Wood Gasifier: A STEP-BY-STEP GUIDE ON HOW TO BUILD YOUR WOOD GASIFICATION SYSTEM. HOW TO MAKE ENERGY AND FUEL OFF THE GRID. by Mask Robert

Author:Mask, Robert [Mask, Robert]
Language: eng
Format: epub
Published: 2021-04-19T00:00:00+00:00

(c) Engine efficiency

The efficiency with which an engine can convert the thermal energy in the fuel into mechanical (shaft) power, depends in the first instance on the compression ratio of the engine.

The influence of increasing the compression ratio of an engine can be calculated from the following formula.

In which:

10

1 = engine thermal efficiency at a compression ratio

0 = engine thermal efficiency at compression ratio H 1 = engine compression ratio in situation

H 0 = engine compression ratio in situation 0

k = a constant equal to 1.3 in the case of producer gas

(d) Engine speed

Because the engine power output is defined per unit time, the engine power output depends on the engine speed. For diesel engines the power output is nearly linear with the rpm. For spark-ignition engines the power increase is less than linear because of changes in the different efficiency factors. When the power output of a 4-stroke engine is calculated, allowance must be made for the fact that only one out of every two rotations represents a compression and combustion stroke.

The maximum speed of engines fueled by producer gas is limited by the combustion velocity of the combustible mixture of producer gas and air. Because this speed is low as compared to combustible mixtures of petrol and air, the efficiency of the engine can drop dramatically if the combustion speed of the mixture and the average speed of the piston becomes of the same order of magnitude.

In the types of engines that are currently mass-produced, one can expect this phenomenon to occur at engine speeds of around 2500 rpm. Engines fueled by producer gas should therefore generally be operated below this speed.

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