Parametric study on interaction of blower and back pressure control valve for a 80-kW class PEM fuel cell vehicle

https://doi.org/10.1016/j.ijhydene.2016.07.218Get rights and content

Highlights

  • Numerical study based on commercial fuel cell vehicle.

  • Major parameters are blower speed and backpressure control valve.

  • Performance map of fuel cell vehicle is developed for different loads, and velocities.

  • Pressure is proportional to the blower speed and the effect of BCV is small.

  • Power increases with higher blower speed and decreases with larger BCV angle.

Abstract

Numerical study on the performance of the polymer electrolyte membrane (PEM) fuel cell vehicle with variable operating pressure was conducted to investigate the effect of blower and backpressure control valve. We conducted system level modeling for PEM fuel cell vehicle to predict its performance, where the model is based on the commercial fuel cell vehicle manufactured by Hyundai-Kia Motors and thus is validated against the real driving data. We considered most parts of PEM fuel cell vehicle powertrain, i.e. blower, membrane humidifier, and backpressure control valve at cathode, hydrogen recirculation system using ejector at anode, and the system for refrigeration and air conditioning. In building such a large system model, most of the sub system models were developed based on either zero- or one-dimensional approach, but still capturing critical physical phenomena in each device. Among these components, we focused on the effect of blower and backpressure control valve in cathode side, since these are the main control parameters in the aforementioned vehicle to influence the operating characteristics of the fuel cell stack and thus the performance of the vehicle. From the system modeling results, as the rotation speed of the blower increases, the stoichiometric number for cathodic air becomes higher and the relative humidity becomes lower. When pressure is higher, power generation from stack is proportional to stoichiometric number, however, it has greatly influence on relative humidity, and the variation of system performance is similar to that of stack. In case of the backpressure control valve, the stoichiometric number is higher and the relative humidity is lower, when back pressure is low. This change begins to reduce system power. In the end, we developed the performance curve based on the blower RPM and the valve angle, at various vehicle speeds. The proposed performance curve could provide a useful means to understand overall operating characteristics of the fuel cell vehicle.

Introduction

In past decades, polymer electrolyte membrane (PEM) fuel cell has been expected to play an important role as alternative power source for automotive and stationary applications. Because of its high power density, zero pollution, moderate operating temperature and quick start-up capability, PEM fuel cell is considered to be the most promising candidate for electric vehicles [1], [2], [3]. In the development of the PEM fuel cell vehicle, it is important to have an accurate model because it could provide profound understanding regarding system performance including the values difficult to measure and it is cost-effective as well [4], [5].

There have been variety of researches to improve performance of PEM fuel cell in the system level. Some studies attempted to resolve water management problem by improving humidifying technique and thermal management [6], [7], [8], [9], [10], [11]. There were studies on the fuel supply system, such as hydrogen recirculation system, or a system including fuel reformer or electrolyzer to enhance fuel efficiency [12], [13], [14], [15], [16], [17], [18]. Lastly, others investigated the air supply system with pressure control by using back pressure regulator or compressor to increase the power density of the stack [19], [20], [21], [22], [23], [24]. However, despite such massive studies, most are not validated against for a large-scale system experiment which is shown in Fig. 1, the numbers in the figure are target capacity of each study, and thus they could not provide useful insight in applying their results to actual vehicle.

In general, performance of an internal combustion engine vehicle is expressed by the performance maps [25], [26], [27], [28]. They are typically expressed as important parameters regarding engine and vehicle operation, such as engine rotation speed, engine torque, engine efficiency, or vehicle speed. As in these conventional vehicles, PEM fuel cell vehicle would better have some form of performance map, in order to measure and control the system performance. Unfortunately, such information for PEM fuel cell vehicle is hardly observed, or at least, not open to public from the manufacturers, therefore, suggesting one for the PEM fuel cell vehicle would be an important topic in this study.

The aim of the present work is to conduct simulation modeling for PEM fuel cell system validated against the actual data of 80 kW-class actual fuel cell vehicle by Hyundai-Kia Motors, and show system performance by interaction of blower and backpressure control valve (BCV), both of which influence the operating pressure of the fuel cell stack. In the following sections, we intensively review and analyze a collection of modeling strategies on each sub-component, and then develop our model based on the best practice for our purpose. Then, we explain iterative methods to solve for the whole system model of the PEM fuel cell vehicle, including humidification system, hydrogen recirculation, thermal management system, and the effect of BCV on system performance. The modeling results are validated with experimental data of 80 kW-class fuel cell vehicle in various vehicle speeds. Finally, we analyze the operating characteristics based on the blower and the BCV interaction, and suggest the useful performance map for the PEM fuel cell vehicle.

Section snippets

Methodology

Many researchers have developed and adopted one-dimensional or even simpler modeling approach for the component when conducting system-level modeling to reduce the computational cost while still capturing important physical phenomena in each device. In this study, we also developed our system model based on these simplified modeling approach.

The PEM fuel cell system in the vehicle mainly consists of four subsystems; air providing system, fuel providing system, thermal management system, and

Validation

The validation of device models for the PEM fuel cell vehicle is performed in this section. Here, we only showed the validation of important components, i.e. blower, BCV, ejector, and pump, which are shown in Fig. 5. The blower and BCV regulates mass flow rate and pressure at cathode, the ejector plays an important role in recirculating hydrogen at anode, and the coolant pump controls mass flow rate of coolant in TMS. Therefore, validation for blower and BCV is conducted by comparing

Conclusion

In this study, system model for variable-pressure PEM fuel cell vehicle validated with 80 kW-class automotive fuel cell is conducted to predict the system performance and provide performance curve, depending on the interaction of blower and backpressure control valve. The important operating parameters in the system are the pressure and the mass flow rate in the fuel cell stack, which are affected by the blower speed and the BCV angle. Here is the summary of the major findings:

  • 1.

    The operating

Acknowledgments

This work was supported by the Institute of Advanced Machinery and Design (IAMD) of Seoul National University. The additional support of the BK plus program and World Class University (WCU) program through the Korea Research Foundation (R31-2008-000-10083-0) is greatly appreciated. The study was also supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2013R1A2A1A01014589). It was

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