Abstract
Keywords
(Truck, CVT, Power Take Off, Ratio Control, Constant Speed)
Abstract
This paper presents a novel Power Take Off system for power levels up to 25 kW. The system, intended for the refrigerated distribution truck market, was developed in order to comply with new restrictions concerning exterior noise, fuel consumption and emissions as well as to meet the demand for better performance of refrigeration units. With a Continuously Variable Transmission (CVT) the variable crankshaft speed of the trucks main engine is transformed into a constant speed. A large capacity generator is connected to the CVT and the generated voltage is constant and supplied to the refrigeration unit. This new concept is called the Constant Speed Power Take Off (CS-PTO).
With a specially developed ratio control system, the output speed of the CVT can be controlled within the available ratio coverage of the CVT. This enables optimisation of the rotational speed of the connected generator with respect to required electrical power, overall efficiency and life-span of electrical and mechanical components.
The new CS-PTO concept is developed and tested in the Automotive Laboratory of the Technische Universiteit Eindhoven and used to drive a refrigeration unit of the company Govers ET BV. After successful experimental results, the CS-PTO is implemented on trucks used for distribution of refrigerated goods. By means of the CVT, the generator speed is controlled to a constant value and the electrical power supplied to the refrigeration unit is optimised for maximum refrigeration capacity and noise emission.
As a result of the constant speed of the generator, the refrigeration unit functions at an optimal frequency and generates a constant refrigeration capacity. All components of the refrigeration unit of Govers ET BV function at their optimum, at constant speeds. This results in a constant refrigeration capacity that is always available when the primary diesel engine is running.
The maximum noise emission of the refrigeration unit is caused by high speeds of the compressor and fans. The CS-PTO supplies a constant and optimal frequency to the compressor and fans, resulting in lower speeds and less noise emission. The maximum noise emission of the refrigeration unit was measured and equals 57 dB(A).
The additional engine power required for the refrigeration unit has a positive influence on the fuel consumption. The implemented CS-PTO shows a reduction in fuel consumption of 5.6%, compared with an identical refrigeration unit driven by a generator without CS-PTO.
The CS-PTO proves to be a silent and fuel-efficient solution that is able to guarantee a constant generated refrigeration capacity, when the primary diesel engine of the distribution truck is running. With the new concept the future restrictions concerning fuel-consumption and noise-emission, as well as the increasing demand for a constant refrigeration capacity are met.