Heavy-duty Diesel Engine Emissions Research Articles

Concordance between In Vitro and In Vivo Relative Toxic Potencies of Diesel Exhaust Particles from Different Biodiesel Blends.

Diesel exhaust particles (DEPs) contribute to air pollution exposure-related adverse health impacts. Here, we examined in vitro, and in vivo toxicities of DEPs from a Caterpillar C11 heavy-duty diesel engine emissions using ultra-low-sulfur diesel (ULSD) and biodiesel blends (20% v/v) of canola (B20C), soy (B20S), or tallow-waste fry oil (B20T) in ULSD. The in vitro effects of DEPs (DEPULSD, DEPB20C, DEPB20S, and DEPB20T) in exposed mouse monocyte/macrophage cells (J774A.1) were examined by analyzing the cellular cytotoxicity endpoints (CTB, LDH, and ATP) and secreted proteins. The in vivo effects were assessed in BALB/c mice (n = 6/group) exposed to DEPs (250 µg), carbon black (CB), or saline via intratracheal instillation 24 h post-exposure. Bronchoalveolar lavage fluid (BALF) cell counts, cytokines, lung/heart mRNA, and plasma markers were examined. In vitro cytotoxic potencies (e.g., ATP) and secreted TNF-α were positively correlated (p < 0.05) with in vivo inflammatory potency (BALF cytokines, lung/heart mRNA, and plasma markers). Overall, DEPULSD and DEPB20C appeared to be more potent compared to DEPB20S and DEPB20T. These findings suggested that biodiesel blend-derived DEP potencies can be influenced by biodiesel sources, and inflammatory process- was one of the potential underlying toxicity mechanisms. These observations were consistent across in vitro and in vivo exposures, and this work adds value to the health risk analysis of cleaner fuel alternatives.

Effect of Pollution Level on Size Distributions and Mixing State of Ambient Black Carbon Particles in an Urban Area during Wintertime

We deployed a Single Particle Soot Photometer (SP2) and Single Particle Aerosol Mass Spectrometer (SPAMS) to investigate the size distribution and mixing state of ambient black carbon (BC) particles in Shanghai during the winter of 2017. The mixing state of the particles changed drastically under different meteorological conditions, and higher concentrations often occurred during haze episodes. The BC particles existed in two size modes: the condensation mode, which mainly consisted of fresh traffic-emitted particles, and the droplet mode, which encompassed heavily aged traffic-emitted particles, biomass burning particles and heavy-duty diesel engine emission particles. Whereas the heavily aged traffic-emitted particles exhibited relatively small BC cores (60–80 nm in diameter) surrounded by a thick coating (100–160 nm), the biomass burning particles displayed slightly larger cores (80–130 nm) covered by an even thicker layer (160–300 nm). However, we observed a large number of particles with large cores (150–200 nm) but a relatively thin coating (40–80 nm) on clean days. Trajectory analyses of the air masses showed that they usually originated in local areas or on the North China Plain during haze episodes but mostly migrated from the East China Sea during clean episodes. Interestingly, the BC particles in the clean air masses contained V more frequently and generated intense mass spectrum signals for Ca+, suggesting that these particles probably arose from heavy machinery emissions near ports. Our real-time single particle data indicates that the sources of BC aerosol can be easily identified by measuring the size distribution and mixing state of the particles.

Effect of EGR and Fuel Injection Strategies on the Heavy-Duty Diesel Engine Emission Performance under Transient Operation

To reduce the smoke and nitrogen oxide (NOx) emissions; a detailed study concerned with exhaust gas recirculation (EGR) and diesel injection strategy was conducted on a two-stage series turbocharging diesel engine under transient operating condition. One transient process based on the constant speed of 1650 r/min and load increases linearly from 10% to 100% within 5 s was tested in this study. The effect of the EGR valve control strategy on engine transient performance was examined. The results show that better air-fuel mixing quality can be obtained with the optimized the EGR valve open loop control strategy and the smoke opacity peak decreased more than 64%. Under the EGR valve close loop control strategy; the smoke opacity peak was lower than with open loop control strategy; but higher than without EGR. The effect of fuel injection strategy on engine transient performance was examined with the EGR valve close loop control. The results show that sectional-stage rail pressure (SSRP) strategy (increasing injection pressure from a turning point load to 100% load) and optimizing fuel injection timing can improve the engine emission performance. The satisfactory results can be obtained with lower NOx (382 ppm) emissions and the smoke opacity peak (3.8%), when the turning point load is set to 60% with the injection timing delay 6° CA.

低セタン価高濃度芳香族の燃料が重量車用ディーゼル機関の 燃焼・排出ガス特性に及ぼす影響

低セタン価高濃度芳香族の燃料が重量車用ディーゼル機関の 燃焼・排出ガス特性に及ぼす影響

The Advanced Collaborative Emissions Study (ACES) of 2007- and 2010-Emissions Compliant Heavy-Duty Diesel Engines: Characterization of Emissions and Health Effects

In 2001, the US Environmental Protection Agency (EPA) adopted stringent new standards for on-highway heavy heavy-duty diesel engine (HHDDE) emissions of particulate matter (PM) and oxides of nitrogen (NOx) that were to become effective during the 2007–2010 time period. The Advanced Collaborative Emissions Study (ACES) was a cooperative, multiparty effort to characterize the emissions (in Phases 1 and 2) and assess the possible health impacts (in Phase 3) of the new, advanced HHDDE technologies, after introducing them to the market. Phase 1 demonstrated that the regulated emissions from four 2007-compliant engines tested were all below the 2007 standards. Both regulated and unregulated emissions were substantially reduced relative to pre-2007 technology engines, except for nitrogen dioxide (NO2) emissions that were higher compared to 2004 technology engines due to the use of diesel oxidation catalyst (DOC) and catalyzed diesel particulate filter (DPF) exhaust aftertreatment technologies. Phase 2 showed another large step in emissions reductions for 2010-compliant diesel engines. The three 2010-compliant engines tested had substantially lower regulated emissions of NOx, CO, NMHC, and PM relative to the emission standards and also relative to the 2007-compliant engines. NOx reductions were achieved using urea-based selective catalytic reduction (SCR) and an ammonia oxidation catalyst (AMOX). A wide spectrum of particle and gas phase unregulated emissions species, including NO2, were also reduced relative to 2007-compliant engines and older engines. Phase 3 consisted of an inhalation bioassay in which rats were exposed for their lifetime to the diluted exhaust from one of the 2007-compliant engines tested in Phase 1. Three exhaust dilutions were selected based on the nitrogen dioxide (NO2) concentrations to achieve three exposure levels: 4.2 ppm (high-DE exposure), 0.8 ppm (mid-DE exposure), and 0.1 ppm (low-DE exposure) NO2. The control exposure consisted of filtered air. NO2 was chosen because the particle concentrations in the exhaust were too low to set the dilution levels. Exposures were conducted 16 h/day, 5 days/week. Rats were evaluated histopathologically and for respiratory function, a large number of noncancer endpoints, and genotoxicity, at interim time points up to the final sacrifice at 28 months (males) and 30 months (females). Histopathological analyses found that exposure to exhaust from a 2007-compliant engine produced no tumors or precancerous effects in lungs and no increase in tumor incidence outside the lung, but induced mild epithelial hyperplasia in the central acinus region of the lung, interstitial fibrosis, and bronchiolization at the high exposure level. The lung histologic changes were consistent with previous findings in rats after long-term exposure to NO2—a major component of the chamber exposure atmosphere, which is substantially reduced in 2010-compliant engines. The majority of the biological endpoints were unchanged with exposure and little inflammation was observed. In summary, the ACES study shows that emissions from 2007- and 2010-compliant HHDDE have been reduced dramatically and that exhaust from a 2007-compliant engine produced no tumors or precancerous effects in rats exposed over their lifetime.

Combining artificial neural network and multi-objective optimization to reduce a heavy-duty diesel engine emissions and fuel consumption

Nondominated sorting genetic algorithm II (NSGA-II) is well known for engine optimization problem. Artificial neural networks (ANNs) followed by multi-objective optimization including a NSGA-II and strength pareto evolutionary algorithm (SPEA2) were used to optimize the operating parameters of a compression ignition (CI) heavy-duty diesel engine. First, a multi-layer perception (MLP) network was used for the ANN modeling and the back propagation algorithm was utilized as training algorithm. Then, two different multi-objective evolutionary algorithms were implemented to determine the optimal engine parameters. The objective of the present study is to decide which algorithm is preferable in terms of performance in engine emission and fuel consumption optimization problem.

Specific engine performance and gaseous emissions characteristics of European test cycle and worldwide harmonized driving cycle for a heavy-duty diesel engine

This study compares the engine operating behavior and regulated gaseous emissions characteristics between the reference European cycles (ESC/ETC) and the worldwide harmonized driving cycles (WHSC/WHTC), which will be applied in the Euro VI heavy-duty diesel engine emissions regulations, for the diesel particulate filter (DPF) equipped Mercedes 12 L diesel engine. The speed and load distribution for two additional representative harmonized cycles which cover a more realistic operating range for a heavy duty engine were established to verify the engine performance over wide range of the cycle work, fuel consumption, and exhaust system temperature as well as engine coolant temperature for repeated validation tests. The WHTC, including an additional test with cold start and transient operation before the hot start, had a substantial influence on the THC, CO, NOx, and PM exhaust emissions levels because of the engine heat-up time and temperature rising characteristics of aftertreatment device. Moreover, the different engine operating conditions of the WHSC influenced on the specific engine performance and gaseous emissions behavior unlike those of the ESC. Finally, the statistical analysis results through repeated tests validated the stationary and transient cycles running at the fully warm-up condition, however, those of WHTC were closely dependent on the inclusion of cold start condition or aggressive acceleration gradient of engine speed and load trace.

An Insight into the Effect of Advanced Injection Strategies on Pollutant Emissions of a Heavy-Duty Diesel Engine

An advanced numerical investigation has been carried out in order to study the effect of multiple injection strategies on Caterpillar heavy-duty diesel engine emissions. Both different injected fuel percentages for each pulse and several dwells between main and post phase were investigated via computational fluid dynamics (CFD) and large eddy simulation (LES). Two sets of simulations were taken into account for 10% and 20% exhaust gas recirculation (EGR) fractions. In the first one, the main injection was split into two identical phases, while in the second one into three pulses. Within each set, three strategies were considered, increasing the amount of fuel injected during the main and concurrently decreasing the post pulse. Overall, 48 simulations were employed, since four different dwells between the last phase of the main and post injection were considered. Results show that the pollutant emissions minimization has been obtained for the Schemes injecting 65% and 70% of fuel for both two and three split strategies, but for different values of dwell. In fact, emissions very close to each other for NOx and particulate matter have been reached for these cases. Reductions of about −30% and −71% were respectively obtained for NOx and soot in comparison with experimental emissions related to the single injection case.

Nanoparticle Emissions from a Heavy-Duty Engine Running on Alternative Diesel Fuels

We have studied the effect of three different fuels (fossil diesel fuel (EN590); rapeseed methyl ester (RME); and synthetic gas-to-liquid (GTL)) on heavy-duty diesel engine emissions. Our main focus was on nanoparticle emissions of the engine. Our results show that the particle emissions from a modern diesel engine run with EN590, GTL, or RME consisted of two partly nonvolatile modes that were clearly separated in particle size. The concentration and geometric mean diameter of nonvolatile nucleation mode cores measured with RME were substantially greater than with the other fuels. The soot particle concentration and soot particle size were lowest with RME. With EN590 and GTL, a similar engine load dependence of the nonvolatile nucleation mode particle size and concentration imply a similar formation mechanism of the particles. For RME, the nonvolatile core particle size was larger and the concentration dependence on engine load was clearly different from that of EN590 and GTL. This indicates that the formation mechanism of the core particles is different for RME. This can be explained by differences in the fuel characteristics.

A Critical Review of the Effectiveness of I/M Programs for Monitoring PM Emissions from Heavy Duty Vehicles

Heavy-duty vehicles (HDV) are estimated to contribute up to 36% of particulate matter (PM) emissions in urban areas. In response, many agencies have established HDV inspection and maintenance (I/M) programs designed to target and repair vehicles with excess emissions. In this review, we conduct an international comparison of legislative context and HDV I/M program characteristics across Europe, North America, and Australia. The results of this analysis show that HDV-I/M programs vary greatly in terms of the ways in which testing is organized, for example, roadside versus periodic testing, whether the fleet is self-tested, and how nonfleet and age exemptions are handled. We also show how the I/M test criteria have changed little in the last 15 years while regulations for new heavy-duty diesel engine emissions have become increasingly stringent. In the U.S., HDV engine PM emissions limits were reduced by a factor of 26 between 1997 and 2007. Most I/M programs have continued to test according to EPA (and often with state legislative confirmation) guidance procedures having cut-points established in 1992. An analysis of data from Washington State show that only a minority of post-1997 vehicles actually exceeds the detection levels of the free-acceleration smoke-opacity test procedures, with the result that malfunctions of these vehicles may not actually be detected. From our review, it is clear that even with the potential adoption of new technologies and a more systematic and efficient framework for HDV-I/M, more research must be conducted in the efficacies of periodic versus roadside testing (and location selection), the use of evaluation methods like fail rates and opacity distributions, and finally, in development of better methods for identifying excess emissions with sensors and duty cycles.

Impact of military JP-8 fuel on heavy-duty diesel engine performance and emissions

Investigating the impact of jet fuel on diesel engine performance and emissions is very important for military vehicles, due to the US Army Single Fuel Forward Policy mandating that deployed vehicles must refuel with aviation fuel JP-8. There is a known torque and fuel economy penalty associated with the operation of a diesel engine with JP-8 fuel, due to its lower density and viscosity. On the other hand, a few experimental studies have suggested that kerosene-based fuels have the potential for lowering exhaust emissions, especially particulate matter, compared to diesel fuel #2 (DF-2). However, studies so far have typically focused on quantifying the effects of simply replacing the regular DF-2 with JP-8, rather than fully investigating the reasons behind the observed differences. This research evaluates the effect of using JP-8 fuel in a heavy-duty diesel engine on fuel injection, combustion, performance, and emissions, and subsequently utilizes the obtained insight to propose changes to the engine calibration to mitigate the impact of the trade-offs. Experiments were carried out on a Detroit Diesel Corporation (DDC) S60 engine outfitted with exhaust gas recirculation (EGR). The results indicate that torque and fuel economy of diesel fuel can be matched, without smoke or NO x penalty, by increasing the duration of injection to compensate for the lower fuel density. The lower cetane number of JP-8 caused an increased ignition delay and increased premixed combustion, and their cumulative effect led to relatively unchanged combustion phasing. Under almost all conditions, JP-8 led to lower NO x and particulate matter (PM) emissions and shifted the NO x-PM trade-off favourably.

Effect of injector flow rate on heavy-duty DI diesel engine performance and emissions for various injection pressures

A computational study to examine the effect of injector flow rate at various injection pressures on the combustion process and mainly, on pollutants emitted from a heavy duty DI diesel engine was conducted using a multi-zone combustion model. The relation of injector flow rate with injection duration and mean injection pressure was taken into account in the present analysis to assess the overall effect of injection parameters. As observed, injector flow rate affects the combustion and pollutants formation mechanism through its effect on the fuel-air mixing rate. Higher injection rates are more beneficial to the improvement of bsfc-NO and soot-NO trade-offs at low engine speed whereas the opposite occurs at high engine speed. Overall, it was revealed that considerable improvements in terms of engine performance and pollutant emissions can be attained using low injector flow rates at the entire engine operating range and significantly increased injection pressures to keep the injection duration constant.

Control strategies for heavy-duty diesel engine emissions

Emission standards for heavy-duty diesel engines have become significantly more stringent throughout the last 20 years and continue towards zero emissions levels in the future. Modern direct-injected diesels include well-developed combustion systems that have electronically controlled injection systems and robust turbochargers. These technological advancements enable heavy-duty engine manufacturers to meet emission standards through an adjustment in injection timing by using a small array of sensors in concert with the engine control module (ECM). Standards targeted for 2002 and 2007 will require the inclusion of external devices and associated sensors that will create additional degrees of freedom for the ECM and thus a larger sensor array in comparison to current diesel engines. This article outlines the potential impact of these emission standards on control strategies for heavy-duty engines and the associated sensors under "warmed up" conditions.