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Biodiesel Test of a Cummins/Onan Genset at Griffin Industries

Objective

The objective of this project was to evaluate the performance of a Cummins/Onan 150KW genset in typical stand-by application in the field. Also to gain additional understanding of all the considerations related to operating a stand-by genset with biodiesel through a complete one year cycle.

Equipment

The genset is a standard unmodified (except for upgrades of external fuel lines and fittings) 150KW Cummins/Onan. The engine is a Cummins C series, 8.3L, six cylinder, with Bosch in-line fuel pump model P3000. Fuel supply is from a 336 gallon tank included in the Onan genset package. All copper connections from tank to fuel pump were replaced by stainless steel.

Test Description

The unit was bought new by Griffin Industries, Cold Spring, KY and was located at their site as back-up electrical power generation, outside in an Onan supplied enclosure. The test ran for one year, May 2002 – June 2003, accumulating 287 hrs of operation. No special maintenance procedures were added beyond standard practice. The unit was visually checked regularly and overall performance recorded, such as start ability, smoke, response, etc. At the end of the test, the pump and injectors were removed and sent to Bosch for evaluation. Regular lube oil analysis was also performed at the Cummins Technical Center.

Fuel

The fuel used in this test was exclusively yellow grease biodiesel blend of B20 (20% biodiesel, 80% 2D), manufactured on site by Griffin Industries. The B100 fuel used to make the blend met the ASTB D6751-02 specification. During the winter months, November thru February, 20% kerosene was missed with the 2D diesel fuel, while the B20 remained constant.

Duty Cycle

The engine operated on a stand0by mode as needed, except for Saturdays, when the engine would run continuously for periods of three to four hours at a load factor of approximately 50%. An average of 25 hrs per month was run by the unit, totaling 287 hours by the end of this test. The engine was also run for approximately 0.5 to 1 hour weekly without load to simulate actual customer exercising.

Results

No performance or reliability/durability issues were detected during the duration of the test. It was observed that the engine ran cleaner than with diesel, particularly in terms of white smoke during start-up on cold mornings. Lube oil analysis results were within normal parameters, except for some oil dilution (4.3%) caused by the biodiesel, detected at 230 hrs operation. This was not believed to be a problem since the dilution level was still below the maximum limit allowed (5%) and an oil change was expected shortly at 250 hrs. It is speculated that the dilution is caused by the multiple starts and short runs of this test.

As mentioned in the Test Description, at the end of the test the fuel pump and injectors were removed and sent to Bosch for analysis. Pump and injectors were tested in a bench and later torn down for evaluation. Overall condition of the fuel system was good. Performance of the components was deemed to be comparable to a pump operating only on diesel fuel. Injector nozzle tips seemed to have slightly more coking than what is characteristic for a pump with 300 hrs of operation time, but this could be related also to the stand-by type of application. Slight camshaft bushing wear was detected but was determined not to be caused by the operation with biodiesel. Only issue of concern detected by Bosch was the removal of the zinc coating on a fuel overflow valve located at one of the ends of the pump, on the main fuel gallery. It could be clearly seen that the coating was removed only on the areas that had contact with the fuel. There was no other damage to the overflow valve or its o ring seal. The coating is typically used to help protect against corrosion and rust from both atmospheric and fuel sources. It is not clear what long term effects may result from coating degradation of the fuel wetted surfaces.

Conclusions

A one year field test of a Cummins/Onan genset in stand-by operation was completed. The unit accumulated 287 hrs of intermittent operation with B20 biodiesel blend fuel. No Performance or reliability/durability issues were identified. An overflow valve in the fuel pump had its zinc coating removed. There is a possibility that the coating material removed could impact the components downstream of the overflow valve, such as the fuel gallery and the pumping elements. Lube oil analysis didn't show any anomalies, except an increase in its dilution due to the biodiesel, although still within acceptable limits by the time of an oil change.

The objectives set for this test were achieved. The genset was evaluated under typical stand-by operation for one year using B20, with positive results. The information obtained in this test serves as additional input in the development of biodiesel compatible power trains. It was not the objective of this test to address long term durability questions.

Acknowledgements: Cummins and Griffin Industries would like to acknowledge the support provided by Cummins Bridgeway (Cummins Distributor), Cummins Power Gen, and Robert Bosch.

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Objective

The objective of this project was to evaluate the performance of a Cummins/Onan 150KW genset in typical stand-by application in the field. Also to gain additional understanding of all the considerations related to operating a stand-by genset with biodiesel through a complete one year cycle.

Equipment

The genset is a standard unmodified (except for upgrades of external fuel lines and fittings) 150KW Cummins/Onan. The engine is a Cummins C series, 8.3L, six cylinder, with Bosch in-line fuel pump model P3000. Fuel supply is from a 336 gallon tank included in the Onan genset package. All copper connections from tank to fuel pump were replaced by stainless steel.

Test Description

The unit was bought new by Griffin Industries, Cold Spring, KY and was located at their site as back-up electrical power generation, outside in an Onan supplied enclosure. The test ran for one year, May 2002 – June 2003, accumulating 287 hrs of operation. No special maintenance procedures were added beyond standard practice. The unit was visually checked regularly and overall performance recorded, such as start ability, smoke, response, etc. At the end of the test, the pump and injectors were removed and sent to Bosch for evaluation. Regular lube oil analysis was also performed at the Cummins Technical Center.

Fuel

The fuel used in this test was exclusively yellow grease biodiesel blend of B20 (20% biodiesel, 80% 2D), manufactured on site by Griffin Industries. The B100 fuel used to make the blend met the ASTB D6751-02 specification. During the winter months, November thru February, 20% kerosene was missed with the 2D diesel fuel, while the B20 remained constant.

Duty Cycle

The engine operated on a stand0by mode as needed, except for Saturdays, when the engine would run continuously for periods of three to four hours at a load factor of approximately 50%. An average of 25 hrs per month was run by the unit, totaling 287 hours by the end of this test. The engine was also run for approximately 0.5 to 1 hour weekly without load to simulate actual customer exercising.

Results

No performance or reliability/durability issues were detected during the duration of the test. It was observed that the engine ran cleaner than with diesel, particularly in terms of white smoke during start-up on cold mornings. Lube oil analysis results were within normal parameters, except for some oil dilution (4.3%) caused by the biodiesel, detected at 230 hrs operation. This was not believed to be a problem since the dilution level was still below the maximum limit allowed (5%) and an oil change was expected shortly at 250 hrs. It is speculated that the dilution is caused by the multiple starts and short runs of this test.

As mentioned in the Test Description, at the end of the test the fuel pump and injectors were removed and sent to Bosch for analysis. Pump and injectors were tested in a bench and later torn down for evaluation. Overall condition of the fuel system was good. Performance of the components was deemed to be comparable to a pump operating only on diesel fuel. Injector nozzle tips seemed to have slightly more coking than what is characteristic for a pump with 300 hrs of operation time, but this could be related also to the stand-by type of application. Slight camshaft bushing wear was detected but was determined not to be caused by the operation with biodiesel. Only issue of concern detected by Bosch was the removal of the zinc coating on a fuel overflow valve located at one of the ends of the pump, on the main fuel gallery. It could be clearly seen that the coating was removed only on the areas that had contact with the fuel. There was no other damage to the overflow valve or its o ring seal. The coating is typically used to help protect against corrosion and rust from both atmospheric and fuel sources. It is not clear what long term effects may result from coating degradation of the fuel wetted surfaces.

Conclusions

A one year field test of a Cummins/Onan genset in stand-by operation was completed. The unit accumulated 287 hrs of intermittent operation with B20 biodiesel blend fuel. No Performance or reliability/durability issues were identified. An overflow valve in the fuel pump had its zinc coating removed. There is a possibility that the coating material removed could impact the components downstream of the overflow valve, such as the fuel gallery and the pumping elements. Lube oil analysis didn't show any anomalies, except an increase in its dilution due to the biodiesel, although still within acceptable limits by the time of an oil change.

The objectives set for this test were achieved. The genset was evaluated under typical stand-by operation for one year using B20, with positive results. The information obtained in this test serves as additional input in the development of biodiesel compatible power trains. It was not the objective of this test to address long term durability questions.

Acknowledgements: Cummins and Griffin Industries would like to acknowledge the support provided by Cummins Bridgeway (Cummins Distributor), Cummins Power Gen, and Robert Bosch.