Internal Combustion Engine
Wood gasifiers can power either spark ignition engines, where 100% of the normal petrol can be replaced with little change to the carburation, or in a diesel engine, feeding the gas into the air inlet that is modified to have a throttle valve, if it didn't have it already. On diesel engines the diesel fuel is still needed to ignite the gas mixture, so a mechanically regulated diesel engine's "stop" linkage and probably "throttle" linkage must be modified to always give the engine a little bit of injected fuel (Often under the standard idle per-injection volume). Wood can be used to power cars with ordinary internal combustion engines if a wood gasifier is attached. This was quite popular during World War II in several European, African and Asian countries because the war prevented easy and cost-effective access to oil. In more recent times, wood gas has been suggested as a clean and efficient method to heat and cook in developing countries, or even to produce electricity when combined with an internal combustion engine. Compared to WWII technology, gasifiers have become less dependent on constant attention due to the use of sophisticated electronic control systems, but it remains difficult to get clean gas from them. Purification of the gas and feeding it into natural gas pipelines is one variant to link it to the existing refueling infrastructure. Liquefaction by the Fischer–Tropsch process is another possibility.
Efficiency of the gasifier system is relatively high. The gasification stage converts about 75% of fuel energy content into a combustible gas that can be used as a fuel for internal combustion engines. Based on long-term practical experiments and over 100,000 km drive with a wood gas-powered car, the energy consumption has been 1.54 times higher compared to the energy demand of the same car on petrol (not including the energy needed to extract, transport and refine the oil from which petrol is derived, and not including the energy to harvest, process, and transport the wood to feed the gasifier). This means that 1000 kg of wood combustible matter has been found to substitute 365 litres of petrol during real transportation in similar driving conditions and with the same otherwise unmodified vehicle. This can be considered to be a good result, because no other refining of the fuel is required. This study also considers all possible losses of the wood gas system, like preheating of the system and carrying of the extra weight of the gas-generating system. In power generation reported demand of fuel is 1.1 kg wood combustible matter / kWh electricity.
Gasifiers have been built for remote Asian communities using rice husk, which in many cases has no other use. One installation in Burma uses an 80 kW modified diesel for about 500 people who are otherwise without power. The ash can be used as Biochar fertilizer, so this can be considered a renewable fuel.
Exhaust gas emission from an internal combustion engine is significantly lower on wood gas than on petrol. Especially the HC emissions are low on wood gas. A normal catalytic converter works well with wood gas, but even without it, emission levels less than 20 ppm HC and 0.2% CO can be easily achieved by most automobile engines. Combustion of wood gas generates no particulates, and the gas renders thus very little carbon black amongst motor oil.
Famous quotes containing the words internal, combustion and/or engine:
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