Search Results

Ethanol fuel blends with gasoline for spark ignition (SI) internal combustion engines are widely used on account of their advantages in terms of fuel economy and emissions reduction potential. The focus of this paper is to study the effects of these blends on combustion characteristics such as in-cylinder pressure profiles, gas-phase emissions (e.g., unburned hydrocarbons, NOx) and particulates (e.g., particulate matter and particle number) using both measurement campaigns and digital engineering workflows. Nineteen load-speed operating points in a 1L 3-cylinder GDI SI engine were measured and modelled. The measurements for in-cylinder pressure and emissions were repeated at each operating point for three types of fuel: gasoline (E0, 0% by volume of ethanol blend), E10 (10 % by volume of ethanol blend) and E20 (20% by volume of ethanol blend).

The combustion characteristics and soot emissions of three types of fuels were studied in a high pressure and temperature vessel. In order to achieve better volatility, proper cetane number and high oxygen content, the newly designed WDEP fuel was proposed and investigated. It is composed of wide distillation fuel (WD), PODE3-6 mixture (PODEn) and ethanol. For comparison, the test on WD and the mixture of PODEn-ethanol (EP) are also conducted. OH* chemiluminescence during the combustion was measured and instantaneous PLII was also applied to reveal the soot distribution. Abel transformation was adopted to calculate the total soot of axisymmetric flame. The results show that WDEP has similar ignition delays and flame lift-off lengths to those of WD at 870-920 K. But the initial ignition locations of WDEP flame in different cycles were more concentrated, particularly under the condition of low oxygen atmosphere.

Conventional diesel-fuelled Partially Premixed Compression Ignition (PPCI) engines have been investigated by many researchers previously. However, the ease of ignition and difficulty of vaporization of diesel fuel make it imperfect for PPCI combustion. In this study, dieseline (blending of diesel and gasoline) was looked into as the Partially Premixed Compression Ignition fuel for its combination of two fuel properties, ignition-delay-increasing characteristics and higher volatility, which make it more suitable for PPCI combustion compared to neat diesel. A series of tests were carried out on a Euro IV light-duty common-rail diesel engine, and different engine modes, from low speed/load to middle speed/load were all tested, under which fuel blend ratios, EGR rates, injection timings and quantities were varied. The emissions, fuel consumption and combustion stability of this dieseline-fuelled PPCI combustion were all investigated.

The effects of different biodiesel blends on engine-out emissions under various transient conditions were investigated in this study using fast response diagnostic equipment. The experimental work was conducted on a modern 3.0 L, V6 high pressure common rail diesel engine fuelled with mineral diesel (B0) and three different blends of rapeseed methyl esters (RME) (B30, B60, B100 by volume) without any modifications of engine parameters. DMS500, Fast FID and Fast CLD were used to measure particulate matter (PM), total hydrocarbon (THC) and nitrogen monoxide (NO) respectively. The tests were conducted during a 12 seconds period with two tests in which load and speed were changed simultaneously and one test with only load changing. The results show that as biodiesel blend ratio increased, total particle number (PN) and THC were decreased whereas NO was increased for all the three transient conditions.

There is an increasing recognition of injector deposit (ID) formation in fuel injection equipment as direct injection spark ignition (DISI) engine technologies advance to meet increasingly stringent emission legislation and fuel economy requirements. While it is known that the phenomena of ID in DISI engines can be influenced by changes in fuel composition, including increasing usage of aliphatic alcohols and additive chemistries to enhance fuel performance, there is however still a great deal of uncertainty regarding the physical and chemical structure of these deposits, and the mechanisms of deposit formation. In this study, a mechanical cracking sample preparation technique was developed to assess the deposits across DISI injectors fuelled with gasoline and blends of 85% ethanol (E85).

Dieseline combustion as a concept combines the advantages of gasoline and diesel by offline or online blending the two fuels. Dieseline has become an attractive new compression ignition combustion concept in recent years and furthermore an approach to a full-boiling-range fuel. High speed imaging with near-parallel backlit light was used to investigate the spray characteristics of dieseline and pure fuels with a common rail diesel injection system in a constant volume vessel. The results were acquired at different blend ratios, and at different temperatures and back pressures at an injection pressure of 100MPa. The penetrations and the evaporation states were compared with those of gasoline and diesel. The spray profile was analyzed in both area and shape with statistical methods. The effect of gasoline percentage on the evaporation in the fuel spray was evaluated.

Atomization of fuel sprays is a key factor in controlling the combustion quality in the direct-injection engines. In this present work, the effect of saturation ratio (Rs) on the near nozzle spray patterns of ethanol was investigated using an ultra-high speed imaging technique. The Rs range covered both flash-boiling and non-flash boiling regions. Ethanol was injected from a single-hole injector into an optically accessible constant volume chamber at a fixed injection pressure of 40 MPa with different fuel temperatures and back pressures. High-speed imaging was performed using an ultrahigh speed camera (1 million fps) coupled with a long-distance microscope. Under non-flash boiling conditions, the effect of Rs on fuel development was small but observable. Clear fuel collision can be observed at Rs=1.5 and 1.0. Under the flash boiling conditions, near-nozzle spray patterns were significant different from the non-flash boiling ones.

The new fuel, 2, 5-dimenthylfuran, known as DMF, captured worldwide attention since the discovery of its new production method. As a potential bio-fuel, DMF is competitive to gasoline in many areas, such as energy density, combustion efficiency and emissions. However, little work has been performed on its unconventional combustion mode. In this work, high speed imaging and thermal investigation are carried out to study DMF and gasoline dual-injection on a single cylinder, direct injection spark ignition optical engine. This dual-injection strategy combines direct injection (DI) and port fuel injection (PFI) simultaneously which means two different fuels can blend in the cylinder with any ratio. It provides a flexible way to use bio-fuels with gasoline. DMF DI with gasoline PFI and ethanol DI with gasoline PFI are studied under different injection proportions (by volume) and IMEPs.

2, 5-Dimethylfuran (DMF) has been receiving increasing interest as a potential alternative fuel to fossil fuels, owing to the recent development of new production technology. However, the influence of DMF properties on the in-cylinder fuel spray and its evaporation, subsequent combustion processes as well as emission formation in current gasoline direct injection (GDI) engines is still not well understood, due to the lack of comprehensive understanding of its physical and chemical characteristics. To better understand the spray characteristics of DMF and its application to the IC engine, the fuel sprays of DMF and gasoline were investigated by experimental and computational methods. The shadowgraph and Phase Doppler Particle Analyzer (PDPA) techniques were used for measuring spray penetration, droplet velocity and size distribution of both fuels.

It is well-known that gasoline is a poor fuel for HCCI operation due to its high autoignation temperature, while the major problem for diesel HCCI is that the ignition temperature of diesel fuel is too low so that diesel autoignites too early. Interestingly a blend of gasoline and diesel fuel could have desirable characteristics for HCCI operation. The negative valve overlap (NVO) is a practical and feasible control mode for production applications of the HCCI concept. At present, the most serious problem is the difficulty to control the moment of auto-ignition and extend the limited operating window of smooth HCCI operation. In this paper, the promotive effects of diesel fuel on gasoline HCCI combustion were experimentally examined. The diesel fuel as additive was added in advance in different proportion (10% and 20% by mass) into gasoline for the purpose of improving its ignitability. The experiments conducted on a gasoline HCCI engine which was naturally aspirated and unthrottled.

Gasoline and diesel, the two fuels with very different characteristics and with wide availability for conventional engine use, were blended as a HCCI engine fuel. Gasoline, with high volatility, easy vaporization and mixture formation, is used to form the homogeneous charge. Diesel fuel which has good ignitability and fast combustion at the conditions predominating in the HCCI environment, is used to dominate the auto-ignition and restrain the knocking combustion. It is expected that these two different fuels with opposite but complementary properties can be used to reach a good compromise in HCCI combustion. Experiments, conducted with moderate compression ratios (CR) and using two modes of HCCI control, i.e. intake heating with CR 15.0 and negative valve overlap (NVO) with CR 10.4, yielded results that prove this expectation.

Liquefied alternative fuels offer great potential benefits in reducing exhaust emissions and improving fuel economy of automotive engines. In order to achieve the best performance of the engine running with such fuels, it is critical to have an appropriate fuel system. In the present work, a new electronically controlled common-rail injection system has been specially designed and tested for the direct injection of liquefied alternative fuels, since a conventional pump-line-injector injection system in the conventional diesel engine was not suitable for the purpose. Experimental work has been carried out to examine and improve matching of the fuel injection system on a new fuel injection pump test bench. The preliminary engine bench test has demonstrated that this arrangement meets the requirement for the operating characteristics of a fuel injection system in a direct injection diesel engine operating with dimethyl ether (DME).

Diesel engines are the versatile power source and is widely used in passenger car and commercial vehicle applications. Environmental temperature conditions, fuel quality, fuel injection strategies and lubricant have influence on cold start performance of the diesel engines. Strategies to overcome the cold start problem at very low ambient temperature include preheating of intake air, coolant, cylinder block. The present research work investigates the effect of coolant temperatures on passenger car diesel engine’s performance and exhaust emission characteristics during the cold start at cold ambient temperature conditions. The engine is soaked in the -7°C environment for 6 hours. The engine coolant is preheated to the desired coolant temperatures of 10 and 20°C by an external heater and the start ability tests were performed.

The combustion timing, work output and in-cylinder peak pressure for HCCI engines often converge to a stable equilibrium point, which implies that the HCCI combustion may have a self-stabilization feature. It is thought that this behavior is due to the competing residual-induced heating and dilution of the reactant gas. As one of the most important features of HCCI combustion, the self-stabilization behavior can give great guidance to people for designing controller for HCCI engine control. The self-stabilization features of HCCI combustion had been observed by many researchers and mentioned in some publications. However, there is no report to experimentally analyze this phenomenon individually. Due to the fuel injection normally ending during the NVO process and the spark plug is turned off for HCCI engines, there is no direct control approach between the Intake Valve Close (IVC) and the start of combustion.

Using EGR instead of throttle to control the load of a stoichiometric dual-fuel dieseline (diesel and gasoline) compression ignition (SDCI) engine with three-way catalyst (TWC) aftertreatment is considered a promising technology to address the challenges of fuel consumption and emissions in future internal combustion engines. High-speed imaging is used to record the flame signal in a single-cylinder optical engine with a PFI+DI dual injection system. The premixed blue flame is identified and separated using green and blue channels in RGB images. The effects of injection timing on SDCI combustion are studied. An earlier injection strategy is found to be ideal for soot reduction; however, the ignition-injection decoupling problem results in difficulties in combustion control. It is also found that a split injection strategy has advantages in soot reduction and thermal efficiency.

Biodiesel is an oxygenated alternative fuel made from vegetable oils and animal fats via transesterification and the feedstock of biodiesel is diverse and varies between the local agriculture and market scenarios. Use of various feedstock for biodiesel production result in variations in the fuel properties of biodiesel. In this study, biodiesels produced from a variety of real world feedstock was examined to assess the performance and emissions in a light-duty engine. The objective was to understand the impact of biodiesel properties on engine performances and emissions. A group of six biodiesels produced from the most common feedstock blended with zero-sulphur diesel in 10%, 30% and 60% by volume are selected for the study. All the biodiesel blends were tested on a light-duty, twin-turbocharged common rail V6 engine. Their gaseous emissions (NOx, THC, CO and CO2) and smoke number were measured for the study.

The design and optimization of a modern spray-guided gasoline direct injection engine require a thorough understanding of the fuel spray characteristics and atomization process. The fuel spray Computational Fluid Dynamics (CFD) modeling technology can be an effective means to study and predict spray characteristics, and as a consequence, to drastically reduce experimental work during the engine development process. For this reason, an accurate numerical simulation of the spray evolution process is imperative. Different models based on aerodynamically-induced breakup mechanism have been implemented to simulate spray atomization process in earlier studies, and the effect of turbulence from the injector nozzle is recently being concerned increasingly by engine researchers. In this study, a turbulence-induced primary breakup model coupled with aerodynamic instability is developed.

Fuel spray atomization process is known to play a key role in affecting mixture formation, combustion efficiency and soot emissions in direct injection engines. The fuel spray Computational Fluid Dynamics (CFD) modeling technology can be an effective means to study and predict spray characteristics such as penetration, droplet size and droplet velocity, and as a consequence, to drastically reduce experimental work during the engine development process. For this reason, an accurate numerical simulation of the spray evolution process is imperative. Different approaches and various models based on aerodynamically induced breakup mechanism have been implemented to simulate spray atomization process in earlier studies, and the effects of turbulence and cavitation from the injector nozzle is recently being concerned increasingly by engine researchers. In this study, an enhanced turbulence and cavitation induced primary breakup model combining aerodynamic breakup mechanism is developed.

Gasoline Direct Injection (GDI) vehicles now make up the majority of European new car sales and a significant share of the existing car parc. Despite delivering measurable engine efficiency benefits, GDI fuel systems are not without issues. Fuel injectors are susceptible to the formation of deposits in and around the injector nozzles holes. It is widely reported that these deposits can affect engine performance and that different fuels can alleviate the buildup of those deposits. This project aims to understand the underlying mechanisms of how deposit formation ultimately leads to a reduction in vehicle performance. Ten GDI fuel injectors, with differing levels of coking were taken from engine testing and consumer vehicles and compared using a range of imaging and engine tests. At the time of writing, a new GDI engine test is being developed by the Co-ordinating European Council (CEC) to be used by the fuel and fuel additive industry.