Rotary Piston Engine Research Articles

Parametric modeling and optimization of the intake port in a naturally aspirated opposed rotary piston engine across the full speed range

The opposed rotary piston (ORP) engine offers advantages such as compact size, simple structure, and high power density, making it highly promising for long-endurance unmanned aerial vehicles (UAVs). Parametric modeling of intake ports and the investigation of structural parameters on intake characteristics for ORP engines are crucial for improving the intake performance. In this paper, based on the kinematic model of the ORP engine, parametric modeling of the intake and exhaust ports are performed, a 3D numerical model is established to explore the intake characteristics at different engine speeds. The impact of intake delayed closing angle (IDCA), intake inclination angle (IIA), and dual intake ports on the intake characteristics of the ORP engine are investigated. Finally, the combustion characteristics and performance metrics of the engine using optimized intake ports are compared against the baseline intake phase. The results indicate that the CGE and pumping loss of the ORP engine initially increase and then decrease with rising engine speed. The CGE exceeds 92 % at 1000 r·min−1 and 94 % at 5000 r·min−1 when the IDCA are set at 8° and the IIA at −20°. The pumping losses at 4000 r·min−1 and 5000 r·min−1 are reduced by 33.3 % and 30.9 %, respectively, after intake port optimization. The performance metrics at 1000 r·min−1 and 2000 r·min−1 show a slight decline compared to pre-optimization due to lower turbulence kinetic energy (TKE) and intake backflow. However, at 3000–5000 r·min−1, the optimized intake port structure significantly improves performance metrics of the ORP engine.

RETRACTED: Research on the kinetics characteristics and in-cylinder combustion of opposed rotary piston engine for different power output modes

As a new type of internal combustion engine, opposed rotary piston (ORP) engine has the advantages of simple structure and high working frequency, and can achieve high power density. Consequently, it stands as an ideal power source for hybrid power systems and unmanned aerial vehicles. The ORP engine has different power output modes, corresponding to different piston rotation and volume evolutions of combustion chamber. However, the effect of power output modes on kinetics characteristics and in-cylinder combustion of ORP engines are still uncovered. In this paper, the kinematic model of an ORP engine is established for scenarios involving power output by different shafts (Shaft 1 and Shaft 3). Meanwhile, the piston rotation patterns and cylinder volume variations are investigated correspondingly. Further, three-dimensional numerical model of the ORP engine is established, enabling analysis of in-cylinder combustion characteristics, engine performance, as well as nitrogen oxides (NOx) emissions. The results indicate that the volume variations of all cylinders follow a consistent pattern under the power output by Shaft 3. A pair of opposed cylinders features longer durations of intake and expansion strokes, and shorter durations of compression and exhaust strokes, the other pair of combustion chambers is the opposite under the power output by Shaft 1. The engine demonstrates a charging efficiency of 95.36 %, with corresponding indicated thermal efficiency and indicated power output of 38.08 % and 40.9 kW, respectively. The two adjacent cylinders present significantly different operation processes in the case of the power output by Shaft 1, achieving charging efficiencies of 94.29 % and 89.11 %, respectively, with the indicated thermal efficiency of 34.49 % and 31.60 %. The corresponding minimum indicated specific fuel consumption under the two power output modes are 211.7 g/kW∙h and 243.7 g/kW∙h, respectively, accompanied by NOx emission factors of 25.3 g/kW∙h and 17.6 g/kW∙h. With the given range of ignition timing, a trade-off relationship exists between the engine performance and NOx emissions. The power density of the case of power output by Shaft 3 is superior to that of Shaft 1.

Анализ концепции роторно-поршневого двигателя с реализацией цикла газотурбинного двигателя V = const

New conceptual solutions are required to significantly increase the internal combustion engine efficiency. Introducing external spool combustion chamber of constant volume and structural separation of the compression and expansion processes in its design are able to provide multi-fuel capacity, qualitative increase in the efficiency and significantly simplify the gearbox. In order to qualitatively improve characteristics of the internal combustion engine, systematic analysis of the created scientific and technical potential is required, followed by comprehensive implementation. The paper considers a concept of an internal combustion engine with continued expansion and ability to approach the gas turbine engine cycle implementation at constant volume with high efficiency on the example of such a basis using the rotary piston engine (CIAM) with the spool combustion chamber of constant volume (PJSC “UEC-Saturn”). The proposed concept makes it possible to effectively implement promising technologies for nitrogen separation and STIG technologies for further increase in the efficiency.

Determining the effect of anti-friction additive on the power of mechanical losses in a rotary piston engine

Experimental studies of the effect of adding the antifriction additive Multi-Tech-Conditioner to lubricating oil on the power of mechanical losses of a rotary piston engine were carried out, the purpose of which was to reduce the cost of potential energy of a compressed working fluid to overcome friction forces. The experimental data obtained make it possible to estimate the value of irretrievable losses of the available power of a rotary piston engine at the stage of its design and operation. Experimentally, a positive effect of the addition of the Multi-Tech-Conditioner antifriction additive to lubricating oil on the change in the power of mechanical losses of the engine was established, which was reflected in a decrease in total losses over the entire operational range of change in the rotor speed by 11.8 %. As a result of the research, it was determined that the losses for pumping strokes (gas exchange) in a rotary piston engine amount to 31.6 % of the total power of mechanical losses. An assessment was made of change in the mechanical efficiency of a rotary piston engine with a hinged-cam mechanism for converting motion under the conditions of applying an antifriction additive to lubricating oil. It has been established that the addition of the Multi-Tech-Conditioner additive to the lubricating oil in a ratio of 1:14 makes it possible to increase the mechanical efficiency of a rotary piston engine depending on the speed by 3.8–5.5 % for all operating pressures in the inlet receiver. Based on the generalization and systematization of the obtained experimental data on the use of the Multi-Tech-Conditioner additive, the most rational operating ranges of a new design rotary piston engine were identified. The maximum mechanical efficiency of a rotary piston engine is achieved in the load range of 65...75 % of the rated power, and the speed range is 63...70 %

Профилирование торцевых окон трохоидной машины

There is a proposal of a method for the profiling the end windows of trochoid rotary machines according to the given geometric parameters for constructing the trochoid and the degree of gas pressure increase. Its area of application is rotary piston engines and trochoid compressors and pumps. Verification of the mathematical model was carried out on the basis of gas flow simulation data in a three-dimensional setting in the AVL Fire software package. The model of the working process of a trochoid machine is based on the fundamental equations of momentum, energy, diffusion and continuity, written in the Reynolds form and supplemented by the k–?–f turbulence model. The developed method makes it possible to estimate quickly the throughput of the windows of a trochoid rotary machine with less computing resources than in a three-dimensional calculation.

Effect of asymmetric fuel injection on combustion characteristics and NOx emissions of a hydrogen opposed rotary piston engine

Opposed rotary piston engines have the characteristics of high-power density and simple mechanisms. The applications of hydrogen fuel to internal combustion engines significantly are without carbon dioxide emission, alleviating the global warming. In this paper, hydrogen fuel was asymmetrically injected into combustion chambers to increase hydrogen penetration distance via; in the meantime, the engine performance and nitrogen monoxide (NO) emission with different ignition timing are explored by numerical simulation method. The symmetrical fuel injection scenario was provided as a baseline. In the scenarios of asymmetrical fuel injection, the engine had the best hydrogen injector position and ignition timing. Peak in-cylinder pressure Pmax reached 56.0 bar under ignition timing ti of −14.2° CA before top dead centre (bTDC) and hydrogen injector position (θ2) of 60.5°; in the meantime, heat loss rate HL and heat release rate Qr reached maximum values. Compared with the symmetric fuel injection engine, the peak NO emission of the asymmetric fuel injection engine was reduced by 15%. The proportions of energy loss by cylinder walls of asymmetric fuel injection engine were low and showed low dependency on ignition timing and hydrogen injector layout. Additionally, the asymmetric hydrogen injection structure makes hydrogen distribute evenly in the combustion chamber.

Determining the power of mechanical losses in a rotary-piston engine

This paper reports an experimental study into the magnitude of the power of mechanical losses of the prototype of a rotary-piston engine with an articulated cam mechanism for transforming movement, which was aimed at resolving the issue related to improving the efficiency of energy conversion. It has been experimentally established that the greatest component of the power of mechanical losses in a rotary-piston engine with an articulated cam motion transformation mechanism is friction losses. Depending on the rotational speed, they are about 68.4...74.4 % of total losses. The influence of the rotor rotation frequency on the total change in the power of mechanical losses and its components has been determined (an increase in the rotations by 3.75 times leads to an increase in the power of mechanical losses by 3.3 times). It is established that the rotation frequency of the rotor does not have the same effect on the power components of mechanical losses. Thus, an increase in the rotations by 3.75 times leads to an increase in friction losses by 3.0 times, and the component of losses on pumping strokes by 4.1 times. It was found that an increase in the pressure of working body by 2.0 times contributes to an increase in the mechanical efficiency of the rotary piston engine by 1.1 times. At the same time, it was determined that the rational speed range, which corresponds to the maximum values of the mechanical coefficient of efficiency, regardless of the pressure of working medium, is 800...1200 min–1. The resulting experimental data on studying the magnitude of the power of mechanical losses in the form of an analytical model of the influence of the main operational parameters of the rotary-piston engine with an articulated-cam mechanism for converting movement into a mechanical coefficient of efficiency have been generalized. The results reported here could make it possible to preliminary assess losses at energy conversion at the design stage and to construct a rotary piston engine for different purposes

Simulation on the effect of compression ratios on the performance of a hydrogen fueled opposed rotary piston engine

Hydrogen internal combustion engines are attracting increasing attention because of no carbon dioxide (CO2) emission and high thermal efficiency for hydrogen combustion. Opposed rotary piston (ORP) engines have simple structures, small size and mass, contributing to the performance improvement of hybrid electric vehicles (HEVs) and range extended electric vehicles (RE-EVs). Compression ratios as an important factor affecting engine performance should be considered in the process of engine designs and optimizations. In this paper, in-cylinder combustion characteristics of a small-scale ORP engine were investigated using a numerical simulation method over different compression ratios (8.90, 9.66, and 10.55). Compression ratio adjustment of the ORP engine may be achieved by the movement patterns of the two shafts. The results indicated that maximum in-cylinder pressure was increased from approximately 3.5 MPa–5.0 MPa when the compression ratios were increased from 8.90 to 10.55. The crank angle (CA) of the maximum in-cylinder pressure was slightly retarded by increasing compression ratios. The hydrogen combustion rates were almost the same before top dead centre (TDC) for the three cases. The combustion durations were dropped from approximately 38.7 °CA to 28.3 °CA when the compression ratios were increased from 8.90 to 10.55; however, the combustion phase of the compression ratio of 9.66 was the earliest among the three cases. The proportions of energy loss by cylinder walls were almost the same under different compression ratios, being approximately 10%; additionally, the indicated thermal efficiency was increased from approximately 34%–39% by changing compression ratios from 8.90 to 10.55. The nitrogen oxides (NOx) emission factors of the ORP engine were almost linearly increased by increasing compression ratios, with the values being higher than 17.2 g/kWh for all the three cases. NOx distributions in combustion chambers around 50 °CA after TDC agreed well with those of in-cylinder temperature and hydrogen residuals.

Effect of hydrogen direct injection strategies and ignition timing on hydrogen diffusion, energy distributions and NOx emissions from an opposed rotary piston engine

Opposed rotary piston (ORP) engines as a new type of internal combustion engines are free of connecting-rod mechanisms, have small engine size and mass. ORP engines have the abilities of delivering high power density. Hydrogen fuel applications in internal combustion engines contribute to nearly zero carbon emissions in the combustion processes. In this paper, the effect of hydrogen direct injection strategies and ignition timing on hydrogen diffusion, in-cylinder combustion, energy distributions, and nitric oxide (NOx) emissions are investigated using a numerical simulation method regarding this novel internal combustion engine. The results showed that hydrogen was the most unevenly distributed in the combustion chambers for the start of injection (SoI) of −68.2° crank angle (CA) after top dead centre (aTDC) among the three hydrogen injection strategies; meantime, it presented the lowest combustion efficiency, being smaller than 98.5%. The peak in-cylinder pressure ranged from 40 bar to 83 bar for the given scenarios. The combustion durations were in the range of 20 °CA ~ 30 °CA for the ignition timing of −20.85 °CA aTDC ~ −11.06 °CA aTDC. The indicated thermal efficiency was higher than 38% over early ignition cases; the energy losses in total fuel energy by cylinder walls were lower than 15%. NOx emissions factors were lower than 36 g/kWh, and they were reduced by the retarded hydrogen injection. The engine performance and NOx emissions under early hydrogen injection scenarios are less sensitive to late ignition; additionally, the crank angle corresponding to the optimal efficiency was almost the same under different hydrogen injection strategies.

Simulation of the impacts on a direct hydrogen injection opposed rotary piston engine performance by the injection strategies and equivalence ratios

Opposed rotary piston (ORP) engines can deliver high power density and have few moving parts, being suitable for the power sources of hybrid electric vehicles, range extended electric vehicles, and unmanned aerial vehicles. Hydrogen as a promising alternative fuel is free of carbon emissions during combustion. Hydrogen direct injection avoids the significant power losses of port injection scenarios resulting from the low hydrogen energy density by volume. This paper firstly investigated the ORP engine performance using a 3D numerical simulation method over various hydrogen direct injection strategies (start of hydrogen injection and injection durations). Hydrogen diffusions in combustion chambers, combustion characteristics, engine performance, nitrogen oxides (NOx) emissions, and knock tendency were researched over various hydrogen injection strategies. Hydrogen was unevenly distributed in the combustion chambers for high equivalence ratio scenarios, leading to low combustion efficiency; additionally, the unburned hydrogen was mainly in the cylinder bowls and bottoms. Combustion durations were the shortest within the equivalence ratio range of 0.577–0.865, being approximately 18° crank angle (CA). The maximum in-cylinder pressure was higher than 8.0 MPa over the equivalence ratio of 0.961; and the corresponding heat release rates were higher than 45 J·(°CA)−1. The indicated thermal efficiency was higher than 38%, and it was increased generally by dropping equivalence ratios, with the maximum efficiency being approximately 42.5%. NOx emission factors, approximately 35 g (kW h)−1, reached the maximum value under the equivalence ratio of 0.673 conditions. Knock tendency was decreased continuously by lowering equivalence ratios. This research made a foundation of improving the engine fuel economy and mitigating NOx emissions for hydrogen direct injection ORP engines.

An effective approach of dropping the backfire possibilities of a hydrogen‐fuelled opposed rotary piston engine

AbstractBackfire of hydrogen‐fuelled internal combustion engines limits the hydrogen fuel applications and drops the power output. Opposed rotary piston (ORP) engines are characterized by high power density, smooth operations, and few moving parts. However, the intake structures of ORP engines tend to deliver high possibility of backfire under hydrogen utilization conditions due to more residual exhaust. This paper proposed an effective approach of eliminating backfire for a hydrogen fuelled ORP engine, and it did not generate any penalty of power output theoretically. The effectiveness of this method was demonstrated using a 3D numerical simulation method. The results indicated that the average in‐cylinder temperature started to increase at the start of the intake process if without any backfire control strategies; however, it decreased continuously if backfire control was applied. The mass flow rates of the intake fluid were at a low level without backfire control, but it increased sharply if backfire control was adopted. Backfire in this investigation was caused by the pre‐ignition of mixture in cylinders. The temperature in intake pipes reached up to 1000 K over backfire scenarios, and heat of reaction was higher than 3 W. Hydrogen mass fractions at the bottom of intake pipes were low at the start of intake process due to the backfire; meantime, slight backflow also happened in the intake process due to the pre‐ignition of cylinders mixture. The fluid velocity was higher than 100 m/s at the beginning of intake process if backfire was controlled.

Explorations of the impacts on a hydrogen fuelled opposed rotary piston engine performance by ignition timing under part load conditions

High power density of opposed rotary piston (ORP) engines provides a possibility for the applications to hybrid vehicles. Under real driving conditions, internal combustion engines as the power sources of hybrid vehicles run under part load conditions in majorities of operation time. Hydrogen applications in internal combustion engines will promote zero-carbon travel, contributing to alleviating global warming. In this investigation, 3D numerical simulations were conducted to explore the performance of an ORP engine fuelled with hydrogen under part load and various ignition timing conditions. The results indicated that peak in-cylinder pressure and corresponding crank angle (CA) changed slightly within the early ignition range of −20.85º CA~ −14.23º CA; peak in-cylinder pressure was decreased significantly by late ignition. Heat release rates were more sensitive to late ignition than early ignition. Start of combustion, combustion phase, and combustion durations presented minor impacts by early ignition and engine loads. Ignition timing of −20.85º CA~ −11.06º CA showed limited impacts on indicated mean effective pressure and indicated power over individual intake manifold pressure. Indicated thermal efficiency was around 40% for the ignition timing of −20.85º CA~ −11.06º CA over the intake manifold pressure of 0.8 bar; indicated thermal efficiency drop caused by ignition timing of −8.33º CA was higher than 7% compared with optimal conditions. Heat loss by cylinder walls in proportions of fuel energy was lower than 25%, 20%, 18% for the intake manifold pressure of 0.4 bar, 0.6 bar, 0.8 bar respectively. Energy loss by the exhaust was higher than 41% for all the scenarios, with the maximum value being approximately 57%. Nitrogen oxides (NOx) emission factors were higher than 11 g (kW h)−1, and they were increased significantly by early ignition.

Performance explorations of a naturally aspirated opposed rotary piston engine fuelled with hydrogen under part load and stoichiometric conditions using a numerical simulation approach

Opposed rotary piston (ORP) engines are characterized by high power density, compact designs, and smooth operations which meet the requirements of the power source for hybrid vehicles. Hydrogen fuel applications will fully present ORP engines’ advantages due to the short cyclic period. Internal combustion engines mainly operate under part load conditions over real world driving, the performance of hydrogen ORP engines over part load needs to be addressed in order to promote the applications to hybrid vehicles. In this paper, combustion and nitrogen oxides emission of this ORP engine under part load and stoichiometric conditions were investigated using a 3D numerical simulation approach. The results indicated that peak in-cylinder pressure during combustion was significantly dependent on the intake manifold pressure, and the corresponding crank angle (CA) was almost kept the same for 1000 RPM and 3000 RPM. Heat release rates for hydrogen combustion presented double-peak under high intake manifold pressure scenarios. Combustion durations over 1000 RPM increased with intake manifold pressure; however, they changed slightly for 3000 RPM. Nitrogen oxides (NOx) emission concentration increased with intake manifold pressure for 3000 RPM and 5000 RPM; however, intake manifold pressure of 0.6 bar presented the highest value for 1000 RPM. Indicated thermal efficiency was higher than 30% for 1000 RPM and 3000 RPM; and the minimum value was approximately 21% over 5000 RPM and 0.4 bar.

Determining a change in the compressed air temperature during the operation of a rotary piston engine

Experimental studies of change in the air temperature in a power unit with a prototype RPD-4.4/1.75 rotary-piston pneumatic motor were carried out to solve the problem of the negative impact of low temperatures of exhaust air on the pneumatic motor performance.It has been established that an increase in rpm by 62 % leads to a drop of air temperature after reducer by 33 %. In this case, the maximum temperature drop during throttling is 21 K under conditions of maximum rpm and pressure of 0.8 MPa in the inlet receiver. It was found that under experimental conditions, the average differential Joule-Thomson effect is in the range of 0.8…3.9 K/MPa when throttling in the reducer for the pressure range of 0.4...0.8 MPa in the inlet receiver.It was found that the temperature drop caused by air expansion in the working cylinder of the pneumatic motor is about 22 K in absence of regulation of the filling degree. At the same time, temperature fluctuations do not exceed 4.5 % depending on the change in the motor rpm and pressure in the inlet receiver.A maximum temperature decrease in the power unit was obtained experimentally. Under the experimental conditions and depending on the study mode, the temperature drop from the initial storage value is from 35 to 43 K.It was found that the amount of energy required for heating air at the inlet to the inlet receiver with a pressure of 0.6 MPa in the air storage temperature range of –5...–20 °С is 0.14...1.99 kW. In this case, the ratio Qp/Ne can reach 0.1...0.58, that is, in some operating modes, more than half of the produced power will actually be spent on air heating. Accordingly, the results obtained are useful and necessary when choosing conditions and operating modes of the pneumatic motor

Three-dimensional numerical simulations on the effect of ignition timing on combustion characteristics, nitrogen oxides emissions, and energy loss of a hydrogen fuelled opposed rotary piston engine over wide open throttle conditions

Opposed rotary piston (ORP) engines have advantages of high power density, few moving parts, and smooth operations, which makes ORP engines as potential power sources for hybrid vehicles and range extended electric vehicles. Ignition timing significantly affects the performance of spark ignition engines including fuel economy and emission factors. In this paper, the effect of ignition timing on the engine performance was investigated using a three-dimensional numerical simulation method. The results indicated that crank angle corresponding to the peak in-cylinder pressure over the ignition timing of −8.2° crank angle (CA) was advanced compared with other cases having earlier ignition timing; however, the crank angle of peak heat release rates were retarded. Start of combustion was delayed by retarding the ignition timing and increasing engine speed; combustion duration over the ignition timing of −18.9° CA ~ −11.1° CA changed slightly for individual engine speed. Indicated specific fuel consumption (ISFC), being hardly dependent on the ignition timing, was less than 74 g/(kW·h) over the ignition timing of −17.3° CA ~ −11.1° CA, where indicated thermal efficiency was approximately 41%, 39% and 35% for 1000 RPM, 3000 RPM and 5000 RPM respectively. When ignition timing was later than −11.1° CA, ISFC and indicated thermal efficiency were deteriorated seriously. Nitrogen oxides (NOx) emission factors increased with engine speed over early ignition timing; however, they were inverse for late ignition cases. Higher engine speed and retarded ignition timing led to higher percentage of exhaust energy in fuel chemical energy.

Numerical simulation on lean-burn characteristics of a naturally aspirated opposed rotary piston engine fuelled with hydrogen at wide open throttle conditions

Opposed rotary piston engines are characterized by high power density, which makes them as an ideal power source for hybrid vehicles and range extended electric vehicles. Hydrogen applications can fully exhibit the merits of opposed rotary piston engines, and achieve zero carbon dioxide emissions; however, the applications seriously worsen the nitrogen oxides emissions. In this investigation, lean-burn was adopted to achieve low nitrogen oxides emissions using a three dimensional numerical simulation approach. The results indicated that engine speed of 3000 r/min presented the highest in-cylinder pressure during combustion among the given scenarios, and the pressure over 3000 r/min depended more on the equivalence ratio than that of 1000 r/min and 2000 r/min. Heat release rates were very sensitive to low equivalence ratio. Combustion duration over the equivalence ratio of 0.8 was the shortest among 1000 r/min cases; however, it decreased with equivalence ratio for 2000 r/min and 3000 r/min. Heat loss rates through cylinder walls increased significantly with engine speed, meanwhile they were more dependent on the equivalence ratio over higher engine speed. Maximum nitrogen monoxide formation rates over 3000 r/min occurred slightly earlier than those of 1000 r/min and 2000 r/min. Equivalence ratio of 0.8 showed the highest indicated thermal efficiency over corresponding engine speed, and nitrogen dioxide emission factors were quite low over the equivalence ratio of 0.7 for the given engine speed.

Lean-burn characteristics of a turbocharged opposed rotary piston engine fuelled with hydrogen at low engine speed conditions

Opposed rotary piston (ORP) engines have high power density and compact designs which meet the requirements of power sources of hybrid vehicles. Hydrogen applications to ORP engines can effectively decrease greenhouse gas emissions; however, hydrogen combustion in ORP engines around stoichiometric ratio generated large quantities of nitrogen oxides (NOx), especially for low engine speed conditions. Lean-burn as an effective method to decrease NOx emissions was adopted in this research. A 3D numerical simulation method was used to explore the effect of equivalence ratio (≤1) on combustion and NOx emission characteristics of this ORP engine fuelled with hydrogen. The results indicated that peak in-cylinder pressure increased with equivalence ratio for 1000 revolutions per minute (RPM); however, the value over the equivalence ratio of 0.9 was the maximum among 2000 RPM scenarios. The effect of equivalence ratio on heat release rates was greatly dependent on the engine speeds. Start of combustion over 1000 RPM engine speed was advanced with the increase of equivalence ratio; and it was the earliest over the equivalence ratio of 0.9 at 2000 RPM conditions. During the exhaust stroke, in-cylinder pressure of free discharge was much higher than atmosphere pressure, which significantly increased the pumping losses of exhaust stroke. Accumulated NOx emissions over the equivalence ratio of 0.9 reached the maximum value for given engine speeds; and the NOx emissions were almost zero for severe lean-burn (<0.7) conditions. Engine power output decreased with the drop of equivalence ratio for 1000 and 2000 RPM engine speeds; indicated thermal efficiency over the equivalence ratio of 0.9 was the maximum at 2000 RPM engine speed.

Numerical simulation on the combustion and NOx emission characteristics of a turbocharged opposed rotary piston engine fuelled with hydrogen under wide open throttle conditions

Under the stress of environmental pollutions and fossil fuel consumption caused by on-road transport, hybrid vehicles are attracting much attention. Opposed rotary piston (ORP) engines are a promising power source for hybrid vehicles, due to their compact designs and high power density. In this paper, combustion and emission characteristics of a turbocharged ORP engine fuelled with hydrogen were investigated to evaluate the overall performance of this engine. The results indicated that volumetric efficiency of this ORP engine was higher than 89.0% for all the given cases. Peak in-cylinder pressure was in the range of 51.0 ~ 69.0 bar; and 4000 RPM scenario had the maximum value, being benefitted from high intake temperature and pressure, and high volumetric efficiency. Combustion duration of this engine ranged 27 ~ 43° crank angle (CA), and combustion phase happened at 7.5 ~ 13°CA after top dead centre (TDC). Peak nitrogen monoxide (NO) formation rates were corresponding to 5 ~ 13°CA after TDC; accumulated NO decreased slightly after reaching the peak value for low engine speed conditions. Discharge pressure at the start of the exhaust stroke was higher than 6.0 bar, especially for 5000 RPM case whose value was approximately 11.0 bar. This ORP engine presented excellent torque characteristics, and the maximum indicated power density was approximately 104.0 kW·L−1 which was much higher than turbocharged four-stroke reciprocating engines fuelled with gasoline.

ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ТЕХНОЛОГІЇ ОТРИМАННЯ ВОДНЮ ШЛЯХОМ ВИКОРИСТАННЯ РЕГЕНЕРАЦІЙНОГО КОНТУРУ З РОТОРНО-ПОРШНЕВОЮ РОЗШИРЮВАЛЬНОЮ МАШИНОЮ

The article discusses a promising technology for the production and safe accumulation of hydrogen from the Black Sea hydrogen sulfide, which includes the following processes: production of hydrogen sulfide from the depths of the Black Sea; separation of hydrogen sulfide and seawater; destruction of hydrogen sulfide to produce a hydrogen-containing gas; separation of hydrogen from a hydrogen-containing gas; safe hydrogen storage; safe transportation of hydrogen. It is proposed to use the regeneration circuit to increase the efficiency of this technology, which includes: an expansion machine for high-pressure hydrogen sulfide, a seawater hydraulic turbine, and a heat pump installation. It is proposed to evaluate the efficiency of the application of the technology for the production and safe accumulation of hydrogen from the Black Sea hydrogen sulfide by effective capacity, which includes: thermal power of hydrogen, power of the regeneration circuit; the power needed to carry out hydrogen production processes. It is proposed to use the 20RPD-4.4/1.75 rotary piston engine as a hydrogen sulfide expansion machine that will satisfy all the requirements. Rational operating modes and limiting values of the efficiency of using the technology for obtaining and safe accumulation of hydrogen from the Black Sea hydrogen sulfide for daily hydrogen production of 200 kg/day were determined depending on the degree of hydrogen sulfide conversion during destruction, the gas content of hydrogen sulfide in seawater and the depth of immersion of the lifting pipeline using the regeneration circuit. The minimum permissible degrees of conversion at which the efficiency of using the technology for obtaining and safe accumulation of hydrogen from the Black Sea hydrogen sulfide for a gas content of hydrogen sulfide of 2.5 m3/m3 at a depth of immersion of the lifting pipeline of 250...1000 m is 0.427 ... 0.413, for 5 m3/m3 – 0.375...0.363, for 7.5 m3/m3 – 0.363...0.350, for 10 m3/m3 – 0.356...0.343. The use of the regeneration circuit allowed us to reduce the minimum permissible degrees of conversion for the gas content of hydrogen sulfide of 2.5...10 m3/m3 at a depth of immersion of the lifting pipeline of 250...1000 m by 0.136 ... 0.069.

RESEARCH OF OPERATING PARAMETERS OF ROTARY PISTON PNEUMATIC ENGINE OF TRANSPORT POWER PLANT

The article considers an alternative to traditional transport power plants - plants operating on compressed air. The main element of such plants is a pneumatic engine, the technical perfection of which determines the effective and operational performance of the entire plant. The most appropriate is the development and creation of a new reliable and efficient pneumatic engine that meets the specifications and satisfies all operating conditions on the vehicle. The RPD-4.4/1.75 rotary piston engine meets all the necessary requirements, namely: it has a small weight and dimensions; it is reversible; works effectively in a wide range of pressures at the engine inlet; provides normal operation at various ambient temperatures. A schematic diagram of an environmentally friendly transport power plant based on the RPD-4.4/1.75 rotary piston pneumatic engine with a maximum power of 6 kW has been developed. The external speed characteristics of the RPD-4.4/1.75 rotary piston pneumatic engine were obtained for a range of working air pressure values in the intake receiver of 1.2...2.0 MPa. According to the obtained characteristics, the maximum values of the torque of the pneumatic engine are achieved at 1100 rpm, while the maximum values of the effective power at 1400 rpm. The components of the power balance and the dynamic factor of the vehicle for all gears and speeds for a range of operating air pressure in the intake receiver of 1.2...2.0 MPa are determined. According to the obtained characteristics, the RPD-4.4/1.75 rotary piston pneumatic engine together with the transmission in the first gear provides the maximum traction force of 2.1...3.2 kN. The dependences of acceleration, time and way of vehicle acceleration to a maximum speed of 50 km/h are determined. So, depending on the air pressure in the intake receiver, the necessary acceleration time is from 20.1 to 30.5 s, and the acceleration path is from 200.2 to 309.3 m. To increase the operational and economic indicators of the transport power plant, it is proposed to regulate the working air pressure in the intake receiver of a rotary piston pneumatic engine.