The Experts below are selected from a list of 204 Experts worldwide ranked by ideXlab platform
Alberto Boretti - One of the best experts on this subject based on the ideXlab platform.
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Latest concepts for combustion and waste heat recovery systems being considered for Hydrogen Engines
International Journal of Hydrogen Energy, 2013Co-Authors: Alberto BorettiAbstract:A more sustainable transportation calls for the use of alternative and renewable fuels, a further increase of the fuel energy conversion efficiency of internal combustion Engines as well as the reduction of the thermal engine energy supply by recovering the braking energy. The paper presents two concepts being developed to improve the fuel conversion efficiency of internal combustion Engines for transport applications. The first concept works on the combustion evolution to increase the amount of fuel energy transformed in piston work within the cylinder. The second concept works on the waste exhaust and coolant energies to be recovered through a power turbine downstream of the turbocharger turbine on the exhaust line and a steam turbine feed with the steam produced by a boiler/super heater made of the coolant passages and a heat exchanger on the exhaust line. The concepts work with Hydrogen (and in this case a water injector is also necessary) as well as lower alkanes (methane, propane, butane). Preliminary simulations show improvement of top fuel conversion efficiencies to above 50% in the high power density operation. The waste heat recovery system also permits faster warm-up during cold start driving cycles.
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Simulations of Multi Combustion Modes Hydrogen Engines for Heavy Duty Trucks
International Journal of Engineering and Technology Innovation, 2012Co-Authors: Alberto BorettiAbstract:The paper presents the numerical study of a diesel direct injection heavy duty truck engine converted to Hydrogen. The engine has a power turbine connected through a clutch and a continuously variable transmission to the crankshaft. The power turbine may be disconnected and by-passed when it is inefficient or inconvenient to use. The conversion is obtained by replacing the Diesel injector with a Hydrogen injector and the glow plug with a jet ignition device. The Hydrogen engine operates different modes of combustion depending on the relative phasing of the main injection and the jet ignition. The engine generally operates mostly in Diesel-like mode, with the most part of the main injection following the suitable creation in cylinder conditions by jet ignition. For medium-low loads, better efficienciy is obtained with the gasoline-like mode jet igniting the premixed homogeneous mixture at top dead centre. It’s permitted at higher loads or at very low loads for the excessive peak pressure or the mixture too lean to burn rapidly. The Hydrogen engine has better efficiency than Diesel outputs and fuel conversion. Thanks to the larger rate of heat release, it has the opportunity to run closer to stoichiometry and the multi mode capabilities. The critical area for this engine development is found in the design of a Hydrogen injector delivering the amount of fuel needed to the large volume cylinder within a Diesel-like injection time.
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Stoichiometric H2ICEs with water injection
International Journal of Hydrogen Energy, 2011Co-Authors: Alberto BorettiAbstract:For the most part, gasoline Engines operate close to stoichiometry because of the high power density and the easy after treatment through the very well established three-way catalytic converter technology. The lean burn gasoline engine suffers major disadvantages for the after treatment still requiring aggressive research and development to meet future emission standards more than for the lower power density compensated by the better fuel conversion efficiency running lean. Hydrogen Engines are usually run ultra-lean to avoid abnormal combustion phenomena and possibly to avoid the emission of nitrogen oxides without the difficult non-stoichiometric after treatment. While the ultra-lean combustion of Hydrogen may reduce the formation of NOx within the cylinder but makes the power density very low, the only lean combustion of Hydrogen requires after treatment for NOx reduction. The suppression of abnormal combustion in Hydrogen Engines has been a challenge for the three regimes of abnormal combustion, knock (auto ignition of the end gas region), pre-ignition (uncontrolled ignition induced by a hot spot prior of the spark ignition) and backfire (premature ignition during the intake stroke, which could be seen as an early form of pre-ignition). Direct injection and jet ignition coupled to port water injection are used here to avoid the occurrence of all these abnormal combustion phenomena as well as to control the temperature of gases to turbine in a turbocharged stoichiometric Hydrogen engine.
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Comparison of fuel economies of high efficiency diesel and Hydrogen Engines powering a compact car with a flywheel based kinetic energy recovery systems
International Journal of Hydrogen Energy, 2010Co-Authors: Alberto BorettiAbstract:Abstract Coupling of small turbocharged high efficiency diesel Engines with flywheel based kinetic energy recovery systems is the best option now available to reduce fuel energy usage and reduce green house gas (GHG) emissions. The paper describes engine and vehicle models to generate engine brake specific fuel consumption maps and compute vehicle fuel economies over driving cycles, and applies these models to evaluate the benefits of a H 2 ICEs developed with the direct injection jet ignition engine concept to further reduce the fuel energy usage of a compact car equipped with a with a flywheel based kinetic energy recovery systems. The car equipped with a 1.2 L TDI Diesel engine and KERS consumes 25 g/km of fuel producing 79.2 g/km of CO 2 using 1.09 MJ/km of fuel energy. These CO 2 and fuel energy values are more than 10% better than those of today’s best hybrid electric vehicle. The car equipped with a 1.6 L DI-JI H 2 ICE engine consumes 8.3 g/km of fuel, corresponding to only 0.99 MJ/km of fuel energy.
Baigang Sun - One of the best experts on this subject based on the ideXlab platform.
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Visualization research on Hydrogen jet characteristics of an outward-opening injector for direct injection Hydrogen Engines
Fuel, 2020Co-Authors: Xi Wang, Qinghe Luo, Baigang Sun, Ling-zhi Bao, Jie LiuAbstract:Abstract The Hydrogen jet characteristics have effect on the performance of direction injector (DI) Hydrogen Engines because they can influence the process of mixture formation and heat release. In this study, the Hydrogen jet characteristics of an outward-opening injector were studied with high-speed schlieren imaging in a constant volume chamber at different injection and ambient pressure ratios (PRs), which ranged from 10 to 140. Results show that the Hydrogen jet in the near-field is a conical structure, while the jet structure develops into a spherical vortex in the far-field. The jet axial penetration, radial penetration, and volume increase with the increasing of the PR. The jet spread angle is not sensitive to the PR except for the low PRs. The entrainment rate decreases with the increasing of the PR. The normalization analysis of jet penetration shows that the Hydrogen jets have a good self-similarity under all PRs. A non-dimensional scaling correlation of axial penetration is proposed for this kind of Hydrogen jets. In the scaling correlation, the exponents of the non-dimensional penetration and time term are 0.18 and 0.83, while the penetration constant is 13.18. The discovery of the above jet characteristics can predict the free jet shape under any PR in the range of 10 to140. These results can also promote the application of DI Hydrogen Engines.
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Effect of equivalence ratios on the power, combustion stability and NOx controlling strategy for the turbocharged Hydrogen engine at low engine speeds
International Journal of Hydrogen Energy, 2019Co-Authors: Qinghe Luo, Baigang Sun, Xi Wang, Fushui Liu, Ling-zhi BaoAbstract:Abstract Increase the equivalence ratio is a good way to improve performance of turbocharged Hydrogen Engines at low engine speeds. To explore the feasibility of this strategy, this paper investigated the experimental data of a 2.3 L turbocharged port fuel injection (PFI) Hydrogen engine at 1500 rpm and 2000 rpm. The results showed that the power can increase from 6.8 kW to 21 kW at 2000 rpm and from 6.4 kW to 16.5 kW at 1500 rpm with increasing of the equivalence ratio. However, the equivalence ratio corroding to the biggest power is 0.8 at 1500 rpm and 0.9 at 2000 rpm because the turbocharged pressure and the volumetric efficiency at 2000 rpm are higher than the ones at 1500 rpm. The biggest BTE can reach to 30.1% at 2000 rpm and 29.3% at 1500 rpm within the range of 0.65–0.8. The covariance of indicated mean effective pressure (CoVimep) of turbocharged Hydrogen is lower than 1.5% at low engine speeds and the combustion stability increased with the increase of equivalence ratio. The NOx can be reduced from 877 ppm to 0 ppm at 1500 rpm and from 1259 ppm to 17 ppm at 2000 rpm, which means the reduction efficiency of H2+TWC can exceed 99%.
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inducing factors and frequency of combustion knock in Hydrogen internal combustion Engines
International Journal of Hydrogen Energy, 2016Co-Authors: Qinghe Luo, Baigang SunAbstract:Abstract Hydrogen is a promising energy carrier, and the port fuel injection (PFI) is a fuel-flexible, durable, and relatively cheap method of energy conversion. However, combustion knock as an abnormal combustion phenomenon does not only limit the brake torque and thermal efficiency, but also breaks the piston or Engines. This paper uses a four-stoke cycle, displacement of 2.0 L PFI Hydrogen internal combustion engine and a calculated model to study the inducing factors and frequency of combustion knock. Results showed that combustion knock occurs at relatively higher engine speed (more than 3000 r/min) than the engine speed occurring knock of gasoline engine. The calculated average temperatures of air–fuel mixture at the end of combustion using thermodynamics dual zone model fall in the range of 1000–1100 K for Hydrogen Engines, which are higher than gasoline ones (about 200 K). Knock and the other abnormal combustion phenomena (backfire and pre-ignite) interact with each other. When the backfire generates, the components in the cylinder will be heated. In the next cycle, the components of the cylinder will release heat to the intake, which can increase the initial temperature at ignition. The high initial temperature will lead to the combustion knock. Otherwise, because of the combustion knock, the temperatures of cylinder components will increase, which generates hot spots and ultimately causes pre-ignite and backfire. Through the figures of Fast Fourier Transform (FFT) amplitude, the frequency of Hydrogen Engines is higher than gasoline ones for every kind of mode. The pressure waves of combustion knock spread with radial direction for light combustion knock and with circumferential direction for heavy combustion knock. These conclusions can be used to explore the working conditions close to combustion knock to achieve higher thermal efficiency and provide a guidance to detect the knock in Hydrogen engine.
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effect of the miller cycle on the performance of turbocharged Hydrogen internal combustion Engines
Energy Conversion and Management, 2016Co-Authors: Qinghe Luo, Baigang SunAbstract:Abstract Hydrogen is a promising energy carrier, and the port fuel injection (PFI) is a fuel-flexible, durable, and relatively cheap method of energy conversion. However, the contradiction of increasing the power density and controlling NOx emissions limits the wide application of PFI Hydrogen internal combustion Engines. To address this issue, two typical thermodynamic cycles—the Miller and Otto cycles—are studied based on the calculation model proposed in this study. The thermodynamic cycle analyses of the two cycles are compared and results show that the thermal efficiency of the Miller cycle (ηMiller) is higher than ηOtto, when the multiplied result of the inlet pressure and Miller cycle coefficient (δMγM) is larger than that of the Otto cycle (i.e., the value of the inlet pressure ratio multiplied by the Miller cycle coefficient is larger than the value of the inlet pressure ratio of the Otto cycle). The results also show that the intake valve closure (IVC) of the Miller cycle is limited by the inlet pressure and valve lift. The two factors show the boundaries of the Miller cycle in increasing the power density of the turbocharged PFI Hydrogen engine. The ways of lean burn + Otto cycle (LO), stoichiometric equivalence ratio burn + EGR + Otto cycle (SEO) and Miller cycle in turbocharged Hydrogen engine are compared, the results show that the Miller cycle has the highest power density and the lowest BSFC among the three methods at an engine speed of 2800 rpm and NOx emissions below 100 ppm. The brake power of the Miller cycle increases by 37.7% higher than that of the LO and 26.3% higher than that of SEO, when γM is 0.7. The BSFC of the Miller cycle decreases by 16% lower than that of the LO and 22% lower than that of SEO. However, the advantage of the Miller cycle decreases with an increase in engine speed. These findings can be used as guidelines in developing turbocharged PFI Hydrogen Engines with the Miller cycle and indicate the boundaries for the development of new Hydrogen Engines.
Qinghe Luo - One of the best experts on this subject based on the ideXlab platform.
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Visualization research on Hydrogen jet characteristics of an outward-opening injector for direct injection Hydrogen Engines
Fuel, 2020Co-Authors: Xi Wang, Qinghe Luo, Baigang Sun, Ling-zhi Bao, Jie LiuAbstract:Abstract The Hydrogen jet characteristics have effect on the performance of direction injector (DI) Hydrogen Engines because they can influence the process of mixture formation and heat release. In this study, the Hydrogen jet characteristics of an outward-opening injector were studied with high-speed schlieren imaging in a constant volume chamber at different injection and ambient pressure ratios (PRs), which ranged from 10 to 140. Results show that the Hydrogen jet in the near-field is a conical structure, while the jet structure develops into a spherical vortex in the far-field. The jet axial penetration, radial penetration, and volume increase with the increasing of the PR. The jet spread angle is not sensitive to the PR except for the low PRs. The entrainment rate decreases with the increasing of the PR. The normalization analysis of jet penetration shows that the Hydrogen jets have a good self-similarity under all PRs. A non-dimensional scaling correlation of axial penetration is proposed for this kind of Hydrogen jets. In the scaling correlation, the exponents of the non-dimensional penetration and time term are 0.18 and 0.83, while the penetration constant is 13.18. The discovery of the above jet characteristics can predict the free jet shape under any PR in the range of 10 to140. These results can also promote the application of DI Hydrogen Engines.
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Effect of equivalence ratios on the power, combustion stability and NOx controlling strategy for the turbocharged Hydrogen engine at low engine speeds
International Journal of Hydrogen Energy, 2019Co-Authors: Qinghe Luo, Baigang Sun, Xi Wang, Fushui Liu, Ling-zhi BaoAbstract:Abstract Increase the equivalence ratio is a good way to improve performance of turbocharged Hydrogen Engines at low engine speeds. To explore the feasibility of this strategy, this paper investigated the experimental data of a 2.3 L turbocharged port fuel injection (PFI) Hydrogen engine at 1500 rpm and 2000 rpm. The results showed that the power can increase from 6.8 kW to 21 kW at 2000 rpm and from 6.4 kW to 16.5 kW at 1500 rpm with increasing of the equivalence ratio. However, the equivalence ratio corroding to the biggest power is 0.8 at 1500 rpm and 0.9 at 2000 rpm because the turbocharged pressure and the volumetric efficiency at 2000 rpm are higher than the ones at 1500 rpm. The biggest BTE can reach to 30.1% at 2000 rpm and 29.3% at 1500 rpm within the range of 0.65–0.8. The covariance of indicated mean effective pressure (CoVimep) of turbocharged Hydrogen is lower than 1.5% at low engine speeds and the combustion stability increased with the increase of equivalence ratio. The NOx can be reduced from 877 ppm to 0 ppm at 1500 rpm and from 1259 ppm to 17 ppm at 2000 rpm, which means the reduction efficiency of H2+TWC can exceed 99%.
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inducing factors and frequency of combustion knock in Hydrogen internal combustion Engines
International Journal of Hydrogen Energy, 2016Co-Authors: Qinghe Luo, Baigang SunAbstract:Abstract Hydrogen is a promising energy carrier, and the port fuel injection (PFI) is a fuel-flexible, durable, and relatively cheap method of energy conversion. However, combustion knock as an abnormal combustion phenomenon does not only limit the brake torque and thermal efficiency, but also breaks the piston or Engines. This paper uses a four-stoke cycle, displacement of 2.0 L PFI Hydrogen internal combustion engine and a calculated model to study the inducing factors and frequency of combustion knock. Results showed that combustion knock occurs at relatively higher engine speed (more than 3000 r/min) than the engine speed occurring knock of gasoline engine. The calculated average temperatures of air–fuel mixture at the end of combustion using thermodynamics dual zone model fall in the range of 1000–1100 K for Hydrogen Engines, which are higher than gasoline ones (about 200 K). Knock and the other abnormal combustion phenomena (backfire and pre-ignite) interact with each other. When the backfire generates, the components in the cylinder will be heated. In the next cycle, the components of the cylinder will release heat to the intake, which can increase the initial temperature at ignition. The high initial temperature will lead to the combustion knock. Otherwise, because of the combustion knock, the temperatures of cylinder components will increase, which generates hot spots and ultimately causes pre-ignite and backfire. Through the figures of Fast Fourier Transform (FFT) amplitude, the frequency of Hydrogen Engines is higher than gasoline ones for every kind of mode. The pressure waves of combustion knock spread with radial direction for light combustion knock and with circumferential direction for heavy combustion knock. These conclusions can be used to explore the working conditions close to combustion knock to achieve higher thermal efficiency and provide a guidance to detect the knock in Hydrogen engine.
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effect of the miller cycle on the performance of turbocharged Hydrogen internal combustion Engines
Energy Conversion and Management, 2016Co-Authors: Qinghe Luo, Baigang SunAbstract:Abstract Hydrogen is a promising energy carrier, and the port fuel injection (PFI) is a fuel-flexible, durable, and relatively cheap method of energy conversion. However, the contradiction of increasing the power density and controlling NOx emissions limits the wide application of PFI Hydrogen internal combustion Engines. To address this issue, two typical thermodynamic cycles—the Miller and Otto cycles—are studied based on the calculation model proposed in this study. The thermodynamic cycle analyses of the two cycles are compared and results show that the thermal efficiency of the Miller cycle (ηMiller) is higher than ηOtto, when the multiplied result of the inlet pressure and Miller cycle coefficient (δMγM) is larger than that of the Otto cycle (i.e., the value of the inlet pressure ratio multiplied by the Miller cycle coefficient is larger than the value of the inlet pressure ratio of the Otto cycle). The results also show that the intake valve closure (IVC) of the Miller cycle is limited by the inlet pressure and valve lift. The two factors show the boundaries of the Miller cycle in increasing the power density of the turbocharged PFI Hydrogen engine. The ways of lean burn + Otto cycle (LO), stoichiometric equivalence ratio burn + EGR + Otto cycle (SEO) and Miller cycle in turbocharged Hydrogen engine are compared, the results show that the Miller cycle has the highest power density and the lowest BSFC among the three methods at an engine speed of 2800 rpm and NOx emissions below 100 ppm. The brake power of the Miller cycle increases by 37.7% higher than that of the LO and 26.3% higher than that of SEO, when γM is 0.7. The BSFC of the Miller cycle decreases by 16% lower than that of the LO and 22% lower than that of SEO. However, the advantage of the Miller cycle decreases with an increase in engine speed. These findings can be used as guidelines in developing turbocharged PFI Hydrogen Engines with the Miller cycle and indicate the boundaries for the development of new Hydrogen Engines.
Eiji Tomita - One of the best experts on this subject based on the ideXlab platform.
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improvement of thermal efficiency and reduction of nox emissions by burning a controlled jet plume in high pressure direct injection Hydrogen Engines
International Journal of Hydrogen Energy, 2017Co-Authors: Yasuo Takagi, Nobuyuki Kawahara, Hiroki Mori, Yuji Mihara, Eiji TomitaAbstract:Abstract A new combustion process called the Plume Ignition Combustion Concept (PCC), in which the plume tail of the Hydrogen jet is spark-ignited immediately after the completion of fuel injection to accomplish combustion of a rich mixture has been proposed by the authors. This PCC combustion process markedly reduces nitrogen oxides (NOx) emissions in the high-output region while maintaining high levels of thermal efficiency and power. On the other hand, as burning lean mixture of fuel and air is the conventional way to improve thermal efficiency and reduce NOx, a high λ premixed mixture of Hydrogen and air formed by injecting Hydrogen in the early stage of the compression stroke has been used in direct-injection Hydrogen Engines. It was recently reported, however, that this mixture condition does not always offer expected improved thermal efficiency under even lean mixture conditions by increasing unburned Hydrogen emissions caused by incomplete flame propagation in the non-uniform and extremely lean portion of the mixture. In this study, the effect of retarding the injection timing to late in the compression stroke but slightly advanced from original PCC was examined as a way of reducing unburned Hydrogen emissions and improving thermal efficiency. These effects result from a centroidal axially stratified mixture that positions a fairly rich charge near the spark plug. This stratified mixture is presumably effective in reducing incomplete flame propagation thought to be the cause of unburned Hydrogen emissions and also promoting increasing burning velocity of the mixture that improve thermal efficiency. Finally, this research is characterized by measuring the Hydrogen fuel concentration at the point and the time of spark ignition quantitatively by spark-induced breakdown spectroscopy in order to identify the changes in mixture ratio mentioned above caused by the parameters involved.
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Jet-guided combustion characteristics and local fuel concentration measurements in a Hydrogen direct-injection spark-ignition engine
Proceedings of the Combustion Institute, 2012Co-Authors: Nobuyuki Kawahara, Eiji Tomita, Takashi FujitaniAbstract:Abstract Spark-ignition (SI) Hydrogen Engines based on direct injection (DI) promise significant advantages in terms of thermal efficiency and power output, and present a means of overcoming problems related to knocking, backfiring, and preignition. A better understanding of the effects of Hydrogen jets on the fuel concentration distribution and mixing process in a DISI engine should provide new and useful insights into combustion optimization. The objective of the present work was to gain a deeper comprehension of the characteristics of late-injection Hydrogen combustion. An experimental combustion setup was applied to a fired, jet-guided DISI engine operated at 600 rpm in stratified mode. GDI injector with the jet directed toward the spark plug was used to develop the stratified combustion concept. A high-speed camera synchronized with the spark was focused on a 52 mm-diameter field of view through a window at the bottom of the piston crown. A series of single-shot images captured at different intervals was used to study the time evolution of the flame distribution. Variations in the fuel injection timing relative ignition timing were found to impact the development of the early flame, as well as the flame propagation. This research also employed spark-induced breakdown spectroscopy (SIBS) to measure the local fuel–air concentration in the spark gap at the time of ignition under stratified-charge conditions.
Ghazi A. Karim - One of the best experts on this subject based on the ideXlab platform.
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Knock in spark ignition Hydrogen Engines
International Journal of Hydrogen Energy, 2004Co-Authors: Ghazi A. KarimAbstract:In engine applications, the onset of knock remains one of the prime limitations that needs to be addressed so as to avoid its incidence and achieve superior performance. In the present contribution relating to the spark ignition Hydrogen-fuelled engine, the effects of changes in key operating variables, such as compression ratio, intake temperature and spark timing on knock-limiting equivalence ratios are established both analytically as well as experimentally. Some other factors considered included the optimization of spark timing for maximum indicated power output and/or efficiency and for the avoidance of knock while maintaining high thermal efficiency values.
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Hydrogen fueled spark ignition Engines predictive and experimental performance
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2003Co-Authors: Ghazi A. KarimAbstract:Hydrogen is well recognized as a suitable fuel for spark-ignition engine applications that has many unique attractive features and limitations. It is a fuel that can continue potentially to meet the ever-increasingly stringent regulations for exhaust and greenhouse gas emissions. The application of Hydrogen as an engine fuel has been tried over many decades by numerous investigators with varying degrees of success. However, the performance data reported often tend not to display consistent agreement between the various investigators, mainly because of the wide differences in engine type, size, operating conditions used, and the differing criteria employed to judge whether knock is taking place or not. With the ever-increasing interest in Hydrogen as an engine fuel, there is a need to be able to model extensively various features of the performance of spark ignition (S.I.) Hydrogen Engines so as to investigate and compare reliably the performance of widely different Engines under a wide variety of operating conditions. In the paper we employ a quasidimensional two-zone model for the operation of S.I. Engines when fueled with Hydrogen. In this approach, the engine combustion chamber at any instant of time during combustion is considered to be divided into two temporally varying zones: a burned zone and an unburned zone. The model incorporates a detailed chemical kinetic model scheme of 30 reaction steps and 12 species, to simulate the oxidation reactions of Hydrogen in air. A knock prediction model, developed previously for S.I. methane-Hydrogen fueled engine applications was extended to consider operation on Hydrogen. The effects of changes in operating conditions, including a very wide range of variations in the equivalence ratio on the onset of knock and its intensity, combustion duration, power, efficiency, and operational limits were investigated. The results of this predictive approach were shown to validate well against the corresponding experimental results, obtained mostly in a variable compression ratio CFR engine. On this basis, the effects of changes in some of the key operational engine variables, such as compression ratio, intake temperature, and spark timing are presented and discussed. Some guidelines for superior knock-free operation of Engines on Hydrogen are also made.
