Mean Effective Pressure Research Articles

Model-Based Calibration and Control of Tailpipe Nitrogen Oxide Emissions in a Light-Duty Diesel Engine and Its Assessment through Model-In-The-Loop

The present paper investigates two different strategies for model-based calibration and control of tailpipe nitrogen oxide emissions in a light-duty 3.0 L diesel engine equipped with an aftertreatment system (ATS). The latter includes a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and an underfloor selective catalytic reduction (SCR) device, in which the injection of diesel exhaust fluid (DEF), marketed as ‘AdBlue’, is also taken into account. The engine was modeled in the GT-SUITE environment, and a previously developed model-based combustion controller was integrated in the model, which is capable of adjusting the start of injection of the main pulse and the total injected fuel mass, in order to achieve desired targets of engine-out nitrogen oxide emissions (NOx) and brake mean effective pressure (BMEP). First, a model-based calibration strategy consisting of the minimization of an objective function that takes into account fuel consumption and AdBlue injection was developed and assessed by exploring different weight factors. Then, a direct model-based controller of tailpipe nitrogen oxide emissions was designed, which exploits the real-time value of the SCR efficiency to define engine-out NOx emission targets for the combustion controller. Both strategies exploit the model-based combustion controller and were tested through a Model-in-the-Loop (MiL) under steady-state and transient conditions. The advantages in terms of tailpipe NOx emissions, fuel consumption, and AdBlue injection were finally discussed.

Construction and verification of dual-fuel engine combustion model

In order to achieve real-time mapping and online optimization of the combustion process of a dual-fuel engine that is in prolonged operation, this paper is the first to combine the Wiebe function with a deep learning neural network to propose a zero-dimensional (0-D) combustion prediction model for a biodiesel-diesel dual-fuel engine. First, the parameters of the double Wiebe functions are calculated by the Pelican Optimization Algorithm (POA), and the operating parameters and Wiebe parameters are used as input and output parameters of neural networks, respectively, to construct parameter identification models. Then, the combustion process is simplified and reconstructed by combining the Wiebe function with the deep learning neural network, and a 0-D prediction model based on the hybrid model-driven and data-driven method is established, which can further obtain combustion results such as cylinder pressure curve and indicated mean effective pressure (IMEP). The results show that the coefficient of determination (R2) value of the dual-fuel engine 0-D prediction model based on the double Wiebe function combined with POA–CNN–Bi-LSTM is 0.9827, and the model has good prediction accuracy and generalization. The development of the combustion model provides reliable numerical model support for the online evaluation and optimization of dual-fuel engine performance.

Assessing the cyclic variability of combustion and NO emissions in hydrogen-methane fueled HSSI engine via quasi-dimensional modeling under the influence of flame-kernel turbulence and equivalence ratio variation mechanisms

This paper assesses the cyclic variability (cycle-by-cycle variations (CCV)) of combustion, performance and nitric oxide (NO) emissions in high-speed (HS), spark-ignition (SI) engine fueled with hydrogen-enriched methane (CH4), for which experimental data are available. Thus, in-house, two-zone, quasi-dimensional turbulent combustion model is used that closely trails the flame-front movement, which was validated before regarding performance, emissions, exergy, and CCV for gasoline- or methane-run HSSI engines. It is enhanced herein to study CCV of performance, combustion, and NO emissions, with engine fueled by various hydrogen-methane blends (up to 50 % by vol. hydrogen) and equivalence ratios (EQR). Hence, the influence of flame-kernel turbulence and EQR variation mechanisms on CCV attributes is considered and assessed. The numerical results are compared with measured data of cylinder pressure, indicated mean effective pressure (IMEP), and NO emissions at ‘steady’ conditions, and further for validation against available experimental CCV results for IMEP at all operating conditions. That CCV analysis is extended to peak pressure, IMEP, and NO emissions using coefficients of variation (COV), frequency distributions, and pertinent diagrams illuminating their cycle-by-cycle variations. The CCV variations decrease with hydrogen content in the blend whereas they increase with the mixture leanness delineating the relative merits of the two mechanisms.

Multi-objective optimization of ternary blends of Algal biodiesel-diesel-1-decanol to mitigate environmental pollution in powering a diesel engine using RSM, ANOVA, and artificial bee colony.

This research presents an in-depth examination that utilizes a hybrid technique consisting of response surface methodology (RSM) for experimental design, analysis of variance (ANOVA) for model development, and the artificial bee colony (ABC) algorithm for multi-objective optimization. The study aims to enhance engine performance and reduce emissions through the integration of global maxima for brake thermal efficiency (BTE) and global minima for brake-specific fuel consumption (BSFC), hydrocarbon (HC), nitrogen oxides (NOx), and carbon monoxide (CO) emissions into a composite objective function. The relative importance of each objective was determined using weighted combinations. The ABC algorithm effectively explored the parameter space, determining the optimum values for brake mean effective pressure (BMEP) and 1-decanol% in the fuel mix. The results showed that the optimized solution, with a BMEP of 4.91 and a 1-decanol % of 9.82, improved engine performance and cut emissions significantly. Notably, the BSFC was reduced to 0.29kg/kWh, demonstrating energy efficiency. CO emissions were lowered to 0.598 vol.%, NOx emissions to 1509.91ppm, and HC emissions to 29.52 vol.%. Furthermore, the optimizing procedure produced an astounding brake thermal efficiency (BTE) of 28.78%, indicating better thermal energy efficiency within the engine. The ABC algorithm enhanced engine performance and lowered emissions overall, highlighting the advantageous trade-offs made by a weighted mix of objectives. The study's findings contribute to more sustainable combustion engine practises by providing crucial insights for upgrading engines with higher efficiency and fewer emissions, thus furthering renewable energy aspirations.

Comparative evaluation of different operating parameters on performance, combustion, and emission characteristics in gasoline compression ignition (GCI) engine by using carbon neutrally biofuels

The stringent emission regulations and energy shortage put forward strict requirements for highly efficient and clean combustion for internal combustion engines. The gasoline compression ignition (GCI), which is a new advanced combustion concept, can obtain high efficiency and low emissions simultaneously without many modifications of standard diesel engines. However, little research has been carried out to synergistically optimize the operation parameters in a wide load range, especially fueled with the carbon neutrally biofuels. Therefore, in this paper, the effects of various operating parameters on engine performance, combustion, and emission characteristics of the gasoline compression ignition (GCI) strategy fueled with a blend of butanol and biodiesel were investigated. Specifically, the impact of butanol energy ratio, fuel direct injection timing, and exhaust gas recirculation (EGR) at the indicated mean effective pressure (IMEP) of 4, 8, and 14 bar and the butanol energy ratio of 60%, 70%, and 80% were examined. Result shown that the increase in butanol energy ratio decreased the fuel reactivity and worsen the combustion process, while the lower butanol energy was also disadvantage to the engine performance. The indicated thermal efficiency could achieve 48.5% when the butanol energy ratio was 70% at medium engine load. The earlier fuel injection timing was needed at low engine load, the EGR was necessary to inhibit the in-cylinder pressure rise at high engine load, in which the EGR rates of 20% at the IMEP of 8 bar and 30% at the IMEP of 14 bar could achieve the optimum engine performance, respectively. Meanwhile, the nitrogen oxides emissions shown a greatly decrease with the EGR rates increase, and it was less than 200 ppm at the IMEP of 14 bar when the EGR rates were 50%.

Experimental analysis of the effect of hydrogen as the main fuel on the performance and emissions of a modified compression ignition engine with water injection and compression ratio reduction

This study aimed to investigate the combined effects of compression ratio (CR), start of injection angle (SOI) and water injection (WI) on the performance, including NOx emissions, of a modified turbocharged compression ignition engine using H2 as the primary fuel and diesel solely as a pilot ignition source. WI and H2 were both injected into the intake manifold just after the charge heat exchanger. Test conditions varied the engine speed from 1500 rpm to 2750 rpm, covering a wide range of the original engine's operating conditions, water mass flow varied from 0 to 0.795 g/cycle and SOI for pilot ignition was studied in the range 10°, 5°, 0° before top dead center. Subsequently, the study examined the combined effect of reducing the engine's CR from 17.5:1 (base) to 13.5:1, in one-point increments, reducing SOI and water addition to further enhance the hydrogen energy share (HES).HES varied from 0 % to 85 % under different engine conditions, and WI and SOI were employed to prevent knocking and ensure that the maximum combustion pressure did not exceed 160 bar. The test results indicate that NOx emissions increase with HES, but reducing the CR results in a reduction in NOx emissions of approximately 50 %. Additionally, WI further reduces NOx emissions by up to 50 %. The experimental evidence demonstrates that combining WI with CR and SOI reduction can effectively lower NOx emissions, achieving an efficiency greater than 35 % and therefore approaching the base diesel mode's efficiency. This also reduces the maximum in-cylinder pressure, allowing for an increase in turbocharger pressure and consequently enhancing the engine's specific power. The maximum engine power achieved was 31.6 kW at 2500 rpm (mean effective pressure of 10.1 bar), with a CR of 15.5, SOI at 10°, 1.5 kg/kWh of water, a HES of 81 %, and a minimum NOx level of approximately 480 ppm, with a maximum combustion pressure below 120 bar.

A sustainable model using RSM and MCDM techniques to evaluate performance and emission characteristics of a diesel engine fueled with diphenylamine antioxidant and CeO2 nanoparticle additive biodiesel blends

Overconsuming fossil fuels has worsened global warming and air pollution, requiring us to investigate alternate fuels for compression ignition engines. Biodiesel is a renewable fuel and environmentally favorable. Biodiesel's most significant disadvantage is increased nitrogen oxide (NOx) emissions. The intent of the present study was to examine the impact of antioxidant diphenylamine (DPA) and nanoparticle ceria (CeO2) additive inclusion in a B30 blend on engine performance and exhaust emission characteristics. For this study, diesel, Jatropha biodiesel (B30), 100 ppm of antioxidant diphenylamine (50 ppm) with ceria nanoparticle (50 ppm) is added to the B30 blend named as B30+DPA100 and antioxidant diphenylamine (50 ppm) with ceria nanoparticle (50 ppm) is added to the B30 blend named as B30+DPA50+CeO250 fuel blends has been used. A hybrid response surface methodology and multi-criteria decision-making techniques (entropy method, TOPSIS, and VIKOR) have been used to develop a sustainable model and find the optimal setting of input parameters in terms of ranking. From experimental findings, the inclusion of antioxidants (DPA) and nanoparticle (CeO2) at 50 ppm to B30 significantly reduced NOx emission. The brake-specific fuel consumption and NOx have been found reduced by 5.67% and 18.87%, respectively, for B30+DPA50+CeO250 as compared to B30. At the same time, brake thermal efficiency increased by 1.01%. The brake mean effective pressure and maximum cylinder pressure) have been found increased by 0.68% and reduced by 4.52%, respectively, for B30+DPA50+CeO250 as compared to B30. The alternative ranking of the input parameters has been found fuel injection pressure (300), compression ratio (17), and load (12) as Rank 1 for TOPSIS and VIKOR. Therefore, the B30+DPA50+CeO250 blend is appropriate for improving diesel engine performance and diminishing exhaust emissions.

Divided Exhaust Period Assessment for Fuel-Enrichment Reduction in Turbocharged Spark-Ignition Engines

<div>Turbocharged spark-ignition (SI) engines, owing to frequent engine knocking events, utilize retarded spark timing that causes combustion inefficiency, and high turbine inlet temperature (Trb-In T) levels. Fuel enrichment is implemented at high power levels to prevent excessive Trb-In T levels, resulting in an additional fueling penalty and higher CO emissions. In current times, fuel-enrichment reductions are of high strategic importance for engine manufacturers to meet the imminent emissions regulations. To that end, the authors investigated the divided exhaust period (DEP) concept in a 2.2 L turbocharged SI engine with a geometric compression ratio of 14 by decoupling blowdown (BD) and scavenge (SC) events during the exhaust process. Using a validated 1D engine model, the authors first analyzed the DEP concept in terms of pumping mean effective pressure (PMEP) and engine knocking (KI) reduction. Subsequently, the authors examined the effectiveness of the DEP concept using a “low-restriction exhaust flowpath” and varying late intake valve closing (LIVC) duration.</div> <div>First, using DEP, significant PMEP and KI reductions benefits were observed at high power engine conditions along with a large increase in Trb-In T from the early blowdown event. Subsequently, use of a low restriction exhaust flowpath and a shortened LIVC duration further elevated the DEP benefits, including Trb-In T reduction that facilitated enrichment reduction. At 4,000 RPM/20 bar BMEP, ~70% lower PMEP and a 2.2 point increase in ITEg were noted relative to the base engine. However, the 2,000 RPM peak torque engine condition was compromised using DEP, due to knock limitation and deteriorated stock turbocharger performance. Finally, DEP design integrated with an off-the-shelf (new) turbocharger system remedied the low-end torque challenges and demonstrated a notable enrichment reduction and thermal efficiency benefits at the full load engine curve including the 200 kW rated condition.</div>

Impact of engine control variables on low load combustion efficiency and exhaust emissions of a methane-diesel dual fuel engine

A conventional diesel engine when operated in the reactivity-controlled compression ignition (RCCI) combustion strategy faces challenges of high total hydrocarbon (THC) and carbon monoxide (CO) emissions leading to poor combustion efficiency at low engine loads. The oxides of nitrogen (NOx) versus smoke trade-off, encountered in conventional diesel combustion, is replaced by the NOx-THC trade-off in the RCCI operation. This work focuses on addressing the NOx-THC trade-off issue by systematically investigating the effects of engine control variables, such as, fuel injection timing, exhaust gas recirculation (EGR) and intake throttling, on a light duty compression ignition engine running in a methane-diesel dual fuel mode. The engine is operated at a load of 3 bar gross indicated mean effective pressure and at a speed of 1500 rev/min. Based on relationships identified between engine control variables, combustion parameters, emissions and engine performance, a bottom-up approach is used to combine the control variables synergistically to improve the NOx-THC trade-off. A combination of advanced start of injection timing of diesel (−35 degree crank angle (°CA) after top dead centre), 50% premix ratio and 55% EGR levels along with the end of port fuel injection of methane in the middle of the intake stroke (−270°CA), has resulted in a ∼34 percentage points (from 56% to 90%) improvement in combustion efficiency and a ∼9.5 percentage points improvement in thermal efficiency compared to the baseline low load dual fuel operation while maintaining good combustion stability. THC emission is reduced from 105 to ∼25 g/kWh whilst maintaining low levels of NOx (<0.3 g/kWh).

Combustion cycle-to-cycle variations of opposed-piston two-stroke gasoline direct injection engine

The combustion characteristics and cycle-to-cycle variations of opposed-piston two-stroke (OP2S) gasoline direct injection (GDI) engine are investigated with experiment. The effects of engine speed on the combustion process and cycle-to-cycle variations are discussed. This paper chooses the indicated mean effective pressure, the maximum cylinder pressure and the maximum pressure rising rate to characterize the combustion cycle-to-cycle variations. The heat release rate of OP2S-GDI engine is in accordance with the conventional gasoline engine, which is divided into flame developing period, rapid burning period and after burning period. With the increase of engine speed, the maximum combustion pressure and maximum pressure rise rate decrease, and the time corresponding to the maximum in-cylinder pressure is delayed. The pressure rise rate associated with different engine speeds all show an increasing trend, with maximum values less than 0.2 MPa/°CA. The peak value of instantaneous heat release rate in the combustion process decreases and the combustion amount in the post-combustion period increases as the engine speed increases. The cycle-to-cycle variation rate of indicated mean effective pressure (IMEP) increases as the engine speed increases. The maximum IMEP cycle-to-cycle variation rate is 6.101% at 4000 rpm, which is less than the traditional gasoline engine cycle-to-cycle variation rate (10%). The cycle-to-cycle variation rate of the maximum cylinder pressure ( pmax) increases as the engine speed increases. The pmax cycle-to-cycle variation rate is 1.083% at 4000 rpm, which is less than traditional gasoline engine cycle-to-cycle variation rate (2%). The R ( pmax, pi) is weakly correlated at 2000 rpm and uncorrelated at 3000 rpm and 4000 rpm. The R( θ( pmax), pi) is strongly correlated at 3000 rpm and uncorrelated at 2000 rpm and 4000 rpm. The cycle-to-cycle variation rate of the maximum pressure rise rate (d p/d φ) is 7.406%%, 7.919% and 7.667% respectively at 2000 rpm, 3000 rpm and 4000 rpm. The R ((d p/d φ) max, pi) is weakly correlated at different engine speed, the R( θ(d p/d φ) max, pi) is moderately correlated at 2000 rpm and positive correlation at 3000 rpm and 4000 rpm.

Effects of hydrogen blending ratio on combustion and emission characteristics of an ammonia/hydrogen compound injection engine under different excess air coefficients

Currently, hydrogen and ammonia are the best green, zero-carbon energies worldwide. Applying ammonia and hydrogen to internal combustion engines is a top priority for achieving the dual-carbon goal for the automotive industry. However, both ammonia and hydrogen have disadvantages that make them unsuitable for use as fuels on their own. Hydrogen internal combustion engines can suffer from abnormal burning, such as premature ignition, backfiring, and detonation. At the same time, the difficulty of hydrogen storage, transportation, and refilling can also lead to the problem of high cost of use. Ammonia suffers from high ignition energy, poor flame-spreading speed, and inadequate burning stabilization. When used alone, it causes incomplete combustion of large amounts of ammonia. Therefore, our group uses the spray pattern of “hydrogen direct injection (HDI) plus ammonia port injection (API). ” The influence of hydrogen blending ratio (HBR) on the combustion and emission characteristics of an ammonia/hydrogen compound injection engine with various excess air coefficients (λ) is investigated. The blending ratios of hydrogen are 6.1 %, 16.8 %, 27.3 %, 37.7 %, 47.8 %, and 57.7 %, respectively. The experimental data suggests that the indicated mean effective pressure (IMEP) shows an incremental trend as the hydrogen blending ratio grows. Not only CA0-10 but also CA10-90 have been reduced. The whole combustion process is shortened. The temperature and pressure rise. When the ratio of hydrogen blending is higher than 27.3 %, the enhancement of the burning characteristics by hydrogen is not apparent. NOX emissions rise with the ratio of hydrogen blending. NH3 emissions tend to drop as the blending ratio of hydrogen rises. Combining the emission and combustion characteristics, the general engine performance is better when the λ is 1.2 and the ratio of hydrogen blending is 27.3 %.

Prediction modeling using artificial neural network (ANN) for the performance and emission characteristics of catalytic co-pyrolytic fuel blended with diesel in a CI engine.

In the present research work, artificial neural network (ANN) is used to model the performance and emission parameters in a four-stroke, single-cylinder diesel engine combusting a blended fuel of diesel and catalytic co-pyrolysis oil produced from seeds of Pongamia pinnata, waste LDPE, and calcium oxide catalyst. The optimum yield of oil obtained was 92.5% at 500 °C temperature. Physical properties of the obtained oil, such as calorific value (44.85 MJ/kg) and density (797 kg/m3), level it by that of diesel while the flash point and fire point were found to be lower than that of pure diesel. An ANN model was then generated for the prediction of performance characteristics (BTE and BSFC) and emission characteristics (NOx and smoke) under varying loads, braking power, brake mean effective pressure, and torque as inputs using the Levenberg-Marquardt back-propagation training technique. The regression coefficients (R2) for BTE, BSFC, smoke, and NOx predictions were determined to be close to unity at 0.99859, 0.99814, 0.96129, and 0.92505, respectively (all values being close to unity). It has been discovered that ANN makes an effective simulation and prediction tool for blended fuels in CI engines. It is also suggested to predict the mechanical efficiency, volumetric efficiency, and CO, CO2, HC emissions using ANN in its future work.

Performance evaluation of a diesel engine fueled with Chlorella Protothecoides microalgal biodiesel

The main objective of the current study is to determine the engine performance, combustion, and emission analysis of compression ignition engines fuelled with Chlorella Protothecoides microalgal biodiesel (CPMB). The biodiesel was derived from Chlorella Protothecoides microalgal oil (CPMO) through transesterification. Under the specified conditions, which included a methanol-to-oil molar ratio of 7.41 (vol/vol), a reaction time of 105.6 min, a reaction temperature of 65 °C, and a catalyst concentration of 1.024 (% wt/vol) and achieved a biodiesel yield of 98.1%. The fuel properties were determined using standard methods, revealing that the density and kinematic viscosity of CPMB were significantly higher than those of diesel. However, CPMB still exhibits satisfactory fuel properties that meet most biodiesel specifications. CPMB boasts a low cloud point (CP) and pour point (PP) of 0 and -3 °C, respectively, indicating its effective usability in cold climates. The oxidation stability of CPMB, determined by the modified Rancimat method, was found to be 4.6 h, satisfying ASTM specifications. The fuel tested in this study was 20% biodiesel with diesel, 100% biodiesel, and neat diesel. These fuels had been tested on a CI engine in which the engine speed and compression ratio were fixed at 1500 rpm and 18:1, respectively. Based on the results, it is found that the indicated thermal efficiency decreases up to 3.68% and 8.22% with B20 and B100 as compared to diesel. However, mechanical efficiency, volumetric efficiency, and indicated power were estimated to be higher at peak engine load conditions when correlated with neat diesel. Furthermore, the mean effective pressure for B20 and B100 was estimated to be decreasing while the mass fraction of fuel burnt and the rate of pressure rise increased compared to diesel at peak load conditions. For exhaust emission analysis, a significant reduction was recorded in CO and UHC emissions, while NOX emission increases at peak engine loads. From the above results, it is accomplished that the performance of B20 blends is nearly identical to diesel, and it can be recommended to be used in engines without any modification.

Real-time predictive model for reactivity controlled compression ignition marine engines

Model-based design is proven to be essential for the development of control systems. This paper presents a real-time predictive control-orientated model (COM) for low-temperature combustion (LTC), dual-fuel, reactivity-controlled compression ignition (RCCI) engines. A comprehensive model-based design methodology must be capable of constructing an RCCI control-orientated model with high accuracy, high noise immunity, good response, predictivity in governing mechanisms, and low computation time. This work attains all of these for the first time for a cutting-edge RCCI marine engine. The real-time model (RTM) captures the key sensitivities of RCCI by controlling the total fuel energy and the blend ratio (BR) of two fuels, while also considering uncertainties arising from variations of inlet temperature and the gas exchange process. It provides not only the cycle-wise combustion indicators but also the crank-angle-based cylinder pressure trend. The RTM is derived by direct linearisation of a physics-based model and is successfully validated against experimental results from a large-bore, RCCI engine and the previously acknowledged UVATZ (University of Vaasa Advanced Thermo-kinetic Multi-zone) model. Validation covers both steady-state and transient modes. With high accuracy in several case studies representing typical load transients and air-path disturbance rejection tests, the model predicts maximum cylinder pressure (Pmax), crank-angle of 5 % burnt (CA5), crank-angle of 50 % burnt (CA50) and indicated mean effective pressure (IMEP) with root means square (RMS) errors of 8.6 %, 0.3 %, 0.6 %, and 0.6 % respectively. The average simulation time without any code optimisation is around 5 ms/cycle, offering sufficient real-time surplus to incorporate a semi-predictive emission submodel within the current approach.

Synergic effect of hydrogen and n-butanol on combustion and emission characteristics of a hydrogen direct injection SI engine fueled with n-butanol/gasoline

Hydrogen, an ideal carbon-free energy carrier with favorable combustion properties, has drawn worldwide attention as a high-expectation way to enhance fossil fuels’ combustion performance. However, currently, limited investigations are about enhancing n-butanol hybrid gasoline engines through hydrogen addition. Thus, in this paper, the hydrogen direct injection (HDI) was put forward to improve an SI engine fueled with n-butanol/gasoline, and the synergic effect of hydrogen and n-butanol on combustion and emission characteristics was studied. Experimental results indicated the favorable influence of a low n-butanol mixing ratio (νN, νN = 25%) on enhancing combustion can relatively weaken the similar promoting effect of hydrogen. And the sequential increase in hydrogen addition ratio (φH, φH = 15–20%) can compensate for the negative impact of unfavorable atomization and vaporization quality caused by higher n-butanol blending (νN = 75–100%), namely the usage amount of n-butanol in engine can be raised. Further, compared with pure gasoline, the percentage change in BMEP (brake mean effective pressure) at νN = 25% and 100% can be increased from 1.79% to 5.04% and −5.38%–2.01% respectively by φH from 0 to 20%. Besides, the HDI can also shorten the combustion duration, accelerate the heat release process and improve the combustion stability of each νN, while the amplitude of promotion exhibits a relative downtrend with the increase of φH. As for emission characteristics, the HC, CO and particulate emissions decreased monotonously with the increasing φH under all νN, but there was a visible increase in NOX emissions.

Flame Characteristics and Abnormal Combustion of Methane Port Injection and Isooctane Direct Injection with Injection Timings Considered

Natural gas (NG) is a low-carbon fuel that can achieve low carbon emissions and high efficiencies. However, the low mean molecular mass and low energy density of methane result in low engine performance, and blending methane with gasoline is an effective way of improving the performance of NG engines. In this study, flame characteristics (including abnormal combustion) and engine performance are optically studied under methane port injection and isooctane direct injection conditions. The results indicate that the addition of isooctane can significantly increase the power output of NG engines. Under partial-load conditions, the minimum ignition advance for best IMEP is delayed with the addition of isooctane because of the higher flame speed of isooctane, and isooctane addition primarily improves the turbulent flame propagation rather than the initial flame formation. As for the isooctane injection timing, the indicated mean effective pressure (IMEP) first increases and then decreases with the delay in isooctane injection. The hot spots in the flame images confirm that late injection results in isooctane inhomogeneity, which reduces the engine’s thermal efficiency. At high loads, the low energy density of methane can lower the knocking intensity, even in the presence of auto-ignition at a speed of 120.7 m/s. The knocking pressure can lead to the ejection of oil droplets, which can increase the flame speed in the subsequent cycle.

Experimental investigation of ternary biodiesel blends combustion in a diesel engine to reduce emissions

The study presents an experimental investigation of two new ternary biodiesel blends, namely, ManCr_Pa (a mixture of Mandarin, Crambe biodiesel and paraffin as an additive) and AvBn_Pa (mix of Avocado, Bush nut biodiesel and paraffin) by modifying the critical fuel properties closer to the diesel fuel. Those ternary blends' performance, emission and combustion characteristics were compared with diesel and typical B5 blends at the same engine conditions. The result reveals that at high engine rpm, the new ternary biodiesel blends exhibited nearly similar engine performance to that of diesel fuel with a significant reduction of carbon monoxide (33.3%), hydrocarbons (33.3 to 73.3%) and particulate matter (17.8 to 28.8%). For instance, brake power (BP), brake mean effective pressure (BMEP), and brake thermal efficiency (BTE) slightly decreased by 0.25 to 0.38, 0.27 to 0.42 and 0.04%, respectively, whereas brake specific fuel consumption (BSFC) slightly increased by 0.52%. The ternary blends also demonstrated closer combustion behaviour, i.e. heat release rate (HRR) with diesel at full load conditions. Compared with the typical B5 blend, the modified ternary biodiesel blends showed better engine performance with a substantial reduction of emissions. Interestingly, the ternary blends exhibited lower NOx emissions than the B5 blend. The study concluded that the newly developed ternary biodiesel blends are superior to ordinary B5 blends and closely performing fuel to standard diesel. The results of this study have important implications for using these new blends as substitutes for diesel while realising similar benefits.

Estimation of the shape factor (m) in Wiebe function at different operating conditions for a SI engine

The burning process is one of the most important periods, which affects thermal efficiency and exhaust gas emissions, in internal combustion engines. The combustion process in internal combustion engines is modeled with one-dimensional or multi-dimensional software because it is cheaper, faster, and more practical than experiment. One of these methods, which is used to model the combustion period, is the Wiebe function. The Wiebe equation is an approach used in calculating the mass fraction burned and the heat release rate. The selection of Wiebe parameters is one of the most important factors affecting the accuracy of the mass fraction burned. In this study, the measured cylinder pressure of a spark ignition engine was directly used to calculate the heat released rate. The experiments were conducted at different brake mean effective pressures, engine speeds and relative air/fuel ratios, which were called independent variables. The shape factor (m) was determined by fitting the Wiebe equation to the heat release rate curves, which were extracted from the experimental results. The relationship between determined shape factor and independent variables was analyzed with a statistical approach. Eventually, a linear regression model, which explains 80% of the change in the shape factor, was created.

Experimental investigation of spark timing on extension of hydrogen knock limit and performance of a hydrogen-gasoline dual-fuel engine

This work focused on the influence of spark timing on the hydrogen knock limit and performance of a hydrogen-gasoline dual-fuel engine. A gasoline direct injection engine with hydrogen port induction was used for this study. The engine speed was kept at 1000 rpm, with a gasoline injection quantity of 6 mg. The hydrogen flow rate was varied until engine knock was detected. The spark timing was varied from 4 to 36֯ CA BTDC with a step size of 4֯ CA. A higher hydrogen flow rate was achieved when the spark timing was retarded close to TDC. The addition of hydrogen increased the cylinder pressure, exhaust temperature, brake mean effective pressure, and brake thermal efficiency. Advancing the spark timing produced a prolonged flame development period and shorter flame propagation period. Cyclic variation increased and then decreased with spark advance. NOX emissions increased with increase in spark advance and hydrogen flow rate, whereas spark timing had little effect on CO2 and CO emissions.

Combustion stability for early and late direct hydrogen injection in a dual fuel diesel engine

The paper presents an analysis of the experimental results of direct hydrogen injection in a dual-fuel diesel engine. The test object is a four-cylinder, four-stroke ADCR engine. An analysis of the following parameters was carried out: indicated mean effective pressure, peak pressure, angle of maximum pressure and released heat. Statistical analysis of the obtained results was carried out for each cylinder separately for four different hydrogen doses. Both early and late direct hydrogen injection were analyzed. The significance of the differences for each of the analyzed parameters and type of injection was determined. The stability of the combustion process was evaluated using the coefficient of variation CoV(IMEP).