The investigation of the effect of thermal barrier coating on the performance of Stirling engine

The shuttle heat transfer is one of the reasons reducing the performance of Stirling engines. This study is concerned with the reduction in shuttle heat transfer by coating the displacer. The displacer of a gamma type Stirling engine was coated with a layer of yttria‐stabilized zirconia (YSZ), and the effect of the coating on the engine performance was evaluated by comparing speed‐power and speed‐torque characteristics of the engine with coated and uncoated displacers. Characteristics were obtained for 700, 800 and 900°C heater temperatures. At each stage of the heater temperature, the charge pressure ranged from 1 to 3.5 bars with 0.5 bar increments. At 900°C heater temperature and 3 bars charge pressure, the shaft power before coating was 34.9 W, after coating the power increased to 43.8 W, which corresponds to a 25% increment. The temperature applied to the engine did not cause any damage on the coating layer. Copyright © 2008 John Wiley & Sons, Ltd.     

Investigation on power output of the gamma-configuration low temperature differential Stirling engines

This paper provides a study on power output determination of a gamma-configuration, low temperature differential Stirling engine. The former works on the calculation of Stirling engine power output are discussed. Results from this study indicate that the mean pressure power formula is most appropriate for the calculation of a gamma-configuration, low temperature differential Stirling engine power output.     

A four power-piston low-temperature differential Stirling engine using simulated solar energy as a heat source

In this paper, the performances of a four power-piston, gamma-configuration, low-temperature differential Stirling engine are presented. The engine is tested with air at atmospheric pressure by using a solar simulator with four different solar intensities as a heat source. Variations in engine torque, shaft power and brake thermal efficiency with engine speed and engine performance at various heat inputs are presented. The Beale number obtained from the testing of the engine is also investigated. The results indicate that at the maximum actual energy input of 1378 W and a heater temperature of 439 K, the engine approximately produces a maximum torque of 2.91 N m, a maximum shaft power of 6.1 W, and a maximum brake thermal efficiency of 0.44% at 20 rpm.     

Performance of a twin power piston low temperature differential Stirling engine powered by a solar simulator

This paper provides an experimental investigation on the performance of a low-temperature differential Stirling engine. In this study, a twin power piston, gamma-configuration, low-temperature differential Stirling engine is tested with non-pressurized air by using a solar simulator as a heat source. The engine testing is performed with four different simulated solar intensities. Variations of engine torque, shaft power and brake thermal efficiency with engine speed and engine performance at various heat inputs are presented. The Beale number, obtained from the testing of the engine, is also investigated. The results indicate that at the maximum simulated solar intensity of 7145 W/m², or heat input of 261.9 J/s, with a heater temperature of 436 K, the engine produces a maximum torque of 0.352 N m at 23.8 rpm, a maximum shaft power of 1.69 W at 52.1 rpm, and a maximum brake thermal efficiency of 0.645% at 52.1 rpm, approximately.     

Experimental investigations of a gamma Stirling engine

The present work deals with the measurement and performance of a gamma Stirling engine of 500 W of mechanical shaft power and 600 rpm of maximal revolutions per minute. Series of measurements concerning the pressure distribution, temperature evolution, and brake power were performed. The study of the different functioning parameters such as initial charge pressure, engine velocity, cooling water flowrate, and temperature gradient (between the sources of heat) has been analyzed. The engine brake power increases with the initial charge pressure, with the cooling water flow, and with the engine revolutions per minute. The working fluid temperature measurements have been recorded in different locations symmetrically along both regenerator sides. The recorded temperature in regenerator side one is about 252 °C and about 174 °C in the opposite side (side two). It shows an asymmetric temperature distribution in the Stirling engine regenerator; consequently, heat transfer inside this porous medium is deteriorated. Copyright © 2011 John Wiley & Sons, Ltd.     

The effect of displacer material on the performance of a low temperature differential Stirling engine

In this study, a gamma‐type low temperature differential Stirling engine was designed and manufactured. The displacer and piston of the engine were concentrically situated to each other. The engine was tested by using a liquefied petroleum gas burner at laboratory conditions. The working fluid was ambient air at atmospheric pressure. Test procedure intended to investigate the speed‐torque and speed‐power characteristics of the engine depending on the hot‐end temperature. Two different displacers made of aluminum alloy and medium density fiberboard were used. The maximum torque and power obtained were 0.166 Nm at 125 rpm speed and 3.06 W at 215 rpm speed, respectively, at 160 °C hot‐end temperature with medium density fiberboard displacer. Copyright © 2011 John Wiley & Sons, Ltd.     

Manufacturing and testing of a gamma type Stirling engine

In this study, a gamma type Stirling engine with 276 cc swept volume was designed and manufactured. The engine was tested with air and helium by using an electrical furnace as heat source. Working characteristics of the engine were obtained within the range of heat source temperature 700–1000 °C and range of charge pressure 1–4.5 bar. Maximum power output was obtained with helium at 1000 °C heat source temperature and 4 bar charge pressure as 128.3 W. The maximum torque was obtained as 2 N m at 1000 °C heat source temperature and 4 bar helium charge pressure. Results were found to be encouraging to initiate a Stirling engine project for 1 kW power output.     

Application of the multi-objective optimization method for designing a powered Stirling heat engine: Design with maximized power,thermal efficiency and minimized pressure loss

In the recent years, numerous studies have been done on Stirling cycle and Stirling engine which have been resulted in different output power and engine thermal efficiency analyses. Finite speed thermodynamic analysis is one of the most prominent ways which considers external irreversibilities. In the present study, output power and engine thermal efficiency are optimized and total pressure losses are minimized using NSGA algorithm and finite speed thermodynamic analysis. The results are successfully verified against experimental data.     

An experimental study on the development of a β-type Stirling engine for low and moderate temperature heat sources

In this study, a β-type Stirling engine was designed and manufactured which works at relatively lower temperatures. To increase the heat transfer area, the inner surface of the displacer cylinder was augmented by means of growing spanwise slots. To perform a better approach to the theoretical Stirling cycle, the motion of displacer was governed by a lever. The engine block was used as pressurized working fluid reservoir. The escape of working fluid, through the end-pin bearing of crankshaft, was prevented by means of adapting an oil pool around the end-pin. Experimental results presented in this paper were obtained by testing the engine with air as working fluid. The hot end of the displacer cylinder was heated with a LPG flame and kept about 200 °C constant temperature throughout the testing period. The other end of the displacer cylinder was cooled with a water circulation having 27 °C temperature. Starting from ambient pressure, the engine was tested at several charge pressures up to 4.6 bars. Maximum power output was obtained at 2.8 bars charge pressure as 51.93 W at 453 rpm engine speed. The maximum torque was obtained as 1.17 Nm at 2.8 bars charge pressure. By comparing experimental work with theoretical work calculated by nodal analysis, the convective heat transfer coefficient at working fluid side of the displacer cylinder was predicted as 447 W/m² K for air. At maximum shaft power, the internal thermal efficiency of the engine was predicted as 15%.     

Torque and power characteristics of a helium charged Stirling engine with a lever controlled displacer driving mechanism

This study presents test results of a Stirling engine with a lever controlled displacer driving mechanism. Tests were conducted with helium and the working fluid was charged into the engine block. The engine was loaded by means of a prony type micro dynamometer. The heat was supplied by a liquefied petroleum gas (LPG) burner. The engine started to run at 118 °C hot end temperature and the systematic tests of the engine were conducted at 180 °C, 220 °C and 260 °C hot end external surface temperatures. During the test, cold end temperature was kept at 27 °C by means of water circulation. Variation of the shaft torque and power with respect to the charge pressure and hot end temperature were examined. The maximum torque and power were measured as 3.99 Nm and 183 W at 4 bars charge pressure and 260 °C hot end temperature. Maximum power corresponded to 600 rpm speed.     

1.2 kW beta type Stirling engine with rhombic drive mechanism

Because of some advantages such as higher theoretical thermal efficiency, lower pollutant release, working with lower noisy, working with any kind of thermal energy, and having longer life time, Stirling engines receive attentions of academic workers. The development studies related to the drive mechanism as well as the other components of Stirling engine are progressing. In the present study, a beta type Stirling engine with a rhombic‐drive mechanism was manufactured and tested. Tests were performed at hot end temperatures of 600 and 800°C for five different stages of charge pressure ranging from 1 to 5 bar with 1 bar increments. Torque and power characteristics of the engine were deduced. The maximum engine torque and power were obtained as 18 Nm and 1215 W at engine speeds of 612 and 722 rpm, respectively, at 4 bar charging pressure. The cyclic work generations of the engine, which is an important parameter indicating the engine performance, were determined as 19, 27, and 25 J corresponding to 1, 3, and 5 bar charging pressures, respectively. In the experiments, the cylinder pressure variation was also measured at various charging pressures. While the charge pressure increases from 1 to 5 bar, the location of the maximum cylinder pressure ranged from 86° to 74° of crankshaft angle, which may have a bit influence on the engine performance. Copyright © 2017 John Wiley & Sons, Ltd.     

Design and performance optimization of GPU-3 Stirling engines

To increase the performance of Stirling engines and analyze their operations, a second-order Stirling model, which includes thermal losses, has been developed and used to optimize the performance and design parameters of the engine. This model has been tested using the experimental data obtained from the General Motor GPU-3 Stirling engine prototype. The model has also been used to investigate the effect of the geometrical and physical parameters on Stirling engine performance and to determine the optimal parameters for acceptable operational gas pressure. When the optimal design parameters are introduced in the model, the engine efficiency increases from 39% to 51%; the engine power is enhanced by approximately 20%, whereas the engine average pressure increases slightly.     

Analytical model for predicting the effect of operating speed on shaft power output of Stirling engines

This paper is concerned with numerical predictions of relationship between operating speed and shaft power output of Stirling engines. Temperature variations in expansion and compression spaces as well as the shaft power output corresponding to different operating speeds were investigated by using a lumped-mass transient model. Effects of major operating parameters on power output were studied. Results show that as the operating speed increased, temperature difference between the expansion and compression spaces was reduced and as a result, the shaft work output decreased. However, the shaft power output is determined in terms of the shaft work output and the operating speed. When the operating speed was elevated, the shaft power output reached a maximum at a critical operating speed. Over the critical operating speed, the shaft power output decreased in high-speed regime. In addition, as air mass was reduced, either a decrease in thermal resistances or an increase in effectivenesses of the regenerator leads to an increase in the engine power.     

Optimum absorber temperature of a once-reflecting full conical concentrator of a low temperature differential Stirling engine

This paper provides a theoretical investigation on the optimum absorber temperature of a once-reflecting full conical concentrator for maximizing overall efficiency of a solar-powered low temperature differential Stirling engine. A mathematical model for the overall efficiency of the solar-powered Stirling engine is developed. The optimum absorber temperature for maximum overall efficiency for both limiting conditions of maximum possible engine efficiency and maximum possible engine power output is determined. The results indicated that the optimum absorber temperatures calculated from these two limiting cases are not significantly different. For a given concentrated solar intensity, the maximum overall efficiency characterized by the condition of maximum possible engine power output is very close to that of the real engine of 55% Carnot efficiency, approximately.     

Design and performance of a moderate temperature difference Stirling engine

The present work developed a prototype Stirling engine working at the moderate temperature range. This study attempts to demonstrate the potential of the moderate temperature Stirling engine as an option for the prime movers for Concentrating Solar Power (CSP) technology. The heat source temperature is set to 350–500 °C to resemble the temperature available from the parabolic trough solar collector. This moderate temperature difference allows the use of low cost materials and simplified mechanical designs. With the consideration of local technological know how and manufacturing infrastructure, this development works with a low charged pressure of 7 bar and uses air as a working fluid. The Beta-type Stirling engine is designed and manufactured for the swept volume of 165 cc and the power output of 100 W. The performance of engine is evaluated at different values of charge pressures and wall temperatures at the heater section. At 500 °C and 7 bar, the engine produces the maximum power of 95.4 W at 360 rpm. The thermal efficiency is 9.35% at this maximum power condition. Results show that the moderate temperature operation offers a clear advantage in terms of the specific power over the low temperature operation. In terms of the West number, the present work demonstrated that the moderate temperature difference operations could offer the performance on par with the high temperature operations with more simple and less costly development.     

Optimum Stirling engine geometry

This paper combines the author's work on mechanical efficiency of reciprocating engines with the classic Schmidt thermodynamic model for Stirling engines and revisits the problem of identifying optimal engine geometry. All previous optimizations using the Schmidt theory focused on obtaining a maximal specific indicated cyclic work. This does not necessarily produce the highest shaft output. Indeed, some optima based upon indicated work would yield engines that cannot run at all due to excessive intrinsic mechanical losses. The analysis presented in this paper shows how to optimize for shaft or brake work output. Specifically, it presents solutions to the problem of finding the piston‐to‐displacer swept volume ratio and phase angle which will give the maximum brake output for a given total swept volume, given temperature extremes, a given mean operating pressure, and a given engine mechanism effectiveness. The paper covers the split‐cylinder or gamma‐type Stirling in detail, serving as a model for similar analysis of the other Stirling engine configurations. Copyright © 2002 John Wiley & Sons, Ltd.     

分置式斯特林发动机热力性能的仿真

对斯特林发动机的压缩与膨胀过程进行了变质量系统热力学分析。利用等温模型分析法,引入流动阻力损失的计算模型,模拟了分置式斯特林发动机内部工质的压力等参数的动态变化规律。仿真结果表明：斯特林发动机在运行过程中压缩腔与膨胀腔的气体压力并不时时相等;提高发动机的转速和高温热源温度,可以增加发动机的输出功率。     

Optimization of Stirling engine performance based on an experimental design approach

The Stirling engine performances depend on several physicals characteristics and functioning parameters. The influence of each parameter and of their interactions is difficult to achieve with classical univariate studies. The experimental design is an alternative to identify the parameters sets allowing optimal Stirling engine performances. Hence, a four factor Central Composite Rotatable Design was used to observe the effect of cooling water flowrate, initial charge pressure, heating temperature, and operation time on a Stirling engine brake power. The influence of each parameter and the effect of the interaction between two or three parameters on the engine performances are presented and discussed. Using the surface response method, it appears that initial charge pressure and heating temperature are the more influencing parameters on the Stirling engine performances. With modeling, optimal conditions for the Stirling engine functioning are the following: charge pressure of 8 bar, heating temperature of 500 °C, and cooling water flow rates of 7.34 l/min, independent of the engine operation time. Copyright © 2012 John Wiley & Sons, Ltd.     

Optimal regenerator performance in Stirling engines

The key component of a Stirling engine is its regenerative heat exchanger. This device is subject to losses due to dissipation arising from the flow through the regenerator as well as due to imperfect heat transfer between the regenerator material and the gas. The magnitudes of these losses are characterized by the Stanton number St and the Fanning friction factor f, respectively. Using available data for the ratio St/f, results are found for the Carnot efficiency and the power output of the regenerator. They depend on the conductance and on the ratio of pressures at the two sides of the regenerator. Optimum results for efficiency and power output of the regenerator are derived in the limit of zero Mach number. The results are applied to the Stirling engine. The efficiency and the power output of the engine are found for given amplitude of the compression piston. Optimization with respect to regenerator conductance and piston phase angle leads to a maximum possible value of the power output. Under optimal conditions, the Carnot efficiency just below this maximum is close to 100%. Copyright © 2009 John Wiley & Sons, Ltd.     

Exergetic analysis and performance evaluation of parabolic dish Stirling engine solar power plant

In this communication, a 50 MW_e design capacity parabolic dish Stirling engine solar power plant (PDSSPP) has been modeled for analysis, where 2000 units of parabolic dish Stirling engine each having capacity of 25 kW_e were considered to get desired capacity. An attempt has been made to carry out the energetic and exergetic analysis of different components of a solar power plant system using parabolic dish collector/receiver and Stirling engine. The energetic and exergetic losses as well as efficiencies for typical PDSSPP under the typical operating conditions have been evaluated. Variations of the efficiency of Stirling engine solar power plant at the part‐load condition are considered for year‐round performance evaluation. The developed model is examined at location Jodhpur (26.29°N, 73.03°E) in India. It is found that year‐round energetic efficiency varies from 15.57% to 27.09%, and exergetic efficiency varies from 16.83% to 29.18%. The unit cost of electric energy generation (kW_eh) is about 8.76 Indian rupees (INR), with 30 years life span of the plant and 10% interest rate on investment. Copyright © 2012 John Wiley & Sons, Ltd.