## 1 Introduction  
Energy consumption has greatly contributed to the promotion of human development and progress. However, its waste emission brings more and more serious environmental pollution and ecological destruction simultaneously. Waste heat recovery and low-grade heat utilization are important measures to solve the problems brought by energy consumption. The organic Rankine cycle (ORC), which applies the principle of the steam Rankine cycle but uses organic working fluidswith low boiling points, is a very promising technique used for waste heat recovery. The group of [PERSON] and [PERSON] [1] focused on both the thermodynamic and economic optimization of a small scale ORC in waste heat recovery application. The working fluids they considered include R245 fa, R123, n-butane, n-pentane, R1234 yf and Solkatherm. They also carried out experimental study using scroll expander and using R123 [2] and R245 fa [3]. The group of [PERSON] conducted much research on ORC configuration optimization [4; 5; 6] and experimental performance [7]. The group of [PERSON], [PERSON], and [PERSON] used isobutane/isopentane and R227 ea/R245 fa as working fluids in ORC for low-enthalpy geothermal resources [8] and conducted a thermoeconomic analysis [9]. They also carried out an experimental characterization and comparison of axial and cantilever micro-turbines for small-scale ORC [10]. Many papers focus on internal combustion engine (ICE) waste heat recovery using ORC technique [11; 12; 13; 14; 15; 16; 17]. Cycle configurations [11; 12; 16; 17], fluids [14; 15] and parameters optimization [13; 14; 15] are usually discussed and analyzed in these papers. However, there are few reports on test bench or experimental system used for ICE waste heat recovery based on ORC technique. Among the four devices making up an ORC, the expander is the critical component because it determines the efficiency and cost of an ORC. Expanders, in general, can be categorized into two types: the velocity type and the volume type. The popular axial turbine expanders belong to the former type while the latter type includes screw expanders, scroll expanders and reciprocal piston expanders [18]. [PERSON] et al. [19] developed a compact ORC system using a compact rotary-vane-type expander for low-temperature waste heat recovery. Approximately 30 W of expander power output with 48% expander efficiency was achieved. [PERSON] et al. [20] conducted experimental and numerical analyses on the rotary vane expander in a micro ORC system. They indicated that a properly designed multi-vane expander is a cheap and mechanically simple alternative to other expansion devices proposed for domestic ORC systems [21]. The group of [PERSON] and [PERSON] [2; 3] modified a scroll compressor to an expander and conducted experimental studies. Measured performance on the prototype is very promising in a wide range of operating conditions. The maximum shaft power is 2.1 kW and maximum achieved isentropic efficiency is 75.7% [3]. [PERSON] and [PERSON] [22] carried out a detailed review on the expander used in ORC. They summarized the prototype research on various types of expansion machines. They also made a comparison of various types of expanders suitable for ORC system. According to the power capacity, radial-inflow turbine is maximum, which is suitable for the large capacity system. For volume type expander, screw and reciprocating piston expanders can also output relatively high power, which can be applied to small- and medium-sized systems. The capacity of scroll and rotary vane expander is minimum, generally applied in small- or micro-ORC systems. In general, the selection of expansion machines should consider many factors, such as the power capacity, isentropic efficiency, cost, complexity, etc., and different expansion machines have their own applicable scope so that reasonable selection is based on system operation and working conditions. In ORC, organic working fluid plays a decisive role.