Effects of ethanol on combustion and emissions of a gasoline engine operating with different combustion modes
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The introduction of fuel economy and CO 2 emission legislations for passenger cars in many countries and regions has spurred the research and development of more efficient gasoline engines. The pumping loss at part-load operations is a major factor for the higher fuel consumption of spark-ignition gasoline engines than the diesel engines. Various approaches have been identified to reduce the pumping loss at part-load operations, leading to improved fuel economy, including early intake-valve closing, positive valve overlap and controlled auto-ignition combustion. On the other hand, in order to reduce the CO 2 emissions from the fossil fuel, ethanol produced from renewable resources is becoming widely used in the gasoline engine. In this article, the performance, combustion and emissions were measured, analysed and compared between gasoline and its mixture with ethanol (E15 and E85) at a typical part-load condition when a direct-injection gasoline engine was operated with the controlled auto-ignition combustion by means of the negative valve overlap and spark-ignition combustion by means of the intake throttled, early intake-valve closing and positive valve overlap. An electro-hydraulic actuated camless system enabled the engine to be operated with controlled auto-ignition combustion and spark-ignition combustion of different valve timings and durations at the same load. The results showed that the controlled auto-ignition combustion reduces nitrogen oxide emissions by more than 90%. The positive valve overlap results in better mixture preparations and improved combustion efficiency and best fuel economy compared to all the other modes. The early intake-valve closing operation led to a moderate improvement in the fuel conversion efficiency over the throttled spark-ignition operation, but it was characterised by the slowest combustion and worst hydrocarbon and carbon monoxide emissions. Fewer and smaller particle numbers were detected in early intake-valve closing using E0 and E15 fuel blends. Using ethanol blends reduces the knocking combustion in controlled auto-ignition modes by about 50%. The use of E85 resulted in an increased number of particulate emissions in early intake-valve closing but increased indicated specific fuel consumption in all the modes. The particulate emission results showed that soot is the dominant particle in the exhaust.Keywords:
Naturally aspirated engine
Ignition timing
Valve timing
The performance of the engine depends on many factors. One of the factors is valve timing known to be the timing of opening and closing of valves that has a significant effect on the in-cylinder performance. However, there is less information in the study about valve timing effect on single cylinder engine performances. In this study, the focus is to analyze in-cylinder pressure characteristics on a single piston fuel injection for a spark-ignition engine. This can be done by simulating the effects of valve timing on in-cylinder pressure. The methodology of this project will be simulation-based by using commercial one-dimensional software. The research results are engine performance parameters which are volumetric efficiency, brake torque, brake power, and cylinder pressure in 1000 to 5500 RPM engines. The results show a positive increment in engine performance from the baseline model (CTA240) which is 9.06% for brake power, 2.85% for brake torque, and 13.09% for volumetric efficiency. At low engine speed, it was also found improvement in cylinder pressure when advancing the intake valve timing opening (IVO) by 20 to 25 degrees bTDC. For high speed, the cylinder pressure was found to improve once the retardation of intake valve timing closing (IVC) was done between 40 to 45 degrees aBDC by comparing it with the baseline results. The result highlights the importance of intake valve timing setup by varying the opening and closing of the intake valve to give better output for engine performance.
Valve timing
Ignition timing
Mean effective pressure
Volumetric efficiency
Piston (optics)
Naturally aspirated engine
Position-sensing hydraulic cylinder
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Throttle
SPARK (programming language)
Ignition timing
Valve timing
Mean effective pressure
Engine knocking
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A Fully Hydraulic Variable Valve System is described in this article which can achieve continuous variation in valve lift, duration, and timing. The system was installed in a four-cylinder port fuel injection spark ignition engine and achieved unthrottled load control through early intake valve closing. The in-cylinder pressure measured experimentally showed that pumping losses of the unthrottled spark ignition engine at 2000 r/min and 0.189 MPa brake mean effective pressure was reduced by 85.4% compared with the throttled spark ignition engine. However, its slow and unstable combustion reduced the indicated thermal efficiency. Compared with the throttled spark ignition engine, the amount of residual exhaust flowing back into the intake port was greatly reduced at the early stage of the intake process. Consequently, it negatively influenced fuel evaporation and fuel–air mixing processes in the intake port of the port fuel injection spark ignition engine and decreased the flow of in-cylinder gases, which resulted in a low combustion rate. A new centrosymmetric helical valve is proposed in this article to improve the fuel–air mixing and combustion rate of the unthrottled spark ignition engine. The experiments demonstrate that the helical valve can generate a strong intake swirl at small intake valve lift. It helps to increase combustion rate and lower cycle-to-cycle variation, which improves indicated thermal efficiency and fuel economy of the unthrottled spark ignition engine at low load.
Ignition timing
Valve timing
Thermal efficiency
Engine knocking
Naturally aspirated engine
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In this research, possible improvements in engine specifications using the simulations developed on the AVL BOOST™ and Ricardo WAVE™ platforms were investigated. These modelling simulations help the author to predict the effect of any improvements in engine specifications without practical experimental challenges and difficulties. Firstly, HCCI and SI engines were modelled with the intention of maximizing the engine’s efficiency and minimizing the emissions. Changes of valve timing and throttle angle influence emissions’ reduction and the efficiency of the engine. In SI engines, the emissions of NOx can be reduced by using EGR, while only having a little effect on performance. The emissions from the HCCI, due to their intrinsically low emission output, were not improved. The effect of increasing the bore to stroke ratio in an opposed piston engine whilst maintaining a constant swept volume, port geometry and combustion timing, shows an increase of heat losses due to the lower ratio of exposed surface area to volume; an increase in thermal and mechanical efficiency; and most importantly, an improvement in fuel consumption. Also, in this research study, different strategies for opposed piston engines were investigated to increase the engine’s efficiency. The effect of a variable compression ratio on an opposed piston engine’s performance indicates different behaviour at various engine speeds and under different running conditions.
Valve timing
Piston (optics)
Thermal efficiency
Ignition timing
Throttle
Volumetric efficiency
Engine efficiency
Naturally aspirated engine
Four-stroke engine
SPARK (programming language)
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A novel fully hydraulic variable valve system is described in this paper, which achieves continuous variations in maximum valve lift, valve opening duration, and the timing of valve closing. The load of the unthrottled spark ignition engine with fully hydraulic variable valve system is controlled by using an early intake valve closing rather than the conventional throttle valve. The experiments were carried out on BJ486EQ spark ignition engine with fully hydraulic variable valve system. Pumping losses of the throttled and unthrottled spark ignition engines at low-to-medium loads are compared and the reason of it decreasing significantly in the unthrottled spark igntion engine is analyzed. The combustion characteristic parameters, such as cyclic variation, CA50, and heat release rate, were analyzed. The primary reasons for the lower combustion rate in the unthrottled spark ignition engines are discussed. In order to improve the evaporation of fuel and mix with air in an unthrottled spark ignition engine, the in-cylinder swirl is organized with a helical intake valve, which can generate a strong intake swirl at low intake valve lifts. The effects of the intake swirl on combustion performance are investigated. Compared with the throttled spark ignition engine, the brake specific fuel consumption of the improved unthrottled spark ignition engine is reduced by 4.1% to 11.2%.
Throttle
Ignition timing
Valve timing
SPARK (programming language)
Naturally aspirated engine
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Abstract The lower part‐load efficiency of the spark‐ignition (SI) engine is because of the higher pumping loss during the gas exchange process. In this study, the part‐load efficiency of a port fuel injection (PFI) and gasoline direct injection (GDI) camless engines were investigated. An in‐house developed electro‐pneumatic variable valve actuation (VVA) system controls the camless engine's intake valve events. The effect of un‐throttled operation with early intake valve closings (EIVC) on performance, combustion, and emissions was analyzed. The IVC timing for GDI camless engine was found to be lower (2°–7° crank angle) than the PFI camless engine for all operating conditions due to the in‐cylinder charge cooling. Hence, the pumping mean effective pressure (PMEP) for GDI camless engine was reduced, and brake specific fuel consumption (BSFC) was improved (maximum 2.1%) compared to the PFI camless engine. The THC and CO emissions were higher for GDI camless engine due to the relatively in‐homogeneous mixture formation, whereas the NO x emission was lower for all operating conditions.
Gasoline direct injection
Valve timing
Volumetric efficiency
Engine efficiency
Mean effective pressure
Naturally aspirated engine
Engine braking
Four-stroke engine
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The simulation model of spark ignition methanol engine was established based on one-dimensional intake and exhaust pipe flow theory and in-cylinder zero-dimensional combustion model theory.Measured data was proved to be consistent with the calculation data.The performance simulation of the methanol engine based on three operate conditions were studied,and three groups of valve timing(IVC and EVO) is optimized firstly.Finally,the optimal valve timing was determined by interactive method through the comparison of calculation results.
SPARK (programming language)
Ignition timing
Valve timing
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In this research, we estimated and summarized the effects of combustion duration on the performance and emission characteristics of a spark-ignition engine using pure methanol and ethanol as fuels, which have not been previously presented. From the results, we demonstrated that an increase in combustion duration causes a decrease in peak firing temperature and peak firing pressure and an increase in trapped residual gas. The level of trapped residual gas when using ethanol as fuel is higher than that of methanol fuel. The indicated mean effective pressure (IMEP) and brake mean effective pressure (BMEP) increase to maximum values and then decrease with increasing combustion duration, while the brake specific fuel consumption (BSFC) reaches a minimum value and then increases. The optimal BSFC improved to 33.31% when the engine used ethanol fuel instead of methanol. The increase in combustion duration helps to reduce NO x and HC emissions, but an increase in CO emissions is observed.
Mean effective pressure
Ignition timing
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Valve timing
Dilution
SPARK (programming language)
Ignition timing
Gas engine
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In order to acquire lower fuel consumption and higher torque output at low and middle speed, an engine cycle simulation of a small turbocharged gasoline engine is conducted by AMESim code. After validated against test data, the simulation model is used to optimize the full load performance of spark ignition(SI) engine. The effects of both intake manifold length and valve timing on the torque, volumetric efficiency and fuel consumption are investigated in details. To overcome the conflicts between low speed and high speed engine performance, variable valve timing(VVT) strategy is also investigated. The results show that, engine torque and brake specific fuel consumption(BSFC) during low and middle speed period can be improved effectively as valve timing is optimized and matched with intake manifold length reasonably using the gas dynamic effect.
Valve timing
Inlet manifold
Volumetric efficiency
Ignition timing
Throttle
Octane rating
SPARK (programming language)
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