Use of methanol in internal combustion engines a status review

Transcription

1 Use of methanol in internal combustion engines a status review PROMSUS Gothenburg Lennart Haraldson WÄRTSILÄ

2 Methanol is used as a fuel already today

3 Historic development of Methanol as motor fuel Alcoholes were actually tried in ICEs in early days by both Otto as well as Diesel. The development of the market for methanol as a motor fuel worldwide started with the shortage of motor fuels during the First World War. Likewise, the use of methanol has received attention primarily during periods when shortage of conventional fuels have been on the agenda. Two such periods besides First World War were the second War and first oil crisis during the 70 s.

4 Interest in Methanol during the oil crisis and later The interest for methanol continued for some years after the oil crisis, but started to decline rapidly in the 1990 s. Most of the activities in the 1970 s and 1980 s were in form of blending (M15). However, dedicated methanol vehicles (M100), but also high-level blends (M85) were investigated. Major research projects were carried out in several countries during this period as USA, Germany, Denmark, Norway, Japan and...sweden. For instance - In the beginning of the 80 s were > 1000 cars converted for M15 in Sweden..and Volvo and Saab were heavily engaged in the activities developing methanol compatible cars. Other car/truck manufacturer which were involved in the methanol activities were: MAN, Volvo Truck,Caterpillar, Ford,Opel, Toyota, Chrysler, Volkswagen...and probably a few more not mentioned here. The latest methanol project carried out in Sweden was actually during , when M3E3 fuel was fieldtested. The current only major market for methanol as motor fuel is China

5 Findings - General For M100 engines (or high-level blends) were problems with corrosion and excess wear of valves, piston rings, valve guides etc. discovered. The source of accelerated wear was found in the lub oil the EP additive were destroyed by the methanol. Gasoline containing > 10% methanol can be corrosive against ceratain metals and also affect elastomers/polymers Methanol is corrosive to zinc, aluminum, magnesium and their alloys Methanol containing water is also corrosive to iron and steel dry methanol not. Methanol is full soulable in gasoline which enable free mixing. In any case is it needed to use stabilizing additives using low blended methanol solutions. (could be ethanol or higher alcohols)

6 Findings - Performance Efficiency is equal, or better due to the high octane number. However due to the fact that no car manufacture optimized their engine for the higher octane numbers for methanol was not the full potential achieved. The high heat of evaporation, high flame speed and lean combustion limit enables further optimization of high blend engines. Exhaust emissions are equal or lower except for formaldehyde which might be a cold start problem for methanol engines. The conclusion from the comprehensive testing of methanol during 80 s and 90 s is that no big technical obstacle will prevent car industry from using methanol as future fuel. Adaptations are rather cost effective and limited to fuel system and piston/piston rings

7 Methanol Characteristics Fuel Methanol Natural Gas Diesel Density (kg/l)* ,44 (as LNG) 0,85 Boiling point ( C) Flash point ( C) min. 60 Auto ignition ( C) Viscosity cst at 20 C ~ 0,6 na ~ 13,5 Octane RON/MON 109/89 120/120 - Cetane No LHV (MJ/kg) 20 50* 42 Flammability Limits, Vol% Flame Speed (cm/s) Heat of Evaporation (kj/kg) 1178 na 233 Stoichiometric Air-Fuel Ratio 6,45 17,2 14,7 Adiabatic flame temp. ( C) * HHV

8 Methanol Concepts for Marine Engines Surface Ignition Fumigation Mixing Concept (Emulsion) Ignition Improvers Pilot fuel assisted Diesel Combustion Premixed Combustion with Spark Plug or Pilot Fuel Ignition

9 Methanol Concepts for Marine Engines Surface Ignition The presence of a hot surface has shown to trigger pre-ignition of methanol to a greater extent than for other fuels. Likely is this due to the dissociation of methanol to CO and hydrogen. A M100 concept. Fumigation To introduce methanol in the inlet port of a diesel engine could be a cheap way to introduce methanol in the diesel process as well as achieving dual fuel properties. However possible well wetting increases the risk for corrosion and oil degradation. Methanol share up to 50-70% at full load might be possible. Mixing Concept Methanol is fully soluble in gasoline but not is Diesel. Because of this will it not be possible to partly replace diesel with methanol in the same way as gasoline is replaced by methanol. However, by making an emulsion of diesel and methanol might it be possible use adapted fuel injection systems. Limiting factors beside the low lubricity, low viscosity and reduced heat value will be reduced cetane number of the blend. Estimated max. blend is 30-40% methanol due to reduced ignition properties.

10 Methanol Concepts for Marine Engines Ignition Improvers By using ignition improvers can the cetane number of the methanol be increased. Scania uses such a concept for their ethanol engine where 5% ignition improver (polyethylene glycol, Beraid 3555). The Scania engine is adapted with higher compression ratio as well (27:1). The high compression ratio might have influence on max. output (high compression ratio high compression pressure). With methanol is possible 9-10% ignition improver needed for similar engine type with Heat value, Autoignition temperature and Heat of evaporation taken into account. Pilot fuel assisted Diesel Combustion Methanol can as well be ignited with a small amount of diesel fuel. With this concept it is important to establish a diesel pilot combustion before methanol is injected to avoid ignition delay problems with the methanol combustion. Possible min. pilot diesel amount is estimated to 5% (95% Methanol) This concept enables real dual fuel properties with pure diesel mode or methanol mode with pilot diesel fuel ignition.

11 Methanol Concepts for marine engines Premixed Combustion Methanol can as well be ignited by a spark plug or with diesel pilot fuel Pilot fuel ignition will produce more ignition energy compared to a spark plug ignition and might be a more robust concept to ignite the methanol Pilot amount for similar natural gas concept require 0,5-1% pilot fuel at full load. Something similar can be expected for methanol... Perhaps slightly higher pilot amount. The concept can be developed to be a dual fuel solution with pure diesel running or methanol running with pilot fuel ignition We expect this solution to fulfil the coming NOx Tier III demand without SCR/EGR Possible disadvantages: - formaldehyde in exhaust emissions - degradation of engine oil due to wall-wetting - knocking behaviour (Otto combustion) limiting load - worse efficiency in diesel mode (due to lower compression ratio)

12 Conclusions by Volvo concerning Methanol concepts Ignition Improvers works: 20% Cetanox increase cetane number to 35. (expensive) Blending not possible: methanol not soluble in diesel Emulsion works: At ambient 25 C max 32% diesel can be replaced with methanol (CN limitation) Converting to Otto engine with spark plug start assistans needed, risk for degradation of engine oil Diesel pilot ignition of methanol: 15% diesel needed at full load. Less NOx ( -35%) and less PM Similar or even higher efficiency than diesel engine Similar or less wear than diesel engine (due to less particulates) Lower exhaust temperatures ( up to 80 C ) No abnormal behaviour of the lub.oil Higher amount of formaldehyde By Volvo (at year 1981) proposed heavy duty methanol concept Source: EPA-460/3-023 August 1981

13 Caterpillar glowplug assisted diesel concept Engine output and efficiency equal to the diesel engine Significant reduced NOx and PM compared to diesel Life time of major components as cylinder head, piston rings, cylinder liners, bearings, camshaft, crankshaft and cylinder block will be similar or better than the diesel engine. ( The lower piston ring/liner wear may result from less particulates in the exhasut gases). However reduced life-time of exhaust valves / seats due to less particles lubricating the mentioned components. No change in oil change intervals Source: SAE paper

14 Wärtsilä Methanol-Diesel retrofit solution Methanol is combusted according to the diesel process. The methanol is injected close to TDC and ignited by a small amount of pilot fuel in this case traditional diesel fuel. The methanol injection pressure is limited to below 650 bar. So far has the concept only been tested in laboratory environmental.

15 Wärtsilä Methanol-Diesel retrofit solution On-engine scope is limited to exchange of cylinder heads, fuel injectors and fuel plungers in existing fuel pumps. A common rail system for methanol injection will be added on the engine. In addition to the Engine related conversion includes the conversion kit a stand-alone high pressure methanol pump with belonging oil unit for supply of sealing oil and control oil to the fuel injectors. An ECU will be added to run the engine ensure communication.

16 Tests on Methanol Wärtsilä MD concept Optimal heat release Lower Exhaust Temperatre ( up to 50 C ) Reduced NOx (-70%) Same efficiency as diesel

17 Summary test results - Wärtsilä MD concept NOx 3-5 g/kwh (Low Tier II) CO acceptable ( < 1 g/kwh) THC acceptable ( < 1 g/kwh) Very low PM (FSN ~ 0,1 with HFO as pilot) Formaldehyde emissions low ~ below TA-luft Engine: 4L32LNGD Output: 410kW/Cylinder Compression ratio: 13.8:1 Efficiency comparable to running on diesel No Formic acid detected in exhaust gases

18 General conclusions using methanol in the diesel process Engine output and efficiency equal to the diesel engine Significant reduced NOx and PM compared to diesel Life time of major components as cylinder head, piston rings, cylinder liners, bearings, camshaft, crankshaft and cylinder block will be similar or better than the diesel engine. ( The lower piston ring/liner wear may result from less particulates in the exhasut gases). However reduced life-time of exhaust valves / seats due to less particles lubricating the mentioned components No change in oil change intervals are expected

19 Thank You