Hydrogen fuel enhancement

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Hydrogen fuel enhancement is a term used to describe the supplementation of an internal combustion engine (ICE) fuel with hydrogen. The term is used for onboard hydrogen injection to inject either a hydrogen-enriched mixture, or pure hydrogen into the intake manifold of the engine and for hydrogen / compressed natural gas blends (HCNG or H2CNG which is premixed at the hydrogen station .

Contents 1 Hydrogen injection 2 HCNG injection 3 Research 3.1 1975 3.2 1977 3.3 2002 3.4 2003 3.5 2004 4 Government 5 References

[edit] Hydrogen injection

Onboard automotive hydrogen injection systems inject either a hydrogen-enriched mixture, or pure hydrogen into the intake manifold of the engine. In some cases, this is combined with air/fuel ratio and timing modifications^[1][2]. 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 NO_x 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, addition of hydrogen 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.^[4]

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 onboard 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,^[5] obtaining interesting fuel economy and emissions reductions.^[4] 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.^[4]

ECU or carburetor modifications are required to establish lean or ultra lean burn engine conditions.^[3][6]

Hydrogen fuel enhancement from electrolysis of water where the required electricity is supplied by the engine’s alternator or 12/24-volt electrical system can produce fuel efficiency improvements on an older diesel truck in the order of 4% and similar modest reductions in emissions, and is currently in use in Canada^[7][8][9] and the United States.^[10] However recent tests by consumer watch groups have also shown negative results. ^{[11][12][13] [14]}

Hydrogen injection is similar to both propane injection and nitrous oxide injection.

[edit] HCNG injection

HCNG (or H2CNG) is a mixture of compressed natural gas and 4-9 percent hydrogen by energy.^[15] 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.^[16] Premixing is done at the hydrogen station. HCNG stations can be found at Hynor (Norway) and the BC hydrogen highway in Canada.

[edit] Research

A simplified single-step combustion reaction is represented as:

[FUEL] + [HYDROGEN] + [AIR] → HC + CO + CO₂ + H₂O + NO_x

[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] 1977

NASA conducted research using hydrogen as a supplemental fuel to gasoline on a 1969 production engine.^[1] Their research specifically demonstrated that the higher flame speed of hydrogen was responsible for being able to extend the efficient lean operating range of a gasoline engine. They successfully used a methanol steam reformer for in situ production of carbon monoxide and hydrogen.

Lean-mixture-ratio combustion in internal-combustion engines has the potential of producing low emissions and higher thermal efficiency for several reasons. First, excess oxygen in the charge further oxidizes unburned hydrocarbons and carbon monoxide. Second, excess oxygen lowers the peak combustion temperatures, which inhibits the formation of oxides of nitrogen. Third, the lower combustion temperatures in­crease the mixture specific heat ratio by decreasing the net dissociation losses. Fourth, as the specific heat ratio increases, the cycle thermal efficiency also increases, which gives the potential for better fuel economy.^[1] (See also: Lean burn)

[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".^[6] Also concluded was that "hydrogen addition lowers HC emissions", and with properly "retarded ignition timing" also reduces NO_x emissions.^[6]

Further research in 2002 achieved results showing "a reduction of NO_x and CO₂ emissions", by modeling an on-board hydrogen reformer and "varying the efficiency".^[4] The research was specifically a "numerical investigation" done to "foresee performances, exhaust emissions, and fuel consumption of a small, multi valve, spark ignition engine fueled by hydrogen enriched gasoline".^[4]

[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 (NO_x) without significant changes to engine efficiency".^[17] 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".

[edit] 2004

Test results in 2004 show "that the H₂-rich reformate gas was an excellent NO_x reductant, and can out perform raw Diesel fuel as a reductant in a wide range of operating conditions".^[18] 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 NO_x 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".^[19] This was achieved by "extending EGR operation" in addition to consuming "gasoline and hydrogen rich reformate".^[19] Emissions results show that "HC-emissions as well as NO_x-emissions could be reduced to near zero".^[19] Overall a 3.5% reduction in CO₂ emissions was achieved during the "FTP test cycle".^[19] The research also concluded that the exhaust aftertreatment system can be simplified, "resulting in cost reduction for the catalysts".^[19]

[edit] Government

To date, Hydrogen fuel enhancement products have not been specifically addressed by the United States Environmental Protection Agency. No research devices or commercial products have reports available as per the "Motor Vehicle Aftermarket Retrofit Device Evaluation Program."^[20]

[edit] References

1. ^ ^{a b c} NASA Technical Note, May 1977, "Emissions and Total Energy Consumption of a Multicylinder Piston Engine Running on Gasoline and a Hydrogen-Gasoline Mixture" (Accessed 2008-08-08)
2. ^ Idaho National Laboratory on Fuel Enhancement
3. ^ ^{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)
4. ^ ^{a b c d e f g} 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. 
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). 
6. ^ ^{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. 
7. ^ Guidelines for use of Hydrogen Fuel in Commercial Vehicles, Booz Allen Hamilton Inc., November 2007
8. ^ Business Name
9. ^ Wired magazine: Truckers Choose Hydrogen Power
10. ^ "GreenChek Technology corporate website". http://www.greenchektech.com/. Retrieved on 2009-02-12. 
11. ^ Popular Mechanics Water-Powered Cars: Hydrogen Electrolyzer Mod Can't Up MPGs.
12. ^ Greenville News Looking Out 4 You: Water 4 Gas Fails to Boost Mileage
13. ^ Hydrogen conversion claims put to the test
14. ^ http://www.consumeraffairs.com/news04/2008/07/water4gas.html Consumer Affairs Water4gas
15. ^ DOE HCNG
16. ^ HCNG and hydrogen embrittlement
17. ^ 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.
18. ^ Yougen Kong, Sam Crane, Palak Patel and Bill Taylor (January, 2004). "NO_x Trap Regeneration with an On-Board Hydrogen Generation Device". SAE Technical Paper Series (2004-01-0582): pp. 6–7. 
19. ^ ^{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. 
20. ^ See list of devices tested under EPA Gas Saving and Emission Reduction Devices Evaluation