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In this study, the effect of injection strategy on the mixture formation and combustion in a hydrogen direct injection engine using CFD analysis was investigated. Four Start of Injection timings and three types of injection rate were used to understand how the fuel and air mixing process and fuel distribution at the spark timing affect the start of combustion and flame propagation. The results shows that injection timing and rate shape significantly influence the formation of the fuel–air mixture and the subsequent combustion process. Uneven mixture formations from direct injection necessitate careful consideration of local equivalence ratios around the spark plug to ensure efficient combustion initiation and flame propagation.

The direct injection of natural gas (NG), which is an important research direction in the development of NG engines, has the potential to improve thermal efficiency and emissions. When NG engines operate in low-load conditions, combustion efficiency decreases and hydrocarbon (HC) emissions increase due to lean fuel mixtures and slow flame propagation speeds. The effect of two combustion modes (partially premixed compression ignition (PPCI) and high pressure direct injection (HPDI)) on combustion processes was investigated by CFD (Computational Fluid Dynamics), with a focus on different injection strategies. In the PPCI combustion mode, NG was injected early in the compression stroke and premixed with air, and then the pilot diesel was injected to cause ignition near the top dead center. This combustion mode produced a faster heat release rate, but the HC emissions were higher, and the combustion efficiency was lower. In the HPDI combustion mode, the diesel was injected first and ignited, and then the NG was injected into the flame. This combustion mode resulted in higher emissions of NOx and soot, with a diffusion combustion in the cylinder. HC emissions significantly decreased. Compared with PPCI combustion, HPDI had a higher thermal efficiency.

Natural gas (NG) engines have very broad application prospects. The pilot-ignited NG diesel engine can be organized into two combustion modes according to the sequence of oil and gas injection: (1) High-pressure direct injection, where NG is mainly diffused combustion; and (2) partially premixed compression ignition, where NG is mainly premixed combustion. In this study, we used CONVERGE to explore the influence of the NG injection timing on the distribution of the mixture equivalence ratio, ignition characteristics, thermal efficiency, emission, and combustion reaction rate under the two combustion modes. We also used a multi-step soot model to analyze the particle mass and quantity. We showed herein that the NG injection timing significantly affects the mixture distribution in the cylinder, thereby consequently affecting the combustion process. Both very early and very late injection times were not conducive to NG combustion. In addition, the mass, quantity, and diameter of the soot produced by diffusion combustion were larger than those produced with premixed combustion.

An existing diesel engine was fitted with a common rail direct injection (CRDi) facility to inject fuel at higher pressure in CRDi mode. In the current work, rotating blades were incorporated in the piston cavity to enhance turbulence. Pilot fuels used are diesel and biodiesel of Ceiba pentandra oil (BCPO) with hydrogen supply during the suction stroke. Performance evaluation and emission tests for CRDi mode were carried out under different loading conditions. In the first part of the work, maximum possible hydrogen substitution without knocking was reported at an injection timing of 15° before top dead center (bTDC). In the second part of the work, fuel injection pressure (IP) was varied with maximum hydrogen fuel substitution. Then, in the third part of the work, exhaust gas recirculation (EGR), was varied to study the nitrogen oxides (NOx) generated. At 900 bar, HC emissions in the CRDi engine were reduced by 18.5% and CO emissions were reduced by 17% relative to the CI mode. NOx emissions from the CRDi engine were decreased by 28% relative to the CI engine mode. At 20%, EGR lowered the BTE by 14.2% and reduced hydrocarbons, nitrogen oxide and carbon monoxide by 6.3%, 30.5% and 9%, respectively, compared to the CI mode of operation.

This paper proposes a dual-mode CMOS analog front-end (AFE) circuit for short-wave infrared (SWIR) image sensors, which integrates a hybrid readout circuit (ROIC) and a 12-bit two-step single-slope analog-to-digital converter (TS-SS ADC). The ROIC dynamically switches between buffered-direct-injection (BDI) and direct-injection (DI) modes, thus balancing injection efficiency against power consumption. While the DI structure offers simplicity and low power, it suffers from unstable biasing and reduced injection efficiency under high background currents. Conversely, the BDI structure enhances injection efficiency and bias stability via an input buffer but incurs higher power consumption. To address this trade-off, a dual-mode injection architecture with mode-switching transistors is implemented. Mode selection is executed in-pixel via a low-leakage transmission gate and coordinated by the column timing controller, enabling low-current pixels to operate in low-noise BDI mode, whereas high-current pixels revert to the low-power DI mode. The TS-SS ADC employs a four-terminal comparator and dynamic reference voltage compensation to mitigate charge leakage and offset, which improves signal-to-noise ratio (SNR) and linearity. The prototype occupies 2.1 mm × 2.88 mm in a 0.18 µm CMOS process and serves a 64 × 64 array. The AFE achieves a dynamic range of 75.58 dB, noise of 249.42 μV, and 81.04 mW power consumption.

Many countries worldwide have introduced a limit for solid particles larger than 23 nm for the type approval of vehicles before their circulation in the market. However, for some vehicles, in particular for port fuel injection engines (gasoline and gas engines) a high fraction of particles resides below 23 nm. For this reason, a methodology for counting solid particles larger than 10 nm was developed in the Particle Measurement Programme (PMP) group of the United Nations Economic Commission for Europe (UNECE). There are no studies assessing the reproducibility of the new methodology across different laboratories. In this study we compared the reproducibility of the new 10 nm methodology to the current 23 nm methodology. A light-duty gasoline direct injection vehicle and two reference solid particle number measurement systems were circulated in seven European and two Asian laboratories which were also measuring with their own systems fulfilling the current 23 nm methodology. The hot and cold start emission of the vehicle covered a range of 1 to 15 × 1012 #/km with the ratio of sub-23 nm particles to the >23 nm emissions being 10–50%. In most cases the differences between the three measurement systems were ±10%. In general, the reproducibility of the new methodology was at the same levels (around 14%) as with the current methodology (on average 17%).

Recently, global warming caused by greenhouse gases has been highlighted, so many studies have been carried out for developing eco-friendly products. In the vehicle industry, various techniques have been developed for eco-friendly engines. A previous fuel injection system, injecting fuel at the intake port, had difficulty precisely controlling the air/fuel ratio in the cylinder. Therefore, the fuel injection system has been changed to a direct injection system injecting fuel directly inside the cylinder. Due to concerns about fossil fuel depletion and the instability of oil prices, various alternative fuels are currently becoming popular. Liquefied petroleum gas (LPG) is an alternative fuel that has similar characteristics to gasoline. LPG can be used in gasoline engines without sophisticated modification of the engine. For these reasons, the present work focuses on a numerical investigation of the combustion and emission characteristics of LPG direct injection (LPDI) engines by using tumble and swirl. For conducting the simulation, commercial software STAR-CD ver. 4.26 was used. The study was performed at the minimum spark advance for best torque (MBT) of the stoichiometric excess air ratio (λ = 1.0) and the lean-burn excess air ratio (λ = 1.5) with changes in the intake port geometry to induce in-cylinder flow changes.

This article presents a procedure for designing footwear production plants with a Decision Support System combined with an expert system and a simulation approach. The footwear industry has many operations and is labour intensive. Optimisation of plant layout, machinery, and human resources is very important to design the footwear manufacturing system, making adequate investment in space and equipment. In the industry it is essential to reduce the process time, so the research is based on a Decision Support System combined with an expert system and simulation to improve the design of the manufacturing plan. This work contains two case studies, direct injection manufacturing and assembly and carburising methods, which are compared to analyse all the necessary resources to have the best cost–benefit ratio. In each case, a precise knowledge of the type and quantity of machinery and human resources is needed to estimate the production. This comparison has been done through simulations and using a knowledge base of an expert system. The conclusions are presented in which an improvement in production time is obtained by applying the methodology developed in the study.

Directly injecting fuel in two-stroke spark-ignition (2S-SI) engines will significantly reduce fuel short-circuiting losses. The liquid phase liquefied petroleum gas (LPG) DI (LLDI) mode has not been studied on 2S-SI engines even though this fuel is widely used for transportation. In this experimental work a 2S-SI gasoline-powered engine used on three-wheelers was modified to operate in LLDI mode with an electronic engine controller. The influences of injection pressure (IP), end of injection (EOI) timing, location of the spark plug, and type of injector on performance, combustion, and emissions were studied at different operating conditions. EOI close to bottom dead center with the spark plug located near the exhaust port was the most suitable for the LLDI mode which significantly enhanced the fuel trapping efficiency and improved the thermal efficiency. At 70% throttle condition the brake thermal efficiency increased from 19% to 25.6% and there was an 87% reduction in hydrocarbon (HC) emission compared to liquid phase LPG manifold injection. The use of multi-hole injector extended the maximum power output due to better in-cylinder mixture formation, whereas the single-hole injector extended the lean operating limit. LLDI has potential to improve the performance of small two-stroke engines significantly.

Numerical modeling of internal nozzle flow can be regarded as an essential investigation in the field of gasoline direct injection system of combustion engines since it is directly connected with fuel spray atomization and subsequently efficiency of exhaust gas emission. Internal nozzle flow can be changed and formed according to several parameters such as; system pressure, chosen fuel type, the orientation of spray holes according to injector axis, conicity of spray holes and distribution of spray holes on valve-seat, etc. The changes in these parameters also affect the formation of cavitation inside of whole domain, spray angle and create wall-wetting on the spray hole surfaces. The present work investigates the parameter and design analysis in the valve-seat region of direct gasoline injection (GDI) injector using Computational Fluid Dynamics (CFD) and Design of Experiments (DOE). CFD is employed to study the behaviors of internal flow inside the valve-seat region according to several design parameters, whereas a mixed-level factorial design is used to test the significance of the effects on the response variables. In conclusion, the effects of the most significant factors on response parameters as amount of vapor formation, spray (Tau) angle, and pre-hole wall wetting are determined for further efficient design.