Frictional and Internal Leakage Losses in Rotary-Vane Two-Phase Refrigerating Expanders

Mahmoud, Ahmad M.; Sherif, S. A.; Lear, W. E.

doi:10.1115/1.4001571

Cited by 12 publications

(11 citation statements)

References 2 publications

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“…The isentropic efficiencies of such expanders are in the range of 45-80%. The lower values of efficiencies and power outputs are due to operational losses such as leakage friction loss and leakage [161]. As can be seen in Kolasinski et al [136], presented in Figure 8, the isentropic efficiency is a flat curve over a wide range of operating conditions.…”

Section: Performance Of Positive Displacement Expandersmentioning

confidence: 77%

Expander Technologies for Automotive Engine Organic Rankine Cycle Applications

Alshammari

Karvountzis-Kontakiotis

Pesyridis

et al. 2018

Energies

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The strive towards ever increasing automotive engine efficiencies for both diesel and gasoline engines has in recent years been forced by ever-stringent emissions regulations, as well as the introduction of fuel consumption regulations. The untapped availability of waste heat in the internal combustion engine (ICE) exhaust and coolant systems has become a very attractive focus of research attention by industry and academia alike. Even state of the art diesel engines operating at their optimum lose approximately 50% of their fuel energy in the form of heat. As a result, waste heat recovery (WHR) systems have gained popularity as they can deliver a reduction in fuel consumption and associated CO2 emissions. Of these, the Organic Rankine Cycle (ORC) is a well matured waste heat recovery technology that can be applied in vehicle powertrains, mainly due to the low additional exhaust backpressure on the engine and the potential opportunity to utilize various engine waste heat sources. ORCs have attracted high interest again recently but without commercial exploitation as of today due to the significant on-cost they represent to the engine and vehicle. In ORCs, expansion machines are the interface where useable power production takes place; therefore, selection of the expander technology is directly related to the thermal efficiency of the system. Moreover, the cost of the expander-generator units accounts for the largest proportion of the total cost. Therefore, selection of the most appropriate expander is of great importance at the early stage of any automotive powertrain project. This study aims to review the relevant research studies for expansion machines in ORC-ICE applications, analyzing the effects of specific speed on expander selection, exploring the operational characteristics of each expander to further assist in the selection of the most appropriate expander, and comparing the costs of various expanders based on publically available data and correlations.

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Section: Performance Of Positive Displacement Expandersmentioning

confidence: 77%

Expander Technologies for Automotive Engine Organic Rankine Cycle Applications

Alshammari

Karvountzis-Kontakiotis

Pesyridis

et al. 2018

Energies

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“…According to conditions for dynamic equilibrium under constant rotational speed, the independent reacting forces can be solved through the following equations 11,19 …”

Section: Simulation Modelmentioning

confidence: 99%

“…Therefore, they can be easily combined as a single inertia force. 11 However, it should be noted that such combination is valid only for radially assembled vanes, otherwise, Fe and Fr would not act along the same line. Note also that the direction of some forces need to be adjusted according to whether the considered vane is extending out of or moving back into the slot, especially the direction of frictional forces between vane and slot.…”

Section: Simulation Modelmentioning

confidence: 99%

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Comparison between modeling and experiments on a two-stage rotary vane expander for an HFC-410A air conditioning system

Wang

Cao

Zhao

et al. 2013

Proceedings of the Institution of Mechanical Engineers, Part A:

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Substituting throttle valve with expander can effectively enhance the performance of a refrigeration system. A novel rotary vane expander with two-stage internal expansion was developed for HFC-410A air conditioning system. The structural characteristics and operating principle of the expander are presented. A simulation model including thermodynamic and dynamic calculations is established. An HFC-410A air conditioning system was built for the purposes of testing the prototype and verifying the model. Through the experimental results, the maximum volumetric efficiency was 55% at 1800 r/min and the maximum isentropic efficiency of the prototype was 31.5% at 1404 r/min. The maximum improvement in the system coefficient of performance was 10.3% at 1404 r/min, in comparison with the coefficient of performance without the expander. Higher rotational speed could reduce leakage time thus improve volumetric efficiency; however, it also generated more frictional loss that eventually deteriorated the expander performance. Properly increasing the condensation pressure could help reducing frictional loss at high speed, thus further improve the overall performance of the expander. The results also show that the expander has a better adaptability to variable operating conditions at high rotational speed.

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“…19 Rotary vane expander, which has similar structure with RVC, is usually used to replace the throttle valve to improve efficiency in refrigeration and air-conditioning fields, especially in CO 2 refrigeration systems. [20][21][22] Several studies [23][24][25][26][27][28][29] on rotary vane expanders were conducted.…”

Section: Introductionmentioning

confidence: 99%

Profile design for the cylinder of a double-acting rotary vane compressor

Song

Zeng

Zhou

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part C:

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Inner wall profile of the cylinder in a rotary vane compressor (RVC), which influences the motion characteristics of vanes, suction volume, friction characteristic, etc., plays an important role in the performance of the compressor. This work mainly aims at the profile design of a new cylinder for a double-acting RVC with harmonic profile cylinder on the basis of not changing integrate size. According to the relation between cylinder profile and vane motion characteristics, a method for the cylinder profile design is proposed in this paper. With an assumed vane motion, equations of the cylinder profile, cell volume of the compressor as well as pressure angles between vanes and cylinder inner wall are constructed preliminarily. And then through adjusting parameters and optimization with an independently developed procedure, a new cylinder with the so-called combined profile is obtained. Theoretical analysis of the cell volume variations and the pressure angles between vanes and cylinder are conducted. The results show that there is neither rigid impulse nor soft impulse between vanes and cylinder due to the vane continuous motion including displacement, velocity and acceleration. And the pressure angles between vane and cylinder and working volume of the compressor with the new profile cylinder are superior to harmonic profile cylinder, which is useful for the reduction of friction power in the operation of compressor. Experiments show that the cooling capacity and COP of the test refrigeration cycle with the proposed combined profile cylinder is higher than the compressor with harmonic profile cylinder. And the volumetric efficiency and isentropic efficiency of the compressor with combined profile cylinder have better performance. This method can be applied to the design of the cylinder for multiple-acting rotary vane compressors, rotary vane expanders and vane pumps.

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Frictional and Internal Leakage Losses in Rotary-Vane Two-Phase Refrigerating Expanders

Cited by 12 publications

References 2 publications

Expander Technologies for Automotive Engine Organic Rankine Cycle Applications

Expander Technologies for Automotive Engine Organic Rankine Cycle Applications

Comparison between modeling and experiments on a two-stage rotary vane expander for an HFC-410A air conditioning system

Profile design for the cylinder of a double-acting rotary vane compressor

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