Automotive Spark Ignition Engine Research Articles

The Influence of N-Butanol Addition in Gasoline on the Combustion in the Spark Ignition Engine

Butanol has good combustion properties and it can be a viable alternative fuel for automotive spark ignition engines due to its ability to improve energy and pollution performance. This paper analyses the influence of butanol content in gasoline blends on engine operation with a focus on operation stability, thermal efficiency and emissions. A Cielo Nubira A15MF engine type with four cylinders and a 1.5 L displacement was turbocharged and it was fueled with butanol in a blend with gasoline in percent’s of 10% vol. and 15% vol. An operation regime of 2500 1/min speed and 55% engine load was used, at different dosages, at which the engine power remained constant. Regarding the engine fueled with butanol in a blend with gasoline, the operation stability was improved, especially when lean dosages were used; the dosages at which the thermal efficiency was higher are comparative to classic fueling. Concerning the use of lean dosages, the combustion duration decreases and the energetic engine performance was improved when butanol was used comparative to gasoline. When butanol was used, polluting emissions and emission with a greenhouse effect were reduced. The sharp reduction in NOx is highlighted in this paper.

Theoretical and experimental research on the use of hydrogen in the automotive spark ignition engine

Reducing the level of pollutant emissions of internal combustion engines requires the adaptation of solutions that improve the combustion process in the cylinder but those solutions may increase their constructive complexity. For this reason, the use of hydrogen is an effective solution, both for replacing fossil fuels and for reducing the concentration of pollutant emissions. The use of hydrogen as an additional fuel for the automotive spark ignition engines offers the possibility of obtaining increased energy performance, decreased pollutant emissions level and decreased concentration of greenhouse gas emissions. The paper presents the results of the some theoretical and experimental investigations carried on an automotive spark ignition engine, analysing the influence of the hydrogen on combustion and implicitly on energy performance and pollution. The simulation of thermo-gas-dynamic processes in the cylinder of the engine fed successively with gasoline/gasoline and hydrogen, allowed the authors to develop a specific and efficient procedure for conducting experimental investigations. The results of the theoretical and experimental research obtained and presented in the paper highlight the advantages of using hydrogen as an additive to gasoline fuelling in the automobile spark ignition engine: the improvement of combustion (reduction of combustion duration, increase of indicated thermal efficiency, reduction of specific energy consumption) and reduction of the level of polluting emissions and of the emission of greenhouse gases. An engine adjustment strategy for the sharp reduction of the concentration of nitrogen oxides is also presented.

Comparison of operational parameters and stability of performance of an automotive SI engine powered by methyl and ethyl alcohols

The article presents research results performed using automotive spark ignition engine run on methyl and ethyl alcohols as well as gasoline as reference fuel. The research was performed on automotive engine of Fiat 1100 MPI type. The subject of the performed analysis was to compare operational parameters of the engine such as: engine power output, overall efficiency, emission of toxic components of exhaust gases, as well as comparison of course of combustion process calculated on the basis of recorded and averaged indicator diagrams, and on the basis of individual combustion cycles. The averaged diagrams were used in analysis of the pressure course during combustion, in analysis of pressure growth rate and heat release rate. Diagrams of individual combustion served for assessment of operational smoothness of the engine when fueled with alcohols. As the reference, parameters measured in case of gasoline fueling were used. The experiments have confirmed stable engine operation on methyl and ethyl alcohols. Increase of engine power output with o 3.8-7.7% was confirmed for methanol and with 1.7-3.3% for ethanol, while increase of the efficiency with 1.5-7.5% was confirmed for methanol and with 1.2-2.5% for ethanol, comparing with gasoline fueling. Obtained results are pointing at possibilities of fueling of modern SI engines with alcohols only, especially including water-logged ethyl alcohol, obtained directly from distillery. This should increase share of alcohols in overall balance of consumed engine fuels.

Numerical study on the use of ammonia/hydrogen fuel blends for automotive spark-ignition engines

The importance of new alternative fuels has assumed great relevance in the last decades to face the issues of global warming and pollutant emissions from energy production. The scientific community is responsible for developing solutions to achieve the necessary environmental restriction policies. In this context, ammonia appears as a potential fuel candidate and energy vector that may solve the technological difficulties of using hydrogen (H2) directly in internal combustion engines. Its high hydrogen content per unit mass, higher energy density than liquid hydrogen, well-developed infrastructure and experience in handling and storage make it suitable to be implemented as a long-term solution. In this work, a virtual engine model was developed to perform prospective simulations of different operating conditions using ammonia and H2-enriched ammonia as fuel in a spark-ignition (SI) engine, integrating a chemical kinetics model and empirical correlations for combustion prediction. In addition, specific conditions were evaluated to consider and to understand the governing parameters of ammonia combustion using computational fluid dynamics (CFD) simulations. Results revealed similar thermal efficiency than methane fuel, with considerable improvements after appropriate H2-enrichment. Moreover, increasing the intake temperature and the turbulence intensity inside the cylinder evinced significant reductions in combustion duration. Finally, higher compression ratios ensure efficiency gains with no evidence of abnormal combustion (knocking), even at high compression ratios (above 16:1) and low engine speeds (800 rpm). Numerical simulations showed the direct influence of the flame front surface area and the turbulent combustion velocity on efficiency, reflecting the need for optimizing the SI engines design paradigm for ammonia applications.

Energy and exergy analyses of hydrogen-fueled spark ignition engine with various air excess ratios and ignition timings

Many studies have been conducted to determine the efficiency and emission of hydrogen internal combustion engines. However, only a few of these investigations have performed exergy analysis (especially when important parameters, such as excess air ratio, vary) based on the second law of thermodynamics. Accordingly, in this study, experiments were conducted on a commercial automotive spark ignition engine. The engine is modified to run on hydrogen as fuel at 1500 rpm with various spark timings and excess air ratios under a wide-open throttle. In addition, zero-dimensional two-zone modeling was conducted by matching and examining the experimental results considering both energy (first law of thermodynamics) and exergy (second law of thermodynamics) analyses.The results indicate that with the same excess air ratio, the trend exergy analysis results, such as increasing exhaust exergy loss and decreasing heat transfer exergy loss by retarding ignition timing, are similar to the energy analysis results. Additionally, irreversibility increased as the spark timing retarded owing to the reduction in combustion temperature caused by prolonged combustion duration. In considering various excess air ratios, the gap between the energy and exergy analysis results was evaluated: the heat transfer exergy loss increased from 27% to 31%, the exhaust exergy loss decreased from 20% to 15%, and irreversibility was maintained at approximately 10%. Irreversibility was maintained because of the offset between the irreversibility increment (due to the decrease in combustion temperature) and decrement (due to the decrease in fuel amount). Moreover, the relationship between the thermo-mechanical exergy rise rate and behavior of each exergy component was examined.

Experimental investigation on effect of misfire and postfire on backfire in a hydrogen fuelled automotive spark ignition engine

This study investigates the effect of misfire and postfire on backfire in a hydrogen-fuelled automotive spark ignition engine. Backfire is a preignition phenomenon and the flame propagates toward the engine's intake manifold during the suction stroke. Postfire is a post-ignition phenomenon occurring in the exhaust manifold during the exhaust stroke and the flame propagates towards the exhaust manifold or backflow to the combustion chamber or combined both. Misfire occurs when cranking the engine (starting), fouled spark plug, and unoptimized spark timing. Several misfire cycles lead to an increase in the accumulation of unburnt hydrogen-air charge inside the cylinder and 13% hydrogen leaves the exhaust manifold resulting in postfire occurrence in a subsequent cycle. The postfire in the current cycle acting as an external ignition source for the preignition of the accumulated hydrogen-air charge results in backfire in the immediate next cycle. The misfire, postfire and backfire stall the engine operation due to a drop in indicated mean effective pressure. The experimental data indicates the backfire limiting equivalence ratio (BLER) should decrease with an increase in the engine speed as the equivalence ratio varies from 0.91 at 2000 rpm to 0.4 at 4900 rpm. As too advancement of spark timing increases the probability of misfire leading to postfire and backfire, the engine must be operated at backfire limiting spark timing to avoid misfire, postfire, and backfire occurrence. An important point emerged from this study that misfire without postfire does not lead to backfire occurrence. Physical mechanisms and mitigative measures for misfire, postfire and backfire are discussed in detail.

Gaseous fueling of an adapted commercial automotive spark-ignition engine: Simplified thermodynamic modeling and experimental study running on hydrogen, methane, carbon monoxide and their mixtures

In the present work, methane, carbon monoxide, hydrogen and the binary mixtures 20 % CH4–80 % H2, 80 % CH4–20 % H2, 25 % CO–75 % H2 (by volume) were considered as fuels of a naturally aspirated port-fuel injection four-cylinder Volkswagen 1.4 L spark-ignition (SI) engine. The interest in these fuels lies in the fact that they can be obtained from renewable resources such as the fermentation or gasification of residual biomasses as well as the electrolysis of water with electricity of renewable origin in the case of hydrogen. In addition, they can be used upon relatively easy modifications of the engines, including the retrofitting of existing internal combustion engines. It has been found that the engine gives similar performance regardless the gaseous fuel nature if the air–fuel equivalence ratio (λ) is the same. Maximum brake torque and mean effective pressure values within 45–89 N·m and 4.0–8.0 bar, respectively, have been obtained at values of λ between 1 and 2 at full load, engine speed of 2000 rpm and optimum spark-advance. In contrast, the nature of the gaseous fuel had great influence upon the range of λ values at which a fuel (either pure or blend) could be used. Methane and methane-rich mixtures with hydrogen or carbon monoxide allowed operating the engine at close to stoichiometric conditions (i.e. 1 < λ < 1.5) yielding the highest brake torque and mean effective pressure values. On the contrary, hydrogen and hydrogen-rich mixtures with methane or carbon monoxide could be employed only in the very fuel-lean region (i.e. 1.5 < λ < 2). The behavior of carbon monoxide was intermediate between that of methane and hydrogen.The present study extends and complements previous works in which the aforementioned fuels were compared only under stoichiometric conditions in air (λ = 1). In addition, a simple zero-dimensional thermodynamic combustion model has been developed that allows describing qualitatively the trends set by the several fuels. Although the model is useful to understand the influence of the fuels properties on the engine performance, its predictive capability is limited by the simplifications made.

EXPERIMENTAL INVESTIGATION OF THE EFFECTS OF WATER ADDING INTO THE INTAKE AIR ON THE ENGINE PERFORMANCE AND EXHAUST EMISSIONS IN A SPARK-IGNITION ENGINE

In the present study, the effects of water addition into intake air (WAIA) on the engine performance and exhaust emissions have been investigated experimentally in an automotive spark-ignition engine (SIE) which is used in Renault Clio vehicles. Experiments have been performed for (3, 6, 9 and 12) % (by vol.) water ratios (WRs) at different engine speeds and different loads. Selected engine speeds were (3000, 4000 5000, and 6000) rpms. 6000 rpm is the maximum speed of this engine. Selected loads were (100, 90, 80, 70, 60, and 50) Nm for (3000, 4000, and 5000) rpms and were (80, 75, 70, 65 and 65) Nm for 6000 rpm, respectively. The test results showed that WAIA decreases significantly brake specific fuel consumption (BSFC) at (3000, 4000, and 5000) rpms, but it increases BSFC at 6000 rpm. The maximum reduction ratios of BSFC at (3000, 4000, and 5000) rpms have been attained at the levels of 28.27 % for 5.60 % WR, 4.160 for 2.67 % WR and 7.19 % for 9.00 % WR, respectively. WAIA generally decreases nitrogen oxides (NOx) and total hydrocarbon (HC) emissions at all of the selected operating conditions. At (3000, 4000, 5000 and 6000) rpms, the maximum reduction ratios of NOx have been reached at the levels of 37.80 % for 8.67 % WR, 58.21 % for 12.18 WR, 57.80 % for 12.17 WR and 66.17% for 12.12.WR, respectively. Approximately 9.40 % decrement in HC was achieved by WAIA at the selected engine speeds. Carbon monoxide (CO) emission decreases by applying WAIA at 3000 rpm whereas it generally increases at (4000 and 5000) rpms. Unlike other engine speeds, WAIA increases CO emission significantly at 6000 rpm. Approximately 9 % WR yields the best results for engine performance and exhaust emissions at all of the selected operating conditions.

Experimental investigations of effects of cycle time on NOx emission in a hydrogen fueled multi-cylinder automotive spark ignition engine

The present study deals with the influence of cycle time on NOx emission in a hydrogen-fueled multi-cylinder automotive spark-ignition engine. The engine was operated at a constant torque of 70 Nm in the speed range of 1000–1900 rpm with a step interval of 300 rpm. FT-IR spectrometer was used to measure the real-time regulated (NO, NO2) and non-regulated (N2O, HCN) emissions. The peak in-cylinder pressure and convective heat transfer rate decreased till cycle time of 75 ms due to reduced available time for combustion and heat exchange resulting in lower NO emission. However, as the cycle time decreased to 63 ms, NO emission shot up. NO emission drastically increased about five times higher at an engine speed of 1900 rpm compared to lower engine speeds due to an increase in peak in-cylinder gas temperature (above 1700 K). Percentage apportionment of NO2 to NOx emission is by half at 1900 rpm due to the rise of NO emission at higher engine speeds. The increasing trend of HCN and NMHC emissions with engine speed indicates the possibility of lubricating oil burning.

DRIVEABILITY INDEX OF COMMERCIAL GASOLINE IN ASEAN COUNTRIES

Motor gasoline is essentialy a complex mixture of hydrocarbons distilling between about 40°C and 225°C and consisting of compounds generaly in the range C5 to C12. Small amounts of additives are also used to exchange various aspects of the performance of the fuel. Gasoline produced from different refin[1]eries can vary widely in compositions, even at the same octane level.The primary requirement of a gasoline is that should burn smoothly without exploding, under the conditions existing in the combustion chamber of the spark-ignition, so that themaximum amount of useful energy is liberated[1].The volatility of a gasoline has a vital influence on the both performance of a car emission. It affects the way car starts, the time it takes to warm up, the exten to which ice will form in the carburator, causing stalling and other problems; it influences vapour lock in the fuel system and indirectly it determines overall fuel economy. Volatility is a measure of the ability of a fuel to pass from the liquid to the vapour state under varying conditions.In cold weather, cars can take a very significant time to warm-up i.e., be capable of smooth, non-hesitating accelerations without the use of the choke. The fuel parameter that is found to have the grestest influence on warm-up is the mid-boiling range volatility as characterized by for example; the 50 per cent distillation temperature. Even after the car has warmed up, fuel volatility can still have an influence on acceleration time. Low volatility fuels obviously give leaner mixture and as mixtures leaner, acceleration performance can fall off quite rapidly.The fraction of the fuel that influences acceleration behaviour to the greatest extent is in the mid and to a lesser extent the higher boiling range. Thus, the 50% distillation temperature, sometimes together with the 90% distillation, must be controlled to ensure optimum acceleration behaviour. The factors which influence vapour lock is the volatility characteristics of the fuel. The degree to which a fuel is liable to give vapour lock depends mainly on its front end volatility. A number of different front-end volatility parameters have been used to define the vapour locking tendency of a fuel, such as RVP, percentage evaporated at 70°C, the 10 and 15% slope of the distillation curve, the vapour/liquid ratio at a given temperature and pressure. These distillation characteristics affect the following performance characteristics: starting, vapour lock and driveability.ASTM D4814-98a the standard specification for Automotive Spark-Ignition Engine Fuel has included Driveability Index as an item of performance requirement of the fuel. The inclusion of the parameter is to provide control of distillation parameters that influence cold start and warm up driveabilities.

Numerical and experimental analysis on the effects of turbocharged compressed bio-methane-fueled automotive spark-ignition engine

This work focuses on the numerical and experimental analysis of turbocharger selection and boost pressure effects on a CNG-fueled spark-ignition engine. Because of this, investigations are carried out on the influence of downsized compression ratio of 10.5:1 at different boost pressures and compared with a naturally aspirated compression ratio of 12.5:1. In order to perform the experimentation, a twin-cylinder, port fuel-injected, CNG engine with 15.5 kW at 3400 rpm is modified to utilize compressed bio-methane as fuel under 100% throttle condition. A simulation is performed to study the compressor impeller for T1 and T2 turbochargers using the ANSYS turbomachinery tool. Results indicate that the circumferential velocity of T1 is higher than of T2 at all boost pressures. Subsequently, experimentation is performed using T1 and T2 at three different boost pressure levels in a compression ratio of 10.5:1 at 1.1, 1.3, and 1.5 bar. T2 developed a maximum boost pressure of 1.1 bar compared to T1. T1 is chosen for further experimentations. At 1.3 bar of boost pressure, a rise in brake power was recorded by 19.3% compared to 12.5:1 under the naturally aspirated mode. Consequently, there is a reduction in fuel consumption by 10.1%, and hydrocarbon, carbon monoxide, and carbon dioxide emission levels reduce by 25%, 8.2%, and 4.9%, respectively. Therefore, turbocharging at a lower compression ratio exhibits better performance and reduces emissions compared to a higher compression ratio under naturally aspirated mode.Graphic abstract

Artificial neural network architecture for rheological property prediction of a novel hybrid nanolubricant for automotive spark-ignition engine

Artificial neural network architecture for rheological property prediction of a novel hybrid nanolubricant for automotive spark-ignition engine

Effects of knock intensity measurement technique and fuel chemical composition on the research octane number (RON) of FACE gasolines: Part 1 – Lambda and knock characterization

The Research and Motor Octane Number (RON and MON) rate the knock propensity of gasoline in the Cooperative Fuel Research (CFR) engine by comparing the knock intensity of sample fuels relative to that of primary reference fuels (PRF), a binary blend of iso-octane and n-heptane. Important differences exist between standard octane testing and automotive spark ignition (SI) engine knock testing including speed, load, air-to-fuel equivalence ratio (lambda), and knock characterization, which lead to a discrepancy between a fuel’s RON rating and its knock resistance characterized on an automotive SI engine based on knock-limited spark advance. This is the first of a set of three publications which modify operating parameters of the RON test method (ASTM D2699) to investigate the effects of these differences with automotive SI engine knock-limited spark advance testing. A fuel’s standard RON is evaluated at the lambda of the highest knock intensity, whereas automotive SI engines typically operate at stoichiometry. This study analyzes the effects of a stoichiometric RON rating methodology. Additionally, the knock intensity response from the standard CFR knockmeter system is compared to a cylinder pressure oscillation-based knock intensity at several lambda settings. All experiments were performed with a set of seven Coordinating Research Council (CRC) Fuels for Advanced Combustion Engines (FACE) gasolines with approximately 95 RON. The fuel chemical composition impacted the lambda of the highest knock intensity, which resulted in fuel-specific offsets between the standard and stoichiometric RON ratings. The knock system comparison showed significant offsets between cylinder pressure-based and knockmeter-based knock intensity levels.

Influence of Higher Alcohol Additives in Methanol–Gasoline Blends on the Performance and Emissions of an Unmodified Automotive SI Engine: A Review

More stringent emission norms are implemented all over the world to protect the environment from vehicular pollution. Biofuels are one of the best alternative solutions to reduce cost and environmental pollution. Among many alternate fuels, alcohol is a leading fuel used in automotive spark-ignition engines in pure or blended form. The capability of methanol to substitute gasoline has been known for a long time. This paper aims to systematically review methanol–gasoline blend with higher alcohol additives (ternary blends) as a transportation fuel in unmodified automotive spark-ignition engines. This review summarizes the previous research in methanol–gasoline blends with and without additives on spark-ignition engines' performance and emission characteristics. Many researchers found that methanol–gasoline blended fuels improve engine performance and emissions. Generally, alcohols burn very effectively and produce only fewer emissions compared to gasoline. Still, lower alcohol may cause some problems such as increased specific fuel consumption, phase separation and corrosion. These problems are further optimized using higher alcohol additives through improved energy content, kinematic viscosity, corrosion resistance, water tolerance and phase stability. Several research studies have been carried out in the past years, which focused mainly on single alcohol blended fuels for spark-ignition engines. Thus, a comprehensive survey of performance, combustion and emission characteristics of methanol–gasoline blended fuel with higher alcohol additives is necessary to show the potential of ternary blends in automotive engines.

An Experimental Investigation on Rheological and Heat Transfer Performance of Hybrid Nanolubricant and Its Effect on the Vibration and Noise Characteristics of an Automotive Spark-Ignition Engine

This research aimed to investigate the feasibility of a new combination of hybrid nanolubricant that can enhance the vibration and noise characteristics of an automotive spark-ignition engine through a comprehensive study of rheological and heat transfer behavior. The ZnO-based mono (ZnO/5W30) and hybrid (ZnO–TiO2/5W30, 50:50) nanolubricants of 0.1 wt% and 0.5 wt% have been prepared, and their rheological behavior was examined by measuring the viscosity at different temperatures ranging from 298.15 K to 338.15 K (25 °C to 65 °C). The results showed that both engine oil and nanolubricant exhibit non-Newtonian behavior. The hybrid nanolubricant presented a comparatively high viscosity index than 5W30 engine oil and mono nanolubricant. The theoretical prediction of thermal conductivity using the Maxwell–Garnetts model showed an increasing trend with nanoparticles’ concentration in hybrid nanolubricant. Experiments were conducted on an unmodified MPFI engine operated under various speeds using regular engine oil and hybrid nanolubricant for investigating noise and vibration characteristics. A significant reduction in longitudinal and lateral vibration accelerations and a maximum decrease of 4.5 % in noise level are observed with hybrid nanolubricant.

Methodological Approach for 1D Simulation of Port Water Injection for Knock Mitigation in a Turbocharged DISI Engine

In the upcoming years, more challenging CO2 emission targets along with the introduction of more severe Real Driving Emissions limits are expected to foster the development and the exploitation of innovative technologies to further improve the efficiency of automotive Spark Ignition (SI) engines. Among these technologies, Water Injection (WI), thanks to its knock mitigation capabilities, can represent a valuable solution, although it may significantly increase the complexity of engine design and calibration. Since, to tackle such a complexity, reliable virtual development tools seem to be mandatory, this paper aims to describe a quasi-dimensional approach to model a Port Water Injection (PWI) system integrated in a Turbocharged Direct Injection Spark Ignition (T-DISI) engine. Through a port-puddling model calibrated with 3D-CFD data, the proposed methodology was proven to be able to properly replicate transient phenomena of water wall film formation, catching cycle by cycle the amount of water that enters into the cylinder and is therefore available for knock mitigation. Moreover, when compared with experimental measurements under steady state operating conditions, this method showed good capabilities to predict the impact of the water content on the combustion process and on the knock occurrence likelihood.

Effect of ternary blends on the noise, vibration, and emission characteristics of an automotive spark ignition engine

ABSTRACT The type of fuel, engine speed, and load are some of the parameters, which influence engine noise, vibrations, and exhaust emissions of an internal combustion engine. The present investigation is carried out to study the effect of isobutanol addition to methanol-gasoline blends on engine’s noise, vibration, and emission characteristics of an unmodified automotive SI engine operated at various engine speeds. The engine was fueled with 10 and 15% (v/v) blended fuels of methanol-gasoline (M10, M15) and methanol-isobutanol-gasoline (iBM10, iBM15). The blended fuels produced relatively high noise levels and less vibration in the vertical and longitudinal direction when compared with gasoline operation. The maximum noise level of 64.43dBA observed with the M15 blend and which is 4 dBA higher than gasoline. Only a slight variation in the total fuel consumption observed for all the test fuels at higher engine speeds. The emissions from the test fuels iBM10 and iBM15 showed a reduction in HC by 25 and 10% and CO emissions by 65 and 87%, respectively. The methanol-gasoline blends produced slightly higher CO2 and NOx emissions than gasoline.

The dual-port fuel injection system for fuel economy improvement in an automotive spark-ignition gasoline engine

The purpose of the present study was to investigate the performance of the dual-port injection (DPI) system in an automotive spark-ignition engine. The DPI system utilizes two port fuel injection (PFI) injectors per cylinder, i.e., one injector at each intake port. An original 4-cylinder PFI engine head was modified to accommodate total 8 PFI injectors. In the present study, three spray angles and two install configurations were investigated in the intake port visualization, steady-state part-load experiments, and cold-start experiment. The intake port spray visualization experiment showed that the wider fuel spray provided better fuel distribution, but also more wall wetting. The steady-state engine experiment at the several critical part-load conditions showed that the DPI system in combination with the open-valve-injection strategy achieved the most brake specific fuel consumption (BSFC) reduction of 4.6%. The average BSFC reduction of the 9-point experiment was 2.8%. The cold-start experiment also showed a fuel economy gain by the DPI system. In the cold-start experiment the wider spray angle exhibited higher total hydrocarbon emission likely due to the greater wall wetting observed in the intake port spray images.

Experimental procedure for the characterization of turbocharger’s waste-gate discharge coefficient

Nowadays, the turbocharger has become one of the key components for automotive spark-ignition engine improvements (fed with both liquid and gaseous fuels), as a support for the boosting and downsizing concept to reduce fuel consumption and exhaust emission. In gasoline engines, the usage of the waste-gate valve typically regulates the maximum boost pressure in the turbocharger system, to protect the engine and the turbocharger at high engine speeds. To improve the transient response at low engine speeds, two-stage turbocharger is widely used. Two-stage systems are composed of several valves to regulate the flow to control the boosting of the system. Like a bypass valve between the turbines, a check valve is present between the compressor and a waste-gate valve for the low-pressure turbines. This article deals with a methodology for characterizing the discharge coefficient of an electronic waste-gate valve in the turbocharger. To estimate the gas flow over the same in one-dimensional models, an empirical model is correlated and validated. For this, a constant-stream experimental work has been carried out on a test rig at different valve position openings, with high turbine inlet temperatures. Finally, an optimal map of discharge coefficient has been drawn out through interpolation method, which can integrate into the full one-dimensional turbocharged engine model system, to calculate the actual mass flow through the waste-gate valve.

The evaluation of the regularity of the combustion process in the SI engine fueled with petrol and ethanol

In the paper are presented results of a research work concerning automotive spark ignition engine fueled with ethyl alcohol. The research was performed on a Fiat 1100 MPI engine adapted to dual fuel feeding. Injection of ethyl alcohol was accomplished in area near inlet valve with use of original injectors, the same as used in case of gasoline feeding. The subject-matter of the study was to compare smoothness of engine operation fueled with alcohol in relation to parameters of the engine fueled traditionally with gasoline. There were analyzed combustion parameters calculated on the basis of recorded indicated diagrams of successive individual combustion cycles and averaged diagrams of successive 50 cycles. Performed investigations are pointing at smooth engine operation running on neat alcohol, and on improvement of performance parameters such as effective power and overall efficiency.