Change search
Refine search result
1 - 3 of 3
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Holmberg, Ted
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlaas, O.
    Pressure Amplitude Influence on Pulsating Exhaust Flow Energy Utilization2018In: SAE technical paper series, ISSN 0148-7191, Vol. 2018-AprilArticle in journal (Refereed)
    Abstract [en]

    A turbocharged Diesel engine for heavy-duty on-road vehicle applications employs a compact exhaust manifold to satisfy transient torque and packaging requirements. The small exhaust manifold volume increases the unsteadiness of the flow to the turbine. The turbine therefore operates over a wider flow range, which is not optimal as radial turbines have narrow peak efficiency zone. This lower efficiency is compensated to some extent by the higher energy content of the unsteady exhaust flow compared to steady flow conditions. This paper experimentally investigates the relationship between exhaust energy utilization and available energy at the turbine inlet at different degrees of unsteady flow. A special exhaust manifold has been constructed which enables the internal volume of the manifold to be increased. The larger volume reduces the exhaust pulse amplitude and brings the operating condition for the turbine closer to steady-flow. The operating points are defined by engine speed and boost pressure. From these values the isentropic turbine work is calculated and with the measured compressor work the mean turbine efficiency is estimated. The results show that more energy has to be provided to the turbine at larger exhaust manifold volumes to maintain a constant boost pressure, indicating that the efficiency of the turbine decreases. 

  • 2.
    Holmberg, Ted
    et al.
    KTH.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlaas, O.
    Pressure Ratio Influence on Exhaust Valve Flow Coefficients2017In: SAE technical paper series, ISSN 0148-7191, Vol. 2017-March, no MarchArticle in journal (Refereed)
    Abstract [en]

    In one dimensional engine simulation software, flow losses over complex geometries such as valves and ports are described using flow coefficients. It is generally assumed that the pressure ratio over the valve has a negligible influence on the flow coefficient. However during the exhaust valve opening the pressure difference between cylinder and port is large which questions the accuracy of this assumption. In this work the influence of pressure ratio on the exhaust valve flow coefficient has been investigated experimentally in a steady-flow test bench. Two cylinder heads, designated A and B, from a Heavy-Duty engine with different valve shapes and valve seat angles have been investigated. The tests were performed with both exhaust valves open and with only one of the two exhaust valves open. The pressure ratio over the exhaust port was varied from 1.1:1 to 5:1. For case A1 with a single exhaust valve open, the flow coefficient decreased significantly with pressure ratio. This trend was not replicated for the other single valve case B1, as pressure ratio only had a small influence on the flow coefficient. For the twin valve case A2, the pressure ratio influence was confined to the lower range of valve lifts as the limiting factor was the exhaust port outlet at higher valve lifts. The flow coefficient for the twin valve case B2 increased with pressure ratio in the mid-range of valve lifts.

  • 3.
    Holmberg, Ted
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlåås, Ola
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Dynamic Exhaust Valve Flow 1-D Modelling During Blowdown Conditions2019In: SAE Technical Papers, 2019Conference paper (Refereed)
    Abstract [en]

    To conduct system level studies on internal combustionengines reduced order models are required in order tokeep the computational load below reasonable limits.By its nature a reduced order model is a simplification of realityand may introduce modeling errors. However what is of interestis the size of the error and if it is possible to reduce the errorby some method. A popular system level study is gas exchangeand in this paper the focus is on the exhaust valve. Generallythe valve is modeled as an ideal nozzle where the flow lossesare captured by reducing the flow area. As the valve movesslowly compared to the flow the process is assumed to be quasisteady,i.e. interpolation between steady-flow measurementscan be used to describe the dynamic process duringvalve opening. These measurements are generally done at lowpressure drops, as the influence of pressure ratio is assumed tobe negligible. As it is very difficult to measure time-resolvedmass flow it is hard to test validity of these modeling assumptions.Experimental data indicates that the model overestimatesvalve flow during the blowdown event. As the blowdown pulsecontains a significant portion of the energy in the cylinder atexhaust valve opening, it is therefore of importance to modelthis correctly. In this paper experimental results from previouslypublished research have been compared to simulationresults and the deviation from quasi-steady behavior has beenquantified. The deviation appears to be a function of pressureratio over the valve and valve opening speed. A model isproposed to compensate for the observed effects.

1 - 3 of 3
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf