SUMMER TRAINING REPORT

On

STUDY OF 16 CYLINDER DIESEL ENGINES

atEngine Development Directorate

ofResearch Designs and Standards

Organization (R.D.S.O.)Lucknow

TABLE OF CONTENT

1. INTRODUCTION2. FUEL INJECTION PUMP3. SNUBBER VALVE4. NOZZLE HOLDER5. NOZZLE6. ELECTRONIC FUEL INJECTION SYSTEM(EFIS)7. COMBUSTION CHAMBER8. EXHAUST MANIFOLD9. TURBOSUPERCHARGER10. AFTERCOOLER11. COOLING WATER CIRCUIT12. LUBE OIL CIRCUIT13. DIESEL FUEL14. MODIFICATIONS DONE FOR A FUEL EFFICIENT LOCOMOTIVE

[A] Modified water connections to after cooler [ [B] 17 mm fuel injection pump with fuel pump support having wider fuel cam roller [C] Modified camshaft with 140 overlap. [ [D] Large after cooler [E] Steel capped pistons [ [F] Steel capped pistons

15. ENGINE TEST BED16. TEST RUN [A] Control Phase [B] Stabilizing Phase [C] Measurement Phase [D] Remaining Step Run Time

17. CONTROL NETWORK

Introduction.

This report is based on the month long training undergone at the

Engine Development (E.D) Directorate of Research Design and Standards

Organisation (R.D.S.O), Lucknow. This Directorate was established in R.D.S.O

in April 1987 and since then various tests have been performed here to achieve

self sufficiency in rail traction diesel engine technology. Presently there are four

test beds in E.D Directorate two 16-cylinder diesel engines, one 12-cylinder

diesel engine and one 6-cylinder diesel engine.

In this report, various components of a 16-cylinder diesel engine

were studied and its performance on the test bed was observed. To observe the

various parameters of the engine in a test bed, a number of sensors were

attached at the critical locations within the engine and data was recorded in the

control processor. This data was then analysed to evaluate the performance of

the engine. Many parameters are observed directly, while some are observed

differentially (e.g. observing the difference in pressure between the inlet and

outlet of lube oil about the lube oil filter) and the rest are calculated from the

observed parameters.

For the 16-cylinder diesel engine test bed 128 channels were used

to determine the various parameters. Out of 128 channels, 24 were used for

pressure measurement (in bars) alone. The pressure gauges used were

diaphragm pressure gauge and Bourdan tube pressure gauge. For temperature

measurement two types of sensors were used. For high temperatures (i.e.

around 600C) sensors used had an accuracy of 1%. While those used for low

temperature measurement (i.e. around 250C) had an accuracy of 0.1%.

To measure the engine rpm, tachometers used had a range from 0

to 1400 r.p.m. The maximum attained was 1050 rpm at a load of 21600 N. For

loading the engine hydraulic brake dynamometer was used. GE turbocharger

with twin after coolers was used and it developed 3100 hp at 32000 rpm. In a 16-

cylinder diesel engine 8 notches are present, 8th notch being the top notch. In

the test bed notches were changed by increasing or decreasing the current with

the help of a rheostat. A full loaded engine runs at top notch. Under tests the

engine's specific fuel consumption was 150 gm/bhp.hr. The overall efficiency

under test conditions of the engine were approximately 75%.

Fuel Injection Pump. Due to high working pressures inside a diesel engine need to inject

fuel at a higher pressure arises. The pump used in a diesel locomotive is of

single acting, constant stroke and plunger type. However, the effective working

stroke is adjustable. Essentially a fuel injection pump consists of a housing,

delivery valve and spring, delivery valve and holder, element(plunger and barrel

assembly), plunger spring, a geared control sleeve and control rack(rod)

assembly. The pump element is a set of a barrel enclosing a plunger, both of

which are machined to very close tolerances and cannot be replaced

individually.

The fuel injection pump has three important functions:

1. To raise fuel oil pressure to a value which will efficiently atomise the

fuel.

2. To supply the correct quantity of fuel to the injection nozzle

commensurate with the power and speed requirement of the engine.

3. To accurately time the delivery of the fuel for efficient and economical

operation of the engine.

Presently the Indian Railways in its diesel locomotives uses MICO

fuel injection pumps (refer figure ). The pumps are of two types, based on the

diameter of plunger, and are used according to their requirements.

1. 15mm diameter pump: It is used for pumping upto 750 bars.

2. 17mm diameter pump: It is used for pumping upto 850 bars.

As the diameter of plunger and barrel increases both the quantity of

fuel pumped and the pressure increase. For cleaning the various parts of the

pump SOVASOL or white kerosene is used.

Fuel oil enters pump from oil header and fills the sump surrounding

the plunger barrel. When the plunger is at the bottom of its stroke (position 1),

fuel flows through the barrel ports, filling the space above the plunger and cut

away area of helix.

As the moves upwards, fuel gets pumped back into the sump untill

the barrel ports are closed. Further movement of the plunger (position 2), raises

the pressure of the trapped fuel. When pressure is sufficient to overcome the

force exerted on delivery valve by valve spring, delivery valve opens and the fuel

is injected into high pressure pipe, leading to injector. Delivery of fuel stops when

the plunger helix opens the barrel ports (position 3). During the remaining

movement of plunger the fuel spills into the sump. This termination of fuel

delivery by helix controls the quantity of fuel injected per stroke. The effective

stroke, and hence the quanitity of fuel injected, is determined by the angular

position of plunger. The total length of plunger stroke remains constant

regardless of engine speed or load. When the plunger is rotated to a position

(6) where the vertical groove is aligned with the control port, no pressure can

build up and consequently, no fuel will be delivered.

The angular position of plunger, with respect to barrel, is altered by

control sleeve, the lower end of sleeve being slotted to engage the flange(vane)

of plunger. The upper end of control sleeve has an integral gear ring, which

engages the control rack. Movement of the control rack by engine governor

rotates plunger, thereby varying the quantity of fuel delivered by pump.

The delivery valve prevents the excess draining of fuel from

discharge line. As the plunger helix uncovers the barrel ports, there is a sudden

pressure drop in barrel resulting in the closure of delivery valve due to high

pressure in delivery pipe and delivery valve spring force. As the valve snaps into

its seat, the pressure is reduced in the injection tubing below the opening

pressure of nozzle. This action of valve eliminates the possibility of secondary

injection (after dribble) from nozzle. The delivery valve also acts as a check

valve to prevent combustion gases from blowing back into the pump.

Snubber Valve.

The snubber valve (refer figure ) is basically a check valve which is

fitted on the fuel injection pump at the top of the delivery valve holder using a

tubing union sleeve and nut. It is used to restrict the fluid flow in the reverse

direction through a small orifice. Another function of snubber valve is to dampen

the shock waves travelling through high pressure line resulting from sudden

closure of delivery valve and nozzle valve.

Nozzle Holder.

The fuel injection nozzle holder conducts fuel from the pump,

snubber valve and high pressure discharge tubingto fuel injection nozzle and

provides a means of adjusting the nozzle valve opening pressure. The mojor

comp[onents of a nozzle holder are nozzle holder body, pressure adjusting

spring, shims(compensating washers), guide bush, intermediate disc and nozzle

capnut.

Shims are used between nozzle hoder body and guide bush(spring

cap) above the spring, for adhusting nozzle valve opening pressure. The lower

end of nozzle holder is ground and lapped to provide leak proof and pressure

tight seal with the lapped upper surface of intermediate disc. The lower surface

of intermediate disc is also lapped to provide a pressure tight sealing with the

lapped surface of nozzle body.

Nozzle.

The fuel injection nozzles are the closed, hydrauliocally operated,

differential type, consisting of two types nozzle body and nozzle valve(pin).

Both these parts are made out of special heat treated alloy steel to minimise

wear. The nozzle valve and nozzle body are matched to form an assembly.

These parts cannot be replaced individually but only as an assembly.

At the tip of nozzle are provide 9 spray holes through which fuel

passes into the combustion chamber. the spring loaded nozzle valve controls the

flow. The spray angle of nozzle is 157. Two types of nozzles, based on the

spray hole diameter, are currently being used in Indian Railways.

1. The DLW 251-B locomotive uses a nozzle which has a spray hole

diameter of 0.350 mm.

2. The DLW 251-D locomotive uses a nozzle which has a spray hole

diameter of 0.375 mm.

A fuel injection nozzle has two main functions:

to atomise the fuel and direct it, in a definite spray pattern into the

combustion chamber.

to raise the pressure of the fuel, to such a value that it becomes

higher than the pressure inside the combustion chamber, for injection to become

possible.

Currently R.D.S.O Lucknow, is testing a microprocessor controlled

electronic fuel pump for its locomotives. These will be implemented in the near

future as test results are exceptionally good. These hold a lot of advantages over

the single helix fuel pumps.

Electronic Fuel Injection System (EFIS).

Present day locomotives in the Indian Railways are fitted with single

helix fuel injection pumps. In thewse pumps, the start of fuel injection is fixed,

and has been optimised to achieve the best specific fuel consumption at the 7th

and 8th notches. Unfortunately this results in inefficient combustion at part load

operation. E.F.I.S gives us flexibility to have different start of injection at different

notches.

Some of the advantages of E.F.I.S over single helix fuel pumps are

listed below:

1. Efficiency of engine can be improved at part load operating

conditions.

2. Flexibility to cut out cylinders at part load operation resulting in

further improvement of efficiency.

3. Automatic reduction of power at full load to eliminate hot engine

alarms during summers.

4. Automatic low idle operation.

5. Controlled engine acceleration to prevent excessive smoke during

notching up.

6. Improved transient operation.

7. Any combination of engine speed and power flexibility.

8. In built smoke control.

9. Cylinder combinations can be cut out in rotation.

Elimination of separate governor, feed rack linkage, over speed trip,

acceleration control devices.

Combustion chamber.

Combustion chamber, or the piston-cylinder assembly, is generally

referred to as the heart of the engine. It is here that the atomised diesel fuel

undergoes combustion and because of the force exerted by the combustion

gases the piston reciprocates inside the cylinder. The reciprocation of the piston

inside the cylinder gets converted into the rotation of wheels of the locomotive by

the crank-shaft connecting rod arrangement.

The cylinder is made of material. Its inside is covered with a lining

material. This liner prevents wear of the inside surface of cylinder due to rubbing

between piston and cylinder. Of all the engine components piston is the most

important and also the most fragile part. A piston consists of a crown and a skirt.

The crown is generally made up of steel, while the skirt is generally of

aluminium. Since the crown of piston is subjected to high temperatures and

pressures, therefore steel is used for crown. Steel can be cooled easily, has high

strength, undergoes lesser wear and most importantly any type of chamber

design is possible with steel. All this is not posssible with aluminium, therefore

aluminium pistons are not preferred.

The minimum clearance, called the bumping clearance, between

the piston and the valve pocket should be 3 mm. The compression ratio of 12.5

is used in diesel locomotive engines. Pistons under test are provided with small

templugs which are used for temperature determination at various critical

locations. The various types of pistons being tested at R.D.S.O are :

1. Deep bowl steel cap piston.

2. Lascasiana mexican steel cap piston.

3. Mahle dish top steel cap piston.

4. ALCO dish top steel cap piston.

5. Aluminium dish top piston.

6. Indian piston ltd. steel cap piston.

7. Super bowl steel cap piston.

8. RDSO-PROP-2 Crown profile steel cap piston.

9. RDSO-PROP-3 Crown profile steel cap piston.

10. Single bolt design steel cap piston.

In IPL piston the crown is secured to the skirt by means of four

stretch bolts while in case of Mahle dish top, RDSO-PROP-2 and RDSO-PROP-

3 there are six stretch bolts. In all the rest a single stretch bolt is present.

With respect to B.S.F.C and combustion temperatures, RDSO-

PROP-2 gave better performance than the other pistons mentioned above. It

was also found that IPL piston was similar to RDSO-PROP-2 in many respects.

A set of five piston rings are provided on each piston. These are

provided to prevent the combustion gases from leaking to the other side of the

piston. They also provide a cushioning and packing effect, thereby preventing

wear to occur at the piston cylinder liner interface.

In DLW 251-B locomotives:

cylinder liner diameter = 9".

piston diameter = 8.98".

stroke = 10.5".

five piston rings (Kaydon's pack(U.S.A)),

1. ) Barrel shape.

2. ) Taper shape-1.

3. ) Taper shape-2.

4. ) Oil conformable.

5. ) Oil conformable.

For cooling the cylinder water is circulated around the cylinder head,

while incase of piston oil cooling is done. Lube oil is circulated inside the piston

by providing cooling galleries in steel cap piston or by mesh tubing in aluminium

top pistons.

Exhaust Manifold.

Exhaust manifold is a rectangular casing in which the exhaust gases

coming from engine numbers 2 to 15 are emptied and then supplied to the

turbocharger. Due to lack of space, outlets of engine numbers 1 and 16 do not

open into the exhaust manifold.

The exhaust gases entering the turbocharger act on its runners and

blades which causes the shaft of the turbecharger to rotate. The exhaust gases

then are let into a chimney from where they are filtered out into the atmosphere.

On the test bed in R.D.S.O a silencer is fitted to the chimney, but in locomotives

it is avoided.

Turbosupercharger.

The power output of an engine depends upon the amount of air

indicated per unit time, the degree of utilisation of this air and the thermal

efficiency of the engine. The amount of air inducted per unit time can be

increased by increasing the engine speed or by increasing the density of air at

intake. Inrease in engine speed requires rigid and robust engines. Also engine

friction and bearing loads increase. Therefore, usually the method of increasing

the density of inlet air is employed to increase the power output of the engine.

This method is called supercharging and is done by usin a device known as

supercharger. Turbochargers are centrifugal compressors driven by the

exhaust gas turbines. By utilizing the exhaust energy of the engine the

turbocharger recovers a substantial part of energy which would otherwise go

waste. Thus the turbocharger will not draw on upon the the engine power.

Before 1991, the Indian Railways used ALCO-720-A for its WDM2

locomotives with 16-cylinder DLW engines. This turbocharger had many areas of

concern. It possesed lower reliability, required frequent maintenance, shorter

period of overhaul and lower life of critical components.

After 1991 the 2600 h.p diesel engine were fitted with either Napier-

NA-295A-720 turbocharger or ABB-VTC-304-VG-13 turbocharger. In case of

Napier two-third of the total failures were taking place on direct account,

establishing the need of product/components improvement. During performance

evaluation, Napier turbocharger deteriorated by 3.1%, while the ABB

turbocharger improved by 55.2%. Also even less than one-third of total failures in

case of ABB were by direct account. Therefore product/components of ABB

turbocharger did not need much improvement and could be used readily.

After upgrading the 2600 h.p diesel engine to 3100 h.p diesel engine

the previous turbochargers were replaced by Napier NA-295-IR and ABB VTC-

3024 turbochargers. One important point which should always be in mind is that

even in emergencies ABB VTC-304-VG-13 and Napier NA-295-A720

turbochargers meant for 2600 h.p engines should not be used for 3100 h.p

engines. This is because the air intake capacity for 2600 h.p engine is 3.75 to

4.0 kg/sec and that for 3100 h.p engine is 4.25 to 4.5 kg/sec.

Recently a GE turbocharger with twin aftercoolers was tested and

implemented. It gave increased efficiency, upto 90%, as compared to 72% got

from Napier and ABB turbochargers. Since it used twin aftercoolers the total

height of the assembly increased hence it posed some problem during

installation in the locomotive. Now-a-days a New Generation turbocharger,

based on air cooling system, HS-5800-NG is being tested. It is expected to give

much better results than its predecers.

Aftercooler:

This component is placed just after the turbocharger. Charged-up air

leaving the turbocharger has temperature and pressure equal to 200C and

2 bar respectively. Such a high temperature of inlet air is undesirable, as it would

have adverse therm affect on the engine components, therefore an aftercooler is

attached to the outlet of turbocharger to cool the charged air. In the aftercooler

cold water from the radiators flows in pipes and the charged air flows around

these pipes. In this way the water takes away the heat of the charged air and the

temperature of air reduces to about 80C.

Earlier, the aftercoolers which were imported from U.S.A, were of

small size. This was because to place them in locomotive first the chimney and

the turbocharger had to be removed and the aftercooler was lowered from the

top. Hence the aftercoolers were made in small size. But now-a-days the

aftercoolers can be fitted inside the locomotive from the side thus alowing them

to be made in large sizes.

Cooling Water Circuit:

Very high temperatures are developed during the operation of a

diesel engine which may lead to the thermal failure of the engine components.

Hence to reduce the high temperatures water is circulated around the engine to

conduct away the excess heat generated. The various important parts of this

cooling circuit are:-

1. Left and Right Header Tubes: Hot water which takes away the heat

from the engine casing is collected in these header tubes. The left and right

header tubes conduct teh hot water to the left and right radiators respectively.

2. Bubble Collector: This deice is installed before the radiators, and is

used to separate out the air bubbles present in the circulating water. Removal of

air bubbles is important as their presence inside the tubes may cause chocking

effects.The air collected is let off through a vent.

3. Radiators: Two sets of radiators, one on left side and the other on right

side of a locomotive, are present. Hot water falls from the top of the radiators

and cold water is collected at the base. Between the two radiators a fan is

rotated for proper ventilation of air.

4. Lube Oil Cooler: Some of the cold water collected is supplied to the

lube oil cooler. This water is used to cool the hot lube oil coming from the engine.

After this the water flows to the water pump.

5. Aftercooler: Again some of teh water collected from the radiator flows to

the aftercooler to cool the hot charged air passing from the turbocharger. After

this, it also is pased to the water pump.

6. Expansion Tanks: During the heating and cooling of circulating water

some amount of this water gets evaporated. Also some of gets leaked away. It is

essential that the quantityof water flowing around the engine casing is same and

it should not fall below a rated value. For this two expansion tanks are provided

at the top so as to compensate for any water loss.

7. Water Pump: Water from the radiator, lube oil cooler, aftercooler and

the expansion tanks enters the water pump from where it is pumped to the

engine casing.

8. Circulation Pipes: Seamless circulation pipes are used to convey water

from one component to another. Earlier these pipes had sharp bends and were

welded together. This caused large frictional losses. Recently, R.D.S.O has

steamlined the whole circulation network and has replaced sharp bends by

smooth curved bends. The material used for circulation pipe is ASTM-A-106.

Lube Oil Circuit.

All the mechanical components of an engine always and at all times

undergoe wear due to friction betwee the moving parts. The piston-cylinder

interface, crank and connecting rod joint and bearings of the crank shaft are

some of the important places where friction occurs in large magnitude. Hence it

becomes necessary to use a lubricant which can reduce friction and wear to a

minimum. In diesel locomotives, lube oils RR-407, HP-713 and MULTIGRADE

OILS are used for the lubrication of various parts of engine. The lube oil is stored

in the sump in the base of the engine. From there it is transported to the various

parts of the engine by a lube oil circuit. The various important components of

the lube oil circuit are :-

1. Pump: The pump sucks the lube oil from the sump and delivers it at

high pressure to the circulation tubes.

2. Relief Valve: If the delivery pressure of pump is above the required

level then a spring loaded relief valve gets opened and some of the lube oil flows

back into the sump. In this way the relief valve prevents excessive pressure build

up in the circulation tubes.

3. Bellow Joints: These have been recently added to the lube oil circuit by

R.D.S.O, Lucknow. They are expansin type joints used for connecting pipe

sections. By using these joints the various errors occuring due to mis-allignment

are eliminated.

4. Bypass Valve: This valve occurs just before the lube oil filter. If the

pressure inside the filter rises above rated value then this valve opens up to

bypass the lube oil and hence preveents damage to the filter.

5. Filter: The lube oil filter is used to remove all the sludge and minute dirt

particles present in the lube oil. If unfiltered, then these particles may clogg the

circulation pipes and also harm the varios components of the engine which are

to be lubricated.

6. Cooler: The lube oil when flowing in the engine gets heated up due to

high temperatures developed inside the engine. Hence arrangement has to be

done to cool this lube oil to the required level. A cooler is installed in the lube oil

circuit where cold water coming from the radiators takes up the heat of lube oil

and hence cools the lube oil to the operating temperature.

7. Strainer:

8. Regulating Valve: This valve regulates the flow of lube oil to the engine

header.

9. Engine Header: This component guides the flow of lube oil inside the

engine.

10. Circulation Pipes: These pipes are responsible for the flow of lube oil to

various components. Earlier these pipes had sharp bends and there ends were

welded. This caused large frictional losses. Hence R.D.S.O streamlined these

pipes, started the use of forged(seamless) pipes and replaced sharp bends by

curved bends. Roller type pipe supports are used for supporting the circulation

pipes.

Diesel Fuel.

Diesel oil for locomotives is of two grades.

a). High speed diesel oil (HSD),

b). Light diesel oil (LDO).

HSD covers distillates of low volatility, while LDO covers the class of

more viscous distillates and blends of these distillates with residuum oil.

The diesel oil to be used in a locomotive should be hydrocarbon oils

derived from petroleum with small amounts of hydrocarbon or non hydrocarbon

addititives. It should be free from grit, suspended matter and other visible

impurities. HSD is used as the fuel for Indian locomotives and should have the

folowing properties.

1. ) Acidity, inorganic NIL

2. ) Acidity, total (mg of KOH/g) 0.5

3. ) Ash (percent by mass) 0.01

4. ) Carbon residue (percent by mass) 0.2

5. ) Cetane number (minimum) 42

6. ) Pour point (maximum) 6C

7. ) Copper strip corrosion for 3 hrs. at 100C Not worse than

no.1

8. ) Water content (percent by mass) 0.05

9. ) Distillation (percent recovery at 366C) 90

10. ) Flash point - Abel's apparatus (minimum) 38C

11. ) Kinematic viscosity (cS) at 38C 2.0 to 7.5

12. ) Sediment (percent by mass) 0.05

13. ) Total sulphur (percent by mass) 1.0

14. ) Total sediments (mg per 100 ml) 1.0

Modifications Done For A Fuel Efficient Locomotive.

In1992 WDM2 locomotive was modified into a fuel efficient 16-

cylinder locomotive. the various modifications carried out were:

[1]. Modified water connections to after cooler. To provide water at the minimum possible temperature into

the aftercooler, in the modified water connections, water inlet of the aftercooler

was fed directly from one radiator and the water outlet of aftercooler was

connected to inlet of water pump. This modification caused saving of 0.6%

S.F.C.

[2]. 17 mm fuel injection pump with fuel pump support having wider fuel cam roller:

To have sharper fuel injection, the 15 mm fuel injection

pump was replaced by 17 mm fuel injection pump. Therefore the fuel pump

support was replaced by the existing 16 cylinder engine fuel support with wider

fuel cam roller. This modification resulted in upto 2% S.F.C saving.

[3]. Modified cam shaft with 140 overlap. The cam shaft was modified to increase the overlap (period

between the air inlet valve opening and exhaust valve closing), from123 to 140

so as to improve scavenging.

[4]. Large aftercooler. A large aftercooler with higher effectiveness was designed

and prototypes evaluated. Owing to different external dimensions of the modified

aftercooler housing, sizes and layouts of certain pipes were changed along with

the turbo mounting bracket. Ater the modification the effectiveness of the

aftercooler was increased to more than 70%.

[5]. Steel capped pistons. With all the six modifications (including fitment of higher

efficiency turbocharger), peak firing pressures exceeded 1800 psi. Thus steel

capped pistons were used.

[6]. High efficiency turbocharger. High efficiency turbochargers fitted in the locomotive were:

a). Napier NA-295 turbocharger, and

b). ABB VTC-304 turbocharger

Engine Test Bed.

The ED Directorate has four test beds. Each test bed has a

microprocessor all of which are connected to a Host Computer. The test bed

microprocessor can be operated in the host computer mode or the floppy mode.

Generally the former mode is preferred. The host computer is PDP 11 or VAX.

The host computer stores and executes the software packages concerning all

necessary programs for test preparation, data management, test run evaluation,

plots and printouts as well as representation of the test bed configuration. The

test bed computer co-ordinates the exchange of data signals between :-

I Fuel balance control,

II Load control,

III Control valves for cooling jacket water temperature,

IV Speed control,

V Temperature measuring devices,

VI Pressure gauges,

VII Vibration gauges.

Test bed computer and the host computer are one unit and

compliment each other to become a powerful system. The definition of

parameters and preparation of the tests is done on the host computer. A TEST

comprises all parameters and definitions needed for a test run. Parameters are

necessary for test execution and are of two types: parameters which describe

the test bed (SYSTEM PARAMETERS) and those describing the test run and the

engine to be tested (TEST RUN PARAMETERS). At the test bed it is possible to

request the system parameters from the host computer. The system parameters

are subsequently loaded into the test bed memory. Now the test run can be

executed independently from the host computer. The measured and calculated

data are sent to the host computer for storage, printing and/or plotting. The

measured results arrive at the host computer via a BUFFER. In case of short

term disconnections on part of the host computer, the data remain in the buffer

until the host is ready again.

TEST RUN

A TEST RUN consists of the following phases:

1. Control Phase.

At the beginning of the control phase, all defined demand values

and digital output signals of the operating step are activated. If ramps are

defined, the set values move along the ramps from the actual values to the

demand values. Test bed equipment such as fans, valves, thermoshock

equipment, etc., may be activated or deactivated by means of the digital signals.

The control phase ends depending on the defined control criteria.

2. Stabilising Phase. The measurement for data storage and printout is not

made until the engine is thermally stable. The engine is considered stable and

measurement can be carried out only if all the stabilisation criteria have been

met. The different stabilising criteria are:

a). Stabilising via waiting time - The engine is considered

stable after the waiting time specified in the operating step has elapsed.

b). Stabilising via temperature gradient - If, e.g., the

exhaust gas temperature changes by less than 5C within one minute, the

engine is considered stable.

c). Stabilisation via measurement criteria - If one or more

measured values are within the specified tolerance range, the engine is

considered stable.

d). Stabilising via bit-in - The engine is considered stable

when external aggregates or devices give a digital message.

3. Measurement Phase. Averaging is done during the measuring time, all

continuous analog values being measured every second. A measuring time of 10

seconds is defined, and the average value of 10 measuring points is calculated

for all continuous analog measured values. These are then stored on the host

computer and/or printed out. The microprocessor uses the fuel balance value

and the calculated average value for finding out the B.S.F.C.

4. Remaining Step Run Time. If after completion of all measurements specified in the

step definition there is still some time left, the system remains in this step until

the step run time has expired.

Exception:- It is possible to define the waiting and/or step run

time as zero. In this case the measuring cycle is started immediately after

completion of the control and stabilisation phases. As soon as the measurement

has been completed, the system switches over to the next step.

A test bed has four main operating states. They are:

1. Monitoring - In this state the system is initiallised.

2. Standby - In this state the test bed computer is ready for an

automatic or semi-automatic test run. All the system and test run parameters are

stored in the test bed microprocessor.

3. Semi-automatic - In this state it is possible to operate the test

bed manually. All parameters have been checked, absolute limit monitoring is

active and data acquisition is possible.

4. Automatic - In this state the entire test run is controlled by the

test bed microprocessor. The operating steps are executed automatically

according to the Step Sequence Table.

COMPUTER NETWORK

TEST

PDP 11/23 + PRNET COMMANDER

DECNET

VIBRATIONAL

CAD ANALYSER

STATIONS

VAX-11/750

PCs ENGINE

TEST BED

3-D COORDINATE

MEASURING

MACHINES