Main Combustion Chamber Research Articles

Numerical investigation of pre-chamber holes diameter geometry on combustion parameters in a hydrogen-powered Turbulent Jet Ignition engine

The search for substitutes for conventional fuels leads to the use of hydrocarbon-free or synthetic fuels. One of them is hydrogen. The use of hydrogen in combination with a two-stage charge creation system leads to the combustion of lean (λ > 1) or very lean (λ > 3) charges. The simulation tests carried out were aimed at determining the best configuration of the chamber connecting the prechamber with the main combustion chamber. Three variants of the diameter of the holes connecting the chambers were selected (d = 0.5; 1.0 and 1.5 mm) in combination with different fuel doses fed to the prechamber. A passive chamber (qo_PC = 0 mg) and an active chamber (qo_PC = 0.4 and 1.2 mg) were used, while simultaneously sending a dose of fuel to the main chamber (qo_MC = 6 mg). The research was conducted using AVL Fire 2022.1 software using the moving mesh of the LDV engine. As a result of simulation work, the most favorable conditions for carrying out the process were determined, considering the thermodynamic effects of the process and the accepted values of nitrogen oxide concentration. The resulting correlation maps of the sizes of the chamber openings and the fuel doses fed to the prechamber may determine the initial selection of possibilities for controlling hydrogen combustion in the TJI system.

Synergy effect of nozzle structure and pre-chamber reactivity on the combustion characteristics of ammonia engines

Ammonia (NH3) offers an attractive opportunity for internal combustion engines (ICE) to be carbon–neutral. An active pre-chamber fueled with hydrogen might be suitable to overcome the poor combustion characteristics of ammonia engines. The primary goal of this work is to numerically study the combustion characteristics of ammonia engines with a hydrogen-fueled pre-chamber, and the synergy effect of nozzle structure and pre-chamber reactivity (hydrogen quantity) are also considered. The results show that the hydrogen fraction is reduced to a low degree in the pre-chamber because of the scavenging process. Thus, it is better to inject hydrogen into the pre-chamber during the compression stroke. Although high pre-chamber reactivity is effective in improving the main chamber combustion, a multi-hole pre-chamber is needed to get the maximum promoting effect of the high reactivity when compared to the single-nozzle pre-chamber. For multi-hole pre-chamber, 2 mm is the recommended nozzle diameter when considering the promoting effect, and the recommended area-volume ratio (nozzle number) is increased with the pre-chamber reactivity. For nitrogen-based emissions, the distribution strongly depends on the flame characteristics. High pre-chamber reactivity can significantly reduce the NH3 emissions, while NO emissions will increase with the pre-chamber reactivity. The current study can give some insights and be a preface for the development of ammonia engines.

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.

Research on maintenance decision-making approach based on dynamic opportunistic window

We have developed a maintenance decision-making approach based on the dynamic opportunistic window, utilizing algorithms such as k-mean clustering, expected maximum, and parameter estimation to address the lack of a reasonable basis for the duration and divided number of opportunistic windows in current maintenance decision-making. Firstly, we have comprehensively summarized the multi-stage opportunistic maintenance decision-making approach, focusing on its current strengths and limitations. Secondly, the modeling concept of the dynamic opportunistic window is analyzed, and the underlying assumptions are established. Furthermore, it elaborates on the theoretical foundation of the proposed approach through a detailed modeling process. Finally, we validate the proposed model by conducting experiments on tandem components from the main combustion chamber in an aero engine. The experimental results demonstrate the significant value of the proposed approach in enhancing equipment reliability and optimizing maintenance support resources.

Controllability of Pre-Chamber Induced Homogeneous Charge Compression Ignition and Performance Comparison with Pre-Chamber Spark Ignition and Homogeneous Charge Compression Ignition

This paper presents an experimental and numerical evaluation of the pre-chamber induced HCCI combustion concept (PC-HCCI) in terms of engine performance, emissions, and controllability. In this concept, a spark-initiated combustion in the pre-chamber is utilized to trigger the kinetically controlled combustion of an ultra-lean mixture in the main combustion chamber. The experimental measurements were performed on a single-cylinder engine with a custom-made active pre-chamber. A high compression ratio of 17.5 was used, which limits the maximum achievable engine load due to high knocking tendency but enables both standard PCSI combustion (flame propagation) at very high dilution levels and HCCI combustion at reasonable intake temperatures. The analysis of combustion characteristics and the resulting performance is performed at indicated mean effective pressures (IMEPs) of 3.5 and 3.0 bars, and three different intake temperatures of 80 °C, 90 °C, and 100 °C. The variation in engine load was achieved by adjusting the excess air ratio in the main chamber. On each combination of intake temperature and engine load, a spark sweep and an injected PC fuel mass sweep were performed to obtain the highest indicated efficiency while satisfying the restrictions in terms of combustion stability and knock intensity. It was shown that, unlike in a conventional HCCI engine, the combustion phasing can be directly and reliably controlled by adjusting either spark timing or the reactivity of the pre-chamber mixture, ensuring adequate combustion stability and eliminating potential misfires. A similar indicated efficiency as with conventional HCCI combustion was obtained, while the NOx emissions, although slightly elevated, are still insignificant. Compared to PCSI combustion at the same engine load, a 4-percentage-point increase in indicated efficiency and two times lower NOx emissions were achieved. Compared to the most efficient PCSI operating point, it was 1 percentage point lower, indicating that efficiency was achieved, but the specific NOx emissions are reduced by approximately 70%. Most importantly, very similar performance was obtained with significant variations in intake temperature, proving the reliability and adaptability of this combustion concept.

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.

Analysis of cooling effects and measurement errors in water-cooled thermocouples for total temperature measurement in aviation engine combustion chambers

Accurate measurement of the total temperature in the main combustion chamber of an aviation engine is crucial for assessing engine performance. However, a significant challenge exists in balancing the heat transfer errors caused by the necessary cooling of the measuring device with measurement precision. The research employs a combination of numerical simulations and experimental methods to investigate this issue. The numerical simulations utilized the Reynolds-averaged Navier Stokes (RANS) coupled with a conjugate heat transfer approach to study the primary flow characteristics and heat transfer properties within the combustion chamber and the probe body. The experiments were conducted in a heat-calibration wind tunnel, validating the results of the numerical simulations. The results show that by implementing water cooling, the probe's body temperature can be reduced from 1200 °C in high-temperature conditions to 400 °C, with localized temperature imbalances still present in the edge areas of the probe. Tracing the cooling water path reveals that the vertical bends in the internal channels lead to an increase in localized pressure loss of the cooling water. The study quantitatively analyzes measurement errors caused by three heat transfer modes: radiation, convection, and conduction. In low-load conditions of the combustion chamber, heat conduction plays a dominant role, with measurement errors due to conduction reaching up to 70 % of the total measurement error. Radiation further increases the temperature measurement errors of the thermocouple's junctions near the chamber wall. As the combustion chamber temperature increases, entering high-load conditions, the cooling effect of water becomes limited, reducing conduction errors and increasing radiation errors. In these conditions, radiation errors constitute 60–70 % of the total measurement error. It suggests the importance of considering temperature corrections when using water-cooled temperature measurement devices. The research reveals several crucial insights regarding the performance and limitations of water-cooled thermocouples.

Numerical Investigation of the Operating Characteristics of the Passive and Active Prechamber Jet Ignition in a Natural Gas Engine.

Prechamber jet ignition is a promising technology that enables stable ignition and fast combustion by combining thermal effects, chemical kinetics, and turbulent disturbance. The development and application of the prechamber ignition require a comprehensive and in-depth understanding of the operating characteristics of the prechamber ignition in the real engine working cycle. Therefore, numerical simulations are conducted to explore the operating performance of the prechamber ignition applied to a large-bore natural gas engine in this study. The differences between the passive prechamber (PPRE) and active prechamber (APRE) near the lean burn limit are compared. The results show that the jet ignition performance of the PPRE is hampered by the high residual gas coefficient and lean mixture in the prechamber under lean burn conditions. The ignition mode of the PPRE is similar to torch ignition, and the combustion process in the main chamber is mainly turbulent flame propagation. The ignition mechanism of the APRE is flame jet ignition. The main chamber combustion process presents a two-stage heat release characteristic, which can be subdivided into three phases: the initial flame development phase, the rapid combustion phase, and the late combustion phase. The heat release rate during the initial flame development phase depends on the physical and chemical properties of the prechamber jet and the mixture conditions in the main chamber. During the rapid combustion phase, the flame propagation along the radial direction of the jet largely depends on the time scale of the chemical reaction. The heat release rate depends on the coverage area of the jet, the jet residual momentum, and the turbulent flame speed. During the late combustion phase, the flame propagation is mainly affected by the turbulent flame speed. These results provide theoretical guidance for the subsequent application of prechamber ignition systems in various powertrains.

Analysis of effects of pre-chamber orifices on torch flame behaviours in lean-burn gas engines

Fuel conversion from heavy oil to natural gas is favoured as a quick remedy for GHG re-duction from industrial engines in ship propulsion and power generation fields thanks to fewer carbon contents in natural gas. In medium-speed gas engines, the ejection of torch flame from a pre-chamber is often used to promote flame propagation within a main com-bustion chamber. Although orifice specifications affect the ejection behaviour of the torch flame and the following combustion in the main chamber, the effects are difficult to fully understand. Some of the authors developed a constant-volume combustion vessel that simu-lated the combustion chamber around the top dead centre of a pre-chamber type gas engine and observed the effects of orifice specifications on the torch flame ejection and the com-bustion in the main chamber. Still, the correlation was not concluded due to the lack of physical examination. In the paper, the above measurement results were confirmed by using RANS-type CFD considering the larger scale of the target engines, and the physical back-ground of the effects of orifice specifications was successfully reproduced.

Comparison Of A Molecularly-Controlled Combustion Engine To A DISI Engine

In addition to the increased use of electromobility, significant improvements in the efficiency of internal combustion engines (ICE) to achieve a considerable reduction of emissions is crucial to advance the transition towards a sustainable transport sector. One approach to increase the efficiency of combustion engines is active pre-chamber ignited engines (Molecularly Controlled Combustion Engines, MCC). The traditional spark ignition is replaced by a chamber that ignites a secondary fuel. The burning fuel is emitted from the pre-chamber via multiple holes, igniting the fuel air mixture in the main combustion chamber. To eject the flame jets tangentially to the pent roof, the pre-chamber protrudes into the main chamber in the center of the main chamber’s pent roof. This particular geometry of an MCCengine, however, alters the flow field inside MCC-engines. To facilitate future developments around MCC-engines and to understand the interactions of the flow field with the pre-chamber, a Stereo Particle-Image Velocimetry (SPIV) study is conducted in an optically accessible MCC-engine model. Previous velocity field data, which were acquired using a Direct Injection Spark Ignition (DISI) engine configuration at the same operating point as the MCC-engine, are compared to those of the MCC-engine. Phase-averaged velocity field data of both engines acquired during the intake stroke are compared based on their in-plane velocity fields and the in-plane vorticity. The two engine configurations show significantly different magnitudes of velocity in their combustion chamber flow field. In the MCC-engine, a downwash flow component can be attributed to flow deflection caused by the pre-chamber protruding from the engine’s pent roof. One important flow feature of ICE, the tumble vortex, is analyzed for both engine configurations. An increased absolute vorticity and a different temporal development of the tumble vorticity is noted for the MCC-engine. The tumble flap, an engine component that influences the intake flow distribution, is considered a main contributor to the difference in flow velocity and tumble vorticity.

Influence of Ambient Pressure on the Jet-Ignition Combustion Performance and Flame Propagation Characteristics of Gasoline in a Constant Volume Combustion Chamber

Based on a constant volume combustion chamber, the initial ambient pressure effect on gasoline combustion performance and flame propagation of the active and passive pre-chamber ignition systems were studied. Compared with the passive pre-chamber, the active pre-chamber can significantly expand the lean combustion limit from 1.2 to 1.5, enhance the ignition and combustion performance, and speed up the combustion of the main combustion chamber. At slightly lean combustion conditions, the heat release performance has a positive correlation with the initial ambient pressure. As the premixed λ increases, the heat release performance and the initial ambient pressure begin to become negatively correlated. Ignition delay can be decreased by approximately 50% at an initial pressure of 0.75 MPa, premixed lambda of 1.2 with APC compared with PPC. The high ambient pressure (1.0 MPa) in the constant volume chamber greatly reduces the mixture entrainment ability of the jet flame at lean combustion conditions, thereby reducing the combustion speed and peak heat release rate.

Study on ignition mode transition of methanol pre-chamber jet ignition system controlled by boundary condition parameters

Optimizing boundary condition parameters is an effective means to substantially improve the combustion performance of methanol pre-chamber turbulent jet ignition systems. In this study, an optically accessible constant-volume combustion chamber was employed to delve deeply into the impacts of critical boundary condition parameters on the combustion performance of the pre-chamber jet ignition system. The findings suggest that adjusting the pre-chamber boundary condition parameters can lead to various jet ignition modes, including jet flame ignition, jet direct ignition, jet delayed ignition, jet wake ignition, and dual jet ignition. Different jet ignition modes result in variations in ignition timing, ignition location, combustion rate, and lean burn limits. Under identical initial temperature and pressure conditions, compared to jet flame ignition with the lowest combustion velocity and jet wake ignition with almost no lean burn capability, dual jet ignition can reduce the combustion duration by about 50% and elevate the lean burn limit by more than double. Unlike the patterns observed in traditional spark ignition systems, within the range of experimental tests, lowering the temperature and increasing the pressure significantly improved the lean combustion limit of the pre-chamber system and reduced the probability of jet wake ignition. This performance enhancement is attributed to the increase in the density of the mixture in the main combustion chamber.

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.

Computational study of the impacts of the nozzle configurations on passive pre-chamber engine combustion

The pre-chamber (PC) nozzle configurations are vital in the narrow-throat pre-chamber design. However, their impacts on the jet and combustion characteristics are poorly understood. In the current study, various parameters of nozzle configurations, including the number of rows, nozzle position, and the jet included angle were evaluated on a well-calibrated numerical model of a passive PC engine fueled with methane. The unique buffering effect of the bottom cavity below the orifice in the PC nozzle was discovered and investigated for the first time. Results show that the PC with double-row orifices exhibits slower general combustion than the single-row for the significant flow bypass from the upper-row orifices that generate low jet velocity. A higher orifice position favors combustion due to less interaction between the flame and the piston. Pressure accumulation at the nozzle was discovered to be the key factor affecting jet velocity. Jet velocity increases with the enlarged pressure accumulation decreasing the effective flow area of the orifices. However, it starts to decrease when the pressure accumulation becomes excessive and the obstruction to the flow outweighs the enhancement to the velocity. For single-row PCs without the bottom cavity, the pressure accumulation is enhanced as the jet included angle increases (from 111° to 180°) and the angle of 157° achieves the highest jet velocity, although the pressure difference decreases as the included angle increases. For single-row-orifice PCs with a bottom cavity, the buffering effect of the cavity produces close pressure accumulation to maintain similar jet characteristics when the jet included angle varies. Comparative analysis shows that the included angle of 157° achieves the fastest main chamber combustion mainly because the proper relative position of the PC jet and piston favors turbulence and flame spread.

Analysis of Unburned Methane Emission Mechanisms in Large-Bore Natural Gas Engines With Prechamber Ignition

Abstract Although precombustion chambers, or prechambers, have long been employed for improving large-bore two-stroke natural gas engine ignition and combustion stability, their design predates modern analysis techniques. Employing the latest computational fluid dynamics (CFD) modeling techniques, this study investigates the importance of temperature and chemistry for ignition of the main chamber, with an emphasis on eliminating unburned methane. The sensitivity of the ignition and complete combustion to main chamber air/fuel mixture homogeneity was also explored. This study compares the effect of purely thermal ignition, purely chemical ignition, and how their interplay can influence the complete combustion of methane in typical mixtures and in homogeneous distributions of fuel in the combustion chamber. The CFD results demonstrated that temperature and chemistry are equally important in the ignition mechanism, and combining the two phenomena is effective at igniting the main chamber. Reduction of residual methane in the main combustion chamber (MCC) is most effective when chemical intermediates and thermal ignition are combined. A rudimentary analysis of the effect of fuel/air stratification was also conducted, and it demonstrated that a dramatic reduction in methane emissions is observed for homogeneous mixtures. The flow field in the main combustion chamber was shown to create detrimental stratification of the fuel/air mixture, which inhibited complete combustion of the methane in the main chamber. By contrast, in the extreme case of a perfectly homogeneous distribution of both chemical intermediates and fuel in the combustion chamber, it is possible to completely eliminate unburned methane in the main combustion chamber.

The Research and Development of a Jet Disturbance Combustion System for Heavy-Duty Diesel Engines

Herein, a diesel engine jet disturbance combustion system was proposed to achieve efficient and clean combustion under heavy load conditions in heavy-duty diesel engines. The key components of the combustion system were designed, and a research platform was constructed. Focusing on the internal combustion conditions of the disturbance chamber and the developmental path of high-speed jets, the design and comprehensive optimization of the jet disturbance combustion system were carried out. Following optimization, the peak internal heat release rate increased from 86 J/deg to 269 J/deg, and the cumulative heat release increased by 112 J, significantly enhancing the energy of the disturbance chamber jet. Then, considering combustion optimization and the heat transfer loss from the piston, it was determined that the optimal configuration for the disturbance chamber jet channel angles was 60 deg inter-channel angle and 10 deg channel incidence angle. This configuration allowed the disturbance chamber jet to precisely disturb the concentrated mixture area in the middle and late stages of combustion. The intervention of the disturbance chamber jet provided sufficient energy for the fuel–air mixing process and complicated the gas flow state in the main combustion chamber. Despite its low-momentum density, the residual mixture in the cylinder maintained a high mixing rate after the end of the fuel injection process. Single-cylinder engine test results showed that a diesel engine using this jet disturbance system and a 180 MPa common rail pressure fuel system achieved 52.12% thermal efficiency.

Experimental investigations on the jet flow field propagation characteristics and ignition mechanisms of stoichiometric CH4/O2/N2 premixed turbulent jet flames

The jet flow field (JFF) and flame propagation of stoichiometric CH4/O2/N2 mixtures under variable thermodynamic conditions were investigated experimentally using Schlieren and natural flame luminosity imaging techniques. A two-color method by wavelength integration was used to characterize the temperature field. The turbulent flame velocity (ST), Damköhler number (Da), Reynolds number (Re), and jet flame regime were explored by a combination of experimental data and theoretical calculations. The flame morphology shows that the propagation process can be subdivided into three stages: first, the JFF enters the main combustion chamber, then the flame propagates in the JFF, and finally, the JFF disappears after the flame front and the JFF front coincide. The vortex motion changes the thin reaction zone and the local high temperature region distribution. The normal jet shifts to the Mach disk jet at higher oxygen content. The ignition location changes from the jet tail to the shear layer. The top secondary vortex is more likely to generate at higher ambient temperatures, which enhances the ignition probability on the flame top. In addition, the degree of orifice blockage determines the jet flame type. Since the initial jet flame is more affected by orifice blockage, the variation in ST is strongly influenced by the change in the length-scale ratio. As the jet flame gradually moves away from the orifice, ST is mainly governed by turbulence intensity. Finally, a strong correlation between the Re number and Da number of the jet flame was found.

Analysis of Causes of Combustion Failure in Burner Incinerators at MT. JS INEOS INNOVATION

Abstraction-Incinerator is an auxiliary machine designed as the main combustion chamber to burn wasted oil after going through the heating process in a sludge incinerator tube. The use of the incinerator on the ship aims to burn the waste on the ship and also burn dirty oil. Based on the author's research, the operation of the incinerator on board is still not optimal due to the failure of the combustion in the incinerator burner. This study aims to find out the causes and efforts to solve the problems raised by researchers, namely combustion failure in the incinerator burner at MT. JS Ineos Innovation
 This study used a descriptive qualitative method. By using fishbone analysis techniques, researchers identified the factors and efforts made related to combustion failure at the Incinerator burner at MT. JS Ineos Innovation. Source of data taken from primary and secondary data. Data collection was carried out by interviews, observation, documentation, and literature study which was carried out during the research.
 Based on the research results, it can be concluded that combustion failure in the incinerator burner is caused by several factors, including a dirty burner nozzle, damaged steam valve, decreased steam supply from the steam service line, and jammed piston valve in the sludge dosing pump incinerator. Efforts made to overcome the occurrence of combustion failure at the incinerator burner are carrying out cleaning of the incinerator burner, carrying out maintenance or replacement of the steam valve, increasing the steam intensity from the steam service line to the inlet heater incinerator, and carrying out maintenance and repair of the piston valve in the sludge. dosing pump incinerator.

Optical study of active narrow throat pre-chamber assisted internal combustion engine at lean limit

The pre-chamber assisted ignition offers several much-needed upgrades to gas engines, ranging from improved combustion efficiency and stability to extended lean limits. The concept has received intermittent attention from researchers over the past century, and the concept's fundamental understanding remains segmented. This study investigates pre-chamber assisted combustion (PCC) in a heavy-duty gas engine fueled by methane at the lean limits. The engine is operated at two lean limits at intake pressures of 1.2 and 1.4 bar. At lower intake pressure, global excess air ratio (λglobal) is 2.4, while at higher intake pressure λglobal is 2.6. The comparison of two lean limits through experimental data and GT-Power 1D model reveals the underlying ignition and combustion. Using a combination of acetone PLIF (N-PLIF) and OH* chemiluminescence imaging allows visualization of both the reacting and non-reacting part of the pre-chamber jet. The results suggest that pressure differential across the pre-chamber and main chamber controls the reacting jet growth speed. The combustion chamber boundaries affect the main combustion through the wall jet part of the impinging pre-chamber jets as higher OH* concentrations are observable at stagnation points of the jet. In addition, the study reports the appearance of post-combustion jets and dispersed OH* pockets as the combustion dwindles. The narrow throat pre-chamber shows a spectral pressure signature reminiscent of the Helmholtz oscillator, and circumferential resonant modes dominate the main chamber combustion. Although the PCC offers great ignitibility, the main chamber mixture cannot sustain prolonged combustion at a lean limit lambda value.

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.