Intake Gas Research Articles

Calculation of mass emissions, oxygen mass fraction and thermal capacity of the inducted charge in SI and diesel engines from exhaust and intake gas analysis

New computational procedures are proposed for experimentally evaluating air–fuel ratio and mass fractions of exhaust emissions as well as EGR rate, oxygen mass fraction and thermal capacity of the inducted charge in IC engines running with diesel oil, gasoline or any alternative liquid or gaseous fuel, such as LPG or CNG. Starting from the chemical reaction of fuel with air, from gaseous and smoke level measurements in the raw gases, the procedures calculate the volume fractions of oxygen in the combustion air and of compounds in the exhaust gases, including those that are not usually measured, such as water, nitrogen and hydrogen. The methods also take the effects of various fuel and combustion air compositions into account, as well as to the presence of water vapor, CO 2, Ar and He in the combustion air. The algorithms are applied to four different automotive engines under wide ranges of steady-state operating conditions: three turbocharged diesel engines featuring high-pressure cooled EGR systems, and an SI naturally aspirated bi-fuel engine running on either gasoline or CNG. The computed air–fuel ratios are compared to those obtained from directly measured air and fuel mass-flow rates as well as from more conventional UEGO sensor data. The mass emissions are worked out in terms of both brake specific mass emissions and emission indexes of each pollutant species, and the results are compared to those obtained by applying SAE and ISO recommended practices. The computed oxygen mass fraction of the inducted charge was then compared to that derived from direct measurement of O 2 concentration in inlet manifold. Finally, the sensitivity of results to the main engine working parameters, the influence of environmental conditions (in particular the effect of air humidity on NO x formation) and the experimental uncertainties are determined.

Effect of hydrogen addition on combustion and emissions performance of a spark-ignited ethanol engine at idle and stoichiometric conditions

Regarding the limited fossil fuel reserves, the renewable ethanol has been considered as one of the substitutional fuels for spark ignition (SI) engines. But due to its high latent heat, ethanol is usually hard to be well evaporated to form the homogeneous fuel–air mixture at low temperatures, e.g., at idle condition. Compared with ethanol, hydrogen possesses many unique combustion and physicochemical properties that help improve combustion process. In this paper, the performance of a hydrogen-enriched SI ethanol engine under idle and stoichiometric conditions was investigated. The experiment was performed on a modified 1.6 L SI engine equipped with a hydrogen port-injection system. The ethanol was injected into the intake ports using the original engine gasoline injection system. A self-developed hybrid electronic control unit (HECU) was adopted to govern the opening and closing of hydrogen and ethanol injectors. The spark timing and idle bypass valve opening were governed by the engine original electronic control unit (OECU), so that the engine could operate under its original target idle speed for each testing point. The engine was first fueled with the pure ethanol and then hydrogen volume fraction in the total intake gas was gradually increased through increasing hydrogen injection duration. For a specified hydrogen addition level, ethanol flow rate was reduced to keep the hydrogen–ethanol–air mixture at stoichiometric condition. The test results showed that hydrogen addition was effective on reducing cyclic variations and improving indicated thermal efficiency of an ethanol engine at idle. The fuel energy flow rate was reduced by 20% when hydrogen volume fraction in the intake rose from 0% to 6.38%. Both flame development and propagation periods were shortened with the increase of hydrogen blending ratio. The heat transfer to the coolant was decreased and the degree of constant volume combustion was enhanced after hydrogen addition. HC and CO emissions were first reduced and then increased with the increase of hydrogen blending fraction. The acetaldehyde emission from the hydrogen-enriched ethanol engine is lower than that from the pure ethanol engine. However, the addition of hydrogen tended to increase NO x emissions from the ethanol engine at idle and stoichiometric conditions.

Gas pressure dependence of composition in Ta–Ti–N films prepared by pulsed high energy density plasma

Tantalum titanium nitride (Ta–Ti–N) films were deposited on silicon wafer substrates by pulsed high energy density plasma (PHEDP), under different intake gas pressures, ranging from 0.1 to 0.4 MPa. The films were investigated by X-ray photoelectron spectroscopy. Results were analyzed in detail, which reveals that the contents of the metallic elements (Ta and Ti) tend to decrease with pressure, while that of nitrogen increases as expected. With increasing pressure, the films can be denoted as TaTi 3.9N 2.8, TaTi 4.7N 6.0, TaTi 2.2N 8.4 and TaTi 3.1N1 3.5, respectively. The bonding state of tantalum, titanium, as well as nitrogen was fitted and discussed. Our results demonstrate that almost all the titanium bonded with nitrogen. The Ta–N and Ti–N bonds have equal shares under low gas intake pressure, while the Ti–N bonds prevail under high pressure. The preferential sputtering between the coaxial electrodes should be responsible for this phenomenon. Under low nitrogen pressure, the preferential sputtering is quite significant; while it could be neglected under high pressure.

J0801-3-1 都市ガス13A-バイオマスガス混合燃料によるHCCIエンジンの運転([J0801-3]エンジン,動力システムにおける燃焼技術(3))

Biomass, a renewable and carbon-neutral energy source, is widely recognized as an alternative to fossil fuels. But, because of the supply instability, it is hard to use Biomass as a single fuel in Engine. In this study, the combustion characteristics of a HCCI Engine using Mixture of City gas 13A and Biomass gas are investigated. As a result, it is noted that the ignition timing advances and the combustion duration becomes longer, when the ratio of 13A decrease and/or the intake gas temperature becomes higher. Moreover, it is suggested that the effect of H_2 on the ignition timing is more significant than other combustible components.

Experimental study on combustion and emissions performance of a hybrid hydrogen–gasoline engine at lean burn limits

Lean combustion is an effective way for improving the spark-ignited (SI) engine performance. Unfortunately, due to the narrow flammability of gasoline, the pure gasoline-fueled engines sometimes suffer partial burning or misfire at very lean conditions. Hydrogen has many excellent combustion properties that can be used to extend the gasoline engine lean burn limit and improve the gasoline engine performance at lean conditions. In this paper, a 1.6 L port fuel injection gasoline engine was modified to be a hybrid hydrogen–gasoline engine (HHGE) fueled with the hydrogen–gasoline mixture by mounting an electronically controlled hydrogen injection system on the intake manifolds while keeping the original gasoline injection system unchanged. A self-developed hybrid electronic control unit (HECU) was used to flexibly adjust injection timings and durations of gasoline and hydrogen. Engine tests were conducted at 1400 rpm and a manifolds absolute pressure (MAP) of 61.5 kPa to investigate the performance of an HHGE at lean burn limits. Three hydrogen volume fractions in the total intake gas of 1%, 3% and 4.5% were adopted. For a specified hydrogen volume fraction, the gasoline flow rate was gradually reduced until the engine reached the lean burn limit at which the coefficient of variation in indicated mean effective pressure (COVimep) was 10%. The test results showed that COVimep at the same excess air ratio was obviously reduced with the increase of hydrogen enrichment level. The excess air ratio at the lean burn limit was extended from 1.45 of the original engine to 2.55 of the 4.5% HHGE. The engine brake thermal efficiency, CO, HC and NO x emissions at lean burn limits were also improved for the HHGE.

Investigation of toluene LIF at high pressure and high temperature in an optical engine

Toluene laser-induced fluorescence (LIF) emission spectra were acquired in an optical engine with excitation at 248 nm. Toluene was homogeneously seeded in pure nitrogen and air which were used as intake gases. Data were acquired during the compression phase without ignition leading to simultaneous increases in temperature and pressure from 20°C and 1 bar to 500°C and 23.6 bar. Compared to LIF emission spectra at high temperature and atmospheric pressure reported in the literature, the toluene-LIF emission signal shifts to longer wavelengths when temperature and pressure increase simultaneously, whereas the spectrally integrated emission intensity is slightly affected by the pressure level.

Study on Characteristics of Auto-ignition and Combustion in Hydrogen Jet with a Rapid Compression and Expansion

Hydrogen has a potential alternative to conventional hydrocarbon fuels, because no carbon dioxides (CO2) is emitted from hydrogen combustion and it is able to make hydrogen by an electrolysis of water as renewable energy resources are used. This study aims to obtain stable auto-ignition and combustion of hydrogen when hydrogen is applied to a direct-injection compression ignition engine. In this study, influences of various ambient conditions such as temperatures, coexistence species etc. on auto-ignition and combustion behaviors of hydrogen jets were investigated with a rapid compression and expansion machine (RCEM). To be able to obtain the stable auto-ignition of hydrogen, in this study, first an ambient temperature in the cylinder of RCEM was raised by adding argon (Ar) gas, which has low specific heat capacity, and secondly the temperature was raised through chemical reactions of a little of di-methyl ether (DME), which was added into intake gas before the start of compression stroke. And effects of intermediates generated during the chemical reactions with DME on auto-ignition of hydrogen jet were also evaluated by both chemical kinetic analysis and experimental investigation.

Numerical Analysis of Intake Gas Conditions on Diesel Combustion (Second report)

Numerical Analysis of Intake Gas Conditions on Diesel Combustion (Second report)

Influence of EGR unequal distribution from cylinder to cylinder on NO x–PM trade-off of a HSDI automotive Diesel engine

The influence of cylinder-to-cylinder variation in EGR distribution on the NO x–PM trade-off (while varying EGR rate) is studied on an automotive high-speed direct injection Diesel engine. Experiments have been conducted on an engine test bench with and without air-EGR mixer and demonstrate that variations in cylinder-to-cylinder EGR distribution results in a deteriorated NO x–PM trade-off (increased NO x emissions level at a given PM emissions level, or increased PM emissions level at a given NO x emissions level) compared to the well mixed configuration with equal EGR rate for all the cylinders. A qualitative study as well an original experiment is conducted to explain this emissions increase induced by unequal distribution of EGR. When recirculating hot exhaust gases, the emissions increase is due to cylinder-to-cylinder variations in intake gas composition and temperature.

Potential of Atkinson cycle combined with EGR for pollutant control in a HD diesel engine

An experimental investigation has been performed on the potential of the Atkinson cycle and reducing intake oxygen concentration for pollutant control in a heavy-duty diesel engine. In this study the Atkinson cycle has been reproduced advancing the intake valve closing angle towards the intake stroke. In addition, the intake oxygen concentration has been reduced introducing exhaust gas recirculation. This research has been carried out at low engine load (25%), where the Atkinson cycle is known to improve the efficiency of the spark-ignition engines. The main interest of this investigation has been the comparison between the Atkinson cycle and the conventional diesel cycle at the same oxygen concentration in the intake gas. This analysis has been focused on in-cylinder gas thermodynamic conditions, combustion process, exhaust emissions and engine efficiency. In compression ignition engines, the Atkinson cycle basically promotes the premixed combustion, but in the range of these tests, a complete premixed combustion was not attained. Regarding exhaust emissions, the Atkinson cycle reduces notably the nitrous oxides but increases soot emissions. Finally, better global results have been found reducing intake oxygen concentration by the recirculation of exhaust gas than by the operation of an Atkinson cycle.

Numerical Simulation of Gasoline Stratified Charge Compression Ignition Using 3D-CFD Coupled with Detailed Chemistry

In this paper, the detailed chemical kinetics was coupled with the three-dimensional CFD code to study the combustion process in HCCI engines. A detailed hydrocarbon oxidation reaction mechanism (89 species, 413 reactions) for high octane fuel was constructed and then used to simulate the chemical process of the ignition, combustion and pollutant formation under HCCI conditions. The three-dimensional FIRE/CHEMKIN model was validated using the experimental data from a Rapid Compression Machine. The simulation results show good agreements with experiments. Finally, the improved three-dimensional CFD code was employed to simulate the intake, spray, combustion and pollutant formation process of the gasoline direct injection HCCI engine with two-stage injection strategy. The models account for intake flow structure, spray atomization, spray/wall interaction, droplet evaporation and gas phase chemistry in complex multi-dimensional geometries. The calculated results show the periphery of fuel-rich zone formed by the second injection which ignited first and worked as an initiation to ignite the surrounding lean mixture zone formed by the first injection. The results provide a detailed insight into the processes governing combustion and pollutant formation in the HCCI engine.

Molecular effects on turbulent diffusion and energy in a low speed closed flow

The coefficient of turbulent diffusion and the total turbulent energy are determined during the compression phase of a motored internal combustion engine with varying flow conditions and using intake gases with varying molecular weights. These turbulent parameters change with time and with intake gas molecular weight. However, under all flow conditions, both parameters first increase and then decrease with increasing molecular weight. In addition, a direct correlation is observed between the average values of the coefficient of turbulent diffusion and the average values of the total turbulent energy, irrespective of the molecular weight.

Combustion characteristics of a closed cycle diesel engine with different intake gas contents

This paper is to carry out a numerical simulation of combustion characteristics for a closed cycle diesel engine (CCDE) with different intake gas contents under different engine speeds and equivalence ratios. The numerical simulation used Kiva3V-Release2 code as the main program by modifying some subroutines containing different intake gas contents of oxygen, argon, and nitrogen and their thermodynamic properties. The results show that the pressure will increase earlier if the percentage of argon is higher when we use argon to replace nitrogen, and the ignition delay will be shorter, too. The higher in-cylinder temperature results from a higher concentration of argon.

Effect of Intake Gas Pressure and Temperature on Combustion Process in HCCI Engine

Effect of Intake Gas Pressure and Temperature on Combustion Process in HCCI Engine

FL1-2: Combustion Method of Diesel Engine Fueled with Hydrogen for High Efficiency(FL: Fuels and Lubricants,General Session Papers)

In order to achieve hydrogen- fueled diesel engine, authors suggest the hydrogen combustion with ignition-assist method of Dimethyl ether(DME). The in-cylinder temperature is raised through a reaction in compression stroke by adding DME to intake gas. The ignition-assist method of DME shortened the auto-ignition delay of hydrogen, and obtained the stable auto-ignition of hydrogen. The characteristics of hydrogen auto-ignition and combustion processes with this method were grasped in several conditions for suitable combustion methodology.

Numerical Analysis of Intake Gas Conditions on Diesel Combustion(First report)

Numerical Analysis of Intake Gas Conditions on Diesel Combustion(First report)

Rapid measurements of temperature and H 2O concentration in IC engines with a spark plug-mounted diode laser sensor

Crank angle-resolved measurements of gas temperature and water vapor concentration are made during the compression stroke of an internal combustion (IC) engine with a novel diode laser absorption sensor. The temperature is determined from the ratio of optical absorption for two overtone transitions of water vapor in the intake gas mixture, and the H 2O concentration is determined from this inferred temperature and the absorption for one of the transitions. The measurements sample a short-path region (6 mm) of the in-cylinder gases near the spark plug, which has been modified to provide optical access. Hence, the sensor can be installed in nearly any engine via the spark plug port. Wavelength modulation spectroscopy is employed with second harmonic detection (WMS-2 f) to enable the short-path measurements over a range of temperatures and pressures from 500 to 1050 K and 1 to 50 atm at a bandwidth of 7.5 kHz. The accuracy of the sensor is validated in a static cell, giving RMS errors of less than 3% in temperature and less than 3.6% in H 2O concentration over a wide range of conditions. Crank angle-resolved measurements are performed in unfired and fired engine cylinders, illustrating the potential of this sensor for investigating a range of difficult-to-model trends in current and proposed IC engine combustion schemes.

A study of the hydrogen production from a small plasma converter

In this paper, the hydrogen production characteristics of a purpose-designed and built small scale plasma converter for small engines was investigated. Hydrogen was produced through the reformation of ionised hydrocarbon fuel and air mixture by means of a spark discharge. The experimental results showed that a suitable size of the reaction chamber can increase the concentration of the produced hydrogen and that under a given methane supply rate, a low O 2/C ratio resulted in high hydrogen production concentration as well as high hydrogen volume flow rate. As the methane supply rate was increased, however, the hydrogen concentration reduced while the hydrogen volume flow rate increased. Hydrogen concentration was also improved when the intake gas mixture resided longer in the reaction channel, although the hydrogen volume flow rate revealed an inversed trend. It was also shown that by combining an intake air swirl with an appropriate O 2/C ratio and methane supply rate, both the methane conversion efficiency and the hydrogen production concentration were improved. In general, under the optimal operating condition, the plasma converter produced a maximum hydrogen concentration of 48% and a hydrogen volume flow rate of 70 mL/min.

Homogeneous Charge Compression Ignition of Natural Gas/Air Mixture with Ozone Addition

Controlling the ignition and the combustion of a homogeneous charge compression ignition (HCCI) engine has been attempted by partially ozonizing the intake gas in a natural gas premixed compression engine. It was experimentally proved that ignition timing can be controlled by changing the ozone concentration. To understand the phenomenon, an investigation using a numerical analysis has been carried out, and it was found that controlling the HCCI operation with ozone addition becomes feasible by generating OH via H 2 O 2 , that the influence of ozone addition to ignition angle is about the same as that of direct injection of an O radical, and that its addition is one order of magnitude more effective than addition of an OH radical.

Gas turbine performance enhancement by intake air cooling

In this work, the influence of air cooling intake on the gas turbine performance is presented. The proposed system, together with the gas turbine, is described. A mathematical model of ACIGT (Air Cooling Intake Gas Turbine) is derived and formulated in dimensionless form from which the constraint multivariable optimisation problem was formulated. To demonstrate the effectiveness of the proposed approach, a numerical simulation of the optimisation problem is presented. The maximum net power is obtained using graphical visualisation as well as numerical computation. The obtained results show that the net power could be increased up to 35% for the operating ranges of the ratio of the compressor air inlet temperature to the ambient air temperature, pressure ratio and the ratio of the turbine air inlet temperature to the ambient air temperature which demonstrates the effectiveness of the approach.