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Waste Heat Recovery in a Heavy-Duty Engine using Rankine Cycles and Humid Air Cycles

Narayanan, Prakash LU (2016)
Abstract
The majority of the fuel energy in any internal combustion engine is lost as heat loss, namely, exhaust gas heat, exhaust gas recirculation cooling, charge air cooling, and cylinder cooling. Utilizing this heat improves the overall efficiency. This thesis analyzes two such waste heat recovery cycles; the more mature Rankine bottoming cycle and the less investigated humid air cycle (HAM), from a heavy duty (HD) diesel engine perspective. The Rankine cycle potential was studied using 0-D and 1-D simulation tools. More emphasis was laid on understanding engine operation with a humid air cycle, which was investigated both virtually using simulation tools and also experimentally using a modified multi-cylinder heavy duty engine.
The Rankine... (More)
The majority of the fuel energy in any internal combustion engine is lost as heat loss, namely, exhaust gas heat, exhaust gas recirculation cooling, charge air cooling, and cylinder cooling. Utilizing this heat improves the overall efficiency. This thesis analyzes two such waste heat recovery cycles; the more mature Rankine bottoming cycle and the less investigated humid air cycle (HAM), from a heavy duty (HD) diesel engine perspective. The Rankine cycle potential was studied using 0-D and 1-D simulation tools. More emphasis was laid on understanding engine operation with a humid air cycle, which was investigated both virtually using simulation tools and also experimentally using a modified multi-cylinder heavy duty engine.
The Rankine cycle potential was studied using a thermodynamic analysis of the different heat sources in an effort to maximize the waste heat recovery (WHR) potential. The Rankine cycle circuit was designed in IPSE-Pro (Thermodynamic modeling software) with various heat sources in both single and dual loops. The possibilities and challenges involved in coupling these multiple sources in a single Rankine cycle, and the selection of suitable working fluid were analyzed. The study shows that it is possible to recover 5-10% of the otherwise wasted heat energy, which results in ~5% increase in power or reduced fuel consumption. Also, a comparative investigation of the WHR potential between the existing conventional diesel combustion and the novel concept of partial premixed combustion (PPC) was carried out. The results implies that PPC offers improved WHR potential compared to conventional combustion.
Humid air cycle was studied as a means of waste heat recovery technology intended to improve efficiency and decreasing emissions. The potential benefits of the HAM cycle were investigated in a virtual environment, with a heavy duty Volvo engine model modified with a humidifier (modeled as vapor injection). The commercial software GT-SUITE was used to build the system model and to perform the simulations. The results suggested a decrease in bulk in-cylinder gas temperature and a potential increase in power. The results showed that the efficiency improvement was on par with Rankine cycle along with the in-cylinder emission reduction potential.To investigate HAM experimentaly a HAM system was built around a 13-litre six cylinder Volvo diesel engine. The performance and emissions were investigated in three different modes, namely conventional operation with or without EGR and with the humid air cycle. The experiments carried out at part load showed that HAM reduced the emissions but without any influence on fuel economy. The experiments were further extended to two other load points in an effort to study the effect of engine load and speed. The results show that HAM reduces NOx emissions significantly together with the soot emissions without affecting the efficiency. CO and HC emissions increase marginally. At higher speeds the brake efficiency was improved by 3% for HAM along with the emissions reduction. With the fact that the HAM engine requires no charge air cooler (HAM tower acts as a cooler) and no EGR, this could further reduce losses in the form of aerodynamic losses in a vehicle application.
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author
supervisor
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Waste heat recovery, Rankine cycle, Humid air cycle
pages
138 pages
publisher
Lund University
ISBN
978-91-7623-872-1
language
English
LU publication?
yes
id
da3ca66b-8a70-41b0-898c-8579c708b704
date added to LUP
2016-05-20 10:35:02
date last changed
2016-09-19 08:45:20
@misc{da3ca66b-8a70-41b0-898c-8579c708b704,
  abstract     = {The majority of the fuel energy in any internal combustion engine is lost as heat loss, namely, exhaust gas heat, exhaust gas recirculation cooling, charge air cooling, and cylinder cooling. Utilizing this heat improves the overall efficiency. This thesis analyzes two such waste heat recovery cycles; the more mature Rankine bottoming cycle and the less investigated humid air cycle (HAM), from a heavy duty (HD) diesel engine perspective. The Rankine cycle potential was studied using 0-D and 1-D simulation tools. More emphasis was laid on understanding engine operation with a humid air cycle, which was investigated both virtually using simulation tools and also experimentally using a modified multi-cylinder heavy duty engine.<br/>The Rankine cycle potential was studied using a thermodynamic analysis of the different heat sources in an effort to maximize the waste heat recovery (WHR) potential. The Rankine cycle circuit was designed in IPSE-Pro (Thermodynamic modeling software) with various heat sources in both single and dual loops. The possibilities and challenges involved in coupling these multiple sources in a single Rankine cycle, and the selection of suitable working fluid were analyzed. The study shows that it is possible to recover 5-10% of the otherwise wasted heat energy, which results in ~5% increase in power or reduced fuel consumption. Also, a comparative investigation of the WHR potential between the existing conventional diesel combustion and the novel concept of partial premixed combustion (PPC) was carried out. The results implies that PPC offers improved WHR potential compared to conventional combustion.<br/>Humid air cycle was studied as a means of waste heat recovery technology intended to improve efficiency and decreasing emissions. The potential benefits of the HAM cycle were investigated in a virtual environment, with a heavy duty Volvo engine model modified with a humidifier (modeled as vapor injection). The commercial software GT-SUITE was used to build the system model and to perform the simulations. The results suggested a decrease in bulk in-cylinder gas temperature and a potential increase in power. The results showed that the efficiency improvement was on par with Rankine cycle along with the in-cylinder emission reduction potential.To investigate HAM experimentaly a HAM system was built around a 13-litre six cylinder Volvo diesel engine. The performance and emissions were investigated in three different modes, namely conventional operation with or without EGR and with the humid air cycle. The experiments carried out at part load showed that HAM reduced the emissions but without any influence on fuel economy. The experiments were further extended to two other load points in an effort to study the effect of engine load and speed. The results show that HAM reduces NOx emissions significantly together with the soot emissions without affecting the efficiency. CO and HC emissions increase marginally. At higher speeds the brake efficiency was improved by 3% for HAM along with the emissions reduction. With the fact that the HAM engine requires no charge air cooler (HAM tower acts as a cooler) and no EGR, this could further reduce losses in the form of aerodynamic losses in a vehicle application.<br/>},
  author       = {Narayanan, Prakash},
  isbn         = {978-91-7623-872-1},
  keyword      = {Waste heat recovery, Rankine cycle,Humid air cycle},
  language     = {eng},
  month        = {06},
  pages        = {138},
  publisher    = {ARRAY(0xb5de1d0)},
  title        = {Waste Heat Recovery in a Heavy-Duty Engine using Rankine Cycles and Humid Air Cycles},
  year         = {2016},
}