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Controlled Auto-Ignition (CAI) combustion can effectively improve the thermal efficiency of conventional spark ignition (SI) gasoline engines, due to shortened combustion processes caused by multi-point auto-ignition. However, its commercial application is limited by the difficulties in controlling ignition timing and violent heat release process at high loads. Stratified flame ignited (SFI) hybrid combustion, a concept in which rich mixture around spark plug is consumed by flame propagation after spark ignition and the unburned lean mixture closing to cylinder wall auto-ignites in the increasing in-cylinder temperature during flame propagation, was proposed to overcome these challenges.

Lean-burn combustion is an effective method for increasing the thermal efficiency of gasoline engines fueled with stoichiometric fuel-air mixture, but leads to an unacceptable level of high cyclic variability before reaching ultra-low nitrogen oxide (NOx) emissions emitted from conventional gasoline engines. Multi-point micro-flame ignited (MFI) hybrid combustion was proposed to overcome this problem, and can be can be grouped into double-peak type, ramp type and trapezoid type with very low frequency of appearance. This research investigates the micro-flame ignition stages of double-peak type and ramp type MFI combustion captured by high speed photography. The results show that large flame is formed by the fast propagation of multi-point flame occurring in the central zone of the cylinder in the double-peak type. However, the multiple flame sites occur around the cylinder, and then gradually propagate and form a large flame accelerated by the independent small flame in the ramp type.

The dual-fuel Reactivity Controlled Compression Ignition (RCCI) combustion could achieve high efficiency and low emissions over a wide range of operating conditions. However, further high load extension is limited by the excessive pressure rise rate and soot emission. Polyoxymethylene dimethyl ethers (PODE), a novel diesel alternative fuel, has the capability to achieve stoichiometric smoke-free RCCI combustion due to its high oxygen content and unique molecule structure. In this study, experimental investigations on high load extension of gasoline/PODE RCCI operation were conducted using late intake valve closing (LIVC) strategy and intake boosting in a single-cylinder, heavy-duty diesel engine. The experimental results show that the upper load can be effectively extended through boosting and LIVC with gasoline/PODE stoichiometric operation.

Lean NOx trap (LNT) is a great potential NOx abatement method for lean-burn gasoline engines in consideration of exhaust aftertreatment cost and installation space. NOx firstly is adsorbed on storage sites during the lean-burn period, then reduced to N2 under catalysis of the catalyst sites in the rich-burn phase. There must be a spillover of NOx species between both types of sites. For a better understanding of this spillover process of NOx species between Pt (as the catalytic center) and BaO sites (as storage components in commercial catalyst), this work focused on the vital first step of spillover, the adsorption of NOx on clean substrate surface (γ-Al2O3 (110) surface) and Ba\Pt cluster supported by the surface. Based on first principles software VASP (Vienna Ab-initio Simulation Package), the most stable adsorption structures of NO with Pt3 clusters and (BaO)3 clusters on carrier γ- Al2O3 (110) surface were confirmed and the adsorption energy of these structures were compared.

The combustion and emission characteristics of a diesel engine running on butanol-diesel blends were investigated in this study. The blending ratio of n-butanol to diesel was varied from 0 to 40 vol% using an increment of 10 vol%, and each blend was tested on a 2.7 L V6 common rail direction injection diesel engine equipped with an EGR system. The test was carried out under two engine loads at a constant engine speed, using various combinations of EGR ratios and injection timings. Test results indicate that n-butanol addition to engine fuel is able to substantially decrease soot emission from raw exhaust gas, while the change in NOx emissions varies depending on the n-butanol content and engine operating conditions. Increasing EGR ratio and retarding injection timing are effective approaches to reduce NOx emissions from combustion of n-butanol-diesel blends.

Aiming at the problem of poor robustness after the combination of lateral kinematics control and lateral dynamics control when an autonomous vehicle decelerates and changes lanes to overtake at a certain distance. This paper proposes a trajectory determination and tracking control method based on a PI-MPC dual algorithm controller. To describe the longitudinal deceleration that satisfies the lateral acceleration limit during a certain distance of lane change, firstly, a fifth-order polynomial and a uniform deceleration motion formula are established to express the lateral and longitudinal displacements, and a model prediction controller (MPC) is used to output the front wheel rotation angle. Through the dynamic formula and the speed proportional-integral (PI) controller to control and adjust the brake pressure.

The increasing demand for lightweight design of the whole vehicle has raised critical weight reduction targets for crash components such as front rails without deteriorating their crash performances. To this end the last few years have witnessed a huge growth in vehicle body structures featuring hybrid materials including steel and aluminum alloys. In this work, a type of tapered tailor-welded tube (TTWT) made of steel and aluminum alloy hybrid materials was proposed to maximize the specific energy absorption (SEA) and to minimize the peak crushing force (PCF) in an oblique crash scenario. The hybrid tube was found to be more robust than the single material tubes under oblique impacts using validated finite element (FE) models. Compared with the aluminum alloy tube and the steel tube, the hybrid tube can increase the SEA by 46.3% and 86.7%, respectively, under an impact angle of 30°.

Transparent materials such as Plexiglas and glass are applied in airplane and boat widely as the windows and hatches. There are three type stresses in the structure made of Plexiglas or glass, which are residual stresses from the casting, residual stresses due to manufacturing process involving sheet forming structure and the stresses from serving period. In the paper the stresses are studied by laser scattered Photoelasticy method. Phase shift method is presented to recognize scattered light patterns automatically. The residual stresses in Plexiglas plate and shell were analyzed by thin plate-shell theory. Stresses in the Plexiglas and shell were tested by laser scattered Photoelastic method.

To understand the working mechanism of the porous medium (PM) internal combustion engine, effects of a porous medium heat regenerator inserted into a combustion chamber on the turbulent flow field and fuel-air mixture formation are studied by numerical simulation. The cylindrical chamber has a constant volume, in which a disk-shaped PM insert is fixed. A simplified model for the random structure of the PM is presented, in which the PM is represented by an assembly of a great number of randomly distributed solid units. To simulate flows in the PM a Brinkman-Forchheimer-extended Darcy's equation is introduced into the numerical solver. A version of two-equation k - ε turbulence model suggested by Antohe and Lage is employed for the turbulence prediction in the PM. A spray model, in which the effects of drop breakup, collision and coalescence are taken into account, is introduced to describe spray/wall interactions.

The inverse boundary element method (IBEM) is presented to accurately identify the noise sources of a diesel engine in this study. The sound pressures on four near-field planes were measured as inputs for the method. Then, the acoustic model of the full diesel engine was established using the boundary element method, and the acoustic transfer vectors (ATV) between the surface normal velocity and acoustic pressure at field points were calculated over the frequency range of interest. Based on the measured sound pressure and the ATVs, the surface normal velocity distribution of the diesel engine was reconstructed by the IBEM. The reconstructed pressures at two reference field points were compared with the measured ones. Furthermore, the panel contribution of each engine component was analyzed through the reconstructed surface velocity.

Chinese new legislations on two wheels and mopeds have been published recently. Depending on the latest exhaust statistic analyses, with the resulting of tighter limits, the application of catalytic converters is becoming a prevalent and a cost-efficient solution for Chinese motorcycle manufacturers. The phenomenon of exhaust temperature changes rapidly during real driving process is well known as one of major destructive factors which have effects upon converter's durability. One 125 cm3 motorcycle is selected as a typical model in this research project. Exhaust temperature of the 125 cm3 motorcycle is measured and recorded during the process of ECE 40 driving cycle. A simulation test system has been set up successfully depending on those temperature data. Conversion ratio of converter sample lost distinctly after 18 hours' thermal impact tests. After further analyses, there were not evident changes in microstructure and substance on the surface of converter.

In this paper, a control-oriented soot model was developed for real-time soot prediction and combustion condition optimization in a gasoline Partially Premixed Combustion (PPC) Engine. PPC is a promising combustion concept that achieves high efficiency, low soot and NOx emissions simultaneously. However, soot emissions were found to be significantly increased with high EGR and pilot injection, therefore a predictive soot model is needed for PPC engine control. The sensitivity of soot emissions to injection events and late-cycle heat release was investigated on a multi-cylinder heavy duty gasoline PPC engine, which indicated main impact factors during soot formation and oxidation processes. The Hiroyasu empirical model was modified according to the sensitivity results, which indicated main influences during soot formation and oxidation processes. By introducing additional compensation factors, this model can be used to predict soot emissions under pilot injection.

The combustion in low-speed two-stroke marine diesel engines can be characterized as large spatial and temporal scales combustion. One of the most effective measures to reduce NOx emissions is to reduce the local maximum combustion temperature. In the current study, multi-dimensional numerical simulations have been conducted to explore the potential of Miller cycle, high compression ratio coupled with EGR (Exhaust Gas Recirculation) and WEF (water emulsified fuel) to improve the trade-off relationship of NOx-ISFC (indicated specific fuel consumption) in a low-speed two-stroke marine engine. The results show that the EGR ratio could be reduced combined with WEF to meet the Tier III emission regulation. The penalty on fuel consumption with EGR and WEF could be offset by Miller cycle and high geometric compression ratio.

In this work, both the ‘SCR-only’ and ‘EGR+SCR’ technical routes are compared and evaluated after the optimizations of both injection strategy and turbocharging system over the World Harmonized Stationary Cycle (WHSC) in a heavy duty diesel engine. The exhaust emissions and fuel economy performance of different turbocharging systems, including wastegate turbocharger (WGT), variable geometry turbocharger (VGT), two-stage fixed geometry turbocharger (WGT+FGT) and two-stage variable geometry turbocharger (VGT+FGT), are investigated over a wide EGR range. The NOx reduction methods and EGR introduction strategies for different turbocharger systems are proposed to improve the fuel economy. The requirement on turbocharging system and their potential to meet future stringent NOx and soot emission regulations are also discussed in this paper.

In this work the gasoline compression ignition (GCI) combustion characterized by both premixed gasoline port injection and gasoline direct injection in a single-cylinder diesel engine was investigated experimentally and computationally. In the experiment, the premixed ratio (PR), injection timing and exhaust gas recirculation (EGR) rate were varied with the pressure rise rate below 10 bar/crank angle. The experimental results showed that higher PR and earlier injection timing resulted in advanced combustion phasing and improved thermal efficiency, while the pressure rise rates and NOx emissions increased. Besides, a lowest ISFC of 176 g/kWh (corresponding to IMEP =7.24 bar) was obtained, and the soot emissions could be controlled below 0.6 FSN. Despite that NOx emission was effectively reduced with the increase of EGR, HC and CO emissions were high. However, it showed that GCI combustion of this work was sensitive to EGR, which may restrict its future practical application.

The intake process plays an important role in the operation of internal combustion engines. In the present study, a three-dimensional transient simulation of a four-valve diesel engine was performed using Large Eddy Simulation (LES) model based on software CONVERGE. The mean velocity components in three directions through the intake valve curtain, the flow separation around the intake valves, the influences of inlet jet on turbulence flow field and cycle-to-cycle variation were investigated in this work. The result shows that the mean velocity distributes non-uniformly near the valve curtain at high valve lifts. In contrast, the mean velocity distribution is uniform at low valve lifts. It is found that the flow separation occurs at valve stem, valve seat and valve sealing through the outlet of the helical port. In contrast, flow separation is only observed in the valve seat through the outlet of the tangential port.

Clean combustion is critical for marine engines to meet the Tier III emission regulation. In this paper, the effects of EGR and injection strategies (including injection pressure, injection timing as well as multiple injection technology) on the performance and emissions of a 2-stroke, low speed marine diesel engine were investigated by using computational fluid dynamics (CFD) simulations to reach the IMO Tier III NOx emissions target and reduce the fuel consumption rate. Due to the large length scale of the marine engine, RANS simulation was performed in combination with the CTC-SHELL combustion model. Based on the simulation model, the variation of the cylinder pressure curve, the average temperature in the cylinder, the combustion heat release rate and the emission characteristics were studied.

Hybrid electric vehicles (HEVs) are considered as the most commercial prospects new energy vehicles. Most HEVs have adopted Atkinson cycle engine as the main drive power. Atkinson cycle engine uses late intake valve closing (LIVC) to reduce pumping losses and compression work in part load operation. It can transform more heat energy to mechanical energy, improve engine thermal efficiency and decrease fuel consumption. In this paper, the investigations of Atkinson cycle converted from conventional Otto cycle gasoline engine have been carried out. First of all, high geometry compression ratio (CR) has been optimized through piston redesign from 10.5 to 13 in order to overcome the intrinsic drawback of Atkinson cycle in that combustion performance deteriorates due to the decline in the effective CR. Then, both intake and exhaust cam profile have been redesigned to meet the requirements of Atkinson cycle engine.

Performance and emissions of a common-rail production diesel engine fueled with soybean-derived biodiesel was investigated. The work was broken down into two categories. First, adjustment of injection timing and EGR ratio was investigated as a means to reduce NOx emissions to levels comparable with those obtained when using pure diesel fuel. Next, simultaneous reduction of NOx and soot emissions was investigated using high rates of EGR combined with late injection timings to approach the low-temperature combustion regime. Results from the first part of the study indicate that optimization of engine control parameters for use with biodiesel can be beneficial to performance and emissions. It was found that adjusting the engine's MAF setpoint table to reflect the difference in stoichiometric air-fuel ratio between diesel and biodiesel brought NOx emissions to comparable or lower levels.

Combustion control strategy for high efficiency and low emissions in a heavy duty (H D) diesel engine was investigated experimentally in a single cylinder test engine with a common rail fuel system, EGR (Exhaust Gas Recirculation) system, boost system and retarded intake valve closing timing actuator. For the operation loads of IMEPg (Gross Indicated Mean Effective Pressure) less than 1.1 MPa the low temperature combustion (LTC) with high rate of EGR was applied. The fuel injection modes of either single injection or multi-pulse injections, boost pressure and retarded intake valve closing timing (RIVCT) were also coupled with the engine operation condition loads for high efficiency and low emissions. A higher boost pressure played an important role in improving fuel efficiency and obtaining ultra-low soot and NOx emissions.