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Journal Article

Transient Emissions Characteristics of a Turbocharged Engine Fuelled by Biodiesel Blends

2013-04-08
2013-01-1302
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.
Journal Article

The Particle Emissions Characteristics of a Light Duty Diesel Engine with 10% Alternative Fuel Blends

2010-05-05
2010-01-1556
In this study, the particle emission characteristics of 10% alternative diesel fuel blends (Rapeseed Methyl Ester and Gas-to-Liquid) were investigated through the tests carried out on a light duty common-rail Euro 4 diesel engine. Under steady engine conditions, the study focused on particle number concentration and size distribution, to comply with the particle metrics of the European Emission Regulations (Regulation NO 715/2007, amended by 692/2008 and 595/2009). The non-volatile particle characteristics during the engine warming up were also investigated. They indicated that without any modification to the engine, adding selected alternative fuels, even at a low percentage, can result in a noticeable reduction of the total particle numbers; however, the number of nucleation mode particles can increase in certain cases.
Journal Article

The Effect of Exhaust Throttling on HCCI - Alternative Way to Control EGR and In-Cylinder Flow

2008-06-23
2008-01-1739
Homogeneous Charge Compression Ignition (HCCI) has emerged as a promising technology for reduction of exhaust emissions and improvement of fuel economy of internal combustion engines. There are generally two proposed methods of realizing the HCCI operation. The first is through the control of gas temperature in the cylinder and the second is through the control of chemical reactivity of the fuel and air mixture. EGR trapping, i.e., recycling a large quantity of hot burned gases by using special valve-train events (e.g. negative valve overlap), seems to be practical for many engine configurations and can be combined with any of the other HCCI enabling technologies. While this method has been widely researched, it is understood that the operating window of the HCCI engine with negative valve overlap is constrained, and the upper and lower load boundaries are greatly affected by the in-cylinder temperature.
Technical Paper

The Comparative Study of Gasoline and n-butanol on Spray Characteristics

2014-10-13
2014-01-2754
n-butanol has been recognized as a promising alternative fuel for gasoline and may potentially overcome the drawbacks of methanol and ethanol, e.g. higher energy density. In this paper, the spray characteristics of gasoline and n-butanol have been investigated using a high pressure direct injection injector. High speed imaging and Phase Doppler Particle Analyzer (PDPA) techniques were used to study the spray penetration and the droplet atomization process. The tests were carried out in a high pressure constant volume vessel over a range of injection pressure from 60 to 150 bar and ambient pressure from 1 to 5 bar. The results show that gasoline has a longer penetration length than that of n-butanol in most test conditions due to the relatively small density and viscosity of gasoline; n-butanol has larger SMD due to its higher viscosity. The increase in ambient pressure leads to the reduction in SMD by 42% for gasoline and by 37% for n-butanol.
Technical Paper

Study on an Electronically Controlled Common-Rail Injection System for Liquefied Alternative Fuels

2005-05-11
2005-01-2085
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).
Technical Paper

Study of Near Nozzle Spray Characteristics of Ethanol under Different Saturation Ratios

2016-10-17
2016-01-2189
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.
Journal Article

Spray Characteristics Study of DMF Using Phase Doppler Particle Analyzer

2010-05-05
2010-01-1505
2,5-dimethylfuran (DMF) is currently regarded as a potential alternative fuel to gasoline due to the development of new production technology. In this paper, the spray characteristics of DMF and its blends with gasoline were studied from a high pressure direct injection gasoline injector using the shadowgraph and Phase Doppler Particle Analyzer (PDPA) techniques, This includes the spray penetration, droplet velocity and size distribution of the various mixtures. In parallel commercial gasoline and ethanol were measured in order to compare the characteristics of DMF. A total of 52 points were measured along the spray so that the experimental results could be used for subsequent numerical modeling. In summary, the experimental results showed that DMF and its blends have similar spray properties to gasoline, compared to ethanol. The droplet size of DMF is generally smaller than ethanol and decreases faster with the increase of injection pressure.
Technical Paper

Split-Injection Strategies under Full-Load Using DMF, A New Biofuel Candidate, Compared to Ethanol in a GDI Engine

2012-04-16
2012-01-0403
It is well known that direct injection (DI) is a technology enabler for stratified combustion in spark-ignition (SI) engines. At full load or wide-open throttle (WOT), partial charge stratification can suppress knock, enabling greater spark advance and increased torque. Such split-injection or double-pulse injection strategies are employed when using gasoline in DI (GDI). However, as the use of biofuels is set to increase, is this mode still beneficial? In the current study, the authors attempt to answer this question using two gasoline-alternative biofuels: firstly, ethanol; the widely used gasoline-alternative biofuel and secondly, 2,5-dimethylfuran (DMF); the new biofuel candidate. These results have been benchmarked against gasoline in a single-cylinder, spray-guided DISI research engine at WOT (λ = 1 and 1500 rpm). Firstly, single-pulse start of injection (SOI) timing sweeps were conducted with each fuel to find the highest volumetric efficiency and IMEP.
Technical Paper

Residual Gas Trapping for Natural Gas HCCI

2004-06-08
2004-01-1973
With the high auto ignition temperature of natural gas, various approaches such as high compression ratios and/or intake charge heating are required for auto ignition. Another approach utilizes the trapping of internal residual gas (as used before in gasoline controlled auto ignition engines), to lower the thermal requirements for the auto ignition process in natural gas. In the present work, the achievable engine load range is controlled by the degree of internal trapping of exhaust gas supplemented by intake charge heating. Special valve strategies were used to control the internal retention of exhaust gas. Significant differences in the degree of valve overlap were necessary when compared to gasoline operation at the same speeds and loads, resulting in lower amounts of residual gas observed. The dilution effect of residual gas trapping is hence reduced, resulting in higher NOx emissions for the stoichiometric air/fuel ratio operation as compared to gasoline.
Technical Paper

Research of the Atkinson Cycle in the Spark Ignition Engine

2012-04-16
2012-01-0390
In the automotive industry, engine downsizing has been widely accepted as an enabler to improving the fuel economy and reducing the CO₂ emissions. The Atkinson cycle is one of the key technologies. In this paper, the Atkinson cycle with different expansion ratios are compared and analyzed. The investigation is compared with the benchmark whose expansion and compression ratio are identical. The aim is to understand the inherent characteristics of the over-expansion and its effect on the engine performance and emissions. The simulation results show that, the Atkinson cycle produces higher efficiency due to over-expansion. The Atkinson cycle has higher internal EGR compared with the benchmark at equivalent conditions, which contributes to lower the NOx and CO emissions.
Technical Paper

Promotive Effect of Diesel Fuel on Gasoline HCCI Engine Operated with Negative Valve Overlap (NVO)

2006-04-03
2006-01-0633
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.
Technical Paper

Phenomenology of EGR in a Light Duty Diesel Engine Fuelled with Hydrogenated Vegetable Oil (HVO), Used Vegetable Oil Methyl Ester (UVOME) and Their Blends

2013-04-08
2013-01-1688
HVO contains paraffin only and UVOME is methyl ester with long chain alkyl while mineral diesel is complex compound and contains lots of aromatic and Naphthenic. This paper compares the effects of EGR on the two different types of biodiesels blends compared to diesel. The combustion performance and emissions of biodiesel blends of UVOME and HVO were investigated in a turbocharged direct injection V6 diesel engine with EGR swept from 0% to the calibration setting for diesel. The EGR sweep tests with increment of 5% were conducted at the engine speed of 1500 RPM for the load of between 72 Nm to 143 Nm, using sulfur-free diesel blended with UVOME and HVO at 30% and 60% by volume respectively. As the EGR rate was increased, the brake specific fuel consumption (BSFC) for each fuel was reduced at lower load but increased at higher load. The BSFC of mineral diesel was lower than UVOME blends and similar to the HVO blends.
Technical Paper

Operating Characteristics of a Homogeneous Charge Compression Ignition Engine with Cam Profile Switching - Simulation Study

2003-05-19
2003-01-1859
A single zone combustion model based on a chemical kinetic solver has been combined with a one-dimension thermo/gas dynamic engine simulation code to study the operating characteristics of a V6 engine in which Homogeneous Charge Compression Ignition (HCCI) operation (also referred to as ‘Controlled Auto-ignition” CAI) is enabled by a cam profile switching (CPS) system with negative valve overlap. An operational window within which HCCI combustion is possible has been identified and the limit of HCCI operating region for varied valve lift possibilities is explored. The mechanisms and potential fuel economy improvements within the HCCI envelope are studied and modelled results compared against data from similar engines. It is shown that for the best fuel economy the valve timing strategy needs to be selected very carefully, despite the engine's capability to operate at a range of valve timing combinations.
Technical Paper

Numerical Study of DMF and Gasoline Spray and Mixture Preparation in a GDI Engine

2013-04-08
2013-01-1592
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.
Technical Paper

Modelling and Experimental Investigations of Supercharged HCCI Engines

2006-04-03
2006-01-0634
This paper focuses on supercharged HCCI engines employing internal EGR that is obtained by the use of negative valve overlap. In HCCI engines, the absence of throttling coupled with the use of high compression ratio to facilitate auto-ignition and with the use of lean mixtures result in improved fuel efficiency. High dilution is required to control the auto-ignition and it also results in reduction of the production of NOx. To compensate for the charge dilution effect, the method used to recover the loss of power is to introduce more air in to the engine which allows introducing also more fuel while maintaining high lambda. A supercharger is required to introduce the required amount of air into the engine. The modelling investigation performed with Ricardo WAVE® coupled with CHEMKIN® and experimental investigation for supercharged HCCI show significant improvement in terms of extension of load range and reduction of NOx over the naturally aspirated HCCI and also over SI operation.
Technical Paper

Modelling Study of Combustion and Gas Exchange in a HCCI (CAI) Engine

2002-03-04
2002-01-0114
The main obstacle for the development of Homogeneous Charge Compression Ignition (HCCI) engines is the control of auto-ignition timing, and one key is to control the trapped gas temperature so as to enable the autoignition at the end of compression stroke. Using special valve mechanisms, very high residual gas mass fraction can be achieved to raise the charge temperature. Gas exchange process hence plays a crucial role in such HCCI engines because of its strong interaction with combustion. The modification of the gas exchange process in a 4-stroke automotive engine for HCCI combustion is not straightforward, since the engine must be able to operate across a considerably wide range of speeds and loads. Intake air temperatures and the valve mechanism need to be controlled in order to deliver optimal engine performance and fuel economy. This paper presents a modelling study of the combustion and gas exchange in a HCCI engine.
Journal Article

Low Ambient Temperature Effects on a Modern Turbocharged Diesel engine running in a Driving Cycle

2014-10-13
2014-01-2713
Engine transient operation has attracted a lot of attention from researchers due to its high frequency of occurrence during daily vehicle operation. More emissions are expected compared to steady state operating conditions as a result of the turbo-lag problem. Ambient temperature has significant influences on engine transients especially at engine start. The effects of ambient temperature on engine-out emissions under the New European Driving Cycle (NEDC) are investigated in this study. The transient engine scenarios were carried out on a modern 3.0 L, V6 turbocharged common rail diesel engine fuelled with winter diesel in a cold cell within the different ambient temperature ranging between +20 °C and −7 °C. The engine with fuel, coolant, combustion air and lubricating oil were soaked and maintained at the desired test temperatures during the transient scenarios.
Technical Paper

Investigation on the Spray Characteristics of DMF- Isooctane Blends using PDPA

2014-04-01
2014-01-1408
Little research has been done on spray characteristics of 2,5-dimethylfuran (DMF), since the breakthrough in its production method as an alternative fuel candidate. In this paper, the spray characteristics of pure fuels (DMF, Isooctane) and DMF-Isooctane blends under different ambient pressures (1 bar, 3 bar and 7 bar) and injection pressures (50 bar, 100 bar and 150 bar) were studied using Phase Doppler Particle Analyzer (PDPA) and high speed imaging. Droplet velocity, size distribution, spray angle and penetration of sprays were examined. Based on the results, DMF had larger SMD and penetration length than isooctane. The surface tension of fuel strongly influenced spray characteristics. Increasing the surface tension by 26 % resulted in 12 % increase in SMD. Higher ambient pressure increased the drag force, but SMD was not influenced by the increased drag force. However, the increased ambient pressure reduced the injection velocity and We number resulting in higher SMD.
Technical Paper

Investigation on the Performance of Diesel Oxidation Catalyst during Cold Start at L ow Temperature Conditions

2014-10-13
2014-01-2712
Cold start is a critical operating condition for diesel engines because of the pollutant emissions produced by the unstable combustion and non-performance of after-treatment at lower temperatures. In this research investigation, a light-duty turbocharged diesel engine equipped with a common rail injection system was tested on a transient engine testing bed to study the starting process in terms of engine performance and emissions. The engine (including engine coolant, engine oil and fuel) was soaked in a cold cell at −7°C for at least 8 hours before starting the test. The engine operating parameters such as engine speed, air/fuel ratio, and EGR rate were recorded during the tests. Pollutant emissions (Hydrocarbon (HC), NOx, and particles both in mode of nucleation and accumulation) were measured before and after the Diesel Oxidation Catalyst (DOC). The results show that conversion efficiency of NOx was higher during acceleration period at −7°C start than the case of 20°C start.
Journal Article

Investigation into Light Duty Dieseline Fuelled Partially-Premixed Compression Ignition Engine

2011-04-12
2011-01-1411
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.
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