Browse Topic: Compressed natural gas
With the expansion of compressed natural gas (CNG) filling station in India, bi-fuel vehicles are gaining popularity in recent times. Bi-fuel engine runs on more than one fuel, say in both CNG and petrol. Hence, the engine must be optimized in both the fuel modes for performance and emissions. However, due to the inherent differences in combustion characteristics: ignition dynamics and fuel properties, they pose a significant challenge in case of detection of misfires. Misfires are caused because of faulty injection systems and ignition systems and incorrect fuel mixture. Accurate detection is essential as misfires deteriorate the catalysts performance and may impacts emission. Misfires (or engine roughness) is calculated from engine crankshaft speed signal. In this study, the effectiveness of crankshaft-based misfires detection method, comparison of misfire signals magnitude in bi-fuel modes and practices developed for accurate detection of misfires is presented.
Hydrogenated nitrile butadiene rubbers (HNBR) and their derivatives have gained significant importance in automotive compressed natural gas (CNG) valve applications. In one of the four-wheelers, CNG valve application, HNBR elastomeric diaphragms are being used for their excellent sealing and pressure regulation properties. The HNBR elastomeric diaphragm was developed to sustain CNG higher pressure However, it was found permanently deformed under lower pressures. In this research work, number of experiments was carried out to find out the primary root cause of diaphragm permanent deformation and to prevent the failure for safe usage of the CNG gas. HNBR diaphragm deformation investigation was carried out using advanced qualitative and quantitative analysis methods such as Soxhlet Extraction Column, Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Thermogravimetric Analysis (TGA). For this purpose, we have carried out experiments on OK (HNBR diaphragm with higher bar pressure) and field-failed diaphragms (HNBR diaphragm deformed after lower bar CNG pressure). We have found that OK and Field failed diaphragms have different filler concentrations and uneven dispersion and distribution. Also, the crosslinking density of the failed Field diaphragms was observed in declining order in comparison with the OK diaphragms. TGA and SEM analysis revealed the filler concentration and morphology of the diaphragms. The chemical nature and thermal properties have been analysed using FTIR and DSC analysis techniques. The Soxhlation extractions study helped to understand the crosslinking density of OK and field failure diaphragms. Preventive measures have been implemented to mitigate the HNBR diaphragm permanent deformation issue.
This study investigates the phenomenon of receptacle icing during Compressed Natural Gas (CNG) refueling at filling stations, attributing the issue to excessive moisture content in the gas. The research examines the underlying causes, including the Joule-Thomson effect, filter geometries, and their collective impact on flow interruptions. A comprehensive test methodology is proposed to simulate real-world conditions, evaluating various filter types, seal materials and moisture levels to understand their influence on icing and flow cessation. The findings aim to offer ideas for reducing icing problems. This will improve the reliability and safety of CNG refueling systems.
Over the past few decades, Compressed Natural Gas (CNG) has gained popularity as an alternative fuel due to its lower operating cost compared to gasoline and diesel, for both passenger and commercial vehicles. In addition, it is considered more environmentally friendly and safer than traditional fossil fuels. Natural gas's density (0.7–0.9 kg/m3) is substantially less than that of gasoline (715–780 kg/m3) and diesel (849–959 kg/m3) at standard temperature and pressure. Consequently, CNG needs more storage space. To compensate for its low natural density, CNG is compressed and stored at high pressures (usually 200-250 bar) in on-board cylinders. This results in an effective fuel density of 180 kg/m3 at 200 bar and 215 kg/m3 at 250 bar. This compression allows more fuel to be stored, extending the vehicle's operating range per fill and minimising the need for refuelling. Natural Gas Vehicles (NGVs), particularly those in the commercial sector like buses and lorries, need numerous CNG cylinders in order to maximise vehicle range on a single fill. However, increasing the number of on-board cylinders results in a proportional increase in refuelling time, which can have a detrimental impact on operational costs for commercial fleet owners. The CNG fuel system, which usually consists of large-volume petrol cylinders (up to 800 litres), is an essential part of vehicle development. A quick petrol fill-up time is ideal because these vehicles must frequently refuel because they frequently travel vast miles each day. At the moment, the refuelling time is calculated by evaluating the CNG filling time following prototype development. Design modifications to the fuel system are necessary if the filling time is too long, which results in severe time and cost penalties as well as delays in the development cycle of new vehicle products. A mathematical model based on a number of influencing factors has been created by combining AI and ML technology. At the initial Zero design release gateway, this model will forecast the time needed to fill up with CNG petrol on all commercial vehicle platforms. This early prediction will enable additional optimization to improve gas filling time. The goal of this research work is to optimize the filling time for various platform before physical vehicle builds.
Compressed Natural Gas (CNG) engines are emerging as a viable alternative to gasoline and diesel in heavy commercial and passenger transport worldwide. They offer reduced CO₂ emissions and support energy independence in regions rich in natural gas. In India, enhanced CNG infrastructure and strict emission regulations have driven OEMs to develop CNG vehicles across all segments. Moreover, from a noise and vibration standpoint, CNG vehicles are expected to deliver cabin refinement comparable to that of their fossil fuel counterparts. However, one of the major challenges associated with CNG vehicles is the excitation due to additional components like CNG Pressure Regulator, Injector et al. The operational metallic/pulsation noises are generally higher as compared to liquid fuels like gasoline due to dry nature of the CNG fuel. This paper describes in detail the pulsation noise phenomena encountered during one of the late-stage vehicle development projects. An experimental root cause analysis methodology was established to identify the structural & cavity resonances phenomena of the CNG Regulator & Low-Pressure gas column along with identification of frequencies of various CNG sub-systems. Studies were carried out to de-couple resonance behavior of the system and improve attachment point stiffness as potential improvement solutions to mitigate this noise. The study also helped to define design guidelines to avoid such issues in future similar development models.
Decarbonizing regional and long-haul freight is challenging due to the limitations of battery-electric commercial vehicles and infrastructure constraints. Hydrogen fuel cell medium- and heavy-duty vehicles (MHDVs) offer a viable alternative, aligning with the decarbonization goals of the Department of Energy and commercial entities. Historically, alternative fuels like compressed natural gas and liquefied propane gas have faced slow adoption due to barriers like infrastructure availability. To avoid similar issues, effective planning and deploying zero-emission hydrogen fueling infrastructure is crucial. This research develops deployment plans for affordable, accessible, and sustainable hydrogen refueling stations, supporting stakeholders in the decarbonized commercial vehicle freight system. It aims to benefit underserved and rural energy-stressed communities by improving air quality, reducing noise pollution, and enhancing energy resiliency. This research also provides a blueprint for replacing diesel in over-the-road Class 8 freight truck applications with hydrogen fueling solutions. The study focuses on the Texas Triangle Megaregion (I-45, I-35, and I-10), the I-10 corridor between San Antonio, TX, and Los Angeles, CA, and the I-5/CA-99 corridors between Los Angeles, CA, and San Francisco, CA. This area represents a significant portion of U.S. heavy-duty freight movement, carrying ~8.5% of the national freight volume. Using the OR-AGENT (Optimal Regional Architecture Generation for Efficient National Transport) modeling framework, the study conducts an advanced assessment of commercial vehicles, road and freight networks, and energy systems. The framework integrates data on freight mobility, traffic, weather, and energy pathways to deliver a region-specific, optimized vehicles powertrain architectures, infrastructure deployment solutions, operational logistics, and energy pathways. By considering all vehicle origin-destination pairs utilizing these corridors and all feasible fueling station location options, the framework's genetic algorithm identifies the minimum number and optimal locations of hydrogen refueling stations, ensuring no vehicle is stranded. It also determines fuel schedules and quantities at each station. A roadmap for station deployment based on multiple adoption trajectories ensures a strategic rollout of hydrogen refueling infrastructure.
As we move towards sustainable transportation, it is essential to look for alternative powertrain technologies that might reduce emissions and depend less on fossil fuels. This paper offers a thorough analysis and comparison of several viable solutions along with their benefits, cost and conclusion for hydrogen fuel cells, solar cells, electric hybrid systems, compressed natural gas (CNG) and CNG hybrid systems alongside the latest proposal of using nuclear batteries. Hydrogen cars have zero emissions from their exhaust and can be refueled quickly, however there are some drawbacks like hydrogen production, storage, and infrastructure. The efficiency, affordability, and scalability of various hydrogen production techniques, fuel cell stack designs and storage technologies (compressed gas, liquid, and metal hydrides) are evaluated in this paper. Solar FCEVs on the other hand, are designed to utilize solar energy like Solar EVs but are very different in their operation and fundamentals. This paper provides a detailed comparison between the two. Hybrid EVs combine an internal combustion engine with an electric motor and battery, giving advantages of both the systems. We detail various hybrid architectures (series, parallel and power-split) and energy management strategies, to assess their performance, fuel savings and emission reduction capabilities. CNG vehicles and CNG hybrid vehicles are a cleaner alternative, and they serve as a transition solution from a non-renewable fossil fuel to a renewable energy source. We investigate CNG storage systems, engine modification and the possibility of using renewable natural gas (RNG) to lower the potential carbon footprint. The paper also presents revolutionary idea of nuclear batteries which use the high energy density of radioactive materials to power automobiles. We review current and potential nuclear battery designs, including betavoltaic cells and miniaturized fission reactors, with a focus on their theoretical energy density, safety characteristics, and regulatory hurdles. This research offers issues for consideration by automotive manufacturers, policymakers, and researchers in making rational decisions and prioritizing the research towards sustainable mobility with a trade-off between the environmental footprint, energy efficiency, and practical feasibility.
Hexagon Agility announced a collaboration with Norwegian EV transmission supplier Brudeli Green Mobility at the 2024 ACT Expo in Las Vegas. The partnership's goal is the integration of Hexagon Agility's CNG/RNG (compressed/renewable natural gas) systems with Brudeli's plug-in PowerHybrid system. This technology will reportedly offer fleets the capability to maintain diesel ICE duty cycles while providing fuel cost savings and help OEMs achieve global decarbonization goals. “The Brudeli PowerHybrid enables fleet owners to retain the power, performance and fuel cost savings offered by natural gas engines, while simultaneously harnessing the efficiencies of electric,” said Eric Bippus, EVP sales & systems development, Hexagon Agility. “We believe hybrids could play a role in commercial trucking in the future, and we are excited to take an active role bringing that to the market.”
Heavy duty engines for long-haul trucks are quite difficult to electrify, due to the large amount of energy that should be stored on-board to achieve a range comparable to that of conventional fuels. In particular, this paper considers a stock engine with a displacement of 12.9 L, developed by the manufacturer in two different versions. As a standard diesel, the engine is able to deliver about 420 kW at 1800 rpm, whereas in the compressed natural gas configuration the maximum power output is 330 kW, at the same speed. Three possible alternatives to these fossil fuels are considered in this study: biodiesel (HVOlution by Eni), bio-methane and green hydrogen. While the replacement of diesel and compressed natura gas with biofuels does not need significant hardware modifications, the implementation of a hydrogen spark ignition combustion system requires a deep revision of the engine concept. For a more straightforward comparison among the alternative fuels, the same engine platform has been considered. The hydrogen engine has been optimized with the support of CFD-1D simulation (GT-Power), using models calibrated with experimental data, obtained on the diesel and compressed natural gas versions. The numerical tool includes a predictive combustion model (SI-Turb), also calibrated with experimental data on a hydrogen prototype. The study shows that the implementation of a combustion system running on lean mixtures of hydrogen, permits to cancel the emissions of CO2, while maintaining the same power output of the compressed natural gas / bio-methane engine (but about 20% lower than the biodiesel). Moreover, the concentration of NOx is very low (<20 ppm) at all the operating conditions, enabling a strong simplification of the after-treatment system, at least in comparison to the original diesel/biodiesel version. Finally, the hydrogen solution exhibits an average increase of approximately 9% in efficiency respect to the compressed natural gas configuration, but it remains less efficient if compared to its biodiesel counterpart (-11%).
Fuel system supplier Hexagon Agility is optimistic about the growth of CNG thanks to the introduction of the Cummins X15N engine. Though some OEMs have signaled that the end of the ICE age is nigh, reports of the combustion engine's death as the backbone of the commercial-trucking industry are greatly exaggerated. Battery-electric vehicles are seeing continued growth in various medium-duty and last-mile delivery sectors, but their lack of energy density and cost per have prevented them from gaining market share for Class 6 and larger commercial vehicles in North America. Several suppliers are anticipating that this trend will persist over the coming decades and are making major investments in the development of alternative fuel systems for diesel combustion engines. One such supplier is Hexagon Agility. Based in the northern suburbs of Charlotte, North Carolina, Hexagon recently announced expansion plans of its Salisbury, North Carolina, facility to field orders and installations of its compressed natural gas (CNG) fuel systems.
Customer preference towards quieter vehicles is ever-increasing. Exhaust tailpipe noise is one of the major contributors to in-cab noise and pass-by-noise of the vehicle. This research proposes a silencer with an integrated acoustic valve to reduce exhaust tailpipe noise. Incident exhaust wave coming from the engine strikes the acoustic valve and generates reflected waves. Incident waves and reflected waves cancel out each other which results in energy loss of the exhaust gas. This loss of energy results in reduced noise at the exhaust tailpipe end. To evaluate the effectiveness of the proposed silencer on the vehicle, NVH (Noise, vibration, and harshness) performance of the proposed silencer was compared with the existing silencer which is without an acoustic valve. A CNG (Compressed natural gas) Bus powered by a six-in-line cylinder engine was chosen for the NVH testing. After NVH evaluation, it was found that when using the proposed silencer, overall exhaust tailpipe orifice noise is reducing by 4-5 dB throughout the engine rpm range. In-cab noise at DEL (Driver ear level) is reducing by 2 dB throughout the engine rpm range except for 1200-1400 rpm range. Pass-by noise is reducing by 1 dB when vehicle is running in 3rd gear and it is reducing by 3 dB when vehicle is running in 4th gear.
With the advent of upcoming stringent automobile emission norms globally, it is inevitable for original equipment manufacturers (OEMs) to shift towards greener alternatives. Use of compressed natural gas (CNG) is a preferred solution as it is a relatively clean burning fuel and it doesn’t have significant loss in vehicle efficiency and performance. Modern day customers are more aware and sensitive towards vehicle noise, vibration and harshness (NVH). Hence, OEMs must cater to this demand through optimized design and layout. In a passenger vehicle, CNG is stored at high pressure and delivered to injectors after pressure reduction at a regulator. During engine idling, the opening and closing motion of the CNG injector generates back pulsation and these pulsations cause vibrations which may propagate through other components in the delivery path and perceived as noise inside vehicle cabin. To identify the frequencies involved in pressure pulsation, a 1-D simulation of CNG fuel system is performed using commercially available simulation software GT-Suite through which excitation frequencies and pressure pulsation peak amplitude has been identified. To validate the model, actual pulsation measurement testing has been performed and pressure peaks amplitude are compared with simulation. Based on correlation with actual testing, multiple resonator designs are created to dampen the identified excitation frequencies range. These designs have been virtually validated for pressure peak reduction by simulating resonators with fuel system layout in GT-Suite.
In this article, we highlight the prime classification of hybrid powertrains for the automotive sector and quantify the scope and benefit of using gasoline and diesel as mono fuel or CNG and Flex-fuel (Ethanol blend) as duel fuel. Such powertrains have a high potential to achieve lower carbon emissions for the near future usage and implementation until the carbon-neutral powertrain reaches its majority in the market. H2 combustion engine powertrain is one of the potential solutions to achieve a carbon-neutral powertrain solution using the optimized IC engine. Further, this article also highlights the benefits and challenges in commercializing the H2 combustion engine powertrains against the e-fuel-based (new-energy) carbon-neutral powertrains for Battery powered (BEVs) and Fuel Cells powered (FCVs) electric vehicles. Finally, we discuss the link between the capacity and size of the thermal cooling system of an automotive vehicle and the type of powertrains chosen for future mobility solutions.
This study investigated the exhaust particle and unregulated emissions emanating from a heavy duty six-cylinder natural gas engine with CNG and HCNG fuels. Experiments were performed at different speeds (1000, 1500, 2000 and 2500 rpm) and load conditions (30%, 50%, 75% and 100%). Exhaust gas samples at each speed-load combination were analyzed for particle number concentration and particle size distribution using engine exhaust particle sizing spectrometer. Unregulated emissions were also measured using FTIR (Fourier Transform Infrared) analyzer. The results indicated that particle number (PN) concentration in exhaust is comparatively lower with HCNG fuel than CNG and it increases with increase in engine speed-load. At higher speed-load condition, engine emits high nucleation mode particles (NMP) and ultrafine particles (UFP). Total PN concentration in the NMP range is comparatively higher than UFP and accumulated mode particles (AMP) for both the test fuels. The surface area of particles corresponds to UFP and NMP are lower for HCNG at all test conditions. The results on unregulated emission shows that major carboxyl (formaldehyde and acetaldehyde), alkane (propane and methane) and alkene (1,3-butadiene and propene) emissions were higher with CNG fuel than HCNG fuel. All these emissions decrease with increase in speed-load condition. Nitrogen oxides like NO2, NO and N2O shows comparatively higher value for HCNG due to proper and complete combustion. Average CO2 emission reduction in HCNG fuel is up to 17% as compared to CNG fuel. As load and speed increases, CO2 emission also increases for both the test fuels. Overall, this study exhibits the benefits of blending hydrogen in CNG in terms of reduction in particulate emission and unregulated emission.
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