Premixed Compression Ignition Engine Research Articles

Exploiting a new combustion regime using a split partially premixed compression ignition engine fueled with n-butanol/diesel

An experimental investigation has been carried out to explore a novel combustion regime. This regime involves the utilization of a split injection partially premixed combustion (PPC) strategy in combination with DB20 fuel, which consists of 20 % n-butanol and 80 % diesel. The primary objective of this investigation is to assess how variations in pilot-main intervals (PMIs) and pilot-main injection ratios (PIRs) affect the emissions, combustion characteristics, and overall performance of a 4-cylinder turbocharged CRDI engine at various loads. Experimental results show that a split injection strategy combined with DB20 fuel reduces the maximum pressure rise (or combustion noise) rate while reducing NOx and smoke simultaneously compared to single-injection PPCI engines. A 20.1 % reduction in NOX emissions was observed at 20° CA PMI of 2 bar BMEP load and an 11.1 % reduction at 10° CA PMI of 6 bar BMEP load, respectively, compared to a single injection PPCI engine. There is a greater sensitivity to PMI when calculating the brake thermal efficiency (BTE) of DB20 blended fuel. In addition, it was observed that the split injection PPCI engine, powered by DB20 blend fuel, showed a 4.78 % increase in BTE for 20 % PIR and 20° CA PMI under 6 bar BMEP engine load.

An experimental investigation into the combustion stability and emissions of an n-butanol/diesel blended fueled partially premixed compression ignition (PPCI) engine

Higher cyclic variability in internal combustion engines (ICE) increases driveability problems, specific fuel consumption, and exhaust emissions. Consequently, quantification of the combustion stability in different combustion parameters is essential for the design of closed-loop control for a partially premixed combustion (PPC). This research examines the impacts of a PPC strategy on the spectral features of IMEP combustion parameters for early, and late injection timings of a 4-cylinder CRDI engine using wavelet transforms (WT). Furthermore, operating points were optimized based on the combustion and emissions characteristics of the partially premixed compression ignition engine. Results indicated that the early start of injection (SOI) timing of 12° CA BTDC has a lower standard deviation in the time-series data of IMEP than the late SOI timing. Moreover, when the amount of n-butanol in diesel fuel was increased from 0% to 20% at a load of 2 bar BMEP, COVIMEP decreased from 3.1% to 2.75% at early SOI timing. The WT results reveal that the continuous strong intensity band pattern changes irregularly when the injection timing is advanced. It was also found that at lower cyclic variability conditions (SOI = 12°CA BTDC), CO and smoke emissions decreased, and there was a noticeable increase in NOx emissions.

Numerical modelling of the premixed compression ignition engine for superior combustion and emission characteristics

The detailed investigation of biodiesel premixing is done in this research in order to make an attempt to reduce greenhouse gas emission, particularly NOx. From the literature survey, it is found that the effect of premixing is not concentrated enough and significant effect of it is yet to be analyzed. The impact of the biofuel premixing on the performance, combustion and emission characteristics was analyzed numerically. Numerical modelling was applied to do such analysis. The simulation for the combustion process in the combustion chamber was done to validate the comparison of a number of cases of different fuel. During the simulation process different fuel conditions were considered. A set of tests was carried out to find the premixing quality. Initially, pure diesel as fuel and the mixture of plain diesel and biodiesel were used to perform the tests. Secondly, biodiesel as fuel and its blends were used but the premixing was done. Similarly, another combination of pure diesel and plain premixed biodiesel in the combustion chamber was also analyzed. The different proportions of the fuel conditions are D (pure diesel), B10, B20 and B100 with B20%, B40% and B60% premixing biodiesel. The premixing effect was also identified by using both without premixing and with premixing fuel conditions in the combustion chamber. The reduced smoke emission was achieved by using the premixed fuels in the chamber in the second case. However, the emission of NOx was increased. Similarly, in the case of plain diesel as fuel and plain biodiesel as premixed fuel, the amount of smoke was reduced significantly but there was no high increment in the emission of NOx. Premixing biodiesel with the combination of pure diesel as the primary fuel provided the improved torque and power output whereas the reduced BSFC.

Effect of gasoline additive on combustion and emission characteristics of an n-butanol Partially Premixed Compression Ignition engine under different parameters

The experiments were conducted on a modified two-cylinder diesel engine to investigate the effects of excess-air coefficient (λ) and intake temperature (Tin) of different blending ratios (volume ratio of gasoline in the blends) on the combustion and emission characteristics of a Partially Premixed Compression Ignition (PPCI) engine. The results show that with the increase of gasoline blending ratio, the peak in-cylinder pressure (Pmax), the peak in-cylinder temperature (Tmax) and the peak heat release rate (HRRmax) of four test fuels all increase first and then decrease. When gasoline volume fraction is 10%, HC and CO emissions are the lowest. In addition, intake temperature (Tin) has a significant effect on the n-butanol/gasoline PPCI engine. With the increase of Tin, the in-cylinder Pmax and HRRmax of four test fuels gradually increase, the combustion phase advances and HC and CO emissions decrease, while NOx emissions increase slightly. Furthermore, as λ increases, the Pmax, Tmax and HRRmax of the four test fuels show monotonously reducing trend. At the same time, mixture concentration has basically no effect on start of combustion (CA10), the combustion duration (CD) gradually extends, and HC and CO emissions increase.

Combustion and emission characteristics of E85 and diesel blend in conventional diesel engine operating in PPCI mode

To study the possibility of operating a traditional diesel engine as a partially premixed compression ignition engine, E85 created from 85% bioethanol and 15% unleaded Iraqi gasoline blend was used as the main fuel. E85 blend fuel has a low evaporation temperature, large latent heat and low cetane number (CN). Iraqi diesel fuel was used as a pilot fuel to assure ignition. High rate of cooled exhaust gas recirculation was used. The engine performance and emissions, particularly NOx–smoke trade-off, was also investigated. In order to reduce the number of experiments to be performed, the tests were conducted at a speed of 1500 rpm, with changes in the recirculated exhaust gas rate (10%, 30% and 50%) and change in injection timing (20°, 22°, 25°, 28° and 32° BTDC).Practical results showed that a significant improvement could be achieved in the NOx–PM trade-off. The ignition delay period can be increased by using a low-CN fuel accompanied with a low oxygen intake charge. When using the PPCI system, low levels of NOx and PM can be achieved without affecting the brake thermal efficiency of the engine. Smoke can be reduced even when the EGR percentage is increased under a mixed condition. ED10 (90% E85 + 10% diesel) had the largest decline in NOx (84.66%) and smoke (55.8%) compared to diesel.

Performance and emission characteristics of biodiesel blends in a premixed compression ignition engine with exhaust gas recirculation

Performance and emission characteristics of biodiesel blends in a premixed compression ignition engine with exhaust gas recirculation

Experimental and computational investigation of soot production from a premixed compression ignition engine using a load extension injection

Low temperature, highly premixed compression ignition strategies have proven to produce high efficiency and low soot emissions, but struggle to reach high loads within normal operating constraints. Recent research has suggested that a mixed mode combustion strategy using a premixed main heat release followed by a mixing controlled load extension injection can retain the part-load thermal efficiency and emissions reduction potential of premixed compression ignition strategies, while enabling high load operation. However, soot emissions under this type of mixed mode combustion strategy have been shown to be problematic. This work investigates soot formation and mitigation methods using a combination of detailed engine experiments and computational fluid dynamics modeling. A premixed compression ignition combustion event was achieved using a premixed charge of gasoline and n-heptane to control combustion phasing, and a load extension injection of gasoline was added near top dead center. The experiments showed negligible engine out soot under the premixed compression ignition operating conditions (i.e. without the load extension injection). When the load extension injection was added, soot increased by several orders of magnitude. Detailed experiments were used to isolate the effects of injection timing, injection pressure, charge conditions (e.g. air–fuel ratio), and fuel type. Computational fluid dynamics modeling considering polycyclic aromatic hydrocarbon chemistry up to pyrene was then used to explain the experimentally observed soot trends. As expected, the soot emission results showed a strong impact of oxygen concentration and injection pressure for injection timings near top dead center; however, as the load extension injection event was delayed beyond the end of the premixed compression ignition heat release, the soot formation decreased and became independent of oxygen concentration. At these conditions, the computational fluid dynamics modeling showed that soot formation is dependent solely on temperature. The results identify a pathway to enable premixed compression ignition load extension, while minimizing soot emissions.

Investigation of the Effect of Fuel Reactivity on Dual-Fuel PCI Combustion

The potential of controlling premixed compression ignition (PCI) combustion by two fuels with different ignitability and volatility was studied numerically by a three-dimensional computational fluid dynamics (CFD) model. The results indicate that the addition of gasoline to diesel fueled PCI engine can retard the ignition timing, lower the in-cylinder temperature, and reduce the exhaust emissions.

Autoignition quality of gasoline fuels in partially premixed combustion in diesel engines

A single-cylinder diesel engine has been run on gasolines of different octane numbers and on model fuels, mixtures of iso-octane, n-heptane and toluene, at different operating conditions. The autoignition quality of the fuel is best described by an Octane Index, OI = (1 − K) · RON + K · MON for fuels in the gasoline autoignition range where RON and MON are, respectively, the Research and Motor Octane numbers and K is an empirical constant which is measured to be negative. Hence for a given RON, a non-paraffinic fuel, of lower MON, will have higher OI and more resistance to autoignition. For a given operating condition, ignition delay increases non-linearly with OI and changes little over the autoignition range of practical diesel fuels. Heat release following the autoignition is influenced by the stratification which will increase as the time between the end of injection and start of combustion decreases and combustion phasing parameters such as Combustion Delay, the difference between the 50% burn time and the start of injection, become less correlated with fuel autoignition quality. Higher ignition delays facilitate premixed combustion in the diesel engine. If two fuels have similar combustion phasing at the same injection timing, their emissions performance is also similar. Hence a good surrogate for gasoline in partially premixed compression ignition engines is a mixture of toluene, iso-octane and n-heptane with the same RON and MON.

Some Effects of Fuel Autoignition Quality and Volatility in Premixed Compression Ignition Engines

Some Effects of Fuel Autoignition Quality and Volatility in Premixed Compression Ignition Engines

Development of a Flame Propagation Model for Dual-Fuel Partially Premixed Compression Ignition Engines

The limitations of an existing characteristic-time combustion (CTC) model are explored and a new combustion model is developed and applied to simulate combustion in dual-fuel engines in which the premixed natural gas is ignited by the combustion flame initiated by a diesel spray. The model consists of a diesel auto-ignition model and a flame propagation model. A G-equation-based model previously developed to simulate SI engine combustion was incorporated with an auto-ignition model to simulate the flame propagation process in partially premixed environments. The computer code is based on the KIVA-3V code and consists of updated sub-models to simulate more accurately the fuel spray atomization, auto-ignition, combustion, and emissions processes. Modifications were made to implement the level set G-equation approach and to track the location of the flame as a function of the turbulent flame speed, flame curvature, flow velocity, and the movement of the computational mesh in the engine environment. Good agreement with engine experiments was obtained by using the present model.

328 ガソリン予混合圧縮着火機関における着火・燃焼過程の数値シミュレーション(OS-2 ガソリン機関シミュレーション)

Gasoline premixed compression ignition engines can operate with high thermal efficiency and can reduce Nox emission by burning very lean homogeneous mixture at high compression ratio. Therefore, the engines are expected to become practicable as one of next-generation engines. In this study, the ignition and combustion process in a gasoline premixed compression ignition engine was numerically simulated using the authors' GTT code. As a result, the ignition timing, heat release rate and cylinder gas pressure at various air-to-fuel ratios and engine speeds were predicted reasonably well.

Numerical Prediction of Mixture Formation and Combustion Processes in Premixed Compression Ignition Engines.

For numerically predicting the mixture formation and combustion processes in premixed compression ignition engines, fuel spray submodels (the authors' modified wave breakup model, etc.), an ignition submodel (Livengood Wu's model or Schreiber's reduced kinetic model) and a combustion submodel (Reitz's model) were incorporated into the authors' GTT code. The combustion processes in the two types of premixed compression ignition engines (side-injection and central injection engines) were numerically analyzed using this code. These submodels were validated by comparing the calculated results of heat release rate with experimental ones.The calculated amount of NO production using the extended Zeldovich mechanism nearly agreed with the experimental one.

318 2 段噴射予混合圧縮着火機関における燃焼過程の数値解析

In premixed compression ignition engines, NOx emission is reduced remarkably under partial load conditions but the engines cannot work under high load conditions. For improving such a defect, a MULDIC (Multiple Stage Diesel Combustion) concept was proposed by New ACE Institute. In a MULDIC engine, the premixed combustion at the first stage and the diffusion combustion at the second stage have to be optimized to realize high output with low NOx emission. In this study, the combustion processes under various injection conditions in a MULDIC engine were numerically analyzed using the authors' GTT code with Schreiber's five-step reduced kinetic model. As a result, the heat release rate and the tendency of NOx emission were predicted reasonably.

Estimation of Heat Loss from Combustion Chamber by Heat Balance Method and Its Validation.

Estimation method of heat loss ratio by heat balance calculation was introduced to claify thermodynamic characteristics of premixed compression ignition engines. The effects of measuring error on calculated heat loss ratio were inlestigated in detail and the results show that it is essential to measure exhaust temperature set T.D.C. timing accurately. The validation was done by comparing the results from heat balance and the results from integrated heat flux measured at piston surface and also lower surface of the cylinder, and the calculated heat loss seems to be reasonable in both qualitatively and quantitatively. The estimation method was applied for a timing swing test of early injection type premixed compression ignition engine and the result explained the characteristics of premixed compression ignition combustion, such as wall wetting fuel and knock.

Performance and Exhaust Emission in a Premixed Compression Ignition Engine with High Pressure Fuel Injection Near a Top Dead Center.

Premixed lean diesel combustion was performed in a condition that a fuel injection timing was near top dead center. To promote fuel-air mixing a micro-hole nozzle (nozzle hole diameter is 0.08 mm) and high pressure injection (up to 250 MPa) were used. Low cetane number fuel was used for main injector mounted at the bore center to make ignition delay. Small quantity of high cetane number fuel was supplied from two side injectors to control the ignition timing. As a result, low NOx combustion was realized in an operating codition when the ignition started after several crank angles from injection end. Important factor to realize this combustion is to complete the fuel injection and vaporization before ignition.

(1-16) Numerical Prediction of Mixture Formation and Combustion Processes in Premixed Compression Ignition Engines((NCS-1)Novel Combustion Systems 1-Homogeneous Charge, Premixed Charge Compression Ignition Engines)

In order to numerically predict the mixture formation and combustion processes in premixed compression ignition engines, submodels for fuel sprays (solid-cone and hollow-cone sprays), ignition and combustion were investigated. As an ignition model, the Livengood-Wu's model and the Schreiber's reduced kinetic model were examined. As a combustion model, the Reitz's model was employed. These submodels were incorporated into the authors' GTT code, and the mixture formation and combustion processes in the two types of premixed compression ignition engines (side-injection and central-injection engines) were numerically analyzed using this code. The validity of the submodels was confirmed by comparing the calculated results with the experimental ones. Figure I shows the mixture formation process in the side-injection engine. It has been found that using the Livengood-Wu's model the curves of heat release rate in the main combustion period in the test engines have been predicted reasonably well with the appropriate model constants. It has been also found that using the Schreiber's reduced kinetic model the curves of heat release rate in both periods of low-temperature oxidation and main combustion for two cases in the side-injection engine have been predicted considerably well with the appropriate parameters for the reaction rate constants. Figure II shows an example of the comparison between the experimental result of the heat release rate in the side-injection engine and the calculated result of the heat release rate using the Schreiber's model and the Reitz's model.

C115 ディーゼル燃焼の多次元モデリング(新技術フォーラム-2 : エンジンの燃焼モデリングの現状と将来)

In order to conduct the three-dimensional numerical analysis of the mixture formation and combustion processes in diesel engines, submodels for fuel sprays, ignition and combustion had been investigated. In this paper, the Livengood-Wu's model or the Schreiber's reduced kinetic model was applied as an ignition model. As a combustion model, the Reitz's model was employed. These submodels were incorporated into the author's GTT code, and the combustion process in a direct-injection diesel engine and that in a premixed compression ignition engine were numerically analyzed using this code. The validity of the submodels was confirmed by comparing the calculated results with the experimental ones.

Study of Operating Region and Combustion Characteristics of Premixed Compression Ignition Engine.

Study of Operating Region and Combustion Characteristics of Premixed Compression Ignition Engine.

706 予混合圧縮着火機関における混合気形成過程の数値解析(OS-6 数値解析・シミュレーション)

706 予混合圧縮着火機関における混合気形成過程の数値解析(OS-6 数値解析・シミュレーション)