engine testing and modelling

[

]

2012University of Sussex

Sunny Pawar

86612

Testing and Modeling for Automotive Power Systems 2012

Contents

Introduction......................................................................................................................................2

Parameters calculated..................................................................................................................3

Measurements for Diesel Test cell..........................................................................................4

Sources of Heat in the test cell...............................................................................................16

Ventilation airflow evaluation................................................................................................17

Ventilation Layout.......................................................................................................................18

Products........................................................................................................................................... 19

Test Cell Design.............................................................................................................................30

Price quotation..............................................................................................................................32

References.......................................................................................................................................33

1


2


Introduction

A test cell is a collective arrangement of instrumentation, machinery and services working

at the same time. As the need for maximum outcome of the fossil fuel usage has become

increasingly crucial, extensive research is carried out in the development of internal

combustion engines. Better technologies are installed in the engines after being extensively

tested in test cells certifying the safety and reliability before introduced into production.

Data is studied and compared to the previous or competing technologies.

Manufacturers are forced to develop their engines in order to produce fewer emissions as

the Euro legislations become more stringent progressively. Along with gasoline and diesel,

companies have started opting for alternative fuels and hybrids in order to match the

standards. This has led the engineers to research deeper in the engine technologies.

This has also led the Test cell product manufacturers to create a solution for the new tests

needed for various fuels and new parameters.

The overall area of the test cell is divided between 3 parts-

Test Bed Area

Control room area

Storage area

3


Parameters calculated

In order to upgrade on the benchmark tables various parameters are calculated during the

tests, Some of them are mentioned below.

Brake Mean Effective Pressure.

Exhaust Smoke and Other Emissions.

Specific Fuel Consumption.

Specific Power Output.

Power and Mechanical Efficiency.

Mean Effective Pressure and Torque.

Specific Output.

Volumetric Efficiency.

Fuel-air Ratio.

Specific Fuel Consumption.

4


Measurements for Diesel Test cell

Test cell 1 (Diesel Test cell)

The engine considered for the test cell is a 1.3 liter diesel engine used in 2012 Chevrolet

Aveo sedan. The Specifications of the engine are as follows: [10]

Capacity (CC) 1248

Net Power (KW) 70 @ 4000 rpm

Maximum torque (Nm) 210 @ 1750 rpm

Thermal efficiency ( th)η 40%

Air Fuel Ratio 20:1

Table 1 : Chevrolet Aveo Specifications [10]

As the maximum torque generated by the engine is 210 Nm , is it essential for the chosen

dynamometer to produce 30% more toque. This factor is used as a precaution.

Therefore ,

Dynamometer toque = 210Nm * 1.3 =273 Nm

Fuel Input:

5


Thermal Efficiency (ηth)¿Power OutputFuel Input (h1)

Fuel Input (H1) = 175 KW

Fuel Mass Flow rate:

This can be calculated using the following formula.

Power (P) = Mass of Fuel (mf) * Thermal Efficiency (ηth) * Calorific Value (cf)

mf = 0.0043 Kg/sec

Air Mass Flow Rate:

As the considered AFR is 20:1

Ma can be calculated by

Ma = mf * 20

Ma = 0.086 Kg/sec

Specific Fuel Consumption:

s.f.c = 0.21 Kg/Kw hr

Steady Flow Energy Equation:

H1 = P + (H2 – H3) + Q1 + Q2

Where;

6


H1 = Energy from Fuel

P = Power Output

H2 = Heat in exhaust gas

H3 = Heat in Inlet Air

Q1 = Heat Passed to Cooling water

Q2 = Heat losses by Convection & Radiation / Unaccounted Losses

Fuel Energy (H1) = mf * Cf

H1 = 175 Kw

Heat Lost in Exhaust (H 2)

Assuming the exhaust temperature 1066 kelvins

H2 = (mf + ma) * Cp * Te

H2 = 86 Kw

Heat in Inlet Air (H3)

Assuming the surrounding temperature 292 kelvin

H3 = ma * Cp * Ta

H3 = 25.11 Kw

Heat to Cooling Water (Q1)

20% of the total heat is lost to the cooling water.

7


Q1 = 35 kW

Energy Balance Sheet

In Out

kW % kW %

Fuel 175 100 Power 70 40

Engine Cooling water 35 20

Exhaust Gas 60.89 34.7

Convection & Radiation 10 5.71

Total 100 Total 100

Table 2 : energy balace Chevrolet aveo 1.3L diesel engine

Specific Fuel Consumption –

s.f.c = 175 (kJ/s)/40600(kJ/kg) * 3600(s/h)/70(kW)= 0.22kg/kW

Induction air flow = 70*0.22*20= 308kg/h

Air Density= 1.2kg/m3

Air Flow = 256m3/h

Fuel Flow = 70 * 0.22/ 0.9 = 17.1L/h

Exhaust Flow = 308+17.1 = 325.1kg/h

8


The second engine considered for the test cell is a 6.3 liter Duramax Turbo diesel engine

used in General Motors Silverado 2500 HD (2012). [3]

Capacity (CC) 6.3 L




Air Fuel Ratio 20:1

Table 3 : Specifications of 6.3L Duramax engine. [3]

Calculation of Torque: As per the precautionary standards it is ideal for the

dynamometer to achieve 30 % more torque than the maximum torque produced by the

engine. Therefore,

Tmax Dyno = 1.3 * 765 = 994.5 Nm

Calculation of Fuel Input:


H1 = 739 KW

Calculation of Fuel Mass Flow Rate:


mf = P/(η th∗Cv)

9


mf = 0.0182 kg/s

Air Flow Rate: As the assumed Air to Fuel Ratio is 20:1 ,

Ma = 0.0182 * 20 = 0.364 kg/s

Heat Balance Analysis:

H1 = P + (H2 – H3) + Q1 + Q2

H2 = (mf + ma) * Cp * Te

H2 = 320.2 KW

H3 = ma * Cp * Ta

H3 = 106.2 KW

Q1 = Heat Lost by Cooling Water is considered 20 % of Total Heat

Q1 = 20% * H1

Q1 = 147.8 KW

In Out

kW % kW %

Fuel 739.4 100 Power 295 39

Heat to cooling water 147.8 20

Heat to exhaust 214 28

10


Convection & Radiation /

Unaccounted Losses

81 11

Total 100 Total 100

Table 4 : Heat Balance Table



Induction air flow = 295*0.22*20= 1310kg/h


Air Flow = 1092m3/h

Fuel Flow = 295 * 0.22/ 0.9 = 72.1L/h

Exhaust Flow = 1310+72.1 = 1382.1kg/h

Test Cell 2 (Gasoline)

The first engine considered for the test cell is a 1.6 liter Variable Timing Valve Train

(VTVT) gasoline engine used in Hyundai Verna Fluidic (2012). [2]

Capacity (CC) 1.6 L




Air Fuel Ratio 14.7:1

Table 5: Specifications of 6.3L Duramax engine. [2]

11


Calculation of Torque for Dynamometer:

As per the precautionary standards it is ideal for the dynamometer to achieve 30 % more

torque than the maximum torque produced by the engine. Therefore,

Tmax Dyno = 1.3 * 260 = 338 Nm



H1 = 259.8 KW



mf = P/(η th∗Cv)

mf = 0.0072 kg/s

Air Flow Rate: It is assumed that the air to fuel ratio is stoichiometric in

order to calculate the optimum results.

Ma = 0.0072 * 14.7 = 0.105 kg/s


H1 = P + (H2 – H3) + Q1 + Q2

H2 = (mf + ma) * Cp * Te

H2 = 112.2 KW

H3 = ma * Cp * Ta

12


H3 = 30.66 KW


Q1 = 20% * H1

Q1 = 60.32 KW

In Out

kW % kW %

Fuel 259.8 100 Power 90.5 34.83

Heat to cooling water 60.32 23.2

Heat to exhaust 81.54 31.3


Unaccounted Losses

27.8 10.7

Total 100 Total 100

Table 6 :Energy balance for 6.3L duramax engine


s.f.c = 259.8 (kJ/s)/41870(kJ/kg) * 3600(s/h)/90.5(kW)= 0.246kg/kW

Induction air flow = 90.5*0.246*14.7= 328kg/h


Air Flow = 394m3/h

Fuel Flow = 90.5 * 0.246/ 0.9 = 22.0L/h

13



The second engine considered for the test cell is a 3 liter V6 Supercharged petrol engine

used in Jaguar XJ (2012). [1]

Capacity (CC) 3.0 L




Air Fuel Ratio 14.7:1

Table 7: Specifications of 3.0L V6 Jaguar XJ engine [1]

Calculation of Torque:

As per the precautionary standards it is ideal for the dynamometer to achieve 30 % more

torque than the maximum torque produced by the engine. Therefore,

Tmax Dyno = 1.3 * 450 = 585 Nm



H1 = 729 KW



14


mf = P/(η th∗Cv)

mf = 0.019 kg/s

Air Flow Rate:

It is assumed that the air to fuel ratio is stoichiometric in order to calculate the optimum results.

Ma = 0.019 * 14.7 = 0.279 kg/s


H1 = P + (H2 – H3) + Q1 + Q2

H2 = (mf + ma) * Cp * Te

H2 = 298.3 KW

H3 = ma * Cp * Ta

H3 = 81.4 KW


Q1 = 20% * H1

Q1 = 165 KW

15


In Out

kW % kW %

Fuel 729 100 Power 248 34

Heat to cooling water 165 22.6

Heat to exhaust 216.9 29.7


Unaccounted Losses

99.5 13.6

Total 100 Total 100

Table 8 Energy Balance for Jaguar Xj



Induction air flow = 248*0.25*14.7= 921kg/h


Air Flow = 767m3/h

Fuel Flow = 248 * 0.25/ 0.9 = 68.8L/h


16


Ventilation

The primary need of an efficient ventilation and air conditioning system is to maintain the

acceptable environment for testing. The constant energy flows within the test cell increase

various difficulties for testing atmosphere. [9]

Need for Ventilation system –

The working environment for a human is essential to comfortable. Ample amount of fresh

air needs to be provided constantly for important and compulsory health regulations.

Engines are tested under atmospheric pressure and temperatures to provide standard

benchmarks. The temperature is supposed to be constant throughout various experiments

unless needed.[9]

Sources of Heat in the test cell

Engine- Water cooled engines and their exhaust system excludes a maximum of 15% of the

heat energy in the fuel to the test cell area. This is divided similarly between the convection

and radiation. As seen in the energy balance calculations, 30% of the diesel engine power

output contributes to this dissipation while the gasoline engines contribute 40%.

Dynamometer- If the dynamometer water cooled such as hydraulic and eddy current,

functions on medium temperature and are unlikely to lose heat above 5% of the total

power input to the brake.[9]

17


Ventilation airflow evaluation

An example using the mentioned 1.6 liter Hyundai Verna engine can be seen below-

Engine 10% of the power output 25 kW

Exhaust manifold and tailpipe 10 kW

Dynamometer, 5% of power output 15 kW

Lights and services 20 kW

Forced draught fan 5 kW

Reduced loss due to cell wall conduction 5 kW

Total 70 kW

Table 9 : Ventilation Airflow Evaluation

Energy Balance in the test Cell can be seen below

In kW Out kW

Fuel 260 Exhaust gas 70

Ventilating fan power 5 Engine cooling water 60

Ventilation air 70

Heat loss, walls and ceiling 15

Electricity for cell services 30 Dynamometer cooling water 80

Total 295 295

Table 10 : Test cell energy balance

18


The values for the input and output parameters match and the energy balance for the test

cell is achieved. Although it is precautionary to obtain a ventilation system that has the

total capacity at least 20% more than the given values.

Therefore, 1.20 * 295 = 354 kW.

Ventilation Layout

In and out ducts can be arranged into different positions. The chose layout is an inlet duct

placed above the test bed allowing direct and efficient cooling and an outlet duct placed on

the lower area making the test cell temperature to be flexible for various conditions

needed.[9]

Air ventilation Control system is placed to allow the speed of fan to increase and decrease

as per the needs. When the operator is inside the test cell along with the engine switched

off, the fan will run at low speeds maintaining the ambience. When the engine is switched

on , the fan speed will increase to dissipate the heat as soon as possible.

19


Products

Dynamometer-The most crucial factor in designing a test cell is the type of dynamometer to

be used. Following is the comparison table for widely used dynamometers in the market

today for automotive engines ranging from 50 kW to 500 kW. [9]

Type of Dynamometer Advantages Disadvantages

Hydraulic Suitable for high speeds Poor low speed performance

Bolt on hydraulic Low cost and minimal

installation required

Inefficient accuracy and

measuring compared to

fixed base machines

D.C electrical Highly efficient in rapid load

changes. Computer control

comply accurately. Cooling

water not required.

Very expensive. Rotational

inertia is high.

A.C electrical Similar to D.C along with the

advantage of the lower

inertia.

Highly expensive. Problems

of clogging are possible.

Eddy current Rapid load changes are

efficiently done. Computer

control is simple. Not

complicated and robust. Low

inertia. Cost is low.

No motoring facility.

Overload could not

sustained.

20


As a result after comparing the factors such as cost , less complicated , automated controls,

and rapid load changes for dynamic and steady state tests , Eddy Current dynamometers

are chosen for Test Cell 1 and Test Cell 2.

Taylor Dynamometer DE 400 [4]

Specification:

Water cooled eddy current dynamometer.

Maximum power capacity: 536 hp (400KW).

Maximum torque capacity: 1,476 ft.lbs (2,000 Nm).

Maximum speed capacity: 8,000 RPM.

Water use: 74 GPM (208L/S).

Kerb weight: 1,620 Kg.

It also can be used for both petrol and diesel engines.

Cost – 38000 GBP [4]

21


Driveshaft

Maximum recommended continuous torque 1898Nm

with no angular misalignment and 2deg ± 1deg slope.

Minimum elastic limit= 4400 lbs (5966 Kg),

represents the maximum torque load the universal

joint will transmit instantaneously without brinelling

bearings ro yield in any part.

Maximum allowable speed 6500 RPM.

Dynamically balanced.

Kerb weight = 36lbs (16kg).

It can also be used for both petrol and diesel engines.

This driveshaft has been selected on the following criteria’s:

After establishing the torque characteristics and speed range Taylor 1310 driveshaft

is capable to run on load throughout the speed ranges.

The driveshaft stress limit is adequate to withstand the maximum engine load

exerted on it.

The compatibility of the driveshaft is high as the dynamometer is also produced by

the same manufacturer. Therefore the alignment of the driveshaft to the dynamometer is

highly accurate.

22


Driveshaft Guard

A driveshaft guard needs to be installed to completely cover driveshaft and the couplings in

order to provide safety inside the test cell.

Taylor Air flow meter

The Taylor air flow meter is designed to work with the dynpro data actuations and

control system. This meter measures the amount of intake air consumed by the engine.

Using the pitot principle to measure the total and static pressure components of air

flow, the pressure sensing ports sense the impact pressure of the approaching air

stream allowing the transmitter to determine the volumetric flow of air. With the ports

positioned at designed angles the meter assures accurate measurement of the sensed

airflow rate and eliminates the need for an air flow straightener upstream.

23


Electronic throttle control

Electronic throttle control [7]

The interface directly connects engine harness without interfering with the engine

controller. The electronic engine throttle interface module is designed for use on both

petrol and diesel engines. The interface utilizes a reference voltage and ground from the

engine for operation. The control signal from the ‘’Dynpro’’system adjusts the throttle

controller output proportionally. Current and frequency throttle options are also available.

[7]

Test Command center :

Test cell command center is designed to provide a single point of connection and control

for all of your basic test cell support functions. This is a stand-alone system that

consolidates your test cell control requirements, such as water systems and HVAC systems.

For complete test cell automation, the command center can be connected to the control

system.

24


Test command center

It can control eight digital devices and two simple analog devices.

Water recirculation system:It is an important parameter to maintain the heat in the eddy

current dynamometer by stabilizing the coolant’s temperature to the desired level. Heat is

let in the surrounding air in the form of vapor. This prevents the overheating of the

dynamometer and provides a long life of usage.

Water recirculation system

25


It includes, water recirculating system command and control center, pumps and motors,

evaporative cooling tower, chiller, heat exchanger or radiator.

Exhaust gas analyzer

Cambustion HFR 500 [8]

Accurate measurement of exhaust emissions brings valuable insights into engine

operation, and assists calibration engineers in reducing the engine out emissions. This can

assist in emissions compliance while reducing after-treatment costs. [8]

The fast FID (sometimes known as an fFID) is carefully designed and calibrated to

be linear to well above misfire HC levels (e.g. 42,000 ppm C3for a complete stoichiometric

misfire in a gasoline engine) so that accurate concentrations during these important events

can be recorded. [8]

Fuel Measurement Unit:

26

http://www.cambustion.com/products/hfr500


Fuel measurement unit

The fuel measurement unit is a gravimetric type system and requires the Dynpro

data acquisition and control system for operation. These system accurately measures the

weight of the fuel in a beaker and calculate the rate od=f fuel consumption by continuously

analyzing the weight of the beaker is self-filling and will automatically maintain the

minimum and maximum amounts of fuel in the beaker.

All units include a chiller to cool the return fuel and maintain a beaker temperature

of 100 deg F.

Engine Starter

27


As the Eddy current dynamometers are not self-started, it requires an engine starter unit to

be attached.

Charge air cooler:

F

Fig 15: Charge air cooler[1].

28


Charge air cooler is also known as intercooler is an air to air heat exchange device

used on a turbo diesel engine to improve the volumetric efficiency of the engine. It removes

the heat from the air in the isobaric process. Lowering the intake charge temperature also

protects the pre-detonation (knock) of the fuel prior to the respective crank angle. It is

used to vary the inlet air temperature in case of the diesel engine where the air is

compressed by the compressor run by a turbine, which is run by the exhaust gas pressure.

This system increases the inlet temperature which can create detonation in case of diesel

engines. Hot air intake also reduces the performance of the engine, so we need to cool the

inlet air before it enters the engine.

Instrumentation control:

Instrumentation control

The engine dynamometer instrumentation system is a display only system intended

for basic engine dynamometer testing requirements. This system provides for the

measurement of torque in either tension or compression and speed from a standard

29


magnetic pick-up. The system is designed to set on a table or near the PC.This system is

exclusively designed for the diesel engine and only controls the fuel input, so there will not

be any spark control.

Engine control Module Test Cell 2 (Gasoline)

The engine control module of the petrol engine is more advanced and it has more

control parameters than the diesel engine. The engine control module main controls are

spark timing, fuel injection, Knock control, exhaust temperature control, petrol engines

always work in a closed loop control, only then it can maintain the value close to 1.λ

It has a trigger input from a magnetic pulse sensor and from this input it finds the

correct time for the fuel injection in the intake port and the spark timing for ignition.

30


Test Cell Design

Control Room and controls

The control room is the area where the operator controls and keep an eye on the

engine. This area is needed to be operator friendly. Consoles indicating the engine and

dynamometer parameters can be seen on the console.

All the necessary changes in the operating conditions of the engine is made on the

console outside the test cell. A large window is placed above the console system in order to

have a total view of the test cell. The window has 2 layers of thick glass which are placed at

least 10 cm apart for safety reasons.

The door is alarmed which can be only turned on when the engine is turned off, or

the engine automatically switched off if the door is opened while the test is running.

An emergency stop button is also placed in the control room. [9]

31


Test cell

Both the test cells are arranged in similar pattern side by side.

32


Engines enter the cell by the large door and a separate door is in place for the

operator for regular checks.

Wall mounted instrumentation, smoke meters and fuel consumption meters are

placed on the side wall remote from access to the double door.

Signal conditioning units such as transducers are placed in a box in an adjustable

boom.

The rigging pipes are flexible leading the exhaust gases to the desired areas.[9]

Price quotation

33


Taylor DE400 Dynamometer 38,000 £

Cambustion HFR500 Exhaust gas analyzer 23,000£

Charge air cooler 8,000£

Instrumentation control 16,000£

TC3 Test command center 7,000£

Fuel measurement unit 8,000£

Water cooling system 55,000 £

Taylor Electronic throttle actuator 10,720£

Taylor Air flow meter 20,000£

Taylor Drive shaft 1310 1,000£

Engine control module for diesel 13000£

Engine control module for petrol 14,000£

Dynpro Data acquisition system 23,000£

Taylor Engine Starter System 3,000 £

Shaft Guard 2,150 £

Pressure sensors 540 £

Engine Stand 17,480 £

Total Amount Test Cell 1 (Gasoline) 246890 £

Total Amount Test Cell 2 (Diesel) 245890 £

34


References

1] Autocar V6 engine.

http://www.autocar.co.uk/car-news/new-cars/new-30-v6-engine-revised-jaguar-xj

2] Hyundai fluidic specifications

http://www.carwale.com/research/hyundai-cars/verna/fluidic16crdi-specifications-

2151.html

3]Chevrolet Silverado 3500hd Specifications

http://www.chevrolet.com/2012-silverado-3500hd-pickup-truck/features-specs/

powertrain.html

4]Taylor DE400 Eddy Current Dynamometer specifications

http://www.taylordyno.com/catalog/engine-dyno/eddy-current-dynamometers/de400-eddy-

current-dyno

35


5] Talyor Driveshaft 1310 specifications

http://www.taylordyno.com/catalog/dyno-accessories/engine-dyno-accessories/1310-

driveshaft

6] Taylor air flow meter specifications

http://www.taylordyno.com/catalog/dyno-accessories/data-acquisition-and-control-

accessories/mass-airflow-meter

7] Taylor electronic throttle control

http://www.taylordyno.com/catalog/dyno-accessories/engine-dyno-accessories/electronic-

throttle-control

8] Cambustion HFR500 Gas analyser

http://www.cambustion.com/products/hfr500

9] Michael Plint, Anthony Martyr, Second Edition, Engine Testing Theory and Practice

10]Chevrolet Aveo Specifications

http://www.aveoforum.com/forum/f113/2012-chevrolet-sonic-specifications-11280/

36

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