Browse Topic: Alternative fuel engines
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.
Due to increasing pollution and climatic cries, newly implemented BS-VI emission norms in India have stressed the reduction of emission. For which many automobiles have been shifted to alternate fuels like CNG. Also, the Indian Automotive market is fuel economy cautious. This challenges to focus on improving fuel economy but without an increase in emissions. Crankcase blow-by gases can be an important source of particulate emission as well as other regulated and unregulated emissions. They can also contribute to the loss of lubricating oil and fouling of surface and engine components. Closed Crankcase Ventilation (CCV) or Open Crankcase Ventilation (OCV) is capable to reduce particulate emissions by removing the oil mist that is caused mainly due to blow-by in the combustion chamber. This paperwork is focused, to measure the effectiveness of the CCV and OCV systems on the engine-out emissions, primarily on the particulate emissions. A comparative analysis of these crankcase ventilation systems is made by monitoring various parameters, like engine speed, torque, crankcase pressure, engine blow-by, etc. to analyze the effectiveness of these systems for the reduction in particulate emissions.
As competent and low-pollution alternative fuel, CNG has revealed its excellence over engine performance and emissions. In recent years, CNG is considered as the diesel engine alternative fuel for heavy-duty engine applications due to its lower emissions and cost effective after-treatment systems. Due to the implementation of stricter emission norms over the years, the evolution of the fuel supply system has become more robust and electronically controlled. In the case of CNG engines, most of the engines were equipped with MPFI fuel system, for its precise fuel control abilities and controlling emission parameters. However, this MPFI system encompasses severe design changes in the intake manifold and is cost worthy to OEMs over the SPFI fuel system. MPFI system adds on the overall cost of the engine unit and its maintenance when compared to SPFI system. SPFI fuel system had proved its robustness to achieve BSIV emission norms but, due to challenging test methods and stringent emission limits, BSVI development with this fuel system seems cumbersome with limited control parameters. This paper presents the research work conducted on a heavy-duty CNG engine with a SPFI fuel system. The challenges involved for achieving the BSVI emissions through engine calibration, without major engine hardware change along with engine performance is incorporated in this work.
Engine calibration involves the interaction of electronic components with various engine systems like intake system, exhaust system, ignition system, etc. Emissions are the by-products of combustion of fuel and air inside the combustion chamber. After-treatment systems generally take up the responsibility to scrape out harmful emissions from the engines. However, a good engine calibration will focus on emission reduction at source i.e., during the combustion itself. Thus, the intake of air and fuel in proper amount at each engine operating point is crucial for optimized engine performance and minimal emissions. The Intake system is an integral part of any internal combustion engine and it plays an important role to improve its performance and emission. Generally, for a SI engine, maintaining the stoichiometric A/F ratio is a challenging endeavour from an operational standpoint. Engine power, BSFC, torque and harmful emissions are much influenced by geometric aspect of intake manifold and its fuelling distribution system. The role of the intake manifold is the distribution of Air-Fuel mixture uniformly in all cylinders of the SI engine. Two different intake system configurations viz. SPFI (Single Point Fuel Injection) and MPFI (Multi Point Fuel Injection) are evaluated in this paper. In the Multipoint Injection System, one injector per cylinder is provided which injects the fuel in appropriate quantity in the admission valve allowing the fuel and air into the cylinder. This provides individual control on the cylinder which in turn improves the fuel consumption as compared to the Single point fuel injection. This paper is related to experimental comparison of CNG fuel distribution for a SPFI and MPFI system and its merits and demerits after analyzing the effects on the engine performance and emissions, which were evaluated on the similar engine configurations with SPFI and MPFI fuel distribution systems.
CNG has proven to be a concrete alternative to gasoline and diesel fuel for sustained mobility. Due to stringent emission norms and sanctions being imposed on diesel fuel vehicles, OEMs have shifted their attention towards natural gas as an efficient and green fuel. Newly implemented BS VI emission norms in India have stressed on the reduction of Nitrogen Oxides (NOx) from the exhaust by almost 85% as compared to BS IV emission norms. Also, Indian Automotive market is fuel economy cautious. This challenges to focus on improving fuel economy but without increase in NOx emissions. Exhaust Gas Recirculation (EGR) has the potential to reduce the NOx emissions by decreasing the in-cylinder temperature. The objective of the paper is to model a CNG TCIC engine using 1D simulation in order to optimize the NOx emissions and maintain exhaust temperatures under failsafe limits. The 1D model is optimized in steady state conditions using the control parameters such as EGR flow rate, power achieved and maximum exhaust temperatures within the boundary conditions. The simulation is carried out using High Pressure (HP) EGR and Low Pressure (LP) EGR design optimization and predictions were made regarding the exhaust gas temperature. This simulation model is validated using actual experimental results and the finalized EGR strategy is used to optimize the NOx emissions.
The intensifying demand of cleaner fuelled vehicles considering current norms of BSIV and upcoming stringent norms of BSVI with low cost solutions has promoted the development of CNG and dual fuel vehicles. CNG vehicle is anticipated to discover its extensive use for environment fortification and effective deployment of energy capitals. Thus, CNG vehicles can be pretty effective in averting environment deterioration. CNG has low carbon to hydrogen ratio, this leads to very low CO2 emissions compared to gasoline and diesel vehicles. CNG engines have the potential of low NOx and particulate emissions. Natural gas vehicle development has been directed on the way to current use of direct injection and port injection with S.I. engines. Generally for low cost development, all OEMs prefer optimization of existing engines. Similarly for this project, a diesel engine was converted to S.I. engine for development of low emission CNG engine. All required changes from diesel to CNG engine have been elaborated in this paper. For optimization of an S.I. engine with port injection, it is vital to understand the combustion propagation. This paper gives the complete insight of CNG fuelled turbocharged engine development with detailed discussion on fuel injection strategies and lambda control for best catalyst efficiency. Further, Emission optimization and exhaust temperature control strategies have been discussed for better understanding of emission development and misfire control. Complete hardware range: spark plug, injector, turbocharger and catalyst selection has been discussed for best engine optimization. The result of this study can contribute some vibrant knowledge for the design and development of S.I. port injection CNG engine.
The evolution of engine technology has so far seen the most beneficial side of progress in the fields of transportation, agriculture, and mobility. With the advent of innovation, there is also an impact on our environment that needs to be balanced. This is where fuels like CNG, LPG, LNG, etc. outperform conventional fossil fuels in terms of pollution & operational cost. This paper enlightens on the use of innovative dual-fuel technology where diesel & CNG fuels are used for combustion simultaneously inside the combustion chamber. Dual fuel system adaptation for farm application ensures self-reliance of the farmer where he can generate Bio-CNG to use the renewable fuel for farming making him less dependent on conventional fossil fuel thus promoting a green economy. The dual-fuel system is adapted to the existing in-use diesel engine with minimum modifications. This makes it feasible to retrofit a CNG fuel system on an existing diesel engine to operate it on dual fuel mode. Major benefits of the dual-fuel system include better operational costs than pure diesel mode along with diesel replacements of around 40% without any change in the existing diesel fuel supply system with a substantial reduction in smoke and PM emissions. However, minor modifications in the exhaust after-treatment system are required to be made for compliance with NOx and NMHC emissions. The existing performance of the base diesel engine is retained in dual fuel mode with improvement in fuel economy. Thus, making this dual-fuel technology affordable especially for the Indian agriculture sector.
The present study depicts cubic polynomial function based parametric mapping of reactivity controlled compression ignition (RCCI) engine, across load sweep and gasoline energy share (GES). Based on the pilot experimental findings, the diesel (main) injection timing is determined followed by a set of experiments across the engine load sweep and GES, not exceeding 50%. Based on cycle to cycle variation of peak pressure, 50% burn crank angle (CA50) and indicated mean effective pressure (IMEP), engine stability values are computed. A set of RCCI engine parameters such as peak pressure, ringing intensity (RI), IMEP, CA50 etc. are normalized. The coefficients of polynomial are generated through surface fit to map all these parameters with normalized load and GES. Good conformity was observed between the predicted and modelled data. Subsequently, an operation window is proposed based on stability, combustion efficiency and thermal efficiency considerations. The proposed polynomials within the prescribed limits can be very much useful for designing look up tables, operation maps etc. and can also be valuable towards low cost RCCI engine development without exhaust gas recirculation (EGR).
In this study, a new system of assessment method was developed to evaluate the characteristics of urban buses based on remote online monitoring. Four types of buses, including China V emission standards diesel bus, lean-burn CNG bus, air-fuel equivalence ratio combustion CNG bus and gas-electric hybrid bus, were chosen as samples to analyze the emission characteristics of urban buses with different engine types in urban scenario. Based on the traffic conditions in Beijing, the actual emission characteristics of buses under newly-built driving conditions were analyzed. Moreover, the emission factor database of urban buses in Beijing was established to analyze the characteristics of excess emission. The research results are shown as follows. 1) Compared with other types of buses, NOX emission factor and emission rate of lean-burn CNG bus are much higher. The equivalent air-fuel ratio CNG engine combined with TWC catalytic converter and hybrid power technology can better reduce NOX emission. 2) There is difference between the type certification under standard operating conditions and the emission results in actual operation to a varying degree. The evaluation of emission performance based on actual operation can more truly reflect the actual performance of the bus. The BJ-FPC (Beijing flat peak cycle) developed in this paper is closer to the actual operating conditions of the sample bus in terms of VSP Bin proportional distribution. 3) As to weighted NOX emission factors, the BJ-HPC (Beijing high peak cycle) of different types of buses are higher than BJ-FPC and actual operating conditions. 4) Based on the excessive emission method assessment, the NOX of China V diesel bus easily exceeds the emissions limits, and the NOx concentration of lean-burn CNG bus is high, and both the NOx over-limit ratio and the quantity of excessive emission buses are also high. Gas-electric hybrid bus can better reduce the NOX emission and the excessive emission frequency under the urban operating condition.
Compressed Natural Gas (CNG) is regarded as a promising fuel for spark-ignited (SI) internal combustion engines (ICE) to improve engine thermal efficiency and reduce both carbon dioxide and pollutant emissions. Significant advantages of CNG are higher-octane number, higher hydrogen to carbon ratio, and lower energy-specific CO2 emissions compared with gasoline. More, it can be produced in renewable ways, and is more widespread and cheaper than conventional liquid fossil fuels. In this regard, the direct injection of CNG engines can be considered a promising technology for highly efficient and low-emission future engines. This work reports an experimental and numerical characterization of high-pressure methane jets from a multi-hole injector for direct injection engines. The tests were performed in a constant volume (CV) combustion chamber under a broad range of operating conditions in terms of injection pressure, in the range 1.0 - 5.0 MPa, and ambient back-pressure in between 0.05 to 1.0 MPa. The schlieren technique was employed to evaluate the effects of the injection pressure and ambient thermodynamic conditions on jet macroscopic characteristics. Then, the overall injection process has been reconstructed thanks to a CFD (computational fluid dynamic) density-based model, properly developed in OpenFOAM environment, featuring a large eddy simulation (LES) turbulence framework. The simulation reproduces the jet’s transient evolution and captures its classical structures. Such model allows evaluating further parameters, not available from the experimental characterization, that provide a better knowledge of the air-fuel mixing process.
The emissions and efficiency of modern internal combustion engines need to be improved to reduce their environmental impact. Many strategies to address this (e.g., alternative fuels, exhaust gas aftertreatment, novel injection systems, etc.) require engine calibrations to be modified, involving extensive experimental data collection. A new approach to modeling and data collection is proposed to expedite the development of these new technologies and to reduce their upfront cost. This work evaluates a Gaussian Process Regression, Artificial Neural Network and Bayesian Optimization based strategy for the efficient development of machine learning models, intended for engine optimization and calibration. The objective of this method is to minimize the size of the required experimental data set and reduce the associated data collection cost for engine modeling. This technique is demonstrated by generating engine performance models for a Dual Fuel High Pressure Direct Injection (HPDI) CNG Engine. Models are generated for the emissions and performance of a pilot ignited, direct injection, natural gas engine using only typical control inputs (e.g.: speed, injection timings, and fuel and air pressures). This modeling technique is first demonstrated on a full-factorial data set collected over a narrow operating space and then compared to a much coarser data set collected over a much larger space using the Box-Behnken approach. Ten sets of neural network and Gaussian process regression models were generated for each engine output. The aggregated model results demonstrate that the machine learning models perform very well for the full factorial data set with correlation coefficients generally over 0.8 and normalized root mean square errors generally under 10%, while the response surface model is unable to characterize the outputs due to the size of the data. While there is a loss in performance using the coarser Box-Behnken data set, the machine learning methods do show some strong results for certain outputs. Models for NOX, CO2, O2, Peak Cylinder Pressure, EQR and Gross Indicated Power have R2 greater than 0.8 and normalized root mean square errors less than 20%. In general, Gaussian process regression shows the higher performing results with less performance variation over multiple tests compared to the neural network models. With further study, this method could enable the rapid evaluation and implementation of technologies and fuels for emission reduction.
Isuzu is making it easier for equipment owners to switch fuels from natural gas to liquid propane, letting users switch by merely sending a signal to the engine. Released in October 2019, the dual-fuel 4HV1 engines and power units also have a higher compression ratio that helps conserve fuel. The alternative fuel engines, designed for non-emergency and emergency standby generator applications and multi-speed applications, let operators switch fuel sources without reconfiguring the base engine. This feature helps to reduce downtime on site, according to Isuzu, which plans to feature the dual-fuel system at ConExpo-Con/Agg in March (South Hall 4, S85406).
The cylinder head gasket with integrated combustion pressure sensors (CHGICPS) reported here targets advanced engine controls and in particular those based on the HCCI, PCCI, or LTC combustion principles, for gasoline, diesel, and alternative fuel engines. Due to the fiber optic combustion pressure sensor's (CPS) accuracy at low pressure during compression integrated into the CHGICPS, this device aims at in-cylinder prediction of mass air flow as well as in-cycle closed loop control of pilot fuel injection in a diesel engine. This paper reports on a replaceable CPS which allows installation and removal from the cylinder head gasket (CHG) without the need for removing the engine head. At the same time the distance layer thickness of CHGICPS is minimized to 2.5 mm and 3.4 mm, depending on the access ability and space constraints around coolant and lubrication ports in the engine. A multilayer steel CHGICPS prototype is constructed with replaceable fiber optic combustion pressure sensors (CPS) that operate on the principle of modulation of light reflected from a metal diaphragm deflecting under effect of cylinder pressure. The signal conditioners are remotely located from the CHGICPS in the tested design. The initial test results of the combustion pressure measurement CHICPS demonstrated high fidelity pressure traces at low and high engine speeds for various throttle positions for the CPS using a heat shield as compared to a recessed and exposed fiber-optic CPS. The difference between the reference sensor and the fiber-optic CPS is less than 0.1 bar during compression below 5 bar and .5 bar for a cylinder pressure range from 0 to 50 bar. The fiber-optic CPS removal and installation was performed successfully on the engine without removing the head with no signs of observable leakage. The measured pressure difference error between reference sensor and the fiber-optic sensor at peak power 2900 rpm and wide open throttle (170 bar peak cylinder pressure) shows a 2.3% error as compared to the water cooled reference sensor. Calibration adjustment of the fiber-optic CPS is shown to improve this performance. Future design considerations for integrating the signal conditioners into the CHGICPS and improved sensor performance are discussed. Overall, combining the pressure performance capabilities of a replaceable fiber-optic CPS that does not require removing the engine head, the suitability of the CHG location for all engine types, and the economic advantages of design simplicity, makes the CHGICPS a viable solution for combustion control technology in the future.
The mass ratio of air to fuel (air-fuel ratio) of an operating internal combustion engine is a very important metric for pollution control. Typically the air-fuel ratio is not directly measured, but instead the excess air factor Lambda (λ) is used. Lambda is the ratio of actual air-fuel ratio to the stoichiometric air-fuel ratio. Commonly switching type sensors are used. Those can detect 3 states: λ =1, λ >1 and λ < 1, and are used under low and medium load conditions to keep λ in the optimum operating range for a catalytic converter. Wideband O2 sensors are exhaust analysis devices that are used to measure air-fuel mixtures over a very large range up to air. These sensors are used in more and more engines today for closed loop fueling control under all operation conditions. They are especially important for new lean-burn technologies, clean diesel applications and for alternative fuel engines. However, todays typical control methodology for these sensors has drawbacks regarding response times, accuracy and drift over time. For example, individual cylinder control for injector balancing requires sensors with very fast response times, if a single sensor is to be used for a group of cylinders. The alternative is to use individual sensors for each cylinder, an approach that is cost-prohibitive. The commonly used control method for wideband sensors today typically limits the 3dB measurement bandwidth to less than 10 Hz for the fastest implementations. This bandwidth is too low to be usable for individual cylinder control with a single sensor per cylinder group. It also severely limits their application in closed loop control of transitional engine states. This paper describes a new approach for wideband O2 sensor control that possibly enables: 1 Individual Cylinder Balancing 2 Automatic calibration to compensate for sensor drift 3 Missfire detection 4 Simplified, low cost implementation 5 Cost reduced single-cell wideband sensors 6 Detailed sensor diagnostics The method described treats a pump-cell wideband not as a feedback controlled system, but as the “analog” front-end of a modified Delta-Sigma Analog-to-Digital Converter. This results in fast, highly linear measurement response and simplified implementation of the control electronic for wideband O2 sensing. This new method is possible now due to the advances in integration of digital systems and the advances in digital signal processing.
In present days, most of researches concerned with vehicle engines have been performed to reduce vehicle emissions and to improve engine efficiency. For the requirements, LPG (Liquefied Petroleum Gas) engine which has lots of advantages such as low emission level, cheaper fuel cost and enough infrastructures has had lots of interest as an alternative fuel engine. What is more, it has a low emission level of CO2 well-known as the factor of ‘Global Warming’, thus the use of LPG engines has been increased. Especially since MPI(Multi Point Injection) type LPLi(Liquid Phase LPG injection) system was used for the fuel supply system, disadvantages of LPG engine such as low engine performance, decreased charging efficiency and cold starting difficulty have been improved and prejudices against LPG engines have been changed a lot. In light of this, the motion to use LPLi engines instead of diesel engines has been increasing. Therefore in this research, spray visualization experiment was performed to find the optimal LPG injection conditions for a modified diesel engine. And the effect of the ambient pressure on spray characteristics of LPLi injector was investigated in a high pressure chamber which simulates the air charging condition of the base diesel engine. As a result, the ambient pressure affects both injection quantity and spray structure. And the results provide valuable information on macroscopic spray structure and design factors for modifying LPG injection system for the engine.
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