Jet Ignition Research Articles

Experimental investigation on the performance of pure ammonia engine based on reactivity controlled turbulent jet ignition

Ammonia-based internal combustion engines (ICEs) produce carbon-free emissions. However, the application of ammonia in ICEs results in difficult ignition, combustion instability, and reduced engine performance. In this study, the pre-chamber turbulent jet ignition (TJI) technology was applied to overcome these issues. Two TJI modes based on a self-designed scavenging pre-chamber were proposed in the engine experiments. These modes were air-assisted injection mode (TJI mode 1) and air-assisted injection mode with an air-scavenging process (TJI mode 2). The results demonstrated that the TJI system optimized the combustion stability and improved the burning rate of the ammonia engine. TJI combustion mode had a superior indicated mean effective pressure (IMEP), coefficient of IMEP variation (CoVIMEP), and indicated specific fuel consumption (ISFC) compared with the SI mode, particularly the TJI mode 2 with scavenging process. The NOx and NH3 emissions were high for the ammonia engine regardless of the ignition mode. However, the emissions decreased after adopting the TJI combustion mode. This study provides valuable insights into the application of the TJI ammonia engine to achieve zero-carbon emissions.

Enhanced combustion of ammonia engine based on novel air-assisted pre-chamber turbulent jet ignition

Ammonia has demonstrated great potential for achieving zero carbon emissions from internal combustion engines. However, the application of ammonia in engines faces the risks of ignition failure, low burning rate, and high nitrogen oxides emissions. Pre-chamber turbulent jet ignition (TJI) can provide multi-point ignition and fast combustion. Thus, in this study, a novel self-designed air-assisted pre-chamber apparatus is proposed to optimize the engine performance and combustion in a spark-ignition ammonia engine. The effects of high-reactivity pre-chamber fuels, including hydrogen, gasoline, and methane, on the performance of a TJI engine are investigated for the first time. The results show that, in the TJI mode considering the pre-chamber fueled with high-reactivity fuels, both the indicated mean effective pressure and indicated specific fuel consumption are improved compared with those in the spark-ignition mode. The enhanced combustion process involving shortened ignition delay and combustion duration is achieved by using the TJI mode. Double-peak phenomena are observed in both the pressure and heat release rate curves. In the TJI mode with the pre-chamber fueled with hydrogen, an optimal engine performance involving a high indicated mean effective pressure, low fuel consumption, and low coefficient of indicated mean effective pressure variation is obtained. Moreover, both peaks of the heat release rate are higher, and the ignition delay and combustion duration are further shortened owing to the jet effect produced by hydrogen combustion in the pre-chamber. Low NOx and NH3 emissions are observed in the TJI mode, particularly when the pre-chamber is fueled with hydrogen.

Experimental Investigations on Detonation Initiation Characteristics of a Liquid-Fueled Pulse Detonation Combustor at Different Inlet Air Temperatures

The detonation initiation characteristics of a single tube liquid-fueled pulse detonation combustor (PDC) is investigated at different inlet air temperatures in this paper. The inner diameter of the PDC is 62 mm. Gasoline and air are used as fuel and oxidant, respectively. The inlet air temperature is 288–523 K and the operating frequency of the PDC is 10~30 Hz. The experimental results show that the deflagration to detonation transition (DDT) distance, detonation initiation time, DDT time and jet ignition time decrease with the increasing operating frequency at the same inlet temperature. When the inlet temperature is 288 K, the DDT distance is shortened from 860.5 mm to 787.7 mm as the operating frequency increases from 10 Hz to 30 Hz. The detonation initiation time, the jet ignition time and the DDT time are reduced from 10.01 ms, 7.66 ms and 2.35 ms to 6.55 ms, 4.99 ms and 1.56 ms, respectively. When the inlet air temperature increases, the atomization and evaporation of the gasoline is improved, which also leads to the decrease in the DDT distance, the detonation initiation time, the jet ignition time and the DDT time. For example, when the inlet air temperature increases from 288 K to 523 K at the frequency of 10 Hz, the DDT distance is shortened from 860.5 mm to 747.2 mm and the detonation initiation time, the jet ignition time and the DDT time is reduced to 5.867 ms, 2.51 ms and 1.11 ms, respectively. Additionally, the self-ignition caused by high inner wall temperature occurs when PDC is operating at high frequency under high inlet air temperature.

Effects of Cooled Exhaust Gas Recirculation Combined With Prechamber Jet Ignition on the Combustion Characteristics in a Kerosene-Fueled Spark Ignition Engine

Abstract For security and logistical convenience, the single fuel forward policy hopes to use a single kerosene fuel to replace a variety of military fuels, especially the unsafe gasoline. However, the performance of kerosene-fueled spark ignition (SI) engines is severely restricted by knock, slow combustion rate, and poor combustion stability. This work innovatively applies cooled exhaust gas recirculation (EGR) combined with prechamber jet ignition (PJI) to a kerosene-fueled engine to suppress knock and improve performance. The results show that applying cooled EGR at a fixed throttle opening can suppress knock and improve fuel economy. However, the power decreased due to the decreased intake of energy. While applying EGR with constant fresh air mass flow makes the knock more prominent because of the microboosting effect caused by the increased throttle opening. This indicates that cooled EGR alone cannot improve the power output. Moreover, combustion instability was also caused due to the slower combustion rate. Therefore, PJI was introduced to compensate for the negative impact of EGR. As a result, a synergistic effect of cooled EGR and PJI was discovered, improving the IMEP by 5% and reducing the ISFC by 4.9% compared to the baseline. The PJI can shorten the combustion duration and improve the combustion stability because of the high kinetic energy jet and high turbulence flame. In addition, a novel two-stage heat release process which includes the unusual first-stage low-temperature heat release was discovered. Overall, EGR dominates the knock suppression, and PJI contributes to the combustion rate improvement.

In-cylinder pressure smart sampling for efficient data management

The present paper proposes an optimized algorithm for minimizing the amount of data processed in order to maintain all critical information from the in-cylinder pressure sensor but with minimum computational cost. The algorithm uses singular value decomposition (SVD) for reducing the number of samples and pivoting QR decomposition to identify the optimal sampling locations. Experimental data from four engines with different combustion modes, namely Spark ignition (SI), Compression ignition (CI), turbulent jet ignition (TJI), and dual fuel ignition (DFCI), was used to validate the algorithm. The impact of the different sampling methodologies on different metrics for engine performance has been addressed and studied showing negligible information loss when reducing to 25 samples per cycle the acquisition buffer size.

Experimental observation of turbulent jet ignition of pre-chamber with scavenging system for carbon dioxide diluted mixtures

The exhaust gas recirculation (EGR) method can suppress knock and improve the thermal efficiency of engines. But it will also deteriorate the combustion stability and engine power. Turbulent jet ignition (TJI) is a reliable ignition resource for improving ignition stability and burning rate. However, the residual productions in the pre-chamber will worsen the performance of the TJI. To this end, a self-designed pre-chamber with a scavenging system has been proposed. In this study, the ignition process and flame propagation phenomena under different EGR dilution ratios for H2/N2/O2 and CH4/N2/O2 mixtures were conducted in a constant-volume combustion chamber. The results suggested that the increase in EGR dilution weakens the influence of cellular instability and causes buoyancy instability, the latter of which could be mitigated by the passive TJI method. For the passive TJI mode, the exit time of the hot jet was delayed, and the turbulent flame speed decreased with the increase of EGR dilution ratio. Four ignition phenomena, namely jet re-ignition, flame buoyancy, re-ignition failure, and misfire, were distinctly identified. However, EGR tolerance cannot be extended by passive pre-chambers. Therefore, the pre-chamber with a scavenging system that can effectively extend the lean combustion tolerance with EGR dilution compared to SI and passive TJI was proposed. The effects of air and fuel injection quantities on ignition and flame propagation were investigated. The flame propagation velocity was positively related to the air injection mass, whereas an optimum fuel mass was required to achieve fast flame propagation. The EGR limit based on dual injections in the pre-chamber was obviously extended. Moreover, under near EGR tolerance conditions, a leaner fuel injection in the pre-chamber was required to realize successful ignition in the main chamber, as strong turbulence could cause high heat transfer loss with the cool unburnt mixture and suppress the occurrence of re-ignition.

The effect of structural parameters of pre-chamber with turbulent jet ignition system on combustion characteristics of methanol-air pre-mixture

Pre-chamber turbulent jet ignition technology is an effective way to optimize the methanol-air mixture combustion process. A literature survey of structures of currently used pre-chambers of turbulent jet ignition systems was conducted, and three levels of four key structural factors were extracted from them, and nine pre-chambers were redesigned using the Taguchi experimental design method. The test showed that there are four typical pre-chamber ignition modes in the methanol-air mixture, namely, jet flame ignition, jet ignition, jet wake ignition, and dual-jet ignition. Compared with a spark plug, these ignition modes can increase the peak heat release rate by 15.78%, 123.51%, 136.96%, and 235.19%, respectively. When the mixture concentration in the pre-chamber is stoichiometric, the lean-burn limit for jet ignition and jet wake ignition is similar to that for spark ignition. By contrast, jet flame ignition can significantly extend the lean-burn limit. Among all the pre-chamber structural parameters, the total cross-sectional area of ​​the nozzles influenced the pre-chamber combustion performance and lean-burn limit performance the most, and the weight of the influence was always greater than 80%. The effects of the transition angle in the pre-chamber, the throat diameter, and the number of nozzles on its performance are discussed in this paper.

Blast Wave Generated by Delayed Ignition of Under-Expanded Hydrogen Free Jet at Ambient and Cryogenic Temperatures

An under-expanded hydrogen jet from high-pressure equipment or storage tank is a potential incident scenario. Experiments demonstrated that the delayed ignition of a highly turbulent under-expanded hydrogen jet generates a blast wave able to harm people and damage property. There is a need for engineering tools to predict the pressure effects during such incidents to define hazard distances. The similitude analysis is applied to build a correlation using available experimental data. The dimensionless blast wave overpressure generated by delayed ignition and the follow-up deflagration or detonation of hydrogen jets at an any location from the jet, ∆Pexp/P0, is correlated to the original dimensionless parameter composed of the product of the dimensionless ratio of storage pressure to atmospheric pressure, Ps/P0, and the ratio of the jet release nozzle diameter to the distance from the centre of location of the fast-burning near-stoichiometric mixture on the jet axis (30% of hydrogen in the air by volume) to the location of a target (personnel or property), d/Rw. The correlation is built using the analysis of 78 experiments regarding this phenomenon in the wide range of hydrogen storage pressure of 0.5–65.0 MPa and release diameter of 0.5–52.5 mm. The correlation is applicable to hydrogen free jets at ambient and cryogenic temperatures. It is found that the generated blast wave decays inversely proportional to the square of the distance from the fast-burning portion of the jet. The correlation is used to calculate the hazard distances by harm thresholds for five typical hydrogen applications. It is observed that in the case of a vehicle with onboard storage tank at pressure 70 MPa, the “no-harm” distance for humans reduces from 10.5 m to 2.6 m when a thermally activated pressure relief device (TPRD) diameter decreases from 2 mm to a diameter of 0.5 mm.

High-efficiency internal combustion engine for hybrid hydrogen-electric locomotives

Hydrogen electric locomotives are receiving growing attention and progressing towards net zero. This letter discusses the improvement of traditional diesel-electric locomotives to use hydrogen and reduce energy demand. An internal combustion engine featuring direct injection and jet ignition of the hydrogen is proposed. The four-strokes, 12 L, V12 engine achieves peak power of 750 kW and peak efficiency above 46%. The propulsion system may be further optimized by adopting battery energy storage to buffer the operation of the engine and provide extra power when accelerating. This way, the engine may be further optimized to work over a narrower range of speeds and loads and be made smaller to provide reduced power.

Laser-induced plasma-ignited hydrogen jet combustion in engine-relevant conditions

This work aims to investigate the mechanisms governing H2 jet flame evolution and stabilisation by precisely controlling the jet ignition location using a laser-induced plasma in compression-ignition engine-relevant conditions. The experiments examine the flame evolution with high-speed schlieren imaging and pressure trace measurements in an optically-accessible constant-volume combustion chamber over a range of ambient O2 concentration (10–21 vol%) and temperature (600–800 K) conditions. Optical results reveal that in most cases, a localised flame kernel forms at the time and location of the laser-induced plasma and grows in connected regions to engulf the entire upstream and downstream jet volume of the ignition spot. The images also reveal that the flame lift-off is sensitive to ambient O2 and temperature changes. The flame appears attached to the nozzle at 21 vol% O2, but becomes lifted at a lower ambient O2 concentration and a colder temperature. A simplified numerical analysis suggests that edge-flame deflagration into stratified premixed fuel-ambient reactant streams explains the lift-off response to ambient O2 and temperature changes. Furthermore, at the lowest tested O2 concentration, the flame stabilisation occurs in leaner mixtures at the jet peripheral where it is likely exposed to stronger turbulence-chemistry interactions.

Hydrogen-diesel dual-fuel direct-injection (H2DDI) combustion under compression-ignition engine conditions

This study investigates the ignition and combustion characteristics of interacting diesel-pilot and hydrogen (H2) jets under simulated compression-ignition engine conditions. Two converging single-hole injectors were used to inject H2 and diesel-pilot jets into an optically accessible constant-volume combustion chamber (CVCC). The parameters varied include fuel injection sequence, timing between injections, and ambient temperature (780–890 K). The results indicate that when diesel-pilot is injected before H2, with increasing time separation, the burnt diesel products mix and cool down, requiring longer jet-jet interaction to ignite the H2 jet. When H2 is injected before diesel-pilot, the H2-air mixing amount prior to pilot-fuel igniting impacts the combustion spreading through the H2 jet. If ignition of the H2 jet occurs beyond its end-of-injection (EOI), the H2 mixture zone where the pilot-diesel interacts with becomes too lean for combustion. At lower ambient temperatures, the combustion variability increases, attributed to the diesel-pilot lean out.

Experimental Study of the Effects of Pre-Chamber Geometry on the Combustion Characteristics of an Ammonia/Air Pre-Mixture Ignited by a Jet Flame

In the future, ammonia is expected to become a carbon-free fuel for internal combustion engines. However, the flammability of ammonia is poorer compared to conventional fuels such as gasoline and diesel fuel. Pre-chamber jet ignition may be an effective way to ensure stable ignition and enhance the combustion of ammonia. In this paper, the effects of pre-chamber geometric parameters, including volume and orifice diameter, on the jet ignition and combustion processes were studied using visualization methods, combined with pressure acquisition. The results showed that ignition energy increased and the jet duration was prolonged with the increase in pre-chamber volume, resulting in a higher maximum pressure and pressure rise rate in the main chamber. The jet characteristics of a larger volume pre-chamber exhibited higher stability when the ambient parameters were changed. The smaller volume pre-chamber showed the superiority of a shorter flame propagation distance inside the pre-chamber, which advanced the timing of the jet appearance and shortened the ignition delay when the flammability of the pre-mixture was adequate. The larger pre-chamber orifice diameter caused an earlier jet ignition timing, shorter ignition delay, and higher ignition location. The jet duration for the pre-chamber with a smaller orifice was longer, which was beneficial for increasing the pressure rise rate in the main chamber. Too small a pre-chamber orifice led to ignition failure in the main chamber.

Ignition and combustion of a dense powder jet of micron-sized aluminum particles in hot gas

Aiming at the potential implementation of aluminum as a primary fuel in powder-fueled ramjets or engines, this work seeks to investigate the ignition and combustion characteristics of a dense gas-suspended jet of micron-sized aluminum particles in a hot flow with controlled temperature and compositions. Aluminum particles with a mean diameter of 40 µm are aerosolized using a custom-made feeder and carried into the burner by a nitrogen stream. The powder jet with a particle density of up to 1–3 kg/m3 can be ignited and burned violently at a surrounding gas temperature as low as 1500 K. The lowered ignition temperature of the powder jet can be attributed to a cooperative mechanism resulting in fast reactions. Meanwhile, the ignition delay time decreases from ∼25 to ∼5 ms when the surrounding temperature increases from 1500 to 2200 K. The burning powder jet generates strong luminance and AlO emission signals detected by a spectrometer. Particle image velocimetry (PIV) and camera pyrometry are used to derive the two-dimensional velocity and average projected temperature distribution, respectively. Furthermore, a high-speed camera with a microscopic lens captures the transition from dispersed combustion to group combustion that forms a large-scale flame column wrapping the entire powder jet. The aluminum oxide produced in the columnar flame forms a large number of nanosized smoke particles in the condensation region. Finally, a numerical model considering the collective effect of the powder jet is developed to predict the particle temperature history during the ignition stage, which shows good agreement with the temperature profiles derived from camera pyrometry and PIV techniques.

Effects of Orifice Diameter of Pre-Chamber Jet Ignition on the Combustion Characteristics and Pressure Oscillations in a Kerosene-Fueled Engine

Abstract Jet orifice diameter directly impacts the combustion process of the pre-chamber jet ignition (PJI) engine and the optimized diameter is varied with the fuel properties. However, research on the optimization of the jet orifice diameter based on aviation kerosene fuel has not been reported. So, this paper investigates the effect of orifice diameter on combustion, pressure oscillation, and performance based on a kerosene-fueled single-cylinder test engine. Two pressure sensors are respectively fitted in the main combustion chamber and the pre-chamber, which can capture the pressure change process and pressure oscillations phenomenon at the two positions, respectively. The result demonstrates that the throttling of the jet orifice leads to a significant three-stage pressure imbalance between the combustion chambers. With the reduction of the orifice diameter, the combustion acceleration of PJI is enhanced, resulting in an advanced combustion phase, improved combustion stability, and enhanced knock. The time-frequency analysis proves that the pressure oscillation propagation to the pre-chamber is frequency-selective and related to the orifice diameter. By matching the pre-chamber Helmholtz resonance frequency with the main chamber resonance frequency, strong pressure oscillations can be excited in the pre-chamber. Meanwhile, the pressure oscillation energy can be absorbed by the pre-chamber, which may help reduce the engine's combustion noise. Moreover, the PJI with an orifice diameter between 2 mm and 4 mm can improve the combustion stability with the ISFC reduced by 4.7–5.6%, and the IMEP increased by 1.2–2.6%.

Effect of initial pressure on the propagation characteristics of supersonic turbulent jets in fuel jet ignition

The effects of initial pressure (Pini) on the propagation characteristics of supersonic turbulent jets (STJ) were studied experimentally in a constant volume chamber. Based on the top vortex motion, three types of flame propagation modes are identified: Mode 1, the vortex in the middle of the jet propagates; Mode 2, the vortex in the middle of the jet moves to the top and the tail; Mode 3, jet tail flame extinguished. Each mode follows a 3-stage propagation method: (a) a jet flame with a with a sharp drop in the flame tip velocity (VFTV); (b) a self-accelerating mushroom-shaped flame followed by turbulent flame with low frequency oscillation; (c) a turbulent flame with a drop in VFTV. The momentum dissipation causes the velocity to drop in stage I and stage III, and stage II is controlled by the eddy motion of the mushroom-shaped flame tip and the pulsation of the flow field. The experimental results show that higher Pini can stimulate a stronger interaction mechanism between flow field oscillation in the main combustion chamber (MCC) and chemical heat release oscillation in the pre-chamber (PCC). Based on an evaluation of the model correlations, we found that the jet penetration length showed a linear relationship with the product of the relative pressure fourth root and the time square root.

Investigations on an active pre-chamber ignition system in a combustion chamber

Pre-chamber ignition systems are one way to enable homogeneous lean or dilute combustion. Both strategies can significantly increase the efficiency of spark ignition engines. Spark initiated combustion in the pre-chamber produces hot gases that rapidly enter the cylinder and ignite the diluted charge at multiple points. Active ignition systems with fuel in the pre-chamber can directly influence the composition of the pre-chamber to ensure good ignition properties and sufficient ignition energy. This paper shows results from a novel test facility that enables investigations on the jet propagation of an active pre-chamber inside a constant pressure vessel. Thereby, the background mixture inside the vessel is variated between λ = 1.0 and λ = 2.0. With a special designed single-hole pre-chamber the flame propagation of a single pre-chamber jet is measured both in direction of the transfer port and perpendicular to this direction. Compared to spark ignition under equal ambient conditions (350°C, 10 bar), the pre-chamber combustion propagates around eight times faster in direction of the transfer port and 60% faster in radial direction. Until λ = 1.6, the flame propagation speed in radial direction can be kept on the level of a stoichiometric spark ignition. The simultaneous record of OH*-chemiluminescence and high-speed Schlieren imaging shows that the dominant ignition mechanism of a passenger-car sized pre-chamber is jet ignition according to the classification of Biswas. In stoichiometric cylinder conditions, a rich pre-chamber hampers the ignition in the main chamber whereas in lean operation points the scavenging of the pre-chamber with a rich λ = 0.8 mixture is beneficial. These measurements indicate how the disrupted flame front of a pre-chamber jet increases the turbulence and enhances the flame propagation. The highest recorded propagation speed occurs in stoichiometric conditions both in the pre-chamber and in the combustion module.

Experimental study of gasoline engine with EGR dilution based on reactivity controlled turbulent jet ignition (RCTJI)

The exhaust gas recirculation (EGR) method can suppress knock and improve the thermal efficiency of engines, but it also deteriorates the combustion stability and engine power. Turbulent jet ignition (TJI) is a reliable ignition way for improving ignition stability and burning rate. However, the EGR in the pre-chamber will worsen the reactivity of the fuel-air mixture in the pre-chamber and subsequently lower the intensity of the TJI. To this end, the reactivity controlled turbulent jet ignition (RCTJI) based on a newly air-assisted pre-chamber turbulent jet ignition with a scavenging function has been proposed to improve the reactivity in the pre-chamber for the first time. The combustion characteristics, pressure oscillation, and combustion stability of a single-cylinder spark-ignition engine under four ignition modes of spark ignition (SI), passive TJI, active TJI, and scavenged TJI have been investigated. The results show that three TJI modes can obviously shorten the combustion duration due to the fast jet flame. Compared to the SI mode, the spark timing of TJI is not sensitive to the change in EGR rate. In particular, the scavenged TJI could effectively promote the chemical reactivity in the pre-chamber, and subsequently improves the intensity of the turbulent jet flame and shortens the ignition delay and combustion duration. As a result, using the scavenged TJI can effectively reduce cycle variation and achieve the lowest indicated specific fuel consumption (ISFC) at high EGR rates. However, with the increase in EGR rate, the SI combustion gradually becomes unstable. In contrast, the scavenged TJI can effectively extend the EGR tolerance. In addition, the present work further has confirmed the three main combustion stages of jet ignition in terms of the heat release rate.

Ignition of hexane-air mixtures by highly under-expanded hot jets

We report an experimental study of ignition of flammable mixtures by highly unexpanded, supersonic hot jets. The high-pressure, hot-gas reservoir supplying the jet is created by impacting a projectile on a plunger to rapidly compress and ignite a rich n-hexane/air mixture, resulting in a peak reservoir pressure of more than 20 MPa. A locking mechanism was used to prevent the plunger from rebounding and the jet was created by rupturing a diaphragm covering a nozzle with an exit diameter between 0.25 and 1 mm. The jet development and ignition processes in the main chamber filled with hexane-air mixture were visualized using high-speed schlieren and OH* chemiluminescence imaging. The ignition threshold was determined as a function of composition in the jet and main chamber, the nozzle diameter, and the initial pressure in the main chamber. Unlike the case of subsonic jets in which ignition occurs at the shear layer near the nozzle exit, ignition of combustion in the main chamber was found to take place downstream of the Mach disk terminating the supersonic expansion and within the turbulent mixing region created by the startup of the supersonic jet. The results are interpreted using a constant-pressure, well-stirred reactor model simulating the mixing between the hot jet and cold ambient gas. The critical conditions for ignition are determined by the competition between energy release due to chemical reactions initiated by the hot jet gas and cooling due to mixing with the cold chamber atmosphere. The critical value (maximum for which ignition occurs) of the mixing rate was computed using a detailed chemical reaction model and found to be a useful qualitative guide to our observations.

Comprehensive model for energetic analyses of a series hybrid-electric vehicle powered by a passive Turbulent Jet Ignition engine

In the last decades, the concern about vehicles’ environmental impact has progressively increased. Therefore, car manufacturers are moving towards vehicles with low emissions like Hybrid Electric Vehicles (HEV), that in the series architecture utilize an internal combustion engine (ICE) to power an electric generator for battery recharging thus extending the driving range of a Battery Electric Vehicle (BEV). For such applications, small four-stroke spark-ignition (SI) engines are a suitable solution, as they are proven low-cost and reliable systems and allow to increase vehicle driving range with reduced environmental impact. In series HEV the ICE is decoupled from the drive wheels and operates at a fixed working point regardless to the instantaneous power demand, thus promoting the lean mixture operation to achieve high efficiency and low CO2 emissions. In this work, the performance, in terms of driving range, energy consumption and CO2 emissions, of a series HEV are analyzed in experimental and simulation environment. Particularly, the Auxiliary Power Unit (APU) is a small ICE equipped with a passive Turbulent Jet Ignition (TJI) that allows to guarantee stable combustion also under lean mixture operation, with an increase of engine efficiency and a reduction of CO2 emissions. The effects of lean air–fuel ratio on combustion process and engine performance are investigated by a one-dimension (1-D) model and validated vs experimental measurements at the test bench on a prototype single cylinder engine equipped with passive prechamber. The benefits of the high efficiency ICE operation on the series HEV performance, energy consumption and CO2 emissions vs standard and arbitrary driving cycles are analyzed in simulation environment, making use of the simulation results gathered by the 1-D engine model. Simulation analyses are carried out to evaluate the best compromise between battery pack downsizing and energy consumption for a fixed target of vehicle drive range. Simulation results show that TJI concept allows to achieve an APU efficiency up to 32 %, by operating with λ equal to 1.26. Additionally, the analysis on battery pack downsizing evidences that switching from 150 % to 50 % of the reference battery pack capacity results in an increase of the overall energy consumption up to 22 %.

Research on the ignition strategy of a methanol/gasoline blends rotary engine using turbulent jet ignition mode

The preparation of methanol can first use renewable energy such as solar energy to produce hydrogen, and then carbon dioxide can be converted into methanol fuel by hydrogenation. Therefore, using methanol as mixed fuel in traditional gasoline rotary engines can effectively reduce the carbon emission of rotary engines. In addition, turbulent jet ignition mode is considered to effectively improve the combustion rate of rotary engines. To deeply study the ignition and combustion process of a methanol/gasoline blends rotary engine using turbulent jet ignition mode, a three-dimensional simulation model and a performance test bench of the rotary engine were established in this paper, respectively. Further, using the experimental data, the reliability of the three-dimensional calculation model was verified. Based on the calculation model, the effects of ignition position and timing on the ignition and combustion process of the methanol/gasoline rotary engine using turbulent jet ignition mode were further studied. The results showed that the ignition position and the ignition timing could significantly change the ignition and combustion process in the cylinder by changing the impact timing between the jet flame and the rotor wall, the intensity of the jet flame and the position where the jet flame enters the cylinder.