Feasibility analysis and performance characteristic investigation of thermal energy storage system based on organic Rankine cycle for engine exhaust temperature modulation

ABSTRACT

The exhaust temperature of the engine has a significant impact on the conversion efficiency of the after-treatment. A thermal energy storage (TES) system with organic fluid for engine exhaust temperature modulation is established in this paper, and the performance characteristics of the TES system with the engine exhaust temperature modulation are analyzed based on the organic Rankine cycle (ORC). First, an accumulator-centered TES system model is established based on GT- SUITE, and the effects of working fluid mass, mass flow rate, supply strategy and working fluid type on the TES system are analyzed. Second, the influence of coupled ORC-TES system on exhaust emission and after-treatment efficiency is analyzed, and the cost–benefit analysis of integrated ORC-TES system is carried out. Finally, the simulation results show that with the increase in working fluid mass, the average temperature, availability, satisfaction, and comprehensive index (CI) of the TES system gradually decrease, while the standard deviation gradually increases. Simultaneously, the average temperature, availability, satisfaction, and CI of the TES system all increase with increasing working fluid mass flow rate for the same mass of working fluid. In the high-performance region (CI = 0.7 ~ 1.0), the modulating performance of exhaust temperature mainly depends on the mass of the working fluid supply. However, in the low-performance region (CI = 0 ~ 0.4), the sensitivity of mass and mass flow should be taken into account. In addition, in the high-performance region, the supply of 4 kg of working fluid at a speed of 1.0 kg/s can also be considered the best solution, and R404a is the most suitable working fluids for thermal energy storage. Under Europe Transient Cycle (ETC), the average temperature, availability, satisfaction, and CI are increased by 2.9%, 7.46%, 34.1%, and 100%, respectively, with the TES system, and the standard deviation is decreased by 53%. Compared to the ORC system, the coupled ORC-TES system leads to an increase in exhaust back pressure (EBP), but does not lead to an increase in fuel consumption due to the improved thermal efficiency of the ORC system. In addition, the integrated ORC-TES system can improve the SCR catalytic efficiency and reduce NOx emissions. From a cost–benefit analysis, the ORC-TES system is practically feasible.

KEYWORDS:

• After-treatment temperature requirement
• exhaust temperature modulation
• thermal energy storage
• waste heat recovery
• organic Rankine cycle

Nomenclature

Q	=	heat quantity (kJ)
m	=	quality (kg)
Cp	=	specific heat capacity (J/kg·℃)
A	=	area (m2)
h	=	enthalpy (kJ/kg)
ΔT	=	temperature variation (℃)
T	=	temperature (℃)
t	=	time (s)
Subscripts	=
exh	=	exhaust
wf	=	work fluid
lm	=	logarithmic mean
wf, in	=	work fluid before entering the heat accumulator
wf, out	=	work fluid after passing through the heat accumulator
exh, in	=	exhaust before entering the heat accumulator
exh, out	=	exhaust after passing through the organic Rankine cycle
ha	=	heat accumulator
Acronyms	=
TES	=	thermal energy storage
ORC	=	organic Rankine cycle
ETC	=	Europe Transient Cycle
SCR	=	selective catalyst reduction
PCM	=	phase change material
NTP	=	non-thermal plasma
TSA	=	temperature swing adsorption
ICE	=	internal combustion engine
WHR	=	waste heat recovery
EGR	=	exhaust gas recirculation
DOC	=	diesel oxidation catalyst
DPF	=	diesel particulate filter
Stdev	=	standard deviation
LHA	=	latent heat accumulators
VG-HEX	=	vortex generator heat exchanger
LTES	=	latent thermal energy storage
VGT	=	variable geometry turbine
CI	=	comprehensive index
ODP	=	Ozone Depletion Potential
GWP	=	Global Warming Potential
CAC	=	charge air cooler
EBP	=	exhaust back pressure
ORC-TES	=	organic Rankine cycle-thermal energy storage

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Science Fund of State Key Laboratory of Engine Reliability (skler-201706) and the Technology Development Program of Jilin Province (20180519005JH). In addition, the authors would like to thank all the reviewers for their valuable comments.

Notes on contributors

Huifang Dang

Huifang Dang is a PhD student at the Department of Energy and Power Engineering, Jilin University, under the supervision of Professor Yongqiang Han. The main research areas are waste heat recovery and energy management strategies for hybrid vehicles.

Yongqiang Han

Yongqiang Han received B.Sc, Sc. and PhD in power machinery and engineering from Jilin University of Technology in 1989, 1994 and 2002, respectively. Dr. Yongqiang Han is currently working as Professor at the Energy and Power Engineering Department, College of Automotive Engineering, Jilin University. He is the responsible professor of ‘Power Engineering and Engineering Thermophysics’ in Jilin Province, the director of Chinese Internal Combustion Engine Society, the vice chairman of Combustion Purification and Energy Saving Branch of Chinese Internal Combustion Engine Society, the member of Combustion Committee of Chinese Society of Engineering Thermophysics, the editorial board member of Combustion Science and Technology, and the reviewer of international journals such as FUEL and Applied Energy. The fourth edition of Internal Combustion Mechanics was awarded the second prize of National Textbook Construction Award. The main research directions are focused on the fine control of combustion process based on the topology index optimization of combustion reaction zone, the comprehensive utilization of waste heat of vehicle power, and the coordinated carbon emission control of oil engine. He has been responsible for more than 40 projects such as the new century excellent talents project of the Ministry of Education, the National Natural Science Foundation project, the national key project, the provincial major project, and the school-enterprise cooperation project. More than 30 high-level journal papers and more than 30 authorized invention patents in the field of energy and power were published by the first / communication authors. As the person in charge, he won four provincial and ministerial science and technology awards and invention patent awards.

Jinshan Liu

Jinshan Liu is a PhD and professor of Energy and Power Engineering at Jilin University. He has been engaged in the research work of fuel, combustion and emission control of internal combustion engines. Six national science and technology research projects and provincial and ministerial projects were completed.

Manzhi Tan

Manzhi Tan is a researcher in the Department of Energy and Power Engineering, School of Automotive Engineering, Jilin University. He is engaged in the research of internal combustion engine and waste heat utilisation at Jilin University and has published several papers in this field.

Xinping Wang

Xinping Wang is a PhD student at the Department of Energy and Power Engineering, Jilin University, under the supervision of Professor Yongqiang Han. The main research areas are variable expansion ratio expander and automobile waste heat recovery and utilization.