engine test cell

Engine Test Cell

Engine Test Cell of 44

Table of Contents

1 Test cell overview........................................................................................................................4

1.1 Types of test cell...................................................................................................................6

1.2 Various inflows and outflows to and from a test cell............................................................7

2 Test cell construction...................................................................................................................7

2.1 Overall size of cell.................................................................................................................7

2.2 Floor and sub-floor...............................................................................................................7

2.3 Doors.................................................................................................................................... 8

2.4 Walls..................................................................................................................................... 8

2.5 Ceiling................................................................................................................................... 9

2.5.1 Fire extinguish (Water Mist Sprinkler) system................................................................9

2.5.2 Crane rail and hoist......................................................................................................11

2.5.3 Lighting system............................................................................................................11

3 Mechanical systems...................................................................................................................11

3.1 Engine mounting.................................................................................................................11

3.1.1 Pallet trolley arrangement:..........................................................................................12

3.1.2 Support columns with T-slotted base...........................................................................14

3.2 Dynamometer.....................................................................................................................15

3.2.1 Eddy current dyno........................................................................................................15

3.2.2 Transient Dyno.............................................................................................................21

4 Inflow to the test cell.................................................................................................................23

4.1 Engine cooling system.........................................................................................................23

4.1.1 Coolant conditioning unit.............................................................................................24

4.1.2 Turbo charger.............................................................................................................. 25

4.1.3 Turbo cooler/Inter cooler.............................................................................................26

4.2 Charge air............................................................................................................................27

4.2.1 Inlet air conditioning unit (IACU)..................................................................................27

4.2.2 Selection of Inlet air conditioning unit..........................................................................29

4.3 Fuel System.........................................................................................................................29

4.3.1 Fuel tank......................................................................................................................29


4.3.2 Fuel lines...................................................................................................................... 29

4.3.3 Fuels.............................................................................................................................30

4.3.4 Fuel lines inside the test cell.........................................................................................33

4.4 Ventilation air..................................................................................................................... 36

4.5 Electricity............................................................................................................................ 36

5 Outflows from test cell.............................................................................................................. 38

5.1 Exhaust............................................................................................................................... 38

5.2 Exhaust Ventilation.............................................................................................................41

5.2.1 Fans..............................................................................................................................41

6 Compressor station....................................................................................................................42

7 Cooling water circuit for plant...................................................................................................44


1 Test cell overview

The test cells are built side-by-side in a line. Engines enter the cell by way of the large door

in the rear wall while the operator enters by way of cell access door in the front side. There is a

double-skinned toughened glass window in front of the control desk for observation. The engine

and dyno base plates are in axis with the test cell axis.

The alternative with test bed axis lying transversely gives better visibility, but special

attention must be paid to safety and strength of observation window. Also there are glass windows

in both the side walls to observe the things happening in adjacent cells.


In all test beds a crane rail located in ceiling along the test bed axis with a chain hoist to

handle engines and dynamometers for maintenance.

The junction box is fixed to the wall by a wall bracket. The junction box containing various

transducers such as RTD, Thermocouple and Pressure sensors are carried by an adjustable boom

over the engine. If the weight of this box is increasing then care should be taken at the wall fixing

point and the strength of the boom. Since it is cantilever type, due to the load at free end,

chances are there for bending of boom.

To overcome this, the boom can also be supported by steel cable as shown in figure above.

This arrangement can withstand load, which is applied at the free end of beam.

The instruments such as fuel meter, fuel-conditioning unit are sidewall mounted. The

smoke meter and opacimeter are placed near the exhaust side.

1.1 Types of test cell

The test cells are namely R&D test cell and Production test cell.


In Research and Development test cell, engines are at development stage. It will undergo

various testing such as emission testing and endurance testing. The time of stay of engine in test

cell is more. That is changeover of engine is less. Compared to production test cells, the R&D test

cells have more sensors for measuring various parameters.

In case of Production test cells, the objective is to check that the engine is complete and

runnable. This has to be carried out in minimum possible time. Because of handling more engines

in a short period of time, this testing imposes heavy wear and tear, particularly on engine rigging

components, and these become a maintenance liability.

1.2 Various inflows and outflows to and from a test cell

Inflow Outflow

Fuel Exhaust

Cooling water Engine cooling water

Ventilation air Dynamometer cooling water

Charge air(When separately supplied) Ventilation air

Electricity for instruments Electricity form dynamometer

2 Test cell construction

2.1 Overall size of cell

The test cell should have enough space to move around in comfort.

As a rule of thumb there should be an unobstructed walkway 1m wide all around the test bed.

The cell height should be sufficient to allow the dynamometer to be lifted over the top of the engine.

When testing vehicle engines with exhaust system as used on the vehicle, and then extra length of cell is required to accommodate the exhaust system.

2.2 Floor and sub-floor

The engine mounting and dyno mounting places are elevated to a height of 2 feet above the ground level.


The surrounding area is covered with well-fitting chequer plates, not weighing more

than about 20kg each, and provided with lifting holes.

The cooling water pipe lines and fuel lines are running below this sub floor.

During maintenance, the chequer plates are removed and service is carried out.

The spaces below floor level should be scavenged by the ventilating system to avoid any possibility of the build-up of explosive vapours.

The plates can be cut as necessary to accommodate service connections.

2.3 Doors

Doors should meet the requirements of noise attenuation and fire containment.

The doors are usually heavy and require more than normal effort to open them.

Forced or induced ventilation fans can give rise to pressure differences across doors, possibly making it dangerous or impossible to open a large door.

Doors should be provided with small observation window.

EXIT signs should be there on doors.

2.4 Walls

The walls must be of sufficient strength and suitable construction to support wall mounted instrumentation cabinets, fuel system, and any equipment carried on booms cantilevered out from the walls.

The walls should provide the necessary degree of sound attenuation.

It must comply with requirements regarding fire retention (usually a minimum of one hour’s containment).

High density building blocks provide good sound insulation but require some form of internal acoustic treatment, such as 50mm thick sound absorbent panels, to reduce the reverberation in the cell. Such panels can be effective on walls and ceilings.

Special construction panels made of sound absorbent materials (acoustic foam, glass wool, non-woven composites) are sandwiched between metal sheets, of which inner (cell) side is perforated as shown in figure.


These 10 cm thick panels can be used with standardized structural frames for the construction of test cells.

If heavy equipment is to be carried, as internal ‘hard mounting’ points must be built into the steel structure.

2.5 Ceiling

The ceiling consists of

Fire extinguish (Water Mist Sprinkler) system. Crane rail and hoist Lighting systems.

2.5.1 Fire extinguish (Water Mist Sprinkler) system

The sprinkler system sprinkles water in case of fire accident. The smoke and flash

detecting sensors are placed at floor, ceiling and middle level.

In case of fire accident, the flash and smoke is detected and the water mist solenoid valve

fixed at the rear side of test cell deliver water in the form of mist to the test cell.


The sprinklers are placed as shown in figure. The Sprinklers are placed in such a way that

water mist should cover all the areas of the test cell.

In addition to this a fire extinguisher is placed above the engine. At the time of fire, the fire

extinguisher valve will open automatically and extinguish the fire.


2.5.2 Crane rail and hoist

A crane rail (I section beam) is fixed along the axis of the test cell axis. In this rail hand

chain hoist is fitted. This hoist is used to carry the engine or dyno and move along the test cell

axis. The capacity of the chain hoist is usually 1 ton. If the hoist is used to handle heavy systems

such as double rotor dyno then hoist of capacity 2 ton is used.

2.5.3 Lighting system

Lights should be securely mounted so as not to move in the ventilation wind.

It should give a high and even level of lighting without causing glare from the observation window.

Lights are working in an atmosphere of oil-laden fumes they must met appropriate safety standards, be easily cleaned and operate at a moderate surface temperature.

The unit of illumination in International System of Units is known as the lux.

The IES code lays down recommended levels of illumination in lux for different visual tasks. A level of 500 lux in a horizontal plane 500mm above the cell floor should be satisfactory, but areas of deep shadows must be avoided.

The switches to turn off the test cell lights should be provided near the control desk and it will be useful to watch for sparks and red-hot surfaces.

Eight to ten lights are used in the cell as shown in figure.

3 Mechanical systems

3.1 Engine mountingThere are two kinds of engine mounting arrangements.

i) Pallet trolley arrangement.ii) Support columns with T- slotted base.

There is trade off between these two arrangements. In trolley system, while one engine is

running, the next engine is mounted in another trolley and is ready for rigging. The advantage of

this arrangement is down time between engine changeovers is minimum. The limitation is, if the

height of engine over the trolley is changed then the dynamometer height has to be adjusted by

adding filler plates to make axis of the crankshaft and dyno are collinear. If the misalignment is

more, then more vibrations will occur. Locking system is necessary to keep the trolley in position

when the engine is running.


3.1.1 Pallet trolley arrangement:

At the time of construction of test cell the trolley’s are designed and fabricated to that

particular cell. The trolleys are designed in such a way that height of engine over trolley is same

as the height of the center of dynamometer.

This trolley is having four wheels made of Teflon and four supports. There is a guide way in

the base plate to place the trolley in position. When the trolley is in locked position, the inclined

supports in trolley will exactly seat over the inclined supports in base plate.

In trolley, columns are there. Over which the steel plate is welded. The rubber material is

placed in between two steel plates and the engine is mounted over this. This will provide damping

and prevent vibrations passing to the structures. The arrangement of rubber material between two

steel plates is same as the engine is mounted in vehicle.


3.1.1.1 Pneumatic locking system:

The pallet trolley is locked in its position by the pneumatic locking system when the engine

is running.

Working:

The pneumatic locking system consist of two 5/3 way hand lever operated direction control

valves. The 5/3 valve has 5 ports and 3 finite positions.


1

2

3

Pneumatic source

Quick exhaust

valve

1 2 34 5

When the lever is in middle position (2) the ports are closed and no supply air will go to system.

When the lever is pushed to right, valve is in position (1), the source (inlet port-2) will go to system through the outlet port (4). Direction is shown as arrow in above figure. The air enters at rod end of cylinder and makes the cylinder to retract. The air at piston end releases to atmosphere by the quick exhaust valve (3).

When the lever is pulled to left, valve is in position (3), the source (inlet port-2) will go to system through the outlet port (5).Direction is shown as arrow in figure. The air enters at the piston end of cylinder and makes the cylinder to extend. The air at rod end releases by the quick exhaust valve (1).

3.1.2 Support columns with T-slotted base

This arrangement has beams and columns which move in all three axes and can

accommodate any size of engine. The X axis movement is achieved by adjusting the beam over T-

slotted base.

The Y axis direction is achieved by moving the columns over the slot in beam. In Z-direction,

suitable height is achieved by screw jack.

At the top of screw jack, rubber material is placed between two steel plates and the engine is

mounted over this.


This is the same arrangement as engine is mounted in vehicle. The vibrations are damped

by the rubber and prevent vibrations passing to the structures.

3.2 Dynamometer

The dynamometer is the device used to measure the torque and power of engine. The dyno

is directly coupled to engine by a propeller shaft. There are different types of dyno and each

having its own advantages and disadvantages. The most widely used dyno’s are Eddy current type

and Transient dyno (AC dynamometer).

3.2.1 Eddy current dyno

The parts of eddy current dyno are

i) Toothed rotorii) Coiliii) Loss plates (with Cooling coils at rear)iv) Statorv) Outer casing and rigid mounting.


3.2.1.1 Inputs

Electrical110V AC – For excitation of coil

0-6 A – For applying torque

Cooling water – At a pressure of 1 bar.

These values are with respect to dyno of torque capacity 43 kg-m.

3.2.1.2 Output

Torque signal (Load cell) Speed signal (Magnetic pick up sensor)

3.2.1.3 Base Plate

The base construction is important in case of dyno. Because the base should withstand the

vibrations produced in dyno. All the vibrations should be dampened and it should not be passed to

structures around dyno.

The base is constructed by concrete over which a cast iron plate of thickness 3cm is bolted.

At the corners, steel blocks are welded over which another cast iron plate of 2.5cm thickness is

bolted. Over this cast iron plate, the dyno is mounted. These plates are fixed to dampen the

vibration. The height of the dyno is adjusted by adding a filler plate in dyno base to make the rotor

axis is collinear with engine crankshaft axis.


3.2.1.4 Construction and operation

The dynamometer consists of a shaft/rotor assembly mounted within a casing supported on

a rigid base plate.

The power absorbed by the dynamometer is controlled by varying the magnetic field

generated by coils housed within the casing. As the shaft rotates, the rotor cuts the magnetic field

and eddy currents are generated with in the loss plates.


These eddy currents acts to oppose the rotation of the shaft applying a load to the prime

mover and generating heat in the loss plates. Thus the absorbed engine power appears as heat in

the loss plates, which is dissipated by cooling water flowing through specially designed passages

machined into the rear of loss plates.

While applying load, there is a small movement in dyno about its axis. This is measured by

the load cell and is proportional to the torque.

The speed is measured by an electromagnetic pulse pick up and a toothed wheel mounted

on the shaft half coupling hub. The bedplate also supports the external water connections and the

electrical terminal box that interfaces the dynamometer to the control system.

3.2.1.5 Cooling water:

The water from the main tank is coming into the test bed by gravity. This water can be

directly given to dynamometer or a pump can increase the pressure.

A magnetic separation filter then filters the water. This filter is important thing in dyno,

because if the water is not filtered then cooling passages of dyno will get block by the particles

and scales. This will affect the water flow and cooling rate is reduced. If there is a pressure drop in

flow line or flow rate is reduced then the filter has to be checked and replaced if needed.


Then the water flows through the cooling chamber inside dyno and carries away the heat.

This hot water goes to drain tank in test bed and then to main ground tank via underground

channel.

Operation of bypass pump:

If the valve 1 is open, valve 2 & 3 are closed and pump is off then the inlet water will go to dyno due to water head and pressure is at 1 bar.

If the valve 1 is closed, valve 2 & 3 are open and pump is on then the inlet water is pumped by the centrifugal type pump and the pressure is high.

3.2.1.6 Pressure Switch

A pressure switch is fixed at the inlet water line of dyno. If there is scale formation or choke

in the filter, then the flow rate will come down and pressure in inlet line also get reduced. For

single rotor dyno the pressure limit is set to 0.3 bar and double rotor dyno 0.5 bar. When the

cooling water pressure goes below this limit, pressure switch NO contact becomes and give

indication to operator by alarm. This is safety measure to ensure proper flow of water.

3.2.1.7 Torque measurement

When dynamometer is applying load to engine there is a small movement in dynamometer

about its axis. This movement is sensed by the load cell and it is proportional to the torque.


Load cell

A load cell is an electronic device that is used to convert a force into an electrical signal.

This conversion is indirect and happens in two stages. Through a mechanical arrangement, the

force being sensed deforms a strain gauge. The strain gauge converts the deformation (strain) to

electrical signals. A load cell usually consists of four strain gauges in a Wheatstone bridge

configuration. The electrical signal output is typically in the order of a few 0-20 mV and requires

amplification by an instrumentation amplifier before it can be used.

Mounting

Rod end bearings are used in load cell. The sensor part is in middle and at both ends rod end

bearings are fixed. These rod end bearings are used in load cell as they are self aligning.

The load cell can be mounted either between dynamometer outer casing and base over

which dyno is mounted or between loading arm and base.


http://en.wikipedia.org/wiki/Instrumentation_amplifier

http://en.wikipedia.org/wiki/Wheatstone_bridge

http://en.wikipedia.org/wiki/Strain_(materials_science)

http://en.wikipedia.org/wiki/Strain_gauge

3.2.1.8 Speed sensor

One end of the dyno rotor is connected to engine. The other end is having a toothed wheel

and magnetic pick up sensor to measure the speed. This sensor output is pulse from which the

speed is calculated.

3.2.2 Transient Dyno

The transient dyno’s are used for running transient cycles. The speed and torque response

of transient dyno’s is high. These are AC dynamometers which will operate in all the four

quadrants. The power produced is feedback into mains and it provide cost saving for power

supply. AC motor with a squirrel cage rotor is used.

3.2.2.1 Base construction

As this dyno is used for running transient cycles, the speed and torque are changed rapidly

and vibrations also more. It needs special arrangements for damping the vibrations. Air cushion

system is used to isolate the base plate from the ground level.


The entire base plate is supported by the pneumatic cylinders at the four corners. The

engine and dyno are mounted over this base plate. Since both the engine and dyno are mounted

on same plate, the amplitude of vibration is same for both engine and dyno. This prevents the

misalignment in connecting shaft due to vibration. A pneumatic source of 6 bar is used for these

cylinders.

The whole system is isolated from the ground level and surrounding structures. This air

cushion system is interlocked with the test cell control system. The engine will start only when the


base plate is lifted by the air cushion system. The clearance between ground and base plate is 2

to 3mm.

4 Inflow to the test cell

4.1 Engine cooling system

The cooling water from main tank is coming into test bed by gravity head. The cooling water

is then used for two purposes.

i) To condition the engine coolantii) To condition the air (In case of engine with intercooler)

The cooling water is branched into two pipes, one is for coolant conditioning unit and

another is for intercooler. In coolant conditioning unit, engine coolant is cooled by the cooling

water after that delivers out to drain tank.


4.1.1 Coolant conditioning unitThe coolant conditioning unit is to maintain the temperature of coolant as set by user in

the controller unit.

The cooling water is filtered by the filter unit. Then the flow rate of water is controlled by actuator valve. If the valve is fully open then

more amount of water will enter the system and cooling takes place rapidly.

The butterfly valve is to control the flow rate manually and bypass the actuator valve.

The pressure switch maintain the set pressure value in system, if the pressure exceeds, it will alert the operator by alarm.

Inside the cooling chamber, coolant is flowing from up to down in small pipes surrounded by the cooling water which is flowing from down to upward.

This cooling water carries away the heat of the coolant.

The Centrifugal pump is used to circulate the coolant.

The water level is sensed by the level sensor which is mounted over the cooling chamber. Also level indicator is there to show the level of water inside the system.


4.1.2 Turbo charger

A turbocharger is a small radial fan pump driven by the energy of the exhaust gases of an

engine.

A turbocharger consists of a turbine and a compressor on a shared shaft. The turbine converts

exhaust to rotational force, which is in turn used to drive the compressor. The compressor draws in

ambient air and pumps it in to the intake manifold at increased pressure, resulting in a greater mass

of air entering the cylinders on each intake stroke.


http://en.wikipedia.org/wiki/Manifold_(automotive)

http://en.wikipedia.org/wiki/Gas_compressor

http://en.wikipedia.org/wiki/Heat_engine

http://en.wikipedia.org/wiki/Heat_engine

http://en.wikipedia.org/wiki/Gas_compressor

http://en.wikipedia.org/wiki/Turbine

4.1.3 Turbo cooler/Inter cooler

Intercooler is used in turbo charged engines. To reduce the temperature of air entering the

cylinder, it is passed through intercooler. An intercooler is a heat exchanger. That means there are

two or more fluids that don't physically touch each other but a transfer heat or energy takes place

between them.

Working of intercooler:

Hot air from the turbo flows through tubes inside the intercooler.

The turbo air transfers heat to the tubes, warming the tubes and cooling the turbo air.

Outside water (or air) passes over the tubes and between fins that are attached to the tubes.

Heat is transferred from the hot tubes and fins to the cool outside water (or air).

This heats the outside air while cooling the tubes.

This is how the turbo air is cooled down. Heat goes from the turbo air to the tubes to the outside water (or air).

Sensors mounted in intercooler:

The temperature of air is measured at the inlet side and outlet side of the intercooler. The pressure also measure at both the inlet and outlet.

The cooling water used in intercooler is drained back to drain tank.


4.2 Charge air

4.2.1 Inlet air conditioning unit (IACU)Inlet air conditioning unit is to supply the air to engine at specified temperature, pressure

and relative humidity. The air is taken from ambient and it is to be conditioned before using it in

engine. IACU consists of radial blower, heat exchanger, condenser, chiller compressor, steam

generator and electric heater.

The temperature control is carried out by cooling the air by a cooler.

Electric heating is used to increase the temperature based on the ambient air temperature.

For efficient drying of air, an air cooled chiller compressor is integrated in the device.

In case of too low water content in ambient air, steam is injected into supply air in order to achieve the required Specific Humidity.

This conditioning unit is placed at terrace or a place where good ventilation is available. From the Inlet air conditioning unit the air is carried to test cell by an isolated stainless steel pipe.

Working:

The air from the ambient is drawn into the system by the blower. The air is dried first by allowing it to pass through cooler. The cooler will condensate the

vapours in inlet air.


The cooler unit consists of a compressor and heat exchanger.

To increase the humidity, steam is injected into air. The steam generator consists of a boiler and electric heater. In some systems, the water is directly fine sprayed into the inlet air.

Finally electric heater is placed to increase the temperature of air to desired temperature.

Inside the test cell, a sensor box is there to measure the temperature and humidity before

entering the engine. This is carried out, because there may be losses in pipe during the course of

travel. An electric heater is also available in this box to increase the temperature if needed.

The pressure control valve is available in this box to control pressure. Depending on degree

of closing of Pressure control valve, the intake air can be adjusted between over pressure and

vacuum.

After the sensor box, a standard length pipe in which mass flow measurement device is fitted.

This measure the mass of air flow in kg/h.

The device used to measure this mass flow rate is ABB Sensyflow P.

4.2.2 Selection of Inlet air conditioning unit


The average air consumption of passenger car engine is around 400 m3/hour. If the

capacity of the inlet air conditioning unit is 1500 m3/hour then it can be used up to 3 test beds in

which passenger car engine testing is carried out.

The same capacity IACU can be used to 2 test beds in which heavy commercial vehicle

engines (each consumes around 700 m3/hour of air) are tested. The sharing of a common IACU

between 2 or 3 test beds is based on the consumption of air by each engine.

4.3 Fuel System

4.3.1 Fuel tank

Design requirements for fuel oil storage tanks are laid down in BS 7993 which lists a variety of tanks of different shapes and sizes.

Horizontal cylindrical mild steel welded tanks more than 1m in diameter may alternatively be fabricated according to BS EN 12285-1:2003 (Corresponding old standard is BS 2594).

All tanks should have their internal surfaces treated prior to installation to avoid contamination with rust or sand blast material.

4.3.2 Fuel lines

If the fuel line is full then standard (non galvanized) drawn steel tubes can be used for fuel lines.

But if fuel lines are likely to spend appreciable periods partially drained then the use of stainless steel should be considered.

The use of threaded fittings is not to be recommended. Although with care and the use of modern sealants they can be satisfactory, provided there is no significant pipe movement, particularly thermally induced movement.

The use of any kind of fibrous ‘pipe jointing’ should be absolutely forbidden as fibre contamination is difficult to clear.

Preferably, all fuel lines, and certainly all underground lines, should be constructed with welded joints and flanges, or with the use of compression fittings.

Buried fuel lines should be wrapped with water-repellent bandage (Denzo tape) and laid in fine gravel in a well compacted trench.


Good practice is to run buried fuel lines in a sealed trench of concrete sections with a load-bearing lid.

In pumped system it must be remembered that for much of the operating life the fuel demand should be below the rated flow and the system must be able to operate under bypass conditions without cavitation or undue heating.

The run of final fuel line to engine from fuel conditioning unit should not interfere with operator access. It is laid under the sub floor.

Maximum recommended fuel line velocity is 0.2 m/s.

4.3.3 Fuels The fuels used in engines are:

Gasoline

Diesel

CNG

4.3.3.1 Gasoline

The gasoline is stored at underground storage tank. From where the fuel is directly pumped

to test bed and the pressure maintained in fuel line is 2 bar. (Like diesel, petrol cannot be stored

in overhead storage tanks, as petrol will catch fire easily).

The number of tanks depends on the different compositions of gasoline used. One tank

contains pure petrol, another with ethanol blended and another contains petrol with ethanol in

different composition. The dipstick hole is to check the level of petrol inside the tank.


Fuel pump system specifications are:

Pump: Piston pump: Pneumatic operated

Air input Pressure max: 6 bar

Transfer ratio: 2:1

Accumulator: Spring loaded


4.3.3.2 Diesel

From the underground storage tank, diesel is pumped to overhead tank from where it is

distributed to all test beds. The diesel is flowing into test bed due to head.

The pressure of the fuel is measured before it enters into overhead storage tank.

Temperature of the storage tank is also measured by an RTD and monitored continuously. An

ultrasonic level sensor is fixed at the top of tank to monitor the level of fuel in tank. At the mid of

the height of tank, the overflow line is connected which will return the fuel to underground tank.

The diesel is not directly pumped to test bed as like petrol. If the fuel is pumped directly to

test bed, then in order to maintain the pressure in fuel line, the pump has to operate continuously.

Petrol is not supposed to store in overhead tanks. So it is directly pumped to test bed and the

piston pump is continuously operating.

Diesel we can store in tanks. So it is pumped to overhead tanks and due to head it is

flowing to test bed. In this case, pump is operated intermittently, only to top up the tank when the

fuel level is low.


4.3.3.3 CNG (Compressed natural gas)

The CNG stored in cylinders is brought to CNG station in mobile cascade vehicle. Then the

CNG is stored in tanks. The pressure of CNG in tank is 250 bar. Then the pressure of CNG is

reduced to 50 bar in pressure reducing unit. From there it is brought to test bed through steel

pipes. Inside the test cell, a pressure regulator is fitted to this pipe. The inlet pressure of the

pressure regulator is 400 bar max and outlet pressure is 0-280 bar (Adjust).

To measure the mass flow rate of CNG, Corioli’s mass flow meter is used.

Pressure reducing station:

The pressure reducing station consists of the pressure reducing valve, safety relief valve

and pressure regulator. There are two pressure reducing trains, one is operating at a time and

other is standby. The inlet pressure at the pressure reducing station is 250 bar and at outlet is 50

bar.

4.3.4 Fuel lines inside the test cell


4.3.4.1 Gasoline line inside test cell

From the gasoline line, the fuel is first filtered by a series of filters. After that fuel meter is

there to measure the amount of fuel consumed by the engine. The unit for fuel meter

measurement is kg/hour.

From fuel meter the fuel flows to fuel conditioning unit. The fuel conditioning unit consists

of heater, heat exchanger and compressor unit. This unit brings the fuel temperature to the

required temperature. The fuel then passed to junction box. This consists of a non-return valve

between inlet and return line. When the engine is not running, the fuel will again return to fuel

conditioning unit through this non-return valve.

When the fuel is flowing from fuel conditioning unit to junction box, there may be change

in temperature. An RTD is placed at this junction box to measure the final fuel temperature. This is

the actual fuel temperature before fuel is entering into the engine.

After this junction box, a fuel pump is used to pressurize the fuel. A filter is placed in the

fuel line after the fuel pump. The fuel is filtered in this before entering into the engine.


4.3.4.2 Fuel line for Diesel

The fuel from diesel line is filtered by a series of filters then the fuel is measured in fuel

meter. The unit of fuel measurement is kg/hour.

The fuel is then conditioned by the fuel conditioning unit. The conditioned fuel is then

flowing to junction box. The temperature of the fuel is measured in junction box. A filter is placed

in fuel line after the junction box. Then the fuel is pumped by the fuel pump which is driven by the

belt connected to engine crank shaft.

A part of inlet fuel is directly goes to fuel rail. The excess fuel at the fuel injector is return

back to inlet line. The excess fuel at fuel pump will be returned to fuel conditioning unit.


4.4 Ventilation air

The air from the ambient is drawn into the test cell by the axial blower fan. There are two

ventilation fans placed in wall of either side of rear door.

The inlet ventilation is designed in such a way that, the air stream is directed towards the

engine.

4.5 Electricity

The electrical substations are located in the plant at remote places. From the substation,

power is coming to Distribution boards which are placed in the test cell building.

A distribution board (or panel board) is a component of an electricity supply system which

divides an electrical power feed into subsidiary circuits, while providing a protective fuse or circuit

breaker for each circuit, in a common enclosure.

From the distribution board, the power is supplied to control panels which are placed at the

rear side of each test cell.

This unit consists of

Incomer section

Metering section

Outgoing section


http://en.wikipedia.org/wiki/Enclosure_(electrical)

http://en.wikipedia.org/wiki/Circuit_breaker

http://en.wikipedia.org/wiki/Circuit_breaker

http://en.wikipedia.org/wiki/Fuse_(electrical)

http://en.wikipedia.org/wiki/Circuit_(electricity)

http://en.wikipedia.org/wiki/Electricity

Incomer section:

The power supply from the distribution board is terminated at incomer section of power

supply panel. It consists of Switch to ON/OFF the Main supply.

Metering section:

Metering section consists of line selector switch, Voltmeter, Ammeter and Indicator LED’s.


Outgoing section:

Outgoing section consists of

Utility sockets Switch to on/off the water pump Socket for single phase(1Φ) and three phase(3 Φ) Miniature Circuit Breakers(32A and 20A) Motor Protection Circuit Breaker(to on/off the inlet and exhaust ventilation fans) Switch to on/off lights inside the test cell.

5 Outflows from test cell

5.1 Exhaust

Inside the test cell, the exhaust gas is tapped from exhaust pipe line and emission

measurements are carried out. In exhaust line, temperature, pressure and lambda sensors are

mounted to measure exhaust gas parameters. In addition to these, sensors for temperature and

pressure measurement for ECU are also mounted at the exhaust side.

If catalytic converter is used, then temperature and pressure is measured at upstream and

downstream of catalytic converter.

Exhaust samples for Opacimeter and Smoke meter are connected at exhaust line. There is

a standard in pipe length, at specified distances the samples are taken. It is shown in figure.

1. Engine

2. Catalytic converterEngine Test Cell of 44

3. Analysis of exhaust gases plant pre-cat.

4. Analysis of exhaust gases plant post-cat.

5. Partial flow dilution tunnel for the gravimetric particle measurement

6. Opacity measuring instrument

7. Smoke Meter

The back pressure valve is fitted at the exhaust line before the place where samples are

taken. This back pressure valve has great impact on engine power. If the back pressure is more,

then the power output of the engine is reduced. The back pressure valve is nothing but a pressure

regulator which regulates the pressure in exhaust line.

In test cells, there are two exhaust tail pipes used. One is for petrol engines and another for

diesel engines. Using a single tailpipe for both type engines will affect the dampers.

The tail pipe carries the exhaust to the outside of test cell. The exhaust duct (or tunnel) is

installed over the terrace. The tail pipes from individual cells are connected to the exhaust tunnel.

RTD’s are installed at the end of tail pipe. The temperature of the exhaust is measured before

entering into duct. At the end of exhaust tunnel there is a centrifugal blower fan which delivers the

exhaust gas to chimney.


The end of exhaust duct is connected to the eye of centrifugal blower fan. The blower

delivers it to chimney. Between the exhaust duct and blower section a leather material is

connected to prevent the vibration passing it to the blower.

If the test cells are arranged in line, the exhaust tunnel arrangement is like as shown in

figure.


5.2 Exhaust Ventilation

Exhaust ventilation is in the opposite side to the inlet ventilation system. The heat

generated by the engine, inside test cell is carried away by the ventilation air.

5.2.1 Fans

Fans are much important in exhaust ventilation systems. They must be the appropriate size

and type to make the ventilation system work effectively. They must provide enough air pressure

difference ("suction") to capture at the source, draw them through the hood, carry them through

the ducting and exhaust them outdoors.

There are two main types of exhaust fans - axial fans and centrifugal fans. Axial fans draw

air straight through the fan. Centrifugal fans draw air into the center of the fan and exhaust it at a

90-degree angle.

Axial or propeller fans are most commonly used for dilution ventilation or for cooling. These

fans are often mounted in a wall or ceiling. They can move large amounts of air if there is little

resistance.

Centrifugal fans can operate at against a high resistance and are typically used in exhaust

ventilation systems. There are several types of centrifugal fans. The rugged radial blade

centrifugal fans are the best type for exhausting heavy amounts of dust because they are less

likely to become clogged or abraded by the dust.

[The detail design and information’s about Exhaust ventilation system is available in “A

Manual of Recommended Ventilation design” published by the American Conference of

Governmental Industrial Hygienists (ACGIH).]

Specifications of an axial fan:


Type: Axial/Radial

RPM: 1440

Flow rate: 15000 m3/hr

Power: 1.5 kW

The figure shows the ventilation air duct.

6 Compressor station

Compressed air source is required for various equipments inside. The air is compressed at

compressor station. This consists of two compressor, controller, air separator, buffer tank and air

conditioning unit.


Compressor

The compressor draws the air from ambient and compresses it to the pressure as set in

controller. The cooling water is supplied to compressor for cooling purpose. There is an outlet for

draining the condensate water. The compressor is controlled by the controller unit.

Controller

The user enters desired pressure in controller and controller will maintain the pressure of

compressed air. A pressure sensor is placed at buffer tank which will give feedback to controller.

Air separator

The air separator unit separates the air from condensed water. When the air compressed,

the temperature will increase. When the compressed air is flowing through the pipe lines the

temperature of air decreases and moisture in the air will condensate. The condensed water is

drained out.Engine Test Cell of 44

Buffer tank

The pressure of the air at compressor output is fluctuating. So it is stored in buffer tank and

then air at constant pressure is supplied to test bed equipments.

A pressure sensor and pressure gauge is fitted in the buffer tank. The pressure sensor is for

controller feedback and pressure gauge is to monitor the pressure.

Air conditioning unit

Since the air is taken from ambient for compression, it contains dust particles and

moisture. The air conditioning unit filters the compress air and gives the dust and moisture free

air.

The air from conditioning unit is flowing to all test beds and used as a source for pneumatic

components.

7 Cooling water circuit for plant

The hot water from the dynamometer and coolant conditioning unit is collected at drain

tank in each test bed. From these drain tanks the water is flowing to common underground tank

through underground canals.

The underground tank is partitioned into two halves. There is an opening in between these

to maintain the same level of water.

Water pumping station:


Form the underground tank, the hot water is pumped to cooling towers which are installed

over terrace.

In underground tank the water at ground level is comparatively less temperature than the

water at surface level. The hot water is pumped by three pumps. One or two of which is working at

a time, and others are standby. Of the three, two are centrifugal pumps and one is axial pump.

The hot water is cooled at cooling towers and delivered to overhead storage tank.

The pump with heat exchanger is used to pump the cold water. This cold water is mixed up

with cold water from cooling tower in overhead tank.

From the overhead tank, the water is delivered to all test beds due to head. The pressure

of 1 bar is maintained in water lines.


engine test cell

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