Hydrogen Enriched Compressed Natural Gas Research Articles

Experimental study on combustion stability and performance of hydrogen-enriched compressed natural gas of a free-piston linear generator

Free Piston linear Generator (FPLG) engine fueled by compressed natural gas (CNG) has recently gained increased research attention. However, due to the low-velocity burning and poor lean limit of CNG fuel, the FPLG engine combustion stability, performance, and efficiency are still low. Hydrogen has a greater burning velocity with wider flame limits that could extend the lean burn limits and combustion characteristics of CNG. This paper compares pure CNG and 10% hydrogen-enriched CNG at various ignition speeds (0.6 ms, 0.8 m/s, and 1 m/s), injection positions (0 mm, 5 mm, 10 mm and 15 mm), and lambda ratios (0.9, 1.4 and 1.7) on the combustion characteristics, performance, and conversion efficiency are duly discussed. The findings show that the FPLG combustion stability limits increase with the hydrogen addition into the CNG. The CNG in-cylinder pressure increases significantly when the injection position is advanced, whereas the hydrogen addition reduces the influence of the injection position. The heat release rate increases by 15.62% and 23.72% with hydrogen addition, corresponding to the advanced and retarded injection positions. Consequently, the hydrogen addition increases the power RMS to 209.21 W and 232.64 W with an increment of 3.46% and 3.13%, respectively. Conclusively, the hydrogen addition into the CNG evidently shortens the combustion duration while improving the heat release rate, combustion stability, power RMS, Cycle-to-Cycle variation, and conversion efficiency.

Green Hydrogen-Compressed natural gas (bio-H-CNG) production from food waste: Organic load influence on hydrogen and methane fusion

Biogenic hydrogen (bioH2) enriched compressed natural gas (bio-H-CNG or biohythane) is emerging interest due to its feasibility to use in the existing transportation infrastructure with induced environmental benefits. This study evaluated the production of bioH2and biomethane (bioCH4) towards bio-H-CNG formation at a varying organic load (OL: 30,40,50 g COD/L) of food waste (FW). Acidogenic reactor operated with FW at 40 g COD/L showed the highest cumulative bioH2production while elevated OL (50 g COD/L)showedhigher cumulative bioCH4production (CMP: 11.92 L) from the methanogenic reactor. BioH2 and bioCH4 produced at different time intervals were combined to assess bio-H-CNG. The nature of biocatalyst and OLsignificantly regulated the composition of bio-H-CNG varying between 0.1 and 0.3 of H2/(H2+CH4) ratio accounting for5–12.6 kJ/g COD. Chain elongation, converting short (C2-C4) to medium-chain fatty acids(Caproic acid,1.16 g/L) was specifically observed during the acidogenic process.

Effect of hydrogen enrichment of compressed natural gas on combustible limit and flame kernel evolution in a constant volume combustion chamber using laser ignition

Laser ignition of hydrogen-enriched compressed natural gas (HCNG) enables lean-burn combustion, a key technology for future emissions norms compliance for internal combustion (IC) engines. HCNG overcomes the limitations of low volumetric energy density and lowers the flame speed of CNG fueled spark ignition (SI) engine-powered vehicles. In this study, laser beam profile and beam quality (M2) of a Q-switched Nd: YAG laser at fundamental wavelength of 1064 nm, having 6–9 ns pulse duration, were characterized. During the Constant volume combustion chamber (CVCC) experiments, relative air-fuel ratio (λ) of different HCNG blends were varied to identify the lean-burn limits, and observe flame kernel evolution, pressure–time history, and detect the start of combustion (SoC). At 10 bar initial chamber filling pressure, lean flammability limit increased due to hydrogen (H2) enrichment of CNG. It was found to be λ = 1.6, 1.8, 1.9, 2.0, and 2.1 for CNG, 10HCNG (10% v/v hydrogen and balance CNG), 20HCNG, 30HCNG, and 40HCNG respectively. Flame kernel displacement (Early stages of flame initiation and its development in µs time-scale) was the highest for λ = 1.1 for all HCNG mixtures, irrespective of the test fuel composition. Knocking or two-stage combustion increased with lowering λ at 10 bar initial chamber filling pressure. SoC advanced and combustion duration (CD) decreased with increasing H2 enrichment of CNG. Increased H2 enrichment of CNG accelerated the flame kernel evolution and made it a predominantly a 3D combustion phenomenon (volumetric combustion). Lower λ and higher H2 enriched CNG mixtures were effective in reducing the CD.

Numerical investigation of the effect of two-step injection (direct and port injection) of hydrogen blending and natural gas on engine performance and exhaust gas emissions

The present work investigates the effect of two-step fuel injection on a four-cylinder engine which has been altered from port injection to direct injection. Hydrogen enriched compressed natural gas (HCNG) blend has been utilized as a substitute in replacement of gasoline. Initially, CNG as a 10% of the total fuel mass fraction is injected into the air manifold and the remaining 90% fuel is HCNG which is injected into the cylinder by direct injection. Primarily, the CNG was injected at 160° BTDC with 20° stroke duration. HCNG fuel was injected at 130° BTDC with a 50° stroke duration being injected from (0%–40%) step.AVL software has been utilized for this investigation to inspect the engine performance, efficiency, fuel consumption, and exhaust emissions. The collected data indicates that by injecting 30% HCNG blend, the brake power, brake thermal efficiency, and in-cylinder pressure is increased from 8% to 13.64%, and the specific fuel consumption is reduced from 6.2% to 18% due to a rise in flame propagation speed in the combustion chamber. The addition of hydrogen has decreased carbon monoxide and unburned hydrocarbons by up to 14% on a complete combustion. NOx has been increased due to the increase in the exhaust gas temperature.

Experimental evaluation of laser ignited hydrogen enriched compressed natural gas fueled supercharged engine

Laser-induced ignition could be the most promising alternative to conventional spark ignition, in order to reduce engine-out emissions. A single-cylinder naturally aspirated, water-cooled, direct injection diesel engine (Kirloskar, DM-10) was adapted/ modified to supercharged spark ignition (SI)/ laser ignition (LI), port fuel injection (PFI) gaseous fueled engine operation at a compression ratio (CR) of 11, and the experiments were conducted at a constant engine speed of 1500 rpm. Compressed natural gas (CNG), Hydrogen (H2) and HCNG mixtures (CNG & H2 mixed on a volume basis) were used as test fuels in this study. Comparison of LI vs. SI mode of ignition was investigated for combustion, performance, and emission characteristics of different HCNG mixtures under identical maximum brake torque (MBT) timing of 31°CA bTDC with an increased boost. For HCNG experiments, a dynamic HCNG mixing system was designed and developed, which delivered HCNG mixtures of desired composition on demand dynamically to the engine. It was observed that during supercharging or boosting the engine, 0.1 bar boost was optimum boost. At optimum boost, engine torque increased in LI mode compared to SI mode and it varied from 29 Nm to 32.5 Nm for CNG and from 20 Nm to 24 Nm for H2. Maximum peak in-cylinder pressure (Pmax) reduced with H2 enrichment of CNG. Pmax was 47.62 bar for CNG, which reduced to 39.77 bar for 40HCNG. At optimum boost, LI mode improved brake thermal efficiency (BTE) from 36.9% to 37.82% for CNG and from 37.7% to 38.6% for 40HCNG. Brake specific fuel consumption (BSFC) in LI mode reduced from 0.20 kg/kWh for CNG to 0.180 kg/kWh for 40HCNG. In LI mode, exhaust gas temperature (EGT) reduced. In LI mode at 0.15 bar boost, BSCO, and BSNOx emissions reduced with H2 enrichment.

Development and comparative experimental investigations of laser plasma and spark plasma ignited hydrogen enriched compressed natural gas fueled engine

A customized port-fuel-injection (PFI) SI engine was operated in spark ignition (SI) and laser ignition (LI) modes at varying brake mean effective pressure (BMEP) and relative air-fuel ratio (λ) under naturally aspirated conditions. Test fuel used were hydrogen enriched compressed natural gas (HCNG) mixtures and results were compared with baseline CNG. For H2 enrichment of CNG, a customized dynamic fuel mixing system was developed. For LI, a solid state Q-switched Nd:YAG laser (200 mJ; 30 Hz; 6–9 ns) was used, and the laser beam was focused using a converging lens of 50 mm focal length. Experiments of HCNG fueling exhibited relatively higher peak pressure (Pmax) with its peak shifted closer to the top dead center (TDC). H2 enrichment of CNG led to increase in peak in-cylinder Pmax (by ∼2.9 bar), RoPR (by ∼0.72 bar/deg) and HRR (by ∼7.2 kJ/m3.deg) for 40HCNG compared to baseline CNG. The maximum BTE was observed to be ∼42.8% (at λ = 1.4) in LI mode for 30HCNG fueled engine. The lowest BSFC obtained were at λ = 1.2 for HCNG in SI mode, while corresponding value in LI mode was obtained at λ = 1.4. BSHC emissions were always lower for LI mode than the SI mode. At 3.96 bar BMEP, BSHC emissions reduced from 0.54 g/kWh (for CNG) to 0.35 g/kWh (for 40HCNG), which further reduced to 0.21 g/kWh (for H2) in LI mode. BSNOx emissions increased with increasing BMEP but reduced from 0.89 g/kWh at λ = 1.5 for CNG to 0.17 g/kWh for 30HCNG at λ = 1.7 at 30 Nm load.

Study of laminar burning speed and calibration coefficients of quasi-dimensional combustion model for hydrogen enriched compressed natural gas fueled internal combustion engine along with exhaust gas recirculation

Utilization of hydrogen fuel in internal combustion engine is regarded as a good choice due to its zero-carbon emission. The experiments have been performed under a wide range of operating conditions and the traces of in-cylinder pressures are obtained. The authors have formulated five laminar burning speed correlations (HCNG/N2, HCNG/N2/P, HCNG/CO2/T, HCNG/CO2/P & HCNG/CO) from the previous experimental work [25,31,33,34,38] while, two correlations (HCNG/N2/O2/T & HCNG/CO/CO2/T) have been imported from the earlier research work [32,35]. The iterations of these models have been staged in the quasi-dimensional combustion program of HCNG engine along with the exhaust gas recirculation but, results were un-satisfactory.Therefore, another laminar burning speed correlation (HCNG/N2/CO2/T) has been developed to improve the quasi-dimensional combustion model of HCNG fuel mixture along with the EGR technique. The kinetic GRI Mech3.0 mechanism has been utilized for the prediction of laminar burning speed of HCNG fuel mixtures at different hydrogen fractions 0 to 20% by volume in compressed natural gas, EGR ratios (0–0.3) and inlet temperatures (300–350 K). The effect of EGR ratio on the laminar burning speed in HCNG fuel mixture is introduced as the simultaneous impact of CO2 and N2 dilution of gases according to the balance chemical equation at stoichiometric condition. The presented model (HCNG/N2/CO2/T) is best suited for the quasi-dimensional combustion code of HCNG fuel mixture along with the exhaust gas recirculation as mean of the sample points of Taylor length & turbulent intensity coefficients are closer to 1 and minimum absolute percentage error for the indicated mean effective pressure.

Particulate characteristics of laser ignited hydrogen enriched compressed natural gas engine

Laser ignition (LI) is emerging as a strong technology to control the oxides of nitrogen (NOx) emissions from spark ignition (SI) engines without the need for any significant exhaust gas after-treatment and is an appropriate technology for meeting future emission norms in the automotive sector. In this study, particulate characteristics of LI engine fuelled with different compressed natural gas (CNG) and hydrogen mixtures [100% CNG, 10HCNG (10% v/v hydrogen with 90% v/v CNG), 30HCNG (30% v/v hydrogen with 70% v/v CNG), 50HCNG (50% v/v hydrogen with 50% v/v CNG) and 100% hydrogen] were investigated. Experiments were performed in a suitably modified single cylinder engine, which operated in LI mode at constant engine speed (1500 rpm) at five different engine loads (5, 10, 15, 20 and 25 Nm). Particulate characteristics were determined using an engine exhaust particle sizer (EEPS). Results showed that particle number concentration increased with increasing engine load. Number-size, surface area-size and mass-size distributions of particulates reflected that addition of hydrogen in the CNG improved particulate emission characteristics especially in nucleation mode particle (NMP) size range (10 nm < Dp < 50 nm). Among the test fuels, hydrogen-fuelled engine emitted the lowest number of particles. It was observed that the difference between particulate characteristics emitted by different test fuels reduced at higher engine loads. Significant contribution of lubricating oil in particulate emissions from both hydrogen as well as HCNG fuelled LI engine was an important finding of this study. Dominant contribution of larger particles (Dp > 50 nm) in total particle mass (TPM) was an important observation of this study. The qualitative correlation between total particle number (TPN) and TPM indicated that suitable fuel composition at different engine loads yielded cleaner exhaust from the LI engine. Overall, this study demonstrated that addition of hydrogen in CNG is advantageous from particulate reduction point of view, however, optimum fuel composition should be adjusted according to engine operating condition in order to reduce particulate emissions.

Effect of spark timing on laser ignition and spark ignition modes in a hydrogen enriched compressed natural gas fuelled engine

In this experimental study, a prototype laser ignited engine was developed and fuelled with hydrogen enriched compressed natural gas (HCNG; mixture of H2 and CNG). Engine performance, emissions and combustion characteristics were compared for laser ignition (LI) and spark ignition (SI) modes. The maximum brake torque (MBT) timing was employed to reduce cycle-to-cycle variations (CCV) and to improve the engine performance, combustion and emission characteristics. Composition of HCNG mixture was changed by dynamically blending H2 with CNG on a volumetric basis. MBT timing was determined for naturally aspirated engine in conventional SI mode, by varying the spark timing (ST) between 22° CA bTDC to 46° CA bTDC and by varying relative air–fuel ratio (λ) from rich-to-lean. Optimum torque for HCNG mixtures was observed at 31° CA bTDC. The 10% mass fraction burn (MFB10) duration reduced continuously with advancing ignition timing up to 31°CA bTDC, which then increased with further advanced ST. For any particular ST, MFB10 and MFB90 decreased with increasing H2 enrichment of CNG. At high λ (lean mixtures), CCV would be higher due to lower engine efficiency and increased emissions. LI mode exhibited lower coefficient of variation in indicated mean effective pressure (COVIMEP) compared to SI mode. The COVIMEP for all HCNG mixtures were within 2% up to λ = 1.2 and it increased further with increasing λ but the variation was within ± 6%. Lower CCV (< 2% of COVIMEP), reduced emissions and improved brake thermal efficiency (BTE) were observed at 31°CA bTDC MBT timing compared to other spark timings. This experimental study indicated that laser ignition is a suitable technology for deployment in HCNG engines.

Well-to-wheels total energy and GHG emissions of HCNG heavy-duty vehicles in China: Case of EEV qualified EURO 5 emissions scenario

Energy security and climate change are critical concerns in the present era. The booming of the vehicle population has worsened the environment and has caused severe air pollution problems, especially in urban areas. The utilization of hydrogen-enriched compressed natural gas in internal combustion engines shows abundant prospects for improved performance and reduced on-road emissions of greenhouse gases and air pollutants. This study aims to provide an insight to well-to-wheels environmental implications of the 20%HCNG fuel mixture in terms of total energy use, and greenhouse gas emissions per megajoules (MJ) of thermal energy output. The well-to-tank (WTT) impacts were evaluated using GREET 1 (2017). GREET 1 is a fuel cycle modeling tool developed by ‘Argonne national laboratory.’ GREET® is extensively used by researchers worldwide to analytically simulate energy use and emission output of various vehicle and fuel combinations. This study uses 12 prospective pathways of gaseous hydrogen production for analysis purposes. In the tank-to-wheels (TTW) phase, the 20%HCNG@EEV reduces the brake specific energy consumption (BSEC) by approximately 5%, and also decreases GHG emissions by 14% compared with 0%HCNG@EURO3. For simplicity, EURO5 is entitled as ‘EEV’ and has been excluded in most of the discussion, only highlighting ‘EEV,’ which abbreviates as ‘Enhanced Environmentally friendly Vehicles.’ For the entire well-to-wheels phase, this research work shows that all of the 20%HCNG@EEV pathways have lower total energy use and GHG emissions than 0%HCNG@EURO3 except the two pathways, such as grid electricity-to-hydrogen (without CO2 sequestration) and coal gasification-to-hydrogen (without CO2 sequestration). The WTW total energy and GHG emissions reduced by approximately 14% and 13%, respectively, with 20%HCNG@EEV based on the coke oven gas pathway compared with 0%HCNG@EURO3. It is essential to note that the use of cleaner feedstock for hydrogen, such as power-to-gas (P2G), biomass, coke oven gas (by-product), and natural gas shows tremendous prospects for realizing and practicing sustainable ‘hydrogen economy’ in China. Further technological advancement and reduction in total costs of HCNG utilization in powertrains will increase the number of HCNG vehicles decreasing the burden of air pollution, climate change, and energy crisis threats.

Optimal Operation of an Integrated Energy System Incorporated With HCNG Distribution Networks

Most industrial practices for turning power into hydrogen face a similar challenge, i.e., hydrogen consumption. One solution is injecting hydrogen into the existing natural gas (NG) infrastructure, so as to enter the market without expensive investments. However, a major concern regarding HCNG (Hydrogen enriched compressed natural gas) is the amount of hydrogen that can be added to the natural gas infrastructure without any modification. The current studies have focused on the modeling of HCNG components under various H2 fractions, but there is a lack of research on the system operation of HCNG, especially when incorporated with dispersed renewables and CHP plants. To fill in the gaps from the component to the system level, this paper proposes a comprehensive HCNG operation model coupled with the operations of an electrical and heating network. Via this model, the system performance incorporated with HCNG distribution networks could be studied under various H2 fractions and HCNG load portfolios (HLP). The numerical studies demonstrate the benefits of integrating the HCNG distribution network, especially in terms of local balancing of distributed generators and minimizing the operational costs.

A review and prospects of gas mixture containing hydrogen as vehicle fuel in China

Nowadays, the environmental problems caused by the burning of fossil fuels as vehicle fuel have become more and more serious in the world. Many countries are carrying out the research on the alternative energy sources and the clean energy. Meanwhile, China has begun to focus on the development of the gas mixture containing hydrogen as the vehicle fuel, mainly hydrogen enriched compressed natural gas (HCNG) and coke oven gas (COG). Application status of HCNG and COG as the vehicle fuel in China were reviewed and their existing problems were analyzed. The analysis results shows that the relevant regulations standards of HCNG vehicle, COG vehicle and their refueling stations have not been formulated and unified yet and the optimal hydrogen ratio of the HCNG requires further experimental investigation and theoretical analysis. In addition, as a country with substantial COG wasted, China can make better use of the wasted hydrogen contained in COG to realize the miniaturization and closed production of the COG without pollution. HCNG and COG as vehicle fuel are beneficial for the development of the hydrogen energy, which can alleviate the crisis of global energy shortage and effectively reduce the production and emission of sulfur oxides. Therefore, the prospects of HCNG and COG as the vehicle fuel are good in China.

The well-to-wheel analysis of hydrogen enriched compressed natural gas for heavy-duty vehicles using life cycle approach to a fuel cycle

Abstract Increasing urban air pollution, greenhouse gases, and declining fossil energy sources are the three major problems of transportation sector which drive the use of alternative vehicular fuels to prevent energy shortage, reduce oil dependency and decrease tailpipe emissions including air pollutants and greenhouse gas emissions. This research work focused on life cycle analysis of HCNG® heavy-duty vehicle in which 20% gaseous hydrogen blended with compressed natural gas has been investigated in terms of net energy ratio, GHG value, and cost-effectiveness over a scale of ‘per MJ energy output’ in two fuel options, i.e. 0%HCNG and 20%HCNG for an entire well-to-wheel cycle. An engineering economic approach has been used to evaluate cost-effectiveness ratio of CNG and 20%HCNG pathways derived from fuel economy improvement. It has been shown that at pump-to-wheel stage, 7% reduction in fuel consumption can be achieved together with 11% reduction in GHGs, 7% reduction in energy consumption at operation and 7% reduction in total costs (RMB/MJ) for 20%HCNG compared with CNG. Rank (1 means ‘best and 10 means ‘worst’) showed that renewable-based hydrogen pathways such as solar, wind and biomass showed dual benefits of lower energy consumption and lower GHG emissions whereas grid electricity-to-hydrogen displayed the worst case in both scenarios. Usually, biomass-based HCNG pathways may have higher net energy ratio, but the sources are cleaner, and renewable in nature. The energy efficiency of fossil-based pathways such as natural gas, coal, etc., is higher than biomass gasification pathway.

Experimental study of hydrogen enriched compressed natural gas (HCNG) engine and application of support vector machine (SVM) on prediction of engine performance at specific condition

The effect of excess air ratio (λ) and ignition advance angle (θig) on the combustion and emission characteristics of hydrogen enriched compressed natural gas (HCNG) on a 6-cylinder compressed natural gas (CNG) engine has been experimental studied in an engine test bench, aiming at enriching the sophisticated calibration of HCNG fueled engine and increasing the prediction accuracy of the SVM method on automobile engines. Three different fuel blends were selected for the experiment: 0%, 20% and 40% volumetric hydrogen blend ratios. It is noted that combustion intensity varies with the excess air ratio and the ignition advance angle, so are the emissions. The optimal value of λ or θig has been explored in the specific engine condition. Results show that blending hydrogen can enhance and advance the combustion and stability of CNG engine, and it also has some benefic influence on the emissions such as reducing the CO and CH4. Meanwhile, a simulation research on forecasting the engine performance by using the support vector machine (SVM) method was conducted in detail. The torque, brake specific fuel consumption and NOx emission have been selected to characterize the power, economic and emissions of the engine with various HCNG fuels, respectively. It can be seen that the optimal model built by the SVM method can highly describe the relationship of the engine properties and condition parameters, since the value of the complex correlation coefficient is larger than 0.97. Secondly, the prediction performance of the optimal model for torque or BSFC is much better than the case of NOx. Besides, the optimal model built by the PSO optimization method has the best prediction accuracy, and the accuracy of the model obtained based on the training group with 20% hydrogen blend ratio is the best compared with those of others. The upshots in this article provide experimental support and theoretical basis for the adoption of HCNG fuel on internal combustion engines as well as the application of intelligent algorithmic in the engine calibration technology field.

Combustion and energy distribution of hydrogen-enriched compressed natural gas engines with low heat rejection based on Atkinson cycle

In order to reduce the heat loss and improve the indicated thermal efficiency of hydrogen-enriched compressed natural gas engines, this article presents a combination of Atkinson cycle with high compression ratio and low heat rejection on the hydrogen-enriched compressed natural gas prototype engine with 55% hydrogen blend. The combustion characteristics and energy distribution of the prototype and modified engines were investigated by simulation, and the conclusions are as follows: the pressure and temperature of modified engines are higher than those of the prototype during the combustion process. Compared with the prototype, the modified engines present lower peak heat release rate, but faster combustion after ignition, and their CA50 are closer to top dead center. Although the high compression ratio engine with Atkinson cycle generates more heat loss, its indicated thermal efficiency still increases by 0.6% with the decrease in the exhaust energy. Furthermore, the high compression ratio engine with low heat rejection and Atkinson cycle combines the advantages of low heat loss and relatively longer expansion stroke, so its heat loss reduces obviously, and 61.6% of the saved energy from low heat rejection and Atkinson cycle can be converted into indicated work that indicates a 4.5% improvement in indicated thermal efficiency over the prototype, which makes it perform better in terms of power and fuel economy simultaneously.

In-Cylinder Combustion Analysis of a SI Engine Fuelled with Hydrogen Enriched Compressed Natural Gas (HCNG): Engine Performance, Efficiency and Emissions

In-Cylinder Combustion Analysis of a SI Engine Fuelled with Hydrogen Enriched Compressed Natural Gas (HCNG): Engine Performance, Efficiency and Emissions

Study on influencing factors of prediction accuracy of support vector machine (SVM) model for NOx emission of a hydrogen enriched compressed natural gas engine

In recent years, support vector machine (SVM) method has been rapidly developed because of its great advantage in solving small sample regression problems. Based on the prediction accuracy of NOx emission, the SVM method is applied to the regression analysis of the steady-state calibration experimental results of a hydrogen enriched compressed natural gas (HCNG) engine in this research article. The effects of the model parameters (penalty factor kernel, function width and insensitive band loss function) and the training sample size on the prediction accuracy of the regression model are studied. Results show that both model parameters and training sample size can influence the prediction accuracy of the SVM model. Additionally, the method of determining the optimal SVM regression model is also summarized. The optimal SVM regression model is obtained by the manifold absolute pressure (MAP) and the fuel equivalence ratio (θ) halved sample, with the training sample size of 270 for the experimental data used in this study. Results show that the optimal SVM regression model can decrease the predicted mean absolute percentage error (MAPE) and the maximum relative prediction error (MRE) of the brake specific NOx emission greatly, from 12.54% to 8.32% and 56.66% to 25.89%, respectively. It indicates that the prediction performance can be improved apparently by the method promoted in the paper, which provides a new perspective for the further application of SVM method in the field of automobile engines calibration.

Experimental and artificial neural network (ANN) study of hydrogen enriched compressed natural gas (HCNG) engine under various ignition timings and excess air ratios

In today's era, the computational capabilities of artificial neural network has endorsed to be a bedrock and inferences in many fields, including internal-combustion engines. The presented research in ANN has been germinated to anticipate the performance and emission characteristics of a turbocharged SI engine fueled with various HCNG mixtures. The experiments were accomplished at various excess air ratios (λ), ignition timings (θi) at MAP of 105 kPa and 140 kPa, while engine speed was kept constant at 1600 rpm to obtain data for testing and training ANN model. The test results show that with the increase in values of λ, MAP, and hydrogen addition, the torque output effectively decreases while BSFC first decreases and after attaining minimum value it further increases. The NOx, CO, THC, and CH4 emissions all declined with the hike of ignition advance angle, and inclined with increase of the load. ANN’s popular backpropagation algorithm is adopted in multilayered feedforward networks. In order to predict the performance and emission characteristics of HCNG engine, the four-input and one-output network structure are used. HCNG0, HCNG20 and HCNG40 blends has been studied in the presented ANN model in which the excess air ratio (λ), engine load, ignition timing, and HCNG blends has been taken as four-input parameters. The bestowed model has been trained using hyperbolic tangent transfer activation function (tansig) and Levenberg-Marquardt learning algorithm (LM) along with numerous neurons.The lowest and highest value of correlation coefficient (R) and mean square errors (MSE) for validation were dig-out for various parameters, which were BSFC, torque, NOx, CO, THC, CH4. The values of R (min–max) and MSE (min–max) were BSFC; 09519–0.9963 and 5.72–64.29, torque; 0.9948–0.9997 and 8.3935–95.8350, NOx; 0.9938–0.9992 and 0.5271–3.4340, CO; 0.8595–0.9960 and 0.0188–1.0154, and THC; 0.9644–0.9972 and 0.0714–1.1695, CH4; 0.7965–0.9973, 0.0351–1.1789 respectively for various number of neurons. This research work provides the gist of ANN as an attractive choice to researchers for classical modelling techniques. In this regard, the ANN modeling can be utilized to minutely predict the performance and emission characteristics of hydrogen added CNG engines.

Knocking behavior and emission characteristics of a port fuel injected hydrogen enriched compressed natural gas fueled spark ignition engine

Natural gas has highest hydrogen-to-carbon ratio among hydrocarbon fuels, which helps in reducing greenhouse gas emissions. Blending natural gas with hydrogen decreases emissions even further because of superior combustion characteristics of hydrogen enriched compressed natural gas (HCNG) mixtures. This study focuses on measurement of carbon dioxide, nitrogen oxides, hydrocarbons, carbon monoxide and particulate emissions from HCNG mixtures and compare them with that of baseline compressed natural gas. Hydrogen enriched fuels are prone to higher knocking therefore, experiments were conducted on a single cylinder port fuel injected spark ignition engine prototype using variety of test fuels such as compressed natural gas, 10, 20, 30, 50, 70% HCNG mixtures and hydrogen for in-depth understanding of relative particulates and gaseous emissions, in addition to determining the engine’s knocking characteristics. Experimental results showed that hydrogen enrichment of natural gas reduced emissions of carbon dioxide, hydrocarbons, and carbon monoxide however emissions of nitrogen oxides increased. Lowest knock intensity was observed for 30HCNG mixture. HCNG mixtures improved the engine out emissions and reduced the knocking tendency experienced with hydrogen fueling in internal combustion (IC) engines. Hydrogen enrichment of natural gas also reduced the carbon intensity of fuels, which in-turn reduced greenhouse gas emissions.

Effect of Biodiesel Fuel Injection Timing and Venture for Gaseous Fuel Induction on the Performance, Emissions and Combustion Characteristics of Dual Fuel Engine

Advancing or retarding pilot fuel injection timing in a diesel engine provided with either conventional mechanical fuel injection (CMFIS) or high pressure injection as in common rail fuel injection (CRDI) systems can significantly affect its performance and tail pipe emissions. Performance of diesel engine when fueled with various biofuels as well as gaseous fuels tends to vary with subsequent changes in pilot fuel injection timings. Biodiesel derived from rubber seed oil called Rubber Seed Oil Methyl Ester (RuOME) and hydrogen (H2) and hydrogen enriched compressed natural gas called (HCNG) both being renewable fuels when used in diesel engines modified to operate in dual fuel mode can provide complete replacement for fossil diesel. In the present study, effect of injection timings and venture design for gas mixing on the performance, combustion and emission characteristics of dual fuel engine fitted with both CMFIS and CRDI injection systems and operated on RuOME and HCNG/hydrogen has been investigated. Results showed that high pressure CRDI assisted injection of RuOME with optimized mixing chamber (carburetor)) for hydrogen induction in dual fuel engine performed improved compared to that with CMFIS. In addition, for the same fuel combinations, CRDI resulted in lower biodiesel consumption, lower carbon monoxide (BSCO) and hydrocarbon (BSHC) emissions and increased NOx emissions than CMFIS operation.