Total Particulate Number Research Articles

Study on the Effect of Secondary Injection on the Combustion and Emission of n-Butanol Engines.

n-Butanol, as a biological alternative fuel containing oxygen, has similar physical and chemical properties to gasoline and has a wide range of sources, which has attracted more and more attention and research. Direct injection technology has been widely used in the field of internal combustion engine due to its advantages of flexibility and control ability. In this paper, the secondary injection of n-butanol engine under the mode of in-cylinder direct injection is discussed to organize stratified combustion of the mixture, optimize combustion to improve the thermal efficiency, and reduce emission. A four-cylinder four-stroke spark ignition (SI) engine was selected to carry out the secondary injection experiment of n-butanol under the excess air ratio (λ) of 1, an engine speed of 1500 r/min, and a low load, and the variables were the second injection ratio and timing. The results show that the secondary injection of n-butanol can achieve stratified combustion of the mixture, but only at a specific second injection timing such as 100°CA before compression top dead center (BTDC) or 125°CA BTDC, the combustion effect is the best. A small second injection ratio can optimize combustion, improve brake thermal efficiency, and reduce hydrocarbon and carbon monoxide emissions. When the second injection ratio is greater than 60%, it results in incomplete fuel combustion, a 3 to 4% reduction in thermal efficiency, and an increase in emissions. Coefficient of variation (COV) was increased by secondary injection, but the effect was insignificant in the small injection ratio, and it will increase with the increase of the second injection ratio. The change of particle number is mainly affected by the nuclear particle number, and with the increase of the second injection ratio, the total particulate number is more affected by the second injection timing. The second injection ratio of 40% can reduce the total particle number under the mixed-gas stratification condition.

Characterisation of particulates and trace metals emitted by a dimethyl ether-fuelled genset engine prototype

Diesel-fuelled CI engines are the primary sources of particulate matter (PM) emissions which harm human health and the urban environment. Elevated PM emission levels can cause respiratory diseases and deteriorate urban air quality and atmospheric visibility. DME, a carbon-neutral and oxygenated fuel, is fast merging as a strong alternative to diesel to reduce PM emissions. The absence of a direct carbon-carbon bond in the molecular structure of DME improves combustion and reduces PM emissions to negligible levels. DME and baseline diesel are experimentally evaluated in a single-cylinder CI genset engine prototype to find the particulate number-size, surface area-size and mass-size distributions. In addition, total particulate number (TPN), total particulate mass (TPM), count mean diameter (CMD) of particulates, particulate morphology and trace metals were assessed. DME genset engine emitted higher numbers of smaller diameter particles, with lower surface area and mass distribution than baseline diesel. For DME, total PM mass emission and CMD of particulates were lower due to particles being finer. Morphological analysis of particulates showed the presence of larger particles from diesel and less bunched agglomerates of nucleation mode particles from the DME genset engine prototype. The trace metal analysis of particulates showed higher presence of trace metals such as Si, Ca, and Na in DME-fuelled engine than in diesel. As an alternative to diesel, DME can reduce PM emissions from genset engines, significantly enhance urban air quality, and minimise the threat of respiratory diseases.

Investigation of Lubricant Additive Interactions on Gasoline Particulate Filters

<div>To understand how the composition of novel lubricant additives and their ash interact with gasoline particulate filters (GPFs), an accelerated aging protocol was conducted using three lubricant additive formulations and two GPF types. The additive packages (adpaks) consisted of Ca+Mg detergent in a 3:1 or 0:1 ratio and an anti-wear component—either zinc dialkyl dithiophosphate (ZDDP) or a novel phosphonium-phosphinate ionic liquid (IL) substitute. The particulate sampling captured amount/compositions of particulate matter (PM) generated, total particulate number, and size distribution. Five ash loadings were completed. GPF position and adpak composition affected the backpressure, ash composition, ash morphology, and captured mass. The particulate sampling indicated that the ash component consisted primarily of particles less than 50 nm in size and that the Mg-only adpak resulted in more particulate of 50–400 nm in size. Postmortem materials characterization indicated GPFs in the underfloor position had deeper penetration of ash into the walls compared to the close-coupled position. Additionally, the Mg-only adpak had a higher filter collection efficiency (>90%) and the ash particles consisted of a higher concentration of dense ash material. In contrast, four of the 3:1 Ca:Mg lubricant adpaks resulted in a collection efficiency of only 40–50%. Although the collection efficiency was higher with the Mg-only adpak, the ash layer in the GPF was not thicker, nor was the penetration into the wall more significant, and surprisingly the full useful life (FUL) backpressure was lower than with Ca:Mg adpaks. The higher density of the Mg-derived ash was the only detectable difference. A possible explanation of this observation is that Mg ash has a lower melting point and is more susceptible to densification during combustion or GPF regeneration. The substitution of IL in place of the ZDDP did not lead to any notable changes in collection efficiency or location of the ash.</div>

Investigation on gas and particle emission characterization of carbon black oxidation process promoted by catalyst/ash

The study of the gas and particle emission characteristics during the oxidation of carbon black particles is the basis for exploring the particle emission characteristics during diesel particulate filter (DPF/CDPF) regeneration process. The gas and particle emission of Printex U (PU) particles oxidation under different oxidation temperatures and sample masses are investigated based on fixed bed and thermogravimetric analysis, and the oxidation processes are conducted under the cooperative effect of catalyst (CeO2)/ash (ZnO). The experimental results show that, with the increase of oxidation temperature, the CO/CO2 concentration, the extent of oxidation (η) and the total emitted solid particulate number (PN) increase, but the average particulate diameter (Da) range reduces from 60 to 100 nm to 20–40 nm. On the other hand, with the increase of PU mass, the CO/CO2 concentration and the total PN increase together, and the Da rises from about 30 nm to 40–160 nm, while the η decreases markedly. Both the CeO2 and ZnO nanoparticles can promote the PU oxidation process, and then reduce CO emissions, which lead to the rise the CO2 emissions. Beneficially, the η and the Da increase under the effect of CeO2 and ZnO, and the total PN decreases sharply. Adding catalyst (CeO2) and ash (ZnO) can effectively reduce the emission of small particle size (<23 nm) during oxidation process, which provides a research basis for controlling the emission of particles below 23 nm during DPF regeneration process.

DI-CNG injector nozzle design influence on SI engine standard emissions and particulates at different injection timings

Compressed natural gas direct injection (DI-CNG) systems in spark ignition (SI) internal combustion engines have shown that it can give several benefits compared to CNG port fuel injection systems. However, the DI-CNG injector nozzle head design and gas jet formation may greatly influence engine exhaust gas emissions and performance. Present experimental study investigated the influence of 7 different nozzle head designs of spray-guided DI-CNG injectors on the combustion process, engine performance, standard emissions, and particulate number (PN) when methane fuel was injected at different injection timings (SOI) and injection pressures (18 bar and 50 bar). The nozzle heads had two main design patterns – heads with small multi holes/orifices and heads with larger crevices (swirl or umbrella spray pattern). Naturally aspirated SI engine tests were conducted at part load (6 bar IMEP) and wide-open throttle (WOT) at 2000 rpm engine speed. The results revealed that the difference between the nozzle heads was small when the fuel was injected at an early stage of the intake stroke (310–350 CAD bTDC) either at part load or high load. However, for late injection timing (130–190 CAD bTDC), the design of the DI-CNG injector nozzle head had a large impact on the combustion stability, standard emissions formation and particulates. Multi-hole nozzle heads showed improved CO2, CO, THC, total PN, and slightly higher NOx emissions compared to nozzle heads with larger crevices. For some of the nozzles, the SOI could be retarded more than for other injector head designs at higher injection pressure whilst still ensuring an acceptable engine performance in terms of combustion stability, power output and emissions formation. Overall, 50-bar injection pressure and a late injection timing under WOT conditions achieved higher engine load levels with all injector nozzle types. Images acquired using an optical endoscope technique with a high-speed video camera showed that a yellow flame was present for all nozzle types at a low injection pressure and late SOI. Increasing the injection pressure reduced the injection duration, improved air/fuel mixing which resulted in the reduced yellow flame formation and lower PN for most of the nozzle heads.

Effects of engine restart strategy on particle number emissions from a hybrid electric vehicle equipped with a gasoline direct injection engine

Hybrid electric vehicle (HEV) tend to emit large amount of gaseous and particle emissions right after engine restart (ER). In this study, on-board particulate number (PN) measurement test and chassis dynamometer tests were conducted to analyze the effects of the ER combustion strategy on the gaseous and particle emission characteristics of a gasoline direct injection (GDI) HEV. The on-board PN measurement tests were conducted to examine the effect of a parameter sweep such as injection pressure, end of injection (EOI), spark timing of ER. It was measured by the pegasor particle sensor (PPS)-M, a device that measures the number of particles with a size from 23 nm to 25 μm, and the ES-582.1 module that can acquire electronic control unit (ECU) data. In the chassis dynamometer test, particle emissions, gaseous emissions and fuel economy of the reference case and the Combination Case 2 were compared and analyzed in the worldwide harmonized light vehicles test cycles (WLTC) mode test using Horiba, MEXA-ONE and MEXA-2000 solid particle counting system (SPCS). Reference case refers to a control strategy that does not touch anything in the vehicle's basic control strategy, and Combination Case 2 is the largest PN reduction case combined by calibrating the parameters. On-board PN measurement tests show that in reference case, ER PN accounted for about 70% of the total PN. Compared to the reference case, the sum of ER PN averages tended to decrease with higher injection pressure, advanced EOI, and retarded spark timing. The results of Combination Case 2 indicate that the sum of ER PN averages decreased by 88.7% compared to the reference case. In the WLTC mode test, THC, CO emissions and fuel economy were almost the same, and NOx was reduced by 85.6%. In both PPS and SPCS, the sum of ER PN average ratios decreased by 20%.

Impact of test cycle on mass, number and particle size distribution of particulates emitted from gasoline direct injection vehicles

This paper presents an investigation of emissions from gasoline direct injection (GDI) vehicles and analyzed the characteristics of emitted particulate matter (PM), the emission factors of particulate number (PN) and size distribution properties, including four test cycles: the new European driving cycle (NEDC), the worldwide harmonized light vehicle test cycle (WLTC), the USA federal test procedure-75 (FTP-75) and the China light-duty vehicle test cycle (CLTC). The results reveal that for China VI standard GDI vehicle, compared with CLTC, which is the newest test cycle according to realistic road conditions in China, the aforesaid evaluation indexes of FTP-75 and WLTC are basically higher due to their higher acceleration and deceleration ratio. Compared with hot start, a cold start followed by warming-up process has a significant impact on PN emissions over all test cycles and different test cycles show diverse sensitivity to the change of start-up conditions. The particles with a diameter of 5.6–23 nm (sub-23 nm) account for 43.1–57.7% of the total PN emission quantity for China V standard GDI vehicle, which is about 5–15% higher than that of theoretical assumptions. Different piecewise speed segments exhibited different impacts on PN characteristics when acceleration and deceleration reveal greater influence. Gasoline particulate filter (GPF) could effectively capture full-size particulates including fine particles as sub-23 nm particles, which is verified over FTP-75 and CLTC, while sub-23 nm PN emission is still at a high level over WLTC for its ultrahigh speed segment. There could have been an underestimation of the real particle number emitted from GDI vehicle while the emission of solid sub-23 nm particles was excluded under current emission regulations.

Engine performance and emissions of furan-series biofuels under stratified lean-burn combustion mode

In the recent decade, concerns over CO2 emitted by internal combustion engines is the driven force behind stringent emission legislations. Stratified lean-burn strategy in spark-ignition engines is effective in improving fuel economy by reducing pumping loss and heat loss. In this study, two biofuel candidates, 2-methylfuran (MF) and 2,5-dimethylfuran (DMF), were tested in this combustion mode in comparison with ethanol and gasoline. All experiments were conducted at an engine speed of 1200 rpm and a load of 5.8 bar indicated mean effective pressure (IMEP) with a fixed spark timing of 25° before top dead centre (BTDC). Engine performance and engine emissions of the stratified lean-burn mode (λ (air/fuel ratio) = 1.2 and 1.5) were studied and compared to that of the homogenous mode (λ = 1). The impact of the second injection timing was examined. Results show that the employment of the stratified lean-burn mode could improve the fuel economy by up to 16% if the second injection timing is optimized. The second injection timing also has significant impacts on the IMEP, combustion duration, coefficient of variation (COV), gaseous emission and particulate number (PN) emissions. Generally, combustion duration increases under stratified lean-burn mode, but it decreases if the second injection timing is very late. The COVs for lean-burn mode under a λ of 1.2 are always below 1.5%. However, under the λ of 1.5, COVs significantly increase to 10% when the second injection timing is too early. With the increase of the excess air, the PN concentration significantly reduces by up to 88% for MF, DMF and gasoline under the stratified lean-burn mode. The reduction of the PN is mainly due to the significant reduction of the small particles (<50 nm). However, for ethanol, the reduction of the total PN is not as significant as the other two fuels due to its physiochemical properties.

Effect of n-pentanol additive on compression-ignition engine performance and particulate emission laws

Biodiesel has a high viscosity, which limits its application to engines. However, n-pentanol has low viscosity and high volatility, which is considered a promising additive. This study examined the influence of n-pentanol/biodiesel/diesel blends on the performance and particulate emissions of a diesel engine at different loads, under the condition of coupling exhaust gas recirculation (EGR) (0–30%). The three test fuels included pure diesel (D100); 80% diesel and 20% biodiesel blended fuel (BD20); 64% diesel, 16% biodiesel, and 20% n-pentanol blended fuel (BDP20). The results indicated that the influence of EGR on the NOx emissions between fuels was greater than that of the physicochemical properties of the fuels. For the same EGR rate, the heat release rate (HRR), peak in-cylinder pressure (IP), and brake thermal efficiency (BTE) increased with the engine load increased. After adding n-pentanol to BD20, the HRR increased. The peak IP and BTE values of BDP20 were similar to those of D100 and BD20. With the addition of n-pentanol, the total particulate number concentration (TPNC), soot, and total particulate mass concentration (TPMC) emissions decreased. Furthermore, the trade-off relationship between TPMC and NOx was improved, and the geometric mean diameter (GMD) of the particles decreased.

Particulate emissions from urban bus fueled with biodiesel blend and their reducing characteristics using particulate after-treatment system

Particulate emissions from an urban bus fueled with B20 (20% biodiesel from waste cooking oil and 80% diesel by volume) were investigated using portable emissions measurement system (PEMS), then the effect of a catalyzed continuously regeneration trap (CCRT) on the particulate emissions of the B20-fueled bus were ascertained. Results show that compared with a D100 (pure diesel), B20 reduced particulate number (PN) and particulate mass (PM) emission rates of the bus by 13.9% and 24.3% under cruise control. Under transient condition, B20 reduced the PN and PM emission rates by 18.4% and 16.3%. B20 decreased the total PN concentration by 6.6% whereas increased the proportion of nucleation particles from 89.0% to 92.0%. Correspondingly causing a decrease in the GMD (geometric mean diameter) from 43.02 nm to 41.25 nm under cruise condition, and from 41.26 nm to 39.57 nm under transient condition. Using a CCRT exhibited an excellent filtration effect on both PN and PM from the B20-fueled bus. Both under cruise and transient conditions, CCRT could reduce more than 93% of the PN and PM. In addition, CCRT had a better filtration effect on accumulation particles. The use of CCRT also changed the particle size bimodal distribution of the B20 by removing the accumulation mode peak.

Effects of coolant temperature coupled with controlling strategies on particulate number emissions in GDI engine under idle stage

As idle condition in gasoline direct injection (GDI) engines always has high particulate number (PN) issue, the effects of coolant temperature coupled with controlling strategies on PN emission has been experimentally studied. Two sets of experiments have been conducted to make a comprehensive understanding. The first set is aimed to analyze ignition timing and excess air ratio characteristics, and the second one mainly investigates injection strategies. The experimental results indicate that the total PN declines with increased coolant temperature. When coolant temperature exceeds 70 °C, PN dramatically decreases. 5–22 nm PN emissions increase and 22–50 nm PN emissions decrease with higher λ. Besides, richer mixture has higher 50–150 nm PN than leaner ones. Properly advanced ignition timing will decrease total PN under idle stage and the decrement is mainly from 5 to 22 nm particles. The total PN minimizes at 5 MPa injection pressure, which can fulfill fuel evaporation and restrict nucleation process simultaneously. The total PN minimizes at 80 CAD BTDC injection timing, which is only 14% of the minimum value in 140 CAD BTDC. Thus, coolant temperature has crucial effect on PN emissions and optimizing other operating parameters will further reduce PN.

Particulate Matter and Gaseous Emission of Hydrous Ethanol Gasoline Blends Fuel in a Port Injection Gasoline Engine

The industrialization that increases day by day needs more and more power/fuel sources that are commonly available, abundant, renewable, and environmentally friendly. Recently, nearly all of the cities in China (PRC) have been influenced by haze. However, the pollutants from automobiles have always been seriously considered to be the main contamination causes of the haze and that influence human health. This study concerns the impact of hydrous ethanol on in-cylinder pressure, particulate matter (PM), and gaseous emissions (oxides of nitrogen (NOx) and unburned hydrocarbon (HC)) from a port fuel injection (PFI) gasoline engine. Tests were conducted on a four-cylinder port injection gasoline engine at different engine loads at an engine speed of 2000 rev/min for commercial gasoline, hydrous ethanol-gasoline blends (10% and 20% hydrous ethanol by volume), and an anhydrous ethanol-gasoline blend (20% anhydrous ethanol by volume). The results show that the peak in-cylinder pressure with the use of gasoline was the highest compared with the hydrous ethanol and anhydrous ethanol blends. Compared with the anhydrous ethanol blend, the hydrous ethanol blends performed well at a high load condition, equivalent to a low load. In addition, the total particulate number (PN) declines with an increase in engine operating loads for all of the fuels tested. The outcome of this study is an important reduction in PM number, mass emissions, and mean diameters of particles as the use of hydrous ethanol blends increases, while the form of the particulate size distribution remains the same. Furthermore, the NOx emission is raised with a rise in engine load, and NOx and HC emissions are reduced with the use of hydrous ethanol and anhydrous ethanol blend as equated with pure gasoline. Moreover, the correlation between the total particle number against NOx and HC has been found; the number of particles increases when the NOx emission decreases, and the opposite trend is exhibited for the HC emission. Therefore, it can be concluded that hydrous ethanol blends look to be a good selection for PM, NOx, and HC reduction for gasoline engines.

Effects of lubricant oil on particulate emissions from port-fuel and direct-injection spark-ignition engines

This work presents experimental tests where lubricant oil was added to the engine in order to highlight its contribution to particle emissions from both gasoline and compressed natural gas spark-ignition engines. Three different ways of feeding the extra lubricant oil and two fuel-injection modes—port fuel injection and direct injection—were investigated to mimic the different ways by which lubricant may reach the combustion chamber. In particular, in the tests using compressed natural gas, the oil was injected either into the intake manifold or directly into the combustion chamber, whereas in both the port-fuel-injection and direct-injection tests using gasoline, the oil was premixed with the fuel. The experiments were performed on a single-cylinder, optically accessible spark-ignition engine, running at 2000 r/min under stoichiometric and full-load conditions, and requiring no lubrication. Particle size distribution functions were measured in the range from 5.6 to 560 nm by means of an engine exhaust particle sizer. Particle samples were taken directly from the exhaust flow, just downstream of the valves. Opacity was measured by an AVL 439 opacimeter, and gaseous emissions were measured by means of an exhaust gas analyzer in order to globally monitor the combustion process. Detailed analysis of the recorded total particulate number and particle size distributions allowed to determine the size ranges and relative amounts associated with the lubricant-oil-derived particles. Oil addition produced a significant increase in the particles emitted in the lowest range size, independent of the way lubricant was added. Only when lubricant was injected directly into the combustion chamber (either blended with the fuel or by itself), an increase in the number of particles with sizes larger than 50 nm was recorded.

Particulate Emissions From Karanja Biodiesel Fueled Turbocharged CRDI Sports Utility Vehicle Engine

Biodiesel has emerged as one of the most promising alternative fuel to mineral diesel in last two decades globally. Lower blends of biodiesel emit fewer pollutants, while easing pressure on scarce petroleum resources, without sacrificing engine power output and fuel economy. However, diesel engines emit significant amount of particulate matter (PM), most of which are nanoparticles. Due to the adverse health impact of PM emitted by compression ignition (CI) engines; most recent emission legislations restrict the total number of particles emitted, in addition to PM mass emissions. Use of biodiesel leads to reduction in PM mass emissions; however, the particle size–numbers distribution has not been investigated thoroughly. In this paper, PM emission characteristics from Karanja biodiesel blends (KB20 and KB40) in a modern common rail direct injection (CRDI) engine used in a sports utility vehicle (SUV) with a maximum fuel injection pressure of 1600 bar have been reported. This study also explored comparative effect of varying engine speeds and loads on particulate size–number distribution, particle size–surface area distribution, and total particulate number concentration from biodiesel blends vis-à-vis baseline mineral diesel. This study showed that particulate number emissions from Karanja biodiesel blends were relatively higher than baseline mineral diesel.

Filtration Characteristics of Fuel Neutral Particulates Using a Heterogeneous Multiscale Filtration Model

Filtration characteristics of fuel neutral soot particulate were studied using a recently developed heterogeneous multiscale filtration (HMF) model. In the HMF model, a probability density function (PDF) based pore size distribution and a porosity distribution across the filter wall are introduced to represent the heterogeneous multiscale porous structure. The HMF model was validated by an exhaust filtration analysis (EFA) system, which was designed for fundamental experimental filtration studies. Various sources of particulates from combustion engines were used in the filtration studies. Some particulates were sampled from a spark ignited direct injection (SIDI) engine fueled with gasoline and ethanol blends. Particulates from a compression ignition engine fueled with diesel for conventional and advanced combustion regimes were investigated as well. The microstructure of the porous wall was found to be more critical and necessary to simulate filtration of particulates from gasoline and advanced diesel combustion engines than those from conventional diesel combustion (CDC) engines. The interactions between the porous wall and trapped particulates were investigated. The dynamic filtration characteristics, including filtration efficiency, pressure drop and particulate distribution inside the wall are strongly dependent on total particulate volume rather than total particulate number concentration. The change of the filter structure as well as the shape of the particulate size distribution play important roles on particulate penetration.

Effect of Karanja biodiesel blends on particulate emissions from a transportation engine

Recent emission control legislations restrict the particulate mass emissions as well as particle numbers due to severe adverse health effects of smaller size particulates. Therefore from health perspective, reduction in particulate mass as well as numbers, both are desired from any potential alternative fuel. In this experimental investigation, effect of Karanja biodiesel and its blends on particulate size-number distribution, size-surface area distribution and total particulate number concentration at various engine operating conditions was experimentally studied using a direct injection compression ignition engine. It was observed that peak number concentration of particulates increased with increasing engine speed for all test fuels. Total particulate number concentration was highest for KOME100 and lowest for KOME10, amongst all test fuels. Smaller concentration of Karanja biodiesel (upto 20%) was effective in reducing the particulate number emissions.

Effect of intake air temperature and air–fuel ratio on particulates in gasoline and n-butanolfueled homogeneous charge compression ignition engine

An experimental study was conducted to investigate the effect of engine operating parameters on exhaust particulate size–number distribution in a homogeneous charge compression ignition engine fueled with gasoline and n-butanol. In this investigation, portfuel injection was done for preparing homogeneous charge, and intake air preheating was used for auto-ignition of the charge. Engine exhaust particle sizer was used for measuring size–number distribution of particulate matter emitted from the homogeneous charge compression ignition engine. Experiments were conducted at different engine speeds by varying intake air temperature and air–fuel ratio of the charge. Effect of engine operating parameters on particulate size–number distribution, size–surface area distribution, and total particulate number concentration was investigated. Most significant particle numbers were in the range of 6–150 nm mobility diameter for all test conditions. n-Butanol showed relatively higher peak number concentration and lower mobility diameter corresponding to the peak concentrations as compared to baseline gasoline. On increasing intake air temperature, mobility diameters corresponding to peak number concentration of particles moved towards lower mobility diameters. Count mean diameter of particles was in the range of 35–80 nm and 20–65 nm for gasoline and n-butanol, respectively, for all test conditions in homogeneous charge compression ignition operating range.

Comparative study of engine control strategies for particulate emissions from direct injection light-duty vehicle fueled with gasoline and liquid phase liquefied petroleum gas (LPG)

To evaluate the potential of a dedicated direct injection liquefied petroleum gas (LPG-DI) vehicle, we investigated several engine control parameters that are closely related to the characteristics of mixture preparation and nano-particle emissions. The fuel supply circuit for the direct injection of LPG in liquid form was modified into a return-type system comprised of a three-way high pressure pump, a low pressure regulator, a brushless direct current (BLDC) pump, and an LPG tank. Particulate number (PN) and size distribution measurements were performed in FTP-75 and HWFET modes, and also using an engine test bench. The experimental results showed that significant PN emissions were produced during the cold start and the transient warm-up operations of the gasoline direct injection (GDI) vehicle; this production of particle emissions was due to application of split injection and catalyst heating function. A bimodal particle size of 10<dp<100nm was formed in the GDI vehicle, whereas a sub 30nm nuclei mode was mainly formed in the LPG-DI vehicle. Excessive particle formation during sudden acceleration of the GDI vehicle in the HWFET mode was improved with LPG fuel. The reduction rate of the PN concentration with LPG application reached approximately 98% (FTP-75 mode) and 99% (HWFET mode) compared to the GDI vehicle. The total PN concentration in the LPG-DI vehicle was significantly improved to 1.6×1010(N/km) for the FTP-75 mode and 3.4×109(N/km) for the HWFET mode.

Evaluating Effects of Engine Operating Variables on Particle Number Emission Rates Using Robust Regression Models

This study examines the dynamics of high-frequency diesel particulate number (PN) emissions and their dependence on engine operating variables. Data collected from a heavy-duty diesel bus during a real-world experiment are analyzed with L1-regression models that are robust to outliers and free from distributional assumptions. The model-building procedure reveals the relative statistical significance of six engine operating variables and their interactions. Different models are estimated for accumulation mode PN (which dominates emitted particle mass) and for the ratio of ultrafine PN (which accounts for more than 90% of total emitted PN) to accumulation mode PN. A major implication from the study results is that interactions between engine operating variables should be thoroughly examined in instantaneous emission models. Specifically, the interaction between fuel-to-air ratio (or engine load) and engine speed exerts a significant effect on the above mentioned PN ratio, while the effect of exhaust temperature becomes statistically significant above 250°C. Boost and injection pressure were not statistically significant in explaining observed PN variability. Models for accumulation mode particles were stronger in terms of predictive power compared with models estimated for PN ratios.

Influence of Methanol–Biodiesel Blends on the Particulate Emissions of a Direct Injection Diesel Engine

In this study, Euro V diesel fuel, biodiesel, and methanol–biodiesel blends were tested in a 4-cylinder direct-injection diesel engine to investigate the combustion characteristics and particulate emissions of the diesel engine under five engine loads at the maximum torque engine speed of 1800 rpm. Compared with Euro V diesel fuel, biodiesel gives lower and earlier heat release rate. For the blended fuels, the peak heat release rate becomes higher and retarded. With regard to particulate mass concentration, biodiesel generates less than Euro V diesel fuel, while the blended fuels result in significant reduction especially at high engine loads. Compare with Euro V diesel fuel, the total particle number concentration of using biodiesel is always higher while the geometric mean diameter (GMD) of the particles is lower. With the blended fuel, the total number concentration and GMD decrease in comparison with pure biodiesel. Further analysis shows that the difference between the total number concentration of biodiesel and Euro V diesel fuel is in particles smaller than 50 nm rather than in the larger particles. The use of methanol–biodiesel blends, compared with biodiesel, could reduce the number concentration of all sizes. A comparison between the particulate mass emission and total particulate number concentration with the mass of fuel burned in the diffusion mode show that they are strongly related to each other, even for the blended fuel.