanol content on fuel consumption and vehicle out emissions of a Euro - vehicle are analyzed.

In a DI diesel engine, THC emissions increase significantly with lower compression ratios, a low coolant temperature, or during the transient state. During the transient after a load increase, THC emissions are increased significantly to very high concentrations from just after the start of the load increase until around the 10th cycle, then rapidly decreased until the 20th cycle, before gradually decreasing to a steady state value after 1000 cycles. In the fully-warmed steady state operation with a compression ratio of 16 and diesel fuel, THC is reasonably low, but THC increases with lower coolant temperatures or during the transient period just after increasing the load. This THC increase is due to the formation of over-lean mixture with the longer ignition delay and also due to the fuel adhering to the combustion chamber walls. A low distillation temperature fuel such as normal heptane can eliminate the THC increase.

Urea Selective Catalytic Reduction (SCR) has been proven to significantly reduce NOx emissions from diesel engines. The thermal decomposition of urea, which forms the ammonia as the reactant, has a crucial effect on the performance and durability of the NOx-SCR system. The incomplete thermal decomposition of urea not only reduces the NOx conversion ratio and increases the ammonia slip, but also leads to deposit formation on the catalyst surface, which will block the pore and the active sites of the catalyst and then decreases the durability of the SCR systems. In this paper, the urea thermolysis was measured using the Thermal Gravimetric Analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR). Then, the performance of the SCR systems under different injection parameters of the Urea-water solution was investigated on a diesel engine test bench. Finally, the deposits on the catalyst were also analyzed using TGA and FTIR.

Biodiesel is an alternative, renewable, clean fuel, which can effectively reduce emissions from diesel engines. However, the effects of biodiesel on engine emissions vary due to the difference in source. In this paper, performance of five different biodiesels was studied: CME, SME, RME, PME and WME. Engine power, fuel consumption, gaseous emissions and PM, DS and none soot fraction (NSF) were investigated in a Cummins ISBe6 Euro III diesel engine fueled with five biodiesels respectively and compared with the diesel fuel. Results revealed that using different biodiesels resulted in PM reductions ranging from 53% to 69%, which included DS reduction ranging from 79% to 83%. Observations showed that fuel oxygen content and viscosity had obvious effects on DS. Higher oxygen content biodiesels produced less DS at high load while lower viscosity biodiesels produced less DS at low load.

Soot emissions in the combustion process of diesel engines are greatly harmful to the environment and human health. Consequently, there is large interest and great efforts in decreasing soot emission from diesel engines to meet the increasingly stringent emission standards. The mechanisms of soot formation and oxidation so far have not been well understood. Laser induced incandescence (LII) is particularly suited to measure the instantaneous spatial distribution of the soot volume concentration, which can offer much needed detailed information of soot distribution for better understanding of soot formation and oxidation. In this paper, a two-color laser induced incandescence (2C-LII) technique was implemented for measuring absolute soot volume fraction in a laminar diesel fuel diffusion flame.

Beijing will implement the 4th stage emission regulations (equivalent to Euro IV) in 2008 ahead of other provinces or cites in China. Beijing Environmental Protection Bureau (EPB) organized petroleum corporations, automobile and engine manufactories as well as research institutes to test the adaptability of the fuels from Chinese refineries to the modern vehicles or engines on the road running conditions in China. In this paper, the effects of diesel fuel quality on combustion and emission of a Euro IV heavy-duty diesel engine as one part of the program were studied to provide technical data to stipulate the feasible diesel fuel standard, which should guarantee modern vehicles or engines to meet the 4th stage regulations. Eight kinds of diesel fuels with different properties, such as cetane number, distillation temperature (T90) and sulfur content, were tested on a Euro IV Cummins heavy-duty diesel engine with urea SCR after-treatment.

Beijing will implement the national 4th stage emissions standards (equivalent to Euro IV emissions standards) in advance in China from 2008. The objective of this study was to provide some technical support for proposing automotive gasoline fuel standards matching with the emission standards. In this paper, tests were conducted on two engines and one gasoline passenger vehicle meeting Euro III or IV emission standards to study the correlation between gasoline fuel properties and engine performances, including power, fuel consumption and emissions. Test results showed that the effect of octane number on engine power depended on engine technologies. High octane number had a negative effect on fuel consumption and emissions. As olefin content increased, the engine-out THC emissions decreased significantly. The vehicle test results also showed that high olefin content greatly reduced the tailpipe THC emissions.

NOx -SCR over Ag/ Al2O3 catalyst using ethanol (C2H5OH) as a reductant has proven its ability to significantly reduce NOx emission in a simulated engine exhaust gas environment. However the real engine exhaust gas environment is too complicated to be simulated. Therefore, the performance evaluation of the Ag/ Al2O3 catalyst in real exhaust gas environment is necessary. Moreover, the ethanol dosing device and control strategy also need to be validated for the practical use. In this paper, firstly the catalyst performance and its sulfur tolerance was tested on an engine test bench and the effect of the catalyst on PM emission was investigated. Then the aftertreatment system composed of Ag/Al2O3 catalyst + Cu/TiO2 catalyst + Pt/TiO2 catalyst and ethanol dosing control based on open loop control was designed, and the diesel engine emission with the aftertreatment system was tested according to ESC test cycle.

This research investigates the influences of the injection timing, injection pressure, and compression ratio on the combustion and exhaust emissions in a single cylinder 1.0 L DI diesel engine operating with ultra-high EGR. Longer ignition delays due to either advancing or retarding the injection timing reduced the smoke emissions, but advancing the injection timing has the advantages of maintaining the thermal efficiency and preventing misfiring. Smokeless combustion is realized with an intake oxygen content of only 9-10% regardless of the injection pressure. Reduction in the compression ratio is effective to reduce the in-cylinder temperature and increase the ignition delay as well as to expand the smokeless combustion range in terms of EGR and IMEP. However, the thermal efficiency deteriorates with excessively low compression ratios.

Ultra-low NOx and smokeless operation at higher loads up to half of the rated torque is attempted with large ratios of cold EGR. NOx decreases below 6 ppm (0.05 g/(kW·h)) and soot significantly increases when first decreasing the oxygen concentration to 16% with cold EGR, but after peaking at 12-14% oxygen, soot then deceases sharply to essentially zero at 9-10% oxygen while maintaining ultra low NOx and regardless of fuel injection quantity. However, at higher loads, with the oxygen concentration below 9-10%, the air/fuel ratio has to be over-rich to exceed half of rated torque, and thermal efficiency, CO, and THC deteriorate significantly. As EGR rate increases, exhaust gas emissions and thermal efficiency vary with the intake oxygen content rather than with the excess air ratio.

A catalyst surfaced on Ag/Al2O3 substrate for the selective catalyst reduction (SCR) of NOx by ethanol was evaluated in a diesel engine, and the effect of the catalyst on the reduction of NOx from the diesel engine under the EURO III ESC test modes was also investigated. The reductant injecting device was designed by means of computational fluid dynamics (CFD) analysis, and the engine test bench including the reductant injection system for the evaluation of the NOx-SCR catalyst performance was established. On the bench, the SCR catalyst with the ethanol reductant was tested at different temperatures and space velocities (SV), and integrated with an oxidation catalyst to reduce the diesel exhaust emissions of NOx, HC and CO. Under the conditions of the SV=30,000 h-1 and the exhaust temperature range of 350∼420°C, the NOx conversion efficiency is high over 90% and low beyond the temperature range.

The combustion characteristics in a partially premixed charge compression ignition (PCCI) engine with n-hexane were compared with ordinary diesel fuel to evaluate combustion improvements with lower distillation-temperature fuels. In the PCCI engine, a lean mixture was formed reasonably with early stage injection and the additional fuel was supplied with a second stage fuel injection after ignition. With n-hexane, thermal efficiency improved while simultaneously maintaining low NOx and smokeless combustion. A CFD analysis simulated the mixture formation processes and showed that the uniformity of the mixture with the first stage injection improves with lower distillation-temperature fuels.

The thermal cracking and polyaromatic hydrocarbon (PAH) formation processes of dimethyl ether (DME), ethanol, and ethane were investigated with chemical kinetics to determine the soot formation mechanism of oxygenated fuels. The modeling analyzed three processes, an isothermal constant pressure condition, a temperature rising condition under a constant pressure, and an unsteady condition approximating diesel combustion. With the same mole number of oxygen atoms, the DME rich mixtures form much carbon monoxide and methane and very little non-methane HC and PAH, in comparison with ethanol or ethane mixtures. This suggests that the existence of the C-C bond promotes the formation of PAH and soot.

Light naphtha, which exhibits two-stage ignition, was induced from the intake manifold for ignition enhancement and a low ignitability fuel or water, which does not exhibit low temperature oxidation, was directly injected early in the compression stroke for ignition suppression in an HCCI engine. Their quantitative balance was flexibly controlled to optimize ignition timing according to operating condition. Ultra-low NOx and smokeless combustion without knocking or misfiring was realized over a wide operating range. Alcohols inhibit low temperature oxidation more strongly than other oxygenated or unoxygenated hydrocarbons, water, and hydrogen. Chemical kinetic modeling for methanol showed a reduction of OH radical concentration before the onset of low temperature oxidation, and this may be the main mechanism by which alcohols inhibit low temperature oxidation.