Hydrogen fuel enhancement
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Hydrogen fuel enhancement methods like HCNG and hydrogen injection are practiced to reduce exhaust emissions of internal combustion engines and improve fuel economy.
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[edit] HCNG
HCNG is a mixture of natural gas and 4-9 percent hydrogen by energy.[1] Hydrogen contents of less than 50% in the HCNG blend have leakage and flammability risks similar to those of CNG alone. With the hydrogen being part of the mixture, there are no special precautions needed to avoid hydrogen embrittlement of the materials coming in contact with the mixture.[2]
[edit] Hydrogen injection
Automotive fuel enhancement systems work by injecting a hydrogen rich mixture, or pure hydrogen into the intake manifold of an internal combustion engine combined with air/fuel ratio, and timing modification. A small amount of hydrogen added to the intake air-fuel charge permits the engine to operate with leaner air-to-fuel mixture than otherwise possible.[3] As the air/fuel mix approaches 30:1 the temperature of combustion substantially decreases effectively mitigating NOx production.[3]
Under idle conditions power is only required for extraneous components other than the drive train, therefore fuel consumption can be minimized. A 50% reduction in gasoline consumption, at idle, was reported by numerically analyzing "the effect of hydrogen enriched gasoline on the performance, emissions and fuel consumption of a small spark-ignition engine".[4]
Under most loads near stoichiometric air/fuel mixtures are still required for normal acceleration, although under idle conditions, reduced loads, and moderate acceleration Hydrogen "addition" in combination with lean burn engine conditions "can guarantee a regular running" of the engine "with many advantages in terms of emissions levels and fuel consumption".[5]
Increases "in engine efficiency are more dominant than the energy loss incurred in generating hydrogen".[3] This is specifically with regard to use of a hydrogen reformer. Overall computational analysis "has marked the possibility of operating with high air overabundance (lean or ultra-lean mixtures) without a" substantial "performance decrease, but with great advantages on pollution emissions and fuel consumption".[4]
Overall comparing "the properties of hydrogen and gasoline, it is possible to underline the possibilities, for hydrogen fueled engines, of operating with very lean (or ultra-lean) mixtures,[6] obtaining interesting fuel economy and emissions reductions".[5] The "concept of hydrogen enriched gasoline, as a fuel for internal combustion engines, has a greater interest than pure hydrogen powered engines because it involves fewer modifications to the engines and their fueling systems".[5]
[edit] Engine Control
ECU or carburetor modifications are required to establish lean or ultra lean burn engine conditions; where the hydrogen permits leaner conditions than possible with solely hydrocarbon fuel.[7][3]
[edit] Research
A simplified single-step combustion reaction is represented as:
- [FUEL] + [HYDROGEN] + [AIR] → HC + CO + CO2 + H2O + NOx
[edit] 1975
Research in 1975 examined hydrogen enhanced gasoline in lean combustion.[3] John Houseman and D.J Cerini of the Jet Propulsion Laboratory produced a report for the Society of Automotive Engineers titled "On-Board Hydrogen Generator for a Partial Hydrogen Injection Internal Combustion Engine", and F.W. Hoehn and M.W. Dowy, also of the Jet Propulsion Lab, prepared a report for the 9th Intersociety Energy Conversion Engineering Conference, titled "Feasibility Demonstration of a Road Vehicle Fueled with Hydrogen Enriched Gasoline."[3]
[edit] 2002
Research done in 2002 shows that the "addition of hydrogen to natural gas increases the burn rate and extends the lean burn-limit".[7] Also concluded was that "hydrogen addition lowers HC emissions", and with properly "retarded ignition timing" also reduces NOx emissions.[7]
Further research in 2002 achieved results showing "a reduction of NOx and CO2 emissions", by modeling an on-board hydrogen reformer and "varying the efficiency".[5] The research was specifically a "numerical investigation" done to "forsee performances, exhaust emissions, and fuel consumption of a small, multi valve, spark ignition engine fueled by hydrogen enriched gasoline".[5]
[edit] 2003
In 2003 Tsolakis et al. of the University of Birmingham showed that "partial replacement of the hydrocarbon fuel by hydrogen combined with EGR resulted in simultaneous reductions of smoke and nitrogen oxides emissions (NOx) without significant changes to engine efficiency".[8] Similar results have been presented by a team of scientists from Zhejiang University, China, which found that "a little amount of hydrogen supplemented to the gasoline-air mixture can extend the flammability of the mixture... improving the economy and emissions of engines".[9]
[edit] 2004
Test results in 2004 show "that the H2-rich reformate gas was an excellent NOx reductant, and can out perform raw Diesel fuel as a reductant in a wide range of operating conditions".[10] This is referring to Diesel fuel being used in excess, as a reductant, to cool the combustion reaction, which indeed has a mitigating effect on NOx production.
In 2004 research was conducted concluding that an "SI engine system fueled by gasoline and hydrogen rich reformate gas have been demonstrated" to achieve a "dramatic reduction of pollution emissions".[11] This was achieved by "extending EGR operation" in addition to consuming "gasoline and hydrogen rich reformate".[11] Emissions results show that "HC -emissions as well as NOx-emissions could be reduced to near zero".[11] Overall a 3.5% reduction in CO2 emissions was achieved during the "FTP test cycle".[11] The research also concluded that the exhaust aftertreatment system can be simplified, "resulting in cost reduction for the catalysts".[11]
[edit] Commercial products
Commercially, Canadian Hydrogen Energy Company, Ltd. produces an Hydrogen Fuel Injection (HFI) system which generates hydrogen during vehicle operation by electrolysis of water (from an onboard storage tank) using power from the vehicle's electrical system. The units cost between $4000 to $14000 according to a 2005 Wired News article.[12] CHEC claims the product provides a 10% fuel savings.[13][14] CHEC competitors filed a motion to stop CHEC from selling its HFI system, but in 2006, this motion was abandoned.[15]
[edit] Government
To date, Hydrogen fuel enhancement, nor the HFI product, nor competing products have been addressed specifically by the EPA, as none of the research devices investigated above, or the HFI have reports available as per the "Motor Vehicle Aftermarket Retrofit Device Evaluation Program".[16] In general there are no references available for the US Government addressing the concept of Hydrogen fuel enhancement.
[edit] References
- ^ DOE HCNG
- ^ HCNG and hydrogen embrittlement
- ^ a b c d e f Houseman J, "Lean Combustion of Hydrogen Gasoline Mixtures". Abstracts of papers of the American Chemical Society (169): 6-6 1975. (meeting abstract)
- Hoehn FW, Baisley RL, Dowdy MW, "Advances In Ultralean Combustion Technology Using Hydrogren-Enriched Gasoline", IEEE Transactions on Aerospace and Electronic Systems 11 (5): 958-958 1975. (meeting abstract)
- ^ a b G. Fontana, E. Galloni, E. Jannelli and M. Minutillo (January, 2002). "Performance and Fuel Consumption Estimation of a Hydrogen Enriched Gasoline Engine at Part-Load Operation". SAE Technical Paper Series (2002-01-2196): p. 4–5.
- ^ a b c d e G. Fontana, E. Galloni, E. Jannelli and M. Minutillo (January, 2002). "Performance and Fuel Consumption Estimation of a Hydrogen Enriched Gasoline Engine at Part-Load Operation". SAE Technical Paper Series (2002-01-2196): p. 4–5.
- ^ Mathur H.B., Das L.M. (1991). "Performance characteristics of a Hydrogen Fueled SI Engine using Timed Manifold Injection". Int. J. Hydrogen Energy (vol 16, pp. 115-117, 1991).
- ^ a b c Per Tunestal, Magnus Christensen, Patrik Einewall, Tobias Andersson, and Bengt Johansson (January, 2002). "Hydrogen Addition For Improved Lean Burn Capability of Slow and Fast Natural Gas Combustion Chambers". SAE Technical Paper Series (2002-01-2686): p. 7–8.
- ^ Tsolakis A, Megaritis A, Wyszynski ML, "Application of exhaust gas fuel reforming in compression ignition engines fueled by diesel and biodiesel fuel mixtures" Energy & Fuels 17 (6): 1464-1473 NOV-DEC 2003.
- ^ Li JD, Guo LS, Du TS, "Formation and restraint of toxic emissions in hydrogen-gasoline mixture fueled engines". International Journal of Hydrogen Energy 23 (10): 971-975 OCT 1998.
- ^ Yougen Kong, Sam Crane, Palak Patel and Bill Taylor (January, 2004). "NOx Trap Regeneration with an On-Board Hydrogen Generation Device". SAE Technical Paper Series (2004-01-0582): p. 6–7.
- ^ a b c d e Thorsten Allgeier, Martin Klenk and Tilo Landenfeld (January, 2004). "Advanced Emissions and Fuel Economy Control Using Combined Injection of Gasoline and Hydrogen in SI-Engines". SAE Technical Paper Series (2004-01-1270): p. 11–12.
- ^ Stephen Leahy (15 November 2005). Truckers Choose Hydrogen Power. Wired News. Accessed 2007-05-03.
- ^ Michael Vaughan (5 October 2005). "The hydrogen bridge to a fuel cell future" The Globe and Mail. (Available here Accessed 2008-01-10.)
- ^ Canadian Hydrogen Energy Company, Ltd (21 November 2005) Fuel Cells Today. Accessed 2008-01-10.
- ^ Canadian Hydrogen Energy Company Ltd. (CHEC) Issues $180 Million Counterclaim ... (13 May 2006) Canada Newswire. Accessed 2008-01-10.
- ^ See list of devices tested under EPA Gas Saving and Emission Reduction Devices Evaluation
