Two-Step Concept for Low-Pressure Direct Hydrogen Injection

2009 ◽  
Author(s):  
S. Zanforlin ◽  
T. Poerio ◽  
S. Frigo ◽  
R. Gentili
Keyword(s):  
Direct Injection ◽  
Pressure Rise ◽  
Low Pressure ◽  
Operating Conditions ◽  
Residual Pressure ◽  
Fuel Distribution ◽  
Spark Timing ◽  
Intermediate Chamber ◽  
Air Mixing ◽  
Ignition Region

In this paper, a low-pressure hydrogen direct-injection solution is presented that entails low storage residual pressure (∼12 bar). The injection is realised in two steps. First, hydrogen is simply metered by an electro-injector (a conventional one for Compressed Natural Gas - CNG application) that feeds a small intermediate chamber. Next, hydrogen enters the cylinder by means of a mechanically-actuated valve which allows higher flow than any electro-injector. Injection must end early enough to allow good charge homogeneity and, in any case, before in-cylinder pressure rise constraints hydrogen admission. Backfire is avoided by starting injection at intake valve closing. A prototype has been realised modifying a single-cylinder 650 cc production engine with three intake valves. The central one has been modified and properly timed to in-cylinder inject hydrogen from the intermediate chamber. Hydrogen injection through different-shape poppet valves in a quiescent, constant volume has been simulated in order to investigate the effects of valve and seat-valve geometries in controlling fuel-air mixing in the cylinder. Additional predictions for the actual engine configuration indicate that an acceptable fuel distribution can be obtained in the combustion chamber at the spark timing, with equivalence ratios in the ignition region that are inside the flammability range of the mixture for all the operating conditions (loads and speeds) that have been considered.

scholarly journals Predicting Cycle-to-Cycle Variation With Concurrent Cycles in a Gasoline Direct Injected Engine With Large Eddy Simulations

2018 ◽  
Author(s):  
Daniel Probst ◽  
Sameera Wijeyakulasuriya ◽  
Eric Pomraning ◽  
Janardhan Kodavasal ◽  
Riccardo Scarcelli ◽  
...  
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Engine Performance ◽  
Turnaround Time ◽  
Operating Conditions ◽  
Gasoline Direct Injection ◽  
Cycle Variation ◽  
Spark Timing ◽  
Large Eddy ◽  
Operating Points

High cycle-to-cycle variation (CCV) is detrimental to engine performance, as it leads to poor combustion and high noise and vibration. In this work, CCV in a gasoline engine is studied using large eddy simulation (LES). The engine chosen as the basis of this work is a single-cylinder gasoline direct injection (GDI) research engine. Two stoichiometric part-load engine operating points (6 BMEP, 2000 RPM) were evaluated: a non-dilute (0% EGR) case and a dilute (18% EGR) case. The experimental data for both operating conditions had 500 cycles. The measured CCV in IMEP was 1.40% for the non-dilute case and 7.78% for the dilute case. To estimate CCV from simulation, perturbed concurrent cycles of engine simulations were compared to consecutively obtained engine cycles. The motivation behind this is that running consecutive cycles to estimate CCV is quite time-consuming. For example, running 100 consecutive cycles requires 2–3 months (on a typical cluster), however, by running concurrently one can potentially run all 100 cycles at the same time and reduce the overall turnaround time for 100 cycles to the time taken for a single cycle (2 days). The goal of this paper is to statistically determine if concurrent cycles, with a perturbation applied to each individual cycle at the start, can be representative of consecutively obtained cycles and accurately estimate CCV. 100 cycles were run for each case to obtain statistically valid results. The concurrent cycles began at different timings before the combustion event, with the motivation to identify the closest time before spark to minimize the run time. Only a single combustion cycle was run for each concurrent case. The calculated standard deviation of peak pressure and coefficient of variance (COV) of indicated mean effective pressure (IMEP) were compared between the consecutive and concurrent methods to quantify CCV. It was found that the concurrent method could be used to predict CCV with either a velocity or numerical perturbation. A large and small velocity perturbation were compared and both produced correct predictions, implying that the type of perturbation is not important to yield a valid realization. Starting the simulation too close to the combustion event, at intake valve close (IVC) or at spark timing, under-predicted the CCV. When concurrent simulations were initiated during or before the intake even, at start of injection (SOI) or earlier, distinct and valid realizations were obtained to accurately predict CCV for both operating points. By simulating CCV with concurrent cycles, the required wall clock time can be reduced from 2–3 months to 1–2 days. Additionally, the required core-hours can be reduced up to 41%, since only a portion of each cycle needs to be simulated.

scholarly journals Inter-plume aerodynamics for gasoline spray collapse

2017 ◽  
Vol 19 (10) ◽  
pp. 1048-1067 ◽  
Author(s):  
Panos Sphicas ◽  
Lyle M Pickett ◽  
Scott A Skeen ◽  
Jonathan H Frank
Keyword(s):  
Ambient Temperature ◽  
High Speed ◽  
Direct Injection ◽  
Engine Performance ◽  
Operating Conditions ◽  
Momentum Exchange ◽  
Flow Recirculation ◽  
Plume Region ◽  
Image Velocimetry ◽  
Air Mixing

The collapse or merging of individual plumes of direct-injection gasoline injectors is of fundamental importance to engine performance because of its impact on fuel–air mixing. However, the mechanisms of spray collapse are not fully understood and are difficult to predict. The purpose of this work is to study the aerodynamics in the inter-spray region, which can potentially lead to plume collapse. High-speed (100 kHz) particle image velocimetry is applied along a plane between plumes to observe the full temporal evolution of plume interaction and potential collapse, resolved for individual injection events. Supporting information along a line of sight is obtained using simultaneous diffused back illumination and Mie-scatter techniques. Experiments are performed under simulated engine conditions using a symmetric eight-hole injector in a high-temperature, high-pressure vessel at the “Spray G” operating conditions of the engine combustion network. Indicators of plume interaction and collapse include changes in counter-flow recirculation of ambient gas toward the injector along the axis of the injector or in the inter-plume region between plumes. The effect of ambient temperature and gas density on the inter-plume aerodynamics and the subsequent plume collapse are assessed. Increasing ambient temperature or density, with enhanced vaporization and momentum exchange, accelerates the plume interaction. Plume direction progressively shifts toward the injector axis with time, demonstrating that the plume interaction and collapse are inherently transient.

Investigation of the Effect of Injection and Control Strategies on Combustion Instability in Reactivity-Controlled Compression Ignition Engines

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
David T. Klos ◽  
Sage L. Kokjohn
Keyword(s):  
Direct Injection ◽  
Combustion Instability ◽  
Pressure Rise ◽  
Operating Conditions ◽  
Combustion Stability ◽  
Cfd Modeling ◽  
Surface Model ◽  
Injection Timing ◽  
Compression Ignition ◽  
Reactivity Controlled Compression Ignition

This paper uses detailed computational fluid dynamics (CFD) modeling with the kiva-chemkin code to investigate the influence of injection timing, combustion phasing, and operating conditions on combustion instability. Using detailed CFD simulations, a large design of experiments (DOE) is performed with small perturbations in the intake and fueling conditions. A response surface model (RSM) is then fit to the DOE results to predict cycle-to-cycle combustion instability. Injection timing had significant tradeoffs between engine efficiency, emissions, and combustion instability. Near top dead center (TDC) injection timing can significantly reduce combustion instability, but the emissions and efficiency drop close to conventional diesel combustion levels. The fuel split between the two direct injection (DI) injections has very little effect on combustion instability. Increasing exhaust gas recirculation (EGR) rate, while making adjustments to maintain combustion phasing, can significantly reduce peak pressure rise rate (PPRR) variation until the engine is on the verge of misfiring. Combustion phasing has a very large impact on combustion instability. More advanced phasing is much more stable, but produces high PPRRs, higher NOx levels, and can be less efficient due to increased heat transfer losses. The results of this study identify operating parameters that can significantly improve the combustion stability of dual-fuel reactivity-controlled compression ignition (RCCI) engines.

Numerical and experimental study on knocking combustion in turbocharged direct-injection engines for a wide range of operating conditions

2021 ◽  
pp. 146808742110601
Author(s):  
Magnus Kircher ◽  
Emmeram Meindl ◽  
Christian Hasse
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Numerical Study ◽  
Direct Injection ◽  
Operating Conditions ◽  
Auto Ignition ◽  
Spark Timing ◽  
Crank Angle ◽  
Wide Range ◽  
The Mean

A combined experimental and numerical study is conducted on knocking combustion in turbocharged direct-injection spark-ignition engines. The experimental study is based on parameter variations in the intake-manifold temperature and pressure, as well as the air-fuel equivalence ratio. The transition between knocking and non-knocking operating conditions is studied by conducting a spark timing sweep for each operating parameter. By correlating combustion and global knock quantities, the global knock trends of the mean cycles are identified. Further insight is gained by a detailed analysis based on single cycles. The extensive experimental data is then used as an input to support numerical investigations. Based on 0D knock modeling, the global knock trends are investigated for all operation points. Taking into consideration the influence of nitric oxide on auto-ignition significantly improves the knock model prediction. Additionally, the origin of the observed cyclic variability of knock is investigated. The crank angle at knock onset in 1000 consecutive single cycles is determined using a multi-cycle 0D knock simulation based on detailed single-cycle experimental data. The overall trend is captured well by the simulation, while fluctuations are underpredicted. As one potential reason for the remaining differences of the 0D model predictions local phenomena are investigated. Therefore, 3D CFD simulations of selected operating points are performed to explore local inhomogeneities in the mixture fraction and temperature. The previously developed generalized Knock Integral Method (gKIM), which considers the detailed kinetics and turbulence-chemistry interaction of an ignition progress variable, is improved and applied. The determined influence of spark timing on the mean crank angle at knock onset agrees well with experimental data. In addition, spatially resolved information on the expected position of auto-ignition is analyzed to investigate causes of knocking combustion.

Numerical Investigation on Mixture Formation of Two-Stroke LPG Direct Injection Engine Used as Range Extender for Electric Car

2016 ◽  
Author(s):  
B. Y. Xu ◽  
Y. L. Qi ◽  
C. D. Sun ◽  
J. Z. Ma
Keyword(s):  
High Speed ◽  
Direct Injection ◽  
Power Source ◽  
Calculation Model ◽  
Injection Timing ◽  
Mixture Formation ◽  
Range Extender ◽  
Electric Car ◽  
Spark Timing ◽  
Air Mixing

The two-stroke DI engine has distinct advantages such as high speed, high power density, and simple structure . LPG has a low boiling point and high saturation vapor pressure, which is very helpful in accelerating the fuel-air mixing. Owing to these characteristics and advantages, the two-stroke LPG engine is generally regarded as the preferred power source of the generator unit for extended-range electrical vehicles. The process of mixture formation is numerically simulated after the calculation model is validated by results from optical experiments. The results show that, under conditions of avoidance of fuel short-circuiting, an injection timing of 50° CA ABDC for engine start and warming (2000 rpm), and an 40° CA ABDC for running as the power source of the generator (4800 rpm) are appropriate. Further analysis of the velocity and concentration fields shows that the fresh mixture is locked in the cylinder when the exhaust port is closed (73° CA ABDC) and the homogeneous mixture can be formed at spark timing.

Combustion Characteristics of Compressed Natural Gas in a Direct Microchannel-Injection Engine under Various Operating Conditions

2013 ◽  
Vol 315 ◽  
pp. 793-798
Author(s):  
Taib Iskandar Mohamad ◽  
How Heoy Geok
Keyword(s):  
Natural Gas ◽  
Ignition Delay ◽  
Direct Injection ◽  
Pressure Rise ◽  
Injection Pressure ◽  
Combustion Characteristics ◽  
Operating Conditions ◽  
Fuel Injector ◽  
Compressed Natural Gas ◽  
Operation Conditions

The combustion characteristics of compressed natural gas (CNG) in a direct microchannel-injection engine under various operating conditions were investigated. In this study, a novel idea for direct CNG microchannel injection was realized with spark plug fuel injector (SPFI). It is a device developed to convert engine to CNG direct injection (DI) operation with minimal cost and technical simplicity. It was installed and tested on a Ricardo E6 single cylinder engine with compression ratio of 10.5:1 without modification on the original engine structure. The engine test was carried out under various operation conditions at 1100 rpm. Burning rates of CNG were measured using normalized combustion pressure method by which the normalized pressure rise due to combustion is equivalent to the mass fraction burned (MFB) at the specific crank angle. The results showed that the MFB of CNG direct injection is substantially faster but initially slower than the ones of port injection. The optimal fuel injection and ignition timings are 190 °CA ATDC and 25 °CA BTDC respectively. The optimal injection pressure was 6 MPa. Combustion durations were not changed with different injection pressures but ignition delay was affected. There was no direct correlation between injection pressure and ignition delay which is most probably due to the effect of charge flow difference. Changing mixture stoichiometry affects the magnitude of ignition delay. Combustion duration, on the other hand increases with leaner mixture.

Prediction of gaseous pollutant emissions from a spark-ignition direct-injection engine with gas-exchange simulation

2021 ◽  
pp. 146808742110050
Author(s):  
Stefania Esposito ◽  
Lutz Diekhoff ◽  
Stefan Pischinger
Keyword(s):  
Gas Exchange ◽  
Combustion Chamber ◽  
Direct Injection ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Operating Parameters ◽  
Gaseous Pollutant ◽  
Fuel Ratio ◽  
No Emissions

With the further tightening of emission regulations and the introduction of real driving emission tests (RDE), the simulative prediction of emissions is becoming increasingly important for the development of future low-emission internal combustion engines. In this context, gas-exchange simulation can be used as a powerful tool for the evaluation of new design concepts. However, the simplified description of the combustion chamber can make the prediction of complex in-cylinder phenomena like emission formation quite challenging. The present work focuses on the prediction of gaseous pollutants from a spark-ignition (SI) direct injection (DI) engine with 1D–0D gas-exchange simulations. The accuracy of the simulative prediction regarding gaseous pollutant emissions is assessed based on the comparison with measurement data obtained with a research single cylinder engine (SCE). Multiple variations of engine operating parameters – for example, load, speed, air-to-fuel ratio, valve timing – are taken into account to verify the predictivity of the simulation toward changing engine operating conditions. Regarding the unburned hydrocarbon (HC) emissions, phenomenological models are used to estimate the contribution of the piston top-land crevice as well as flame wall-quenching and oil-film fuel adsorption-desorption mechanisms. Regarding CO and NO emissions, multiple approaches to describe the burned zone kinetics in combination with a two-zone 0D combustion chamber model are evaluated. In particular, calculations with reduced reaction kinetics are compared with simplified kinetic descriptions. At engine warm operation, the HC models show an accuracy mainly within 20%. The predictions for the NO emissions follow the trend of the measurements with changing engine operating parameters and all modeled results are mainly within ±20%. Regarding CO emissions, the simplified kinetic models are not capable to predict CO at stoichiometric conditions with errors below 30%. With the usage of a reduced kinetic mechanism, a better prediction capability of CO at stoichiometric air-to-fuel ratio could be achieved.

Effect of altitude conditions on combustion and performance of a turbocharged direct-injection diesel engine

2021 ◽  
pp. 095440702110262
Author(s):  
Zhentao Liu ◽  
Jinlong Liu
Keyword(s):  
Diesel Engine ◽  
High Altitude ◽  
Diesel Engines ◽  
Direct Injection ◽  
Pressure Rise ◽  
Ambient Conditions ◽  
Allowable Limit ◽  
Spray Formation ◽  
Direct Injection Diesel Engine ◽  
And Performance

Market globalization necessitates the development of heavy duty diesel engines that can operate at altitudes up to 5000 m without significant performance deterioration. But the current scenario is that existing studies on high altitude effects are still not sufficient or detailed enough to take effective measures. This study applied a single cylinder direct injection diesel engine with simulated boosting pressure to investigate the performance degradation at high altitude, with the aim of adding more knowledge to the literature. Such a research engine was conducted at constant speed and injection strategy but different ambient conditions from sea level to 5000 m in altitude. The results indicated the effects of altitude on engine combustion and performance can be summarized as two aspects. First comes the extended ignition delay at high altitude, which would raise the rate of pressure rise to a point that can exceed the maximum allowable limit and therefore shorten the engine lifespan. The other disadvantage of high-altitude operation is the reduced excess air ratio and gas density inside cylinder. Worsened spray formation and mixture preparation, together with insufficient and late oxidation, would result in reduced engine efficiency, increased emissions, and power loss. The combustion and performance deteriorations were noticeable when the engine was operated above 4000 m in altitude. All these findings support the need for further fundamental investigations of in-cylinder activities of diesel engines working at plateau regions.

scholarly journals Improving Blowout Performance of the Conical Swirler Combustor by Employing Two Parts of Fuel at Low Operating Condition

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1681
Author(s):  
Yixiang Yuan ◽  
Qinghua Zeng ◽  
Jun Yao ◽  
Yongjun Zhang ◽  
Mengmeng Zhao ◽  
...  
Keyword(s):  
Distribution Ratio ◽  
Performance Enhancement ◽  
Experimental Testing ◽  
Stability Boundary ◽  
Operating Conditions ◽  
Nox Emission ◽  
Combustion Stability ◽  
Gas Temperature ◽  
Contact Ratio ◽  
Fuel Distribution

Aiming at the problem of the narrow combustion stability boundary, a conical swirler was designed and constructed based on the concept of fuel distribution. The blowout performance was studied at specified low operating conditions by a combination of experimental testing and numerical simulations. Research results indicate that the technique of the fuel distribution can enhance the combustion stability and widen the boundary of flameout within the range of testing conditions. The increase of the fuel distribution ratio improves the combustion stability but leads to an increase in NOx emission simultaneously. The simulation results show the increase of the fuel distribution ratio causes contact ratio increase in the area of lower reference velocity and gas temperature increase. The increased contact ratio and temperature contribute to the blowout performance enhancement, which is identical to the analysis result of the Damkohler number. The reported work in this paper has potential application value for the development of an industrial burner and combustor with high stability and low NOx emission, especially when the combustion system is required to be stable and efficient at low working conditions.

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