As I see it,
g/bhp.h is not a concentration per se but an emission measure of whatever (soot in this case) from a combustion process as carried out mainly in internal combustion engines.
The
bhp.h is a unit of energy and is also expressed in other units such as kcal, Btu, N.m, J, electron volts, volt.coulomb, and so on.
As an example, a diesel motor would consume about 0.22 L of fuel per delivered
bhp.h .
Thus 1 bhp.h would be equivalent to the energy obtained from burning 0.00022 m
3 of fuel. Thus 1 g soot/bhp.h would be equivalent to ~4500 g soot/m
3 of fuel. If the density of the fuel is 800 kg/m
3, the result would be ~5.7 g soot/kg fuel.
This conversion depends on the calorific value of the fuel, the efficiency of the combustion process and of the machine.
Now, if you'd like to express the soot, as a concentration, in g soot/m
3 of exhaust gas one has to estimate an exhaust volume of the combustion gases. In our case let's say 14 normal m
3/kg fuel. The above result would become ~0.41 g soot/Nm
3 of emitted gas.
Nm
3 is 1 cubic meter at 0 deg C and 1 atm abs.
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