Jun Deng

The nozzle geometry has a significant impact on the nozzle internal flow, which affects the fuel spray atomization and combustion of internal combustion engine. In this study, the internal geometry and flow characteristics of the nozzle was studied visually by using X-ray phase contrast imaging technique. The results indicate that the angle between the orifice wall and sac significantly influences the formation and development of cavitation in the orifice. A numerical model including the nozzle internal flow and the spray near-field characteristics was established to provide a more detailed description of how the inlet included angle affects the orifice's internal flow. It has been found that the hydraulic flip width increases with the decrease of the inlet included angle. The symmetry of cavitation distribution is greater when the inlet included angles on the left and right sides of the orifice are equal. When the inlet included …

Argon power cycle hydrogen engine is a novel approach to increasing the thermal efficiency of hydrogen engines while achieving zero CO2 emissions. This paper presents a combination of experiments and simulations used to examine the effects of hydrogen direct injection on the combustion characteristics and thermal efficiency of argon power cycle engines. The results of the study indicate that, in comparison to port hydrogen injection, hydrogen direct injection produces a delay of CA50 exceeding 12.36°CA at an engine speed of 1000 r/min. This delay optimizes combustion and diminishes knock intensity to below 0.1 MPa by creating a stratified mixture, which in turn decelerates the combustion rate. Through adjusting hydrogen direct injection timing and incorporating super lean combustion, a maximum gross indicated thermal efficiency of 53.72% is achieved. By optimizing the first injection timing, the …

To prevent the explosion hazards of hydrogen energy, in this work, the deflagration behaviors of H2-air mixtures at equivalence ratios from 0.6 to 1.4 under the effects of C3HF7 and CO2 are experimentally investigated. Deflagration pressure and time indexes at ambient pressure and temperature are obtained. The characteristic parameters of chemical kinetics are analyzed according to a detailed mechanism. The results suggest that C3HF7 has dual effects of pressure enhancement and suppression with the rising volume ratio in fuel-lean H2-air mixtures. It is the F-involved reactions that govern the exothermic process, facilitate the comprehensive conversion of crucial free radicals, and augment the exothermicity of the principal reaction, leading to the elevation in peak pressure. Dilution of CO2 would decrease the heat release rate of the F-involved reactions and reduce the explosion enhancement effect of C3HF7 …

Argon Power Cycle (APC) is a novel concept for high efficiency and zero carbon emissions, which replaces the air by an argon-oxygen mixture. Previous studies have experimentally demonstrated that APC has a great efficiency enhancement potential for methane-fueled engines. However, the port methane injection tends to cause knock and limits thermal efficiency gains. In addition, few researches have focused on the power of APC methane-fueled engines. In this study, fundamental experiments are first conducted in a spark ignition methane direct injection engine with compression ratio = 9.6. Strategies such as lean combustion, dilution combustion (increasing argon mole ratio in argon-oxygen mixture), and boosting intake pressure are adopted. Results indicate that lean combustion has a more significant effect in efficiency enhancement under APC compared with air cycle due to the high specific heat ratio of …

In this study, the examination of the explosion pressure and flame propagation characteristics were investigated for premixed CH4–H2-air mixtures, with varying equivalence ratios (φ = 0.8–1.5) and methane volume ratios (R = 0–100%). This investigation was conducted employing a 20 L explosion vessel and a high-speed ripple shadow meter, while maintaining ambient temperature and pressure. The most critical primitive reactions effecting the formation and consumption of OH* were obtained by normalisation through rate analysis. The result found that as the R increased at the same φ, the premixed system exhibited a gradually decreased in the Pmax, (dP/dt)max, and KG. The increase in the R caused the flame structure to stabilise, extending the flame front distance and the time to reach the wall. The reaction process was divided into three phases based on the R: 0 < R<40% (dominated by hydrogen …

Argon power cycle hydrogen engine is the internal combustion engine that employs argon instead of nitrogen of air as the work mass, oxygen as the oxidizer, and hydrogen as the fuel. Since argon has a higher specific heat ratio compared to air, argon power cycle hydrogen engines have theoretically higher indicated thermal efficiencies according to the Otto cycle efficiency formula. However, argon makes the end mixture more susceptible to spontaneous combustion, and thus is accompanied by stronger knock at a lower compression ratio, thus limiting the improvement of thermal efficiency in engine operation. In order to suppress the limitation of knock on the thermal efficiency, this paper adopts a combination of experimental and simulation methods to investigate the effects of port water injection on the knock suppression and combustion characteristics of an argon power cycle hydrogen engine. The results show …

Hydrogen is considered a leading clean energy carrier and versatile industrial raw material, playing a crucial role in driving down greenhouse gas emissions. Ensuring the safe utilization of hydrogen holds paramount significance. The present study investigated the variation law of the lower flammability limit of hydrogen under the influence of inhibitors (carbon dioxide, nitrogen, and heptafluoropropane) through experimental testing. The critical inhibitory concentration required for complete suppression was determined. Additionally, the explosive characteristics under the influence of inhibitors were evaluated, and the inhibitory mechanism was analyzed in conjunction with chemical kinetics. With an increase in the quantity of inhibitors added, there was a corresponding increase in the lower flammability limit of hydrogen, as demonstrated by the results. When 10% volume fraction of heptafluoropropane was added …

Pre-chamber ignition, as a novel ignition technology, can increase the ignition energy, promote flame propagation and enhance turbulence. While the technology holds promise, the commercialization process will undoubtedly face challenges, particularly in terms of emission regulations. This research mainly focused on the transient characteristics of combustion and particulate number emissions under a quick start condition in gasoline engines for HEV (Hybrid Electric Vehicle) based on an active pre-chamber ignition. The results show that the active pre-chamber ignition in gasoline engine has a lower PN (Particulate Number) concentration of less than 7× 107 N/mL in the first cycle. And the particulates are mainly dominated by nuclear mode (NM,< 50 nm), with almost no accumulation mode (AM,> 50 nm) compared to the conventional gasoline engine. When the quick start speed is set to 800r/min. It has been …

Ammonia is an efficient hydrogen energy carrier and a potential zero-carbon fuel for internal combustion engines. However, the poor ignition and combustion performances of ammonia limit its further application in homogeneous charge compression ignition engines. This study proposes to employ an inert gas argon as a diluent to improve ammonia's ignition and combustion performances. Furthermore, the effect of adding hydrogen is also investigated under a wide calculation range of compression ratio, excess oxygen ratio, and argon ratio through thermodynamic analysis. The calculation results indicate that replacing nitrogen with argon can significantly shorten the ignition delay time and promote the thermal conversion efficiency and power density. Under a specific condition (compression ratio= 19 and excess oxygen ratio= 3.0), when replacing air with an argon-oxygen mixture of argon/oxygen ratio= 79: 21, the …

The present work implements a numerical simulation to investigate the combustion process in a porous-free flame burner. The non-equilibrium thermal condition is performed, and discretization and solving of the governing equations are conducted in a two-dimensional axisymmetric model. In order to simulate the combustion process, a reduced chemical kinetic mechanism of GRI 3.0, which includes 16 species and 41 reactions, is used. In order to prove the precision of the numerical method, some experimental tests are carried out and the numerical results are in a good agreement with the experimental measurements. The numerical results demonstrate that the porous-free flame burner has a higher flame stability compared to the conventional porous burner and the radiative efficiency of the porous-free flame burner is less than the porous burner. In addition, an increase in thermal conduction of the porous …

Ammonia is used as the carbon-free fuel in the engine, which is consistent with the requirements of the current national dual-carbon policy. However, the great amount of NOx in the exhaust emissions is produced after combustion of ammonia and is one kind of the most tightly controlled pollutants in the emission regulation. Nitrous Oxide (N2O) is a greenhouse gas with a very strong greenhouse effect, so that the N2O emissions needs to be paid close attention. In this paper, the CFD simulation of the N2O formation and emission characteristics during combustion is carried in the ammonia/hydrogen fueled pre-chamber jet ignition engine. The simulation results show that the turbulent kinetic energy (TKE) around the orifices of the pre-chamber is enhanced due to the local temperature difference between the main-chamber and the pre-chamber, and then the residual ammonia/hydrogen fuel in the crevice or near the …

Turbocharger technology has become an essential method for the internal combustion engine to improve fuel economy. However, too high a boost pressure leads to too high a temperature in the combustion chamber at the end of the compression stroke, which can cause knocking or worsen abnormal combustion. Water injection technology plays a role in cooling the intake air and components in the cylinder, which can control the combustion process and suppress knock. This work focused on the influence of direct water injection (DWI) on knock suppression and efficiency improvement using a small turbocharged gasoline engine, investigating the fuel-saving potential of DWI and the optimal strategy of DWI for different engine operating conditions. Taking knock intensity (KI) as the evaluation index, KI decreases from 0.052 to 0.04 MPa, and knock limit spark angle (KLSA) increases with increasing water injection …

GDI engine has gained much popularity in vehicle market with its high thermal efficiency. However, because of higher particulate emissions, it becomes harder for GDI engines to fulfill the iteration of emission regulations in various countries. As a result, Gasoline Particulate Filter (GPF) has received more and more attention and applications. It is important to study the particulate emission and GPF performance especially for transient cycles. With a self-designed test bench with burner named Exhaust Gas Simulator, a transient control strategy to simulate the exhaust state of the WLTC cycle has been developed and achieved a fast and stable ash accumulation rate. Three levels of ash loading, in terms of 0g/L, 5g/L and 35g/L, were accumulated on respective GPF for different aging degrees with this test bench. The effect of ash loading on GPF performance was investigated. A Cambustion DMS500 was used to record …

Hydrogen-fueled Argon Power Cycle engine is a novel concept for high efficiency and zero emissions, which chooses high specific heat ratio argon‑oxygen mixture as working fluid. However, the low specific heat of argon also increases the in-cylinder temperature, causing severe knock, which limits the efficiency of the engine. A typical knock-limited compression ratio for a hydrogen port-injected Argon Power Cycle engine is about 5.5:1 if no specific method is used. This article presents experimental research on the effect of water port injection under 1000 r/min at a compression ratio of 9.6:1 with IMEP ranging from 0.1 to 0.6 MPa and argon ratios of 79%, 85%, and 90%. The net indicated thermal efficiency peaks at 53.50% without a water injection but the knock intensity reaches 3.4 MPa. With the water injection, 16 mg/cycle water is sufficient to eliminate knock and the maximum net indicated thermal efficiency …

Increasing efficiency and reducing emissions are fundamental approaches to achieving peak carbon emissions and carbon neutrality for the transportation and power industries. The Argon power cycle (APC) is a novel concept for high efficiency and zero emissions. However, APC faces the challenges of severe knock and low power density at high efficiency. To elevate efficiency and power density simultaneously of APC, the Miller cycle is applied and combined with APC. The calculation method is based on a modification of the previous thermodynamic method. The mixture of hydrogen and oxygen is controlled in the stoichiometric ratio. The results indicate that to obtain a thermal conversion efficiency of 70%, in the Otto cycle, the compression ratio and the AR (argon molar ratio in the argon-oxygen mixture) could be 9 and 95%, respectively. In comparison, for the Miller cycle, these two parameters only need to be …

The efficiency enhancement of argon power cycle engines through theoretical means has been substantiated. However, the escalation of in-cylinder temperatures engenders abnormal combustion phenomena, impeding the augmentation of compression ratios and practical efficiency. This study presents a comprehensive investigation employing experimental and simulation techniques, aiming to extend the boundaries of thermal efficiency and operational capabilities for hydrogen-powered argon cycle engines. The impact of hydrogen direct injection, intake boost, and port water injection is evaluated in conjunction with an argon power cycle hydrogen engine. The hydrogen direct injection, particularly at an engine speed of 1000 rpm, significantly increases the indicated mean effective pressure from 0.39 MPa to 0.72 Mpa, surpassing the performance of the port hydrogen injection. Manipulating the hydrogen direct injection timing results in the formation of a stratified mixture, effectively attenuating the combustion rate, and resolving the issue of excessively rapid hydrogen combustion within an Ar/O2 environment. The implementation of super lean combustion, combined with intake-boosting, achieves a maximum gross indicated thermal efficiency of 57.89%. Furthermore, the port water injection proves to be an effective measure against knock, broadening the operational range of intake-boosted conditions. Notably, the maximum gross indicated thermal efficiency recorded for the port water injection group under intake-boosted conditions reaches 59.35%.

Ammonia (NH3) is considered a promising alternative fuel, capable of producing energy with zero CO2 emissions. Its combustion, however, poses a series of challenges due to the low reactivity of NH3 and the formation of very high quantities of NOx. This work numerically investigates the combustion and emission characteristics of ammonia in three modern stationary gas turbine concepts, namely (a) lean-burn dry-low emissions (DLE); (b) rich-burn, quick-quench and lean-burn (RQL); and (c) moderate or intense low oxygen dilution (MILD), under operating conditions typical of commercial gas turbines (inlet temperatures of 500 K and pressure of 20 bar). Numerical simulations employing detailed chemical kinetic mechanisms are carried out to study the propagation speed of ammonia, the combustor temperatures, and the emissions of NOx and NH3. The simulations are first validated against literature NOx data …

Homogenous Charge Compression Ignition (HCCI) have drawn lots of attentions due to its high efficiency and low emissions. But HCCI engines are prone to random abnormal combustion phenomena at load boundaries. In this paper, innovatively implement online prediction and control of knock at high load boundary for HCCI utilizing only cylinder pressure as the diagnostic parameter based on neural networks. The results show that the neural network model with previous cycle heat release, previous cycle crank angle at 50 % cumulative heat release (CA50), peak cylinder pressure during previous and current cycle negative valve overlap (NVO) as inputs can realize the prediction of 87.5 % early combustion cycle in the intake phase before the early combustion occurs, and the diagnosis accuracy is 89.4 %. The frequency of early combustion can be reduced from 2.3 % to 0.3 % with the help of prediction model …

This paper reviews the theoretical and experimental researches on Argon Power Cycle (APC) engines. Hydrogen-fueled APC is an innovative power system for a high efficiency and zero emissions, which employs argon rather than nitrogen as a diluent. Due to the large specific heat ratio of argon, the thermodynamic efficiency of APC engines is significantly higher compared to conventional internal combustion engines. However, APC engines face the challenge of knock inhibition, especially when using hydrogen as a fuel. Therefore, this paper summarizes the strategies and technologies to suppress the knock of hydrogen-fueled APC engines, including using alternative fuels with greater anti-knock capacity, lean combustion, and water injection. Furthermore, some guidance opinions are also provided for reference about the development and industrialization of APC engines, such as ultra-lean combustion, which uses pistons with thermal insulation coatings, employing low-friction lubricants, and developing efficient multi-component membrane separation system for argon separation.

Argon Power Cycle (APC) is an innovative future potential power system for high efficiency and zero emissions, which employs an Ar-O2 mixture rather than air as the working substance. However, APC hydrogen engines face the challenge of knock suppression. Compared to hydrogen, methane has a better anti-knock capacity and thus is an excellent potential fuel for APC engines. In previous studies, the methane is injected into the intake port. Nevertheless, for lean combustion, the stratified in-cylinder mixture formed by methane direct injection has superior combustion performances. Therefore, based on a methane direct injection engine at compression ratio= 9.6 and 1000 r/min, this study experimentally investigates the effects of replacing air by an Ar-O2 mixture (79% Ar+ 21% O2) on thermal efficiencies, loads, and other combustion characteristics under different excess oxygen ratios. Meanwhile, the influences …