Engines have to be matched to their load for efficient operation, in particular it is critical for diesel engines to operate near heavy load. Diesels suffer from a phenomenon referred to as “wet stacking”. This occurs when a diesel is operated at light loads preventing optimized operational temperature. Without sufficient heat, fuel collects in the exhaust system. This manifests itself as wet discharge from the exhaust, being unburned fuel. This build up of excess fuel clogs fuel injectors, creates deposits around the exhaust valves and inside turbochargers shortening engine life and efficiency.
Diesel Generator Low Operational Heat
Low operational heat doesn’t allow the piston rings to seat properly, causing fuel and gas leaks into the crankcase and oil pan. This causes emissions and thins the lubricating oil. All this leads to premature engine failure, higher polluting emissions, reduced power, excessive fuel consumption and higher maintenance.
Excess Diesel is Flammable & a Fire Hazard
With excess fuel, though diesel is hard to ignite, a fire hazard may exist. The National Fire Protection Association (NFPA) issues guidelines for diesel powered electrical generation equipment. Monthly they should be run at 30% or more of the engine power source (EPS) power rating for 30 minutes. Next to sustained loading to maintain the minimum exhaust temperature as per the engine manufacturer. The trick is to run the system to 75% load to reach effective operating temperatures. Two smaller units, one acting as a primary and the other as the auxiliary would provide loads so as to maintain optimum operating efficiency.
Diesel Engine RPM Range
The thing to remember is that an EPS needs to maintain the same rpm (revolutions per minute) to generate a steady 60 Hz cycle that is the U.S. standard for A/C power. Regardless of load, the engine governor maintains the engine rpm to provide the proper power. After running at light load and then having the load and temperature go up, the residual oil burns producing clouds of black smoke. Natural and LPG engines do not suffer from this problem, and the primary reason so many emergency power units are fueled by these spark ignition engines. Diesels are used because under normal load and operating temperature they are more efficient at converting fuel to usable power output. Diesels typically convert 45% of the potential chemical energy into mechanical energy compared to only 30% for gasoline engines.
Diesel Generator Thermal Efficiency
This efficiency derives from the high compression ratio creating a high expansion ratio and the diesels inherent lean burn of the fuel. This creates a high thermal efficiency; in some marine engines this thermal efficiency exceeds 50%. Thermal efficiency is the amount of heat generated by combustion in doing work versus wasted heat due to friction and heat loss through the exhaust and cooling systems. As diesel fuel has a higher density (heavier per gallon) coupled with efficient combustion diesels tend to be more effective and economical than their spark ignition cousins. However it is incumbent upon the diesel operator to maintain loads at the proper operating temperature.
Diesel Generators for Lease, Rent or Sale
Diesel technology is well over 100 years old and much has been learned in that time. Modern diesels using electronic fuel injection and management coupled with effective turbochargers have raised the bar for compression ignition engines. Contact Environmental Power Solutions to learn more about our clean diesel generators.