Energy balance Gas engine

1 energy balance

1.1 thermal efficiency
1.2 combined heat , power
1.3 engine cooling
1.4 gas consumption calculation

energy balance
thermal efficiency

gas engines run on natural gas typically have thermal efficiency between 35-45% (lcv basis)., best engines can achieve thermal efficiency of more 48% (lcv basis). these gas engines medium speed engines bergen engines fuel energy arises @ output shaft, remainder appears waste heat. large engines more efficient small engines. gas engines running on biogas typically have lower efficiency (~1-2%) , syngas reduces efficiency further still. ge jenbacher s recent j624 engine world s first 24-cylinder gas engine high efficiency running on methane.

when considering engine efficiency 1 should consider whether based on lower heating value (lcv) or higher heating value (hcv) of gas. engine manufacturers typically quote efficiencies based on lower heating value of gas, i.e. efficiency after energy has been taken evaporate intrinsic moisture within gas itself. gas distribution networks typically charge based upon higher heating value of gas (i.e. total energy content). quoted engine efficiency based on lcv might 44% whereas same engine might have hcv of 39.6% based on hcv on natural gas. important ensure efficiency comparisons on like basis. example manufactures have mechanically driven pumps whereas other use electrically driven pumps drive engine cooling water, , electrical usage can ignored giving falsely high apparent efficiency compared direct drive engines.

combined heat , power

engine reject heat can used building heating or heating process. in engine, half waste heat arises (from engine jacket, oil cooler , after-cooler circuits) hot water can @ 110 °c. remainder arises high-temperature heat can generate pressurised hot water or steam use of exhaust gas heat exchanger.

engine cooling

two common engine types air-cooled engine or water cooled engine. water cooled nowadays use antifreeze in internal combustion engine

some engines (air or water) have added oil cooler.

cooling required remove excessive heat, on heating can cause engine failure, wear, cracking or warping.

gas consumption calculation

the formula shows gas flow requirement of gas engine in norm conditions @ full load.

q
=


p
η


⋅


1

l
h

v

g
a
s







{\displaystyle q={\frac {p}{\eta }}\cdot {\frac {1}{lhv_{gas}}}}

where:

q


{\displaystyle q}

gas flow in norm conditions





p



{\displaystyle {p}}

engine power





η



{\displaystyle {\eta }}

mechanical efficiency
lhv low heating value of gas




^ chp | cogeneration | ge jenbacher | gas engines . clarke energy. retrieved 2013-09-28. 
^ cite error: named reference claverton-energy.com invoked never defined (see page).
^ products & services . ge-energy.com. retrieved 2013-09-28.