Compression Ratio Spark Ignition Engine Research Articles

Potentials of Air-EGR Dilution for Improving Performance of a High Compression Ratio Spark-Ignition Engine Fueled with Methanol

Potentials of Air-EGR Dilution for Improving Performance of a High Compression Ratio Spark-Ignition Engine Fueled with Methanol

Performance improvement and CO and HC emission reduction of variable compression ratio spark-ignition engine using n-pentanol as a fuel additive

This study tests binary and ternary n-pentanol, ethanol, and petrol blends to increase spark-ignition (SI) engine performance and minimize CO and HC emissions. To improve brake thermal efficiency (BTE) and reduce emissions, adding ethanol into gasoline is one of the practices used in Automobiles. But the literature reported some performance limitations and problems with adding a high ethanol concentration to gasoline as phase separation problem occurs in fuel tank due to the hygroscopic nature of ethanol, a higher ethanol concentration may corrode some parts of the fuel supply system. Ethanol has a lower calorific value than gasoline, so a higher ethanol concentration in blends beyond a specific limit reduces BTE. N-pentanol as a fuel additive in gasoline can better solve these problems due to its high caloric value compared to ethanol. Also, when n-pentanol is mixed with gasoline and exposed to moisture, it does not separate in stages as in the ethanol case. Accordingly, this research aims to evaluate n-pentanol's viability as a fuel additive in petrol and ethanol-gasoline blends at different compression ratios. The experiments were carried out on a single-cylinder, four-stroke spark-ignition engine running at a constant speed. Different blends of n-pentanol with gasoline and ethanol were tested, and results were compared against gasoline and E10 (the optimal blend of ethanol-gasoline, 10/90 v/v %). Various parameters were examined, including BTE, brake-specific fuel consumption (BSFC), and different exhaust pollutants. The effects of compression ratio values on these parameters were also recorded. The 1.5 vol% pentanol with E10 (E10P1.5) mix has the best overall characteristics, including low BSFC, high BTE, and low CO and HC emissions compared to petrol and E10 fuels. E10P1.5 shows a maximum enhancement in BTE, low BSFC, CO reduction, and HC reduction by 23.79%, 19.80%, 37.79%, and 19.46%, respectively, over gasoline. Compared to E10, the improvement is 3.64% for BTE, 4.59% for BSFC, 8.88% for CO emission reduction, and 4.13% for HC emission reduction.

Low thermal inertia thermal barrier coatings for spark ignition engines: An experimental study

Application of thermal barrier coatings in spark ignition engines have historically been avoided due to the knock penalty associated with higher surface temperatures induced by the ceramic layer. However, advances in low thermal inertia coatings (i.e. temperature swing coatings) that combine low thermal conductivity with low volumetric heat capacity can prevent excessively high surface temperatures during the intake stroke and reduce or avoid knock while improving performance and efficiency. In this study, a novel coating material was tested in a low compression ratio spark ignition engine to evaluate the performance of an advanced low thermal inertia coating during steady and cold-start conditions. A total of four pistons with this novel material was tested, with an additional piston coated with gadolinium zirconate. Spark timing sweeps demonstrated a maximum 0.8% relative thermal efficiency gain with a thin coating of the novel material. The novel material coated above 200-microns showed a deterioration in performance and efficiency due to charge heating increasing knock propensity. Cold-start tests demonstrated that charge heating is beneficial for reducing unburned hydrocarbons and particle matter emissions.

Exergy evaluation of equivalence ratio, compression ratio and residual gas effects in variable compression ratio spark-ignition engine using quasi-dimensional combustion modeling

This study is founded on previously validated, in-house, comprehensive, two-zone, quasi-dimensional combustion model, predicting performance and emissions in spark-ignition engines. The model is extended to include exergy terms complementing the first-law analysis results, which provide further useful information by implementation on test results acquired from an experimental, Ricardo E6, variable compression ratio (VCR) gasoline engine at the authors’ laboratory, operated under various CR and equivalence ratio (EQR) values at wide-open throttle. The model consists of unburned and burned zones simulating the combustion process, following strictly the flame-front movement in combustion chamber. The eventual combustion of the unburned mixture turbulent entrainment into burned zone through the flame-front area is followed closely. The exergy terms of each simulated zone are identified and computed, considering also chemical exergy components (diffusion plus reactive). The accurate account of temperature and species histories in burned zone after entrainment from the unburned one, should lead to more precise evaluation. This is important if irreversibility is computed from balance of all other exergy terms. The investigation examines and compares exergy-wise various EQR, CR and residual gas fractions. Presented diagrams of exergy terms for each zone and cylinder charge provide detailed information for chemical exergy, irreversibility and exergy losses.

PERFORMANCE AND EMISSION STUDY OF ETHANOL-BLENDED GASOLINE POWERED SMALL VCR ENGINE

PERFORMANCE AND EMISSION STUDY OF ETHANOL-BLENDED GASOLINE POWERED SMALL VCR ENGINE

Numerical comparative study on knocking combustion of high compression ratio spark ignition engine fueled with methanol, ethanol and methane based on detailed chemical kinetics

Methanol, ethanol and methane are three kinds of common high-octane alternative fuels, which are ideal fuels for SI engines with high compression ratio. High compression ratio generates high thermal efficiency and also causes knocking combustion. Knock is one of the main obstacles for improving performance of SI engine. In this paper, the SAGE models combined with detailed chemical reaction kinetics were used to study knock combustion. The effect of equivalence ratio was discussed on the knocking combustion of SI engines fueled with methanol, ethanol and methane. The evolution of important components were analyzed in details during the combustion of methanol, ethanol and methane. The results showed that as the equivalence ratio increased, the intensity of knocking increased and the onset time occurred in advance for all three fuels. The knocking intensity of methane was significantly weaker than that of methanol and ethanol at any equivalent ratio. When the equivalence ratio was less than 0.9, the knocking combustion of methane disappeared. The knocking intensity of methanol was larger than that of ethanol. The ignition delay of methanol at low temperature depended largely on the consumption rate of H2O2, the auto-ignition was triggered by the dissociation of H2O2. For ethanol, the hydrogen abstraction by HO2 radicals suppressed auto-ignition, while the decomposition of H2O2 promoted auto-ignition. CH2O radical was important intermediate for the low-temperature reaction process of methane, which mainly distributed in the flame front region. The formation of CH2O radical could reflect the degree of low temperature oxidation of methane.

Advantages of hydrogen addition in a passive pre‐chamber ignited SI engine for passenger car applications

Hydrogen is one of the most promising alternative fuels for the transportation industry. The use of hydrogen to enable lean burn in internal combustion engines is an attractive solution for reducing CO2 emissions from two points of views: the substitution of carbon-based fuels and the increased thermal efficiency due to lean operation. Combining this strategy with the passive pre-chamber ignition system with gasoline/hydrogen blends is even more interesting. The main limitations of the passive pre-chamber concept in a high compression ratio spark-ignition engine were shown through engine experiments. A numerical study was then performed to evaluate the chance of extending the dilution limit by using hydrogen along with this technology. Results show how the use of hydrogen provides considerable benefits in the main chamber combustion process by enhancing the thermo-chemical properties of the mixture, increasing the flame speed, and improving the flame structure. Using an adequate gasoline-hydrogen blend proved to enable optimum burning rates at lean conditions, leading to a relevant thermal efficiency gain.

Effect of vertical location of the spark plug on the performance of a raw biogas-fueled variable compression ratio spark ignition engine

The present experimental investigations deal with the spark plug location and its effect on the performance and emission of a 100% raw biogas-fueled variable compression ratio engine. Different mea...

Combined impact of compression ratio and re-circulated exhaust gas on the performance of a biogas fueled spark ignition engine

The usage of biogas as a potential fuel in a spark ignition (SI) engine is the theme for the present study. The exhaust gas recirculation (EGR) is a significant technique for improving the performance of the SI engine. Thus, the novelty of the experimental investigations lies in implementing the EGR technique for emission control of the biogas-fueled engine. The raw biogas (52% methane and 47% carbon dioxide), obtained from a biogas digester (using cow dung as the source), was the engine fuel for a four stroke, water cooled, variable compression ratio SI engine set-up. Here, the engine performance and emission related parameters were measured. When operated in the raw biogas mode at an optimum spark timing of 45 °CA before the top dead center, the engine produced maximum torques of 11 N m, 14 N m, and 16 N m for compression ratios 8, 9, and 10, respectively. The effect of different EGR rates on the emission control was also investigated. The net heat release rate without EGR was found to be 22.623J/°CA at 368 °CA, which further reduced to 14.233 J/°CA at 386 °CA for EGR10. Moreover, it was clearly evident that low EGR rates (below 10%) were effective in reducing NOX significantly, with minor compromise in power and brake specific fuel consumption. But the emissions of hydrocarbon and carbon monoxide were found to be higher with the increase in EGR. The operation of the engine with medium or heavy EGR rates resulted in issues related to intense pressure fluctuations and large cycle-to-cycle variation in performance. Thus, the present investigations recommend the use of low EGR (below 10%) in a biogas-based engine for lower NOX emission and better fuel efficiency.

Energy and exergy based performance evaluation of variable compression ratio spark ignition engine based on experimental work

The present communication deals with the study of energy and exergy analysis of variable compression ratio four stroke spark ignition engine based on experimental work. The effect of varying compression ratio from 6 to 10 is analysed on both energy and exergy based approach. Both energy and exergy distributions are evaluated at different compression ratios for different rpm. The results show that as compression ratio increased from 6 to 10, the maximum power output is obtained at compression ratio 10 at 1800 rpm i.e. 3.80 kW. The maximum energy and exergy efficiencies are found to be 28.55% and 27.35% respectively at compression ratio 9 for 1200 rpm. Entropy generation found to be maximum for compression ratio 7 i.e. 36.47 W/K at 1800 rpm and minimum for compression ratio 9 i.e. 15.68 W/K at 1200 rpm. The results of this work revealed that exergy destruction of 10.87 kW found to be maximum at compression ratio 7 for 1800 rpm. This conclusion drawn from the study that applying both energy and exergy analysis give a more valuable understanding of performance and improvement of internal combustion engines by locating and then reducing the exergy loss at that location. Application of alternative gaseous fuels, exhaust heat recovery techniques, lean and low temperature combustion strategies reduce these exergy losses.

Concept development and prediction of VCR engine performance using slider crank pin mechanism based on quasi-dimensional combustion modeling

Energy, economy and pollution factor of internal combustion engine profoundly influence the development of the society. It is well known that efficiency of an internal combustion engine increases by compression ratio, and is limited due to knocking and high thermal stress development in the combustion chamber of an engine. On another side, an efficiency of internal combustion engine decreases toward the more top engine speed. Considering this, a concept is proposed which can change its compression ratio with speed. Variation in compression ratio is achieved by a change in stroke length through moving crank pin within the crank. In this paper the mechanism of operation and prediction of performance characteristics of variable compression ratio spark ignition engine with varying speed using quasi-dimensional combustion simulation mode is presented. It was observed that proposed mechanism provides better fuel efficiency at higher engine speed. Further, it is inferred that 3 mm increase in crank length results in 7% increment in thermal efficiency and 8% decrement in brake specific fuel consumption for 13 compression ratio at 6000 rpm.

Interactive control of combustion stability and operating limits in a biogas-fueled spark ignition engine with high compression ratio

The use of high compression ratios on spark ignition engines enables the increase of thermal efficiency, but also contributes to the reduction of high load limit because of the higher auto-ignition tendency in the end-gas. Gaseous fuels provide a good option to expand the high load limits because of their high octane ratings, mostly in small engines. Biogas is a renewable fuel, mainly composed by $$\hbox {CH}_{4}$$ and $$\hbox {CO}_{2}$$ that exhibits high auto-ignition temperature and slow laminar flame speed. When biogas is burned in spark ignition engines partial and total misfire at low loads counteract the benefits achieved at high loads in which knocking combustion is reduced, hence the design of an effective control of the operating range based on the real-time observation of combustion instabilities is desirable. This paper presents an interactive control of the safe operating range through the modification of the spark time, equivalent ratio and throttle valve opening, taking as feedback the combustion instabilities, which are calculated from the in-cylinder pressure evolution for a biogas-fueled high compression ratio spark ignition engine. The interactive control was tested on a modified diesel engine converted to spark-ignition, original compression ratio of 15.5:1 and fueled with biogas. Control was able to keep a safe operating range with a maximum throttle valve opening of 39%, equivalence ratios within 0.6 and 1, and spark advances in the range of 329–358 crank angle degree. The coefficient of variation of IMEP was lower than 8%, whereas the maximum average knocking intensity was close to 2.5.

The Effect of Exhaust Gas Recirculation (EGR) on the Emission of a Single Cylinder Spark Ignition Engine

A single cylinder variable compression ratio spark ignition engine type PRODIT was used in this study. The experiments were conducted with gasoline fuel (80 octane No.)at equivalence ratio (Ø =1). This study examined the effects of exhaust gas recirculation on emission. It was conducted at engine speeds (1500, 1900, 2300 and 2700 r.p.m.).The exhaust gases were added in volumetric ratios of 10%, 20% and 30% of the entering air/fuel charge. The results showed that the EGR addition decreases the CO2 concentrations, in the same time CO and HC concentrations increase remarkably. NOx concentration decreased highly with the increase of EGR percentage at variable engine speeds and constant torque. Also, it decreased when the engine run at constant speed and variable engine torque. The exhaust gas temperature decreased with increasing EGR ratio.

Criterios para el procesamiento y evaluación de datos experimentales para un motor de encendido provocado de alta relación de compresión

Este artículo presenta los resultados de la evaluación de estrategias de análisis desarrolladas para los motores de combustión convencionales aplicadas al estudio de un motor de encendido provocado de alta relación de compresión. El motor objeto de análisis ha sido obtenido a partir de la transformación a modo encendido provocado de un motor Diesel estacionario. Se ha analizado la precisión del cálculo del dosado relativo a partir de la composición de los gases de escape, el criterio para establecer el inicio de la combustión usando la fracción de calor liberado y el efecto del cálculo de la masa residual en el balance de energía al interior del cilindro. Los resultados sugieren que las estrategias de análisis utilizadas son aplicables a este tipo de motores, pese a tener diferencias de diseño y operacionales respecto a las tecnologías convencionales.

The Effect of Exhaust Gas Recirculation (EGR) on the Emission of a Single Cylinder Spark Ignition Engine

A single cylinder variable compression ratio spark ignition engine type PRODIT was used in this study. The experiments were conducted with gasoline fuel (80 octane No.)at equivalence ratio (O =1). This study examined the effects of exhaust gas recirculation on emission. It was conducted at engine speeds (1500, 1900, 2300 and 2700 r.p.m.).The exhaust gases were added in volumetric ratios of 10%, 20% and 30% of the entering air/fuel charge. The results showed that the EGR addition decreases the CO2 concentrations, in the same time CO and HC concentrations increase remarkably. NOx concentration decreased highly with the increase of EGR percentage at variable engine speeds and constant torque. Also, it decreased when the engine run at constant speed and variable engine torque. The exhaust gas temperature decreased with increasing EGR ratio.

Influence of air and EGR dilutions on improving performance of a high compression ratio spark-ignition engine fueled with methanol at light load

Methanol is a promising alternative fuel for the spark-ignition engines and it is applicable to dilution combustion for improving the thermal efficiency in the engine port load due to desirable fuel characteristics. However, under the pressures pursuing lower energy consumption rate and emission reduction of internal-combustion engines, how to achieve lower NOx emission while keeping the high thermal efficiency at the same time becomes a key challenge for dilution combustion. To get better “trade-off” relationship between specific fuel consumption and NOx emissions, the effect of three dilution substances, including air, cooled EGR and hot EGR on the engine combustion, performance and emissions was experimentally investigated at a port-injection spark ignition methanol engine which was modified from a diesel engine. The research results indicated that comparing with the air dilution, the cooled EGR has a more sensitive effect to the combustion characteristics. Under a same dilution level, the ignition delay and combustion duration were longer and cycle-by-cycle variations were increased for EGR dilution. Both air and cooled EGR dilutions have a possibility of improving the fuel consumption rate of the engine. Meanwhile, the cooled EGR dilution could decrease the NOx emission faster than the air dilution at the same dilution coefficients, and it also reduces the brake-specific emissions of HC and CO. If a higher NOx emission is tolerant, the air could be a superior dilution charge due to its higher torque output and lower application costs. However, the cooled EGR dilution can achieve a better balance relationship between torque output and NOx emission under the very low NOx level. Compared with cooled EGR, the hot EGR can improve the engine combustion performance, and it can achieve a better relationship between torque output and NOx emission under dilution coefficients of 1.45 and 1.65.

A comprehensive engine to drive-cycle modelling framework for the fuel economy assessment of advanced engine and combustion technologies

A comprehensive engine to drive-cycle modelling framework has been developed for evaluating fuel economy improvements of new engine technologies. The framework comprises three key components: (a) full engine system models and routines for the generation of engine performance and fuel consumption maps; (b) an improved experimental heat release analysis and model calibration tool, which was created by coupling an in-house heat release analysis program to an engine cycle simulation, and which can be used for model calibration and validation when experimental data are available; and (c) an integrated vehicle modelling and drive-cycle simulation platform for fuel economy assessment. The framework implementation has been demonstrated through a fuel economy study of three engine and combustion technologies: a conventional spark-ignition (SI) engine, a high compression ratio SI engine with early intake valve closing (EIVC), and a homogeneous-charge compression ignition engine (HCCI) employing a recompression valve strategy, used in dual-mode SI-HCCI operation. Simulation results for three drive cycles indicate potential fuel economy gains of the order of 7–11% for the high-compression EIVC SI engine and 7–21% for the dual-mode HCCI engine configurations. Further analysis of the latter, however, reveals frequent mode switching and short excursions in the HCCI region, which could be a challenge during practical implementation, and potentially result in reduced fuel economy gains.