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Rotary engine is an ideal electric vehicle range extender. However, the combustion chamber of rotary engine is very narrow and long at the top dead center, which is detrimental to fuel combustion performance. In order to improve its economic and emission performance, this paper built an ethanol/gasoline dual-fuel rotary engine test bench, and the combustion and emission performance of gasoline rotary engine under five ethanol blending ratios were studied. The experimental results showed that, when the fuel pulse width is not adjusted, since the calorific value of ethanol is lower than that of gasoline and the latent heat of vaporization of ethanol is higher than that of gasoline, the addition of ethanol in gasoline lowers the peak pressure. When the ethanol blending ratio reaches 30 vol%, the pressure curve shows a distinct double peak. Under the theoretical air-fuel ratio condition, mixing ethanol in gasoline increases the heat release rate, shortens the combustion duration while prolonging delay period. After blending ethanol, HC, CO and NOx emissions have been reduced under various operating conditions. Excessive ethanol blending ratio increases NOx emissions and increases cycle variation coefficient. When the ethanol blending ratio is 15 vol%, it has better power ability while maintaining low cycle variation coefficient and emissions.

Detonation performances of methane/hydrogen/oxygen (CH4/H2/O2) mixtures were investigated experimentally in a 3000 mm long tube with an inner diameter of 30 mm at different initial pressures p 0 (ranging from 10 kPa to 50.5 kPa). Mixtures with different proportions of H2 in the total fuel α (0%, 14.29% and 25%) and different equivalence ratios Φ (0.8, 1.0 and 1.2) were tested. Signals of flame front and pressure were obtained by ion probes and high frequency pressure transducers, respectively. Results showed that with the increase of p 0 , α and Φ , the average velocity of steady detonation V a v e increased. For mixtures with the given α , when Φ increased by 0.2, V a v e increased by 100 m/s. In the present study, velocity deficits were found to be within 5%, and when p 0 was higher than 20 kPa, the velocity deficits were within 2%. The average peak pressure of steady detonation p a v e was close to the von Neumann pressure p v N . Both the increase of p 0 and Φ led to the increase of the p a v e . But the addition of H2 led to the decrease of p a v e , and p a v e decreased with the increased of α .

In view of the gradual promotion of Single Fuel Concept in the military field and also the rotary engine (RE) which has been widely applied in specialized equipment, it is necessary to study the basic spray characteristics of aviation kerosene under RE operation conditions and optimize the fuel injection strategies. In this research, an optically visible constant volume combustion chamber platform for Mie-scattering and a validated three-dimensional dynamic simulation model of aviation kerosene fueled direct injection rotary engine (DI-RE) were established. The experimental results show that the ambient temperature and pressure affect the spray process differently. There is no linear relationship between ambient temperature and penetration length. The ambient temperature of 600 K is a watershed, when it is below 600 K, the penetration length increases as the temperature rises. When the temperature reaches 600 K, the penetration length decreases rapidly which means a prominent improvement of atomization quality. On the basis of experimental results, the simulation was carried out and the results show that different injection strategies have important effect on distribution of fuel in cylinder, the larger injection angle will promote the atomization of fuel due to the collision between the spray and air flow field. In Case A3, B2 and C2, the fuel mainly distributes near the spark plugs in the center of the combustion chamber, which is supposed to be more conducive to the ignition and diffusion combustion process of the fuel.

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 CO2 also increased.

This study aimed at further improving the combustion efficiency of the diesel rotary engine (DRE), and in this regard a novel natural gas-diesel rotary engine (NG-DRE) was numerically studied. Based on the experimental validated computational fluid dynamics (CFD) model, a 3D-dynamic numerical study of the NG-DRE was carried out by adopting NG port injection plus diesel direct injection mode. The influence of natural gas injection timing (NGIT) and diesel injection timing (DIT) on air-fuel mixing, combustion and emission characteristics were explored. Simulation results showed that NG-DRE performance was better than DRE. During the entire air-fuel mixing process, NG movement was easily affected by the vorticity density due to its good diffusion characteristics, however its influence on diesel movement was relatively minimal. At assisted ignition timing, NG concentrated at the rear of the combustion chamber, and diesel concentrated at the front and middle of the combustion chamber. Delaying NGIT and DIT, the mixture became more concentrated due to a shorter mixing time. Moreover, the delayed NGIT and DIT resulted in improvement of the pressure and combustion rate, while for a further delayed DIT the pressure was decreased due to the pressure negative work. Considering the engine power and emission performance, for dual-fuel injection schemes, 340°CA BTDC and 70°CA BTDC were the preferred application schemes for NG and diesel respectively. Their peak combustion pressure (Pmax) increased by 16.34% and 27.38% respectively, but due to the richer mixture, soot value increased by 0.023% and 0.054% and CO (carbon monoxide) value also increased by 0.026% and 0.039% respectively.

This work aimed to numerically study the effect of hydrogen injection strategy on mixture formation and combustion process in a port injection (PI) rotary engine fueled with natural gas/hydrogen blends. The two main considered factors were hydrogen injection timing (IT) and hydrogen injection duration (ID). Simulation results indicated that for mixture formation, in terms of hydrogen IT, hydrogen IT of 390°CA (BTDC) is a watershed. When the hydrogen IT is before 390°CA (BTDC), the changes in hydrogen IT have little effect on the hydrogen distribution at ignition timing. Hydrogen distribution is uniform across the whole combustion chamber. However, when the hydrogen IT is after 390°CA (BTDC), with the retarded hydrogen IT, there is obvious increase in hydrogen stratification phenomenon, and more hydrogen distributes in the middle and back of combustion chamber at ignition timing. In terms of hydrogen ID, at the fixed hydrogen IT of 360°CA (BTDC), with the extended hydrogen ID, more hydrogen distributes in the back of trailing spark plug (TSP). For combustion process, to obtain a higher overall combustion rate for the PI rotary engine, the hydrogen injection strategy should make more hydrogen located at the front of TSP at ignition timing. In engineering applications, for higher peak cylinder pressure to be obtained, the continued optimization of hydrogen IT should be selected between 390°CA (BTDC) and 330°CA (BTDC). Under the hydrogen IT range of 390°CA (BTDC) to 330°CA (BTDC), the continued optimization of hydrogen ID should select between 8°CA and 24°CA.

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...

During the decades past, the engine industries have witnessed a remarkable upsurge in the research and development (R&D) of modern technologies due to factors such as energy security and environmental concerns. Focus is on improved engine performance, sustainable energy, fuel economy, and minimal harmful exhaust emissions. Even though globally large database now captures modern engine technologies, a skillful presentation of those data is a demanding task. Based on this analogy, the authors made a conscious effort to brief audience on the various fuels used in Wankel rotary engine (RE) which is a type of internal combustion engine (ICE). Wankel REs various operating models, their merits, and demerits regarding modern engine technologies, the type of fuels and their utilization methods, and the future prospect of biofuel as its engine fuel has been made accessible in a subtle manner in this paper. In summary, this paper provides a wide scope review of basic principles that govern practical Wankel RE design and operation, the widely used single fuels and multi fuels in Wankel RE operation with their properties as well as emissions, and the practical Wankel RE design and operation in the present era and the prospects in the near future. It also outlines simplified frameworks of modern Wankel RE technologies structured in a systematic way to contribute to enhanced engine performance, sustainable energy, reduce fuel consumption, and reduce exhaust emissions in this pragmatic field.

The aim of this research is to investigate the influences of apex seal leakage on the formation mechanism of flow field in a side-ported rotary engine by particle image velocimetry (PIV) and computational fluid dynamics (CFD). In this study, a PIV was used to acquire the two-dimensional (2D) flow field on the rotor housing central plane at an engine speed of 700 rpm. A three-dimensional (3D) dynamic simulation model considering leakage through apex seals was established and verified by the 2D-PIV experiment results. Thereafter, CFD analysis was used to further understand the 3D flow field in combustion chamber under the action of apex seal leakage. The simulation results showed that for the three engine speeds (2000, 3500, and 5000 rpm), in the intake stroke, the vortex generated in the front end of combustion chamber under the condition with no leakage, was strengthened and destroyed by the effects of the small (0.02 mm) and the large (0.08 mm) apex seal leakage gaps, respectively. As the apex seal leakage gap increased, the volume efficiency and the peak pressure decreased continuously. The volume efficiency and the peak pressure caused by any fixed apex seal leakage gap decreased with the increase of the engine speed. Compared with the volumetric efficiency of the condition with no leakage at 2000 and 5000 rpm, the volumetric efficiency of apex seal leakage gap of 0.08 mm decreased only by 24.6% at 5000 rpm, but by 41.2% at 2000 rpm.

Hydrogen direct injection (HDI) in cylinder is considered as an effective method to improve natural gas engine performance. The present study aims to bridge the gap on the HDI in rotary engine, and to investigate the effect of hydrogen injection timing (IT) and hydrogen injection duration (ID) on mixture formation and combustion process of a hydrogen direct injection plus natural gas port injection (HDI + NGPI) rotary engine. Numerical approach was used in this study for obtaining some critical information, which was difficult to obtain through experiment, such as flow field, fuel distribution and some intermediate concentration fields in cylinder. The research results showed that for mixture formation, the distribution law of the hydrogen and the natural gas at the late stages of the compression stroke (100°CA (BTDC)), was as follows: at a fixed ID of 24°CA, with retarded hydrogen IT, the stratification phenomenon of hydrogen became obvious increasingly, and the hydrogen distribution area moved towards the back of the combustion chamber continuously. At a fixed IT of 210°CA (BTDC), with the extension in ID, the accumulation area of hydrogen reduced significantly, and the hydrogen continued to gather in the middle of the combustion chamber. For combustion process, the overall combustion rate for the hydrogen injection strategy which had an IT of 210°CA (BTDC) and ID of 40°CA (case ID5), was the fastest. This was due to the fact that compared with the leading spark plug (LSP), the combustion condition around the trailing spark plug (TSP) has a great influence on the combustion process. For case ID5 at ignition timing, the hydrogen concentration near the TSP is high enough for the rapid formation of flame kernel. Compared with case IT1 which had an IT of 390°CA (BTDC) and an ID of 24°CA, the improved combustion rate of case ID5 had a 11.7% increase in peak pressure, and a 7% decrease in NO emissions.

This work aimed to numerically study the effect of hydrogen injection strategies on mixture formation and combustion process in a hydrogen direct injection plus natural gas port injection (HDI + NGPI) rotary engine. Two major factors, namely hydrogen injection timing (HIT) and hydrogen injection angle (HIA), were considered. Four HITs which were used in simulation, were from the early stages of intake stroke to the late stages of compression stoke. Comparing the fuel movement and combustion process among the four HITs with three HIAs (−60°, 0° and 60°), it was found that for hydrogen movement, when the HIT was at early stages of intake stroke, this advanced HIT led to the fact that the hydrogen distribution areas at ignition timing all spread across the whole combustion chamber for all three HIA cases. When the HIT was at the late stages of the intake stroke and the whole compression stroke, with an increased hydrogen injection angle (HIA) (from −60°, 0° to 60°), the hydrogen accumulation area moved from the front towards the rear of combustion chamber. In addition, with retarded HIT, the hydrogen aggregation degree increased continuously. For combustion process, to obtain a higher overall combustion rate, the hydrogen injection strategy should make as much hydrogen spread between the two spark plugs at ignition timing. In addition, the hydrogen concentration near the LSP and the TSP should be conducive to the flame kernel formation. This is mainly because of the fact that the above hydrogen distributions, not only lead to the rapid formation of the flame kernel near the LSP and the TSP, but also make use of the hydrogen at the early stage of combustion stroke. Under the computational condition, the overall combustion rate for case A: 140 − 60 which had a HIT of 140°CA (BTDC) and a HIA of −60°CA, was the fastest. Compared with case C: 300 + 60 which had a HIT of 300°CA (BTDC) and a HIA of 60°CA, the peak pressure of case A: 140 − 60 was raised by 31.1%. However, compared with other cases, the NO emissions of case A: 140 − 60 at 80°CA (ATDC) was the maximum. Furthermore, for engineering applications, this study also provided a scheme of the change of the optimum HIA under different HITs for improving the performance of the HDI + NGPI rotary engine.

It is important to improve the combustion performance of the diesel Wankel engine for its further engineering applications. Therefore, the main objective of this study was to study the dual-fuel mixture formation and stratified combustion process in the novel natural gas blended diesel Wankel engine. Meanwhile, the effects of assisted-ignition timing and assisted-ignition position on engine combustion characteristics were investigated. The results indicated that when the assisted-ignition timings and positions were changed, natural gas distribution near assisted-spark plugs changed slightly, while the variation of diesel distribution was conspicuous. Moreover, adopting dual assisted-ignition spark plugs could accelerate the fuel burning rate and improve engine combustion performance. Besides, it was found that more mixture concentrated near the assisted-spark plugs was beneficial to increase the pressure in-cylinder and combustion rate. The symmetrical arranged dual assisted-ignition spark plugs that were respected to the X-axis (Case 4) and assisted-ignition timing of 35°CA BTDC (Case 6) were the preferred practical application schemes. Compared to the schemes of single spark plug ignition (Case 1) and 20°CA BTDC ignition timing (Case 9), the peak pressure in-cylinder of the preferred application schemes increased by 42.96% and 10.91%, respectively.

The catalytic reaction characteristics of the hydrogen and oxygen mixture in the catalytic micro-combustor were detected by thermocouple, infrared thermal imager and OH-PLIF. The equivalence ratio of transition stage from coupling reaction (coupled homogeneous-heterogeneous combustion) to pure catalytic reaction (heterogeneous combustion) was obtained. The three-dimensional pure catalytic reaction model with detailed catalytic reaction mechanism was established in a rectangular catalytic micro-combustor. The simulation model was validated with experimental data. The effects of the intermediate and final products from gas-phase reactions on the pure catalytic reaction were discussed as well as the effects of gas-phase reactions on the catalytic reaction in the process of coupling reactions were studied. The intermediate product OH radical can improve the hydrogen conversion of the surface reaction, and the effect of O radical is not obvious. The final product H2O has an inhibitory effect on the surface reaction. Since the mass fraction of H2O is much higher than other gas-phase reaction products, the dominant effect of the gas-phase reaction on the catalytic reaction is suppression. In the coupling reactions, the fuel consumed by the gas-phase reaction weakened the catalytic reaction.

Rotary engine has a flat combustion chamber that results in high unburned fuel leading to fuel inefficiency and emissions. Biodiesel regarded as a clean source of energy is an alternative fuel due to its ability to minimize environmental pollution resulting from unwanted emissions. In this regard, the improvement of combustion efficiency of a direct injection rotary engine fueled with biodiesel was numerically investigated. Experimental data was used in validating the established three-dimensional computational fluid dynamics (3D-CFD) model. On this basis, investigation of various biodiesel injection timing (IT) (100, 80, 60) °CA before top dead center (BTDC), spark timing (ST) (35, 30, 25, 20) °CA BTDC and equivalence ratios ( ∅ ) (0.6, 0.8, 1.0, 1.2) on mixture formation and combustion process was carried out. Results revealed that when IT retarded fuel distribution narrows and the mixture formed is concentrated. Conversely when ST retarded there is broad and dispersed fuel distribution. For lean condition the mixture formed is less concentrated compared to rich condition. For combustion process, when biodiesel was concentrated at the middle of in-cylinder at 30 mm (X-axis) and 15 mm (Z-axis) from the centerline in opposing directions it was better for spark-on. Also, the in-cylinder pressure and temperature reduced with advanced IT, retarded ST and decreased ∅ . When ∅ leaned, flame development and propagation periods decreased. The suitable rate for combustion considering emissions was obtained when IT was 80°CA (BTDC) and ST 35°CA (BTDC) at a ∅ of 0.8 because when compared to the original scheme (case B4), maximum combustion pressure increased by 28.57% and increase of CO2, CO, soot and NO emissions were reasonable due to increase in temperature and fuel evaporation.

Investigating the adaptability of aviation kerosene in the direct injection rotary engine is of great significance and practical value. In this paper, an optically visible constant volume combustion chamber platform with various optical diagnostic techniques was firstly set up to study the spray combustion characteristics of the fuel. Secondly, a reliable three-dimensional dynamic simulation model of direct injection rotary engine was established to investigate the combustion process of aviation kerosene under optimized injection strategies. The experimental results show that the ambient temperature of 800 K and ambient pressure of 20 bar is the ignition limit of aviation kerosene under the condition of rotary engine. With the increase of ambient conditions, the ignition delay and the flame lift-off length shorten continuously. At 850 K ambient temperature, when the ambient pressure reaches 25 bar, the lift-off length will no longer shorten and remains at about 6 mm. The simulation results indicate that under the Injection position A-Injection angle 90° (Case A3), higher combustion efficiency before top dead center can be achieved due to more appropriate distribution, concentration and atomization quality of fuel at ignition timing. The peak pressure in cylinder reaches 38.89 bar, which means a better engine dynamic performance. Meanwhile, acceptable CO and Soot emissions are obtained by the complete combustion of fuel in Case A3, however, the higher combustion temperature makes the production of pollutant NO slightly higher than other injection strategies.