Increase Of Isentropic Efficiency Research Articles

Experimental Study and Sensitivity Analysis of Performance for a Hydrogen Diaphragm Compressor

As the critical infrastructure of hydrogen in transportation, the energy consumption of hydrogen refuelling stations plays a pivotal role in the progress of hydrogen energy within the transportation sector. Volumetric and isentropic efficiencies serve as metrics for evaluating compressor performance. To investigate the extent of factors, including suction pressure, pressure ratio, overflow pressure, and rotational speed, to the efficiencies of the diaphragm compressor, an experimental rig was set up in this study. The volume and energy losses were analysed by studying pressure–volume diagrams. The result shows that elevating suction pressure results in an increased isentropic efficiency. Specifically, raising suction pressure from 0.2 MPa to 0.8 MPa yields a 10.2% increase in isentropic efficiency. The increase in pressure ratio leads to a reduction in volumetric efficiency but an increase in isentropic efficiency. When the pressure ratio increased from 3 to 7, the volumetric efficiency decreased by 6.5% in volumetric efficiency, but the isentropic efficiency increased by 9.8%. Moreover, the escalation in rotational speed corresponds to a decrease in both volumetric and isentropic efficiencies. As the rotational speed increased from 420 r/min to 660 r/min, volumetric efficiency dropped by 9.6%, and isentropic efficiency experienced a 19.2% decrease.

Performance Improvement of a Limaçon Gas Expander Using an Inlet Control Valve: Two Case Studies

Renewable energy-based compact energy-generation systems based on the organic Rankine cycle (ORC) can be employed to meet the ever-growing thirst for affordable and clean energy. The overall performance and effectiveness of ORC systems are constrained by the low efficiency of the gas expander, specifically the positive displacement expander, which is responsible for energy conversion from the working fluid. This low-efficiency scenario can be significantly improved by employing a control valve to regulate and restrict the flow of the working fluid into the expander. A control valve can effectively curve the loss of costly compressed and energized working fluids by allowing them to expand in the expander chamber before discharging through the outlet port. They can thus be used to regulate the amount of energy yield and output power. In this work, two direct drive rotary valves (DDRVs) operated by a stepper motor (SM-DDRV) and rotary solenoid (RS-DDRV) are suggested, and the behavior of the valves is examined. The effect of friction and temperature on the valve response is also studied. Additionally, the effect of inlet control valves on the overall system performance of the limaçon expander is assessed. Thermodynamic properties such as the isentropic efficiency and filling factor are also computed. The effect of leakage due to valve response delay is analyzed at different inlet pressures. The performance indices are compared to the expander performance without any inlet valve. The SM-DDRV setup results in a 14.86% increase in isentropic efficiency and a 220% increase in the filling factor, whereas the RS-DDRV performs moderately with a 2.58% increase in isentropic efficiency and an 80% increase in the filling factor compared to a ported expander. The SM-DDRV provides better performance indices compared to the RS-DDRV and without valve setups. However, the performance of the limaçon expander with the SM-DDRV is sensitive to the inlet pressure and degrades at higher pressure. Overall, the valves proposed in this work present key insights into improving the performance characteristics of gas expanders of ORC systems.

Numerical investigation on the combined effects of pinching and rotation on the performance of a high-speed centrifugal compressor with a vaneless diffuser

Computational investigations are carried out on a high-speed centrifugal compressor with the vaneless diffuser to study the combined pinch and rotation effect. The axial inlet width of the rotating vaneless diffuser is reduced at diffuser inlet, either at the hub wall or at the shroud wall, or both the walls. The reduction is varied from 0% (base case) to 20% at an interval of 5%. Numerical simulations are conducted for different speed range by varying the rotating diffuser diameter ratio from 1.25–1.75. Among all these cases, the best performance of 25% increase in pressure recovery with uniform diffusion and 2.3% increase in isentropic efficiency is obtained with 15% shroud pinch at a diameter ratio of 1.375 at the design mass flow rate.

A study on the single screw expander with exhaust kinetic energy utilization in organic Rankine cycle conditions

Using high-performance expanders is one of the keys to improve the efficiency of Organic Rankine Cycle (ORC). However, in large expansion ratio conditions, the performance deterioration caused by under-expansion seriously affects the performances of the ORC. For single-screw expanders, it is possible to utilize the kinetic energy of the screw groove exhaust to produce extra power. But there is still a lack of theoretical support for optimizing the exhaust kinetic energy utilization process of this new expander at present. Therefore, the energy conversion mechanism of Single Screw Expander with exhaust Kinetic energy Utilization (SSEKU) was investigated in this paper, and a mathematical model of SSEKU was developed to investigate the energy conversion mechanisms and predict the performances. The results show that introducing exhaust kinetic energy utilization process in single screw expander can reduce under-expansion losses effectively, and the effects in large size expanders were stronger than that in small scale machines. It was also found that the maximum increase in isentropic efficiency was 3.01, 5.47, and 9.38 percentage points for the expander with a screw diameter of 117 mm, 200 mm, and 350 mm, respectively.

Analisis Pengaruh Turbine Washing Terhadap Efisiensi dan Daya Pembangkit Turbin Uap

The steam turbine is one of the main components in the Geothermal Power Plant which acts as the prime mover is used to convert heat energy in steam into rotation energy. At PLTP X, steam is used to drive the turbine is in saturation conditions. The principle of the steam turbine is dry steam plant cycle. From July to August, it was known that there have been several decreases in generating power at Unit 2 at PLTP X. The efforts that can be done to overcome this problem is by turbine washing. This study aims to compare the performance of steam turbines based on thermal efficiency, isentropic efficiency and steam turbine generator power before and after turbine washing from the calculation results based on CEI/IEC 953-1, CEI/IEC 60953-3 and ASME PTC 6-2004 standards using the actual steam system operating parameter data collection, interviews and analysis. So that it gets an average increase in isentropic efficiency of 0,0564 %, thermal efficiency of 0,0082 %, the actual power generation of steam turbine is 162,72 kW and the largest power generation reaches 54.500 kW after the turbine washing steam rate of 7,5963 kg/kWh and the turbine heat rate of 3.607,3453 kJ/kWh.

Experimental Validation of the Aerodynamic Performance of an Innovative Counter-Rotating Centrifugal Compressor

Turbomachinery with double counter-rotating impellers offers more degrees of freedom in the choice of design and control parameters compared to conventional machines. For these innovative machines, the literature review shows that more publications concerning axial type turbomachines are available than centrifugal ones. This work deals with a design and experimental performance analysis, applied to two counter-rotating impellers of a centrifugal compressor “CRCC”. CRCC was designed with a specifically developed tool based on mean-line approach coupled with optimization algorithms and a stream-curvature through-flow method to satisfy the design criteria. This paper presents an experimental validation of the CRCC design tool and its performances against the baseline “SR”, composed of one centrifugal impeller and a volute for which experimental data are available. CRCC numeric simulations are also validated by experimental data. For a fair comparison between CRCC and SR, the same volute is used for both configurations. The CRCC studied here includes a first conventional impeller with an axial inlet and a radial outlet, while the second impeller is parametrically designed and can be considered a rotating bladed diffuser with a radial inlet and outlet. The obtained results show that CRCC can deliver a pressure rise increase of two compared to SR, along with an increase of isentropic efficiency and also validate the design method of this novel layout. The experimental results also show that the speed ratio of CRCC has a positive effect on the surge and shock margin.

Numerical investigation of a highly loaded centrifugal compressor stage with a tandem bladed impeller

This study numerically investigated a highly loaded centrifugal compressor stage with various tandem-designed impellers and a wedge diffuser using a state-of-the-art multi-block flow solver to better understand the fundamental mechanism of tandem impellers. The flow topologies in the impeller are analyzed in detail to identify the underlying physical mechanism of the effect of the tandem-impeller design on the performance of the compressor stage. Particular emphasis is placed on the evolution of the flow structure in the tandem bladed impeller by varying the inducer–exducer clocking arrangements. The results demonstrate that a tandem compressor design is more efficient than a conventional compressor design for the majority of the tested clocking configurations, and the tandem clocking friction significantly affects the impeller performance. For the tested centrifugal compressor stage, an approximately 1.4% increase in isentropic efficiency and 1.3% increase in stall margin are achieved with an inducer–exducer clocking fraction of 25%. The improvement in the primary centrifugal compressor stage performance by the tandem-impeller design is a result of the manipulation of the flow structure and the reduction in the highly distorted jet/wake exit flow pattern. Compared to the conventional impeller designs, the tandem-impeller clocking arrangement variation significantly affects the high-momentum flow along the exducer suction surface and inducer wake diffusion, inlet axial velocity, and flow angle of the exducer blade. Therefore, this variation is advantageous for shortening the length of the boundary layers on both parts of the blade and enables an intense mixing at the exducer passage to improve the flow uniformity of the impeller exit. As a result, the impeller efficiency, diffuser recovery, and stalling margin can be improved compared with the conventional design.

On the performance enhancement of thermo-compressor and steam turbine blade cascade in the presence of spontaneous nucleation

In the present study, increasing the performance of thermo-compressors and steam turbines by volumetric cooling and inlet superheating is addressed. The efficacies of these two proposed methods are assessed using a numerical code developed based on Eulerian-Eulerian description of the two-phase fluid flow accounting for the spontaneous nucleation. The results show that maximum increase of 2.8% in entrainment ratio and 4.2% increase in isentropic efficiency are achieved for thermo-compressor and steam turbine blade cascade respectively. As the result, flow passage cooling and increasing the superheating level at the flow inlet could be considered as reliable techniques for wetness loss reduction in industrial apparatuses.

Adaptive flow optimization of a turbocharger compressor to improve engine low speed performance

To improve the engine overall performance, an adaptive flow optimization procedure is proposed in this paper to synthesize turbocharger compressor optimum designs. Two objective functions are involved in the adaptive optimization. They are the traditional compressor design and the compressor design with consideration of improving engine overall performance. The two-step decomposition approach is chosen to generate optimum designs. The optimized designs not only satisfy turbomachinery and engine constraints but also have optimum objective function values in the two fields. Performance sensitivity analysis of compressor main design variables is performed for the flow optimization design process. A centrifugal compressor is redesigned for a turbocharged gasoline engine, as an example, based on the adaptive flow optimization process. The calculating results show a more than 5% increase of isentropic efficiency in comparison with the base line compressor, resulting in a more than 19% increase of engine torque at low speed conditions.

Experimental studies of a linear MHD generator with fully ionized seed

Power generation experiments for a linear nonequilibrium Faraday generator with small seed fractions of 10 ~5 ~ 10 4 have been conducted in order to show the recovery of the effective electrical conductivity and the power density due to the suppression of ionization instability and to demonstrate the possible operation of a linear MHD generator with fully ionized seed. Results of the present experiments have shown the recovery of the apparent conductivity up to 20-27 mho/m, and the ratio of the apparent conductivity to the ideal conductivity decreases from 0.8 to 0.2 as the seed fraction increases from lxlO~ 5 to 7x10 ~ 5. The high apparent conductivity indicates the possible operation of a linear generator with fully ionized seed, and the increase of isentropic efficiency of a closed-cycle inert-gas MHD generator can be expected.