Efficiency Of Gasoline Engines Research Articles

Advancements in homogeneous charge compression ignition technology: Efficiency, emissions, and applications in the modern automotive industry

Homogeneous charge compression ignition (HCCI) technology is a novel approach in internal combustion engines that combines the efficiency of gasoline engines with the spontaneous ignition characteristics of diesel engines. HCCI engines offer cleaner emissions, reduced noise, and wider fuel adaptability, overcoming many drawbacks of traditional engines. The paper explores the HCCI combustion process, highlighting its unique features and advantages over spark ignition (SI) and compression ignition (CI) engines. It also discusses innovations in HCCI technology, including its combination with other strategies like spark-controlled compression ignition (SCCI) and low-temperature combustion (LTC) to expand its load range. The challenges of HCCI technology, especially in combustion timing control, are addressed, along with suggestions for future research directions. The application of HCCI technology for energy savings and emission reduction and its impact on the automotive industry are also discussed, citing examples from manufacturers like Volvo, Nissan, and General Motors. The paper concludes by emphasizing the importance of ongoing research, integration with other technologies, and financial support to further advance HCCI technology and its market potential.

In-cylinder air mass flow estimation of gasoline engines based on map self-learning

Accurate in-cylinder air mass flow estimation is important for reducing emissions and improving the fuel efficiency of gasoline engines. Especially, the air-fuel ratio (AFR) control for gasoline engines is directly affected by the air mass flow estimation, which is used in feedforward control. At present, the transient air intake estimation for an engine is much more complex than the steady-state case. In practice, the working conditions of gasoline engines are always changeable to adapt to different traffic conditions, so it is important to improve the air intake estimation under the transient conditions. In order to improve the accuracy of intake air estimation, an appropriate filtering method is designed to eliminate the periodic fluctuations of the signals. And an estimation method based on the map self-learning algorithm is proposed, which considers the full working state of the engine, especially the transient conditions. The convergence of the proposed algorithm is guaranteed theoretically, and the method is designed to realize real-time identification and recursively correct of the volumetric efficiency value. The parameters of the observer are designed and adjusted through experiments to verify the effectiveness of the algorithm. With the continuous recursion of the algorithm, the accuracy of the air intake estimation will be improved and the error will be reduced. At last, the proposed strategy is analyzed and verified by a large number of experiments on the engine test bench to show its promising potentials.

Experimental investigation of thermal swing piston insulation at single cylinder gasoline engine

The reduction of carbon dioxide emissions and the corresponding increase in gasoline engine efficiency are crucial in engine development. Wall heat losses are a major cause of efficiency loss, accounting for 15–30% of the total fuel energy. One promising solution is the use of "thermal swing" coatings at the combustion chamber walls because of offering the possibility that the surface wall temperature following the working gas temperature, whereby the wall heat transfer can be reduced at any time during the engine cycle. This type of coating material is characterized by low thermal conductivity and, at the same time, low heat capacity. Based on the idea of the “thermal swing” coatings, yttria stabilized zirconia (YSZ) was selected as the coating material for the piston surface and its efficiency potential was experimentally investigated on a single-cylinder gasoline engine. The use of highly dynamic temperature probes in the piston allowed precise analysis of cycle-based temperature fluctuations, especially on the piston surface. The transmission of the piston temperatures was cable-based and accomplished through the use of a lever system in the engine. The measurement results confirmed the minimal impact on the efficiency that was determined in preliminary simulations. However, the effect of the coating could be established through the measurements.

Lean combustion and emission performance of a gasoline direct injection engine with active pre-chamber

Pre-chamber jet ignition technology can effectively improve flame propagation speed and in-cylinder combustion rate, so it is conducive to the improvement of thermal efficiency and fuel economy. While, studies on the key parameters of the influence of active pre-chamber on combustion and emissions are not systematic. The influence of the key parameters of injection control in active pre-chamber on combustion and emission is not clear at present. Thus, in this paper, an active pre-chamber jet ignition system was designed and used in a single cylinder GDI engine, and the effects of compression ratio and pre-chamber injection strategy on pre-chamber jet ignition were experimentally studied, as well as the comparison of pre-chamber jet ignition and conventional spark ignition. The results show that, at 2750 r/min, IMEP 11 bar operation point, lean burn can effectively reduce the fuel consumption and increase the thermal efficiency of gasoline engine. Adopting traditional spark plug system can extend the lean burn limit to excess air ratio of 1.5 with the gross indicated thermal efficiency (GITE) of 45% limited by unstable combustion, while resembling active pre-chamber system can achieve GITE of 46.5% with the excess air ratio of 2.0 with the help of much more stable combustion. And the NOx emission of active-pre-chamber system has been reduced by 78% compared by conventional spark plug system. Increasing the compression ratio to 14.8 can further reduce the indicated fuel consumption to 177 g/kWh, and increase the GITE to 48.5% and further reduce the NOx emission to lowest 0.53 g/kWh with the excess air ratio of 2.1. With the increase of pre-chamber injection pressure, the ignition stability increases, the combustion duration decrases, and thermal efficiency increases. With the increase of the pre-chamber injection duration, the ignition delay first decreases and then increases. When the injection duration increases to 800 μs, COV is greater than 3%. If the pre-chamber injection duration further increase, the COV increases, the combustion phasing retard, and the thermal efficiency decreases. With the increase of pre-chamber injection duration and pressure, the wetting wall fuel increases, which leads to the increase of PN emission.

New Combustion Process for Higher Efficiency of Gasoline Engines

New Combustion Process for Higher Efficiency of Gasoline Engines

Combined effects of high energy ignition and tumble enhancement on performance of lean combustion for GDI engine

Lean combustion can greatly improve the thermal efficiency of gasoline engine. Increasing ignition energy and tumble level can effectively expand its application range. Optical glass liner was used to clearly observe the in-cylinder state. Particle image velocimetry(PIV) was used for quantitative evaluation of tumble modification. The integral tumble ratio of the high tumble intake port is 1.67 times that of the basic intake port. Ignition energy was increased from 65 mJ to 300 mJ. Under the condition of no fuel injection, the duration of 300 mJ ignition arc is longer, and the peak arc area is about 4 times that of 65 mJ. The effects of ignition energy and tumble level on combustion stability, lean-burn limit, fuel economy and flame development were studied. The results show that high energy ignition can enlarge the lean-burn limit, but has no significant effect on combustion stability. High tumble has the opposite effect and can effectively improve fuel economy. The micro flame development images under the ultra-lean condition are different. The flame area of 300 mJ is larger and the combustion is more intense. High energy ignition contributes to the formation of initial flame kernel and flame propagation, so it can improve the lean-burn limit.

Implementation of 1D–3D integrated model for thermal prediction in internal combustion engines

The need to improve the thermal efficiency of gasoline engines used in hybrid vehicles, has led to explore new solutions for reducing engine heat losses. Hence, it is important for the car manufacturers to be able to predict the heat transfer in the engine components. Numerical methods such as CFD (Computational Fluid Dynamics) or CHT (Conjugate Heat Transfer) can be used to assess the heat losses through the combustion chamber walls, but they are long and costly. In this regard, it is particularly interesting for the industry to use simplified models, which may play a key role in the design stage. In this work a 1D model integrated with 3D finite elements based on a commercial software is used to calculate the heat losses in a single-cylinder gasoline direct injection engine. The model is first validated, then a detailed heat transfer analysis is performed, and its results compared to those of a full CFD–CHT simulation. Results demonstrate that this approach is suitable to predict in a short time the heat losses and the spatial temperature distribution in the solid regions of an internal combustion engine. The model also yields accurate values in terms of engine performance.

Numerical investigation of Miller cycle with EIVC and LIVC on a high compression ratio gasoline engine.

Previous studies have shown that increase compression ratio (CR) is an effective way to improve thermal efficiency of gasoline engine without changing the mechanical structure and working cycle, however, it is limited by engine knock when increasing the intake boosting under high load operation. This study aimed to solve the knock problem of gasoline engine with higher CR by application of Miller cycle, which can be implemented by either early or late intake valve closing (EIVC or LIVC). Therefore, in this paper, based on the engine with CR of 13.5 and electromagnetic valves train (EMVT), a comparative study was carried out to investigate the effects of EIVC and LIVC on engine performance, by theoretical modeling and calculation. The results show that, at high load, EIVC strategy is more preferred than LIVC owing to its lower total power consumption, which can improve the indicated mean effective pressure (IMEP) by 0.0371 bar, while enhance turbulence intensity and improve combustion. And at part load, the advantage for EIVC declines gradually, nevertheless, it can still sensitively adjust the EGR rate and thus reduce NOx. This results of quantitative analysis about two Miller cycles can provide valuable reference for engine designers and researchers.

Water injection for gasoline direct injection engines: fundamental investigations in an evaporation chamber

Today’s combustion engine development is strongly driven by reduction of $$\hbox {CO}_2$$ and exhaust gas emissions. Modern turbocharged downsizing concepts with gasoline direct injection are well established in all major markets and contribute to current and future mobility as a cost attractive and efficient solution. Further improvement of gasoline engine efficiency and performance is mainly limited by knocking. Water injection (WI) has the potential to reduce knocking significantly. To improve the effectiveness of water injection, fundamental knowledge of the thermodynamic process has to be built up. Therefore, a zero dimensional evaporation model was developed and simulations were carried out. This model was derived and validated on the basis of measurements which were carried out on a specifically designed and assembled WI evaporation chamber. Conditions in terms of temperature and pressure were varied to determine the evaporation behaviour of water droplets influenced by temperatures of e.g. air or water. The model describes the process of droplet heating and finally the evaporation of the droplets depending on their size at relevant engine boundary conditions. The simulation results support interpretation of engine measurements and allow further optimization of water injection concepts.

Simultaneous needle lift and injection rate measurement for GDI fuel injectors by laser Doppler vibrometry and Zeuch method

Achieving an adequate knowledge of the fuel injector dynamic operation is an important step in the global effort of improving direct injection gasoline engine efficiency while limiting pollutant emissions. In this frame, needle displacement measurement is an important add-on to evaluate the injector actual performances and can be very useful for developing predictive numerical models to support both the component and engine development. In this study the dynamic behavior of a GDI injector was investigated by the simultaneous measurement of injector needle lift and of the resulting injection rate. With this methodology, the needle displacement is measured by laser Doppler vibrometry, while the injector is tested by an injection analyzer based on the Zeuch method. The vibrometer laser beam points on the needle back surface, passing through a quartz window allowing the fuel pressurization and the normal injector operation. The analysis of the simultaneously acquired needle displacement, injection rate, fuel inlet pressure and current time-history profiles allows a complete insight in the injector dynamic operation. The pressure effect on the needle dynamics was assessed with a detailed analysis of the opening and closing transients; further, multiple actuation strategies were analyzed focusing on the influence of dwell time on the injector dynamics evidencing how the resulting injection rate profile is affected by the needle inertia and by the pressure wave propagation along the fuel line.

Effect of TRIPMEXX Additives on Engine Performance of a 1.6L Multi-Cylinder Gasoline Engine

This study discusses the findings of the project data obtained from the experimental work. It was based on the analysis of experimental output responses obtained which were Brake Specific Fuel Consumption (BSFC), power and engine torque. A 1.6L multi-cylinder gasoline engine was used to investigate the effect of TRIPMEXX on the fuel economy. The experiment was performed at variations of engine speed (1500, 2000, 2500 and 3000 rpm) with a constant engine load of 40 Nm. From the results obtained, it showed that brake specific fuel consumption (BSFC), power and engine torque for TRIPMEXX were better than gasoline fuel without TRIPMEXX fuel additive. Combustion efficiency of gasoline engine has improved with the use of TRIPMEXX fuel additives. Overall, Fuel Economy, Power and Engine Torque for 1 ml + 10L RON95 fuel sample showed the best results for all measured parameters at all engine test conditions.

Enhancing the Efficiency of Gasoline Engines using Solar Powered Supercharger

The world presently depends heavily on non-renewable sources of energy like crude oils. These conventional energy sources have certain limitations, that is, they will eventually run out, fuel prices can rise without warning and most importantly growing environmental concerns over the climate change associated with the release of CO2 on burning fossil fuels[1]. Renewable energy is the key to a clean energy future. In the last few decades, solar energy is the fastest growing renewable energy source[2]. We can harness this energy of the sun in increasing the efficiency of our automobiles. Forced induction system (supercharger and turbocharger) in automobiles helps in the improvement of the efficiency of internal combustion engines by pushing extra atmospheric air into the cylinder which results in the proper combustion of fuel and thus reducing the smoke from the exhaust gas. Conventional Supercharger draws power from the engine and though the overall mechanical efficiency is increased but some energy is lost in powering the supercharger. The main purpose of this paper is to develop a solar-powered supercharger which will not consume extra power from the engine and thus increase the overall efficiency of the engine along with a reduction in CO2 emission.

Effect of water - methanol blends on engine performance at borderline knock conditions in gasoline direct injection engines

One of the limiting factors improving the efficiency of gasoline engines is engine knock. Various techniques including using fuels that result in charge cooling are employed to mitigate knock and improve efficiency. Water and methanol have higher heat of vaporization than gasoline. When water or methanol is injected into the intake manifold, it evaporates by exchanging energy with the charge mixture resulting in charge cooling. This allows the engine to be run with advanced spark timing without engine knock. With this motive, the impact of water - methanol injection on the engine performance of a gasoline direct injection engine was investigated. Experimental studies were conducted on a single-cylinder 0.55L engine with a compression ratio of 10.9:1 at 800 kPa net indicated mean effective pressure and 1500 revolutions per minute. Baseline tests without water injection were conducted by direct injection of gasoline fuel blended with 10% ethanol (E10). Four mixtures: 100% water, 75% water + 25% methanol, 50% water + 50% methanol and 100% methanol were used with port injection. Spark ignition timing, flow rate of the fuel and the four mixtures were varied to be within the controlled knock limit while maintaining an excess air ratio of 1.0. Comparisons on the effectiveness of these mixtures indicate that higher methanol content in the mixture helped in reaching the maximum brake torque condition at lower mixture fuel ratios. Combustion stability of the engine was improved with the addition of water and water-methanol blends due to the sensitivity of combustion phasing at advanced spark timings reducing the variation in indicated mean effective pressure. Exhaust gas temperatures decrease with the addition of water and water-methanol blends due to the combined effect of increased charge cooling and improved combustion phasing.

Increasing the Performance of Existing IC Engines by Free Valve Actuation Technology

In this current generation, the efficiency of gasoline engines is around 50%. This isbecause of many losses within the system. The most important losses are because of moving parts. Moving parts comprises piston, cams, rod etc. Investigations are being conducted to cut the losses to enhance efficiency. One such outcome is that the free Valve Mechanism which uses poppet valves operated by means of pneumatic actuators rather than cams. Actuators are used to open and shut the valves and control combustion within each cylinder and hence improving the efficiency.

Study on the influence of masking on the high tumble intake ports of GDI engine by three-dimensional simulation

The high intensity tumble motion has a significant effect on the combustion system and the thermal efficiency of gasoline engine. The tumble ratio and discharge coefficient of high tumble ratio intake ports with masking were simulated by CFD three-dimensional simulation. The influence of masking on the intake process was emphatically discussed. The width, height, radius fillet and circumferential range of masking were changed and then simulated. The results shown that, the tumble intensity at the low valve lift was greatly affected by the masking. The smaller width, higher height, smaller radius fillet and larger circumferential range are favorable for the higher tumble intensity in low valve lift and also higher in average tumble ratio. Among these parameters, masking height has much more effect on mean tumble ratio and mean discharge coefficient. When the valve lift exceed masking height, the difference of tumble ratio and discharge coefficient between intake ports decreased.

A combination of electric supercharger and Miller Cycle in a gasoline engine to improve thermal efficiency without performance degradation

Miller cycle makes the expansion ratio larger than effective compression ratio by early or late closing intake valves thereby improving the thermal efficiency of gasoline engines at the risk of power degradation. Electric supercharging efficiently improves transient response and output of engines. This paper proposes an electrically supercharged non-backflow Miller cycle by combining electric supercharging and Miller cycle to improve thermal efficiency of gasoline engines without power output reduction. The results indicate that electrically supercharged non-backflow Miller cycle can effectively improve the thermal efficiency of gasoline engines. Compared to the original Otto-cycle gasoline engine, the electrically supercharged Miller-cycle engine has the highest thermal efficiency of 35.54% which is an improvement of 4.32% at 3500 rpm full load operation. The electric supercharger ensures that the power output is not reduced. Therefore, electrically supercharged non-backflow Miller cycle is an effective method to improve thermal efficiency of gasoline engines without performance degradation.

The thermodynamic analysis of an electrically supercharged Miller Cycle gasoline engine with early intake valve closing

Electric superchargers are able to improve the thermodynamic process of gasoline engines by self-adapting running state to dominate intake air in all operation conditions. This paper proposes a novel approach for electrically supercharged Miller Cycle with early intake valve closing based on thermodynamics to settle the fuel economy problem of gasoline engines at low load operations by taking advantages of the domination of electric superchargers to intake air. Electrically supercharged Miller Cycle with early intake valve closing was realized by matching an electric supercharger, redesigning the inlet cam, and setting the intake valves closing before bottom dead center while keeping intake valves opening constant. An over-expanded engine cycle is attempted to be used to promote thermal efficiency by increasing geometric compression ratio, in addition to maintaining the effective compression ratio. Here, it has been attempted to systematically analyze the law of the energy losses of the electrically supercharged Miller Cycle gasoline engine with early intake valve closing using a reliable thermodynamic model from the perspective of heat engine. The results indicate that electrically supercharged Miller Cycle with early intake valve closing could improve the thermal efficiency of gasoline engines by significantly decreasing the pumping and exhaust losses.

Hydrogen effects on the combustion stability, performance and emissions of a turbo gasoline direct injection engine in various air/fuel ratios

Lean combustion has been identified as a way of improving the thermal efficiency of gasoline engines. However, it is difficult to operate gasoline engines in lean conditions, because the stability of the combustion deteriorates. Hydrogen has properties that can be exploited to improve the combustion stability, and hence solve the combustion instability problem. In this paper, we describe an experimental study into the effects of hydrogen on the combustion stability, performance, and emissions at various air/fuel ratios using a four-cylinder 2.0-L turbo gasoline direct-ignition engine. The engine speed was fixed at 2000 RPM with a brake mean effective pressure of 2–18 bar. The results of these experiments indicate that combustion is improved, thermal efficiency enhanced, and emissions reduced except for NOX. Especially, in terms of combustion stability, the cycle-to-cycle variation and cylinder-to-cylinder variation decreased when hydrogen was added. This was caused by two effects. First, when the brake mean effective pressure was 10 bar or below, the burn duration was reduced by the fast flame speed, high adiabatic temperature, and high diffusion coefficient of hydrogen. This led to an increase in the combustion stability and thermal efficiency. Second, when the brake mean effective pressure was above 10 bar, knock resistance was enhanced by hydrogen: spark timing could be advanced upon hydrogen addition. Therefore, the combustion stability and performance improved. Additionally, the improvements to the combustion, especially in terms of combustion stability, became more pronounced as the in-cylinder air–fuel mixture became leaner: the lean limit was thus extended.

Realization of variable Otto-Atkinson cycle using variable timing hydraulic actuated valve train for performance and efficiency improvements in unthrottled gasoline engines

Variety of technologies along with the mechanisms for their implementations have been developed in order to pursue possible improvements in the performance and efficiency of gasoline engines. However, most of the commonly used techniques, such as the cam-based variable valve timings (VVT) and variable compression ratio (VCR), are realized by different kinds of complicated mechanisms, providing an extended but still relatively limited adjustability for attaining improved valve timings and different engine cycles according to the varying working conditions of the engine. In this research, by using the flexibility offered by the hydraulic actuated valve train (HAVT), a set of new valve motion strategies is developed for realizing a newly introduced engine cycle, the variable Otto-Atkinson cycle (VOAC), to achieve an unthrottled engine load control. The demonstrative VOAC test engine in this research is a converted baseline single-cylinder engine that is able to carry out a variable Otto cycle (VOC) at full load operations for achieving higher power performance while realizing a variable Atkinson cycle (VAC) at partial load operations for gaining better fuel economy without having any further modifications or attaching additional components to the engine. The baseline single-cylinder engine is modeled in GT-Suite and carefully calibrated by a series of experiments. Benefited from the HAVT features, the tunings of the VOAC engine can be realized easily to fulfill any requirements towards different desired engine characteristics. By adopting the proposed VOAC with optimized parameters, a 13.5% average improvement in the engine's output can be achieved under full load operations across the entire speed range. On top of that, it also shows that the resulted BSFC could be lowered by 16.1 g/kW·h on average over the sampled speed-load map of the engine running at partial load operations.

Fuel economy in gasoline engines using Al2O3/TiO2 nanomaterials as nanolubricant additives

Energy resources are of strategic interest worldwide. Transportation sector is a principal consumer of different energy resources, therefore reducing the consumption of vital energy resources is critical in automobiles. The friction and wear issues impact the energy efficiency of engines, therefore it is an important development of the lubricant for saving energy. The current study supports that goal. This study deals contribution of Al2O3/TiO2 hybrid nanoparticles as nanolubricants to improve gasoline engine efficiency and fuel economy. The gasoline engine performance characteristics were evaluated experimentally using an AVL dynamometer under different operating conditions including the New European Driving Cycle (NEDC). Additionally, the engine was tested under critical operating conditions (warm-up phase). The results showed that using Al2O3/TiO2 nanolubricants increases the brake power, torque, and mechanical efficiency, while the brake specific fuel consumption (BSFC) reduced owing to the mechanical efficiency of the engine improved by 1.7–2.5%, as compared to the engine oil without nanoparticles. Hence, the vehicle fuel consumption during NEDC could be improved up to 4 L per 100 km in the urban. Furthermore, FESEM, EDS line scanning, XPS, and Raman spectroscopy were conducted to understand the major tribological reasons for improving the engine performance to link tribological tests in the laboratory with actual engine performance. Eventually, the results suggest that nanolubricants provide economical engines with high efficiency that it may be an appropriate direction for vehicle manufacturers and users to suppress the engine fuel cost with engine durability under different operating conditions.