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Due to increasingly strict global emission regulations and energy conservation policies, gasoline engines are facing significant challenges. Achieving high efficiency and ultra-low emissions in gasoline engines has become a critical technical challenge that requires attention. Pre-chamber (PC) Turbulent Jet Ignition (TJI) is a highly promising technology for improving thermal efficiency and reducing emissions in gasoline engines. This study employs a three-dimensional flow simulation analysis combined with a detailed chemical reaction mechanism. The investigation is based on eight distinct passive PC structural configurations. The effects of various structural parameters, including the orifice number (ON), orifice axis angle (OAA), orifice diameter (OD), and volume ratio (VR), on the in-cylinder combustion process and emission characteristics are investigated, in which the formation of the fire nucleus and the propagation of the flame are intensively involved. The investigation is conducted under equivalence ratio working condition. Among these, the ITE of the best configuration is relatively 5.46% higher than the baseline engine. The combustion duration decreased by 55.95% to 7.4 °CA compared to the baseline engine, while particulate soot emissions also decreased by 51.22%.

[Display omitted] • The in-cylinder flow of ORP engine shows consistency at different altitudes. • General decrease in the speed of flame propagation with altitude increasing is observed. • The fuel economy is less sensitive to altitudes than power output. • NO x emissions are reduced with increasing altitude. Opposed rotary piston (ORP) engines boast a theoretical power density that is double that of traditional four-stroke reciprocating engines. Additionally, the ORP engines are free of connecting-rod mechanisms, which contributes to the compactness and efficiency of ORP engines. This study explores the performance of ORP engine under variable altitudes using three-dimensional simulation. The findings revealed that the charging efficiency diminishes as the altitude increases. During the compression stroke, the vortex formed in the intake stroke progressively dissipates, forming a flow field suitable for combustion. The combustion rate decreases as the altitude rises. However, the intense vortex formation within the cylinder at an altitude of 1000 m obstructs the flame propagation process, resulting in slower flame propagation. When the ORP engine operates at 4000 m, the combustion is enhanced due to the rich mixture around the spark plug. Additionally, the post-combustion phenomenon emerged at an altitude of 5000 m. The reduced cycle charge is a contributing factor to the lower in-cylinder temperature and pressure at high altitudes. As the altitude increases by 1000 m, the power output decreases by approximately 11.8 %. In contrast, the fuel economy is less sensitive to altitudes than power output. Nitrogen oxides (NO x) emission decreases with increasing altitudes as a result of the drop of in-cylinder temperature. NO x and hydrocarbon (HC) factors approach zero when the ORP engine operates at an altitude of 5000 m. However, the emission of carbon monoxide (CO) increases due to the significant percentage of post-combustion. [ABSTRACT FROM AUTHOR]

Combustion process in internal combustion engines involve significant temperature and pressure, carbon deposit, turbulence flame, swirling and tumbling flows which are considered necessary for operating these engines. This study examines the in-cylinder effects of swirling and tumbling motion along with the in-cylinder temperature during combustion process of air-fuel mixture. A detailed port flow analysis was carried out using ANSYS R-16 software and a valve lift of 8 mm. The velocity magnitude and mass flow rate were monitored using swirl motion simulated profiles and cut planes. Motion analysis was carried out to determine the angular velocity of the cycle using SOLIDWORKS 2017. The average angular velocity of the crankshaft was found to be 1315 rpm, with percentage deviation of less than 20%. It was also found that the area-weighted average velocity of charge was 11 m/s with corresponding mass flow rate measured as -0.055479 kg/s. The maximum flow rate was calculated at 8 mm as 0.005417 kg/s. The ICE swirl plane 1, 2 and 3 were characterized by different contours of velocity magnitude, indicating that the swirl intensity increased as the charge moved further down the cylinder while the charge volume of swirl increased along the cylinder length. For the ICE cut plane, the velocity increased as the swirl increased while the mass flow rate decreased as the fluid went further away from the poppet valve. Therefore, the intensity of swirl increased along the stroke length of the engine cylinder. In addition, increase in the swirl number led to uniform radial temperature distribution as well as reduction in the in-cylinder flame temperature which can mitigate against the formation of toxic pollutants.

Gasoline direct injection (GDI) engine are widely adopted in the automobile industry since its advantage in the fuel economy. Injection Timing (IT) is an important parameter for the GDI engine, having a great impact on the spray atomization, mixture evenness, combustion characteristics, and therefore performance of the GDI engine. With the motive of IT optimization, a three-dimensional CFD model of a single cylinder 4-stroke spark ignition GDI engine with bore of 84 mm and compression ratio of 10.3 was utilized to analyze the detailed process at different IT (270, 280, 290, 300-degree CA BTDC), while the other conditions were invariant like rotate speed at 2000 RPM. The spray, turbulence, G-equation combustion were included. The result indicated that delayed IT tended to reduce drop-wall impingement significantly but still intensified unevenness of mixture concertation severely, resulting in fuel-rich region appeared around cylinder. Because the duration available for mixing was shortened, which dominantly intensified the unevenness of the mixture. The combustion was deteriorated as the IT delayed because the excessive equivalence ratio region severely slowed flame propagation and frozen at the most uneven region, which finally degraded thermal efficiency and engine performance. In conclusion, this paper demonstrated the whole process from injection to combustion, revealing that droplet-wall impingement and available duration for mixing are dominant trade-off factors for mixture formation and following combustion process, as the IT changes.

A finite element analysis-computational fluid dynamics coupled analysis on the thermo-mechanical fatigue of cylinder head of a turbo-charged diesel engine was performed, and the complete simulation process is illustrated in this paper. In-cylinder combustion analysis and water jacket coolant flow analysis were conducted to provide heat transfer boundary conditions to the temperature field calculation of the cylinder head. Comparing with the conventional finite element analysis of cylinder head by which the heat transfer boundary conditions of the combustion and coolant sides are estimated, the present method coupled the three-dimensional combustion computational fluid dynamics and coolant computational fluid dynamics with the finite element analysis. Both computational fluid dynamics and finite element analysis obtain more accurate boundary conditions on their interface from each other, and thus, the present method improves accuracy of thermo-mechanical fatigue prediction. Based on the measured material performance parameters such as stress–strain curve under different temperatures and E–N curve, creep, and oxidation data material performance, the cylinder head–gasket–cylinder block finite element transient stress–strain field was calculated using ABAQUS. The thermo-mechanical fatigue analysis of cylinder head submodel was performed by using FEMFAT software that is based on the Sehitoglu model to predict the thermo-mechanical fatigue life of cylinder head. By comparing the measured and predicted temperatures of cylinder head, the temperature results showed a good agreement, and the error is less than 10%. [ABSTRACT FROM AUTHOR]

For an improved understanding of the in-cylinder processes in internal combustion (IC) engines, advanced diagnostics are needed to measure the thermodynamic state of the in-cylinder fluid. This is essential to validate numerical simulations which aim at predicting the in-cylinder processes during motored engine operation. Here, knowledge of the in-cylinder temperature is essential, as it strongly influences in-cylinder gas viscosity as well as the in-cylinder mass and thus the peak pressure. This work presents temperature measurements at 2.3 ∘CA resolution of a motored, optically accessible engine by applying tunable diode laser absorption spectroscopy (TDLAS) to in-cylinder water vapor. The temperature was investigated in different heights along the cylinder axis for variations of intake temperature and engine speed. Temperature uncertainties of ± 2.3 K were achieved at various cycle phases, and the absolute temperatures are verified using thermodynamic calculations of simultaneously measured water vapor concentration. The measured temperature dependency is compared to isentropic and polytropic changes of state, the incylinder gas mass is calculated and an estimation of the heat transfer to the walls is given. Based on the in-cylinder mass, different numerical simulations of the engine found in literature are compared. [ABSTRACT FROM AUTHOR]

Sustainable liquid fuels will be needed for decades to fulfil the world’s growing energy demands. Combustion systems must be able to operate with a variety of renewable and sustainable fuels. This study focused on how the use of various alternative fuels affects combustion, especially in-cylinder combustion. The study investigated light fuel oil (LFO) and six alternative liquid fuels in a high-speed, compression-ignition (CI) engine to understand their combustion properties. The fuels were LFO (baseline), marine gas oil (MGO), kerosene, rapeseed methyl ester (RME), renewable diesel (HVO), renewable wood-based naphtha and its blend with LFO. The heat release rate (HRR), mass fraction burned (MFB) and combustion duration (CD) were determined at an intermediate speed at three loads. The combustion parameters seemed to be very similar with all studied fuels. The HRR curve was slightly delayed with RME at the highest load. The combustion duration of neat naphtha decreased compared to LFO as the engine load was reduced. The MFB values of 50% and 90% occurred earlier with neat renewable naphtha than with other fuels. It was concluded that with the exception of renewable naphtha, all investigated alternative fuels can be used in the non-road engine without modifications.

This study examines the effect of in-cylinder combustion parameters on soot and NOx emissions at rated EGR levels by using the data obtained from the CFD implemented code. The obtained data were subsequently used to construct an artificial neural network (ANN) model to predict the soot and NOx productions. To this aim, at three different engine speeds of 2000, 3000 and 4000 rpm, heat release rate, equivalence ratio, turbulence kinetic energy and temperature varied to obtain the relevant soot and NOx data at three EGR levels of 0.2, 0.3 and 0.4. It was discovered that wherein the application of higher EGR rates reduced the NOx as a result of mixture dilution, equivalence ratio increment makes soot production to be increased as well as NOx emission. It was also found that the application of higher EGR from 20% to 40% decreased soot mass fraction in the combustion chamber. Increment of EGR reduced the emissions where the equivalence ratio had contradictory effect on the produced emissions. Various ANN topological configurations and training algorithms were incorporated to yield the optimal solution to the modeling problem applying statistical criteria. Among the four adopted training algorithms of trainlm, trainscg, trainrp, and traingdx, the training function of Levenberg–Marquardt (trainlm) with topological structure of 5-19-17-2 denoted MSE equal to 0.0004627. [ABSTRACT FROM AUTHOR]

Polyoxymethylene dimethyl ethers (PODE) and methanol are both promising alternative fuels with high oxygen content, and the combustion and emission characteristics of PODE/methanol blends were investigated in a common-rail engine. The premixed charge compression ignition (PCCI) combustion was realized by appropriate match of main injection and pilot injection strategies. The effects of methanol ratio (0– 20%) on fuel economy and emissions formation were studied in conventional compression ignition (CI) and PCCI modes. The combustion and emission characteristics were improved by adjusting the pilot injection timing (−40 ~ −24 °CA ATDC) and pilot injection ratio (0– 20%). The results show that the increase of methanol ratio prolongs the ignition duration, increases the premixed combustion ratio and reduces NOx emissions. PCCI combustion increases the brake thermal efficiency (BTE) and improves the trade-off relationship between NOx and soot. The delay of pilot injection timing increases the BTE, decreases HC, CO and HCHO emissions, but increases NOx and soot emissions. The appropriate pilot injection ratio can significantly increase the BTE, and has little effect on the emission characteristics. Under the optimized pilot injection strategy and appropriate methanol ratio conditions, the maximum BTE of the blends can reach 46.58% and maintain low emission level. [Display omitted] • PODE/methanol blends can completely replace diesel fuel on the common-rail engine. • The addition of methanol increases HC, CO and HCHO emissions, while reduces NOx. • PCCI mode can improve the BTE and the trade-off relationship between NOx and soot. • Delaying pilot injection makes heat release process from single-peak to double-peak. • BTE of P95M5 reaches the highest value of 46.58% with optimized injection strategy. [ABSTRACT FROM AUTHOR]

The work presented here had two main aims: first, it investigated the relationship between in-cylinder combustion performance and particulate size distribution and number count; second, it examined the possibility of reconstructing transient events using steady state test data relating to particulate size distribution and number count. It identified a strong correlation between the geometric mean diameter (GMD) of the engine-out particulate matter and the rate of burning during the early stage of combustion. In addition, it identified correlations between the coefficient of variance for 50 per cent mass fraction burned and the coefficient of variance for particulate GMD. The tests relating to transient events identified that steady state data can be used to reconstruct acceleration events, but not deceleration events. The methodology followed to obtain these findings is detailed in this paper. [ABSTRACT FROM AUTHOR]

Sustainable liquid fuels will be needed for decades to fulfil the world's growing energy demands. Combustion systems must be able to operate with a variety of renewable and sustainable fuels. This study focused on how the use of various alternative fuels affects combustion, especially in-cylinder combustion. The study investigated light fuel oil (LFO) and six alternative liquid fuels in a high-speed, compression-ignition (CI) engine to understand their combustion properties. The fuels were LFO (baseline), marine gas oil (MGO), kerosene, rapeseed methyl ester (RME), renewable diesel (HVO), renewable wood-based naphtha and its blend with LFO. The heat release rate (HRR), mass fraction burned (MFB) and combustion duration (CD) were determined at an intermediate speed at three loads. The combustion parameters seemed to be very similar with all studied fuels. The HRR curve was slightly delayed with RME at the highest load. The combustion duration of neat naphtha decreased compared to LFO as the engine load was reduced. The MFB values of 50% and 90% occurred earlier with neat renewable naphtha than with other fuels. It was concluded that with the exception of renewable naphtha, all investigated alternative fuels can be used in the non-road engine without modifications. [ABSTRACT FROM AUTHOR]