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Abstract: Homogeneous charge compression ignition (HCCI) engines are amenable to a large variety of fuels as long as the fuel can be fully vaporized, mixed with air, and receive sufficient heat during the compression stroke to reach the autoignition conditions. This study investigates an HCCI engine fueled with ethanol-in-water mixtures, or “wet ethanol”. The motivation for using wet ethanol fuel is that significant energy is required for distillation and dehydration of fermented ethanol (from biosources, not from petroleum), thus direct use of wet ethanol could improve the associated energy balance. Recent modeling studies have predicted that an HCCI engine can operate using fuel containing as little as 35% ethanol-in-water with surprisingly good performance and emissions. With the previous modeling study suggesting feasibility of wet ethanol use in HCCI engines, this paper focuses on experimental operation of a 4-cylinder 1.9-L engine running in HCCI mode fueled with wet ethanol. This paper investigates the effect of the ethanol-water fraction on the engine''s operating limits, intake temperatures, heat release rates, and exhaust emissions for the engine operating with 100%, 90%, 80%, 60%, and 40% ethanol-in-water mixtures. [Copyright &y& Elsevier]

Free-piston engine generator (FPEG) is a new type of energy conversion system directly coupled with the free piston engines and linear motors, and it is expected to be the next-generation substitution to traditional internal combustion engine because its high efficiency, high volumetric power density and multi-fuel adaptability potential. However, the continuous and stable operation of FPEG is one of the biggest challenges for its large-scale application. In this paper, a complete dual-cylinder type FPEG system test bench was established to experimentally investigate the dynamic and combustion fluctuations. The results of the experiments showed that the dead centre position increased from 16.1 mm to 26.0 mm, and the peak gas pressure increased from 2.4 bar to 7.5 bar when the starting current increased from iq/iqmax = 15% to iq/iqmax = 21%. The low-pressure cold start strategy is feasible, as the experimental results showed that the ignition was achieved at the starting pressure of 4 bar. Compared with the combustion process with linear motor thrust, the operation of the system tends to be more stable, and the coefficient of variation (COV) of the peak in-cylinder gas pressure is 22.78% and 10.12%, respectively. The COV results of the top dead centre (TDC) position, compression ratio, peak in-cylinder pressure and peak in-cylinder pressure position are 0.84%, 3.33%, 2.27% and 0.84%, respectively in the single-cylinder working mode. This means that there is still a large room for the improvement of the stable operation of the FPEG system. • A complete dual-cylinder type FPEG system test bench was established. • The prototype realizes single-cylinder and dual-cylinder operation modes. • A low-pressure cold start strategy is proposed and implemented by experiment. • Breakthrough in continuous and stable operation of FPEG prototype. • The stable operation of the FPEG system still has great room for improvement. [ABSTRACT FROM AUTHOR]

Injection strategies and fuel properties have significant effect on the mixing process of fuel and air in the cylinder, which further affects the combustion and emissions. Three types of gasoline surrogate fuels were tested on a gasoline direct injection (GDI) engine in this paper. The effects of different injection pressures and injection timings on the combustion and emissions of the surrogate fuels were investigated, and the results were compared with those of a commercial gasoline with an octane number of 95. Also, the experiments were conducted at a stoichiometric air-fuel ratio with the engine speed of 2000 rpm and a load of 6 bar. The results show that injection pressure and injection timing have certain effects on the combustion and emissions of the surrogate fuels, which indicates clear differences with the commercial gasoline. In addition, the combustion and emissions of the surrogates are also different due to different compositions. The surrogates have higher in-cylinder pressure and temperature and more advanced combustion phase than commercial gasoline. The surrogates have advantages in NOx emissions and PM emissions under all the testing conditions. Nevertheless, gasoline has much lower CO emissions, THC emissions and most irregular emissions. Generally, low injection pressure and retarded injection timing can be applied to obtain higher thermal efficiency of the surrogate fuels, whereas for gasoline, the injection timing need to be kept at around 300 o CA BTDC. To obtain low CO and THC emissions, gasoline should be applied with low injection pressure and the injection timing should be postponed. On the other hand, for low PM and NOx emissions, the surrogate fuels should be utilized with high injection pressure and the injection timing should be around 300 o CA BTDC. [ABSTRACT FROM AUTHOR]

One of attracting concepts has been the use of Turbosail principle to produce lift from aspirated cylinders with flap in various engineering applications. The Emerging of the Turbosail principle in wind turbine technology is promising to develop and to design innovative devices. The objective of this project paper is to develop an efficient numerical code, for the prediction of the aerodynamic characteristics of Turbosail type wind turbine with very thick aspirated profiles. A vortex model has been treated based on the lifting line theory. The results predicted by the code developed, have been compared and validated by some numerical and experimental data. [ABSTRACT FROM AUTHOR]

Periodic revisions in the emission norms demands refinement of engine design as well as combustion process. Of late HCCI (Homogeneous charge compression ignition) has gained interest among the combustion community for its adoption in automotive engines. Control of NOx emissions is rather difficult compared to other emissions as it interferes with in–cylinder phenomena which in turn reflect on the performance of the engine. In the present work, an attempt is made in achieving further reduction in NOx emission in HCCI mode of operation. For this purpose, premixed charge is inducted into the HCCI combustion chamber assisted with a swirl motion to enhance the convective heat transfer inside the combustion chamber. The effect of swirl in enhancing the convective heat transfer and reduction of NOx emissions was discussed in this paper. An extensive numerical experiment are conducted considering a 1.6 L single cylinder engine with a reentrant piston bowl running in HCCI mode employing a validated ECFM-3Z (Extended Coherent Flame Model-3 Zones) (STAR-CD) combustion model. Emphasis was laid on effective reduction of NOx emissions with enhanced heat transfer by simultaneously varying Boost pressure, Compression ratio, EGR (Exhaust gas recirculation) under different swirl ratios. The study revealed that higher swirl ratios play vital role in improving the convective heat transfer rate and reduction of NOx emissions. Also, it was observed that higher boost pressures & higher swirl ratios, lower EGR proportions & higher swirl ratios and higher compression ratios and higher swirl ratios are favorable in increasing the convective heat transfer. Higher compression ratios, higher boost pressures, higher EGR concentrations were observed to be favorable to reduce the NOx emissions. The results showed that apart from adopting higher compression ratios and boost pressures use of high swirl ratios is observed to be contributing to a large extent in enhancing the rates of heat transfer which would lead to significant reduction in in–cylinder temperatures suitable for low NOx emission formation in HCCI mode. [ABSTRACT FROM AUTHOR]

In this paper, an innovative fuel injection rate measurement methodology for the natural gas and diesel co-direct injection injector was designed to study the dual-fuel injection characteristics for a high-pressure natural gas direct injection engine. The results indicate that the injection mass shows two different upward trends as the energizing time (ET) increases, and it appears more sensitive to the length of ET when it is short. The gas injection duration is affected by both the injection pressure and ambient pressure under the same ET, thus any increase in either will significantly increase the injection duration, resulting in a pronounced increase in gas injection mass. The process of diesel pilot injection has a remarkable effect on the gas injection rate. According to the actual engine working condition, provided that the pilot diesel ET is 0.8 ms, the gas injection mass reaches the minimum value when the split time is about 0.8 ms, meanwhile, it reaches the maximum value when the split time is about 0.2 ms or 2 ms. The results of this study can provide an accurate database for the performance of the injector and accurate fuel injection boundary conditions for the combustion process in the engine cylinder. • A measurement method of the two-phase fuel injection characteristics is realized. • The gas injection mass shows a linear upward trend with the increase of energizing time. • The gas injection mass is significantly increased by increasing the ambient pressure. • The pilot diesel injection lead to regular fluctuations in gas injection mass. [ABSTRACT FROM AUTHOR]

A Stirling engine configuration consisting of two cylinders, a regenerator and a sliding disc actuating mechanism (“swashplate”) is considered in this paper. A mathematical model, which combines fundamental and empirical correlations, and principles of classical thermodynamics, mass and heat transfer accounting for variable heat transfer coefficients, is developed. The proposed model is then utilized to simulate numerically the system transient and steady state response under different operating and design conditions. A system global optimization for maximum performance in the search for optimal parameters that lead to maximum cycle efficiency is performed with low computational time. Appropriate dimensionless groups are identified and the results presented in normalized charts for general application. The numerical results show that the two-way maximized system efficiency, , occurs when two system characteristic parameters, the ratio between the total swept volume during the expansion, and the total swept volume, , and the ratio between the heat transfer area of the hot side heat exchanger and the total heat exchange area, y, are optimally selected, i.e., . The two-way maximized cycle efficiency found with respect to the optimized parameters is sharp, in the sense that a 225% variation of the calculated efficiency values was observed within the range of tested configurations in this study, and “robust” (i.e., relatively insensitive) to the variation of several parameters, thus stressing the importance to be considered in actual design. It is also found that the twice-maximized cycle efficiency and the total engine work output increase monotonically with the temperature of the hot source, T h. As a result, the model is expected to be a useful tool for simulation, design, and optimization of Stirling engines. [ABSTRACT FROM AUTHOR]

Phase change material (PCM), has been widely researched in many previous works, shows a good potential for thermal energy storage. The present paper investigated the mesoscopic morphologies and evolution mechanism of microencapsulated phase change materials (MEPCMs) using dissipative particle dynamics (DPD) simulations, which has rarely been performed in PCM related studies. The adequate coarse-grained and Flory-Huggins-type models were used to replace the molecular structures and calculate interaction parameters. The MEPCMs were fabricated with methyl trimethoxysilane (MTMS), 3-aminopropyl trimethoxysilane (APTMS) and n-eicosane in watery environment. The results showed that the simulated final configuration presented a cylindrical structure when the relative amount of water is less than the desired value. The size of the encapsulation decreased with the increasing of water concentration and increased with the increasing of core material concentration. The rational proportion of the components can be optimized or confirmed by the DPD simulations. The research indicates that the DPD simulation is an effective method for understanding the encapsulation process. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the entropy generation due to flow and heat transfer of nanofluids between Co-rotating cylinders with constant heat flux on the walls is studied, analytically. The governing equations in cylindrical coordinates are simplified and solved to find the effect of using nanofluids with different volume fractions on the entropy generation rate in the annulus. The results are presented at various values of Brinkman number (Br), velocity ratio (λ), radius ratio (Π), heat flux on the inner cylinder (Q 0), and a parameter (Ψ) which determines the contribution of the fluid friction in the overall entropy generation. The analysis has been done mainly using Al2O3–EG nanofluid, though some comparisons with TiO2–Water nanofluid are made. The thermophysical properties of nanofluids are calculated using the available relations based on experimental data. From the average entropy generation viewpoint, at different conditions, an optimum volume fraction of nanoparticles is obtained in which the average entropy generation is minimized. Finally, some comparisons between the effects of using Al2O3–EG, and TiO2–Water nanofluids are made. The results show that TiO2–Water nanofluid is more suitable than Al2O3–EG nanofluid to use as the working fluid at low Brinkman numbers. [Copyright &y& Elsevier]

Abstract: An analysis of in-cylinder gas density and oxygen mass concentration (YO2) impact on the mixing and oxidation processes and the final soot emissions in conventional high temperature diffusive Diesel combustion conditions is presented in this paper. Parametrical tests were performed on a single cylinder heavy duty research engine. The density was modified adjusting the boost pressure following two approaches, maintaining the YO2 either before or after the combustion process. The YO2 was modified by diluting fresh air with exhaust gas maintaining a constant density. The possibility of controlling the soot emissions combining both parameters (YO2 and density) is evaluated and, in a final part, the NOX emission results are also addressed. Results show that YO2 has a strong effect on both mixing and oxidation processes while density affects principally the mixing process. Both parameters affect the final soot emissions. The density modification through adjustment of boost pressure modifies the trapped mass and has a strong impact on the evolution of YO2 (thus on the evolution of the mixing process) during combustion. If the density is increased maintaining constant the YO2 at the beginning of the combustion, the NOX-Soot trade-off is enhanced. [Copyright &y& Elsevier]

Abstract: Because of the low combustion temperature and high throttling loss, SI (spark-ignited) engines always encounter dropped performance at low load conditions. This paper experimentally investigated the co-effect of cylinder cutoff and hydrogen addition on improving the performance of a gasoline-fueled SI engine. The experiment was conducted on a modified four-cylinder SI engine equipped with an electronically controlled hydrogen injection system and a hybrid electronic control unit. The engine was run at 1400 rpm, 34.5 Nm and two cylinder cutoff modes in which one cylinder and two cylinders were closed, respectively. For each cylinder closing strategy, the hydrogen energy fraction in the total fuel was increased from 0% to approximately 20%. The test results demonstrated that engine indicated thermal efficiency was effectively improved after cylinder cutoff and hydrogen addition, which rose from 34.6% of the original engine to 40.34% of the engine operating at two-cylinder cutoff mode and . Flame development and propagation periods were shortened with the increase of the number of closed cylinders and hydrogen blending ratio. The total cooling loss for all working cylinders, and tailpipe HC (hydrocarbons), CO (carbon monoxide) and CO2 (carbon dioxide) emissions were reduced whereas tailpipe NO x (nitrogen oxide) emissions were increased after hydrogen addition and cylinder closing. [ABSTRACT FROM AUTHOR]

This paper investigates use of artificial neural network (ANN) model in prediction of brake specific energy consumption (BSEC), nitrogen oxides (NO x), unburnt hydrocarbon (UHC), and carbon dioxide (CO 2) emissions of a single cylinder diesel engine operates with diesel-palm biodiesel-ethanol blends. The engine is run at different load form 20–100% and 1500 rpm constant speed. The fuel used in this present study are diesel and six different diesel-palm biodiesel-ethanol blends. The Levenberg-Marquardt back propagation training algorithm with logistic-sigmoid activation function results best prediction of performance and emission characteristics with accurate overall correlation coefficient (R) (0.99329–0.99875) and minimum mean square error (MSE) (0.000179082–0.000465809). The mean absolute percentage errors (MAPE) are observed to be in range of 2.32–4.54% with the acceptable margin of mean square relative error (MSRE). Furthermore, experimental and ANN predicted data are compared in fuzzy interface system (FIS) to find optimum engine operating parameters. Compared to other blends, at 20% load, D85BD10E5 blend exhibits the highest MPCI (multi performance characteristics index) values of 0.718 and 0.705 for experimental and ANN predicted data respectively. Robustness and reliability of the proposed techniques clearly explain the application of ANN and fuzzy logic system in the prediction and optimization of engine parameters. • An ANN model was developed for prediction of BSEC, NOx, UHC & CO 2 emissions. • Types of transfer function, training algorithm & number of neurons were acquainted. • MSE values were obtained very low, ranges between 0.000179 and 0.000466. • MAPE (2.32–4.54%) and R (0.99329–0.99875) values were under the acceptable range. • ANN-Fuzzy approach found effective in engine parameters prediction & optimization. [ABSTRACT FROM AUTHOR]