A major concern for a high-power density, heavy-duty engine is the durability of its components, which are subjected to high thermal loads from combustion. The thermal loads from combustion are unsteady and exhibit strong spatial gradients. Experimental techniques to characterize these thermal loads at high load conditions on a moving component such as the piston are challenging and expensive due to mechanical limitations. High performance computing has improved the capability of numerical techniques to predict these thermal loads with considerable accuracy. High-fidelity simulation techniques such as three-dimensional computational fluid dynamics and finite element thermal analysis were coupled offline and iterated by exchanging boundary conditions to predict the crank angle-resolved convective heat flux and surface temperature distribution on the piston of a heavy-duty diesel engine.
In this study, engine-out gaseous emissions are being reviewed from Fourier Transform Infrared (FTIR) spectroscopy measurement of methanol diesel dual fuel combustion experiments performed in a heavy-duty diesel engine. Comparison to the baseline diesel-only condition shows that methanol-diesel dual fuel combustion leads to higher regulated carbon monoxide (CO) emissions and unburned hydrocarbons (UHC). However, NOX emissions were reduced effectively with increasing methanol substitution rate (MSR). Under dual-fuel operation with methanol, nitrogen oxides (NOx) emissions, including nitric oxide (NO), nitrogen dioxide (NO2), and nitrous oxide (N2O), indicate the potential to reduce the burden of NOX on diesel after-treatment devices such as selective catalytic reduction (SCR).
It is widely recognized that internal combustion engines (ICE) are needed for global transport for years to come, however, demands on ICE fuel efficiency, emissions, cost, and performance are extremely challenging. Gasoline compression ignition (GCI) is one approach to achieving demanding efficiency and emissions targets. At Aramco Research Center-Detroit, an advanced, multi-cylinder GCI engine was designed and built using the latest combustion system, engine controls, and lean aftertreatment. The combustion system uses Aramco's PPCI-diffusion process for ultra-low NOx and smoke. A P2 48V mild hybrid system was integrated on the engine for braking energy recovery and improved cold starts. For robust low-load operation, a 2-step valvetrain system was used for exhaust rebreathing. The fuel injection system was a modified diesel system with high injection rate and 2000 bar pressure rating.
Hydrogen has recently become a primary focus as a future carbon-free fuel for transportation, especially for heavy duty commercial vehicles. The hydrogen internal combustion engine (H2 ICE) shows promise, as current manufacturing facilities and vehicle architectures can be largely maintained while keeping the initial purchase price of the vehicle relatively low. However, hydrogen combustions engines have challenges to overcome. One of the main challenges is to provide transient response on par with current diesel engines while maintaining low NOx emissions from the engine. Previously, simulations were performed by AVL List GmbH and SuperTurbo Technologies of a mechanically driven turbocharger, the SuperTurbo, on a 13L H2 ICE. This paper covers follow on work of actual engine testing of the H2 ICE with the SuperTurbo in an effort to reproduce the simulation results with engine test data.
This study experimentally investigates the combustion stability in RCCI engines along with the gaseous (regulated and unregulated) and particle emissions. Multifractal analysis is used to characterize the cyclic combustion variations in the combustion parameters (such as IMEP, CA50, Pmax) of the RCCI engine. The investigation is carried out on a modified single-cylinder diesel engine to operate in RCCI combustion mode. The RCCI combustion mode is tested for different fuel premixing ratio (r_p) and diesel injection timing (SOI) at fixed engine speed (1500rpm) and load (1.5 bar BMEP). The particle number characteristics and gaseous emissions are measured using a differential mobility spectrometer (DMS500) and Fourier Transform Infrared Spectroscopy (FTIR) along with Flame Ionizing Detector (FID), respectively. The results indicate that the NOx emissions decrease with advanced SOI while the methane (CH4) emission increases.
To mitigate the NOx emissions from diesel engines, the adoption of exhaust gas recirculation (EGR) has gained widespread acceptance as a technology. Nonetheless, employing EGR has the drawback of elevating soot emissions. The use of hydrogen-enriched air with EGR in a diesel engine (dual-fuel operation), offers the potential to decrease in-cylinder soot formation while simultaneously reducing NOx emissions. The present study numerically investigates the effect of hydrogen energy share and engine load on the formation and emission of soot and NOx emission from hydrogen-diesel dual-fuel engine. The numerical investigation is performed using an n-heptane/H2 reduced reaction mechanism with a two-step soot model in ANSYS FORTE. To enhance the accuracy of predicting dual-fuel combustion in a hydrogen-diesel dual-fuel engine, a reduced n-heptane reaction mechanism is integrated with a hydrogen reaction mechanism using CHEMKIN.
Ammonia (NH3), a zero-carbon fuel, has great potential for internal combustion engine development. However, its high ignition energy, low laminar burning velocity, a narrow range of flammability limits, and high latent heat of vaporization are not conducive for engine application. This paper numerically investigates the feasibility of utilizing ammonia in a heavy-duty diesel engine, specifically through the method of low-pressure direct injection (LP-DI) of hydrogen to ignite ammonia combustion. The study compares the engine's combustion and emission performance by optimizing four critical parameters: excess air ratio, hydrogen blending ratio, ignition timing, and hydrogen injection timing. The results reveal that excessively high hydrogen blending ratios lead to an advanced combustion phase, resulting in a reduction in indicated thermal efficiency.
Since Non-Road Mobile Machinery (NRMM) China stage IV legislation has been implemented from 2023, some engines within maximum rated power between 37 to 560 kW are required for gaseous emissions, particulate matter(PM) and particulate number (PN) limitation, evaluated over testing cycle of Non-Road Transient Cycle (NRTC) and Non-Road Steady Cycle (NRSC). The pollutants from diesel engines, widely used in NRMM applications, can be controlled using aftertreatment systems which are comprise of a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF), or optionally a selective catalytic reduction (SCR). In this presentation, a compact D-DPF design is introduced and discussed on application in harvesters, tractors, and forklifts. Because harvesters have higher exhaust gas temperature than other applications, more passive regeneration behaviors were occurred during working conditions.
In recent years, with the development of computing infrastructure and methods, the potential of numerical methods to reasonably predict aerodynamic noise in compressors has increased. However, aerodynamic acoustic modeling of complex geometries and flow systems is currently immature, mainly due to the greater challenges in accurately characterizing turbulent viscous flows. Therefore, recent advances in aerodynamic noise calculations for automotive turbocharger compressors were reviewed and a quantitative study of the effects for turbulence modeling (Shear-Stress Transport (SST) and Detached Eddy Simulation (DES)) and time-steps (2°and 4°) in numerical simulations on the performance and acoustic prediction of a compressor under full operating conditions was investigated. The results showed that for the compressor performance, the turbulence models and time-step parameters selection were within 1.5% error of the simulated and measured values for pressure ratio and efficiency.
In the perspective of a reduction of emissions and a rapid decarbonization, especially for compression ignition engines, hydrogen plays a decisive role. The dual fuel technology is perfectly suited to the use of hydrogen, a fuel characterized by great energy potential. In fact, replacing, at the same energy content, the fossil fuel with a totally carbon free one, a significant reduction of the greenhouse gases, like carbon dioxide and total hydrocarbon, as well as of the particulate matter can be obtained. The dual fuel with indirect injection of gaseous fuel in the intake manifold, involves the problem of hydrogen autoignition. In order to avoid this difficulty, the optimal conditions for the injection of the incoming mixture into the cylinder were experimentally investigated. All combustion processes have been carried out on a research engine with optical access. The engine speed has been set at 1500 rpm, while the EGR valve has been deactivated.
Tanks play a pivotal role in swiftly deploying firepower across dynamic battlefields. The core of tank mobility lies within their powertrains, driven by diesel engines or gas turbines. To better understand the benefits of each power system, this study uses geo-location data from the National Training Center (NTC) to understand the power and energy requirements from a main battle tank over an 18-day rotation. This paper details the extraction, cleaning, and analysis of the geo-location data to produce a series of representative drive cycles for an NTC rotation. These drive-cycles serve as a basis for evaluating powertrain demands, chiefly focusing on fuel efficiency. Notably, findings reveal that substantial idling periods in tank operations contribute to diesel engines exhibiting notably lower fuel consumption compared to gas turbines. Nonetheless, gas turbines present several merits over diesel engines, notably an enhanced power-to-weight ratio and superior power delivery.
Opposed piston two-stroke (OP2S) diesel engines have demonstrated a reduction in engine-out emissions and increased efficiency compared to conventional four-stroke diesel engines. Due to the higher thermal efficiency and absence of a cylinder head, the heat transfer loss to the coolant is lower near the ‘Top Dead Center’. The selection and design of the airpath are pivotal in realizing the benefits of the OP2S engine architecture. Like any two-stroke diesel engine, the scavenging process and the composition of the internal residuals are predominantly governed by the pressure differential between the intake and the exhaust ports. Moreover, a significant portion of the work involved in pumping air is carried out externally to the engine cylinder which needs to be accounted for when calculating brake efficiencies.
The need for even more efficient internal combustion engines in the road transportation sector is a mandatory step to reduce the related CO2 emissions. In particular, this sector is presently responsible of about 12% of the greenhouse gases worldwide, and the path toward hybrid and electric powertrains has just begun. In particular, in heavy-duty vehicles the full electrification of the powertrain is far to be imagined. So, internal combustion engines will still play a significant role in the near/medium future. Hence, technologies having a low costs to benefits ratio will be favorably introduced in existing engines to reduce emissions. The thermal management of engines is today a recognized area of research. Inside this area, the interest toward the lubricant oil has a great potential but not yet fully exploited. Engine oil is responsible of the mechanical efficiency of the engine and has a significant potential of improvement.
Ammonia is one of the carbon-free alternatives considered for power generation and transportation sectors. But ammonia’s lower flame speed, higher ignition energy, and higher nitrogen oxides emissions are challenges in practical applications such as internal combustion engines. As a result, modifications in engine design and control and the use of a secondary fuel to initiate combustion such as natural gas are considered for ammonia-fueled engines. The higher-octane number of methane (the main component in natural gas) and ammonia allows for higher compression ratios, which in turn would increase the engine's thermal efficiency. One simple approach to initiate and control combustion for a high-octane fuel at higher compression ratios is to use a spark plug. This study experimentally investigated the operation of a heavy-duty compression ignition engine converted to spark ignition and ammonia-methane blends.
World is moving towards cleaner, greener and energy efficient fuels. The increase in fuel consumption in various industries, especially in road transport sector has created interest for the blending of biofuels in conventional fuel and renewable fuels. Among biofuels ethanol is one of them and preferable choice for blending in gasoline which is a fuel for spark ignition engines and flex fuel vehicles. As such ethanol/methanol cannot be used in compression-ignition diesel engines without engine modifications due to inherent low cetane number and lubricity of alcohols. Therefore, fuel consisting of certain concentrations of alcohols such as methanol / ethanol in diesel blends is being promoted. The lower alcohols (methanol/ethanol) are not miscible in diesel due to their polarity differences. An additive package is essential for the solubility and stability of alcohol (methanol/ethanol) in diesel phase or diesel blends.
Smoke emission from compression ignition engines is directly tied to mixing and combustion processes. Engine boundary conditions such as ambient pressures and temperatures, particularly at higher altitudes, have significant impacts on both available ignition energy and on the mixing-controlled combustion process. However, the effects of boundary conditions are difficult to explore without thorough pressure and temperature control of the engine intake air and exhaust gas at higher altitude conditions. The objective of this research is to investigate the relationship between engine smoke emission and engine power at various ambient conditions including higher altitudes. A multi-cylinder compression-ignition engine was operated on a jet fuel at various ambient pressure and temperature conditions, as low as 60 kPa and -12ºC, respectively. Single and multi-injection strategies were applied depending on engine power.
When used with urea-water solution forming ammonia, Selective Catalytic Reduction (SCR) catalyst is a proven technology for greatly reducing tailpipe emission of nitrogen oxides (NOx) from Diesel engines. However, one major shortcoming of an SCR-based system is forming damaging urea deposits (crystals) in low temperature exhaust operations, especially exacerbated during lower exhaust temperature operations or higher injection rates. Deposits reduce SCR efficiency, damage exhaust components and induce high concentration ammonia slips. We describe here an Electrically Heated Mixer (EHM™) demonstrated on a Diesel engine markedly inhibiting deposit formation in urea SCR systems, including in low (near 200 °C) exhaust temperature operations in both low and high urea injection rates in various, realistic engine operations. Engine test runs were conducted in long durations, 10 to 20 hours each, for a total of nearly 100 hours.