Direct Injection Compression Ignition Combustion Research Articles

DETERMINE SIMULATION MODEL OF ELECTRONIC CONTROL SYSTEM FOR DIRECT INJECTION COMPRESSION COMBUSTION ENGINE

The aim of this research is to determine a simulation of an electric control unit (ECU) for direct injection compression ignition combustion engine, in order to improve an engine performance and reduced fuel consumption. The simulation comprises thermodynamic model for determining engine parameters according to Spray Penetration Mixing Length, and imposes in Matlab and Simulink. This model allows closed loop control interferences with Arduino MEGA-2560 to manage amount of injected fuel and start of injection that, could be lead to obtain the optimum thermodynamic energy. The results of thermodynamic model show that, the engine parameters can be related linearly, and matching the other published researches on the same conditions and specifications. The results of (ECU) show synchronization between desired and output signals and appear more accuracy when compared with other methods.

Characteristics of auto-ignition in gasoline–biodiesel blended fuel under engine-like conditions

The purpose of this study is to demonstrate the effects of biodiesel fraction on auto-ignition for gasoline–biodiesel blended fuel, which combines two fuels with widely different auto-ignition characteristics. First, gasoline was blended with biodiesel at 5%, 10%, 15%, and 20% by volume, and then tested in a rapid compression expansion machine at a compression ratio of 11 and a temperature range of 720–850 K to observe the auto-ignition delay phenomenon under engine-like conditions. The experimental conditions are focused on improving the auto-ignition characteristic of gasoline direct-injection compression ignition combustion strategies under low load and cold start. The heat release rate of the blended fuels was calculated from the pressure trace and displacement history of the piston in order to identify first-stage ignition and second-stage (auto-ignition) ignition delay. Second, a gasoline–biodiesel reaction mechanism was developed to predict the chemical ignition delay of the blended fuels. The reaction mechanism with 4285 species and 15,246 reactions was validated and implemented using the CHEMKIN PRO software. Finally, the chemical ignition delay was predicted by the simulation which was further compared to the experimental measured results. These results revealed that a higher biodiesel fraction helps to obtain shorter ignition delay, which reduces the requirement of intake temperature. The blended fuel with 20% biodiesel showed the lowest ambient temperature at the injection timing requirement and was 80 K lower than gasoline. Each blended fuel exhibited two-stage ignitions in the measured temperature range. The combustion duration and pressure peak of every blended fuel were similar to each other after increasing the biodiesel fraction.

Experimental and modelling investigations of the diesel surrogate fuels in direct injection compression ignition combustion

Experimental investigations on the combustion and emission characteristics of diesel and three potential diesel surrogate fuels have been performed, including the 85% (vol.) n-heptane blended with 15% toluene (T15), 81% n-heptane blended with 14% toluene and 5% c-hexane (T15+CH5), and 80% (vol.) n-heptane blended with 20% toluene (T20). The experimental results showed that due to the lower reactivity of the three diesel surrogate fuels, the combustion phases were more retarded and the indicated thermal efficiencies were lower compared to diesel. For the diesel surrogate fuels with higher volatility, the soot emissions were lower than those of diesel due to more premixed combustion. Moreover, a reduced n-dodecane-toluene reference fuel-c-hexane-polycyclic aromatic hydrocarbon (PAH) mechanism composed of 167 species and 671 reactions was formulated and was extensively validated against the experimental results. To clarify the experimental results, the reduced mechanism was then used for the three-dimensional (3-D) modelling investigations. The modelling results showed that the reduced mechanism can reasonably capture the combustion characteristics of T15+CH5 in the direct injection compression ignition combustion. The NOx and soot emissions were both reasonably predicted. From the modelling investigations, it was inferred that the physical effects on the soot emission were larger than the chemical effects of the different fuel carbon-chain structures. According to the 0-D modelling investigations, the soot tendency of the four pure diesel surrogate constituents can be sequenced as toluene>c-hexane>n-dodecane>n-heptane. Given that toluene is the dominant factor affecting the soot formation than the other three components, the soot tendency of the four diesel surrogate fuels can be sequenced as T20>T15+CH5 (n-dodecane)>T15+CH5 (n-heptane)≈T15.

Development of a combined reduced primary reference fuel-alcohols (methanol/ethanol/propanols/butanols/n-pentanol) mechanism for engine applications

A combined reduced primary reference fuel (PRF)-alcohols (methanol/ethanol/propanols/butanols/n-pentanol) combustion kinetic mechanism composed of 161 species and 622 reactions was developed for engine combustion simulations. The obtained reduced PRF-alcohols mechanism was constructed with a hierarchical structure. Minor adjustments were performed to ensure the predictive performance against experimental results. The reduced PRF-alcohols mechanism adequately predicted experimental ignition delays, laminar flame speeds, and species mole fraction profiles. New homogeneous charge compression ignition experiments fueled with 75% (mol.) n-propanol/25% n-heptane, 75% i-propanol/25% n-heptane, and 75% n-pentanol/25% n-heptane blends were also collected and served as further mechanism validations. By coupled with the toluene-polycyclic aromatic hydrocarbons sub-mechanism, the reduced PRF-alcohols mechanism was used for the three dimensional modeling studies to investigate the direct injection compression ignition (DICI) combustion fueled with diesel/alcohol blends at the 5% fuel oxygen content. Zero-dimensional modeling studies were also conducted. The modeling results indicated that in DICI combustion, it was the different physical mixing qualities incurred by the different fuel reactivity dominated the soot formation but not the different carbon chain chemical structures. The O atom of the fuel molecule was more efficient than the O2 molecule for the soot oxidation.

Development of a reduced toluene reference fuel (TRF)-2,5-dimethylfuran-polycyclic aromatic hydrocarbon (PAH) mechanism for engine applications

A reduced TRF-2,5-dimethylfuran (DMF25)-PAH combustion mechanism composed of 136 species and 617 reactions was developed for the engine combustion simulations. This mechanism was constructed based on a previous reduced TRF-PAH mechanism and a detailed DMF25 mechanism. First, the reduced DMF25 sub-mechanism was formulated using various mechanism reduction methods, and was then incorporated into the base reduced TRF-PAH mechanism. Further optimizations based on sensitivity analyzes of ignition delay were conducted, and an evaluation process of the most sensitive reactions was proposed. This reduced TRF-DMF25-PAH mechanism was extensively validated against the experimental results, including measured ignition delays, species mole fraction profiles and laminar flame speeds. The generally good predictions indicate that the proposed mechanism can be applied for practical applications like the combustion simulations in both spark ignition and compression ignition engines. Homogeneous charge compression ignition and direct injection compression ignition experiments were performed and compared with the modeling results. In direct injection compression ignition combustion cases, the combustion characteristics as well as the soot and NOx emissions were all well predicted. Lower soot emissions were obtained with diesel-DMF25 blends compared to diesel and diesel/iso-octane blends, mainly due to the longer ignition delay, which allows sufficient mixing prior to combustion.

Dimethyl ether energy ratio effects in a dimethyl ether-diesel dual fuel premixed charge compression ignition engine

The combination of port DME induction and in-cylinder diesel direct-injection compression ignition combustion was studied in a two-cylinder engine. The port DME energy ratio was proved to be one of main variables affecting the combustion. Thus, the main goals of this paper were to investigate the effects of DME energy ratio on combustion and emission characteristics of the diesel engine at this dual-fuel PCCI combustion mode. In order to evaluate the characteristics of this combustion mode, the conventional direct-injection compression ignition engine performance was provided to make a detailed comparison. Furthermore, special concern was focused on the complex combustion process analysis. DME port induction and diesel in-cylinder direct-injection combustion process was composed of the homogeneous charge compression ignition combustion and conventional diffusive combustion. Although DME energy ratio had little impact on the start timing of cool flame, the negative temperature coefficient region shortened and the start timing of HCCI high-temperature reaction advanced as DME energy ratio increased. It could also be discovered that, as DME energy ratio increased, the maximum heat release rate of DME HCCI increased as well as the peak values of cylinder pressure and mass-averaged temperature; however, the maximum heat release rate of diesel combustion decreased. Results also showed the brake thermal efficiency slightly increased with a rise of DME energy ratio. In the case of emission, smoke emissions decreased, NOx emissions decreased first but this decreasing trend was inhibited later, while HC and CO emissions increased with a rise of DME energy ratio.

Effects of DME pilot quantity on the performance of a DME PCCI-DI engine

The combination of premixed charge compression ignition and conventional direct-injection compression ignition combustion is studied in a DME engine. This combustion mode is referred to as PCCI-DI combustion. The pilot quantity is found to be one of main variables affecting the PCCI-DI combustion. So, the main objectives of this paper are to examine the effect of different DME pilot quantities on combustion and emission characteristics in a single-cylinder direct-injection DME engine and to determine whether PCCI-DI is a viable in-cylinder NO x emissions reduction technology. In order to evaluate the characteristics of PCCI-DI combustion, the conventional direct-injection compression-ignition engine performance is supplied to make a comparison with their results. Furthermore, special emphasis is put upon the combined combustion process analysis. Results show that DME engine can operate at a wide range of speeds and loads at PCCI-DI mode. In comparison to the conventional DME CI combustion, the brake thermal efficiency slightly increases for DME PCCI-DI operation. PCCI-DI is capable to decrease NO x effectively for all loads. NO x emission shows an obviously descending tendency with an increase in DME pilot quantity at low loads, while it shows a mildly elevating tendency with an increase in DME pilot quantity at high loads. HC and CO emissions increase for DME PCCI-DI operation under various DME pilot quantities.

Experimental study on the effects of mixture homogeneity on stratified-charge compression ignition combustion

In this paper, an investigation of the n-heptane stratified-charge compression ignition (SCCI) combustion on a single-cylinder engine using port fuel injection combined with in-cylinder direct injection is reported. The effects of mixture homogeneity, overall equivalence ratio, and fuel delivery advance angle of directly injected fuel on the SCCI combustion characteristics and emissions were evaluated. The experimental results revealed that the heat release curve of SCCI combustion exhibited a three-stage combustion mode, which includes low-temperature reaction (LTR), high-temperature reaction (HTR), and diffusion burn. The operating ranges can be significantly broadened by mixture stratification, owing to the smooth heat release. As the mixture homogeneity increases, the peak value of the heat release in the HTR increased but the maximum heat release in the third stage decreased. For a fixed overall equivalence ratio, with an increase in the mixture homogeneity, the nitrogen oxide (NO x) emissions from SCCI combustion started to decrease initially and attained the lowest level, but carbon monoxide (CO) emissions increased initially and achieved the highest level. Once the mixture homogeneity further increased, NO x emissions began to increase but CO emission decreased. Compared with the traditional direct-injection compression ignition combustion mode, NO x emissions from SCCI combustion can be reduced markedly. Also, hydrocarbon emissions from SCCI combustion were much lower than from neat homogeneous charge compression ignition combustion. The fuel delivery advance angle also had an important influence on SCCI combustion and the emissions. In particular, NO x emissions can be further significantly reduced using the late fuel injection strategy.