200 HOUR TEST

Three test stands, designed and built at the University of Idaho were used to load and monitor the test engines. Each stand uses a hydraulic dynamometer which consists of a Hydreco gear pump (cradled for torque measurement) coupled directly to the engine clutch shaft. A Sperry Vickas electronically modulated relief valve (EMRV) was used to control the pressure on the pump and thus the load applied to the engine. A constant volume flowmeter, which measures the time for a known volume of fuel to be consumed, and a magnetic pickup, which measures engine speed at the clutch shaft have been incorporated into each stand. Throttle control was provided by a DC gearhead motor linked to the throttle shaft of each engine's fuel injection pump. Each test stand can be controlled either manually from the stand or remotely with a data acquisition and control system.

The data acquisition and control system consists of a microcomputer and a Hewlett Packard 3497 data acquisition control unit. The system capabilities include control of engine speed and load as well as measurement of engine torque, speed, power output, fuel consumption, and temperatures (exhaust, crankcase oil, fuel, and hydraulic oil).

Diesel exhaust quality is usually expressed in terms of the opacity of the exhaust smoke. A Telonic Berkley model 200 portable opacity meter was connected to the data acquisition unit and collected data at the 50 hour torque test intervals. The opacity meter consists of a light source positioned on one side of the exhaust stream and a photo resistor mounted on the opposite side. The meter provides an output voltage ranging from 0 to 1.00 volts. One hundred percent opacity (1.0 volt) corresponds to no light transmission whereas 0 percent opacity corresponds to complete light transmission.

Load Cycle
The standard EMA test was designed to initiate durability problems associated with the use of alternative fuels in a relatively short period o time. Thus the load cycle is quite severe. The standard test utilizes four engine load cycles (1 set) over a three hour period. The standard test calls for five consecutive sets (15 hours of continuous operation) followed by a nine hour (minimum) period during which the engines are shut down and allowed to reach ambient temperature. In order to accommodate the schedules of the lab staff, this study used a shortened version of the standard test which consisted of 3 consecutive sets (9 hours of continuous operation). This was continued until 200 hours were logged on each engine.

The four conditions are described as follows:

1. Rated condition (60 minute): Operating at full throttle, a load is applied until engine speed decreases to the manufacturer specified rated speed.

2. Maximum torque (60 minute): Operating at full throttle, a load is applied until the engine speed decreases to the speed of rated torque as described by the manufacturer.

3. High idle (30 minute): the load is set at 25 percent of maximum torque and the throttle is varied to achieve an engine speed of 90 percent of rated speed.

4. Low idle (30 minute): At no load the throttle is varied to achieve the manufacturers recommended curb idle.

The following data (averaged over the duration of the cycle) were measured and collected for each load cycle of every set:

Lubricating Oil
A 208 litre drum of Chevron Delo Multigrade SAE 15W-40 heavy duty motor oil was procured at the beginning of the test. The engine oil and filter were changed at 100 hour intervals and an oil analysis was performed at 50 hour intervals for each engine.

PROCEDURES
The 200 hour test cycle described above was run to evaluate the engine durability effects of long term usage. The tests were performed on three identical engines simultaneously and controlled by the microcomputer based data acquisition and control system.

Prior to the test, the engines were completely rebuilt. New pistons, rings and valves were installed and the cylinder heads were glass bead cleaned to remove all carbon build-up in the intake and exhaust ports. Following the rebuild, the engines were subjected to a short break in period on 100% 2-D as recommended by the manufacturer before beginning the described test.

At 100 hour intervals the engine oil and filter were changed and oil samples were taken from each engine's crankcase and analyzed by a commercial lab for wear metal concentrations and viscosity changes. At 50 hour intervals, the test was halted to run the following tests with each engine running on its respective test fuel:

Constant throttle - variable speed torque tests
Injector performance check
Cylinder compression check
Opacity check

At each of these 50 hour intervals the injectors were removed, photographed and digitized to provide a quantitative record of injector coking. The results of the injector digitizing method are reported as a relative coking number. This number is obtained by, first, digitizing a clean injector photograph and using its projected area as a reference. Then each used injector is photographed from two positions, 90 degrees apart, and both profiles are digitized. The areas are then corrected through use of a scale factor to compensate for variations in the photograph printing process. The profile which gives the maximum corrected area is selected and subtracted from the corrected area of the clean injector.

All engine service and maintenance was performed as specified in the manufacturers service manual. No modifications were made to any three of the engines for testing the Biofuels.

EMA Tests with B100 RME, B100 REE, and 2-D
Fuels
The fuels used in this study were 100% Phillips 0.05 sulfur diesel fuel (2-D), 100% ethyl ester of rapeseed oil (B100 REE), and 100% methyl ester of rapeseed oil (B100 RME). The rapeseed was Dwarf Essex variety and was expelled and processed using the facilities of the University of Idaho's Department of Biological and Agricultural Engineering. The fuel properties were determined by university of Idaho technicians and a commercial lab and are displayed in Table 1.

RESULTS AND DISCUSSION
Fuel Consumption
The engine fueled on 2-D consumed 630 liters of fuel, the B100 REE fueled engine consumed 742 liters of fuel, and the B100 RME fueled engine consumed 780 liters of fuel. The differences in fuel consumption reflects the differences in heat of combustion and density of the individual fuels and are affected by variations in settings between engines.

Table 1. Fuel Characterization Data

Engine Performance
The observed performance trend, shown in Figure 1, shows the change in power relative to output at zero hours for each 50 hour interval. Relative power change is shown instead of actual power to compensate for the differance in engines.

Cylinder compression varied from 2.65 MPa (385 psi) to 3.10 MPa (450 psi) between cylinders and engines, but varied only 40 psi for the same cylinder during the test. The fuel injector valve opening pressure (psi) varied from 20.34 MPa (2,950 psi) to 21.37 MPa (3,100 psi) for all the fuel injectors. Individual injector valve opening pressure varied only 344 kPa (50 psi) for the duration of testing. Engine blowby was measured at each 50 hour interval with no difference form beginning to and for each of the three engines.

Oil Analysis
All engines show a decrease in engine oil viscosity compared to new lubricating oil. A slight increase in engine oil viscosity, compared to B100 RME and B100 REE, was observed with the diesel fueled engine. The engine oil viscosity versus time data is shown in Figure 2, and the total base number (TBN) versus time is shown in Figure 3. The TBN indicates the potential of the oil to neutralize strong acids as the mineral acids derived from sulfur, chlorine, and bromine. Decreases in TBN are associated with corrosion of engine parts and increases in varnish deposits.

Engine wear was evaluated on the basis of the concentrations of three wear metals in the lubricating oil. The metals, and their primary source, used as the wear basis are as follows:

1. Iron - cylinder, camshaft, valve train, gear wear
2. Aluminum - piston and bearing wear
3. Silicon - anti-foam additive, ingested dirt

Wear metal concentration results are shown in Figures 4 through 6. All the engine oil analysis were within the allowable limits.

Figure 1. Engine Power Change Relative to the Engine Power at 0 Hours.

Figure 2. Engine Oil Viscosity vs Time.

Figure 3. Engine Oil Total Base Number vs Time.

Figure 4. Engine Oil Iron Concentration vs Time.

Figure 5. Engine Oil Aluminum Concentration vs Time.

Figure 6. Engine Oil Silicon Concentration vs Time.

Injector Coking
The coking results from the quantitative digitizing method are presented in Figure 7. At the conclusion of the test the injectors were disassembled and inspected for internal deposits. The lift needles of the injectors operated on these fuels were clean and showed no wear and discoloration.

Figure 7. Injector Coking vs Time.

Engine Inspection
Following the 200 hour EMA test, the three engines were disassembled and inspected.

Engine fueled with 2-D fuel. The oil in the bottom of the oil pan was dark in color but there were no large particles or foreign material. The engine oil pickup screen was free from debris. The cylinder walls look good with no visible or measurable wear. All the valve seats in the cylinder head were clean and shiny. A small amount of carbon build up was present in the exhaust ports, and the intake ports were clean. The intake valve faces were clean and the stem area had a slight amount of hard carbon deposits. The exhaust valve faces were fairly clean. The piston ring lands were very clean. The tops of the pistons had minimal amounts of carbon build up and grayish in color. The rod and main bearings had no visible wear with very small scratches on the lower halves. There was no measurable wear in the engine components that move. The overall condition of this is engine is normal for a 200 hour EMA test.

Engine fueled with 100 percent B100 REE. The oil in the bottom of the oil pan was dark in color but there were no large particles or foreign material. The engine oil pickup screen was free from debris. The cylinder walls look good with no visible or measurable wear. All the valve seats in the cylinder head were clean and shiny. A small amount of carbon build up was present in the exhaust ports, more so than the diesel fueled engine, and the intake ports were clean. The intake valve faces were clean and the stem area had a slight amount of gummy carbon deposits. The exhaust valve faces were dull. The top piston ring lands had carbon build up one-eighth the circumference. The tops of the pistons had minimal amounts of carbon build up. The rod and main bearings had no visible wear. There was no measurable wear in the engine components that move. The overall condition of this is engine is normal for a 200 hour EMA test.

Engine fueled with 100 percent B100 RME. The oil in the bottom of the oil pan was dark in color but there were no large particles or foreign material. The engine oil pickup screen was free from debris. The cylinder walls look good with no visible or measurable wear. All the valve seats in the cylinder head were clean and shiny. A small amount of carbon build up was present in the exhaust ports and the intake ports were clean. The intake valve faces were clean and the stem area had a slight amount of hard carbon deposits. The exhaust valve faces were fairly clean and the carbon on the heads of the valves were orange in color. The top piston ring lands on number one and two pistons had carbon in them about one halfway around, number three piston top ring land had a small area of carbon build up. The second and third ring lands were clean. The tops of the pistons had minimal amounts of carbon build up. The rod and main bearings had no visible wear. There was no measurable wear in the engine components that move. The overall condition of this is engine is normal for a 200 hour EMA test.

Weights and Measurements
Table 2 is the change in weight relative to 2-D for the given engine components.

Table 2. Engine Component Change in Weights Relative to 2-D

CONCLUSIONS
There were no modifications to the engine for testing the B100 fuels. The EMA 200 hour test demonstrated that these fuels are suitable alternatives to diesel fuel and further testing is appropriate. Results of the engine oil analysis for the B100 fuels were similar to the diesel fueled engine. There was no cylinder wall to piston scuffing with any of the fuels. All the piston rings for the three different fuels were clean and free. The crankshaft bearings in each engine showed normal wear with no measurable difference in the crank journals. The injector pressures did not vary more than 50 psi during the course of testing. The injector needles moved freely at the end of the test. Injector coking varied for each fuel throughout the test series but on the whole the B100 REE was comparable to 2-D and B100 RME was 1.3 times that of 2-D.

The top piston ring for the B100 REE fueled engine had 86 percent less wear, by weight, and 89 percent less for the B100 RME fueled engine than the 2-D fueled engine. The B100 REE and B100 RME pistons, the three averaged together, had 33 percent more and 25 percent more weight respectively than the average of the 2-D pistons. The intake valve averages by weight were 8 percent less for B100 REE and 25 percent more for B100 RME compared to 2-D. The exhaust valves for the B100 RME and B100 REE fueled engines had 60 percent less weight compared to the 2-D fueled engine.

Fuel characterization data showed some similarities and differences between B100 REE and B100 RME and diesel fuel. a) Specific weight is higher for B100, heat of combustion is 8 percent lower, and viscosities are 2 times that of 2-D. b) Pour points for B100 REE and B100 RME are 10 and 5 degrees celsius higher than diesel. c) Sulfur content is 40 percent less for B100 REE and B100 RME than 2-D.