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In this work, an innovative piston bowl design that physically divides the combustion chamber into a central zone and a peripheral zone is employed to assist the control of the ethanol-diesel combustion process via heat release shaping. The spatial combustion zone partition divides the premixed ethanol-air mixture into two portions, and the combustion event (timing and extent) of each portion can be controlled by the temporal diesel injection scheduling. As a result, the heat release profile of ethanol-diesel dual-fuel combustion is properly shaped to avoid excessive pressure rise rates and thus to improve the engine performance. The investigation is carried out through theoretical simulation study and empirical engine tests. Parametric simulation is first performed to evaluate the effects of heat release shaping on combustion noise and engine efficiency and to provide boundary conditions for subsequent engine tests.

The majority of transportation systems have continued to be powered by the internal combustion engine and fossil fuels. Heavy-duty applications especially are reliant on diesel engines for their high brake efficiency, power density, and robustness. Although engineering developments have advanced engines towards significantly fewer emissions and higher efficiency, the use of fossil-derived diesel as fuel sets a fundamental threshold in the achievable total net carbon reduction. Dimethyl ether can be produced from various renewable feedstocks and has a high chemical reactivity making it suitable for heavy-duty applications, namely compression ignition direct injection engines. Literature shows the successful use of DME fuels in diesel engines without significant hardware modifications.

Internal combustion Rankine cycle (ICRC) engine uses oxygen instead of air as oxidant during the combustion process, therefore totally eliminates the emission of NOx. CO2 could be captured after separated from the exhaust gas, the latter are mainly water vapor and CO2, through condensation at a relatively low price, and thus an ultra-low emission working cycle is achieved. Moreover, water is heated up by exhaust gas and injected into the cylinder during the combustion process to control combustion temperature, and evaporation of the water mist would increase working fluid inside the cylinder, therefore enhance indicated thermal efficiency. This study investigates the combustion characteristics of a quasi ICRC on a single-cylinder SI engine fueled with propane. Gas mixture of O2/CO2 is employed to simulate EGR in order to control in-cylinder temperature.

This paper presents the simulation of in-cylinder stratified mixture formation, spray motion, combustion and emissions in a four-stroke and four valves direct injection spark ignition (DISI) engine with a pent-roof combustion chamber by the computational fluid dynamics (CFD) code. The Extended Coherent Flame Combustion Model (ECFM), implemented in the AVL-Fire codes, was employed. The key parameters of spray characteristics related to computing settings, such as skew angle, cone angle and flow per pulse width with experimental measurements were compared. The numerical analysis is mainly focused on how the tumble flow ratio and geometry of piston bowls affect the motion of charge/spray in-cylinder, the formation of stratified mixture and the combustion and emissions (NO and CO₂) for the wall-guided stratified-charge spark-ignition DISI engine.

With the increasing worldwide concern on environmental pollution, battery electrical vehicles (BEV) have attracted a lot attention. However, it still couldn’t satisfy the market requirements because of the low battery power density, high cost and long charging time. The range-extended electrical vehicle (REEV) got more attention because it could avoid the mileage anxiety of the BEVs with lower cost and potentially higher efficiency. When internal combustion engine (ICE) works as the power source of range extender (RE) for REEV, its NVH, emissions in starting process need to be optimized. In this paper, a 2-cylinder PFI gasoline engine and a permanent magnet synchronous motor (PMSM) are coaxially connected. Meanwhile, batteries and load systems were equipped. The RE co-control system was developed based on Compact RIO (Compact Reconfigurable IO), Labview and motor control unit (MCU).

In this study, a spray hot-impingement system was set up to analyze the spray characteristics when spray impinged onto a flat hot surface by high-speed photography technology. The angle between spray axis and normal line of the flat surface could be changed, and the surface temperature could exceed 400°C. The influences of surface temperature and heating power on spray atomization were investigated too. At atmospheric pressure, when the wall temperature was 340∼380°C, the impinging diesel spray was well atomized. In this experiment, the wall heating power could be set at 1∼25 Wcm-2. When the heating power was about 1.6 Wcm-2, the impinging spray atomized well, and when it was about 10.1 Wcm-2 the spray atomized better though the heating power requirement should be high.

Biodiesel has been paid more and more attention as a renewable fuel due to some excellent properties such as renewable, high cetane number, ultralow sulfur content, no aromatic hydrocarbon, high flash point, low CO2 emission when compared with diesel. While others physical properties like high viscosity, high surface tension, big density and bad volatility would spoil the spray characteristics of biodiesel fuel, which will affect the thermal efficiency when running in diesel engine. Accompanied with constant volume vessel and high speed video camera system, a high pressure common rail system, which could provide an injection pressure of 180 MPa, is used to investigate the characteristics of jatropha curcas biodiesel, palm oil biodiesel and diesel fuel. The effects of injection pressures and ambient densities on spray characteristics of these fuels are studied.

Spray characteristics and spray wall-impingement events are the key factors for the direct injection spark ignition (DISI) engines, affecting fuel/air mixture preparation and its combustion process. Thus, the spray characteristics of a multi-hole injector for DISI engines, such as spray tip penetration and spray cone angle were investigated in an optical chamber employing the high-speed shadow photography. Furthermore, the effects of the injection pressure, ambient pressure and piston top shape on the impinging spray development were studied in the optical chamber, when the impinging distance is 26.1 mm, corresponding to about 60 CAD ATDC. In addition, the SMD and wall film thickness of the spray impinging on the piston top were studied by means of CFD technique. The results showed that the ambient pressure had the greater effect on the changes of the spray penetration and spray cone angle than the injection pressure.

The spark ignition circuit inside an internal combustion engine system is the source which provides the initiation energy required for triggering combustion in a spark ignition (SI) engine in-cylinder air/fuel mixture. Proper spark phasing and adequate spark energy release in spark ignited combustion would yield significant combustion efficiency improvement and affect the in-cylinder production species composition. In this work a simplified spark ignition circuit model constructed based on circuit theorems is proposed. Measurements on how ignition pressure, secondary circuit series resistance and dwell duration would affect the ignition energy migration are presented. Simulations using the proposed model have also demonstrated similar energy migration trends to measurement results which show the influences caused by different secondary series resistance and dwell durations.

Extensive experiments were conducted on a low emission DI diesel engine by using Dimethyl Carbonate (DMC) as an oxygenate fuel additive. The results indicated that smoke reduced almost linearly with fuel oxygen content. Accompanying noticeable reductions of HC and CO were attained, while a small increase in NOx was encountered. The effective reduction in smoke with DMC was maintained with intake charge CO2, which led to low NOx and smoke emissions by the combined use of oxygenated fuel and exhaust gas recirculation (EGR). Further experiments were conducted on an optically accessible combustion bomb and a thermal cracking set-up to study the mechanisms of DMC addition on smoke reduction.

Recently, it has been wildly recognized that active pre- chamber has a significant effect on extending the lean burn limit of gasoline engines. Ion current signals in the combustion is also considered as a promising approach to the engine knock detection. In this study, the feasibility of employing ion current in an active pre- chamber for combustion diagnosis was analyzed by three-dimensional numerical simulation on a single- cylinder engine equipped with active pre-chamber. The flow characteristics of charged species (NO+, H3O+ and electrons) in the main chamber and pre-chamber under knock conditions are investigated at different engine speeds, intake pressures and ignition timings. The results show that the ion current can theoretically be used for the knock detection of the active pre- chamber. The peak value of the electron or H3O+ mass fraction caused by knocking backflow can be used as knock indication peak.

The present work discusses the effects of intake manifold water injection in a six-cylinder heavy duty natural gas (NG) engine through one-dimensional simulation. The numerical study was carried out based on GT-Power under different engine working conditions. The established simulation model was firstly calibrated in detail through the whole engine speed sweep under full load conditions before the model of intake manifold water injector was involved, and the calibration was based on experimental data. The intake manifold water injection mass was controlled through adjustment of intake water/gas (water/natural gas) ratio, a water/gas ratio swept from 0 to 4 was selected to investigate the effects of intake manifold water injection on engine performance and emissions characteristics. On the other hand, the enhancement potential of intake manifold water injection in heavy duty NG engine under lean and stoichiometric condition was also investigated by the alteration of air-fuel ratio.

The rapid development of the automobile industry has brought energy and environmental issues that scholars are increasingly concerning about. Improving efficiency and reducing emissions are currently two hot topics in the internal combustion engine industry. Direct water injection technology (DWI) can effectively reduce the cylinder temperature, which is due to the absorption of the heat by the injecting liquid water. In addition, lower temperature in the cylinder will reduce the formation of NO. In this paper, a CFD simulation of DWI application in a lean-burning single-cylinder engine with pre-chamber jet ignition was carried out. And the engine was experimentally tested for the simulation model validation. And then the effect of DWI strategy with different injecting water mass on the combustion and emissions characteristics are analyzed. Physically, injected water not only absorbs heat but also provides heat insulation.

The present work discusses a novel oxy-fuel combustion cycle utilized in compression ignition internal combustion engine. The most prominent feature of this cycle is that the air intake is replaced by oxygen; therefore nitric oxide (NOX) emission is eliminated. The enrichment of oxygen leads to higher flame speed and mass fraction consumption rate; on the other hand, the high concentration of oxygen presented during combustion will result in intense pressure rise rate which may cause severe damage to engine hardware. As water injection is already utilized in gasoline engine to control knocking, the utilization of water injection in optimizing oxy-fuel combustion process has been tested in this study. To understand the relationship between water injection strategy and cycle efficiency, computational fluid dynamics (CFD) simulations were carried out. The model was carefully calibrated with the experimental results; the errors were controlled within 3%.

Ultra-lean combustion of GDI engine could achieve higher thermal efficiency and lower NOx emissions, but it also faces challenges such as ignition difficulties and low-speed flame propagation. In this paper, the sparked-spray is proposed as a novel ignition method, which employs the spark to ignite the fuel spray by the cooperative timing control of in-cylinder fuel injection and spark ignition and form a jet flame. Then the jet flame fronts propagate in the ultra-lean premixed mixture in the cylinder. This combustion mode is named Sparked-Spray Induced Combustion (SSIC) in this paper. Based on a 3-cylinder 1.0L GDI engine, a 3D simulation model is established in the CONVERGE to study the effects of ignition strategy, compression ratio, and injection timing on SSIC with a global equivalence ratio of 0.50. The results show it is easier to form the jet flame when sparking at the spray front because the fuel has better atomization and lower turbulent kinetic energy at the spray front.

In the ultra-lean combustion mode, the combustion temperature is relatively low, which is expected to avoid the high-temperature NOx generation. And it also can use excess air to fully oxidize CO, HC and Soot, to achieve cleaner combustion. But at the same time, ultra-lean combustion has difficulties in ignition and flame propagation. This paper used CONVERGE to simulate the combustion process and products of a new ultra-lean combustion mode, which ignited the ultra-lean premixed fuel/air mixture with the spark-ignited micro-fuel-jet, in a constant-volume vessel with a 6-hole GDI injector. The differences of combustion processes and products were simulated for two spark-ignition positions, including ‘on’ the micro-jet spray and ‘between’ two micro-jet sprays. It was found that the combustion duration (the time for burned-fuel-ratio from 10% to 90%) could be shortened by about 14.3% if igniting ‘on’ the micro-jet spray, but the amount of NOx generated would increase about 21.0%.

Based on the principle of carbon footprint, this paper selects typical passenger cars, such as internal combustion engine vehicles (ICEV), plug-in hybrid electric vehicles (PHEV) and battery electric vehicles (BEV) in the market of China as the research objects, and compares the energy consumption and carbon emissions of the three vehicle models in the whole life cycle for three major stages of manufacturing, driving and recycling in three representative cities. The results show that the manufacturing energy consumption of BEV is 5 times of HEV and 10 times of ICEV. For the BEV, only after driving a certain mileage it can be a less the unit energy consumption and emissions than ICEV. The whole life cycle carbon emissions of passenger cars with different power types is not only related to mileage, but also related to the energy structure of local electric power supply.

A novel method is applied to analysis the autoignition phenomenon. Experiments on the study of autoignition characteristics of diesel fuel were carried out with a Controllable Active Thermo-Atmosphere Combustor. The results show that the method for autoignition studying of liquid fuel is of feasibility. Autoignition delay time and autoignition height from the nozzle increase with the coflow temperature decreasing and autoignition delay time changes sensitively under lower coflow temperature. Liftoff height of diesel spray flame decreases with the increasing of coflow temperature. Lower temperature causes higher variance of liftoff height. It might be speculated that there are two different mechanisms of flame stabilization that the lower lift-off heights flames are related to a balance between the flow velocity and flame speed while the higher lift-off heights flames are stabilized by the mixture autoignition.

As a renewable energy source, the ethanol fuel was employed with a diesel fuel in this study to improve the cylinder charge homogeneity for high load operations, targeting on ultra-low nitrogen oxides (NOx) and smoke emissions. A light-duty diesel engine is configured to adapt intake port fuelling of the ethanol fuel while keeping all other original engine components intact. High load experiments are performed to investigate the combustion control and low emission enabling without sacrificing the high compression ratio (18.2:1). The intake boost, exhaust gas recirculation (EGR) and injection pressure are independently controlled, and thus their effects on combustion and emission characteristics of the high load operation are investigated individually. The low temperature combustion is accomplished at high engine load (16~17 bar IMEP) with regulation compatible NOx and soot emissions.

A number of cylinder-pressure derived parameters including the crank angles of maximum pressure, maximum rate of pressure rise, and 50% heat released are considered as among the desired feedback for cycle-by-cycle adaptive control of diesel combustion. For real-time computation of these parameters, the heat release analyses based on the first law of thermodynamics are used. This paper intends to identify the operating regions where the simplified heat release approach provides sufficient accuracy for control applications and also highlights those regions where its use can lead to significant errors in the calculated parameters. The effects of the cylinder charge-to-wall heat transfer and the temperature dependence of the specific heat ratio on the model performance are reported. A new computationally efficient algorithm for estimating the crank angle of 50% heat released with adequate accuracy is proposed for computation in real-time.