Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors

I have read your paper. It was hard to read. It is (too) long. From my point of view, it is annoying to read the same words on several places. (back pressures, rack positions). I have an impression that chapters were written individually and “forcefully” stacked together. I am not a native speaker so I will not judge English, but I have no problems reading the article. I have some experience on truck/bus diesel engines testing and turbo charger components production (except rotating parts), so I have some comments on that.

I presume the 1800 rpm is the speed corresponding to the maximum engine power. Can you specify air/fuel ratio.

You have validated your model at 0 kPa back pressure. Did you made some more measurements to validate the exhaust temperatures at increased back pressure. From my point of view and according to our measurements the temperatures should be higher than in your paper.

How did you implement cooling of compressed air in your simulation.

What is A/R ratio of turbine housing.

Did you consider temperature limitations of other engine or TC parts (central housing of the TC)

What kind of bearing is in the TC

Please add the reference to 1000, 000 rpm (line 190)

Best regards

Author Response

Thank you for your correction. Our additional description is as attachment. We hope that can meet the requirements.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The work is interesting, but it does not prove the innovation and scientific interest. The use of VGT is common in several types of engines, with different conditions and the present results and conclusions do not introduce any progress in knowledge or any novelty.

Comments on the Quality of English Language

The written English is ok, but the grammar can be improved, mainly considering the construction of the sentences.

Author Response

Our additional description is as attachment. We hope that can meet the requirements.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Applicability of Variable Geometry Turbocharger for Diesel Generators under High Exhaust Back Pressure

Review

In this paper, the variable geometry turbocharger is applied to a diesel engine, and then, are studied the engine performance, and the improvement of brake output and brake specific fuel consumption of engine. The results show that the brake output is improved under full-load operation by suitable variable geometry turbocharger rack position.

The manuscript is interesting. It contains analytical modeling, and numerical simulation. However, some clarifications would improve the quality.

1.      The state of the art should be enriched.

2.      The novelty must be better explained and based on knowledge derived from the studied literature.

3.   The mathematical equations deducted by the authors must be clearly demonstrated. Their deduction is missing.

4.  The software used for the simulation, computations and figures must be clearly described.

5.      In the section Conclusions should be indicated some applications using the described variable geometry turbocharger.

6.   Please avoid the excessive use of ad-hoc abbreviations in abstract, and in the main narrative.

7.       The too big paragraphs should be fragmented to make easier the readability.

Comments on the Quality of English Language

The English language must be edited for syntax, style, order of words, and terminology.

Author Response

Thank you for your correction. Our additional description is as attachment. We hope that can meet the requirements.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The authors study VGT applied to a diesel engine from a marine genset, with high exhaust backpressure. They study engine performance characteristics aimed at further improvement of brake output and brake specific fuel consumption of the engine. The basic setting of a reduced valve overlap of 12 ℃A is adopted in the performance simulations. Exhaust backpressure levels of 25kPa, 45kPa and 65kPa (gauge pressure) are studied for the turbocharged diesel engine. The simulation tool is GT-Power engine simulation software.

 

This is an interesting paper on a subject of importance for modern marine applications.

 

The authors should address the following issues in a carefully revised version of their manuscript:

 

Lines 245 versus line 256: avoid repetition.

 

Figure 4: why arrows for backpressures above zero drop outside the map?

 

For all operating points simulated, could you please compile a Table with the respective pressures, from inlet, compressor exit, engine exit (turbine inlet), turbine exit, exhaust line exit.

 

Have you examined the possibility to change turbine for better matching at high backpressure levels?

 

The Conclusions section should contain some indicative quantitative results.

Comments on the Quality of English Language

Minor English editing required, however, the writing must be improved in style and avoid repetitions.

Author Response

Thank you for your correction. Our additional description is as attachment. We hope that can meet the requirements.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors 

You have considered most of my remarks. I still have a feeling that you do not have the engine and you made some simulations using available data. A/R should be cast on compressor housing. Just by googling C32 ACERT Tier 3 Commercial Propulsion Engines | Cat | Caterpillar you can see it has water cooled TC most likely due to maximum exhaust temperatures reaching close to 700 C. As I hinted to the possible issues with the maximum temperature of central housing in the temperature limitations of lamellar grey cast iron (most likely material of the central housing). I could not find the air temperature after cooler and this parameter can have significant influence on engine performance. I believe you did a good job doing simulations and showed general trend, but I believe your work can have very limited practical implications. I will suggest minor revision and suggest to write the statement that the focus of your work is on simulation and numerical investigation or try to address the mentioned issues.

Best regards  

Author Response

Please find our response in the attachment, thanks.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I understand what was referred to by the authors, but again, in the highly transient mode of operation in heavy-duty vehicles and even in automobile applications, the use of variable geometry turbocompressors has been very common and used for several decades. I cannot understand the novelty of this work, and that is not also proved in the actual paper.

Comments on the Quality of English Language

No further comments, considering the answer of the authors.

Author Response

Please find our response in the attachment, thanks.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript can advance for publication.

Author Response

Please find our response in the attachment, thanks.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Accept

Comments on the Quality of English Language

Minor English improvement required

Author Response

Please find our response in the attachment, thanks.

Author Response File: Author Response.pdf