Performance Of Rotary Engine Research Articles

Potential improvement in combustion performance of a natural gas rotary engine mixed with hydrogen by novel bluff-body

Hydrogen/natural gas blends fuel is considered one of the ideal alternative fuels for improving the thermal efficiency and reducing carbon emissions of rotary engine. In order to further enhance the combustion and power performance of rotary engine, a new method of the setting of bluff bodies in the cylinder was proposed. The influence of bluff-body settings in the cylinder on the combustion, power performance, and NO generation was numerically studied under different ignition timings. The results indicated that in-cylinder bluff-body settings could influence flame propagation by affecting the turbulent kinetic energy and mixture distribution during the process from the late compression stroke to the combustion stroke. Further, for any fixed bluff-body shape in the cylinder, there is a trade-off relationship between the non-blockage ratio and squish velocity at the cylinder block center section as the ignition timing is progressively advanced or delayed. Consequently, considering the above trade-off relationship, the triangular slotted bluff-body in combination with an ignition timing of 30° CA (BTDC) could be used to achieve the maximum improvement in the combustion and power performance of rotary engine. The peak pressure exhibited a growth of 4.83%, and the indicated mean effective pressure increased by 1.46%.

Insights into syngas-fueled Wankel rotary engine performance from varied CO/H2 ratio

Syngas is a fuel with a huge market and low carbon emission, which has been proven to be well applied to internal combustion engines. WRE with high power density can effectively improve the power characteristic when syngas is employed as fuel in engines, however, which has not been reported publicly. This work aims to provide insights into the performance of syngas-fueled WRE under different CO/H2 ratios and thus gives theoretical guidance for its application. The test is done at 1500 r/min and part load. It is found that with the increase of the volumetric ratio of CO in syngas (CO%), the efficiency, torque and carbon emissions are deteriorated, however, the NO emission is significantly improved and the knock level is also reduced. In addition, on the premise of constant CO%, a high brake thermal efficiency, low NO emission and knock intensity can be achieved at lean combustion. In particular, when CO% is 10%, the combustion efficiency of CO is independent of the excess air ratio, while when CO% is 20%, that is decreased with increasing excess air ratio. In summary, the syngas-fueled WRE is recommended to adopt the qualitative control and the syngas with low CO%.

The effect of hydrogen additives on fuel consumption and hydrocarbon emissions in gasoline fuelled Wankel rotary engine

Experimental data for Wankel rotary engine performance on hydrogen blends with hydrocarbon fuel is presented. Researches are performed on partial loads and idle. Hydrogen mass fraction additions to the fuel mixture didn’t exceed at partial loads 5% and idle mode 9%. The excess air ratio was stoichiometric. It is shown that for partial loads (20% of full load) and engine speed 2000 rotary per minute 5% hydrogen addition yields to 4.2% decrease of brake specific fuel consumption (hydrogen consumption was converted to gasoline consumption computed proportionally to their combustion heats ratio). Amount of unburned hydrocarbons for the conditions mentioned reduces in a factor of 1.8 and emission of carbon monoxide in a factor of 2.3. Hydrogen addition notably increase effective leaning limit, thus for idle mode tests Wankel rotary engine showed steady performance even for excess air ratio 1.16, while in the absence of addition instability displayed itself for excess air ratio exceeding 0.95.

Research on the behavior of CO2 on hydrogen-fueled Wankel rotary engine performance

To prevent global warming, vigorously developing hydrogen energy has become one of research focuses of various countries and regions in recent years. Hydrogen-fueled engines have been proven to be a potential alternative to current fossil-fueled engines. Among various engines, Wankel rotary engine (WRE) is praised for its simple structure and excellent dynamic characteristics, which can greatly compensate for the low specific-volume heat value of hydrogen. However, hydrogen-fueled WRE suffers from low efficiency, high NOx emission and severe knock. For methanol-reforming hydrogen-fueled ICEs, CO2 as the by-product can be used as variant-cooled-EGR to improve ICEs performance and prevent abnormal combustion. Therefore, this work researches the behavior of CO2 on the hydrogen-fueled WRE. The work is conducted at 1500 r/min and wide-open throttle. The results show that CO2 has a significant influence on the heat release process of hydrogen-fueled WRE. Due to this influence, when the volume fraction of CO2 in intake (CO2%) is increased from 0 to 19.28%, the brake thermal efficiency can be improved by 8% with a 7% decline in power output. The NO emission has two orders of magnitude of reduction with increasing CO2% from 0 to 19.28%.. In addition, compared with cooled-EGR, CO2 has a better effect on knock suppression. If methanol-reforming to produce hydrogen becomes the mainstream of on-board hydrogen production in the future, the application of CO2 is of great significance.

Numerical assessment of interchangeability potential for syngas-fueled rotary engine

The syngas-fueled rotary engine can be considered as a promising solution for small–scale decentralized power generation due to high specific power, engine simplicity, smoothness and a low tendency for abnormal combustion. Since the decisive feature of syngas refers to feedstock flexibility, in this study we consider syngas with various compositions, produced from biomass, coal and natural gas, as a primary fuel for rotary engines. It was shown that rotary engine performance, efficiency and emission are mostly affected by the balance between combustion promoters and diluents in the air-syngas mixture. Particularly, high hydrogen concentration and lower inert content result in maximum power, heat release and thermal efficiency for stoichiometric and lean conditions. For the rotary engine with a homogeneous charge of the fuel, the combustion process is characterized by the weak influence of turbulence, while the laminar flame speed is an influential parameter in combustion behavior. The high magnitude of specific fuel consumption makes it difficult for engine operation at lean conditions. Although, the lean mixture cannot provide enough high flame temperature for NOx formation. The CO2 emission is affected by the hydrogen to carbon ratio. The opposite trend is observed between NOx and CO emission pathways due to oxygen availability. The power generation system based on the syngas-fueled rotary engine with syngas produced by not only well-known technology such as gasification or steam reforming but novel concepts (non-catalytic partial oxidation) can provide sustainability to the energy sector and reduce consumption of fossil fuels..

Combined effects of intake oxygen enrichment, intake pressure and temperature on combustion behavior and emission characteristics of a small-scaled rotary engine

Intake oxygen enrichment has a promising potential to improve the combustion performance of a small-scaled rotary engine (RE) operating at high altitudes. However, the process is complicated because the intake temperature and pressure are sensitive to altitudes as well as the elongated rotor chamber. In this study, a three-dimensional CFD simulation model coupling with a suitable turbulent model and a reduced chemical kinetic mechanism was established and validated. The combined effects of intake oxygen enrichment as well as intake pressure and temperature under different altitudes on early flame growth, combustion behavior, and emission characteristics of small-scaled REs were numerically investigated. Results showed that intake oxygen enrichment promotes the formation of OH, O, H radicals, which leaded to the significant improvements of the early flame growth, especially for the flame near leading spark plug. The promotion effect due to intake oxygen enrichment became weak with increasing altitude. Moreover, the early flame growth duration at high altitudes was more dramatically shortened by intake oxygen enrichment than that at low altitudes. It is interesting to note that when oxygen concentration of 25% and 29% were applied to the small-scaled RE working at 2000 m and 3000 m altitude, respectively, the engine performance could be restored to the level of that working at sea level at the price of a smaller increment of NO emissions. Under high intake oxygen concentration conditions, the effect of altitude on indicated thermal efficiency of the engine could be ignored. Besides, increasing oxygen concentration significantly reduces HC and CO emissions, especially more significant reduction for HC emissions at higher altitudes. • Early flame growth of the rotary engine was analyzed numerically. • Early flame growth near LSP was more significantly improved by oxygen enrichment. • Effect of intake oxygen enrichment on rotary engine performance was quantified. • Oxygen enrichment significantly reduced HC and CO emissions.

Understanding the role of turbulence-induced blade configuration in improving combustion process for hydrogen-enriched rotary engine

Benefits from the strong one-way flow within the rotor chamber, inducing turbulence is an effective means to improve flame evolutions and combustion characteristics of rotary engines. With the help of three-dimensional CFD simulations, the role of the turbulence-induced blade (TIB) configuration in strengthening ignition and combustion was assessed in a rotary engine fueled with hydrogen and gasoline, and the mixture formation, combustion process, and pollutants performance were addressed under different operating conditions. The numerical results show that introducing TIB in the rotor chamber is beneficial for improving the turbulent flow. The closer the blade position is to the spark plug, the higher the turbulent velocity and turbulent dissipation rate within the spark region. The leading-blade rotor chamber shows better combustion and emissions characteristics of the rotary engine. The TIB configuration is more sensitive to the combustion improvement of pure gasoline rotary engines compared with hydrogen-enriched rotary engines. The indicated power of the leading-blade engine is higher than that of the no-blade engine under various excess air ratio conditions. Especially for the excess air ratio of 1.1, the difference in the burned volume between the leading-blade and no-blade cases is more pronounced. Compared with stoichiometric operations, the TIB configuration shows better emission performance at lean-burn operations. The improvement of the turbulence level increases significantly by the leading-blade configuration at a lower engine speed. With the increase of the engine speed, the decrease in peak pressure is more significant in the leading-blade rotor chamber. The results shall give insights into the feasibility of the TIB configuration on the improvement of rotary engine performance in engineering applications.

Influence of Intake Pipe Deflection Angle on In-Cylinder Flow and Combustion Characteristics of a Rotary Engine

Abstract Intake pipe design is important for rotary engine performance due to great influence on in-cylinder flow and combustion characteristics. This paper analyzes the effect of intake pipe deflection angle on the performance of a gasoline rotary engine. In the parametric study, the intake pipe is deflected from the left to the right with a 10 deg interval and the maximum deflection range of 30 deg at each side. A computational fluid dynamics numerical simulation model of the rotary engine is established. The simulation results show that when the intake pipe is deflected to the left from the original design, the engine volumetric efficiency first increases and then decreases with an increasing deflection angle. During ignition, the turbulent kinetic energies in the cylinder increase with an increasing deflection angle. When the intake pipe is deflected to the left by 30 deg, the turbulent kinetic energy is increased by 85.9% compared to the original design. The peak cylinder pressures first increase and then decrease with an increasing deflection angle. When the intake pipe is deflected by 10 deg to the left, the peak cylinder pressure is 9.3% higher than that of the original design. The maximum NOx emission can be increased by 4.8% and the minimum NOx emission can be decreased by 13.3%. It is found that deflecting the intake pipe to the left enhances the tumble effect and increases the combustion velocity. Overall, deflecting the intake pipe to the right is less effective than deflecting to the left. This analysis provides a comprehensive understanding on intake pipe design for rotary engines.

Combustion Chamber Design Effect on The Rotary Engine Performance - A Review

Combustion Chamber Design Effect on The Rotary Engine Performance - A Review

Idle performance of a hydrogen rotary engine at different excess air ratios

Rotary engine has flat chamber and longs for fuel with high flame speed and small quenching distance. Hydrogen has many excellent characteristics that are suitable for the rotary engine. In this paper, the performance of a rotary engine fueled with pure hydrogen at different excess air ratios was experimentally investigated. The investigation was carried out on a single-rotor hydrogen-fueled rotary engine equipped with port fuel injection system. An online electronic control module was used to govern the hydrogen injection duration and excess air ratio. In this study, the engine was operating at the idle speed of 3000 rpm and different excess air ratios varied from 0.993 to 1.283. The test results demonstrated that the fuel energy flow rate of the hydrogen rotary engine and engine stability were reduced with the increase of excess air ratio. When the excess air ratio increased from 0.993 to 1.283, the hydrogen energy flow rate was decreased from 14.91 to 11.55 MJ/h. Both the flame development and propagation periods were increased with excess air ratio. CO emission was negligible, but HC, CO2 and NOx emissions were still detected due to the evaporation and possible burning of the lubrication-used gasoline, and oxidation reaction of nitrogen of the intake air.

Improving the combustion performance of a gasoline rotary engine by hydrogen enrichment at various conditions

The combustion process within the cylinder directly influences the thermal efficiency and performance of the engines. As for the rotary engine, the long-narrow combustion chamber prevents the mixture from fully burning, which worsens the performance of the rotary engine. As a fuel with excellent properties, hydrogen can improve the combustion of the original engine. In this paper, improvements in combustion of a gasoline rotary engine by hydrogen supplement under different operating conditions were experimentally investigated. The experiment was conducted on a modified hydrogen-gasoline dual-fuel rotary engine equipped with an electronically-controlled fuel injection system. An electronic control module was specially made to command the fuel injection, excess air ratio and hydrogen volumetric fraction. Integral heat release fraction (IHRF) was employed to evaluate the combustion of the tested engine. The tested engine was first run at the idle speed of 2400 rpm and then operated at 4500 rpm to investigate the combustion of the hydrogen-blended gasoline rotary engine under different hydrogen volume fractions, excess air ratios and spark timings. The testing results demonstrated that the combustion of the gasoline rotary engine were all improved when the hydrogen was blended into the chamber under all tested conditions.

Investigation on performance of a hydrogen-gasoline rotary engine at part load and lean conditions

Lean combustion is a promising method for getting ameliorate engine performance. However, due to the small flammability of gasoline and elongated combustion chamber of rotary engine, gasoline rotary engine tends to encounter partial burning and even misfire when mixtures are dilute. Hydrogen (H2) occupies many advantages that may remit the aforementioned problems. For this motivation, a rotary engine installed gasoline-H2 port-injection system was developed to explore the performance of rotary engine fueled with H2-gasoline blends at part load and lean conditions. A speed of 4500rpm, a manifold absolute pressure (MAP) of 35kPa and a spark advance of 25°CA were adopted for this research. Hydrogen volume fraction (αH2) was kept at 0, 3% and 6%, respectively. Excess air ratio (λ) was gradually enlarged from 1.00 with a step of 0.05. For a given λ, when αH2 was increased, the results were showed subsequently. Peak chamber pressure was increased and its corresponding crank angle was advanced. Brake mean effective pressure, peak combustion temperature and brake thermal efficiency were simultaneously increased. Flame development and propagation periods, cooling loss and cyclic variation were reduced. HC and CO emissions were lessened whereas NOx emissions were heightened due to the raised combustion temperature.

Influences of Ignition Timing, Spark Plug and Intake Port Locations on the Combustion Performance of a Simulated Rotary Engine

AbstractThe purpose of this paper is to study the flow field of the combustion chamber in a simulated rotary engine by using a computational approach. A dynamic mesh technique is employed to overcome the moving and shape varying computational domain inside the combustion chambers as the rotor is spinning. The key parameters include spark plug timing, leading side spark plug location and intake port location, which are used to investigate their influences on flow field and combustion performance of a rotary engine. It was discovered, with a dual spark plug configuration, that better flame propagation could be obtained through the change of ignition timing. In addition, to change the leading side spark plug location, it was also found that combustion efficiency is improved by shortening the distance from the top dead center (TDC) center line, which is consistent with available experimental results. This research also discovered that the intake port should be properly located in order to prevent pressure loss in the combustion chamber during the compression stroke.

Numerical Investigation on the Effects of Flame Propagation in Rotary Engine Performance With Leakage and Different Recess Shapes Using Three-Dimensional Computational Fluid Dynamics

This study was carried out with an objective to develop a 3D simulation methodology for rotary engine combustion study and to investigate the effect of recess shapes on flame travel within the rotating combustion chamber and its effects on engine performance. The relative location of spark plugs with respect to the combustion chamber has significant effect on flame travel, affecting the overall engine performance. The computations were carried out with three different recess shapes using iso-octane (C8H18) fuel, and flame front propagation was studied at different widths from spark location. Initially, a detailed leakage study was carried out and the flow fields were compared with available experimental results. The results for first recess with compression ratio 9.1 showed that the flow and vortex formations were similar to that of actual model. The capability of the 3D model to predict the combustion reaction rate precisely as that of practical engine is presented with comparison to experimental results. This study showed that the flame propagation is dominant toward the leading apex of the rotor chamber, and the air/fuel mixture region in the engine midplane, between the two spark plugs, has very low flame propagation compared to the region in the vicinity of spark. The air/fuel mixture in midplane toward the leading apex burns partially and most of the mixture toward the trailing apex is left unburnt. Recommendations have been made for optimal positioning of the spark plugs along the lateral axis of the engine. In the comparison study with different recess shapes, lesser cavity length corresponding to a higher compression ratio (CR) of 9.6 showed faster flame propagation toward leading side. Also, mass trapped in working chamber reduced and developed higher burn rate and peak pressure resulting in better fuel conversion efficiency. Third recess with lesser CR showed reduced burn rates and lower peak pressure.

Effects of Various Geometric Designs on the Flow Characteristics of a Triangular Rotary Engine

Although rotary engines can potentially be used as hydrogen fuel engines, the contact condition between the casing and the apex seal on the triangular rotor impacts sealing performance, which then directly affects leakage problems. In this paper, therefore, a rotary engine’s internal gas flow characteristics are investigated by using the CFD package FLUENT to construct a fluid analysis model. For comparative convenience, assuming that the simulated gas is air, and then, using a set circular radius outside the casing, analyze three different cases with various geometric design parameters (the K factor) and their effects on the internal pressure, streamlining, and leakage. The results indicate that the K factor design produces different rotor profiles with different working chamber volumes: the lower the K factor, the larger the working chamber volume. Nevertheless, although this design can improve the combustion and compression efficiencies, it may lead to increased internal pressure variation and raised pressure. In addition, when the clearance is small, it may result in a larger leakage problem, negatively affecting rotary engine performance.

Development of a single-section demonstrator rotary engine on the basis of a modern complex design procedure

There is no manufacture of aviation engines in power range of 100-300 hp. One of the most perspectivedecisions of the domestic low-sized aviation engines developing is creation of engines on the basis of modularityprinciple. This principle consists in designing of the unified power part and creation on the basis of itmultisection or multicylinder engines for maintenance necessary performance. Most simply given problem daresat creation of rotary engines. The paper presents modern design procedure of single rotary engine. This procedureincludes statement of target engineering performance, calculation of the basic dimensions of rotary engine,engine performance assessment subject to gas dynamics and mechanical losses, simulation of working processsubject to basic dimensions of rotary engine and heat transfer into combustion chamber wall. 3D-model of rotaryengines is created on the basis of calculations mentioned above. Calculation of engine geometry is carried out by analytical methods. Performance of rotary engine is calculated by using modern software. The 100 hp single rotary engine project was developed on the basis of this design procedure. In future this design procedure will be applied for developing 200 hp and 300 hp aviation rotary engines.

Couette Flow Heat Loss Model for the Rotary Combustion Engine

A novel model for predicting heat transfer in a rotary engine was formulated and implemented in a zero-dimensional engine performance model. Results were compared with a commonly used intermittent combustion engine heat transfer model and with results from a three-dimensional simulation of flow within a rotary engine. When squish effects associated with fluid motion within the chamber were included, the Couette flow model reproduced peak heat transfer rates and timing for the peak heat transfer rate was better than that of the commonly used heat transfer model. Previously, rotary engine performance models have employed flat plate type heat transfer correlations. These correlations, though useful, do not model the flow physics in the rotary engine faithfully. Rather than flow over a flat plate, flow in the rotary engine was approximated as turbulent Couette flow. The Couette model was altered to account for centre-line velocities higher than half the rotor speed. There are two advantages to using the Couette flow model. Firstly, as noted, the underlying physics of the Couette flow model is closer to conditions in the rotary engine. Secondly, with the Couette flow model it is possible to differentiate between the rotor and housing heat transfer coefficients.

Second Paper: Recent Studies on Rotary-Engine Lubrication

Rotary-engine lubrication studies have been conducted on four engines covering the two types of rotary engine now in production. Metallic or carbon-metallic apex seals were used.Results presented have been obtained with 13 different oil formulations, including passenger-car-engine oils corresponding to API SC, SD or SE categories, automatic-transmission fluids of the Dexron II type, and oils for two-stroke engines. Seven different test procedures have been used in these investigations, employing either engine bench test stands or vehicles on chassis dynamometers.Satisfactory rotary-engine performance has been obtained with oils containing from 0 to 1·2 per cent by weight of sulphated ash. The ability of the base stock to provide good film thickness has also been found of benefit in reducing rotary-engine wear. Passenger-car-engine oils can be excellent rotary-engine lubricants and those oils corresponding to the latest API SE classification exhibit better performance than previous API SC or SD oils. Automatic-transmission fluids have also given promising results.