Heavy-duty Spark Ignition Engine Research Articles

Investigating the impacts of charge composition and temperature on ammonia/hydrogen combustion in a heavy-duty spark-ignition engine

Ammonia, as a hydrogen carrier with mature production technology and convenient storage, has become one of the most promising zero carbon fuels in recent years. The use of ammonia/hydrogen mixture fuel in spark ignition (SI) engines has drawn significant attentions since it solves the problems of low flame speed, high ignition energy requirement and narrow flammable range of pure ammonia. In this study, the combustion and emission processes of an ammonia/hydrogen port fuel injection (PFI) engine at high load operation are numerically analyzed to investigate the effects of intake hydrogen energy ratio (HER), equivalence ratio (φ), intake temperature and combustion chamber wall temperature on energy distribution and pollutants. The results indicate that under the same HER of 25%, the lean-burned mode provides favorable thermal efficiency compared to stoichiometric mode due to reduced combustion and wall heat loss. However, lower cylinder temperature at lean condition inhibits the participation of NH3 in the reduction reactions and the consumption of N2O, increasing the residuals of both pollutants. The NOx emission is promoted by excessive O radicals at lean conditions, and the pathways of fuel NOx and thermal NOx are also discussed using an isotope labeling method. At stoichiometric mode, increasing fuel HER (10%–25%) only has minor impacts on improving thermal efficiency, but can promote the consumption of NH3 and N2O by increasing H radicals and cylinder temperature. The study also shows that optimizing the intake and wall temperatures can effectively reduce NH3 and N2O emissions by 87.5% and 71.7%, respectively, while slightly reducing NOx.

Exploiting Lubricant Formulation to Reduce Particle Emissions from Gas Powered Engines

The present paper illustrates the results of an experimental study aimed at evaluating the effect of lubricant oil features on the emissive behaviour of a heavy duty spark ignition engine fuelled with methane. The activity was performed within a research project between CNR-STEMS and TotalEnergies in which oils with different formulations were characterized, focusing on their potentiality in particle emission reduction. Considering the ultralow particle emission level in the exhaust of gas engines, a specific testing procedure was designed to guarantee highly reliable and accurate results. In particular, the engine was operated under transient conditions, along the World Harmonized Transient Cycle in cold- and hot-start conditions. The results of the test campaign clearly highlight that the lubricant formulation is a key technology for the control of particles, revealing this as an important aspect in view of the upcoming severe regulation limits on particle emissions. The experimental findings show the capability of reformulated oils to drop down the total particle number to 60–70% with respect to a baseline standard oil. The interest in the present study also lies in providing information extendable to more sustainable fuels, like hydrogen or biomethane, nowadays of great interest as alternative energy sources.

Analysis of Particle Number Emissions in a Retrofitted Heavy-Duty Spark Ignition Engine Powered by LPG

Analysis of Particle Number Emissions in a Retrofitted Heavy-Duty Spark Ignition Engine Powered by LPG

Assessment of exhaust raw emissions and aftertreatment performance in a retrofitted heavy duty-spark ignition engine operating with liquefied petroleum gas

This study investigates the effects of varying Liquefied Petroleum Gas compositions on pollutant emissions and three-way catalyst performance in retrofitted heavy-duty spark-ignition engines. It focuses on fuels with varying propane and butane ratios, providing new insights into the influence of the composition of Liquefied Petroleum Gas on catalyst activity and tailpipe emissions. Representative conditions from the world Harmonized Transient Cycle were selected to comprehensively assess engine emissions and catalyst performance. Experiments under constant and variable λ conditions tested the catalyst's response concerning raw emissions, exhaust temperature, and space velocity, all variables affected by engine operation. Key findings indicate that catalyst performance is not significantly affected by Liquefied Petroleum Gas composition. Under constant λ conditions, the catalyst achieved high conversion efficiency of carbon monoxide, unburned hydrocarbons, and nitrogen oxides, especially under rich conditions (λ = 0.990). However, rich conditions can lead to elevated ammonia levels, although nitrous oxide generation remains low in all circumstances. Implementing λ pulse strategies reduced ammonia formation to around 25 mg/kWh, ensuring high catalyst conversion efficiency for all pollutant species after optimizing the amplitude and frequency of the pulses to establish the balance of reducing-oxidizing species and oxygen storage for each operation mode. Crucially, Liquefied Petroleum Gas composition was determined to be non-critical for the catalyst in these engines, promoting the use of this fuel in retrofitted engines and promoting for a shift towards cleaner transportation.

Natural Gas/Hydrogen blends for heavy-duty spark ignition engines: Performance and emissions analysis

In view of the strong interest in the adoption of hydrogen as an alternative fuel for internal combustion engines, the authors present the results of an experimental activity aimed at evaluating the effect of hydrogen use on performance and emissions of a heavy-duty (HD) spark ignition engine.The engine, installed on a test bench and working with compressed natural gas (CNG) in its standard version, has been fed with blends of CNG and H2, at various percentages (15% and 25% of H2 by volume) and tested in steady-state and transient driving conditions. The analysis in steady state was performed in two working modes: at the same combustion barycentre and at the same nitrogen oxides (NOx) emissions of the pure CNG case, by means of proper spark advance calibrations.A detailed combustion and emissions analysis were performed, highlighting a coherent response of the engine to the replacement of CNG with H2. The NOx increment tendency is easily counteracted by reduced SA settings, while total hydrocarbons and carbon oxides emissions reduction were measured when the blends were burnt. Consistent carbon dioxide emission mitigation was revealed, mainly in transient conditions, operated at the same ECU calibration of the pure CNG case.The main novelty of the work is in providing an in-depth study of the engine behaviour to hydrogen addition in transient condition. The response of engine management system to different fuels when rapid speed and torque variations occur, were evaluated. In this sense, the study offers detailed information on the feasibility of the use of hydro methane in existing engine architecture; such mixtures can represent, in the next future, a probable fuel option in view of the oncoming decarbonization process.Moreover, new insights on particle emission burning hydro-methane are presented. The results of engine-out PN emissions along a transient cycle revealed a correlation between particle emissions spikes with specific phases of the driving cycle and a trend in PN reduction in case of hydrogen addition.

Energy efficiency improvements and CO2 emission reduction by CNG use in medium- and heavy-duty spark-ignition engines

This research studies the mechanism of improving energy efficiency and reducing CO2 emissions from medium- and heavy-duty spark-ignition engines by replacing gasoline fuels with natural gas. Detailed experimental analyses are conducted on a multi-cylinder research engine using 91RON, 98RON gasoline, and natural gas fuels. Under 7 key operating conditions, energy efficiency breakdown is performed for each fuel to quantify the individual impact of the fuel's carbon content, pumping work, knock tendency, and fuel enrichment. Complete engine mapping is thereafter carried out with all three fuels, and CO2 emissions are compared over the emission certification test cycle. As demonstrated by the test results, the lower carbon content of natural gas is the major contributor to CO2 emission reduction. At idle and part load conditions, engine operation on natural gas shows reduced pumping loss, improved idle stability, and thus increased fuel efficiency. At high load conditions, the greater resistance to knock allows natural gas to operate at optimal combustion phasing. At the peak power condition, the earlier combustion phasing helps to lower exhaust temperatures, thereby avoiding fuel enrichment. With proper calibration, natural gas outperforms its gasoline counterparts to produce 4% better peak power performance and emits 22.5% lower CO2 emissions.

The Impact of Miller Valve Timing on Combustion and Charging Performance of an Ethanol- and Methanol-Fueled Heavy-Duty Spark Ignition Engine

The Impact of Miller Valve Timing on Combustion and Charging Performance of an Ethanol- and Methanol-Fueled Heavy-Duty Spark Ignition Engine

Conceptual Approach on Feasible Hydrogen Contents for Retrofit of CNG to HCNG under Heavy-Duty Spark Ignition Engine at Low-to-Middle Speed Ranges

Hydrogen-based engines are progressively becoming more important with the increasing utilization of hydrogen and layouts (e.g., onboard reforming systems) in internal combustion engines. To investigate the possibility of HICE (hydrogen fueled internal combustion engine), such as an engine with an onboard reforming system, which is introduced as recent technologies, various operating areas and parameters should be considered to obtain feasible hydrogen contents itself. In this study, a virtual hydrogen-added compressed natural gas (HCNG) model is built from a modified 11-L CNG (Compressed Natural Gas) engine, and a response surface model is derived through a parametric study via the Latin hypercube sampling method. Based on the results, performance and emission trends relative to hydrogen in the HCNG engine system are suggested. The operating conditions are 1000, 1300, and 1500 rpm under full load. For the Latin hypercube sampling method, the dominant variables include spark timing, excess air ratio (i.e., λCH4+H2), and H2 addition. Under target operating conditions of 1000, 1300, and 1500 rpm, the addition of 6–10% hydrogen enables the virtual HCNG engine to reach similar levels of torque and BSFC (brake specific fuel consumption) compared to same lambda condition of λCH4. For the relatively low 1000 rpm speed under conditions similar to those of the base engine, NOx formation is greater than base engine condition, while a similar NOx level can be maintained under the middle speed range (1300 and 1500 rpm) despite hydrogen addition. Upon addition of 6–10% hydrogen under the middle speed operation range, the target engine achieves performance and emission similar to those of the base engine.

Particle and Gaseous Emissions from a Heavy-Duty SI Gas Engine over WHTC Driving Cycles

<div class="section abstract"><div class="htmlview paragraph">The use of gaseous fuels in internal combustion engines is increasing, due to several reasons, first of all their low environmental impact, large availability and low cost. Nevertheless, the need to reduce emissions also from gas engines is an important aspect to be considered in order to comply with future engine emissions regulations.</div><div class="htmlview paragraph">In this scenario, an extensive experimental activity was performed to fully characterize an heavy duty spark ignition engine, under development for Euro VI compliance and designed to run with gaseous fuels. Two separate sets of experiments were carried out, in order to analyze the engine behavior when burning LPG and CNG, respectively. To this aim, the engine was installed on a dynamic test bench, accurately instrumented to characterize the combustion evolution, performance and exhaust pollutant emissions, along the World Harmonized Transient Cycle (WHTC), the new European driving homologation cycle.</div><div class="htmlview paragraph">The main part of the manuscript addresses the analysis of the exhaust particulate emissions, in terms of soot concentration, particle number (PN) and particle size distribution function (PSDF). More in detail, a photo-acoustic sensor and a fast particulate spectrometer were adopted for on-line soot, PN and particle size measurements, during the transient engine tests.</div><div class="htmlview paragraph">The results revealed that although the gaseous emissions were within homologation limits, soot and PN could represent an issue for this class of engines. The experiments allowed to highlight that most part of the particles are emitted during specific phases of the driving cycle and could be ascribed to the engine oil vapors combustion.</div><div class="htmlview paragraph">Moreover, the investigation, indicating which engine operating conditions displayed the highest contribution to particles emissions, may provide helpful insights to deal with such critical conditions.</div></div>

Effects of natural gas composition and compression ratio on the thermodynamic and combustion characteristics of a heavy-duty lean-burn SI engine fueled with liquefied natural gas

In this study, the effects of natural gas composition and compression ratio on thermodynamic and combustion characteristics were comprehensively investigated using a spark ignition liquefied natural gas engine modified from a heavy-duty compression ignition engine. LNG fuel samples with two different methane compositions and a series of compression ratios were tested and analyzed with the same boundary conditions at a lean burn condition of 1.38 excess air/fuel ratio. The results indicated that the in-cylinder pressures of the heavy-duty spark ignition engine increased with increasing compression ratio (CR), while the magnitude of the increase of the peak combustion pressure firstly increased, reached a peak value at the compression ratio of 14 and then decreased. However, the heat release phasing advanced with increasing CR, the ignition delay and the combustion duration shortened with the 50% combustion location advancing toward the top dead center with increasing CR. Apart from that, the cycle-to-cycle variations of the combustion duration and peak combustion pressure were decreased with increasing CR. The peak combustion pressure declined with the prolonged the combustion duration. In addition, the location of the maximum pressure rise rate advanced and the coefficient of variation of the indicated mean effective pressure decreased with increasing CR. Consequentially, the brake thermal efficiency increased and the brake specific fuel consumption decreased with the increase of the CR. The laminar flame speed of LNG 1-air was slightly higher than that LNG 2-air due to the higher ethane concentration and its higher laminar flame speed.

Experimental study the effects of various compression ratios and spark timing on performance and emission of a lean-burn heavy-duty spark ignition engine fueled with methane gas and hydrogen blends

To investigate effects of various compression ratios (CRs) and spark timing on characteristics of performance and emissions, a high CR six-cylinder heavy-duty compression ignition diesel engine was modified into the port fuel injection hydrogen and liquefied methane gas lean-burn heavy-duty SI engine and tested by using 13.6 and 14.0 CRs. Combination of alternative fuels, high CRs and control strategies was implemented in this study. Results indicated that the equivalent fuel consumption (EFC) dramatically decreased with increase of the hydrogen energy share. Additionally, the EFC reduced as higher CR was adopted. The brake thermal efficiency (BTE) firstly increased and then declined with increase of the hydrogen energy share. Besides, the BTE increased with CR. The maximum additional 1.8% of BTE was obtained by employing higher CR (14.0) for a specific operating condition. Furthermore, the NOX emissions remarkably ascended while the HC emissions significantly declined with increase of the hydrogen energy share. The CO emission formation did not show a strong relationship with the hydrogen energy share and the CR. However, the CO2 emission gradually declined with increase of the percentage of hydrogen and CR.

Performance, combustion and knock assessment of a high compression ratio and lean-burn heavy-duty spark-ignition engine fuelled with n-butane and liquefied methane gas blend

An experimental investigation was conducted on the performance, combustion and knock characteristics of a high compression ratio, lean-burn heavy-duty spark ignition (SI) engine fuelled with n-butane and liquefied methane gas blend. Specifically, some technical adaptations were carried out on the original compression ignition (CI) engine for changing the direct fuel injection system into the electronic controlled intake port gas injection and implementing a high-energy ignition system. Results indicate that the in-cylinder pressure, heat release rate and cumulative heat release amount increase with the increased n-butane energy share. Once the n-butane energy ratio exceeds 5% in 1400 r/min, full-load, light knock occurs at this operating condition. In addition, the 50% burning location is advanced, the 10–90% combustion duration is shortened, and knocking intensity is strengthened. Furthermore, the maximum pressure rise rate fluctuates around the average value, and the oscillation amplitude also ascends with increased n-butane energy share which results in higher cycle-by-cycle variation. However, the IMEP and indicated thermal efficiency firstly go up with the increased percentage of the n-butane energy share and then decrease.

Experimental study on the performance, combustion and emission characteristics of a high compression ratio heavy-duty spark-ignition engine fuelled with liquefied methane gas and hydrogen blend

The aim of this paper investigated the performance, combustion and emission characteristics of a high compression ratio heavy-duty spark ignition engine fuelled with liquefied methane gas (LMG) and different hydrogen blends under at low engine speed. In this study, a compression ignition engine was modified to inject hydrogen and LMG using port fuel injection in spark ignition mode. The results showed that the brake thermal efficiency increased with increasing percentage of hydrogen energy content. The equivalent fuel efficiency value dramatically decreased with increasing load and slightly decreased with increasing percentage of hydrogen energy content. In-cylinder pressures of all the blends with hydrogen are higher than that only LMG fuel. The heat release rate shifted to the top dead center (TDC) and the 50% combustion location was remarkably advanced with the increasing of hydrogen energy content. Furthermore, the maximum pressure rise rate increased and the location of the maximum pressure rise rate shifted to the TDC with increasing of hydrogen energy content, respectively. NOx emission dramatically increased with increasing load and hydrogen energy content, respectively. Conversely, HC and CO2 emission concentration declined with increasing of hydrogen energy content. CO emission concentration kept low value at all the loads.

Effect of mixing CO2 with natural gas–hydrogen blends on combustion in heavy-duty spark ignition engine

Because further reduction in carbon dioxide (CO2) will require upgrading the existing engine technology or developing a new type of engine, the addition of hydrogen to natural gas is considered as an alternative that could meet the required emission standards. However, the carbon monoxide/CO2 generated in the reforming process of natural gas can affect the engine performance and emissions characteristics. The content of CO2 in the reformed gas can be varied by varying the ingredients or the conditions of the process. Therefore, it is essential to control the air-fuel mixture condition and combustion phasing. In this research, the performance and emission characteristics of an 11 L spark ignition engine using natural gas–hydrogen blends with various CO2 contents were examined, and an optimization strategy for controlling the excess air ratio and the spark advance timing was assessed. The thermal efficiency decreased with the increased content of CO2 under a given excess air ratio condition. The increased heat capacity of the mixture reduced the combustion temperature, so that the generation of nitrogen oxides was suppressed. However, total hydrocarbon (THC) emissions and the methane portion of the THC emissions were increased by the introduction of CO2. The decrease in the exhaust gas temperature also resulted in low conversion efficiency of the oxidation catalyst.

Transient Control of Combustion Phasing and Lambda in a Six-Cylinder Port-Injected Natural-Gas Engine

Fuel economy and emissions are the two central parameters in heavy duty engines. High exhaust gas recirculation rates combined with turbocharging has been identified as a promising way to increase the maximum load and efficiency of heavy duty spark ignition engines. With stoichiometric conditions, a three way catalyst can be used, which keeps the regulated emissions at very low levels. The Lambda window, which results in very low emissions, is very narrow. This issue is more complex with transient operation, resulting in losing brake efficiency and also catalyst converting efficiency. This paper presents different control strategies to maximize the reliability for maintaining efficiency and emissions levels under transient conditions. Different controllers are developed and tested successfully on a heavy duty six-cylinder port injected natural gas engine. Model predictive control was used to control lambda, which was modeled using system identification. Furthermore, a proportional integral regulator combined with a feedforward map for obtaining maximum brake torque timing was applied. The results show that excellent steady-state and transient performance can be achieved.

Closed-Loop Combustion Control for a 6-Cylinder Port-Injected Natural-gas Engine

High EGR rates combined with turbocharging has been identified as a promising way to increase the maximum load and efficiency of heavy-duty spark ignition engines. With stoichiometric conditions a three-way catalyst can be used which means that regulated emissions can be kept at very low levels. Obtaining reliable spark ignition is difficult however with high pressure and dilution. There will be a limit to the amount of EGR that can be tolerated for each operating point. Open-loop operation based on steady state maps is difficult since there is substantial dynamics both from the turbocharger and from the wall heat interaction. The proposed approach applies standard closed-loop lambda control for controlling the overall air/fuel ratio for a heavy-duty, 6-cylinder, port-injected natural gas engine. A closed-loop load control is also applied for keeping the load at a constant level when using EGR. Furthermore, cylinder pressure-based dilution limit control is applied on the EGR in order to keep the coefficient of variation at the desired level of 5%. This way confirms that the EGR ratio is kept at its maximum stable level all times. Pumping losses decrease due to the further opening of the throttle, thereby the gas exchange efficiency improves and since the regulator keeps track of the changes the engine all the time operates in a stable region. Our findings show that excellent steady-state performance can be achieved using closed-loop combustion control for keeping the EGR level at the highest level while the stability level is still good enough. (Less)