Indicated Thermal Efficiency Research Articles

Exploring the benefits of hydrogen-water injection technology in internal combustion engines: A rigorous experimental study

Previous hydrogen researchers have demonstrated the great potential of hydrogen as a zero-carbon fuel and its wider operational ability to directly replace the existing fossil-fuelled internal combustion engines (ICE). Hydrogen direct-injection technology can operate at stoichiometric combustion conditions, fully eliminating the intake backfire phenomena, which has the benefit of low airflow requirements and is a suitable solution for naturally aspirated ICE platforms. However, significant challenges must be addressed when operating an H2 ICE at or near stoichiometric. These include rapid pressure rise rate, high in-cylinder gas pressure and temperature and the consequential higher engine-out NOx emissions. This study provides a comprehensive experimental analysis of the effect of water injection on a light-duty H2 engine’s performance, efficiency, burn durations and NOx emission. The engine was modified to operate with hydrogen via a centrally-mounted direct H2 injector and an intake port-mounted water injection system. The study included water vapour measurements, NOx concentrations and other exhaust gases. The practical implications of these findings are significant. The results demonstrated that the NOx emissions were reduced by 79% when the water was injected at a rate of 5 kg/h at 10 bar IMEP and 2000 rpm. This reduction in emissions, coupled with the observed decrease in cylinder pressure and the rate of pressure rise, could substantially improve engine performance and efficiency. At higher load regions, the water injection extended the maximum engine load to 24 bar IMEP and increased the engine torque output by 10%. The maximum Indicated Thermal Efficiency (ITE) increased from 41% at 16.5 bar IMEP to 42.5% at 18 bar IMEP at a lower lambda, with a corresponding reduction in the intake-air-boost pressure requirement. Of particular note, the use of water injection decreased the engine-out NOx emissions under high-load conditions by more than 55%, even at richer AFR compared to pure hydrogen operation.

Study of activity stratification-controlled NH3–H2 combustion in a large-bore gas engine utilizing split-channel supercharge and fuel-air mixing technology

In this study, the split-channel supercharge and fuel-air mixing technology (SCS-FAM) is firstly proposed for large-bore ammonia (NH3)-hydrogen (H2) engine, which involves the separation of fuel and air intake ports to mitigate the risk of H2 backfire in intake system. We explored the activity stratification under different intake schemes and H2 blend ratios through simulation, as well as how it affects the NH3–H2 combined combustion characteristics including in-cylinder flow turbulence, temperature, concentration, and key intermediates distribution. The results show that in Scheme 2 when air entered the high swirl ratio intake 1 and fuel entered the low swirl ratio intake 2, a rich mixture was formed near the spark plug, accompanied by localized NH3 thermal reforming phenomena, which improved the activity distribution of H2. Additionally, the strong swirl promoted combustion in the squish zone and significantly shortened the post-combustion period. Scheme 2 achieved a higher indicated thermal efficiency (ITE) than Scheme 1 with a small amount of H2 addition, with the highest ITE of 42.1% obtained at 15 vol% H2 blend ratio. Notably, the addition of H2 promoted NH3 consumption and the generation of active radicals, resulting in reduced N2O emissions during the expansion stroke, but causing an increase in NO emissions.

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

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

Effect of ignition timing and hydrogen injection phase on HDI engine combustion and NOx emissions

ABSTRACT In order to improve the ITE and reduce NOx emissions in direct-injected hydrogen (HDI) engines under at medium and high loads, the effects of IT and hydrogen injection phase on the combustion and NOx emission characteristics of the HDI engine at high rpm and medium load were investigated numerically. The base engine is a four-cylinder turbocharged direct-injected gasoline (GDI) engine, which is modified into a HDI engine with direct-injected hydrogen fuel. The simulation is performed using GT-Power software. The operating condition of HDI engine is set to 5500 rpm and 50% load. Firstly, IT is optimized, and then based on the IT optimization results, the hydrogen injection phase is optimized. The results show that as the IT is advanced, the maximum pressure rise rate (MPRR) shows a gradual increasing trend, while the combustion intensity and the indicated thermal efficiency (ITE) increases firstly and then decreases, and the former reaches a maximum value at 25° CA BTDC, while the latter reaches a maximum value of 40.5% at 18°CA BTDC. In addition, the nitrogen oxide (NOx) emissions decrease as the IT is delayed. Based on 18°CA BTDC of IT, the results indicated that the later the moment of hydrogen injection, the higher the MPRR, resulting in the greater the knock intensity. The ITE is less affected by the hydrogen injection phase. When the hydrogen injection phase is delayed, NOx emissions increase slightly.

Study on the impacts of injection parameters on knocking in HPDI natural gas engine at different combustion modes

Based on three-dimensional (3D) computational fluid dynamics (CFD) software, a 3D numerical model was constructed to investigate the effects of injection timing, pilot diesel energetic ratio (PDER), and angle between the central axis of the diesel jet and the horizontal direction (α) on combustion and knock in the natural gas mixing-limited combustion (NMLC) mode and natural gas slightly premixed combustion (NSPC) mode. The results indicate that advancing the start of injection of natural gas (NSOI) leads to a slight improvement in indicated thermal efficiency (ITE), but also an increase in peak cylinder pressure (Pmax) and maximum pressure rise rate (MPRR). In the NMLC mode, as the diesel and natural gas injection interval (IDN) decreases, the interference between the diesel and natural gas jets intensifies, ultimately leading to instability in the flame propagation process and increased fluctuations in cylinder pressure. At different NSOIs, when IDN is 0°CA, the maximum amplitude of pressure oscillations (MAPO) is the highest. When the PDER is increased from 5 % to 15 %, ITE increases by 7.1 %. Under different combustion modes, as α increases, ITE first increases and then decreases. However, the NSPC mode achieves a higher ITE, reaching up to 44.4 %.

An Experimental Study on the Effect of Intake Pressure on a Natural Gas-Diesel Dual-Fuel Engine

Abstract Natural gas-diesel dual-fuel (NDDF) combustion can be a viable method to reduce diesel usage in compression ignition (CI) internal combustion engines. Potential benefits of NDDF engines in comparison to conventional diesel engines include decreases in soot and carbon dioxide emissions. This study focuses on the effect of intake pressure on a dual-fuel engine with intake port injected natural gas (NG) and direct injected diesel at two engine operation conditions – low load-high speed and high load-low speed. The research work was performed on a heavy-duty, single-cylinder engine at a NG-diesel energy ratio of approximately 3:1. The results show that when the intake pressure was increased, the indicated thermal efficiency (ITE) increased for diesel combustion. The trend was similar at the high load-low speed condition but opposite at the low load-high speed condition for NDDF. ITEs of diesel combustion were generally higher than NDDF combustion due to higher unburned hydrocarbon (HC) emissions associated with the latter. For low load-high speed dual-fuel combustion, increasing intake pressure increased the HC and soot emissions, but decreased the nitrogen oxides (NOx) emissions. For high load-low speed case, increasing intake pressure caused the HC emissions to increase and the NOx and soot emissions to decrease. In-cylinder temperature measured at the tip of the diesel injector showed that the injector tip temperatures were higher for NDDF cases compared to diesel cases. These temperatures could be correlated with the combustion phasing and NOx emissions.

Investigation of low carbon emission and high thermal efficiency of diesel engine combined with high-pressure direct injection of hydrogen carrier: Ammonia

Ammonia, as a zero-carbon fuel, has the potential to serve as a medium for the production, transportation, and utilization of clean energy. The scaling up of green ammonia production also necessitates broader utilization channels for ammonia. Applying ammonia as a fuel in engines is an effective way to reduce carbon emissions. This paper employs dual direct injection technology of ammonia and diesel in a novel ammonia-fueled engine to implement various control strategies and investigates their effects on combustion and emission performance. The results indicate that when the ammonia injection timing is advanced from −40°CA ATDC to −60°CA ATDC, the flash boiling of liquid ammonia decreases the indicated thermal efficiency (ITE) below 39% and increases unburned gas emissions. Globally, injecting ammonia during the intake stroke could receive better performance. Split injection strategies of diesel significantly improve the ITE, especially under a higher pilot-injection ratio of 75%. Additionally, increasing the load benefits the ammonia combustion process. Raising the IMEP to 12 bar improves ammonia combustion efficiency to over 95%, with an ITE reaching 49%.

The performance of a spark ignition gasoline engine with hydrogen addition under low-load conditions

With continuously increasing populations and industrialization, more and more green consumers and stringent emission regulations promote low-carbon or zero-carbon alternative fuels in transportation sector. Hydrogen is considered carbon-free when produced using environmentally friendly methods, and could achieve zero carbon emission in the internal combustion engines. This study comprehensively explores the influences of the hydrogen addition on the performance of the gasoline spark ignition (SI) engine operated at low-load conditions. The experimental results showed that the abnormal combustion cycles of the test gasoline engine are greatly reduced with hydrogen enrichment. In addition, the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) of the gasoline engine is 2.66 % under the 1500 rpm and 0.2 Mpa (brake mean effective pressure: BMEP) condition, while the COV of IMEP of the engine fuelled with gasoline and hydrogen is 2.34 % at the same condition. Furthermore, the knocking intensity of the gasoline engine is strengthened by adding hydrogen because the averaged maximum pressure rise rate (MPRR) of the gasoline SI engine is slightly increased. Besides, the indicated thermal efficiency (ITE) of the gasoline engine is increased 0.9 % and its maximum increase rate of the ITE is 4.27 % with hydrogen addition at the 1300 rpm and 0.2 MPa condition. Last, unburned HC, CO, and CO2 of the gasoline engine are reduced while NOx emissions increase with adding hydrogen due to high combustion temperature.

Numerical Study on the Potential of Stratified Mixture to Improve Thermal Efficiency and Reduce Carbon Emissions in High-Speed Gasoline Direct Injection Engine

Abstract Stratified combustion improves the indicated thermal efficiency (ITE) of gasoline direct injection (GDI) engines, but the mechanism of its impact on unregulated emissions remains unclear. In this simulation-based study, double injection strategies were used to create stratified mixtures in the cylinder. The results indicated that as the second fuel injection quantity (FIQ) was increased or as the second fuel injection timing (FIT) was delayed, the oil-film mass increased, leading to an increase in soot emissions. The formation of a large area of stoichiometry (STO) region at the spark plug and at its right side increases the laminar flame velocity and improves the ITE. At 4000 rpm, the ITE of case2-2 (with a second FIT of −220 °CA after top dead center (ATDC) and a second FIQ of 65.5 mg) increased by 1.6% compared to the original scheme. With the increase in STO area, NOx emissions and the content of CH3OH and CH2O increased, while carbon monoxide (CO) and greenhouse gas emissions showed a decreasing trend. Compared to the original scheme, CO and greenhouse gas emissions decreased by 1.97% and 6.7%, respectively, in case2-2. This study provides guidance for the development of GDI engines with high ITE and low carbon emissions.

Effect of Atkinson cycle coupling compression ratio on the combustion characteristics of natural gas engines

Optimizing the combustion system is crucial for improving the efficiency of equivalent combustion natural gas (NG) engines owing to its high thermal load and decreased break thermal efficiency (BTE). Decoupling the effective compression ratio (CR) and expansion ratio of the engine by adjusting the intake valve timing and geometric CR emerges as a pivotal approach for BTE improvement. This study, leveraging bench tests and GT-power simulation, delves into the impact of the late intake valve closing (LIVC) coupling CR strategy on the combustion performance of NG engines. The findings indicated that, under high load conditions, the temperature in the cylinder during the compression stage experiences relatively minor variations concerning the intake valve closing time. Conversely, under low load conditions, the combustion duration is less influenced by the late closure angle, primarily affected by variations in geometric CR. By increasing the CR and delaying the late closing angle of the intake valve, a substantial enhancement in the net indicated thermal efficiency (ITEn) is achievable. Despite a comparable effective CR, the ITEn of CR12.5 & LIVC45 demonstrates a mean increase of 2.04 % under high load conditions and 1.69 % under low load conditions when compared with the CR11.5 & LIVC30 strategy.

Effects of ammonia energy ratio and PODE injection timing on combustion and emissions in a PODE/ammonia RCCI engine

The application of ammonia as an alternative carbon-free fuel has attracted increasing attention. In this paper, the effects and mechanisms of ammonia energy ratio (AER) and polyoxymethylene dimethyl ethers (PODE) injection timing on the combustion and emissions characteristics of a PODE/ammonia RCCI engine are investigated by both experimental and numerical methods. Results show that increasing AER from 10% to 40% leads to the delayed low temperature heat release (LTHR) due to reduced OH radical generated by PODE and the competition between PODE and ammonia for OH radical consumption. The larger AER increases the indicated thermal efficiency (ITE) by lowering combustion temperature and reducing heat transfer losses at the cost of higher hydrocarbon (HC), carbon monoxide (CO), and unburned NH3 emissions. The reduction of fuel-based nitrogen oxide (NOx) emissions with a larger AER is attributed to the enhanced in-cylinder thermal denitrification reactions. The delayed start of injection (SOI) from −60 °CA ATDC to −45 °CA ATDC leads to the higher peak in-cylinder pressure and temperature, resulting in the larger heat transfer losses and lower ITE. The impact of retarding SOI on NOx is insignificant under the combined effect of more thermal NO formation, less fuel-based NO generation, and weakened denitrification reactions. Additionally, nitrous oxide (N2O) shows dominant effects on the total greenhouse gas (GHG) emissions, and increasing AER or advancing injection timing produces more GHG. Under low loads and low AERs, although the introduction of ammonia helps to improve ITE, more researches are required to further reduce exhaust emissions.

Comprehensive effects of ammonia substitution rate, compression ratio, and ignition timing on knock, NOx emissions and indicated thermal efficiency in a hydrogen fuel engine

AbstractTo reduce knock and keeping low NOx emissions and high indicated thermal efficiency (ITE) in a hydrogen fuel engine, the comprehensive effects of ammonia substitution rate (ASR), compression ratio (CR), and ignition timing (IT) on its combustion and its NOx emissions were studied numerically. Based on a four‐cylinder gasoline direct injection (GDI) engine, it was modified into an ammonia/hydrogen dual‐fuel (AHDF) spark ignition (SI) engine. The simulation was conducted by GT‐Power software, and simulation data were validated through experiments. 2500 rpm_50% load was selected for the research. ASR, CR and IT vary from 0% to 20%, 10.5 to 8.5, and −24 to 0°CA ATDC, respectively. The findings indicate that increasing ASR decreases the maximum pressure rise rate (MPRR) and the knock index (KI), improving the ITE, but increasing NOx emissions. Based on 20% ASR, CR was optimized. The findings indicate that decreasing CR reduces the MPRR and KI, but increasing NOx emissions and decreasing the ITE. Finally, based on CR of 9, IT was optimized. The findings indicate that delaying IT reduces the MPRR and KI, but also has a certain impact on NOx emissions and ITE. After compromise consideration, the optimal IT in this study was selected as −9°CA ATDC.

Optimization of direct-injection ammonia-diesel dual-fuel combustion under low load and higher ammonia energy ratios

Ammonia (NH3), as a potential zero-carbon fuel, has garnered significant attention for its application in compression ignition (CI) engines. Due to the low reactivity, ammonia is primarily used as dual fuel in CI engines. Therefore, the decarbonization potential is influenced by the ammonia energy ratio (AER). In this study, experimental research was conducted on expanding the AER at low load conditions in a direct-injection ammonia-diesel dual-fuel engine. The ammonia post-injection strategy was explored and significantly improved the suppression effect of high-concentration ammonia on diesel ignition, which could advance ignition timing and increase the peak heat release rate. As a result, coupled with intake heating, it expanded AER to 86 % at an indicated mean effective pressure (IMEP) of 4 bar. This strategy also increased the indicated thermal efficiency (ITE) by 8 % and significantly reduced unburned ammonia emissions. However, the combustion and emission performance was limited by the post-injection ammonia quantity and the injection timing of both diesel and ammonia, especially under high AER conditions.

Effect of injection and ignition strategy on an ammonia direct injection–Hydrogen jet ignition (ADI-HJI) engine

High-efficiency, low-emission ammonia-hydrogen engines with low hydrogen energy share (XH2) help promote a carbon-neutral transition in heavy-duty, long-distance transportation. In this study, numerical investigations were carried out on a hydrogen jet ignition (HJI) ammonia engine to study the effects of ammonia port fuel injection (PFI) and ammonia direct injection (ADI) on the engine performance, including combustion and emission characteristics, at XH2 = 3 % with varied spark timing (ST). The results show that the ADI mode has higher volumetric efficiency, lower in-cylinder temperature, and lower heat transfer loss compared with the PFI mode, and more retarded injection can further increase the volumetric efficiency and reduce the temperature. ADI mode results in a more inhomogeneous fuel distribution and a lower local equivalence ratio, with hydrogen consumed earlier than ammonia, potentially resulting in more rapid early-stage combustion. ADI mode with multiple injections is more conducive to engine performance than single injection and can achieve the higher indicated mean effective pressure (IMEP) and indicated thermal efficiency (ITE) than PFI mode. By further optimizing ST, the ADI mode improves ITE by 2.8 % and reduces NO emission by 70 % compared with the PFI mode under acceptable NH3 and N2O emission conditions.

The impact of scavenging air state on the combustion and emission performance of marine two-stroke dual-fuel engine

The scavenging process significantly affects the combustion and emission performance of marine low-speed two-stroke dual-fuel engines. Optimizing scavenging air pressure and temperature can enhance the engine's combustion efficiency and emission control performance, thereby achieving more environmentally friendly and efficient operation of dual-fuel engines. This study focuses on marine low-speed two-stroke dual-fuel engines, analyzing the effects of scavenging air pressure (3.0 bar, 3.25 bar, 3.5 bar, and 3.75 bar) and scavenging air temperature (293 K, 303 K, and 313 K) on engine performance and emission products. The results indicate that scavenging air pressure has a greater impact on engine performance than scavenging air temperature. An increase in scavenging air pressure leads to higher thermal efficiency and power. As the scavenging air pressure increases from 3 to 3.75 bar, the indicated thermal efficiency (ITE) increases from 44.02 to 53.26%, and indicated mean effective pressure (IMEP) increases by approximately 0.35 MPa. Increased scavenging air pressure improves nitrogen oxide (NOx) and hydrocarbons (HC) emissions. For every 0.25 bar increase in scavenging air pressure, NOx emissions decrease by 3.53%, HC emissions decrease by 33.35%, while carbon dioxide (CO2) emissions increase by 0.71%. An increase in scavenging air temperature leads to lower ITE and IMEP. As the air temperature changes from 293 to 313 K, the ITE decreases by approximately 1%, and IMEP decreases by about 0.04 MPa. Increased scavenging air temperature improves CO2 emissions. For every 10 K increase in the air temperature, the CO2 emissions decrease by 0.02%, while NOx emissions increase by 4.84%, HC emissions increase by 34.39%. Therefore, controlling scavenging air pressure is more important than scavenging air temperature in the operational management of marine two-stroke engines. Higher power and lower NOx and HC emissions can be achieved by increasing the scavenging air pressure.

Applying fischer tropsch and its pentanol blends into an aviation compression ignition engine for PM emissions control

The aviation industry is recovering from COVID-19 to regain rapid growth at an increasing rate of over 5 % annually. Aviation compression ignition (CI) engines attributed to their economic fuel consumption and adorable reliability, have been widely utilized in the general aviation (GA) industry. To fill in the knowledge gap of the compatibility of Fischer Tropsch (FT) blended with long-chain oxygenated fuel applied into the aviation engines, this research focuses on analyzing the combustion performance and particle matter (PM) emissions of an aviation CI engine by burning FT alternative fuel and its pentanol blends (FT80P20 - 80 % FT + 20 % pentanol), in comparison with baseline diesel/pentanol-diesel blends (D80P20 - 80 % diesel + 20 % pentanol). It was found that FT80P20 significantly increases the indicated thermal efficiency (ITE) by 6.5 %, and remarkably decreases the indicated specific fuel consumption (ISFC) by 12 % in contrast to neat diesel at high load (8.5 bar IMEP), which is due to better homogeneous charge that alternates heterogeneous combustion. Moreover, the PM size-resolved number distributions of emissions were characterized. It was observed that the integrated PM emissions from diesel were predominant (∼1.4 × 1014 #/kg∙fuel), while those from FT80P20 were significantly reduced by nearly 85 % (∼0.2 × 1014 #/kg∙fuel). Concurrently, the particulate geometric mean diameter (GMD) were decreased apparently from 80 nm to 35 nm correspondingly. The research findings reveal that “main diffusion combustion” was predominant as burning diesel, while “main premixed combustion” was prominent as using FT80P20, which has a promising impact on effective engine-work promotion with superior PM mitigation.

Experimental study on ammonia-diesel co-combustion in a dual-fuel compression ignition engine

Ammonia, as a carbon-free renewable fuel and a potential hydrogen carrier, is gaining increasing interest in addressing greenhouse gas emissions in industrial applications and transportation. This paper presents experimental studies on the co-combustion of ammonia with diesel fuel in a single-cylinder industrial compression ignition engine operating in dual-fuel mode. The energy share of ammonia ranged from 0 to 60%. Increasing the proportion of ammonia compared to diesel fuel in the compression ignition engine leads to a change in the combustion process character, increasing the kinetic combustion phase at the expense of diffusive combustion. However, it does not result in an increase in the peak pressure rise (PPR) beyond the permissible value of 1 MPa/deg for piston engines. It increases ignition delay and shortens the combustion duration, while also increasing thermal efficiency and decreasing specific energy consumption. An increase in the NH3 share results in a decrease in combustion efficiency, a reduction in unit emissions of NO, CO2, and soot, and an increase in CO emissions. Beyond 42% ammonia share, it reduces unit THC emissions. At a 42% ammonia share, the dual-fuel engine achieves the highest indicated thermal efficiency (ITE), lowest specific energy consumption (SEC), shortest combustion duration, and lowest unit soot emissions.

Impact on air-assisted direct injection on knock and energy conversion in a downsized elliptical rotary engine with high compression ratio

The elliptical rotor engine (ERE) is a novel engine type that enables a high power-to-weight ratio and high compression ratio (CR), resulting in a significant increase in thermal efficiency. However, the high CR also makes the engine prone to knock, limiting its performance potential. Addressing the challenge of knock induced by high CR is essential for optimizing ERE performance. This study introduces an innovative approach, combining CR with an air-assisted direct injection (AADI) device, using advanced computational fluid dynamics simulations to investigate their effects on knock and energy conversion characteristics of a downsized gasoline ERE. The findings reveal that increasing CR from 9.26 to 11 boosts indicated thermal efficiency (ITE) by 18.27%. However, knock occurrence disrupts energy distribution, leading to increased heat transfer losses. Notably, knock appears earlier and more intensely at the front end of the combustion chamber compared to the back end. The incorporation of AADI markedly reduces knock tendency, enhances ITE by 14.28% relative to the prototype, and reduces heat transfer loss by 42.41%. This study demonstrates that AADI not only effectively inhibits knocking, but also significantly improves the overall performance of the ERE, providing a promising solution for the development of high-performance rotary engines.

Influence of structure parameters of pre-chamber on lean combustion of active pre-chamber jet ignition engine

Turbulent jet ignition (TJI) technology has the potential to improve engine efficiency. To elucidate the influence of different factors (diameter and number of holes) affecting the nozzle's total cross-sectional area, internal structure of the pre-chamber, and nozzle angle on the combustion characteristics of the engine. A 3 × 3 orthogonal test was designed and machined. The experiments were carried out on a pre-chamber single-cylinder engine.The results show that the pre-chamber's internal volume ratio has a great effect on the combustion characteristics in the cylinder. While the volume ratio of top of pre-chamber, transition region, and pre-chamber throat is 1:1:1, the engine's peak heat release rate is the highest. The highest Indicated thermal efficiency (ITE) can reach 43.43 %, with an absolute increase of 1.24 %, and the lean burn limit can reach λ = 2.6. Too large or too small nozzle angle will worsen the combustion state in the cylinder. The aperture and Nozzle number, which are the factors influencing the nozzle's total cross-sectional area, have different effects on the ignition delay, CA10-CA50, and CA50-CA90 of the engine. Various factors affecting the nozzle's total cross-sectional area have no apparent influence on the changing trend of ITE, but the aperture greatly influences ITE.

Performance analysis of methanol fuelled SI engine with boosted intake pressure and LIVC: A thermodynamic simulation and optimization approach

Methanol (CH3OH) is a low-carbon alternative fuel that can be derived through renewable power-to-fuel conversion, offering lower emissions and a higher resistance to knock in SI engines. However, the sole methanol-powered SI engine delivers less brake power. Fuels with a higher calorific value have been blended to solve this problem. However, this may cause overburden with storage, handling, and correct blending (like when methane and hydrogen are blended). To resolve this, this research suggested a novel approach for increasing the power and efficiency of a SI engine using the LIVC (late inlet valve closing) miller cycle and boosted intake pressure under 14 geometrical compression ratio (GCR) with the addition of the start of spark timing (SOI) and equivalency ratio (λ) effects. A quasi-dimensional thermodynamic model (QTDM) was applied to simulate the engine performance with respect to operating variables of 0.6–1.0 λ, 35.50 ––650 aBDC (after Bottom Dead Centre) LIVC timing, 30.00 ––150 bTDC (before Top Dead Centre) SOI Timing and 0.8–1.5 bar intake pressure. After that, design of experiments (DoE) based response surface methodology (RSM) was applied to determine optimum operating setting to maximize power and efficiency and minimize emission and fuel consumption. The results from the RSM illustrate the optimum input parameters to be 0.793 equivalence ratio, 46.900 aBDC-LIVC, 20.750 bTDC-SOI timing, and 1.5 bar intake pressure. Correspondingly, response output performances were found to be 12.36 kW-indicated power (IP), 11.20 kW- brake power (BP), 43.32 % indicated thermal efficiency (ITE), 39.32 % brake thermal efficiency (BTE), 9150.6 kJ/kWh brake specific energy consumption (BSEC), and 0.3 V%- carbon mono oxide (CO), 1247.8 ppm-nitric oxide (NO) emission at exhaust valve opening (EVO). The ANOVA regression models resulted in 95 % accuracy in forecasting output response and composite desirability of optimization of 0.83. Overall, it was found that miller-based LIVC and boosted intake pressure considerably improve the performance of SI engines, and the results projected would be helpful for further study and industry application.