Off-road Engines Research Articles

Impact of off-road engine electrification through EGR pumping on CO2, soot, and NOx emissions reductions during steady-state operating conditions

Impact of off-road engine electrification through EGR pumping on CO₂, soot, and NO_x emissions reductions during steady-state operating conditions

Educating Engineers on the Use of Renewable Ethanol Fuel as a Drop-in Replacement for Gasoline in Small Engines

The use of high-blend ethanol fuels to reduce emissions produced by on-road vehicles has been extensively studied. However, much less research has been done to study the effect of operating small off-road engines on high-blend ethanol fuel as a drop-in replacement for gasoline. Most small engine manufacturers only certify proper operation on low ethanol blends such as E10 (10% ethanol, 90% gasoline by volume). Most engineering students are unaware of the benefits that can be achieved when using high-blend ethanol fuel in small engines without substantial modifications. In this study, students conducted performance testing and analysis of a small engine using a dynamometer and a raw exhaust emissions analyser. The exhaust emissions and performance of the engine were evaluated using the U. S. Environmental Protection Agency (EPA) 6-mode duty cycle for small recreational engines (under 19 kW). Testing and analysis followed the recommendations of the SAE J1088 recommended practice. Students were motivated by the contemporary nature of the project and the use of commercially available equipment for testing. Further, students learned about the use of standardized testing to demonstrate the performance and emissions results.

Diesel Control Strategy in Dual-Fuel Engine

Dual-fuel engines are capable of operating using a mixture of two different fuels. Generally, the primary fuel is a gaseous fuel (CNG, LPG, Hydrogen), while diesel is used as a pilot ignition source, i.e. functioning on heat of compression and not a spark plug. There have been a few dual-fuel engine strategies to control the speed of the engine based on varying loads, but these require the addition of complex mechanisms to the existing systems. This paper discloses a methodology for controlling the diesel quantity during dual-fuel operation. According to the engine speed and accelerator pedal position, a gaseous fuel injector in the system injects a predetermined quantity of gaseous fuel. Based on the regulated quantity of gaseous fuel, the intake manifold creates an air-gas fuel mixture. The air-gaseous fuel mixture and a metered quantity of diesel are delivered to the combustion chamber via the intake manifold, fuel injection pump, and other components. The governor and fuel injection pump work together to measure the quantity of diesel according to speed and load conditions. During dual-fuel operation, the governor regulates engine speed by controlling the quantity of diesel delivered to the engine based on speed and load conditions. Keywords: Dual-fuel, Control Strategies, Off-Road Engines, Combustion, Emissions, Diesel Replacement

Turbocharger turbine map scaling for virtual engine use

Emissions requirements, performance expectations, and expanding range of fuels for off-road engines are broadening engine air system requirements. As part of reducing engine development cost and risk, virtual engine simulation is used to select architecture and components capable of covering a broad range of requirements through low risk changes to the turbocharger turbine. A method is presented for predicting turbine performance changes due to turbine housing area change, the most effective of these low risk changes, from available turbine map data. The method, developed from a mean line model, learns four simplified geometry parameters, three loss coefficients, and two maximum efficiency rotor inlet incidence coefficients from a training turbine map data set, then predicts a scaled turbine map for changes to a simplified geometry parameter associated with housing area. Reduced mass flow RMS errors less than 4.3% and efficiency RMS errors less than 5.2% are expected when generating scaled turbine maps with this method, which is additional 2% error for flow and 3% error for efficiency over that expected when modeling actual turbine map data.

Variable Valve Actuation for Next Generation Marine and Off-Road Engines - A Comprehensive Review Oriented on Meeting Future Emission Legislation

Variable Valve Actuation for Next Generation Marine and Off-Road Engines - A Comprehensive Review Oriented on Meeting Future Emission Legislation

Study on Selection of Diesel Engine Exhaust After-Treatment System Materials and Emission Performance for Genset Applications

The use of diesel engines for the transportation sector is ubiquitous and covers a broad continuum, like buses, trucks, agriculture, construction equipment, generators, and industrial applications. However, because of their increased use of off-road engines, they contribute more emissions in various sectors than on-road. As a result, worldwide, regardless of ongoing emission control efforts, these off-road, stationary engines also continue to be a substantial source of air pollutant emissions in the United States, European Union and Asian markets. Accordingly, while improving emissions performance, the selection of after-treatment system materials and the use of compatible after-treatment specification selections are also critical. This is only possible by effectively combining clean diesel technologies such as Fuel Injection Equipment (FIE), Turbocharger with Intercooler (TCIC), Cooled Exhaust Gas Recirculation (C-EGR), and after-treatment systems like Diesel Oxidation Catalyst (DOC), Selective Catalytic Reduction (SCR), and Diesel Particulate Filter (DPF). Overall, in this study, the influence of after-treatment system configurations and their effect on emission reduction performance are studied for three different DOC specifications based on emission testing for catalyst and size optimization. With the selected DOC catalyst specification, suitable combinations of DPF and SCR specifications are optimized further using GT-SUIT software simulation. This study was carried out during the conversion of a 15 kW NA engine to a 27 kW TCIC engine to meet diesel engine emission norms.

Computational approach for the acoustic modelling of large aftertreatment devices with multimodal incident sound fields

The influence of multimodal incident sound fields on the acoustic behaviour of large aftertreatment devices incorporating a monolith is modelled and analysed in detail. The analytical mode matching method is applied to the compatibility conditions of the three-dimensional acoustic fields at the device geometric discontinuities, leading to the computation of the complex wave amplitudes in all the subdomains involved and the corresponding device transmission loss. To have a realistic model, three-dimensional propagation must be considered in the inlet/outlet ducts and chambers, while one-dimensional wave propagation has to be assumed along the small capillaries of the aftertreatment device monolith (such catalytic converters and particulate filters); therefore, the monolith can be replaced by a plane wave four-pole transfer matrix from an acoustical point of view. On the other hand, for large aftertreatment device inlet ducts such as those found in heavy-duty and off-road engines, the usual models with plane incident wave excitation are not accurate since the onset of higher order incident modes in the inlet duct is expected for the frequency range of interest. Therefore, a variation of the acoustic attenuation performance is likely to occur depending on these modes, similar to the results previously found in the case of large dissipative silencers. Results are presented for three different multimodal incident sound field hypotheses: equal modal amplitude, equal modal power and equal modal energy density. A relevant influence on the sound attenuation is found for the test problems considered in the current investigation.

Impact of fossil and non-fossil fuel sources on the molecular compositions of water-soluble humic-like substances in PM2.5 at a suburban site of Yangtze River Delta, China

Abstract. Atmospheric humic-like substances (HULIS) affect the global radiation balance due to their strong light absorption at the ultraviolet wavelength. The potential sources and molecular compositions of water-soluble HULIS at a suburban site in the Yangtze River Delta from 2017 to 2018 were discussed, based on the results of the radiocarbon (14C) analysis and combining the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) technique in this study. The 14C results showed that the averaged non-fossil-fuel source contributions to HULIS were 39 ± 8 % and 36 ± 6 % in summer and winter, respectively, indicating significant contributions from fossil fuel sources to HULIS. The Van Krevelen diagrams obtained from the FT-ICR-MS results showed that the proportions of tannin-like and carbohydrate-like groups were higher in summer, suggesting significant contribution of HULIS from biogenic secondary organic aerosols (SOAs). The higher proportions of condensed aromatic structures in winter suggested increasing anthropogenic emissions. Molecular composition analysis on the CHO, CHON, CHOS, and CHONS subgroups showed relatively higher intensities of high O-containing macromolecular oligomers in the CHO compounds in summer, further indicating stronger biogenic SOA formation in summer. High-intensity phenolic substances and flavonoids, which were related to biomass burning and polycyclic aromatic hydrocarbon (PAH) derivatives indicating fossil fuel combustion emissions, were found in winter CHO compounds. Besides, two high-intensity CHO compounds containing condensed aromatic ring structures (C9H6O7 and C10H5O8) identified in the summer and winter samples were similar to those from off-road engine samples, indicating that traffic emissions were one of the important fossil fuel sources of HULIS at the study site. The CHON compounds were mainly composed of nitro compounds or organonitrates with significantly higher intensities in winter, which were associated with biomass burning emissions, in addition to the enhanced formation of organonitrates due to high NOx in winter. However, the high-intensity CHON molecular formulas in summer were referring to N-heterocyclic aromatic compounds, which were produced from the atmospheric secondary processes involving reduced N species (e.g., ammonium). The S-containing compounds were mainly composed of organosulfates (OSs) derived from biogenic precursors, namely long-chain alkane and aromatic hydrocarbon, which illustrate the mixed sources of HULIS. Generally, different policies need to be considered for each season due to the different seasonal sources (i.e., biogenic emissions in summer and biomass burning in winter for non-fossil-fuel sources, traffic emissions and anthropogenic SOA formation in both seasons, and additional coal combustion in winter). Measures to control emissions from motor vehicles and industrial processes need to be considered in summer. Additional control measures on coal power plants and biomass burning should be applied in winter. These findings add to our understanding of the interaction between the sources and the molecular compositions of atmospheric HULIS.

Development of an Engine Power Binning Method for Characterizing PM2.5 and NOx Emissions for Off-Road Construction Equipment with DPF and SCR

Aftertreatment technologies in Tier 4 off-road engines have resulted in significant emission reductions compared to older tier engines without aftertreatments. The appropriate characterization of Tier 4 engine emissions in consideration of aftertreatment operation is important for projecting emissions and developing mitigation strategies. The current method of aggregating emissions over an entire duty cycle and averaging them by engine load has a limitation in developing emission profiles over various duty cycles of Tier 4 engines, especially at low-load operations, where aftertreatment control for NOx may not be effective. In this study, an engine power binning method was developed to characterize emissions for Tier 4 construction equipment with aftertreatment systems, especially at low-power operating conditions. This binning method was applied to real-time emissions and activity data for four different types of Tier 4 construction equipment. Results show that low-power operations (<20% engine power) are responsible for 38–60% NOx and 11–51% of PM2.5 emissions depending on the equipment types. These results underscore the need for controlling NOx emissions during low-power operations. PM2.5 EFs for non-DPF backhoes were one to two orders of magnitude greater than all the other equipment due to the lack of a DPF, despite being certified to the same PM2.5 standard. This shows the benefits of DPFs on construction equipment and that they are substantial in reducing PM2.5 emissions. Estimated emission differences between using the binning and the averaging methods were 49–86% and 16–82% for NOx and PM2.5, respectively. These differences may change once the binning method is applied to larger emission datasets obtained from real-world vocational activities.

Evaluation of small off-road diesel engine emissions and aftertreatment systems

Off-road engines represent one of the largest categories for mobile source emissions in the United States. Emissions standards for small off-road diesel engines (SORDEs), which have not been updated since 2004, can be met without the use of aftertreatment on engines below 75 horsepower (hp) for nitrogen oxides (NOx) or below 25 hp for particulate matter (PM). It has been well established that aftertreatment systems can significantly decrease mobile source emissions, and improvements in these technologies since 2004 could warrant consideration for adopting more stringent standards for the SORDE category. This study evaluated the feasibility, efficiency, durability, and cost benefit of implementing regulations strict enough to require the use of selective catalytic reduction (SCR) and diesel particulate filter (DPF) controls on off-road engines under 75 hp. Durability testing was performed and emissions assessed on four stock engines equipped with retrofitted aftertreatment systems. The results suggest adding a DPF can provide >98% PM reductions. SCR systems provided NOx reductions ranging from 26 to 91% largely dependent on the cycle tested and engine exhaust temperature profile. Adoption of new SORDE standards could provide a PM reduction of 3.8% and a NOx reduction of 8.8–13.7% for the total off-road equipment inventory in California.

Numerical Study on the Performance and NOx Emission Characteristics of an 800cc MPI Turbocharged SI Engine

The main purpose of this study is to optimize engine performance and emission characteristics of off-road engines with retarded spark timing compared to MBT by repurposing the existing passenger engine. This study uses a one-dimensional (1D)-simulation to develop a non-road gasoline MPI turbo engine. The SI turbulent flame model of the GT-suite, an operational performance predictable program, presents turbocharger matching and optimal operation design points. To optimize the engine performance, the SI turbulent model uses three operation parameters: spark timing, intake valve overlap, and boost pressure. Spark timing determines the initial state of combustion and thermal efficiency, and is the main variable of the engine. The maximum brake torque (MBT) point can be identified for spark timing, and abnormal combustion phenomena, such as knocking, can be identified. Spark timing is related to engine performance, and emissions of exhaust pollutants are predictable. If the spark timing is set to variables, the engine performance and emissions can be confirmed and predicted. The intake valve overlap can predict the performance and exhaust gas by controlling the airflow and combustion chamber flow, and can control the performance of the engine by controlling the flow in the cylinder. In addition, a criterion can be set to consider the optimum operating point of the non-road vehicle while investigating the performance and exhaust gas emissions accompanying changes in boost pressure With these parameters, the design of experiment (DoE) of the 1D-simulation is performed, and the driving performance and knocking phenomenon for each RPM are predicted during the wide open throttle (WOT) of the gasoline MPI Turbo SI engine. The multi-objective Pareto technique is also used to optimize engine performance and exhaust gas emissions, and to present optimized design points for the target engine, the downsized gasoline MPI Turbo SI engine. The results of the Pareto optimal solution showed a maximum torque increase of 12.78% and a NOx decrease of 54.31%.

Experimental Investigation of Neat Biodiesels’ Saturation Level on Combustion and Emission Characteristics in a CI Engine

The fuel qualities of several biodiesels containing highly saturated, mono, and poly unsaturated fatty acids, as well as their combustion and exhaust emission characteristics, were studied. Six biodiesel samples were divided into two groups based on their fatty acid composition, including group 1 (coconut, castor, and jatropha) and group II (palm, karanja, and waste cooking oil biodiesel). All fuels (in both groups) were tested in a single-cylinder off-road diesel engine. Castor and karanja biodiesel, both rich in mono-unsaturation level, have a high viscosity of about 14.5 and 5.04 mm2/s, respectively. The coconut and palm biodiesels are rich in saturation level with cetane numbers of 62 and 60, respectively. In both groups, highly saturated and poly-unsaturated methyl esters presented better combustion efficiency and less formation of polluted emissions than mono-unsaturation. At full load, coconut and palm biodiesel displayed 38% and 10% advanced start of combustion, respectively, which reduced ignition delay by approximately 10% and 3%, respectively. Mono-unsaturated methyl esters exhibited a higher cylinder pressure and heat release rate, which results in higher NOx gas emissions. The group II biodiesels showed about 10–15% lower exhaust emissions owing to an optimum level of fatty acid composition. Our study concluded that highly saturated and poly-unsaturated fatty acid performed better than mono-unsaturated biodiesels for off-road engine application.

Molecular characterization of polar organic aerosol constituents in off-road engine emissions using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS): implications for source apportionment

Abstract. The molecular compositions of polar organic compounds (POCs) in particles emitted from various vessels and excavators were characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and possible molecular structures of POCs were proposed. POCs were extracted with purified water and sorted by elemental composition into three groups: CHO, CHON, and S-containing compounds (CHONS and CHOS). The results show the following. (i) CHO (accounting for 49 % of total POCs in terms of peak response) was the most abundant group for all tested off-road engines, followed by CHON (33 %) and CHOS (35 %) for diesel and HFO (heavy-fuel-oil)-fueled off-road engines. (ii) The abundance and structure of the CHON group in water extracts were different in terms of engine type and load. The relative peak response of CHON was the highest for excavator emissions in working mode, compared to the idling and moving modes. Furthermore, dinitrophenol and methyl dinitrophenol were potentially the most abundant emission species for high-rated speed excavators, while nitronaphthol and methyl nitronaphthol were more important for low-rated speed vessels. (iii) The composition and structure of the S-containing compounds were directly influenced by fuel oil characteristics (sulfur content and aromatic ring), with more condensed aromatic rings in the S-containing compounds proposed in HFO-fueled vessel emissions. More abundant aliphatic chains were inferred in diesel equipment emissions. Overall, higher fractions of condensed hydrocarbons and aromatic rings in POCs emitted from vessels using HFO cause strong optical absorption capacity. Different structures in POCs could provide a direction for qualitative and quantitative analysis of organic compounds as tracers to distinguish these emissions from diesel or HFO-fueled off-road engines.

A Generic Framework for Generalized Virtual Age Models

This paper presents a generic framework for modeling and assessment of preventive and corrective maintenances. The virtual age (VA) models of Kijima are generalized. The proposed definition provide many existing models as VA models. New models are also proposed. Covariates effects can be considered. The framework is generic in the sense that we propose an iterative way to compute the characteristics of the model that does not depend on the number of maintenances, on their types, on their effect models, and on the way of planning the preventive maintenances. Such a framework is particularly interesting in order to develop adaptive software tools, such as the virtual age models (VAM) package of R language. Methods are proposed for maintenance times simulation, maximum likelihood parametric estimations, and reliability indicators computation. Finally, we present two applications to real dataset issued from off-road engines of Brazilian mining trucks and bladder cancer study.

Developing an Ontology-Based Rollover Monitoring and Decision Support System for Engineering Vehicles

The increasing number of rollover accidents of engineering vehicles has attracted close attention; however, most researchers focus on the analysis and monitoring of rollover stability indexes and seldom the assessment and decision support for the rollover risk of engineering vehicles. In this context, an ontology-based rollover monitoring and decision support system for engineering vehicles is proposed. The ontology model is built for representing monitored rollover stability data with semantic properties and for constructing semantic relevance among the various concepts involved in the rollover domain. On the basis of this, ontology querying and reasoning methods based on the Simple Protocol and RDF Query Language (SPARQL) and Semantic Web Rule Language (SWRL) rules are utilized to realize the rollover risk assessment and to obtain suggested measures. PC and mobile applications (APPs) have also been developed to implement the above methods. In addition, five sets of rollover stability data for an articulated off-road engineering vehicle under different working conditions were analyzed to verify the accuracy and effectiveness of the proposed system.

Simulation of HCCI combustion in air-cooled off-road engines fuelled with diesel and biodiesel

The present work describes the elaboration of a predictive tool consisting on a phenomenological multi-zone model, applicable to the simulation of HCCI combustion of both diesel and biodiesel fuels. The mentioned predictive tool is created with the aim to be applied in the future to perform engine characterization during both pre-design and post-design stages. The methodology applied to obtain the proposed predictive model is based on the generation of an analytical mechanism that, given a set of regression variables representing the engine operative conditions, provides the user with the optimal figures for the scaling coefficients needed to particularize both the ignition delay and the heat release rate functional laws, which rule the combustion development in the proposed multi-zone model for HCCI engines. The validation of the proposed predictive multi-zone model consists on the comparison between chamber pressure curve derived from the simulations and experimental data based on a DEUTZ FL1 906 unit modified in order to allow HCCI combustion operation mode using diesel EN590 and rapeseed biodiesel. Finally, evidences of the capabilities of the proposed model to be used as a predictive tool applicable to the analysis of off-road engines under HCCI conditions are provided, consisting in the characterization and optimization of the operational maps related to both Brake Specific Fuel Consumption and NOx emissions.

Off-road 엔진의 EGR율에 따른 촉매코팅 DPF의 자연재생율 예측

This paper aims to predict oxidation amounts of catalyst and heat produced through passive regeneration on DPF according to different EGR rates and loads of off-road engines. Soot oxidation model and parameter assumption model were used for the test. Engine data were measureed with 25%, 50% and 75% of 1600 RPM loads and with 0% and 30% of EGR rates in order to estimate parameters. Oxygen levels calculated on the DPF downstream and oxygen levels measured were compared through all of the experimental conditions for validating the model. Oxidation rates on DPF according to different EGR rates and oxygen levels on the DPF downstream were estimateed successfully, which can be applied for off-road vehicles.

Russia's black carbon emissions: focus on diesel sources

Abstract. Black carbon (BC) is a significant climate forcer with a particularly pronounced forcing effect in polar regions such as the Russian Arctic. Diesel combustion is a major global source of BC emissions, accounting for 25–30 % of all BC emissions. While the demand for diesel is growing in Russia, the country's diesel emissions are poorly understood. This paper presents a detailed inventory of Russian BC emissions from diesel sources. Drawing on a complete Russian vehicle registry with detailed information about vehicle types and emission standards, this paper analyzes BC emissions from diesel on-road vehicles. We use the COPERT emission model (COmputer Programme to calculate Emissions from Road Transport) with Russia-specific emission factors for all types of on-road vehicles. On-road diesel vehicles emitted 21 Gg of BC in 2014: heavy-duty trucks account for 60 % of the on-road BC emissions, while cars represent only 5 % (light commercial vehicles and buses account for the remainder). Using Russian activity data and fuel-based emission factors, the paper also presents BC emissions from diesel locomotives and ships, off-road engines in industry, construction and agriculture, and generators. The study also factors in the role of superemitters in BC emissions from diesel on-road vehicles and off-road sources. The total emissions from diesel sources in Russia are estimated to be 49 Gg of BC and 17 Gg of organic carbon (OC) in 2014. Off-road diesel sources emitted 58 % of all diesel BC in Russia.

Physical and chemical properties of RME biodiesel exhaust particles without engine modifications

A major contributor to ambient particulate air pollution is exhaust from diesel engines and other vehicles, which can be linked to different adverse health effects. During the last decades, a global drive towards finding sustainable and clean bio-based alternative fuels for the transport sector has taken place and biodiesel is one of the most established alternatives today. To better assess the overall effects on a public health level when introducing biodiesel and other renewable fuels, a better understanding of the detailed exhaust particle properties, is needed. In this work, the physical and chemical properties of biodiesel exhaust particles were studied in comparison to standard diesel exhaust emissions, in an existing engine without modifications, focusing on particulate carbonaceous matter and PAH/Oxy-PAH as well as fine particle size distribution. An older off-road engine, produced between 1996 and 2004, was used with three different fuels/fuel blends; (1) 100wt% low-sulfur standard petro diesel (SD), (2) 100wt% rapeseed methyl ester biodiesel (B100) and (3) a blended fuel – B30 consisting of 30wt% RME and 70wt% SD. The study focused mainly on emissions from transient engine operation, but includes also idling conditions. The gaseous emissions measured for the biodiesel fuel were in general in accordance with previous reported data in the literature, and compared to the standard petro diesel the emissions of CO was lower while NOx emissions increased. The particulate mass concentration during transient operation was almost halved compared to when petro diesel was used and this was associated with a decrease in average particle size. The shift in particle mass and size was associated with a higher fraction of organic matter in general, considerable less PAH’s but a relative higher fraction of Oxy-PAH’s, when shifting from petro diesel to biodiesel.

배기가스재순환 적용에 따른 Off-road 엔진의 연료 분사 시기 전략에 관한 연구

배기가스재순환 적용에 따른 Off-road 엔진의 연료 분사 시기 전략에 관한 연구