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Featured Application: Usage of series/parallel power systems for ultralight aviation to increase safety. The conventional powertrain for ultralight aviation consists of a fixed pitch propeller connected to an internal combustion engine (ICE). Since ICEs have a limited thermal efficiency (<40%), new and more efficient powerplant configurations have recently been proposed in the scientific literature by adopting hybrid electric solutions. Hybridization has the additional benefit of increased safety thanks to redundancy. This is a very important issue in ultralight aviation, where a high percentage of accidents are caused by engine failure. In a previous investigation, the authors proposed the design of a series/parallel hybrid electric power system to increase safety and optimize fuel economy by controlling the engine working points during flight. A new powertrain, derived from an automotive Honda i-MMD system, is analyzed in this study and a reliability analysis is performed to underline the improved safety obtained with the proposed system. [ABSTRACT FROM AUTHOR]

In recent years, there has been great interest in Wankel-type rotary engines, which are one of the most suitable power sources for unmanned aerial vehicle (UAV) applications due to their high power-to-size and power-to-weight ratios. The purpose of the present study was to investigate the potential of a hydrogen enrichment strategy for the improvement of the performance and reduction of the emissions of Wankel engines. The main motivation behind this study was to make Wankel engines, which are already very advantageous for UAV applications, even more advantageous by applying the hydrogen enrichment technique. In this study, hydrogen addition was implemented in a spark-ignition rotary engine model operating at a constant engine speed of 6000 rpm. The mass fraction of hydrogen in the intake gradually increased from 0% to 10%. Simulation results revealed that addition of hydrogen to the fuel accelerated the flame propagation and increased the burning speed of the fuel, the combustion temperature and the peak pressure in the working chamber. These phenomena had a very positive effect on the performance and emissions of the Wankel engine. The indicated mean effective pressure (IMEP) increased by 8.18% and 9.68% and the indicated torque increased by 6.15% and 7.99% for the 5% and 10% hydrogen mass fraction cases, respectively, compared to those obtained with neat gasoline. In contrast, CO emissions were reduced by 33.35% and 46.21% and soot emissions by 11.92% and 20.06% for 5% and 10% hydrogen additions, respectively. NOx emissions increased with the application of the hydrogen enrichment strategy for the Wankel engine. [ABSTRACT FROM AUTHOR]

Analysis of the possibility of using a rotary engine based electric generator to propell a powered sailplane. The paper presents analysis of utilising Wankel type enine as a power input for an electric generator in the motor glider propulsion system. This generator would be a part of the propulsion system of a hybrid motor glider using the AOS 71 motor glider airframe. In the research, the rotational characteristics of the LCR 407ti wankel engine were determined experimentally. Driving torque run, power and fuel consumption were determined as a function of engine speed. The obtained results are presented in diagrams. The conceptual diagram of the hybrid drive is presented. The electric generator was selected and its effectiveness, as well as the effectiveness of entire propulsion system was assessed from the motor glider's performance point of view. Basing on the research conducted, conclusions were drawn and there were indicated the objectives and directions of further research on hybrid propulsion with specific aerodynamic and mass limitations of the aircraft

The goal of this investigation is to propose a series/parallel hybrid electric power system for ultralight aviation designed to improve safety and, possibly, reduce fuel consumption. The power system consists of a Wankel engine, two electric machines, a battery, and a planetary gear set, all acquired from the automotive market. After a preliminary design based on takeoff power, the system is simulated over a typical flight mission and in case of engine failure for a first validation of the proposed powertrain. The investigation also shows a comparison in terms of performance and fuel consumption between the initial configuration (reciprocating piston engine), a non-hybrid Wankel arrangement, and the proposed hybrid electric configurations by using in-house simulation software. A heuristic energy management strategy is proposed as well. During a typical mission, the new powertrain works as a parallel hybrid during takeoff and climb, thus ensuring high performance and safety. During the cruise, the system behaves like a parallel hybrid with a continuously variable transmission that makes the engine work always at high efficiency. The battery is partially recharged during the descent by the extra power of the engine. The preliminary results reported in this work predict an improvement in fuel consumption by about 20% compared with the initial piston engine configuration and 28% compare with the non-hybrid Wankel powertrain, despite the larger takeoff weight. [ABSTRACT FROM AUTHOR]

The conventional powertrain for ultralight aviation consists of a fixed pitch propeller connected to an internal combustion engine (ICE). Since ICEs have a limited thermal efficiency (

The researches on Wankel engines are very rare and considered new in modelling and prediction. Therefore this study deals with the artificial neural network (ANN) modelling of a Wankel engine to predict the power, volumetric efficiency and emissions, including nitrogen oxide, carbon dioxide, carbon monoxide and oxygen by using the change of mean effective pressure, intake manifold pressure, start of ignition angle and injection duration as inputs. The experiment results were taken from a research which is performed on a single-rotor, four stroke and port fuel injection 13B Wankel engine. The number of datas which are taken from experimental results were scarce and varied in six different data set (for example; mean effective pressure, from 1 to 6 bar) at 3000 rpm engine speed. The standard back-propagation (BPNN) Levenberg-Marquardt neural network algorithm is applied to evaluate the performance of middle speed range Wankel engine. The model performance was validated by comparing the prediction data sets with the measured experimental data. Results approved that the artificial neural network (ANN) model provided good agreement with the experimental data with good accuracy while the correlation coefficient R varies between 0.79 and 0.97.

In recent years, there has been great interest in Wankel-type rotary engines, which are one of the most suitable power sources for unmanned aerial vehicle (UAV) applications due to their high power-to-size and power-to-weight ratios. The purpose of the present study was to investigate the potential of a hydrogen enrichment strategy for the improvement of the performance and reduction of the emissions of Wankel engines. The main motivation behind this study was to make Wankel engines, which are already very advantageous for UAV applications, even more advantageous by applying the hydrogen enrichment technique. In this study, hydrogen addition was implemented in a spark-ignition rotary engine model operating at a constant engine speed of 6000 rpm. The mass fraction of hydrogen in the intake gradually increased from 0% to 10%. Simulation results revealed that addition of hydrogen to the fuel accelerated the flame propagation and increased the burning speed of the fuel, the combustion temperature and the peak pressure in the working chamber. These phenomena had a very positive effect on the performance and emissions of the Wankel engine. The indicated mean effective pressure (IMEP) increased by 8.18% and 9.68% and the indicated torque increased by 6.15% and 7.99% for the 5% and 10% hydrogen mass fraction cases, respectively, compared to those obtained with neat gasoline. In contrast, CO emissions were reduced by 33.35% and 46.21% and soot emissions by 11.92% and 20.06% for 5% and 10% hydrogen additions, respectively. NOx emissions increased with the application of the hydrogen enrichment strategy for the Wankel engine.

Analysis of the possibility of using a rotary engine based electric generator to propell a powered sailplane. The paper presents analysis of utilising Wankel type enine as a power input for an electric generator in the motor glider propulsion system. This generator would be a part of the propulsion system of a hybrid motor glider using the AOS 71 motor glider airframe. In the research, the rotational characteristics of the LCR 407ti wankel engine were determined experimentally. Driving torque run, power and fuel consumption were determined as a function of engine speed. The obtained results are presented in diagrams. The conceptual diagram of the hybrid drive is presented. The electric generator was selected and its effectiveness, as well as the effectiveness of entire propulsion system was assessed from the motor glider's performance point of view. Basing on the research conducted, conclusions were drawn and there were indicated the objectives and directions of further research on hybrid propulsion with specific aerodynamic and mass limitations of the aircraft. [ABSTRACT FROM AUTHOR]

Comparative analysis of harmful compounds emission of classical and distributed propulsions applied on the AOS motor glider, taking into account the perspective of the development of hybrid propulsions. A novel path is indicated by so-called distributed aircraft propulsion. The advantages and disadvantages of this type of solutions are presented, as well as the conceptual design of the distributed propulsion for the AOS 71 motor glider. In the paper there were compared the emissions of harmful compounds generated by a hybrid power unit developed for the airframe of AOS 71 motor glider – traditional propulsion, so-called focused (one-propeller) and dispersed propulsion (multi-propelled). Functional diagrams of both types of propulsions solutions are presented. Construction and aerodynamic constraints of both propulsions are discussed and comparative analysis is made. In the traditional version of the propulsion (so-called focused propulsion). the propeller is driven by an Emrax 228 electric engine with effective parameters: N = 55 kW, M = 120 Nm. The power source is a battery set with a capacity of 16 Ah and a range extender powered by a LCR 407ti rotating piston engine with maximum power of 28 kW. In the variant of the distributed propulsion. Ten electric engines of AXI 8120 type were used to drive small propellers arranged along the wingspan. The power source in this variant is analogous to the variant with the Emrax electric engine. For the adopted variant of the flight mission of the motor glider. a flight trajectory model was developed, which was used to determine the load of the power unit. In laboratory conditions. emission tests of both propulsions were conducted. The results are summarized in charts and discussed in the conclusions.

Comparative analysis of combustion and hybrid propulsion unit in aviation application in terms of emission of harmful compounds in the exhausts emitted to the atmosphere. For the propulsion of the AOS 71 motor glider, two types of propulsion were planned as de-velopment versions. The first analysed propulsion is based on a combustion engine, but of the Wankel type (LCR 814 engine with the power of 55 kW). The second designed propulsion is an hybrid based on a LCR 407 combustion engine with a power of 28 kW, which is connected in series with an electric generator propelling the engine (Emrax 228 engine), total power of the propulsion is 55 kW. The comparison of emissions of harmful compounds emitted to the atmosphere generated by the combustion and hybrid power unit intended for assembly in the AOS 71 motor glider, assuming various loads and methods of hybrid propulsion control, was made. The tests were conducted in laboratory conditions. Several different programs were designed to simulate different energy management methods in a hybrid system, depending on the predicted mission and load of the motor glider. On the basis of laboratory tests, exhaust emission was determined from both propulsions as a function of rotational speed and load. Then, based on the assumed flight trajectory and collected test data, the emission for both propulsions variants was determined. The values of emission parameters were compared and the results were presented in diagrams and discussed in the conclusions

Analysis of the possibility of using an engine with a rotating piston as the propulsion of an electric generator in application to a motor glider propulsion The paper presents an analysis of the possibilities of application of a rotating piston engine (Wankel type) as a propulsion for an electric generator in the motor glider propulsion system. This generator would be a part of the propulsion system of a hybrid motor glider using the AOS 71 motor glider airframe. In the research, the rotational characteristics of the LCR 407ti engine were determined experimentally. Driving torque run, power and fuel consumption were determined as a function of engine speed. The obtained results are presented in diagrams. The conceptual diagram of the hybrid drive is presented. The current generator was selected and the effectiveness of the generator and the entire propulsion were assessed from the motor gliders performance point of view. On the basis of the conducted research, conclusions were drawn and there were indicated the objectives and directions of further research on hybrid propulsion with specific aerodynamic and mass limitations of the aircraft

This paper provides an explanation of the geometry, design, and operational principles for the three engines; having special emphasis in the Szorenyi rotary engine which has a deforming rhombus revolving inside a mathematically defined stator. A basic ideal mathematical simulation of those engines were performed, assuming the Otto cycle for the three engines. Also, it assumes the volumetric efficiency of 100%, a wide-open throttle (WOT), no knock nor any mechanical or thermal losses. This simulation focuses on how the fuel burns during combustion, creating pressure and thus, net work. A comparison in pressure traces and cycle performance is made. The study concludes analysing and comparing the ignition advance; finding the best advance for each engine thus the net work between the three engines during one working cycle. Finally, this paper analyses how the different volume change ratio for the combustion chamber of the Szorenyi, Wankel and the reciprocating engine have an effect in the pressure, net work and thermal efficiency generated inside the chamber during combustion for every working cycle.

The goal of this investigation is to propose a series/parallel hybrid electric power system for ultralight aviation designed to improve safety and, possibly, reduce fuel consumption. The power system consists of a Wankel engine, two electric machines, a battery, and a planetary gear set, all acquired from the automotive market. After a preliminary design based on takeoff power, the system is simulated over a typical flight mission and in case of engine failure for a first validation of the proposed powertrain. The investigation also shows a comparison in terms of performance and fuel consumption between the initial configuration (reciprocating piston engine), a non-hybrid Wankel arrangement, and the proposed hybrid electric configurations by using in-house simulation software. A heuristic energy management strategy is proposed as well. During a typical mission, the new powertrain works as a parallel hybrid during takeoff and climb, thus ensuring high performance and safety. During the cruise, the system behaves like a parallel hybrid with a continuously variable transmission that makes the engine work always at high efficiency. The battery is partially recharged during the descent by the extra power of the engine. The preliminary results reported in this work predict an improvement in fuel consumption by about 20% compared with the initial piston engine configuration and 28% compare with the non-hybrid Wankel powertrain, despite the larger takeoff weight.

In this study, an electronic control unit was designed and developed for a single rotor Wankel engine. The code was written the Arduino IDE. An interface is designed in Visual Studio for computer control of a single rotor test engine. Thanks to the control unit, the injection advance, injection duration, engine speed, dwell time and ignition advance were controlled. In the hardware part, firstly solid state relay was used for switching, and then a MOSFET circuit was tested. It was observed that the ignition and spraying signals received from the oscilloscope for both switching came regularly and continuously at different speeds (600, 1000 and 3000 rpm). Afterwards, according to the results obtained with the oscilloscope and high speed camera, there was no delay in opening time of the injector with the solid state relay. However, there was 0.6 milliseconds delay in closing time of it. This situation caused the engine to run erratically and unstable at high speeds. In the circuit established with Mosfet, there was no delay at the opening and closing times of the injector. As a result, it was concluded that it would be more appropriate to use the circuit designed with MOSFET in the control unit. [ABSTRACT FROM AUTHOR]

In this work, port crank angles strategies for maximizing engine volumetric efficiency of a commercial rotary engine are studied. The internal combustion engines computer program, which simulates an actual working processes, has been used. Overall performance characteristics such as the cycle efficiency, engine power are calculated by a mathematical model. The model is calibrated with data obtain from a measured in-cylinder pressure, and validated against the experimental data. Intake opening and closing time, exhaust opening and closing time are chosen as optimization variables when volumetric efficiency was taken as the objective function. First, the intake opening time is the only optimization variable and it can be found that intake opening time is in advance as engine speed is increased. Second, four variables including intake opening and closing, exhaust opening and closing have been taken as the optimization variables, a further increase in volumetric efficiency was obtained, with the highest gain being of 1.03% at 17000 rpm. But opening the exhaust opening very late will reduce the power. [ABSTRACT FROM AUTHOR]

• A Wankel engine simulation model at various altitudes was established and validated. • Combustion duration in the working chamber of the Wankel engine is extended at higher altitudes. • The Wankel engine performance decreases, and the emissions deteriorate when the altitude increases. This study investigates the effects of altitude on the combustion, emissions, and performance of a Wankel engine for unmanned aerial vehicles (UAVs). The main motivation behind the presented study is to contribute to the Wankel engine designs used as a power source in UAVs by revealing the operating conditions at various altitudes. For these purposes, a gasoline fueled Wankel engine was simulated at sea level conditions for different equivalence ratios and results were validated with their experimental counterparts. Then, CFD simulations were carried out at various altitudes (6000 ft, 10,000 ft, and 15,000 ft). The simulation results show that decreasing ambient air temperature, and pressure at higher altitudes reduces the fresh charge density, hence combustion efficiency and heat release rate (HRR). As a result, the performance characteristics such as the indicated mean effective pressure (IMEP), the indicated torque, and indicated power decrease and exhaust emissions increase. For 6000 rpm, IMEP decreases by 39.11%, 53.79%, and 69.22%, and the indicated power reduces by 35.51%, 52.47%, and 65.05% at the altitudes of 6000 ft, 10,000 ft, and 15,000 ft, respectively, compared to those obtained at the sea level conditions. As for exhaust emissions, CO and CO 2 are lowest at sea level conditions and increase with altitude. [ABSTRACT FROM AUTHOR]

A numerical methodology for three-dimensional fluid dynamics and chemical kinetics simulation of the combustion and gas-exchange processes in the Wankel engine was developed and validated. Two approaches of performance enhancement were studied—the addition of a slot in the rear side of the rotor recess, and installation of a third plug in the trailing side of the working chamber, in addition to the two available plugs mounted in the leading side of the baseline engine. The obtained results showed that the suggested three-plug arrangement significantly improves the engine performance. Furthermore, positioning the trailing plug further from the passage between the trailing and leading sides is of preference for higher mean in-chamber pressures. Nevertheless, for maximum performance, the distance should be brought to an optimum as during the intake stroke there is a loss of inducted charge due to backflow from the trailing plug hole. For the three-plug arrangement the presence of a slot is necessary for the prevention of early flame quenching in the trailing side, while keeping the added volume to a minimum. Moreover, positioning the slot and the trailing plug off-center, results in higher flow intensity towards the leading plugs, and accordingly, to a higher combustion efficiency. For dual-plug ignition system (two plugs in the leading side) it is preferable to maintain minimum clearance in the trailing side.

• A CFD model of gasoline-H 2 blends Wankel engine was established and verified. • H 2 was direct injected in the rotor chamber under varying mass and directions. • Flame spread and combustion pressure decreased with the widened injection angle. • The optimal engine performance was acquired when α H2 of 3% and IA of 45°. • NO x generations still remained lower, though chamber pressure notably rise. To analyze the effects of hydrogen charge concentration (HCC) and injection angle (IA) on the lean combustion in a gasoline Wankel engine, the present work implemented a numerical simulation model coupling with the kinetic mechanisms and validated with the experimental data. Results found that with the increase in HCC, the penetration of hydrogen injection is enlarged and the area of the high-speed jet flow is expanded. The jet-flow area for IAs of 45° or 135° is larger than that of 90°. Changing IA could obtain the hydrogen distribution at different regions of the rotor chamber and IA of 90° acquires the smallest hydrogen-rich region. Increasing IA brings about the reduced flame speed substantially; the flame area for IAs of 45° and 90° expands with the increment of HCC whereas the contrary pattern is witnessed at the IA of 135°. Smaller IA leads to the major burning occurring untimely, which resulting in less work delivery of the engine. The hydrogen consumption for IAs of 45° and 90° increases as HCC is ascendant while that for IA of 135° is just the reverse. Variations in the mixture distribution and turbulence are the intrinsic mechanism of how the HCC and IA reflects the combustion progress. As hydrogen is injected with larger HCC and smaller IA, a relatively richer mixture and higher turbulent kinetic energy are distributed close in the spark ignition region. The peak combustion pressure reduces and its corresponding crank position delays with the widened IA at any HCC. Considering the fuel combustion and nitric oxide formation, as hydrogen volume fraction is 3% and IA is 45°, the engine could realize the optimized performance under the computational condition. An efficient combustion performance may be performed in engineering application if the hydrogen IA is in accordance with the rotor rotating direction at lower HCC. [ABSTRACT FROM AUTHOR]

Highlights • A CFD model of gasoline/H 2 fueled Wankel engine was established and verified. • The ignition mode consisted of synchronous ignition and asynchronous ignition. • H 2 was direct injected in the combustion chamber under varying twin-spark timing. • The optimal combustion was achieved when the TSP ignited asynchronously. • There was no increase in NO x generation with the enhanced combustion rate. Abstract A Wankel engine with hydrogen direct-injection enrichment is recognized as an attractive method to enhance combustion efficiency. In this paper, on the basis of the chemical kinetic mechanisms, a three-dimensional simulation model was established and validated by the measured results. The ignition and combustion processes in a gasoline Wankel engine with hydrogen direct-injection enrichment were implemented for numerical simulation. The influence of twin-spark timing was firstly analyzed by synchronous ignition. Further investigation was then conducted to simulate how to effect the combustion by asynchronous ignition based on the favorable synchronous ignition timing. Results showed that, the average flow velocities were 18.8, 20.7, 23.6, and 25.4 m/s for the spark timings (ST) of 45, 35, 25, and 15°CA BTDC respectively. With retarded ST, the rich equivalence ratio approached to twin-spark plug continually. For synchronous ignition, at a larger advance of ST, the duration between the timing of the vortex dissipation and ST was longer, and the ignition delay was more prolonged. As the ST advanced, the combustion rate was enhanced with the increment in chamber temperature, the reactants (C 8 H 18 , C 7 H 16 , and H 2) consumption and intermediates (H 2 O 2 , OH, and CH 2 O) generation were accelerated, the maximum H 2 O 2 and CH 2 O decreased whereas the maximum OH increased, and nitrogen oxides (NO x) and carbon monoxide (CO) increased sequentially. For asynchronous ignition, the accelerated flame front was in accordance with the rotating direction of the rotor while the opposite direction was inhibited during the combustion process. An earlier ignition of leading-spark plug (L-plug) or trailing-spark plug (T-plug) provided the higher flame speed and faster H 2 consumption, which contributed to the higher in-cylinder pressure, combustion temperature, and NO x and CO production. The preferable ignition and combustion characteristics was realized when the L-plug angle was 25°CA BTDC, and the T-plug angle was 35°CA BTDC. Compared with the favorable synchronous ignition timing, the flame propagation and H 2 consumption were expedited, the peak pressure increased by 2.8%, the corresponding crank position advanced by 3°CA and there was no increase in NO x and CO generation. Therefore, it was recommended in engineering applications that the ST of T-plug advanced appropriately while the ST of L-plug remained constant. [ABSTRACT FROM AUTHOR]

Highlights • A CFD model of H 2 -gasoline fueled rotary engine was established and validated. • H 2 was direct injected in the combustion chamber under different strategies. • In-cylinder pressure increased with retarded HIT and extended HID. • The lowest CO emission was achieved in HIT of 110 °CA BTDC, HID of 40 °CA. • Higher NO x emissions were acquired in retarded HIT and extended HID. Abstract In Wankel rotary engine (WRE), high mainstream velocity in combustion chamber blocks flame propagating to the end of combustion chamber, which causes high emissions and low combustion efficiency due to unburned mixtures. To solve this problem, a three-dimensional dynamic simulation model of a hydrogen-gasoline blends fueled WRE is built and validated. The in-cylinder mixture formation and combustion process are investigated under different hydrogen injection timing (HIT) and duration (HID) conditions. The study results show that the concentration of hydrogen distributed between the spark plug region and rear combustion chamber increases with retarded HIT and extended HID. Faster flame speeds are obtained for HIT of 110 °CA BTDC and HID of 40 °CA. At a fixed HID of 20 °CA, compared with HITs of 210 and 160 °CA BTDC, the peak in-cylinder pressures for HIT of 110 °CA BTDC are increased by 14.3% and 6.8%, respectively. At a fixed HIT of 110 °CA BTDC, the peak in-cylinder pressure in HID of 40 °CA is 52.3% and 9.21% higher than HIDs of 20 and 30 °CA. The highest in-cylinder pressure is achieved with the hydrogen injection strategy that HIT of 110 °CA BTDC, HID of 40 °CA. However, as the temperature increases with pressure, nitrogen oxide emissions are also increased with retarded HIT and extended HID obviously. Considering the lowest carbon monoxide is achieved and the unburned zone in the rear region of combustion chamber is eliminated in HIT of 110 °CA BTDC, HID of 40 °CA. The hydrogen direct injection strategy that HIT of 110 °CA BTDC, HID of 40 °CA acquires the best engine performance in this research. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a gasoline Wankel engine was modified and equipped with self-developed hybrid electronic control unit to experimentally investigate the effect of hydrogen-enrichment level on combustion characteristics of a gasoline Wankel engine at wild open throttle position and lean burn regime. Testing were carried out under constant engine speed of 3000 rpm and the lean operating limit of the original gasoline engine. The spark timing was set at 15 °BTDC. The hydrogen energy fraction in the intake was gradually increased from 0% to 10%. The results showed that hydrogen enrichment was effective on improving the combustion process through the shortened of the flame development and the flame propagation periods, advancing the central heat release, increasing the HRRmax and reducing the cyclic variation proportionally to the amount of hydrogen added to the air fuel mixture. Furthermore, increasing hydrogen fraction in the intake improves the engine economy by reducing the cooling loss. Highlights • H 2 was added at the intake of a single-rotor gasoline Wankel engine. • The engine was operating at LOL condition, WOT and 3000 rpm. • H 2 enrichment improves the combustion process through shortening the burn duration. • H 2 enrichment enhances the engine stability and improves the fuel economy of a gasoline Wankel engine. [ABSTRACT FROM AUTHOR]

Hydrogen (H 2 ) owns some excellent fuel specialties and can be used as enhancer to improve the performance of original engine. In the present survey, percent of performance improvement of a Wankel gasoline rotary engine by H 2 enrichment was experimentally studied. The tested engine was initially run at idling and then 3000 rpm with an intake pressure of 37.5 kPa. For the two tested operations, H 2 energy percent ( β H2 ) in the total energy was varied from 0% to 37.0% and 0% to 28.3%, respectively. Results indicated that engine performance was improved by extending β H2 . Overall, performance improvement of idling was more effective than that of 3000 rpm. Percent of performance improvement of idling was generally bigger than that of 3000 rpm. Besides, performance improvement by adding H 2 was relatively efficient at low β H2 , especially below 10%. [ABSTRACT FROM AUTHOR]

The rotary engine of the Wankel type is currently undergoing a renaissance in the combustion engine industry, mainly because of the simplicity of its design and high power to weight ratio. Strong reliability increases the demand in the aero industry where it is used mainly in small aircrafts such as drones. In the engine development process, there is a high demand for 1 dimensional (1D) simulation software which reduces the time of the development. The commercially available software provides a possibility of predicting the performance of the piston-reciprocating engine to a very high level of accuracy given initial conditions. As the demand for the rotary engines isn't comparable to the piston-reciprocating engines, currently commercially available software doesn't include the required equations for the rotary engine prediction calculations. This paper includes an approach for design of the virtual comparable piston engine, that can be used as an initial data source for the calculation of the rotary engine using commercially available software. [ABSTRACT FROM AUTHOR]

A CFD model of hydrogen-enriched gasoline Wankel rotary engine is established and validated. The mixture formation and combustion processes are investigated under both hydrogen port and direct injection enrichment conditions with different hydrogen addition levels. It was found that, under hydrogen port injection enrichment conditions, the peak in-cylinder pressure of 6% is 8.4% higher that of 3%. Meanwhile, under hydrogen direct injection enrichment conditions, the peak in-cylinder pressure of 3% hydrogen direct injection enrichment is 15.3% higher than that of 3% hydrogen port injection enrichment. It was also found that the mainstream field with same direction of rotor rotation is formed during the compression stroke and a vortex with high vorticity existed in the combustion chamber. With the effects of mainstream field and vortex, the hydrogen fills more than half volume of the entire combustion chamber under 4%, 5% and 6% HDIE conditions. At the same time, a local low velocity zone is formed around the vortex because the hydrogen direct injection flow slows down the dissipation of vortex. According to the analysis by PREMIX, the fastest flame speed is achieved at equivalence ratios around 1.4. The proper rich hydrogen region distribution is obtained under 4%, 5% and 6% hydrogen direct injection enrichment conditions. Both the enhanced flame propagation by proper equivalence ratio distribution and the reduced local mainstream flow velocity by vortex existence contribute to solving the unburned zone problem. Compared with 6% hydrogen port injection enrichment, the maximum value of in-cylinder pressure of 4%, 5% and 6% hydrogen direct injection enrichment is improved by 59.6%, 88.4% and 91.6%, respectively. However, carbon monoxide and nitrogen oxide emissions are increased obviously. As a relatively low carbon monoxide emission is obtained with 4% case under hydrogen direct injection enrichment conditions and the problem of unburned zone in the rear region of combustion chamber is solved. The hydrogen volume fraction of 4% with direct injection enrichment achieves the best engine performance in this study. [ABSTRACT FROM AUTHOR]

Off-design characterization of energy systems has become interesting, especially for waste heat recovery application, where the heat source temperature and mass flow rate can vary over time. Low-grade heat is generally converted into power through ORC modules: the problem of the constant temperature evaporation lead to the definition of alternative architectures, among which organic flash cycles. In this work, the off-design behavior of two different architectures of single-stage Organic Flash Cycles has been analyzed in steady-state condition, for small scale waste heat recovery (WHR) purposes. The main difference between the two architecture is the regeneration: in the first architecture (Single-Stage Organic Flash Cycle SS-OFC), the liquid of the flash evaporator, after lamination is mixed with the vapor from the expander and then sent to the condenser; in the second architecture Single-Stage Organic Flash Regenerative Cycle, SS-OFRC, the liquid from the flash evaporator is mixed with the liquid from the condenser, to regenerate the cycle. The most appropriate fluid for the two cycles was selected from a list of sixteen fluids with the objective of minimizing volume flow rates and maximizing the system efficiency and i-Pentane was chosen. For the off-design behavior, a rotary volumetric expander derived from a Wankel engine was considered, taking into account the performance variation of the device at various rotating speed and pressure ratios. Three different control strategies were considered and compared in off-design analysis for both the cycle architectures: sliding-pressure, in which the expander speed was constant and flash pressure varied with the load; sliding-velocity, in which the load was controlled by the speed variation of the expander and flash pressure was retained constant; combined strategy in which the expander speed was varied to drive the flash pressure according to a function which maximized the system efficiency. Results showed that the efficiency of the two cycles was similar in all the operating field whatever was the control strategy considered: SS-OFRC demonstrated a better behavior at low temperatures of the heat source (<170 °C), while SS-OFC had a better efficiency at higher temperature. The maximum absolute efficiency difference in off-design conditions between the two cycles was lower than 0.3%. SS-OFRC however had a wider field of operation than SS-OFC, due to the better flexibility of this type of cycle. As for the control strategy, with both the architectures, combined strategy maximized the system efficiency and flexibility for every temperature and mass flow rate of the heat source considered. [ABSTRACT FROM AUTHOR]

The article presents the possibility of using a rotary piston engine, called the Wankel engine, to drive for unmanned aerial vehicles. It describes the principle of engine operation, its advantages and disadvantages. The article specifies the categories of drones to which these engines are dedicated. The author presents the modular Wankel engine of 5-120 hp for unmanned aerial vehicles, manufactured by Advanced Innovative Engeeniering. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to research the oil film thickness between apex seal and epitrochoidal housing in a small Wankel rotary engine. Firstly, a quasi-static equilibrium equation of apex seal is derived with considering interacting forces. It is supposed that oil pressure is the only force supporting the apex seal against other loads. Then, the oil film thickness is evaluated by solving the equilibrium equation and Reynolds equation within a cycle. In addition, the operation speed's influence on the oil film thicknesses is studied. Results indicate that the oil film thickness is a comprehensive parameter affected by many factors, and these factors exert varying degree of influence on the oil film thickness at different positions within a cycle. [ABSTRACT FROM AUTHOR]

This paper presents a numerical model of the fluid dynamic processes and mechanical losses of a Wankel-type expansion device for microgeneration purposes. The prototype was built at the University of Pisa using the rotating parts of a gasoline-fueled Wankel engine. Considering the geometrical features of the prototype, the model simulates the fluid-dynamic losses across the valves, the thermal exchange with the outer ambient and the mechanical losses of the whole mechanism. The numerical results were then validated by the comparison with the pressure cycle obtained at the dynamic test bench using compressed air. [ABSTRACT FROM AUTHOR]

This paper deals with the creation of modern high-performance aircraft power units based on the Wankel rotary piston engine. One of the main problems of Wankel engines is high specific fuel consumption. This paper solves the problem of improving the efficiency of this type of engine. The mathematical model of non-stationary processes of transfer of momentum, energy, mass, and the concentration of reacting substances in the estimated volume provides for the determination of local gas parameters in the entire computational region, which are presented as a sum of averaged and pulsation components. The k-ζ-f model is used as the turbulence model; the combustion is described by the coherent flame model (CFM) based on the concept of laminar flame propagation. As a result of the calculation, we obtained the values of temperature, pressure, and velocity of the working fluid in the working chamber cross-sections of a rotary−piston engine. Various options of the rotor recess shape are considered. Based on the data obtained, the rotor design was improved. The offered shape of the rotor recess has reduced emissions of both nitrogen oxides and carbon dioxide.