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The development of rotary engines is severely restricted by its low combustion efficiency and high emission. In‐cylinder flow field is known to play a major role in combustion process for rotary engines. Therefore, in the present article, a three‐dimensional dynamic simulation model considering leakage through apex seals was developed and verified by the two‐dimensional particle image velocimetry experiment results on the rotor housing central plane. Based on the three‐dimensional dynamic simulation model, the formation mechanisms of flow field in a compound intake ported rotary engine under different apex seal leakage gap sizes (0.02, 0.04, 0.06, and 0.08 mms) and engine speeds (2,000, 3,500, and 5,000 rpms) were numerically studied. The simulation results showed that there exist two formation mechanisms of the flow field in the intake stroke, that is, "side intake port dominance" and "peripheral intake port dominance." For the three engine speeds (2,000, 3,500, and 5,000 rpms), with the increase of apex seal leakage gap size, the formation mechanism of the flow field gradually changed from "side intake port dominance" to "peripheral intake port dominance." In addition, the influences of apex seal leakage on the volume coefficient and the turbulence kinetic energy in the combustion chamber were also investigated in detail. [ABSTRACT FROM AUTHOR]

Energy conservation is important in this modern era because of its high demand in transportation systems coupled with the depletion of fossil fuels. Biodiesel is thus an alternative fuel to replace conventional diesel. This study investigates the effect of chamber pressure (Pamb) and chamber temperature (Tamb) on biodiesel spray penetration length (SL) and spray pattern (SP) characteristics in a constant-volume vessel, under rotary engine working conditions, using spray visualization and image processing techniques. Furthermore, a three-dimensional (3D) direct-injection rotary engine model was developed and used for computational fluid dynamics (CFD) simulation studies of biodiesel distribution, mixture forming, and combustion process at different injection timing (IT) in the cylinder. Results indicate that increasing Pamb decreases SL and broadens SP , while increasing Tamb decreases SL and narrows SP. At advanced IT, biodiesel diffuses and disperses, and at retarded IT, which is the suitable rate for combustion, biodiesel concentrates and narrows. Compared with the original scheme [80° crank angle before top dead center (CA BTDC)], Pmax increases by 16.79%, ϕmax decreases by 28.75%, NO and CO change a little, and CO2 decreases. Its drawback is a 15.65% increase in soot formation. [ABSTRACT FROM AUTHOR]

Biodiesel is a clean energy source that helps in the reduction of environmental pollution as compared to fossil fuel. This study aimed to improve the performance of combustion and reduce emission in direct injection rotary engine by fueling it with biodiesel as well as selecting the best ignition time. A 3D‐dynamic simulation model was established and then coupled with biodiesel chemical kinetics mechanism. On this basis, investigation of five ignition timings (IT) was conducted to know their various effects on combustion process. The simulation results showed that properly advancing IT increased in‐cylinder pressure, with the peak pressure (Pmax) of 35°CA (BTDC) IT of 45.99 bar the largest. Comparing IT of 35°CA (BTDC) with the IT of the original engine showed an 18.14% increase in peak pressure. The corresponding crank angle (φmax) for Pmax values also proved that when the IT was advanced, φmax values decreased and that of 35°CA (BTDC)‐10.37°CA (ATDC), 30°CA (BTDC)‐11.46°CA (ATDC), and 25°CA (BTDC)‐13.88°CA (ATDC) were better because they were generally between 10–15°CA (ATDC), which contributes to better engine performance. With advanced IT, phase of total period during combustion was continuously brought forward due to flame propagation acceleration by tumble as well as increase of tumble residence effect time that aided in improving the combustion rate. The burnt fuel mass fractions at TDC of 40°CA (BTDC) IT of 0.94 was the highest followed by 35°CA (BTDC) IT of 0.88. Under this computational condition, 35°CA (BTDC) was deemed to be the improved combustion scheme though soot exhaust increased. [ABSTRACT FROM AUTHOR]

This work is aimed at improving the performance of the air‐powered rotary engine. A dynamic simulation model which includes an eccentric motion and rotary valve movement was established by our particle image velocimetry (PIV) experimental data. Then the power and specific steam consumption (SSC) was evaluated. The pressure distribution in the chamber was obtained which was difficult to obtain through experiment. Simulation results showed that for the work process and pressure distribution, the intake valve timing mainly affected the intake expansion stage (A2) and pure expansion stage (B). Due to this, a relatively low pressure was distributed in the middle of the chamber and this was beneficial to the intake and work processes. The exhaust valve timing mainly affected the exhaust stage (C) and initial intake stage (A1). Therefore, a relatively high pressure which was distributed in the middle‐rear of the chamber was beneficial to the exhaust processes. For the power and SSC, the power increased initially then decreased and the SSC decreased with the increase of intake advance angle respectively. Both the power and the SSC increased with the increase of intake duration angle. The power increased while the SSC decreased with the increase of exhaust advance angle. The power increased and the SSC decreased initially then increased with the increase of exhaust duration angle. The preferred parameters were found to be 30° CA, 240° CA, 30° CA, and 280° CA. These improved parameters had a 2.7% increase in the power and also a 2.4% decrease in the SSC. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1462–1474, 2018 [ABSTRACT FROM AUTHOR]

• The NHBF was used to improve the combustion and emission performance of rotary engine. • A calculation model of a peripheral ported rotary engine considering ASL was established. • The mixture formation and combustion process of NHBF under the action of ASL were analyzed. • The ideal blend fuel distribution which can improve the combustion efficiency was given. • The optimized hydrogen injection strategy was provided for improving the engine performance. Natural gas/hydrogen blended fuel (NHBF) is considered to be one of the ideal alternative fuels for rotary engine, which can effectively reduce the carbon emission of the rotary engine. The purpose of this paper is to numerically study the influence of hydrogen injection timing (HIT) and hydrogen injection angle (HIA) on mixture formation, flame propagation, and NO emission in the cylinder. In addition, considering that the apex seal leakage (ASL) of rotary engine is difficult to avoid, the NHBF in the cylinder will inevitably leak from the apex seal leakage gap to the adjacent cylinders. Therefore, the NHBF leakage under the action of ASL should be considered. In this paper, a 3D dynamic model of the NHBF rotary engine considering the action of ASL was established. Further, the diffusion and combustion processes of NHBF in the cylinder with different HITs and HIAs were calculated. The results showed that the HIT and HIA can significantly change the flame propagation process by changing the fuel stratification pattern in the cylinder. For improving the combustion efficiency of the engine, the HIA of +45° and HIT of 155°CA (BTDC) adopted by Case:155 + 45 should be set as the hydrogen injection strategy. This is mainly because that for Case: 155 + 45, both natural gas and hydrogen are mainly distributed in the FOC, and the concentration of hydrogen and natural gas near the spark plug is also high. However, the defect of Case:155 + 45 is the significant increase of NO emission. [ABSTRACT FROM AUTHOR]

The highly advanced wankel rotary engine is a promising energy system because of its favorable energy to weight ratio, multi-fuel capability and large specific power output. This work aims to numerically study the performance, combustion and emission characteristics of a side-ported rotary engine fueled with natural gas/hydrogen blends under different hydrogen blending modes. Simulations were performed using multi-dimensional software FLUENT 14.0. On the basis of the software, a three-dimensional dynamic simulation model was established by writing dynamic mesh programs, choosing the RNG k - ε turbulent model, the eddy-dissipation concept (EDC) combustion model and a reduced reaction mechanism. The three-dimensional dynamic simulation model based on the chemical reaction kinetics was also validated by the experimental data. Meanwhile, further simulations were then conducted to investigate how to impact the combustion process by the coupling function between hydrogen distribution and the flow field inside the cylinder. Simulation results showed that in order to improve the combustion efficiency, the low-pressure early injection should be used as the hydrogen blending mode. The low-pressure early injection, not only allowed the hydrogen in the combustion chamber to be distributed evenly, but also resulted in the high concentration areas of hydrogen located at the front of the trialing spark plug, which can be used to increase the combustion rate. For the hydrogen low-pressure early injection, the improved combustion rate made in-cylinder pressure and the intermediate OH increase significantly. Compared with no hydrogen induction, it shows a 29% increase in the peak pressures. Meanwhile, the drawback is the increase in NO emissions. [ABSTRACT FROM AUTHOR]

The performance of rotary engines is significantly influenced by the flow field. In this study, a detailed mathematical model was integrated into the simulation software FLUENT to investigate the gas flow field in a peripheral ported rotary engine by including a dynamic mesh model and a turbulent flow model. The models were also validated by experimental data. The basic flow mechanism in the combustion chamber was numerically studied. Meanwhile, the effects of the three major parameters on the flow field inside the combustion chamber, namely, rotating speed, intake shape, and intake angle, were also investigated. Results showed that a constantly changing swirl was formed in the combustion chamber during the intake and compression strokes as a result of the combined effects of the pocket of the rotor and the swirls in the combustion chamber. The swirl eventually broke into a unidirectional flow near the top dead center because of the significant decrease in combustion chamber volume. Furthermore, with the change in rotating speed, intake shape, and intake angle, significant differences in flow speed, inertia, and distribution were observed when the fluid entered the combustion chamber, which, in turn, led to obvious differences in the flow field, volume coefficient, and average turbulence kinetic energy in the combustion chamber. [ABSTRACT FROM AUTHOR]

The pre‐eminent gasoline rotary engine may be criticized for its unsatisfactory fuel consumption rate and unburnt emissions. The clean and renewable hydrogen fuel is a promising alternative for conventional fuels to improve the combustion process and power performance of the rotary engine. In this article, highly advanced numerical simulation was used to obtain some pivotal results such as the distribution of combustion intermediates, the turbulent kinetic energy, the kinetic rate of reactions, and the fuel concentration fields which are difficult to experimentally achieve. An experimentally validated three‐dimensional dynamic simulation model of a rotary engine coupled with chemical kinetics skeletal mechanism was set up to exactly investigate the effects of hydrogen blending on the combustion process, power performance, and pollutant emissions. The results showed that with the increase of hydrogen mixing ratio, the average pressure and the peak pressure increased in the combustion process. Meanwhile, more combustion active intermediates were generated in both the flame development period and flame propagation period. The mass fraction of OH and H radicals has an increase of 36% and 34%, respectively. The fuel combustion rate rose and the turbulent kinetic energy increased which are conducive to improving flame diffusion in the rear part of the chamber and thus facilitate the complete combustion of the fuel. Moreover, the hydrogen blending led to an effective reduction in the CO emission of gasoline‐fueled rotary engine; however, the NO emission slightly increased due to the rise of temperature in cylinder. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019 [ABSTRACT FROM AUTHOR]

Highlights • A novel natural gas-diesel dual-fuel rotary engine was proposed and studied. • Fuel spray characteristics under rotary engine working conditions were obtained. • Dynamic simulation model was validated in detail for diesel rotary engine. • Mixture formation process and combustion characteristics were analyzed. • Blending natural gas could effectively improve the total combustion rate. Abstract To further improve the performance of diesel rotary engine, a novel natural gas-diesel rotary engine was proposed and studied in this paper. Based on a spray experimental setup, the diesel spray characteristics under diesel rotary engine working conditions were obtained and analyzed. Thereafter it was used to validate the spray model for diesel rotary engine modeling and simulation. The effect of different natural gas blending ratios on mixture formation and combustion process in the natural gas-diesel rotary engine were investigated. Simulation results showed that for fuel-air mixing process, the natural gas movement process was susceptible to the airflow motion. However, the diesel distribution range was obviously enlarged under the influence of high-speed unidirectional flow. At assisted ignition timing, the stratified distributed diesel made the combustion process mainly occured at the front and middle of the combustion chamber. Besides, the flame propagation speed was accelerated with natural gas blending ratio increasing, which effectively improved the total combustion rate. Compared to single-fuel mode, when natural gas blending ratio increased to 20%, the maximum combustion pressure increased by 24.17%. Meanwhile, soot and CO decreased obviously, but NO and CO 2 also increased. [ABSTRACT FROM AUTHOR]