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The diesel particulate filter (DPF) is an effective technology for particulate matter (PM) and particle number (PN) reduction. On heavy-duty diesel engines, the passive regeneration by Diesel Oxidation catalysts (DOC) and catalyzed DPFs (CDPF) is widely used for its simplicity and low cost, which is generally combined with the active regeneration of exhaust fuel injection. This study investigated a DOC-CDPF system with exhaust fuel injection upstream of the DOC. The system was integrated with a 7-liter diesel engine whose engine-out PM emission was below the Euro IV level and tested on an engine dynamometer. PM and PN concentrations were measured based on the Particle Measurement Programme (PMP), and the number/size spectrum for particles was obtained by a Differential Mobility Spectrometer (DMS). The filtration efficiency of DPF on PN was higher than 99% in ESC test, while the efficiency on PM was only 58%.

Fuel quality, including antiknock rating, plays a critical role in enabling optimal operation of advanced gasoline engines. As new designs introduced into the market implement technologies to improve fuel efficiency, the overall octane level of the gasoline pool may need to be increased to ensure optimal performance. Turbocharging, higher compression ratios and downsized displacement all lead to higher combustion pressures and temperatures that make engines more susceptible to knocking. All modern gasoline engines are equipped with knock sensors that detect abnormal combustion resulting from autoignition caused by insufficient octane quality. The ability of an engine to account for the use of lower octane fuel by retarding spark timing and enriching air-fuel ratio to reduce knock is limited, and engine efficiency is directly and adversely impacted when the use of lower octane gasoline is accommodated, resulting in higher fuel consumption.

HVO contains paraffin only and UVOME is methyl ester with long chain alkyl while mineral diesel is complex compound and contains lots of aromatic and Naphthenic. This paper compares the effects of EGR on the two different types of biodiesels blends compared to diesel. The combustion performance and emissions of biodiesel blends of UVOME and HVO were investigated in a turbocharged direct injection V6 diesel engine with EGR swept from 0% to the calibration setting for diesel. The EGR sweep tests with increment of 5% were conducted at the engine speed of 1500 RPM for the load of between 72 Nm to 143 Nm, using sulfur-free diesel blended with UVOME and HVO at 30% and 60% by volume respectively. As the EGR rate was increased, the brake specific fuel consumption (BSFC) for each fuel was reduced at lower load but increased at higher load. The BSFC of mineral diesel was lower than UVOME blends and similar to the HVO blends.

2, 5-Dimethylfuran (DMF) has been receiving increasing interest as a potential alternative fuel to fossil fuels, owing to the recent development of new production technology. However, the influence of DMF properties on the in-cylinder fuel spray and its evaporation, subsequent combustion processes as well as emission formation in current gasoline direct injection (GDI) engines is still not well understood, due to the lack of comprehensive understanding of its physical and chemical characteristics. To better understand the spray characteristics of DMF and its application to the IC engine, the fuel sprays of DMF and gasoline were investigated by experimental and computational methods. The shadowgraph and Phase Doppler Particle Analyzer (PDPA) techniques were used for measuring spray penetration, droplet velocity and size distribution of both fuels.

The new fuel, 2, 5-dimenthylfuran, known as DMF, captured worldwide attention since the discovery of its new production method. As a potential bio-fuel, DMF is competitive to gasoline in many areas, such as energy density, combustion efficiency and emissions. However, little work has been performed on its unconventional combustion mode. In this work, high speed imaging and thermal investigation are carried out to study DMF and gasoline dual-injection on a single cylinder, direct injection spark ignition optical engine. This dual-injection strategy combines direct injection (DI) and port fuel injection (PFI) simultaneously which means two different fuels can blend in the cylinder with any ratio. It provides a flexible way to use bio-fuels with gasoline. DMF DI with gasoline PFI and ethanol DI with gasoline PFI are studied under different injection proportions (by volume) and IMEPs.

A new combustion mode namely multiple premixed compression ignition (MPCI) for gasoline engines was proposed. The MPCI mode can be realized by two or more times gasoline injections into cylinder with a high pressure around the compression TDC and featured with a premixed combustion after each injection in the cylinder, which is different from the existed gasoline direct injection compression ignition (GDICI) modes such as homogeneous charge compression ignition (HCCI) mode with gasoline injection occurred in intake stroke, and partially premixed compression ignition (PPCI) mode with multiple gasoline injections in intake and compression strokes before the start of combustion (SOC). Therefore the spray and combustion of the MPCI mode are alternatively occurred as "spray-combustion-spray-combustion" near the TDC, rather than "spray-spray-combustion" sequence as traditional PPCI gasoline engines.

Conventional diesel-fuelled Partially Premixed Compression Ignition (PPCI) engines have been investigated by many researchers previously. However, the ease of ignition and difficulty of vaporization of diesel fuel make it imperfect for PPCI combustion. In this study, dieseline (blending of diesel and gasoline) was looked into as the Partially Premixed Compression Ignition fuel for its combination of two fuel properties, ignition-delay-increasing characteristics and higher volatility, which make it more suitable for PPCI combustion compared to neat diesel. A series of tests were carried out on a Euro IV light-duty common-rail diesel engine, and different engine modes, from low speed/load to middle speed/load were all tested, under which fuel blend ratios, EGR rates, injection timings and quantities were varied. The emissions, fuel consumption and combustion stability of this dieseline-fuelled PPCI combustion were all investigated.

The paper presents analysis of performance and emission characteristics of a common rail diesel engine operating with RME, with and without EGR. In both cases, the RME fuel was pre-heated in a heat exchanger to control its temperature before being pumped to the common rail. The studied parameters include the in-cylinder pressure history, rate of heat release, mass fraction burned, and exhaust emissions. The results show that when the fuel temperature increases and the engine is operated without EGR, the brake specific fuel consumption (bsfc) decreases, engine efficiency increases and NOx emission slightly decreases. However, when EGR is used while fuel temperature is increased, the bsfc and engine efficiency is independent of fuel temperature while NOx slightly increases.

In this paper, a hybrid combustion mode in four-stroke gasoline direct injection engines was studied. Switching cam profiles and injection strategies simultaneously was adopted to obtain a rapid and smooth switch between SI mode and HCCI mode. Based on the continuous pressure traces and corresponding emissions, HCCI steady operation, HCCI transient process (combustion phase adjustment, SI-HCCI, HCCI-SI, HCCI cold start) were studied. In HCCI mode, HCCI combustion phase can be adjusted rapidly by changing the split injection ratio. The HCCI control strategies had been demonstrated in a Chery GDI2.0 engine. The HCCI engine simulation results show that, oxygen and active radicals are stored due to negative valve overlap and split fuel injection under learn burn condition. This reduces the HCCI sensitivity on inlet boundary conditions, such as intake charge and intake temperature. The engine can be run from 1500rpm to 4000rpm in HCCI mode without spark ignition.

This study improved the computational efficiency significantly using parallel computation and reduced mechanisms. A 3-dimensional engine moving mesh of intake port, exhaust port and combustion chamber was established for HCCI engine cycle simulation. To achieve a more accurate analysis, chemical kinetics was implemented into the CFD code to study the intake, spray, ignition, combustion, and pollution formation process in HCCI engine. The simulations were run on a cluster of 16-CPU, parallelized by Message-Passing Interface (MPI) mode. The cases with detailed and reduced reaction mechanisms were calculated using 1, 2, 4, 8, 16 CPUs respectively and the corresponding computational time and speed-up were discussed. Using MPI 8-CPU with reduced mechanism (less than 40 species) is the optimal scheme for CFD/Chemistry calculation of typical HCCI engine.

The detailed chemical kinetics was implemented into the 0D single-zone model, 1D engine cycle model and 3D CFD model respectively. Both simulation and experiment were carried out on a four-stroke gasoline HCCI engine with direct injection. The 0D model (HRG) was developed to study the isolating effect of HCCI parameters. The 1D engine cycle model with HRG was established to study the gas exchange process and the direct injection strategy in the gasoline HCCI engine with two-stage direct injection (TSDI) and negative valve overlap (NVO). The 3D model with HRG was constructed to study the ignition control mechanism in “two-zone HCCI” combustion via analysis the auto-ignition spots distribution in combustion chamber. “Two-zone HCCI” is defined in this paper as premixed ultra-lean compression ignition combining with premixed ultra-rich compression ignition. The three models were validated by experiments.

There is a worldwide interest in the research of various alternative fuels for automotive engines for the purpose of reduction of CO2 and toxically harmful exhaust emissions. Coal-bed gas, the main component of which is methane, has been considered an attractive alternative fuel for combustion engines due to its abundant resources, high hydrogen-carbon ratios and very low soot formation tendency. The composition of available coal-bed gas, however, can vary considerably, and this has made its combustion stability difficult to control in conventional spark ignition engines. To overcome the problem, a combustion system with a swirl chamber connected to the main combustion chamber through an orifice has been developed for the use of coal-bed gas in spark ignition engines, and the corresponding combustion process has been studied using a developed combustion model involving flame kernel formation and flame front propagation.

HCCI combustion was studied in a 4-stroke gasoline engine with a direct injection system. The electronically controlled two-stage gasoline injection and spark ignition system were adopted to control the mixture formation, ignition timing and combustion rate in HCCI engine. The engine could be operated in HCCI combustion mode in a range of load from 1 to 5 bar IMEP and operated in SI combustion mode up to load of 8 bar IMEP. The HCCI combustion characteristics were investigated under different A/F ratios, engine speeds, starts of injection, as well as spark ignition enabled or not. The test results reveal the HCCI combustion features as a high-pressure gradient after ignition and has advantages in high thermal efficiency and low NOx emissions over SI combustion. At the part load of 1400rpm and IMEP of 3.5bar, ISFC in HCCI mode is 25% lower and NOx emissions is 95% lower than that in SI mode.

In order to enhance the thermal efficiency of gasoline engines, a combustion mode namely Homogeneous Charge Induced Ignition (HCII) was introduced and examined in this paper. Port-injected gasoline was used as the main fuel and formed a homogeneous charge in the cylinder. Diesel was used as the pilot fuel, directly injected into the cylinder, and self-ignited and this induced the ignition of the premixed gasoline-air charge. The images of HCII combustion process were taken on an optical engine through a high-speed CMOS camera. The multi-point induced ignition phenomena were observed and the parameters like flame luminance, ignition delay and combustion duration were analyzed by image analysis. The result shows that as the gasoline/diesel ratio increases with a fixed low pilot amount, the ignition delay increases, the initial ignition area extends from the center towards the periphery of the combustion chamber, and the combustion velocity increased.

Gasoline Direct Injection (GDI) engines developed at nineties of the twentieth century can greatly improve the fuel economy. But the combustion chamber design and mixture control of the engines are very complex compared with Port Fuel Injection (PFI) gasoline engines. A two-stage gasoline direct injection (TSGDI) combustion system is developed and aimed to solve the problem of the complexity. Two-stage fuel injection and flexible injection timings are adopted as main means to form reasonable stratified mixture in the cylinder. A simple combustion chamber and helical intake port are designed to assist the mixture's stable combustion, which reduces the difficulties of the combustion system design. Systematical simulation and experimental studies of the effects of injection strategies such as different first,second injection timings and injection ratios, on the mixture formation processes and engine performanc are made in detail.

Homogeneous charge combustion and emissions of ethanol ignited by pilot diesel fuel were investigated on a two-cylinder diesel engine. The results show that emissions depend on loads and ethanol volume fraction. At low loads, ethanol has little effects on smoke. With the increase of ethanol, NOx decreases, but CO emissions increase. At high loads, smoke emissions reduce greatly with increasing ethanol, but NOx and total hydrocarbon (THC) emissions increase. With the increase of ethanol, ignition delays, combustion duration shortens. The maximum rates of heat release for the fuel containing 10 vol% ethanol (E10) and 30 vol% ethanol (E30) increase. Brake specific energy consumption (BSEC) of E10 and E30 is improved slightly only at full loads. Compared to smoke emissions obtained on the same engine using ethanol blended diesel fuels, the tendency of smoke reduction is similar to that of homogeneous charge combustion of ethanol at the same operating conditions.

In this paper a Particle Image Velocimetry (PIV) was used to measure flow velocity fields in different inlet cones under different mass flux conditions on a steady state flow rig. Meanwhile, a mathematical model of the flow in catalytic converters was established and simulated using CFD code. Validation of the model shows that simulation results have a good agreement with experiments, which means that the established model is feasible and can be applied to predict the flow characteristics in catalytic converters with different inlet cone configurations. Experimental and computational results indicate that the inlet cone configuration significantly affects flow distribution. For a conventional inlet cone, the cone angle is one of the key factors to affect flow characteristics and should be kept as small as possible in a design. An enhanced inlet cone can greatly improve flow uniformity in catalytic converters.

This paper measured unsteady temperature fields of uncoated-monolith and catalytic monolith under real engine operating conditions using thermocouples. A multi-dimensional flow mathematical model of the turbulence, heat and mass transfer, and chemical reactions in monoliths was established using a computational fluid dynamics (CFD) code and numerically solved in the whole flow field of the catalytic converter. The purpose of this paper is to study unsteady warm-up characteristics of the monoliths and to investigate effects of inlet cone structure on temperature distribution of the catalytic converter. Experimental results show that the warm-up behaviors between uncoated-monolith and catalytic monolith are quite different. Simulation results indicate that the established model can qualitatively predict the warm-up characteristics.