Pre-combustion Chamber Research Articles

Impact of fuel injection pressure on GDI engine performance: a numerical study with pre-combustion chamber

Impact of fuel injection pressure on GDI engine performance: a numerical study with pre-combustion chamber

Combustion and emissions of an ammonia heavy-duty engine with a hydrogen-fueled active pre-chamber ignition system

Combustion and emission characteristics of a heavy-duty single-cylinder ammonia engine with a hydrogen-fueled active pre-chamber ignition system are investigated experimentally at the condition of IMEP 10 bar, 1000 rpm, where effects of spark timing, excess air ratio (λ), and hydrogen energy ratio are tested. Three distinguishable combustion phases are observed, including pre-chamber combustion, turbulent-jet-controlled combustion, and ammonia-chemical-kinetics-controlled combustion. Advancing spark timing makes combustion phases earlier, increasing pressure rise rate, combustion pressure, and NOx emissions. The optimal spark timing for the highest indicated thermal efficiency (ITE) is −12°CA ATDC in the experiment. λ range for stable combustion is 1.1–1.5 and ITE peaks at λ = 1.3. The hydrogen energy ratio, 7.9%∼10.5%, has little influence on the engine performance. However, a low hydrogen energy ratio could increase the risk of misfire. The optimal hydrogen energy ratio is about 9∼10%.

Experimental investigation of the ignition dynamics in a premixed annular combustor using a pre-chamber ignition system

In this paper, the ignition characteristics in a MICCA-type annular combustor are studied for the first time using a pre-chamber combustion (PCC) system. The PCC is proposed to replace the traditional spark electrode ignitor in the annular combustor, aiming to shorten ignition time and prevent misfiring. The PCC system is commonly utilized to initiate the ignition process in internal combustion (IC) engines by generating high-temperature turbulent jets that ignite the fuel/air mixture in the main combustion chamber (MCC). The PCC is integrated into a premixed annular combustor consists of sixteen swirling burners. The ignition characteristics and flame propagation patterns are investigated using a high-speed camera under varying conditions of equivalence ratios, bulk velocities, and thermal power levels. Experimental results demonstrate that the PCC exhibits a high ignition response without misfire. The induced turbulent jet from the PCC is observed to propagate into both sides of the annular combustor with high energy, creating a significant initial flame area along the jet trajectory. This enhances the ignition probability compared to traditional spark electrode ignition systems. Due to the higher burning rate resulting from the jet ignition, the light-round time is reduced by 41 % compared to traditional spark electrode ignition systems operating at the same equivalence ratio of 0.81 and the same bulk velocity of 3.22 m/s. This improvement is particularly advantageous for high-altitude re-ignition scenarios.

Experimental and simulation study on lean combustion characteristics of passive pre-combustion chamber ignition boosted GDI engine

In order to verify the potential application of passive pre-combustion chamber technology in commercial GDI engines, the efficiency characteristics, combustion characteristics (CA50, Knock Index and COV) and emission characteristics of a pre-combustion chamber ignition engine in a boosted environment were studied by three-stage injection strategy to form a lean burn environment (λ = 1.3). A 3D simulation model of pre-combustion chamber ignition engine is established. Combined with the engine bench test results, the process of intake, mixture formation, combustion and emission generation under different working conditions is simulated by simulation method. The development process of TKE (turbulent kinetic energy), air-fuel ratio, temperature and combustion emissions in the main/pre-combustor is studied. It is found that under high load conditions in boosted pre-combustion chamber engine, the average knock index can be controlled between 2 and 3.4 bar, and the COV can be controlled between 3% and 3.5%. The indicated thermal efficiency reaches over 40% within the load range of IMEP from 10 to 14 bar. When the load increases, NOx and soot emissions show a downward trend, the HC and CO emissions slight increase. The pre-combustion chamber engine exhibits a tumble intake pattern around the cylinder axis perpendicular to the cylinder axis. The TKE reaches its maximum value 20 CAD before the top dead center and then rapidly decreases. The use of a three-injection strategy can form a uniform stratified mixture at the ignition moment. The fuel air equivalence ratio in the ignition area of the pre-combustion chamber is 0.8–0.9, slightly higher than the average fuel air equivalence ratio of 0.75.

Enhancing ignition stability in an annular combustor using a pre-chamber ignition system

The traditional method using spark electrode ignition in annular combustors lacks safety due to its long ignition delay and deficiencies in reliability and repeatability. The present work investigates the ignition characteristics of a premixed annular combustor using pre-chamber combustion (PCC) as an ignition source. The ignition process of the annular combustor is studied experimentally with PCC and is compared to the one with the traditional spark electrode ignition under the same equivalence ratio and bulk velocities. The ignition process is recorded using a high-speed camera. The two-dimensional time-resolved Mie scattering technique is employed to determine the flame front position in the annular combustor. It was found that the jet issued from PCC generates hot radicals associated with strong turbulence, exhibiting distributed ignition sites along the jet trajectory inside the annular combustor. Introducing PCC to the annular combustor increases the ignition probability and burning rate, as well as reduces the light-round time by about 24 % compared to the spark electrode at a thermal power of 18.6 kW. Moreover, the experimental results indicate that flame propagation in the annular combustor is significantly influenced by the PCC operating parameters. In contrast, combustion within the PCC is less affected by the local flow structure in the annular combustor, making the PCC a favourable solution for various operating conditions. Additionally, a slightly rich mixture in the PCC increases the burning rate, whereas a very rich mixture decreases the burning rate.

Analysis on monofuel: Methane and hydrogen in passive TJI engine using Center of Combustion and lambda-value control

The search for new combustion systems makes the two-stage combustion system (TJI) widely used when burning poor mixtures of methane and, increasingly, hydrogen. This paper presents the thermodynamic conditions for the combustion of methane and hydrogen when using a passive pre-combustion chamber. Thermodynamic analyses were carried out on a single-cylinder AVL 5804 research engine at varying values of excess air ratio (CH4: λ = 1.0–1.3; H2: λ = 2.16–2.70) and by changing the position of the center of combustion (CoC = 6; 8; 10; 12; 14; 16 deg TDC). As a result of the analyses carried out, the ignition advance was found to be significantly smaller when burning hydrogen than methane to maintain the same CoC value. A larger range of changes in ignition advance is required to determine CoC when burning hydrogen, indicating hydrogen's greater sensitivity to changes in ignition angle. During the combustion of the two fuels, different values of overall efficiency were determined: about 48% when burning hydrogen, and about 33% when methane combustion (in both cases, the maximum efficiency was obtained at the highest value of the λ, for methane and hydrogen, respectively: 1.3 and 2.7).

The Influence of Pre-Chamber Parameters on the Performance of a Two-Stroke Marine Dual-Fuel Low-Speed Engine

With increasing environmental pollution from ship exhaust emissions and increasingly stringent International Maritime Organization carbon regulations, there is a growing demand for cleaner and lower-carbon fuels and near-zero-emission marine engines worldwide. Liquefied natural gas is a low-carbon fuel, and when liquefied natural gas (LNG) is used on ships, dual-fuel methods are often used. The pre-chamber plays a key role in the working process of dual-fuel engines. In this paper, an effective three-dimensional simulation model based on the actual operating conditions and structural characteristics of a marine low-pressure dual-fuel engine is established. In addition, the effects of changing the Precombustion chamber (PCC) volume ratio and the PCC orifice diameter ratio on the mixture composition, engine combustion performance, and pollutant generation were thoroughly investigated. It was found that a small PPC volume ratio resulted in a higher flame jet velocity, a shorter stagnation period, and an acceleration of the combustion process in the main combustion chamber. When the PCC volume was large, the Nitrogen oxygen (NOx) ratio emission was elevated. Moreover, the angle of the PCC orifice affected the flame propagation direction of the pilot fuel. Optimizing the angle of the PCC orifice can improve combustion efficiency and reduce the generation of NOx. Furthermore, reasonable arrangement of the PCC structure can improve the stability of ignition performance and accelerate the flame jet velocity.

Investigation of the effect of HHO-assisted flame-jet ignition on in-cylinder combustion, engine performance, and environmental indicators in a propane-fueled SI engine

In this paper, a spark ignition (SI) engine is modified to operate by flame-jet ignition using oxy-hydrogen (HHO) gas in a small pre-combustion chamber (PCC) at partial load. The air-propane mixture in the main combustion chamber was ignited with an HHO-assisted flame jet, and the effects on in-cylinder combustion, engine performance, and environmental factors were investigated. In experimental studies, the SI engine was operated at 2300 rpm with a throttle opening of 1/2 at 24 different operating points generated by combining six different mixtures (λ = 0.9–1.4) and four different HHO flow rates (HHO = 0–1.0 l.min−1). The situation in which the HHO gas is not injected into the PCC is passive, while the situation in which it is injected is active. The findings showed that operating conditions with active PCC at λs significantly improved engine performance and environmental impact. The effect of active PCC was greater with lean mixtures (λ = 1.3–1.4) and decreased as the mixture shifted towards the rich (λ = 0.9). In addition, the effect of active PCC at all λs slowed down after 0.7 l.min−1 HHO flow rate. At λ = 1.4 and 1.0 l.min−1 HHO flow rate, where the highest effect occurs, Pmax and IMEP with active PCC are 76.09 % and 58.9 % increased, respectively; ISFC decreased by 38.3 % and ηt reached by 37 %; mfb’s of 0–10 %, 10–90 %, and 90–100 % 38.27, 20.83 %, and 47.62 % shorten, respectively; COVIMEP decreased by 6043 units; HC decreased by 95.18 %; CO2 and NOx emissions increased by 44.6 % and 24 %, respectively. In addition, at λ = 1.4, ΣE&SC decreased up to 164.5 €.kWh−1 which is 11 % lower than the lowest value of 183.5 €.kWh−1 obtained at passive PCC.

Effect of ignition pattern on combustion characteristics in a hydrogen Wankel rotary engine: A numerical study

Hydrogen is considered the optimal solution for achieving high efficiency and low emissions in Wankel rotary engines (WREs). This paper aims to reveal the effect of ignition patterns on the combustion process of a hydrogen-fueled WRE. The results show that the combustion rate of the trailing spark plug (TSP), due to its structural similarity with the passive precombustion chamber, surpasses that of the leading spark plug (LSP). The unidirectional flow field promotes the forward development of the flame of TSP but inhibits the backward development of the flame of LSP. Moreover, the recess in combustion chamber facilitates flame propagation of TSP. Asynchronous ignition mode exhibits a higher indicated thermal efficiency (ITE) than synchronous ignition mode, facilitating effective control of the combustion phase. When the ignition timing of LSP is delayed, and TSP is earlier, the flame of TSP exceeds LSP, resulting in unchanged ITE. When the ignition timing of TSP is delayed, and LSP is earlier, the peak of free radicals and burned volume rate are the highest, resulting in a faster combustion rate. It is recommended that the LSP ignition timing is set earlier for practical operations.

Enhancing ammonia engine efficiency through pre-chamber combustion and dual-fuel compression ignition techniques

In pursuit of unleashing ammonia’s potential in internal combustion engines, an extensive computational study was conducted to explore the effects of two advanced combustion techniques: pre-chamber combustion (PCC) and dual-fuel compression ignition (DF−CI) on a heavy-duty ammonia engine. In the PCC mode, hydrogen was introduced into the pre-chamber (PC) to generate distributed reacting jets, with a small energy fraction of 0.5%. The case featuring a slightly narrower PC throat (diameter of 5.4 mm) yielded the highest indicated thermal efficiency (ITE) of 50.4%, owing to the rapid distribution of reacting jets and advanced combustion phasing. Further increase in hydrogen energy fraction and reduction in throat diameter resulted in a lower ITE because of the enhanced wall heat transfer loss. The DF−CI mode also exhibited significant potential for achieving high efficiency. Through a systemic optimization of parameters such as diesel injection timing, spray included angle, injection pressure, swirl ratio, and piston shape, a significantly enhanced ITE of 50.3% was attained, 7.2% higher than the baseline scenario. The improvement was primarily attributed to the promoted mixing of diesel with air. Among the design parameters, the swirl ratio and spray included angle exhibited the most significant impact on the engine performance. Overall, both the PCC and DF−CI modes were found to yield high ITE and low ammonia emissions. However, because 20% of the diesel energy fraction was utilized to mitigate ammonia slip in the DF−CI mode, notably higher greenhouse gas emissions (carbon dioxide of 96 g/kW-h) were generated than in the PCC mode. In this regard, the ammonia-hydrogen PCC mode should be a more promising solution to achieve zero-carbon emissions for future ammonia engines.

Influence of Passive Pre-Chamber Nozzle Diameter on Jet Ignition in a Constant-Volume Optical Engine under Varying Load and Dilution Conditions

<div>Despite the growing prominence of electrified vehicles, internal combustion engines remain essential in future transportation. This study delves into passive pre-chamber jet ignition, a leading-edge combustion technology, offering a comprehensive visualization of its operation under varying load and dilution conditions in light-duty GDI engines. Our primary objectives are to gain fundamental insights into passive pre-chamber jet ignition and subsequent main combustion processes and evaluate their response to different load and dilution conditions. We conducted experimental investigations using a light-duty, optical, single-cylinder engine equipped with three passive pre-chamber designs featuring varying nozzle diameters. Optical diagnostic imaging and heat release analysis provided critical insights. Findings reveal that as load decreases, fuel availability and flow conditions deteriorate, leading to delayed and suboptimal jet characteristics impacting main chamber ignition and combustion. Notably, at high and medium loads without dilution, the 1.2 mm-PC (smallest nozzle diameter) excels, exhibiting superior jet ignition and main combustion. This is attributed to earlier jet ejection, improved penetration, and intensified jets, all enabled by the smaller nozzle diameter. Conversely, under low load conditions, the 1.6 mm-PC (largest nozzle diameter) performs better due to enhanced scavenging and reduced pre-chamber residuals, resulting in more balanced pre-chamber combustion and jet characteristics. Furthermore, nozzle diameter significantly influences cycle-to-cycle variations, with smaller diameters enhancing jet ignition but intensifying variability. The impact of external residuals (dilution) on jet ignition performance varies with nozzle diameter, with the 1.6 mm-PC displaying less degradation and demonstrating earlier jet ejection and CA50 timing under higher dilution conditions. In summary, this research underscores the importance of scavenging and residual levels in pre-chamber design, influencing dilution tolerance, and extending possibilities for high-efficiency engines. It contributes essential insights into the behavior of passive pre-chamber jet ignition systems, facilitating their optimization for future internal combustion engines.</div>

The Ammonia Combustion Engine for Future Power Generation Applications

Energy storage is one of the big challenges for the energy transition and ammonia as a hydrogen carrier is considered a promising candidate for efficient and medium‐ to long‐term chemical storage. Gas engines are well suited for power generation using ammonia as a carbon‐free fuel, making it unnecessary to convert ammonia back to hydrogen for the utilization in the power plant. This study investigates operating strategies for a prechamber combustion concept for a large‐bore gas engine suitable for power generation applications. To overcome the high ignition energy and low laminar flame speed of ammonia, different quantities of hydrogen as a promoting agent to improve the combustion properties of ammonia have been employed in the experimental investigations on a single‐cylinder research engine. The combustion concept shows a wide operating range with stable and robust combustion from 0.3 to 2.5 MPa indicated mean effective pressure and will be transferred to a multicylinder engine for the first combined heat and power demonstration.

Optimizations of energy fraction and injection strategy in the ammonia-diesel dual-fuel engine

Fuel consumption and emissions are growing concerns, driving the need for cleaner alternative fuels in engine research. Ammonia is a competitive alternative fuel. To enhance the effective utilization and provide a new direction for the marine application of ammonia, an ammonia-diesel dual-fuel engine model with the pre-combustion chamber structure was designed. Numerical simulations were carried out in this paper, considering variations in diesel energy fraction, ammonia injection timing, diesel injection pressure, and diesel injection timing. The findings indicate that an appropriate amount of pilot diesel accelerates jet flame formation, improving combustion efficiency. Advancing ammonia injection timing improves mixture homogeneity but increases ammonia slip, while delaying ammonia injection timing leads to mixture stratification. Locally rich areas in the mixture improve combustion efficiency. The timing and pressure of diesel injection significantly impact both combustion efficiency and emissions. Advancing diesel injection timing improves power output but increases NOX emissions. Increasing diesel injection pressure improves combustion efficiency, but excessive pressure leads to deterioration. Overall, this study provides valuable insights into the potential use of ammonia as a sustainable fuel for marine low-speed engines, selecting the optimal energy fraction and injection strategy to achieve efficient and environmentally friendly combustion.

Numerical investigation of a GDI engine with pre-combustion Chamber

Numerical investigation of a GDI engine with pre-combustion Chamber

Optimization of combustion organization scheme for pre-combustion chamber of pre-cooled engine

Pre-cooled engines, in which the incoming air is cooled by a pre-cooler before it enters the subsequent components for operation, are one of the important developments in combined power solutions. Therefore, how to optimize the gas temperature uniformity of the high temperature gas stream at the outlet of the pre-combustion chamber to achieve higher efficiency of the pre-cooled engine will be the main research content. In this paper, grid partitioning was performed on the pre combustion chamber model, and the k-omega model and EDC model were used to simulate the internal flow field of the pre combustion chamber. And verify the correctness of the simulation through engine hot testing. Explored the changing trends of the internal velocity and temperature fields of the engine under different secondary injection structures. The larger the secondary injection flow rate, the more obvious the obstruction to high-temperature gas, and the better the uniformity of gas temperature. However, in experiments, the secondary injection components often cannot withstand a large flow rate ratio. Ultimately, the gas temperature uniformity is best when the secondary injection flow rate ratio is 65%. Circumferential deflection will cause the gas to spin, and the spinning process will make the gas temperature at the same radius more uniform. However, due to the decrease in radial velocity, the obstruction effect on the overall high-temperature gas is weakened. When the gas is deflected towards the head by 30°, the velocity of the incoming gas and the velocity of the secondary injection gas are combined and perpendicular to the axis. At this time, the gas temperature uniformity is the best.

The influence mechanism of pre-combustion chamber orifice structure on natural gas engines: Combustion, emissions, and thermofluid analysis

The pre-combustion chamber (PCC) can enhance ignition stability, promote flame propagation and thus improve thermal efficiency. However, the mechanism by which the structure of the PCC orifice affects the combustion characteristics of engines is still unclear. In this study, thermal fluid simulation was used to investigate the effects of different volume ratios (ratio of PCC to main combustion chamber), apertures, and orifice structures (under stoichiometric and lean-burn conditions) on a PCC-type natural gas engine. The results showed that as the volume ratio and pore size increased, the indicated thermal efficiency (ITE) of the engine first increased and then decreased. Furthermore, the ITE of the engine reached its highest value when a PCC structure with a volume ratio of 1.5% and a pore diameter of 1.6 mm was adopted. As the orifice taper increased, the flame propagation velocity in the W-shaped orifice (Din > Dout) and N-shaped orifice (Din < Dout) decreased. The flame produced by the direct orifice (Din = Dout) had the longest penetration distance and the highest propagation velocity, which increased the cylinder pressure. In addition, under lean-burn conditions, in-cylinder combustion was more complete, with the lowest CO and THC emissions.

Experimental study on the influence of cracked kerosene gas temperature on the propagation characteristics of rotating detonation waves

The product of kerosene pre-combustion pyrolysis is typically used as the fuel for rotating detonation, and pure air at an ambient temperature is used as the oxidizer. The temperature of cracked kerosene gas (CKG) is determined by changing the supply conditions of the pre-combustion chamber. Therefore, the influence of the CKG temperature on the detonation range and rotating detonation wave (RDW) propagation was determined in this study. The experimental results show that the initiation delay time decreases with increasing CKG temperature. The temperature of CKG increased from 633 to 980 K, and two modes of RDW propagation appeared: the single rotating detonation wave (SRDW) and intermittent single rotating detonation wave (ISRDW) modes. In the temperature range of each propagation mode, the RDW velocity increased with the CKG temperature. Moreover, the average pressure of RDW propagation decreased with increasing CKG temperature. The stability of RDW propagation was reduced mainly because the propagation mode was changed to ISRDW. Thus, increasing the CKG temperature widens the range of CKG and air initiation. Moreover, the equivalent ratio interval of RDW propagation in the SRDW mode increases from low to high with an increase in the CKG temperature.

Computational investigation of methanol pre-chamber combustion in a heavy-duty engine

This work explored the potential of methanol pre-chamber combustion (PCC) for heavy-duty engine applications. An optical engine experiment was conducted to visualize the jet flame development. The measured pressure traces and natural flame luminosity images were also used for the validation of three-dimensional computational fluid dynamics simulations. It was demonstrated that the main chamber (MC) combustion was successfully established by the reactive jet issued from the pre-chamber. Compared to methane PCC in our previous study, the distributed reacting jets were significantly thinner, in particular at the learner condition. The active PCC mode, which comprises enrichment of the mixture in the pre-chamber (PC) by means of direct methane injection, was effective in improving the engine performance. However, excessive PC fueling ratio (PCFR) resulted in lower thermal efficiency due to the higher wall heat transfer and combustion losses. In addition, the effects of various PC and piston geometries on the methanol/methane PC combustion were evaluated. The combination of an optimized PC and a flat piston yielded the highest thermal efficiency owing to the relatively lower combustion and wall heat transfer losses. At engine loads higher than 12.5 bar indicated mean effective pressure, exhaust gas recirculation must be implemented to avoid end-gas autoignition and reduce nitric oxides (NOx) emissions. As expected, the increase in (CR) further promoted engine work because of the higher expansion ratio. With CR of 13 and 14, higher thermal efficiency and lower NOx emission were simultaneously achieved under both intermediate and high loads when the engine was operating at the pure methanol PC combustion mode.

Influence of blade angle in the outer secondary air for swirl burner on the flow, combustion, and slagging characteristics in the pre-combustion chamber under the air-staged condition

Influence of blade angle in the outer secondary air for swirl burner on the flow, combustion, and slagging characteristics in the pre-combustion chamber under the air-staged condition

Computational study of hydrogen engine combustion strategies: Dual-Fuel compression ignition with Port- and Direct-Injection, Pre-Chamber Combustion, and Spark-Ignition

This work attempted to identify the best strategy for hydrogen internal combustion (IC) engines. Computational simulations were conducted to evaluate the combustion and emission characteristics of four combustion strategies: H2/diesel dual-fuel combustion with port-(DF-PI) and direct-injection (DF-DI) of H2, pre-chamber combustion (PCC), and port-injection spark-ignition (SI). Two ultra-lean conditions with an overall lambda (λ) of 2.5 and 3.0 were considered. A pilot energy fraction of 3% was applied in both DF modes to limit carbon oxide emissions. Note that since the DF-DI mode is free of end-gas autoignition, a high compression ratio at 17:1 was applied in contrast to the other three cases (13:1). Of the four strategies, the DF-DI and SI operations tended to yield the higher optimal indicated thermal efficiency (ITE) than the DF-PI and PCC modes, due to the highest expansion ratio and usable earliest spark timing, respectively. However, the diffusion combustion-dominant DF-DI operation generated the highest nitric oxides (NOx) emission, owing to the wide stoichiometric high-temperature flame periphery. Because of the pilot-intensified combustion process, the DF-PI operation was easy to induce end-gas autoignition, which considerably limited its load extension and improvement of ITE. In addtition, for both the DF-PI and DF-DI operations, their NOx emissions were challenging to be eliminated even with a modeled exhaust gas recirculation rate at 50% using water injection, indicating that a DI water injection method or an after-treatment system must be implemented for the further reduction of NOx emission. In contrast, both the PCC and SI modes were able to fulfill the EU VI regulation limit of NOx emission with a relatively high ITE. Considering that these two modes only need a single fuel supply system, they are considered more promising for practical applications than the DF-PI and DF-DI modes.