German engine test data symbols

[brianwnz]

Hi All,

I'm trying to translate some German test data, and struggling with the subscript 'o' - anyone know what it stands for?

In particular, if Ne (subscript e) = effective power (brake hp), what is No (subscript o), and Neo (both e & o subscript)? Calling them all Leistung is not helping me .....

I've thought 'o' might be short for "obere" (upper/top), but it doesn't really make sense; nor does overload, takeoff, maximum (all start with different letter)......context below:

Google is not up to the task ..... any handy lists of all this stuff as it relates to engines anywhere?

Thanks in advance

 

[Vanni]

Ne may indicate the effective power of a motor measured at the end of the shaft. I am not sure what Ne0 or N0 means, though. Maybe they have something to do with Seal level power? Hope some more learned members can reply.

 

[ThomasP]

Hey brianwnz,

>begin translation

With the liquid-cooled 9-cylinder radial engine that was tested, the following values initially resulted for the maximum output with the relatively low supercharging of 1.175 ata:

mean effective working pressure Pme = 9.3 kg/cm2

output Ne = 590 PSe (Neo = 625 PSe)

displacement output NeL = 21 PSe/liter (NeoL = 22.5 PSe/liter)

specific fuel consumption be 195 - 200 gram/PSe-hr

After various modifications of the injection ratios, the adjustment and control, and of part of the combustion chamber. The values at 1960 rpm were:

effective working pressure_____ Po = 8.8 kg/cm2

output_______________________No = 530 PSe

specific fuel consumption______bo = 150 gram/PSe-hr

<end translation


Although I cannot guarantee my interpretation of the subscript 0 is correct, in engineering the subscript 0 was/is sometimes used to indicate a value or series of values using new methods/systems, or data values (sometimes sets of data). Before computers and modern typesetting mechanisms, typewriters did not have a lower case 0, so a lower case o was usually substituted.

To me it looks like they were testing a liquid-cooled version of the BMW 132 (27.7 L) engine (or similar), with added and/or modified fuel injection system and modified combustion chamber - probably to see what it was possible to achieve with the new water-cooled variant - and comparing the new version either to either the liquid-cooled variant output before addition/modification of the fuel injection system and combustion chamber, or to a prior air-cooled variant.

So the 625 PSe(o) is the output using the new engine with all the mods mentioned vs the 590 PSe of the old version without the mods. The 530 PSo at 1960 rpm is probably the setting at which best SFC was achieved using the new engine with all the mods.

 

[brianwnz]

Hey brianwnz,

>begin translation

With the liquid-cooled 9-cylinder radial engine that was tested, the following values initially resulted for the maximum output with the relatively low supercharging of 1.175 ata:

mean effective working pressure Pme = 9.3 kg/cm2

output Ne = 590 PSe (Neo = 625 PSe)

displacement output NeL = 21 PSe/liter (NeoL = 22.5 PSe/liter)

specific fuel consumption be 195 - 200 gram/PSe-hr

After various modifications of the injection ratios, the adjustment and control, and of part of the combustion chamber. The values at 1960 rpm were:

effective working pressure_____ Po = 8.8 kg/cm2

output_______________________No = 530 PSe

specific fuel consumption______bo = 150 gram/PSe-hr

<end translation


Although I cannot guarantee my interpretation of the subscript 0 is correct, in engineering the subscript 0 was/is sometimes used to indicate a value or series of values using new methods/systems, or data values (sometimes sets of data). Before computers and modern typesetting mechanisms, typewriters did not have a lower case 0, so a lower case o was usually substituted.

To me it looks like they were testing a liquid-cooled version of the BMW 132 (27.7 L) engine (or similar), with added and/or modified fuel injection system and modified combustion chamber - probably to see what it was possible to achieve with the new water-cooled variant - and comparing the new version either to either the liquid-cooled variant output before addition/modification of the fuel injection system and combustion chamber, or to a prior air-cooled variant.

So the 625 PSe(o) is the output using the new engine with all the mods mentioned vs the 590 PSe of the old version without the mods. The 530 PSo at 1960 rpm is probably the setting at which best SFC was achieved using the new engine with all the mods.

Thanks Tom,

Yeah it was the 114 water-cooled diesel (same capacity as the 132); they changed to pilot-injection (can't be 100% sure on this particular engine test, but they certainly experimented with it), and I'm reasonably confident that's what they are saying; and had made changes to the Lanova energy cell.

I'll run with what you've explained, although they've certainly made it as confusing as it can be by doing so, lol.

Maybe that's why there are a few different published ratings for the 114 models (air- & water-cooled).....

Thanks for your help; appreciated.

Regards, Brian

 

[Deleted member 68059]

"e" is Effektiv, in other words actual or brake power (as opposed to "indicated") So, for example Pme is brake mean effective pressure.

I cant make a definitive statement on the lower case "0" because the subscripts depend a bit who/which firm wrote it,
but its most likely the conditions at sea level, ie. zero altitude.

 

[brianwnz]

"e" is Effektiv, in other words actual or brake power (as opposed to "indicated") So, for example Pme is brake mean effective pressure.

I cant make a definitive statement on the lower case "0" because the subscripts depend a bit who/which firm wrote it,
but its most likely the conditions at sea level, ie. zero altitude.

Thanks Calum,

I was rather hoping you might respond, as you've probably studied more than a few German reports, and can presumably speak a little more German than me (mine is solely Google, and Commando comics from many moons ago).

The report is by Wunibald Kamm, about the BMW diesels; I'll attach it here so you can get full context, if you have the time. In the spirit of others on this site, I should have probably shared it from the start.......

If the tests were in Munich originally, 520m above sea level, would they have 'corrected' the results for sea level, to get that 2nd reading?

Appreciate your reply

 

[brianwnz]

I may have found a little more evidence regarding these symbols, so thought I would share again.

I've given the original German text also, as my translation is only ever courtesy of Google

Which seems to translate as:

"Pre-calculation of Altitude Performance

By Otto Schwager

For the manufacturer of aircraft, it is often of great importance to know the altitude performance of an aircraft engine, since the climb times and flight speeds to be guaranteed at the various altitudes depend on this. The most reliable way of obtaining the performance at altitude is to examine the engine in the vacuum chamber under the actual pressure and temperature conditions encountered during altitude flight. Unfortunately, there are currently only very few such vacuum chambers, so that it is not possible to record the performance, throttle and consumption curves for every type of aircraft engine in the same way as the altitude performance curve. As a result, people make do with the pre-calculation of the height performance and use a wide variety of formulas for this, some of which are theoretically based and some are based purely empirically on test results.

It can be assumed with sufficient accuracy that, given the same mixture ratio and the same speed, the indicated engine power is directly related to the air weight, and also that part of the power loss at sea level remains the same for all altitudes, while a second part changes in relation to the air weights.

It denotes:
No the braking power at,
yo unit air weight,
Nz the braking power in,
Z km altitude,
yz the air weight at height Z,
to, To, tz, Tz the air temperatures at 0 and Z km altitude,
bo, Po, bz, Pz the air pressures at 0 or Z km altitude,
nm the mechanical efficiency,
a the variable part of the power loss,
b the constant part of the power loss,
NRo the power loss at yo,
NRz the power loss at yz,
Nio is the indicated power at yo,
Niz the indicated power at yz."

(excuse the subscripts being too large)....... So, seems to agree with the sea-level power correction.

I've also attached the entire document, there is a series of these factory aircraft engine newsletters available at address below - some very interesting articles from BMW pre-WWII.

Files Archive - E28 Goodies

Thanks to all for their input; always appreciated