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Biodiesel is a renewable and environmentally friendly alternative fuel derived from natural fats or vegetable oils and it is considered as an attractive alternative to replace diesel fuels. To optimize the application of biodiesel on vehicle diesel engines, the power and fuel economies performances of a diesel fueled with soybean biodiesel were investigated under different engine loads and speeds. Experimental results show that, compared with diesel fuel, with increase in the biodiesel in the blends, the brake power and torque and the brake specific energy consumption increase, the smoke density under free acceleration decreases except B10, the NO X emissions increase. The trade-off relationship is clear between the NO X and smoke density when the diesel engine fueled with different biodiesel percentage in the blends. From the trade-off relationship between NO X and smoke density, the optimum blend ratio is B20 in the experimental study.

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Compressed air energy storage system has the advantages of high reliability, low cost, flexible layout, and negligible environmental impact. Meanwhile, the low efficiency of compressed air energy storage system is a key obstacle currently faced by researchers all around the world. Compressor and expander are the key components of compressed air energy storage system; thus, their efficiency directly affects the compressed air energy storage system efficiency. In order to improve the economic performance of compressed air energy storage system, this study proposes an expander/compressor integration based on pneumatic motor. The overall performance of the compressor under dynamic conditions, which are represented by the pressure change of the air tank and the load fluctuation, is investigated through experiments. The effect of torque, air tank pressure, mass flow rate, and rotating speed on compressor power consumption and energy conversion efficiency are studied. The experimental results show that the power consumed by the compressor increases with the increasing of torque, air tank pressure, mass flow rate, and rotating speed. When the rotation speed is 2700 r/min and the torque is 4 N·m, the work consumed by the compressor reaches the maximum value of approximately 1095 W. The maximum energy efficiency value of η1, η2, η3, and η4 are approximately 73.7%, 90%, 56.8%, and 52%, respectively.

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