35,626 research outputs found
Injection and combustion analysis and knock detection models for high-efficiency natural gas engines
Between different sectors, GHG emissions released by automotive one in 2010 were 4.5 GtCO2, the 14% of the total (32 GtCO2). Moreover, transport sector depends by more than 93% on oil, to be refined into gasoline and diesel fuel. Natural gas demand in transport sector has clearly increased in the last decade considering the lowest CO2 emissions per units of energy produced among different fossil fuels but it will be used mostly in the next future. Among different sectors, the 21 % of the energy demand is indeed supplied by NG, due to lower price and reduced GHG emissions. Storage type (compressed natural gas or liquefied natural gas) and vehicle type (road transport, marine transport, etc.) mainly discriminate natural gas engine layouts. Spark-ignition natural gas engine with different configurations will be indeed taken into consideration in this research project. Today, vehicles for the road transport fueled with compressed natural gas are mainly bi-fuel ones with both gasoline and natural gas feeding system with a manual or automatic switch. To mitigate knock event, engine layout is designed up to gasoline characteristics and engine performances with natural gas are not fully exploited. Mono-fuel configuration is capable to totally exploit the potential of natural gas. Therefore, this thesis will focus on the development of mono-fuel natural gas engines and improvements in injection and combustion strategies have to be reached by implementing new combustion chamber shape, improved ignition management and improved injection systems.
A detailed analysis of the natural gas injection system will be hence carried out. Different injection system layouts will be analyzed: single-point, multi-point and direct injection systems, focusing on pressure reducing valve dynamic. As a matter of fact, its behavior affects the dynamic response of the injection system: mismatch between estimated injected fuel and real one could be appreciated. Typically, average rail pressure evaluated by ECU differs from mean value during injection window. Therefore, detailed analysis will be carried out on experimental data and a 0D-1D numerical model will be
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developed to enhance the problem understanding. The research activity has been carried out in order to reproduce properly all the components of the pressure reducing valve which affects the dynamic response of the injections system. The numerical model will give useful explanation of the fuel mass injected mismatch.
Then, a heavy-duty spark ignition compressed natural gas engine provided with two different injection systems will be examined. A standardized single-point injection system and a prototypal multi-point one will be evaluated so as to evaluate the possibility for performance enhancement. Cyclic variation and combustion efficiency for each configuration will be analyzed, proving the highest combustion efficiency of the prototypal configuration. Moreover, possible improvements with new engine control strategies will be investigated by adopting a 0D-1D numerical model. Single-point injection system modelling will prove the impossibility for efficiency improvement whereas multi-point injection system can be optimized by adopting enhanced strategies. As a matter of fact, fire-skipping mode will be simulated. Feasible reductions of fuel consumption under partial load conditions will be shown: decrease in fuel consumption up to 12% will be proved.
Finally, a new methodology for combustion, cyclic variation and knock onset modelling will be presented. Indeed, high-efficiency natural gas engines could in turn lead to knock conditions due to higher CR and different combustion chamber shape. Experimental analysis at test bench could be carried out to calibrate appropriate ECU control strategies for knock mitigation, but an experimental campaign under knock condition is dangerous and costly due to possible failure of mechanical parts of the engine. Numerical models for auto-ignition prediction could hence overcome this problem. Therefore, a predictive fractal combustion tool will be calibrated: it will be able to perform a correct mass fraction burned evolution estimation for different operating conditions (speeds, loads, relative air-to-fuel ratio, etc.). Then, knock onset estimation based on auto-integral (its usage is satisfactory considering the high natural gas chemical stability) coupled with a new method for cyclic variability simulation will be adopted; these two phenomena are indeed strictly correlated. A correct estimation of the percentage of knocking cycles will be shown. This new methodology will be carried out and verified on two light-duty spark ignition engines with different characteristics so as to verify its goodness
Reducing NOx Emissions of Cargo Handling Equipment (CHE) with Humid Air Systems
The authors designed and tested a humid air system (HAS) for reducing NOx emissions of an LPG-powered forklift. The HAS uses distilled water and heat from the exhaust to generate steam that is injected into the intake air of the engine to increase humidity and thus achieve NOx reduction. Field tests with HAS have shown 2.2 ppm of NOx reduction with each percent increase in humidity of the intake air. A provisional patent based on the developed system has been filed
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Thermodynamic analysis of a novel fossil-fuel–free energy storage system with a trans-critical carbon dioxide cycle and heat pump
This paper presents and analyzes a novel fossil-fuel–free trans-critical energy storage system that uses CO2 as the working fluid in a closed loop shuttled between two saline aquifers or caverns at different depths: one a low-pressure reservoir and the other a high-pressure reservoir. Thermal energy storage and a heat pump are adopted to eliminate the need for external natural gas for heating the CO2 entering the energy recovery turbines. We carefully analyze the energy storage and recovery processes to reveal the actual efficiency of the system. We also highlight thermodynamic and sensitivity analyses of the performance of this fossil-fuel–free trans-critical energy storage system based on a steady-state mathematical method. It is found that the fossil-fuel–free trans-critical CO2 energy storage system has good comprehensive thermodynamic performance. The exergy efficiency, round-trip efficiency, and energy storage efficiency are 67.89%, 66%, and 58.41%, and the energy generated of per unit storage volume is 2.12 kW·h/m3, and the main contribution to exergy destruction is the turbine reheater, from which we can quantify how performance can be improved. Moreover, with a higher energy storage and recovery pressure and lower pressure in the low-pressure reservoir, this novel system shows promising performance
Nature versus built
Nature is made up of various living and non-living things which is related to plants, animals and other features such as mountains, deserts and seas. They are connected and some of the relationships between members are direct and obvious and ecosystem occurred to balance the amount of living things. Built environment is referring to aspects of creature human-made surroundings. Human activities caused some environmental issues and disturbance the nature. However, the technologies introduce sustainability building and creature as conservation our nature. There also some ways can be practice at house to save the environment
Large scale gas injection test (Lasgit) performed at the Äspö Hard Rock Laboratory: summary report 2007
The deposition hole was closed on the 1st February 2005 signifying the start of the hydration
phase. Groundwater inflow through a number of conductive discrete fractures resulted in
elevated porewater pressures leading to the formation of conductive channels (piping), the
extrusion of bentonite from the hole and the discharge of groundwater to the gallery floor. This
problem was addressed by drilling two pressure-relief holes in the surrounding rock mass.
Artificial hydration began on the 18th May 2005 after 106 days of testing. Initial attempts to raise
porewater pressure in the artificial hydration arrays often resulted in the formation of preferential
pathways. These pressure dependent features were not focused in one location but occurred at
multiple sites at different times in the test history. These pathways appear to be relatively short
lived, closing when water pressure is reduced.
It was determined that both pressure relief holes should remain open until the bentonite had
generated sufficient swelling pressure to withstand the high water pressure in the system when
these holes are closed. Packers were installed into the pressure relief holes on 23rd March 2006
and sections in them closed off over the period to 5th July 2006. There was no repeat of the
formation of piping through discrete channels so, on 20th November 2006, pressures to the
artificial hydration filters on the canister were increased to 2350 kPa
Electricity powering combustion: hydrogen engines
Hydrogen is ameans to chemically store energy. It can be used to buffer energy in a society increasingly relying on renewable but intermittent energy or as an energy vector for sustainable transportation. It is also attractive for its potential to power vehicles with (near-) zero tailpipe emissions. The use of hydrogen as an energy carrier for transport applications is mostly associated with fuel cells. However, hydrogen can also be used in an internal combustion engine (ICE). When converted to or designed for hydrogen operation, an ICE can attain high power output, high efficiency and ultra low emissions. Also, because of the possibility of bi-fuel operation, the hydrogen engine can act as an accelerator for building up a hydrogen infrastructure. The properties of hydrogen are quite different from the presently used hydrocarbon fuels, which is reflected in the design and operation of a hydrogen fueled ICE (H2ICE). These characteristics also result in more flexibility in engine control strategies and thus more routes for engine optimization. This article describes the most characteristic features of H2ICEs, the current state of H2ICE research and demonstration, and the future prospects
Bi-fuel NGVM engine emission results based on non-loaded system operation
Alternative fuels for the internal combustion engines are introduced as an improved fuel over mainstream conventional fuels such as petrol and diesel. Compressed Natural Gas (CNG) is the most successful and widely used alternative fuels that helps mitigate emission problem caused by vehicles. Mainstream fuelled vehicles are fitted with a conversion kit to enable the operation with CNG, these converted vehicles are called Natural Gas Vehicles. A bi-fuel engine test rig was fabricated using a 1500cc 12 Valve engine fitted with a Landi Renzo conversion kit enabling operations on petrol and natural gas. This test rig was used to conduct experiments to obtain the fuel consumption and the corresponding exhaust emission quality. The results obtained were compared with the actual data of NGV taxi fitted with Tartarini conversion kit for validation purpose. The findings from this experimental rig are used as a comparison between the use of petrol and natural gas as fuel for vehicles. The results clearly prove that the use of natural gas provides improved exhaust emission at lower cos
Thermodynamic, economic and environmental assessment of energy systems including the use of gas from manure fermentation in the context of the Spanish potential
One of the prospective technologies that can be used for energy generation in distributed systems is based on biogas production, usually involving fermentation of various types of biomass and waste. This article aims to bring novelty on the analysis of this type of systems, joining together thermodynamic, economic and environmental aspects for a cross-cutting evaluation of the proposed solutions. The analysis is made for Spain, for which such a solution is very promising due to availability of the feedstock. A detailed simulation model of the proposed system in two different cases was built in Aspen Plus software and Visual Basic for Applications. Case 1 involves production of biogas in manure fermentation process, its upgrading (cleaning and removal of CO2 from the gas) and injection to the grid. Case 2 assumes combustion of the biogas in gas engine to produce electricity and heat that can be used locally and/or sold to the grid. Thermodynamic assessment of these two cases was made to determine the most important parameters and evaluation indices. The results served as input values for the economic analysis and environmental evaluation through Life Cycle Assessment of the energy systems. The results show that the analysed technologies have potential to produce high-value products based on low-quality biomass. Economic evaluation determined the break-even price of biomethane (Case 1) and electricity (Case 2), which for the nominal assumptions reach the values of 16.77 €/GJ and 28.92 €/GJ, respectively. In terms of environmental assessment the system with the use of biogas in gas engine presents around three times better environmental profile than Case 1 in the two categories evaluated, i.e., carbon and energy footprint.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie SkĹ‚odowska-Curie grant agreement No 799439. Dr. MartĂn-Gamboa states that thanks are due to FCT/MCTES for the financial support to CESAM (UID/AMB/50017/2019), through national funds
Performance analysis of turbocharger effect on engine in local cars
The performance of a gasoline-fueled internal combustion engines can be increased with the use of a turbocharger. However, the amount of performance increment for a particular engine should be studied so that the advantages and drawbacks of turbocharging will be clarified. This study is mainly concerned on the suitable turbocharger unit selection, engine conversions required and guidelines for testing a Proton 4G92 SOHC 1.6-litre naturally aspirated gasoline engine. The engine is tested under its stock naturally aspirated condition and after been converted to turbocharged condition. The effect of inter cooled turbocharged condition is also been tested. Boost pressure is the main parameter in comparing the performance in different conditions as it influences the engine torque, power, efficiency and exhaust emissions. The use of a turbocharger on this test engine has clearly increased its performance compared to its stock naturally aspirated form. The incorporation of an intercooler to the turbocharger system increases the performance even further. With the worldwide effort towards environmental-friendly engines and fossil fuel shortage, the turbocharger can help to create engines with enhanced performance,minimum exhaust emissions and maximum fuel economy
Optimal Control of Transient Flow in Natural Gas Networks
We outline a new control system model for the distributed dynamics of
compressible gas flow through large-scale pipeline networks with time-varying
injections, withdrawals, and control actions of compressors and regulators. The
gas dynamics PDE equations over the pipelines, together with boundary
conditions at junctions, are reduced using lumped elements to a sparse
nonlinear ODE system expressed in vector-matrix form using graph theoretic
notation. This system, which we call the reduced network flow (RNF) model, is a
consistent discretization of the PDE equations for gas flow. The RNF forms the
dynamic constraints for optimal control problems for pipeline systems with
known time-varying withdrawals and injections and gas pressure limits
throughout the network. The objectives include economic transient compression
(ETC) and minimum load shedding (MLS), which involve minimizing compression
costs or, if that is infeasible, minimizing the unfulfilled deliveries,
respectively. These continuous functional optimization problems are
approximated using the Legendre-Gauss-Lobatto (LGL) pseudospectral collocation
scheme to yield a family of nonlinear programs, whose solutions approach the
optima with finer discretization. Simulation and optimization of time-varying
scenarios on an example natural gas transmission network demonstrate the gains
in security and efficiency over methods that assume steady-state behavior
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