Two-Stroke Spark Ignition Engine Research Articles

Parameter optimization for two-stroke direct-injection spark-ignition aviation kerosene engine

The type of two-stroke spark-ignition(SI) engine is still the main power sources of small and medium unmanned aerial vehicles. A transition from gasoline to aviation kerosene or light diesel fuel and from carburetor or port-injection equipment to direct-injection(DI) equipment is prevailing. However, the performance of two-stroke DI-SI engine fueled with aviation kerosene is not very good under medium and high loads. Therefore, using the two-stroke DI-SI kerosene engine modified from port-injection SI gasoline engine as the research subject, the effects of different parameters on engine combustion and performance were studied and parameter optimization was also carried out at high loads. Based on the optimal fuel injection parameters, the influences of ignition time, compression ratio, scavenging/exhaust port area and scavenging/exhaust phase on the operating characteristics of two-stroke engine were analyzed. It was indicated that ignition timing, compression ratio and scavenging/exhaust phase have obvious impacts on engine performance, while the scavenging port area shows little impact on engine performance. An optimization calculation with genetic algorithm was made by determining the optimal values of six parameters such as compression ratio, ignition time, scavenging port area, exhaust port area, scavenging phase and exhaust phase. After optimization, the power(P) of the engine was increased by 7.6 % and the thermal efficiency(η) was enhanced by 3.2 % without knock. The results will lay a foundation for further design and research of two-stroke aviation RP-3 SI-DI engine.

Impacts of Injection Parameters on the Mixture Formation and Performance of Two-Stroke Spark-Ignition Direct-Injection Aviation Kerosene Engine

Abstract Two-stroke spark-ignition engines play a significant role in the field of power sources of small and medium unmanned aerial vehicles. There is a certain transition from burning gasoline to aviation kerosene (or heavy oil) and from carburetor or inlet injection system to direct-injection fuel system. However, the performance of two-stroke spark-ignition direct-injection engines fueled with aviation kerosene was not very ideal under heavy loads. Generally, the mixture formation is very important for engine combustion and performance, while injection parameters have great effects on mixture formation. Thus, various injection parameters of a two-stroke direct-injection kerosene engine were examined here. The results showed too early or too late injection timing (tinj) would deteriorate the mixture formation, resulting in lower brake power and brake thermal efficiency. Here the most suitable tinj was 150 deg CA BTDC. Too high or too low injection pressure (pinj) caused fuel short circuit loss and poor mixture quality, so the optimum pinj was 10 MPa. Too large injector installation angle (β) easily results in fuel spray impingement, and too small β causes fuel short circuit loss. Therefore, the best β was concluded to be 30 deg in this paper.

Emission Characterization of Petrol, Ethanol and Spent Engine Oil Blends for Two-Stroke Spark Ignition Engine

Exhaust emission has remained a big global concern in atmospheric change, and has thus, lead to stiffer polices on emission. To achieve the set emission targets different fuel mix and combustion process are continuously been investigated. This work is used to practically model the condition of a two-stroke engine that has run over time whose used lubricating oil finds its way from the sump to the combustion chamber and thus resulting to greater rate of incomplete combustion and higher emission. An exhaust analyser with a deep probe was deployed to access the out-going burnt gasses from a two-stroke spark ignition engine that is fed with multi blends of petrol, ethanol and spent engine oil. The characteristics of the emission constituents were investigated and compared to the global limits set by different organizations such as California Air Resources Board, Environmental Protection Agency in USA, International Council on Clean Transportation, Road Transport Bureau- in Japan, and European Emission Standard Agency, among others. The result shows an increase in , and emissions with samples that contain spent oil as against those with new engine oil which is also more effective. It was also found that samples with higher quantity of ethanol show lower emission of , and gases. This is likely due to interstation of ethanol molecules with that of the spent oil, thus making it more potent for further combustion. This was also supported with the fact that emission was higher in blends with higher quantity of ethanol. Thus, the presence of ethanol in fuel blend used in two-stroke spark ignition engine may be considered to be a source of improvement in combustion and hence a means of reducing emission in two-stroke port operated spark ignition engines.

Investigation of In-Cylinder Pressure Measurement Methods within a Two-Stroke Spark Ignition Engine

<div>This work describes an investigation of measurement techniques for the indicated mean effective pressure (IMEP) on a 55 cc single-cylinder, 4.4 kW, two-stroke, spark ignition (SI) engine intended for use on Group 1 and Group 2 remotely piloted aircraft (RPAs). Three different sensors were used: two piezoelectric pressure transducers (one flush mount and one measuring spark plug) for measuring in-cylinder pressure and one capacitive sensor for determining the top dead center (TDC) position of the piston. The effort consisted of three objectives: to investigate the merits of a flush mount pressure transducer compared to a pressure transducer integrated into the spark plug, to perform a parametric analysis to characterize the effect of the variability in the engine test bench controls on the IMEP, and to determine the thermodynamic loss angle for the engine. The results indicate that as a spark plug, the measuring spark plug is not statistically different from the stock spark plug at the 95% confidence level. The results indicate a statistically significant, 4% difference in the measured IMEP between the pressure transducer in the measuring spark plug and the flush mount transducer. The results also suggest a statistically significant difference in performance between the modified and unmodified engine heads, verifying the suppositions of other researchers who suggested that even a small modification to a combustion chamber this size could measurably affect the engine performance. While run-to-run variation resulted in a 2% to 5% variation in IMEP, a sensitivity analysis determined that 1% to 3% of that variation arose from variability in the control variables, while the remainder was caused by variation in other engine operating parameters. Between 1000 rpm and 2000 rpm, where the engine was typically motored to determine the TDC, the thermodynamic loss angle was 0.3 crank angle degrees (CAD) to 0.7 CAD, larger than loss angles observed in automotive-sized gasoline engines. The results indicate that using tabulated thermodynamic loss angles to set the TDC location of the engine using a mono-directional peak pressure method would lead to a −1% to −2.5% bias in the IMEP.</div>

Characterization of flame front wrinkling in a highly pressure-charged spark ignition engine

Particle Image Velocimetry (PIV) technique has been employed to investigate turbulent flame propagation in a relatively quiescent, optically accessed, boosted, two-stroke spark ignition engine. Turbulence scales and flame structure have been characterized based on Fourier analysis of an independent stationary coordinate at elevated pressures. Analysis shows that turbulence, with an initial rms value of u', is modified by flames, and the strong induced velocity field ahead of it. As the flame grows, the persistence of larger scale structures as well as smaller scale wrinkling is apparent. Power spectral density (PSD) of flame wrinkling exhibit the same general trend under different operating conditions. These are in a good agreement with the previous data measured from other rigs (i.e. burners and bombs), which featured lower pressures. These functions have been normalized by terms of wrinkling parameters and other turbulence parameters. General PSD functions are developed. These can predict the flame wrinkling behavior at low and high pressures, in different experimental apparatuses.

Performance Enhancement Using Different Nitromethane Blends in a Small Two-Stroke Engine

Abstract Nitromethane being immiscible in gasoline is often added to methanol to enhance the engine power output. But with the use of methanol as the base fuel, the brake specific fuel consumption (BSFC) of the spark ignition (SI) engine often doubles due to its lower heating value. To constrain this increase to a marginal value, a tri-component fuel blend consisting of nitromethane-alcohol-gasoline was prepared and observed to be stable. Methanol, ethanol, and butanol were the chosen alcohols for the tests due to their popularity as alternate fuels for SI engines. Tests on a small (35cc) two-stroke SI engine revealed that the torque produced with the use of tri-component blends was comparable with nitromethane-methanol blend and was on an average 1.35 times higher than gasoline. However, the BSFC with the nitromethane-butanol-gasoline blend was 50% lower than nitromethane-methanol blend and was only 14% higher than gasoline. The emission analysis showed lower HC emissions with the tri-component blends proving the improved combustion efficiency due to better mixing of the fuel-air mixture. Combustion analysis showed the increased heat release rate with nitromethane addition due to its higher flame speeds.

High pressure direct fuel injection as a solution for performance enhancement in two-stroke spark-ignition engine

ABSTRACT Two-stroke spark-ignition engines mainly suffer from the poor fuel economy and high exhaust emission. However, the methodology presented here has adequate potential that can salvage these engines from becoming extinct as the compactness and their power to weight ratio are the two favorable characteristics that provide sufficient leverage for their salvation. The present paper makes an attempt to investigate the influence of the direct fuel injection at moderately high pressure on two-stroke spark-ignition engine performance as well as emission. In this paper, the conventional carbureted two-stroke spark-ignition engine has been modified with a high pressure fuel injection system installed on the cylinder head. The injection of fuel is timed with the closure of exhaust port shut by the piston, which helps in saving fresh fuel from getting short-circuited through the exhaust port. The experimental investigation has been carried out on the engine at various throttle positions of both carburetor as well as fuel injector for different speeds. The experimental measurements revealed that results of direct fuel injection mode compared well as opposed to the carburetor mode. It was observed that brake power exhibited significant improvement approximately 20.1% as compared to the conventional engine. The brake thermal efficiency is found to be 16.3% higher than that of the conventional engine. Above all, fuel loss through short-circuiting noted to have reduced brake specific fuel consumption by 17%. The direct injection system has shown 27.5 and 88.5% reduction in carbon monoxide and unburned hydrocarbons emission, respectively, as compared to the conventional engine.

Optimization of Fuel Injection Control System of Two-Stroke Aeroengine of UAV

Power efficiency of two-stroke spark-ignition engine is generally low because improper amount of fuel injection leads to a lot of unburned fuel loss during the engine working process. However, parameters of the fuel injection system are hard to confirm by aviation experiments due to expensive test costs. This paper proposes a method of calibrating injection parameters of two-stroke spark-ignition engine based on thermodynamic simulation and parameter optimum algorithm. Firstly, the one-dimensional thermodynamic model is built according to the internal structure and thermodynamic process of the engine; then, the model parameters are corrected according to the operating principle of the injector; after experimental verification of the model, considering both the engine power sufficiency and fuel economy, Analytic Hierarchy Process method is applied to look for the optimal injection amount and fuel injection advance angle at different engine working speeds; finally, an aeroengine experiment station with an electronic fuel injector system is built. Through simulation and experiment studies, it can be seen that when the engine speed changes from 3000 to 3500 RPM, the oil consumption rate of the optimal results is higher than that of the previous ones; when the aeroengine speed is higher than 4000 RPM, the oil consumption rate results of the optimal method are 10% to 27% higher than the original results. This paper can be a reference in the optimization of UAV aircraft engine.

Effect of Nitromethane Addition on the Performance of Two-Stroke Spark Ignition Unmanned Aerial Vehicles Piston Engine

Abstract Nitromethane has a stoichiometric air–fuel ratio of 1.7, which is 8.5 times lower than gasoline. For the same amount of air being drawn by the engine, more amount of nitromethane blends and hence more energy can be added. Methanol was used as a medium to mix nitromethane and gasoline, which are normally immiscible. Engine performance tests were carried out to study the effect of nitromethane addition to the methanol-gasoline blend. A large rise in engine torque and brake thermal efficiency (BTE) was obtained during the investigation. However, the brake specific fuel consumption (BSFC) also increased for the nitromethane blends. The engine parameters like spark timing, equivalence ratio, and compression ratio were optimized to further increase the engine power and also bring down the BSFC. A net torque improvement of 42%, BTE improvement of 35%, and BSFC rise of 9% were obtained by adding nitromethane and methanol in small fractions to gasoline. Combustion analysis was carried out using the cylinder pressure trace. High heat release rate and shorter combustion duration with nitromethane addition were observed. Emission measurements showed decrease in HC and CO emissions with nitromethane addition. However, a drastic rise in NO emissions was observed. Hence, it can be concluded that the specific power of small two-stroke spark ignition (SI) engines can be enhanced using nitromethane as a fuel additive to increase the payload of the unmanned aerial vehicles.

Determining the characteristics for the rational adjusting of an fuel-air mixture composition in a two-stroke engine with internal carburation

An operating process for engines with spark ignition and direct fuel injection engines which ensures the formation of a stratified lean fuel-air charge under the modes of partial loads and the power composition of the fuel-air mixture at high loads has been developed. The design of a two-stroke spark-ignition engine was modernized by installing a direct fuel injection system, placing the nozzle in the cylinder wall, and changing the combustion chamber shape. A procedure of adjustment of the composition of the fuel-air mixture in the cylinder of a two-stroke spark-ignition engine has been developed. The procedure features the recording of engine parameters and indicators at a constant cycle fuel feed and intake air adjustment. The proposed procedure makes it possible to more accurately adjust the composition of the fuel-air mixture due to a more accurate dosage of air than the cycle fuel feed. Experimental studies were carried out and adjustment characteristics were constructed in terms of the air-fuel mixture composition in the cylinder of a two-stroke engine with a developed operating process. Load characteristics (at n=3,000 rpm) of rational adjustment in terms of economy and maximum power were constructed based on data on the adjustment characteristics for the composition of the fuel-air mixture. It was found that in terms of the load characteristic of rational economy adjustment, the composition of the fuel-air mixture in the engine cylinder (λ cyl.ec ) varied from 1.31 to 1.94 and the minimum fuel consumption was g e min =259 g/(kWh). In terms of the load characteristic of rational power adjustment, the composition of the fuel-air mixture in the engine cylinder (λ cyl. pow ) varied from 1.31 to 1.7, and the fuel consumption at partial loads was g e =270 g/kWh. Characteristics of airflow rate depending on the cycle fuel feed can be used to change the composition of the fuel-air mixture with automatic adjustment of the engine load

A thermodynamic comparison of rhombic-drive and slider–crank mechanisms for a two-stroke SI engine

ABSTRACT In this study, mathematical models of a novel mechanism, rhombic-drive, for a two-stroke, spark ignition (SI) engine, and a two-stroke SI engine with a conventional slider–crank mechanism were performed in MATLAB software. Their performances were compared with kinematic and thermodynamic analyses. Mathematical model was conducted according to real cycle approach and some of the operating parameters such as compression ratio, swept volume, heat release time, and lambda were kept identical for both engines. Pressure, volume, temperature, heat release, heat transfer coefficient, work, piston speed, and acceleration changes were examined. Maximum in-cylinder pressure was taken at 222°CA with 4,188 kPa for rhombic-drive engine while 190°CA with 4,003 kPa for slider–crank mechanism engine and maximum temperature was only 39 K higher for rhombic-drive mechanism engine. Theoretical thermal efficiencies of rhombic-drive and slider–crank mechanism were 31.14% and 31.87%, respectively. Effective power of rhombic-drive mechanism engine was 2.12 kW, whereas slider–crank mechanism engine was 2.17 kW. Mechanical efficiency of rhombic-drive engine was obtained 85.89%, while this was only 86.21% for slider–crank mechanism engine.

The Control Space for Knock Mitigation in Two-Stroke Engines for 10–25 kg Remotely Piloted Aircraft

Interest is growing in converting commercially available, two-stroke spark-ignition engines from motor gasoline to low-anti-knock-index fuel such as diesel and Jet A, where knock-limited operation is a significant consideration. Previous efforts have examined the knock limits for small two-stroke engines and explored the effect of engine controls such as equivalence ratio, combustion phasing, and cooling on engine operation during knock-free operation on high octane number fuel. This work culminates the research begun in those efforts, investigating the degree of knock-mitigation achievable through varying equivalence ratio, combustion phasing, and engine cooling on three small (28, 55, and 85 cm3 displacement) commercially available two-stroke spark-ignition engines operating on a 20 octane number blend of iso-octane and n-heptane. Combustion phasing had the largest effect; a 10 deg retardation in the CA50 mass-fraction burned angle permitted an increase in throttle that yielded a 9–11% increase in power. Leaning the equivalence ratio from 1.05 to 0.8 resulted in a 10% increase in power; enriching the mixture from 1.05 to 1.35 yielded a 6–7% increase in power but at the cost of a 25% decrease in fuel-conversion efficiency. Varying the flow rate of cooling air over the engines had a minimal effect. The results indicate that the addition of aftermarket variable spark timing and electronic fuel-injection systems offer substantial advantages for converting small, commercially available two-stroke engines to run on low-anti-knock-index fuels.

Fuel Flow Control for Starting a Crankcase-Injected Two-Stroke Spark Ignition Engine Fueled with Kerosene (RP-3)

AbstractTo investigate the fuel flow control for starting a crankcase-injected two-stroke spark ignition (SI) engine that is fueled with rocket propellant 3 (RP-3), a fuel film compensation model f...

Experimental Investigation of Fuel Anti-Knock-Index Requirements in Three Small Two-Stroke Engines for Remotely Piloted Aircraft

Small remotely piloted aircraft (10–25 kg) that are powered by internal combustion engines typically operate on gasoline with an anti-knock index (AKI) > 80. To comply with the single-battlefield-fuel initiative [Department of Defense (DoD) Directive 4140.25], interest has increased in converting power plants for these platforms to run on low-AKI fuels such as diesel and Jet-A with AKIs of ∼20. It has been speculated that the higher losses (short circuiting, incomplete combustion, heat transfer) that cause these engines to have lower efficiencies than their conventional-scale counterparts may also relax their required fuel AKI. The fuel-AKI requirements of three two-stroke spark ignition (SI) engines with 28, 55, and 85 cm3 displacements were mapped, and the performance was compared to that on 98 ON (octane number) fuel. Switching from 98 ON fuel to 20 ON (Jet-A and diesel equivalent AKI) fuel while maintaining optimum combustion phasing led to a 3–5 crank-angle degree (CAD) reduction in burn angle, a 2–3% increase in power, and a 0.5–1% (absolute) increase in fuel-conversion efficiency at non-knock-limited conditions through shortening of the CA0–CA10 burn angle. The efficiency improvement translates to a 6% increase in range or endurance. The results indicate that abnormal combustion is not a significant obstacle to operating small commercial-off-the-shelf (COTS) engines on low-AKI fuels and that most of the power and efficiency improvements demonstrated in previous heavy-fuel conversion efforts were the result of modifications made to accommodate low-volatility fuels, not the faster burn rate of the low-AKI fuels themselves.

Effect of key parameters on knock suppression in a two-stroke spark ignition engine with aviation kerosene fuel

This research work studies the impact of the mixture concentration, spark timing, and ignition energy on the knock suppression of a two-stroke spark ignition aviation kerosene-fueled engine. Bench tests on different working conditions were conducted and some related data including in-cylinder pressure, cylinder head temperature, exhaust temperature, engine power, and torque were collected to analyze the influence of different control parameters on the knock characteristics of the engine. The results show that the knock can be suppressed at leaner and richer (than the stoichiometric) mixtures, and the richer mixture has a more obvious effect on suppressing knock. Retarding the ignition advanced angle will reduce the knock intensity but will make the exhausted temperature exceed and the output power decrease. The use of a rich mixture with early spark timing has a better effect on the knock suppression as compared to the use of a lean mixture with late spark timing. Reducing the ignition energy can suppress the knock slightly, but experimental results show that it is not an effective way.

Differential air/fresh charge demand, supply and utilisation in two-stroke spark ignition engines

Differential air/fresh charge demand, supply and utilisation in two-stroke spark ignition engines

Investigating the performance and emission characteristics of an SI engine using Peltier element cooling effect

ABSTRACTAn internal combustion engine can convert only 30–35% of the heat energy supplied to it into useful work, and the remaining heat is lost through exhaust gases. The temperature of gases will be around 600°C. Reduction of heat carried away by the exhaust gases can be done by providing proper engine cooling system. This study deals about improving a two-stroke spark ignition engine’s efficiency by cooling its head using Peltier element. The Peltier element is placed in the engine head by cutting the fins to improve the efficiency of the two-stroke engine by maintaining the working temperature of the engine at 70°C. As per the experimental results, a decrease of 14% in brake-specific fuel consumption and an efficiency improvement of 19% were achieved. The % reduction in carbon monoxide, nitrogen oxides and hydrocarbons recorded are 5%, 20% and 40%, respectively.

The influence of the ignition system characteristic on the two-stroke engine operating conditions

This paper presents an indicator analysis of the impact of the characteristics of an electronic ignition system on the operating conditions of a two-stroke spark ignition engine. The tests were carried out on a single-cylinder two-stroke engine equipped with a combustion pressure sensor using the apparatus for recording fast-varying signals. The influence of changes of the ignition angle of advance at constant engine speeds on the engine operating indicators was analysed. The assessment of the impact of the changes to the settings of the ignition system was analysed in terms of thermodynamic conditions: combustion pressure and average effective pressure. It was found that the ignition angle of advance has positive influence on engine operating conditions and uniformity of engine operation. As a measure of non-uniformity of engine operation were accepted the coefficient of variation of the engine speed and the mean indicated pressure. It was indicated that, along with the ignition angle of advance, the indicators of two-stroke engine operation also increase with simultaneous increase in the non-uniformity of engine operation. Keywords: two-stroke engine, ignition system, combustion, thermodynamic analysis

A novel twin injector strategy for direct cylinder barrel injection of LPG in a 2S-SI engine

A novel strategy of using twin injectors mounted on the cylinder barrel of a two-stroke spark ignition (2S-SI) engine for direct injection of Liquefied petroleum gas (LPG) is developed and compared with manifold injection. Gaseous LPG at a low pressure of about 4–4.5bar was used and the injectors were located opposite each other and above the transfer ports. Experiments were conducted at the best injection and spark timings at 3000rpm. Results at 25% and 100% throttle positions over different overall equivalence ratios are presented. The twin direct injection system led to significant reductions in hydrocarbon (HC) emissions of about 80% at both the throttle positions as compared to the manifold injection method due to reduction in short-circuiting losses. The best brake thermal efficiency was also improved from 19.7% to 25.2% at full throttle. Oxides of Nitrogen (NO) emissions were lower and carbon monoxide (CO) levels were higher due to charge non homogeneity. Experiments were also done with a single injector mounted on the cylinder barrel. The twin direct injection system resulted in significantly lower HC emissions and allowed operation under wider range of equivalence ratios with later injection timings as compared to the single injector strategy indicating its superior mixture preparation characteristics.

Advantages and Challenges of Lean Operation of Two-Stroke Engines for Hand-Held Power Tools

Today, hand-held power tools facilitate specific jobs in many application areas, e.g. garden/landscape maintenance, construction industry and forestry. This market is highly diversified and demands special tools which are optimized for each application purpose (brush cutters, chain saws, etc.). Most of them are driven by two-stroke SI (spark ignition) engines equipped with a carburetor. High specific power, simplicity, low weight, low costs and compact design are characteristics of these two-stroke engine powered tools. The use of piston control or reed valves, oil-in-gasoline lubrication and loop scavenging is well established. Significant improvements regarding emission behavior have been achieved in recent years due to stratified scavenging systems which have become a standard. In order to respond to future challenges like continuing emissions and fuel consumption reduction the present engine technology has to be further developed. Several research areas are considered in order to improve the overall product, i.e. injection systems, ECU hardware and functionality, exhaust gas after-treatment and combustion systems [1, 3, 4, 5]. To date, the research on combustion systems for hand-held power tools tended to focus on rich mixture setting. The demands for high power and quick engine response are met by a rich mixture in part load and WOT (wide open throttle) operation. Moreover, the rich mixture reduces NOx formation and reduces thermal stress.