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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]

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]