Conceptual Analysis of Air Supply Systems For In-Flight PEM-FC

2006 ◽  
Author(s):  
Lukas P. Barchewitz ◽  
Joerg R. Seume
Keyword(s):  
Fuel Cell ◽  
Combustion Chamber ◽  
High Efficiency ◽  
Combustion Engine ◽  
Pressure Ratio ◽  
Inlet Temperature ◽  
Thermodynamic Evaluation ◽  
Radial Turbine ◽  
Air Supply ◽  
Inlet Conditions

To cover the increasing demand of on-board electrical power and for further reduction of emissions, the conventional auxiliary power unit (APU) shall be replaced by a fuel cell system. The main components are a compressor-turbine unit, a kerosene reformer, and the fuel cell. Polymer exchange membrane fuel cells (PEM-FC) are favoured because of their currently advanced level of development. During in-flight operation, the inlet conditions of the PEM-FC system must be kept constant in order to avoid mechanical and thermal damage of the membrane and to ensure low levels of pressure fluctuations in the reformer section. A centrifugal compressor is chosen for pressurization of the system. The advantages of turbomachinery are low specific weight, high efficiency, and good controllability by inlet guide vanes and/or adjustable diffuser vanes. To drive the compressor, a radial turbine is used so that the air supply system resembles the turbocharger for a combustion engine (Fig. 1). A steady state thermodynamic evaluation of the entire system is carried out to identify an optimal system configuration that covers the large range of pressure, temperature, and humidity of ground operation of the aircraft in various regions on the earth as well as take-off, cruise, and landing. A catalytic combustion chamber is located between the PEM-FC and the radial turbine. In this combustion chamber, the hydrogen which is not used in the fuel cell is used to raise the turbine inlet temperature (TIT) and thus the mechanical power delivered by the turbine. To overcome an additional pressure loss of the reformer section, which occurs in the anode stream, an additional low-pressure-ratio compressor is used. The result is a highly thermally integrated PEM-FC system with three centrifugal turbomachines.

Surge Prevention Techniques for a Turbocharged Solid Oxide Fuel Cell Hybrid System

2021 ◽  
Author(s):  
L. Mantelli ◽  
M. L. Ferrari ◽  
A. Traverso
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
High Energy ◽  
Cell System ◽  
Solid Oxide ◽  
Pollutant Emissions ◽  
Inlet Temperature ◽  
Oxide Fuel

Abstract Pressurized solid oxide fuel cell (SOFC) systems are one of the most promising technologies to achieve high energy conversion efficiencies and reduce pollutant emissions. The most common solution for pressurization is the integration with a micro gas turbine, a device capable of exploiting the residual energy of the exhaust gas to compress the fuel cell air intake and, at the same time, generating additional electrical power. The focus of this study is on an alternative layout, based on an automotive turbocharger, which has been more recently considered by the research community to improve cost effectiveness at small size (< 100 kW), despite reducing slightly the top achievable performance. Such turbocharged SOFC system poses two main challenges. On one side, the absence of an electrical generator does not allow the direct control of the rotational speed, which is determined by the power balance between turbine and compressor. On the other side, the presence of a large volume between compressor and turbine, due to the fuel cell stack, alters the dynamic behavior of the turbocharger during transients, increasing the risk of compressor surge. The pressure oscillations associated with such event are particularly detrimental for the system, because they could easily damage the materials of the fuel cells. The aim of this paper is to investigate different techniques to drive the operative point of the compressor far from the surge condition when needed, reducing the risks related to transients and increasing its reliability. By means of a system dynamic model, developed using the TRANSEO simulation tool by TPG, the effect of different anti-surge solutions is simulated: (i) intake air conditioning, (ii) water spray at compressor inlet, (iii) air bleed and recirculation, and (iv) installation of an ejector at the compressor intake. The pressurized fuel cell system is simulated with two different control strategies, i.e. constant fuel mass flow and constant turbine inlet temperature. Different solutions are evaluated based on surge margin behavior, both in the short and long terms, but also monitoring other relevant physical quantities of the system, such as compressor pressure ratio and turbocharger rotational speed.

Mechanical Design and Testing of a 2.5 MW sCO2 Compressor Loop

2021 ◽  
Author(s):  
Stefan D. Cich ◽  
J. Jeffrey Moore ◽  
Chris Kulhanek ◽  
Meera Day Towler ◽  
Jason Mortzheim
Keyword(s):  
High Efficiency ◽  
Mechanical Design ◽  
Guide Vane ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Inlet Temperature ◽  
Design Changes ◽  
Wide Range ◽  
Inlet Conditions ◽  
Design And Testing

Abstract An enabling technology for a successful deployment of the sCO2 close-loop recompression Brayton cycle is the development of a compressor that can maintain high efficiency for a wide range of inlet conditions due to large variation in properties of CO2 operating near its dome. One solution is to develop an internal actuated variable Inlet Guide Vane (IGV) system that can maintain high efficiency in the main and re-compressor with varying inlet temperature. A compressor for this system has recently been manufactured and tested at various operating conditions to determine its compression efficiency. This compressor was developed with funding from the US DOE Apollo program and industry partners. This paper will focus on the design and testing of the main compressor operating near the CO2 dome. It will look at design challenges that went into some of the decisions for rotor and case construction and how that can affect the mechanical and aerodynamic performance of the compressor. This paper will also go into results from testing at the various operating conditions and how the change in density of CO2 affected rotordynamics and overall performance of the machine. Results will be compared to expected performance and how design changes were implanted to properly counter challenges during testing.

Thermoeconomic Optimization of COOLCEP-S: A Novel Zero-CO2-Emission Power Cycle Using LNG (Liquified Natural Gas) Coldness

2008 ◽  
Author(s):  
Meng Liu ◽  
Noam Lior ◽  
Na Zhang ◽  
Wei Han
Keyword(s):  
Natural Gas ◽  
Capital Investment ◽  
Power Plants ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Payback Period ◽  
Inlet Temperature ◽  
Pinch Point ◽  
Cost Of Electricity ◽  
The Cost

This paper presents a thermoeconomic optimization of a novel zero-CO2 and other emissions and high efficiency power and refrigeration cogeneration system, COOLCEP-S† which uses the liquefied natural gas (LNG) coldness during its revaporization. It was predicted that at the turbine inlet temperature (TIT) of 900°C, the energy efficiency of the COOLCEP-S system reaches 59%. The thermoeconomic optimization determines the specific cost, the cost of electricity, and the system payback period. The optimization started by performing a thermodynamic sensitivity analysis, which has shown that for a fixed TIT and pressure ratio, the pinch point temperature difference in the recuperator, ΔTp1, and that in the condenser, ΔTp2, are the most significant unconstrained variables to have a significant effect on the thermal performance of this novel cycle. The thermoeconomic analysis of the cycle (with fixed net power output of 20 MW and plant life of 40 years) shows that the payback period with the revenue from electricity and CO2 mitigation was ∼5.9 years, and would be reduced to ∼3.1 years when there is a market for the refrigeration byproduct. The capital investment cost of the economically optimized plant is estimated to be about $1,000/kWe, and the cost of electricity is estimated to be 0.34–0.37 CNY/kWh (∼0.04 $/kWh). These values are much lower than those of conventional coal power plants being installed at this time in China, which, in contrast to COOLCEP-S, do produce CO2 emissions at that.

Thermodynamic Evaluation of Gas Turbine Cogeneration Cycles: Part I—Heat Balance Method Analysis

1987 ◽  
Vol 109 (1) ◽  
pp. 1-7 ◽  
Author(s):  
I. G. Rice
Keyword(s):  
Gas Turbine ◽  
Heat Balance ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Pressure Ratio ◽  
Turbine Rotor ◽  
Balance Method ◽  
Inlet Temperature ◽  
Thermodynamic Evaluation ◽  
Exhaust Temperature

This paper presents a heat balance method of evaluating various open-cycle gas turbines and heat recovery systems based on the first law of thermodynamics. A useful graphic solution is presented that can be readily applied to various gas turbine cogeneration configurations. An analysis of seven commercially available gas turbines is made showing the effect of pressure ratio, exhaust temperature, intercooling, regeneration, and turbine rotor inlet temperature in regard to power output, heat recovery, and overall cycle efficiency. The method presented can be readily programmed in a computer, for any given gaseous or liquid fuel, to yield accurate evaluations. An X–Y plotter can be utilized to present the results.

The Effect of Size on Optimisation of Solid Oxide Fuel Cell/Gas Turbine Hybrid Cycles

2009 ◽  
Author(s):  
Michael J. Brear ◽  
Michael J. Dunkley
Keyword(s):  
Fuel Cell ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Solid Oxide ◽  
Total Power ◽  
Oxide Fuel ◽  
Component Size ◽  
System Pressure

The integration of high temperature solid oxide fuel cells with gas turbines to form high efficiency, hybrid generators is receiving significant attention within both the academic and industrial communities. Various systems have been proposed or demonstrated, and which cover a range of sizes from low power generators suitable for domestic power generation through to larger systems in the megawatt size range. The performance of such hybrid systems depends on the matching of the fuel cell and gas turbine through optimisation of the system pressure ratio and reactant flow rates. Losses associated with non-ideal cycle components are significant and vary with component size, and must be taken into account if optimal performance is to be achieved. This paper presents an intentionally very simple numerical model of the hybrid system, so that the effect of key component efficiencies on the overall cycle efficiency can be examined easily. These component efficiencies of course scale with size, and the results presented suggest that hybrid cycles with total power output of order several MW are preferable.

scholarly journals Development of a High Pressure Ratio Centrifugal Compressor for 300kW-Class Ceramic Gas Turbine

1997 ◽  
Author(s):  
T. Sakai ◽  
Y. Tohbe ◽  
T. Fujii ◽  
T. Tatsumi
Keyword(s):  
Research And Development ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Efficiency ◽  
Pressure Ratio ◽  
Flow Distribution ◽  
Leading Edge ◽  
Inlet Temperature ◽  
Angle Distribution ◽  
Gas Generator

Research and development of ceramic gas turbines (CGT), which is promoted by the Japanese Ministry of International Trade and Industry (MITI), was started in 1988. The target of the CGT project is development of a 300kW-class ceramic gas turbine with a 42 % thermal efficiency and a turbine inlet temperature (TIT) of 1350°C. Two types of CGT engines are developed in this project. One of the CGT engines, which is called CGT302, is a recuperated two-shaft gas turbine with a compressor, a gas-generator turbine, and a power turbine for cogeneration. In this paper, we describe the research and development of a compressor for the CGT302. Specification of this compressor is 0.89 kg/sec air flow rate and 8:1 pressure ratio. The intermediary target efficiency is 78% and the final target efficiency is 82%, which is the highest level in email centrifugal compressors like this one. We measured impeller inlet and exit flow distribution using three-hole yaw probes which were traversed from the shroud to the hub. Based on the measurement of the impeller exit flow, diffusers with a leading edge angle distribution adjusted to the inflow angle were designed and manufactured. Using this diffuser, we were able to attain a high efficiency (8:1 pressure ratio and 78% adiabatic efficiency).

Dynamic Modelling and Controls of an Air Supply System for In-Flight Proton Exchange Membrane Fuel Cells (PEM-FC)

2007 ◽  
Author(s):  
Lukas P. Barchewitz ◽  
Joerg R. Seume
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Power Density ◽  
Supply System ◽  
Operating Conditions ◽  
Design Parameters ◽  
Radial Turbine ◽  
Air Supply ◽  
Exchange Membrane ◽  
Turbomachinery Design

To cover the increasing demand of on-board electrical power and for further reduction of emissions, the conventional auxiliary power unit (APU) may be replaced by a fuel cell system with an expected efficiency increase of 25% to 50% when compared to start-of-the-art GT-APU. The main components of an in-flight FC system are a compressor-turbine unit, a kerosene reformer, and the fuel cell. Polymer exchange membrane fuel cells (PEM-FC) may be favored because of their currently advanced level of development, their high power density and the available liquid water in the cathode-off gases which can be used as service water on-board. Transient requirements may have significant impact on system design and operating range and will therefore be addressed in this paper. During in-flight operation, air has to be compressed from the ambient to a pressure near standard conditions, which allows the application of state-of-the-art PEM-FC and ensures a constant power density independent from the operating altitude. A centrifugal compressor is chosen for pressurization of the system and is powered by a radial turbine, which allows autonomous operation at cruising altitude without external power. For off-design operation and transients, electric support from the PEM-FC is necessary, see [1]. The radial turbine itself is run by the hot exhaust gases from a post-combustor using the remaining energy in the cathode off-gases. A thorough trade-off between suitable compressor techniques for the air supply system was carried out in [1]. Turbomachinery revealed to be favourable for the PEM air supply system due to their low specific weight and high efficiency. The air supply system resembles the turbocharger for a combustion engine (Fig. 1), which represents a good starting point for a successful integration into the flight environment and further development due to known technology. Based on a turbomachinery design which satisfies the system requirements, the dynamic behavior of the air supply system is analyzed when coupled to the PEM fuel cell. The main focus is on the detection of sensitive system parameters causing system response delay or critical operating conditions. The present paper suggests system features, turbomachinery design parameters and controller types which achieve inherent stability and fast response of the air supply system throughout the entire flight envelope.

A Comparative Study on the Options in Combining Solid Oxide Fuel Cell With Gas Turbine

2015 ◽  
Author(s):  
Ji Hye Yi ◽  
Ju Hwan Choi ◽  
Tong Seop Kim
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Gas Turbine ◽  
Pressure Ratio ◽  
Solid Oxide ◽  
Inlet Temperature ◽  
Oxide Fuel ◽  
System Efficiency ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet

Various options in combining a solid oxide fuel cell (SOFC) with a gas turbine (GT) were compared in this study. The combination of an SOFC with either a simple gas turbine or a gas/steam turbine combined cycle was investigated. For each combined system, the effect of using a recuperative heat exchanger was examined. The design parameters of a state-of-the-art gas turbine for central power stations were used. The GT modeling included modulation of turbine coolant flow depending on turbine working conditions. An SOFC temperature of 900°C was used. Given a currently available reference voltage, pressure-dependent SOFC cell voltage was used. The analysis was divided into two parts. In the first part, the turbine inlet temperature of the reference gas turbine was given and the influence of pressure ratio was analyzed. In the second part, the influence of varying turbine inlet temperature was analyzed to search for optimal design conditions. The results showed that the SOFC/GTCC systems would provide considerably higher efficiencies than the SOFC/GT systems. The optimal pressure ratio in terms of system efficiency is over 30 for non-recuperated systems but is around 10 for recuperated systems. Reducing the extra fuel to the gas turbine combustor improves system efficiency, especially in the SOFC/GT systems. With zero extra fuel, efficiencies of all of the four systems exceed 70%, the highest of which is obtained by the recuperated SOFC/GTCC layout.

The Potential of GT Combined Cycles for Ultra High Efficiency

2012 ◽  
Author(s):  
Hans E. Wettstein
Keyword(s):  
High Efficiency ◽  
Pressure Ratio ◽  
Specific Power ◽  
Variable Pressure ◽  
Inlet Temperature ◽  
Gas Temperature ◽  
Calculation Results ◽  
Combined Cycles ◽  
Exit Temperature ◽  
Exergy Losses

Gas turbine combined cycles (GTCC) using a steam bottoming cycle are a widely used technology for electric power generation. From [1] it is known that the best current large GTCC’s loose around 25% of the fuel exergy just by combusting the fuel while all other exergy losses sum up to around 15%. For the net efficiency of such plants 60% is remaining. This paper shows thermodynamic calculation results of GTCC’s with variable pressure ratio and turbine inlet temperature (TIT) aimed at understanding the efficiency potential associated with further increases of the TIT thus reducing the exergy loss by combustion. The assumptions of these calculations correspond to published industrial experience and standard assumptions in two different scenarios. The results are curves showing net efficiency and specific power as functions of TIT. Other data like the related pressure ratio and compressor exit temperature are shown too. The conclusion shows that a net efficiency of 63…65% is feasible with a hot gas temperature of around 1750°C based on the two scenarios. The winning cycle arrangement uses an adiabatic compressor. A GTCC with GT-compressor having one intercooling stage is clearly less favorable in several respects.

Gradient-Based Optimization of a Radial Turbine Volute and a Downstream Bend Using Vertex Morphing

2020 ◽  
Author(s):  
Nicolas Lachenmaier ◽  
Daniel Baumgärtner ◽  
Heinz-Peter Schiffer ◽  
Johannes Kech
Keyword(s):  
Shape Optimization ◽  
Combustion Engine ◽  
Pressure Ratio ◽  
Load Condition ◽  
Adjoint Methods ◽  
Turbine Wheel ◽  
Pressure Drops ◽  
Radial Turbine ◽  
Efficiency Increase ◽  
Gradient Based

Abstract The higher the efficiency of a turbocharger’s radial turbine, the lower is the necessary pressure ratio to deliver a specified power to the compressor. This, in turn, reduces the fuel consumption of the internal combustion engine as a lower pressure upstream of the turbine increases the obtained charge-cycle work. In this paper, two components of a nozzled radial turbine system are redesigned: Both the volute upstream and the 90°-bend downstream of the turbine wheel will be improved. To reduce pressure drops, a gradient-based shape optimization workflow based on adjoint methods is applied. The scheme works in an iterative manner, i.e. after running a primal and an adjoint simulation to gather shape sensitivities, the geometry is deformed and the next iteration is started. A steepest descent approach is used to guide the optimization process. As parametrization strategy the Vertex Morphing Method is used to explore design potential, while maintaining smooth surfaces. Both the volute and the bend are optimized successfully leading to an efficiency increase of the turbine system of up to 3%, depending on the load condition.

Sign in / Sign up

Export Citation Format

Share Document