Natural Gas Spark Ignition Engine Research Articles

Investigating the Effect of Ammonia Addition on the Performance of a Heavy-Duty Natural Gas Spark Ignition Engine Operated at Stoichiometric Conditions

Abstract Due to the pressing issue of global warming, there has been a significant focus on zero- and low-carbon fuels globally. Among hydrocarbon fuels, methane is widely used in spark ignition engines due to its abundance and relatively low carbon footprint. However, to further reduce carbon emissions, interest is growing in the use of ammonia, a zero-carbon fuel, as a partial replacement for methane. Consequently, it is crucial to investigate the impact of ammonia addition on the performance of natural gas spark ignition engines. A key challenge in studying ammonia-methane engines is that the introduction of ammonia alters the formation mechanisms of nitrogen-based pollutants, resulting in the coupling of fuel-borne and air-borne nitrogen pollutants. As a result, research on the nitrogen-based emissions of ammonia-methane engines has been limited. This study addresses this issue by differentiating between atmospheric nitrogen and fuel nitrogen elements, effectively decoupling fuel-borne and air-borne nitrogen pollutants. This approach provides valuable insights into the effects of ammonia addition on the nitrogen-based pollutant characteristics of natural gas engines. The results indicate that ammonia addition introduces N2O, a species absent in pure methane engines. The N2O primarily originates from cold wall regions and the partial oxidation of ammonia released from engine crevices during the late oxidation process. Although NO remains the dominant nitrogen-based pollutant and the amount of N2O is small, the significant greenhouse gas potential of N2O warrants further attention. Furthermore, while ammonia addition increases the NO concentration in the burning zone, it slightly reduces the NO concentration at chemical equilibrium under stoichiometric conditions. As a result, engines operating with an ammonia energy substitution ratio of 0.4 exhibit lower NOx emissions compared to those fueled solely by methane. These findings underscore the need for further research into the combustion and emission characteristics of ammonia-methane spark ignition engines.

Effects of charge motion on knock and thermal efficiency under high load condition of a heavy-duty natural gas engine

Nowadays, the carbon-neutral trend and the crude oil crisis have brought natural gas into increasing focus. However, heavy-duty engines fueled by natural gas have been plagued by thermal efficiency and knocking limitation problems. Well-structured charge motions can enhance thermal efficiency and concurrently mitigate knock, however, there is a lack of comprehensive work involving charge motions. In this paper, numerical simulation is employed to investigate the impact of charge motion on knock and thermal efficiency under high load conditions for a heavy-duty spark-ignition natural gas engine. The findings indicate that in the configuration with intense swirl, the diminished turbulent kinetic energy (TKE) at the combustion chamber’s base lessens the convective heat exchange between the fresh charge and the heated exhaust gases, resulting in a noticeable high-temperature zone and triggering hot spots. In configurations with inclined swirl and strong tumble motion, the extensive tumble motion near the spark plug region close to top dead center leads to an asymmetric flame front shape, determining the location of hotspots. The research also revealed that excessive tumbling motion and TKE can increase the likelihood of engine knock, while appropriate cylinder charge motion can improve the knock resistance of the engine to some extent, the maximum reduction in knocking intensity can reach 92.5%. The optimized combustion systems can significantly improve the initial combustion rate, shorten the ignition delay period, and advance the combustion center. With the combined effects of ignition timing and charge motion, the total indicated specific power per unit of fuel mass is increased in the optimized systems. Compared to the original combustion system, the indicated thermal efficiency within the knocking boundary can be improved by 1.11%.

Evaluating potential of increasing flow intensity and reducing crevice volume to improve thermal efficiency and hydrocarbon emission in spark-ignition natural gas engines

Low thermal efficiency and high hydrocarbon emissions caused by slow combustion rates and high methane emissions hinder the development of natural gas (NG) engines. Engine structure modifications have always been an important means of improving the combustion effects of engines. This study investigates the effects of combustion chamber improvements on the thermal efficiency and hydrocarbon emissions of stoichiometric spark-ignition NG engines through numerical simulations. The improvements aimed to enhance squish flow, organize high tumble flow, and reduce crevice volume. The results indicate that strengthening the squish intensity by increasing the squish area of the piston can accelerate flame propagation and reduce exhaust loss. However, this improvement is hindered by a significant rise in heat transfer loss, which limits further gains in thermal efficiency. Compared to the traditional high swirl combustion chamber, a high tumble combustion chamber (dual straight intake port combined with a hemispherical piston) can promote flame propagation in the early stages of combustion and increase thermal efficiency by 1.43%. However, the accelerated flame propagation rate resulting from increased flow intensity has little potential to reduce hydrocarbon emissions due to the small contribution of flame quenching to unburned hydrocarbon production. The primary source of hydrocarbon emissions from NG engines is unburned methane in the piston crevice. Therefore, when addressing hydrocarbon emissions from NG engines, the first consideration should be to minimize the volume of the piston crevice, which will significantly reduce methane emissions and incomplete combustion loss.

Quantitative analysis of the relationship between charge motion and knocking combustion in spark-ignition natural-gas engines under critical knocking conditions

Increasing the in-cylinder flow intensity is considered to have the potential to restrain engine knock and improve thermal efficiency. However, the effect of charge motion on the knocking combustion in natural gas (NG) engines is unclear. Therefore, swirl, tumble, and squish motions of different intensities were organized by changing the shape of the combustion chamber and initializing the in-cylinder flow velocity. Subsequently, the effect of charge motion on the knocking combustion of a spark-ignition NG engine under critical knocking conditions was investigated via numerical simulations. The results indicate that the knock intensity (KI) first increases and then decreases with an increase in swirl and tumble intensities and linearly increases with an increase in squish intensity. Swirl had the smallest impact on KI, followed by tumble, whereas squish had the greatest impact. The differences in flame propagation resulted in differences in KI under different charge motion patterns. The obvious non-uniformity of the radial and axial flame propagation is a potential cause of the significant increase in KI. Therefore, while increasing the flow intensity, matching a suitable combustion chamber to make the flame propagation more uniform helps achieve anti-knock and rapid combustion. Improving the swirl and tumble intensities can help NG engines achieve anti-knock and rapid combustion, whereas improving the squish intensity does not. This study provides an important reference for determining whether increasing flow intensity can improve NG engines’ knock characteristics and combustion performance.

Performance, emissions and combustion analysis of hydrogen-enriched compressed natural gas spark ignition engine by optimized Gaussian process regression and neural network at low speed on different loads

The transportation industry is increasingly focused on hydrogen based fuel as a promising alternative due to its potential for reduced emissions and enhanced performance. The purpose of this study is to improve efficiency and reduce emissions on low speed on different loads for heavy duty vehicles. This study can be impactful to train the electronic control unit (ECU) for heavy duty vehicles working on aforementioned conditions. This study investigates the effect of hydrogen ratios (0%–40 %) in HCNG, (0%–15 %) exhaust gas recirculation (EGR) ratios, and spark timing (8°-34o CA bTDC) at low and high loads (15 % & 75 %) under stoichiometric conditions at low speed (700 rpm). Performance, emissions and combustion parameters were thoroughly analysed across these conditions. Brake thermal efficiency increases by 20.7 % & 19.4 % by the addition of (0 %–40 %) hydrogen at low and high load at 14o CA bTDC running on 5 % and 0 % EGR respectively. NOx emissions reduces by 11.9 % & 17.9 % by the addition of (0 %–15 %) EGR and increases by 46.1 % & 46.4 % by increasing the amount of hydrogen in HCNG at low and high load at 14o CA bTDC at 0 % EGR respectively. Coefficient of variation reduces 13.8 % by (0 %–40 %) hydrogen addition at 11 % EGR at 16o CA bTDC. Optimized Gaussian process regression (GPR) and neural network (NN) machine learning techniques were applied to the dataset, and found GPR matern 5/2 is best one. The findings can be utilized in the development of HCNG engine.

Feasibility and Performance Analysis of Cylinder Deactivation for a Heavy-Duty Compressed Natural Gas Engine

The rising interest in the use of gaseous fuels, such as bio-methane and hydro-methane, in Heavy-Duty (HD) engines to reduce Greenhouse Gases pushed by the net-zero CO2 emissions roadmap, introduced the need for appropriate strategies in terms of fuel economy and emissions reduction. The present work hence aims at analysing the potential benefits derived from the application of the cylinder deactivation strategy on a six-cylinder HD Natural Gas Spark Ignition (SI) engine, typically employed in buses and trucks. The activity stems from an extensive experimental characterisation of the engine, which allowed for validating a related 1D model at several Steady-State conditions over the entire engine workplan and during dynamic phases, represented by the World Harmonized Transient Cycle (WHTC) homologation cycle. The validated model was exploited to assess the feasibility of the considered strategy, with specific attention to the engine working areas at partial load and monitoring the main performance parameters. Moreover, the introduction in the model of an additional pipeline and of valves actuated by a dedicated control logic, allowed for embedding the capability of using Exhaust Gas Recirculation (EGR). In the identified operating zones, the EGR strategy has shown significant benefits in terms of fuel consumption, with a reduction of up to 10%. Simultaneously, an appreciable increase in the exhaust gas temperature was detected, which may eventually contribute to enhance the Three-Way Catalyst (TWC) conversion efficiency. Considering that few efforts are to be found in the literature but for the application of the cylinder deactivation strategy to Light-Duty or conventionally fuelled vehicles, the present work lays the foundation for a possible application of such technology in Natural Gas Heavy-Duty engines, providing important insights to maximise the efficiency of the entire system.

Combustion Process of the Compound Supply CNG Engine

Objective: In order to study the lean combustion process of a natural gas engine by separating the combustor, a spark ignition natural gas engine with separated combustors was retrofitted from a S195 single-cylinder diesel engine. Methods: The electronic control system controlled the gas supply and the spark plug ignition. A low pressure injection valve was set in the inlet pipe to form a lean mixture while a high pressure injection valve was placed in the subsidiary chamber to create a rich mixture, which was then ignited and injected into the main combustor, where the lean mixture was subsequently ignited again to achieve stratified combustion. Results: The test results showed that steady ignition is feasible in the system and verified the impact of the shape of the main combustor on HC, the impact of channel diameter on NOX production, and the impact of the ratios of high-pressure gas and low-pressure gas on HC and NOX. The combustion conditions of high-pressure gas and low-pressure gas in the engine combustor vary greatly. Our results signify that the shape of the main combustor has a great impact on the performance of the engine, that is, a shorter propagation distance can reduce the generation of HC. Conclusion: The best ignition advance angle under different conditions was determined using a spark ignition natural gas engine. The ratios of high-pressure gas and low-pressure gas greatly impact the performance and emission of the engine. The reduced diameter of the channels between the main and subsidiary combustors can enhance the stratification and facilitate the secondary ignition.

Advanced turbulence and combustion modeling for the study of a swirl-assisted natural gas spark-ignition heavy-duty engine

Increasing demands on higher performance and lower fuel consumption and emissions have led the path for internal combustion engine development; this race is nowadays directly related to CO2 emissions reduction. To drive engine development and reduce the time-to-market, the employment of numerical analysis is mandatory. This requires a continuous improvement of the simulation models toward real predictive analyses able to reduce the experimental R&D efforts. In this framework, 1D numerical codes are fundamental tools for system design, energy management optimization, and calibration. The present work is focused on the improvement of the phenomenological turbulence model, originally conceived to describe turbulence evolution in tumble-promoting engines. The turbulence model is developed with reference to a SI heavy-duty CNG engine derived from a diesel engine. In this architecture, due to the flat cylinder head, turbulence is also generated by swirl and squish flow motions, in addition to tumble motion. The presented turbulence model is validated against 3D CFD results, demonstrating to properly predict turbulence and swirl/tumble evolution under two different operating conditions, without the need for any case-dependent tuning. The developed turbulence model is coupled to a phenomenological combustion model based on the fractal geometry theory applied to the flame front surface, where the turbulence is assumed to support flame propagation through an enhancement of the flame front area with respect to the laminar counterpart. The combustion model is validated against an extensive experimental dataset, composed of 25 operating points at different engine rotational speeds and loads. The numerical/experimental comparisons of global performance parameters are satisfactory, leading to maximum errors around ±2% for the BSFC, ±2° for the main combustion events, and ±1 bar for the in-cylinder peak pressure. Burn rate profiles are very well captured by the combustion model at changing operating conditions, not requiring any case-dependent tuning. The presented results demonstrate that the turbulence/combustion models could constitute a reliable virtual test facility, contributing to supporting and driving experimental activities.

A Review of Ultra-lean and Stratified Charged Combustion in Natural Gas Spark Ignition Engines

A Review of Ultra-lean and Stratified Charged Combustion in Natural Gas Spark Ignition Engines

Exergy Analysis of Organic Rankine Cycles with Zeotropic Working Fluids

Waste heat recovery is one of the possible solutions to improve the efficiency of internal combustion engines. Instead of wasting the exhaust stream of an energy conversion system into the environment, its residual energy content can be usefully recovered, for example in Organic Rankine Cycles (ORC). This technology has been largely consolidated in stationary power plants but not yet for mobile applications, such as road transport, due to the limitations in the layout and to the constraints on the size and weight of the ORC system. An ORC system installed on the exhaust line of a bus powered by a natural gas spark ignition engine has been investigated. The thermal power available at engine exhaust has been evaluated by measuring gas temperature and mass flow rate during real driving operation. The waste thermal power has been considered as heat input for the ORC plant simulation. A detailed heat exchanger model has been developed because it is a crucial component for the ORC performance. The exergy analysis of the ORC was performed comparing different working fluids: R601, R1233zd(E) and two zeotropic blends of the two organic pure fluids. The model allowed the evaluation of the ORC produced energy over the driving cycle and the potential benefit on the engine efficiency.

Influence of Intake Port Structure on the Performance of a Spark-Ignited Natural Gas Engine

Spark-ignited natural gas engines have received increasing attention in the heavy-duty market due to their low cost and reliability advantages. However, there are still some issues with natural gas engines retrofitted from 10 to 15 L diesel engines, which is a valuable medium-term goal for the automotive industry. In this work, the effect of intake port structure on the performance of a spark-ignited heavy-duty natural gas engine was investigated by multidimensional numerical simulations. A newly designed intake port was proposed, with strengthened in-cylinder turbulent kinetic energy and homogeneous air-fuel mixtures. Bench tests show that the proposed intake port has impressive thermal efficiency, cycle variation, and acceptable emissions performance. The effective thermal efficiency improves from 41.0% to 41.4%, and the cycle variation is 36% lower than traditional schemes. However, with the accelerated flame propagation, the in-cylinder temperature and NOx emission of the mixed-flow port increase while the CO emission decreases. In summary, a proper balance of in-cylinder swirl and tumble flow can significantly affect the economy and stability of natural gas engines. The proposed structure solves the inherent problems of slow natural gas flame propagation and harmful cyclic variations.

Multi-scale dynamics for a lean-burn spark ignition natural gas engine under low load conditions

This work investigates the multi-scale dynamics of the combustion system in a lean-burn spark ignition natural gas engine using different gas injection timings (GIT). The in-cylinder pressure time series are measured, and the indicated mean effective pressure (IMEP) time series are calculated. The influence of GIT on the combustion system is investigated through wavelet analysis, multi-resolution analysis, and the return maps with the GIT covering from 0 to 90°CA after top dead center at the intake stage. Results show that the combustion system has multi-scale chaotic characteristics, and it is sensitive to the change of GIT. The unreasonable GIT will result in serious combustion variations. Meanwhile, the combustion instability of the engine evolves on multiple time scales, showing evident multi-scale oscillation characteristics. All the wavelet power spectrums (WPS) present the characteristics of intermittent short-time periodic oscillations and persistent large-scale periodic oscillations concealed inside the IMEP time series. When the GIT approaches the medium value, the persistence of large-scale periodic oscillations is weakened, while the characteristics of high-frequency intermittent oscillations are enhanced. Under all working conditions, the contribution rate of high-frequency signal D1 decomposed by the IMEP time series to the overall time series fluctuation is about 40% or even higher. The contribution rate of the signal D1 also increases with the aggravation of combustion instability. The return map structures of high-frequency signals D1 and D2 show bifurcation structures, and the bifurcation characteristics of the signal D1 are more evident under medium GIT conditions, indicating a certain correlation between the 2–8 engine cycles, and the correlation between the adjacent engine cycles is stronger. The deterministic relationship between the multiple engine cycles found can help in developing a more reasonable and efficient combustion control strategy, which provides a theoretical basis for improving the stability of a natural gas engine.

Numerical Investigation of the Effects of Engine Speed on Performance and Combustion Characteristics on a Converted Spark-Ignition Natural Gas Engine

In this study, the effects of different engine speed values on performance and combustion characteristics were investigated by converting a diesel engine to a spark-ignition engine using natural gas. In numerical analysis, G-equation combustion model, reduced methane chemical kinetic mechanism that represent natural gas consisting of 29 types and 171 equations, and RANS k-e turbulence model were used. Analyzes were performed at full load, 17.5:1 compression ratio, constant ignition timing, and 6 different engine speeds. In order to examine only the effect of speed, the initial value, boundary conditions and spark plug ignition time were considered constant. While engine power and fuel consumption increased with increasing engine speed, engine efficiency decreased. In addition, increasing engine speed also increased the ignition delay time and combustion duration, and the flame front reached the squish zone later.

Parallel perturbation analysis of combustion cycle-to-cycle variations and emissions characteristics in a natural gas spark ignition engine with comparison to consecutive cycle method

Severe combustion cycle-to-cycle variations (CCVs) in spark ignition (SI) engines significantly increase partial or incomplete combustion cycles, which may result in combustion instability or even misfire under extreme conditions, thereby seriously affecting the engine performance and increasing the unburned hydrocarbon and carbon monoxide emissions. In this study, the consecutive cycle method (CCM) and parallel perturbation method (PPM) are utilized to simulate the CCVs in a natural-gas (NG) SI engine. Specifically, 25 consecutive and concurrent cycles of the SI engine are simulated, and simulation results are compared with the experimental data. Further, the factors affecting the CCVs and exhaust emissions in the NG SI engine are verified by analyzing the low-pressure (LP) and high-pressure (HP) cycles. The results indicate that the simulated in-cylinder pressures of the NG SI engine based on PPM are basically in agreement with the experimental in-cylinder pressure distribution range, which suggests that the PPM can effectively predict the CCVs in NG SI engines. Furthermore, the required wall clock time for the simulation of CCVs is greatly reduced from 1 to 2 months (using CCM) to 2–3 days by using the PPM, which makes it particularly suitable for the industrial applications. Besides, the velocity field of the HP cycle is obviously stronger than that of the LP cycle. During the early stage of flame development, the flame area and volume of LP and HP cycles do not show much difference. However, the flame front surface-volume ratio of the HP cycle is larger than that of the LP cycle at 15 CA after the spark timing. Furthermore, the emissions formation and oxidation of the NG SI engine are strongly depended on the HP and LP cycles due to the combustion rate and flame propagation in the cylinder.

Investigations on combustion system optimization of a heavy-duty natural gas engine

Nowadays, the carbon-free policies and the crisis of crude oil make natural gas get increasing attention. However, spark-ignited natural gas engines continually suffer from problems of thermal efficiency and NOx emissions. Optimizing intake and combustion systems are effective ways to improve combustion and emission performance, but comprehensive work involving both intake and combustion systems is still lacking, especially for heavy-duty commercial engines. In this work, both intake and combustion systems of spark-ignited heavy-duty natural gas engines were investigated using muti-dimensional numerical simulations. Two intake ports and four combustion chambers were considered. An optimized chemical model was employed to accelerate the computation efficiency of combustion processes. The optimal combination of intake and combustion systems was obtained, with impressive thermal efficiency and acceptable emission performance. The results show that the mixed-flow intake port performs better than the swirl intake port for the natural gas engine with premixed combustion mode, manifesting increased in-cylinder tumble ratio and turbulent kinetic energy. Meanwhile, the eccentric hemispherical combustion chamber (EHCC) combined with mixed-flow intake ports presents the best optimal combustion performance, exhibiting an effective thermal efficiency beyond 41.53%. However, the EHCC scheme shows an increased NOx emission due to fast combustion speed and high combustion temperature while negligible CO and CH4 emissions. Despite this, natural gas engines equipped with three-way catalysis after-treatment can still meet emission regulations under stoichiometric operating conditions.

An Evaluation of the Conversion of Gasoline and Natural Gas Spark Ignition Engines to Ammonia/Hydrogen Operation From the Perspective of Laminar Flame Speed

Abstract Power generation systems will reduce carbon emissions primarily through the application of low or even zero carbon fuels under the global decarbonization trend. Ammonia is an ideal alternative fuel because it is cheap, readily available, and easy to store and transport. However, its mediocre combustion performance has raised concerns about its use in engines. The objective of this paper was to evaluate the amount of hydrogen that would need to be added to the ammonia from a laminar flame speed perspective if converting existing spark ignition engines to ammonia operation. The benchmark for determining the hydrogen blending ratio was to help ammonia achieve efficient combustion in the cylinder comparable to that of gasoline or natural gas. The results showed that hydrogen addition had the potential to greatly improve engine efficiency and emissions, although the combustion kinetics of ammonia-hydrogen mixtures were still dominated by ammonia with hydrogen addition levels below 60%. In addition, the hydrogen addition ratio was mainly determined by the kernel inception process, as this burning stage heavily influenced the repeatability of the combustion and the ease of combustion control. Also, at least 20% of hydrogen was required to be added to ammonia to adapt the engine to various operating conditions, while such a strategy still cannot help ammonia to obtain a rapid burning event compatible with gasoline or methane. Moreover, natural gas engines were more suitable for retrofitting to ammonia-hydrogen operation because they have a higher compression ratio and their combustion chambers are less demanding on the fuel laminar flame speed. Further, ammonia lean operation was recommended to be avoided in spark ignition configurations. Altogether, all of these findings support the need for additional efforts in ammonia engine optimizations and onboard ammonia dissociation system efficiency improvements.

Spark-Induced Breakdown Spectroscopy In A Direct-Injected Natural Gas Spark-Ignition Engine

The purpose of this study is to investigate the fuel concentration around the spark plug obtained using spark-induced breakdown spectroscopy (SIBS) method with the spark plug with an optical fiber in the direct-injected natural gas SI engine. Effect of exposure duration on measurement accuracy of fuel concentration was discussed. Equivalence ratio around the spark plug in the direct-injected natural gas SI engine were measured under different natural gas injection timing. When the exposure duration is shortened, the emission of potassium elements near the emission wavelength of oxygen elements can be suppressed, and the measurement accuracy in the calculation of the emission intensity ratio can be improved. The relationship between the luminescence intensity ratio of hydrogen and oxygen (Hα/O) and the equivalence ratio of homogeneous mixture of natural gas and air was investigated and it was found that there was a positive correlation between the luminescence intensity ratio of hydrogen and oxygen (Hα/O) and the equivalence ratio. As a result of measuring the equivalence ratio around the spark plug of direct-injected natural gas SI engine using the SIBS method, an equivalence ratio of 0.67 was measured for a set value of 0.8 using the luminescence intensity ratio of hydrogen and oxygen.

Influences of the control parameters and spark plug configurations on the performance of a natural gas spark-ignition engine

Lean-burn and exhaust gas recirculation (EGR) strategies have been used in natural gas spark ignition (SI) engines for meeting the increasingly stringent emission standards. However, the combustion rate of the natural gas (NG) decreases under the lean or ultra-lean and EGR operating conditions. In this paper, a simulation model based on the two-zone combustion modelling approach is established and validated with the experimental data. Then, configuration with different lambdas and EGR ratios, and twin-spark plugs are simulated by using this calibrated model to predict the performance of the NG SI engine. The results indicate that the EGR strategy is more effective in decreasing NOx emissions than that of the lean-burn strategy due to its thermal, dilution, and chemical effects of the EGR components. In addition, the formations of the HC emissions are amplified due to the dilution and chemical effects of the EGR components. Furthermore, under the lambda value of 1.5, the 50% mass fraction burned of the NG SI engine is located at 21.77 °CA after the top dead center (TDC) when the single-spark plug configuration is used, while it is located at 16.58 °CA after the TDC when the twin-spark plugs configuration is used. Besides, compared to the single-spark configuration, using the twin-spark plugs configuration in the NG SI engine is more conducive to decreasing the ignition delay period and combustion duration. Overall, it is verified that the use of twin-spark plugs configuration can effectively extend the lean-burn limit and enhance the combustion rate for the NG SI engine, particularly under the ultra-lean mixture.

Low-speed performance compensation of a turbocharged natural gas engine by intake strategy optimization

Power output at the low engine speed is limited for natural gas engines, even though the turbocharging technology is used. In this paper, the intake system of a turbocharged spark-ignition natural gas engine with 4 valves (2 intake valves and 2 exhaust valves) was optimized by considering the intake strategy effects on the engine torque output and fuel economy improvement. Firstly, a 1D numerical model with hierarchical 1D/3D approach based on GT-SUITE was developed and validated against the experimental data of engine torque and fuel consumption rate. This approach combined detailed analysis of in-cylinder flow, charge movement and combustion. Secondly, different intake strategies were designed and their effects on the intake mass flow rate and in-cylinder mass during the intake process, the swirl flow, tumble ratio and the turbulent kinetic energy during the compression process, the flame propagation and temperature distribution evolution after the spark ignition, and the pressure and heat release rate were numerically investigated. The results showed that compared with the original intake strategy, the asynchronized intake strategy (the intake valves close earlier and the intake valve lifts are reduced, while two intake valves have different intake strategy) reduces the backflow in the end of intake stroke, improves the in-cylinder swirl flow, increases the maximum heat release rate and shortens the combustion duration, and it is believed to be the optimized intake strategy. Finally, different cam profiles corresponding to the numerically designed intake strategies were applied to the bench test engine and the dyno experiments showed that the optimized intake strategy improves the torque and reduces the brake specific fuel consumption by 41.42% and 8.1% respectively at a low engine speed of 1200 rpm.

Corrigendum to “Effects of gas injection timing on combustion instability for a spark ignition natural gas engine under low load conditions” [Appl. Therm. Eng. 206 (2022) 118144

Corrigendum to “Effects of gas injection timing on combustion instability for a spark ignition natural gas engine under low load conditions” [Appl. Therm. Eng. 206 (2022) 118144