Rui Chen

Loughborough University | Lough · Department of Aeronautical and Automotive Engineering

Organic Rankine cycle (ORC) and thermoelectric generator (TEG) have both been identified as reliable waste heat recovery (WHR) technologies, although they are different in energy conversion efficiency, volume size and operating temperatures. The combined thermoelectric generator and organic Rankine cycle (TEG-ORC) system enables TEG and ORC to be c...

Ammonia as a carbon-free fuel used in IC engines always suffers from large cyclic variations and high NOx emissions. Ammonia blending with high-reactivity fuels is recognized as an effective attempt to overcome these shortcomings. In this work, for the first time, the combustion and emission characteristics of n-heptane/ammonia were investigated un...

As a carbon-free hydrogen-carrier fuel with a high content of hydrogen, ammonia (NH3) exhibits unfavorable combustion properties such as low flammability and large cyclic variations, requiring further investigation in actual engines. In this work, for the first time, using a single-cylinder optical spark ignition (SI) engine with a high compression...

Hybrid electric vehicles constitute an important stage in the global paradigm shift from conventional fossil-fuelled vehicles to electric vehicles. Thermoelectric generators, as a promising waste heat recovery system, also need to transfer their implementation from conventional vehicles to hybrid electric vehicles. In this paper, a performance comp...

The deflagration to detonation transition (DDT) remains one of the most interesting and mysterious physical phenomena in the combustion of energetic materials, which contains substantial complicated and nonlinear characteristics. In the present work, the effect of the chemical reactivity of different fuels and diluent gases on the end-gas autoignit...

Lean combustion has the potential to achieve higher thermal efficiency for internal combustion (IC) engines. However, natural gas engines often suffer from slow burning rate and large cyclic variations when adopting lean combustion. In this study, using a dual-fuel optical engine with a high compression ratio, the effects of direct-injected hydroge...

Diluent gases are used in practical industrial applications that involve flame propagation and detonation. In this study, we investigated the effect of diluent gases on end-gas autoignition and detonation development in a constant volume combustion chamber. High-speed Schlieren photography was employed to capture the flame–shock wave interaction an...

Incremental capacity analysis (ICA) is a widely used method of characterising state of health (SOH) in secondary batteries through the identification of peaks that correspond to active material phase transformations. For reliable ICA, cells are cycled under low constant currents to minimise resistance and diffusion effects, making deployment into a...

The effect of the rib width to height ratio t/e and width to pitch ratio t/p on the local heat transfer distribution in a rectangular matrix ribbed channel with two opposite in line 45o ribs are experimentally investigated for Reynolds Numbers from 54000 to 150000. The rib height to channel height ratio e/H is 0.5, t/p and t/e both varies in range...

In compression ignition engines, split-injection strategy has shown great benefits in reducing pollutant emissions and improving combustion efficiency. Spray–flame interaction involving in split injections is significantly complex, which affects the ignition process and even pollutant emissions. Therefore, the objective of this study is to investig...

In the present work, end-gas autoignition formation, and the effects of oxygen concentration on the flame/shock waves propagation and pressure oscillation, are investigated in a self-designed constant-volume chamber equipped with a perforated plate. A hydrogen–oxygen–nitrogen mixture with adjustable oxygen to nitrogen ratio is chosen as the test fu...

In this present work, the effect of anode electrocatalyst materials is investigated by adding NiTiO3 with Pt/C and Pt-Ru/C for the performance enhancement of direct methanol fuel cells (DMFCs). The supportive material NiTiO3/C has been synthesized first by wet chemical method followed by incorporation of Pt and Pt-Ru separately. Experiments are con...

Proton exchange membrane fuel cells (PEMFCs) using porous metallic foam flow-field plates have been demonstrated as an alternative to conventional rib and channel designs, showing high performance at high currents. However, the transport of liquid product water through metal foam flow-field plates in PEMFC conditions is not well understood, especia...

Flow-field PEMFC X-ray CT Porosity Compression a b s t r a c t Porous metal foams have been used as alternative flow-fields in proton exchange membrane fuel cells (PEMFCs), exhibiting improved performance compared to conventional 'land and channel' designs. In the current work, the mechanical behaviour of PEMFCs using metal foam flow-fields is inve...

Porous metal foams have been used as alternative flow-fields in proton exchange membrane fuel cells (PEMFCs), exhibiting improved performance compared to conventional ‘land and channel’ designs. In the current work, the mechanical behaviour of PEMFCs using metal foam flow-fields is investigated across different length scales using a combination of...

In this work, the potential of multi-injection strategies coupled with EGR to improve the trade-off relationship of NOx-BSFC (Brake specific fuel consumption) is carefully studied by multi-dimensional simulation using CONVERGE in a low-speed two-stroke diesel engine. The present study reveals that by introducing high EGR rate, the reduction of NOx...

Thermoelectric generators (TEGs) have the characteristics of low maintenance, silent operation, stability, and compactness, which make them outstanding devices for waste heat recovery in light-duty vehicles. Significant strides have been made in the high temperature (300–800 °C) thermoelectric materials and recent work is beginning to translate tho...

Spark assisted compression ignition (SACI) is a proven method for extending the load range and controlling the combustion phase of homogeneous charge compression ignition (HCCI) while maintaining high thermal efficiency. However, the occurrence of abnormal combustion, such as knock, limits the improvement of efficiency in SACI combustion. In this s...

The super-knock phenomenon is a major obstacle for further improving the power density in SI engines. The objective of this paper is to experimentally investigating the mechanism involved in the occurrence of super-knock. In this work, a high compression ratio (CR = 13) coupled with advanced spark timings were employed to achieving intense or criti...

The flow distribution behaviour of open-cell metallic foam fuel cell flow-fields are evaluated using ex-situ optical analysis and X-ray computed tomography (X-ray CT). Five different manifold designs are evaluated and flow distribution and pressure drop quantitatively evaluated with reference to applications in polymer exchange membrane fuel cells...

The spray model for the study was calibrated and the predicted penetration length showed good agreement with the experimental data. Then, the effect of swirl on the interaction of fuel spray and ambient gas, which was described by spray configuration, spray penetration length, evaporated fuel mass and Sauter mean diameter(SMD) of droplets(hereinaft...

Optical analysis of flow distribution in porous metal foam flow fields. • Findings show Increasing manifold inlet area reduces residence time and pressure drop. • New hybrid foam using pressed channels demonstrates controllable fluid distribution. • Hybrid foam performance correlated to X-ray CT scans and porosity analysis. The flow distribution be...

Air Cycle Machines (ACMs) were developed to meet the cabin conditioning requirement onboard gas turbine powered aircraft. Typical ACMs utilise a compressor, heat exchanger and turbine to employ a reverse-Brayton thermodynamic cycle on high pressure, engine bled air. This Environmental Control System (ECS), is implemented in an open loop architectur...

Experiments were conducted in a newly designed constant volume combustion chamber with a perforated plate by varying the initial conditions. Hydrogen–air mixtures were used and the turbulent flame, shock wave, and the processes of flame–shock interactions were tracked via high-speed Schlieren photography. The effects of hole size and porosities on...

Experimental test and analytical modeling are conducted to investigate the operating behavior of an alkaline electrolyte membrane (AEM) fuel cell fed by H2/air (or O2) and explore the effect of various operating pressures on the water transfer mechanism. According to the experimental test, the cell performance is greatly improved through increasing...

The Gas Diffusion Layer (GDL) of a Polymer Electrolyte Membrane Fuel Cell (PEMFC) plays a crucial role in overall cell performance. It is responsible for the dissemination of reactant gasses from the gas supply channels to the reactant sites at the Catalyst Layer (CL), and the adequate removal of product water from reactant sites back to the gas ch...

Proton exchange membrane fuel cells (PEMFCs) require mechanical compression to ensure structural integrity, prevent leakage, and to minimize the electrical contact resistance. The mechanical properties and dimensions of the fuel cell vary during assembly due to manufacturing tolerances and during operation due to both temperature and humidity. Vari...

Waste heat recovery using a thermoelectric generator (TEG) is a promising approach for vehicle original equipment manufacturers to reduce fuel consumption and lower CO2 emissions. A TEG can convert otherwise wasted thermal energy from engines to electricity directly for use in the vehicle systems. This paper focuses on the development of a dynamic...

Pressure wave propagation behavior is an essential feature for the combustion under enclosed conditions, e.g. internal combustion engines. Previous work (by Pan et al. (2016) and Yu et al. (2015) showed that pressure wave disturbance not only affects hot-spot formation and knocking origin, but also induces detonation wave through a coupling mechani...

In this work, the main contribution is an understanding of different combustion phenomena involving the flame acceleration, flame propagation and the pressure oscillation resulted from flame-shock interactions. These physical phenomena were experimentally studied using a newly developed confined combustion chamber equipped with one or two orifice p...

For security issue of alkane used in Organic Rankine Cycle, a new model to evaluate the upper flammability limits for mixtures of alkanes, carbon dioxide and air has been proposed in present study. The linear relationship was found at upper flammability limits between molar fraction of diluent in alkane-CO2 mixture and calculated adiabatic flame te...

Electrification of aircraft is on track to be a future key design principal due to the increasing pressure on the aviation industry to significantly reduce harmful emissions by 2050 and the increased use of electrical equipment. This has led to an increased focus on the research and development of alternative power sources for aircraft, including f...

Phase-locked particle imaging velocimetry measurements are carried out in a direct-injected spark-ignition single-cylinder optical research engine equipped with fully variable valve timing to assess the impact of asymmetric intake valve lift strategies on the in-cylinder flow. The engine was operated under a range of asymmetric strategies, with one...

End gas auto-ignition and transition of flame front are considered as the main causes of severe pressure oscillation in spark-ignition engines, which is one of the major features of knock and super-knock. The knowledge of characteristics of auto-ignition, flame front development, propagation of pressure wave and relations between them, still needs...

Based on fundamental electrochemical theory, an impedance model for analysis of electrochemical impedance spectroscopy (EIS) of Nickel-Metal Hydride (NiMH) batteries is presented in this study. The resulting analytical expression is analogous to the impedance response of the Randles electrical circuit used for EIS analysis on NiMH batteries. The im...

The present work investigates the interaction of the turbulent flame and shock wave as well as the end-gas autoignition in a newly designed constant volume combustion chamber equipped with a perforated plate using a stoichiometric hydrogen-air mixture. Detailed high speed schlieren photography is used to track the turbulent flame fronts and shock w...

The present work investigates the interaction of the turbulent flame and shock wave as well as the end-gas autoignition in a newly designed constant volume combustion chamber equipped with a perforated plate using a stoichiometric hydrogen-air mixture. Detailed high speed schlieren photography is used to track the turbulent flame fronts and shock w...

Thermoelectric generator (TEG) has received more and more attention in its application in the harvesting of waste thermal energy in automotive engines. Even though the commercial Bismuth Telluride thermoelectric material only have 5% efficiency and 250°C hot side temperature limit, it is possible to generate peak 1kW electrical energy from a heavy-...

The application of state-of-art thermoelectric generator (TEG) in automotive engine has potential to reduce more than 2% fuel consumption and hence the CO 2 emissions. This figure is expected to be increased to 5%~10% in the near future when new thermoelectric material with higher properties is fabricated. However, in order to maximize the TEG outp...

Reynolds-averaged Navier–Stokes simulations with an improved spray model and a realistic chemistry mechanism are performed for turbulent spray flames under diesel-like conditions in a constant-volume chamber. Comprehensive numerical analyses including two turbulence models (the renormalisation group k–ε model and the standard two-equation k–ε model...

The effects of methane addition to PRF95 (primary reference fuel with 95% volume of iso-octane and 5% volume of n-heptane) on the fundamental combustion parameters are experimentally investigated in a cylindrical combustion vessel using classical schlieren technique. In this study, methane is added with three energy fractions of 25%, 50% and 75% to...

Differentiating between the various polytetrafluoroethylene based structures inside polymer electrolyte membrane fuel cells with a degree of certainty is necessary to optimize manufacturing processes and to investigate possible degradation mechanisms. We have developed a novel method using fluorescence microscopy for distinguishing the origin and l...

Natural gas is a promising alternative fuel. The main constituent of natural gas is methane. The slow burning velocity of methane poses significant challenges for its utilization in future energy efficient combustion applications. The effects of methane addition to PRF95 on the fundamental combustion parameters, laminar flame velocity (Su0) and Mar...

Fuel cells are promising technologies for zero-emission energy conversion and power generation. However, durability and reliability are among the main barriers to their commercialisation. Clearly the system performance depends on the reliability of the overall system including both the stack and the balance of plant. This paper seeks to introduce a...

In this study, an impedance model based on electrochemical theory of platinum oxide formation has been developed and combined with the impedance model based on hydrogen peroxide formation during the oxygen reduction reaction (ORR) and reported in a previous study to characterise inductive loops in impedance spectra of polymer electrolyte fuel cells...

Natural gas as an alternative fuel offers the potential of clean combustion and emits relatively low CO2 emissions. The main constitute of natural gas is methane. Historically, the slow burning speed of methane has been a major concern for automotive applications. Literature on experimental methane-gasoline Dual Fuel (DF) studies on research engine...

Proton Exchange Membrane (PEM) fuel cells are a chemically fuelled power supply which generally have a higher energy density than Lithium-Polymer Battery (LIPOs) but a much lower power density. In order for PEM fuel cells to increase the endurance of an in-service battery power supply, without decreasing the peak power, it should be hybridised with...

This paper presents the computational fluid dynamics (CFD) modelling results of the transient flow inside an engine cylinder with spark ignition valve timing. Transient flow simulations at 1,500 rpm are conducted and take into account the movement of the inlet, exhaust valves and the piston. The simulated in-cylinder velocities are compared to publ...

The validity of electrochemical impedance measurements of polymer electrolyte fuel cells (PEFCs) have to be evaluated before an attempt is made to interpret the electrochemical mechanisms represented in the Nyquist plot. This evaluation can be carried out by data transformation of impedance measurements using Kramers-Kronig (K-K) relations. However...

This paper was also presented at JSAE/SAE 2015 Powertrains, Fuels & Lubricants International Meeting, Kyoto, Japan, SAE 2015-01-1974 / JSAE 20159333. The paper is in closed access until 1st March 2016.

Correctly describing oxygen reduction within the cathode catalyst layer (CL) in modelling proton exchange membrane fuel cell is an important issue remaining unresolved. In this paper we show how to derive an agglomerate model for calculating oxygen reactions by describing dissolved oxygen in the agglomerates using two independent random processes....

This paper illustrates the differences between mechanical and electrical water pumps of internal combustion engines. Literatures have been studied in regard to engine cooling with the water pumps. Main design features of the mechanical and electrical water pumps have been illustrated. Engine dyno tests have been performed to evaluate if increased t...

In this study, an impedance model based on electrochemical theory considering hydrogen peroxide formation during a two-step oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs) has been developed. To validate the theoretical treatment, electrochemical impedance spectroscopy (EIS) measurements were carried out in an open-cathode...

Hydrogen fuelled polymer electrolyte fuel cells (PEFC) offer clear environmental benefits. Lack of viable hydrogen infrastructure in the near future means that a key issue is availability of hydrogen at the point of use. Liquefied petroleum gas (LPG) offers advantages as a fuel over other hydrocarbons because there is already an infrastructure in p...

This paper describes the construction of the centrifugal compressor model and its validation with the experimental data. The compressor model in this paper uses One-dimensional (1D) thermo-fluid equations to analyse the compressor side of a turbocharger. Under a specified set of turbocharger geometry, atmospheric conditions, rotational speed, and f...

The hydrophobic microporous layer (MPL) in PEM fuel cell improves water management but reduces oxygen transport. We investigate these conflict impacts using nanotomography and pore-scale modelling. The binary image of a MPL is acquired using FIB/SEM tomography. The water produced at the cathode is assumed to condense in the catalyst layer (CL), and...

The calculations of laminar burning velocity are mostly based on empirical correlations obtained from combustion bomb experiments. There is a noticeable scarcity of the fitting parameters in these correlations, especially under increased temperature and pressure conditions. The effects of flame stretch and instabilities further complicate the situa...

Electrical and thermal conductivity models from Mamunya et al. and Kerner’s equation for elastic and flexural modulus have been applied to experimental data to assess model accuracies. Experimental data were gained from a previous study where polyethylene and carbon black, graphite and magnetite composites produced by injection and compression moul...

Numerical calculations have been carried out to investigate the in-cylinder transient flow structure of a controlled auto-ignition (CAI) engine running at speeds of 1500 rpm and 2000 rpm. The calculated turbulent flow structure and velocities are validated against published laser doppler anemometry (LDA) experimental data (Pitcher et al., 2003). Th...

After validation of the numerical model against published laser doppler anemometry (LDA) experimental data (Pitcher et al., 2003), numerical calculations have been carried out to investigate the in-cylinder transient flow structure of a controlled auto-ignition (CAI) engine running at speeds of 1,500 rpm and 2,000 rpm. The geometry configuration of...

In this study, an analysis of the performance in a commercial open-cathode polymer electrolyte fuel cell (PEFC) stack is conducted using simultaneous electrochemical impedance spectroscopy (EIS) measurements. The factors that limit the performance of the PEFC stack were evaluated with EIS measurements and the impedance model developed in the author...

The effect of image resolution on gas permeability through the x-ray reconstructed carbon paper gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEFC) was examined in this paper. The 3D models of the GDL at 6 different resolutions were obtained by the x-ray computed tomography imaging technique. Each GDL image was then characterized it...

The wettability of channel walls and gas diffusion layer has a great influence on the water management of fuel cells. In this paper, a numerical study has been carried out to examine the effect of the wall and gas diffusion layer wettability on gas channels. The investigation employed a three dimensional numerical simulation using the volume-of-flu...

The effect of image resolution on gas permeability through the x-ray reconstructed carbon paper gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEFC) was examined in this paper. The 3D models of the GDL at 6 different resolutions were obtained by the x-ray computed tomography imaging technique. Each GDL image was then characterized it...

The wettability of channel walls and gas diffusion layer has a great influence on the water management of fuel cells. In this paper, a numerical study has been carried out to examine the effect of the wall and gas diffusion layer wettability on gas channels. The investigation employed a three dimensional numerical simulation using the volume-of-flu...

Hybrid electric vehicles (HEVs) are sensitive to the driving conditions under which they are used, leading to greater fuel consumption than quoted by the manufacturer, and therefore higher CO2 emissions. Real-world driving can be very different from the legislative drive cycles as speeds are greater, there are faster changes in speed, and these cha...

Engine downsizing is undertaken in the automotive industry in order to reduce the emissions and the fuel consumption of the vehicle. Turbocharging is one of the important methods to enable downsizing of the engine; however, increased noise is the side-effect of this introduction. The noise generation is assumed to be due to the operation of turboch...

In this study, a new electrical equivalent circuit is developed to evaluate the performance of polymer electrolyte fuel cell (PEFC) stacks using electrochemical impedance spectroscopy (EIS). Experimental EIS measurements were carried out in an open-cathode PEFC stack to validate the new electrical equivalent circuit. The electrical equivalent circu...

Water management is an effective way of improving Proton Exchange Membrane (PEM) fuel cell performance and durability. Changing the wettability of gas channel walls and gas diffusion layer (GDL) is one way of controlling the water management in a fuel cell for its influence on the liquid water dynamic behavior. The objective of this study is to inv...

The elimination of corrosion, reduction of mass and the improvement of mechanical, electrical and thermal conductivity properties are the main aims to progress bipolar plate technology for polymer electrolyte membrane fuel cells. In addition, the large numbers of bipolar plates required in automotive fuel cell stacks (on the order of 400 plates per...

Turbochargers are introduced in petrol engines to facilitate downsizing and hence to reduce emissions and fuel consumption. However, increased noise is the side effect of this introduction. The noise generation is assumed to be due to the operation of turbocharger very close to the surge zone of the compressor map. For example, the compressor map i...

In this study, a generic electrical circuit is presented to characterise the frequency response of the Polymer Electrolyte Fuel Cell (PEFC), Cathode Catalyst Layer (CCL) at different current densities. The new electrical circuit is derived from fundamental electrochemical and diffusion theory. It consists of a transmission line in combination with...

The porous gas diffusion layers (GDLs) are key components in hydrogen fuel cells. During their operation the cells produce water at the cathode, and to avoid flooding, the water has to be removed out of the cells. How to manage the water is therefore an important issue in fuel cell design. In this paper we investigated water flow in the GDLs using...

In this study, an analysis of the current distribution and oxygen diffusion in the Polymer Electrolyte Fuel Cell (PEFC) Cathode Catalyst Layer (CCL) has been carried out using Electrochemical Impedance Spectroscopy (EIS) measurements. Cathode EIS measurements obtained through a three-electrode configuration in the measurement system are compared wi...

Numerical calculations have been carried out to investigate the in-cylinder transient flow structure of a controlled auto-ignition (CAI) engine running at speeds of 1,500rpm and 2000rpm. The calculated turbulent flow structure and velocities are validated against published laser Doppler anemometry (LDA) experimental data (Pitcher et al., 2003). The...

Utilisation of pure electric vehicles (EV) enables a step change in vehicle efficiency when compared to those powered by an internal combustion engine. Cenex, the UK’s Centre of Excellence for Low Carbon and Fuel Cell technologies specialises in understanding the real-world and whole-vehicle performance of low carbon vehicles and in collaboration w...

The high frequency electrochemical impedance measurements with positive imaginary components in the impedance complex plot of a polymer electrolyte fuel cell (PEFC) are attributable to the inductance of the electrical cables of the measurement system. This study demonstrates that the inductive effect of the electrical cables deforms the high freque...

Using high-speed Schlieren and Shadow photography, the instabilities of outwardly propagating spherical hydrogen-air flames have been studied in a constant volume combustion bomb. Combustion under different equivalence ratios (0.2 ∼ 1.0), temperatures (298 K ∼ 423 K) and pressures (1.0 bar ∼ 10.0 bar) is visualized. The results show that flames exp...