BSFC question

[dicer]

Since alot of you people here have worked on many various projects. I would like to know what the best BSFC is that you have seen, on either SI or CI engines? And any special particulars on them.

 

[patprimmer]

Try the google site search function. It has been discussed at length in the past. The google feature works a lot better than the search feature.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[reidh]

Large 4 stroke diesels can have under .3 lb/hp-hr, while many two stroke diesels are just under .4. 4 stroke gasoline injected engines are about .4 to .5, while carburetted engines will be just a hair higher. Two stroke engines can be as high as .6 or higher.

Reidh

 

[dicer]

Pat, I just did the google thing as you suggested. It did not show any thing in the first 5 requests for this site that answers the question asked. I used "best BSFC".
I know that there are large marine/stationary 2 stroke engines that do .277lbs/bhph, I would like to know if anyone has come close with smaller engines?
And the info online for an SI aircraft engine of 50's vintage was in the .38 range, and actually I think it betters thatlike more into the .32 range I would have to dig into the flight manuals for that one.
So I'm still curious, what is the best that some of you folks have personally seen?

 

[patprimmer]

I just got a few hundred hits with bsfc, including this one as the first hit.

javascriptpenindex(450,450,'

http://www.tipmaster.com/includes/refinfo.cfm?w=450&h=450')

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[patprimmer]

Try thread71-130422

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Marquis]

I have seen 235 g/KWH on a 625cc per cylinder direct injection (piezo spray guided) Spark ignition engine running at Lambda=1 at best point. Injects at about 200 bar pressure. Engine also has twin cam phasing. 11.3:1 CR.

However this doesnt sound very impressive when you look at the data quoted by Open/Vauxhall for their gasoline 4 valve 2 litre C20 XE engine of the late 1980s, which they quote 232 g/KWh for. I was initially dubious of these figures until people I work with who worked at either Cosworth or Opel assured me it was true and better at best point than the pre chamber diesel engine sitting on the dyno next door! It's only a 10.5:1CR, 500 ccs per cylinder. This figure was at best point and achieved running lambda=1.

I've seen 234g/KWH on the S54 BMW straight six M3 engine (the 343 Bhp version) for benchmarking. 11.3:1 CR, 3.246 litres, port throttles (which lowers pumping losses) port fuel injection, smallish bearings-60 mm mains and 48mm con rod bearings, running lambda=1, dual variable cam phasing (60 degree intake range 48 deg exhaust), 0%EGR.

The above represent some of the best gasoline figures I've seen.

More common at best point is around 240g/KWH

The most impressive small diesel engine I've seen was the pumpeduse (pump unit) VW 1.9 2 valver. This thing can achieve 195g/KWH at best point! These are the kinds of figures that medium duty engines have trouble achieving!
For reference it was an 85 KW 1.896 litre 4 cylinder, running about 18.5:1 CR.because it's not common rail it's difficult to quite injection pressures, but about 2000 bar sounds about right.

Jaguar Lion 2.7 diesel achieves about 202 g/KWH at best point. Common rail, 1600 bar injection pressure, 17.1 :1 CR, twin turbo.

A medium duty 3.9 litre 4 cylinder bus engine has I've worked on achieved 197 g/KWH at best point. Is common rail, has an injection pressure of about 1800 bar. as a design life of about 1000,000 kms even with a cylinder pressure design limit of 220 bar! CR or 17.0:1

 

[turbomotor]

Hi dicer,

I have some interesting experience that addresses the letter while perhaps not the intent of your question. I have recently been involved in testing a spark ignition engine where we achieved a bsfc of less than 80 gm/kW-hr. But - let me qualify that answer - the engine was an asymmetric cycle engine running on gaseous hydrogen at a 50% equivalence ratio. As you are probably aware, the LHV for hydrogen is about 121 MJ/kg. The LHV for a typical hydrocarbon fuel is about 42 to 43 MJ/kg. See hydrogen.pnl.gov/filedownloads/hydrogen/ datasheets/lower_and_higher_heating_values.xls