• Energy Research

This paper investigates the energy distribution and the waste heat energy characteristics of a compression ignition engine for micro-cogeneration applications, at different engine speeds and loads. The experimental activity was carried out on a three-cylinder, 1028 cc, common-rail engine. Tests were performed with diesel fuel and a 20% v/v biodiesel blend (B20). The quantity and the quality of the waste heat energy were studied through energy and exergy analyses, respectively. Combustion characteristics were investigated by means of indicating data. Gaseous emissions were measured and particles were characterized in terms of number and size at exhaust. It was found out that the addition of 20% v/v of RME to diesel fuel does not affect significantly the brake fuel conversion efficiency and the energetic flows. On the other hand, biodiesel blend allows to reduce the combustion noise and the pollutants emissions in most of the operating conditions. A proper phasing of the injection strategy for the biodiesel blend could further reduce the exhaust emissions, mainly at high engine speeds. The results presented in this paper could be useful for the development of diesel engine based micro-cogeneration systems working at different engine speeds and loads.

This study explores the potentiality of low/zero carbon fuels such as methanol, methane and hydrogen for motor applications to pursue the goal of energy security and environmental sustainability. An experimental investigation was performed on a spark ignition engine equipped with both a port fuel and a direct injection system. Liquid fuels were injected into the intake manifold to benefit from a homogeneous charge formation. Gaseous fuels were injected in direct mode to enhance the efficiency and prevent abnormal combustion. Tests were realized at a fixed indicated mean effective pressure and at three different engine speeds. The experimental results highlighted the reduction of CO and CO2 emissions for the alternative fuels to an extent depending on their properties. Methanol exhibited high THC and low NOx emissions compared to gasoline. Methane and, even more so, hydrogen, allowed for a reduction in THC emissions. With regard to the impact of gaseous fuels on the NOx emissions, this was strongly related to the operating conditions. A surprising result concerns the particle emissions that were affected not only by the fuel characteristics and the engine test point but also by the lubricating oil. The oil contribution was particularly evident for hydrogen fuel, which showed high particle emissions, although they did not contain carbon atoms.

The paper aims to evaluate the capabilities of consolidated technique and of a novel system on the measurement of sub-23 nm particles. Moreover, the impact of ethanol both pure and in blend on their emissions was analyzed. The investigation was carried out on small displacement PFI and DI SI engines fueled with gasoline, ethanol and blend of ethanol in gasoline. The investigation was performed through an EEPS coupled with a PMP compliant system, a well-consolidated procedure for the particle measurement, and a new developed system, HM-DMA, developed within the European project Sureal-23, coupled to a single diluter were used.

The European Commission is planning to lower the particle cut off size down to 10 nm to consider the contribution of the sub-23 nm particles. Within the European project Sureal-23, a comprehensive study on the sub-23 nm particles was performed and novel technologies for their sampling and measurement were developed. One new proposed instrument, the Half Mini Differential Mobility Analyser (HM-DMA), was used in the present study. The investigation was carried out on a small direct/port fuel injection, spark ignition engine fueled with gasoline, ethanol and a 30 %v/v ethanol blend. Results highlighted a general reduction of the number and the size of the particles emitted by pure ethanol. The effect of the ethanol blend on sub-23 nm particle emissions was affected by the operating condition and the injection strategy. The extent of the VOF depends on the fuels as well as on the engine configuration and operating condition. Some differences were noted between the results from EEPS and HM-DMA ascribable to the different measurement principle and to the processes occurring in the dilution system.

This case study is aimed to investigate how the injector fouling can influence both the injection system and engine performances. In particular, the presence of deposits in the nozzle of the injector could affect the injection system performance along its life. The investigation was carried out on transparent compression ignition engine equipped with the head of a commercial multi-cylinder engine and secondgeneration common rail injection system. Two indirect-acting piezoelectric injectors were tested: one new another fouled. Optical engine was fueled with diesel and tests were performed with engine running in continuous mode. Two operating conditions were investigated. The new and fouled piezo injectors were characterized by injection rate profiles. The injection and combustion phases were investigated by optical measurements. Two-color pyrometry was used to analyze the pollutants formation and exhaust emission. Experimental results showed that the fouled injector has slower dynamic response and it injects a smaller amount of fuel during the main event. It has shorter jets penetration and wider spray angle that affect in negative way the mixing formation and the combustion evolution. High temperature regions and high sooting flames are detected for the fouled injector. Therefore, it emits high nitrogen oxides and particulate matter at the engine exhaust.

In view of the new emission regulations seeking to lower the particle cut-off size down to the current 23 nm, an extensive comprehension on the nature of sub-23 nm particles is crucial. In this regard, a new challenge lies ahead considering an even more massive use of biofuels. The objective of this research study was to characterize the sub-23 nm particles and to evaluate their volatile organic fraction (VOF) from a high performance, 1.8 L gasoline direct injection (GDI) engine under the Worldwide harmonized Light vehicles Test Cycle (WLTC). Particle emissions were measured through an Engine Exhaust Particle Sizer (EEPS) capable of particle sizing and counting in the range 5.6 - 560 nm. The sampling and conditioning were performed by both a single diluter and the Dekati Engine Exhaust Diluter (DEED) a Particle Measurement Programme (PMP) compliant sample conditioning system. The temperature of the dilution air at the first dilution stage and of the evaporation chamber in the DEED were varied to promote nucleation and condensation phenomena thus allowing to distinguish the VOF. The effect of ethanol at 10 %v/v (E10) and 85 %v/v (E85) blend on particle emissions was analyzed. The weight of sub-23 particles on the total emissions was assessed at each phase of the cycle. Main results highlighted that sub-23 nm particles give an important contribution to the total particle emissions. A strong reduction of particle concentration as the ethanol content in the fuel increases was observed. Moreover, the test performed at low dilution temperature showed a large number of su-23 nm particles thus revealing a large fraction of volatile components in specific phases of the cycle.

The increasing spread of alternative fuels for compression ignition engines has required an improved knowledge of the energetic potentiality and the exhaust emissions of biodiesel. In this paper, energy and exergy analyses were performed to assess the energy distribution and to characterize the waste heat energy of a small compression ignition engine. The investigation was carried out on a three-cylinder, 1028 cm3 engine equipped with a CR (common-rail) injection system. Gas emissions and particulate matter concentration were measured and particles were characterized in terms of number and size at exhaust. The engine was fuelled with commercial diesel fuel, a blend of 50% v/v rapeseed methyl ester (RME) and pure RME. Operating conditions at different engine speeds, at both medium and full load, were investigated. It was found out that the combustion efficiency is improved by biodiesel. A trade-off between the waste heat of the exhaust gas and the cooling water was observed. The quantity and quality of energy recovered by exhaust gas decreases as the content of biodiesel increases. A defined trend of the heat recovered from cooling water was not detected for the tested fuels. Lower exhaust emissions were measured when the engine was fuelled with both blended and pure RME with respect to diesel fuel. However, the analysis of the data has shown that a proper engine calibration could further optimize the combustion process and emission formation when the engine is fuelled with biodiesel

The energy crisis and environmental issues make the alternative fuels, both liquid and gaseous, even more attractive because of their potentiality in reducing the fuel consumption and the pollutant emissions. Ethanol is the most promising alternative liquid fuel for spark ignition engines. It has a higher octane number, which provides good anti-knock characteristics and in the possibility to work with higher compression ratios, so improving the engine efficiency. The higher heat of vaporization compared to gasoline leads to an increased power output. Moreover, the larger oxygen content provides a more complete combustion and therefore reduced emissions. Among gaseous fuels, methane is considered one of the most interesting. It has wider flammable limits and better anti-knock properties than gasoline. Moreover, it is characterized by lower CO2 emissions. On the other hand, the slow flame propagation speed and its poor lean-burn capability produce lower engine power output with respect to gasoline. The addition of a high burning velocity fuel, such as hydrogen, allows to improve the combustion process in terms of burning velocity and extend the lean operation limit. The objective of this paper is the analysis of the effect of different fuels on the engine performance and emissions. Experimental investigations were carried out in an optically accessible small single-cylinder, spark ignition four-stroke engine. It was equipped with the cylinder head of a Port Fuel Injection commercial 244 cc engine. The engine was fueled with gasoline, ethanol, methane and a blend of hydrogen in methane. Optical measurements were performed to analyze the combustion process with high spatial and temporal resolution. In particular, the optical techniques based on 2D-digital imaging were used to follow the flame propagation in the combustion chamber. UVevisible spectroscopy allows the detection of chemical markers of the combustion process such as the radicals OH* and CH*. The exhaust emissions were characterized by means of gaseous analyzers. The measurements were performed at steady state conditions.

This study was conducted to determine the effects of the fouling process on the piezoelectric injectors in a transparent common-rail diesel engine. Piezoelectric injectors are characterized by a ceramic actuator that can dilate or retract when it receives a pulse of current. The piezo element controls a valve, which creates an imbalance in the pressure that is exerted at each end of the needle, causing the needle rising or closing. Two same model injectors were tested; one was new and the other one was fouled on a vehicle. The aim of the experimental investigation was to evaluate the performance of a new and a fouled piezoelectric injector in terms of injection and flame evolution. It was evaluated how the nozzle carbon deposits affect the injection quantity and combustion. The experimental apparatus was a single cylinder research engine equipped with a Euro 5 multicylinder head. A second-generation common rail injection system and 6-hole piezoelectric injectors were used too. The engine was optically accessible; a sapphire window was set in the bottom of an elongated piston. The engine was fuelled with commercial diesel fuel and it run at 1500 rpm in continuous mode during the tests. Pressure signal in the engine was detected by a quartz pressure transducer that replaced the glow plug of the real engine. Injection rate was measured for both injectors. Optical techniques based on 2Ddigital imaging were used to detect the injection phase and combustion evolution. A high speed camera captured the images from the combustion chamber reflected by a 45° inclined mirror set in the elongated piston. Steady-state measurements of nitrogen oxide and opacity were carried out in the raw exhaust by commercial instruments. It was found that piezoelectric injectors had a shorter injection delay than more traditional solenoid injectors whether they were new or fouled. The new injector guaranteed a good jet penetration that allowed a more efficient combustion than the fouled one. The main consequence was that the new injector produced lower exhaust emissions.