Showing papers in "International Journal of Engine Research in 2007"
TL;DR: In this paper, the effect of fatty acid methyl ester content in biodiesel on characteristics of oxidation stability as quality parameters, including peroxide value, acid value, kinematic viscosity and induction period obtained from a Rancimat test.
Abstract: The current paper describes two topics. The first is a study of the effect of fatty acid methyl ester content in biodiesel on characteristics of oxidation stability as quality parameters, including peroxide value, acid value, kinematic viscosity, and induction period obtained from a Rancimat test. The second is a study of the effect of biodiesel oxidation on diesel combustion and emission characteristics. An accelerated oxidation stability test was conducted by the Rancimat test method on methyl esters with different unsaturated fatty acid components. The unsaturated fatty acid components exert a large influence on oxidation deterioration as well as thermal and auto-oxidation stability. In addition, characteristics of oxidation were obtained from a thermal oxidation test using a tank equipped with an injection system test rig. These experiments clarified relationships between oxidation quality parameters. The autoignition characteristics of deliberately oxidized biodiesel were analysed by means of...
90 citations
TL;DR: In this paper, three different approaches for modelling in-cylinder compression-ignition engine processes for partially premixed combustion modes are compared with experimentally observed cylinder pressure and incylinder images of liquid-and vapour-fuel penetration, ignition, combustion, and soot formation in an optically accessible heavy-duty direct injection engine.
Abstract: Three different approaches for modelling in-cylinder compression-ignition engine processes for partially premixed combustion modes are compared with experimentally observed cylinder pressure and in-cylinder images of liquid- and vapour-fuel penetration, ignition, combustion, and soot formation in an optically accessible heavy-duty direct injection engine. A multi-dimensional computational fluid dynamics model for engine combustion, KIVA-3V, served as a common platform into which three different combustion submodels were integrated: (1) characteristic time combustion (KIVA-CTC); (2) representative interactive flamelet (KIVA-RIF); and (3) direct integration using detailed chemistry (KIVA-CHEMKIN). Three different engine operating strategies with significant premixing of fuel and air prior to ignition were investigated: Low-temperature combustion achieved by charge dilution, with fuel injection either (1) early, or (2) late in the engine cycle, and (3) long ignition delay, high-temperature combustion...
72 citations
TL;DR: In this paper, cold exhaust gas recirculation (EGR) was used to achieve ultra-low NOx and smokeless operation at higher loads up to half of the rated torque.
Abstract: Ultra-low NOx and smokeless operation at higher loads up to half of the rated torque is attempted with large rates of cold exhaust gas recirculation (EGR). NOx decreases below 6 ppm (0.05 g/kW h) and soot significantly increases when first decreasing the oxygen concentration to 16 per cent with cold EGR. However, after peaking at 12–14 per cent oxygen, soot then decreases sharply to essentially zero at 9–10 per cent oxygen while maintaining ultra-low NOx, regardless of fuel injection quantity and injection pressure. However, at higher loads, with the oxygen concentration below 9–10 per cent, the air-fuel ratio has to be over-rich to exceed half of the rated torque, and thermal efficiency, CO, and THC deteriorate significantly. As the EGR rate increases, exhaust gas emissions and thermal efficiency vary with the intake oxygen content rather than with the excess air ratio. Longer ignition delays due to either advancing or retarding the injection timing reduced the smoke emissions, but advancing the ...
66 citations
TL;DR: In this paper, the authors extended a zero-dimensional probability density-function-based stochastic reactor model (SRM) for HCCI engines in order to incorporate MDI and an improved turbulent mixing model.
Abstract: Multiple direct injection (MDI) is a promising strategy to enable fast-response ignition control as well as expansion of the homogeneous charge compression ignition (HCCI) engine operating window, thus realizing substantial reductions of soot and NOx emissions. The present paper extends a zero-dimensional-probability-density-function-based stochastic reactor model (SRM) for HCCI engines in order to incorporate MDI and an improved turbulent mixing model. For this, a simplistic spray model featuring injection, penetration, and evaporation sub-models is formulated, and mixing is described by the Euclidean minimal spanning tree (EMST) sub-model accounting for localness in composition space. The model is applied to simulate a gasoline HCCI engine, and the in-cylinder pressure predictions for single and dual injection cases show a satisfactory agreement with measurements. From the parametric studies carried out it is demonstrated that, as compared with single injection, the additional second injection contributes to prolonged heat release and consequently helps to prevent knock, thereby extending the operating range on the high load side. Tracking the phase space trajectories of individual stochastic particles provides significant insight into the influence of local charge stratification owing to direct injection on HCCI combustion. (Less)
47 citations
TL;DR: In this paper, an artificial neural network (ANN) was trained on chassis dynamometer data and used to predict the oxides of nitrogen (NOx), carbon dioxide (CO2), hydrocarbons (HC), and carbon monoxide (CO) emitted from heavy-duty diesel vehicles.
Abstract: An artificial neural network (ANN) was trained on chassis dynamometer data and used to predict the oxides of nitrogen (NOx), carbon dioxide (CO2), hydrocarbons (HC), and carbon monoxide (CO) emitted from heavy-duty diesel vehicles. Axle speed, torque, their derivatives in different time steps, and two novel variables that defined speed variability over 150 seconds were defined as the inputs for the ANN. The novel variables were used to assist in predicting off-cycle emissions. Each species was considered individually as an output of the ANN. The ANN was trained on the Highway cycle and applied to the City/Suburban Heavy Vehicle Route (CSHVR) and Urban Dynamometer Driving Schedule (UDDS) with four different sets of inputs to predict the emissions for these vehicles. The research showed acceptable prediction results for the ANN, even for the one trained with only eight inputs of speed, torque, their first and second derivatives at one second, and two variables related to the speed pattern over the l...
42 citations
TL;DR: In this article, the effects of cetane number on homogeneous charge compression ignition performance and emissions were investigated in a single-cylinder engine with port fuel injection, using intake air temperature for control.
Abstract: The effects of cetane number (CN) on homogeneous charge compression ignition (HCCI) performance and emissions were investigated in a single-cylinder engine with port fuel injection, using intake air temperature for control. Commercial fuels and blends of the diesel secondary reference fuels were evaluated, covering a CN range from 19 to 76. Sweeps of intake air temperature showed that low-CN fuels needed higher intake temperatures than high-CN fuels to achieve ignition. As a function of intake air temperature, each fuel passed through a point of maximum indicated mean effective pressure (i.m.e.p.). High-CN fuels required a combustion phasing approximately 10 crank angle degrees (CAD) earlier than the lowest CN fuels in order to prevent misfire. The high-CN fuels exhibited a strong low-temperature heat release (LTHR) event, while no LTHR was detected for fuels with CN < 34. All of the fuels yielded comparable NO2 emissions (< 6 ppm at 3.5 bar i.m.e.p.) at their respective maximum i.m.e.p. timeing. Low-CN fuels were prone to excessive pressure rise rates and NO2 emissions at advanced phasing, while high-CN fuels were prone to excessive CO emissions at retarded phasing. These results suggest that the products of LTHR, which are high in CO, are more sensitive to the quenching effects of cylinder expansion. Engine speed was found to suppress LTHR since higher engine speed reduces the time allowed for the LTHR reactions. In addition to measurements of standard gaseous emissions, additional sampling and analysis techniques were used to identify and measure the individual exhaust HC species including an array of oxygenated compounds. In addition to high concentrations of formaldehyde and other low molecular weight carbonyls, results showed an abundance of organic acids, ranging from formic to nonanoic acid. Concentrations of high molecular weight partially oxidized species were highest for the high-CN fuels at retarded phasing, and are believed to be a direct product of LTHR. (A)
41 citations
TL;DR: In this paper, the authors used a single-cylinder research engine at a constant speed of 1700 r/min to evaluate the performance of low pilot-ignited natural gas (ALPING) combustion.
Abstract: The development of the advanced injection low pilot-ignited natural gas (ALPING) combustion concept that employs very small diesel pilots (1-5 per cent by energy) to compression ignite a premixed natural gas-air mixture to achieve very low NOx (0.2 g/kWh) and high efficiencies (about 41 per cent) has been described in a previous work. However, at part loads the ALPING combustion mode suffers from higher HC emissions (mostly unburned methane) and poor engine stability. To resolve this problem, tests were carried out employing various levels of hot EGR (0-26 per cent) at different loads on a single-cylinder research engine at a constant speed of 1700 r/min. Experimental results compared with baseline ALPING mode (0 per cent EGR) for quarter load operation are presented in the current paper. The results show that, at 60° BTDC injection timing, the application of hot EGR reduced HC emissions by up to 70 per cent without any significant NOx emissions penalty. The fuel conversion efficiencies were improved by 8 percentage points, while COVi.m.e.p. and CO emissions decreased 20 percentage points and 40 per cent, respectively. To identify the upper limits of hot EGR substitution, engine knock tests, which were conducted to identify audible knock limits, are also presented for a representative case (half load). The progress made by this project better positions ALPING combustion as a potentially viable approach to meet the regulatory and economic challenges of the future.(A)
40 citations
TL;DR: In this article, the effects of split injection with various dwells and mass ratios on the spray and mixture characteristics in an ambient environment similar to the late stage of compression stroke in dire...
Abstract: The effects of split injection with various dwells and mass ratios on the spray and mixture characteristics in an ambient environment similar to the late stage of compression stroke in dire...
32 citations
TL;DR: In this article, the authors expressed their appreciation for support by the National Research Laboratory scheme, Korea and in part by the Hyundai Motor company for the development of the HMD platform.
Abstract: The authors would like to express their appreciation for support by the National Research Laboratory scheme, Korea and in part by the Hyundai Motor company
25 citations
TL;DR: A major effort has been made to surmount the current obstacles to expanding the operating window of homogeneous charge compression ignition (HCCI) engines as discussed by the authors, which involves extensive experimental studies on single and multi-cylinder engines and the work is devoted to the development of on-board fuel-reforming technology and to the application of supercharging combined with trapping of residual gases in the cylinder.
Abstract: A major effort has been made to surmount the current obstacles to expanding the operating window of homogeneous charge compression ignition (HCCI) engines. The research involves extensive experimental studies on single-cylinder and multi-cylinder engines and the work is devoted to the development of on-board fuel-reforming technology and to the application of supercharging combined with trapping of residual gases in the cylinder. Fuel reforming yields significant quantities of hydrogen and is used to extend the lower load boundary while supercharging and internal exhaust gas recirculation (EGR) trapping are used to increase the upper load limit of HCCI engines. The present paper highlights the main findings of the research to date; in particular it reveals that using a combination of technical elements for effective control of auto-ignition in a typical passenger car engine configuration is possible and promising.
24 citations
TL;DR: In this paper, two experimental methods have been designed to determine the residual gas fraction, one based on an in-cylinder sampling method and the second based on a hydrocarbon analysis of the exhaust gases.
Abstract: To meet future pollutant emissions standards, it is necessary to be able to estimate not only the cycle-by-cycle mass but also the cycle-by-cycle composition of the combustion chamber charge. This charge consists of fresh air, fuel, and residual gas from the previous cycle. Unfortunately the residual gas fraction cannot be measured. Two experimental methods have been designed to determine the residual gas fraction. The reference method is based on an in-cylinder sampling method. The second one is based on a hydrocarbon (HC) analysis of the exhaust gases. Two models were compared with the experimental results. A one-dimensional computational fluid dynamics (CFD) code (WAVE) and a zero-dimensional model (AMESIM), which takes into account gas compressibility. The aim of the study was to compare the results of CFD codes (one- and zero-dimensional) to experimental results. If the code is validated by the experiments, it should be possible to determine residual gas fractions without needing a large experimental set-up.
TL;DR: In this article, a variable valve timing mechanism is applied to achieve premixed diesel combustion at higher load for low emissions and high thermal efficiency in a light duty diesel engine by means of late intake valve closing (LIVC).
Abstract: A variable valve timing mechanism is applied to achieve premixed diesel combustion at higher load for low emissions and high thermal efficiency in a light duty diesel engine By means of late intake valve closing (LIVC), compressed gas temperatures near the top dead centre are lowered, thereby preventing too early ignition and increasing ignition delay to enhance fuel-air mixing The variability of an effective compression ratio has significant potential for ignition timing control of conventional diesel fuel mixtures At the same time, the expansion ratio is kept constant to ensure thermal efficiency Combining the control of LIVC, exhaust gas recirculation, supercharging systems, and high-pressure fuel injection equipment can simultaneously reduce nitrogen oxides and smoke The nitrogen oxides and smoke suppression mechanism in the premixed diesel combustion is analysed using a three-dimensional computational fluid dynamics (3D-CFD) code combined with detailed chemistry LIVC can achieve a significant nitrogen oxides and smoke reduction due to lowering combustion temperatures and avoiding local over-rich regions in the mixtures, respectively
TL;DR: In this article, a NARX neural network is adapted for cylinder pressure trace reconstruction on a multicylinder engine and two fully recurrent training algorithms are developed and applied to real engine data.
Abstract: A NARX neural network is adapted for cylinder pressure trace reconstruction on a multicylinder engine. Following a systematic study to establish the required NARX input information (using measured pressure traces and simulated crank kinematics), two fully recurrent training algorithms are developed and applied to real engine data. These include a back-propagation-through-time algorithm (BPTT) and an extended Kalman filter (EKF). For multi-cylinder engines, two cases are examined, both assuming crank kinematics is obtained from a single shaft-encoder fitted at the forward end of the crankshaft. In one case, a NARX model is constructed to provide an inverse relationship between the kinematics at the encoder location and the pressure trace in an arbitrary cylinder. In the second case, by transforming the kinematics (to emulate a local encoder), a different NARX model is constructed to relate the kinematics at the crank location of a particular cylinder to the corresponding pressure trace. The accuracy and efficiency of both NARX models is examined for application to a three-cylinder in-line DISI engine (in which pressure traces are measured on all cylinders). The paper shows that the computational requirements of training are substantial and, although the efficiency of the EKF algorithm is better than the BPTT, the fitting accuracies are similarly good. For generalization, however (to unseen data), neither method is yet sufficiently accurate (even for steady state engine operation) unless substantially more training data are used to achieve the target accuracy of ± 4 per cent. The overall conclusion of the paper is that the NARX model has the correct architecture for multicylinder pressure reconstruction.
TL;DR: In this paper, fuel stratification in a gasoline homogenous charge compression ignition (HCCI) engine was studied, independent of thermal and residual gas stratification, and the results indicated that fuel stratifying in the absence of thermal or residual stratification does not appear to be a viable method for HCCI engines.
Abstract: Fuel stratification, independent of thermal and residual gas stratification, was studied in a gasoline homogenous charge compression ignition (HCCI) engine. The unmixed charge was created by injecting fuel (iso-octane) into the intake port after being prevaporized and heated to the same temperature as the intake stream. Planar laser-induced fluorescence measurements showed that local equivalence ratios in the charge differed from the mean equivalence ratio by up to 50 per cent for the latest possible injection timing. Experimental results showed little to no change in combustion phasing and performance between prevaporized port (unmixed) or premixed (homogeneous) fuelling. Increases in NOx and CO emissions were observed with the prevaporized port fuelling and are believed to result from the regions richer or leaner than the mean equivalence ratio. These results indicate that fuel stratification in the absence of thermal and residual stratification does not appear to be a viable method for HCCI com...
TL;DR: In this paper, the characteristics of the spray behavior and ignition delay of DME were investigated in both experiment and simulation and it was found that the spray development was dependent on the ambient density.
Abstract: The characteristics of the spray behaviour and ignition delay of dimethyl ether (DME) were investigated in both experiment and simulation. DME spray images were taken in a constant-volume vessel by using Mie scattering and shadowgraph methods to measure the spray tip penetration and the spray angle of the liquid and vapour phase. The images were acquired at low- and high-temperature conditions and it was found that the spray development was dependent on the ambient density. The ignition delay of DME spray was also measured under high pressure and temperature conditions and compared with that of diesel spray in the same conditions.To predict the ignition and combustion characteristics of DME, a reduced chemical kinetic mechanism consisting of 28 species and 45 reactions was derived from a detailed mechanism. Calculated results in homogeneous conditions agreed well with the measured data from shock tube experiments. Then three-dimensional simulation of spray development and ignition delay of DME spr...
TL;DR: In this article, the effects of different species representative of those found in rich PCI exhaust on a diesel oxidation catalyst (DOC) in a background of exhaust from an engine operating in a lean PCI regime were quantified.
Abstract: Low-temperature premixed-charge compression ignition (PCI) can significantly reduce both nitric oxide and nitrogen dioxide and particulate matter emissions in compression ignition engines through a range of engine operating conditions. Exhaust hydrocarbons and carbon monoxide can be removed with a diesel oxidation catalyst (DOC). Although PCI normally utilizes a globally fuel-lean mixture, it is independent of equivalence ratio provided that local combustion temperatures are sufficiently low. A more fuel-rich PCI mode of operation could be useful in exhaust after-treatment strategies such as providing carbon monoxide and hydrocarbons for regeneration of a lean nitrogen oxides trap (LNT). In a previous study, it was found that a rich PCI strategy deactivates a platinum-based DOC within seconds and may allow excessive harmful emissions to be passed into the environment. This study attempts to quantify the effects of different species representative of those found in rich PCI exhaust on a platinum-based DOC in a background of exhaust from an engine operating in a lean PCI regime. Excess carbon monoxide, propane, propylene, and methane were injected in varying concentrations while catalyst outlet temperature, carbon monoxide, and hydrocarbon conversion were measured for a period of 200 s. Of the injected species, it is shown that propylene has the greatest deactivation effect on the catalyst followed by carbon monoxide, both in terms of time and concentration. Propane is found not to deactivate the catalyst even in very globally fuel-rich conditions whereas methane acts as an inert gas over the catalyst in the temperature range of interest. It is concluded that high concentrations of carbon monoxide do not act alone in the poisoning process for the rich PCI condition. The presence of some partial oxidation products such as unsaturated hydrocarbons can also have an adverse effect on DOC performance.
TL;DR: In this paper, the authors examined premixed diesel combustion near top dead centre (TDC) with a hole-type nozzle suitable for fuel-air mixture formation at high temperature and air density.
Abstract: With conventional diesel combustion, heterogeneity of the mixture has been one of the major difficulties in improving the NOx and particulate matter (PM) trade-off or relationship. Premixed (injection completed before ignition) compression ignition (PCI) combustion significantly improves the fuel-air mixture quality and consequently improves the cleanliness of diesel combustion. This research examines premixed diesel combustion near top dead centre (TDC) with a hole-type nozzle suitable for fuel-air mixture formation at high temperature and air density. This combustion concept can simultaneously reduce NOx and smoke emissions by increasing the turbulent mixing rate. Furthermore, the hydrocarbon (HC) emissions were lower than premixed diesel combustion with injection earlier in the cycle. This combustion system can also be used in conventional diesel combustion mode, in which it has also shown good performance. This paper describes such a dual mode system for practical application of PCI combustion...
TL;DR: In this article, the authors deal with destroying a high-velocity diesel fuel jet by impingement on small cylindrical obstacles, which permits very quick jet distribution in the volume.
Abstract: The paper deals with ‘destroying’ a high-velocity diesel fuel jet by impingement on small cylindrical obstacles. This process permits very quick jet distribution in the volume. Essential is...
TL;DR: In this paper, a two-degree-of-freedom dynamic model is constructed to simulate the instantaneous crank kinematics and total mechanical losses arising in a multicylinder gasoline engine coupled to a dynamometer.
Abstract: A two-degree-of-freedom dynamic model is constructed to simulate the instantaneous crank kinematics and total mechanical losses arising in a multicylinder gasoline engine coupled to a dynamometer. The simulation model is driven using specified cylinder gas pressures, and loaded by nominal brake torque and total friction losses. Existing semi-empirical torque loss models (based on calibrated single-cylinder diesel engine data) are used to account for the instantaneous friction losses in the piston-ring assembly, in bearings, and in auxiliaries. The model is specialized to the simulation of crank kinematics and matched brake torque for a three-cylinder in-line direct injection spark ignition (DISI) engine, without a gearbox. This allows the total friction loss to be separated from the brake torque for an engine not fitted with the very large number of sensors otherwise needed to calibrate analytical friction models. An equivalent simulation model is also constructed using GT-Crank, which excludes explicit reference to friction. In using both models to simulate steady state operation at a specified mean engine speed, the output torque is matched by iteration. The GT-Crank model necessarily compensates for internal losses by exaggerating the total output torque. Both simulation models are compared with measured crank kinematics and brake torque obtained from a dynamometer-loaded I3 DISI engine. The paper shows that by comparing the matched output torque from simulation with the measured output torque from the engine, the proposed model gives a very good high-speed prediction of the total mechanical losses. At low speed, the instantaneous model is still not accurate. It is also shown, however, that apart from the no-load condition, use of an average torque to compensate for friction (as in GT-Crank) is wholly acceptable for simulating instantaneous crank kinematics. This is the first reported instance of a simulation model (which includes the particu
TL;DR: The use of ionization sensors for controlled auto-ignition (CAI) gasoline engines, where the air-fuel mixture ignites without the need of a spark, is well known.
Abstract: The use of ionization sensors, by means of a standard spark plug, in gasoline engines is well known. This paper focuses on the use of these sensors for controlled auto-ignition (CAI) gasoline engines, where the air-fuel mixture ignites without the need of a spark. The averaged ion current signals obtained are first observed and compared to the heat release rate and then a method to detect with accuracy the location of the 50 per cent mass fraction burned is described. The variation of emissions is studied and the effects of using a pressure sensor (to calculate the heat release rate) or an ion current sensor are portrayed. Thus it is proved possible to keep the emissions under strict control by using an ion current sensor.
TL;DR: Experimental studies carried out at the New ACE Institute revealed that a combination of high-pressure fuel injection, high pressure supercharging, and high exhaust gas recirculation (EGR)...
Abstract: Experimental studies carried out at the New ACE Institute revealed that a combination of high-pressure fuel injection, high-pressure supercharging, and high exhaust gas recirculation (EGR) ...
TL;DR: In an optically accessible single-cylinder engine fuelled with hydrogen, chemiluminescence imaging was used to measure flame propagation characteristics, cycle-to-cycle variability, and... as discussed by the authors.
Abstract: In an optically accessible single-cylinder engine fuelled with hydrogen, OH* chemiluminescence imaging is used to measure flame propagation characteristics, cycle-to-cycle variability, and ...
TL;DR: In this paper, a control-oriented, physics-based model for the estimation of the NO emissions of spark-ignition engines has been developed, which consists of three submodels for estimating the in-cylinder pressure, burned gas temperature, and formation of NO.
Abstract: A control-oriented, physics-based model for the estimation of the NO emissions of spark-ignition engines has been developed.The model consists of three submodels for the estimation of the in-cylinder pressure, of the burned gas temperature, and of the formation of NO. All submodels are based on physics first principles and chemical reactions. However, they are simplified in order to allow for an efficient evaluation in a control-oriented environment. The submodel of the pressure estimation incorporates a combustion model whose parameters are continuously adapted using the feedback of crankshaft angular velocity measurements. Measurement data have been acquired from a V6 3.2 1 engine at a set of reference operating points, each of them serving as a support point of the model parameters. Measurement data were obtained from variations of the operating conditions and compared with the corresponding simulations.The simulation results for the in-cylinder pressure and the engine-out NO emissions agree well with measured values, while the evaluation time of the model was shorter than the duration of one engine cycle. The calibration effort was found to be small, while the model demonstrated its capability to extrapolate engine behaviour beyond the calibration data set.(A)
TL;DR: In this article, the impact of homogeneous charge compression ignition (HCCI) on the combustion and intake orifice noise was quantified using either directly measured noise and vibrations from the development dynamometer or a noise prediction method based on recorded cylinder pressures and known transfer functions.
Abstract: The homogeneous charge compression ignition (HCCI) gasoline engine promises low fuel consumption without expensive NO2 aftertreatment. Owing to the self-ignition, HCCI has a faster combustion and therefore a higher level of vibration and acoustic excitation than DI-spark ignition (SI) engines. To effect a gasoline engine running in HCCI mode, residual gases must be trapped in the combustion chamber in HCCI mode. One solution to trap residual gases is to establish a negative valve timing overlap. This was done on a gasoline I4 engine, which is able to run in SI or HCCI mode by using independently controlled overhead camshafts. Noise and vibration analysis has been carried out on such an HCCI engine to quantify the impact of HCCI on the combustion and intake orifice noise. The noise and vibration analysis was done using either directly measured noise and vibrations from the development dynamometer or a noise prediction method based on recorded cylinder pressures and known transfer functions. The investigations were carried out at different speed and load points while changing control parameters such as intake cam timing, throttle, spark and injection timing and strategy. Using different data evaluation methods it was found that the HCCI mode with base settings can deliver higher NVH excitation than the SI mode at the same speed and load. However, by applying different combinations of control parameters, the NVH of the HCCI operation mode can be controlled in order to reduce its level of excitation and noise characteristics. (A0
TL;DR: In this article, the characteristics of combustion control with direct methanol injection in homogeneous charge compression ignition (HCCI) combustion were investigated over a wide operating range under several operating conditions.
Abstract: Characteristics of combustion control with direct methanol injection in homogeneous charge compression ignition (HCCI) combustion were investigated over a wide operating range under several...
TL;DR: In this article, the effect of mixture inhomogeneity in HCCI engines utilizing high levels of residual gas and to estimate accurate initial conditions, a sequential numerical procedure is proposed.
Abstract: In order to account for the effect of mixture inhomogeneity in HCCI engines utilizing high levels of residual gas and to estimate accurate initial conditions, a sequential numerical procedu...
TL;DR: In this article, a pre-chamber-type compression ignition natural gas engine was constructed and its performance and NO emissions were investigated, where the pre- and main chambers made of ceramics were connected by a throat valve that opened during the compression stroke.
Abstract: A pre-chamber-type compression ignition natural gas engine was constructed and its performance and NO emissions were investigated. The pre- and main chambers made of ceramics were connected by a throat valve that opened during the compression stroke. An homogenous fuel air charge mixed with exhaust gas recirculation (EGR) gases was introduced into the main chamber, while a smaller amount of fuel was supplied into the pre-chamber during the intake stroke. The mixture in the pre-chamber was auto-ignited when the compressed hot gases in the main chamber were introduced into the pre-chamber through the throat valve during the compression stroke. The engine was operated without knock under various load conditions by adjusting the throat valve opening timing appropriately. The influences of the throat valve opening timing, compression ratio, and pre-chamber volume ratio on torque and NO emissions were investigated. Test results showed that: (a) at conditions when the thermal efficiencies were high, the ...
TL;DR: In this article, a residual-effected homogeneous charge compression ignition (HCCI) is defined as an approach which relies on the reintroduction of combustion products to achieve both the required dilution and sensible energy rise to enable compression ignition.
Abstract: Residual-effected homogeneous charge compression ignition (HCCI) is defined as an approach which relies on the reintroduction of combustion products to achieve both the required dilution and sensible energy rise to enable compression ignition. While convenient, this strategy introduces a coupling between the initial charge temperature and composition which is unique to this approach. Increasing the residual fraction tends to increase the initial charge temperature while simultaneously lowering reactant (fuel-air) concentrations. While intuition into chemical kinetics suggests that the initial thermal state should have the most significant impact on combustion phasing, experimental data for residual-effected HCCI show that increasing residual fraction delays phasing, despite higher apparent initial charge temperature. A kinetics-based model of residual-effected HCCI shows that two regimes of operation exist: A thermally-limited regime, in which phasing is most sensitive to the initial charge temper...
TL;DR: In this paper, a single-cylinder engine with a cylinder volume of 0.421 litre was used to assess the potential of homogeneous charge compression ignition (HCCI) diesel combustion compared to the conventional heterogeneous operation mode.
Abstract: Single-cylinder engine tests were carried out to assess the potential of homogeneous charge compression ignition (HCCI) diesel combustion compared to the conventional heterogeneous operation mode. For the experiments a single-cylinder engine with a cylinder volume of 0.421 litre was used. Besides the comparison of conventional operation and HCCI operation of the same engine special emphasis was put on the utilization of synthetic fuels such as gas-to-liquid (GtL) or biomass-to-liquid (BtL) fuels. Therefore, in addition to a standard winter diesel, a fuel with mid-sized n-alkanes and mixtures of n-alkanes and aromatic hydrocarbons was used to investigate the influence of different ignitabilities and boiling curves on the combustion. A great advantage of synthetic fuels is the possibility to design them according to the combustion process requirements. In addition, these GtL or BtL fuels will lead to a higher independence from fossil fuels.To assess the potential of HCCI combustion compared to conve...
TL;DR: In this paper, a thermogravimetric analysis (TGA) procedure has been adapted from existing soot procedures to determine the levels of semi-volatile compounds in progressively aged lubricating oil samples from a natural gas engine dynamometer test cell run.
Abstract: Semi-volatile in internal combustion engine lubricating oil may be responsible for limiting service life and can lead to in-cylinder deposit formation. In order to measure semivolatile content, a new thermogravimetric analysis (TGA) procedure has been adapted from existing soot procedures to determine the levels of semi-volatile compounds in progressively aged lubricating oil samples from a natural gas engine dynamometer test cell run. The per cent weight remaining at 550 °C, while heated at a constant rate in an inert atmosphere, varied linearly with running time, viscosity, and oxidation and nitration. The method yielded reproducible run-to-run results and showed good agreement between helium and argon atmospheres. Mass spectroscopy data confirmed increased levels of high molecular weight species during engine operation. This method may be applicable to diesel engine oil samples.