Potential of Variable Geometry Radial Inflow Turbines as Expansion Machines in Organic Rankine Cycles Integrated with Heavy-Duty Diesel Engines
, Abdullah Alghafis 2, Ibrahim Alatawi 1, Ahmed S. Alshammari 3, Ahmed Alzamil 3 and Abdullah Alrashidi 4
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear authors!
The article devoted to research on the potential of variable geometry radial inflow turbines as expansion machines in organic Rankine cycles integrated with heavy duty diesel engines.
The topic is current. The article may be published after significant changes are made and questions are answered.
Line 22: You need to add Brake-specific fuel consumption (BSFC).
What is the novelty of the presented work?
There is no literature review!
Figure 1: How is the temperature versus entropy plotted?
Figure 4: Illegible Flow chart.
Figure 5: What are the enthalpy and entropy values for P1-P4?
Figure 6 shows the different stator holes. You need to provide a model of a stator or turbine.
Figure 7: What equations were used to build these relationships?
Figure 8, Figure 9: Where did you get the data?
Conclusions: It is necessary to provide a description of what was and what has become, to describe the novelty of the work.
All figures and tables are not clear.
Good luck!
Comments on the Quality of English LanguageCheck the English.
Author Response
Dear respected reviewer,
We would like to express our sincere thanks for the constructive comments and we kindly ask you to refer to the attached file for our responses.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe presented article is very relevant and presented in good quality. This is not to say that the topic is very new. The Rankine cycle has been known for a long time. Turbines have been widely used in large marine engines for many decades. However, the presented material allows us to speak about a deep study of the issue and a fairly high quality of writing. The title of the article, which evaluates the potential of variable geometry radial inlet turbines as expanders in organic Rankine cycles integrated with high-power diesel engines, correlates well with the abstract and conclusions of the article. The authors have completed a completely sufficient description of the modeling processes and a description of the features of the processes occurring in the turbine apparatus and high-power engine. The article can definitely be recommended for publication in a journal. Among the shortcomings, I would like to note the low quality of figures 4 and 5. It is necessary to increase the resolution and scale of the figures.
Author Response
Dear respected reviewer,
We would like to express our sincere thanks for the constructive comments and we kindly ask you to refer to the attached file for our responses.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe article ‘Potential of Variable Geometry Radial Inflow Turbines as Expansion Machines in Organic Rankine Cycles Integrated with Heavy Duty Diesel Engines’.
Thank you for the opportunity to review this paper. I read it with very interest. The paper presents the possibility of using the organic Rankine cycle (ORC) as waste heat recovery in internal combustion engines. The activity was aimed at confirming the possibility of meeting emission reductions resulting from the combustion of fossil fuels. The authors demonstrated computationally that a variable geometry turbine in an ORC cycle raised the BSFC by about 5.5%, increasing the thermal efficiency of the cycle by at least 20% compared to a system with a fixed geometry turbine.
The work presents a good scientific level and is based on correctly selected literature reports. The research issues presented are scientifically relevant and important in the context of entering the green transition and reducing the consumption of fossil fuels. The results are a source of knowledge not only in the research area, but as possible future guidelines for the design of ORC systems. Although the work in its present form is already valuable, I suggest considering the following amendments:
1) The Abstract mentions stringent regulations to reduce emissions from burning fossil fuels, which is not confirmed in the manuscript.
2) Fig. 1 - where the turbine is located in the figure.
3) Table 1 - where the data was obtained from (source). Correct the abbreviation BSFC.
4) How the mass flow were calculated Eq. (3..5).
5) Fig. 3 - the figure is missing in the plane of interest due to the inflow angle.
6) Lines 147-148 - which is the meridional velocity, not marked in Fig. 2.
7) Fig 6 does not show the essence of the issue. It should be supplemented with visualization of inflow angles and their distributions into the part affecting the turbine torque and the part sliding on the blade.
8) Before Eq. (26) - what was the reference value of convergence. By how much should the results not differ to be considered significant.
9) How EoS was determined in Eq.`s (16, 17, 24 and 28).
10) Before 3.1 - was any commercial software used in solving the problem, if so, what software and what calculation procedures contributed.
11) Lines 212-213 - how to relate this physically to Fig.2.
12) Fig. 7 - 3 research points greatly limit the ability to assess impact. With such a small number, it is difficult to resolve whether it is a straight line or a curve. As one might guess this was due to the data in Table 1.
13) Before Fig. 8 - for what reasons is the variable geometry turbine shown as one result, when it has the ability to adjust the inflow angle within a certain range.
14) Fig. 8b shows an approximate 15kW turbine at P3. Does the mathematical model correctly capture the flow losses at different flux values. How does the pump-turbine balance look like in terms of power, this is one of the most important parameters.
15) Before Fig. 9 - A 1% increase may be within the measurement error of the test equipment. It should be borne in mind that these are the results of calculations, which need not be reflected in the experiment. How the issue of integration relates to the costs incurred, after what time or other benchmark the investment pays off.
16) Conclusions must be thoroughly rewritten with an indication of specific results in bullet form. Manuscript strengths and directions for future research should be indicated.
Author Response
Dear respected reviewer,
We would like to express our sincere thanks for the constructive comments and we kindly ask you to refer to the attached file for our responses.
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsAs pdf file attached.
Comments for author File: Comments.pdf
Overall acceptable.
Author Response
Dear respected reviewer,
We would like to express our sincere thanks for the constructive comments and we kindly ask you to refer to the attached file for our responses.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsDear authors!
Major issue:
- line 25: What is BSFC? It is not clear for readers!
- Figure 1 is not clear; How has been built T(s)?
- Figure 4: Illegible Flow chart (Ë 3);
- Figure 3, 5 are not clear;
- Figure 5: What are the enthalpy and entropy values for P1-P5?
- Table 2 is not clear;
- Figure 7-9: For readers needed how were built these Figures;
- line 300: Needed add the title of Figure 9, a.
Good luck!
Comments on the Quality of English LanguageCheck the English
Author Response
Sincerest thanks the reviewers’ valuable comments on our manuscript. our responses to the reviewer can be seen below:
1. line 25: What is BSFC? It is not clear for readers!
ANS: As defined in the nomenclature. BSFC is the brake specific fuel consumption. This term has been also defined in line 25 for clarity.
- Figure 1 is not clear; How has been built T(s)?
ANS: Figure is the typical T-s diagram of subcritical Rankine cycles. It is a description of the states through the system. Below you can see some references showing the T-s diagram of subcritical ORC.
- https://doi.org/10.3390/app12073557
- http://dx.doi.org/10.1016/j.applthermaleng.2012.10.017
- https://doi.org/10.1016/j.egyr.2020.11.150
- https://doi.org/10.3390/pr11071982
- Figure 4: Illegible Flow chart (Ë 3)!
ANS: Thank you for the comment. It is a well-known term in airfoil design. It is the stator setting angle and calculated iteratively to set the throat width. Nomenclature has been updated.
- Figure 3, 5 are not clear.
ANS: Figure 3 is just a cross section of the radial turbine stage defined in Figure 2. Figure 5 is the typical enthalpy-entropy diagram of radial inflow turbines. Both Figure 3 and Figure 5 can be seen in all radial turbine studies such as:
- http://dx.doi.org/10.1016/j.enconman.2014.12.003
- https://doi.org/10.1177/0957650916637966
- Figure 5: What are the enthalpy and entropy values for P1-P5?
ANS: Each throat opening for each engine point has its own values. A sample of engine point 3 and throat opening 100% can be seen in the table below. For brevity and since the global parameters (power, efficiency etc) are of interest, enthalpy-entropy values were not included in the manuscript.
|
Point |
Enthalpy (kJ/kg) |
Entropy (kJ/kg.K) |
mass flow rate (kg/s) |
|
1 |
510.04 |
1.8212 |
0.5 |
|
2 |
507.88 |
1.8169 |
|
|
3 |
490.83 |
1.783 |
|
|
4 |
488.72 |
1.778 |
|
|
5 |
473.64 |
1.7823 |
6. Table 2 is not clear;
ANS: The table presents a well-established and common losses model of radial inflow turbines. Designers of radial inflow turbines integrate these expressions to account for the losses in the turbine that result in efficiency decrements.
- Figure 7-9: For readers needed how were built these Figures
ANS: They were built using the mathematical model explained in the preceding section. Turbine efficiency, turbine power, thermal efficiency, engine power, engine BSFC are defined in the model in section 2.
- line 300: Needed add the title of Figure 9, a.
ANS: Thank you for the notice. Caption has been improved.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe article ‘Potential of Variable Geometry Radial Inflow Turbines as Expansion Machines in Organic Rankine Cycles Integrated with Heavy Duty Diesel Engines’.
Thank you for giving me the opportunity to read the manuscript again after the corrections made. All my comments have been taken into account. The revised version of the manuscript has gained scientific value and is more communicative for the potential audience.
Author Response
We would like to express our great thanks to the reviewer for the compliment.
