improvement of 510 cc single cylinder water cooled...
TRANSCRIPT
IMPROVEMENT OF 510 CC SINGLE CYLINDER WATER
COOLED DIESEL ENGINE IN THE AREAS OF
STARTABILITY AND LOW END TORQUE
A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
BACHELOR OF TECHNOLOGY
(MECHANICAL ENGINEERING Spec. in AUTOMOTIVE
ENGINEERING)
BY
SAGAR BHATT
10BMA0061
Project guide from The ARAI
Saravanan Kumarasamy
Engineer
Project Guide from VIT University
K. Nanthagopal
Assistant Professor
Project work done at
Project guide from Greaves Cotton Ltd.
Mr Sunil Pandit
Manager
R&D
ii
CERTIFICATE
This is to certify that the dissertation work titled “Improvement of 510 cc single
cylinder water cooled diesel engine in the areas of: Startability and Low end
torque” is submitted by Sagar Bhatt bearing registration Number 10BMA0061 to the
School of Mechanical and Building Sciences of the VIT University, Vellore and ARAI
Academy, The Automotive Research Association of India, Pune, in partial fulfilment of
the requirements for the degree of BACHELOR OF TECHNOLOGY in MECHANICAL
[spec. in AUTOMOTIVE ENGINEERING]). This is a bonafide work carried out at
Greaves Cotton Ltd., Aurangabad by him under our supervision. The contents of
this dissertation, in full or in parts have not been submitted to any other institute or
university for the award of any degree.
Mr Sunil Pandit Manager
R&D
Saravanan Kumarasamy Engineer ARAI Academy The Automotive Research Association of India
K. Nanthagopal Assistant Professor
School of Mechanical and Building Science
VIT University
Dr K. C. Vora
Dy. Director & Head,
ARAI Academy,
The Automotive Research Association of
India
Internal Examiner External Examiner
1.____________________
2.____________________
Date of Submission: /06/2014
iii
ACKNOWLEDGEMENT
I would start of by thanking my project guide Mr Sunil Pandit, Manager, R&D, Greaves
Cotton Ltd., Aurangabad for guiding me throughout the project duration. His
experience and knowledge were a vital help for me in understanding and completing
the project.
I would like to express my gratitude to Mr S. Bhattacharya, VP, R&D, Greaves Cotton
Ltd., Aurangabad for allowing me to undertake my project in his department at
Greaves and for the valuable inputs he provided from time to time. Also, I would like
to thank everyone involved in the 510cc water cooled diesel engine project for their
guidance, encouragement and inputs throughout the duration of the project. In fact, I
would like to express my gratefulness toward everyone in Test Centre and Design
Centre of Greaves R&D who helped me when I needed theoretical or practical
guidance.
I would like to thank my guide at ARAI, Mr Saravanan Kumarasamy for his valuable
help. I would also like to acknowledge my guide at VIT University, Vellore – Mr K.
Nanthagopal for the invaluable knowledge that he imparted. Most of my understanding
of IC engines comes from him, which turned out to be an asset in this project. Also, I
would like to thank Dr K.C. Vora, Dy. Director & Head ARAI Academy for giving me
the opportunity to pursue final year projects at Greaves.
Finally, I would like to thanks all those who were directly or indirectly involved with the
project.
Sagar Bhatt
iv
ABSTRACT
The aim of this project is to improve the startability and lower end torque of a
510 cc water cooled diesel engine. The engine with current configuration does
not start without the use of excess fuel device (EFD), the target was to make
the engine start without the operation of EFD. The lower end torque affects the
acceleration and drivability of the vehicle. The target here was to improve low
end torque to a minimum of 23 Nm from the current 18-22 Nm.
The targets were achieved by carrying out performance tests on engines with
existing configuration, by doing so we identified the main cause of the problem
– lack of fuelling at lower speeds. At the same time, it was found during these
tests that that there was negligible fuelling at starting speed. Tests with a torque
adaption device were undertaken to find out the required fuelling for our torque
demand. A new FIP with fuelling pattern close to our requirement was procured
and final tests were carried out.
Results obtained were extremely satisfactory. The lower end torque in the two
tested engines was found to be a in the range of 25-29 Nm. The startability of
the engine was found to be in the range of 2-4 sec without the operation of EFD.
v
PROJECT EXECUTIVE SUMMERY
The project target was to increase the low end torque of a 510 cc water cooled diesel engine from 18-22 Nm to a minimum of 23 Nm and to improve the startability of the engine to enable it to start without the operation of EFD which it normally requires. The first two tests (FTP and Startability) for this project was carried out on an engine with existing configuration. This test provided us with the necessary baseline performance data. This helped us understand the problem and to narrow down the cause of the problem. The next few tests involved use of a torque adaption device that helped us adjust torque to our need and then find out the fuelling required to meet our targets. The fuelling requirement was then supplied to the FIP supplier (Bosch) to get a new FIP that offered similar fuelling. Once the new FIP was procured, FTP tests and startability tests were carried out on two engines to verify the effect of the FIP with increase fuelling per stroke. The fuelling of the existing FIP, the fuelling (that we got by using Torque Adaption Device) we supplied to Bosch for the procurement of new FIP and the fuelling of the modified FIP are compared in the following figure:
Fuelling comparison of existing FIP, Torque adaption and Modified FIP
The torque comparison of the final result (with two engines – referred to as Engine 1 and Engine 2 here) and the original specification is presented in the following figure:
15
17
19
21
23
25
27
29
31
33
1400 1600 1800 2000 2200 2400 2600 2800 3000
Fuel
ing
(mm
3/s
tro
ke)
Speed (RPM)
Fuelling comparison of Existing FIP, Torque Adaption and New FIP
Existing FIP
TorqueAdaption
Modified FIP
vi
Torque comparison of Engine 1&2 with modified FIP and Engine with existing configuration
The startability comparison of engine with existing configuration and the final result (with two engines – referred to as Engine 1 and Engine 2 here) is represented in the following figure:
Startability comparison of Engine 1&2 with modified FIP and Engine with existing configuration
18
20
22
24
26
28
30
1400 1600 1800 2000 2200 2400 2600 2800 3000
TOR
QU
E (N
M)
SPEED (RPM)
TORQUE COMPARISON
Engine 1 with Modified FIP Engine 2 with Modified FIP Engine with existing Configuration
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6 7 8
SPEE
D (
RP
M)
TIME (SEC)
Engine with Existing Configuration Engine 1 with Modified FIP Engine 2 with Modified FIP
vii
TABLE OF CONTENTS
Certificate………………………………………………………………………..ii
Acknowledgement……………………………………………………………..iii
Abstract………………………………………………………………………….iv
Project Executive Summary………………………………………………….v
Table of Contents………………………………………………………………vii
List of Figures…………………………………………………………………..x
List of Tables……………………………………………………………………xii
Abbreviations…………………………………………………………………...xiii
1. Introduction………………………………………………………………….1
1.1. Company Profile…………………………………………………………1
1.1.1. History and Development………………………………………..2
1.1.2. R&D………………………………………………………………...2
1.1.3. Recent Developments…………………………………………....3
1.1.4. Customers………………………………………………………....3
1.1.5. Light Engines……………………………………………………...3
1.1.6. Applications………………………………………………………..4
1.1.7. Testing Lab………………………………………………………...4
1.2. Problem Definition………………………………………………………..4
1.2.1. Startability………………………………………………………….4
1.2.2. Low End Torque…………………………………………………..5
1.3. PPS…………………………………………………..……………………7
1.4. Project Plan……………………………………………………………….10
2. Literature Review…………………………………………………………….11
2.1. Diesel Engines…………………………………………………………….11
2.2. Fuel Injection in Diesel Engines…………………………………………13
2.2.1. Fuel Pump…………………………………………………………..14
2.3. Excess Fuel Device……………………………………………………….15
2.4. Performance parameters…………………………………………………17
2.4.1. Specific Fuel Consumption………………………………………..18
2.4.2. Torque……………………………………………………………….18
2.4.3. Power………………………………………………………………..18
2.4.4. Mechanical Efficiency……………………………………………...18
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2.4.5. Brake Mean Effective Pressure…………………………………...18
2.4.6. Volumetric Efficiency……………………………………………….19
2.5. Improving low end torque…………………………………………………19
2.6. Improving startability……………………………………………………....19
3. Engine Specifications and Components..………………………………...21
3.1. Engine Specifications……………………………………………………...21
3.2. Engine Components……………………………………………………….22
4. Methodology……………………………………………………………………24
5. Experimental Setup……………………………………………………………25
5.1. Basic Measurements……………………………………………………….25
5.2. Measurement of Brake Power and Speed……………………………….26
5.2.1. Dynamometer………………………………………………………..26
5.2.1.1. Eddy Current Dynamometer………………………………..26
5.2.2. Dynamometer Operation……………………………………………26
5.2.3. Dynamometer Controllers…………………………………………..27
5.2.4. Power Testing: Further explanation and Data……………………28
5.3. Measurement of Fuel Consumption………………………………………29
5.3.1. AVL Fuel Balance……………………………………………………29
5.3.1.1. Description……………………………………………………30
5.3.1.2. Technical Insight……………………………………………..30
5.4. Measurement of exhaust smoke…………………………………………..31
5.4.1. AVL Smoke Meter……………………………………………………31
5.5. Fuel Conditioning System…………………………………………………..32
5.6. Coolant Conditioning System………………………………………………33
6. Experiments……………………………………………………………………...34
6.1. Tests on engine with existing configuration……………………………….34
6.1.1. Performance Tests……………………………………………………34
6.1.2. Startability Tests………………………………………………………34
6.1.3. Inference……………………………………………………………….35
6.2. Tests on engine with torque adaption device……………………………..36
6.2.1. Performance Tests……………………………………………………36
6.2.2. Startability Tests………………………………………………………37
6.2.3. Inference……………………………………………………………….37
6.3. Tests on engine with Modified FIP…………………………………………38
ix
6.3.1. Performance Tests……………………………………………………38
6.3.2. Startability Tests………………………………………………………39
7. Results…………………………………………………………………………….41
8. Conclusion………………………………………………………………………..43
9. References………………………………………………………………………..44
x
LIST OF FIGURES
Figure Title Pg. No.
1. Figure 1.1: Greaves Cotton Ltd., Technology Centre……………………….3
2. Figure 1.2: Startability with and without EFD…………………………………5
3. Figure 1.3: Torque of engine with existing configuration and Target band
of torque required…………………………………………………6
4. Figure 2.1: Four strokes of a Diesel engine…………………………………11
5. Figure 2.2: Valve timing diagram……………………………………………..12
6. Figure 2.3: P-V diagram of Diesel cycle……………………………………..12
7. Figure 2.4: Spray pattern of a Diesel fuel injector………………………….13
8. Figure 2.5: Fuel Supply system………………………………………………14
9. Figure 2.6: Cut Section view of a mechanical FIP………………………….14
10. Figure 2.7: Working of plunger in a FIP ……………………………………..15
11. Figure 2.8: Governor Assembly………………………………………………16
12. Figure 2.9: Control rack position and the corresponding fuelling…………16
13. Figure 2.10: Working of EFD……………………………………………………17
14. Figure 3.1: The 510 cc water cooled Diesel engine concerned with this
project………………………………………………………………21
15. Figure 3.2: Isometric View-1 of the engine…………………………………..23
16. Figure 3.3: Isometric View-2 of the engine…………………………………..23
17. Figure 5.1: Schematic view of a general test cell……………………………26
18. Figure 5.2: Diagram of Eddy Current Dynamometer………………………..28
19. Figure 5.3: Schematic of a Speed Controlled test of engine at WOT……..29
20. Figure 5.4: Schematic of an engine and eddy current dynamometer……..29
21. Figure 5.5: Front View of an AVL Fuel balance……………………………...30
22. Figure 5.6: Working of an AVL Fuel Balance………………………………...31
23. Figure 5.7: Front View of an AVL smoke meter……………………………...32
24. Figure 5.8: Interior View of an AVL smoke meter……………………………32
25. Figure 5.9: Working of an AVL smoke meter………………………………..33
26. Figure 5.10: Interior View of a Fuel Conditioning System…………………...33
27. Figure 5.11: Coolant Conditioning System…………………………………….34
28. Figure 6.1: Startability of Engine with Existing Configuration……………...36
29. Figure 6.2: Torque Comparison of setup with different adaptions ………..38
xi
30. Figure 6.3: Fuelling Comparison of setup with different adaptions………..38
31. Figure 6.4: Startability of Engine 1 with Modified FIP………………………40
32. Figure 6.5: Startability of Engine 2 with Modified FIP………………………41
33. Figure 7.1: Comparison of Torque of engine with existing configuration
with the target and final result………………………...………….41
34. Figure 7.2: Startability comparison of engine with existing configuration
with the final result………………………………………………..43
xii
LIST OF TABLES
Table Title Pg. No.
1. Table 1.1: Business Groups and Products of Greaves Cotton Ltd. …………..1
2. Table 1.2: Engine speed classification of the given engine…………………….5
3. Table 3.1: Engine specifications of the given engine…………………………....21
4. Table 3.2: Components of the given engine…………………………………….24
5. Table 6.1: Observations of the FTP test on engine with existing
configuration..…………………………………………………………35
6. Table 6.2: Starting fuelling of the existing FIP…………………………………..36
7. Table 6.3: Observations of FTP test on engine with 0.6mm adaption……….37
8. Table 6.4: Observations of FTP test on engine with 0.8mm adaption……….37
9. Table 6.5: Observations of FTP test on engine 1 with modified FIP…………39
10. Table 6.6: Observations of FTP test on engine 2 with modified FIP………….40
11. Table 7.1: Comparison of starting fuelling of existing FIP and modified FIP…43
xiii
ABREVIATIONS
EFD: Excess Fuel Device
NTP: Nozzle Tip Protrusion
SIT: Static Injection Timing
RPM: Rotations Per Minute
GCL: Greaves Cotton Limited
HP: Horse Power
CMVR: Central Motor Vehicles Rules
EGR: Exhaust Gas Recirculation
IC Engine: Internal Combustion Engine
CI Engine: Compression Ignition Engine
TDC: Top Dead Centre
BDC: Bottom Dead Centre
SFC: Specific Fuel Consumption
BSFC: Brake Specific Fuel Consumption
ISFC: Indicated Specific Fuel Consumption
BMEP: Brake Mean Effective Pressure
BP: Brake Power
IP: Indicated Power
HSU: Hartridge Smoke Unit
FSN: Filter Smoke Number
FTP: Full Throttle Performance
1
1. INTRODUCTION The Automotive industry has become a very competitive field these days. To stay ahead in these cut-throat markets, companies are investing millions and millions on R&D. A lot of these investments go in performance improvement and customer satisfaction. The concerned engine is a 510 c diesel engine meant for Light Commercial Vehicles (LCVs). The customers of such vehicles are usually concerned with “Kitna uthati hai” (amount of payload a vehicle can carry and still offer a good drivability). That essentially means the vehicle must have good acceleration (or ‘pick-up’) under laden conditions, which technically means higher low end torque. When a customer turns the key, he expects the vehicle to start immediately. Hence, as a part of the improvement, the startability of the engine was also targeted to improve the startability of the engine. The project aims at improving these two parameter.
1.1 COMPANY PROFILE:
Greaves Cotton Limited, established in 1859, is one of India’s leading and well-diversified engineering companies. It manufactures a wide range of industrial products to meet the requirement of core sectors in India and abroad. The Company’s core competencies are in Diesel/Petrol engines, Gensets, Agro Equipment and Construction Equipment. The businesses operations of the Company are divided into various Business Groups strategically structured to ensure maximum focus on each business area and yet retain a unique synergy in the operations.
Table 1.1: Business Groups and Products of Greaves Cotton Ltd.
Business Groups Product Lines
Power Generation Large Diesel Engines, Generating Sets up to 1000KVA
Agro Equipment Group Petrol/ Kerosene Engines: 1 to 4 HP, Gensets, Pump Set and Power Tillers
Light Engine Group Diesel engines: 4.4 to 20 HP
Infrastructure Equipment Concreting Pumps, Transit Mixers, Vibratory Compactors and Crucibles
Besides the Business Groups, Greaves has an independent Division marketing high technological systems for marine, aviation and electronic applications
Greaves has 6 Manufacturing Units located all over India.
Greaves is involved in new projects like single cylinder air cooled gasoline engines. Also, Greaves is stepping into twin cylinder engines for four wheelers, Gensets and tractor applications.
2
An extensive sales and services network managed by highly skilled and dedicated workforce keeps Greaves in touch with the customers anytime anywhere.
1.1.1 History and development
The journey of India’s leading manufacturer of engines, Greaves Cotton Limited (GCL) started in 1859. With the aim of delivering well thought – out quality products and services to the customers at competitive prices, Mr Karan Thapar expanded his enterprise. Today GCL is one of the respected manufacturers of engines due to their practice of achieving efficiency and performance. The company has 9 different centres within India. Some of which are situated in Aurangabad, Pune, Chennai etc. In Aurangabad, Greaves has two plants: one is of production in Chikalthana and another in Waluj MIDC area for production. Greaves light diesel engines are highly fuel efficient engines with high power to weight ratio and are used extensively for automotive applications like 3/4- wheeler, industrial, agricultural and marine applications, construction equipment and a host of other applications. GCL engines are available in 4-20 HP range. These engines are manufactured at ISO 9000 certified units located in Aurangabad and Ranipet. Currently, these units have a combined capacity of producing 80000 engines per year which is progressively improved to 1,50,000 engines per year. Greaves Petrol Engine Unit in Chennai, also ISO 9000 certified, manufactures Petrol/ kerosene engines in 1-3.1 HP range, which are more popular for Pumpset, Power Sprayers and Genset applications. The engines are available as such or coupled with pumps for different water pumping requirements. The unit also manufactures low-emission, low-noise and eco-friendly portable generator sets for domestic and external use.
1.1.2 Research & Development:
Research & Development is Heart of any organization. The objective of R&D is to validate the performance of the engine and transmission by conducting various tests like Endurance, Full load, Part load, Engine emission, Vehicle emission etc.
With well-equipped R&D facility in Design and testing, it has the capability to design and develop IC engines and various application products independently. Over the years, it has improved the performance and reliability of its products and incorporated a lot of innovative ideas and features to meet customers’ demands. The CAD facility includes latest software tools like Pro-E, ANSYS, Ideas, GT-Suite, AutoCAD etc.
3
Figure 1.1: Greaves Cotton Ltd., Technology Centre
Testing facilities include Dynamometer, Emission analyser (for engine and vehicle), multi-channel sensors for measuring temperature (engine water, oil, Exhaust gas) and pressure (Lubrication oil, exhaust gas). Noise and vibration measuring equipment are present with well-equipped test cells to simulate standard conditions e.g. NTP at sea-level.
1.1.3 Recent Developments:
The company has announced opening 4th light diesel engine manufacturing facility in Aurangabad, Maharashtra. The new state-of-the-art plant which has been built with an investment of over ₹ 60 crore investment is dedicated to producing twin-cylinder engines for small commercial as well as passenger 4-wheelers, Gensets and construction equipment. Recently GCL acquired Bukh Farymann Diesel GmbH, a diesel engine manufacturing company in Germany. This acquisition fits well with the GCL strategy to move more aggressively into global markets.
1.1.4 Customers:
GCL products include ‘Power Gensets’ for Defence purposes.
Piaggio Vehicles Private Ltd. (PVPL)
Mahindra & Mahindra
Scooter India Ltd.
ATUL Auto & 50 minor Auto rickshaw manufacturers
1.1.5 Light Engines:
Air Cooled: 400cc, 435cc, 510cc
Water Cooled: 265cc, 400cc, 510cc, 600cc, 870cc & 900cc
4
1.1.6 Applications:
Three Wheelers: o 500 Kg payload capacity (GVW 1000 Kg) o Three seater (Passenger o 750 Kg payload capacity (GVW 1400 Kg) o Six Seater
Four Wheelers o Passenger vehicles o Load Carriers
Gensets
Lawn Mowers
Fire Fighting Pumps
Marine
Platform Trucks
Vibrators
Pumps etc.
1.1.7 Testing Lab:
4 Test Cells for Raw emission: 2 equipped with Horiba Mexa-7100D & 2 equipped with Horiba Mexa-7400D
3 Test Cells for Gasoline engine testing
2 Test Cells for endurance and performance
1 Test Cell equipped with Chassis Dynamometer and state-of-the-art emission measurement facilities for three and four wheeler emission as well as performance tests.
1 Test Cell for Transmission testing.
Apart from all these, R&D department has an extra facility, which used to house old testing department. This facility houses few more test beds for endurance and performance testing.
1.2 PROBLEM DEFINITION:
1.2.1 Startability: It is the ability of an engine to start in minimum time. The time taken for an engine to start is defined as the point after ignition where the speed of the engine stops dropping and rises at a constant rate till it reaches its low-idle speed, where it can sustain the speed.
5
Figure 1.2: Startability with and without EFD
As we can see in figure 1.2, the curve of speed vs. start time of ‘With EFD’ stopped dropping at around 3 sec; from there on, the speed continued to climb till it reached a stable 1200±50 RPM. The time of start is denoted in the figure. Whereas, in case of ‘Without EFD’ curve, the speed reached a limit at about 300-400 rpm – which is the starter motor speed, which denotes that the engine failed to start. So, the main objective of this task is to make the engine capable of starting without the use of EFD.
1.2.2 Low End Torque:
Low end torque means the torque generated by the engine at lower speeds. In the given 510 cc diesel engine, the engine speed classification was as follows:
Table 1.2: Engine speed classification of the given engine
Sr. No. Speed (RPM) Description
1. 3400−50 High Idle
2. 1200±50 Low Idle
3. 3000 Rated Speed Hence classifying 1200-1600 rpm as the low end speed range. The engine speed is usually in this range when it is accelerating from rest. Hence, to
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6 7 8
SPEE
D (
RP
M)
TIME (SEC)
Startability
Without EFD With EFD
Start
Failed to start
6
increase the acceleration (or pick-up) and drivability, the torque generated by the engine must be increase in this range.
The current torque generated by the engine lies in the range of 18-22 Nm. The figure 1.2 shows one such engine with low end torque close to 22 Nm @ 1400 RPM. The target of this project is to increase the low end torque to a minimum of 23 Nm.
20
22
24
26
28
30
32
1400 1800 2200 2600 3000
Torq
ue
Engine Speed (RPM)
Engine with existing Configuration
Target Band
Figure 1.3: Torque of engine with existing configuration and Target
band of torque required
7
1.3 PPS:
8
9
10
1.4 PROJECT PLAN:
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2. LITERATURE REVIEW
2.1 DIESEL ENGINES: Diesel engines work on the basis of the Diesel cycle, which means they are essentially ‘compression-ignition’ engines. We are going to limit ourselves to 4 - stroke diesel engines here. A 4-stroke diesel engine works as follows:
Figure 2.1: Four strokes of a Diesel engine
Intake Stroke: The intake valve opens, the piston travels downwards sucking in a charge of air. In case of a CI Engine, the air is not premixed with fuel. [4]
Compression stroke: Both valves are closed, and the piston travels up the cylinder. In the case of compression ignition engines, the fuel is injected toward the end of the compression stroke. As the piston approaches top dead centre (TDC), ignition occurs by auto-ignition. [4]
Power Stroke: Combustion propagates throughout the charge, raising
the pressure and temperature, and forcing the piston downward. At the end of the power stroke, as the piston approaches bottom dead centre (BDC), the exhaust valve opens, and the irreversible expansion of the exhaust gases is termed "blow-down." [4]
Exhaust Stroke: The exhaust valve remains open, and the piston travels
up the cylinder and expels most of the remaining gases. At the end of the exhaust stroke, when the exhaust
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valve closes, some exhaust gas residuals will remain. These will dilute the next charge. [4]
The opening and closing of the valves is demonstrated (with respect to crank angle) in the next figure:
Figure 2.2: Valve timing diagram
The thermodynamic cycle followed by the diesel engine is called ‘Diesel Cycle’. The diesel cycle has heat addition at constant pressure. With the combination of a high compression ratio (to cause self-ignition of the fuel) and constant-volume combustion, the peak pressures would be very high. In large compression ignition engines such as marine engines, fuel injection sometimes is arranged so that combustion occurs at approximately constant pressure to limit the peak pressures. Ideal Diesel Cycle is represented in the following figure [1]:
Figure 2.3: P-V diagram of Diesel cycle
13
The compression and expansion processes are assumed to be adiabatic (i.e., no heat transfer) and thus isentropic. The processes in the diesel cycle are as follows [4] :
1→2 Isentropic compression of air through a volume ratio 𝑉1𝑉2⁄ , the volumetric
compression ratio r,
2→3 Addition of heat Qin at constant pressure while the volume expands through
a ratio 𝑉3𝑉2⁄
3→4 Isentropic expansion of air to the original volume 4→1 Rejection of heat Qout, at constant volume to complete the cycle
Efficiency of diesel engine is given by [1]:
𝜂 = 𝑊
𝑄𝑖𝑛=
𝑄𝑖𝑛 − 𝑄𝑜𝑢𝑡
𝑄𝑖𝑛= 1 −
𝑄𝑜𝑢𝑡
𝑄𝑖𝑛
2.2 FUEL INJECTION IN DIESEL ENGINES:
Figure 2.4: Spray pattern of a Diesel fuel injector
Diesel fuel delivery is determined by the diesel fuel properties and engine structure.
Diesel is more viscous than gasoline which makes it difficult to atomize.
Higher boiling point also requires better atomization to achieve fast air-fuel mixing process.
High injection pressure is a must for diesel fuel injection, generally more than 200 bar depending on different combustion chamber design [3]
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Fuel Supply System:
Figure 2.5: Fuel Supply system
2.2.1 Fuel Pump:
Figure 2.6: Cut Section view of a mechanical FIP
15
A diesel engine injection pump is used to increase the pressure of the diesel fuel from very low values from the lift pump to the extremely high pressures needed for injection. A fuel system using a single injection pump is driven by a gear train on the front of the engine that also drives the camshaft. The central injection pump feeds a separate injection nozzle located in the cylinder head above each cylinder. Lines must be of exactly equal length linking each pump plunger with the associated nozzle. Each nozzle incorporates a needle valve and the orifices which actually handle atomization. [3]
A fuel pump increases fuel pressure in the following way: The fuel cam, which is rotated by a set of gears (which are in turn powered by the crank shaft), pushes the plunger up. This movement compresses the fuel against the delivery valve. As the pressure reaches a certain point where the DV spring gets compressed, the pressurized diesel gets pushed into the high pressure pipe and then to the combustion chamber through the injector. At the same time, the control rack rotates the toothed sector gear (pinion). This movement rotates the plunger along a designed helical profile. When this helical profile matches the spill-port, the excess fuel is spilled and the pressure is lost hence cutting off the injection. [3]
The whole process is explained in the following figure:
Figure 2.7: Working of plunger in a FIP
2.3 EXCESS FUEL DEVICE: Excess fuel device is a mechanical contraption that helps us increase the fuelling by removing the constraints on the amount of fuel being injected. The following figure shows the governor of our engine. This governor controls the
16
position of the rack on the fuel pump, hence controlling the amount of fuel being injected.
Figure 2.8: Governor Assembly
Now, there is a stop lever to stop the control rack of the FIP at a certain point so as to control the maximum fuelling. That position is called fuel lock point.
Figure 2.9: Control rack position and the corresponding fuelling
17
The stop lever stops the rack at a certain point where the fuelling is as per requirement. The stop lever is held at that position by the fuel screw. The EFD is just a mechanical contraption that helps us to pull the stop lever from this fixed position so as to allow the control rack to move without any constraint. Hence, with the use of EFD, we allow momentary excess fuelling. This helps the concerned engine to start. The procedure is explained in the following figure:
Figure 2.10: Working of EFD
2.4 PERFORMANCE PARAMETERS: Engine performance is an indication of the degree of success of the engine performs its assigned task, i.e. the conversion of the chemical energy contained in the fuel into the useful mechanical work. The particular application of the engine decides the relative importance of these performance parameters. For Example: For an aircraft engine specific weight is more important whereas for an industrial engine specific fuel consumption is more important. For the evaluation of an engine performance few more parameters are chosen and the effect of various operating conditions, design concepts and modifications on these Parameters is studied. [2]
The performance of an engine is determined in terms of following:
SFC (Specific Fuel Consumption)
Torque
Power
Speed
Mechanical Efficiency
BMEP
Volumetric Efficiency
18
2.4.1 Specific Fuel Consumption: Specific fuel consumption is defined as the amount of fuel consumed per unit power developed per hour. It is a clear indication of the efficiency with which the engine develops power from fuel.
𝑺𝑭𝑪 =𝑭𝒖𝒆𝒍 𝑪𝒐𝒏𝒔𝒖𝒎𝒆𝒅 𝑲𝒈/𝒉𝒓
𝑯𝒐𝒓𝒔𝒆 𝑷𝒐𝒘𝒆𝒓 𝒅𝒆𝒗𝒆𝒍𝒐𝒑𝒆𝒅
Brake specific fuel consumption (BSFC) is determined on the basis of brake output of the engine while indicated specific fuel consumption (ISFC) is determined on the basis of indicated output of the engine. [2]
2.4.2 Torque: The power output P from an engine is determined by the available
torque and the engine speed. The torque is produced from the torque generated by the combustion process, reduced by the friction torque (friction losses in the engine) and the charge-cycle losses, and the torque required for operating the auxiliary systems. The combustion torque is generated in the power cycle and determined by the following variables [2] :
The air mass that is available for combustion once the intake valves have closed,
The fuel mass available at the same time,
The fuel injection timing,
The point at which combustion of the air/fuel mixture starts, and
Bore to stroke ratio. Its unit is Nm (Newton-metre)
2.4.3 Power: The power or Break horse power of en engine is defined as the power output of that engine. Its unit is hp. 1hp =746watts. If torque and angular speed are known, the power can be calculated as:
𝑷 = 𝝉𝝎 Where, P = Power
τ = Torque
ω = Angular speed
2.4.4 Mechanical Efficiency: The ratio of brake power (BP) to indicated power (IP) of an engine defines its mechanical efficiency, ηm. At high speeds, the mechanical efficiency of a modern automobile engine would be in the range of 75% - 95% when running at wide-open throttle. [2]
2.4.5 Brake Mean Effective Pressure: Mean effective pressure BMEP is defined as the hypothetical pressure which is thought to be acting on the piston throughout the power stroke. [2]
19
𝐵𝑀𝐸𝑃 =𝑰.𝑷.×𝟔𝟎
𝑳×𝑨×𝑵×𝒌
Where, I.P. = Indicated power L = Length of the stroke, m, A = Area of the piston, m2,
N = Rotational speed of the engine, rpm (It is 𝑁/2 for four stroke engine), k = Number of cylinders. If the mean effective pressure is based on Brake Power it is called Brake mean effective pressure (BMEP)
2.4.6 Volumetric Efficiency: Volumetric efficiency of an engine is an indication
of measure of degree to which the engine fills its swept volume. It is given by
𝑉𝑜𝑙𝑢𝑚𝑒𝑡𝑟𝑖𝑐 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 =𝑀𝑎𝑠𝑠 𝑜𝑓 𝑐ℎ𝑎𝑟𝑔𝑒 𝑎𝑐𝑡𝑢𝑎𝑙𝑙𝑦 𝑖𝑛𝑑𝑢𝑐𝑒𝑑
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑐ℎ𝑎𝑟𝑔𝑒 𝑐𝑜𝑟𝑟𝑒𝑠𝑝𝑜𝑛𝑑𝑖𝑛𝑔 𝑡𝑜 𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟 𝑣𝑜𝑙𝑢𝑚𝑒 𝑎𝑡 𝑖𝑛𝑡𝑎𝑘𝑒 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑎𝑛𝑑 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒
The amount of air taken inside the cylinder is dependent on the volumetric efficiency of an engine and hence puts a limit on the amount of fuel which can be efficiently burned and the power output. [2]
2.5 IMPROVING LOW END TORQUE:
Unlike mechanical fuel pumps, where the injection of fuel is governed by the mechanical components and the injection quantity and pressure depend on the engine speed as well as the fuel pump design. Now, one of the simpler solutions to improve the low end torque would be to increase the injection quantity and pressure. This task, however, is not easily achieved with a mechanical pump. Whereas, on a common rail system, it can be done as per our wish. Hareendranath et al. investigated this by increasing the quantity of injection at low speeds in a system equipped with common rail injection [7]. They further improved the process by splitting the pilot injection into two separate injection at part load and reported improved performance at lower speeds.
2.6 IMPROVING STARTABILITY:
Hiroaki Hara et al. investigated effects of different cetane number and other additives on engine additives in the startability of the engine [6]. The results they found were in agreement with the fact that higher cetane number corresponds to faster ignition of the fuel hence better startability. Hence one of the ways of improving startability would be to use a fuel with higher cetane number.
20
Increasing the injection pressure in another method for improving startability as investigated by Edward J. Timm et al. They tested startability at different injection pressures [8]. After finding that the startability improved with higher injection pressures, they concluded that it was because higher injection pressure the fuel droplet size decreases. This results in improved combustion hence improving the startability. Unlike spark ignition engines, where there is a positive source of heat, the diesel engines rely on the compression to attain the combustion temperature. Hence the charge air temperature also contributes to the startability of diesel engines at low temperature as explained by Hannu Jääskeläinen [5]. He goes on to explain that heating the charged air will improve the startability at lower temperatures. He also states that other than the charged air heating, variable valve timing can be another method to improve the cold startability.
21
3. ENGINE SPECIFICATIONS AND COMPONENTS
3.1 Engine Specifications:
Table 3.1: Engine specifications of the given engine
Type of engine Single cylinder, four stroke, direct injection.
Bore - mm 85
Stroke - mm 90
Displacement - cm3 510
Compression ratio 17.5 : 1
Rated rpm 3000
Idling rpm 1200±50
Max rpm 3350±50
H.P. As per CMVR rating 10
Max. Torque in kgm. ( nm) (@2000-2400 rpm) 2.7 (27) @2200±200 rpm
Specific fuel consumption (S.F.C.) gm/h.p./hr. 196
Lubrication Oil consumption – (gm/hr) 7 gm/hr. Max. (340.0 ml / 1000 km)
Engine oil quantity - litre 1.75 + 0.150
Dry weight - kg 68 ( Without air filter / alternator / exhaust system )
Type of drive ( power take off ) Dia. 30 conical.
Direction of rotation Anticlockwise when viewed from PTO end
Governor type Centrifugal governor-mechanical
Muffler ( silencer ) type Absorptive & reflection Type
Type of lub oil filter Spin-on
Type of fuel filter 0.5 LIT BOSCH
Type of air filter Dry Type - remote mounted
Type of lubrication Forced & mist
Type of feed pump Mechanical engine mounted
Starting 12 V electric start.
Dimensions L X W X H ( mm ) 463x439x686
22
3.2 Engine Components:
Figure 3.2: Isometric View-1 of the engine
Figure 3.3: Isometric View-2 of the engine
23
Table 3.2: Components of the given engine
Components Sr. No.
Flywheel 1
V- belt 2
Water outlet manifold 3
Water pump assembly 4
EGR pipe assembly 5
Injector 6
HP pipe 7
Breather assembly 8
Catalytic Converter 9
Exhaust bend tube 10
Silencer mounting bracket 11
Exhaust muffler 12
Exhaust manifold 13
Starter motor 14
Feed pump 15
Spin on filter 16
Lubrication oil adaptor 17
Pressure switch 18
Rocker lubrication pipe 19
Alternator 20
Dipstick 21
Oil pan 22
Breather extension pipe 23
Intake manifold 24
Air intake flange assembly 25
Oil return pipe 26
PTO Cover 27
Crank shaft 28
Catalytic Converter support bracket
29
24
4. METHODOLOGY
Understanding the Problem: FTP and Startability tests on engine with existing
configuration to get baseline performance and to understand the root cause of
the problem.
Finding a possible solution: Once the root cause is found – low fuelling at
lower RPM – FTP tests were carried out on the engine with a torque adjustment
device. With this device, the torque can be adjusted to requirement. The tests
revealed the amount of fuel required per stroke to achieve the target torque.
Part Procurement: The target fuelling was supplied to the fuel pump supplier
– BOSCH. They dispatched a fuel pump with fuelling pattern close to our
requirement.
Rectifying the problem: FTP and Startability tests were carried out on engine
with modified pump to evaluate the final results.
25
5. EXPERIMENTAL SETUP The basic measurements to be undertaken to evaluate the performance of an engine on almost all tests are the following:
a) Speed and power b) Fuel consumption c) Air consumption d) Smoke density e) Exhaust gas analysis
Apart from the measurement setup, the test setup requires :
a) Fuel Conditioning Unit b) Coolant Conditioning Unit
Figure 5.1: Schematic view of a general test cell
5.1 BASIC MEASUREMENTS: The basic measurements to be undertaken to evaluate the performance of an engine on almost all tests are the following:
Fuel consumption
26
Speed and Brake horse-power
Smoke
Exhaust temperature
Exhaust pressure
Lubrication oil temp
Lubrication oil pressure
5.2 MEASUREMENT OF BRAKE POWER AND SPEED:
The brake power measurement involves the determination of the torque and the angular speed of the engine output shaft. The torque measuring device is called a dynamometer.
5.2.1 Dynamometer:
A dynamometer is a load device which is generally used for measuring the power output of an engine. There are several kinds of dynamometers: Dry Friction Brake Dynamometers, Hydraulic or Water Brake Dynamometers and Eddy Current Dynamometers. For the measurement of speed and torque of engine in the test cell we generally prefer Eddy Current Dynamometer.
5.2.1.1 Eddy Current Dynamometer:
Eddy Current Dynamometers are electromagnetic load devices. The engine being tested spins a disk in the dynamometer. Electrical current passes through coils surrounding the disk, and induces a magnetic resistance to the motion of the disk. Varying the current varies the load on the engine. The dynamometer applies a resistance to the rotation of the engine. If the dynamometer is connected to the engine’s output shaft it is referred to as an Engine Dynamometer. When the dynamometer is connected to the vehicle’s drive wheels it is called a Chassis Dynamometer. The force exerted on the dynamometer housing is resisted by a strain measuring device (for example a strain gauge).
5.2.2 Dynamometer operation:
Several components are typically packaged together in a dynamometer: the shaft with bearings, the resistance surface, the resistance mechanism in a “free” rotating housing, a strain gauge, and a speed sensor (see figure 5.2 for a schematic of an Eddy Current Dynamometer). Generally some method of cooling is also required, and this may require either a heat exchanger or air or water circulation, this is not shown in figure. The entire assembly is typically mounted on a stout frame, which is mechanically linked to the frame of the engine being tested.
27
Figure 5.2: Diagram of Eddy Current Dynamometer
The force signal (F) from the strain gauge may be converted into a torque (T) by multiplying by the distance from the centre of the shaft to the pivot point of the strain gauge (R):
𝑇 = 𝑅 × 𝐹 If the units are in Newton-meters and shaft speed (S) is measured in radians per second, then the shaft power or break power (P) of the engine can be calculated by multiplying the speed and the torque.
𝑃 = 𝑇 × 𝑆
5.2.3 Dynamometer controllers: In order to test the engine it is generally necessary to use a dynamometer controller. This is usually an electronic unit which has the capability of controlling the load on the dynamometer (i.e. it controls the current to the resistance coils in an eddy current dynamometer) and can measure or sense the load and speed. Dynamometer controllers generally operate in two modes: Speed Controlled operation or Load Controlled operation. In Speed Controlled mode a set speed is given to the controller (either as a voltage or a setting on the front panel of the controller, see figure 5.3). If the measured speed of the shaft is less than that of the set speed, the load is decreased. If the measured speed of the shaft is greater than that of the set speed, then the load is increased. Assuming the engine has sufficient torque to attain the set speed; this will maintain a constant speed.
28
Figure 5.3: Schematic of a Speed Controlled test of engine at WOT
In Load Controlled mode a set load is given to the controller (either as a voltage or a setting on the front panel of the controller). If the measured load on the dynamometer is greater than that of the set load, the load is decreased. If the measured load on the dynamometer is less than that of the set load, then the load is increased. Assuming the engine has sufficient torque to attain the set load, this will maintain a constant load while the speed varies.
5.2.4 Power testing: further explanation and data:
To test an engine under load and measure its power output it was connected to a dynamometer via the knuckle joint. An eddy current type dynamometer was used for control and measurement of engine power. The dynamometer consists of a drive shaft rotating a 60 tooth speed wheel and an induction disk as seen schematically in figure. The induction disk rotates inside a housing which contains electromagnetic coils. The housing pivots freely about the shaft. Rotation of the housing is resisted by a strain gauge connected to the frame of the engine.
Figure 5.4: Schematic of an engine and eddy current dynamometer
29
Current running in the coils induces drag in the induction disk, resisting rotation of the drive shaft. The torque produced in the housing is measured by the strain gauge and was recorded. The dynamometer controller measures the speed of the engine, and compares it to a speed set point which is either adjusted via the front panel of the dynamometer controller, or an external voltage. If the speed of the shaft is greater than the speed set point the current in the coils is increased thereby increasing the drag on the drive shaft and slowing the engine. If the speed is below that of the set point the current in the coils is reduced. Near the set point, the controller sends a Pulse Width Modulated control signal to the coils. This allows the controller to vary the load on the engine in order to maintain a given shaft speed.
5.3 MEASUREMENT OF FUEL CONSUMPTION:
Fuel consumption is measured in two ways:
Volumetric type: In the volumetric measurement, a vessel of suitable capacity is connected to the main fuel tank and the engine is supplied with the fuel from the vessel during test. The vessel is filled to its capacity and then this vessel connected to the fuel tank by means of valve. The time required in emptying out the vessel is noted with a stopwatch. The volume of the vessel divided by the time then gives the fuel consumption.
Gravimetric type: In the weight method, the fuel tank is placed on the weighing platform, which directly reads the amount of fuel consumed. The time taken to consume a specified quantity of the fuel is then noted and the fuel consumption is calculated. There are different types of gravimetric type systems which are commercially available include Actual weighing of fuel consumed, Four Orifice Flow meter, etc.
5.3.1 AVL Fuel Balance:
Figure 5.5: Front View of an AVL Fuel balance
30
5.3.1.1 Description:
The AVL Fuel Balance is a gravimetric type fuel measurement device and is mainly used where high measuring accuracies are required. The built in calibration device enables calibration of the system under real test bed conditions. The fuel system AVL Fuel Balance enables a high precise fuel consumption measurement even at low consumptions and short measuring times. Reducing the fuel consumption of engines requires the measurement of increasingly small differences in fuel flow. The AVL Fuel Balance allows measuring these slight differences with maximum reliability. The AVL Fuel Balance is based on the principle of gravimetric measurement. The amount of fuel consumption is determined directly by measuring the time related weight decrease of the measuring vessel by means of a capacitive sensor. Convenient calibration and easy maintenance provide optimum ease of operation. 5.3.1.2 Technical Insight:
The fuel consumption is determined using an appropriate weighing vessel linked by a bending beam to a capacitive displacement sensor. Due to the fact that the weighting vessel has to be refilled for each measurement this is a discontinuous measurement principle. The mass of fuel consumed is therefore determined gravimetrically, which means that the density does not have to be determined in addition. The fuel consumption can thus be determined to an accuracy of 0.12%. The built-in calibration unit is standard scope of supply and allows calibration and accuracy check according to ISO 9001 which helps to reduce downtimes.
Figure 5.6: Working of an AVL Fuel Balance
31
5.4 MEASUREMENT OF EXHAUST SMOKE:
All the three widely used smoke meters, namely, Bosch, Hartridge, and PHS are basically soot density (g/m3) measuring devices, that is, the meter readings are a function of the mass of carbon in a given volume of exhaust gas. For the measurement of exhaust smoke, AVL smoke meter is used in test cell which works on the light extinction principle (Hartridge smoke unit). The basic principles of the smoke meter is one in which a fixed quantity of exhaust gas is passed through a fixed filter paper and the density of the smoke stains on the paper are evaluated optically. In a recent modification of this type of smoke meter units are used for the measurement of the intensity of smoke stain on filter paper. 5.4.1 AVL smoke meter:
Figure 5.7: Front View of an AVL smoke meter
Figure 5.8: Interior View of an AVL smoke meter
32
The AVL Smoke Meter is a filter-type smoke meter for measuring the soot content in the exhaust of diesel and related internal combustion engines. The result of the measurement is displayed as Filter Smoke Number (FSN) conforming to the standard ISO 10054 or as soot concentration.
Figure 5.9: Working of an AVL smoke meter
A defined flow rate is sampled from the engine’s exhaust pipe and passed through clean filter paper in the instrument. The filtered soot causes blackening on the filter paper which is detected by a photoelectric measuring head and evaluated in the microprocessor to produce the result in FSN. The extremely high reproducibility of the AVL Smoke Meter is guaranteed by its variable sampling volume method. The sampling volume can be set automatically depending on the exhaust soot concentration. This makes it possible to measure even the low soot levels of modern CI engines. 5.5 FUEL CONDITIONING SYSTEM:
Figure 5.10: Interior View of a Fuel Conditioning System
33
Main purpose of fuel conditioning system is to maintain fuel temperature up to 40 °C. The system consist of heat exchanger, Rota meter, relief valve etc. Fuel comes into inlet valve from fuel balance system and enters into filter. After that it passes through the fuel pump and relief valve is attached to fuel pump which maintain constant pressure of the fuel throughout system. From fuel pump fuel passes through the Rota meter. Main purpose of Rota meter is to measure the flow of fuel in LPM. Now the fuel enters into heat exchanger where temperature is maintain up to 40 °C. Provision is made from bottom side of heat exchanger for water supply. From heat exchanger fuel is supplied to engine and excess fuel returns to air separator. If any air gap are presents throughout system, they are remove from the fuel outlet pipe otherwise fuel flows to fuel pump
5.6 COOLANT CONDITIONING SYSTEM:
Coolant conditioning unit is used to maintain the constant temperature and avoid high temperature and steam pocket in engine jacket.
Figure 5.11: Coolant Conditioning System
This system consists of tubular heat exchanger through which the cold water is circulated continuously as shown in fig by blue line. The hot water from the engine comes from bottom side shown in pink line. The required coolant temperature is set on the controller. This controller controls the flow of coolant from the system as per required condition by controlling the valves fitted in the system. Coolant from the engine does not flow from heat exchanger unless the temperature increases beyond the set point. As soon as temperature reaches beyond set value, the conditioning system allows the coolant to flow through the heat exchanger and so as to maintain the required coolant temperature. The whole process is controlled by the controller.
34
6. EXPERIMENTS
6.1 TESTS ON ENGINE WITH EXISTING CONFIGURATION: These tests were carried out to gather data on the current performance and startability of the engine, thus helping us establish a baseline performance characteristic of the engine upon which we had to improve. 6.1.1 Performance Test:
This test was carried out at full throttle (FTP) with the static injection timing (SIT) set as 12˚ before TDC (which is the recommended SIT as per design). Other parameters included DBT of 31˚C and WBT of 22˚C. The engine was warmed up with coolant temperature more than 75˚C and Lubrication oil temperature at least 90˚C. The required observations were recorded and are tabulated in the following table:
Table 6.1: Observations of the FTP test on engine with existing configuration
Speed (RPM)
Torque (Nm)
Fuelling (mm3/Stroke)
3000 23.65 25.85
2800 24.48 26.68
2600 25.28 26.35
2400 26.33 26.42
2200 25.52 25.48
2000 25.35 25
1800 24.9 24.52
1600 24.09 24.47
1400 23.85 23.18
6.1.2 Startability Test: This test was carried out at ambient temperature. [DBT: 30˚C, WBT: 22˚C] The test was carried out after a soaking period of 8-10 hours. As per the requirement, the test was undertaken without the operation of EFD i.e. – since our objective was to start the engine without the use of EFD, we did not operate EFD in this case.
35
Figure 6.1: Startability of Engine with Existing Configuration
With no way of knowing the fuelling at starter motor speed, we had to rely on the fuelling data supplied by BOSCH regarding the starting fuel which was practically negligible. The data indicated that the starting fuel was in the range of 0-7 mm3/stroke.
Table 6.2: Starting fuelling of the existing FIP
Fuel Cam Speed (RPM) CRP Existing Pump
fuelling (mm3/stroke)
200 10 0
200 11 0
200 12 7.2
As we know that fuel cam speed is half the speed of the crank shaft. Hence, at 200 rpm of the cam shaft, the engine speed is actually 400 rpm which is our starter motor speed. From the above table we can see that there is hardly any fuelling at that speed. 6.1.3 Inference: One of the important factors that govern the combustion in an engine is the amount of fuel supplied for the combustion. The torque generated by the engine is directly proportional to the amount of fuel present during combustion. As we can see from the test results in Table 7.1, the fuelling corresponding to higher torque is generally higher than the fuelling corresponding to lower torque. Also, the fuelling at starting speed (speed of starter motor) is practically negligible. This is the reason that the engine required operation of EFD to start.
0
200
400
600
800
1000
1200
0 1 2 3 4 5 6 7 8
SPEE
D (
RP
M)
TIME (SEC)
Engine with ExistingConfiguration
36
Hence, a very plausible solution for these problems would be increased fuelling per stroke at lower speeds as well as at starter motor speed.
6.2 TESTS ON ENGINE WITH TORQUE ADAPTION DEVICE: These tests were carried out with a device called ‘Torque Adaption Device’ instead of stop lever. Where the stop lever would lock the fuel at a point, this device employed a spring which would allow the rack to move a little further. This allowed us to set the torque, and the fuelling required to achieve that torque was recorded. As the fuelling is very sensitive to the Control Rack position, the tests were carried out carefully with first at just 0.6 mm adaption then increasing it to 0.8 mm adaption.. 6.2.1 Performance Test:
0.6 mm Adaption:
Table 6.3: Observations of FTP test on engine with 0.6mm adaption
Speed (RPM)
Torque (Nm)
Fuelling (mm3/Stroke)
3000 22.65 26.4
2800 23.77 26.59
2600 24.16 25.89
2400 24.42 25.62
2200 23.97 25.5
2000 24.53 25.52
1800 27.26 28.09
1600 27.45 27.96
1400 25.69 26.1
0.8 mm Adaption:
Table 6.4: Observations of FTP test on engine with 0.8mm adaption
Speed (RPM)
Torque (Nm)
Fuelling (mm3/Stroke)
3000 22.77 26.28
2800 24.01 26.64
2600 24.61 26.23
2400 24.98 26.04
2200 24.21 25.87
2000 25.12 26.04
1800 27.91 29.05
1600 27.97 28.77
1400 26.62 27.25
37
6.2.2 Startability Test:
Unfortunately startability could not be achieved with the Torque Adaption device as it allowed us to set torque and observe the fuelling and had no role in controlling or improving the startability.
6.2.3 Inference: The fuelling provided by 0.8mm adaption was more, hence the lower end torque achieved with 0.8mm adaption was also higher as we can see from the following graphs:
Figure 6.2: Torque Comparison of setup with different adaptions
Figure 6.3: Fuelling Comparison of setup with different adaptions
20
21
22
23
24
25
26
27
28
29
1400 1600 1800 2000 2200 2400 2600 2800 3000
Torq
ue
(Nm
)
Speed (RPM)
Torque Comparision
0.6 mm Adaption
0.8 mm Adaption
23
24
25
26
27
28
29
30
1400 1600 1800 2000 2200 2400 2600 2800 3000
Fuel
ling
(mm
3/S
tro
ke)
Speed (RPM)
Fuelling Comparision
0.6 mm Adaption
0.8 mm Adaption
38
After careful consideration, this fuelling was sent to BOSCH so that they can send a fuel pump that can achieve a fuelling pattern close to our requirement. As discussed above, the starting fuel was low and we could just trust the BOSCH specification that it was somewhere in the range of 0-7 mm3/stroke. So we requested this fuelling be increased to 25-30 mm3/stroke in the new pump.
6.3 TESTS ON ENGINE WITH MODIFIED FIP:
The modified pump supplied by BOSCH was tested on two separate engine for their startability and performance tests. These tests were undertaken in order to verify the results that was expected from the fuelling of the modified pump.
6.3.1 Performance Test:
These tests were also taken in ambient conditions [DBT: 35˚C, WBT: 28˚C]. The Static Injection Timing (SIT) was set as 12˚ before TDC. The engine was warmed up with coolant temperature more than 75˚C and Lubrication oil temperature at least 90˚C. The test was carried out at full throttle (FTP).
The tests were undertaken on two separate engines to verify the effect of the modification on the torque. The Observations were:
Engine 1 with modified pump:
Table 6.5: Observations of FTP test on engine 1 with modified FIP
Speed (RPM)
Torque (Nm) Fuelling
(mm3/Stroke)
3000 23.6 28.27
2800 25.3 28.5
2600 26.3 28.34
2400 26.5 28.08
2200 27.3 28.5
2000 27.1 29.94
1800 27.0 30.11
1600 27.7 29.42
1400 28.2 30.26
39
Engine 2 with modified pump:
Table 6.6: Observations of FTP test on engine 2 with modified FIP
Speed (RPM)
Torque (Nm) Fuelling
(mm3/Stroke)
3000 23.5 26.56
2800 24.2 26.62
2600 24.3 26.69
2400 24.6 27.06
2200 26.0 28.91
2000 26.1 29.3
1800 26.6 28.71
1600 27.2 28.71
1400 26.1 29.17
6.3.2 Startability Test:
The startability tests were carried out under ambient conditions [DBT: 34˚C, WBT: 25˚C] with a soaking period of at least 8-10 hours. During these tests, the EFD was not used.
Figure 6.4: Startability of Engine 1 with Modified FIP
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6 7 8
SPEE
D (
RP
M)
TIME (SEC)
STARTABILITY OF ENGINE 1 WITH MODIFIED FIP
Start
40
Figure 6.5: Startability of Engine 2 with Modified FIP
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6 7 8
SPEE
D (
RP
M)
TIME (SEC)
STARTABILITY OF ENGINE 2 WITH MODIFIED FIP
Start
41
7. RESULTS The results were well above the minimum requirement mark. The torque comparison of the original specification, the target and the final result is as follows:
Figure 7.1: Comparison of Torque of engine with existing configuration with
the target and final result
As we can see from the above comparison, low end torque for Engine 1 far exceeded the minimum requirement and for Engine 2, the low end torque fall just in the target band of minimum low end torque requirement. The startability achieved was satisfactory. Both the engines started under 3 sec without the operation of EFD. The comparison of startability of both engines with the existing startability is shown in the following figure:
20
22
24
26
28
30
32
1400 1800 2200 2600 3000
Torq
ue
Engine Speed (RPM)
Engine with existing ConfigurationEngine 1 with Modified FIPEngine 2 with Modified FIP
42
Figure 7.2: Startability comparison of engine with existing configuration with
the final result
This startability was achieved because of the increased fuelling at starter motor speed. The comparison of old and new fuelling at this speed is given in the following table:
Table 7.1: Comparison of starting fuelling of existing FIP and modified FIP
Fuel Cam Speed (RPM) CRP Existing Pump Fuelling
(mm3/Stroke) Modified Pump
Fuelling (mm3/Stroke)
200 10 0 13.1
200 11 0 22.4
200 12 7.2 30.5
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6 7 8
SPEE
D (
RP
M)
TIME (SEC)
Engine with Existing Configuration Engine 1 with Modified FIP Engine 2 with Modified FIP
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8. CONCLUSIONS The improvement of low end torque and startability of a 510 cc water cooled diesel engine was achieved successfully at Greaves Cotton Ltd., Aurangabad. The baseline tests revealed lack of fuelling at lower speeds. New fuelling requirement based on torque demand was found and a modified FIP was procured which gave the fuelling as per our requirement. This FIP helped us achieve the low end torque target and the startability improved as well by the increased fuelling at starter motor speed.
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9. REFERENCES
1. Baranescu, Rodica; Challen, Bernard, Diesel Engine Reference Book, Second
Edition, Butterworth Heinemann, 1999, pp. 7-8
2. Pulkrabek, Willard W., Engineering Fundamentals of the Internal Combustion
Engine, Prentice Hall, New Jersey, pp. 47
3. Bosch Electronic Automotive Handbook, First edition, Robert Bosch GmbH,
2002, pp.756-760
4. Stone, Richard; Ball, Jeffery K., Automotive Engineering Fundamentals, SAE
International, ISBN 0-7680-0987-1, Warrendale, 2004, pp. 20-23, 26-27
5. Hannu Jääskeläinen, Charged Air Heating, Dieselnet.com/tech/airheat
6. Hara, H., Itoh, Y., Henein, N., and Bryzik, W., "Effect of Cetane Number with
and without Additive on Cold Startability and White Smoke Emissions in a
Diesel Engine," SAE Technical Paper 1999-01-1476, 1999
7. Hareendranath, D., Gajarlawar, N., Tagare, A., and Ghodke, P., "Experiences
in improving the Low end performance of a Multi Purpose Vehicle (MPV)
equipped with a common rail Diesel engine.," SAE Technical Paper 2009-28-
0008, 2009
8. Timm, Edward J.; Stuecken, Thomas R. and Schock, Harold J., Measurement
and Visualization of Spray Characteristics of a Fuel Injector under Different
Operating Temperatures and Pressures, SAE Technical Paper, 2002