Diesel Prime Movers
There are several reasons for someone wanting to prime his refrigerating compressor directly with a diesel engine. There may be no electric power available on the site or the supply may be insufficient or unreliable - or simply too expensive. In applications of industrial dimensions, diesel - or natural gas - prime movers sometimes offer substantial savings in the operating expences and may in some cases mean the difference between a company being competitive or not.
RPE Units (Refrigeration-Power-Electricity)The unit pictured below consists a GRASSO RC69 reciprocating compressor for refrigerant R717, directly coupled over a Twin Disc disengaging clutch to the flywheel end of a Daimler Benz 120 kW diesel engine. At the back, a 35 kVA Brush electric alternator, driven off the engine's front end, powers auxilliary motors in the plant (pumps, fans, conveyors etc). Select the picture above for an enlarged view of two packages with air cooled Deutz diesel engines. A typical enlarged view of a Daimler Benz diesel engine and a Twin Disc disengaging clutch.
The picture below displays a similar unit from the other side, thus emphasizing the diesel engine and the alternator. These particular units - shown in the pictures above and below - have a capacity to produce 25 (twenty-five) metric tonnes of block ice in twenty-four hours under tropical conditions. Select the picture below for an isometric view of a diesel powered screw compressor package.
Economy and Efficiency
The picture on the left (below) shows a conventional set-up, where the compressor-motor package (blue and beige) receives electric power from a diesel generating set (red and beige) via electric switch gear (green). There are 10% losses in the alternator (generator) and another 10% losses in the electric motor, totalling 20% electric losses in this set-up.
The picture on the right (above) shows the alternator (generator), the switch gear and the motor pale or 'albino' coloured; they have been idled and the compressor is now directly driven from the diesel engine (shaft-to-shaft), thus increasing the fuel economy by 20%.
RMPE Units (Refrigeration-Motor-Power-Electricity)
Stand-by Diesel Power Unit
The picture below shows a conventional reciprocating compressor (Bitzer) directly coupled to an electric motor (TECO). The motor has a second shaft end at the rear, to which an air cooled diesel engine (Lombardini) is coupled via a manual disengaging clutch on the flywheel end. An electric alternator (Brush) is driven off the front end of the diesel engine.
The last picture (above) shows an RMPE set-up with a BOCK F16 compressor-motor package driven with a V-belt drive from a diesel-alternator package on slide rails. Two such set-ups were recently delivered for a 20 mTon/24 block ice plant in Mullaittivu, Sri Lanka.
Normally, the compressors would be primed with the electric motors. In case of a power failure, or to save on the power cost, the diesel engines can drive the compressor directly - through the shaft of the electric motor - and generate electricity for auxilliary motors in the plant (pumps, fans etc) at the same time.
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Last updated: Monday 10/07/06 6:16