Theory of a Diesel Engine

[Bluey]

Hi Folks,
There have been a few questions on Diesels lately and some of the answers given leave a bit to be desired. First, without bragging, my qualifications. When working for Leyland Motors in England in 1956 I was invited, as an Australian to attend a C.A.V. overseas traing school. For 41 years up until 2003 I owned and operated 4 Diesel Ijection businesses.(Not all at the one time.) You do not necessarily learn a lot WORKING at something for 50 years, but if you own a business and are ignorant you do not last long.

There have been questions about TIMING. This is extremely complex as it depends on many factors such as engine size, combustion type and fuel pump and injector designs. With a Lanova air cell as commonly used in the US for years the timing (spill cut off or theoretical start of injection) was typically 30 to 35 BTDC. Most direct Injection engines for many years were 24 to 28 BTDC. One I.H. system went as high as 50 BTDC. Later systems and fuel pumps have Auto speed advance, light-load advance, speed advance plus light load retard and any variation the fiendish designers can think up. It is quite complex and some things I have not bothered to mention, so if you DO want to vary from specs you will probably need trial and error and DO NOT ALTER TIMING WITH THE ENGINE RUNNING. It can cause mal-alignment with serious consequences.
Alaskastar mentioned a timing of I think 6 BTDC. Do not be misled here because while almost all manufacturers time at THEORETICAL start of injection, Stanadyne almost ALWAYS time on END of injection


INJECTORS. These are designed to deliver fuel into a combustion chamber so as to attain maximum fuel air mix. Provided they are operating as designed they have a minimum effect on fuel input. That is controlled by the fuel pump/governors. ALL diesels have governors. Some suggect many holes in the injectors is an answer. A large US Company fitted injectors with 6 holes to "better distribute the fuel." The small holes tended to clog and with a Rooasamaster/Stanadyne Pump fitted this caused pump siezures. They changed to 5 holes and soon to 4 holes like most others with a zero difference in fuel economy. Injector nozzles are manufactured to very close tolerances, clearance to about one Micron (one 40,000th of an inch) and lifts to within .0004 of an inch. If anyone thinks that they can improve on this, be my guest.

Some Bosch codes on nozzles are say, DN12SD12 meaning D Dusen or sprayer or nozzle. N Pintle type nozzle. 12 The spray angle at normal operation. S the size of the nozzle, 18mm at the mating surface. D Delay type. This is important as the needle at low deliveries lifts very little and has very little spray angle as required for idling. As power increases more orifice is required and the needle lifts up to 1mm to remove this choking effect. (When Alaskastar "modified " his nozzles he reduced this lift and merely overloaded the pump. About 1970 Stanadyne fitted a high pressure relief valve into the Heads of their pump to prevent this type of overload, otherwise the pump would not have lasted one second without siezure.) The final digits 12 record the individual features of the component.
DLL150S1234 D Dusen L Hole type in German. L Long stem (Mostly used with direct Injection) 150 Spray angle S Size 18mm at mating surface. The last 3 or 4 digits record the individual features.

To achieve a desired spray pattern of a DLL nozzle for instance they employ the following.
A Differential between needle diameter and needle seat. This basicly creates the familiar chatter.Usually 5mm to about 3mm, nowadays often less.
B Needle Lift. This helps control spray penetration.
C Hole diameters. To some extent detemined by Max. Fuel quantities.
D Hole LENGTH. These later two control penetration and distribution. It is desireable to spray the fuel to the extremities of the combustion chamber WITHOUT ACTUALLY HITTING THE SIDES
E Pressure. This is crucial in controlling spray penetration. Too little pressure, (such as fitting injectors for naturally aspirated engines into a Turboed engine) will produce dark gray smoke indicating that some fuel did not mix and merely vaporised, and if the pressure is too high the fuel sprays against the chamber and cooks into carbon with most of it displayed as black smoke. When a turbo is fitted it is necessary to increase injector pressure and often hole size.

Fuel pump designs are many and varied. Of course the modern trend is towards common rail of which I confess I know little. HOWEVER I suggect that IF sufficient Hydroxy can be produced to run a Diesel, say 90% then Computerised Common Rail may be the only way to go. I have racked my brains to think of a LOGICAL way of modifying any current pump but there is one large stumbling block:- If you set a pump at small deliveries at low RPM and LOCK it there, increase the RPM and the fuel delivery increases through inertia.

If you require more on pumps I would need some idea of type and application

Regards Bluey

[Pinhead]

[HugeDuallie]

Hi, would a rail set up for a CNG set up work for this? Honda has it for a 4cyl and Ford has them for V8's

[Aerco]

Hi, bluey
I just joined this form and I was going to send a private message, but noticed this board doesn't allow that.

You seem to have some in-depth knowledge that might be useful to me; my interest lies in the application of diesel technology to aircraft engines (think Jumo 205 in a different configuration). While in principle this project is progressing well on paper, I am getting to the stage where I need some advice on actual available hardware, such as injection pumps and nozzles. I am lone tinkerer and not somebody who thinks he will change the world of internal combustion (and the work in general), but I do believe my ideas have some merit.

Could I pick your brains via personal e-mail? My e-mail is :

zamfire@sbcglobal.net

[Hybrid]

Hi Red/Bluey. You're a bit longer on the tooth than I am. I was smacked
on the arse when you were working in 56. Very interesting post !!
Cheers !

[Bluey]

Hi Hybrid,
As a bananabender I was wondering what State you were in

Regards Blue

[Hybrid]

[Aerco]