SCANIA P380 — dual-fuel mining dump-truck

Mining dump-truck SCANIA consumes 400-500L of diesel fuel in 24 hours or 200-250L in one 12-hr shift. Having 60% substitution coefficient when 1 L of DF is substituted with 1,1nm3 of CNG, we need 165nm3 CNG storage capacity. Because of CNG reducer requires 10bar additional pressure, we got minimum 173nm3 of necessarily storage capacity.
Our a kind of traditional solution with cylinders behind a cabin looked doubtful from the mechanical strength under extreme load angle and from the cylinder valves safety angle (valves may be damaged by coal stone pieces while loading).
We decided to mount CNG cylinders at the truck frame both sides, which required brake reservoirs removing inside the frame and diesel fuel tank shifting.
Please see below what we got:

 

Total volume CNG storage system – 2 x ( 3х100 liters and 1х80 liters ) = 760 liters = 178 gas cubic meters.

We added some new features to our existing dual-fuel Triol system. ( Description TRIOL system )

1Now Triol supports 24V power, which resulted in possibility to use high-performance CNG injectors and remove 24-12 converter. Max CNG supply is 90nm3/hr.

2New symmetrical calibration table 2х20х20х32=25,600 cells with turbopressure, PPS, rpm axis for diesel fuel and CNG. This results in even acceleration and precise thrust control, which is in high demand for powerful high-load engines at off-road vehicles climbing and descending under extreme slippery slopes.

 

3Calibration field extension lead to more laborious calibration work. But we implemented service functions which make calibration easy and simple. Now you need 5 minutes for calibration only. You need to assign max and min values at calibration axis (turbopressure, RPM, PPS), than assign CNG supply max value, CNG/diesel fuel ratio and that’s all!
Software will propose you default settings also.

4 Smart speed limitation. At mining and other special regions with heavy-duty vehicle intensive traffic speed limitation is often implemented both because of government regulation and safety reasons. Normally discordant diesel ECU and dual-fuel ECU works results in truck annoying twitch when close to speed limit. Our Triol dual-fuel ECU speed limit is adjusted to decrease CNG supply exactly before diesel ECU starts to do this, so vehicle slowly brakes, it looks like invisible wall prevented to speed up, no any twitches and annoyance.

5Smart exhaust gas temperature limitation. You never know all engine loads and regimes possible, heavy-duty off-roads bring unpleasant surprises sometimes. If load is abnormally high during long time, so in order to prevent turbine destruction Triol ECU decrease CNG supply if exhaust gas temperature exceed assigned limit. It is very useful function when truck is stucked.

6Possibility to change CNG/diesel ratio according to gear. Normally it is not necessary but mining hardships and extreme supply difference at low and normal gears don’t leave another choice sometimes

7Instant snapshot of all engine parameters red by Triol ECU. It is very convenient- just press space button and all variables are saved in special table for further analysis.

8 PPS emulator automatic calibration, it was quite a piece of work before. Emulation level is analog signal issued by DAC under PWM control. Previously you need to manually issue 32 PWM signals, using multimeter measure and adjust 32 voltage levels in accordance with those 32 PWMs. Now all you left to do is to press corresponding software button and calibration run automatically.

Two tests were conducted: first in order to demonstrate Triol system capabilities, second – in order to estimate dual-fuel influence to engine durability.

Test conditionsAt both tests Scania performed round trip coal-preparation plant-mine-coal preparation plant. First leg was without load, at the mine truck was loaded by coal and then trip back. 2 legs length is 70-80km, climbing from mine 3-5 km 15-20% angle off-road.
Straight part is broken hilly ground, 2 ridges between 2 river valleys crossing. All tests were done with the same driver, at the beginning round trip was performed using diesel fuel only, then dual-fuel round trip. Diesel fuel consumption, CNG consumption mileage were noted at each round trip.
Diesel fuel consumption was measured by calibrated metering pump (see picture below). Vehicle was stopped at even ground at the same place during whole tests, before first test fuel tank was filled full by pump (until fuel dropped from inlet), after round trip tank was refilled again and liters added became round trip consumption.
CNG consumption was calculated using pressure gauge value at the beginning and at the end of each trip, knowing cylinder volume CNG consumption was calculated later

Substitution coefficient, power and torque. At first tests we got 62% substitution coefficient, at second tests 12 trips average coefficient was 57%. Average load was 34tons.
Drivers noted increased haulage a t dual-fuel regime, they described this as a possibility to run one gear up comparing with diesel regime under the same road conditions

Dual-fuel influence to engine In order to estimate dual-fuel influence to engine it was overhauled after first test in order to perform second tests at virtually new engine. Mileage was 670 000km.
After second tests we ordered engine disassembling at Scania official service with pistons, seals and valves removing and analysis (see pictures below)
No pistons/valves wear-and-tear, no oil consumption at all.