Design of limaçon gas expanders
- Authors: Phung, Truong , Sultan, Ibrahim , Boretti, Alberto
- Date: 2016
- Type: Text , Book chapter
- Relation: Nonlinear Approaches in Engineering Applications : Advanced Analysis of Vehicle Related Technologies Chapter 3 p. 91-119
- Full Text:
- Reviewed:
- Description: Limaçon is a simple and yet reliable technology, which can be employed to manufacture gas expanders to extract work or electrical power from low-grade heat or solar power resources; Limaçon technology can also be applied to smallscale power generation applications or can be used to improve energy efficiency of existing processes. Sultan (Journal of Mechanical Design, 787-793, 2006) and Sultan and Schaller (Journal of Engineering for Gas Turbines and Power, 2011) have come up with an optimum design of Limaçon-to-Limaçon expanders based on their thermodynamics performance; the design presented a model to calculate the cross-sectional area as well as the velocity of fluid flow through the inlet and discharge ports. However, the problem of optimum geometric characteristics of the inlet and discharge manifolds and the best parameters of various Limaçon embodiments are left to be solved.Additionally, the effect of the phase change on the expander performance is yet to be investigated. Aim of this document is to provide the framework of the Limaçon machines to achieve optimum expander geometries for power generation systems with various types of working fluids. © Springer International Publishing Switzerland 2016.
Conversion of a heavy duty truck diesel engine with an innovative power turbine connected to the crankshaft through a continuously variable transmission to operate compression ignition dual fuel diesel-LPG
- Authors: Boretti, Alberto
- Date: 2013
- Type: Text , Journal article
- Relation: Fuel Processing Technology Vol. 113, no. (September 2013 2013), p. 97-108
- Full Text: false
- Reviewed:
- Description: This paper considers the option to convert the diesel engine to LPG retaining the diesel-like behaviour. LPG is an alternative fuel with a better carbon to hydrogen ratio permitting reduced carbon dioxide emissions. It flashes immediately to gaseous form even if injected in liquid state for a much cleaner combustion almost cancelling some of the emissions of the diesel. Within Australia, LPG permits a much better energy security and the refueling network is widespread. In this paper, a latest heavy duty truck diesel engine with a novel power turbine connected through a continuously variable transmission to the crank shaft and fitted with a by-pass is modified to accommodate a second direct injector for the LPG fuel and operate full load with 5% diesel and 95% LPG. Results of engine performance simulations with diesel and diesel-LPG are presented. The engine retains the diesel performances while permitting the advantages of LPG in terms of particulate, carbon dioxide emissions and diversification of fuel supplies and energy security. (C) 2013 Elsevier B.V. All rights reserved.
- Description: C1
Discussion of Christine C. Shepard, Vera N. Agostini, Ben Gilmer, Tashya Allen, Jeff Stone, William Brooks and Michael W. Beck. Reply: Evaluating alternative future sea-level rise scenarios, Natural Hazards, 2012 doi:10.1007/s11069-012-0160-2
- Authors: Boretti, Alberto
- Date: 2013
- Type: Text , Journal article
- Relation: Natural Hazards Vol. 65, no. 1 (January 2013 2013), p. 967-975
- Full Text: false
- Reviewed:
- Description: C1
Discussion of Natalya N. Warner, Philippe E. Tissot, Storm flooding sensitivity to sea level rise for Galveston Bay, Texas, Ocean Engineering 44 (2012), 23-32
- Authors: Boretti, Alberto
- Date: 2012
- Type: Text , Journal article
- Relation: Ocean Engineering Vol. 55, no. (2012), p. 235-237
- Full Text: false
- Reviewed:
- Description: Discussion of Natalya N. Warner, Philippe E. Tissot, Storm flooding sensitivity to sea level rise for Galveston Bay, Texas, Ocean Engineering 44 (2012), 23-32
Dual fuel H2-diesel heavy duty truck engines with optimum speed power turbine
- Authors: Boretti, Alberto
- Date: 2012
- Type: Text , Conference paper
- Relation: FISITA 2012 World Automotive Congress Vol. 191 LNEE, p. 77-99
- Full Text: false
- Reviewed:
- Description: The turbocharged direct injection lean burn Diesel engine is the most efficient engine now in production for transport applications with full load brake engine thermal efficiencies up to 40-45 % and reduced penalties in brake engine thermal efficiencies reducing the load by the quantity of fuel injected. The secrets of this engine's performances are the high compression ratio and the lean bulk combustion mostly diffusion controlled in addition to the partial recovery of the exhaust energy to boost the charging efficiency. The major downfalls of this engine are the carbon dioxide emissions and the depletion of fossil fuels using fossil Diesel, the energy security issues of using foreign fossil fuels in general, and finally the difficulty to meet future emission standards for soot, smoke, nitrogen oxides, carbon oxide and unburned hydrocarbons for the intrinsically "dirty" combustion of the fuel injected in liquid state and the lack of maturity the lean after treatment system. Renewable hydrogen is a possible replacement for the future of the Diesel that is free of carbon dioxide and other major emissions, with the only exception of nitric dioxides. In this paper, a Diesel engine is modelled and converted to run hydrogen retaining the same of Diesel full and part load efficiencies. The conversion is obtained by introducing a second direct fuel injector for the hydrogen. The dual fuel engine has slightly better than Diesel fuel efficiencies all over the load range and it may also permit better full load power and torque outputs running closer to stoichiometry. The development of novel injectors permitting multiple injections shaping as in modern Diesel despite the extremely low density of the hydrogen fuel is indicated as the key area of development of these engines. © 2013 Springer-Verlag.
- Description: 2003010657
Improving the efficiency of LPG Compression Ignition Engines for Passenger Cars through Waste Heat Recovery
- Authors: Boretti, Alberto
- Date: 2012
- Type: Text , Journal article
- Relation: SAE International Journal of Fuels and Lubricants Vol. 4, no. 2 (2012), p. 223-236
- Full Text: false
- Reviewed:
- Description: The turbocharged direct injection lean burn Diesel engine is the most efficient now in production for transport applications with full load brake efficiencies up to 40 to 45% and reduced penalties in brake efficiencies reducing the load by the quantity of fuel injected. The secrets of this engine's performances are the high compression ratio and the lean bulk combustion mostly diffusion controlled in addition to the partial recovery of the exhaust energy to boost the charging efficiency. The major downfalls of this engine are the carbon dioxide emissions and the depletion of fossil fuels using fossil diesel, the energy security issues of using foreign fossil fuels in general, and finally the difficulty to meet future emission standards for soot, smoke, nitrogen oxides, carbon oxide and unburned hydrocarbons for the combustion of the fuel injected in liquid state and the lack of maturity the lean after treatment system. LPG is an alternative fuel with a better carbon to hydrogen ratio therefore permitting reduced carbon dioxide emissions. It flashes immediately to gaseous form even if injected in liquid state for a much cleaner combustion almost cancelling some of the emissions (even if unfortunately not all of them) of the diesel and it permits a much better energy security within Australia. The paper presents a passenger car diesel engines converted to LPG. In this engine the efficiency is then improved recovering the waste heat. This recovery has impacts on both the in cylinder fuel conversion efficiency and the efficiency of the after treatment. Results of engine performance simulations are performed for a in-line four cylinder 1.6 litres LPG CI passenger car engine with a power turbine following the turbine of the turbocharger or an heat exchanger to recover the exhaust (and other) waste heat and compared with the experimental results for the diesel without waste heat recovery. © 2011 SAE International.
Optimum speed power turbine to recover the exhaust energy of compression ignition diesel and gas engines
- Authors: Boretti, Alberto
- Date: 2012
- Type: Text , Journal article
- Relation: World Journal of Modelling and Simulation Vol. 8, no. 4 (2012), p. 260-270
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- Reviewed:
- Description: The efficiency of internal combustion engines may be improved recovering the fuel energy loss in the exhaust gases or the coolant that is the predominant portion of the fuel energy, being the amount of fuel energy transformed in mechanical energy usually less than 50% in the top efficiency operating points and well below that figure in the other operating points of the load and speed map. This paper consider the opportunity to recover part of the exhaust energy with a power turbine that is operational only when convenient and it is run at optimum speed thanks to a by-pass and a continuously variable transmission link to the crankshaft. The power turbine operates at optimum speed only when producing more power than the power loss for back pressure while permitting temperatures to the downstream after treatment system high enough. Simulations for a 12.8 liters straight 6-cylinder Diesel engine with turbocharger and intercooler show improvements in both the fuel conversion efficiency at medium-to-high speeds and medium-to-high loads.
- Description: 2003010684
The inconvenient truth : Ocean level not rising in Australia
- Authors: Boretti, Alberto , Watson, Thomas
- Date: 2012
- Type: Text , Journal article
- Relation: Energy and Environment Vol. 23, no. 5 (2012), p. 801-817
- Full Text: false
- Reviewed:
- Description: There is a claim that, by the end of this century, Australian coastal communities will experience rising sea levels of up to more than 1 metre because of the anthropogenic carbon dioxide emissions causing global warming. This is the major argument supporting the Australia's Carbon Tax set to become law early next year. Under this legislation, 500 large Industrial manufacturers who emit carbon dioxide will be compelled to pay, from profitable income, for every tonne of carbon dioxide. Most of these emitters are electrical power generation and mining companies and heavy industry manufacturers. To compensate households for projected rising costs, due to the increased taxing pricing caused by this Carbon Tax, the government will cut income tax for smaller industries, boost payments to pensioners and offer various lump sum payments to small companies. This Australian scheme covers approximately 60% of Australia's emissions, making it the most broad-based scheme presented to the world. This carbon pricing will affectively apply to the 22.6 million Australians (2011) living in a 7,682,300 square kilometres country which is a relatively small number, proportional to the 7 billion people worldwide. The paper shows that locally and globally measured data, collected over short and long time scales, prove that the claim of sea level sharply accelerating is false.
A new method to warm up lubricating oil to improve the fuel efficiency during cold start
- Authors: Will, Frank , Boretti, Alberto
- Date: 2011
- Type: Text , Journal article
- Relation: SAE International Journal of Engines Vol. 4, no. 1 (2011), p. 175-187
- Full Text: false
- Reviewed:
- Description: Cold start driving cycles exhibit an increase in friction losses due to the low temperatures of metal and media compared to normal operating engine conditions. These friction losses are responsible for up to 10% penalty in fuel economy over the official drive cycles like the New European Drive Cycle (NEDC), where the temperature of the oil even at the end of the 1180 s of the drive cycle is below the fully warmed up values of between 100°C and 120°C. At engine oil temperatures below 100°C the water from the blowby condensates and dilutes the engine oil in the oil pan which negatively affects engine wear. Therefore engine oil temperatures above 100°C are desirable to minimize engine wear through blowby condensate. The paper presents a new technique to warm up the engine oil that significantly reduces the friction losses and therefore also reduces the fuel economy penalty during a 22°C cold start NEDC. Chassis dynamometer experiments demonstrated fuel economy improvements of over 7% as well as significant emission reductions by rapidly increasing the oil temperature. Oil temperatures were increased by up to 60°C during certain parts of the NEDC. It is shown how a very simple sensitivity analysis can be used to assess the relative size or efficiency of different heat transfer passes and the resulting fuel economy improvement potential of different heat recovery systems system. Due to its simplicity the method is very fast to use and therefore also very cost effective. The method demonstrated a very good correlation for the fuel consumption within ±1% compared to measurements on a vehicle chassis roll.
Advances in hydrogen compression ignition internal combustion engines
- Authors: Boretti, Alberto
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal of Hydrogen Energy Vol. 36, no. 19 (2011), p. 12601-12606
- Full Text: false
- Reviewed:
- Description: The turbocharged direct injection lean burn Diesel engine is the most efficient engine now in production for transport applications within heavy duty trucks applications full load brake engine thermal efficiencies up to 45% and reduced penalties in brake engine thermal efficiencies reducing the load by the quantity of fuel injected. The secrets of this engine's performances are the high compression ratio and the lean bulk combustion mostly diffusion controlled in addition to the partial recovery of the exhaust energy to boost the charging efficiency. The major downfalls of this engine are the carbon dioxide emissions and the depletion of natural resources using fossil Diesel, the energy security issues of using foreign fuels in general, and finally the difficulty to meet future emission standards, for the intrinsically "dirty" combustion of the fuel made up of a mixture of many hydrocarbon being injected in liquid state and the lack of maturity for the lean burn after treatment system. Renewable hydrogen is a possible replacement for the future of the Diesel that is free of carbon dioxide and other major emissions with the only exception of nitric dioxides, and it therefore makes sense to discuss the option to convert not only passenger car engines, but also heavy duty truck engines to run hydrogen. In this paper, a heavy duty Diesel truck engine is modelled and converted to run hydrogen only with goals retaining the same of Diesel full and part load efficiencies and power and torque outputs. The modelled hydrogen engine has actually better than Diesel fuel efficiencies all over the load range and it also permits better full load power and torque outputs running about same stoichiometry. Hydrogen has been considered so far mainly as a fuel alternative to gasoline in passenger car applications operating with spark ignition, with just a couple of examples of use of hydrogen as a fuel alternative to Diesel in passenger car applications operating compression ignition. The novelty of the manuscript is the heavy duty truck (HDT) application of hydrogen in a converted Diesel engine retaining the compression ignition operation of the Diesel. This application requires the design of a novel combustion system made up of a jet ignition pre-chamber with a glow plug and a fuel injector and a main chamber direct fuel injector. The pre-chamber injection of hydrogen permits combustion to start assisted by a glow plug and then to move to the main chamber. At this stage, the hydrogen already injected in the main chamber and mixed with the air will burn premixed gasoline-like, while the remaining hydrogen to be injected in the main chamber will then burn diffusion Diesel-like. This innovative combustion mode is the core of the technical note. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Advantages of the direct injection of both diesel and hydrogen in dual fuel H2ICE
- Authors: Boretti, Alberto
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal of Hydrogen Energy Vol. 36, no. 15 (2011), p. 9312-9317
- Full Text: false
- Reviewed:
- Description: The turbocharged Diesel engine is the most efficient engine now in production for transport applications with full load brake engine thermal efficiencies up to 40-45% and reduced penalties in brake engine thermal efficiencies reducing the load. The secrets of the turbocharged Diesel engine performances are the high compression ratio and the lean bulk combustion mostly diffusion controlled in addition to the better use of the exhaust energy. Despite these advantages and the further complications of hydrogen in terms of abnormal combustion phenomena and displacement effect, the most part of the dual fuel Diesel-hydrogen engines has been developed so far injecting hydrogen in the intake manifold or in the intake port, and then injecting the Diesel fuel in the cylinder to ignite there a homogeneous mixture. This paper shows how a latest production common-rail Diesel engine could be modified replacing the Diesel injector by a double injector as those proposed by Westport since more than two decades for CNG first and then for CNG and hydrogen to provide much better performances. A model is first developed and validated versus extensive high quality dynamometer data for the Diesel engine only covering with almost 200 points the load and speed range. This model replaces the multiple injection strategy with a single equivalent injection for the purposes of the brake efficiency results still providing satisfactory accuracy. The model is then used to simulate the dual fuel operation with a pilot Diesel followed by a main hydrogen injection replacing the Diesel fuel with the hydrogen fuel and using the same parameters for start and duration of the equivalent injection at same percentage load and speed. While the top load air-to-fuel ratio of the Diesel is a lean 1.55, the top air-to-fuel ratio of the hydrogen is assumed to be a stoichiometric 1. Within the validity of these assumptions it is shown that the novel engine has better than Diesel fuel conversion efficiencies and higher than Diesel power outputs. These results clearly indicate the development of the direct injection system as the key factor where to focus research and development for this kind of engines. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Diesel-like and HCCI-like operation of a truck engine converted to hydrogen
- Authors: Boretti, Alberto
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal of Hydrogen Energy Vol. 36, no. 2 (November 2011 2011), p. 15382
- Full Text: false
- Reviewed:
- Description: In addition to the traditional spark ignition (S1), premixed, gasoline-like and compression ignition (CI), diffusion, Diesel-like operation of internal combustion engines, premixed, homogeneous charge, compression ignition (HCCI) operation has also been proposed to improve the fuel conversion efficiency and reduce the pollutant formation. To be attractive, the operation in HCCI mode has to be coupled with the other traditional operations, being HCCI in general difficult to be controlled and limited to values of the air-to-fuel equivalence ratio
- Description: C1
Direct injection of hydrogen, oxygen and water in a novel two stroke engine
- Authors: Boretti, Alberto , Osman, Azmi , Aris, Ishak
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal of Hydrogen Energy Vol. 36, no. 16 (2011), p. 10100-10106
- Full Text: false
- Reviewed:
- Description: This short communication proposes novel two stroke engine burning hydrogen in oxygen in presence of large amounts of steam as residual gases. This engine has a bowl-in-piston combustion chamber, exhaust valves only and it uses direct injection of hydrogen, oxygen and water. Diesel-like compression ignition combustion is achieved by injecting the oxygen and the hydrogen in the surrounding steam close to a continuously operated glow plug. The operation of the engine is simulated by commercial softwares. The water injection enables acceptable metal temperatures and reduced heat losses. First computational results show brake efficiencies above 55% achieved with mass of water injected about twice the mass of oxygen and hydrogen mixture and operation with a significant amount of exhaust gas recirculation. It seems reasonable to guess efficiencies of the fully optimised and developed engine approaching the 60% mark, 20% higher than those of the state-of-the-art H 2ICEs designed for operation with air using the spark-ignition engine concept as well as of those projected for Diesel engines operating with exhaust energy recovery. Worth of mention is also the much higher power density following the two stroke operation. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Fuel cycle CO2-e targets of renewable hydrogen as a realistic transportation fuel in Australia
- Authors: Boretti, Alberto
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal of Hydrogen Energy Vol. 35, no. 5 (2011), p. 3290-3301
- Full Text: false
- Reviewed:
- Description: The claim of catastrophic man made climate change or global warming through anthropogenic CO2 has presently focused the interest on the tailpipe emissions of CO2 per km, with recent legislations obsessively targeting these emissions of CO2 with defectively implemented procedures. With a variety of different propulsion solutions (electric, hybrid electric, hybrid mechanic, conventional) and different fuels (Diesel, Petrol, alternative fossil, alternative renewable) available in the near future, a more comprehensive approach based on the full fuel cycle, and eventually also the full life cycle of the vehicle appear to be necessary. The paper is a contribution to trigger further improvement to currently implemented procedures. The paper discusses the CO2 emission data in the present form, some simple but effective measures to improve the accuracy of the data collection procedure, and propose results of fuel cycle CO2-e analysis of vehicles with electric and thermal engines having different fuels. Vehicles with advanced internal combustion engines and power trains fuelled with Diesel may reach CO2-e values of 100 g/km in Australia. Use of bio-ethanol in these vehicles may deliver in Australia a significant reduction of CO2-e emissions to values below 36 g/km. Emission factors for Victoria are presently 1.23 kg CO2-e/kWh for the purchased electricity and vehicles powered by electric motors will need a significant reduction of this indirect CO2-e emission to become competitive. Values below 0.5 kg CO2-e/kWh are needed to make electric cars competitive with Diesel cars while values below 0.1 kg CO2-e/kWh are needed to make electric cars competitive with bio-ethanol cars. Compared with all these alternatives, renewable hydrogen may possibly compete with Diesel when produced with renewable energy sources and made available at the pump for less than 0.1 kg CO2-e/MJ of fuel energy, and with bio-ethanol if produced and distributed at a cost below 0.02 kg CO2-e/MJ of fuel energy.
Improvements of vehicle fuel economy using mechanical regenerative braking
- Authors: Boretti, Alberto
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal of Vehicle Design Vol. 55, no. 1 (2011), p. 35-48
- Full Text: false
- Reviewed:
- Description: The paper presents a mixed theoretical and experimental evaluation of the improvements in fuel economy that follow the introduction of a mechanical Kinetic Energy Recovery System (KERS) on a full size passenger car. This system, made up of a high speed storage flywheel and a Constant Variable Transmission (CVT), has a full regenerative cycle overall efficiency about twice the efficiency of battery-based hybrids. With reference to the baseline configuration having a 4L gasoline engine, adoption of a KERS may reduce the fuel consumption covering the NEDC by 25% without downsizing, and by 33% downsizing the engine to 3.3L. Copyright © 2011 Inderscience Enterprises Ltd.
Is New Zealand globally warming?
- Authors: Boretti, Alberto , Watson, Thomas
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal of Global Warming Vol. 3, no. 3 (2011), p. 219-231
- Full Text: false
- Reviewed:
- Description: NIWA proposes a seven-station temperature series to assess a globally warming trend. The warming trend predicted by NIWA is a result of their arbitrary corrections of measured temperatures to account for change of site. These changes are always increasing the temperatures and they magnify the effect of the heat island build-up around urban areas. The individual analysis of the raw temperature data from different measuring stations clearly shows that there is no warming globally occurring, with warming being conversely very well localised in time and space. Copyright © 2011 Inderscience Enterprises Ltd.
Numerical evaluation of the performance of a compression ignition CNG engine for heavy duty trucks with an optimum speed power turbine
- Authors: Boretti, Alberto
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal of Engineering and Technology Innovation Vol. 1, no. 1 (2011), p. 12-26
- Full Text: false
- Reviewed:
- Description: The turbocharged direct injection lean burn Diesel engine is the most efficient engine now in production for transport applications. CNG is an alternative fuel with a better carbon to hydrogen ratio therefore permitting reduced carbon dioxide emissions. It is injected in gaseous form for a much cleaner combustion almost cancelling some of the emissions of the Diesel and it permits a much better energy security within Australia. The paper discusses the best options currently available to convert Diesel engine platforms to CNG, with particular emphasis to the use of these CNG engines within Australia where the refuelling network is scarce. This option is determined in the dual fuel operation with a double injector design that couples a second CNG injector to the Diesel injector. This configuration permits the operation Diesel only or Diesel pilot and CNG main depending on the availability of refuelling stations where the vehicle operates. Results of engine performance simulations are performed for a straight six cylinder 13 litres truck engine with a novel power turbine connected to the crankshaft through a constant variable transmission that may be by-passed when non helpful to increase the fuel economy of the vehicle or when damaging the performances of the after treatment system.
Radiative and nonradiative decay rates in chromium-related centers in nanodiamonds
- Authors: Castelletto, Stefania , Boretti, Alberto
- Date: 2011
- Type: Text , Journal article
- Relation: Optics Letters Vol. 36, no. 21 (2011), p. 4224-4226
- Full Text: false
- Reviewed:
- Description: We address for the first time the measurement of nonradiative decay rates in Cr-related centers in nanodiamonds. Compared to our previous quantum efficiency measurement of Cr centers created in bulk diamond, separate measurements of radiative and nonradiative decay rates in grown nanodiamonds prove more challenging due to size dependence effects. We demonstrate in this Letter that, using defocused dipole imaging and collection efficiency calculation via finite-difference time-domain (FDTD), a quantum efficiency up to 0.9 can be inferred to Cr-related centers showing a 2-level system photon statistics.
Short term comparison of climate model predictions and satellite altimeter measurements of sea levels
- Authors: Boretti, Alberto
- Date: 2011
- Type: Text , Journal article
- Relation: Coastal Engineering Vol.60, no. (2011), p.319-322
- Full Text: false
- Reviewed:
- Description: Climate models (http://climatecommission.govspace.gov.au/files/2011/05/4108-CC-Science-Update-PRINT-CHANGES.pdf, 2011; http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_synthesis_report.htm, 2011; Rahmstorf, 2007, 2010) calculate that temperatures are increasing globally and sea level rises are increasing due to anthropogenic carbon dioxide emissions. More recent predictions (http://climatecommission.govspace.gov.au/files/2011/05/4108-CC-Science-Update-PRINT-CHANGES.pdf, 2011; Rahmstorf, 2007, 2010) have forecasted that sea level rises by 2100 will be higher than the 2007 projections by the Intergovernmental Panel on Climate Change (http://www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_synthesis_report.htm, 2011), with projected sea level rises increasing from 18-59 cm to 100 cm. In this brief communication, the predictions of Rahmstorf (2007) are validated against the experimental evidence over a 20 year period. The University of Colorado Sea Level satellite monitoring shows that the rate of rise of the sea level is not only well below the values computed in http://climatecommission.govspace.gov.au/files/2011/05/4108-CC-Science-Update-PRINT-CHANGES.pdf (2011) and Rahmstorf (2007, 2010), but actually reducing rather than increasing (http://sealevel.colorado.edu/, 2011b; 10,11). These results suggest that sea level predictions based solely on the presumed temperature evolution may fail to accurately predict the long term sea levels at the end of the century. © 2011.
Stoichiometric H2ICE with water injection and exhaust and coolant heat recovery through organic Rankine cycles
- Authors: Boretti, Alberto
- Date: 2011
- Type: Text , Journal article
- Relation: International Journal of Hydrogen Energy Vol. 36, no. 19 (2011), p. 12591-12600
- Full Text: false
- Reviewed:
- Description: High power density, stoichiometric, turbocharged, directly injected engines with water injection and a three way catalytic converter after treatment have been proposed as one of the most promising H2ICE [1]. These throttle controlled engines have top brake efficiencies exceeding 40%, but large penalties in efficiency reducing the load with 1 bar BMEP values approaching 10%. Recovery of the large amount of fuel energy lost in the coolant especially at low loads as well as the fuel energy lost in the exhaust that is significant at high loads and speeds may push not only the top brake efficiencies to exceed the 45% mark, but also to dramatically increase the low load efficiency compromised by the throttling. In this paper, recovery of the waste heat from the exhaust gases and the coolant in a H2ICE is performed with Organic Rankine Cycles (ORC). The engine without ORC has a maximum efficiency of 42% and an average efficiency over the map points of 32.7%. With the exhaust ORC, neglecting the possible back pressure increase due to the heat exchanger downstream of the catalytic converter the maximum efficiency increases to 45.6%, and the average efficiency rises to 35.3%. With the coolant ORC, neglecting the reduced mechanical efficiency for the coolant back pressure increment, the maximum efficiency increases to 43.4% and the average efficiency increases to 34.6%. Finally, combining the two ORC with same assumptions, the maximum efficiency increases to 46.9% and the average efficiency to 38%. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.