Journal ofScience & Technology 100 (2014) 047-050
Research and Install the Dual Fuel CNG - Diesel Supply Control System on Small Diesel Engine
Do Van Dung*, Huynh Phuoc Son, Thai Huy Phat, Nguyen Van Long Giang
University of Technical Education Ho Chi Minh City, No.l, Vo Van Ngan, Thu Due District, Ho Chi Minh City Received: March 3, 2014, accepted: April 22, 2014
Abstract
Compressed Natural Gas (CNG) is considered as a source of clean fuel and have large reservation to use as alternative fuels for internal combustion engines. In paritcular, the research interest for using dual-fuel in engines is considered to be feasible, cost savings and suitable for CNG gas supply infrastructure, i-lowever, when CNG gas is burned in compression ignition engines with high compression ratio, it is easy to cause detonation phenomenon therefore reduce ability to use CNG. The CNG - Diesel mixed system is electronic controlled, including CRDI with injection for initial ignition and the CNG injection system into the intake manifold, with various injection timing and ignition pressure to prevent of detonation, increase the maximum rate of CNG/diesel. Test results on VIKYNO RV125-2 engine, showed that the engine work stably at different speeds. This result Is the fundamental for the funther reseach to control supply CNG for compression ignition engines.
Key words: CNG; CRDI; VIKYNO RV 125-2; HP3 fuel pump; Fuel pressure sensor; ECU; Dual fuel control system CNG - Diesel.
1. Introduction
The work stiidies tiie dual fiiel Diesel/CNG supply system that is designed to replace for the conventional ftiel system in VIKYNO RVI25-2 engine. Authors use the optimal method to conttol the pilot injection for initial ignition for dual fijel CNG- Diesel supply system.
The research contents include;
- Research, improve and install dual fuel CNG - Diesel supply system on engine. The input sensors, diesel fuel supply system as high pressure fuel pump, common rail and diesel injection injector [I], CNG supply system, the relief valve for CNG, CNG injector have been installed on VIKYNO RV 125-2 engine to replace the conventional fuel supply system.
- Design and program the ECU that supplies dual fuel CNG-Diesel supply system.
- Test and evaluate the operatmg regulations via experimental results.
2. Set u p experiment
2.1. Design and install dual fuel Diesel - CNG supply system on VIKYNO R V125-2 engine.
VIKYNO RV 125-2 is a I-cylinder diesel engine with small power and steady load. Engine specifications are shown in Table I [2].
Table 1 VIKYNO RV 125-2 engine specifications
stroke x Bore (mm) Cylmder volume (cm^) Max power
Max torque Compression ratio BSFC Iniection pressure
9 4 x 9 0 624 12.5 HP/2400 rpm 4.04 tgm/1800 rpm
18 185g/HP/liour
220(kg/cm')
' Correspondmg author: Tel.: (+84) 903.644.706 Email: [email protected]
Fig. I, Designed diagram for dual fuel supply system m VIKYNO RV 125-2 enguie.
Journal of Science & Technology 100 (2014) 047-050
The study didn't change the structure of the engine. A CRDI system [1] has been designed and installed to replace the conventional diesel pump for servmg experiment as shown in Fig. I.
A belt drive system was designed to drive HP3 pump that supplies a high fuel to injector. The gear ratio between the pump shaft and crankshaft is 2:1 as shown in Fig. 2.
Fig. 2. Drive HP3 pump system diagram I- Large intermediate gear Z l = 82 , 2- Small intermediate gear Z2=52, 3- Drive supply pump gear Z3=52, 4- Drive supply pump pulley, 5- Belt, 6- HP3 pump pulley, 7- Crankshaft pulley wheel Z4=41.
An electtomagnetic sensor which determines crankshaft position and speed, is set on the drive supply pump gear. The common rail pressure sensor was installed on engine block. Electromagnetic injector was fitted at the same conventional injector position. Engine temperature sensor was also installed on cylmder head.
The CNG supply system includes CNG tank, the relief valve ensures constant pressure at 2 bar, CNG pressure and temperature sensors, CNG injector (on manifold). Besides, the input sensors such as acceleration pedal position sensor, knock sensor, MAE sensor ...are added to the system. These sensors will support ECU to control operating regulations in experimental process. Fig. 3 shows some main components for setting up experiment.
Fig. 3. Set up experiment for dual fuel Diesel - CNG supply system in VIKYNO - RV 125-2 engine
2.2. Design and install ECU for controlling diesel injector, CNG injector and suction control valve ( SCV)
CRDI and dual fiiel Diesel - CNG supply systems are based on the input signals: crankshaft position, acceleration pedal position (VPA), engine coolant temperamre (THW), mass att flow (MAF), common rail pressure (CPS), CNG temperature (CPS) sensors...The sensors are tiansfened to ECU that will process and contiol the actuators as suction contiol valve, diesel and CNG injectors.
Fig. 4. Diagram for contiollmg SCV, diesel and CNG injectors.
ECU is designed to collect the input signals, calculates and sends the output signals to conttol SCV and ttijectors. ECU is based on ATMEGA-32 microcontioller which is programmed by Assembler programming language. The input signals of sensors are tiansferred to ADC filter and counter [3].
ATMEGA-32 will process and send the output signals which conttol SVC, injectors corresponding to operatmg regulations.
Injection timing and duration diagram is illustrated as following:
^
Fig. 5. Dual fuel CNG - Diesel injection timmg and duration diagram.
Journal ofScience & Technology 100 (2014) 047-050
- Td: Diesel injection starting time before TDC when ECU receiving pulse signal.
- Tpd: Diesel injection lift time.
- Tk: Time between two impact pulses in engine.
- Tpc: CNG injection duration.
- Tc: CNG injection starting time before TDC when ECU receiving pulse signal.
2.3 Control program design
The dual fuel systems have been conttolled by ECU, ECU will conttol the outputs as: spill conttol valve (SCV), diesel and CNG injectors. Dual fuel supply calculation relied on the minimum diesel pilot injection that supplies enough energy to ignite att - CNG mixture in the chamber.
Algonthm chart for dual fuel Diesel - CNG supply conttol system is shown in Fig. 6. To begin a cycle, ECU will update the inputs. Engine speed signal (Ne input) is main factor to determine diesel injection timing. In addition, the other outputs such as knock (KNK), throttle position (VTA), electonic conttol throttle (ECT), fuel pressure sensor (FPS) ...have been used to control and correct the injection timing, injection opening period.
Apply input sensor
Calculate input sign Ne
Read value input sensors (Ne, ECT, KNK, OzS, MAF, CPS, CTS, VTA, FPS...) Output timer delay Diesel injection Td, timer delay CNG injection
Timer Diesel injection Tpd, Timer CNG injection Tc
3. Experimental results a n d discussion 3.1 Experiment for the regime of engine working on 100% diesel with common rail injection system
The engine was set up and experimented by hydraulic test bench (as Fig. 3), The test was carried out at 25 N-m braking torque and operated at various engine speeds fi-om 1,200 to 2,200 rpm, respectively.
To keep the desired engine speed, the study has adjusted ECU that controls injector with the suitable injection timing and duration. The study has measured uijection flow rate, HC and CO emissions by HORIBA emission testing equipment. The experiment has been performed corresponding to the different engine speeds with I minute interval for specimen. The experimental results are shown in Table 2,
Table 2. Injection flow rate, HC, CO emissions for the 100% Diesel operation
RPM 1,200 1,400 1,600 1,800 2,000 2,200
HC (ppm)
12 13 10.5 9.5 10.5 9
CO
(%)
0.033 0.033 0.035 0.045 0.10 0.12
Injection flow rate (ml/minute)
7.2 11.6 17.7 18.5 26 36 3.2 Experiment for dual fuel Diesel - CNG system The test was carried out in the same manner as for the above state. The study used diesel fuel as pilot injection to ignite the mixture. To examine fuel consumption between diesel and CNG, the work used the minimum injection flow for diesel and conttolled the CNG fiow rate by adjusting mjection timing at each RPM. These values are conttolled by ECU that is programmed by researchers. The specimen interval also is 1 minute for every testing. Besides, HC and CO emissions also measured in this testing case. The results are shown in Table 3.
Table 3. CNG flow rate, HC. CO emissions for dual fuel Diesel - CNG sysiem by using diesel as the
inilial ignition.
Fig. 6. Algorithm flow chart for ECU conttol
RPM
1200 1400 1600 1800 2000 2200
HC (ppm)
440 467 483 261 71 20
CO (%ml)
0 16 0.20 0.24 0.12 0.09 0.03
Diesel injection flow rate (ml/mm)
4.4 5 5.8 4.8 8.0 8.2
CNG injection pulse width
(ms) 3.8 5.0 5.9 6.8 7.6 8.1
Journal of Science & Technology 100 (2014) 047-050
3.3 Result discussions
3.3.1 Evaluate diesel injection flow rate experiment
n(rpm) Fig. 7. Diesel mjection fiow rate in 2 cases (conventional fiiel and dual fuel CNG - Diesel systems)
The diesel injection flow rate for the dual fiiel CNG-Diesel system considerably decreases compared with its in 100% diesel working condition. This value increases at higher engine speed since the diesel was injected as initial injection to ignite the air - CNG mixture in dual fuel Diesel-CNG case. Therefore, this injection is minimum quantity to maintain ignition.
The result shows that using diesel fuel is the most effective fiiel economy in dual fuel diesel-CNG system.
3.3.2 Evaluate HC and CO emissions in experiment HC (ppmvoi)
Fig. 8 shows that H C emission ui dual fiiel diesel-CNG system is higher tiian its in the conventional fijel system. The highest value at 1,600 RPM and it ttends toward as gradual reducing as engine speed increasing. Due to the increasing of air charge into cylinder at high RPM, hence combustion process in the chamber occurs better and consequently the HC emission also reduces.
CO emission in dual fuel diesel - CNG system has the higher value at initial stage. However, it will reduce gradually corresponding to the engine speed increasing. Whereas, CO emission in the conventional fuel system increases at the higher RPM. Because the air-CNG mixture will ignited completely at higher engine speed, therefore, the chamber temperature will increase significantly and CO ermssion decreases.
4. Conclusions
The study has researched and installed a dual ftiel diesel - CNG system that applies in conventional I-cylinder diesel engine. A common rail diesel system has been designed and set up as pilot injection to ignite the air-CNG mixture. The experimental results have shown the effectivness of using dual fuel diesel-CNG in conventional diesel engines. This further smdy need be carried out to reduce the depending of fossil energy source and emissions ifi intemal combustion engines.
References
[I] Tran Thanh Hai Tung, Do Van Dung, Huynh Phuoc Son, Nguyen Van Long Giang, Phan Nguyen Quy Tam,
"Research and install Common Rail Diesel Injection CRDI on VIKYNO RV125-2 engine", Science and Technology joumal (Danang limvsTsity), 1 (2013) 120.
[2] http://www.sveam.com.
[3] Ngo Dien Tap, AVR microconttoUer techniques,, Science and Technology pulisher, 2003.
1200 1400 1600 2000 2200
0 25 •100% Diesel
'CNG+Diesel
1500 180O 2000 2200 Fig. 8. HC and CO emissions in experimental c (100% diesel and CNG + diesel)
