Low Temperature Differential Stirling Engine Research Articles

Low temperature differential Stirling engines using displacers moving intermittently

Low temperature differential Stirling engines using displacers moving intermittently

Effect of geometry and speed on the temperatures estimated by CFD for an isothermal model of a gamma configuration low temperature differential Stirling engine with Flat-shaped heat exchangers

In the temperature distribution in a hot-side displacer chamber of a low temperature differential Stirling engine, a relation between the inlet temperature, average temperature and heat exchanger temperature is calculated by CFD and is expressed by the ratio of temperatures. The parameters of the CFD are the inlet velocity; the sizes of the inlet, heat exchanger and displacer; the positions of the inlet, heat exchanger and displacer chamber wall; and the temperatures of the inlet and heat exchanger. The calculation result and the estimated regenerator efficiency produce the temperature difference in the working fluid, which can be utilized for isothermal model analysis. In the Schmidt cycle, only a phase angle and the dimensionless value introduced here dominate the shape of the P-V diagram. The maximum fluctuation of the ensemble averaged working fluid temperatures (MFEAWFTs) is utilized to evaluate a P-V diagram. When the analyses are compared with experimental results, estimated MFEAWFTs are approximately 80% of the experimental results. In comparing the calculation results, a higher engine speed causes a lower average temperature on the hot side of a displacer chamber and the larger indicated power. A wider inlet reduces the difference between inlet temperature and average temperature. The longer stroke of displacer motion makes the indicated work larger to some extent.

Indicated diagrams of low temperature differential Stirling engines with channel-shaped heat exchangers

The low temperature differential Stirling engine with channel-shaped heat exchangers and regenerators achieved approximately 5 times the indicated power per a stroke volume of displacer of the cases using flat-shaped heat exchangers. The ratio of the maximum fluctuation of ensemble averaged working fluid temperatures, which is the ratio of the internal energy fluctuation to the heat capacity of the working fluid, to the temperature difference between the two heat exchangers in cases using flat-shaped heat exchangers was 0.08–0.09, that in cases using channel-shaped heat exchangers was 0.10–0.17, and that in case using channel-shaped heat exchangers and regenerators was 0.21. The improvement in the experiments is lower than the estimation by the CFD. In terms of the polytropic index, low temperature differential Stirling engines with channel-shaped heat exchangers and regenerators obtained a higher value than low temperature differential Stirling engines with flat-shaped heat exchangers before the displacer reached the dead center.

A study on the effects of geometric parameters in a low-temperature-differential γ-type Stirling engine using CFD

This study conducts a parametric investigation on a γ-type low temperature differential Stirling engine (LTDSE) using CFD. The effects on engine performance posed by four geometrical parameters namely phase angle between power piston and displacer, gap width between displacer and displacer cylinder, length of displacer, and length of power piston linkage bar, are systematically examined. One crucial advantage of using CFD is that temperature and velocity vector fields in engine space can be obtained, allowing important physical processes to be studied in great detail. Then the physical mechanisms through which a parameter affects engine performance can be identified. It is found that all four parameters are quite influential on engine performance despite that they are of little effect on the magnitude of engine’s compression ratio. Within the ranges of parameters examined here, they affect engine performance by margins up to 32% on indicated power and 13% on efficiency. The results highlight the importance of every geometrical parameter on overall engine performance, and the information concluded in this study is very useful for the design of a new LTDSE.

低温度差スターリングエンジンの工作教室を準備するための治具とテンプレート

低温度差スターリングエンジンの工作教室を準備するための治具とテンプレート

B-03 低温度差スターリングエンジンの工作教室で使う部品の工作

B-03 低温度差スターリングエンジンの工作教室で使う部品の工作

B-02 コの宇型伝熱面と再生器を用いた低温度差スターリングエンジンの数値計算

B-02 コの宇型伝熱面と再生器を用いた低温度差スターリングエンジンの数値計算

工作教室で用いる模型低温度差スターリングエンジンのリンク機構における誤差と遊び

工作教室で用いる模型低温度差スターリングエンジンのリンク機構における誤差と遊び

コの字型伝熱面と再生器を備えた低温度差スターリングエンジンの死容積低減

コの字型伝熱面と再生器を備えた低温度差スターリングエンジンの死容積低減

低温度差スターリングエンジンにおけるコの字型伝熱面の数値解析

低温度差スターリングエンジンにおけるコの字型伝熱面の数値解析

Design, Manufacture and Measurements of Beta-Type Stirling Engine with Rhombic Drive Mechanism

The purpose of carrying out present work is to design, build and test a rhombic drive Stirling engine with a β-type configuration consisting of two dynamic pistons (displacer and power) reciprocates in the in-line concentric cylinder arrangement. The displacement rod is assembled concentrically inside the power piston rod. The rhombic drive mechanism is proposed in such a way that, by using a pair of gear wheels the sliding motion of both piston rods is controlled and thus, an engine is balanced. The developed prototype has a swept volume of 75 cm3 with the displacer piston and power piston cylinder hot ends heated by liquefied petroleum gas (LPG) burner and cooled water, respectively. It uses air as the working gas at atmospheric pressure for initial charging of the engine. Several designs were studied before settling on a β-type configuration. The LPG gas burner was considered as a potential heat source. The various elements of an engine (heater, cooler, re-generator, flywheel and piping systems) were designed, constructed and analyzed. The testing results revealed that the engine at initial atmospheric air filling started working in only about 120 seconds at an LPG heater temperature of 400℃ (824°F) with 280 rpm. At a heater temperature of 550℃ (1022°F), the engine speed was 630 rpm. At the engine speed of 245 rpm, the maximum torque was 0.215 Nm, while the maximum power was 8 Watts at 355 rpm. Engine speed increased with the increase of flame temperature. Several tests were performed on the engine to improve its running efficiency and critical problem areas were isolated and addressed. Moreover, results revealed that Stirling engines working with relatively low-temperature air are potentially attractive engines of the future, especially LPG powered low temperature differential Stirling engines. The Stirling engine was capable of generating between 50 to 100 Watts of electricity.

ガンマ型低温度差スターリングエンジンのサイクル中の負のトルクを抑制するリンク機構

ガンマ型低温度差スターリングエンジンのサイクル中の負のトルクを抑制するリンク機構

A CFD parametric study on the performance of a low-temperature-differential γ-type Stirling engine

An in-house CFD code has been applied to a low-temperature-differential (LTD) γ-type Stirling engine to understand the effects posed by several geometrical and operational parameters on engine performance. The results include variations of pressure, temperature, and heat transfer rates within an engine cycle as well as variations of engine’s power and efficiency versus these parameters. It is found that power piston stroke and radius influence engine performance very similarly, and power and efficiency both increase as these two parameters increase. In fact, the effects of the two parameters can be assimilated into those by the parameter of compression ratio. The stroke of displacer is observed to affect strongly on heat input but weakly on power, thus causing the efficiency to decrease as it increases. As expected, both power and efficiency increase as temperature difference between the hot and cold ends increases. Lastly, engine speed is observed to pose strong positive effects on power but exert weak effects on efficiency. This study reveals the effects produced by several important parameters on engine performance, and such information is very useful for the design of new LTD Stirling engines.

Indicated diagrams of a low temperature differential Stirling engine using flat plates as heat exchangers

Indicated diagrams of a low temperature differential (LTD) Stirling engine (SE) were obtained. The evaluation of LTDSE performance was carried out using the results. The heat source temperatures were 75, 80, 85, 90 and 95° Celsius. The working fluid was air with a mean pressure of atmospheric pressure. The shape of the heat exchangers was flat. The stroke volume of the power piston was 3.9 cc, and the stroke volume of the displacer was 238 cc. The LTDSE did not have any regenerators. The maximum indicated power was 3.34 mW. The polytropic exponents becomes larger than 1.4 before the displacer reached dead center, and the working fluid temperatures fluctuated. These behaviors suggest that the heat exchanger did not work effectively. The evaluation of LTDSE performance was carried out using “the maximum fluctuation of ensemble averaged working fluid temperature”. The value is the fluctuation of the internal energy per the heat capacity, and has dimensions of temperature. The obtained values were from 3.2 to 4.7 °C. The comparison of these values with actual temperature differences suggests that the indicated work of conventional LTDSE was much lower than the thermodynamic upper limit.

스프레이 열전달을 이용한 저온도차 스털링 엔진의 고온수 공급 유량 및 온도에 따른 기계 부하성능 실험

스프레이 열전달을 이용한 저온도차 스털링 엔진의 고온수 공급 유량 및 온도에 따른 기계 부하성능 실험

T01 コの字型伝熱面と再生器を用いた低温度差スターリングエンジン(模型スターリングエンジン並びに教材用熱音響機器(1))

T01 コの字型伝熱面と再生器を用いた低温度差スターリングエンジン(模型スターリングエンジン並びに教材用熱音響機器(1))

T08 運動方程式を用いた低温度差スターリングエンジンの機関回転数推定(模型スターリングエンジン並びに教材用熱音響機器(2))

T08 運動方程式を用いた低温度差スターリングエンジンの機関回転数推定(模型スターリングエンジン並びに教材用熱音響機器(2))

T02 コの字型伝熱面の形状が低温度差スターリングエンジンの性能に与える影響(模型スターリングエンジン並びに教材用熱音響機器(1))

T02 コの字型伝熱面の形状が低温度差スターリングエンジンの性能に与える影響(模型スターリングエンジン並びに教材用熱音響機器(1))

C201001 16人限定低温度差模型スターリングエンジン組立体験

C201001 16人限定低温度差模型スターリングエンジン組立体験

Study of Some Power Influencing Parameters of a Solar Low Temperature Stirling Engine

The aim of this paper is to study experimentally and theoretically the effect of some geometrical parameters on low temperature differential Stirling engines (LT-SE) performance. The studied parameters are: the phase angle, the compression ratio and the dead volume. Results show that for optimizing the performance of these engines, dead volume should be minimized, the compression ratio should be maximized and the optimal phase angle for the gamma type is 90°. For the adopted theoretical model, based on Schmidt theory, even if theoretical numerical results are different from those found experimentally, but it still remains a valid model for finding out some parameters effect on the LT-SE performance, and for calculating approximately the engine work and power. Key words : Stirling engine, low temperature, Solar, Phase angle, compression ratio, dead volume.