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Double Compression Expansion Engine Concepts: A Path to High Efficiency

Lam, Nhut LU ; Tunér, Martin LU ; Tunestål, Per LU ; Arne, Andersson; Lundgren, Staffan and Johansson, Bengt LU (2015) In SAE International Journal of Engines 8(4). p.1562-1562
Abstract (Swedish)
Internal combustion engine (ICE) fuel efficiency is a balance between good indicated efficiency and mechanical efficiency. High indicated efficiency is reached with a very diluted air/fuel-mixture and high load resulting in high peak cylinder pressure (PCP). On the other hand, high mechanical efficiency is obtained with very low peak cylinder pressure as the piston rings and bearings can be made with less friction. This paper presents studies of a combustion engine which consists of a two stage compression and expansion cycle. By splitting the engine into two different cycles, high-pressure (HP) and low-pressure (LP) cycles respectively, it is possible to reach high levels of both indicated and mechanical efficiency simultaneously. The HP... (More)
Internal combustion engine (ICE) fuel efficiency is a balance between good indicated efficiency and mechanical efficiency. High indicated efficiency is reached with a very diluted air/fuel-mixture and high load resulting in high peak cylinder pressure (PCP). On the other hand, high mechanical efficiency is obtained with very low peak cylinder pressure as the piston rings and bearings can be made with less friction. This paper presents studies of a combustion engine which consists of a two stage compression and expansion cycle. By splitting the engine into two different cycles, high-pressure (HP) and low-pressure (LP) cycles respectively, it is possible to reach high levels of both indicated and mechanical efficiency simultaneously. The HP cycle is designed similar to today's turbo-charged diesel engine but with an even higher boost pressure, resulting in high PCP. To cope with high PCP, the engine needs to be rigid. The usage of higher piston ring tension and larger bearings are examples of measures to cope with higher PCP. These measures will cost in terms of friction. Hence, mechanical efficiency is not as good as other engine concepts with lower PCP. The low-pressure cycle on the other hand, uses a design more similar to current naturally aspirated (NA) spark ignited (SI) engines, but designed for even lower PCP. Because of this, the engine does not need to be as rigidly designed and the overall friction levels will be much lower. By combining these two engine philosophies, a total engine concept with both high indicated and mechanical efficiencies can be achieved. Simulations show net indicated efficiency above 60% and a brake efficiency of 56%. (Less)
Abstract
Internal combustion engine (ICE) fuel efficiency is a balance between good indicated efficiency and mechanical efficiency. High indicated efficiency is reached with a very diluted air/fuel-mixture and high load resulting in high peak cylinder pressure (PCP). On the other hand, high mechanical efficiency is obtained with very low peak cylinder pressure as the piston rings and bearings can be made with less friction. This paper presents studies of a combustion engine which consists of a two stage compression and expansion cycle. By splitting the engine into two different cycles, high-pressure (HP) and low-pressure (LP) cycles respectively, it is possible to reach high levels of both indicated and mechanical efficiency simultaneously. The HP... (More)
Internal combustion engine (ICE) fuel efficiency is a balance between good indicated efficiency and mechanical efficiency. High indicated efficiency is reached with a very diluted air/fuel-mixture and high load resulting in high peak cylinder pressure (PCP). On the other hand, high mechanical efficiency is obtained with very low peak cylinder pressure as the piston rings and bearings can be made with less friction. This paper presents studies of a combustion engine which consists of a two stage compression and expansion cycle. By splitting the engine into two different cycles, high-pressure (HP) and low-pressure (LP) cycles respectively, it is possible to reach high levels of both indicated and mechanical efficiency simultaneously. The HP cycle is designed similar to today's turbo-charged diesel engine but with an even higher boost pressure, resulting in high PCP. To cope with high PCP, the engine needs to be rigid. The usage of higher piston ring tension and larger bearings are examples of measures to cope with higher PCP. These measures will cost in terms of friction. Hence, mechanical efficiency is not as good as other engine concepts with lower PCP. The low-pressure cycle on the other hand, uses a design more similar to current naturally aspirated (NA) spark ignited (SI) engines, but designed for even lower PCP. Because of this, the engine does not need to be as rigidly designed and the overall friction levels will be much lower. By combining these two engine philosophies, a total engine concept with both high indicated and mechanical efficiencies can be achieved. Simulations show net indicated efficiency above 60% and a brake efficiency of 56%. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
SAE International Journal of Engines
volume
8
issue
4
pages
1578 pages
publisher
SAE
external identifiers
  • scopus:84928721323
  • wos:000421671200011
ISSN
1946-3944
DOI
10.4271/2015-01-1260
language
English
LU publication?
yes
id
53ccc0b8-a56e-4441-99c4-71d2dcbdc9e2
date added to LUP
2017-12-12 09:49:16
date last changed
2018-05-13 04:37:13
@article{53ccc0b8-a56e-4441-99c4-71d2dcbdc9e2,
  abstract     = {Internal combustion engine (ICE) fuel efficiency is a balance between good indicated efficiency and mechanical efficiency. High indicated efficiency is reached with a very diluted air/fuel-mixture and high load resulting in high peak cylinder pressure (PCP). On the other hand, high mechanical efficiency is obtained with very low peak cylinder pressure as the piston rings and bearings can be made with less friction. This paper presents studies of a combustion engine which consists of a two stage compression and expansion cycle. By splitting the engine into two different cycles, high-pressure (HP) and low-pressure (LP) cycles respectively, it is possible to reach high levels of both indicated and mechanical efficiency simultaneously. The HP cycle is designed similar to today's turbo-charged diesel engine but with an even higher boost pressure, resulting in high PCP. To cope with high PCP, the engine needs to be rigid. The usage of higher piston ring tension and larger bearings are examples of measures to cope with higher PCP. These measures will cost in terms of friction. Hence, mechanical efficiency is not as good as other engine concepts with lower PCP. The low-pressure cycle on the other hand, uses a design more similar to current naturally aspirated (NA) spark ignited (SI) engines, but designed for even lower PCP. Because of this, the engine does not need to be as rigidly designed and the overall friction levels will be much lower. By combining these two engine philosophies, a total engine concept with both high indicated and mechanical efficiencies can be achieved. Simulations show net indicated efficiency above 60% and a brake efficiency of 56%. },
  articleno    = {2015-01-1260},
  author       = {Lam, Nhut and Tunér, Martin and Tunestål, Per and Arne, Andersson and Lundgren, Staffan and Johansson, Bengt},
  issn         = {1946-3944},
  language     = {eng},
  month        = {04},
  number       = {4},
  pages        = {1562--1562},
  publisher    = {SAE},
  series       = {SAE International Journal of Engines},
  title        = {Double Compression Expansion Engine Concepts: A Path to High Efficiency},
  url          = {http://dx.doi.org/10.4271/2015-01-1260},
  volume       = {8},
  year         = {2015},
}