Pre-ignition is a type of irregular combustion that occurs in boosted direct injection gasoline e... more Pre-ignition is a type of irregular combustion that occurs in boosted direct injection gasoline engines when one or more auto-ignition events occur before to spark ignition. Due to the direct injection of fuel into the cylinder, some liquid fuel may splash off the walls, dragging along lubricating oil. The self-ignition of liquid fuel/lubricant droplets is one of the pre-ignition sources studied. To test this stochastic behavior in a controlled manner, we examined the auto-ignition of a single droplet of a hexadecane-fuel mixture, with hexadecane serving as a surrogate for the lub oil. This experiment involved suspending a single hexadecane-fuel mixture droplet on a thermocouple bead in preheated air at temperatures ranging from 150 to 300 ° C over a wide range of pressures (4-30 bar). Various fuels with RON values ranging from 0 to 120 were blended with hexadecane at varying volume percentages of fuel in hexadecane from 0% to 100% to determine the droplet's time to ignition, de...
N umerous studies have attributed pre-ignition events in turbocharged spark ignited engines to th... more N umerous studies have attributed pre-ignition events in turbocharged spark ignited engines to the autoignition of lubricant oil-fuel mixture droplets. These droplets result from the interaction of the directly injected fuel spray on the lubricant oil film on the cylinder walls, causing fuel splashing to pull oil off the walls, forming droplets. The dilution of the oil by the fuel also changes lubricant oil droplet properties. Therefore, it is important to understand lubricating oils, with and without fuel dilution, as a possible ignition source in pre-ignition and super knock events. In this work, a constant volume (4 L) combustion chamber (CVCC) that allows the introduction of a single droplet of lubricating oil has been built. It is capable of operation at elevated pressures and temperatures. To simulate the droplet-induced pre-ignition event, a droplet injection system was incorporated into the vessel. The oil droplet was suspended on the junction of a thermocouple where the instantaneous internal droplet temperature was measured throughout the oil droplet lifetime. The experiments were carried out in an air atmosphere heated to 300 °C. The ambient pressure was varied from 2-15 bar. In the present work, the effect of pressure on droplet ignition of conventional engine oil (SAE 15 W-40), its surrogate hexadecane (C 16 H 34), and hexadecane mixed with lubricant oil additives has been investigated to understand the fundamental physics of droplet-induced ignition. The objective of this study is to determine the probability that an oil droplet will ignite at temperatures and pressures relevant to modern turbocharged GDI engines.
T he auto-ignition of liquid fuel and lubricant oil droplets is considered as one of the possible... more T he auto-ignition of liquid fuel and lubricant oil droplets is considered as one of the possible sources of preignition. Researchers are continually finding new ways to form advanced lubricant oil by changing its composition and varying different oil additives to prevent the occurrence of this event. This study investigates additives for lubricants to suppress its auto-ignition tendency. Three sets of mixtures were prepared. The first set of mixtures were prepared by adding different alcohols namely ethanol, and methanol to the commercial lubricant oil (SAE 15W-40) in ratio of 1-5 % by vol The second set of mixtures were prepared by mixing SAE 15W-40 with aforementioned alcohols (1 % vol.) and H 2 O (1 % vol.). Lastly, the third set of mixtures were prepared by adding toluene to SAE 15W-40 in (1 %-5% by vol.). Two experimental setups were used in the current work. An Ignition Quality Tester (IQT) was used to investigate the mixtures' ignition delay time (IDT) following standard ASTM D6890 procedure, and a larger constant volume combustion chamber (CVCC) was used to investigate the combustion characteristics of a suspended single oil droplet. In the CVCC chamber, the droplet was ignited in an atmosphere of air at 300 °C and pressure ranging from 4 bar-22 bar at 6 bar interval pressures. IDT of lubricant oil was considered as the base IDT, which was compared to those of other mixtures. Addition of alcohols and water in lubricant oil showed a significant increase in IDT compared to toluene addition. On the contrary, the addition of toluene resulted in a decrease in IDT. Among the alcohols, methanol addition showed higher IDT than ethanol addition. Alcohols increased the IDT effectively only beyond the addition of > 4 % by vol.
Pre-ignition is an abnormal combustion event that may occur in boosted direct injection gasoline ... more Pre-ignition is an abnormal combustion event that may occur in boosted direct injection gasoline engines, where one or more auto-ignition events are observed before spark ignition. Due to the direct injection of fuel into the cylinder, some liquid fuel may splash off the walls, pulling lubricating oil with it. The auto-ignition of liquid fuel/lubricant droplets is considered as one of the possible sources of pre-ignition. To assess this stochastic phenomenon in a controlled way, the autoignition of a single droplet of a hexadecane-fuel mixture was investigated, with hexadecane serving as a surrogate for the lubricating oil. This experiment included suspending a single hexadecane-fuel mixture droplet on a thermocouple bead in preheated air, at a temperature of 300 ± 4°C, in a constant volume chamber over a wide range of pressures (4−30 bar). Four different fuels with a range of research octane number (RON) between 70 and 120 were mixed with hexadecane at a volume percentage of 75% hexadecane to 25% fuel to investigate the time to ignition of the droplet, designated as TI. The TI was measured by recording the droplet temperature history simultaneously with high-speed droplet imaging. The droplet ignition is triggered by the auto-ignition of the combustible mixture formed by the hexadecane-fuel mixture's vapor that mixes with the hot ambient air around the droplet. An empirical model was proposed to predict the TI in terms of pressure and the mixture's RON. At constant pressure, the rate of evaporation of the mixture's droplet increases with increasing RON. The time to ignition is seen to increase exponentially as the fuel's RON used in the mixture increases. On the other hand, for a given fuel RON, the time to ignition decreases with increasing ambient pressure. The empirical model shows that at pressures above 20 bar, the dilution of hexadecane by the different fuels has no significant effect on delaying the auto-ignition of the droplet.
In Taiwan, due to the limited capacity of waste cooking oil, palm oil has been viewed as the pote... more In Taiwan, due to the limited capacity of waste cooking oil, palm oil has been viewed as the potential low-cost imported feedstock for producing biodiesel, in the way of obtaining oil feedstock in Malaysia and producing biodiesel in Taiwan. This study aims to evaluate the cradle-to-grave life cycle environmental performance of palm biodiesel within two different Asian countries, Malaysia and Taiwan. The phases of the life cycle such as direct land-use-change impact, plantation and milling are investigated based on the Malaysia case and those of refining, and fuel production as well as engine combustion is based on Taiwan case. The greenhouse gas (GHG) emission and energy consumption for the whole life cycle were calculated as-28.29 kg CO 2-equiv. and ?23.71 MJ/kg of palm-derived biodiesel. We also analyze the impacts of global warming potential (GWP) and the payback time for recovering the GHG emissions when producing and using biodiesel. Various scenarios include (1) clearing rainforest or peat-forest; (2) treating or discharging palm-oil-milling effluent (POME) are further developed to examine the effectiveness of improving the environmental impacts Keywords Life cycle assessment Á Palm biodiesel Á Global warming potential Á Energy consumption Á Land-usechange Á Payback time
Pre-ignition is a type of irregular combustion that occurs in boosted direct injection gasoline e... more Pre-ignition is a type of irregular combustion that occurs in boosted direct injection gasoline engines when one or more auto-ignition events occur before to spark ignition. Due to the direct injection of fuel into the cylinder, some liquid fuel may splash off the walls, dragging along lubricating oil. The self-ignition of liquid fuel/lubricant droplets is one of the pre-ignition sources studied. To test this stochastic behavior in a controlled manner, we examined the auto-ignition of a single droplet of a hexadecane-fuel mixture, with hexadecane serving as a surrogate for the lub oil. This experiment involved suspending a single hexadecane-fuel mixture droplet on a thermocouple bead in preheated air at temperatures ranging from 150 to 300 ° C over a wide range of pressures (4-30 bar). Various fuels with RON values ranging from 0 to 120 were blended with hexadecane at varying volume percentages of fuel in hexadecane from 0% to 100% to determine the droplet's time to ignition, de...
N umerous studies have attributed pre-ignition events in turbocharged spark ignited engines to th... more N umerous studies have attributed pre-ignition events in turbocharged spark ignited engines to the autoignition of lubricant oil-fuel mixture droplets. These droplets result from the interaction of the directly injected fuel spray on the lubricant oil film on the cylinder walls, causing fuel splashing to pull oil off the walls, forming droplets. The dilution of the oil by the fuel also changes lubricant oil droplet properties. Therefore, it is important to understand lubricating oils, with and without fuel dilution, as a possible ignition source in pre-ignition and super knock events. In this work, a constant volume (4 L) combustion chamber (CVCC) that allows the introduction of a single droplet of lubricating oil has been built. It is capable of operation at elevated pressures and temperatures. To simulate the droplet-induced pre-ignition event, a droplet injection system was incorporated into the vessel. The oil droplet was suspended on the junction of a thermocouple where the instantaneous internal droplet temperature was measured throughout the oil droplet lifetime. The experiments were carried out in an air atmosphere heated to 300 °C. The ambient pressure was varied from 2-15 bar. In the present work, the effect of pressure on droplet ignition of conventional engine oil (SAE 15 W-40), its surrogate hexadecane (C 16 H 34), and hexadecane mixed with lubricant oil additives has been investigated to understand the fundamental physics of droplet-induced ignition. The objective of this study is to determine the probability that an oil droplet will ignite at temperatures and pressures relevant to modern turbocharged GDI engines.
T he auto-ignition of liquid fuel and lubricant oil droplets is considered as one of the possible... more T he auto-ignition of liquid fuel and lubricant oil droplets is considered as one of the possible sources of preignition. Researchers are continually finding new ways to form advanced lubricant oil by changing its composition and varying different oil additives to prevent the occurrence of this event. This study investigates additives for lubricants to suppress its auto-ignition tendency. Three sets of mixtures were prepared. The first set of mixtures were prepared by adding different alcohols namely ethanol, and methanol to the commercial lubricant oil (SAE 15W-40) in ratio of 1-5 % by vol The second set of mixtures were prepared by mixing SAE 15W-40 with aforementioned alcohols (1 % vol.) and H 2 O (1 % vol.). Lastly, the third set of mixtures were prepared by adding toluene to SAE 15W-40 in (1 %-5% by vol.). Two experimental setups were used in the current work. An Ignition Quality Tester (IQT) was used to investigate the mixtures' ignition delay time (IDT) following standard ASTM D6890 procedure, and a larger constant volume combustion chamber (CVCC) was used to investigate the combustion characteristics of a suspended single oil droplet. In the CVCC chamber, the droplet was ignited in an atmosphere of air at 300 °C and pressure ranging from 4 bar-22 bar at 6 bar interval pressures. IDT of lubricant oil was considered as the base IDT, which was compared to those of other mixtures. Addition of alcohols and water in lubricant oil showed a significant increase in IDT compared to toluene addition. On the contrary, the addition of toluene resulted in a decrease in IDT. Among the alcohols, methanol addition showed higher IDT than ethanol addition. Alcohols increased the IDT effectively only beyond the addition of > 4 % by vol.
Pre-ignition is an abnormal combustion event that may occur in boosted direct injection gasoline ... more Pre-ignition is an abnormal combustion event that may occur in boosted direct injection gasoline engines, where one or more auto-ignition events are observed before spark ignition. Due to the direct injection of fuel into the cylinder, some liquid fuel may splash off the walls, pulling lubricating oil with it. The auto-ignition of liquid fuel/lubricant droplets is considered as one of the possible sources of pre-ignition. To assess this stochastic phenomenon in a controlled way, the autoignition of a single droplet of a hexadecane-fuel mixture was investigated, with hexadecane serving as a surrogate for the lubricating oil. This experiment included suspending a single hexadecane-fuel mixture droplet on a thermocouple bead in preheated air, at a temperature of 300 ± 4°C, in a constant volume chamber over a wide range of pressures (4−30 bar). Four different fuels with a range of research octane number (RON) between 70 and 120 were mixed with hexadecane at a volume percentage of 75% hexadecane to 25% fuel to investigate the time to ignition of the droplet, designated as TI. The TI was measured by recording the droplet temperature history simultaneously with high-speed droplet imaging. The droplet ignition is triggered by the auto-ignition of the combustible mixture formed by the hexadecane-fuel mixture's vapor that mixes with the hot ambient air around the droplet. An empirical model was proposed to predict the TI in terms of pressure and the mixture's RON. At constant pressure, the rate of evaporation of the mixture's droplet increases with increasing RON. The time to ignition is seen to increase exponentially as the fuel's RON used in the mixture increases. On the other hand, for a given fuel RON, the time to ignition decreases with increasing ambient pressure. The empirical model shows that at pressures above 20 bar, the dilution of hexadecane by the different fuels has no significant effect on delaying the auto-ignition of the droplet.
In Taiwan, due to the limited capacity of waste cooking oil, palm oil has been viewed as the pote... more In Taiwan, due to the limited capacity of waste cooking oil, palm oil has been viewed as the potential low-cost imported feedstock for producing biodiesel, in the way of obtaining oil feedstock in Malaysia and producing biodiesel in Taiwan. This study aims to evaluate the cradle-to-grave life cycle environmental performance of palm biodiesel within two different Asian countries, Malaysia and Taiwan. The phases of the life cycle such as direct land-use-change impact, plantation and milling are investigated based on the Malaysia case and those of refining, and fuel production as well as engine combustion is based on Taiwan case. The greenhouse gas (GHG) emission and energy consumption for the whole life cycle were calculated as-28.29 kg CO 2-equiv. and ?23.71 MJ/kg of palm-derived biodiesel. We also analyze the impacts of global warming potential (GWP) and the payback time for recovering the GHG emissions when producing and using biodiesel. Various scenarios include (1) clearing rainforest or peat-forest; (2) treating or discharging palm-oil-milling effluent (POME) are further developed to examine the effectiveness of improving the environmental impacts Keywords Life cycle assessment Á Palm biodiesel Á Global warming potential Á Energy consumption Á Land-usechange Á Payback time
Uploads
Papers by Sumit Maharjan